Numerical Analysis of Drag Characteristics of 209 Submarine with Various Roughness Distribution

Submarines and other underwater vessels are widely employed in the naval sector for defense purposes as well as in the civilian realm for scientific and recreational purposes. However, challenges such as biofouling caused by bacteria and algae can significantly impact performance and environmental effects. This study investigated the impact of biofouling on the U209 submarine by analysing how the location of roughness affects drag, with particular emphasis on frictional drag. Computational Fluid Dynamics (CFD) was employed to assess the impact of biofouling on the turbulent flow characteristics of ship hull surfaces with varying roughness, operating within the range of velocity = 9.7 knot – 29.1 knot. The submarine analysis was conducted under complete submersion without any water disturbance. The increase in drag resulted from the variation in the surface of the submarine hull. The drag increased from 8.5% to 18.2% for partial hull roughness and from 30.5% to 46.9% for overall roughness. The entire surface irregularity of the hull led to a significant increase in the drag. This can be explained by the results that as the surface area affected by biofouling increases, the amount of turbulent flow around the hull also increases, resulting in greater resistance, particularly in terms of frictional drag.