Drag reduction characteristics of an underwater vehicle with porous medium and ventilation seam

The drag of underwater vehicle is much higher than that of air vehicle in the process of movement, so drag reduction is the key to improve the speed. Ventilation around the vehicle can form a layer of gas film between the vehicle and the fluid, which will greatly reduce the frictional drag generated by the interaction between the vehicle and the fluid during the movement, so as to achieve the purpose of drag reduction. In this paper, the drag reduction effects of two different ventilation methods, porous media ventilation and ventilation seam ventilation, are discussed in depth, and water tunnel tests are carried out for different head types under different ventilation rates to explore drag reduction characteristics and gas film surface volatility. The experimental results show that the gas film drag reduction method has good drag reduction characteristics. The drag reduction rate can reach up to 40.4% by using porous media ventilation. The flow field disturbance is small, but it is sensitive to the ventilation volume, and there is a ventilation volume for each working condition to achieve the best drag reduction effect. The drag reduction rate can reach up to 54.7% by using the ventilation seam, but the gas film state formed by different head shapes is different. The anti-cavitation head shape is beneficial to drag reduction, while the cavitation head shape is not conducive to drag reduction, and the gas film oscillation is more severe than that of porous media by using the ventilation seam.