جستجوی مقالات مرتبط با کلیدواژه « نرم افزار flow 3d » در نشریات گروه « آب و خاک »

Labyrinth weirs have always received special attention compared to linear weirs due to the increase in flow capacity through the increase in width. The number of 23 models was simulated using Flow-3D software to investigate the effect of various factors such as changing in the height of the dam body, changing the height of the weir apexes (weir height), the discharge passing over the weir, and the effects of different angles of the weir apex in the plan on the amount of bed erosion in the downstream of Labyrinth weir was studied. Validation of the numerical simulation results with the experimental model indicated a very good agreement between the numerical simulation and the experimental values. This reduction in the weir with an apex angle of 60 degrees is more than other models and the scour depth is reduced from 31 to about 90%. Also, the amount of flow traversability in this type of weir is more than other models, which made the weir with an angle of 60 degrees to be introduced as the most optimal weir in investigating the efficiency of the weir and the reduction of scouring compared to linear models, 45 and 90.

Weirs are among the structures used in water transfer channels, hydraulic structures, irrigation and drainage channels, and they are used to regulate the water level and control the flow. Weirs are flow diversion tools that are widely used in irrigation and drainage systems and urban sewage systems. Increasing the capacity of each weirs in a certain width is one of the important issues. These changes cannot be implemented in all structures because limiting factors such as topographical conditions and construction materials may not allow. The use of weirs with non-linear crests is one of the ways to increase the capacity of each weir. During the construction of dam structures, due to the high cost, they are looking for a solution to optimize costs, and one of the best ways to build a dam is to use a weir with a non-linear crest. One of the advantages of non-linear weir is to increase the flow rate capacity. Simulation using various software including Flow3d to investigate the flow pattern has become very popular in recent years. The most important reason for using simulation software, in addition to cost reduction, is the possibility of creating different forms of labyrinth weirs in the software. Meanwhile, in the laboratory, it is not possible to investigate the labyrinth weirs of different shapes and dimensions.In this research, the hydraulic model was tested inside a glass flume with a length of 10 meters, a height of 80 cm and a width of 80 cm. This flume has a pump with a maximum flow rate of 90 lit/s. The flow rate is measured using an ultrasonic flow meter. To measure the water level, several rail gauges points that can move along the flume are used. The labyrinth weir is triangular with 4 mm thick and height of 15 cm. The length of the model is 126 cm and the L/W ratio is 1.58. At first, the laboratory model was compared with the simulated model with the same magnification ratio. For this purpose, 9 discharges with a head ratio of 0.2 to 0.7 were investigated in the laboratory. The purpose was to check the accuracy of the model used in the simulation compared to the laboratory model. Then, three triangular and three arched labyrinth weirs models were simulated with 2, 3 and 4 magnifications. K-Ɛ RNG turbulence model was used to solve the turbulence flow. This model has an additional term compared to other turbulence equations, which will give us a more accurate solution for solving and discretizing the turbulence equations. In the current research, the flow depth boundary conditions were used in the flow entry, the exit flow boundary conditions were used in the exit sections, the wall boundary conditions were used in the walls and the floor, and the symmetry boundary conditions were used in the water surface.In order to validate the model, comparison of numerical and laboratory of discharge coefficient (Cd) was used. The results showed that RMSE is equal to 3.9% and MSE is equal to 0.16%. Therefore, the error is acceptable and the model will be used in the simulation of triangular and arched labyrinth weirs. The results showed that the discharge coefficient increased at first and then decreased. At first, gradually increasing the flow over the weirs, the amount of air trapped under the nappe decreases. This has caused a decrease in the amount of momentum introduced by the rotating air under the nappe, as well as a decrease in the negative pressure in that area, and as a result, it has resulted in an increase in the discharge coefficient. Investigations showed that with the increase of the water head ratio (HT⁄P) and magnification ratio (L/W), the nappe interference and local submergence increased and caused a decrease in the discharge coefficient. Thus, in the triangular and arched labyrinth weir, the discharge coefficient decreases up to 38% and 39% with the increase of the water head ratio from 0.1 to 1 and up to 29% and 37% with the increase of the magnification ratio from 2 to 4. On the other hand, arched labyrinth weirs have a lower discharge coefficient of up to 14% at a same magnification ratio than triangular labyrinth weirs. The reason for this problem is the smaller angle of the arched labyrinth weir with the channel wall compared to the triangular labyrinth weir, which causes the nappe interference to hit the channel wall and also cause more local submergence in the arched weir. Also, the impact angle of the flow jets at the top of the arched weir is higher than that of the triangular weir, which will cause more disturbance of the flow and decrease the flow coefficient.

