Hydrodynamicists use classical force estimation methods for the design of underwater vehicles when captive model experiments and CFD based simulations are uneconomical. They are also used during real time manoeuvring simulations of submarines for which experiments and CFD simulations are impractical. Present methods poorly estimate the contribution of the hull to the forces and moments about the centre of buoyancy, especially at moderate to high incidence angles. This is largely due to their inability to adequately model flow separation and leeside body vortices. This thesis presents a new viscous impulse method for estimating the normal force distributions along axisymmetric bodies with tapered tails.

The foundation for the formulation is a database consisting of both experimental and CFD data. A comprehensive computational study was performed on two generic axisymmetric streamlined hullforms in translation at angles of incidence up to 30°. The computations were based on the Reynolds Averaged Navier Stokes equations applied using hybrid adaptive meshes to ensure proper discretisation through the separation shear layer and afterbody wake. The two equation Shear Stress Transport (SST) and the Baseline Reynolds Stress (BSL-RSM) turbulence models were tested and evaluated. The BSL-RSM model was superior to the SST model when compared to experimental data, consistently predicting earlier separation and increased normal force predictions at a given incidence. Predictions of overall hydrodynamic forces and moments show good agreement with experimental data, being within experimental uncertainty for up to 25° incidence using the BSL-RSM. The development of the after body vortex and normal force distributions also show close agreement with experimental data. Afterbody vortex characteristics are analyzed at a level of detail not previously available from experiment.

Using slender body theory, a method is presented for determining the normal force distribution based on the longitudinal distribution of the axial vorticity component. Force and moment predictions based on this method compare well to those determined by integrating surface pressure and skin fiction. Using the enhanced database, scaling laws are developed for predicting the longitudinal distribution of hydrodynamic impulse for geometrically different axisymmetric streamlined bodies with length to maximum diameter ratios ranging from 6 to 9. These scaling laws are validated using CFD predictions at incidence angles up to 30 degrees and Reynolds numbers up to 230×10⁶. The comparison shows that this new estimation method accurately predicts the viscous contribution to the hydrodynamic impulse along the body, leading directly to reliable predictions of normal force and pitching moment.