Heat transfer behind a step in high enthalpy super-orbital flow

Heat transfer levels have been investigated behind a rearward-facing step in the X2 super-orbital expansion tube. Using nickel-quartz thin film gauges the heat transfer was measured along a flat plate and behind 2 and 3 mm steps with the same length to step height ratio. Results were obtained with air as the test gas at velocities of 6.7 km/s and 9.6 km/s corresponding to stagnation enthalpies of 30 MJ/kg and 47 MJ/kg respectively. A laminar boundary layer was established on the flat plate with flat plate data consistent with the estimated flow conditions and empirical correlations. Preliminary results indicate that the heat transfer levels behind the steps are similar in shape to those obtained at moderate to low enthalpies. The measurements showed a gradual rise in heat transfer from the rear of the step to a plateau several step heights downstream for both flow conditions. The heat transfer levels downstream of the step plateaued at the undisturbed flat plate level for the high enthalpy condition while a plateau slightly less than the undisturbed level was reached for the low enthalpy condition. The type of distribution and level of heat transfer were found to depend on the viscous interaction parameter for the same hypersonic small disturbance parameter value