One of the effective methods to reduce the kinetic energy downstream of hydraulic structures are the aprons. The horizontal aprons is one of these structures in the river that are often used downstream of stilling basins. At the time of execution, the apron and the riverbed are at the same level but when there is a flow in the boundary between the connection of the river bed and the aprons, scouring occurs, which causes the destruction of the apron and there is a possibility of destroying other water structures. In this research, using Flow 3D software, different scenarios were simulated for five Froude values of 0.32, 0.3, 0.25, 0.2, and 0.15, three Manning roughness coefficients of 0.025, 0.02, and 0.014 per particle diameter of 1.8 mm for horizontal aprons. In this numerical model, the graph of scouring depth changes in relation to Froude numbers in different roughness coefficients, the effect of Froude numbers on the location of the scour hole for different roughness coefficients of the horizontal aprons, the shear stress changes in relation to the length of the horizontal aprons with different roughness coefficients and different Froude numbers, as well as Erosion changes with respect to the length of the horizontal aprons were calculated with different roughness coefficients and different Froude numbers.

From environmental aspects, the exchange of surface and subsurface flows in riverbeds due to river morphology and in stream structures is very important. The flow path structures especially control structures have a more effective role than the river morphology in the formation of these exchanges. In this study, the effect of penetration depth of such structures in the porous bed on the characteristics of exchange flows was investigated both experimentally and numerically. The experiments were performed in a flume with a length of 10 m, width of 20 cm, depth of 30 cm and a slope of 0.01, at three penetration depths of 9, 11 and 13 cm respectively. Potassium permanganate tracer was used for tracking the flow. In addition, to obtain the characteristics of the exchange flow; the mainstream and the exchange pattern were simulated by particle tracking method using Flow 3D software. The results showed that in the Reynolds range of 1020 to 3450, increasing the penetration depth of the structure from 9 to 13 cm, would increase the residence time but decreases the exchange rate. However, increasing the flow rate would decrease the exchange rate and increase the retention time. Accordingly, the use of a step with a higher penetration depth is recommended to create a longer residence time. However, a step with a smaller penetration depth may be used to produce a higher exchange rate.

The Flip bucket is one of the spillway components of dams used to dissipate the flow kinetic energy. In these dissipaters, Part of supercritical flow energy due to air friction and partly due to mixing and turbulence in the erosion cavity that is formed at the landing site is dissipated. One of the geometrical parameters affecting the hydraulic performance of flip buckets is the angle of the bucket edge. In this study, using FLOW 3D software and RNG K-ε turbulence model, flow on Gavoshan Dam spillway and flip bucket was simulated in order to determine the hydraulic flow characteristics and the effect of bucket edge angle on the hydraulic flow pressure, outlet depth, velocity and developing of outlet jet as well. In order to validate the parameters obtained from numerical analysis, the experimental results of Gavoshan dam spillway hydraulic model have been used. Comparison of the results of numerical model with experimental data indicates acceptable agreement of the numerical results. The results show that increasing the angle of the bucket edge has a little effect on the maximum pressure on the bucket while it increases the depth and decreases the outlet flow velocity of the bucket. The 30° angle was determined as the optimum angle of the flip bucket edge in terms of increasing energy dissipation rate. Also for a fixed flip bucket edge angle with increasing discharge, the horizontal length of the upper and lower nappes of the jet are increased.

One of the most common ways to reduce kinetic energy dissipation is to use a stilling basin. One of the most important parameters of the stilling basin, which has a great impact on its construction costs, is the length of the basin, so it is possible to reduce construction costs by examining and studying it carefully. In this study, the stilling basin was first performed and calibrated using the laboratory data of Chanson and Chachru. Then the spillway of the Chaili dam was investigated using Flow-3D software with RNG turbulence modeling model and flow hydraulic parameters by applying changes along the stilling basin. Studies show that increasing and decreasing the length of the stilling basin and the placement of the end-sill have different effects on the flow characteristics as well as the amount of energy loss. Since increasing the amount of energy consumption is desirable, so among the various modes of the length of the stilling basin, increasing the length of the basin is selected. Increasing the length of the stilling basin increases the energy dissipation and reduces the pressure and force on the end-sill. So that the energy dissipation by increasing the length of the stilling basin to 90 meters and 120 meters compared to the reference model with a length of 75 meters increased by 0.55 and 2.8 percent, respectively, and the force applied to the vertical wall of the end sill, respectively, 5.63 and 3.45 percent decreased. The effect of the placement of the rectangular block on the force and the amount of energy dissipation of the flow was evaluated. The results showed that creating a rectangular block inside the stilling basin reduced the secondary depth of jump and reduced the strength by 7.1% and increased the relative energy loss by 14.31% compared to the stilling basin in the flat state so that the use of blocks They will make the stilling basin than the changes along the stilling basin. Based on this, the results of this research and the methods used in it can be used as an idea to determine the optimal stilling basin.

