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Showing 2 results for Cohesive Sediment
Investigation of the Effect of the Kind of Sediments and the Change in the Bottom Outlet Form Using a Semi-Cylinder Structure on the Score Cone by a Physical Model
R. Amirjani, A. Kamanbedast, M. Heydarnejad, A. Bordbar, A. Masjedi,
Volume 22, Issue 4 (3-2019)
Abstract
In a pressure flushing method, when the water is discharged from the bottom outlet, after a period of flushing, a flushing cone will be formed at the front of the bottom outlet; the dimension of this cone is affected by several parameters such as outlet discharge flow, water depth of reservoir, and the kind of sediments accumulated in the reservoir. In this study, for the effect of cohesive & non-cohesive sediments, a physical model using specific dimensions was employed in order to develop the sediment evacuation method, and them a Semi-Cylinder structure in front of the lower drain was tested. The experiments were carried out using cohesive & non-cohesive sediments under two conditions: with the semi-cylinder and without it, at 90 experiments. The results indicated that the with discharge was increased, on i average, under both conditions and the volume of the score cone was increased. With decreasing the water depth, the flow mood was changed to free flushing, increasing the length and volume of the score cone. Semi-Cylinder form, on average, increased the volume of sedimentation and the length of sedimentation; this increase could be due to the formation of a pair of rotating Vortexes inside the Semi-Cylinder structure on both sides of the central axis of the valve.

Effect of Angle, Height of Support and Pipe Line Diameter Size on Scour Hole
N. Alami, M. Saneie, H. Haji Kandi,
Volume 26, Issue 1 (5-2022)
Abstract
Scouring holes under the oil, gas, and water pipelines threaten their stability by bending and demolishing. This phenomenon can cause damage to the environment and the oil and gas industry. The present study investigated the effect of the pipe diameter, the height of support, and the angle of the pipeline with flow direction by applying the experimental aspects to the cohesive sediments. The experiments were carried out by considering three angles of deviation as zero,15, and 30 degree based on the flow direction. Three opening gaps were considered through the experiments based on the pipe height as 0, D/2, and D/4 from the sand bed. Furthermore, three pipe diameters were employed to investigate the effect of diameter size. The results indicated that by increasing the angle of deviation, the height of scour hole decreased significantly, however, the raising the opening gap between pipe and bed increased the sediment deposition and it causes the height of scour hole is decreased consequently which was constituted approximately 18 percent. Moreover, the pipe diameter affects the scour hole formation and its effect on a downward jet and horseshoe vortexes and the result indicate by increasing the piper diameter the scour hole is increased based on its effect on the flow configuration. Finally, based on the experimental data, an equation was estimated to predict the scour depth by employing the non-linear regression technique.

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