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49 results on '"Department of Aerodynamics and Fluid Mechanics"'

1. Localized layers of turbulence in vertically-stratified plane Poiseuille flow

Author

Labarbe, Joris, Le Gal, P, Harlander, U, Le Dizès, S, Favier, B, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Physiologie Intégratives de l’Arbre en environnement Fluctuant (PIAF), Institut National de la Recherche Agronomique (INRA)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020]), Department of Aerodynamics and Fluid Mechanics, and Brandenburg University of Technology [Cottbus – Senftenberg] (BTU)

Subjects
[PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn]
Abstract

This article presents a numerical analysis of the instability developing in horizontal plane Poiseuille flow, when stratification extends along the direction orthogonal to the plane of shear. Our study builds up on the previous work that originally detected the linear instability of such configuration, by means of experiments, theoretical analysis and numerical simulations (Le Gal et al. 2021). We extend hereafter this former investigation beyond linear theory, investigating nonlinear regimes with direct numerical simulations. We notice a tendency for the flow to lose its vertical homogeneity through a point of secondary bifurcation, due to harmonic resonances, and further describe this symmetrybreaking mechanism in the vicinity of the instability threshold. When departing away from this limit, we observe a series of bursting events that break down the flow into disordered motions driven by localized shear instabilities. This intermittent dynamics leads to the coexistence of localized layers of stratified turbulence surrounded by quiescent regions of meandering waves.

Published
2022

2. Electric Fields

Author

Futterer , Birgit, Yoshikawa , Harunori, Mutabazi , Innocent, Egbers , C., Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Laboratoire Jean Alexandre Dieudonné (JAD), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Ondes et Milieux Complexes (LOMC), Centre National de la Recherche Scientifique (CNRS)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Normandie Université (NU), Brandenburg University of Technology (BTU) Cottbus, Laboratoire Jean Alexandre Dieudonné ( JAD ), Université Nice Sophia Antipolis ( UNS ), Université Côte d'Azur ( UCA ) -Université Côte d'Azur ( UCA ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Ondes et Milieux Complexes ( LOMC ), Université Le Havre Normandie ( ULH ), and Normandie Université ( NU ) -Normandie Université ( NU ) -Centre National de la Recherche Scientifique ( CNRS )

Subjects
[ PHYS.MECA.MEFL ] Physics [physics]/Mechanics [physics]/Mechanics of the fluids [physics.class-ph], [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, [ SDU.STU ] Sciences of the Universe [physics]/Earth Sciences, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2022
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3. Localized layers of turbulence in stratified horizontally sheared Poiseuille flow

Author

J. Labarbe, P. Le Gal, U. Harlander, S. Le Dizès, B. Favier, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology, Cottbus-Senftenberg, D-03046 Cottbus, Germany

Subjects
[PHYS]Physics [physics], Mechanics of Materials, Mechanical Engineering, Applied Mathematics, Fluid Dynamics (physics.flu-dyn), FOS: Physical sciences, Physics - Fluid Dynamics, Condensed Matter Physics
Abstract

This paper presents a numerical analysis of the instability developing in horizontally sheared Poiseuille flow, when stratification extends along the vertical direction. Our study builds on the previous work that originally detected the linear instability of such a configuration, by means of experiments, theoretical analysis and numerical simulations (Le Gal et al., J. Fluid Mech., vol. 907, 2021, R1). We extend this investigation beyond linear theory, investigating nonlinear regimes with direct numerical simulations. We find that the flow loses its vertical homogeneity through a secondary bifurcation, due to harmonic resonances, and describe this symmetry-breaking mechanism in the vicinity of the instability threshold. When departing from this limit, we observe a series of bursting events that break down the flow into disordered motions driven by localized shear instabilities. This intermittent dynamics leads to the coexistence of horizontal localized layers of stratified turbulence surrounded by quiescent regions of meandering waves.

Published
2022
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4. The instability of the vertically-stratified horizontal plane Poiseuille flow

Author

Le Gal, P, Harlander, U, Borcia, I, Le Dizès, Stéphane, Chen, J, Favier, B, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Institute of Physics, and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics::Fluid Dynamics, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Mechanics of the fluids [physics.class-ph], [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph]
Abstract

International audience; We present here the first study on the stability of the plane Poiseuille flow when the fluid is stratified in density perpendicularly to the plane of the horizontal shear. Using laboratory experiments, linear stability analyses and direct numerical simulations, we describe the appearance of an instability that results from a resonance of internal gravity waves and Tollmien-Schlichting waves carried by the flow. This instability takes the form of long meanders confined in thin horizontal layers stacked along the vertical axis.

Published
2021
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5. Experimental investigation of turbulent boundary layers at high Reynolds number with uniform blowing, part I: statistics

Author

Ch. Egbers, S. Merbold, Jean-Marc Foucaut, V. Motuz, G. Hasanuzzaman, Christophe Cuvier, Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology Cottbus-Senftenberg, Cottbus, Germany, Laboratoire de Mécanique des Fluides de Lille – Kampé de Fériet - UMR 9014 (LMFL), Centrale Lille-ONERA-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM), and HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)-HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)

Subjects
Turbulence, Computational Mechanics, General Physics and Astronomy, Reynolds number, Mechanics, [PHYS.MECA]Physics [physics]/Mechanics [physics], Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, symbols.namesake, Flow control (fluid), Particle image velocimetry, Shear (geology), Mechanics of Materials, Drag, Bounded function, 0103 physical sciences, symbols, 010306 general physics, Geology, ComputingMilieux_MISCELLANEOUS
Abstract

Uniform blowing in wall bounded shear flows is well known for its drag reducing effects and has long been investigated ever since. However, many contemporary and former research on this topic has c...

Published
2020
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6. L'instabilité linéaire de l'écoulement de Poiseuille plan stratifié

Author

Le Gal, P., Harlander, U., Borcia, I, Le Dizès, S., Chen, J, Favier, B., Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Laboratoire de Physique et Physiologie Intégratives de l’Arbre en environnement Fluctuant (PIAF), Institut National de la Recherche Agronomique (INRA)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020]), Le Gal, Patrice, Laboratoire de Physique et Physiologie Intégratives de l'Arbre Fruitier et Forestier (PIAF), and Institut National de la Recherche Agronomique (INRA)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)

Subjects
[PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], [PHYS.PHYS.PHYS-FLU-DYN] Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn]
Abstract

International audience; Nous présentons ici la première étude-à notre connaissance-de l'instabilité linéaire de l'écoulement de Poiseuille plan lorsque le fluide est stratifié dans une direction perpendiculaire au cisaillement. A l'aide d'expériences de laboratoire, d'analyses théoriques et de simulations numériques directes, nous décrivons l'apparition d'une instabilité qui provient de la résonance d'ondes de gravité internes transportées par l'écoulement et subissant un décalage Doppler. Cette instabilité fait apparaître des méandres visibles dans des plans horizontaux et disposés en couche le long de l'axe vertical. Abstract : We present here the first study-to our knowledge-of the linear instability of the plane Poiseuille flow when the fluid is stratified in a direction perpendicular to shear. Using laboratory experiments, theoretical analyzes and direct numerical simulations, we describe the appearance of an instability that results from the resonance of internal gravity waves carried and Doppler shifted by the flow. This instability reveals meanders visible in horizontal planes and arranged in layers along the vertical axis.

