Vortical and turbulent structures for KVLCC2 at drift angle 0, 12, and 30 degrees

Abstract

Detached Eddy Simulation on a 13M grid is conducted for a KVLCC2 tanker hull form at drift angle 30°. The objective is to identify and analyze the vortical structures, instabilities, and turbulent structures with analogy to the vortex breakdown and helical instability analysis for delta wing at large angles of attack. One shear layer, one Karman-like vortex shedding, and three helical mode instabilities are identified. The after-body side vortex, fore-body side vortex, and after-body bilge vortex exhibit all characteristics for vortex breakdown. For helical instability in the wake of the vortex breakdowns, Strouhal number using the ship length or the distance along vortex core shows the same trend with delta wings. The turbulent kinetic energy peaks near the separation point at the bow and on the vortex core of all vortices. For the after-body side vortex, turbulent kinetic energy reaches local maximum right after the vortex breakdown and is intensified along the vortex core further downstream. The simulations at drift angle 0° show four unsteady aft-body vortices, significantly improve the prediction of integral variables and local flows. In addition to the three steady vortices identified before, the simulations at drift angle 12° show unsteady aft-body hairpin and after-body side vortices.