Modelling a Moving Propeller System in a Stratified Fluid Using OpenFOAM

Moving propeller systems can introduce significant disturbances in stratified environments by mixing the surrounding fluid. Restorative buoyancy forces subsequently act on this region/patch of mixed fluid, causing it to eventually collapse vertically and spread laterally in order to recover the original stratification. This work describes the use of an OpenFOAM solver, modified using existing functionality, to simulate a moving propeller system in a stratified environment. Its application considers a rotating KCD-32 propeller in a laboratory-scale wave tank which mimics published experiments on mixed patch collapse. The numerically-predicted collapse behaviour is compared with empirical data and scaling laws. The results agree closely, both qualitatively and quantitatively, thereby representing a successful step towards the validation of the numerical model.