Paradoxes in Aerohydrodynamics by Shakhbaz A. Yershin

Author:Shakhbaz A. Yershin
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Code of a porous insert

Porosity, ε

Thickness, h × 103 (m)

Flow velocity, u avg (m/s)

ΔP (Pa)

ξ

0.755

8.0

4.9

245

18.7

15.9

2390

17.3

0.706

0.9

4.9

158

12.0

15.9

1250

9.1

20.3

1900

8.5

0.706

2.7

4.9

468

35.7

Based on the analysis of the experimental data presented in Figs. 6.6 and 6.7 and in Table 6.7, it can be assumed that the characteristic of the porous layer, affecting the flow spillage, is the resistance coefficient ξ.

At a sufficiently high value of the resistance coefficient, the transverse pressure difference is, probably, much lower than the hydraulic resistance of the layer (e.g., in the case of the porous insert of spheres), such that a flattening of the flow occurs directly at the inlet boundary of the layer. When the lateral pressure differential at the boundary of the layer is higher than or at least comparable with the Δp of the layer, then the spillage of the flow before it will be partial. Thus, a uniform distribution of axial velocity is achieved within the porous layer. This is confirmed by the experimental data for the pack of fine-mesh screens.

Thus, based on the above, it can be concluded that a uniform flow distribution in front of a fixed granular bed will occur only if there is a sufficient hydraulic resistance of the layer. The authors [16] also arrived at a similar conclusion.

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