30 results on '"MATHEMATICAL models of fluid dynamics"'
Search Results
2. Weak solutions for Euler systems with non-local interactions.
- Author
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Carrillo, José A., Feireisl, Eduard, Gwiazda, Piotr, and Świerczewska‐Gwiazda, Agnieszka
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EULER equations , *PRESSURE , *MODIFICATIONS , *MATHEMATICAL models of fluid dynamics , *EULER method - Abstract
We consider several modifications of the Euler system of fluid dynamics, including its pressureless variant driven by non-local interaction repulsive-attractive and alignment forces in the space dimension [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
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3. Landau's theorems for biharmonic mappings (II).
- Author
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Liu, Mingsheng, Xie, Lin, and Yang, Li ‐ Mei
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LANDAU theory , *BIHARMONIC functions , *DIFFERENTIABLE mappings , *MATHEMATICAL models of fluid dynamics , *ELASTICITY , *PROBLEM solving , *MATHEMATICAL models - Abstract
In this paper, we derive five new versions of Landau-type theorems for biharmonic mappings of unit disk. Moreover, we prove that all five results are sharp when the bounds are equal to 1. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
4. Modeling complex flow structures and drag around a submerged plant of varied posture.
- Author
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Boothroyd, Richard J., Hardy, Richard J., Warburton, Jeff, and Marjoribanks, Timothy I.
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PLANKTON ,MATHEMATICAL models of fluid dynamics ,VEGETATION management - Abstract
Although vegetation is present in many rivers, the bulk of past work concerned with modeling the influence of vegetation on flow has considered vegetation to be morphologically simple and has generally neglected the complexity of natural plants. Here we report on a combined flume and numerical model experiment which incorporates time-averaged plant posture, collected through terrestrial laser scanning, into a computational fluid dynamics model to predict flow around a submerged riparian plant. For three depth-limited flow conditions (Reynolds number = 65,000-110,000), plant dynamics were recorded through high-definition video imagery, and the numerical model was validated against flow velocities collected with an acoustic Doppler velocimeter. The plant morphology shows an 18% reduction in plant height and a 14% increase in plant length, compressing and reducing the volumetric canopy morphology as the Reynolds number increases. Plant shear layer turbulence is dominated by Kelvin-Helmholtz type vortices generated through shear instability, the frequency of which is estimated to be between 0.20 and 0.30 Hz, increasing with Reynolds number. These results demonstrate the significant effect that the complex morphology of natural plants has on in-stream drag, and allow a physically determined, species-dependent drag coefficient to be calculated. Given the importance of vegetation in river corridor management, the approach developed here demonstrates the necessity to account for plant motion when calculating vegetative resistance. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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5. Combining economic and fluid dynamic models to determine the optimal spacing in very large wind farms.
- Author
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Stevens, Richard J. A. M., Hobbs, Benjamin F., Ramos, Andrés, and Meneveau, Charles
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WIND power plant design & construction ,WIND turbine design & construction ,MATHEMATICAL models of fluid dynamics ,BOUNDARY layer separation ,VORTEX motion ,RENEWABLE energy sources - Abstract
Wind turbine spacing is an important design parameter for wind farms. Placing turbines too close together reduces their power extraction because of wake effects and increases maintenance costs because of unsteady loading. Conversely, placing them further apart increases land and cabling costs, as well as electrical resistance losses. The asymptotic limit of very large wind farms in which the flow conditions can be considered 'fully developed' provides a useful framework for studying general trends in optimal layouts as a function of dimensionless cost parameters. Earlier analytical work by Meyers and Meneveau (Wind Energy 15, 305-317 (2012)) revealed that in the limit of very large wind farms, the optimal turbine spacing accounting for the turbine and land costs is significantly larger than the value found in typical existing wind farms. Here, we generalize the analysis to include effects of cable and maintenance costs upon optimal wind turbine spacing in very large wind farms under various economic criteria. For marginally profitable wind farms, minimum cost and maximum profit turbine spacings coincide. Assuming linear-based and area-based costs that are representative of either offshore or onshore sites we obtain for very large wind farms spacings that tend to be appreciably greater than occurring in actual farms confirming earlier results but now including cabling costs. However, we show later that if wind farms are highly profitable then optimization of the profit per unit area leads to tighter optimal spacings than would be implied by cost minimization. In addition, we investigate the influence of the type of wind farm layout. © 2016 The Authors Wind Energy Published by John Wiley & Sons Ltd [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
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6. Vanishing viscosity limit for the 3D magnetohydrodynamic system with generalized Navier slip boundary conditions.