In this study, flow characteristics in 90 degree four-branch open channel junction with two inlets and two outlets simulated using FLOW 3D. Effect of parameters such as ratio of lateral to main inlet discharge, height of weirs on ratio of main outlet discharge to inlet discharge and water surface profile in junction were investigated and were compared with experimental results. Compression of experimental and numerical results showed good agreement, in simulation outlet discharge, so that RMSE and NRMSE in main outlet channel obtained 0.00047 m3/s and %3.357, in lateral outlet channel obtained 0.00488 m3/s and %4.834, respectively. For a constant discharge ratio, a decrease in height of outlet weirs, led to higher Froude number. Also comparison of experimental and numerical results for water surface profile showed good agreement, Too. In a constant height of weirs, when flow approaching the junction water surface profile decreased, and as crossing the junction, water surface profile showed increasing trendency, so that RMSE and NRMSE for water surface profile in main channel were obtained 0.036884 m and %15.75 and in lateral channel obtained 0.04891 m and 1.996%, respectively. An increase in inlet discharge ratio led to more water surface fluctuation in junction whereas height of weir decreased water surface fluctuations

Labyrinth weirs are some cost-effective structures, having trapezoidal, triangular and other formats, utilized for increasing the output efficiency in a limited width. Raising the capacity of labyrinth weirs via increasing their width is not always possible. The labyrinth weirs are used due to the increase in their efficient length on a given hydraulic height and width. The present study investigates the weirs having trapezoidal polyhedron format, on the wings of which some new labyrinth have been added so that their spillover discharge rate will be reinforced. The experiments in this study were conducted on 27 laboratory models having 9 different discharge rates, on whose wings double labyrinth have been added, totally through 243 experiment. Besides the spillover simulations were performed using the Flow-3D software. The results obtained from the numerical analysis for the determining the spillovers discharge rate coefficient were validated using laboratory data and it demonstrated a good correspondence between the numerical solutions and laboratory findings. It is also suggested that the Flow-3D software has a high potential in simulating the flow on labyrinth weirs. Laboratory results also indicated that, regarding all the compound polyhedron trapezoidal weirs, the parameter ratio, flow rate coefficient to ratio (Ht: total hydraulic load and P: spillways height) firstly raise and then start to reduce once they reach the maximum level. The spillover discharge rate increases for a given when the effective length of the weirs’ wing is raised. The discharge rate on the weirs having semi-circular compound format is better than this rate of ones having the square format and the ones having compound square format have spillover discharge rates better than the ones having simple trapezoidal format, in a manner that the discharge rate of the current flow is increased 15 percent more than the trapezoidal dam labyrinth spillways and flow rate coefficient interval increases from 0.4 percent of dam labyrinth spillways to 0.65 on the compound spillways.

Successive sluice gates are utilized to deliver a relatively constant amount of flow rate for a range of water levels variations at the upstream of the water distribution channels. In this study, the flow through successive sluice gates in four different models with five input flow depths were simulated and investigated using FLOW-3D software. Comparison between the numerical and experimental results indicated that the differences of the output flow rates were less than 10%. Therefore, the accuracy of simulated models was desirable. After validation of models, the output flow rate was calculated for each model and compared with design flow rate. Comparing the output flow rates of models with the design flow rate indicated that in the all investigated cases, there was an approximate difference of 8 percent. Therefore, the successive sluice gates showed acceptable accuracy in delivery of constant flow rate during variation of water depth at upstream of the channel. Also, the evaluation of energy dissipation in the models showed that the energy dissipation was negligible when just the first gate was active. But by increasing the depth of input flow and utilization of the next gates, the rate of energy dissipation caused by the flow through successive sluice gates was increased to about 15-22 percent. Therefore, in addition to precise flow regulation, this structure was also effective in energy dissipation if input flow depths were high.

