Measurements of Real Gas Effects on Regions of Laminar Shock Wave/Boundary Layer Interaction in Hypervelocity Flows for “Blind’ Code Validation Studies

Abstract

Detailed surface heat transfer and pressure measurements have been made in laminar separated regions of shock wave/boundary layer interaction in high-enthalpy flows over double cone and hollow cylinder/flare configurations to provide data sets with well-defined boundary conditions for comparison with Navier-Stokes computations including the effects of nonequilibrium air chemistry. In these experimental studies, which were conducted in the LENS I and XX shock/expansion tunnels, measurements were made in air, nitrogen, and oxygen for a range of Reynolds number conditions at velocities from 8,000 to 22,000 ft/s to provide measurements with which to evaluate the models of real gas chemistry employed in Navier-Stokes codes. Flowfield measurements have been made with high-speed Schlieren photography and interferometry to provide additional measurements to define the size and structure of the separated interaction region. Details of the model configurations and the freestream conditions at which these studies have been conducted, together with earlier measurements and measurements upstream of the interaction regions are presented in this paper to enable computations to be performed with both Navier-Stokes and DSMC prediction methods for “blind comparisons” with the experimental data. These comparisons will be presented at an AIAA meeting during the coming year. Introduction and Review of Earlier Studies Laminar Shock Interactions in Hypersonic Flows in LENS I and XX Hypervelocity Tunnels with Emphasis on Real Gas Effects The major objective of the current experimental program is to study real gas effects on the scale and distribution of heat transfer and pressure in laminar regions of shock wave/boundary layer interaction with well-defined boundary conditions to evaluate the models of gas chemistry employed in the Navier-Stokes and DSMC codes. These studies, which have been conducted in high-enthalpy flows in the LENS I and XX tunnels, provide accurate measurements for a range of total enthalpies from 5 MJ/kg to 18 MJ/kg in air, nitrogen and oxygen. The heat transfer and pressure measurements made in these studies on a double cone and a hollow cylinder/flare configuration will be published only after detailed computations of these test cases have been made in a “blind” code validation activity. The measurements made in the LENS I shock tunnel on a double cone configuration to investigate real gas effects prior to this study (discussed below) are presented together with the calculated freestream conditions in Appendix 1. Earlier Studies of Real Gas Effects on Flows over Double Cone Model Earlier experimental research of real gas effects conducted in the LENS I shock tunnel at 5MJ/kg and 10 MJ/kg, were initially focused on examining the laminar flow over a double cone configuration where the shock structure and distributions of surface heat transfer and pressure can be strongly influenced by local flow chemistry. Comparisons between Navier-Stokes computation with state-of-the-art chemistry models