Study of Aerodynamic Characteristics Evaluation under Hypersonic Rarefied Flows

Preliminary studies are made to determine the aerodynamic and accommodation characteristics of the wind tunnel model under hypersonic rarefied flow. In the method, the wind tunnel models are exposed to the test flow in the hypersonic rarefied wind tunnel in JAXA. The displacements of the models due to the aerodynamic forces are measured during the testing. The flowfield around the wind tunnel model in the test section is also analyzed by using the numerical calculation. In the calculation, the accommodation coefficient of wind tunnel model surface is parametrically changed. The accommodation parameter of the wind tunnel model surface is then deduced from the comparison between the calculation and the measurement. For the sphere wind tunnel model, agreement between measurement and calculation could be obtained by present method with the accommodation coefficient from 0.8 to 0.9. It is also found that the determination of accommodation parameter becomes more achievable by using the displacement along the flow direction rather than that along the horizontal direction. On the other hand, further detailed modeling is required in the numerical analysis for the flat plate model. The uncertainties in the force measurement in the HRWT are discussed in this paper.