Experimental Study On Low Speed Water Entry Of Truncated Cone

In recent years,the Sports body into water has gradually become a hot research direction,and the most concerned is the movement law of the Sports body and the change law of the cavitation attitude with the Sports body into water.Cavitation in water is a complex and interesting physical phenomenon.The formation,expansion,closure and collapse of cavitation will affect the motion and hydrodynamic characteristics of the Sports body entering water.Cavitation flow affects the attitude and motion characteristics of the moving body.The research on it is the basis of the design of underwater weapons such as torpedo.The most obvious influence on the cavitation is the head shape of the Sports body contacting with it when it enters the water.There are great differences in the cavitation and motion parameters of the Sports body with different head shapes.It is of great significance to study the water entry process of the Sports body with different head shapes.In this paper,the research on water entry cavitation in recent decades at home and abroad is summarized,the research direction of cavitation is discussed,and the experimental research on the water entry process of different truncated cone shaped Sports bodys is carried out.A high-speed camera was used to photograph the cavitation flow during the process of Sports body entering water,including the comparison of different head diameter,different cone angle,different water entry angle and different water entry velocity.The ballistic characteristics of Sports body entering water were summarized and analyzed.The variation of water inflow parameters of truncated cone-shaped Sports bodys under various conditions is compared.The law of cavitation change and the law of Sports body motion in the process of different water entry angles of each truncated cone shaped Sports body are discussed.The relevant introduction and the corresponding kinematics mechanism explanation are given.In conclusion,the research results of this paper are as follows:(1)Firstly,the vertical water entry of truncated cone Sports body is analyzed,and the influence of water entry velocity on cavitation,motion and hydrodynamic characteristics is obtained.The results show that :The velocity of Sports body in deep closed state is basically the same,and the velocity rule begins to change in the process of turning to surface closed state;the larger the initial velocity of water entering,the earlier the surface closed;The earlier the trailing cavity separated from the trailing cavity,the later the trailing cavity contacted the liquid surface;In the stage of surface closure,the general velocity rule of the Sports body is: first increase and then decrease,and then increase after smooth transition;when the velocity is higher,the velocity rule changes to continuous decline;the larger the diameter of the truncated Sports body head,the more obvious the wall fluctuation phenomenon.;(2)In this paper,the inclined water entry process of different head diameters of frustum head is studied experimentally.Taking two working conditions,the law chart of the inclined water entry process at a specific speed is given.The influence of the structure size and water entry parameters of the water entry Sports body on the attitude,motion characteristics and hydrodynamic characteristics of the water entry cavity is analyzed comprehensively.The results show that: the larger the diameter of the head of the truncated Sports body is,the earlier the tail collides with the cavitation;The diameter of the head of the truncated Sports body has little effect on the closure time of the cavitation;The cavitation at the liquid surface increases with the increase of the head diameter;the too large or too small diameter of the head of the truncated cone head Sports body is not conducive to the stability of water entry;when the water entry speed of the truncated cone head Sports body is low,when the water entry speed of the Sports body is lower than its critical value,the speed shows an upward trend;when the speed is higher than the critical value,the speed shows a downward trend.(3)In this paper,nine groups of experiments were carried out to investigate the process of different head cone angles inclining into the water of the truncated head Sports body.The effects of the head cone angle and the initial velocity of the Sports body on the attitude,motion and hydrodynamic characteristics of the cavitation were obtained.The results show that: the smaller the head cone angle is,the earlier the tail collides with the lower wall of the cavity;the smaller the head cone angle is,the faster the initial velocity is,and the later the time of deep cavity closure is;The larger the cone angle is,the smaller the clockwise force moment is or the larger the counterclockwise force moment is,which has a great influence on the change of pitch angle;In this paper,we have carried out the relevant experimental research on the water cavitation problem of the truncated cone Sports body,and analyzed various practical situations of the Sports body entering the water at low speed,which can provide reference and technical support for the relevant research and projects.