PASSIVE CONTROL OF SHOCKWAVE AND BOUNDARRY LAYER INTERACTION

Abstract

Shock-wave/boundary-layer interactions (SWBLIs) are ubiquitous in high-speed flows such as the inlet of supersonic engine. SWBLIs can cause boundary layer separation which may in turn result in a large increase in aerodynamic drag and unsteady loads. In the most severe situation, this can lead to a dramatic performance degradation and failure of high-speed vehicles. Therefore, understanding and controlling SWBLIs are very important for the design and safe operation of supersonic and hypersonic vehicles. Micro vortex generators (MVGs) have widely been used to control separation due to SWBLIs. However, since a typical MVG has a height on the order of the boundary layer thickness, it produces a considerable amount of parasitic drag which reduces the net gain in flow control. Herringbone riblets are a new type of directional surface roughness which is inspired by the surface pattern on bird secondary flight feathers. They are capable of inducing secondary cross-stream flow structures within a boundary layer. In the research work reported in this thesis, a spanwise array of herringbone riblets strips is applied upstream of the interaction region between an impinging shockwave and a turbulent boundary layer developing along a flat plate boundary layer at a freesteram Mach number of 1.85. Several experimental techniques are used to examine the effect of herringbone riblets on the characteristics of the SWBLIs. It shows that despite that the height of the riblets is just 1.7 % of the local thickness of the undisturbed boundary layer, a profound modification to the shockwave-boundary layer interaction zone is observed. The results exhibit that herringbone riblets not only mitigate the boundary layer separation but alleviate the unsteady oscillation of shockwave induced by SWBLIs. Following this, the findings of the computational investigation reveal that control effects are attributed to the large-scale secondary flow structures produced by the yawed riblets. Those findings suggest that herringbone riblet is a promising method for flow control in the engineering application.

Date of Award	1 Mar 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Lin Li (Co Supervisor) & Shan Zhong (Main Supervisor)