Davoud Davoudmaghami; Hossein Banejad; Mojtaba Saneie; Seyyed Asadollah Mohseni Movahhed
Abstract
Sharp-crested weirs are widely used for the purposes of flow measurement, flow diversion and water level control in hydraulics, irrigation, and environmental projects. Discharge coefficient at these weirs is a function of head to weir height ratio (H/P). In a constant head, flow increases by increasing ...
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Sharp-crested weirs are widely used for the purposes of flow measurement, flow diversion and water level control in hydraulics, irrigation, and environmental projects. Discharge coefficient at these weirs is a function of head to weir height ratio (H/P). In a constant head, flow increases by increasing the length of weir in the plan. One of these weirs is the duckbill weir. Sometimes, it is changed upstream and downstream bed level by deposition of sediments in the upstream of weir, erosion in the downstream of the weir, etc. These changes cause changes in the flow characteristics such as discharge coefficient. In this study, the effect of these changes on the discharge coefficient of duckbill weir is studied. The results showed that the change in the height of duckbill weir has no effect on the discharge coefficient. But, increasing L/W ratio (L and W are respectively length of weir and width of flume) decreases discharge coefficient. Also, with increasing, maximum of discharge coefficient gives in the amount of H/P less. So that maximum of discharge coefficient in L/W ratio 2, 3 and 4 is respectively 0.73, 0.68 and 0.63 which respectively occurred in the amount of H/P of 0.5, 0.3 and 0.25. Discharge coefficient is reduced with increasing upstream bed level. In submerged flow, Reducing the downstream bed level increase discharge coefficient but changes in downstream bed level have no effect on discharge coefficient until flow is not submerged, also, conditions of aeration are the same. By increasing the L/W ratio in duckbill weir from 3 to 4, amount of H/P in threshold of flow Interference and local Submergence decreased from 0.5 to 0.3.
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.
Seyed Ali Ayyoubzadeh; Mahdi Habibi; Mohammad Rostami; Mojtaba Sanei; Mohammad Faramarz
Abstract
Side weirs are widely used to divert water from rivers. In movable bed rivers, deposition of sediment particles along the side weir may cause some problems in diverting water. This research is done in a laboratory flume of 0.9 meter wide and 10 meter long with a longitudinal slope of 0.001. Three value ...
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Side weirs are widely used to divert water from rivers. In movable bed rivers, deposition of sediment particles along the side weir may cause some problems in diverting water. This research is done in a laboratory flume of 0.9 meter wide and 10 meter long with a longitudinal slope of 0.001. Three value of weir length i.e. 0.6, 0.4 and 0.2 with a single weir height of 0.08 meter were used in the experiments. The variations of water surface profiles along the side weir were measured for various upstream Froude Numbers. The obtained results from experiments on movable bed condition were compared with those from rigid bed condition and also with the results from analytical solution. The results showed that bed form made by flow regime in the vicinity of the side weir does effect on the water surface profile over the weir and thus changes the diverted flow discharge. Water surface and discharges over the side weir were found in good agreement with the results obtained from the analytical solution in compare with the results obtained from channel with movable bed. The computed relative error for flow discharge in channels with movable and rigid bed is 6.35% and 24.18% respectively. This amount for variations of water surface profiles along the side weir is 8.03% and 9.88% respectively.
Farhad Shiva; Jalal Attari; Mojtaba Saneie
Abstract
Scour phenomena can impair infrastructures and result in non-reparable damages. Few researches conducted so far show that application of non-cohesive criteria for situations where the bed is formed of cohesive materials, overestimates dimensions of the scour hole and will impose large costs to the project. ...
