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


Tuesday 03/05

Wednesday 04/05