Research Projects

The surge in the global demand for energy has pushed the performance of every engineering product to its limit. In industries such as the air transport and process industry, this requires operation at faster speeds and at greater through-flow rates. This results in larger airspeeds over components such as aircraft wings, control surfaces, intakes, and prime mover components such as the blades of compressors and turbines so that they exchange energy with the surrounding fluid in the most efficient manner. In doing so, a limiting phenomenon is the occurrence of a shock wave, as it prevents further improvement in performance without an associated penalty. The present work addresses one such phenomenon pertaining to the unsteady effects of shock waves generated by vibrating surfaces, where the prediction of the unsteady forces and heating load is still challenging. Specifically, the project proposes to study the interaction between an oscillating oblique shock wave and the boundary layer in the transonic (approximately Mach 1.2) regime using experimental techniques. The motivation for the study stems from the shock wave oscillation that causes adverse aeroelastic interactions in geometries, such as flow over an aircraft wing, in intakes and nozzles, and flows over a transonic compressor or turbine blade. The overall objective is to understand this interaction and develop a model to predict the unsteady pressure fluctuations that develop at the solid surface as the shock wave interacts with boundary layers of different characteristics. The experiments are proposed to be conducted in an intermittent blowdown transonic tunnel by interfacing with existing infrastructure, such as a compressed air system. A distinctive feature of the proposed tunnel is the ability to generate an oscillating oblique shock wave, to emulate the low-amplitude oscillation in a vibrating system. The unsteadiness is generated by introducing periodic perturbations in the flow at the second throat of the tunnel. The local boundary layer properties will be modified using trip wires. The primary measurements are the wall static pressures taken in the vicinity of the shock, whose amplitudes indicate the quantitative unsteadiness in the force experienced by the reference surface. Also, high-speed Schlieren imaging will further provide information on shock unsteadiness. By subjecting the time series data to further analysis, such as spectral and low-order modelling, the unsteady loads can be explained and predicted. Such an understanding will help developers design the aerodynamic shapes of the structures on which shocks are created. The calculation of such loads is critical, failing which the components may fail when tested, requiring a costly redesign.