On streamwise vortices in turbulent wakes of cylinders

Bays‐Muchmore, Byram; Ahmed, Anwar

doi:10.1063/1.858862

Cited by 61 publications

(17 citation statements)

References 12 publications

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“…In the implementation of the fractional-step procedure, a slight change in the final step, Equation (11), is made so that efficient tridiagonal solvers can be used and iteration on v n + 1 is avoided. The viscous term in Equation (11) is replaced by…”

Section: Fractional Step Methodsmentioning

confidence: 99%

A three-dimensional simulation of a steady approach flow past a circular cylinder at low Reynolds number

Zhang

Dalton

1998

Int. J. Numer. Meth. Fluids

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Section: Fractional Step Methodsmentioning

confidence: 99%

A three-dimensional simulation of a steady approach flow past a circular cylinder at low Reynolds number

Zhang

Dalton

1998

Int. J. Numer. Meth. Fluids

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“…This suggests that the Mode-B streamwise vortices may be originating from the instabilities existing in the shear layer prior to separation, which then undergo stretching between the von Kármán vortices. The Mode-B instability, which has a spanwise wavelength of k z = 1d, continues to exist at higher Reynolds numbers in the order of 10 4 , as shown by Bays-Muchmore and Ahmed (1993), Lin et al (1995), and Hangan et al (2001).…”

Section: Introductionmentioning

confidence: 91%

Secondary wake instabilities of a blunt trailing edge profiled body as a basis for flow control

2012

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Flow in the wake of a blunt trailing edge profiled body, comprised of an elliptical leading edge and a rectangular trailing edge, has been investigated experimentally, to identify and characterize the secondary instabilities accompanying the von Kármán vortices. The experiments, which involve laser-induced fluorescence for visualization and particle image velocimetry for quantitative measurement of the wake instabilities, cover Reynolds numbers ranging from 250 to 2,150 based on thickness of the body, to include the wake transition regime. The dominant secondary instability appears as spanwise undulations in von Kármán vortices, which evolve into pairs of counterrotating vortices, with features resembling the instability mechanism predicted by Ryan et al. (J Fluid Mech 538:1-29, 2005). Feasibility of a flow control approach based on interaction with the secondary instability using a series of discrete trailing edge injectors has also been investigated. The control approach mitigates the adverse effects of vortex shedding in certain conditions, where it is able to amplify the secondary instability effectively.

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“…The E Â B shear not only stabilizes the turbulence and decreases the level of transport in all channels but also pinches (co-current) TAM radial transport. 7 The c p , M jj , and c E momentum transport drivers were treated with local gyrokinetic code simulations in Ref. 3 and more recently in Ref.…”

Section: Introductionmentioning

confidence: 99%

Gyrokinetic simulation of momentum transport with residual stress from diamagnetic level velocity shears

2011

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Residual stress refers to the remaining toroidal angular momentum (TAM) flux (divided by major radius) when the shear in the equilibrium fluid toroidal velocity (and the velocity itself) vanishes. Previously [Waltz et al., Phys. Plasmas 14, 122507 (2007); errata 16, 079902 (2009)], we demonstrated with GYRO [Candy and Waltz, J. Comp. Phys. 186, 545 (2003)] gyrokinetic simulations that TAM pinching from (ion pressure gradient supported or diamagnetic level) equilibrium E Â B velocity shear could provide some of the residual stress needed to support spontaneous toroidal rotation against normal diffusive loss. Here we show that diamagnetic level shear in the intrinsic drift wave velocities (or "profile shear" in the ion and electron density and temperature gradients) provides a comparable residual stress. The individual signed contributions of these small (rho-star level) E Â B and profile velocity shear rates to the turbulence level and (rho-star squared) ion energy transport stabilization are additive if the rates are of the same sign. However because of the additive stabilization effect, the contributions to the small (rho-star cubed) residual stress is not always simply additive. If the rates differ in sign, the residual stress from one can buck out that from the other (and in some cases reduce the stabilization.) The residual stress from these diamagnetic velocity shear rates is quantified by the ratio of TAM flow to ion energy (power) flow (M/P) in a global GYRO core simulation of a "null" toroidal rotation DIII-D [Mahdavi and Luxon, Fusion Sci. Technol. 48, 2 (2005)] discharge by matching M/P profiles within experimental uncertainty. Comparison of global GYRO (ion and electron energy as well as particle) transport flow balance simulations of TAM transport flow in a high-rotation DIII-D L-mode quantifies and isolates the E Â B shear and parallel velocity (Coriolis force) pinching components from the larger "diffusive" parallel velocity shear driven component and the much smaller profile shear residual stress component.

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On streamwise vortices in turbulent wakes of cylinders

Cited by 61 publications

References 12 publications

A three-dimensional simulation of a steady approach flow past a circular cylinder at low Reynolds number

A three-dimensional simulation of a steady approach flow past a circular cylinder at low Reynolds number

Secondary wake instabilities of a blunt trailing edge profiled body as a basis for flow control

Gyrokinetic simulation of momentum transport with residual stress from diamagnetic level velocity shears

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