Similarity Law of Aero-Heating to Sharpened Noses in Rarefied Chemical Nonequilibrium Flows WANG Zhi-hui, BAO Lin, TONG Bing-gang

With a research background on the near-space hypersonic cruise vehicles, this paper is a comprehensive review and in-depth discussion of recent successive theoretical modeling studies of the similarity law of the chemical nonequilibrium flow along a stagnation streamline towards a slightly blunted nose and the related aero-heating performance. Under rarefied condition, series of new flow and heat transfer features emerge near the stagnation point, which are different from those of the continuous flow model and beyond the application scope of the classical aero-heating prediction theories. A general model of the energy transfer and conversion along the stagnation streamline was proposed here, and two flow criteria with specific physical meanings were introduced to characterize the nonequilibrium flows outside and inside the stagnation point boundary layer, respectively. Based on the criteria, a bridging function was established to predict the nonequilibrium aero-heating performance at the stagnation point, and then the rarefied nonequilibrium real gas flow and aero-heating similarity law were discussed. It turns out that the nonequilibrium aero-heating performance of the new generation near-space vehicles with sharpened leading edges is different from that encountered in the re-entry process of traditional blunt vehicles, and the traditional ground-to-flight extrapolation methodology will become invalid. These analytical results provided a reliable benchmark for experiments and numerical simulations of the rarefied nonequilibrium reacting flow and aero-heating problems.