Effect of slenderness ratio and aft fins on the hydrodynamic forces for an underwater body in oblique flows

This paper presents the hydrodynamic effects due to slenderness ratio and aft fins for an underwater axisymmetric body at incidence. The body is torpedo shaped with elliptical nose, tapered tail and cylindrical middle body. The slenderness ratio is varied from 10.8 to 14.4 and flow inclination varied from 0 degrees to 18 degrees. The estimation is done by experimental and numerical means. The axial force, normal force and pitch moment acting on the model was measured during the experiments. Numerical study based on Reynolds Averaged Navier Stokes was carried out using commercial Computational Fluid Dynamics (CFD) code. Sources of experimental and numerical uncertainties were identified and quantified. Pressure measurements and flow visualization were done and compared with CFD flow field predictions. An empirical formulation for estimation of normal force and pitch moment for an axisymmetric body at incidence is suggested based on experimental results.