Experimental Investigation of Paint Roughness on the Resistance of a Flat Plate

In this work, an experimental investigation of the hydrodynamic resistance of a flat plate painted with newly developed marine antifouling paints of polyurethane (PU) and silicone (Si) formulations was performed. In total, six different paint systems of Si, PU, and acrylic formulations were applied, both experimental and commercial. The total resistance of each painted condition of the plate was measured through towing tank tests for the range of 0.75–2.5m/sec, with a step of 0.25m/sec. The Si and PU formulations exhibited similar hydrodynamic behavior, fluctuating around the smooth condition, whereas the acrylic system exhibited the highest resistance increase of all. The roughness function calculation was based on Ra and the correlation with the Colebrook roughness function was generally limited for most systems. Extrapolation to ship scale revealed that no significant drag differences are expected in the as-painted condition among the different paint system types.