Coupled Simulation of Hypersonic Fluid-Structure Interaction with Plastic Deformation

Abstract

Supersonic and hypersonic vehicles experience significant aerothermal loads from the exterior flowfield and/or their propulsion system. Thus, reliable prediction of aerothermal heating is important for the design of such vehicles. However, even modest temperature changes can lead to buckling of mechanically constraint lightweight structures. This deformation changes the flowfield, which can lead to locally amplified heating, which in turn increases deformation and temperature even further. Thus, fluid-structure coupled modeling of such problems is crucial for the reliable prediction of the resulting temperatures. To investigate these phenomena numerically, we conducted a three-dimensional thermomechanical simulation of fluid-structure interaction (FSI) for thermal buckling. It is necessary to use a thermomechanically coupled model because the temperature and deformation distributions across the panel are highly nonlinear and dependent on both the flowfield and the state of the structure. Due to the high temperatures (>1400  K) in the metallic panel and the constrains, which allow no uniform expansion, the stresses exceed the yield stress, and plasticity occurs. A strong two-way coupled FSI simulation was set up and split into a thermal solid, a mechanical solid, and a fluid computation. The simulated temperature and displacement distribution were compared to experiments conducted in the arc-heated wind tunnel L3K at the German Aerospace Center (DLR). We obtained good agreement between the simulation and experimental results. The observed deformation of the structure was found to locally increase the wall heat flux by up to 40%.