Numerical investigation on influence of boundary-layer transition on resistance performance in underwater axisymmetric bodies

During underwater vehicle navigation, laminar-to-turbulent transition in the hull boundary layer significantly influences resistance performance. In order to study the effect of transition on the drag performance of underwater vehicles, the present study combines Reynolds-averaged Navier–Stokes simulations, water tunnel experiments, and theoretical analysis to investigate boundary-layer transition effects on axisymmetric bodies. Results demonstrate that the transition kT-kL-ω model provides an appropriate framework for predicting transition behaviors of underwater vehicles. Notably, numerical prediction results exhibit strong agreement with those of both experimental measurements and linear stability theory. Quantitative analyses reveal that at body-length Reynolds number (ReL) of 1.3 × 107, the total resistance predicted by the transition model is 17.8% lower than that of the turbulence model, primarily through frictional resistance reduction while minimally affecting pressure resistance. Crucially, transition reverses the advantages and disadvantages of the drag performance between different bow shapes compared to the fully turbulent boundary layer. These findings demonstrate that overlooking transition effects in computational fluid dynamics simulations compromises the accuracy of hydrodynamic predictions for low-resistance vehicle designs.