Published
2019

7. The linear instability of the stratified plane Poiseuille flow

Author

Le Gal, Patrice, Harlander, Uwe, Borcia, Ion, Chen, Jun, Le Dizès, Stéphane, Favier, Benjamin, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Dalian Institute of Chemical Physics, and Le Gal, Patrice

Subjects
Physics::Fluid Dynamics, [PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], [PHYS.PHYS.PHYS-FLU-DYN] Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn]
Abstract

International audience; In the non stratified case, plane Poiseuille flow is known to be linearly unstable for Reynolds numbers larger than 5572. Above this value, two dimensional waves-known as Tollmien-Schlichting waves-are viscously unstable and can propagate in the flow.We present here the stability analysis of a plane Poiseuille flow which is stably stratified in density along the vertical direction, i.e. orthogonal to the horizontal shear. Density stratification is ubiquitous in nature and we may think here to water flows in submarine canyons, to winds in valleys or to laminar flows in rivers or canals where stratification can be due to temperature or salinity gradients. Our study is based on laboratory experiments, on a linear stability analysis and on direct numerical simulations. This study follows recent investigations of instabilities in stratified rotating or non rotating shear flows: the stratorotational instability [1,2], the stratified boundary layer instability [3] or the stratified Plane Couette flow instability [4] where it is shown that these instabilities belong to a class of instabilities caused by the resonant interaction of Doppler shifted internal gravity waves. A particularity of the present case is that for the Poiseuille flow, Tollmien-Schlichting waves can also interact and possibly resonate with non viscous gravity waves. The experiments are realized in an annular channel having an inner diameter of 1.4 m and a rectangular vertical section of 85 x 200 mm 2. This channel is filled up to a level of 130 mm (position of the free surface) with salt stratified water using the classical double bucket technique. The free surface fluid is then entrained by the side and bottom walls of the canal when this one is set into slow rotation. However, a barrier, placed radially inside the channel, blocks the fluid, prohibiting solid body rotation and resulting in a nearly parabolic horizontal velocity profile. Visualizations and PIV measurements show the appearance of a stationary (versus the laboratory frame) braided pattern of waves above a given threshold that depends on the Reynolds and Froude numbers (Re c ∼ 2000, F r c ∼ 0.5). The comparison with the theoretical threshold and the critical wavenumbers calculated by linear analysis is excellent. Finally, direct numerical simulations permit to complete the description of this instability that can be interpreted as a resonant interaction of boundary trapped waves.

Published
2019

8. Low Mach Number Modeling of Stratorotational Instability in a water-filled Taylor-Couette cavity

Author

Raspo, Isabelle, Viazzo, Stéphane, Randriamampianina, Anthony, Meletti, Gabriel, Harlander, Uwe, Seelig, Torsten, Krebs, Andreas, Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), ANR-10-EQPX-0029,EQUIP@MESO,Equipement d'excellence de calcul intensif de Mesocentres coordonnés - Tremplin vers le calcul petaflopique et l'exascale(2010), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Boutin, Olivier, and Equipements d'excellence - Equipement d'excellence de calcul intensif de Mesocentres coordonnés - Tremplin vers le calcul petaflopique et l'exascale - - EQUIP@MESO2010 - ANR-10-EQPX-0029 - EQPX - VALID

Subjects
[SPI.GPROC] Engineering Sciences [physics]/Chemical and Process Engineering, [SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2018

9. High-Order Compact scheme for High-Performance Computing of stratified rotating flows

Author

Abide, S., Viazzo, S., Raspo, I., Randriamampianina, A., Meletti de Oliveira, G., Harlander, Uwe, Krebs, A., LAboratoire de Mathématiques et PhySique (LAMPS), Université de Perpignan Via Domitia (UPVD), Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), LAboratoire de Modélisation Pluridisciplinaire et Simulations (LAMPS), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and ANR-10-EQPX-0029,EQUIP@MESO,Equipement d'excellence de calcul intensif de Mesocentres coordonnés - Tremplin vers le calcul petaflopique et l'exascale(2010)

Subjects
[PHYS]Physics [physics], [SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2018

10. Experimental Confirmation of Linear Stability Results on Stratified Taylor-Couette Flows

Author

Meletti, Gabriel, Harlander, Uwe, Seelig, Torsten, Viazzo, Stéphane, Abide, Stéphane, Krebs, Andreas, Randriamampianina, Anthony, Raspo, Isabelle, Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), LAboratoire de Mathématiques et PhySique (LAMPS), Université de Perpignan Via Domitia (UPVD), DFG, Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and LAboratoire de Modélisation Pluridisciplinaire et Simulations (LAMPS)

Subjects
[PHYS]Physics [physics], [SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2018

11. Baroclinic, Kelvin and inertia-gravity waves in the barostrat instability experiment

Author

Uwe Harlander, I. D. Borcia, Costanza Rodda, P. Le Gal, Miklos Vincze, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), and Le Gal, Patrice

Subjects
[PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], 010504 meteorology & atmospheric sciences, Baroclinic instability, media_common.quotation_subject, Baroclinity, Computational Mechanics, Inertia, 01 natural sciences, Instability, 010305 fluids & plasmas, Physics::Fluid Dynamics, inertia-gravity waves, Geochemistry and Petrology, waves in rotating and stratified 31 fluids, 0103 physical sciences, Annulus (firestop), Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Galaxy Astrophysics, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences, media_common, Gravitational wave, Astronomy and Astrophysics, [PHYS.PHYS.PHYS-FLU-DYN] Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], Mechanics, Geophysics, 13. Climate action, Mechanics of Materials, differentially heated rotating annulus, Astrophysics::Earth and Planetary Astrophysics, Laboratory experiment, Geology
Abstract

International audience; The differentially heated rotating annulus is a laboratory experiment historically designed for modelling large-scale features of the mid-latitude atmosphere. In the present study, we investigate a modified version of the classic baroclinic experiment in which a juxtaposition of convective and motionless stratified layers is created by introducing a vertical salt stratification. The thermal convective motions are suppressed in a central region at mid-depth of the rotating tank, therefore double-diffusive convection rolls can develop only in thin layers located at top and bottom, where the salt stratification is weakest. For high enough rotation rates, the baroclinic instability destabilises the flow in the top and the bottom shallow convective layers, generating cyclonic and anticyclonic eddies separated by the stable stratified layer. Thanks to this alternation of layers resembling the convective and radiative layers of stars, the planetary's atmospheric troposphere and stratosphere or turbulent layers at the sea surface above stratified waters, this new laboratory setup is of interest for both astrophysics and geophysical sciences. More specifically, it allows to study the exchange of momentum and energy between the layers, primarly by the propagation of internal gravity waves (IGW). PIV velocity maps are used to describe the wavy flow pattern at different heights. Using a co-rotating laser and camera, the wave field is well resolved and different wave types can be found: baroclinic waves, Kelvin, and Poincaré type waves. The signature of small-scale IGW can also be observed attached to the baroclinic jet. The baroclinic waves occur at the thin convectively active layer at the surface and the bottom of the tank, though decoupled they show different manifestation of nonlinear interactions. The inertial Kelvin and Poincaré waves seem to be mechanically forced. The small-scale wave trains attached to the meandering jet point to an imbalance of the large-scale flow. For the first time, the simultaneous occurrence of differentwave types is reported in detail for a differentially heated rotating annulus experiment.

