PIV measurements on the passive control of flow past a circular cylinder

Oruç, Vedat; Akıllı, Hüseyin; Şahi̇n, Beşi̇r

doi:10.1016/j.expthermflusci.2015.09.019

Cited by 43 publications

(8 citation statements)

References 33 publications

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“…The experiment results indicate that the dimpled surface contributes to a drag reduction of 10% and affects the vortex-shedding strength in the near wake of the cylinder. Oruç et al (2016) conducted PIV measurements on flow around a cylindrical test model modified with drop-shaped mesh. They found that the vortex formation length is longer, the turbulence kinetic energy and normalized Reynolds shear stress contours are conspicuously weaker than the bare cylinder without control.…”

Section: Introductionmentioning

confidence: 99%

Effects of steady wake-jets on subcritical cylinder flow

Gao

Chen

et al. 2019

Experimental Thermal and Fluid Science

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We investigate the effects of active wake-jets (characterized by a dimensionless jet momentum coefficient C µ) on the suppression of aerodynamic forces and the manipulation of wake flow topology behind a cylindrical model through wind tunnel tests. The active jets are positioned at the rear stagnation points of the cylindrical test model. The experimental campaign is conducted at a subcritical Reynolds number of Re= 3.33 × 10 4. The surface pressure distributions around the bare and controlled cylinders are obtained by using a pressure measurement system. Apart from pressure measurements, we also obtain the streamwise and spanwise flow structures around the circular cylinder with different C µ (including C µ = 0) by employing the particle image velocimetry (PIV) technique. Pressure measurement results demonstrate that the lift force acting on the cylindrical test model is greatly reduced and drag decreased with the implementation of active wake-jets. Besides, it is found that a higher C µ contributes to a better control effectiveness in unsteady lift forces but not necessarily a better drag reduction. PIV measurement results indicate that the mechanism of the active jet control scheme is to impose steady and symmetric perturbations into the unsteady and asymmetric flows in the cylinder wake. Owing to the dynamic competition of the wake-jet flow and shear layer flows, the vortex shedding pattern behind the controlled cylinder is greatly modified, vortex formation length significantly elongated and the fluctuations of aerodynamic forces conceivably suppressed.

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Section: Introductionmentioning

confidence: 99%

Effects of steady wake-jets on subcritical cylinder flow

Gao

Chen

et al. 2019

Experimental Thermal and Fluid Science

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“…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]. 3D unsteady LES shows the broadband nature of shear-layer instability behind a circular cylinder and the dependence of shear-layer frequency on high Re [59].…”

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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“…It was found that the closer the wake vortex is to the wall, the smaller the cutting speed is. Oruc et al [12] used PIV to demonstrate the vortex structure of a single-cylinder wake region with different Reynolds numbers that arose due to the shear layer decoupling from the cylindrical surface. It was proved by investigating the vorticity, Reynolds stress and turbulent energy of the flow field that arranging a water droplet-shaped mesh structure around the cylinder suppresses the formation of a vortex during the flow around the cylinder.…”

Section: Introductionmentioning

confidence: 99%

A Study of Drag Reduction on Cylinders with Different V-Groove Depths on the Surface

Chen

et al. 2021

Water

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In this study, the drag reduction effect is studied for a cylinder with different V-groove depths on its surface using a k-ω/SST (Shear Stress Transport) turbulence model of computational fluid dynamics (CFD), while a particle image velocimetry (PIV) system is employed to analyze the wake characteristics for a smooth cylinder and a cylinder with different V-groove depths on its surface at different Reynolds numbers. The study focuses on the characteristics of the different V-groove depths on lift coefficient, drag coefficient, the velocity distribution of flow field, pressure coefficient, vortex shedding, and vortex structure. In comparison with a smooth cylinder, the lift coefficient and drag coefficient can be reduced for a cylinder with different V-groove depths on its surface, and the maximum reduction rates of lift coefficient and drag coefficient are about 34.4% and 16%, respectively. Otherwise, the vortex structure presents a complete symmetry for the smooth cylinder, however, the symmetry of the vortex structure becomes insignificant for the V-shaped groove structure with different depths. This is also an important reason for the drag reduction effect of a cylinder with a V-groove surface.

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PIV measurements on the passive control of flow past a circular cylinder

Cited by 43 publications

References 33 publications

Effects of steady wake-jets on subcritical cylinder flow

Effects of steady wake-jets on subcritical cylinder flow

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

A Study of Drag Reduction on Cylinders with Different V-Groove Depths on the Surface

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