Optimization problems at the water surface: From boat hulls to oar propulsion.

Summary Several optimization problems - in water or at the interface with air - are addressed, ranging from the optimization of the shape of boat hulls to that of propulsion in rowing and fin swimming. Theoretical, experimental and numerical approaches are combined. We first develop a minimal theoretical approach to determine, for a given immersed volume and power, the optimal aspect ratios of boat hulls, which are discussed and compared to the aspect ratios of real boats. The effect of fore-and-aft hull asymmetry is then discussed. In a second part, we study propulsion in rowing and finning. In the case of rowing, we revisit the issue of the synchronization of the rowers on the boat using a model of a robotic boat and investigate which synchronization allows the crew to go the fastest. Finally, we analyze the effect of fin geometry to find the optimal swimming strategies.