Published
2018

12. Numerical and experimental study of inertia-gravity waves in the differentially heated rotating annulus

Author

Rodda, Costanza, Dan Borcia, Ion, Hien, Steffen, Achatz, Ulrich, Le Gal, Patrice, Harlander, Uwe, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Department of Aerodynamics and Fluid Mechanics, and Brandenburg University of Technology [Cottbus – Senftenberg] (BTU)

Subjects
[PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn]
Abstract

International audience; The occurrence and source mechanism of inertia-gravity waves (IGWs) are studied in the differentially heated rotating annulus via laboratory experiments (BTU) and numerical simulations (GUF). Two differentially heated rotating annulus experiments are used for this purpose at the BTU laboratories. The first is a modified version of the classical baroclinic experiment in which a juxtaposition of convective and motionless stratified layers can be created by introducing a vertical salt stratification. The thermal convective motions are suppressed in a central region at mid depth of the rotating tank, therefore baroclinic waves can only build up in thin layers located at the top and bottom, where the salt stratification is weakest. This new experimental setup, coined "barostrat instabil-ity", allows to study the exchange of momentum and energy between the layers, especially by the propagation of IGWs. Moreover, in contrast to the classical tank without salt stratification we have layers with N/f > 1. A ratio larger than unity implies that the IGW propagation in the experiment is expected to be qualitatively similar to the atmospheric case. Interestingly, we found local IGW packets along the jets in the surface and bottom layers where the local Rossby number is larger than 1, suggesting spontaneous imbalance as generating mechanism [1], and not boundary layer instability [2]. Theoretical considerations and numerical simulations have led to the identification of an annulus configuration, much wider and shallower, with a much larger temperature difference between the inner and outer cylinder walls, which is more atmosphere-like since it shows an N / f >1 even without the vertical salt stratification. Flow regime stability has been tested for this new differentially heated rotating annulus and compared with findings from the small tank. In view of the different geometries of the two experimental systems, their correspondence was excellent with respect to the large-scale. Moreover, direct numerical simulations were performed (GUF) for this atmosphere-like configuration of the experiment and possible regions of IGW activity were characterised by a Hilbert-transform algorithm. The simulations show a clear baroclinic wave structure exhibiting a realistic jet-front system superimposed by small-scale structures which are associated with IGWs occurring in wave packets [3]. The comparison of observations from a corresponding big tank experiment with numerical simulation shows that for both cases (as we already observed in the barostrat experiment), small scale wave packets are clearly correlated with an increased local Rossby number.

Published
2018

13. On the instability of radially sheared and axially stratified vortex flow

Author

Meletti de Oliveira, Gabriel, Raspo, Isabelle, Seelig, Torsten, Viazzo, Stephane, Randriamampianina, Anthony, Abide, Stéphane, Krebs, Andreas, Harlander, Uwe, Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Instabilités et Turbulence, Modélisation et Simulation Numérique (en mécanique des fluides) (M2P2), Université de la Méditerranée - Aix-Marseille 2-Université Paul Cézanne - Aix-Marseille 3-Université de Provence - Aix-Marseille 1-Centre National de la Recherche Scientifique (CNRS)-Université de la Méditerranée - Aix-Marseille 2-Université Paul Cézanne - Aix-Marseille 3-Université de Provence - Aix-Marseille 1-Centre National de la Recherche Scientifique (CNRS), LAboratoire de Modélisation Pluridisciplinaire et Simulations (LAMPS), Université de Perpignan Via Domitia (UPVD), Wilhelm Schickard Institute, Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Centre National de la Recherche Scientifique (CNRS)-Université de Provence - Aix-Marseille 1-Université Paul Cézanne - Aix-Marseille 3-Université de la Méditerranée - Aix-Marseille 2-Centre National de la Recherche Scientifique (CNRS)-Université de Provence - Aix-Marseille 1-Université Paul Cézanne - Aix-Marseille 3-Université de la Méditerranée - Aix-Marseille 2, and LAboratoire de Mathématiques et PhySique (LAMPS)

Subjects
[PHYS]Physics [physics], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2018

14. Instabilities and small-scale waves within the Stewartson layers of a thermally driven rotating annulus

Author

Miklos Vincze, Anthony Randriamampianina, Uwe Harlander, Stéphane Viazzo, Thomas von Larcher, Institute of Mathematics [Berlin], Freie Universität Berlin, Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Biophysics Research Group [Budapest] (ELTE-MTA 'Lendület'), Hungarian Academy of Sciences (MTA), and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, 010504 meteorology & atmospheric sciences, Scale (ratio), Mechanical Engineering, Computation, Prandtl number, Flow (psychology), Mechanics, Internal wave, Condensed Matter Physics, 01 natural sciences, Signal, 010305 fluids & plasmas, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph], Physics::Fluid Dynamics, symbols.namesake, Mechanics of Materials, internal waves, 0103 physical sciences, symbols, Annulus (firestop), Gravity wave, baroclinic flows, geophysical and geological flows, 0105 earth and related environmental sciences
Abstract

International audience; We report on small-scale instabilities in a thermally driven rotating annulus filled with a liquid with moderate Prandtl number. The study is based on direct numerical simulations and an accompanying laboratory experiment. The computations are performed independently with two different flow solvers, that is, first, the non-oscillatory forward-in-time differencing flow solver EULAG and, second, a higher-order finite-difference compact scheme (HOC). Both branches consistently show the occurrence of small-scale patterns at both vertical sidewalls in the Stewartson layers of the annulus. Small-scale flow structures are known to exist at the inner sidewall. In contrast, short-period waves at the outer sidewall have not yet been reported. The physical mechanisms that possibly trigger these patterns are discussed. We also debate whether these small-scale structures are a gravity wave signal.

