Effect of biofouling roughness on the full-scale powering performance of a submarine

The aim of this study is to investigate the impact of barnacle type biofouling roughness on the full-scale powering performance of a submarine in calm seas. The importance of the diversified biofouling accumulations in terms of hull location is also examined over the submarine hull by implementing homogeneous and heterogenous roughness distribution. In this study, a Reynolds Averaged Navier Stokes (RANS) based CFD model was used for predicting the effects of biofouling roughness on the self-propulsion characteristics for the full-scale submarine form. The powering performance analyses are performed with discretised propeller geometry, and the Moving Reference Frame approach is used to model the rotational motion of the propeller. A proportional-integral (PI) approach is adopted to obtain the self-propulsion point efficiently by modifying the propeller's rotational speed. First, the resistance and the self-propulsion characteristics of the model scale submarine are validated with the experimental and other numerical studies in the literature. Following this validation task, a roughness function model is employed within a CFD software's wall function to represent the rough surfaces over the submarine hull. The results showed that although roughness has a varying effect on the submarine's self-propulsion characteristics depending on the roughness distribution, it increases the hull resistance and, hence, the delivered power overall. Roughness on the forward section of the hull has a more pronounced effect on the resistance and delivered power. The study demonstrated that the presence of partial hull fouling should not be ignored, and required precautions should be taken to prevent losses in submarine performance, especially for the fouling at the forward section of the submarine.