Research On Cavitation Morphology And Testing Technology Of High Speed Projectile Underwater

Supercavitation drag reduction technology has been widely used in the development of underwater high-speed vehicle.The research on supercavitation drag reduction technology consists mainly of two aspects: numerical simulation and experimental research.Compared to numerical simulation,the results of experiment evaluate the performance of different underwater vehicle directly,and the cavitation phenomenon of supercavitation projectile in the tank is more similar to the real situation.However,due to the difficult control of the launch state,the limited test conditions and the lack of analysis methods,the results are not abundant.This paper proposed a measruement scheme which can measure the cavitation shape and 3D motion trajectory of supercavitation projectiles with high precision.Image prossing programs based on Canny edge dection method are writed to obtain coordinate changes of the warhead and cavity shape information for the underwater images took by high speed cameras.Programes are also writed to get 3D motion trajectory by ballistic fitting according to the ballistic equation and the principle of kalman filter.At the same time,the paper designs a target area velocity measuring laser device with high precision based on photoelectric conversion technology.The main work includes:(1)A small experimental system used for horizontal firing experiment measurement is designed and manufactured.The high-speed cameras are used for filming and recording the pictures of six different kinds of projectiles in X-Z plane and X-Y plane with two high power LED lamps.(2)For the image obtained in the experiment,a image processing programs based on canny edge detection method is writed to obtain the warhead coordinate change of the model bombs and the cavity contour information generated by the model bombs.According to the semi-empirical formula of cavity shape,the model bomb bubble outline read by the program is compared with the theoretical bubble shape.According to the Principle of Kalman filtering,the coordinates are fitted to obtain the trajectory of the model bomb in 3D space.(3)Based on the photoelectric detection technology,the laser light screen velocity measurement device is designed and made.The test software is writed with labview.The projectile’s passing speed can be accurately tested in the cutting area accurately.The results of the laser light screen velocity measurement device and the scheme proposed above are compared in the paper.From the experimental analysis results contrast,the analysis scheme proposed in this paper can complete the underwater measurement aims which include 3D ballistic curve,cavity shape,velocity in fixed location and other motion characteristics with high percision.