Physical and Numerical Aspects of Simulating Rarefied Hypersonic Wedge Flow

This paper presents numerical simulations of truncated wedges in rarefied hypersonic flow. The impact of the geometric bluntness, dictated by heating, handling, or manufacturing requirements, on the aerodynamic heating has been investigated by employing the direct simulation Monte Carlo method. The results presented highlight the sensitivity of the heat transfer coefficient to changes on the frontal-face thickness of the leading edges. Some significant differences on the heat transfer coefficient provided by the direct simulation Monte Carlo method and by the free-molecular-flow equation were noted along the body surface at the immediate vicinity of the frontal-face/afterbody junction for the leading edges with thickness Knudsen numbers of 100, 10, and 1. It was found that the heat transfer rate for the smallest frontal-face thickness approached the free-molecular limit from above, whereas that obtained for the largest frontal-face thickness approached from below. The flowfield behavior and its influence on the heat transfer coefficient was investigated by using a model that classifies the molecules in three distinct classes: 1) undisturbed freestream, 2) reflected from the body surface, and 3) scattered (that is, molecules that had been indirectly affected by the presence of the leading edge). According to the results, for the conditions investigated, there is a particular frontal-face thickness that represents the crossover point in which the approach to the free-molecular limit is at the level of the free-molecular limit.