- Author
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Guo, Boling and Wang, Guangwu
- Subjects
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VISCOSITY , *MAGNETOHYDRODYNAMICS , *BOUNDARY value problems , *SMOOTHNESS of functions , *MATHEMATICAL models of fluid dynamics - Abstract
In this paper, we investigate the vanishing viscosity limit problem for the 3D incompressible magnetohydrodynamic (MHD) system in a general bounded smooth domain of R3 with the generalized Navier slip boundary conditions. We also obtain rates of convergence of the solution of viscous MHD to the corresponding ideal MHD. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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7. Advection-Based Function Matching on Surfaces.
- Author
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Azencot, Omri, Vantzos, Orestis, and Ben‐Chen, Mirela
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VECTOR fields , *ADVECTION , *FLOW measurement , *MATHEMATICAL models of fluid dynamics , *SURFACE potential , *MATHEMATICAL models - Abstract
A tangent vector field on a surface is the generator of a smooth family of maps from the surface to itself, known as the flow. Given a scalar function on the surface, it can be transported, or advected, by composing it with a vector field's flow. Such transport is exhibited by many physical phenomena, e.g., in fluid dynamics. In this paper, we are interested in the inverse problem: given source and target functions, compute a vector field whose flow advects the source to the target. We propose a method for addressing this problem, by minimizing an energy given by the advection constraint together with a regularizing term for the vector field. Our approach is inspired by a similar method in computational anatomy, known as LDDMM, yet leverages the recent framework of functional vector fields for discretizing the advection and the flow as operators on scalar functions. The latter allows us to efficiently generalize LDDMM to curved surfaces, without explicitly computing the flow lines of the vector field we are optimizing for. We show two approaches for the solution: using linear advection with multiple vector fields, and using non-linear advection with a single vector field. We additionally derive an approximated gradient of the corresponding energy, which is based on a novel vector field transport operator. Finally, we demonstrate applications of our machinery to intrinsic symmetry analysis, function interpolation and map improvement. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
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8. A maximum entropy approach to the parametrization of subgrid processes in two-dimensional flow.
- Author
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Verkley, W. T. M., Kalverla, P. C., and Severijns, C. A.
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ENTROPY , *PARAMETRIC modeling , *GEOPHYSICAL fluid dynamics , *MATHEMATICAL models of atmospheric circulation , *MATHEMATICAL models of fluid dynamics , *VORTEX motion , *ATMOSPHERIC models - Abstract
In numerical models of geophysical fluid systems, parametrization schemes are needed to account for the effect of unresolved processes on processes that are resolved explicitly. Usually, these parametrization schemes require tuning of their parameters to achieve optimal performance. We propose a new type of parametrization that requires no tuning, as it is based on an assumption that is not specific to any particular model. The assumption is that the unresolved processes can be represented by a probability density function that has maximum information entropy under the constraints of zero average time derivatives of key integral quantities of the unresolved processes. In the context of a model of a simple fluid dynamical system, it is shown that this approach leads to definite expressions for the mean effect of unresolved processes on processes that are resolved. The merits of the parametrization, regarding both short-range forecasting and long-term statistics, are demonstrated by numerical experiments in which a low-resolution version of the model is used to simulate the results of a high-resolution version of the model. For the fluid dynamical system that is studied, the proposed parametrization turns out to be related to the anticipated potential vorticity method with definite values of its parameters. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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9. A high order finite volume method for one dimensional nonlocal reactive flows of parabolic type.
