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Active control of a cylinder wake flow by using a streamwise oscillating foil
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10.1063/1.4802042
/content/aip/journal/pof2/25/5/10.1063/1.4802042
http://aip.metastore.ingenta.com/content/aip/journal/pof2/25/5/10.1063/1.4802042

Figures

Image of FIG. 1.
FIG. 1.

Geometry configuration of the flow over a stationary cylinder with a streamwise oscillating foil.

Image of FIG. 2.
FIG. 2.

Computational domain and boundary conditions for the simulation.

Image of FIG. 3.
FIG. 3.

Time-dependent drag and lift coefficients of the upstream cylinder calculated under different grid densities at / = 3.

Image of FIG. 4.
FIG. 4.

Close-up view of the unstructured mesh for the cylinder-foil system at / = 3.0.

Image of FIG. 5.
FIG. 5.

Flow pattern for the stationary cylinder with non-oscillating foil at different gap spacings ( = 100): (a) / = 0.5; (b) / = 2.0; (c) / = 3.0; and (d) / = 4.0.

Image of FIG. 6.
FIG. 6.

Flow regimes in the phase diagram of gap spacing ratio versus oscillation amplitude ( = 100). (red circle): flow regime I; (green square): flow regime II; (blue diamond): flow regime III.

Image of FIG. 7.
FIG. 7.

Instantaneous vorticity contours for the different flow regimes ( = 100): (a) flow regime I (/ = 0.3 and / = 1.0); (b) flow regime II (/ = 0.8 and / = 3.0); and (c) flow regime III (/ = 0.8 and / = 4.0).

Image of FIG. 8.
FIG. 8.

The comparison of the time-averaged flows for the cases of / = 0.3 (left) and / = 0.8 (right) at / = 3.0 ( = 100): (a) and (b) streamwise velocity contour; (c) and (d) vorticity contour; and (e) and (f) velocity profiles in the wake region. The flow field is averaged over a full motion cycle.

Image of FIG. 9.
FIG. 9.

Time series of the hydrodynamic force coefficients at different gap spacing and oscillating amplitude ( = 100): (a) drag coefficient of the cylinder; (b) drag coefficient of the foil; (c) lift coefficient of the cylinder; and (d) lift coefficient of the foil.

Image of FIG. 10.
FIG. 10.

Statistical parameters of the hydrodynamic forces exerted on the cylinder and the foil ( = 100): (a) mean drag coefficient, cylinder; (b) mean drag coefficient, foil; (c) r.m.s. value of the drag coefficient, cylinder; (d) r.m.s. value of the drag coefficient, foil; (e) r.m.s. value of the lift coefficient, cylinder; and (f) r.m.s. value of the lift coefficient, foil. In the plot, the corresponding results of the isolated cylinder and the cylinder-stationary system (/ = 0.0) are also included.

Image of FIG. 11.
FIG. 11.

Instantaneous variation of the vorticity contours against frequency ratio at / = 1.0 and / = 0.3 ( = 100): (a) / = 1.0; (b) / = 2.0; (c) / = 4.0; and (d) / = 5.0.

Image of FIG. 12.
FIG. 12.

Time series of lift coefficient for the cylinder with different frequency ratios (/ = 1.0, / = 0.3) at = 100.

Image of FIG. 13.
FIG. 13.

Mean and r.m.s. drag coefficient and r.m.s. lift coefficient as functions of the frequency ratio ( = 100).

Image of FIG. 14.
FIG. 14.

Instantaneous variation of the vorticity contours against oscillation amplitude at / = 3.0 and / = 1.0 ( = 100): (a) / = 0.1; (b) / = 0.3; (c) / = 0.4; (d) / = 0.6; (e) / = 0.7; and (f) / = 0.8, respectively.

Image of FIG. 15.
FIG. 15.

Instantaneous vorticity contours at different offset distances for the typical case / = 0.8 and / = 3.0 ( = 100): (a) / = 0.0; (b) / = 0.1; (c) / = 0.2; (d) / = 0.3; (e) / = 0.4; and (f) / = 0.5, respectively.

Image of FIG. 16.
FIG. 16.

Instantaneous variation of the vorticity contours against Reynolds number at / = 0.8 and / = 3.0: (a) = 100; (b) = 120; (c) = 180; and (d) = 200.

Image of FIG. 17.
FIG. 17.

Mean and r.m.s. drag coefficient and r.m.s. lift coefficient as functions of Reynolds number.

Image of FIG. 18.
FIG. 18.

The variation of the effectiveness of drag reduction as a function of (a) the oscillation amplitude at different gap ratios ( = 100) and (b) for the case with / = 0.8 and / = 3.0.

Image of FIG. 19.
FIG. 19.

Instantaneous streamline pattern (left), streamwise velocity contour (middle), and vorticity contour (right) at four phases in a cycle (/ = 0.8 and / = 3.0 at = 100).

Image of FIG. 20.
FIG. 20.

Time series of hydrodynamic coefficients for the cases of (a) / = 0.8 and / = 3.0, and (b) / = 0.8 and / = 2.0 at = 100. The initial field used for the simulation is a fully saturated unsteady flow obtained from corresponding stationary cylinder-foil system.

Image of FIG. 21.
FIG. 21.

Comparison of the instantaneous vorticity contours at = 100: (a) = 5.0 (/ = 0.8 and / = 3.0); (b) = 500.0 (/ = 0.8 and / = 3.0); (c) = 5.0 (/ = 0.8 and / = 2.0); and (d) = 1200.0 (/ = 0.8 and / = 2.0). The initial field used for the simulation is a fully saturated unsteady flow obtained from corresponding cylinder-stationary foil system.

Tables

Generic image for table
Table I.

Mesh generation parameters for the two grid systems.

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/content/aip/journal/pof2/25/5/10.1063/1.4802042
2013-05-01
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Active control of a cylinder wake flow by using a streamwise oscillating foil
http://aip.metastore.ingenta.com/content/aip/journal/pof2/25/5/10.1063/1.4802042
10.1063/1.4802042
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