Published
2018
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15. Transition to geostrophic turbulence within a baroclinic cavity

Author

Randriamampianina, Anthony, Viazzo, Stéphane, von Larcher, Thomas, Harlander, Uwe, Read, Peter, Laboratoire de Mécanique, Modélisation et Procédés Propres ( M2P2 ), Aix Marseille Université ( AMU ) -Ecole Centrale de Marseille ( ECM ) -Centre National de la Recherche Scientifique ( CNRS ), Institute of Mathematics [Berlin], Freie Universität Berlin [Berlin], Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology (BTU) Cottbus, Department of Atmospheric, Oceanic and Planetary Physics [Oxford] ( AOPP ), University of Oxford [Oxford], Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Freie Universität Berlin, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Department of Atmospheric, Oceanic and Planetary Physics [Oxford] (AOPP), University of Oxford, and Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)

Subjects
[ SPI.MECA.MEFL ] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Abstract

International audience

Published
2017

16. Instabilités lors de la transition vers la turbulence géostrophique dans une cavité barocline

Author

Randriamampianina , Anthony, Viazzo , Stéphane, von Larcher , Thomas, Harlander , Uwe, Read , Peter, Laboratoire de Mécanique, Modélisation et Procédés Propres ( M2P2 ), Aix Marseille Université ( AMU ) -Ecole Centrale de Marseille ( ECM ) -Centre National de la Recherche Scientifique ( CNRS ), Institute of Mathematics [Berlin], Freie Universität Berlin [Berlin], Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology (BTU) Cottbus, Department of Atmospheric, Oceanic and Planetary Physics [Oxford] ( AOPP ), University of Oxford [Oxford], Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Freie Universität Berlin, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Department of Atmospheric, Oceanic and Planetary Physics [Oxford] (AOPP), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and University of Oxford

Subjects
[ SPI.MECA.MEFL ] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Abstract

International audience

Published
2017

17. Small−scale flow patterns at the vertical sidewalls of the thermally driven rotating annulus

Author

von Larcher, Thomas, Viazzo, Stéphane, Randriamampianina, Anthony, Harlander, Uwe, Institute of Mathematics [Berlin], Freie Universität Berlin, Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), and Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)

Subjects
ComputingMilieux_MISCELLANEOUS, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Abstract

International audience

Published
2017

18. Instabilities and small−scale waves within the Stewartson layers of the thermally driven rotating annulus

Author

von Larcher, Thomas, Viazzo, Stéphane, Harlander, Uwe, Vincze, Miklos, Randriamampianina, Anthony, Institute of Mathematics [Berlin], Freie Universität Berlin, Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), MTA-ELTE Theoretical Physics Research Group, Budapest, Hungary, and Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)

Subjects
ComputingMilieux_MISCELLANEOUS, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Abstract

International audience

Published
2017

19. Influence of the temperature-dependent viscosity on convective flow in the radial force field

Author

Vadim Travnikov, Philippe Beltrame, Christoph Egbers, Florian Zaussinger, Department of Aerodynamics and Fluid Mechanics, Environnement Méditerranéen et Modélisation des Agro-Hydrosystèmes (EMMAH), Avignon Université (AU)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), ESA AO-99-049, DLR 50 WM 0122, and 50 WM 0822

Subjects
Physics, Convection, échange convectif, 010504 meteorology & atmospheric sciences, Field (physics), Computer simulation, [PHYS.PHYS]Physics [physics]/Physics [physics], viscosité, Thermodynamics, Viscometer, simulation numérique, Rayleigh number, Radius, 01 natural sciences, 010305 fluids & plasmas, répartition radiale, Physics::Fluid Dynamics, caractérisation tridimensionnelle, Viscosity, numerical simulation, 0103 physical sciences, viscosity, Fluid dynamics, 0105 earth and related environmental sciences
Abstract

The numerical investigation of convective flows in the radial force field caused by an oscillating electric field between spherical surfaces has been performed. A temperature difference (T-1 > T-2) as well as a radial force field triggers a fluid flow similar to the Rayleigh-Benard convection. The onset of convective flow has been studied by means of the linear stability analysis as a function of the radius ratio eta = R-1/R-2. The influence of the temperature-dependent viscosity has been investigated in detail. We found that a varying viscosity contrast beta =nu(T2)/nu(T1) between beta = 1 (constant viscosity) and beta = 50 decreases the critical Rayleigh number by a factor of 6. Additionally, we perform a bifurcation analysis based on numerical simulations which have been calculated using a modified pseudospectral code. Numerical results have been compared with the GeoFlow experiment which is located on the International Space Station (ISS). Nonturbulent three-dimensional structures are found in the numerically predicted parameter regime. Furthermore, we observed multiple stable solutions in both experiments and numerical simulations, respectively.

Published
2017
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20. The Barostrat instability: the baroclinic instability in a rotating stratified fluid

Author

Le Gal, Patrice, Vincze, Miklos, Borcia, Ion, Harlander, Uwe, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), and Le Gal, Patrice

Subjects
Physics::Fluid Dynamics, [PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], Physical Sciences and Mathematics, [PHYS.PHYS.PHYS-FLU-DYN] Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], Physics::Atmospheric and Oceanic Physics
Abstract

International audience; Our project aims to describe the baroclinic instability that destabilizes an initially stratified layer of fluid. Classically, this instability is studied using pure fluid. Here, the originality of our experiment comes from the use of a layer of water initially stratified with salt. Before rotation is started, double convection sets in within the stratified layer with a strongly nonhomogeneous pattern consisting of a double diffusive staircase at the bottom of the container in the very dense water layer and a shallow convective cell in the top surface layer. These two layers are separated by a motionless stably stratified zone. As radial motions take place due to the presence of these convective cells, the action of the Coriolis force generates strong zonal flows as soon as rotation is started. Then, above a rotation rate threshold, the baroclinic instability destabilizes the flow in the top shallow convective layer, generating a ring of pancake vortices sitting above the stably stratified layer. Therefore, this laboratory arrangement mimics the presence of a stratosphere above a baroclinic unstable troposphere. Infrared camera images measure the temperature distributions at the water surface and PIV velocity maps describe the wavy flow pattern at different altitudes. In some regimes, some wave trains have been detected. These waves might be traces of Internal Gravity Waves generated by the fluid motions in the baroclinic unstable layer.

Published
2016

21. Taylor-Couette flow with asymmetric end-walls boundary conditions

Author

Seelig, T., Kiełczewski, K., Ewa Tuliszka-Sznitko, Harlander, U., Egbers, C., Bontoux, P., Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Poznan University of Technology (PUT), Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and Constant, Eddy

Subjects
[PHYS.MECA.MEFL] Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience; no abstract

Published
2015

22. Multi-scale flow phenomena in the thermally driven rotating annulus

Author

Larcher, Thomas Von, Harlander, Uwe, Seelig, Torsten, Randriamampianina, Anthony, Viazzo, Stephane, Institute for Mathematics, Freie Universität Berlin, Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Laurette TUCKERMAN, and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2015

23. Study of transitional and turbulent flows in rotor/stator cavities

Author

Seelig, Torsten, Harlander, Uwe, Kielczewski, Kamil, Tuliszka-Sznitk, Ewa, Bontoux, Patrick, Egbers, Christoph, Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Constant, Eddy, and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.MECA.MEFL] Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience; no abstract

Published
2015

24. Multiple scales in the thermally driven rotating annulus : time-series data analysis of experiments and numerics

Author

Larcher, Thomas Von, Harlander, Uwe, Seelig, Torsten, Randriamampianina, Anthony, Viazzo, Stephane, Institute for Mathematics, Freie Universität Berlin, Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Professor C. EGBERS, and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2015

25. The baroclinic instability of an initially stratified fluid layer

Author

Le Gal, Patrice, Vincze, Miklos, Harlander, Uwe, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), EGU, Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), and Le Gal, Patrice

