The effects of wake splitter plates on bluff-body flow in the range 104 &lt; R &lt; 5 × 104. Part 2

Apelt, C. J.; West, G. S.

doi:10.1017/s0022112075002479

Cited by 195 publications

(76 citation statements)

References 2 publications

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“…Roshko (1954) showed that, when a long splitter plate is attached downstream of a circular cylinder with diameter D, c d is reduced as a result of the vortex shedding suppression. Apelt and West (1975) performed experiments on splitter plates past bluff bodies and investigated the effect of L sp , where L sp is the length of the splitter plate. They found that regular vortex shedding is completely suppressed when the reattachment of the flow occurs on the splitter plate.…”

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confidence: 99%

Vortex shedding effects in grid-generated turbulence

2016

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The flow on the centerline of grid-generated turbulence is characterised via hot-wire anemometry for 3 grids with different geometry: a regular grid (RG60), a fractal grid (FSG17) and a single square grid (SSG).Thanks to a higher value of the thickness t0 of its bars, SSG produces greater values of turbulence intensity T u than FSG17, despite SSG having a smaller blockage ratio. However the higher T u for SSG is mainly due to a more pronounced vortex shedding contribution. The effects of vortex shedding suppression along the streamwise direction x are studied by testing a new 3D configuration, formed by SSG and a set of four splitter plates detached from the grid (SSG+SP). When vortex shedding is damped, the centerline location of the peak of turbulence intensity x peak moves downstream and T u considerably decreases in the production region. For FSG17 the vortex shedding is less intense and it disappears more quickly, in terms of x/x peak , when compared to all the other configurations. When vortex shedding is attenuated, the integral length scale Lu grows more slowly in the streamwise direction, this being verified both for FSG17 and for SSG+SP.In the production region, there is a correlation between the vortex shedding energy and the skewness and the flatness of the velocity fluctuations. When vortex shedding is not significant, the skewness is highly negative and the flatness is much larger than 3. On the opposite side, when vortex shedding is prominent, the non-Gaussian behaviour of the velocity fluctuations becomes masked.

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confidence: 99%

Vortex shedding effects in grid-generated turbulence

2016

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“…This flow pattern almost exactly repeats over time, and the frequency of vortex shedding is St ≡ f D/u ∞ = 0.161, which is somewhat lower than that from a cylinder in a free space (St = 0.209 based on the formula by Fey, König & Eckelmann 1998). We may be able to explain this trend in terms of the experimental fact that the shedding frequency decreases when the wake is disrupted by a splitter plate (Apelt & West 1975).…”

Section: Resultsmentioning

confidence: 90%

Effects of a synthetic jet acting on a separated flow over a hump

Suzuki

2006

J. Fluid Mech.

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The effects of an oscillatory zero-net-mass-flux jet (i.e. synthetic jet) acting on a separated flow over a hump are investigated in terms of two actuation parametersactuator position and forcing frequency. By considering the vorticity flux balance and introducing a centroid of vorticity production over the hump surface, lift and drag acting on the hump can be expressed as a function of this centroid and the rate of vorticity production. To study the parametric dependence of lift and drag, direct numerical simulation (DNS) is performed by solving compressible, unsteady, laminar flows over a half-cylindrical hump in two dimensions. The DNS results show that periodic actuation significantly reduces the rate of vorticity production at the wall and shifts the centroid upstream so that the drag is reduced and the lift is increased, respectively. When the actuation parameters are varied, it is found that the lift is governed by the horizontal coordinate of the vorticity-production centroid, while the drag is determined by both the vertical coordinate of the centroid and the rate of vorticity production over the hump. This paper explains by using ideal flow models that the vorticity-production centroid is controlled by two factors: one is the actuator position at which clockwise vorticity is generated, and the other is the point where the separation vortex is pinched off, thereby the clockwise vorticity being absorbed.

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“…In [Apelt et al, 1973], the authors run a set of experiments involving splitter plates fixed to the basis of the cylinder, for Re in the range: 10 4 ≤ Re ≤ 5×10 4 . The length l/d = 1 was set as a limit to differentiate between long and short splitter plates.…”

Section: Literature Surveymentioning

confidence: 99%

“…A first group is primarily concerned with the universal dimensionless frequencies (St) of vortex shedding [Roshko, 1954a, Roshko, 1954b, Gerrard, 1966. A second group is concerned with the way the plate affects the flow field and, hence, with its effects on lift and drag [Bearman, 1965, Apelt et al, 1973, Apelt et al, 1975.Finally, a third group focuses on the heat transfer characteristics of the turbulent separated flow region behind the cylinder, as is the case of a later work of his [Igarashi, 1984].…”

Section: Literature Surveymentioning

confidence: 99%