Three dimensionality in the wake of the flow around a circular cylinder at Reynolds number 5000

Abstract

The turbulent flow around a circular cylinder has been investigated at Re=5000Re=5000 using direct numerical simulations. Low frequency behavior, vortex undulation, vortex splitting, vortex dislocations and three dimensional flow within the wake were found to happen at this flow regime. In order to successfully capture the wake three dimensionality, different span-wise lengths were considered. It was found that a length LZ=2pDLZ=2pD was enough to capture this behavior, correctly predicting different aspects of the flow such as drag coefficient, Strouhal number and pressure and velocity distributions when compared to experimental values. Two instability mechanisms were found to coexist in the present case study: a global type instability originating in the shear layer, which shows a characteristic frequency, and a convective type instability that seems to be constantly present in the near wake. Characteristics of both types of instabilities are identified and discussed in detail. As suggested by Norberg, a resonance-type effect takes place in the vortex formation region, as the coexistence of both instability mechanisms result in distorted vortex tubes. However, vortex coherence is never lost within the wake.Peer ReviewedPostprint (author's final draft

Asymmetric wake of a horizontal cylinder in close proximity to a solid boundary for Reynolds numbers in the subcritical turbulence regime

“…A transition in the sub-critical wake dynamics occurs at a Reynolds number around 5,000 to 5,500 where a distinct change in the shedding typology has been observed in both experimental and numerical studies [7][8][9] . This transition is distinguished by the presence of undulations in the vortex filaments shedding across the cylinder span and the occurrence of vortex dislocations 7,9 which also leads to a change from parallel to oblique vortex shedding 8 .…”

“…Nonetheless, the Reynolds number governs the flow features developed around both ver-tically and horizontally oriented cylinders. Several laboratory experiments and numerical simulations focusing on the sub-critical flow regime (3 • 10 2 < Re < 1 • 10 5 ) have highlighted the higher shedding frequency of the shear layer generated vortices (f SL ) compared to that of the large-scale von-Kármán-type (VK) vortices (f K ), where the frequency of the former vortices can occur at a factor of 6.7 to 8.0 times greater than the wake ones [4][5][6][7] , and 8 demonstrated the correlation between the ratio f SL /f K and Reynolds number. Furthermore, at…”

“…A cylindrical body is often in close proximity of a solid boundary, for example, a pipeline across an erodible river or sea bed, a bridge-pier close to an abutment or a mast located close to a building. Only a few studies have examined the close proximity of a solid boundary on a horizontal cylinder wake's flow structure [1][2][3][15][16][17][18][19] . In this configuration, the ratio of the horizontal cylinder diameter (D) and the vertical gap between the bottom wall and the cylinder (G), referred to hereafter as the gap ratio (G/D), is highly influential on the vortex dynamics developed downstream.…”

Analysis of heat and fluid flow around two co-rotating side-by-side cylinders

“…Among the bluff bodies, the flow around the cylinders has historically found considerable attention for numerous researchers due to its fundamental flow nature. A general review of the published works shows that the flow around a single cylinder in the free-stream and near a wall [1][2][3][4][5][6][7][8][9][10][11][12] has been studied in terms of the vortex shedding phenomenon, active and passive flow control, and wake structure in laminar, transitional, and turbulent regimes. Beyond the single cylinder, the flow around the dual cylinders in various arrangements such as the side-byside and tandem [13][14][15][16][17][18][19][20][21] has been attractive among the researchers not only using different numerical studies but also with various experiments to reveal the interaction level between the cylinders at different gap spaces.…”

Analysis of the convective heat transfer and flow behavior around two counter‐rotating side‐by‐side cylinders

“…On the other hand, flow around the cylinders is the subject of many different engineering applications such as the heat exchangers, bridge piers, chimney stacks, transmission cables, cooling towers, and various offshore and onshore structures. To date, several publications have been performed around a stationary single cylinder in terms of the vortex shedding phenomenon and heat transfer process . In addition, the interaction between two stationary cylinders with different arrangements such as the tandem and side‐by‐side have been presented not only with different numerical simulations but also using various experiments.…”