Seminars

Abstract: The design of flight vehicles that operate in the supersonic regime is often characterized by lightweight structures with high compliance. This makes them susceptible to adverse fluid-structure interactions. The presence of geometric discontinuities such as control surfaces or fins can induce compression shocks that can interact with the boundary layer, leading to flow separation. The interaction of flow, compression shock and structural dynamics is very difficult to model and currently only poorly understood. It is the goal of this work to investigate such an interaction experimentally and to characterize the changes in the system dynamics that result from the impinging compression shock.

This study investigates the interaction of compliant panels of different thickness with a Mach 2 flow in the presence of an impinging shock. The panels are inserted in a wind tunnel just upstream of a 20° compression ramp. A ramp induced shock impinges on the panel leading to separation of the turbulent boundary layer close to the ramp starting at about 80% of the panel length. The deformation of the panels is measured using stereoscopic digital image correlation. A novel methodology to obtain modal parameters from high-speed video is implemented and validated. The surface pressure field of the panels is measured using a ruthenium-based polymer-ceramic pressure sensitive paint. The pressure and deformation data are recorded simultaneously. The response of the thin panels exhibits coupling with the flow. Linearized potential flow theory is used to predict the surface pressure fluctuations from the deformation and leads to good agreement in the flow region upstream of the shock impingement. Comparisons are made between tests with and without the compression ramp. The results show that for the given flow conditions the vibratory response of a compliant panel with a ramp-induced impinging shock can be approximated by its response without the ramp and only small adjustments are needed.