An investigation into the effect of ventilation, bulbs and flow turbulence on lifting T foil performance

Duncan, Iain and Goodman, Thomas and Cocard, Margot and Day, Sandy and Dai, David (2023) An investigation into the effect of ventilation, bulbs and flow turbulence on lifting T foil performance. In: the 6th international conference on Innovation in High Performance Sailing yachts and Wind-Assisted Ships, 2023-05-29 - 2023-05-31, Lorient France.

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Flapped lifting T foils are a key part of modern high-performance craft due to their ability to reduce wetted surface area and hence drag at high speed. The performance of these foils is significantly affected when ventilated. Ventilation on a T-foil normally leads to a dramatic and uncontrolled loss of lift and overall vessel drag increment due to the hull coming into contact with the water surface. Limited research of ventilated T foils has been published due to challenges associated with reproducing ventilations in a relatively low-speed tow tank environment. The current study looks into the performance of a Waszp rudder fitted with modifications. The position of the horizontal foil relative to the vertical strut was varied as was the flow turbulence around the vertical strut using a turbulence stimulating wire. Towing test of the modified Waszp rudder was carried out at the Kelvin Hydrodynamics Laboratory of University of Strathclyde. Results were compared against the original Waszp T-foil. Experimental testing results shows how the foil can be modified to the T foil performance. It also shows changes in the characteristics in the ventilated cavity when the foil is operating in fully ventilated flow. A new method capable of stimulating foil ventilation repeatably was developed utilizing turbulence wire which can potentially enable more T-foil ventilation-related experimental studies in the future.