Velocity and surface pressure measurements in an open cavity

Ukeiley, Lawrence; Murray, Nathan E.

doi:10.1007/s00348-005-0948-x

Cited by 105 publications

(47 citation statements)

References 19 publications

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“…In all figures a similar pattern is observed, which is also known from rectangular cavity flows (see e.g. Haigermoser et al 2008;Ukeiley and Murray 2005). Downstream, the fluctuations grow in amplitude and the region spreads in wall-normal direction.…”

Section: Vertical Planesupporting

confidence: 81%

Investigation of the flow in a circular cavity using stereo and tomographic particle image velocimetry

2008

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The turbulent flow over a circular cavity with an aspect ratio of D/H = 2 is investigated by multi-planar stereoscopic particle image velocimetry and with tomographic particle image velocimetry (PIV). The main aim of the study is the flow topology and the turbulent structure of the asymmetrical flow pattern that forms inside the cavity at these specific conditions. The flow field is measured in the vertical symmetry plane to describe the overall recirculation pattern in the cavity and the turbulent shear layer developing from the separation point. In this specific regime the shear layer fluctuations are recognized as those caused by instabilities together with the effect of the incoming boundary layer turbulence. Additional observations performed at several wall-parallel planes at different height inside the cavity allow to further evaluate the secondary flow circulation generated by this asymmetric regime. The observed flow pattern consists of a steady vortex, occupying the entire cavity volume and placed diagonally inside the cavity such to entrain the external flow from one side, capture it into a circulatory motion and eject it from the opposite side of the cavity. The spatial distribution of the turbulent fluctuations also reveals the same structure. The tomographic PIV measurement returns a visual inspection to the instantaneous three-dimensional structure of the turbulent fluctuations, which at the investigated height exhibit a low level of coherence with slightly elongated vortices in the recirculating flow inside the cavity.

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Section: Vertical Planesupporting

confidence: 81%

Investigation of the flow in a circular cavity using stereo and tomographic particle image velocimetry

2008

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“…It was shown that the highest growth rate belongs to the cavity exposed to a turbulent boundary layer, indicating that more momentum is entrained into the cavity compared to a cavity of the same h/D ratio, exposed to a laminar boundary layer. The linear growth of the shear layer thickness in the case of turbulent boundary layer was also confirmed by other studies [23]- [26]. [29].…”

Section: Cavity Flowssupporting

confidence: 84%

“…In another study, a wider range of h/D (0.2-0.7) for nominally two-dimensional rectangular cavities with a turbulent boundary layer (Re D = 2.7×10 5 -3.3×10 5 ) were investigated [26]. Their findings in the case of the shallow cavity (h/D = 0.2) were similar to those described in the previous paragraphs.…”

Section: Cavity Flowssupporting

confidence: 72%

“…The method for determining these two parameters has been described in section 4.10. Murray et al [25], and Ukeiley and Murray [26] indicate that the shear layer separated from the upstream edge of nominally two-dimensional rectangular cavities exposed to turbulent boundary layers displays a similar behaviour, in which growth rate is linear and independent of the geometric proportions of the cavities such as relative depth and length. The behaviour of the shear layer depth will be related to the flow structure in the cavity in the following section, in which the flow structure for cavities with various h/D at 0° yaw angle will be investigated in detail.…”

Section: Behaviour Of the Shear Layermentioning

confidence: 97%

“…(h/D = 0.7), Ukeiley and Murray reported one dominant circulation zone, driven by the shear layer [26]. Using quadratic stochastic estimation, they reconstructed the timedependent behaviour of the flow, and reported flapping of the shear layer regardless of resonant conditions, which they named "breathing".…”

Section: Cavity Flowsmentioning

confidence: 99%

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Experimental and Numerical Study of Flow Structures Associated With Low Aspect Ratio Elliptical Cavities

Khadivi¹,

Savory

2013

Journal of Fluids Engineering

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The flow regimes associated with a 2:1 aspect ratio, elliptical planform cavity in a turbulent flat plate boundary layer have been systematically examined for various depth/width ratios (0.1 to 1.0) and yaw angles (0° to 90°), using a combination of wind tunnel experiments (involving Particle Image Velocimetry and helium bubble visualization) and Computational Fluid Dynamics (CFD) simulations (employing threedimensional steady calculations with the Reynolds Stress model turbulence closure).Satisfactory agreement has been found between the results using the two methods, indicating that the steady numerical simulations can be a cost-effective tool to predict the mean flow features.The flow has been found to be highly dependent on yaw angle and cavity depth. For each of the three broad flow categories specified according to yaw angle, which include the symmetric flow regime (yaw angle = 0°), the straight vortex regime (yaw angle = 90°) and the asymmetric flow regime (15° ≤ yaw angle ≤ 60°) different regimes are found to exist, depending on cavity depth. For each combination of yaw angle and depth, the flow has been analyzed through investigation of shear layer parameters, the three-dimensional vortex structure, pressure distribution and drag, wake flow, and vortex oscillations.While the elliptical cavity flows have been found to have some similarities with those of nominally two-dimensional and rectangular cavities, the three-dimensional effects due to the low aspect ratio and curvature of the walls give rise to features exclusive to low aspect ratio elliptical cavities, including formation of cellular structures at intermediate depths and unique vortex structures within and downstream of the cavity.The three-dimensional flow structure of the flow is most pronounced in the asymmetric regimes with large yaw angles (45° and 60°). The dominant feature in this regime is the formation of a trailing vortex that is associated with high drag and flow oscillations within the cavity.iv Keywords

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Active control of flow separation and structural vibrations of wind turbine blades

Maldonado¹,

Farnsworth²,

Gressick³

et al. 2009

Wind Energy

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The feasibility of using synthetic jet actuators to enhance the performance of wind turbine blades was explored in wind tunnel experiments on a small scale model blade. Using this technique, the global fl ow fi eld over the blade was altered such that fl ow separation was mitigated. Consequently, this resulted in a signifi cant decrease in the vibration of the blade. Global fl ow measurements were conducted, where the moments and forces on the blade were measured using a six component wall-mounted load cell. The effect of the actuation was also examined on the surface static pressure at two spanwise locations; near the blade's root and near its tip. In addition, Particle Image Velocimetry (PIV) technique was used to quantify the fl ow fi eld over the blade. Using synthetic jets, the fl ow over the blade was either fully or partially reattached, depending on the angle of attack, and the Reynolds number. Furthermore, the changes induced on the moments and forces, as well as on the blade vibrations were found to be proportionally controllable by either changing the momentum coeffi cient, the number of synthetic jets used, or by the driving waveform. Finally, a proof-of-concept closed-loop control system was developed to test the ability of using synthetic jet actuators to restore and maintain fl ow attachment and reduce the vibrations in the blade during dynamic pitching maneuvers. The control system demonstrated the ability of synthetic jet actuators to reduce blade vibrations during dynamic motion depending upon their control concept, which might be either pitch or active stall control. 222Active control of fl ow separation and structural vibrations V. Maldonado et al.

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Velocity and surface pressure measurements in an open cavity

Cited by 105 publications

References 19 publications

Investigation of the flow in a circular cavity using stereo and tomographic particle image velocimetry

Investigation of the flow in a circular cavity using stereo and tomographic particle image velocimetry

Experimental and Numerical Study of Flow Structures Associated With Low Aspect Ratio Elliptical Cavities

Active control of flow separation and structural vibrations of wind turbine blades

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