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Instability of a backward-facing step flow modified by stationary streaky structures
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10.1063/1.4761838
/content/aip/journal/pof2/24/10/10.1063/1.4761838
http://aip.metastore.ingenta.com/content/aip/journal/pof2/24/10/10.1063/1.4761838
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Sketch of the experimental model, dimensions are in millimeters.

Image of FIG. 2.
FIG. 2.

Mean-velocity profiles around the step measured at z = ±6.1.

Image of FIG. 3.
FIG. 3.

Mean-velocity profiles behind two roughness elements (□ and ■) and in symmetry planes between the neighboring ones (○ and ●) measured in cross section x = 12.1 at s = 1.52 and b = 0.61.

Image of FIG. 4.
FIG. 4.

Maximum mean-flow disturbance in the wake of a roughness element (□) and in a symmetry plane between two neighboring elements (■). (a) s = 1.52 and b = 0.30; (b) s = 1.52 and b = 0.61.

Image of FIG. 5.
FIG. 5.

Spectra of natural separated-flow disturbances in the wake of a roughness element (solid line) and in a symmetry plane between two neighboring elements (dotted line) measured in cross section x = 12.1 at s = 1.52 and b = 0.61.

Image of FIG. 6.
FIG. 6.

Equally spaced contours of the separated-flow perturbations in cross section x = 12.1 at s = 1.52 and b = 0.61: (a) excited at St = 0.0596; (b) excited at St = 0.0829; (c) natural velocity fluctuations in the frequency range St = 0.0516–0.1289.

Image of FIG. 7.
FIG. 7.

Streamwise growth of the controlled oscillations behind the 2D step (■) and modified by the roughness elements at b = 0.30 (□), 0.61 (○), and 0.91 (Δ). (a) St = 0.0596 at s = 1.52; (b) St = 0.0829 at s = 1.52; (c) St = 0.0596 at s = 3.03; (d) St = 0.0829 at s = 3.03.

Image of FIG. 8.
FIG. 8.

Equally spaced contours of rms amplitude of the fundamental modes calculated at x = 12.1, s = 1.52, and b = 0.61; u max/u min = 3.33. (a) St = 0.0596 and (b) St = 0.0829.

Image of FIG. 9.
FIG. 9.

Amplification rates of the perturbations determined through exponential approximation of the experimental data of Fig. 7 (□) and calculation results averaged in the range x = 3.0–9.1 (■). (a) St = 0.0596 at s = 1.52; (b) St = 0.0829 at s = 1.52; (c) St = 0.0596 at s = 3.03; (d) St = 0.0829 at s = 3.03.

Image of FIG. 10.
FIG. 10.

Experimental (□) and calculated (■) propagation velocities of the perturbations in the range x = 3.0–9.1. (a) St = 0.0596 at s = 1.52; (b) St = 0.0829 at s = 1.52; (c) St = 0.0596 at s = 3.03; (d) St = 0.0829 at s = 3.03.

Image of FIG. 11.
FIG. 11.

Amplification rates of the disturbances calculated for the present experimental configurations (solid lines) and for the averaged mean-velocity profiles (dotted lines). (a) 2D flow; (b) s = 1.52 and b = 0.30; (c) s = 1.52 and b = 0.61.

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/content/aip/journal/pof2/24/10/10.1063/1.4761838
2012-10-23
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Instability of a backward-facing step flow modified by stationary streaky structures
http://aip.metastore.ingenta.com/content/aip/journal/pof2/24/10/10.1063/1.4761838
10.1063/1.4761838
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