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ACTA AERONAUTICAET ASTRONAUTICA SINICA ›› 2022, Vol. 43 ›› Issue (1): 124930.doi: 10.7527/S1000-6893.2020.24930

• Fluid Mechanics and Flight Mechanics • Previous Articles     Next Articles

Unsteadiness of flow separation in an asymmetric supersonic nozzle

HE Chengjun1, LI Jianqiang2, HUANG Jiangtao1, LI Yaohua2,3, CHEN Xian1   

  1. 1. China Aerodynamics Research and Development Center, Mianyang 621000, China;
    2. High Speed Aerodynamics Institute, China Aerodynamics Research and Development Center, Mianyang 621000, China;
    3. College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
  • Received:2020-10-29 Revised:2020-12-21 Online:2022-01-15 Published:2020-12-18

Abstract: Using flow visualization and dynamic pressure measurement technology, the shock structure and dynamic pressure on the wall in an asymmetric supersonic nozzle with flow separation were experimentally measured. The time and frequency domain features of the wall pressure were analyzed to obtain the characteristics of the unsteady flow in different modes of flow separation inside the nozzle. The results show that when the Nozzle Pressure Ratio (NPR) increased from 1.8 to 12.70, the flow field structure inside the nozzle shifted from the downward to upward pattern. On the upper wall of the nozzle, there were three different modes of flow separation: Restricted Shock Separation (RSS), end effect, and Free Shock Separation (FSS). On the lower wall, the main mode of flow separation was FSS. In the RSS mode, the separation data began to deviate from the Schmucker’s criterion. In both the RSS and end effect modes, the wall in the intermittence region was under low-frequency pressure and the shock motion exhibited obvious low-frequency characteristics. In the end effect mode, the frequency value was slightly higher as the reattachment point comes in very close proximity to the nozzle lip, the separated shear layer impinges on the nozzle exit, and instability of the separated shear layer has obvious influence on motion of the separation shock.

Key words: asymmetric nozzle, restricted shock separation, end effect, unsteadiness, separated shear layer

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