Numerical study of biofouling effects on the flow dynamic characteristics of blade sections

Generally blade surfaces are of polished metal and have no antifouling provision, which makes them susceptible to biofouling, yet its effects on the hydrodynamic performance of blade sections are rarely studied. The present work aims at quantifying the effects and providing a deep insight into the physical mechanism by means of Computational Fluid Dynamics (CFD). The simulation employs the SST k-omega turbulence model and is carried out on NACA 4424 airfoils. Being selected as the study subject from fouling community, barnacles are directly modeled at geometry level instead of the well-known wall function methods. The results show that flow separation occurs earlier and the separation region becomes larger around airfoils with increase of the fouling height. Fouling on airfoils leads to a significant reduction of lift-drag ratio (C-L/C-D) and hence would result in a remarkable decrease of propulsive efficiency of propellers. Once the height of fouling exceeds a certain limit, however, the increase of the height will have little effect on C-L/C-D.