Effect of Hull–Form Variation on the Stratified Near Wake of a Self–Propelled Body

Abstract

This study investigates the influence of hull–form variation on a self–propelled body in a linearly–stratified environment typical of the ocean. The Reynolds number is $Re_{L}=3.1\times 10^{8}$ , based on the freestream velocity and body length. The unsteady Reynolds–Averaged Navier Stokes equations are solved numerically, incorporating an Actuator–Line–modeled propeller. Previously, the authors have shown good comparison to experiment with this approach. The axisymmetric Iowa Body cross–sectional aspect ratio is varied to produce five parametrically–defined hull forms. Flow visualization shows the influence of hull–form geometry on propeller–driven vortex structures. Steady, cross–plane wake profiles emerge by half of a body length downstream. The distribution of momentum and vorticity at this location is uniquely–modified by variations in the upstream geometry. Although propeller swirl is the most significant generator of potential energy, hull effects also alter the thermal–saline distribution, further increasing the total potential energy. Integrated terms from the Vorticity Transport Equation suggest that buoyancy may function as an important driver of vorticity in the far wake.