Experimental Study of the Flow Characteristics on Corrugated Wall with Perforation

Abstract

In this study, the flow characteristics of two-dimensional corrugated walls with perforation are investigated using particle image velocimetry (PIV) experiments. Analysis of the flow on perforated corrugated walls at perforation ratios φ = 1%, 2.5%, 5%, 10% and the same wavelength Reynolds number, Reλ, shows that the friction coefficient, Cf, decreases with increasing perforation ratio, φ, and the followability becomes more obvious, indicating that perforations on the corrugated wall can reduce the drag. Analysis of the dimensionless circulation, G+ Q, reveals that the perforation effectively controls separation on the corrugated wall, which is consistent with observations of the recirculation area. After elucidating the mechanism of action of the perforation on the corrugated wall, the turbulence characteristics at different Reynolds numbers are explored for φ = 2.5% by varying the velocity of the flow field. When Reλ = 8800, the free flow velocity is insufficient to achieve the inverse pressure gradient required to produce stable separation in the flow field. With an increase in Reλ, the recirculation region in the time-averaged flow field becomes incomplete due to the effect of the perforation, and the turbulent fluctuation is also weakened. The following behavior of the friction coefficient, Cf, with the oscillations of the wave crest and trough also differs from the behavior observed with increasing wavelength Reynolds number, Reλ.

Keywords

• separation
• flow control
• turbulence flow
• piv
• wavy wall