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Scour phenomena can impair infrastructures and result in non-reparable damages. Few researches conducted so far show that application of non-cohesive criteria for situations where the bed is formed of cohesive materials, overestimates dimensions of the scour hole and will impose large costs to the project. According to the previous researches, type and content of clay also significantly affects scour in the cohesive materials. In this paper, the local scour in the cohesive bed due to a horizontal submerged jet issued from a vertical sluice gate is experimentally studied. Initially, the effective factors were identified and Bentonite clay was selected as cohesive material. A total of 48 tests, considering four different clay contents, three amounts of gate openings and four different tailwater depths, were conducted in a rectangular flume of Soil Conservation and Watershed Management Research Institute laboratory. The results show that by adding Bentonite clay to the erodible bed, effect of cohesion appears in the 10% ratio and with further increase of the clay content the scour depth decreases considerably. So that in a bed containing 20% Bentonite clay the maximum scour depth reduces by 76% on average in relation with a non-cohesive bed. Based on the experimental results, a general equation for predicting the maximum scour depth valid in both conditions of presence and absence of the cohesive materials is presented. A sensitivity analysis on the existing parameters that effect on scour depth was conducted and compared with the results of previous researches. Finally, two types of scour hole profiles were defined which showed a relatively good agreement with previous empirical relationships.
Zeynab Mokarian; Seyed Hsshem Hosseini; Seyed Mojtaba Saneie; Majid Hosseini
Abstract
Acquiring sufficient knowledge about soil structure of the river side wall and arrangement quality of its layers will be helpful to prevent soil erosion and distraction. The main purpose of this research is to find a proper way to decrees effects of river bank erosion with regard to studying the effects ...
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Acquiring sufficient knowledge about soil structure of the river side wall and arrangement quality of its layers will be helpful to prevent soil erosion and distraction. The main purpose of this research is to find a proper way to decrees effects of river bank erosion with regard to studying the effects of clay on the rate of the river bank erosion. To conduct the research, some experiments have been performed by using an experimental model with 14m length, 90cm width, and 50cm depth. The results demonstrate the major role of clay in decreasing the rate of side wall erosion and the depth of scour. In the final analysis, the research comes to this conclusion that there is an inverse relationship between the increasing percentage of clay and the side wall erosion rate and scour depth. By increasing the amount of clay materials, adhesives, wall scour depth profiles, the declining trend is involved. So that the figure in clay materials 7/5% to almost zero. Scour depth at the top of the wall to increase the adhesion of materials resulting from the addition of bentonite clay to 7/5%, compared to non-clay materials has decreased by about 97% And at the beginning of the clay wall materials 7/5% of the action occurring is very low.
Seyed Javad Meshkavati Toroujeni; Mojtaba Saneie; Mohsen Masoudian; Mir Khalegh Ziatabar Ahmadi
Abstract
Scouring around the bridge piers is one of the most important issues in bridge piers hydraulic. This phenomenon has led to a discharge under the bridge piers and the results caused their reversal. The local scour mechanism around the piers is very complicated issue and many researchers were conducted ...
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Scouring around the bridge piers is one of the most important issues in bridge piers hydraulic. This phenomenon has led to a discharge under the bridge piers and the results caused their reversal. The local scour mechanism around the piers is very complicated issue and many researchers were conducted to discuss the investigation of this important matter. Many bridges are destroyed due to their often piers scouring and causing human and financial losses. Generally, two fundamental factors of flow contact with the bridge pier and water flow separation from the pier, led to the formation of vortices around the pier at the bridge piers site and cause the local scour. The present research has investigated the effect of flow discharge and pier diameter in depth and scour volume around the bridge piers using a physical model. For analyzing the effect of flow discharge and also the size of the pier diameter on local scour around the bridge piers, three piers were used with 21, 30 and 40 mm diameter with five different discharges in each pier. Experiments were carried out in a sandy bed (with a median size of 0.88 mm) flume of 8.0, 0.255 and 0.3 m in length, width and height a, respectively. The results showed that by increasing the discharge and Froude number in each pier, the volume and scour depth were increased. In a constant Froude number, the volume and scour depth increased by increasing the pier diameter. In 21, 30 and 40 mm piers, the scour depth also increased by 128.5, 94.7 and 135.1 percent by increasing of 40, 68.7 and 23.9 percent of flow discharge.
