Numerical investigation on the flow around a square cylinder with an upstream splitter plate at low Reynolds numbers

An, Byungjin; Bergadà, Josep M.; Mellibovsky, Fernando; Sang, Weimin; Chu, Xi

doi:10.1007/s11012-020-01148-8

Cited by 12 publications

(9 citation statements)

References 26 publications

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“…In the present manuscript, we have chosen to place the square cylinder in a thin shear layer created by a piecewise-constant velocity profile with the discontinuity separating the top and bottom homogeneous streamwise velocities precisely located at cylinder mid-height. The same configuration was previously used by Mushyam and Bergada 60 , An et al 61 , although the flow was intentionally kept two-dimensional. This kind of upstream conditions may be obtained experimentally in a wind or water tunnel 62 , and the development of the shear layers thus generated have been thoroughly investigated [63][64][65] .…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic performances and wake topology past a square cylinder in the interface of two different-velocity streams

et al. 2022

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We analyse the incompressible flow past a square cylinder immersed in the wake of an upstream splitter plate which separates two streams of different velocities, UT (top) and UB (bottom). The Reynolds number associated to the flow below the plate is kept constant at ReB=D UB/ν=56, based on the square cylinder side D as characteristic length. The top-to-bottom flow dissymmetry is measured by the ratio R≡ ReT/ReB∈[1,5.3]. The equivalent bulk Reynolds, taken as the mean between top and bottom changes with R in the range Re∈( ReT+ReB)/2∈[56,178]. A Hopf bifurcation occurs at R=2.1{plus minus}0.1 ( Re=86.8{plus minus}2.8), which results in an asymmetric Kármán vortex street with vortices only showing on the high-velocity side of the wake. A spanwise modulational instability is responsible for the three-dimensionalisation of the flow at R≈3.1 ( Re≈115) with associated wavelength λ z≈2.4.For velocity ratios R{greater than or equal to}4, the flow becomes spatio-temporally chaotic. The migration of the mean stagnation and base pressure points on the front and rear surfaces of the cylinder as R is increased determine the boundary layer properties on the top and bottom surfaces and, with them, the shear layers that roll up into the formation of Kármán vortices, which in turn help clarify the evolution of the lift and drag coefficients. The symmetries of the different solutions across the flow transition regime are imprinted on the top and bottom boundary layers and can therefore be analysed from the time evolution and spanwise distribution of trailing edge boundary layer displacement thickness at the top and bottom rear corners.

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Section: Introductionmentioning

confidence: 99%

Aerodynamic performances and wake topology past a square cylinder in the interface of two different-velocity streams

et al. 2022

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“…Here we choose to submerge the square cylinder in a thin shear layer by replacing the classic upstream homogeneous shear by a piecewise-constant velocity profile with the discontinuity separating the top and bottom homogeneous streamwise velocities precisely located at cylinder mid-height. This same set-up has been used twice before, but the flow was expressly kept two dimensional (Mushyam & Bergada 2017;An et al 2020). In order to simulate experimentally reproducible conditions, we choose to separate the top and bottom homogeneous velocity streams by a flat plate, such that the shear layer results from the reunion, at its trailing edge, of the top and bottom boundary layers and develops smoothly downstream before reaching the cylinder.…”

Section: Introductionmentioning

confidence: 99%

Square cylinder in the interface of two different velocity streams

Mansy

Sarwar²,

Bergadà³

et al. 2022

J. Fluid Mech.

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We investigate the incompressible flow past a square cylinder immersed in the wake of an upstream nearby splitter plate separating two streams of different velocity. The bottom stream Reynolds number, based on the square side, $Re_B=56$ is kept constant while the top-to-bottom Reynolds numbers ratio $R\equiv Re_T/Re_B$ is increased in the range $R\in [1,6.5]$ , corresponding to a coupled variation of the bulk Reynolds number $Re\equiv (Re_T+Re_B)/2\in [56,210]$ and an equivalent non-dimensional shear parameter $K\equiv 2(R-1)/(R+1)\in [0,1.4667]$ . The onset of vortex shedding is pushed to higher $Re$ as compared with the square cylinder in the classic configuration. The advent of three dimensionality is triggered by a mode-C-type instability, much as reported for open circular rings and square cylinders placed at an incidence. The domain of minimal spanwise-periodic extension that is capable of sustaining spatiotemporally chaotic dynamics, namely one accommodating about twice the wavelength of the dominant eigenmode, has been chosen for the analysis of the wake transition regime. The path towards spatiotemporal chaos is, in this minimal domain, initiated with a modulational period-doubling tertiary bifurcation that also doubles the spanwise periodicity. At slightly higher values of $R$ , the flow has become spatiotemporally chaotic, but the main features of mode C are still clearly distinguishable. Although some of the nonlinear solutions found along the wake transition regime employing the minimal domain might indeed be unstable to long wavelength disturbances, they still are solutions of the infinite cylinder problem and are apt to play a relevant role in the inception of spatiotemporally chaotic dynamics.

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“…The geometric shape of the cylinder strongly influences the wake behind a cylinder on the hydrodynamic forces. Several articles and scientific research papers based on the study of this physical phenomenon and the importance of the problem have been found [1][2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of the flow around circular cylinder with slits

Bensedira

Salhi

El-Hadj

et al. 2022

Preprint

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The flow around a cylinder with slits has been investigated numerically. The main purpose of this study is to show the effect of the slits on the vortex detachment behind a cylinder smooth, and stationary using the finite element approach to solve the fluid governing equations system at Re = 200. The variation of the spacing ratio (D/S) of the slit is strongly influenced both the various physical parameters and the vortex detachment behind a cylinder. We found that the drag coefficient varies between 1.43 and 1.24 in the case of the horizontal slit and between 1.45 and 1.39 in the case of the vertical slit. In the case of the double horizontal-vertical slit, the values vary between 1.47 and 1.38. We also found that the values of the Strouhal number vary between 0.201 and 0.268 according to the spacing ratio (D/S) of the slit. A comparison was made with experimental works for the Strouhal number. The results are very important, and the error found is less than 7%.

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Numerical investigation on the flow around a square cylinder with an upstream splitter plate at low Reynolds numbers

Cited by 12 publications

References 26 publications

Aerodynamic performances and wake topology past a square cylinder in the interface of two different-velocity streams

Aerodynamic performances and wake topology past a square cylinder in the interface of two different-velocity streams

Square cylinder in the interface of two different velocity streams

Numerical simulation of the flow around circular cylinder with slits

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