New challenges in shear-driven and buoyancy-driven turbulent flow
Following the last two SIG 35/Henri Bénard PC/ ERCOFTAC workshops in D’Alembert, on May 2014 and May 2015, a part of the meeting will illustrate progresses in modelling multipoint statistics, from weak to strong turbulence, in both shear-driven and buoyancy-driven flows. The most complex statistical theories and models are computationally demanding, so that their numerical resolution is a significant task, only permitted by recent computational ressources. Of course, quantitative validation with respect to DNS at their highest Reynolds numbers allows new development, and extrapolation by statistical models only, yield results for a huge range of Reynolds numbers, and an unprecedented parametric analysis.
Beyond that aspect, other themes will be addressed, with non-conventional cascades in non-homogeneous turbulence, unsteady non-Kolmogorov cascades, stochastic modelling, internal intermittency, applications of wave turbulence for magnetohydrodynamics, practical subgridscale models in LES, two-phase flows, namely. Finally, the rather recent success story in revisiting USHT (unstably stratified homogeneous turbulence) illustrates a system approach to turbulence, with a nonlinearly modified linear dominant operator and a feed-back from the fluctuating flow to the mean one (mediated by generalized Reynolds stresses, this effect is not present in strictly homogeneous turbulence). Interestingly, this approach may include a complex nonlinear model (e.g. generalized EDQNM for USHT) as well, so that very high Reynolds numbers can be accommodated, and the dynamical approach is far beyond conventional stability analysis. To which extent this can be applied to much more complex bounded flows, or geophysical flows, is an open challenge: dynamics and stability of a mean flow, which is not given a priori (such as the base flow in conventional hydrodynamic stability) is the first aspect, nonlinear interactions of the fluctuating flow with itself is the second one.
du mardi 3 mai 2016 au mercredi 4 mai 2016
Salle de conf., IJLRA, Jussieu
Stéphane Zaleski et Claude Cambon
IJLRA, Paris et LMFA, Lyon
14h00 Transition entre la turbulence faible et forte en MHD incompressible
14h30 Scalaire passif en turbulence anisotrope cisaillée
15h00 A statistical theory of mixing in stratified fluids
Lab. Phys, ENS Lyon
15h30 Croissance non-normale et turbulence dans les disques d’accrétion
16h30 Recent spring school New challenges in turbulence research IV and beyond
Fabien S. Godeferd
LMFA, EC Lyon
17h30 Discussion ouverte sur le GDR relancé en turbulence
18h30 Fin première journée
09h30 The most common turbulence cascades are not conventional
John Christos Vassilicos
Imperial college, London
10h00 Formation de gouttes en turbulence stratifiée
Univ. Sheffield, Sheffield
10h30 Quality assessment of LES for complex applications
Maria Vittoria Salvetti
Univ. de Pise, Pise
11h30 Intermittence lagrangienne et irréversibilité
Obs. de Paris, Meudon
12h00 Fractality and Schrödinger type equation in turbulence
Obs. de Paris, Meudon
12h30 Pause déjeuner
14h00 Agitation induite par des bulles oscillant dans un liquide proche de la courbe de saturation
14h30 Stability analysis of the mean field to determine coherent structures in a step turbulent flow
15h00 Round table: A nonlinear system approach to turbulence, far beyond conventional hydrodynamic stability ?
Benoît-Joseph Gréa, Fabien S. Godeferd, Denis Sipp et Claude Cambon .
16h00 Cascades en turbulence avec interfaces
16h30 Turbulence cascades II in Lyon. First proposal and discussion.
17h00 End of the meeting