Mojtaba Saneie; Mahdi Azhdarimoghadam; Amin Hajiahmadi
Abstract
One of the sediment controlling methods in the hydraulics structures is application of the vortex settling basin. Such basins represent the higher speed in sediment separation in comparison with other usual settling structures. One of the problems of such settling structure is the settlement of a portion ...
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One of the sediment controlling methods in the hydraulics structures is application of the vortex settling basin. Such basins represent the higher speed in sediment separation in comparison with other usual settling structures. One of the problems of such settling structure is the settlement of a portion of the sediments on the basin floor as a result of disruption on the structure operation caused by remaining loads. Therefore, the curvature submerged vane was introduced by this research in order to solve the problem. Several curvature vanes patterns was applied in an experimental model of the vortex settling basin to investigate the efficiency and sediment removal from the basin floor. Experiments were carried out in a basin with diameter of 96 cm and a height of 206 cm. In this model, curvature submerge vanes were used for modification and their different arrangement in 60 degree diameter section for increasing in vortexes power. Experiments were continued by 45 and 37 Ls-1 water discharge, flushing orifice diameters of 36, 46 and 59 mm and six different arrangement of vane (R2, R3, R4, R23, R34, R234). Results showed that application of submerged vane on the vortex basin floor with suitable arrangement resulted in sediment removal from basin floor and in replacement of sediments toward the orifice. Present research showed that the best efficiency was obtained from R3, R4 and R34 arrangements which were located in the farther distance from orifice. Furthermore, results showed that variation in water discharge and orifice diameter is an effective factor in the efficiency of curvature submerged vane. In the most optimum case of curvature submerged vane arrangement, 25.56 percent of the sediment was removed from the floor of vortex settling basin.
Mojtaba Saneie; Hoda Hadidi; Mohammad Ali Bani Hashemi
Abstract
Investigating local scour phenomena due to jet flow on downstream of hydraulic structure is an important and necessary issue. In this article, the results of a laboratory study about the impact of tail water depth on local scour below of jet flow are provided. Circular, square and rhombus sections with ...
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Investigating local scour phenomena due to jet flow on downstream of hydraulic structure is an important and necessary issue. In this article, the results of a laboratory study about the impact of tail water depth on local scour below of jet flow are provided. Circular, square and rhombus sections with a water jet from a hole, and, with a discharge of 2.46 to 4.8 liters per second, on a medium material bed of d50 of three mm made of sand, with tail water depth ranged from 10 to 24.8 cm, for 60 minutes, was simulated. The dimensions of scour holes were measured and analyzed. Results demonstrated that the maximum scour depth, with increased tail water depth to a certain extent, increased, and then, tail water will be reduced with more depth. It also became clear that the dimensions of scour holes with the following parameters of and their relation with power. Finally, the dimensional relationships for the estimation of scour depth of discharge and the tail water variety have been proposed.
Mojtaba Saneie; Moen Asefi Asefi; Kazem Smaeeli
Abstract
The vortex settling basin is a sediment control structure in conveyance water system which can be more economical than other designs in specific conditions. Deposition of sediment in the basin is a major problem. Mechanism of separates solids and water in these basins, based on flow vortex and difference ...
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The vortex settling basin is a sediment control structure in conveyance water system which can be more economical than other designs in specific conditions. Deposition of sediment in the basin is a major problem. Mechanism of separates solids and water in these basins, based on flow vortex and difference of density between water and sediments. Therefore the sediment increases in the basin for long time. In this study the hydraulic characteristics of these basins are investigated and offered a method to increase the efficiency of it. In this offer the submerge vans were used on the bed of the basin. Experimental results were showing that increase in deposition with a decreasing vanes interval (r<R/2). But in further distances (r>R/2), vanes with guidance sediments toward orifice bottom, flashing from bottom occur more than another. Results also indicated that located vanes with constant total flashing efficiency and flow losses, and has been able to change bottom sediments in the basins. Experiments show that if the vanes are placed in less radial intervals, the discharge loss increases. As well as increase input flow because that total deposition efficiency, hydraulic efficiency and vanes efficiency in flashing have been increased.
