Visualization of stratified flows aro und a vertical plate: laboratory experiment and numerical simulation

Abstract

On the basis of the fundamental system, which includes equations of continuity, momentum, and substance transfer with a linearized equation of state, methods of experimental and numerical study are developed for visualizing the flow perturbation fields generated by uniform horizontal movement of a vertical plate in a stratified medium. The stratified flows were visualized in the laboratory tank by the high-sensitive and high-resolution Schlieren instrument Iab-458 at the stand ‘laboratory Mobile Tank’ of the unique research facility ‘hPC IPMech raS’ and numerically calculated within the frame of the open source CfD utility OpenfOaM using computing resources of cluster systems and supercomputers. both the computation results and the laboratory visualization data show that a vertical plate uniformly moving in a stratified fluid generates flow patterns which contain complex systems of internal waves, including upstream, attached and short ones, and thin interfaces, such as ligaments, formed due to the combined influence of the stratification and dissipation effects. Increase in the velocity of the plate movement leads to an essential restructuring of the wake flow past the plate, where typical vortex elements, such as vortex dipoles and ‘vortex bubbles’, are formed in the divergence zones of the phase surfaces of internal waves. all the flow structural components evolve and actively interact with each other and with the free stream. The observation and calculation results are in a good qualitative and quantitative agreement with each other.