مجله هیدرولیک
سال هجدهم شماره 3 (پاییز 1402)

Numerical simulation has increasingly become a very important tool for solving complex phenomena in fluid mechanics. Today, computational fluid dynamics (CFD), which uses numerical simulation to solve fluid flow problems, has become a major tool in many scientific and engineering studies. So far, most simulations have been performed using network-based Euler methods. The main problem with using such methods is the presence of sharp and mobile joints as well as free surface cells that require complex behaviors. In recent years, a new generation of numerical methods called mesh-free particle methods (Lagrangian) has been developed to solve computational fluid dynamics (CFD) problems. In these methods, the domain of the fluid is represented by a set of moving particles in the Lagrangian system. Mesh-free Lagrangian methods, including SPH and MPS, allow numerical modeling of flow in the face of large deformations or Discontinuity of boundaries. Due to the importance of the subject, the purpose of this study is to simulate the hydrodynamics of flow on the overflow of Dahan Ghaleh dam using a mesh-free Lagrangian method based on weakly compressible moving particle semi-implicit formulation (WC-MPS).

In Lagrangian methods, unlike the Eulerian method, instead of networking the solution field and discrete the equations on the nodes, the solution field is divided into a number of particles and the discrete equations are solved on these particles. In fact, the governing equations are transformed into particle interaction equations using different operators. In the WC-MPS method, the system is considered as a system with weakly compressibility and calculates the pressure of each particle using the state equation. The MPS method uses particle density to track the free surface. Because there are no particles outside the free surface, the density of the particles on the free surface decreases severely. A particle is known as a free surface particle whose density is somewhat lower than the standard particle density. The value of this limit may be selected from 80% to 99% depending on the problem. Therefore, the pressure of this particle on the free surface will be set to zero in each time step and there is no need to apply any additional conditions for the free surface. For solid (impermeable) boundaries, such as walls or beds, In the vicinity of solid boundaries, the particle density decreases, which can lead to computational disturbances. Therefore, a number of ghost particles are located outside the boundaries to prevent this density reduction. In order to model the inlet and outlet flow, the particle recycling method at the inlet and outlet boundaries, which was developed by Jafari Nodoushan et al. (2016) was used.

In this study hydraulic parameters of the flow on the broad crested weirs, chute, and flip bucket of Dahan Ghaleh dam are investigated. At first, the free surface profile was compared at times t = 1, 5, 10, 15, 30 seconds for three flow rates of 461, 600, and 904 m3/s. when the discharge is 600 m3/s, the depth and velocity of the flow at the beginning of the channel will be 1.1 m and 9.1 m/s, respectively. The value of the depth and velocity of the flow at the beginning of the channel in WCMPS modeling is 1.191 m and 8.420 m/s, respectively, which shows the accuracy of the model in predicting the depth and velocity of the flow. In this research, the pressure is simulated in the form of pressure contour at different points in terms (pa) for three different flow rates. The highest pressure is near the bed in the approach channel and no part of the broad crested weirs, chute, and flip bucket is under negative pressure. Simulation of cavitation index has been done in broad crested weirs, chute, and flip bucket. the results showed that the cavitation index in the range of 110m to 140m has approached the critical value and the possibility of creating cavitation phenomenon in this area is more than in other places, but considering the cavitation index value in this area is greater than 1.8, according to the recommendation Falvey (1990) it does not need to be protected against cavitation. At the end, the height and length of the jump from the edge of the bucket for different discharges have been investigated.

In this study, the hydraulic parameters of the flow on the broad crested weirs, chute, and flip bucket of Dahan Ghaleh dam are investigated. The desired model has simulated the depth and velocity of the flow at the beginning of the channel after of the overflow, depth, velocity, and Froude number of the flow in the bucket floor with an error of less than 10%, and the jump length per discharge 600 (m3/s) with a maximum error of 12% has simulated. The comparison of the results indicates the accuracy and reliability of the results of the developed model.

A compound channel usually consists of a main channel in the middle and one or two floodplains around it. The flow velocity in the main channel is higher than the floodplains, due to its greater depth and smaller roughness. This difference causes the formation of a shear layer at the interface between the main channel and floodplains (as shown by Sellin, 1964); Shiono and Knight, 1991; Tominaga and Nezu, 1991; Bousmar, 2002; and Rezaei, 2006). Tominaga and Nezu (1991), Rezaei (2006), and Sum (2007) investigated the velocity distribution in prismatic compound channels. Their observations showed that the highest flow velocity is below the free surface. In prismatic compound channels, as the relative depth increases, the difference between the velocity in the main channel and floodplains decreases. At high relative depths, the effect of the shear layer formed between the main channel and floodplains can be almost ignored (Knight et al., 2018). The maximum interactions between the main channel and floodplains have been observed in relative depths between 0.1 and 0.3 (Shiono and Knight, 1991; Rezaei, 2006). Investigations reviled that, so far, the effect of the floodplain's side slope in prismatic compound channels has not been investigated. The main objective of this research is the experimental study of the flow field in the prismatic compound channel with inclined floodplains.

