Abstract
Erosion is defined as the displacement of the bottom materials due to the flow energy and moving them to the farthest distance, which negatively affects the stability of the hydraulic structures. In this research, the effect of the properties of the screen walls on scour in open channels was studied. Therefore, the study included evaluating the effect of the diameters of the screen walls openings (φ), wall thickness (t), and the ratio of the distance of the screen walls from the gate to the height of the opening below the gate on the scour process. A total of 140 experiments were conducted in concrete channel including one size of gravel, two opening heights (4 and 5 cm) at the bottom of the gate, three diameters of the screen wall openings (0.8, 1.2 and 1.6) cm, two thicknesses of the screen wall (0.4 and 0.8) cm, one value of screen wall porosity (40%), using five discharges in the range of (50.06-27.98) l/sec when x=40d, 45d, and in the range of (44.8-23.68) l/sec when x=50d, 56.25d. The results showed that the screen walls with a diameter of (1.2) cm resulted in the lowest volume of the scour hole while experiments conducted without screen walls led to largest volume of scour hole. Moreover, the screen walls of (0.8) cm thickness leads to less volume of the scour hole as compared to those for the screen walls of (0.4) cm, especially for high discharge i.e. for high values of Fr number. Two empirical relations were proposed to compute the scour depth ratio and its length in term of dimensionless variables using dimension analysis.