- Author
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Wang, Lejuan and Yang, Min
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FINITE volume method , *REACTIVE flow , *MATHEMATICAL models of fluid dynamics , *STOCHASTIC convergence , *PARABOLIC differential equations - Abstract
In this paper, we consider a high order finite volume approximation of one-dimensional nonlocal reactive flows of parabolic type. The method is obtained by discretizing in space by arbitrary order vertex-centered finite volumes, followed by a modified Simpson quadrature scheme for the time stepping. Compared to the existed finite volume methods, this new finite volume scheme could achieve the desired accuracy with less data storage by employing higher-order trial spaces. The finite volume approximations are proved to possess optimal order convergence rates in the H1-norm and L2-norm, which are also confirmed by numerical tests. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
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- 2016
- Full Text
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10. Clear-sky stable boundary layers with low winds over snow-covered surfaces. Part 2: Process sensitivity.
- Author
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Sterk, H. A. M., Steeneveld, G. J., Bosveld, F. C., Vihma, T., Anderson, P. S., and Holtslag, A. A. M.
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ATMOSPHERIC boundary layer , *TURBULENT mixing , *COMPUTER simulation of turbulence , *MATHEMATICAL models of fluid dynamics , *SURFACE energy - Abstract
This study evaluates the relative impact of snow-surface coupling, long-wave radiation, and turbulent mixing on the development of the stable boundary layer over snow. Observations at three sites are compared to WRF single-column model (SCM) simulations. All three sites have snow-covered surfaces but are otherwise contrasting: Cabauw (Netherlands, grass), Sodankylä (Finland, needle-leaf forest) and Halley (Antarctica, ice shelf). All cases are characterized by stable, clear-sky, and calm conditions. Part 1 of this study determined the optimal SCM forcing strategy. In this study, the process intensities from that reference are perturbed to study their relative significance and to assess which process could be responsible for the most optimal agreement between model and observation. The analysis reveals a large variability in the modelled atmospheric state and surface parameters. Overall, the modelled gradients of temperature and moisture are underestimated but decreasing the process intensities improves this. The impact is strongest with reduced mixing, though this then causes the model to overestimate the near-surface wind speed. To study the surface energy balance terms, we use so-called 'process diagrams'. The achieved variation between the sensitivity runs indicates the model sensitivity to each process. The overall sensitivity is similar for the three sites but the relative offsets in the position of the sensitivity runs with respect to the observations differ, hampering general recommendations for model improvement. Furthermore, sometimes a meaningful interpretation of observations is troublesome, which hampers the comparison with model results. Radiation is relatively more important at Cabauw and Sodankylä, whilst coupling plays a more important role at Halley. The sensitivity analysis is performed with two boundary-layer schemes (MYJ, YSU). YSU generates larger, more accurate gradients of atmospheric temperature and humidity, while wind speeds are predicted better with MYJ. The behaviour of an increase in 2 m temperature with decreased mixing is most obvious with YSU. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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11. Extending the MODPATH Algorithm to Rectangular Unstructured Grids.
- Author
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Pollock, David W.
- Subjects
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PARTICLE tracking velocimetry , *GROUNDWATER flow , *MATHEMATICAL models , *WATER balance (Hydrology) , *DARCY'S law , *MATHEMATICAL models of fluid dynamics - Abstract
The recent release of MODFLOW-USG, which allows model grids to have irregular, unstructured connections, requires a modification of the particle-tracking algorithm used by MODPATH. This paper describes a modification of the semi-analytical particle-tracking algorithm used by MODPATH that allows it to be extended to rectangular-based unstructured grids by dividing grid cells with multi-cell face connections into sub-cells. The new method will be incorporated in the next version of MODPATH which is currently under development. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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12. Mild solutions of stochastic Navier-Stokes equation with jump noise in.
