Three-dimensional Numerical Simulation Of Underwater Vehicle With Grid Fins

As a new kind of stability and control surface, grid fin has been widely appliedto the spacecraft escape system. Because of its aerodynamic characteristics of higherlift, lower hinge moment, and the bigger stall angle of attack than the planarcouterparts, it is possible to protect the aircraft in steady flight. It also provides asolution to keep underwater vehicle stability and controllability. But a new problemgenerates with the grid fins applying for sailing and underwater weapons,that iscavtition occures in the area of low pressure which is different from aerodynamics.The appearance of cavitations will dramatically reduce the hydrodynamicforces and affect the flow pattern, it will also have the machinery to be damaged. Soit is significant to investigate the application of grid fin to underwater vehicle..In this paper, the multiphase model provided by F luent was used to simulate theflow field around the vehicle with and without the grid fin in the conditions ofdifferent cavitations numbers and angles of attack. After the simulation, thecoefficients like normal-force coefficients, moment coeffic ients were calculated tostudy the hydrodynamic character of the grid fin. During the simulation, the changeof flow field in the region of vehicle’s tail was focused on. The difference betweenthe vehicle with and without the grid fin was found out by comparing thehydrodynamic character. At last, the role that grid fin played during the vehicleworking in the water was shown up.From the paper, we can know that there exists some difference bewteen theunderwater vehicle with and without grid fin, all the coefficients caused by the gridfin in the paper have a slight increase. And it will help improve the overallperformance if the size of the grid fin increases. But it should be noted that thehydrodynamic characteristics of grid fin decreases when it was worked with thevehicle. So a certain margin should be considered in the design.