后甲板长度对带后甲板双 S 弯喷管流动特性影响研究

To investigate the flow characteristics of double S-shaped nozzle with aft deck under different aft deck lengths，numerical simulation studies of five double S-shaped nozzles with different aft deck lengths under four different drop pressure ratio conditions were conducted. The results show that under the fully expanded condition，there is no wave system structure on the aft deck，and the jet does not deflect significantly. Under incomplete expansion conditions，a series of expansion waves and shock waves appear in the jet on the aft deck，and the static pressure fluctuates up and down along the flow direction. The length of the aft deck has a greater influence on the thrust vector angle. As the length of the deck increases，the number of the wave section increases，which makes the wave mode at the end of the deck is different. When the boundary layer does not separate at the end of the deck（nozzle pressure ratio NPR=3），the jet leaves the deck after the compression wave，and the thrust vector angle is negative. The jet leaves the deck after the expansion wave，and the thrust vector angle is positive. As the drop pressure ratio increases，the incident angle of the first expansion wave decreases，the wave length increases，and the shock wave position moves backward. Under high drop pressure ratio conditions（NPR= 4.5，6），the deflection angle of the thrust line is affected by the expansion wave，the shock wave and the degree of separation of the boundary layer，and its variation range can reach 14°.