Uncertainty Analysis of Inflow Parameters for Mid-Lift-to-Drag Vehicle Transition

Abstract

The boundary-layer transition and aerothermal environment for mid-lift-to-drag-ratio entry vehicles are highly complex and influenced by several factors. The uncertainty and sensitivity of transition and aeroheating predictions on such vehicles with respect to the inflow parameters are investigated in this paper. Five inflow parameters (freestream Mach number, freestream pressure, freestream temperature, wall temperature, and angle of attack) are chosen as the uncertainty variables. The transition predictions are obtained using Reynolds-averaged Navier–Stokes simulations with the -- transition model. The point-collocation nonintrusive polynomial chaos method is employed to describe and propagate the uncertainty of the output quantities of interests. Moreover, the Sobol index is adopted to quantify the contribution of each variable to the total uncertainty. Our results reveal that small changes (less than 3.4%) in the inflow parameters could yield roughly 10% uncertainty in the transition lengths and more than 15% uncertainty in the transitional aeroheating and skin friction. The freestream temperature and angle of attack strongly influence the transitional aeroheating. The angle of attack, freestream pressure, and freestream temperature are the major uncertainty contributors to the skin friction. The freestream pressure and angle of attack significantly impact the transition onset and length.