Investigation on hydrodynamic effects of using a supercavitating section in surface piercing hydrofoils

The purpose of this paper was to numerically investigate the effects of using supercavitation sections in ventilated semi-submerged hydrofoils.Studying the flow around such hydrofoils is often very complicated due to its multiphase nature and the simultaneous occurrence of cavitation and ventilation phenomena.The desired foil was the Waid section foil which has been examined at different attack angles and for different cavitation numbers.In this numerical simulation, the RANSE finite volume solver along with the VOF method have been used to model the multiphase flow around the semisubmerged hydrofoil.According to the obtained results, the formation of cavitation bubbles and the formation of ventilation around a supercavitating section is different from the conventional sections in semi-immersed foils.This could be due to the specific geometric shape of the supercavitating sections, especially in their front area.The pressure and flow contours around the hydrofoil have been predicted in semi-submerged form, and the ventilating air flow around the hydrofoil has also been investigated.Also, it has shown that the effect of cavitation at high speeds causes the formation of continuous bubbles, which will lead to the reduction of drag coefficients and increase the efficiency of supercavitating hydrofoils.According to the results obtained in this simulation, by increasing the cavitation number, the drag coefficient also increases in proportion to the lift coefficient.This process continues until the foil enter the completely wet phase, which with this phase change, the lift-todrag coefficient ratio also decreases.Therefore, due to its high efficiency, the Waid section, is recommended for the design of surface piercing hydrofoils.