Development and validation of a Fluid-Structure Interaction Coupling Tool for Mach 4.0 Supersonic Flows

The work has been carried out at DLR - Deutsches Zentrum für Luft- und Raumfahrt, Institute of Aerodynamics and Flow Technology, Supersonic and Hypersonic Technology Department, Köln, Germany.

Advisers at DLR:
Dr. Dennis Daub DLR - Deutsches Zentrum für Luft- und Raumfahrt
Dr. Sebastian Willems DLR - Deutsches Zentrum für Luft- und Raumfahrt
KTH adviser and examiner: Prof. Mihai Mihaescu

Abstract:
The design of supersonic and hypersonic vehicles, like reusable launchers and high-speed aircraft, must account for extreme aerothermodynamic loads that can trigger complex Fluid–Thermal–Structural Interaction (FTSI) phenomena. These include flutter and thermal buckling, potentially leading to structural fatigue or even catastrophic failure. To predict such interactions, this work develops an efficient aeroelastic coupling tool and methodology using DLR’s Tau flow solver along with Ansys ® structural and thermal solvers within the ATSI framework [7]. The resulting tool aims to support the preparation and interpretation of future experimental campaigns. The methodology was validated using three benchmark cases of increasing complexity based on the canonical problem of shock impingement on a thin elastic panel. A first verification was conducted using a static setup where the significance of thermal effects was highlighted. The second case, where dynamics were introduced, posed a stringent test to capture the expected stable Limit Cycle Oscillation (LCO) under the complete absence of dissipative mechanisms. A quasi-steady formulation was used to improve efficiency, which proved accurate, while structural velocity effects, initially neglected due to a limitation on the steady-state formulation of the Tau solver, proved to have significant effects when introduced through Enriched Piston Theory (EPT). Added structural damping showed similar improvements. The third case, based on an experimental configuration, exhibited higher uncertainty but maintained good agreement. Further enhancements are expected through a simplified implementation of EPT for viscous setups and additional sensitivity studies to be performed on timestep refinement and structural modelling improvements. Despite challenges in the last configuration, the developed tool demonstrated strong predictive capabilities and good efficiency, establishing a robust foundation for future coupled studies.

Keywords:
Fluid-Structure Interaction, Fluid-Structure-Thermal Interaction, Limit Cycle Oscillation, Panel Vibration, Piston Theory, Shock-Wave/Boundary-Layer Interaction