Locked-on vortex shedding modes from a rotationally oscillating circular cylinder

Mittal, H. V. R.; Al‐Mdallal, Qasem M.; Ray, Rajendra K.

doi:10.1016/j.oceaneng.2017.09.034

Cited by 34 publications

(10 citation statements)

References 48 publications

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“…Thiria, Goujon-Durand & Wesfreid (2006) performed experiments on the wake of a rotationally oscillating cylinder at Re = 150 using PIV and found that the wake structures are strongly affected by the forcing parameters. New two-dimensional wake modes at Re = 150 and their dependence on forcing conditions were observed experimentally by Sellappan & Pottebaum (2014b) and numerically by Mittal, Al-Mdallal & Ray (2017). These studies provided insights on how the lock-on parameter space was affected by changing the amplitude and forcing frequency of the cylinder.…”

Section: Introductionmentioning

confidence: 81%

Experimental investigation of three-dimensional modes in the wake of a rotationally oscillating cylinder

et al. 2022

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Three-dimensionalities in the wake of flow past a circular cylinder executing sinusoidal rotary oscillations about its axis is studied experimentally. The results of water tunnel experiments on a rotationally oscillating cylinder for Reynolds number of 250 with varying amplitude and forcing frequency are discussed. Qualitative studies using hydrogen bubble and laser-induced fluorescence flow visualisation techniques are performed. Observation made for oscillating amplitude, $\theta _{0} = {\rm \pi}/4$ and $\theta _{0}=3{\rm \pi} /4$ , and a low normalised forcing frequency, $FR$ , of 0.75 and 0.5, respectively, confirmed a mode having a spanwise non-dimensional wavelength of $\sim$ 1.8 which is also observed for a rotating cylinder. On increasing forcing frequency this mode disappears and a new mode with a bean-shaped structure and a much smaller spanwise normalised wavelength of $\sim$ 0.8 appears at an $FR$ of 1 and an oscillation amplitude of ${\rm \pi} /2$ . This mode remains almost stable until a forcing frequency of $FR=1.4$ . At higher forcing frequency, $FR=2.75$ , and oscillation amplitude of $3{\rm \pi} /4$ , a mode with cellular structure and a normalised spanwise wavelength of $\sim$ 1.6 is identified. The cells in this mode flatten up with increasing downstream distance and are shed alternately with respect to the adjacent cell. Certain combinations of forcing parameters resulted in a forced two-dimensionality of the wake. Quantitative studies using hot-wire measurements and particle image velocimetry confirm the presence of these modes and wake characteristics. Wake mode map in the forcing frequency and amplitude plane is presented showing regions of newly discovered modes and wake lock-on boundaries.

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Section: Introductionmentioning

confidence: 81%

Experimental investigation of three-dimensional modes in the wake of a rotationally oscillating cylinder

et al. 2022

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“…Otherwise, they are categorized as regular. Our numerical algorithm is based upon enforcing a nine point HOC scheme (Mittal et al, 2016(Mittal et al, , 2017a(Mittal et al, , 2017bMittal and Al-Mdallal, 2018) for discretization at regular points and a higher order accurate immersed interface method at the irregular points. However, as we contemplate on using a nine point HOC scheme on the regular points, if all the eight neighbours of a regular point cannot be found on the same side across Γ , there is a need for redefining such regular points.…”

Section: Immersed Interface Treatmentmentioning

confidence: 99%

A coupled immersed interface and level set method for simulation of interfacial flows steered by surface tension

Mittal

Ray

Gadêlha

et al. 2020

Exp. Comput. Multiph. Flow

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This work presents a methodology to address the problems of bubbles and drops evolving in incompressible, viscous flows due to the effect of surface tension. It is based on the combination of a recently developed immersed interface method to resolve discontinuities, with the level set (LS) method to reproduce the evolving interfaces. The paramount feature of this immersed interface method is the use of Lagrange interpolation enclosing grid points positioned in the vicinity of the interface and few exceptional grid points positioned on the interface. Different problems are considered to assert the accurateness of the proposed methodology, involving both simple and complex interface geometries. Precisely, the following problems are addressed: circular flow with a fixed interface, the dispersion of capillary waves, initially circular, ellipse, star shaped bubbles oscillating to an equilibrium state, and circular drops deforming in shear flows. The transient evolution of bubbles/drops in terms of their shapes, pressure profiles, velocity vectors, deformation ratios of major and minor axis is analyzed to observe the effect of surface tension. The proposed methodology is seen to recover the exact numerical equilibrium between the surface tension and pressure gradient in the vicinity of complex interface geometries as well, while recreating the flow physics with an adequate level of accuracy with well representation of overall trends. Moreover, the numerical results yield a good level of agreement with the reference data.

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“…One can also see that for K = 0.0, there is almost no crossing of fluid flow across the centerline. The wake behind both the downstream cylinders 'C2' and 'C3' is termed as anti-phase synchronized pattern (Chatterjee et al 2009;Mittal et al 2017) with phase difference 188 • (see Fig. 7a).…”

Section: Instantaneous Flow Phenomenon For S/d = 06mentioning

confidence: 99%

Theoretical understanding of unsteady flow separation for shear flow past three square cylinders in vee shape using structural bifurcation analysis

Kumar

Ray

2020

Comp. Appl. Math.

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The unsteady flow separation of two-dimensional (2-D) incompressible shear flow past three identical square cylinders arranged in vee shape is studied in this paper, using theoretical structural bifurcation analysis based on topological equivalence. Through this analysis, the exact location and time of occurrence of bifurcation points (flow separation points) associated with secondary and tertiary vortices on all cylinders are studied. The existence of saddle points is also studied during primary flow separation. Different gap ratios between the downstream cylinders, s/d = 0.6-3.0 (where s is the gap between cylinders, d is the length of cylinder side) with fixed gap 2d between upstream and downstream cylinders for different shear parameter (K) values ranging from K = 0.0 to 0.4 are considered at Reynolds number (Re) 100. In this process, the instantaneous vorticity contours and streakline patterns, centerline velocity fluctuation, phase diagram, lift and drag coefficients are studied to confirm the theoretical results. Computations are carried out by using higher order compact finite difference scheme. Present study mainly investigates the effect of K and gap ratio on unsteady flow separation and vortex-shedding phenomenon. All the computed results very efficiently and very accurately reproduce the complex flow phenomenon. Through this study, many noticeable and interesting results are reported for the first time for this problem.

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Locked-on vortex shedding modes from a rotationally oscillating circular cylinder

Cited by 34 publications

References 48 publications

Experimental investigation of three-dimensional modes in the wake of a rotationally oscillating cylinder

Experimental investigation of three-dimensional modes in the wake of a rotationally oscillating cylinder

A coupled immersed interface and level set method for simulation of interfacial flows steered by surface tension

Theoretical understanding of unsteady flow separation for shear flow past three square cylinders in vee shape using structural bifurcation analysis

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