Labyrinth weirs are considered from important hydraulic structures to regulate the water level and control flow in canals, rivers and dam reservoirs. In this research a comparison of numerical modeling with softwareFLOW-3Dwith laboratory results in the case oflabyrinth weirs has been carried out. To review and evaluate different scenarios of overflow location like changing the geometric arrangement and labyrinth weirshas been considered In terms of form and direct or reverse direction weirs discharge coefficient. Therefore, selected a labyrinth weirs model with three side angles 15 and 22.5 and 30 degrees have been selected. To calibrate the selected models according to laboratory conditions5 discharge in the range of 2.8 to 18.1 liters per second were chosen to pass them. Numerical model after calibration Simulated with laboratory results different scenarios of overflow application. Results show outputs of numerical model with experimental results good coordination. In the same vein amount of discharge coefficient in weirs form-1 and the inverse form increase of discharge coefficient with increasing the side of the weirs has been found.

There are numerous investigations, which carried out regarding solution of lateral distribution of flow velocity and flow discharge computation in compound channels. Most of these researches have been in the case of rigid beds. However, compound river channels have alluvial beds and hydraulically have many differences with the experimental channel with rigid beds. In the case of alluvial bed channels due to the interaction effect of flow and bed sediments in main channel, bed forms as dunes develop and change the riverbed roughness coefficient. Furthermore, the flow pattern in compound channels is essentially three-dimensional and hence it is better to use 3-D mathematical models for solution of their hydraulic problems. In this study using mathematical model of FLOW-3D, two and three-dimensional variations of flow velocity in straight compound channels with rigid and alluvial beds have been simulated and compared with the experimental data of Wallingford Hydraulic Research. The lateral distribution of velocities and stage-discharge curves from two large-scale trapezoidal chanals including FCF-A with rigid bed and FCF-C with alluvial bed were used in this study. The results showed that flow velocity contours and the lateral distribution of velocity obtained by FLOW-3D model have suitable agreement with the experimental data in both cases of main channel and floodplains. The results of these comparisons also showed that the flow rates of the FLOW-3D model are in great agreement with laboratory data, so that the maximum and average of the relative errors of these results for the channel with rigid bed were 5 and 2.7% and for channels with alluvial bed it was 6% and 3.8%, respectively. Finally, the results obtained from the FLOW-3D model with the results of a one-dimensional DCM, SCM, HEC-RAS,COH, WDCM, EDM and the results of the SSIIM model. This comparison highlighted the superior ability of the FLOW-3D model in flow hydraulic simulation of compound channels with rigid and alluvial beds.

Modeling of flow through the compound open channel is one of the main problems in the field of hydraulic engineering. One of the main parameter related to the flow properties in the compound open channel is Shear Stress. The shear stress is because of difference of velocities between the main channel and floodplains. The Shear Stress causes of turbulence and vortex creation on the border of main channel and floodplains. The difference between the roughness of main channel and floodplains intensities the shear stress in the border zone. In this investigation using the physical and numerical modeling the flow properties in the heterogeneous roughness prismatic compound open channel was studied. The study was carried out in the hydraulic laboratory of Tehran University and numerical modeling was conducted using the Flow 3D as famous computational fluid dynamic (CFD) tool. The results indicated that the Flow 3D software has high ability for modeling the flow characteristics in heterogeneous roughness prismatic compound open channel and the RNG turbulence mode is suitable for modeling the vortex on the border of both sections.

Stepped spillway's are one of hydraulic components of dams that made by straight step's near the spillway's crest to the toe to dissipate energy. In this study to simulate the flow over the stepped spillway, Flow3D software that is analytic flow field was used. The k-ε(RNG) model was the turbulence model which had been applied, and to determine the free surface flow profiles VOF model was used. The skimming flow regime was only considered. For this purpose 112 spillway models was designed that from which, 96 models were stepped models and 16 models were smooth models. Stepped models had six configurations, two step sizes and four different slopes (15degrees, 30degrees, 45degrees and 60degrees) below the contact points and also step edges were followed WES profile. Smooth spillways had also corresponding specifications for the slope and crest profiles. The goal of this study was investigating on the effects of discharge, spillway's slope, number of steps, configuration and steps roughness on energy dissipation. It was observed that discharge flowing over the spillway and slope of spillway were among the most effective parameters to achieve the highest energy dissipation on stepped spillways and in higher discharges, the number of steps and its configurations had less effects. Also a mentioned configuration considering the parameters to reach the maximum energy dissipation was introduced.