Study On Underwater Drag Reduction Of Amphibious Vehicles

As a kind of amphibious vehicle,the amphibious vehicle can not only travel on land,but also float on the water.But under normal circumstances,the amphibious vehicle does not have the ability to move underwater,which limits its role in ocean exploration.For the amphibious vehicle with the ability to move underwater,the existence of the on-land walking device increases its resistance to move in the water and affects its sailing speed and mileage.Based on this,this article takes a water-entry amphibious vehicle as the research object,and studies the impact of different drag reduction methods on the underwater resistance of the amphibious vehicle through numerical simulation.Firstly,several typical underwater drag reduction technologies are introduced,with emphasis on bionic non-smooth surface drag reduction technologies.According to the ratio of 1:1,the simulation model of amphibious vehicle was established by 3D drawing software.In order to improve the simulation efficiency,the amphibious vehicle was properly simplified in the modeling process.And using the numerical simulation software,the model of the amphibious vehicle is simulated under the constant speed of direct navigation.Secondly,based on the analysis of the velocity field,pressure field and turbulence field obtained from the simulation,the optimization measures of adding the track guard plate are proposed in view of the high turbulence intensity inside the track and at the bottom of the vehicle,in view of the large pressure difference between front and rear when the tail flow separation occurs,an optimization measure of adding a tail fin is proposed.And the corresponding numerical simulation results show that the optimal drag reduction effect can be obtained by adding the optimization measures of the track guard plate and the tail fin.Then,in order to ensure the smooth progress of the research on drag reduction of nonsmooth surface,the amphibious vehicle was scaled in a ratio of 8:1,and the characteristic size of the non-smooth surface structure was determined according to the motion speed of the amphibious vehicle,and the groove structure with different characteristic size was added to the fixed area below the tail wing.Through simulation,the drag reduction effect of the continuous V-groove structure under different incoming flow speeds and characteristic sizes are studied.Finally,the effects of adding grooves at the tail,the bottom of the vehicle and the side plate of the track on the navigation resistance of the amphibious vehicle are studied.It is found that adding grooves at these three positions can reduce the resistance of the amphibious vehicle,and the effect of adding grooves at the tail is the best.At the inflow speed of 1.5m/s,the maximum resistance coefficient of 4.225% can be obtained.