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Time filter

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Marseille, France

The basis of the partially integrated transport modeling (PITM) method was introduced by Schiestel and Dejoan ["Towards a new partially integrated transport model for coarse grid and unsteady turbulent flow simulations," Theor. Comput. Fluid Dyn.18, 443 (2005)]10.1007/s00162-004-0155-z and Chaouat and Schiestel ["A new partially integrated transport model for subgrid-scale stresses and dissipation rate for turbulent developing flows," Phys. Fluids17, 065106 (2005)]10.1063/1.1928607. This method provides a continuous approach for hybrid RANS-LES (Reynolds averaged Navier-Stokes equations-large eddy simulations) simulations with seamless coupling between RANS and LES regions. The main ingredient of the method is the new dissipation-rate equation that can be applied as a subfilter scale turbulence model. Then, it becomes easy to convert almost any usual RANS transport model into a subfilter scale model. In particular, the method can be applied to two equation models and to stress transport models as well. In the derivation of the method, the partial integration technique allows to keep a link between the spectral space and the physical space of the resulting model. The physical turbulent processes involving the production, dissipation, and flux transfer of the turbulent energy are introduced in the equations. The present work, after recalling the main building steps of the PITM method, brings further insight into the physical interpretation of the method, its underlying hypotheses and its internal acting mechanisms. In particular, the finiteness of the coefficients used in the dissipation-rate equation is discussed in detail from a theoretical point of view. Then, we consider the analytical example of self-similar turbulent flow for analyzing the dissipation-rate equation. From an analytical solution obtained by Taylor series expansions taking into account the Kovasznay hypothesis for evaluating the transfer term, we compute the functional coefficients and used in RANS and LES methodologies, respectively, and we demonstrate that both coefficients take on finite values when the Reynolds number goes to infinity. Finally, after briefly mentioning some flow illustrations to get a real appraisal of the PITM method in its capabilities to simulate unsteady flows on relatively coarse grids with a sufficient accuracy for engineering computations, we study the coefficient through one chosen example. © 2012 American Institute of Physics.


Carballido-Landeira J.,Free University of Colombia | Trevelyan P.M.J.,University of Santiago de Compostela | Almarcha C.,University of South Wales | De Wit A.,IRPHE
Physics of Fluids | Year: 2013

In a gravitational field, a horizontal interface between two miscible fluids can be buoyantly unstable because of double diffusive effects or because of a Rayleigh-Taylor instability arising when a denser fluid lies on top of a less dense one. We show here both experimentally and theoretically that, besides such classical buoyancy-driven instabilities, a new mixed mode dynamics exists when these two instabilities act cooperatively. This is the case when the upper denser solution contains a solute A, which diffuses sufficiently faster than a solute B initially in the lower layer to yield non-monotonic density profiles after contact of the two solutions. We derive parameter plane, where R is the buoyancy ratio between the two solutions and δ is the ratio of diffusion coefficient of the solutes. We find an excellent agreement of these theoretical predictions with experiments performed in Hele-Shaw cells and with numerical simulations. © 2013 American Institute of Physics.


Chaouat B.,ONERA | Schiestel R.,IRPHE
Physics of Fluids | Year: 2013

The basis of the partially integrated transport modeling method was introduced in papers of Schiestel and Dejoan ["Towards a new partially integrated transport model for coarse grid and unsteady turbulent flow simulations," Theor. Comput. Fluid Dyn.18, 443 (2005)] and Chaouat and Schiestel ["A new partially integrated transport model for subgrid-scale stresses and dissipation rate for turbulent developing flows," Phys. Fluids17, 065106 (2005)]. This method provides a continuous approach for hybrid Reynolds averaged Navier-Stokes (RANS)-large eddy simulation (LES) simulations with seamless coupling between RANS and LES regions. The method, like in usual LES techniques, makes use of space filtering in the turbulent field. In the foundation papers cited above and in the main applications considered so far, the filter width has been supposed constant or at least slowly varying. In the present paper, we examine the effect of variable filter width in the model equations and how to account for this effect in practical numerical simulations. With the aim to illustrate the theoretical development of the effect of varying filter width in time and space on the governing equations of mass, momentum, and turbulence model, and to show the usefulness of the proposed approach, we perform then numerical simulations of isotropic decaying turbulence. © 2013 AIP Publishing LLC.


Ruban V.,Moscow State Textile University | Kodama Y.,Ohio State University | Ruderman M.,University of Sheffield | Dudley J.,University of Franche Comte | And 15 more authors.
European Physical Journal: Special Topics | Year: 2010

This paper contains the discussion inputs by the contributors of the special issue on the subject of rogue waves. © 2010 EDP Sciences and Springer.


Kharif C.,IRPHE | Touboul J.,University of Toulon
European Physical Journal: Special Topics | Year: 2010

Within the framework of the fully nonlinear water waves equations, we consider a Stokes wavetrain modulated by the Benjamin-Feir instability in the presence of both viscous dissipation and forcing due to wind. The wind model corresponds to the Miles' theory. By introducing wind effect on the waves, the present paper extends the previous works of [6] and [7] who neglected wind input. It is also a continuation of the study developed by [9] who considered a similar problem within the framework of the NLS equation. The marginal stability curve derived from the fully nonlinear numerical simulations coincides with the curve obtained by [9] from a linear stability analysis. Furthermore, it is found that wind input goes in the subharmonic mode of the modulation whereas dissipation damps the fundamental mode of the initial Stokes wavetrain. © 2010 EDP Sciences and Springer.

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