Physics-based Simulation Of Multi-AUV Self-propulsion

With the widespread application of AUVs(Autonomous Underwater Vehicles,AUVs)in scientific research and military fields,AUVs are increasingly developing towards reorganization and hybrid formation.AUV formation can expand AUV functions,improve operational efficiency,reduce AUV energy consumption,and increase voyage.AUV formation movement is of great significance to the energy consumption and safety of forecasters AUV.In this paper,the discrete propeller method is used to simulate the maneuvering movement of self-propelled AUV formations,including towed AUV formation,tandem self-propelled AUV formation,parallel self-propelled AUV formation and echelon self-propelled AUV formation.First of all,this paper carries out a numerical simulation of single AUV self-propulsion.Establish the fully attached geometric model of AUV,propeller and rudder.The multi-block hybrid grid method is used to divide the grid of the model.Based on the CFD and the six-degree-of-freedom motion equation,load the self-propelled UDF to simulate the self-propelled motion of the AUV.The numerical results are compared with the experiments to verify the repeatability of the numerical method.Numerical simulation of conventional towed AUV formation is carried out,and the flow field of towed AUV formation and self-propelled AUV formation flow field are analyzed.It is found that there is difference between the wake of the AUV formation with or without propeller.In order to study the real AUV formation movement,numerical simulation of self-propelled AUV formation is very important.Secondly,this paper carries out a numerical simulation of the tandem self-propelled AUV formation.The two AUVs are distributed tandem,the maneuverability of the two AUVs under different initial tandem spacing’s((1)D/L = 0.25,(2)D /L=0.5,(3)D/L=1,(4)D/L=2,(5)D/L=3,(6)D/L=4)is studied.The numerical results show that the change of the initial tandem spacing has no effect on the speed,resistance,and thrust of the former,but the propeller wake of the former seriously affects its hydrodynamic performance of the latter.The smaller the initial tandem spacing,the smaller the resistance of the latter at constant speed,the smaller the thrust,and the greater the speed reduction,which leads to an increase in the tandem spacing of two AUVs,and also causes the latter to generate a larger rolling moment.Subsequently,this paper studies the numerical simulation of the parallel self-propelled AUV formation.The two AUVs are distributed parallel,the maneuverability of the two AUVs under different initial parallel spacing’s((1)S/ L = 0.17,(2)S/ L = 0.27,(3)S/ L = 0.37,(4)S/ L = 0.47)is studied.The numerical results show that the change of the initial parallel spacing has no effect on the thrust of the AUV.The larger the initial parallel spacing,the greater the AUV’s constant speed,the smaller the suction,and the smaller the rotation torque.Finally,this paper studies the numerical simulation of the echelon self-propelled AUV formation.The two AUVs are distributed echelon,the maneuverability of the two AUVs under different initial echelon spacing’s((1)S/L = 0.17,D / L = 1;(2)S/ L = 0.27,D / L = 2;(3)S/L=0.35,D/L=0,19°28’ for short)is studied.The numerical results show that the change of the initial spacing has no effect on thrust,and has a small effect on speed.In the echelon formation,formation(1)and formation(2),the former has a damping effect on the latter,the latter’s speed decreases,and the distance between the two increases,but its influence is not as great as that of a tandem formation with the same tandem distance.However,in the 19°28’formation,the former has a suction effect on the latter,making the latter faster than the former at a constant speed.Compared with other echelon formations,this AUV formation has an energy-saving effect.