Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.
The problem of turbulent flow-canopies interaction has been
extensively studied in literature. Interaction between flow and
aquatic riparian vegetation is an extremely complex problem.
Although many studies have attempted to explore it, flow
through vegetation phenomenon has not yet been fully
described quantitatively. At the beginning, effects of vegetation
on turbulent air flow have been studied through wind tunnel
and fields measurements. Afterwards researcher’s attention has
been aimed at turbulent characteristics of a water flows
developing in experimental flumes with vegetated bottom.
Generally, turbulence characteristics whose changes were
described were mean velocity, standards deviation, skewness,
kurtosis. In their studies some researchers deepened the effect
of vegetation on more specific characteristics of the turbulent
flow as the integral length scales. The aim of the paper is to
experimentally study the effects of vegetation density on the
longitudinal integral length scales of a uniform turbulent flow
above and inside sparse canopies. Water flume experiments
were conducted in a channel 8m long and with a square section
0.40 × 0.40m2. The model of canopies consisted of sparse rigid
cylinders of the same heights but set in three different aligned
allocations (squares or rectangles), with three different
densities. Two different measurement locations were
considered, in any case in a reach of the channel where the
uniform flow was attained. In order to measure instantaneous
velocities an LDA system was used. Experiments were carried
out by varying the flow rate and the slope of the channel.
Starting from instantaneous velocity data collected,
distributions of longitudinal integral length scales were
determined and analyzed. Finally more correct methodologies
in order to evaluate integral length scales and to normalize
them were proposed.
