Abstract: The fluid dynamic problem of the underwater ignition of an axisymmetric missile is studied in this paper. A mathematical model is presented for solving the nonlinear transient flow. On the assumption that the water flow is incompressible and potential and the gas flow in the jet pipe is quasi-one-dimensional and inviscid, the flows are solved by using boundary integral method and characteristic line method respectively. An isobric bubble model is adopted to simplify the jet flow ejected into water through a nozzle. The evolution of bubble is simulated by means of mixed Eulerian-Lagrangian method and computational techmique. Using the time-stepping algorithm,the calculation is accomplished successfully on the gas-water flow coupled with the missile's motion. The numerical results show some important special properties of the gas-water flow of underwater ignition of missile.

Key words: nonlinear transient flow, gas-water interaction, bubble dynamics, underwater igni- tion, missile