Thermal reduced order model adaptation to aero-thermo-structural interactions

The application of reduced order modeling (ROM) techniques to hypersonic structures has gained significant momentum in recent years owing to its ability to deliver accurate structural-thermal response predictions with reduced computational costs relative to full order methods. Accurate response prediction is dependent on the selection of an appropriate basis which is relatively straightforward for single discipline problems. For structural problems, the basis is comprised of the natural mode shapes of the structure and duals, which are modes constructed to capture the nonlinear membrane stretching effect. Similarly, eigenvectors of the generalized conductance-capacitance eigenvalue problem have been shown to provide an adequate basis for thermal ROMs. Selecting a basis for multidisciplinary problems may be significantly more difficult because of the unexpected behavior that may result from the interactions between the disciplines. It is proposed here that reduced order models first be developed as above on single discipline arguments, then be adapted, specifically their bases, to account for the interaction as the computations proceed. An adaptive model is most likely needed for the thermal problem, since the corresponding eigenvalues are more densely clustered than for the structural problem, resulting in significant contributions from more modes as the thermal loading conditions change. To investigate these concepts, a representative hypersonic panel is considered here and a thermal reduced order model of it is first developed and validated under single discipline conditions. The applicability of this basis to represent the temperature distribution resulting from a fully coupled aero-thermo-structural interaction is then assessed and a methodology to adapt the thermal basis is proposed and discussed.