Near wake structure behind a 3D square prism with the aspect ratio of 2.7 in a shallow boundary layer flow

Kawai, Hiroyuki; Okuda, Yasuo; Ohashi, M.

doi:10.1016/j.jweia.2012.04.019

Cited by 34 publications

(18 citation statements)

References 7 publications

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“…Thus, the wake structure belongs to the dipole model. This phenomenon is consistent with well-documented experimental and numerical studies when the aspect ratio is similar (Wang & Zhou 2009;Bourgeois et al 2011;Kawai et al 2012;Saeedi et al 2014;Sumner et al 2017), and Re is of the order of magnitude of 10 4 . Figure 20 quantifies the amount of upward flow in the symmetry plane when z/D ≤ 1.0, which is represented by the area-averaged vertical velocity in the sub-regions of the near, moderate and far wakes.…”

Section: Tip Vortices In the Far And Moderate Wakessupporting

confidence: 91%

“…For example, Bourgeois et al (2011) could not provide near-wall flow patterns even though they applied the PIV technique to propose a half-loop shed structure in the wake and Unnikrishnan et al (2017) failed to measure the velocity vectors in the recirculation zone behind the cylinder using a seven-hole probe. In some cases, a relatively complete flow field was attempted using PIV or numerical simulations (Kawai et al 2012;Saeedi et al 2014). However, the flow topology was schematically described without any strict reasoning.…”

Section: Methodology For Near-wall Flow Descriptionmentioning

confidence: 99%

“…Whether the Re affects the formation of the upwash may also be considered. To verify this possibility, we collected the previous and present results when Re ≥ 500 in figure 24, including those of Wang et al (2006), Wang & Zhou (2009), Bourgeois et al (2011), Kawai et al (2012), Hosseini et al (2013), Uffinger, Ali & Becker (2013), Saeedi et al (2014), Sumner et al (2017), Zhang et al (2017), Unnikrishnan et al (2017), Zu & Lam (2018), Cao et al (2019), da Silva et al (2020, Yauwenas et al (2019), Rastan et al (2021), Behera & Saha (2021) and Zhao et al (2021). The aforementioned data have a range of aspect ratios of H/D = 2.7-18.6.…”

Section: Relationship Between Tip and Near-wake Vorticesmentioning

confidence: 98%

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Topological description of near-wall flows around a surface-mounted square cylinder at high Reynolds numbers

et al. 2021

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This study topologically describes near-wall flows around a surface-mounted cylinder at a high Reynolds number ( $Re$ ) of $5\times 10^4$ and in a very thick boundary layer, which were partially measured or technically approximated from the literature. For complete and rational flow construction, we use high-resolution simulations and critical-point theory. The large-scale near-wake vortex is composed of two connected segments rolled up from the sides of the cylinder and from the free end. Another large-scale side vortex clearly roots on two notable foci on the lower side wall. In the junction region, the side vortex moves upwards with a curved trajectory, which induces the formation of nodes on the ground surface. In the free-end region, the side vortex is compressed, which results in a smaller trailing-edge vortex and its downstream movement. Only tip vortices are observed in the far wake. The origin of the tip vortices and their distinction from the near-wake vortex are discussed. Further analyses suggest that $Re$ independence should be treated with high caution when $Re$ increases from 500 to ${O}(10^4)$ . The occurrence of upwash flow behind the cylinder strongly depends on the increase in $Re$ , the mechanism of which is also provided. The separation–reattachment process in the junction region and the trailing-edge vortices are discovered only at a high $Re$ . The former should significantly affect the strength of the side vortex in the junction region and the latter should cause a sharp drop in pressure near the trailing edge.

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Section: Tip Vortices In the Far And Moderate Wakessupporting

confidence: 91%

Section: Methodology For Near-wall Flow Descriptionmentioning

confidence: 99%

Section: Relationship Between Tip and Near-wake Vorticesmentioning

confidence: 98%

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Topological description of near-wall flows around a surface-mounted square cylinder at high Reynolds numbers

et al. 2021

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“…Note that other studies assessing the characteristics of the arch vortex include Refs. [134,135]. As discussed by Monnier et al [77], there is a wide range of criteria to identify vortical structures, and perhaps the most straighforward approach is to evaluate the vorticity components.…”

Section: Flow Structures and Data-driven Methodsmentioning

confidence: 99%

On the Experimental, Numerical and Data-Driven Methods to Study Urban Flows

2021

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Understanding the flow in urban environments is an increasingly relevant problem due to its significant impact on air quality and thermal effects in cities worldwide. In this review we provide an overview of efforts based on experiments and simulations to gain insight into this complex physical phenomenon. We highlight the relevance of coherent structures in urban flows, which are responsible for the pollutant-dispersion and thermal fields in the city. We also suggest a more widespread use of data-driven methods to characterize flow structures as a way to further understand the dynamics of urban flows, with the aim of tackling the important sustainability challenges associated with them. Artificial intelligence and urban flows should be combined into a new research line, where classical data-driven tools and machine-learning algorithms can shed light on the physical mechanisms associated with urban pollution.

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“…Both the tip and base vortices induce downwash and upwash flow in the near wake, which attenuate the spanwise Karman vortex shedding [2] . A number of investigations suggest that the flow over the free end of a cantilevered cylinder and the flow around its both sides form a connected arch type vortex structure in the near wake [3] [4] . The two 'legs' of this arch type __________________________ School of Civil Engineering, Central South University, Changsha, China e-mail: wanghf@csu.edu.cn structure may be shed symmetrically or alternately into the wake.…”

Section: Introductionmentioning

confidence: 99%

Free-End Suction Control of the Aerodynamic Forces of a Cantilevered Square Cylinder

Peng¹,

Wang²,

Li³

2017

dtetr

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Steady slot suction is applied near the leading edge of the free end of a cantilevered square cylinder to investigate its effects on the aerodynamic forces. The slot suction significantly changes the flow separation on the free end and also the aerodynamic forces on the entire cylinder span. The best control result appears at the suction coefficient Q = 1 (Q = U s /U ∞ , where U s is the suction velocity at the slot, and U ∞ is the oncoming flow velocity), with the fluctuation drag and lift reduced by 17.8% and 45.5%, respectively. At Q = 1, the shear flow at the leading edge is weakened and reattaches on the cylinder free end, which results in stronger momentum transport between the free-end shear flow and the wake, thus suppressing the vortex shedding and aerodynamic forces efficiently.

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Near wake structure behind a 3D square prism with the aspect ratio of 2.7 in a shallow boundary layer flow

Cited by 34 publications

References 7 publications

Topological description of near-wall flows around a surface-mounted square cylinder at high Reynolds numbers

Topological description of near-wall flows around a surface-mounted square cylinder at high Reynolds numbers

On the Experimental, Numerical and Data-Driven Methods to Study Urban Flows

Free-End Suction Control of the Aerodynamic Forces of a Cantilevered Square Cylinder

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