Showing 24 results for Masjedi
H. Masjedian, H. Seyedoleslami,
Volume 6, Issue 4 (winter 2003)
Abstract
Pistachio oyster shell scale is one of the important pests of pistachio in Iran whose females are reported to exist in two or three forms, each form developing on a specific part of the pistachio tree. In this study, abundance of the pest is investigated on leaves and branches for different ages, two heights and four cardinal directions of tree crown. Paralelly seasonal population fluctuations of three forms were studied on leaves, and one-and two-year-old branches separately.
This insect overwintered as female mostly on one and two-year-old branches. It had two separable periods of activity, through the season. In the first period, eggs mostly hatched in April and crawlers mostly settled on leaves, fruits and newly grown twigs but rarely on older branches.These populations are male and female. In the second period, eggs mostly hatched in June, and crawlers settled mostly on leaves and one and two-year-old branches, but all individuals settled on leaves are males and those on branches are females. Population density is significantly higher on upper surface of leaves than on the lower surface. Analysis of variance showed that only significant differences existed in densities observed between trees in both generations, and also between two heights of tree crown for populations settled on wood. Two predatory species from Cybocephalidae and Coccinellidae, one ectoparasitoid from Aphelinidae and two endoparasitoids from Encyrtidae were collected as natural enemies of this pest in Isfahan.
A Masjedi, M Fathi Moghadam, B Shomalnasab,
Volume 12, Issue 46 (1-2009)
Abstract
Tamarix sricta plant grows in riversides of Karun river. Outer body plant in the flood times causes decrease in water velocity, preventing erosion. One of the factors by which the hydraulic resistance is expressed is the roughness coefficient. Measurement of roughness coefficient of the existing plants in these riversides and floodplains, and surveying their effects on the velocity decrease and shear stress of the flow are important. The present research studies roughness coefficient of the plants manning existing in the riverside. Tamaix sricta was studied in non-submerged and sub-critical conditions in a flume with the length of 12.6 m, width of 0.5 m and height of 0.6 m in different velocity, discharge and depth ranges. The height of plants in this study was 35 cm with a natural arrangement in a bench of 2.8 m in length put in the bed of the flume. The total number of the experiments is 22. The results of this study show that roughness coefficients of plants are functions of velocity, depth, hydraulic radius and type of plants. Roughness coefficients in non-submerge condition change nonlinearly with changes in velocity, depth, Reynolds number, submerge depth and (VR) in natural conditions.
A Masjedi, A Shokohfar, M Alavi Fazel,
Volume 12, Issue 46 (1-2009)
Abstract
The increasing cultivation of corn in Ahwaz and the direct relation between the increase of the summer corn yield and its perfect irrigation in sowing period all together have made the research regarding this crop necessary. Deciding over the suitable irrigation scheduling of corn (hybrid SC.704) in summer by utilization of class A evaporation pan is the focal point of this research. Accordingly, a project was conducted in the form of stadistical perfect accidendal block in four repetitions and four treatments in 1383 on Ahwaz Azad university research land situated in Choneibeh. The irrigation treatment had four levels of T1,T2,T3 and T4 in class A evaporation pan containing of four levels of 50,75,100 and 150 mm, carried out in split plot. The suitable irrigation period was chosen according to the best treatment performance and its components, and the total amount of water in the taking period defines the depth of irrigation. The soil texture is clay lomy silty and the internal soil is silty clay. According to the amount of the accumulated evaporation from class A evaporation pan and taking the plant coefficient (Kc) into consideration, the amount of needed evapotrans piration was calculated and the amount of needed water for plot was measured by water counter. Then a comparison between the means by the use of Donken multi domains test was made and in this way the superior treatment was selected. Accordingly, the most suitable time for irrigation of summer corn in Ahwaz was after 50 mm of accumulated evaporation from class A evaporation pan which equals ten irrigation in the growing period. So in order to acquire 12 tons of seed yield in each hectare, at least 9600 m^3 of water for every hectar is needed. However, given the equal amount of water, with 3 times decrease in irrigation in treatment T2 in comparison with T1, a performance near 11 tons and with five times decrease in irrigation and ten tons in treatment T3 a performance near 10 tons can be attained.
