Calcul des sources areoaccoustiques sur les parois par la méthode BOLTZMANN sur réseau (thèse: 2014 - 2017)
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2017
Félix Gendre, Denis Ricot, Guillaume Fritz, Pierre Sagaut. Grid refinement for aeroacoustics in the lattice Boltzmann method: A directional splitting approach. Physical Review E , 2017, 96 (2), pp.023311. ⟨10.1103/PhysRevE.96.023311⟩. ⟨hal-01596329⟩ Plus de détails...
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.
Félix Gendre, Denis Ricot, Guillaume Fritz, Pierre Sagaut. Grid refinement for aeroacoustics in the lattice Boltzmann method: A directional splitting approach. Physical Review E , 2017, 96 (2), pp.023311. ⟨10.1103/PhysRevE.96.023311⟩. ⟨hal-01596329⟩
Félix Gendre, Denis Ricot, Guillaume Fritz, Pierre Sagaut. Grid refinement for aeroacoustics in the lattice Boltzmann method: A directional splitting approach. Physical Review E , 2017, 96 (2), pp.023311. ⟨10.1103/PhysRevE.96.023311⟩. ⟨hal-04348563⟩ Plus de détails...
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.
Félix Gendre, Denis Ricot, Guillaume Fritz, Pierre Sagaut. Grid refinement for aeroacoustics in the lattice Boltzmann method: A directional splitting approach. Physical Review E , 2017, 96 (2), pp.023311. ⟨10.1103/PhysRevE.96.023311⟩. ⟨hal-04348563⟩
G. Félix, V. Falk, Umberto d'Ortona. Granular flows in a rotating drum : the scaling law between velocity and thickness of the flow. European Physical Journal E: Soft matter and biological physics, 2007, 22 (1), pp.25-31. ⟨10.1140/epje/e2007-00002-5⟩. ⟨hal-00275307⟩ Plus de détails...
The flow of dry granular material in a half-filled rotating drum is studied. The thickness of the flowing zone is measured for several rotation speeds, drum sizes and beads sizes (size ratio between drum and beads ranging from 47 to 7400). Varying the rotation speed, a scaling law linking mean velocity vs. thickness of the flow, v ∼hm, is deduced for each couple (beads, drum). The obtained exponent m is not always equal to 1, the value previously reported for a drum in litterature, but varies with the geometry of the system. For small size ratios, exponents higher than 1 are obtained due to a saturation of the flowing zone thickness. The exponent of the power law decreases with the size ratio, leading to exponents lower than 1 for high size ratios. These exponents imply that the velocity gradient of a dry granular flow in a rotating drum is not constant. More fundamentally, these results show that the flow of a granular material in a rotating drum is very sensible to the geometry, and that. the deduction of the "rheology" of a granular medium flowing in such a geometry is not obvious.
G. Félix, V. Falk, Umberto d'Ortona. Granular flows in a rotating drum : the scaling law between velocity and thickness of the flow. European Physical Journal E: Soft matter and biological physics, 2007, 22 (1), pp.25-31. ⟨10.1140/epje/e2007-00002-5⟩. ⟨hal-00275307⟩
Journal: European Physical Journal E: Soft matter and biological physics
Eric Serre, Sandrine Hugues, Emilia Crespo del Arco, Anthony Randriamampianina, Patrick Bontoux. Axisymmetric and three-dimensional instabilities in an Ekman boundary layer flow. International Journal of Heat and Fluid Flow, 2001, 22 (1), pp.82-93. ⟨hal-01023080⟩ Plus de détails...
Eric Serre, Sandrine Hugues, Emilia Crespo del Arco, Anthony Randriamampianina, Patrick Bontoux. Axisymmetric and three-dimensional instabilities in an Ekman boundary layer flow. International Journal of Heat and Fluid Flow, 2001, 22 (1), pp.82-93. ⟨hal-01023080⟩
Journal: International Journal of Heat and Fluid Flow
