The Unsteady Wake of a Circular Cylinder near a Free Surface

Reichl, Paul J; Hourigan, Kerry; Thompson, Mark C.

doi:10.1023/b:appl.0000014926.99751.b1

Cited by 24 publications

(8 citation statements)

References 21 publications

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“…They provide limited information on the time-dependent forces acting on the cylinder. Reichl, Hourigan & Thompson (2003) have presented some results from computations of the flow at Re = 180, mainly focusing on the evolution of the vorticity field for the metastable state first described by Sheridan et al (1995).…”

Section: Introductionmentioning

confidence: 99%

Flow past a cylinder close to a free surface

2005

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Two-dimensional flow past a cylinder close to a free surface at a Reynolds number of 180 is numerically investigated. The wake behaviour for Froude numbers between 0.0 and 0.7 and for gap ratios between 0.1 and 5.0 is examined. For low Froude numbers, where the surface deformation is minimal, the simulations reveal that this problem shares many features in common with flow past a cylinder close to a no-slip wall. This suggests that the flow is largely governed by geometrical constraints in the low Froude number limit. At Froude numbers in excess of 0.3-0.4, surface deformation becomes substantial. This can be traced to increases in the local Froude number to unity or higher in the gap between the cylinder and the surface. In turn, this is associated with supercritical to subcritical transitions in the near wake resulting in localised free-surface sharpening and wave breaking. Since surface vorticity is directly related to surface curvature, such high surface deformation results in significant surface vorticity, which can diffuse and then convect into the main flow altering the development of Strouhal vortices from the top shear layer, affecting wake skewness and suppressing the absolute instability. The variations of parameters such as Strouhal number and formation length are provided for Froude numbers spanning the critical range. At larger Froude numbers good agreement is obtained with recently published experimental investigations. The previously-seen metastable wake states are observed to occur for similar system parameters to the experiments despite the difference in Reynolds numbers by a factor of about 40. The wake state switching appears to be controlled by a feedback loop. Important elements of the feedback loop include the cyclic generation and suppression of the absolute instability of the wake, and the role of surface vorticity and vortices formed from the bottom shear layer in controlling vortex formation from the top shear layer. The proposed mechanism is presented. Shedding ceases at very small gap ratios (∼ 0.1 − 0.2). This behaviour can be explained in terms of the fluid flux through the gap, vorticity diffusion into the surface and opposite-signed surface vorticity from the strong surface deformation.

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Section: Introductionmentioning

confidence: 99%

Flow past a cylinder close to a free surface

2005

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“…Givler et al [1] studied the wake of a submarine using the finite element method at Re=1.2x10 7 by utilizing the k-ε RANS turbulence model. Reichl et al [2] investigated the wake of a cylinder near the free-surface. They carried out their investigation at low Froude numbers for different immersion ratios and reported significant changes in the Strouhal number, St, as the immersion ratio was changed.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Attack Angle Effect on Flow Characteristics Around Torpedo-Like Geometry Placed Near the Free-Surface via CFD

et al. 2021

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“…mirror, glass and perspex) have a leading impact on the heat transfer from the obstacle in the proximity of a wall. As G decreased from 5 to 0.7 at Re = 180, Strouhal number (St) rises to a maximum at a gap ratio of 0.7 [5][6][7]. Further gap reduction from 0.7 to 0.1 leads to a rapid decrease in St, with shedding finally ceasing altogether at gap ratios below 0.16.…”

Section: Introductionmentioning

confidence: 99%

Computations of incompressible fluid flow around a long square obstacle near a wall: laminar forced flow and thermal characteristics

Kumar

Dhiman

2017

Sādhanā

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Computations of incompressible fluid flow and heat transfer around a square obstacle with a nearby adiabatic wall have been performed in a horizontal plane. The ranges of dimensionless control parameters considered are Prandtl number (Pr) = 10-100, Reynolds number (Re) = 1-150 and gap ratio (G) = 0.25-1. The steady-flow regime is observed up to Re = 121 for G = 0.5, and beyond this Re, time-periodic regime is observed. The shift to a time-periodic regime from a steady regime occurred at greater Re than that for an unconfined square obstacle. With increasing Pr, increase in average Nusselt number values is recorded for all Re and G studied. The heat transfer augmentation is approximately 1332% at Re = 150 (Pr = 100, G = 0.25) with regard to the corresponding values at Re = 1. Lastly, a correlation for j h factor is determined for the preceded conditions.

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The Unsteady Wake of a Circular Cylinder near a Free Surface

Cited by 24 publications

References 21 publications

Flow past a cylinder close to a free surface

Flow past a cylinder close to a free surface

Analysis of Attack Angle Effect on Flow Characteristics Around Torpedo-Like Geometry Placed Near the Free-Surface via CFD

Computations of incompressible fluid flow around a long square obstacle near a wall: laminar forced flow and thermal characteristics

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