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.
Computation of physiological bifurcation flows using a patched grid
Abstract A finite volume method in a boundary-fitted coordinate system together with a zonal grid method is employed to compute the flow field of a real-shape two-dimensional aortic bifurcation. The steady terms in the governing equations are treated by a fully explicit scheme. The zonal gridding procedure is discussed in detail. The numerical method is first tested in a laminar backward facing step flow to demonstrate the features of the method. The effect of the interface treatment on the flow fields can be significant. A 90° T-junction is then computed. The results are in good agreement with the available experimental data. The method is then applied to simulate the flows of an atherosclerotic human aorta. Both the steady and pulsatile flows are considered. It is shown that the mean shear stresses in recirculation regions of a pulsatile flow cannot be adequately described by a corresponding steady flow with a mean Reynolds number. In pulsatile flows, a sinusoidal input pulse and a realistic input pulse are both used in the computations. It is found that the “averaged” flow behavior is similar in both cases. However, the details of the flow field are significantly different. During pulsatile flow, permanent eddies are not present. That is, for a certain period in a cycle, the entire wall is free from eddies. On the other hand, in another period, the overall wall is almost completely in the reversing flow near the walls. These phenomena have been observed by other authors experimentally. Distributions of wall shear stresses and locations of recirculation zones in a realistic flow are shown and discussed briefly.