An experimental study into the effect of transitional flow on the performance of underwater glider wings

The experimental procedures developed to measure small forces generated by underwater vehicle appendages in a wind tunnel are described. These involve using precision load cell sensors arranged into a bespoke dynamometer, that has been integrated into a stand-alone wind tunnel rig. The set up is used to quantify performance of a scaled underwater glider hydrofoil, with particular care being paid to the effects of laminar and transitional flow features. Present data are benchmarked against similar measurements and simulations and it is shown that satisfactory results may be obtained with the current approach despite its simplicity and low cost. The apparatus is then used to show that the presence of laminar flow significantly affects performance of the considered foil at Reynolds numbers corresponding to a typical regime in which underwater gliders operate.