Yaw Dynamic Characteristics Of Underwater Vehicle With Water-jet Vector Propulsion With A Screw Mixed-flow Pump

The water-jet submarine with screw mixed-flow pump is powered by a new type of water-jet pump to advance and control the hull.The thrust is not only related to the rotational speed of the screw mixed-flow pump,but also to the angle of the vector nozzle.Compared with the traditional power devices such as fin and propeller propulsion,it has better maneuverability and stealth performance.In this paper,the water-jet submarine with screw mixed-flow pump is taken as the object.Based on the maneuverability theory of submarine,the yaw dynamic characteristics of pump-jet submarine are studied by computational fluid dynamics method.Firstly,the three-dimensional model of the water-jet submarine with screw mixed-flow pump in direct motion state is established.The accuracy of numerical simulation method is verified by comparing with circulating flume experiment.Then,monitor the lateral force and moment of direct navigation to obtain the vector angle coefficient.Secondly,the oblique motion and yaw motion of the water-jet submarine with screw mixed-flow pump are simulated,the characteristics of the motion are analyzed,and the velocity coefficient and angular velocity coefficient are monitored.Finally,the mathematical model of water-jet submarine with screw mixed-flow pump is established to study its horizontal dynamic behavior.The conclusions are summarized as follows:1.In the direct motion of the water-jet submarine with screw mixed-flow pump,the efficiency of water-jet pump decreases with the increase of nozzle angle.The efficiency is high between 0 ° ～20 ° vector angles.The biggest drop in efficiency is between 30 ° ～50 ° vector angles.Through numerical simulation of direct motion under variable speed conditions,using polynomial fitting method,mathematical model of the vector angle coefficient changing with the speed of the rotation is established.2.In the oblique motion of the water-jet submarine with screw mixed-flow pump,a positive pressure zone is formed in the bow of the hull,and an inverse pressure zone appears in the middle of the pump shell.The lateral force,lateral velocity and lateral torque of the submersible are positively correlated with the oblique angle.Through numerical simulation of oblique motion under variable speed conditions,using polynomial fitting method,mathematical model of the speed coefficient changing with the speed of the rotation is established.3.In the yaw motion of the water-jet submarine with screw mixed-flow pump,negative pressure appears on the right side of the bow,and local positive pressure appears on the left.With the increase of rotational speed,the wake of the submersible is gradually obvious.Through the numerical calculation of yaw motion at variable speed,using polynomial fitting method,the mathematical model of angular velocity coefficient of water-jet submarine varying with rotational speed is established.4.In the horizontal rotary motion,under the condition of constant speed,the rotation radius of water-jet submarine with screw mixed-flow pump increases exponentially with the decrease of vector angle.With the vector angle constant,the rotational radius increases exponentially with the decrease of rotational speed.Under the condition of changing rotational speed and vector angle,numerical simulation of horizontal rotary motion of submarine,the mathematical model of the water-jet submarine’s radius changing with the pump speed and the vector angle is established.5.In the harmonic motion of horizontal plane,give the nozzle the same response excitation.Solving the wavelength of harmonic motion under variable speed conditions,using polynomial fitting method,the mathematical model of water-jet submarine with screw mixed-flow pump wavelength changing with pump speed is established.