Conference on Turbulence and Interactions TI2006, May 29 - June 2, 2006, Porquerolles, France Interaction between a deformable buoyant bubble and a homogeneous isotropic turbulence A. Toutant , E. Labourasse , O. Lebaigue , O. Simonin LMDL, CEA-Grenoble, Grenoble, France IMFT, UMR 5502 CNRS/INPT/UPS, Toulouse, France Email: adrien.toutant@cea.fr ABSTRACT This communication reports on results of a 3D Direct Numerical Simulation (DNS) of a strongly deformable bubble in isotropic turbulent flows. The complex interaction between interface and turbulence is fully resolved. This two-way coupling phenomenon is found to be of great importance for the flow dynamic. An explicit filtering of the simulation has been employed to evaluate the order of magnitude of the specific subgrid contributions in the Large Eddy Simulation (LES) modelling case. Closure models are proposed. I NTRODUCTION Two-phase flows abound in nature and in engi- neering applications. In most cases, both phases are turbulent (with high Reynolds numbers) and complex turbulence/interface interaction takes place. Consequently, DNS calculations have to entail a number of degrees of freedom propor- tional to the third power of the Reynolds number to correctly describe the flow behaviour. This extremely hard constraint makes it impossible to use DNS for industrial applications. In order to successfully carry out industrial simulations their numerical cost has to be reduced. In one- phase flow, LES allows a drastic reduction of the number of nodes in the space discretization. Until now, most numerical calculations for multi- phase turbulent flows use RANS (Reynolds Aver- aged Navier-Stokes) or LES modelling in order to add a diffusion-like term. However, very few the- oretical or experimental justifications have been proposed. Because local experimental measure- ments of complex turbulence interface interac- tion are very difficult, the only tool that is able to provide information seems to be numerical ex- periments. In the context of DNS of two-phase flow, most of the literature is dedicated to two types of studies: On the one hand, calculations focus on de- formable interfaces but no really on developed turbulence. For instance, Bunner and Tryggva- son (2003) study the effect of bubble deforma- tion on the properties of bubbly flows [1]. In their simulations, vortical structures are only produced by the wake of bubbles. The so- called pseudo-turbulence induced by a bubble swarm does not have the same properties than a really developed turbulence whose the en- ergy spectrum has an inertial zone. On the other hand, the turbulence is fully de- veloped but the interfaces are not physically deformed. So, complex interactions between fluid velocity fluctuations and interface defor- mations can not exist. In a large amount of works in this category, the size of the parti- cles is smaller than the Kolmogorov length scale and, even when the particle’s diame-