Fluid-Thermal-Structural Modeling and Analysis of Hypersonic Structures under Combined Loading

Accurate predictions of structural response and life in extreme environments are necessary to achieve the United States Air Force’ goals of affordable, reusable platforms capable of sustained hypersonic flight and responsive access to space. However, the predictive capability of current commercial software is limited for combined aerothermal and aeropressure loading due in part to the inability to seamlessly address multi-coupled, multi-scale fluid-thermal-structural interactions. This study aims to quantify the significance of a frequently neglected interaction, namely: the mutual (2-way) coupling of structural deformation and aerodynamic heating, on response prediction in hypersonic flow. In order to accomplish this objective, an additional focus is on the use of partitioned solution procedures to couple separate: fluid, thermal, and structural models. The response of a carbon-carbon hypersonic skin panel in Mach 12 flow is investigated. It is determined that the 2-way coupled quasi-static solution is converged for O(10) thermal time steps and O(10) deformation updates in aerodynamic heating computations within the characteristic thermal response time. Subsequently, it is shown that including the dependence of aerodynamic heating on structural deformation results in O(20%) increase in peak skin temperature and O(200%) increase in surface ply failure index for relatively modest peak displacement, O(2%) of panel length. Dynamic aeroelastic stability of the quasi-static response predictions is verified through the use of short-duration, transient dynamic response tests that use subiterations to converge the fluid-structural response. Additionally, a long-duration, staggered dynamic solution procedure is investigated. It is determined that the use of sequential cold restarts of the dynamic structural solution results in numerical errors that can alter the predicted response.