Subjects
[PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], [PHYS.PHYS.PHYS-FLU-DYN] Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2015

26. Inertia gravity waves linked to baroclinic waves in a rotating, differentially heated annulus with an upper free surface

Author

Randriamampianina, Anthony, Harlander, Uwe, Vincze, M, Seelig, Torsten, Larcher, Thomas Von, Viazzo, Stéphane, Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Institute for Mathematics, Freie Universität Berlin, Paul LINDEN and Jean-Marc CHOMAZ, Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and Professor C. EGBERS

Subjects
[SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2015

27. Application of advanced methods of time-series analysis for investigating multi-scale flow phenomena in a thermally driven rotating annulus

Author

Larcher, Thomas Von, Harlander, Uwe, Randriamampianina, Anthony, Viazzo, Stephane, Institute for Mathematics, Freie Universität Berlin, Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Paul LINDEN and Jean-Marc CHOMAZ, and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2015

28. Stratorotational Instability : nonlinear aspects at higher Reynolds numbers

Author

Harlander, Uwe, Seelig, Torsten, Gellert, M., Viazzo, Stephane, Randriamampianina, Anthony, Egbers, C., Rudiger, G., Randriamampianina, Anthony, Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Leibniz-Institut für Astrophysik Potsdam (AIP), Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Paul LINDEN and Jean-Marc CHOMAZ, and Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)

Subjects
[PHYS.MECA.MEFL] Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2015

29. Thermo-electro-hydrodynamic convection under microgravity: a review

Author

Harunori Yoshikawa, B. Futterer, Vadim Travnikov, Mireille Tadie Fogaing, Innocent Mutabazi, Olivier Crumeyrolle, Christoph Egbers, Laboratoire Ondes et Milieux Complexes ( LOMC ), Université Le Havre Normandie ( ULH ), Normandie Université ( NU ) -Normandie Université ( NU ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Jean Alexandre Dieudonné ( JAD ), Université Nice Sophia Antipolis ( UNS ), Université Côte d'Azur ( UCA ) -Université Côte d'Azur ( UCA ) -Centre National de la Recherche Scientifique ( CNRS ), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology (BTU) Cottbus, CNES, PEPS-PTI OndInterGE, THETE (CPER Normandie), ANR-10-LABX-09-01,LABEX EMC3, Laboratoire Ondes et Milieux Complexes (LOMC), Centre National de la Recherche Scientifique (CNRS)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Normandie Université (NU), Laboratoire Jean Alexandre Dieudonné (JAD), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS), Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), and ANR-10-LABX-0009,EMC3,Energy Materials and Clean Combustion Center(2010)

Subjects
Fluid Flow and Transfer Processes, Convection, Physics, Buoyancy, Natural convection, Operations research, Mechanical Engineering, [ PHYS.MECA.MEFL ] Physics [physics]/Mechanics [physics]/Mechanics of the fluids [physics.class-ph], General Physics and Astronomy, Mechanics, engineering.material, 01 natural sciences, 010305 fluids & plasmas, Physics::Fluid Dynamics, Spherical geometry, Temperature gradient, Combined forced and natural convection, 0103 physical sciences, engineering, Astrophysics::Solar and Stellar Astrophysics, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], Electrohydrodynamics, 010306 general physics, Physics::Atmospheric and Oceanic Physics, Rayleigh–Bénard convection
Abstract

International audience; Recent studies on thermo-electro-hydrodynamic (TEHD) convection are reviewed with focus on investigations motivated by the analogy with natural convection. TEHD convection originates in the action of the dielectrophoretic force generated by an alternating electric voltage applied to a dielectric fluid with a temperature gradient. This electrohydrodynamic force is analogous to Archimedean thermal buoyancy and can be regarded as a thermal buoyancy force in electric effective gravity. The review is concerned with TEHD convection in plane, cylindrical, and spherical capacitors under microgravity conditions, where the electric gravity can induce convection without any complexities arising from geometry or the buoyancy force due to the Earth’s gravity. We will highlight the convection in spherical geometry, comparing developed theories and numerical simulations with the GEOFLOW experiments performed on board the International Space Station (ISS).

Published
2016
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30. Double-diffusive convection and baroclinic instability in a differentially heated and initially stratified rotating system: the barostrat instability

Author

Ion Dan Borcia, Miklos Vincze, Patrice Le Gal, Uwe Harlander, Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), and Le Gal, Patrice

Subjects
[PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], Fluid Flow and Transfer Processes, Convection, 010504 meteorology & atmospheric sciences, Mechanical Engineering, Baroclinity, Fluid Dynamics (physics.flu-dyn), FOS: Physical sciences, General Physics and Astronomy, Stratification (water), [PHYS.PHYS.PHYS-FLU-DYN] Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], Physics - Fluid Dynamics, Mechanics, 01 natural sciences, Instability, 010305 fluids & plasmas, Particle image velocimetry, Eddy, 0103 physical sciences, Annulus (firestop), ComputingMilieux_MISCELLANEOUS, Geology, 0105 earth and related environmental sciences, Double diffusive convection
Abstract

International audience; A water-filled differentially heated rotating annulus with initially prepared stable vertical salinity profiles is studied in the laboratory. Based on two-dimensional horizontal particle image velocimetry (PIV) data, and infrared camera visualizations, we describe the appearance and the characteristics of the baroclinic instability in this original configuration. First, we show that when the salinity profile is linear and confined between two non stratified layers at top and bottom, only two separate shallow fluid layers can be destabilized. These unstable layers appear nearby the top and the bottom of the tank with a stratified motionless zone between them. This laboratory arrangement is thus particularly interesting to model geophysical or astrophysical situations where stratified regions are often juxtaposed to convective ones. Then, for more general but stable initial density profiles, statistical measures are introduced to quantify the extent of the baroclinic instability at given depths and to analyze the connections between this depth-dependence and the vertical salinity profiles. We find that, although the presence of stable stratification generally hinders full-depth overturning, double-diffusive convection can yield development of multicellular sideways convection in shallow layers and subsequently to a multilayered baroclinic instability. Therefore we conclude that by decreasing the characteristic vertical scale of the flow, stratification may even enhance the formation of cyclonic and anticyclonic eddies (and thus, mixing) in a local sense. ‡ Corresponding author: vincze.m@lecso.elte.hu 2

Published
2016
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31. Multivariate data analysis methods for detecting baroclinic wave interactions in the thermally driven rotating annulus

Author

Larcher, Thomas Von, Harlander, Uwe, Egbers, C., Institute for Mathematics, Freie Universität Berlin, Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), and Brandenburg University of Technology

Subjects
Data_FILES, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Abstract

see pdf file

Published
2011

32. Occurrence of an attractor in a laboratory experiment on internal-tide generation at a shelf break

Author

Gostiaux, Louis, Gerkema, Theo, Sommeria, Joël, Harlander, U., Laboratoire des Écoulements Géophysiques et Industriels [Grenoble] (LEGI), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Royal Netherlands Institute for Sea Research (NIOZ), Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology [Cottbus – Senftenberg] (BTU), and Gostiaux, Louis

