The Generation And Fluid Mechanics Mechanism Of Horizontally Moving Supercavitaties

When a high speed solid body immerges into or sails in a flow, cavitation will be generatedaround it. When the formative cavitation bubbles surround the whole vehicle, the zone ofbubbles is called supercavitation. In the fields of maritime and national defense weapons, thesupercavitation theory has got certain important applications. However, these applications aresimply based on the present preliminary study of supercavitation phenomenon. In order tofurther develop the value of supercavitation technology, so as to better serve the various fieldsof engineering application, deep study to supercavitation phenomenon is very necessary.By mainly using experimental investigation method in combination with numericalsimulation method, this paper carried out systematic and in-depth investigations on the fluidmechanics mechanism of the horizontal water entry of supercavitation phenomenon, and got anumber of innovative achievements. The main work content and research results are as follows:(1) Horizontal motion of supercavitation generating device was designed and made by self. Theflow field visualization of the supercavitation movement was achieved. Through theexperimental apparatus, horizontal projectile supercavitation experiments at different depth ordifferent angles can be carried out. The investigation on the interaction between horizontalmovement supercavitation and free water surface has been carried out.(2) The cavitation deviceand the length-diameter ratio have some influence on the shape and stability of supercavitation.At the same length-diameter ratio, the slender body with flat head has better stability, and thesupercavitation is bigger. Using the same type of cavitation device, the increase of thelength-diameter ratio is beneficial to the stability of the cavitation.(3) For given the cavitationnumber, the drag coefficient increases as the length-diameter ratio or cavitation diameter ofslender body increases. The drag coefficient may also be affected by head type. The dragcoefficient of flat head is larger, followed by the cuspidal head.(4) About the change rule ofdimensionless size along with cavitation number, the fitness between the result of empiricalformula and experimental results is better, and the experimental value is more close toSavchenko`s experience value.(5) The relative diameter and relative length of cavitation arerelevant with the diameter and length-diameter ratio of cavitation device, cavitation number andthe cavitation device type. The augment of the diameter of cavitation device or length-diameter ratio are advantageous to the augment of cavitation size, but the augment of cavitation numberis counterproductive.(6) The fitness between Logvinovich`s cavitation contour curve equationand experimental value is better. The actual value is slightly smaller than theoretical value.(7)When horizontal motion supercavitation interacts with free water surface, cavitation willexpand and maintain a certain cavity shape in a period of time.(8) Numerical study show: Fromthe generating of cavitation to the forming of supercavitation, the time is roughly0.6ms.Cavitation is generally generated at the joint region of the head and cylindrical section of theslender body. The cavitation generated at the head and the tail of the slender body are graduallygrowing and merging together, and then the natural supercavitation surrounding the slenderbody is formed. The numerical results also show that the length-diameter ratio and head type ofslender body have influence to the size and stability of cavitation, which are consistent with theexperimental results.The research results of the generation and flow mechanism of horizontal motion ofsupercavitation in the paper not only tests the availability of the existing supercavitation theory,but also complements a new knowledge of supercavitation flow.