URANS and DES analysis for a Wigley hull at extreme drift angles

Vortical structures and associated instabilities for flows around the Wigley hull for a wide range of drift angles (10A degrees A a parts per thousand currency signA alpha a parts per thousand currency sign 60A degrees) with free surface are identified and analyzed. Quantitative verification and validation are conducted on three systematically refined grids with comparison to the experimental data for alpha = 10A degrees. Analysis of the flow pattern shows a strong correlation between the vortical structures and free-surface wave elevation. For alpha = 10A degrees and 30A degrees, the flows remain steady and vortices are generated at the keel and fore and aft perpendiculars of the hull. The strength and complexity of these vortices increase with increasing alpha. At alpha = 45A degrees, flow becomes unsteady without any significant change in the main flow pattern. At alpha = 60A degrees, a complex and unsteady flow field on the leeward side of the hull is formed with a large recirculation region from the aft to the fore end, which prevents the flow coming from below the keel from moving up and generating the keel vortices observed at lower drift angles. Karman-like and helical instabilities are analyzed. The effect of Froude number is more apparent for large than for small drift angles.