CFD Validation Studies for Hypersonic Flow Prediction

A series of experiments to measure pressure and heating for code validation involving hypersonic, laminar, separated flows was conducted at the Calspan-University at Buffalo Research Center (CUBRC) in the Large Energy National Shock (LENS) tunnel. The experimental data serve as a focus for a code validation session but are not available to the authors until the conclusion of this session. The first set of experiments considered here involve Mach 9.5 and Mach 11.3 N2 flow over a hollow cylinder-flare with 30 o flare angle at several Reynolds numbers sustaining laminar, separated flow. Truncated and extended flare configurations are considered. The second set of experiments, at similar conditions, involves flow over a sharp, double cone with fore-cone angle of 25 and aft-cone angle of 55. Both sets of experiments involve 30 compressions. Location of the separation point in the numerical simulation is extremely sensitive to the level of grid refinement in the numerical predictions. The numerical simulations also show a significant influence of Reynolds number on extent of separation. Flow unsteadiness was easily introduced into the double cone simulations using aggressive relaxation parameters that normally promote convergence. † Senior Research Engineer, Aerothermodynamics Branch, Associate Fellow AIAA Copyright © 2001 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U. S. Code. The U.S. Government has a royalty –free license to exercise all rights under the copyright claimed herein for Governmental Purposes. All other rights are reserved by the copyright owner. Nomenclature Cp pressure coefficient, 2(p-p∞)/ρ∞V∞ L reference length from leading edge to junction M Mach number 0 molecular weight, kg/k-mole p pressure, N/m Pr Prandtl number qw wall heat transfer rate, W/m 2 Re ρ∞V∞/μ∞, Reynolds number, m s arc length, mm St hypersonic approximation to Stanton number, 2qw/ρ∞V∞ T temperature, K TV vibrational temperature, K u, v velocity components in x and r directions, respectively, m/s V∞ free stream velocity, m/s x, r cylindrical coordinates, cm ε eigenvalue limiter γ specific heat ratio μ viscosity, kg/m-s ρ density, kg/m Subscripts att attachment point, zero shear i stream wise coordinate direction j normal coordinate direction sep separation point, zero shear w wall surface conditions ∞ free stream conditions