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, [PHYS.MECA.MEFL] Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [SPI.MECA.MEFL] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph], [PHYS.PHYS.PHYS-FLU-DYN] Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [PHYS.PHYS.PHYS-AO-PH] Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Abstract

International audience; As part as the European funded project Hydralab (www.hydralab.eu) we carried out a series of laboratory experiments on internal-tide generation at the Grenoble Coriolis Turntable. The original aim of this work was to study the generation of internal tidal beams at the shelf break, as well as the influence of the coriolis effect and of the presence of a seasonal thermocline. The setup consisted of a 7m long and 4m wide canal, with at one of its ends an oscillating paddle generating an homogeneous barotropic flow, and at the other end a shelf-like topography, connected to the basin by a slope, which acts as the internal-tide generation region. Velocity fields in the whole tank could be estimated using simultaneous PIV measurement with different cameras. The generation process was shown to be extremely efficient, but the trapezoidal shape of the canal unexpectedly concentrated the energy on internal-wave attractors, occurring for various values of the forcing period. We present the dynamical aspects of these attractors, which to our knowledge are the largest ones ever observed in laboratory experiments, as well as a study on the energetics of the barotropic-baroclinic conversion. Our results are in good agreement with predictions from a numerical internal tide generation model, and those simulations allow us to identify the regions and rates of conversion, which are otherwise hard to obtain experimentally.

Published
2008

33. GEOFLOW: simulation of convection in a spherical shell under central force field

Author

Beltrame, Philippe, Travnikov, V., Gellert, M., Egbers, C., Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology, and EGU, Publication

Subjects
[PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], [PHYS.ASTR.CO] Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, [SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph]
Abstract

International audience; Time-dependent dynamical simulations related to convective motion in a spherical gap under a central force field due to the dielectrophoretic effect are discussed. This work is part of the preparation of the GEOFLOW-experiment which is planned to run in a microgravity environment. The goal of this experiment is the simulation of large-scale convective motion in a geophysical or astrophysical framework. This problem is new because of, on the one hand, the nature of the force field (dielectrophoretic effect) and, on another hand, the high degree of symmetries of the system, e.g. the top-bottom reflection. Thus, the validation of this simulation with well-known results is not possible. The questions concerning the influence of the dielectrophoretic force and the possibility to reproduce the theoretically expected motions in the astrophysical framework, are open. In the first part, we study the system in terrestrial conditions: the unidirectional Earth's force is superimposed on the central dielectrophoretic force field to compare with the laboratory experiments during the development of the equipment. In the second part, the GEOFLOW-experiment simulations in weightless conditions are compared with theoretical studies in the astrophysical framework's, in the first instance a fluid under a self-gravitating force field. We present complex time-dependent dynamics, where the dielectrophoretic force field causes significant differences in the flow compared to the case that does not involve this force field.

Published
2006

34. Parabolic flight experiment 'Convection in a Cylinder' – Convection patterns in varying buoyancy forces

Author

Christoph Egbers, B. Futterer, Innocent Mutabazi, Olivier Crumeyrolle, N. Dahley, Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology, Laboratoire Ondes et Milieux Complexes (LOMC), Centre National de la Recherche Scientifique (CNRS)-Université Le Havre Normandie (ULH), and Normandie Université (NU)-Normandie Université (NU)

Subjects
Convection, History, Buoyancy, Convective heat transfer, 02 engineering and technology, engineering.material, 01 natural sciences, 010305 fluids & plasmas, Education, Physics::Fluid Dynamics, [SPI]Engineering Sciences [physics], 0203 mechanical engineering, Combined forced and natural convection, 0103 physical sciences, ComputingMilieux_MISCELLANEOUS, Physics::Atmospheric and Oceanic Physics, Convection cell, Physics, Natural convection, Film temperature, Rayleigh number, Mechanics, Geophysics, Computer Science Applications, 020303 mechanical engineering & transports, engineering
Abstract

Within the project "Convection in a Cylinder" (CiC) heat transfer enhancement is studied for the case of two concentric, vertically aligned cylinders. The cylindrical gap is filled with a dielectric liquid, which viscosity is just few times higher than that of water. The inner cylinder is heated and the outer one is cooled. This setup in a gravitational buoyancy field leads to a fluid movement in a single convective cell with hot fluid rising at the inner boundary and cold fluid sinking at the outer boundary. The top and bottom part of the system shows horizontal movement, again in boundary layers. The strengthening of temperature gradient induces instabilities of that convective motion. If we vary the buoyancy force by means of electro-hydrodynamic effects, the patterns of convection differ from those instabilities rising only from variation of the temperature gradient.

Published
2011
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35. DATIV-Remote Enhancement of Smart Aerosol Measurement System Using Raspberry Pi-Based Distributed Sensors.

Author

Hasanuzzaman G, Buchwald T, Schunk C, Egbers C, Schröder A, and Hampel U

Abstract

Enclosed public spaces are hotspots for airborne disease transmission. To measure and maintain indoor air quality in terms of airborne transmission, an open source, low cost and distributed array of particulate matter sensors was developed and named Dynamic Aerosol Transport for Indoor Ventilation, or DATIV, system. This system can use multiple particulate matter sensors (PMSs) simultaneously and can be remotely controlled using a Raspberry Pi-based operating system. The data acquisition system can be easily operated using the GUI within any common browser installed on a remote device such as a PC or smartphone with a corresponding IP address. The software architecture and validation measurements are presented together with possible future developments.

Published
2024
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36. Extreme temperature fluctuations in laboratory models of the mid-latitude atmospheric circulation.

Author

Vincze M, Hancock C, Harlander U, Rodda C, and Speer K

Abstract

Using two laboratory-scale conceptual fluid dynamic models of the mid-latitude atmospheric circulation we investigate the statistical properties of pointwise temperature signals obtained in long experiment runs. We explore how the average "equator-to-pole" temperature contrast influences the range and the jump distribution of extreme temperature fluctuations, the ratio of the frequencies of rapid cooling and warming events, and the persistence of "weather" in the set-ups. We find simple combinations of the control parameters-temperature gradient, rotation rate and geometric dimensions-which appear to determine certain scaling properties of these statistics, shedding light on the underlying dynamics of the Rossby wave-related elements of the mid-latitude weather variability., (© 2023. The Author(s).)

Published
2023
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37. Large-scale flow field and aerosol particle transport investigations in a classroom using 2D-Shake-The-Box Lagrangian Particle Tracking.