- Author
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Fernando, B. P. W., Rüdiger, B., and Sritharan, S. S.
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NAVIER-Stokes equations , *STOCHASTIC differential equations , *EQUATIONS in fluid mechanics , *MATHEMATICAL models of fluid dynamics , *MATHEMATICAL research - Abstract
In this paper, we study solvability of the local mild solution of stochastic Navier-Stokes equation with jump noise in [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
13. Comparison of Different Approaches for Analyzing Converging Flows for Polymer Fluids.
- Author
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Yang, Jia, Zhu, Lin, Qin, Gang, and Li, Jigong
- Subjects
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VISCOUS flow , *FLOW measurement , *MEASUREMENT of viscosity , *MATHEMATICAL models of fluid dynamics , *SHEAR flow , *MATHEMATICAL models - Abstract
Entrance converging flow of the circular pipe was analyzed to reveal the flow mechanism and optimize the pipe geometry in entrance converging region. Based on the principle of minimum energy, different equations involving entrance converging flow were proposed by considering the friction effect and introducing the elongational rate of Cogswell's analysis, and then the predicted vortex length ratio and elongational viscosity were compared with the experimental data of different polymer melts. In final, the predictive ability of the proposed equations, Cogswell's equations, Binding's equations, and Gibson's equations was discussed. It was found that the predicted vortex length ratio and elongational viscosity of the proposed equations were close to the experimental results. Based on the shear flow measurement of polymer fluids, it was demonstrated that the proposed equations were helpful to optimize the geometry in the pipe contraction region and evaluate the elongational viscosity. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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- View/download PDF
14. Bounds, monotonicity, uniqueness, and analytical calculation of a class of similarity solutions for the fluid flow over a nonlinearly stretching sheet.
- Author
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Van Gorder, Robert A.
- Subjects
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FLUID dynamics , *MATHEMATICAL models of fluid dynamics , *FLUID mechanics , *MATHEMATICAL models , *DYNAMICS , *NONLINEAR analysis - Abstract
Invoking some estimates obtained in [F.T. Akyildiz et al., Mathematical Methods in the Applied Sciences 33 (2010) 601-606] (which presented an alternate method of proof for the present problem), we correct the parameter regime considered in [R.A. Van Gorder, K. Vajravelu, and F. T. Akyildiz, Existence and uniqueness results for a nonlinear differential equation arising in viscous flow over a nonlinearly stretching sheet, Applied Mathematics Letters 24 (2011) 238-242] and add some details, which were omitted in the original proof. After this is done, we formulate a more elegant method of proof, converting the nonlinear ODE into a first nonlinear order system. This gives us a more natural way to view the problem and lends insight into the behavior of the solutions. Finally, we give a new way to approximate the shooting parameter α = f ′ ′ (0) analytically, through minimization of the L2([0, ∞ )) norm of residual errors. This approximation demonstrates the behavior of the parameter α we expect from the proved theorems, as well as from numerical simulations. In this way, we obtain a concise analytical approximation to the similarity solution. In summary, from this analysis, we find that monotonicity of solutions and their derivatives is essential in determining uniqueness, and these monotone solutions can be approximated analytically in a fairly simple way. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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15. Numerical simulations of wave interactions with vertical wave barriers using the SPH method.
