Turbulent Flow Studies in Two Arc-Heated Duct Facilities

The results of preliminary investigation of the flow conditions in two arc-heated duct facilities are presented. These facilities were developed to simulate space shuttle vehicle entry conditions by providing high-temperature, supersonic, turbulent boundary-layer flows over relatively large samples of candidate materials for thermal protection systems. In one facility, a rectangular duct provides two-dimensional flow over a flat plate model, whereas in the other facility a contoured nozzle provides axisymmetric flow through a hollow circular cylinder of test material. Convective heating rate measurements are compared to theory and other experimental data and, with Teflon ablation measurements, are used to verify turbulent flow in both facilities. The ranges of heattransfer rate, heat-transfer coefficient, and surface temperature attained are shown to provide adequate simulation of the space shuttle entry heating environment.