Author

Buchwald T, Hasanuzzaman G, Merbold S, Schanz D, Egbers C, and Schröder A

Abstract

Infections with COVID-19 in enclosed public spaces, where virus-laden aerosol particles can accumulate over time, have significantly contributed to the rapid spread of the virus. It is therefore of great importance to understand the transport and dispersion process of aerosol particles in such spaces, especially against the background of future pandemics. In this work, we present a Lagrangian-Particle-Tracking experiment to assess the mixed convective flow in a classroom with different ventilation strategies. For this purpose, thermal plumes were created by heated dummies, and a collimated LED light-sheet with ∼0.4 m thickness was used for illumination of helium filled soap bubbles (HFSB) acting as passive tracer particles. In this way, the Lagrangian trajectories of the particles were recorded at two approximately 4.2 m × 2.8 m large fields using the novel 2D-Shake-The-Box-Method. As a result, time-resolved trajectories of over 300,000 simultaneously tracked HFSB have been reconstructed, so that both small-scale and large-scale properties of the flow are visualized quantitatively across the entire cross-section of the room. The trajectories show that the thermal plumes create lengthwise circulating vortices, which cannot be destroyed across the entire cross-section of the room by opening or tilting a window. Furthermore, the mixing in the room through the operation of an air purifier is higher compared to opening a window, which suggests that this strategy in combination with its air filtering capability is the most effective strategy to prevent infections., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

Published
2023
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38. A parameter study of strato-rotational low-frequency modulations: impacts on momentum transfer and energy distribution.

Author

Meletti G, Abide S, Viazzo S, and Harlander U

Abstract

Previous comparisons of experimental data with nonlinear numerical simulations of density stratified Taylor-Couette (TC) flows revealed nonlinear interactions of strato-rotational instability (SRI) modes that lead to periodic changes in the SRI spirals and their axial propagation. These pattern changes are associated with low-frequency velocity modulations that are related to the dynamics of two competing spiral wave modes propagating in opposite directions. In the present paper, a parameter study of the SRI is performed using direct numerical simulations to evaluate the influence of the Reynolds numbers, the stratification, and of the container geometry on these SRI low-frequency modulations and spiral pattern changes. The results of this parameter study show that the modulations can be considered as a secondary instability that are not observed for all SRI unstable regimes. The findings are of interest when the TC model is related to star formation processes in accretion discs. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (Part 2)'.

Published
2023
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39. Flow regimes in a very wide-gap Taylor-Couette flow with counter-rotating cylinders.

Author

Merbold S, Hamede MH, Froitzheim A, and Egbers C

Abstract

In this study, we discuss the observed flow regimes in Taylor-Couette flow of radius ratio [Formula: see text] for various Reynolds numbers up to [Formula: see text]. We investigate the flow using a visualization method. The flow states in the centrifugally unstable flow are investigated in the case of counter-rotating cylinders and pure inner cylinder rotation. Beside classical known flow states as Taylor-vortex flow and wavy vortex flow, we observe a variety of new flow structures in the cylindrical annulus, especially for the transition to turbulence. Coexisting turbulent and laminar regions inside the system are observed. Turbulent spots and turbulent bursts are observed, as well as an irregular Taylor-vortex flow and non-stationary turbulent vortices. Especially, a single axially aligned columnar vortex between the inner and outer cylinder is found. The principal regimes observed in flow between independently rotating cylinders are summarized in a flow-regime diagram. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (Part 2)'.

Published
2023
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40. Thermoelectric instabilities in a circular Couette flow.

Author

Meyer A, Yoshikawa HN, Szabo PSB, Meier M, Egbers C, and Mutabazi I

Abstract

The stability of a non-isothermal circular Couette flow is analyzed when subjected to a dielectrophoretic force field. Outward and inward heating configurations are considered when the inner cylinder is rotating and the outer cylinder is at rest. In addition, an alternating voltage is applied between the two cylinders to induce a radial electric buoyancy that acts on the dielectric fluid. The linear stability analysis provides the threshold for the first transition to instability, as well as the corresponding wavenumber and frequency of the modes. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (part 1)'.

Published
2023
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41. Numerical investigation of atmospherelike flows in a spherical geometry.

Author

Travnikov V and Egbers C

Abstract

Buoyancy-driven convection flows play a crucial role in global heat and momentum transport in atmosphere. Simplified planetary and stellar atmospheres can be described by a spherical gap geometry with special boundary conditions for the temperature. In the spherical gap, the dielectrophoretic effect is used to synthesize the radial gravity field. Lateral thermal boundary conditions are used to model solar radiation at the equator and at the poles. The temperature reaches a maximum value at the equator and becomes colder near the poles. In the case of a rotating gap, the influence of the Coriolis and centrifugal forces are taken into account. Different regimes of the two-dimensional steady basic flow are discussed in dependence on the Taylor number and Rayleigh number and for the radii ratio η=R_{in}/R_{out}, where R_{in},R_{out} are the radii of the inner and outer surfaces, respectively. Linear instability theory is used to study when the basic flow becomes unstable. The critical Rayleigh number at which the steady axisymmetric basic flow becomes time-dependently axisymmetric or three dimensional is found to be a function of the Taylor number. Furthermore, the critical azimuthal wave number m_{c}, which is responsible for the structure of the supercritical three-dimensional flow, and the critical frequency of the perturbation ω_{c} were found. The spatial location of the perturbation helps to understand the origin of the instability.

Published
2021
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42. The Drake Passage opening from an experimental fluid dynamics point of view.

Author

Vincze M, Bozóki T, Herein M, Borcia ID, Harlander U, Horicsányi A, Nyerges A, Rodda C, Pál A, and Pálfy J

Abstract

Pronounced global cooling around the Eocene-Oligocene transition (EOT) was a pivotal event in Earth's climate history, controversially associated with the opening of the Drake Passage. Using a physical laboratory model we revisit the fluid dynamics of this marked reorganization of ocean circulation. Here we show, seemingly contradicting paleoclimate records, that in our experiments opening the pathway yields higher values of mean water surface temperature than the "closed" configuration. This mismatch points to the importance of the role ice albedo feedback plays in the investigated EOT-like transition, a component that is not captured in the laboratory model. Our conclusion is supported by numerical simulations performed in a global climate model (GCM) of intermediate complexity, where both "closed" and "open" configurations were explored, with and without active sea ice dynamics. The GCM results indicate that sea surface temperatures would change in the opposite direction following an opening event in the two sea ice dynamics settings, and the results are therefore consistent both with the laboratory experiment (slight warming after opening) and the paleoclimatic data (pronounced cooling after opening). It follows that in the hypothetical case of an initially ice-free Antarctica the continent could have become even warmer after the opening, a scenario not indicated by paleotemperature reconstructions., (© 2021. The Author(s).)

Published
2021
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43. Influence of dielectrical heating on convective flow in a radial force field.

Author

Travnikov V, Zaussinger F, Haun P, and Egbers C

Abstract

We present results of numerical and experimental investigations of thermal convection induced by internal heating in both a nonrotating and a rotating spherical gap filled with dielectric fluid. The inner and outer surfaces are maintained at constant temperatures T_{in} and T_{out}, respectively. A radial force field is produced due to the dielectrophoretic effect. The buoyancy force in the Navier-Stokes equation and the source term in the energy equation depend on the imposed oscillating electric field according to V_{rms}^{2}r^{-5} and V_{rms}^{2}r^{-4}, respectively, where V_{rms} is the root mean squared value of the voltage between spherical surfaces and r is the radial distance. Beginning with the nonrotating case, we perform linear instability analysis in the case of purely internal heating, i.e., both surfaces are maintained at the same temperature ΔT=T_{in}-T_{out}=0. Next, we consider a situation in which there is not only internal heating but also a temperature difference ΔT>0. While the spherical gap rotated, the occurring two-dimensional steady basic flow was calculated numerically. The stability of the basic flow was investigated by means of linear instability theory. The critical Rayleigh numbers and the critical azimuthal wave numbers are presented in dependence on the Taylor number. We calculate supercritical three-dimensional flows for comparison with experimentally obtained patterns in frames of the GeoFlow experiment on the International Space Station.

