The gas temperature within hypersonic boundary layer flow is so high that the specific heat of gas is no longer a constant but relates to temperature. How variable specific heat influences on boundary layer flow stability is worth researching. The effect of the variable specific heat on the stability of hypersonic boundary layer flows is studied and compared with the case of constant specific heat based on the linear stability theory. It is found that the variable specific heat indeed has some effects on the neutral curves of both the first-mode and the second-mode waves and on the maximum rate of growth also. Therefore, the relationship between specific heat and temperature should be considered in the study of the stability of the boundary layer.
When an aircraft flies at a hypersonic speed,the temperature of gas inner boundary layer near the wall is so high that the specific heat is no longer a constant but dependent upon the temperature.It is necessary to consider its effect on transition location.In this paper,the transition locations of hypersonic plane boundary layer are predicted with the improved e N method,and the results of the specific heat dependent upon temperature are compared with those of constant specific heat.The flow parameters are taken as those corresponding to the condition at a height of 40 km and the Mach numbers of oncoming flow are 6,7,and 8,respectively.It is found that the transition locations calculated by the variable specific heat are closer to the leading edge than those by the constant specific heat.The deviations in most cases are around 30 percent.All the results prove that the real gas effect should be taken into consideration when one predicts transition location for hypersonic flow.Whether the first or second mode wave determines the transition location relies on the oncoming flow Mach number and the wall condition.