This research was carried out on the flume located in the hydraulic research laboratory of Bu-Ali Sina University. The flume is 18 meters long, 1.2 meters wide, and 0.6 meters deep with a bed slope of 1.63×10-3. Figure 1 shows an overview of the research channel used in this research. In this flume, smooth and rigid boundaries were constructed using PVC material. As seen in Figure 2(b), the flume has a compound cross-section with a 0.4 m main channel wide, 0.05 m deep, and also two 0.4 m wide inclined floodplains (lateral slope of 0.075). The downstream end of the flume has an adjustable tailgate which is used to control the water surface profile and make uniform flow along the flume. In all experiments, the water surface profiles were measured using a pointer gauge with an accuracy of 0.1 mm. Velocity distributions were measured using an Acoustic Doppler Velocimeter (ADV) every 20 mm laterally and every 10 mm vertically (see Figure 3). The lateral distributions of boundary shear stress were also measured using a Preston tube (outer diameter 4 mm). The velocity distributions and boundary shear stress were measured for five discharges of 27, 30, 35, 40, and 45 lit/s.

The velocity distributions for different discharges are shown in Figure 4. From the figure, it is clear that in the vicinity of the junction edge, the isovel lines bulge upward, and the velocity is decelerated, probably due to low mass and momentum exchanges in this region. Near the main channel walls (0.1 m < y < 0.18 m), the isovel lines bulge downward, and the velocity is accelerated. Also, near the middle of the main channel (0 < y < 0.1 m), the isovel lines bulge upward, and flow is decelerated due to flowing away from the main channel bed.As seen in Figure 3, the flume cross-sectional area was divided into subareas. The point velocity distributions were integrated numerically over the local water depth at each subarea to get the streamwise depth-averaged velocity. The results of depth-averaged velocity calculations for different relative depths are shown in Figure 5. In order to investigate the effect of the floodplain's side slope on the velocity distribution, the depth-averaged velocity has been normalized (Ud/Um) and compared to Rezaei’s Data (see Figure 7). The normalized depth-averaged velocities in the main channel, are almost equal to Rezaei’s data (with some fluctuations). While on the floodplains, those velocities are less than Rezaei’s Data (velocity in compound channels with flat floodplains).Boundary shear stress is used in river engineering and in studies related to riverbed protection and sediment transport. The boundary shear stress distributions for different discharges are measured and shown in Figure 8. As seen in Figure 8, the bed shear stress distribution follows the same pattern as the depth-averaged velocity.The apparent shear forces at the vertical interface between the main channel and floodplains can be calculated using the momentum equation for a control volume in the main channel (see Figure 12). The results of the apparent shear forcecalculation show that by increasing discharge or relative depth, the apparent shear force increases and reaches its peak value at a relative depth of 0.363 (see Table 3). The apparent shear forces expressed as a percentage of the total channel shear force on the vertical interface are shown in Figure 13. From Figure 13, it can be seen that the percentage of apparent shear forces at the interface between the main channel and floodplains are always smaller than those values in the compound channel with flat floodplains.

In this research, the flow field, including the velocity and bed shear stress distribution, in a prismatic compound channel with inclined floodplains (side slope 0.075) has been studied, experimentally. The results of experiments have been also compared with Rezaei’s data. The most important results obtained from this research are as follows:The depth-averaged velocity and boundary sear stress distributions follow the same pattern. Both of them show almost uniform flow in the main channel with some fluctuations. While in the flood plains, they are non-uniform with an extreme decreasing trend. In the main channel, the normalized depth-averaged velocity and normalized boundary shear stress are almost similar to Rezaei’s Data. While on floodplains, the normalized velocity and shear stress are non-uniform and less than Rezaei’ data. The study also shows that the apparent shear force at the interface between the main channel and floodplains increases with the increasing relative depth and reaches a peak value at the relative depth of 0.3. The same observations were made by Shiono and Knight (1991), and Rezaei (2006).

