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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Investigation of a Sub-Boundary Layer Vortex Generator for the Control of Separation in Boundary Layer-Shock Wave Interaction

Author: ZARE SHAHNEH, Agolghasem

Year: 2007

Supervisor(s): Fariborz Motallebi

It is well known that in transonic flows, shock waves are formed over the wings of aircraft. Depending on the strength of the shock wave and the state of the boundary layer, a region of boundary layer separation can occur downstream of the shock. This separation can lead to drastic changes in the flow over the wing which in turn can lead to an increase in drag, reduction of lift and buffeting.

The aim of this investigation is to assess the potential of sub-boundary layer devices (Sub Boundary Vortex Generators, SBVG) to control a normal shock wave/boundary layer interaction. The experiments have been performed at a nominal Mach number of 1.4 and a freestream Reynolds number of 16 x 106 per unit length. Detailed measurements of a fully developed flat plate turbulent boundary layer were used to assess the performance of 8 different SBVG configurations. The SBVG performance was assessed by comparing flow before separation and after the reattachment. Mean flow data such as static and surface total pressure distributions, boundary layer total pressure and velocity profile, surface oil flow visualisation and schlieren method were used in evaluating the performance of SBVGs.

The experimental results indicate that the optimum SBVG for the current flow condition is a pair of Tetrahedral Vortex Generator with 30mm length with base and height dimensions of 3mm by 3mm, which the height is 40% of the boundary layer thickness. The leading and trailing edge of this configuration were 18mm and 3 mm correspondingly.