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On the transition between distributed and isolated surface roughness and its effect on the stability of channel flow
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10.1063/1.3644694
/content/aip/journal/pof2/23/10/10.1063/1.3644694
http://aip.metastore.ingenta.com/content/aip/journal/pof2/23/10/10.1063/1.3644694
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Geometry model. Roughness elements in the form of triangular “ridges.” (A) Distributed roughness; and (B) transition towards the isolated roughness limit.

Image of FIG. 2.
FIG. 2.

Geometry model. Roughness elements in the form of triangular “trenches.” (A) Distributed roughness and (B) transition towards the isolated roughness limit.

Image of FIG. 3.
FIG. 3.

Geometry of the roughness elements. Elements 1-4 correspond to the “ridges” while 5-8 are opposite to 1-4 and correspond to the “trenches.” The sketch is not in scale. All elements have the same height (H = 0.032) and bases with the length B = π/2, π/4, π/8, and π/16; the slopes of the side walls are 2.3°, 4.6°, 9.25°, and 18.05°, respectively.

Image of FIG. 4.
FIG. 4.

Sketch of the flow domain. The computational domain is contained between y = min(yL) and y = 1.

Image of FIG. 5.
FIG. 5.

The neutral curves in the (Re, β) plane for disturbances in the form of streamwise vortices for the roughness system made of “ridges” with the base B = π/2 and spacing characterized using parameter κ  =  λ/B (larger values of κ corresponds to larger distances between the roughness elements).

Image of FIG. 6.
FIG. 6.

The neutral curves in the (Re, κ) plane for disturbances in the form of streamwise vortices for different values of the flow Reynolds number Re for the roughness system made of “ridges” with the base B = π/2 and spacing characterized using parameter κ  =  λ/B.

Image of FIG. 7.
FIG. 7.

Curvature of streamlines of the base flow over roughness system made of “ridges” with the base B = π/2 and located at distances apart from each other corresponding to κ = 1, 1.5, 2, 3, 4 (see (A)–(E), respectively).

Image of FIG. 8.
FIG. 8.

Variations of the critical Reynolds number for disturbances in the form of streamwise vortices as a function of the roughness spacing parameter κ  =  λ/B for the roughness system made of triangular elements with the base B  =  π/2, π/4, π/8, and π/16. Continuous and dashed lines correspond to the “ridges” and the “trenches,” respectively.

Image of FIG. 9.
FIG. 9.

Variations of the critical Reynolds number for disturbances in the form of streamwise vortices as a function of the wavelength λ of the roughness system. Other conditions as in Fig. 8.

Image of FIG. 10.
FIG. 10.

Curvature of streamlines of the base flow over roughness system made of “trenches” with the base B = π/2 and located at a distance away from each other corresponding to κ =  3.

Image of FIG. 11.
FIG. 11.

The neutral curves in the (Re, δ) plane for disturbances in the form of traveling waves for the roughness system made of “ridges” with the base B = π/2 and spacing characterized in terms of parameter κ  =  λ/B (larger values of κ corresponds to larger distances between the roughness elements). κ  =  ∞ denotes smooth surface.

Image of FIG. 12.
FIG. 12.

Variations of the critical Reynolds number for disturbances in the form of traveling waves as a function of the spacing parameter κ  =  λ/B for the roughness system made of triangular elements with the base B  =  π/2, π/4, π/8, and π/16. Continuous and dashed lines correspond to the “ridges” and to the “trenches”, respectively.

Image of FIG. 13.
FIG. 13.

Variations of the critical Reynolds number for disturbances in the form of traveling waves as a function of the wavelength λ of the roughness system. Other conditions are as in Fig. 11.

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/content/aip/journal/pof2/23/10/10.1063/1.3644694
2011-10-06
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: On the transition between distributed and isolated surface roughness and its effect on the stability of channel flow
http://aip.metastore.ingenta.com/content/aip/journal/pof2/23/10/10.1063/1.3644694
10.1063/1.3644694
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