Advances In Compressible Turbulent Mixing

In this volume, compressible turbulent mixing is discussed from the viewpoints of experiment, numerical simulation and theoretical models. The major problem areas include Rayleigh-Taylor and Richtmyer-Meshkov instabilities, and multiphase mixing problems. A variety of initial configurations are discussed, including single and multiple mode perturbations and nonlinear geometries in both two and three dimensions. The effects of experimental and numerical artifacts are also considered.

Turbulent mixing plays a preponderant role in the evolution of stars. In particular, they are necessary to explain the abundance of some elements or to account for the dissipation of angular momentum observed in some stars. These turbulent mixing are generated and maintained by various mechanisms: from rotation to magnetic instabilities and shearing. Among these different processes, Rayleigh-Taylor convective instabilities have already been the subject of numerous theoretical, experimental and numerical studies. However, most of these studies are restricted to situations where radiation is absent. On the contrary, in stars, the consideration of radiation is essential: the latter is generally more effective in transporting temperature fluctuations than the turbulent motions themselves. The comparison of these two modes of transport is done using a dimensionless number called Péclet number. The turbulent stellar mixing impacted by the Rayleigh-Taylor instability is then characterized by a small number of Péclet below one. The aim of this work is to study turbulent mixing flows generated by Rayleigh-Taylor instabilities in the presence of radiation, within the limits of low Péclet numbers. In particular, the major outcome deals with the derivation and the validation of a RSM (Reynolds stress model) type of turbulence model accounting for mixing effects and adapted to radiative compressible flows within the small Péclet limit.

Advances in Turbulence VI presents an update on the state of turbulence research with some bias towards research in Europe, since it represents an almost complete collection of the paper presentations at the Sixth European Turbulence Conference, sponsored by EUROMECH, ERCOFTAC and COST, and held at the Swiss Federal Institute of Technology in Lausanne, July 2-5, 1996. The problem of transition, together with the structural description of turbulence, and the scaling laws of fully developed turbulence have continued to receive most attention by the research community and much progress has been made since the last European Turbulence Conference in 1994. The volume is thus geared towards specialists in the area of flow turbulence who could not attend the conference, as well as anybody who wishes quickly to assess the most active current research areas and the groups associated with them.

This book highlights recent research advances in the area of turbulent flows from both industry and academia for applications in the area of Aerospace and Mechanical engineering. Contributions include modeling, simulations and experiments meant for researchers, professionals and students in the area.