Variable Acceleration And Yaw Dynamic Characteristics Of Water-Jet Propulsion With A Screw Mixed-Flow Pump

The research of water-jet propulsion pumps has focused on more and more attention from scholars at home and abroad.The research on the submarine motion after the water-jet propulsion pumps are installed mainly focuses on the dynamic characteristics and motion status.Underwater submarines have a lot of direct acceleration and plane yaw movements while sailing.The realization of these movements is based on accurate dynamic parameters.In this paper,the screw mixed-flow pump-jet thruster is taken as the research object,and the variable acceleration and yaw motion of the pump-jet thruster are numerically calculated by the RNG k-ε turbulence model.In order to study the dynamic characteristics of the pump-jet thruster under different motion forms,this paper firstly establishes the mathematical model of the variable acceleration dynamics of the pump-jet thruster to obtain the relationship of the speed function,and comparatively analyzes the dynamic parameters under different direct acceleration conditions Change law;Secondly,the drift angle is introduced to calculate and analyze the change law of the force characteristics of t he pump-jet propeller under different yaw motion states.The main research conclusions of this article are as follows:(1)The drag characteristics of the pump-jet propeller at different speeds are analyzed.The research shows that when the speed of the pr opeller reaches a certain value,that is,when the Reynolds number is in the square of resistance,the drag coefficient does not change with the increase of the speed.Through the numerical simulation and experimental verification of the thrust and torque at different speeds,the study found that the thrust,torque and speed of the pump propeller are distributed in a quadratic function relationship,which is consistent with the test value.(2)By establishing the variable acceleration dynamics mathematical model of the pump-jet thruster,it is found that the change of the speed of the pump-jet thruster with time satisfies the distribution of hyperbolic tangent function.According to the principle of automatic control,it is found that the relationship betwee n the speed of the pump jet propeller and the acceleration time is similar to the step transient response of the first-order system,and the time constant ζ is related to the speed of the screw mixed-flow pump.(3)The initial boundary conditions of variable acceleration based on UDF are used to simulate the acceleration of the pump-jet thruster.The research shows that the change of the drag of the pump-jet thruster with acceleration time is similar to the step response curve of the critical damping second-order system.(4)Through research on the dynamic characteristics of partial deviation of the pump-jet propeller under different working conditions,it is found that the change law of the drag coefficient is similar to that of the direct movement;drift angle and speed are the main factors affecting the drag characteristics of the pump-jet propeller.In the speed stage,the influencing factors of drag are different.(5)The total thrust received by the pump-jet propeller increases with the speed close to the parabola trend,indicating that the speed is a direct factor affecting the total thrust;the speed and drift angle directly affect the normal thrust,and the growth trend of the normal thrust is close to the parabola distribution.