Evaluation of Vortex Generators for Separation Control in a Transcritical Cylinder Flow

Shur, M. L.; Strelets, M. Kh.; Travin, Andrey; Spalart, Philippe R.

doi:10.2514/1.j053851

Cited by 9 publications

(4 citation statements)

References 21 publications

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“…The effectiveness of VGs was not studied experimentally at supercritical and transcritical Re. This motivated Shur et al, [65] to carry out a numerical simulation to evaluate the performance of VGs at transcritical Re (5x10 6 ). They found that with a set of optimum parameters, the VGs were still effective at transcritical Re and reduced the drag by as much as 60% when compared to the uncontrolled flow.…”

Section: Vortex Generatorsmentioning

confidence: 99%

Aerodynamic Devices to Reduce/Suppress Vortex Induced Vibrations on a Wind Turbine Tower: A Review

Krishnappa

Sander

Thoben

2022

J. Phys.: Conf. Ser.

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The flow of air over a cylinder at sufficiently high Reynolds number (Re) leads to the formation of vortices. The vortices formed undergoes the process of shedding, exerting lift and drag forces onto the cylinder causing the cylinder to oscillate. These oscillations are termed as Vortex Induced Vibrations (VIV). VIV’s can induce very high fatigue loads onto the structure, leading to its failure. Hence, the suppression/mitigation of these VIV’s is of utmost importance in practical situations. Vortex suppression techniques such as active, passive or compound techniques can be used for the same. This paper focuses on providing a brief overview on the available passive techniques with particular interest in the flow modification, flow separation control devices and their implementation on a wind turbine tower. From this study, it was observed that most of the experimental research related to the testing of the flow modification devices were carried out in a flow channel with water as the flow medium. Therefore, their effectiveness on a wind turbine tower is questionable. However, flow separation control devices were tested in air but these devices have been tested at different Re and therefore their effectiveness cannot be comprehensively compared. The paper concludes by giving a brief overview of the work that will be carried out in the future to tackle this particular problem.

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Section: Vortex Generatorsmentioning

confidence: 99%

Aerodynamic Devices to Reduce/Suppress Vortex Induced Vibrations on a Wind Turbine Tower: A Review

Krishnappa

Sander

Thoben

2022

J. Phys.: Conf. Ser.

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“…Increasing L/d from 1 to 2 has insignificant lower effect on heat transfer and Nu of circular tube [55]. Vortex generators with height equal to half the boundary-layer thickness produce a significant delay of separation and 60 % drag reduction in incompressible steady flow past a circular cylinder in a transcritical flow regime, with turbulent boundary layers ahead of separation [56].…”

Section: Effect Of Blockage Ratio and Position Ratiomentioning

confidence: 99%

“…As the immersion level ratio of a horizontal circular cylinder in shallow water increases, the magnitude of jet-like flow velocity goes up and result a difference between primary and developing circulation bubble and this stimulates the momentum transfer between the core and wake flow region [57]. A 30 % frequency was reduced independent of Re, downstream of a circular cylinder, and shear layers were elongated in wake so that the Karman vortex street was not developed in water flow; and vortex formation length was considerably extended downstream of cylinder and peak magnitudes of turbulence parameters were comparably smaller [58].…”

Section: Effect Of Blockage Ratio and Position Ratiomentioning

confidence: 99%

Performance Index in MHD Duct Nanofluid Flow Past a Bluff Body at High Re

ARJUN

Kumar

2017

SV-JME

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The quasi-two-dimensional Al 2 O 3 -water nanofluid magneto hydro-dynamics (MHD) flowing over a circular cylinder at higher Reynolds number has been modelled using Ansys FLUENT 15.0 in a rectangular duct to determine the viability of heat transfer enhancement. The effect of the numerical simulations on performance indices were analysed for the range of 1000 ≤ Re ≤ 3000 Reynolds numbers, 10 ≤ Ha ≤ 100 modified Hartmann numbers, 0.5 ≤ φ ≤ 2 nanoparticle volume concentrations, 0.1 ≤ β ≤ 0.4 blockage ratios, 1 ≤ γ ≤ 0.25 position ratios, 0.75 ≤ G/d ≤ 1.5 gap ratios and 0 ≤ d ≤ 10 distance downstream of cylinder along heated duct wall. The results are presented graphically and discussed quantitatively. Grid independence is achieved with the domain having 3 upstream and 20 downstream cylinder diameter distance lengths with element polynomial degree 7 with respect to mean drag coefficient and Strouhal number. Cylinder placement with gaps to the heated wall of diameters between 0.75 and 1.25 and 10 diameters downstream of cylinder performed best, achieving 117 % enhancement of the performance indices at Re = 3000, Ha = 20, φ = 2 %, β = 0.4, γ = 1 and G/d = 1. The performance indices were greater than one for all the cases tested, which indicates that the heat transfer enhancement for this flow is viable. The Nusselt number values of the present study were compared with the analytical and experimental data published earlier and found to be in perfect agreement validating the reliability of the present model. Highlights• A very high performance index enhancement is achieved, incorporating the impacts of Re, Ha and φ in rectangular duct flow. • A circular cylinder is used as bluff body in MHD nanofluid flow at higher Reynold numbers. • Ideal cylinder placement conditions of blockage, position and gap ratios are proposed. • Viable heat transfer enhancements analysed using numerical simulations and the resulting quasi-2D model predictions are validated.

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“…Their study shows that vortex generators enforced the shear layers to bend towards the centreline and decrease the width of the wake. Shur et al [17] show that VGs can produce a significant delay of separation and drag reduction in flows past smooth bluff bodies in the transcritical flow regime, with turbulent boundary layers ahead of separation.…”

Section: Introductionmentioning

confidence: 99%

Vortex-Induced Vibration Suppression of a Circular Cylinder with Vortex Generators

Tao

Tang

Xin

et al. 2016

Shock and Vibration

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The vortex-induced vibration is one of the most important factors to make the engineering failure in wind engineering. This paper focuses on the suppression method of vortex-induced vibration that occurs on a circular cylinder fitted with vortex generators, based on the wind tunnel experiment. The effect of the vortex generators is presented with comparisons including the bare cylinder. The experimental results reveal that the vortex generators can efficiently suppress vortex-induced vibration of the circular cylinder. Vortex generator control can make the boundary layer profile fuller and hence more resistant to separation. The selections of skew angles and the angular position have a significant influence on the vortex generator control effect. By correlation analysis, it can be concluded that the vortex generators can inhibit the communication between the two shear layers and produce streamwise vortices to generate a disturbance in the spanwise direction.

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Evaluation of Vortex Generators for Separation Control in a Transcritical Cylinder Flow

Cited by 9 publications

References 21 publications

Aerodynamic Devices to Reduce/Suppress Vortex Induced Vibrations on a Wind Turbine Tower: A Review

Aerodynamic Devices to Reduce/Suppress Vortex Induced Vibrations on a Wind Turbine Tower: A Review

Performance Index in MHD Duct Nanofluid Flow Past a Bluff Body at High Re

Vortex-Induced Vibration Suppression of a Circular Cylinder with Vortex Generators

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