Time-Marching Considerations for Response Prediction of Structures in Hypersonic Flows

This study examines time-marching procedures for fluid–thermal–structural analysis using time-accurate thermal and structural solvers combined with quasi-steady aerothermodynamic models. Four coupling schemes are considered, including a conventional scheme with explicit time integration, a basic loose coupling scheme with implicit time integration, a predictor-based implicit scheme, and a subiteration-based implicit scheme with strong coupling. The first three schemes also incorporate structural subcycling, in which the structural time step is smaller than the thermal time step. Convergence studies reveal that the conventional explicit and basic implicit schemes are first-order accurate in time, whereas the predictor implicit and strong implicit schemes retain second-order accuracy. Structural subcycling is found to preserve the order of accuracy for the predictor implicit scheme. Additional analysis of the long-term behavior of the solution of two configurations indicates that the conventional explicit and basic implicit schemes can predict spurious behavior at larger time steps compared to the predictor implicit and strong implicit schemes. Finally, the predictor implicit scheme is found to provide significant computational savings for both a dynamically stable response and a dynamically unstable limit-cycle response compared to the other schemes.