An experimental study of unsteady hydrodynamics of a single scull

Abstract: The effect of hull dynamics on the hydrodynamic performance of a single scull is investigated via a combination of field trials and tank tests. The location of laminar-turbulent transition in unsteady flow is explored via several series of hot-film measurements on the bow of a full-scale single scull in unsteady flow in both towing tank and field-trial conditions. Results demonstrate that the measured real-world viscous-flow behaviour can be successfully reproduced in the tank using an oscillating sub-carriage to reproduce the surging motion mea-sured in the field trials. It can be seen that there is a strong link between turbulence and accel-eration; results show that the link is relatively insensitive to mean velocity, but that small changes in acceleration time-histories can have a marked effect, as can the presence of small waves. The impact of the location of laminar turbulent transition is investigated by way of a series of resistance tests, both with free transition and with transition forced by turbulence stimula-tion at two different locations. Results indicate that an aft movement of 200mm of the loca-tion of transition can reduce resistance by almost 0.5 per cent. Unsteady tests using the oscillating sub-carriage indicate that unsteady effects add around 3per cent to the total mean resistance with free transition