Experimental FSI study of adaptive shock control bumps

Gramola, Michela; Bruce, Paul J.; Santer, Matthew

doi:10.1016/j.jfluidstructs.2018.05.005

Cited by 22 publications

(12 citation statements)

References 13 publications

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“…The tunnel is operated using a LabVIEW program, consisting of a proportional-integral-derivative (PID) controller, which controls the pressure in the settling chamber by adjusting the aperture of a pneumatic pressure valve. The desired stagnation pressure is typically obtained with a standard deviation of 0.16% [14]. The inherent low frequency stagnation pressure oscillations (of the order of 1 Hz) are somewhat representative of the unsteady flow conditions encountered by a real transonic wing.…”

Section: Methodsmentioning

confidence: 99%

“…The bump has a loaded beam geometry, with y 1 = 1.1%L at x 1 /L = 0.25 and y 2 = 1.6%L at x 2 /L = 0.5. This bump shape was chosen based on previous experiments on adaptive bumps carried out at Imperial College [14]. The computational results presented in the next Sections provide a methodology to estimate wave drag from experiments, and do not depend on the exact bump shape.…”

Section: Cfd Simulationsmentioning

confidence: 99%

“…In both plots, M was calculated from pressure ratios (P/P 0 ) on the floor (either from pressure tappings on the flexible bump or from computational results at y/L = 3 × 10 −5 for the solid bump), assuming that P 0 = P 0,in , i.e. neglecting stagnation pressure losses due to the shocks, which leads to an inaccuracy of the order of 1% in M estimation [14]. On design, when the rear leg impinges on the flexible surface close to the bump crest (e.g.…”

Section: A Flow Featuresmentioning

confidence: 99%

“…Specifically: the streamwise location of the triple point and the intersection between the rear leg of the λ-shock and the flexible surface. As described in [14], the triple point position (x TP ) is detected from schlieren images, while the location of the rear leg of the lambda shock (x RL ) is defined to be the point at which M = 1, according to the pressure readings on the bump. Throughout this paper, the shock Given that the wind tunnel exhausts to atmosphere (which fixes the stagnation pressure loss in the working section for a given inlet P 0 ) and that viscous losses in the supersonic boundary layer are greater than in the subsonic boundary layer, in previous studies [14] P 0 /P e has been regarded as an indication of the wave drag associated with the λ-shock structure: thus, for a given shock position, a lower P 0 /P e corresponds to lower wave drag.…”

Section: Average Shock Positionmentioning

confidence: 99%

“…As described in [14], the triple point position (x TP ) is detected from schlieren images, while the location of the rear leg of the lambda shock (x RL ) is defined to be the point at which M = 1, according to the pressure readings on the bump. Throughout this paper, the shock Given that the wind tunnel exhausts to atmosphere (which fixes the stagnation pressure loss in the working section for a given inlet P 0 ) and that viscous losses in the supersonic boundary layer are greater than in the subsonic boundary layer, in previous studies [14] P 0 /P e has been regarded as an indication of the wave drag associated with the λ-shock structure: thus, for a given shock position, a lower P 0 /P e corresponds to lower wave drag. x TP /L = 0.38, the presence of a clear lambda means that the flow is compressed more efficiently by an oblique shock (front leg) and a weak normal shock (rear leg) below the triple point (y/L < 0.6), with a pressure recovery coefficient close to 1 outside the boundary layer.…”

Section: Average Shock Positionmentioning

confidence: 99%

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Off-design performance of 2D adaptive shock control bumps

Gramola

Bruce

Santer

2020

Journal of Fluids and Structures

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Adaptive shock control bumps can exploit the on-design drag-reducing potential of 2D bumps, while mitigating their off-design performance deterioration through geometric modifications. In this study, experiments and simulations have been employed to investigate the wave-drag reducing potential of (actuated and unconstrained) 2D adaptive shock control bumps over a wide range of shock positions. Experiments were carried out in the Imperial College supersonic wind tunnel, modelling the adaptive bump as a flexible surface placed beneath a Mach 1.4 shock wave. 2D RANS CFD simulations of the flow in a parallel channel with a solid bump complement experiments. Wave drag was demonstrated to be proportional to the ratio of inlet to exit stagnation pressure in a blow-down wind tunnel for a given shock position. The shock exhibits a hysteretic behaviour when travelling in the wind tunnel working section, governed by the wave drag reducing potential of the bump. The actuated adaptive bump tested reduces wave drag over a wider operational envelope than solid bumps as experiments revealed the presence of three preferred structural configurations, which lead to a significantly enlarged hysteresis region. Finally, tests on unconstrained bumps were shown to increase wave drag, both on-and off-design, due to the unfavourable bump shapes that result from (only) passive actuation, suggesting that some constraints are required to achieve desirable surface deformations.

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Section: Methodsmentioning

confidence: 99%

Section: Cfd Simulationsmentioning

confidence: 99%

Section: A Flow Featuresmentioning

confidence: 99%

Section: Average Shock Positionmentioning

confidence: 99%

Section: Average Shock Positionmentioning

confidence: 99%

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Off-design performance of 2D adaptive shock control bumps

Gramola

Bruce

Santer

2020

Journal of Fluids and Structures

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Photogrammetry for accurate model deformation measurement in a supersonic wind tunnel

2018

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The interest in adaptive devices for high-speed applications leads to the need for an accurate and reliable technique to obtain model deformation measurements during experiments. Point-tracking photogrammetry has been applied to supersonic wind tunnel testing, using four Phantom high-speed cameras placed on either side of the working section, where coded targets were applied to the surface of interest. Calibration experiments on a solid plate beneath a M = 1.4 normal shock and a M = 2 oblique shock allowed the quantification of the sources of optical distortion, namely the wind tunnel glass windows and aerodynamic effects (the lower pressure in the working section and the interaction between shock waves and the boundary layer). A correction matrix was applied to account for the optical distortion due to the glass, and the root-mean-square error due to aerodynamic effects ( < 0.03 mm) is believed to be negligible for applications with significant displacements (of the order of 1 mm). The application of photogrammetry to a flexible shock control bump has shown that the bump shape can be detected accurately, while disclosing some complex 3D effects that could not have been revealed by spanwise-averaged techniques such as schlieren photography.

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