LDV Measurements of Periodic Fully Developed Main and Secondary Flows in a Channel With Rib-Disturbed Walls

Abstract

Laser-Doppler velocimeter measurements of mean velocities, turbulence intensities, and Reynolds stresses are presented for periodic fully developed flows in a channel with square rib-disturbed walls on two opposite sides. Quantities such as the vorticity thickness and turbulent kinetic energy are used to characterize the flow. The investigated flow was periodic in space. The Reynolds number based on the channel hydraulic diameter was 3.3×104. The ratios of pitch to rib-height and rib-height to chamber-height were 10 and 0.133, respectively. Regions where maximum and minimum Reynolds stress and turbulent kinetic energy occurred were identified from the results. The growth rate of the shear layers of the present study was compared with that of a backward-facing step. The measured turbulence anisotropy and structure parameter distribution were used to examine the basic assumptions embedded in the k–ε and k–ε–A models. For a given axial station, the peak axial mean-velocity was found not to occur at the center point. The secondary flow was determined to be Prandtl’s secondary flow of the second kind according to the measured streamwise mean vorticity and its production term.

Numerical sensitivity analysis of 3- and 2- dimensional rib-roughened channels

“…The spanwise flow structure at the same plane is shown in Fig. 8a and is compared with the Laser Doppler Velocimetry (LDV) data of Liou et al [11] (re-produced in Fig. 8b).…”

“…Since 1970s there have been many experimental studies of the rib-roughened surfaces including those of Webb et al [8], Han et al [9], Park et al [10], Liou et al [11], Okamoto et al [12], Rau et al [7] and Krogstad et al [13].…”

Numerical Prediction of Flow and Heat Transferin a Two‐pass Square Channel with 90° Ribs

“…Figure 4 shows the cross-stream velocity vectors and the isothermal contours at selected planes. up-and-down flow movement and simultaneously generated the small vortex near the bottom surface on the both inner and outer surfaces, which was measured by Liou et al (1993b) using LDV. On the other hand, secondary flow occurred near the top surfaces (Fig.…”

Secondary flow and heat transfer coefficient distributions in the developing flow region of ribbed turbine blade cooling passages

“…Mixing is enhanced by interaction of the secondary flows, induced by the inclined ribs, and the mainstream flow, while local turbulence increases mixing in the weak areas of the ribs. Flow development is commonly ignored in the literature and more commonly is assumed to reach a steady, fully developed state (Lau et al 1991;Liou et al 1993). However, a considerable length of internal cooling passages is in fact in the initial developing region (typically up to half the span).…”