Hassan Goleij; Amirhamze Haghiabi; Mojtaba Saneie; Hojattallah Yonesi
Abstract
The percentage of flow diversion is the major cause of the formation of dimensions of separation zone such that with increasing the percentage of flow diversion, width and length of the separation zone decreased in the basic and sill experiments. However, by adding a 10ᵒskimming wall, the changing ...
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The percentage of flow diversion is the major cause of the formation of dimensions of separation zone such that with increasing the percentage of flow diversion, width and length of the separation zone decreased in the basic and sill experiments. However, by adding a 10ᵒskimming wall, the changing trend is different. At low percentage of flow diversion, dimensions of the eddy area decreased significantly and it increased with increasing the percentage of flow diversion. However, in general, the simultaneous usage of a 10 degree skimming wall and sill structures compared to basic and sill experiments, dimensions of separation zone in lateral intake decreased and the useful width of outlet flow at lateral intake increased and the separation zone and sediment accumulation at the entrance of lateral channel decreased. By examining the effect of the Froude number of flow (inlet flow) on dimensions of the eddy region, this parameter did not have any significant effect on it and its low impact could be connived. By investigating the width of separation line of flow in the surface and near the bed of channel bend, it was found that the flow diversion rate was the most important factor affecting this hydraulic parameter; since, at surface level of flow with increasing flow diversion ratio, this parameter increases and due to the creation of secondary flow and the change of surface flow pattern under the influence of the simultaneous application of a 10 degree skimming and dike structures, this parameter increases more. However, near the bed, in basic and sill experiments, this parameter increases with increasing flow diversion rate. However, the simultaneous application of 10-degree skimming and sill structures, the width of separation line of flow near the bed reduces by increasing the diverted flow
Hani Tabrizi; amirhamze haghiabi; Mojtaba Saneie; Hojjatollah Younesi
Abstract
The process of water diversion from the rivers always involve with sediment diversion in different sizes. The sediments that transported to the branch channel cause the expenditure to the water conveyance system and power-generation installations. One of the common methods to control the bed load and ...
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The process of water diversion from the rivers always involve with sediment diversion in different sizes. The sediments that transported to the branch channel cause the expenditure to the water conveyance system and power-generation installations. One of the common methods to control the bed load and water diversion increasing, is to modify the approach flow pattern by the control structures. In this study, the efficiency of spur dikes in modifying of diversion flow to the intakes that located at curved channels are investigated. Experiments carried out in ten main groups in a 180° curve channel with a diversion located at the 118° on the external curve. Results of this study show that the sediment discharge ratio increased by discharge ratio increasing and severely related to it. The spur dike at upstream of the intake decreases the sediment discharge ratio by modifying the approaching flow pattern such that in C2 experiments, the sediment discharge ratio until the discharge ratio is equal to 0.05, 0.15, 0.25, 0.35 decreased up to 86.6, 73.3, 64.7, 46.7 respectively. But this effectiveness limited to Qr=0.4, because the strength of secondary flow diminished due to flow diversion increasing. Also, study of the effect of spur dike on sediment volume fraction in diversion channel show that, the maximum value of Vr diminished from 0.4 in type A experiments to 0.18 in type D experiments by reduction of the distance between the spur dike and the intake centerline. According to the experiments, positioning the spur dike at upstream of the intake change the dimensions of stream tube and decrease the diversion from near bed high-sediment flow and increase the diversion from near surface low-sediment flow. The dimensions of the separation zone severely decreased in type D experiments by presence of spur dike and discharge ratio increasing.
