Rapid Prediction of Unsteady Aeroelastic Loads in Shock-Dominated Flows

Abstract

A capability needed for the development of high-speed systems is accurate and efficient prediction of aerodynamic pressure, particularly for light-weight systems where the unsteady aerodynamic loads may be strongly coupled with the structural response. This is particularly challenging in shockdominated environments (i.e., inlets, near control surfaces, etc.) where the flow is discontinuous, highly nonlinear, and leads to severe loading. This study extends a previously developed modeling approach one that corrects steady-state CFD surrogates for dynamic fluid-structural coupling using piston theory to conditions with oblique impinging shock waves. The approach is based on the “local” piston theory method, where relevant freestream flow parameters are replaced with spatially local quantities. The approach is examined for cases with oblique shocks impinging on two and three-dimensional surfaces. Mean errors in the generalized aeroelastic forces are less than 1.3% when compared to the full unsteady Reynold’s Averaged Navier-Stokes solutions for both stationary and oscillating shocks impinging on vibrating surface panels. Furthermore, the approach is found to reproduce shock induced limit cycle oscillations recently reported in the literature based on high fidelity CFD solvers. The high accuracy of this approach is based on two important factors. First, the shock-induced steady-state pressure dominates the structural loading. Second, the unsteady perturbations to the steady flow solution, due to dynamic surface motion, is effectively captured using inviscid flow theory. Finally, the computational cost of the developed model is orders of magnitude less than that required for the full CFD prediction, making it a viable approach for long time record response prediction of high speed structural systems in shock-dominated environments.