- Author
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Ni, Xingye, Feng, W. B., and Wu, Di
- Subjects
COMPUTER simulation ,MATHEMATICAL models of fluid dynamics ,WAVE analysis ,BOUNDARY layer (Aerodynamics) ,BREAKWATERS ,SLOSHING (Hydrodynamics) ,FLUID-structure interaction - Abstract
SUMMARY This paper focuses on the fluid boundary separation problem of the conventional dynamic solid boundary treatment (DSBT) and proposes a modified DSBT (MDSBT). Classic 2D free dam break flows and 3D dam break flows against a rectangular box are used to assess the performance of this MDSBT in free surface flow and violent fluid-structure interaction, respectively. Another test, water column oscillations in a U-tube, is specially designed to reveal the applicability of dealing with two types of particular boundaries: the wet-dry solid boundary and the large-curvature solid boundary. A comparison between the numerical results and the experimental data shows that the MDSBT is capable of eliminating the fluid boundary separation, improving the accuracy of the solid boundary pressure calculations and preventing the unphysical penetration of fluid particles. Using a 2D SPH numerical wave tank with MDSBT, the interactions between regular waves and a simplified vertical wave barrier are simulated. The numerical results reveal that the maximum horizontal force occurs at the endpoint of the vertical board, and with the enlargement of the relative submerged board length, the maximum moment grows linearly; furthermore, the relative average mass transportation under the breakwater initially increases to 11.14 per wave strike but is later reduced. The numerical simulation of a full-scale 3D wave barrier with two vertical boards shows that the wave and structure interactions in the practical project are far more complicated than in the simplified 2D models. The SPH model using the MDSBT is capable of providing a reference for engineering designs. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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16. A method for computing curved meshes via the linear elasticity analogy, application to fluid dynamics problems.
- Author
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Abgrall, R., Dobrzynski, C., and Froehly, A.
- Subjects
TRIANGULATION ,MATHEMATICAL models of fluid dynamics ,BOUNDARY value problems ,BOUNDARY layer (Aerodynamics) ,ELASTICITY - Abstract
SUMMARY We propose and analyze an algorithm for the robust construction of curved meshes in two and three dimensions. The meshes are made of curved simplexes. The algorithm starts from a mesh made of straight simplexes, and using a linear elasticity analogy applied on well-chosen data, one can generate a curved mesh. Note that if the initial mesh has a boundary layer, this method allows to conserve it on the final mesh. This algorithm is used on several airfoils in two and three dimensions, including a turbulent M6 wing. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
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17. Optimization and scale-up of oligonucleotide synthesis in packed bed reactors using computational fluid dynamics modeling.
- Author
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Wolfrum, Christian, Josten, Andre, and Götz, Peter
- Subjects
FLUID dynamic measurements ,OLIGONUCLEOTIDE synthesis ,MATHEMATICAL models of fluid dynamics ,FLUID mechanics ,CHEMICAL kinetics - Abstract
A computational fluid dynamics (CFD) model for the analysis of oligonucleotide synthesis in packed bed reactors was developed and used to optimize the scale up of the process. The model includes reaction kinetics data obtained under well defined conditions comparable to the situation in the packed bed. The model was validated in terms of flow conditions and reaction kinetics by comparison with experimental data. Experimental validation and the following model parameter studies by simulation were performed on the basis of a column with 0.3 g oligonucleotide capacity. The scale-up studies based on CFD modelling were calculated on a 440 g scale (oligonucleotide capacity). © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1048-1056, 2014 [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
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18. A CWENO ghost fluid method for compressible multimaterial flow.
- Author
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Lahooti, Mohsen and Pishevar, Ahmadreza
- Subjects
COMPRESSIBLE flow ,RIEMANN-Hilbert problems ,MATHEMATICAL models of fluid dynamics ,LEVEL set methods ,SHOCK waves ,METHODOLOGY - Abstract
SUMMARY In this work a new ghost fluid method (GFM) is introduced for multimaterial compressible flow with arbitrary equation of states. In previous researches, it has been shown that accurate wave decomposition at the interface by solving a Riemann problem alleviates the shortcomings of the standard GFM in dealing with the impingement of strong waves onto the interface but these Riemann-based GFM are not consistent with the framework of the central WENO scheme in which the emphasis is to avoid solving Riemann problems at control volume faces and enjoy the black box property (being independent of equation of state). The aim of this work is to develop a new GFM that is completely consistent with the methodology behind central schemes; that is, it enjoys a black box property. The capabilities of the proposed GFM method is shown by solving various types of multimaterial compressible flows including gas-gas, gas-water and fluid-solid interfaces interacting with strong shock waves in one and two space dimensions. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
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19. Multifluid Modeling of the Desulfurization Process within a Bubbling Fluidized Bed Coal Gasifier.