A Masjedi, A Moradi,
Volume 13, Issue 50 (winter 2010)
Abstract
In order to study the effect of spur dike position in the bend on the process of scoring, some tests were done in a laboratory flume of Plax glass material with 180 deg bend and R/B=4/7. In this research, by setting an spur dike in the laboratory flume with positions of 30,60,90,120,150and 160 degrees, discharge rates of 20 ,24 and 28 Lit/s , and fixed depth of 13 cm, the process of scoring around spur dike in pure water was investigated. For flume bed, gravels of uniformly granulated sizes were used. The results showed that the maximum scoring in the length of river bend is obtained with increasing the rate and angle of position up to the angle of 60 deg, and then from position of 60 deg the rate of scoring decreases up to the position of 120 deg, and finally the increase in the position up to 160 deg results in the maximum scoring.
A. Masjedi, M. Gholamzadeh Mahmoodi,
Volume 15, Issue 55 (spring 2011)
Abstract
Every year river flooding causes serious damage to the bridges at the time needed most. One of the most effective factors causing bridge failure is scouring around the piers in a river bend. One of the methods to decrease scouring around the bridge piers is fitting them with a coller on the piers. The collars protect the river bed against vortex flow in the vicinity of the pier base. An experiment was conducted to study lab flumes made of Plaxiglass with a 180 degree bend and 2.8 m central radius and a 0.6 m width. In this study, a 6cm diameter pier was placed with a circular collar with four different collar sizes in one position in bend with constant discharge and depth under clear-water conditions. The collar was placed at four different elevations. The soil material had a diameter of d50 = 2mm and geometric standard deviation of σg = 1.3. The results of the model study indicated that the maximum depth scouring was highly dependent on the experimental duration. It was observed that as the size of a collar plate increases, the scour decreases. So, minimum depth of scour is dependent on the 3D coller and -0.1D elevation. Circular collar results in maximum reduction in scour depth (93%) compared with no circular collar.
A. R. Masjedi, H. Kazemi, A. Moradi ,
Volume 15, Issue 57 (fall 2011)
Abstract
In this research, the effect of installing position of bridge pier on scouring depth was studied in a bend laboratory flume, which is made of Plexiglas with 180 bend and a relative radius of Rc/B=4.7. Tests were conducted using one pier 6 cm in diameter under four discharge conditions with constant depth of 12 cm and clear-water conditions. Flume bed was fully paved by uniform sand. It was found that maximum scouring depth occurred in bend when bridge pier was installed in the position of 60 degrees. Also, in all situations increased scouring depth occurred by increasing discharge.
A. Masjedi, A. Taeedi,
Volume 18, Issue 67 (Spring 2014)
Abstract
Floor intake is one of the best options for diverting mountain rivers' flow. Determination of discharge diverted in different conditions of flow in main channel is one of the main objectives for intake under rack floor condition. Gradient and shape of grid rod floor can affect the discharge deviated. In this experiment, placement and gradient of grid rods and also their effects on the discharge coefficient and hydraulic parameters were investigated. For this purpose, a physical model made of glass with variable gradient was used for the main channel. To conduct and measure the discharge diverted, a sub-channel 8 meters away from the entrance of main channel was installed below the main channel. Length and width of intake entrance were 10 and 50 cm, respectively. At the entrance of intake a longitudinal grid with four different rod diameters, constant-space passing, and four different gradients were used. Meanwhile, for the investigation of flow rate four discharges were used. The results showed that intake discharge coefficient was increased with an increase in diameter of grid rod floor, reduction in floor gradient, and increasing of depth in the upstream network. In all cases, increasing the Froude number resulted in an increase in the intake discharge coefficient in the upstream network
E. Nohani, M. Shafai Bejestan, A. R. Masjedi,
Volume 18, Issue 68 (summer 2014)
Abstract
Local scour around piers is the major cause of their foundation failure in the river bends that endangers the stability of the structure and its efficiency. Riprap is commonly placed around the bridges piers for local scour protection. The aim of this study was to present an equation for estimating stable riprap diameter around a cylindrical bridge pier in river bends. In this study, using an experimental model with a 180 degree bend stability, four different riprap diameters under different flow conditions and clear water flow were studied. Empirical relationships based on dimensional analysis for stable riprap design around the bridge foundation was presented. The experimental results were compared with equations provided by other researchers, including Lauchlan (1999), Parola (1995) and Chiew (1995). Results showed that the presented equation in this paper has a good precision. The simple equation presented in this study included all factors important to the instability of the riprap, and recommends designing ripraps around the bridge pier in river bends.
