Uncertainty Analysis of Fluid-Structure Interaction of a Deformable Hypersonic Inflatable Aerodynamic Decelerator

Abstract

The objective of this paper is to present the results of a detailed uncertainty analysis for high-fidelity fluid-structure interaction modeling of a deformable hypersonic inflatable aerodynamic decelerator at peak heating conditions for lifting Mars entry with a turbulent flow assumption. Uncertainty results are presented for the structural deformation response and surface conditions (pressure, shear stress, and convective heat transfer) of the inflatable decelerator with an efficient polynomial chaos expansion approach. The uncertainty results are compared with results obtained in a previous study for ballistic Mars entry. Approximately half of the flowfield and structural modeling uncertainties show at least 90% combined contribution to the inflatable decelerator deflection and resulting surface condition uncertainties. For lifting Mars entry, global nonlinear sensitivity analysis shows that the tensile stiffness of the inflatable structure's axial cords and radial straps and the torus torsional and tensile stiffnesses are the main contributors to the inflatable decelerator deflection uncertainty. As a result of these structural uncertainty contributions, the shape deformation contributes up to 10% of the uncertainty in the surface conditions. However, the freestream density dominates the uncertainty in the surface conditions experienced by the inflatable decelerator. In addition, the CO 2 −CO 2 binary collision interaction is a significant contributor to aerodynamic heating and shear stress uncertainty. Nomenclature= lift-to-drag ratio N s = number of samples N t = number of terms in a total-order polynomial chaos expansion n = number of random dimensions P = surface pressure, Pa p = order of polynomial expansion q = dynamic pressure, Pa Re = Reynolds number per unit length, /m S e = percent absolute error S T = total Sobol index T = static temperature, K V = velocity, m∕s x = deterministic variable vector α = deterministic coefficient in the polynomial chaos expansion α = generic uncertain response function β = ballistic coefficient, kg=m 2 γ FPA;i = initial entry flight path angle, deg δ = truncation error or deflection angle, deg μ e = mean error ξ = standard input random variable ρ = static density, kg=m 3 Ψ = random basis function Ω 1;1 = diffusion collision integral Ω 2;2 = viscosity collision integral ∞ = freestream condition