Experimental and numerical study of the hydrodynamic forces acting on a surface-piercing hydrofoil in muddy environments

This work presents the experimental and numerical results of towing experiments with a 0.16 m chord surfacepiercing hydrofoil in muddy environments. Various test conditions were examined to understand the fluid flow behaviour and forces on the hydrofoil. The experiments were conducted in a flume tank where the hydrofoil was towed at a steady velocity at different drift angles and Under Keel Clearances (UKCs) with respect to the mud layer. A 6DoF load cell measured the hydrodynamic forces and moments acting on the hydrofoil. Pressure sensors placed at mid -span recorded the pressure variations on the surface of the object while moving. The presence of the natural mud significantly affected the measured forces for the cases of negative UKCs. The viscoplastic properties of the natural mud display an additional force when the hydrofoil is fully or partially submerged in the mud layer. The experimental measurements were compared for different conditions with CFD simulations. The numerical results presented in this work demonstrated a fair prediction of the forces and pressure variations along the surface of the body for the whole velocity range in single and two interface conditions.