A. Masjedi, M. Sobhani,
Volume 19, Issue 74 (Winter 2016)
Abstract
Riprap is used to control scouring around the bridge abutment. In order to study the stability of riprap around two bridge abutments with two different shapes, experiments were conducted in a laboratory flume made of Plexiglass in 180 degree bend. In this research, several experiments were done by placing the two bridge abutments made of Plexiglas in a series of riprap. Experiments included two different types of riprap with different densities, four different diameters and constant rate of discharge under pure water condition. In each experiment, flow depth was measured in terms of moving threshold, then stability was calculated by using the data obtained. The results showed that in the same conditions chamfered wing-wall is greater than vertical-wall. So, chamfered wing-wall is, on average, 9 percent more stable than the vertical wall.
M. Halvaeifard, A. Masjedi,
Volume 20, Issue 78 (Winter 2017)
Abstract
One of the methods for sediment control in lateral intake can be application of submerged vanes in front of the inlet. The establishment of submerged vanes in flow path causes a flow diversion toward the inner arc. In this research, the performance of submerged vanes on sediment transport to the inlet at 180 degree of intake has been investigated. Several experiments were carried out in a laboratory channel made of Plexiglas at a 180-degree arc, under clear water condition. In this research a series of experiments were done by inserting several vanes made of Plexiglas in front of lateral intake. Experiments were done by using two rows of parallel vanes with variable angles at four different discharges under two conditions of with and without vanes. In each experiment, the main channel discharge and diversion channel discharge, sediment discharge through the diversion and transmission were measured. The results of research showed that the performance of the parallel submerged vanes in diverting the path of sediments depends on contacted vanes angle by water flow. Also, entering water rate is directly proportional with entering sediment rate and entering sediment rate are increased with the increase of entering water rate at all angles. Suitable performance in reducing the sediment transport to the inlet was observed at an angle of 15 degrees of vanes relative to the axis of water flow. In other words, by increasing the angle relative to the axis of flow, sediment transport to the inlet will be increased.
M. Naserian, A. Masjedi,
Volume 21, Issue 4 (Winter 2018)
Abstract
River bend due to particular pattern, called 'Vortex Flow,' has greater erosion than straight path. Occurrence of scour around bridge abutment on curved paths is one of the main reasons for destruction of bridges. Riprap is one of the methods to control the scouring around the bridge abutment. The purpose of this study was to assess stability of the riprap around the bridge abutment at 180 degree river bend. In order to study stability of riprap around the bridge abutment, experiments were done in a laboratory flume made of Plexiglas under 180 degree bend, 2.8 m in central radius, 0.6 m in width and R/B=4.67. In this research, several experiments were done by placing a bridge abutment with vertical winged wall made of Plexiglas surrounded by a series of riprap. Experiments were done by three different types of riprap with different density 1.7, 2.1 and 2.42, four different diameters 4.76, 9.52, 12.7 and 19.1 mm and four rates of discharge under pure water condition. In each experiment, flow depth was measured in terms of moving threshold and failure threshold and then the formulas were calculated by using data obtained. The results showed that the relative diameter of riprap increased with increasing Froude number in terms of moving threshold and failure threshold. Finally, the suitable formula to estimate diameter of riprap around the bridge abutment at 180 degree bend were presented in terms of moving threshold and failure threshold.
A. Masjedi, B. Jafari,
Volume 22, Issue 3 (Fall 2018)
Abstract
In this study, the performance of slot in the spur dike was evaluated as a way to reduce the scouring around the installed flat spur dike in a 180 degree bend and the development of scouring in the slotted spur dike was compared with that of the spur dike with no slot. To evaluate the effect of the slot on the development of scouring around it, a flat spur dike made of Plax Glass was installed in a position of 70 degrees from a bend (180 degrees) in the flume bed. After determining the maximum of scouring depth at the tip, to reduce the scouring around the spur dike, two slots with the determined height were placed in 4 different positions in the spur dike. Experiments with 4 different discharges and constant flow depth in clear water conditions were conducted. The results of the experiments showed that the created the slot reduced the scouring depth toward the spur dike. In both slots, the minimum of scouring depth was seen in a model with the closest position of the slot toward tip, and its maximum was seen in a model with the farthest position from the slot.
