Control of cavity tones using a spanwise cylinder

Keirsbulck, Laurent; Hassan, Marwan; Lippert, Marc; Labraga, L.

doi:10.1139/p08-086

Cited by 11 publications

(12 citation statements)

References 20 publications

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“…Hotwire measurements of velocity profiles at this location showed that for low velocity (U 0 = 2 m/s) the boundary layer was fully developed [12]. This was also the case for U 0 = 43 m/s [13].…”

Section: Wind Tunnel and Cavity Model Detailssupporting

confidence: 58%

“…The sound pressure levels and normalized velocity spectra for "no control", cylinder "control" cases and with a shaped cylinder for L/H = 0.2 with respect to the optimal cylinder position (y c /d = 1.67), permitted to compare "shedding on" performance with "shedding off" performance. It was confirmed [13] that the cylinder resulted in a sharp high energetic peak in the velocity spectrum whereas the shaped cylinder exhibited no such energetic peak. El Hassan et al [16] found that the noise frequency of the present studied configuration is around 151Hz.…”

Section: Cylinder and Shaped Cylinder Control Of The Cavity Resonancementioning

confidence: 84%

“…For the same cavity configuration, the authors showed in previous studies (El Hassan et al [12], Keirsbulck et al [13]) that the cylinder in cross flow is an effective device for suppressing acoustic resonance. It was stated in the literature [4][5][6] that the high frequency forcing (pulsing effect) of the cylinder is responsible for the cavity tone attenuation.…”

Section: Cylinder and Shaped Cylinder Control Of The Cavity Resonancementioning

confidence: 92%

“…The vertical position of the cylinder to the wall (y c = 10 mm) is chosen to allow an optimal control of the cavity resonance [13]. The cylinder induces a wake of vortices at a frequency dependent on its diameter and freestream velocity.…”

Section: Wind Tunnel and Cavity Model Detailsmentioning

confidence: 99%

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Passive control of deep cavity shear layer flow at subsonic speed

Hassan

Keirsbulck²

2017

Can. J. Phys.

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Passive control of the flow over a deep cavity at low subsonic velocity is considered in the present paper. The cavity length-to-depth aspect ratio is L/H = 0.2. particle image velocimetry (PIV) measurements characterized the flow over the cavity and show the influence of the control method on the cavity shear layer development. It is found that both the “cylinder” and the “shaped cylinder”, placed upstream from the cavity leading edge, result in the suppression of the aero-acoustic coupling and highly reduce the cavity noise. It should be noted that the vortical structures impinge at almost the same location near the cavity downstream corner with and without passive control. The present study allows to identify an innovative passive flow control method of cavity resonance. Indeed, the use of a “shaped cylinder” presents similar suppression of the cavity resonance as with the “cylinder” but with less impact on the cavity flow. The “shaped cylinder” results in a smaller shear layer growth than the cylinder. Velocity deficiency and turbulence levels are less pronounced using the “shaped cylinder”. The “cylinder” tends to diffuse the vorticity in the cavity shear layer and thus the location of the maximum vorticity is more affected as compared to the “shaped cylinder” control. The fact that the “shaped cylinder” is capable of suppressing the cavity resonance, despite the vortex shedding and the high frequency forcing being suppressed, is of high interest from fundamental and applied points of view.

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Section: Wind Tunnel and Cavity Model Detailssupporting

confidence: 58%

Section: Cylinder and Shaped Cylinder Control Of The Cavity Resonancementioning

confidence: 84%

Section: Cylinder and Shaped Cylinder Control Of The Cavity Resonancementioning

confidence: 92%

Section: Wind Tunnel and Cavity Model Detailsmentioning

confidence: 99%

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Passive control of deep cavity shear layer flow at subsonic speed

Hassan

Keirsbulck²

2017

Can. J. Phys.

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“…Stanek et al (2007) argued that this phenomenon was due to the high-frequency forcing triggered by the vortex shedding behind the small rod which generated perturbations that rendered the mean flow stable. Keirsbulck et al (2008), on the other hand, argues that it is the steady part of the forcing related to the mean drag of the control cylinder which is responsible for the stabilization.…”

Section: Introductionmentioning

confidence: 99%

Open-loop control of cavity oscillations with harmonic forcings

Sipp

2012

J. Fluid Mech.

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This article deals with open-loop control of open-cavity flows with harmonic forcings. Two-dimensional laminar open-cavity flows usually undergo a supercritical Hopf bifurcation at some critical Reynolds number: a global mode becomes unstable and its amplitude converges towards a limit cycle. Such behaviour may be accurately captured by a Stuart–Landau equation, which governs the amplitude of the global mode. In the present article, we study the effect on such a flow of a forcing characterized by its frequency ${\omega }_{f} $, its amplitude ${E}^{\ensuremath{\prime} } $ and its spatial structure ${\mathbi{f}}_{E} $. The system reacts like a forced Van der Pol oscillator. In the general case, such a forcing modifies the linear dynamics of the global mode. It is then possible to predict preferred forcing frequencies ${\omega }_{f} $, at which the global mode may be stabilized with the smallest possible forcing amplitude ${E}^{\ensuremath{\prime} } $. In the case of a forcing frequency close to the frequency of the global mode, a locking phenomenon may be observed if the forcing amplitude ${E}^{\ensuremath{\prime} } $ is sufficiently high: the frequency of the flow on the limit cycle may be modified with a very small forcing amplitude ${E}^{\ensuremath{\prime} } $. In each case, we compute all harmonics of the flow field and all coefficients that enter the amplitude equations. In particular, it is possible to find preferred forcing structures ${\mathbi{f}}_{E} $ that achieve strongest impact on the flow field. In the general case, these are the optimal forcings, which are defined as the forcings that trigger the strongest energy response. In the case of a forcing frequency close to the frequency of the global mode, a forcing structure equal to the adjoint global mode ensures the lowest forcing amplitude ${E}^{\ensuremath{\prime} } $. All predictions given by the amplitude equations are checked against direct numerical simulations conducted at a supercritical Reynolds number. We show that a global mode may effectively be stabilized by a high-frequency harmonic forcing, which achieves suppression of the perturbation frequencies that are lower than the forcing frequency, and that a near-resonant forcing achieves locking of the flow onto the forcing frequency, as predicted by the amplitude equations.

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