Effects of oncoming flow turbulence on the near wake and forces of a 3D square cylinder

Zhao, Chongyu; Wang, Hanfeng; Zeng, Lingwei; Alam, Md. Mahbub; Zhao, Xuejuan

doi:10.1016/j.jweia.2021.104674

Cited by 38 publications

(17 citation statements)

References 76 publications

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“…(2021), Behera & Saha (2021) and Zhao et al. (2021). The aforementioned data have a range of aspect ratios of –18.6.…”

Section: Discussionmentioning

confidence: 98%

“…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: 95%

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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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“…(2021), Behera & Saha (2021) and Zhao et al. (2021). The aforementioned data have a range of aspect ratios of –18.6.…”

Section: Discussionmentioning

confidence: 98%

Section: Relationship Between Tip and Near-wake Vorticesmentioning

confidence: 95%

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

et al. 2021

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“…The effects of aspect ratio H/d (where H and d are the cylinder height and width, respectively), Reynolds number Re, oncoming flow conditions, etc., on the flow around a finite square cylinder have been widely investigated (Kawamura et al 2008;Sakamoto, 1985;Sakamoto and Arie, 1983;Wang et al 2006;Zhao et al 2021). Wang and Zhou (2009) found two most representative instantaneous configurations of this arch-type vortex structure: anti-symmetrical (Regime A) and symmetrical (Regime B) spanwise vortex shedding.…”

Section: Introductionmentioning

confidence: 99%

Control of the flow around a finite square cylinder with a flexible plate attached at the free end

et al. 2022

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A flexible plate vertically clamped at the free-end leading edge was used to modulate the aerodynamic forces on a wall-mounted finite square cylinder. The side width (d) of the cylinder was 40 mm and the aspect ratio (H/d) was 5. The flexible plate was made of low-density Polyethylene, with a width of d and thickness of 0.04 mm. The length of the flexible plate ranged from d/8 to d.All measurements were carried out in a low-speed wind tunnel with the free-stream velocity (U∞) ranging from 4 to 20 m/s, corresponding to the Reynolds number ranging from 10960 to 54800. It was found that the flexible plate behaves distinctly depending on its length and has significant effects on the aerodynamic forces on the finite square cylinder. When U∞ is smaller than the critical velocity Ucr, which is closely related to the length of the plate, the plate statically deforms, having a negligible influence on the aerodynamic forces on the cylinder. When U∞ exceeds Ucr, the plate flaps periodically, resulting in a significant reduction in the aerodynamic forces. The maximum reduction in the mean drag, fluctuating drag and fluctuating lateral force reaches approximately 5%, 25% and 60%, respectively. The reduction in the aerodynamic forces is insensitive to both plate length and flapping frequency. Flow visualization and particle image velocimetry (PIV) results point out that the flapping plate induces large-scale vortices in the free-end shear flow, which suppress the formation of spanwise vortex shedding and make the upper part of the near wake symmetrical.The flapping configuration of the flexible plate and the corresponding pressure fluctuation on the This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Hanfeng Wang (王汉封), Chongyu Zhao (赵崇宇), Lingwei Zeng (曾令伟), Md. Mahbub Alam, and Hui Tang (唐辉), "Control of the flow around a finite square cylinder with a flexible plate attached at the free end", Physics of Fluids 34, 027109 (2022) and may be found at

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“…x/D =0.7 at each z * when I u = 20.0% , while it displays only a gradually increase for I u = 6.0% and 13.2%. Previous studies (Lee, 1975;Lauder et al, 2016;Zhao et al, 2021) indicated that for a 2D cylinder, increasing turbulence intensity respectively increases and reduces the mean and fluctuating pressures due to the weakened vortex shedding process. Therefore, it can be concluded that the effects of turbulence intensity on the mean and fluctuating pressure distributions on the 3D square cylinder are different from those on 2D square cylinders.…”

Section: Wake Fluctuationsmentioning

confidence: 92%

Experimental investigation of the effects of free-stream turbulence on aerodynamic characteristics of a 3D square cylinder by pressure measurement and PIV visualization

Shi

et al. 2022

Preprint

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This paper investigates the effects of free-stream turbulence such as longitudinal turbulence intensity (Iu) and integral length scale (Lxu) on the flow fields around, and aerodynamic pressures and forces on a surface-mounted three-dimensional (3D) square cylinder with a height-to-width ratio of 5. The flow fields, aerodynamic pressures and forces were experimentally studied by the particle image velocimetry (PIV) visualizations and pressure measurements in grid-generated turbulent flows and smooth flow. The PIV flow visualizations show that increasing (Lxu) has limited effect on the characteristics of wake flow, except slightly weakens and intensifies the downwash and upwash flows, respectively. The influences of turbulence intensity are noteworthy. The Kármán vortices influence the flow features more significantly in turbulent flows with high intensity. The mean pressures on the side faces of the cylinder decrease as(Iu) increases, but increases on the leeward face. Increasing(Iu) and (Lxu) both enhance the fluctuating lift forces and reduce the mean drag forces at all cylinder spans. The spanwise vortex shedding of the cylinder is respectively enhanced and weakened with increasing ( Iu)and (Lxu)The strong vortex shedding occurs near the cylinder’s mid-span. The analyzed results by Proper orthogonal decomposition (POD) method show the symmetric vortex shedding process on the side faces of the 3D cylinder in smooth flow, resulting in small lift fluctuations. In turbulent flows, the vortex shedding process is symmetric near the free-end, alternating at cylinder’s lower half.

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Effects of oncoming flow turbulence on the near wake and forces of a 3D square cylinder

Cited by 38 publications

References 76 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

Control of the flow around a finite square cylinder with a flexible plate attached at the free end

Experimental investigation of the effects of free-stream turbulence on aerodynamic characteristics of a 3D square cylinder by pressure measurement and PIV visualization

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