Sediment Entry Investigation at the 30 Degree Water Intake Installed at a Trapezoidal Channel
2 Abstract: A major problem which most of lateral intakes are faced with is sedimentation and sediment delivery. This process causes many problems such as reduction flow discharge capacity in irrigation canals as well as threatening of blockage of water during low water flow. Therefore it is the main goal of engineer to design an intake with higher flow discharge and low sediment delivery. Since most of lateral intakes are installed at trapezoidal which has not received the same attention as intake from rectangular canals, it is the main goal of this study to investigate sediment delivery to an intake from trapezoidal canal. In this study, sediment tests carried out for different hydraulic conditions at a 30 degree water intake installed at main channel with inclined bank. From analysis of these it was found that the flow patterns at the upstream of the intake has been modified in such a way that more water from surface layers are diverted. Therefore less suspended sediment enters the intake. Also it was found that in all tests the amount of sediment enters the intake reaches its minimum value at Froude Number between o.35 to o.4. In low flow depth because of the effect of bed roughness over strength of secondary current, the suspended sediment enters the intake is lower compare to the higher flow depth for the same conditions.
Flow in a branching open channel: a review
Branching channel flow refers to any side water withdrawals from rivers or main channels. Branching channels have wide application in many practical projects, such as irrigation and drainage network systems, water and waste water treatment plants, and many water resources projects. In the last decades, extensive theoretical and experimental investigations of the branching open channels have been carried out to understand the characteristics of this branching flow, varying from case studies to theoretical and experimental investigations. The objectives of this paper are to review and summarise the relevant literatures regarding branching channel flow. These literatures were reviewed based on flow characteristics, physical characteristics, and modeling of the branching flow. Investigations of the flow into branching channel show that the branching discharge depends on many interlinked parameters. It increases with the decreasing of the main channel flow velocity and Froude number at the upstream of the branch channel junction. Also it increases with the increasing of the branch channel bed slope. In subcritical flow, water depth in the branch channel is always lower than the main channel water depth. The flow diversion to the branch channel leads to an increase of water depth at the downstream of the main channel. From the review, it is important to highlight that most of the study concentrated on flow characteristics in a right angle branch channel with a rigid boundary. Investigations on different branching angles with movable bed have still to be explored.
Characteristics of secondary flow in steady and pulsatile flows through a symmetrical bifurcation.
Steady and pulsatile flow in a glass model simulating an arterial bifurcation was investigated by flow visualization techniques. Secondary flow generated at the bifurcation has a similar pattern to a vortex, called the horseshoe vortex, produced around a wall-based protuberance in a circular tube. The same flow disturbance was clearly observed during the decelerating phase of pulsatile flow. The vortex produces a stagnation point on the top and bottom wall just upstream from the bifurcation apex. When aluminium dust was suspended in the test fluid perfusing the blood vessel model, particles deposited over an area spreading from the stagnation point to the lateral corners of the bifurcation. Comparison between the present results and topographical patterns of atherosclerosis reported in the literature suggests that it is in such low shear regions that lipid deposition tends to occur most.