Laboratory Study to Decrease the Scour Downstream Weirs Using screen Walls
AbstractIn this research, a laboratory study of the phenomenon of scour in the stone floors (gravel, crushed) using single and double screen walls used as energy dissipation. The study includes the effect of weir height (P), the diameters of screen wall hole (∅), the number of screen walls (Sw) on scour behind walls screen.Seventy experimentswere carried out (ten of them without using screen walls).One size of crushed stone (Dm = 0.79) mm were used with two height of weir (P = 25, 30) cm and three different diameters of screen walls (Ø = 0.8,1.2,1.6) cm were used and single and double screen walls (Sw = 1, 2) with five different discharge, with porosity 40% for single and double screen walls.
The results of the experimental work showed that the depth and length of the scour hole was minimum when using screen walls of (P = 25) cm in comparison with (P = 30) cm. Also the use of single and double screen walls decrease the depth and length of scour hole with ratios of (28-83.33)% and ratio of (47.37-85.71)% respectively compared with the state of without using screen. Using dimensional analysis two empirical relations were determined to compute the ratio of depth and length scour in term of dimensionless variables.
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