Mojtaba Saneie
Abstract
Spur dikes are used widely to prevent outer bank river bends and path-modification river projects. Local scouring in spur dile nose is due to contraction and strong eddy is among the important problems occurring in designing Super dikes. Experimental study has been done on effect of length and alignment ...
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Spur dikes are used widely to prevent outer bank river bends and path-modification river projects. Local scouring in spur dile nose is due to contraction and strong eddy is among the important problems occurring in designing Super dikes. Experimental study has been done on effect of length and alignment of minor spur dike to reduction of main spur dike scouring. In order to do this study a shorter spur dike was used in two stages, one perpendicular and one angled to flow channel direction. By non dimensional parameters, contraction ratio L/B=0.3, 0.35, 0.4, 0.45, (L=length of spur dike, B=width of channel), Length ratio L’/L=0.5, 0.6, 0.7, (L’= length of minor spur dike) and distance ratio x/L=0.5, 1, 1.5, 2, 2.5 have been studied. Scour depths at nose of minor and main spur dike have been measured. Data collection were fitted by regression analysis and a relation for reducing scour depth at nose of first spur dike is provided, with and without minor spur dike.
Masoud Sajedi Sabegh; Mojtaba Saneie; Mehdi Habibi; Ali Akbar Abbasi; Mehdi Ghadimkhani
Volume 2, Issue 4 , January 2011, , Pages 206-210
Abstract
In this paper the effect of tree planting in a river bank on the shear velocity of flow was studied in a laboratory environment. At first a physical model was established in a 1.5m wide, 30m long experimental flume with a longitudinal slope of 0.01. Then a number of bars with 6.5mm in diameter, ...
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In this paper the effect of tree planting in a river bank on the shear velocity of flow was studied in a laboratory environment. At first a physical model was established in a 1.5m wide, 30m long experimental flume with a longitudinal slope of 0.01. Then a number of bars with 6.5mm in diameter, stimulated as trees, were located on the bank surface with a slope of 1:3 in two different orientations (square and triangular forms), three different heights (5, 6.5 and 8cm), and three different intensities (6*6/6*3, 8*8/8*4, 10*10/10*5). After that, the flow hydraulic parameters (such as discharge, water level and velocity) and their variation versus the change in experimentally planted trees were measured and analyzed. At least 19 series of laboratory tests with 5 different discharges were implemented. The results showed that, there is a relationship between planted tree and shear velocity. Also relationship between shear Reynolds () and the average velocity to shear velocity ratio () showed that vegetation could increase the roughness coefficient also by increasing the tree density, the ratio of and the roughness are increased. The roughness coefficient in all cases of not using vegetation, tree planted in square form and tree planted in triangular form, was increased respectively.
Mojtaba Saneie
Volume 2, Issue 3 , October 2010, , Pages 179-186
Abstract
One of the common methods of river training and bank protection is using spur dikes to modify flow path. Because of the concentration of flow in the middle part of the river it causes the river side not to be washed out. This new river path makes the river bed next to the end of the spur dikes ...
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One of the common methods of river training and bank protection is using spur dikes to modify flow path. Because of the concentration of flow in the middle part of the river it causes the river side not to be washed out. This new river path makes the river bed next to the end of the spur dikes to be washed out. Usually the spur dikes are built in groups to extend the protected zone. The stability of these spur dikes against the river flow depends on stability of the first spur dike. The purpose of this laboratory research is to investigate different ways for reduction of erosion around the first spur dike. It is suggested to use a shorter spur dike at the upstream part perpendicular to the flow direction. In this research, it is intended to find the optimum distance between the shorter spur dike and the first spur dike in order to have minimum erosion around the first spur dike. From the hydraulics point of view, L’/L (the length of shorter spur dike to the length of first spur dike), X/L (the distance between first spur dike and shorter spur dike to the length of first spur dike) and H/L’ (the depth of water at upstream to the length of shorter spur dike) have been studied and results has been presented in the form of equations.
