Numerical Simulation of the High-Speed Leg of the National Transonic Facility

Abstract

Numerical simulations for the flow inside the high-speed leg of the National Transonic Facility were conducted. Simulations were conducted for three configurations: the empty tunnel, an installed body of revolution, and the NASA Common Research Model installed in the test section. Simulations were performed for a test-section Mach numbers of 0.7 and 0.85 and a corresponding Reynolds number of 8 million per ft. The numerical simulations were performed using the NASA USM3d-ME Navier-Stokes flow solver with the Spalart-Almaras one-equation turbulence model and were run in the steady-state mode. USM3D-ME supports solutions on mixed-element grids which provide improved numerical simulation using the flow-aligned anisotropic hexahedral or prismatic cells in the boundary layer and isotropic tetrahedral cells away from the boundary layer. A controller was developed that automated the outflow boundary and streamlined the process of running multiple simulations. The use of a dynamic outflow boundary was the key parameter to drive a simulation to the desired tunnel test section conditions. The numerical simulations captured the expected flow features in the NTF test section and in the tunnel plenum. The simulations revealed that the separation of the flow inside the diffuser is asymmetric and more extensive toward the bottom wall. Analysis of the flowfield was conducted, and the computed drag coefficient was compared to wind tunnel data.