FLUID-SURFACE INTERACTION INSIDE DIAMOND-SHAPED CYLINDER BUNDLES EXPLORED BY MEANS OF LDV

摘要

Two-dimensional laser Doppler velocimetry (LDV) is employed to investigate interaction between the intersecting main stream and wake flow in the diverging-flow region of the flow passages inside diamond-shaped cylinder bundles. Flow cross-sectional area and flow rate are varied to change the Reynolds number (Re) in the bundles- Power spectra representing the oscillating characteristics of the flip-flop flow are determined from LDV data. The dominant frequency is observed. Special features are disclosed in the relationship between the Reynolds number and the Strouhal number (St) representing the dimensionless dominant frequency in all power spectra of the flip-flop flow. Results exhibit the characteristics of typical edge-tone phenomena with the value of St diminishing in parabolic shape with Re over a period followed by a step-decrease to a lower value. This finding is critical in application of the devices for flow control.