- Author
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Armstrong, Lindsay‐Marie, Gu, Sai, Luo, Kai H., and Mahanta, Pinakeswar
- Subjects
MATHEMATICAL models of fluid dynamics ,DESULFURIZATION ,FLUIDIZED bed reactors ,COAL gasification plants ,PARTICULATE matter ,CHEMICAL reactions - Abstract
The desulfurization process to a two-dimensional (2-D) and three-dimensional (3-D) Eulerian-Eulerian computational fluid dynamic ( CFD) model of a coal bubbling fluidized gasifier is introduced. The desulfurization process is important for the reduction of harmful SO
x emissions; therefore, the development of a CFD model capable of predicting chemical reactions involving desulfurization is key to the optimization of reactor designs and operating conditions. To model the process, one gaseous phase and five particulate phases are included. Devolatilization, heterogeneous, and homogeneous chemical reactions as well as calcination and desulfurization reactions are incorporated. A calcination-only model and a calcination plus desulfurization model are simulated in 2-D and 3-D and the concentrations of SO2 leaving the reactors are compared. The simulated results are assessed against available published experimental data. The influence of the fluidized bed on the desulfurization is also considered. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1952-1963, 2013 [ABSTRACT FROM AUTHOR]- Published
- 2013
- Full Text
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20. An immersed boundary method wall model for high-Reynolds-number channel flow over complex topography.
- Author
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Anderson, William
- Subjects
REYNOLDS number ,CHANNEL flow ,CHANNEL flow measurement ,MATHEMATICAL models of fluid dynamics ,TURBULENCE ,EDDIES ,SIMULATION methods & models - Abstract
The article discusses research investigating the use of an immersed boundary method wall model for high-Reynolds-number channel flow over complex topography. Topics include the impact immersed obstacles on increased velocity gradients, turbulence production, and manifestation of wakes in channel flows, some common approaches to numerically describing the presence of obstacles in channel flows, such as the immersed boundary method, and their limitations.
- Published
- 2013
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21. Comparison of patient-specific inlet boundary conditions in the numerical modelling of blood flow in abdominal aortic aneurysm disease.
- Author
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Hardman, David, Semple, Scott I., Richards, Jennifer M.J., and Hoskins, Peter R.
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AORTIC aneurysms , *MATHEMATICAL models of fluid dynamics , *BLOOD flow , *TOMOGRAPHY , *AORTIC diseases , *HELICAL gears - Abstract
SUMMARY Three inlet boundary condition datasets were derived from phase-contrast MRI: (i) centre line velocity data converted to two-dimensional (2D) velocity profile using Womersley equations (Womersley), (ii) 2D velocity profile with one axial component of velocity (1CV), (iii) 2D velocity profile with three components of velocity (3CV). Computational fluid dynamics was performed using a rigid wall approach with geometry data extracted from the computed tomography dataset. Helical flow was present in the 1CV and 3CV simulations, with more complex patterns for the 3CV case. The Womersley method produced simplified flow patterns with an absence of helical flow. Mean values of quantitative indices (helical flow index, mean wall shear stress, oscillatory index) were compared with the 3CV inlet data. These were lower for both the Womersley inlet data (28%, 71%, 56%) and the 1CV inlet data (9%, 24%, 69%). It was concluded that inlet methods based on centre line velocity, such as might be obtained from Doppler ultrasound, lead to significantly simplified abdominal aortic aneurysm haemodynamics and thus are not recommended. Single velocity component (axial) data from MRI might suffice when general flow characteristics and spatial wall shear stress are required. Ideally 2D MRI velocity profiles with 3-velocity component data are preferred to fully account for helical flow. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