Published
2020
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44. A Vision-Based Method for Determining Aircraft State during Spin Recovery.

Author

Kapuscinski T, Szczerba P, Rogalski T, Rzucidlo P, and Szczerba Z

Abstract

This article proposes a vision-based method of determining in which of the three states, defined in the spin recovery process, is an aircraft. The correct identification of this state is necessary to make the right decisions during the spin recovery maneuver. The proposed solution employs a keypoints displacements analysis in consecutive frames taken from the on-board camera. The idea of voting on the temporary location of the rotation axis and dominant displacement direction was used. The decision about the state is made based on a proposed set of rules employing the histogram spread measure. To validate the method, experiments on flight simulator videos, recorded at varying altitudes and in different lighting, background, and visibility conditions, were carried out. For the selected conditions, the first flight tests were also performed. Qualitative and quantitative assessments were conducted using a multimedia data annotation tool and the Jaccard index, respectively. The proposed approach could be the basis for creating a solution supporting the pilot in the process of aircraft spin recovery and, in the future, the development of an autonomous method.

Published
2020
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45. Influence of the temperature-dependent viscosity on convective flow in the radial force field.

Author

Travnikov V, Zaussinger F, Beltrame P, and Egbers C

Abstract

The numerical investigation of convective flows in the radial force field caused by an oscillating electric field between spherical surfaces has been performed. A temperature difference (T_{1}>T_{2}) as well as a radial force field triggers a fluid flow similar to the Rayleigh-Bénard convection. The onset of convective flow has been studied by means of the linear stability analysis as a function of the radius ratio η=R_{1}/R_{2}. The influence of the temperature-dependent viscosity has been investigated in detail. We found that a varying viscosity contrast β=ν(T_{2})/ν(T_{1}) between β=1 (constant viscosity) and β=50 decreases the critical Rayleigh number by a factor of 6. Additionally, we perform a bifurcation analysis based on numerical simulations which have been calculated using a modified pseudospectral code. Numerical results have been compared with the GeoFlow experiment which is located on the International Space Station (ISS). Nonturbulent three-dimensional structures are found in the numerically predicted parameter regime. Furthermore, we observed multiple stable solutions in both experiments and numerical simulations, respectively.

Published
2017
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46. Temperature fluctuations in a changing climate: an ensemble-based experimental approach.

Author

Vincze M, Borcia ID, and Harlander U

Abstract

There is an ongoing debate in the literature about whether the present global warming is increasing local and global temperature variability. The central methodological issues of this debate relate to the proper treatment of normalised temperature anomalies and trends in the studied time series which may be difficult to separate from time-evolving fluctuations. Some argue that temperature variability is indeed increasing globally, whereas others conclude it is decreasing or remains practically unchanged. Meanwhile, a consensus appears to emerge that local variability in certain regions (e.g. Western Europe and North America) has indeed been increasing in the past 40 years. Here we investigate the nature of connections between external forcing and climate variability conceptually by using a laboratory-scale minimal model of mid-latitude atmospheric thermal convection subject to continuously decreasing 'equator-to-pole' temperature contrast ΔT, mimicking climate change. The analysis of temperature records from an ensemble of experimental runs ('realisations') all driven by identical time-dependent external forcing reveals that the collective variability of the ensemble and that of individual realisations may be markedly different - a property to be considered when interpreting climate records.

Published
2017
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47. Chaotic motion of light particles in an unsteady three-dimensional vortex: experiments and simulation.

Author

Vanyó J, Vincze M, Jánosi IM, and Tél T

Subjects
Time Factors, Motion, Nonlinear Dynamics
Abstract

We study the chaotic motion of a small rigid sphere, lighter than the fluid in a three-dimensional vortex of finite height. Based on the results of Eulerian and Lagrangian measurements, a sequence of models is set up. The time-independent model is a generalization of the Burgers vortex. In this case, there are two types of attractors for the particle: a fixed point on the vortex axis and a limit cycle around the vortex axis. Time dependence might combine these regular attractors into a single chaotic attractor, however its robustness is much weaker than what the experiments suggest. To construct an aperiodically time-dependent advection dynamics in a simple way, Gaussian noise is added to the particle velocity in the numerical simulation. With an appropriate choice of the noise properties, mimicking the effect of local turbulence, a reasonable agreement with the experimentally observed particle statistics is found.

Published
2014
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48. The CoLaPipe--the new Cottbus large pipe test facility at Brandenburg University of Technology Cottbus-Senftenberg.

Author

König F, Zanoun el-S, Öngüner E, and Egbers C

Abstract

The CoLaPipe is a novel test facility at the Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology Cottbus-Senftenberg (BTU Cottbus-Senftenberg), set up to investigate fully developed pipe flow at high Reynolds numbers (Re(m) ⩽ 1.5 × 10(6)). The design of the CoLaPipe is closed-return with two available test sections providing a length-to-diameter ratio of L/D = 148 and L/D = 79. Within this work, we introduce the CoLaPipe and describe the various components in detail, i.e., the settling chamber, the inlet contraction, the blower, bends, and diffusers as well as the cooling system. A special feature is the numerically optimized contraction design. The applications of different measuring techniques such as hot-wire anemometry and static pressure measurements to quantitatively evaluate the mean flow characteristics and turbulence statistics are discussed as well. In addition, capabilities and limitations of available and new pipe flow facilities are presented and reconsidered based on their length-to-diameter ratio, the achieved Reynolds numbers, and the resulting spatial resolution. Here, the focus is on the facility design, the presentation of some basic characteristics, and its contribution to a reviewed list of specific questions still arising, e.g., scaling and structural behavior of turbulent pipe flow as well as the influence of the development length on turbulence investigations.

Published
2014
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49. Torque measurements and numerical determination in differentially rotating wide gap Taylor-Couette flow.

Author

Merbold S, Brauckmann HJ, and Egbers C

Subjects
Computer Simulation, Rotation, Torque, Energy Transfer, Models, Theoretical, Rheology methods
Abstract

We investigate experimentally and numerically turbulent Taylor-Couette flow with independently rotating cylinders and radius ratio η=0.5. The torque acting on the inner wall is measured to analyze the transverse current of azimuthal motion J(ω). The scaling of the torque with shear Reynolds number is determined for the outer cylinder at rest. For constant shear Reynolds number we investigate various ratios of angular velocities and find a torque maximum for counter-rotating cylinders that deviates from the prediction suggested by van Gils et al. [J. Fluid Mech. 706, 118 (2012)]. The direct comparison between the experiment and the numerical simulation shows a good agreement in the torques.

Published
2013
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