THE RESEARCH ON HIGH-SPEED GAS JET OF ROCKET NOZZLE UNDERWATER

In this paper, a study of the high-speed gas jet of a rocket nozzle underwater was carried out using commercially available CFD software FLUENT with it‘s user-definedfunction. The volume of fluid technique based on finite volume method was adopted to solve the time dependent multiphase flow including a compressible phase, and the PISO algorithm was included. The computed results show that this problem was calculated successfully. The gas bubble behind the nozzle, and the wave structure existing in highly compressed gas in water were captured accurately.     

EFFECT OF A PROPELLER AND GAS DIFFUSION ON BUBBLE NUCLEI DISTRIBUTION IN A LIQUID

A multi-bubble dynamics code accounting for gas diffusion in the liquid and through the bubble wall was developed and used to study the modification of a bubble nuclei population dynamics by a propeller.The propeller flow field was obtained using a Reynolds-Averaged Navier-Stokes(RANS) solver and bubble nuclei populations were propagated in this field.The numerical pro-cedure enabled establishment of the possibility of production behind the propeller of relatively large visible bubbles starting from typical ocean nuclei size distributions.The resulting larger bubbles are seen to cluster in the blade wakes and tip vortices.Parametric investigations of the initial nuclei size distribution,the dissolved gas concentration,and the cavitation number were conducted to ide-ntify their effects on bubble entrainment and the resultant void fractions and bubble distribution modifications downstream from the propeller.Imposed synthetic turbulence-like fluctuations unto the average RANS flow field were also used to study the effect avera-ging in the RANS procedure has on the results.