Similarity Parameters for Surface Melting of a Blunt Nosed Body in a High Velocity Gas Stream

Abstract

By employing a simple model for the two-phase boundary layer produced by surface melting, scaling laws'' are obtained for the regime in which vaporization does not occur at the gas-liquid interface. When the liquid is fairly viscous, the gas boundary layer is virtually independent of the liquid film. The temperature rise across this film depends not only on the local heat transfer rate, but also on the difference in total enthalpy across the gas boundary layer. Thus, tests in rocket exhaust jets may not simulate vaporization or film instability phenomena that could occur in flight. Calculations of the behavior of Corning glass No. 7740 are carried out for some typical flight conditions. One interesting result is the low value of the liquid film Reynolds number, which indicates that the liquid film is almost certainly laminar. This liquid-solid system absorbs about 1125 Btu/lb, or about six times the heat capacity of a nonmelting copper heat sirk. A study of the effect of mass addition to the gas phase shows that the amount of heat blocked'' by this process is sensitive to the total enthalpy difference across the gas boundary layer. The possible increase in effective heat capacity with vaporization at themore » gas-liquid interface is quite substantial at hypersonic flight velocity. Finally, this phenomenon can also be analyzed along the lines of the present paper.« less