10 results on '"Ricot D"'
Search Results
2. A study of wake effects on the drag of Ahmed׳s squareback model at the industrial scale
- Author
-
Grandemange, M., Cadot, O., Courbois, A., Herbert, V., Ricot, D., Ruiz, T., and Vigneron, R.
- Published
- 2015
- Full Text
- View/download PDF
3. A new directional splitting approach for grid refinement in the lattice Boltzmann method
- Author
-
Gendre, F., Ricot, D., Fritz, G., Sagaut, Pierre, Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), conf, M2P2, and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)
- 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
- 2016
4. Characterizations of force and pressure fluctuations on real vehicles
- Author
-
Cadot, Olivier, Courbois, A, Ricot, D, Ruiz, Tony, Harambat, F, Herbert, V, Vigneron, R, Délery, J, Unité de Mécanique (UME), École Nationale Supérieure de Techniques Avancées (ENSTA Paris), Technocentre Renault [Guyancourt], RENAULT, PSA Peugeot - Citroën (PSA), PSA Peugeot Citroën (PSA), Groupement d’Intérêt Economique Souffleries Aéroacoustiques Automobiles (GIE S2A), and cadot, olivier
- Subjects
Physics::Fluid Dynamics ,[SPI]Engineering Sciences [physics] ,bistability ,[SPI] Engineering Sciences [physics] ,road vehicle aerodynamics ,drag sources ,three-dimensionnal wake dynamics ,full-scale experiments ,separated flows - Abstract
International audience; Both the unsteady aerodynamics force and base pressure distributions are investigated for four model cars in real flow conditions. The low pass cutoff frequency of the measurements is about 5 Hz which is sufficient to consider the global fluctuations of drag, lift and side forces. The drag fluctuations are very low, they never exceed 1% of the mean drag. A clear correlation is found with the base pressure distribution fluctuations. It is found that the regions of smallest pressure fluctuations on the vehicle base are the most correlated to the drag fluctuations or in other words, the regions of largest pressure fluctuations on the base are not associated with the drag fluctuations. Sideslip effect is studied, and one of the model presented a clear bistable behavior on the lift creating huge fluctuations as investigated in the academic experiment of Grandemange, Gohlke and Cadot, Physics of Fluids 25 (2013) 095103.
- Published
- 2016
5. Characterization of the flow past real road vehicles with blunt afterbodies
- Author
-
Grandemange, M, Ricot, D, Vartanian, C, Ruiz, T, Cadot, Olivier, Unité de Mécanique (UME), École Nationale Supérieure de Techniques Avancées (ENSTA Paris), PSA Peugeot - Citroën (PSA), PSA Peugeot Citroën (PSA), Renault, Technocentre, Guyancourt, GIES2A, and cadot, olivier
- Subjects
Physics::Fluid Dynamics ,[SPI]Engineering Sciences [physics] ,[SPI] Engineering Sciences [physics] - Abstract
International audience; The flow past two different road vehicles with blunt afterbodies is studied at a Reynolds number based on the vehicle length of 10 7. The boundary layer thickness and the pressure distribution around the body are characterized. Then, the wake is investigated through static pressure and velocity measurements. Similar properties are obtained for both vehicles, in particular the lowest pressure on the after-body is reported on the lower part of the base. Hot-wire anemometry is also used to depict the dynamics of the flow. The detached shear from the roof behaves as free shear turbulent flows whereas the flow from the underbody rather corresponds to homogeneous shear turbulent flows. In addition, global mode dynamics is reported in the wake of one vehicle and is associated with an antisymmetric coupling of the lateral mixing layers. However, the intensity of this mode is limited and it may not be a contributor to the drag since its maximum of amplitude is downstream the recirculation bubble. Eventually, these results are analyzed to orient future drag reduction control strategies.
- Published
- 2014
6. Characterisations of force and pressure fluctuations of real vehicles
- Author
-
Cadot, O., primary, Courbois, A., additional, Ricot, D., additional, Ruiz, T., additional, Harambat, F., additional, Herbert, V., additional, Vigneron, R., additional, and Délery, J., additional
- Published
- 2016
- Full Text
- View/download PDF
7. Aeroacoustic Analysis of the Automotive Ventilation Outlets Using Extended Proper Orthogonal Decomposition
- Author
-
Hekmati, A., Ricot, D., and Philippe DRUAULT
- Subjects
Physics ,Noise generation ,business.industry ,Acoustics ,Compressibility ,Automotive industry ,Proper orthogonal decomposition ,Aerodynamics ,Aerospace engineering ,3d simulation ,business ,Sound pressure ,Conservation of mass - Abstract
Extended Proper Orthogonal Decomposition based on snapshot POD is used to investigate the correlation between the aerodynamic quantities of interest in an automotive ventilation outlet and the associated sound pressure field. A 3D simulation of the flow and the associated sound field of a real engineering application is obtained thanks to a Direct Noise Calculation. The flow field on a 2D measurement plane is decomposed on three components using the POD decomposition : The large and small scale coherent structures and the background quasi-Gaussian fluctuations. Based on this POD flow partitioning, the far-field acoustic pressure is used to calculate the extended modes. We exhibit that each part of the far-field acoustic pressure spectrum can be related to each POD aerodynamic flow partitioning. I. Introduction Noise is a major concern in modern automotive industry due to the car manufacturers wish to reduce the noise level for passengers. The purpose of this study concerns the analysis of noise generation mechanisms occuring in automotive ventilation outlets. Historically, fifty years ago, Lighthill 1 reformulated the momentum and the mass conservation equations in the form of a wave equation. While this equation provides an analytical expression for the aerodynamic sound generation, the understanding of the underlying physics and the noise production mechanisms still needs further investigations. Experimental studies have been contributing to a better understanding of the governing mechanisms but they are usually hindered by the complexity of the acoustic sources, requiring the measurement of the fluctuating quantities in a highly resolved space-time extent. The recent progresses in the numerical simulations facilitate the access to the reliable data in those zones where the sound generation is concentrated. The flow simulation and its related acoustic field could be simultaneously performed thanks to the Direct Noise Calculation (DNC). The DNC of compressible flows provides a spatio-temporal database for a particular case. This database can be employed to check the theoretical models and to investigate the phenomena involved in the sound production. The
