TURBULENT MECHANISMS IN STRATIFIED FLUIDS

Probability distribution of basic instabilities appearing in stratifie d flows and point density fluctuations have been studied. Various para meters of the mixing process have been changed in the experiments, to investigate mixing. Detailed flow visualization as well as density mea surements have been used in zero-mean-flow laboratory experiments invo lving grid-stirred turbulent mixing across a density interface and bub ble-induced mixing. The overall mixing efficiency of the processes dep ends on the local Richardson number as well as on the local vorticity. Parameter distributions of low and high mixedness corresponding to di fferent instabilities are presented, showing that dipolar vortices pen etrating the interface are the most efficient mixing instabilities.