Reduction in drag and vortex shedding frequency through porous sheath around a circular cylinder

Bhattacharyya, S.; Singh, A. K.

doi:10.1002/fld.2210

Cited by 59 publications

(31 citation statements)

References 33 publications

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“…Based on Ergun's model [39], the porous medium can be represented using particles of mean diameter d p . The method used to model the flow transport within the porous material in this paper is similar to that of Bhattacharyya and Singh [40] and Bae et al [41,42].…”

Section: Methodsmentioning

confidence: 94%

Tandem cylinder aerodynamic sound control using porous coating

Liu

Azarpeyvand

Wei

et al. 2015

Journal of Sound and Vibration

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a b s t r a c tThis study is concerned with the application of porous coatings as a passive flow control method for reducing the aerodynamic sound from tandem cylinders. The aim here is to perform a parametric proof-of-concept study to investigate the effectiveness of porous treatment on bare tandem cylinders to control and regularize the vortex shedding and flow within the gap region between the two bluff bodies, and thereby control the aerodynamic sound generation mechanism. The aerodynamic simulations are performed using 2D transient RANS approach with k À ω turbulence model, and the acoustic computations are carried out using the standard Ffowcs Williams-Hawkings (FW-H) acoustic analogy. Numerical flow and acoustic results are presented for bare tandem cylinders and porous-covered cylinders, with different porosities and thicknesses. Experimental flow and acoustic data are also provided for comparison. Results show that the proper use of porous coatings can lead to stabilization of the vortex shedding within the gap region, reduction of the vortex shedding interaction with the downstream body, and therefore the generation of tonal and broadband noise. It has also been observed that the magnitude and the frequency of the primary tone reduce significantly as a result of the flow regularization. The proposed passive flow-induced noise and vibration control method can potentially be used for other problems involving flow interaction with bluff bodies.

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Section: Methodsmentioning

confidence: 94%

Tandem cylinder aerodynamic sound control using porous coating

Liu

Azarpeyvand

Wei

et al. 2015

Journal of Sound and Vibration

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“…It is further found that, as the asymmetric cross section of the cylinder causes the wake centerline to shift toward the sharp corner side of the bluff body, the wake remains globally symmetric about the shifted centerline. A numerical study on the laminar vortex shedding and wake flow due to a porous-wrapped solid circular cylinder has been made by Bhattacharyya and Singh [13]. The laminar vortex shedding behind a porous-wrapped solid cylinder was investigated for Reynolds number up to 250.…”

Section: Introductionmentioning

confidence: 99%

Flow control behind a circular cylinder via a porous cylinder in deep water

Gözmen

Fırat

Akıllı

et al. 2013

EPJ Web of Conferences

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Abstract. In this present work, the effects of surrounding outer porous cylinder on vortex structure downstream of a circular inner cylinder are investigated experimentally in deep water flow. The porosity of outer cylinder were selected as β = 0. 4, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8 and 0.85. Porosity is defined as the ratio of the gap area on the body to the whole body surface area. The ratio of outer cylinder diameter to inner cylinder diameter, D o /D i was selected as 2.0, i.e. the inner cylinder diameter is D i = 30 mm where the outer cylinder diameter is D o = 60 mm. All experiments were carried out above a platform. The water height between the base of the platform and the free surface was adjusted as 340 mm. Free stream velocity is U = 156 mm/s, which corresponds to the Reynolds number of Re i = 5,000 based on the inner cylinder diameter. It has been observed that the outer porous cylinders have influence on the attenuation of vortex shedding in the wake region for all porosities. The turbulent intensity of the flow is reduced at least 45% by the presence of outer porous cylinder compared to the bare cylinder case. The porosities β = 0.4 and 0.5 are most suitable cases to control the flow downstream of the circular cylinder.

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“…The effect of permeability on the flow transition from steady to periodic viscous flow was studied for the case of an unbounded solid circular cylinder wrapped in a porous layer by Bhattacharyya and Singh (Bhattacharyya and Singh, 2011) and also for the case of an unbounded porous square cylinder by Babu and Narasimhan (Babu and Narasimhan, 2010) and by Jue (Jue, 2004). These studies show that high permeability ( > 10 −4 ) dampens the vortex shedding behind the cylinder.…”

Section: 4)mentioning

confidence: 99%

Interception efficiency in two-dimensional flow past confined porous cylinders

Shahsavari¹,

Wardle

McKinley³

2014

Chemical Engineering Science

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The flow interception efficiency, which provides a measure of the fraction of streamlines that intercept a porous collector, is an important parameter in applications such as particle capture, filtration, and sedimentation. In this work, flow permeation through a porous circular cylinder located symmetrically between two impermeable parallel plates is investigated numerically under different flow and geometrical conditions. A flow interception efficiency is defined and calculated based on the flow permeation rate for a wide range of system parameters. The dependencies on all physical variables can be captured in three dimensionless numbers: the Reynolds number, the Darcy number (ratio of permeability to the square of cylinder diameter), and the plate separation relative to the cylinder size. The flow interception efficiency is very low in the limit of unbounded cylinders but significantly increases by restricting the flow domain. The fluid permeation rate through the porous cylinder varies nonlinearly with the relative plate/cylinder spacing ratio, especially when the gap between the cylinder and the confining plates is small compared to the cylinder size. In general, the effects of the Reynolds number, the Darcy number, and confinement on the flow interception efficiency are coupled; however, for most practical cases it is possible to factorize these effects. For practical ranges of the Darcy number ( < 10 −4 , which means that the pore size is at least one order of magnitude smaller than the porous cylinder diameter), the interception efficiency varies linearly with , is independent of the Reynolds number at low Reynolds numbers ( < 10), and varies linearly with Reynolds number at higher flow rates. In addition to numerical solutions, theoretical expressions are developed for the flow interception efficiency in two limiting cases of confined and unbounded flow, based on modeling the system as a network of hydrodynamic resistances, which agree well with the numerical results. Furthermore, an expression for

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Reduction in drag and vortex shedding frequency through porous sheath around a circular cylinder

Cited by 59 publications

References 33 publications

Tandem cylinder aerodynamic sound control using porous coating

Tandem cylinder aerodynamic sound control using porous coating

Flow control behind a circular cylinder via a porous cylinder in deep water

Interception efficiency in two-dimensional flow past confined porous cylinders

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