Abstract:
The quincunx array is a common structure appearing on rough bed surfaces. However, the study on the variation of flow turbulence characteristics between particles and the distribution of different quadrants is still weak. Using round glass beads of different sizes, three different quincunx arrays with arrangements of different intervals were made. From the particle-image-velocimetry (PIV) data of turbulent flow over these arrays in an open channel flume, the distributions of the dimensionless longitudinal turbulence intensity
Tu, Reynolds stress
R, and turbulent kinetic energy
E were analyzed. They show that the area above the top of the beads features a strip-shaped change indicating the beads have little influence, whereas in the area below the tops, the beads have a greater influence. The vertical distribution of
Tu,
R and
E is relatively complex displaying a certain periodicity and regionality that permits a classification into sphere region (SR) and inter-sphere region (ISR). The vertical distribution of
Tu,
R and
E above the top of the particle basically coincides with each other, while the vertical distribution of
Tu,
R and
E below the top of the particle fluctuates obviously, and the distribution curves are shaped like an “S” and an inverted “L”. The longitudinal variations of
R and
E of different quadrants in the ISR are smooth and close to constant, the values of
R and
E in the 2
nd and 4
th quadrants are generally greater than those of the 1
st and 3
rd quadrants. However, in the SR, the distribution of
R and
E shows a ∪-like shape and there are minimum values near the position of
x+ = 0. The research results have a certain guiding significance for the design of fishway and waterway engineering.