关键词: 水下射流;超声速气体射流;线性稳定性;Chebyshev配置点法;气液两相流

Abstract: Linear stability of underwater supersonic gas jet is the core field of underwater propulsion and underwater welding. The linearized small disturbance gas-liquid two-phase flow governing equations have been established to study the linear stability of underwater supersonic gas jet. The form of the governing equations indicate that the stability of underwater supersonic gas jet can be affected by the jet’s velocity and concentration distribution， Reynolds number， relative density and relative viscosity. Chebyshev collocation point method has been used to solve the governing equations. The calculation results show that the velocity and concentration distribution of the jet and the relative density are the main factors affecting the stability of the jet. The more flat the velocity and concentration distribution of the jet， the smaller the maximum growth rate of the jet. The smaller the relative density， means the smaller the density difference between gas and liquid， the smaller the maximum growth rate of the jet. As the Reynolds number increases， the maximum growth rate of the jet decreases first and then increases. The maximum growth rate of the jet approaches a constant when the Reynolds number is greater than 10⁵. The jet maximum growth rate-wavenumber curves are highly coincident for different relative viscosities. The stability of different jet’s cross-sections also has been analysed. The maximum growth rate of the jet decreases with increasing the distance from the nozzle， which is shown by the calculation.

Key words: Underwater jet;Supersonic gas jet;Linear stability;Chebyshev collocation point method;Gas-liquid two-phase flow