Three-dimensional unsteady flow over a bluff body located parallel to a wall, kept at different gap height from the wall, has been studied numerically. The bluff body considered is a rectangular cylinder with two different aspect ratios, B/D=1 and B/D=2, where B and D are the width and height of the cylinder, respectively. The flow is considered as a laminar flow, and the Reynolds number based on the height of the cylinder cross section and oncoming reference velocity is 450. Numerical study is carried out by varying the distance of the cylinder from the wall, and the development of the vortex shedding phenomenon under the influence of the wall is investigated. From previous experiments, it is observed that as the distance between the wall and the cylinder decreases, the wake behind the cylinder becomes stationary and the vortex shedding is suppressed. The present numerical study confirms a similar trend. Periodic activity in the downstream of the flow is disturbed completely with decreasing gap between the wall and the cylinder.

S. Vengadesan

Department of Applied Mechanics

Aspect ratio

Laminar flow

Reynolds number

Velocity measurement

Vortex shedding

BLUFF BODIES

GAP HEIGHTS

PERIODIC ACTIVITIES

REFERENCE VELOCITIES

Unsteady flow

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Flow Characteristics Behind Rectangular Cylinder Placed Near a Wall

Numerical Heat Transfer; Part A: Applications

Two-dimensional flow over a circular cylinder placed in-line behind a control rod of the same diameter is studied with and without the influence of a plane wall. Thermal patterns observed during various vortex shedding modes are discussed in detail. POD analysis of temperature data reveals that, with the decrease in wall height, modal structures are moved closer to the cylinder surface, which increases the heat transfer fluctuation. The plane wall increases the heat transfer from the bottom surface of the cylinder and decreases the heat transfer from the top surface, while the rotation of control rod contributes in an opposite manner. As the cylinder is moved closer to the wall, the time-averaged Nusselt number increases for a stationary control rod. In the case of a rotating control rod, the rotation of the control rod acts in the opposite sense to nullify this wall effect. © 2014 Taylor & Francis Group, LLC.

Heat transfer characteristics of flow over a circular cylinder with an upstream control rod in wall vicinity

The transition of square cylinder wake flow from two-dimensional (2-D) to three-dimensional (3-D) when inflow is subjected to linear shear is examined numerically. The value of the non-dimensional shear parameter (K) considered in this study are 0.0, 0.1, and 0.2. The range of Reynolds number (Re) defined based on the centerline velocity and cylinder width is from Re = 150 to 700. The transition of the wake flow from 2-D laminar to 3-D is marked by streamwise vortical structures. Unlike in uniform flow, in shear flow the transition is characterized by single mode of spanwise wavelength. The critical Reynolds number (Recrit), at which the transition from 2-D to 3-D occurs, is less in case of shear flow. The magnitude of the mean lift coefficient increases with increasing shear parameter on the positive side. The strength of the Karman vortices on the top side is higher and on the bottom side is lower when compared with the same in the uniform flow. © 2010 John Wiley &amp; Sons, Ltd.

International Journal for Numerical Methods in Fluids

Shear effect on square cylinder wake transition characteristics

Incompressible linear shear flow across a square cylinder is numerically analyzed by solving unsteady 2-D Navier-Stokes equations. Simulations are carried out for three sets of shear parameters, 0.0, 0.1 and 0.2 and two sets of solid blockage ratios, 6.25% and 10%. The aim of the present simulations is to find out the influence of shear on the onset of periodic time dependent flow, which is observed using time varying lift coefficient. With increasing shear, the critical Reynolds number, at which flow becomes time dependent, is reduced. The mean drag coefficient decreases either with increasing shear for a particular Reynolds number or with increasing Reynolds number for a particular shear parameter. © 2008 Elsevier Inc. All rights reserved.

International Journal of Heat and Fluid Flow

Onset of vortex shedding in planar shear flow past a square cylinder

Numerical simulations have been performed for flow past two equal-sized square cylinders in tandem arrangement subjected to incoming planar shear flow. Effect of L/d ratio and the shear parameter has been studied. The range of L/d ratio (ratio of center-to-center distance (L) to cylinder width (d)) is varied from 2 to 7 and the non-dimensional shear parameter (K) is varied from 0.0 to 0.4 in steps of 0.1. For all the cases the Reynolds number (Re) based on centerline velocity and cylinder width is fixed at 100. The results are compared with that of isolated square cylinder with uniform flow. Strouhal number decreases with increasing shear parameter. There are more than one shedding frequency at high shear parameters and L/d ratios. The mean drag coefficient is decreased with shear parameter and lesser than that of the single cylinder. The root mean square (RMS) value of both lift and drag coefficients is higher for the downstream cylinder for all values of shear parameter. With increasing L/d ratio, for both lift and drag, the RMS value increases and then decreases for upstream cylinder, whereas it continuously increases for the downstream cylinder. The stagnation point is moved towards the top leading edge with increasing shear. The critical L/d ratio, which is defined as the distance between two cylinders, beyond which the vortex shedding from the upstream cylinder occurs, decreases with increasing shear parameter. Copyright © 2007 John Wiley & Sons, Ltd.

Interference effect of two equal-sized square cylinders in tandem arrangement: With planar shear flow

Numerical Heat Transfer, Part A: Applications

Influence of Buoyancy on Vortex Shedding and Heat Transfer from a Square Cylinder in Proximity to a Wall

Unsteady Heat Transfer and Pressure Drop in Channels with Obtacles Mounted on the Upper and Lower Walls

Prediction of Vortex Shedding with Heat Transfer

EFFECT OF CHANNEL CONFINEMENT ON THE TWO-DIMENSIONAL LAMINAR FLOW AND HEAT TRANSFER ACROSS A SQUARE CYLINDER

Experiments in Fluids

Influence of wall proximity on vortex shedding from a square cylinder

Flow characteristics behind rectangular cylinder placed near a wall

Journal	Numerical Heat Transfer; Part A: Applications
ISSN	10407782
Open Access	No