نوع مقاله : مقاله پژوهشی
نویسندگان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Dam reservoirs are among the most important sources of fresh water. In the event of a loss in the useful volume of the reservoirs, their capacity for water containment and storage decreases. The most important factor in reducing the useful volume of the reservoirs is sedimentation, and the most important factor of sediment transfer in reservoirs is dense current. The dense current is a stream created by density difference between two fluids under the gravitational acceleration.
Experiments were carried out at the Hydraulic Research Laboratory of Faculty of Water Science Engineering, Shahid Chamran University of Ahvaz, in a flume with 780 mm long and 70 cm height with a slope of minus 1 to 3.86%. The flume was divided into two sections using a sluice gate. The right side of this gate was filled with the clear water. The gate at the flume’s end maintained the clean water level. On the left side, the water and salt solution is entered. This gate was able to be rapidly opened and discharge the water and salt solution with a specific flow rate into the clear water. In the present study, four different modes of application of three successive obstacles were investigated for dense current controlling. The height of the obstacles was considered by three ratios of dense current body height as hr =0.5, 0.75, 1(hr = hm/h, where hm is the obstacle height and h is the average height of the dense current body). In three obstacle configuration modes, the heights of the obstacles were equivalent and in the fourth state, three obstacles with similar dimensions were placed ascendingly. Experiments were performed at 3 slopes of 0, 1.5 and 2.5%, with two concentrations of 10 and 20 gr/L and a constant flow rate of 1 L/s.
The results showed that the frontal dense flow at all slopes and both concentrations of 10 and 20 gr/L, had almost the same velocity before reaching the obstacles. As the frontal dense current encounters the first obstacle, its speed significantly decreases and continues to decrease until the last obstacle. The highest percentage of frontal discharge control at two concentrations of 10 and 20 gr/L was for and was calculated to be 84 and 87%, and the lowest percentage of the frontal discharge control at same concentrations was for , and was calculated to be 25 and 31%, respectively. For the ascending configuration obstacles, the percentages of frontal dense current discharge control at the slopes of 0, 1.5 and 2.5% for the concentration of 10 gr/L were 74, 52 and 44%, and for the concentration of 20 gr/L was 78, 58 and 48%, respectively.
کلیدواژهها [English]
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