Research On Gas-liquid Multiphase Flow Characteristics Of Pinhole Jet Flow Field

A large number of exhaust holes are designed on the surface of the submersible vehicle.During underwater launching and floating,the ambient pressure gradually changes.The pressure difference between the internal cavity of the vehicle and the external environment makes the air in the cavity continue to discharge through the exhaust hole,generating the phenomenon of small hole efflux.Keyhole jet flow is a kind of cavitation flow containing unsteady,turbulent,gas-liquid two-phase interaction and other complex factors.Improper design of vent hole may cause delayed exhaust,affect the structural safety of navigation vehicle,and interfere with the water trajectory.The research on gas-liquid flow characteristics of the keyhole jet process is helpful to optimize the vent structure of the underwater vehicle,so as to further optimize the hydrodynamic characteristics of the underwater vehicle and provide reference for practical engineering application.The main research contents and achievements of this paper are as follows:The water tunnel test and numerical calculation method of gas-liquid multiphase flow characteristics in keyhole jet process were studied.A flat plate model for multi-row spacing porous jet experiments is designed.Was carried out by a single jet with double hole jet flow field characteristic value calculation of gas-liquid multiphase flow research,based on the theory of homogeneous equilibrium flow model with the basic theory of basic equations,turbulence model,established the hole jet gas-liquid flow characteristics of numerical simulation method,and the numerical simulation results compared the test results,verify the validity of the numerical simulation method and the grid independence.The single-hole jet water tunnel experiment and numerical simulation were carried out.According to the single-hole jet flow condition with different pressure ratio and different cross-flow velocity,the gradual curves of flow field characteristics,such as cavitation morphology,model surface pressure coefficient,dimensionless transverse velocity and vorticity,along with cross-flow direction,vertical direction and side direction,were obtained.The flow field characteristics such as cavitation morphology,surface pressure coefficient,characteristic transverse velocity and vorticity change with pressure ratio and transverse velocity.Combined with the pressure field,velocity field and vorticity field in the experiment and numerical simulation,it is concluded that ventilation volume and ventilation rate are the influencing factors of cavity width and thickness respectively in the high cross-flow velocity environment.Water tunnel test and numerical simulation of double-row jet flow field were carried out.According to different pressure ratios and cross-flow velocities,the cavity morphology,pressure field,velocity field and vorticity field distribution of doublerow holes as well as the influences of pressure ratio and cross-flow velocity on them were studied.Compared with the flow characteristics of single-hole jet flow field,it is concluded that the flow field environment with double-row holes is better.In view of the double-hole jet flow condition with different row spacing,the influence of double-row hole spacing on the flow characteristics of the isobaric line,isobaric velocity line and isobaric vorticity line of cavity morphology was studied,and the influence rule of row spacing on the flow characteristics of the flow field was obtained.