E. Gravandi, A. Kamanbeadst, A. R. Masjedi, M. Heidarnejad, A. Bordbar,
Volume 22, Issue 3 (Fall 2018)
Abstract
Rivers has long been regarded as one of the most basic human water supplies. If the topography, a morphology, water requirements conditions, etc. allow water to be transferred to gravity, the use of the dike can have a significant impact on the flow rate and the sediment input to Intake. Dike design needs to consider several parameters such as position, length, type, etc. Using a good design can increase the input flow rate and reduce the sediment entering it. In this study, to evaluate the dike impact on flow hydraulic conditions in the Intake with different situations, 30, 45, 60 and 90 degrees two simple L-shaped dikes in the upstream and downstream Intake and for five inlet flows (0.7, 1.12, 2.84, 5.04 and 6.23 Lit/s) were considered in the laboratory flume made by the author as a physical model to simulate the flow of the basin; then different effects of the dike on the hydraulic flow were studied. The results of the tests showed that the L-shaped dike in the upstream and downstream Intake in the internal arc flume increased the inflow flow rate into the Intake. Also, the best angle of deviation for the maximum flow entered the Intake angle of 60 degrees.
R. Amirjani, A. Kamanbedast, M. Heydarnejad, A. Bordbar, A. Masjedi,
Volume 22, Issue 4 (Winter 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.
R. Monjezi, M. Heidarnejad, A. R. Masjedi, M. H. Pourmohammadi, A. Kamanbedast,
Volume 23, Issue 2 (Summer 2019)
Abstract
Nonlinear weirs are regarded as important hydraulic structures for water level adjustment and flow control in channels, rivers and dam reservoirs. One example of non-linear weirs is shaped as curved-zigzag. The crest axis of these weirs is non-linear. At a given width, the crest length is greater than that of the conventional linear weirs. Thus, they achieve a higher flow rate for an identical hydraulic load. This research experimentally focused on the discharge coefficient and flow rate of curved weirs with three different curve radii in two triangular linear and zigzag shapes. The discharge coefficients of these weirs were comparatively explored in terms of the hydraulic performance as a function of the total hydraulic load to weir crest height ratio (hd/P) and curvature angle (θ) (or curve radius). The results indicated that for the same hydraulic load, the increase of θ (the decrease in curve radius) led to a lower discharge coefficient; this was first because of the increased topical rise of water level, and then the more indirect path with a greater curvature through which the flow had to transport. Both factors could negatively affect the water discharge coefficient. In practice, the runoff coefficient at a weir with a curve radius of R/w=1.25 was approximately 8.5% greater than that of a weir with a curve radius of R/w=0.75 under a hydraulic load of 0.2.
H. Davodi, A. R. Masjedi, M. Heidarneja, A. Bordbar, A. A. Kamanbedast,
Volume 23, Issue 2 (Summer 2019)
Abstract
In this study, some experiments were carried out in a rectangular plexiglass flume to study the effect of the cable around a vertical tripod and two piles groups with different angles. In this research, a series of experiments were performed by placing a cylindrical vertical pileand two piles groups with different angles separately in two modes including with cable and without cable. The experiments were carried out using three types of cable with various diameters, number of threads and thread angles at a constant discharge in clear water. In each experiment, scour depth at the end of the test was measured; then, the scour depth was calculated in different conditions using the obtained data. The best configuration in the vertical pier and piers group was found for the cable-pier diameter ratio of 0.1, the thread angle of 15° and the triple threads. The result indicated that the scour reduction was enhanced as the cable diameter and threads were increased and the thread angle was decreased. So in the piers group of 28 and 38°, scour depth was reduced to about 43, 49 and 56%.
J. Rouzegar, A. A. Kamanbedast, A. Masjedi, M. Heidarnejad, A. Bordbar,
Volume 23, Issue 3 (Fall 2019)
Abstract
Morning glory spillway is one of the spillways that used to passing of flood from high to low level. This spillway is used in the reservoir dams that are placed in narrow valleys and in many locations with high slope in reservoir walls. In the Morning glory spillways, the vortex flow can reduce discharge, discharge coefficient and the performance of spillway. The zigzag spillway, as another type, is introduced as a proper option for compensating the problem of passing maximum possible flow rate, usually encountered by spillways. In the present study, the experimental results of a physical model were used to develop a hydraulic design with squire and circle inlet and analysis method for Labyrinth Morning Glory Spillway. The analysis of experimental data in circle and square inlet showed, that increase in length of spillway and zigzag, causes decrease in the discharge coefficient. Finally the result of effect spillway inlet on flow rate demonstrate that discharge coefficient in square inlet is more than circle, whereas without vortex breaker.
