A computational study on the influences of wavy wall mimicking bio-fouling on friction resistance of ships

As biofouling on ship hulls can reach several millimeters in thickness, accurately predicting frictional resistance requires consideration of roughness effects beyond the scope of traditional empirical formulas developed for microscale surfaces. To address this, the complex and irregular surface geometry of biofouling was simplified by decomposing it into a series of single-wave models. Large Eddy Simulations (LES) were conducted to simulate turbulent channel flow over wavy walls, generating a comprehensive dataset of frictional resistance components. The frictional force acting on the wavy surface was defined as the effective shear stress, accounting for both viscous shear and pressure-induced forces. The distribution of friction velocity exhibited a strong correlation with the pressure component acting on the surface. The friction coefficient was found to be highest in regions characterized by large wave amplitudes and short wavelengths.