Piano key weirs (PKW) is the newest type of long crest weirs, which achieve more crest length in the same width as congress weirs, and therefore, the capacity of the void is higher than that of the mounted piano key weirs, with the aim of increasing the amount of energy dissipation in them. It was noticed that the piano key weir oscilloscopes are used in the crest of reservoir dams and in irrigation and drainage networks. This has been implemented due to the importance of the issue of energy dissipation in these types of instruments. So far, many studies have been done on the discharge coefficient of the piano key weir, but no research has been done on the relative energy dissipation of the triangular Piano key weir.

This research is a continuation of previous research on PK weirs. Figure 1 shows the rotating flume environment, which experiments were performed in that laboratory at the Tarbiat Modares University of Tehran (Dimensions: 10 meters long, 2 meters wide, and 0.9 meters high). Experiments have been performed on a triangular weir with a zero slope (i.e., Tri-Base model) (Fig. 2 and 3) and 10 degrees in the flow direction (Fig. 2 and 4). In this article, PK weir with horizontal and sloped crest is called Tri-Base and Tri-B1 models. The weir characters used in the laboratory are provided in Table1. Eq (3).The upstream depth (ho = P+h) and downstream (h1) was measured with an accuracy of ± 0.1 mm at a distance of 4P for the upstream depth (Crookston, 2010) and 10P for the downstream of the overflow (Eslinger & Crookston, 2020).

For the ∆E/E0
curves, firstly, the relative energy dissipation curves for triangle PK weir with horizontal crest have been plotted (Fig 5) and compared with the present study and other researchers' results. The differences between results are because of the differences in geometric characteristics. Because the head and weir height changes for every discharge, Fig 6 has been plotted curves of (q - E1/E0).The trend of the relative energy dissipation curve of nonlinear weir may be according to a logarithmic curve (Lopes et al., 2011). Figure 5 shows the changes in energy consumption for the Tri-Base and Tri-B1 models and their comparison with the results of other researchers. According to Figure 5, the highest relative consumption of energy is for the Tri-Base model. In other words, at the same flow rate, the highest relative amount of energy dissipation is related to the weir model with a horizontal crest. It is also clear that the highest relative energy loss in all samples occurred at the lowest flow rates.As the flow rate increases, the relative dissipation of energy decreases in both models. The reason for this is that with the increase in flow rate and flow speed, the amount of flow friction is reduced, and as a result, the dissipation of the flow is reduced.With the increase of Froude Number, the acceleration increases, and the flow travels a longer path towards the separation, which causes the separation area to decrease and the Drag force to decrease. Because of the slope of the weir walls, the flow speed in the Tri-B1 model is higher than the Tri-Base model (the flow moves like a slide from the spillway to the downstream side), so the separation area in the Tri-B1 model is reduced, and the Drag force and consequently the relative depreciation The energy in the Tri-B1 model (about 24%) is lower than the Tri-Base model.Figure 6 shows the residual energy curve of the piano key weir in relation to the flow rate per unit of the overflow width. According to Figure 6, the E1/E2 ratio increases with the increase of flow per unit width. In other words, the relative residual energy in both models occurs at high flow rates. Also, in both models, at low flow rates, the increase in E1/E2 ratio is higher than at high flow rates. The reason for this is the local sinking upstream of the weir in high discharges; so that in high heads, the aeration on the weir is reduced.Finally, Fig 7 shows the comparison of measured and calculated values of triangular PK weir.

In the triangular piano key weir, by increasing the slope of the side walls (θ) from zero to 10 degrees in the flow direction, the relative dissipation of energy has decreased by 24%. Also, the highest dissipation of energy in the weir with a horizontal crest occurred in the lower heads, and this value decreases with the increase of the head.The highest amount of energy dissipation for Tri-Base and Tri-B1 models is 0.74 and 0.85, respectively, in this case. Finally, relationships (9) and (10) are proposed to calculate the relative energy consumption of the overflow of the piano key with horizontal and sloping crest, respectively.

In recent years, with the expansion of urban planning and the larger and more complex water supply networks, the need for energy consumption to carry out the process of water supply and distribution has increased. On the other hand, the increase in energy costs nowadays, due to the limited resources and power plants that produce electricity, has made it necessary to quota available energy for various purposes and activities. Water pumping requires a lot of energy, which is a significant part of the network's operating cost. In this research, intelligent operation of these infrastructures using optimization tools and mathematical models has been considered to be useful by increasing the efficiency of pumping stations in urban areas and reducing costs. Over the past decade, many studies have proposed various automated systems for optimal planning of pump operation with the aim of saving energy and reducing operating and maintenance costs, but a small number of these studies have investigated the optimization of the rotation speed of the pumps, the parameter that has been investigated in this research. The main purpose of this study is to achieve the best energy efficiency in water distribution networks (reducing energy consumption and its costs) while achieving other operating goals (providing standard limits of node pressure, etc.). Optimum adjustment of pumps rotation speed is a topic that has not been investigated in previous researches by considering the historical series of water consumption data.

