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The three-dimensional wake of a cylinder undergoing a combination of translational and rotational oscillation in a quiescent fluid
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10.1063/1.3147935
/content/aip/journal/pof2/21/6/10.1063/1.3147935
http://aip.metastore.ingenta.com/content/aip/journal/pof2/21/6/10.1063/1.3147935
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Contours of vorticity around the cylinder undergoing combined translational and rotational oscillation at , , and (a) , (b) , (c) , taken at from numerical simulation. The dashed lines (enclosing blue) correspond to clockwise direction of vorticity (negative). The solid lines (enclosing red) correspond to counterclockwise direction of vorticity (positive).

Image of FIG. 2.
FIG. 2.

Schematic of the problem geometry and important parameters relevant to the combined forcing. Left: the two-dimensional overview (-plane) of the cylinder. Right: spanwise view of the cylinder (-plane) with end plate and field of view (PIV).

Image of FIG. 3.
FIG. 3.

Comparison of the velocity components at three cross sections of the translationally oscillating cylinder in a quiescent fluid at constant values. The values from the top to bottom rows are −0.6, 0.6, and 1.2, respectively. The measurements are taken at and , similar to previous numerical and experimental results (Ref. 8). The left column depicts the and the right column . The solid lines (red) show the present experiment, the dashed lines (black) the present numerical simulation and the filled circle points (blue) the experimental results of Dütsch et al. (Ref. 8).

Image of FIG. 4.
FIG. 4.

Floquet multipliers for for the three-dimensional instability of regime B at . The current results (solid line) are compared to those from Elston et al. (Ref. 16) (squares).

Image of FIG. 5.
FIG. 5.

Vorticity contours around the cylinder undergoing combined translational and rotational oscillation at and . The numerical result is presented at the left, and the experimental result at the right. The experimental result is a phase-average of ten successive cycles. The phase shown corresponds to . The dashed lines (enclosing blue) correspond to clockwise direction of vorticity (negative), and the solid lines (enclosing red) corresponds to counterclockwise direction of vorticity (positive).

Image of FIG. 6.
FIG. 6.

Flow produced by a cylinder with combined oscillatory translation and rotation. This figure shows the sequence and development of the vorticity for one complete cycle, (a) to (h) at and , where is the period of oscillation. The radial line shows the rotational displacement of the cylinder. The dashed lines (enclosing blue) correspond to clockwise direction of vorticity (negative), and the solid lines (enclosing red) correspond to counterclockwise vorticity (positive).

Image of FIG. 7.
FIG. 7.

Experimental results of the spanwise distribution of flow for two values of at : (a) , streamlines; (b) , velocity isocontours; (c) , vorticity isocontours; the dashed lines (enclosing blue) correspond to clockwise direction of vorticity (negative), and the solid lines (enclosing red) correspond to counterclockwise vorticity (positive).

Image of FIG. 8.
FIG. 8.

Floquet multipliers for several Reynolds numbers for the spanwise instability at . (a) Floquet multipliers as a function of spanwise wavelength. The open (closed) symbols represent the shortest (longest) wavelength mode. The circles and black line represent results for ; the squares and blue line represent results for ; the diamonds and red line represent results for ; the lower triangles and magenta line represent results for . (b) Comparison of the Floquet analysis predicted wavelength values as a function of Reynolds number with experimental measurements. The blue dashed line corresponds to the wavelength range of the longest spanwise wavelength mode. The red dashed dotted line corresponds to the extent of the shortest spanwise wavelength mode. The thick blue and red lines correspond to the predicted values of the long and short wavelengths, respectively. The black circles represent the present experimental measurements with error bars reporting the standard deviation of the measurements.

Image of FIG. 9.
FIG. 9.

Contours of streamwise perturbation vorticity taken at and and when the cylinder is at for the following: (left) the long wavelength; (right) the short wavelength. The dashed lines correspond to the base flow clockwise direction of vorticity (negative), and the solid lines correspond to the counterclockwise vorticity (positive).

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/content/aip/journal/pof2/21/6/10.1063/1.3147935
2009-06-04
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: The three-dimensional wake of a cylinder undergoing a combination of translational and rotational oscillation in a quiescent fluid
http://aip.metastore.ingenta.com/content/aip/journal/pof2/21/6/10.1063/1.3147935
10.1063/1.3147935
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