| This thesis studies the three-dimensional underwater supersonic gas jets,then analyses theflow character and instability of gas jets. Through designing an experimental device ofthree-dimensional underwater supersonic gas, I research the underwater supersonic gas jets indifferent condition with laval nozzle of different design Mach number respectively, then showthe evolution process of “back attack†phenomenon and the flow situation in different condition..At last I present a statistical result of the frequency of back attack. I focus on the evolutionprocess of how the “initial bubble†grow and move. The change of “bubble†form shows thecomplex movement of gas water boundary, so I establish the analytical model of “initial bubbleâ€form, then gain some law of bubble movement by using the experimental data. I explain thenon-roundness concept and point out the importance of momentum jet in theoretical analysis andpractical application. In the experimental analysis, we may obtain steady and long momentum jeteasily using laval nozzle of low design Mach number compared with laval nozzle of high designMach number in the same experimental condition. I also research the evolution process oftransitional region of underwater gas jets and point out that the movement of energy exchangeinside transitional region may play an important role in underwater gas jets. Aimed at theconcept of water piercing missile launcher, we acquire the non-dimensional relation about thelength of momentum jet with Froude number and Strouhal number based on the experimentaldata.of two-dimensional submerged vertical supersonic gas jets. The relation curves we acquiredmay be helpful to the water piercing missile launcher. |
