In order to reveal the influence mechanism of pressure distribution in the extension section on the mode transition of the dual-bell nozzle,the mode transition process of the dual-bell nozzle with different wall pressure distribution in the extension sec-tion was studied by means of simulation,experiment and theoretical analysis.The analysis shows that,when the actual working pressure ratio is greater than the maximum theoretical separation pressure ratio,the pressure ratio equilibrium condition of the sepa-ration point on the non-negative pressure gradient contour is destroyed,so the mode transition occurs rapidly with the movement of the separation point.Meanwhile,due to the unbalance mechanism of the nozzle pressure ratio,the hysteresis between the positive/inverse mode transition is also found.However,the negative pressure gradient contour can meet the equilibrium condition required for the stable existence of the separation point,so the mode transition process is slow,and there is no hysteresis in this process.
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