A. Saki, A. A. Kamanbedast, A. Masjedi, M. Heidarnejad, A. Bordbar,
Volume 23, Issue 4 (Special Issue of Flood and Soil Erosion, Winter 2019)
Abstract
After Hamidieh Diversion Dam near the city of Hamidieh, Karkheh River is divided into two streams known as Hufel and Nissan. At the lower flow rates, Nissan makes up a greater share than Hufel due to the steeper slope of the former. This study attempted to construct a hydraulic structure to appropriately divide water flow in Hufel. In a laboratory experiment, a flume with a 90-degree bend was used at Islamic Azad University of Ahvaz. Various experiments were conducted at different widths and heights. Furthermore, this model was simulated through CCHE2D, the results of which were compared against those of physical and mathematical models. The results indicated that the weir height increased the deviation flow percentage to the Hufel stream due to rising water level. Moreover, the deviation flow percentage to Hufel was declined as the weir width was increased due to falling water level. At Hufel, the installation of rectangular weir in different dimensions yielded the minimum of 34.3% and the maximum of 61.5% increase in the flow rate. In the normal mode without any weirs installed, however, there would be an increase in the flow rate, as compared to the mode where a weir has been installed. This can be associated with the flow controlled by the weir. On average, the deviation flow rate was increased by 2.8% in the weir mode and 7.7% in the weir-less one. An increase in the Froude number from 0.21 to 0.38 led to a lower average deviation flow rate by 19.3%. Moreover, the results of the simulation through CCHE2D were demonstrated to be largely similar to those of physical model experiments. However, an increase in the Froude number did not lead to a decline in the deviation flow rate (i.e. it remained constant). This trend was inconsistent with the results of the physical model.
S. A. Banishoaib, A. Bordbar, A. A. Kamanbedast, A. Masjedi, M. Heidarnejad,
Volume 23, Issue 4 (winter 2020)
Abstract
A ‘spillway’ is a structure used to provide the controlled release of flood water from upstream into downstream area of a dam. As an important component of every dam, a spillway should be constructed strongly, reliably and efficiently to be used at any moment. Labyrinth and stepped spillways are presented as appropriate modifications to those spillways hardly capable of managing the maximum potential discharge. Owing to their nonlinear crests for a given width, labyrinth and stepped spillways have a larger discharge rate than linear- crest spillways at an identical height. Compared to other energy dissipaters, the combination of stepped and labyrinth spillways is known as a very strong energy dissipater. In the following part, the combination of these two structures and their dimensional change for increasing the water- energy dissipation are addressed. To conduct this study, an experimental flume with a 90- degree bend in the Islamic Azad University of Ahwaz was used. In total, 90 experiments were conducted on three different labyrinth- shape stepped spillway models with two different lengths, three different widths, and five different discharges. Analysis of the results showed a greater energy loss reduction in triangular rather than rectangular or trapezoidal labyrinth- shape stepped spillways. In addition, energy loss was greater in labyrinth spillways with two cycles than those with one cycle. Energy loss was increased by raising the Froude number from 0.05 to 0.1; in contrast, energy loss was decreased with increasing the Froude number from 0.1 to 1.0, which was due to the submergence of steps, a decrease in the roughness of steps and an increase in the intensity of aeration.
P. Heidarirad, A. A. Kamanbedast, M. Heidarnezhad, A. R. Masjedi, H. Hasoonizadeh,
Volume 24, Issue 1 (Spring 2020)
Abstract
Water supply at a desired rate at any time to meet the water requirements regardless of river discharge must be considered in the general design of intakes provided that the needs do not exceed the river flow. Due to the lack of necessary information in this field and the importance of sediment transport to the lateral intakes at river bends, this study aimed at understanding the mechanism of this phenomenon. To this end, the combined effect of convergence and divergence in lateral intakes on the sediment transport was investigated. According to the results, the diversion discharge to the intake was increased by converging the laboratory flume. By narrowing and converging the end of the flume, the diversion discharge was increased further, so that as the flume was converged to the size (b/B) of 0.75 and 0.5, the diversion discharge to the intake was increased by 13.6% and 75%, respectively. This could be connected to narrowing, flow obstruction and backflow to the intake. In contrast, different results were found by diverging the flume. In other words, the inflow to the intake was decreased by diverging the flume. As the flume end was diverged, the diversion discharge was decreased further. By diverging the flume to the size (b/B) of 0.75 and 0.5, the diversion discharge to the intake was decreased by 21.9 and 31.8%, respectively. The average diversion discharge to the intake at 30, 60 and 90º was 13.2, 15.2 and 11.5%, respectively. By converting the flume to the size (b/B) of 0.75 and 0.5, the diversion sediment to the intake was increased by 18.5 and 71.4%. In contrast, by diverging the flume to the size (b/B) of 0.75 and 0.5, the diversion sediment to the intake was decreased by 35.4 and 49.9%, respectively.