22. Prediction of turbulent gas-solid flow in a duct with a 90° bend using an Eulerian-Lagrangian approach.
- Author
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Njobuenwu, Derrick O., Fairweather, Michael, and Yao, Jun
- Subjects
MATHEMATICAL models of fluid dynamics ,MATHEMATICAL models ,TURBULENCE ,PARTICLES ,ALGORITHMS ,FOURIER analysis - Abstract
A dilute, particle-laden turbulent flow in a square cross-sectioned duct with a 90° bend is modeled using a three-dimensional Eulerian-Lagrangian approach. Predictions are based on a second-moment turbulence closure, with particles simulated using a Lagrangian particle tracking technique, coupled to a particle-wall interaction algorithm and a random Fourier series method used to model particle dispersion. The performance of the model is tested for a gas-solid flow in a horizontal-to-vertical duct, with predictions showing good agreement with experimental data. In particular, the consistent use of anisotropic and fully three-dimensional approaches throughout yields predictions that result in fluctuating particle velocities in acceptable agreement with data. © 2011 American Institute of Chemical Engineers AIChE J, 2012 [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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23. Power-law polymer solution flow in a converging annular spinneret: Analytical approximation and numerical computation.
- Author
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Tung, Kuo-Lun, Li, Yu-Ling, Hu, Che-Chia, and Chen, Yu-Shao
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MATHEMATICAL models of fluid dynamics ,SHEAR (Mechanics) ,SPINNERETS (Textile machinery) ,ARTIFICIAL membranes ,SIMULATION methods & models - Abstract
A simplified analytical solution for the flow of power-law liquids through a conical annulus was derived to estimate the flow profile, wall shear rate, and elongation rate in the spinneret during the spinning of hollow fiber membranes. The velocity profiles and shear and elongation rates of the power-law fluid showed good agreement with those obtained from computational fluid dynamic simulations. Although the actual spinneret is characterized by an annulus with a converging cross section, most studies to date have used a geometrical concentric annulus for the sake of simplicity. The results of the current work indicate that neglecting the converging characteristics of the actual spinneret can lead to significant underestimation of the wall shear rate. Using the equations derived in our work, we were able to predict not only the velocity profile but also the wall shear rate and the elongation rate; the influence of the spinneret design on the membrane morphology and properties were also examined. © 2011 American Institute of Chemical Engineers AIChE J, 2012 [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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24. Direction of unsaturated flow in a homogeneous and isotropic hillslope.
- Author
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Lu, Ning, Kaya, Basak Sener, and Godt, Jonathan W.
- Subjects
ISOTROPIC properties ,SOIL moisture ,RAINFALL ,GRAVITY ,MATHEMATICAL models of fluid dynamics - Abstract
The distribution of soil moisture in a homogeneous and isotropic hillslope is a transient, variably saturated physical process controlled by rainfall characteristics, hillslope geometry, and the hydrological properties of the hillslope materials. The major driving mechanisms for moisture movement are gravity and gradients in matric potential. The latter is solely controlled by gradients of moisture content. In a homogeneous and isotropic saturated hillslope, absent a gradient in moisture content and under the driving force of gravity with a constant pressure boundary at the slope surface, flow is always in the lateral downslope direction, under either transient or steady state conditions. However, under variably saturated conditions, both gravity and moisture content gradients drive fluid motion, leading to complex flow patterns. In general, the flow field near the ground surface is variably saturated and transient, and the direction of flow could be laterally downslope, laterally upslope, or vertically downward. Previous work has suggested that prevailing rainfall conditions are sufficient to completely control these flow regimes. This work, however, shows that under time-varying rainfall conditions, vertical, downslope, and upslope lateral flow can concurrently occur at different depths and locations within the hillslope. More importantly, we show that the state of wetting or drying in a hillslope defines the temporal and spatial regimes of flow and when and where laterally downslope and/or laterally upslope flow occurs. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
25. MODELING HEAT EXCHANGER PERFORMANCE FOR NON-NEWTONIAN FLUIDS.
- Author
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ASTERIADOU, KONSTANTIA, HASTING, A.P.M., BIRD, M.R., and MELROSE, JOHN
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HEAT exchangers ,PERFORMANCE evaluation ,NON-Newtonian fluids ,COMPUTATIONAL fluid dynamics ,FOOD industry equipment ,MATHEMATICAL models of fluid dynamics ,COST effectiveness - Published
- 2010
- Full Text
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26. Investigation of Flow Characteristics in a Six-Strand CC Tundish Combining Plant Measurements, Physical and Mathematical Modeling.
