This book gathers papers presented at an international conference which emphasized the fruitiful interactions amongst research workers interested in various aspects of variable density fluid turbulence. Indeed, in addition to geophysics and astrophysics situations, as far as industrial applications are concerned, the variation of fluid density in a turbulent motion can originate from various and sometimes interacting sources, including high Mach number flows and low speed mixing as well, with strong heat release, variable composition mixing, chemical reactions... Papers are arranged on the basis of the following four topics : – Non reacting jet flows ; – Theoretical aspect ; – Unsteady and reacting flows ; – Turbulence modelling and direct numerical simulations.