Effect of turbulence on the wake of a wall-mounted cube

Hearst, R. Jason; Gomit, Guillaume; Ganapathisubramani, Bharathram

doi:10.1017/jfm.2016.565

Cited by 78 publications

(69 citation statements)

References 30 publications

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“…At sufficiently far downstream cross‐sectional planes, the high‐frequency peak disappears and instead a low energy peak is observed at

S t \approx 0.1

. This Strouhal number is comparable to

S t = 0.06 - 0.08

which was observed for a backward facing step (Eaton, ; Le et al, ), and

S t = 0.13 - 0.14

for a cubical obstacle (Hearst et al, ). Particularly, Eaton () and Le et al () attributed the peak Strouhal number in a backward facing step flow to a low‐frequency flapping motion of the reattachment location.…”

Section: Resultsmentioning

confidence: 67%

Experimental Investigation of Three‐Dimensional Flow Structure and Turbulent Flow Mechanisms Around a Nonsubmerged Spur Dike With a Low Length‐to‐Depth Ratio

Jeon

Lee

Kang

2018

Water Resources Research

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Flume experiments were conducted to investigate the three-dimensional flow structure and turbulent flow mechanisms around a nonsubmerged, sidewall-attached rectangular spur dike with a low length-to-depth ratio. Velocity measurements show that the wake of the spur dike in the middepth region consists of a single, large recirculation zone, while that in the near-bed region is composed of a horizontal recirculation zone and a corner vortex with its axis perpendicular to the flume sidewalls. A horseshoe vortex system observed in front of the spur dike is found to interact with the downstream recirculation zone, which results in the increase in lateral turbulent mixing especially in near-bed regions. Another vortex, which rotates in the opposite direction to the horseshoe vortex, is found beneath the free surface in front of the spur dike, which is associated with increased free surface elevation and its fluctuation. Power spectra of the transverse velocity show evidence of a periodic behavior of the near-wake shear layer emanating from the tip of the spur dike with a Strouhal number of about 2. It is also shown that the two experiments conducted at different Reynolds and Froude numbers show very similar flow fields in spite of large differences in free surface elevations, which indicates that the effects of free surface deformation on mean velocities and Reynolds stresses are marginal.

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“…At sufficiently far downstream cross‐sectional planes, the high‐frequency peak disappears and instead a low energy peak is observed at

S t \approx 0.1

. This Strouhal number is comparable to

S t = 0.06 - 0.08

which was observed for a backward facing step (Eaton, ; Le et al, ), and

S t = 0.13 - 0.14

Section: Resultsmentioning

confidence: 67%

Experimental Investigation of Three‐Dimensional Flow Structure and Turbulent Flow Mechanisms Around a Nonsubmerged Spur Dike With a Low Length‐to‐Depth Ratio

Jeon

Lee

Kang

2018

Water Resources Research

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“…Figure 7 represents U maps in both cases. In these figures, the classical behaviour of the flow past a wall-mounted object can be seen [10,27]: the flow separates at the leading edges of the cube into the outer steady region and the recirculation area downstream of the cube. A shear layer develops in-between and then the flow reattaches.…”

Section: Reference Case Of the Wall-mounted Cubementioning

confidence: 99%

“…The wall-mounted cube is a common obstacle studied in wind tunnels or water tanks. For this obstacle, we count the studies performed by Hearst et al [10] at R e = 1.8 × 10 6 or Castro & Robins [6] going up to Re = 10 5 , both in wind tunnels. Hearst at al.…”

Section: Introductionmentioning

confidence: 99%

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Experimental analysis of the floor inclination effect on the turbulent wake developing behind a wall mounted cube

Ikhennicheu¹,

Gaurier²,

Druault³

et al. 2018

European Journal of Mechanics - B/Fluids

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The present study aims at investigating turbulence characteristics in high flow velocity areas like those suitable for marine energy application. The Reynolds number, based on the rugosity height and mean flow velocity, is rather high: . For that purpose, experiments are carried out in a flume tank with as high as achievable in Froude similitude (in the tank: and ). Obstacles are canonical wall-mounted elements chosen to be representative of averaged bathymetric variations: a cube and a cube followed by an inclined floor. First, the wake topology past a canonical wall-mounted cube is illustrated from PIV measurements. Results show a flow behaviour already observed in the literature but for different upstream conditions ( and turbulence intensity). Second, the impact of the addition of an inclined floor is studied. It is shown that the inclination causes a squeezing of the cube wake that strongly impacts the shape and intensity of the shear layer (up to 10% more intense with the inclined floor). To fully grasp the turbulence organization in the wake for both test cases, an analysis using both complementary Proper Orthogonal Decomposition and quadrant method is performed. POD acts as a turbulent noise filter and quadrant method decomposes turbulent events. Results show the predominance of ejection (Q2) and sweep (Q4) events in the flow Reynolds shear stress. Q2 events are more energetic although Q4 events prevail. It is observed that the inclined floor causes a persistence of Q2 and Q4 events higher into the water column, more than the impulsion given by the floor altitude variations. The rise of the cube wake due to the inclined floor is thus illustrated using Q4 predominance area. Highlights► Tests are carried out on a wall-mounted cube with and without an inclined floor representative of seabed elements, in Froude similitude with high Reynolds number. ► PIV measurements are performed in horizontal and vertical measurement planes and spatial analyses are performed. ► POD filter and quadrant analyses show the rise of coherent energetic structures.

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“…Hearst et al [23]. They studied experimentally the influence of turbulence on the flow around a wall mounted cube in a turbulent boundary layer using particle image velocimetry and hot wire anemometry.…”

Section: Introductionmentioning

confidence: 99%

Impact of Geometry of Electronic Components on Cooling Improvement

Meghdir¹,

Benabdallah²,

Dellil³

2019

IJHT

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In this paper we have numerically treated the thermal and dynamic aspect of different prismatic bodies simulating electronic components, heated and mounted on the lower wall of a channel. These components are cooled by forced convection using a turbulent flow flowing along the channel and an impinging jet flowing from the upper wall perpendicularly to them. The fluid used is air of which we vary the Reynolds number in order to see its impact on the component cooling. We opted for four different geometries of the prismatic body taken in the same working conditions. We compared the results obtained to propose one of the geometries which will permit a better evacuation of the heat, thus a good cooling of the component. By combining an unstructured mesh with the finite volume method, the solution is obtained by using the SIMPLE algorithm (pressure-velocity coupling). Turbulence is modeled using the so-called Shear Stress Transport (SST) model to evaluate the heat exchange in these configurations. This numerical study is carried out with the code ANSYS.CFX 14 to evaluate the thermal exchanges.

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Effect of turbulence on the wake of a wall-mounted cube

Cited by 78 publications

References 30 publications

Experimental Investigation of Three‐Dimensional Flow Structure and Turbulent Flow Mechanisms Around a Nonsubmerged Spur Dike With a Low Length‐to‐Depth Ratio

Experimental Investigation of Three‐Dimensional Flow Structure and Turbulent Flow Mechanisms Around a Nonsubmerged Spur Dike With a Low Length‐to‐Depth Ratio

Experimental analysis of the floor inclination effect on the turbulent wake developing behind a wall mounted cube

Impact of Geometry of Electronic Components on Cooling Improvement

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