- Author
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Warzecha, M., Merder, T., Pfeifer, H., and Pieprzyca, J.
- Subjects
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CONTINUOUS casting , *MATHEMATICAL models of fluid dynamics , *FLOW control (Data transmission systems) , *MATHEMATICAL models of turbulence , *MANGANESE steel , *COMPUTER simulation - Abstract
The tundish plays a major role in the continuous casting process. The flow in a tundish has a very substantial effect on the quality of the final product and on efficient casting conditions. Efforts are being made worldwide to obtain the most favourable shape of tundish interior by using dams, weirs and gas curtains. The aim of these flow control devices is to reduce the dead zone areas and improve the conditions for the separation of non-metallic inclusions. Numerous model studies are being carried out to explain the effect of the tundish working space shape and steel flow conditions on the inclusions floating processes. The presented article shows the results of investigations performed to obtain the mass exchange characteristics in the investigated tundish. The measurements were done directly at the steel plant during normal working conditions. By controlling the changing content of manganese in steel, the residence time distribution (RTD) characteristics were acquired. The RTD characteristics are also obtained with a water model of the tundish with dimensional scale of 1:3. Parallel to the water model, numerical simulation based on mathematical modelling of fluid flow, relying on the system of differential equations, is employed in the research work. Numerical simulations were carried out with the finite-volume commercial code FLUENT using the standard k-ε turbulence model. The primary purpose of the investigations carried out is to present the characteristics describing the transitory zone in a six-strand tundish. It is shown that the F-curve, describing the transitory zone, can be obtained by using different measurement techniques. Tracer concentration characteristics for the model of tundish obtained from both modelling techniques - physical as well as numerical - are very similar. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
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27. Fully Automated Objective-Based Method for Master Recession Curve Separation.
- Author
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Posavec, Kristijan, Parlov, Jelena, and Naki, Zoran
- Subjects
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HYDRAULICS , *MATHEMATICAL models of fluid dynamics , *ELECTRONIC spreadsheets , *WATER springs , *COMPUTER software - Abstract
The fully automated objective-based method for master recession curve (MRC) separation was developed by using Microsoft Excel spreadsheet and Visual Basic for Applications (VBA) code. The core of the program code is used to construct an MRC by using the adapted matching strip method (Posavec et al. 2006). Criteria for separating the MRC into two or three segments are determined from the flow-duration curve and are represented as the probable range of percent of flow rate duration. Successive separations are performed automatically on two and three MRCs using sets of percent of flow rate duration from selected ranges and an optimal separation model scenario, having the highest average coefficient of determination R2, is selected as the most appropriate one. The resulting separated master recession curves are presented graphically, whereas the statistics are presented numerically, all in separate sheets. Examples of field data obtained from two springs in Istria, Croatia, are used to illustrate its application. The freely available Excel spreadsheet and VBA program ensures the ease of use and applicability for larger data sets. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
28. Issue Information.
- Subjects
MATHEMATICAL models of fluid dynamics ,PUBLISHING - Abstract
No abstract is available for this article. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
29. Issue Information.
- Subjects
FLUIDS ,MATHEMATICAL models of fluid dynamics - Abstract
No abstract is available for this article. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
30. Issue Information.
- Subjects
MATHEMATICAL models of fluid dynamics ,SUBSCRIPTIONS to serial publications ,MANUSCRIPTS - Abstract
No abstract is available for this article. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
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