Quantifying Mixing in Penetrative Convection Experiments

Penetrative convection in a stably stratified fluid has been reproduced in laboratory by employing a tank filled with water and subjected to heating from below. The goal of the experiments is predicting the mixing layer growth as a function of initial and boundary conditions and describing the fate of a tracer dissolved in the fluid phase. The equipment employed is suitable for simultaneously providing temperatures inside the domain through thermocouples and Lagrangian particle trajectories by feature tracking. The field of view is illuminated through a thin light sheet with suitable optical equipment. To fully characterize the transport feature of the phenomenon under investigation, the mixing layer growth is detected employing both temperature data and statistics of the velocity field, i.e., the vertical velocity component standard deviation. The velocity spatial correlation allows the plume horizontal dimension to be determined. This information coupled with the knowledge of the mixing layer height allows the spatial extension of the convective region to be fully described.