- Published
- 2009
- Full Text
- View/download PDF
8. Grid refinement for aeroacoustics in the lattice Boltzmann method: A directional splitting approach.
- Author
-
Gendre F, Ricot D, Fritz G, and Sagaut P
- Abstract
This study focuses on grid refinement techniques for the direct simulation of aeroacoustics, when using weakly compressible lattice Boltzmann models, such as the D3Q19 athermal velocity set. When it comes to direct noise computation, very small errors on the density or pressure field may have great negative consequences. Even strong acoustic density fluctuations have indeed a clearly lower amplitude than the hydrodynamic ones. This work deals with such very weak spurious fluctuations that emerge when a vortical structure crosses a refinement interface, which may contaminate the resulting aeroacoustic field. We show through an extensive literature review that, within the framework described above, this issue has never been addressed before. To tackle this problem, we develop an alternative algorithm and compare its behavior to a classical one, which fits our in-house vertex-centered data structure. Our main idea relies on a directional splitting of the continuous discrete velocity Boltzmann equation, followed by an integration over specific characteristics. This method can be seen as a specific coupling between finite difference and lattice Boltzmann, locally on the interface between the two grids. The method is assessed considering two cases: an acoustic pulse and a convected vortex. We show how very small errors on the density field arise and propagate throughout the domain when a vortical flow crosses the refinement interface. We also show that an increased free stream Mach number (but still within the weakly compressible regime) strongly deteriorates the situation, although the magnitude of the errors may remain negligible for purely aerodynamic studies. A drastically reduced level of error for the near-field spurious noise is obtained with our approach, especially for under-resolved simulations, a situation that is crucial for industrial applications. Thus, the vortex case is proved useful for aeroacoustic validations of any grid refinement algorithm.
- Published
- 2017
- Full Text
- View/download PDF
9. Measured wavenumber: frequency spectrum associated with acoustic and aerodynamic wall pressure fluctuations.
- Author
-
Arguillat B, Ricot D, Bailly C, and Robert G
- Subjects
- Equipment Design, Fourier Analysis, Noise, Pressure, Reproducibility of Results, Sound Spectrography, Time Factors, Transducers, Pressure, Vibration, Wind, Acoustics instrumentation, Models, Theoretical, Signal Processing, Computer-Assisted
- Abstract
Direct measurements of the wavenumber-frequency spectrum of wall pressure fluctuations beneath a turbulent plane channel flow have been performed in an anechoic wind tunnel. A rotative array has been designed that allows the measurement of a complete map, 63×63 measuring points, of cross-power spectral densities over a large area. An original post-processing has been developed to separate the acoustic and the aerodynamic exciting loadings by transforming space-frequency data into wavenumber-frequency spectra. The acoustic part has also been estimated from a simple Corcos-like model including the contribution of a diffuse sound field. The measured acoustic contribution to the surface pressure fluctuations is 5% of the measured aerodynamic surface pressure fluctuations for a velocity and boundary layer thickness relevant for automotive interior noise applications. This shows that for aerodynamically induced car interior noise, both contributions to the surface pressure fluctuations on car windows have to be taken into account.
- Published
- 2010
- Full Text
- View/download PDF
10. Aerodynamic excitation and sound production of blown-closed free reeds without acoustic coupling: the example of the accordion reed.
- Author
-
Ricot D, Caussé R, and Misdariis N
- Abstract
The accordion reed is an example of a blown-closed free reed. Unlike most oscillating valves in wind musical instruments, self-sustained oscillations occur without acoustic coupling. Flow visualizations and measurements in water show that the flow can be supposed incompressible and potential. A model is developed and the solution is calculated in the time domain. The excitation force is found to be associated with the inertial load of the unsteady flow through the reed gaps. Inertial effect leads to velocity fluctuations in the reed opening and then to an unsteady Bernoulli force. A pressure component generated by the local reciprocal air movement around the reed is added to the modeled aerodynamic excitation pressure. Since the model is two-dimensional, only qualitative comparisons with air flow measurements are possible. The agreement between the simulated pressure waveforms and measured pressure in the very near-field of the reed is reasonable. In addition, an aeroacoustic model using the permeable Ffowcs Williams-Hawkings integral method is presented. The integral expressions of the far-field acoustic pressure are also computed in the time domain. In agreement with experimental data, the sound is found to be dominated by the dipolar source associated by the strong momentum fluctuations of the flow through the reed gaps.
- Published
- 2005
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.