Numerical and theoretical analysis of the influences of surface treatment on drag reduction in submarine

In this study, we investigated the impacts of different riblet types of submarine surfaces on the drag force, which is directly related to the operating efficiency of submarine. We examined four cases of submarine surface: smooth surface as the reference case and three cases of sawtooth riblet with the same ratio between the height and spacing (h/s = 0.5) under different angles between the riblet edge and flow direction (α=300,450, and 600). We employed the Reynolds-averaged Navier-Stokes equation coupled k−ω SST turbulence model for solving incompressible flow passing through a submarine. Moreover, we proposed theoretical equations for predicting the total drag of submarine under different riblet types on submarine surface. The results revealed that riblet surfaces induced pressure drag while reducing friction drag on the submarine surface. This led to a significant effect on total drag compared to the reference case. Among riblet cases, the case of α=600 shows the best performance. In addition, theoretical predictions showed a good agreement with simulation results (maximum difference of 6.7%). This study provides extensive information about riblet design for drag reduction in underwater objects, especially submarines.