Investigation of the effect of permeable obstacles on salt density current head

Subject Areas : Subjects

mehdi derakhshannia ¹ (Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran.)
mehdi ghomeshi ² (Department of Water Structures, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.)
saied saeid Eslamian ³ (Department of Water Engineering, College of Agriculture, Isfahan University of Technology, Isfahan, Iran.)
seyed mahmood kashefipour ⁴ (Department of Water Structures, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.)

Received: 2020-10-01 Accepted : 2021-10-26 Published : 2021-10-23

Keywords: Momentum, Density currents, Permeable obstacle, Head flux,

Abstract :

Density currents are often the main cause of sediment transport in deep water and reservoirs. To prevent sedimentation in critical locations of dams, various methods have been proposed, including placing obstacles in the path of these currents. in this study, the effect of discharge, inlet concentration, slope and height of trapezoidal permeable obstacle on the behavior of density current has been investigated . 72 experiments were performed with variable discharge of 1, 1.5, and 2 liters per second and variable concentrations of 10 and 15 g/l, slope of 0.5%, 1% and 1.5% and obstacle height of 1,1.5 and 2 times the body of density current. The percentage of flux reduction was determined and the effect of other parameters was evaluated. The results showed that slope, concentration and inlet discharge are the factors affecting the momentum and by increasing each of these parameters, the efficiency of obstacle with heights of 1 and 1.5 times body density current decreases. In case of obstacle with a height of 2 times the body, when the current collides with the obstacle, there is a lot of turbulence, which decreases the momentum of the current, and complete control is performed. Thus, the average percentage of flux reduction for the dimensionless ratio of height 1 is about 38%, for the dimensionless ratio of height 1.5 is about 52% and for the dimensionless ratio of height 2 is about 86%. Finally, linear and nonlinear regression of the average percentage of flux reduction data was obtained.

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