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Acta Aeronautica et Astronautica Sinica ›› 2023, Vol. 44 ›› Issue (16): 127956-127956.doi: 10.7527/S1000-6893.2022.27956

• Fluid Mechanics and Flight Mechanics • Previous Articles     Next Articles

Effects of rectangular micro-scale structures on hypersonic rarefied shear flow

Yanting LIU, Jihui OU, Yufeng HAN, Jie CHEN()   

  1. School of Mechanical Engineering,Tianjin University,Tianjin 300072,China
  • Received:2022-08-30 Revised:2022-10-11 Accepted:2022-11-11 Online:2022-12-02 Published:2022-11-29
  • Contact: Jie CHEN E-mail:jie.chen@tju.edu.cn
  • Supported by:
    National Natural Science Foundation of China(92152103);Natural Science Foundation of Tianjin(20JCQNJC01240)

Abstract:

Complex micro-scale roughness structures usually exist on the surface of hypersonic vehicles. With their scale of roughness almost in the same order as the mean free path of gas molecules for vehicles in near space, these microstructures will significantly affect the flow characteristics in the near surface region and surface aerodynamics. In this paper, a high-speed shear flow between a smooth wall and a rough wall, where the microstructures are simplified as periodically distributed rectangular elements, is simulated using the Direct Simulation Monte Carlo (DSMC) method. The effects of roughness element heights and surface accommodation coefficients are investigated. The results show that the microstructures enhance the momentum and energy exchanges between gas and surface. Compared with a smooth surface, the gas velocity and temperature near the rough surface decrease while the total drag and heat load increase. As the element height increases, the effects of roughness become stronger. When the roughness height is larger than one mean free path, a vortex between roughness elements is fully formed and the effect is no longer sensitive to the element height. The microstructures and surface accommodation coefficients have a coupling effect on the momentum and energy exchange. Smaller accommodation coefficients lead to stronger enhanced effect induced by roughness.

Key words: microstructures, direct simulation Monte Carlo (DSMC) method, rarefied gas effect, hypersonic shear flow, accommodation coefficients

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