Sensitivity Analysis of a HIFiRE-6 Design Variant Using Minimum-Resource Statistical Designs

Abstract

An uncertainty-based simulation work flow is used to automate the prediction of steadystate aerodynamic loads for a design variant of the HIFiRE-6 hypersonic flight research vehicle. Tools distributed with the Chimera Grid Tools (CGT) framework are exercised to perform overset mesh generation and verify domain connectivity. OVERFLOW is used to compute Reynolds-Averaged Navier-Stokes estimates of static aerodynamic loads at different points within a design space representative of the vehicle's planned flight test environment. Sensitivity analysis of a design space composed of Mach number, angle of attack, sideslip angle, and dynamic pressure is performed to assess the suitability of using secondorder central-composite statistical designs to capture modest variations in customer-defined system response quantities. Within the specified bounds, automated simulation analytics suggest that for the fixed vehicle being analyzed, variations in axial and normal force coefficients are driven by perturbations in angle of attack and Mach number. Perturbations in sideslip angle induce the most variation in side force coefficient. Perturbations in an interaction term involving sideslip angle and angle of attack, and sideslip angle are the primary drivers impacting variation in rolling moment coefficient. Perturbations in angle of attack and Mach number are predicted to be the primary drivers of variations in pitching moment coefficient. Perturbations in sideslip angle and Mach number are predicted to be the primary drivers for variations in yawing moment. Perturbations in dynamic pressure were determined to be statistically insignificant for the design space analyzed. Analysis of variation results of the design indicate that second-order surrogates, based on a small number of independent simulations, are able to capture 90 to 100% of the variations in steady-state aerodynamic loads predicted by simulation associated with a vehicle at a fixed point along its trajectory. We expect these automated techniques and observations to be useful for future design, testing, and evaluation activities involving high-speed vehicles.