Vortical flow over the free end surface of a finite circular cylinder mounted on a flat plate

Roh, SC; Park, Seung O

doi:10.1007/s00348-002-0532-6

Cited by 81 publications

(39 citation statements)

References 12 publications

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“…Figure 8 represents the secondary motion at various cross sections and allows us to follow the trailing vortices produced on the top of the upstream cylinder. In the first plane, located at the middle of the first cylinder, the formation of the two trailing vortices can be observed, similar to the structures obtained by smoke visualization by Roh and Park [19]. These trailing vortices are moved downstream and downward by the mean motion, and in the middle of the gap between both cylinders their centers are located at y/D 1.5 (similar values were obtained by Fröhlich and Rodi [18] for a single cylinder with the same ratio H/D=2.5).…”

Section: Average Flowsupporting

confidence: 63%

“…On the top of the upstream cylinder, the flow separates at the front corner and reattaches at x/D 0.2 (see Figure 5), leading to a re-circulation and reverse flow in the front part of the top as can be observed as well in Figure 4. This separation was not found in the experiments of Kadota et al [4], probably due to a lack of resolution of the PIV measurements, but it has been reported in various single finite-height cylinder measurements [19][20]. In these also the corresponding pair of vertical vortices on the top surface have been observed by oil flow pictures and smoke visualization, which represent the spiral nodes of the well known owl-face configuration that can be seen in Figure 4.…”

Section: Average Flowmentioning

confidence: 70%

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LES of the flow around two cylinders in tandem

Palau-Salvador

Stoesser

Rodi

2008

Journal of Fluids and Structures

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Abstract. The flow around an arrangement of two-in-tandem cylinders exhibits a remarkably complex behaviour that is of interest for many engineering problems, such as environmental flows or structural design. In the present paper, a Large Eddy Simulation using a staggered Cartesian grid has been performed for the flow around two-in-tandem cylinders of diameter D=20mm and height H=50mm submerged in an open channel with height h=60 mm. The two axes have a streamwise spacing of 2D. The Reynolds number is 1500, based on the cylinder diameter and the free-stream velocity u . The results obtained show that no vortex shedding occurs in the gap between the two cylinders where the separated shear layers produced by the upstream cylinder reattach on the surface of the downstream one. The flow separates on the top of the first cylinder with the presence of two spiral nodes known as owl-face configuration. On top of the downstream cylinder, the flow is attached. A complex mean flow develops in the gap and also behind the second cylinder. Comparisons with PIV measurements reveal good general agreement, but there are differences concerning some details of the flow in the gap between the cylinders.

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Section: Average Flowsupporting

confidence: 63%

Section: Average Flowmentioning

confidence: 70%

LES of the flow around two cylinders in tandem

Palau-Salvador

Stoesser

Rodi

2008

Journal of Fluids and Structures

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“…Mean pressure field acting on the lateral surface as a function of z/h and measured at different y at U1 ¼ 15 m=s. and at a radial distance of about 19 mm from the model axis are observed, which are located roughly at the same positions where nuclei of vorticity structures were detected through oil flow visualizations by Roh and Park (2003) and Pattenden et al (2005).…”

Section: Pressure Measurementsmentioning

confidence: 91%

“…Oil and smoke-laser sheet visualizations were carried out in Roh and Park (2003) for circular cylinders with aspectratios 1.25 and 4.25. It was found that, apart from the well-known couple of side counter-rotating tip-vortices detached from the free-end, another couple of counter-rotating vortices are present for inner positions than the former ones.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on the aerodynamic loads and wake flow features of a low aspect-ratio circular cylinder

Iungo

Pii

Buresti

2012

Journal of Fluids and Structures

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a b s t r a c tAn experimental investigation on the flow features of the wake generated from a circular cylinder with finite height and placed vertically on a plane is presented. Through force measurements the mean drag coefficient is found to be roughly invariant by varying Reynolds number in a range between 6 Â 10 4 and 11 Â 10 4 . As for the fluctuating forces, a dominant spectral component is clearly detected for the signals of the cross-flow force. A spectral contribution with roughly the same Strouhal number is detected from velocity signals acquired, through hot-wire anemometry, in proximity to the lateral wake boundary; its energy is found to decrease by moving the probe away from the wake and upwards. Simultaneous velocity measurements showed that these fluctuations can confidently be ascribed to an alternate vortex shedding. Subsequently, dynamic measurements of the pressure field over the lateral surface and the free-end of the model were carried out, which highlight that the spectral component connected to vortex shedding is found over the lateral surface, with maximum energy at an azimuthal position just before the separation of the shear layers. The fluctuating energy connected to vortex shedding decreases by moving towards regions immersed in the separated wake, and with increasing vertical coordinate; as a matter of fact, above about half model height an evident energy peak cannot be detected anymore. This feature highlights that a regular alternate vortex shedding occurs only for the lower half-span of the model and that the remaining part is dominated by the upwash generated by the flow passing over the free-end. From the spectral analysis of the pressure measurements carried out over the model free-end no evidence of the presence of the spectral component connected to the alternate vortex shedding is found, as expected. However, a significant fluctuating energy is observed at lower dominating frequencies.

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“…There has been some debate over the topology of the flow over the free-end [18,19]. This is one area in which the experimental data gathered so far does not fully identify the flow behaviour due to its strong three dimensionality.…”

Section: Flow Over the Free Endmentioning

confidence: 99%

Unsteady simulations of the flow around a short surface‐mounted cylinder

Pattenden

Bressloff

Turnock

et al. 2006

Numerical Methods in Fluids

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SUMMARYThe flow around a surface-mounted circular cylinder, of height/diameter ratio 1 with a free end, is simulated using large-eddy simulation (LES) and detached-eddy simulation (DES) at a Reynolds number based on diameter of 200 000. A comparison is made between the abilities of the two models to capture flow features observed in particle image velocimetry (PIV) experiments carried out by the authors. The flow contains three interacting features formed from the junction flow between the cylinder and the ground, separation from the cylinder wall and resultant turbulent wake, and the flow over the free-end of the cylinder. Both LES and DES overpredict the length of the recirculation region by 30%, but the turbulence quantities are close to the measured values. The topology of the flow over the free-end is confirmed as consisting of an arch or 'mushroom' vortex. Due to the high Reynolds number the grid resolution is insufficient to resolve the approaching ground-plane boundary layer flow with LES, leading to inaccuracies in the horseshoe vortex system. The DES model improves this area, though still has grid induced separation effects.

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Vortical flow over the free end surface of a finite circular cylinder mounted on a flat plate

Cited by 81 publications

References 12 publications

LES of the flow around two cylinders in tandem

LES of the flow around two cylinders in tandem

Experimental investigation on the aerodynamic loads and wake flow features of a low aspect-ratio circular cylinder

Unsteady simulations of the flow around a short surface‐mounted cylinder

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