Suppression of Downstream Vortex-Street of an Oscillating Cylinder by a Splitter Plate

2011 ◽  
Author(s):  
S Wang ◽  
C. P. Shao ◽  
Jiachun Li ◽  
Song Fu
Keyword(s):  
Splitter Plate ◽  
Vortex Street ◽  
Oscillating Cylinder

Effect of Channel Inlet Blockage on the Wake Structure of a Rotationally Oscillating Cylinder

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
S. Kumar
Keyword(s):  
Mode Shape ◽  
Channel Wall ◽  
Shape Change ◽  
Vortex Street ◽  
Channel Width ◽  
Channel Inlet ◽  
Oscillating Cylinder ◽  
Wake Structure ◽  
Freestream Velocity ◽  
Cylinder Diameter

This paper investigates, experimentally for the first time, the effect of channel inlet blockage induced by bringing the channel inlet walls closer together on the wake structure of a rotationally oscillating cylinder. The cylinder is placed symmetrically inside the channel inlet. The Reynolds number (based on constant upstream channel inlet freestream velocity) is 185, and three channel wall spacings of two, four, and eight cylinder diameters are used. Cylinder oscillation amplitudes vary from π/8 to π, and normalized forcing frequencies vary from 0 to 5. The diagnostics is done using hydrogen-bubble flow visualization, hot-wire anemometry, and particle image velocimetry (PIV). It is found that rotational oscillations induce inverted-vortex-street formation at channel width of two cylinder diameter where there is no shedding in unforced case. The channel wall boundary layers at this spacing undergo vortex-induced instability due to vortex shedding from cylinders and influence the mechanism of inverted-vortex-street formation near the cylinder. At channel width of four cylinder diameter, the inverted-vortex-street is still present but the mode shape change seen at normalized forcing frequency of 1.0 in the absence of channel walls is delayed due to the presence of nearby walls. The wake structure is observed to resemble the wake structure in unbounded domain case at channel width of eight cylinder diameter with some effect of channel walls on forcing parameters where mode shape change occurs. The lock-on diagram is influenced by the closeness of the channel walls, with low-frequency boundary moving to lower frequencies at smallest channel width.

Flow past a rotationally oscillating cylinder with an attached flexible filament

2021 ◽  
Vol 930 ◽  
Author(s):  
Puja Sunil ◽  
Sanjay Kumar ◽  
Kamal Poddar
Keyword(s):  
Control Volume ◽  
Transverse Velocity ◽  
Experimental Studies ◽  
Vortex Street ◽  
Oscillating Cylinder ◽  
Karman Vortex Street ◽  
Flexible Filament ◽  
Flow Past ◽  
Kármán Vortex Street ◽  
Karman Vortex

Experimental studies are conducted on a rotationally oscillating cylinder with an attached flexible filament at a Reynolds number of 150. Parametric studies are carried out to investigate the effect of cylinder forcing parameters and filament stiffness on the resultant wake structure. The diagnostics are flow visualization using the laser-induced fluorescence technique, frequency measurement using a hot film, and characterization of the velocity and vorticity field using planar particle image velocimetry. The streamwise force and power are estimated through control volume analysis, using a modified formulation, which considers the streamwise and transverse velocity fluctuations in the wake. These terms become important in a flow field where asymmetric wakes are observed. An attached filament significantly modifies the flow past a rotationally oscillating cylinder from a Bénard–Kármán vortex street to a reverse Bénard–Kármán vortex street, albeit over a certain range of Strouhal number, $St_{A} \sim 0.25\text {--}0.5$ , encountered in nature in flapping flight/fish locomotion and in the flow past pitching airfoils. The transition from a Kármán vortex street to a reverse Kármán vortex street precedes the drag-to-thrust transition. The mechanism of unsteady thrust generation is discussed. Maximum thrust is generated at the instants when vortices are shed in the wake from the filament tip. At $St_{A} > 0.4$ , a deflected wake associated with the shedding of an asymmetric vortex street is observed. Filament flexibility delays the formation of an asymmetric wake. Wake symmetry is governed by the time instant at which a vortex pair is shed in the wake from the filament tip.

Effect of Vortex Street on Mixing Enhancement in a Mixing Layer

2015 ◽  
Author(s):  
DongMing Zhang
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Mixing Layer ◽  
Splitter Plate ◽  
Vortex Street ◽  
Good Effect ◽  
Mixing Enhancement ◽  
Square Cylinder ◽  
Velocity Difference ◽  
Initial Stage

In this paper, the effect of vortex street on increasing mixing in a mixing layer is investigated numerically. The end of the splitter plate is made into square cylinder shape in order to set a square cylinder in the mixing layer for generating the vortex street. The vortex street is formed behind the cylinder in the initial stage of the mixing layer when the top and bottom streams flow over the square cylinder. The large scale vortices in the vortex street are utilized to enhance mixing of two different-speed streams in the mixing layer. The reason of the asymmetry of the vortex street is explained. The case of a mixing layer between two walls is also studied numerically. The results of numerical simulation show that small velocity difference between two streams is good for mixing enhancement in the confined mixing layer. The vortex street has a good effect on mixing enhancement in a mixing layer.

Formation of a vortex street behind an oscillating cylinder

1995 ◽  
Vol 30 (1) ◽  
pp. 40-44 ◽  
Author(s):  
Ya. D. Afanasyev ◽  
I. A. Filippov
Keyword(s):  
Vortex Street ◽  
Oscillating Cylinder

The Pressure Distribution at Low Speeds on Two-Dimensional Aerofoils with Blunt Trailing Edges at Zero Incidence

1966 ◽  
Vol 70 (667) ◽  
pp. 727-729 ◽  
Author(s):  
D. J. Maull
Keyword(s):  
Pressure Distribution ◽  
Boundary Problem ◽  
Mixed Boundary ◽  
Splitter Plate ◽  
Vortex Street ◽  
Two Dimensional ◽  
The Past ◽  
Mixed Boundary Problem ◽  
Trailing Edges ◽  
Base Bleed

For the past few years there has been some interest in aerofoils with blunt trailing edges but most work has been associated with the investigation of the base pressure and the pressure distribution on the aerofoil has received little attention. Nash proposed a method of calculating the pressure distribution on aerofoils with blunt trailing edges in the absence of a vortex street, that is with the vortex street suppressed by means of a splitter plate or base bleed. He assumed that the wake of the aerofoil could be taken into account in the calculation by specifying a pressure distribution along the wake and then applying thin aerofoil theory to the aerofoil and wake. This leads to a mixed boundary problem with the aerofoil shape and the wake pressure distribution specified and the calculation is laborious.

Numerical Investigation of Flow and Heat Transfer around Two Semi-Circular Cylinders with a Splitter Plate

2011 ◽  
Vol 42 (7) ◽  
pp. 595-612
Author(s):  
Masome Heidary ◽  
Mousa Farhadi ◽  
Kurosh Sedighi ◽  
Mostafa Nourollahi
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Splitter Plate ◽  
Circular Cylinders ◽  
Flow And Heat Transfer

MANIPULATION OF THE STARTING SEMICIRCULAR-CYLINDER NEAR-WAKE BY MEANS OF A SPLITTER PLATE

1997 ◽  
Vol 4 (3) ◽  
pp. 211-221 ◽  
Author(s):  
Alain Texier ◽  
Madeleine Coutanceau ◽  
Nathalie Boisaubert
Keyword(s):  
Splitter Plate ◽  
Near Wake
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