Abstract：In order to study the interaction of gas flow field evolution in subsonic nozzle, the coupling effect of pressure-velocity-contraction ratio on the velocity profile was quantitatively evaluated. Based on the standard k-ε turbulence model, the numerical simulation was utilized for the uniform gas flow field in the subsonic nozzle under coupling effect and the key parameters of top-hat flow field distribution were defined. The results show that within multi-factor coupling, the subsonic nozzle can change the quality of the flow field distribution by influencing the key points of the strengthening process including the equilibrium point and the critical position point of the pressure gradient. Increasing the gas pressure can effectively reduce the boundary layer thickness in the tectonic flow field, reduce the dependence of the key points on the flow velocity in the process, and improve the stability of the boundary layer thickness under different flow velocities. The increase of contraction ratio leads to the further deviation of the flow field from the ideal distribution.
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