Multistability and symmetry breaking in the two-dimensional flow around a square cylinder

Shiau, Yuo-Hsien; Peng, Yih‐Ferng; Hwang, Robert R.; Hu, Chin–Kun

doi:10.1103/physreve.60.6188

Cited by 20 publications

(6 citation statements)

References 7 publications

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“…Flow field past a square cylinder is investigated for moderate Reynolds numbers (Re = 150-500, Sohankar et al 1999). Shiau et al (1999) used 2D numerical simulations to examine square cylinder instabilities for low Re numbers, where they concluded that as Re > 320, the system could change from bi-stability which maintains the spatial symmetry with a periodic lift coefficient, to tri-stability, which breaks the spatial symmetry resulting in a non-periodic lift coefficient with a non-zero mean. Davis and Moore (1982) investigated numerically 2D flow around rectangles for Re numbers from 100 to 2,800 and the resulting Strouhal numbers were comparable to those from windtunnel tests for Re numbers less than 1,000.…”

Section: Introductionmentioning

confidence: 99%

Unsteady aerodynamic forces estimation on a square cylinder by TR-PIV

Kurtuluş

Scarano

Lee³

2006

Exp Fluids

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The unsteady aerodynamic forces acting on a square cross-sectional cylinder are investigated by means of time-resolved particle image velocimetry (TR-PIV) at Reynolds number 4,900. The objective of the investigation is to prove the feasibility of nonintrusive force measurements around two-dimensional bodies. The PIV measurements performed at a rate of 1 kHz enable a time resolved (TR) description of the vortex shedding phenomenon occurring at 10 Hz and to follow the time evolution of vortex dominated wake. The instantaneous aerodynamic force coefficients are obtained from the integration of the force equations within a control volume enclosing the object. The required instantaneous pressure distribution is inferred making use of two physical models: Bernoulli relation is adopted in the potential slowly-evolving flow region; in the turbulent wake, the Navier-Stokes equations are invoked to determine the pressure gradient spatial distribution, which integrated in space yields the pressure distribution. The spatial acceleration field is directly obtained from the temporal difference of the time-filtered velocity field. For a choice of the control volume approximately one model height away from the surface the contributions to the aerodynamic forces coming from the different terms of the force equation are individually examined. The convective term dominates the unsteady lift forces whereas the pressure term prevails for the drag. The temporal evolution of C L returns a clear periodic pattern in phase with the vortex shedding at a frequency of 10.1 Hz (Strouhal number St = 0.128) with oscillation amplitude of 0.9, whereas C D barely shows periodicity. The measurement uncertainties associated to the evaluation of all the terms in the force equation and especially in relation to TR-PIV measurements are discussed.

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Section: Introductionmentioning

confidence: 99%

Unsteady aerodynamic forces estimation on a square cylinder by TR-PIV

Kurtuluş

Scarano

Lee³

2006

Exp Fluids

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“…Recent studies, however, show this to be actually an intermediate wavelength quasi‐periodic mode as opposed to a subharmonic one . Period‐doubling bifurcations have also been reported by Shiau et al although for a higher Reynolds number

false(italicRe = 294 false)

and moving channel wall boundary conditions. An aspect common to all Period‐ N ( N being a small non‐zero integer

\geq 2

) bifurcations reported so far, is that they have only been seen in 2D simulations .…”

Section: Introductionmentioning

confidence: 52%

On the transition to 3D modes for channel flow past a square cylinder

et al. 2014

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We consider the case of transient three-dimensional, incompressible and isothermal channel flow of a newtonian fluid past a symmetrically confined obstacle of square cross section at zero incidence. The blockage ratio (ratio of cylinder diameter to channel width) is fixed at 1/4. Results from both Laser Doppler (LDV) experiments and direct simulations upto Reynolds numbers (Re ≤ 250) have been reported.Starting from the onset of instability (Re cr ≈ 58), close examination of the apparent region of influence that envelopes the cylinder reveals a clear vortex shedding signature which extends up to about three diameters upstream. While the fundamental vortex shedding frequency displays a fairly steady monotonic increase with Reynolds number, the Strouhal number (St) shows an inflexion point around Re ≈ 115. No signs of hysteresis were detected around this region. Furthermore, incommensurate harmonics observed for Reynolds numbers in the range 127 ≤ Re ≤ 175 suggest a quasi-periodic transition to three-dimensionality. This is shown to be followed by an intermediate periodic window starting around Re ≈ 180. Results from direct simulations performed using OpenFOAM (the Open Source CFD Toolbox) are used not only to enhance confidence in the accuracy of the reported LDV measurements, but also to help explain the observed phenomena through frequency power spectra and spanwise velocity correlations. Finally, it is concluded that only a parametric variation of transverse and spanwise blockage ratios can bring closure to the subject of bluff-body wake transitions.

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“…The unfortunate tradeoff to this approach is a significant loss in simulation fidelity. To combat this, some have employed higher-order numerical methods to improve solution accuracy while still lowering the number of computational cells (Peng et al, 2003;Shiau et al, 1999;Sau et al, 2004). This approach has been shown to be effective when compared to low-order schemes primarily due to the cost savings associated with fewer computational cells.…”

Section: Discussionmentioning

confidence: 99%

Large-Eddy Simulation Analysis of Unsteady Separation Over a Pitching Airfoil at High Reynolds Number

You¹,

Bromby²,

Sifounakis³

2013

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a. REPORT 14. ABSTRACT 16. SECURITY CLASSIFICATION OF:Unsteady flow separation during dynamic stall often leads to unacceptably large vibra-tory loads and acoustic noise, and limit forward flight speeds and maneuverability. To gain a quantitative understanding of the unsteady separation process, large-eddy simula-tion (LES) of turbulent flow over a pitching airfoil at realistic Reynolds and Mach numbers is performed. Numerical stability at high Reynolds number simulation is maintained us-ing an unstructured-grid LES technology, which obeys higher-order conservation principles and employs a globalcoefficient subgrid-scale turbulence model. A hybrid implicit-explicit time-integration scheme is employed to

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Multistability and symmetry breaking in the two-dimensional flow around a square cylinder

Cited by 20 publications

References 7 publications

Unsteady aerodynamic forces estimation on a square cylinder by TR-PIV

Unsteady aerodynamic forces estimation on a square cylinder by TR-PIV

On the transition to 3D modes for channel flow past a square cylinder

Large-Eddy Simulation Analysis of Unsteady Separation Over a Pitching Airfoil at High Reynolds Number

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