Laboratory, numerical and theoretical modeling of a far wake flow in a stratified fluid

Abstract

A laboratory study and direct numerical simulation (DNS) of far wake flow in a stratified fluid are performed. The laboratory study employs the PIV technique to measure the velocity field in a wake behind a towed sphere at high Reynolds and Froude numbers. The DNS parameters and initialization are prescribed in accordance with the experimental data, which allows a direct comparison between numerical and experimental results. The results of the DNS and the laboratory experiment are compared with predictions of a theoretical model, which considers the wake as a quasi-two dimensional turbulent jet flow with the main mechanism of evolution associated with transfer of momentum from the mean flow to quasi-two dimensional sinuous disturbances growing due to hydrodynamic instability. The time evolution of the wake axis velocity and its width obtained within the framework of the model is in good agreement with the experimental and numerical data.