ADAPTIVE SHOCK CONTROL BUMPS

Lead Research Organisation: Imperial College London
Department Name: Dept of Aeronautics

Abstract

The rising demand for air travel requires the engineering community to improve the aerodynamic efficiency of aircraft, especially in the context of tightening emission regulations such as the Vision 2020 directive. The plateau reached in the refinement of airframe technology in the last few decades has shifted the research focus on flow control devices such as shock control bumps (SCBs). Other flow control techniques include variable camber aerofoils, or the use of suction and vortex generators, but, as the two EUROSHOCK programs have highlighted, shock control bumps are one of the most promising shock control systems (Stanewsky et al. 1997, Stanewsky et al. 2002).

Shock control bumps have the potential to improve the performance of transonic wings through the manipulation of the airflow over the suction surface. They generally take the form of small local deformations consisting of a ramp upstream of the nominal location of the normal shock wave, which generates near-isentropic compression waves and bifurcates the normal shock, followed by a tail, which brings the flow back to the aerofoil surface (Bruce and Colliss 2014). Shock control bumps can either be 2D or 3D. In the first case, the bump profile is constant along the span; in the second, several bumps are placed along the wing.

One of the main issues associated with (both 2D and 3D) shock control bumps is that the beneficial smearing effects and stagnation pressure savings achieved at design are accompanied by an increase in drag off-design, when the position of the shock wave relative to the bump crest has changed.

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509486/1 01/10/2016 31/03/2022
1817443 Studentship EP/N509486/1 01/10/2016 31/03/2020 Michela Gramola
 
Description During my research, I have studied the beneficial effect of applying 2D adaptive shock control bumps to the upper surface of next generation transonic wings through experiments and Computational Fluid Dynamics (CFD) simulations. The flexible nature of these bumps makes this a complex fluid-structure-interaction problem. In particular, I have focused on their impact on wave drag reduction, and I have found that adaptive bumps can reduce wave drag over a wider operational envelope than fixed-geometry bumps as geometrical deformations can mitigate their well known off-design performance penalty. I have also investigated how the presence of a shock control bump affects the transient shock behaviour in wind tunnel testing and I have related the presence of instability regions to the drag-reducing potential of the bumps. Finally, I have developed and characterised a technique to accurately measure model deformation during wind tunnel experiments: point-tracking photogrammetry applied to a flexible surface.
Exploitation Route I believe that the additional knowledge generated on the fluid-structure-interaction features of adaptive bumps, their wave drag reduction potential, and their impact on the transient shock behaviour can be used by others to keep investigating adaptive shock control bumps and determine their suitability for the application on next generation transonic wings. In addition, the experimental technique that I have developed can be used in wind tunnel experiments.
Sectors Aerospace, Defence and Marine