The hydraulic model of the network, pumping station and its control equipment are simulated by EPANET hydraulic solver. Hydraulic solver coupling with differential evolution (DE) algorithm as a random search algorithm is used to adjust the motor speed of water distribution network pumps optimally. In the DE algorithm, a string of numbers with the range [0.5-2], which is the network pump's rotation speed coefficient, is randomly generated. The objective function evaluates these random values to obtain the optimal answer finally. Constraints monitored in the optimization problem are continuity, energy conservation, and minimum node pressure constraints. In the static operating policy developed in this research, the operational variables of the rotational speed of the pumps are in 15-minute time steps for one day. The DE algorithm optimizes the rotational speed values for one day in 15-minute time steps, and then the optimal pattern is applied uniformly for all days. Hassanabad water distribution network in Tehran has been selected for a case study, and the optimal pumps speed pattern has been extracted as an operation policy.

We received water demands of the entire network for 219 days in 15-minute time steps as the initial research data. The amount of energy consumed by the pumps for these 219 days in the current state of the network is equal to 491496.97 kWh. In the current state, the pumps rotate at a constant speed of 1450 rpm. According to the number of decision variables in this issue (192 variables), the initial population is equal to 400, and the number of iterations of the optimization algorithm is defined as 100. The completion condition of the optimization process is completing 100 iterations. After optimizing and determining the optimal rotation pattern of the pumps, by statically considering this optimal pattern for these 219 days and simulating the network by EPANET software, the energy consumption of the pumps for these 219 days was obtained to be 444212.54 kWh. This optimization-simulation process took about 27 days on a system with "8 core, 2.3 GHz" CPU and "10 GB" RAM. The obtained model shows a significant saving in energy consumption compared to the current state of the network while determining this optimal model by the operator through work experience alone is practically impossible. The obtained energy savings show the efficiency and proper performance of the proposed approach.

In this research, an optimization-simulation model was presented to determine how to adjust the speed of variable speed pumps in water distribution networks with the aim of minimizing energy consumption. The conclusion obtained from the comparison of the results of the optimal model developed for the water distribution network of Hassanabad town using the differential evolution algorithm against the current state of the network indicates that the approach adopted in this study has reduced energy consumption by 47284.42 kilowatt-hours equivalent to 9.6%. Also, in the peak hour of water consumption, the presented approach has been able to reduce the energy consumption by 19914.4 kilowatt-hours, equivalent to 74.3%. This is an important advantage over traditional methods and can be effective in saving energy. The main advantage of this operation approach is simplicity, comprehensibility for the operator and its operationality. In addition to this advantage, perhaps the most important limitation of this method is the lack of consideration of special events and possible accidental conditions in the network and non-compliance with it in the way of operation.

The main objective of this research is to prepare a temporal and spatial classification of suspended sediment values using Sentinel-2 satellite imagery and physical methods on the wells in Sistan and Baluchestan province. Specifically, this study aims to produce an accurate classification of suspended sediment values in space and time using satellite data and physical methods. Furthermore, by comparing the suspended sediment values with the input flow rate of the wells, more information about the suspended sediment values was obtained. Finally, a regression-based model was presented to estimate the suspended sediment values based on the input flow rate. By analyzing this information, it is possible to gain a better understanding of the behavior of suspended sediments and the factors affecting them over time. Overall, this research can contribute to a better understanding of the behavior of suspended sediments and the factors affecting them.

The aim of this study is to accurately classify suspended sediment values in space and time using Sentinel-2 satellite imagery and physical methods on wells in the Sistan and Baluchestan province. To achieve this goal, the researchers utilized the C2RCC processor for spectral calculations and modeling, which is based on deep learning approaches and simulated water reflectance outputs for high-altitude correction algorithms. The processor allows for the calculation of water reflectance in different spectral bands and the estimation of three main water quality parameters, including the concentration of total suspended solids, chlorophyll-a, and colored dissolved organic matter, using various relationships. After retrieving the maps of the concentration classification of suspended sediment parameters in the reservoirs, the researchers aim to examine the monthly input flow rates to the wells with the estimated concentration of suspended sediments. By comparing the input flow rate values with the concentration of suspended sediments in well 1, the researchers can gain more information about the behavior of suspended sediments and the factors affecting them over time. Finally, a regression model will be developed using the corresponding input flow rate and suspended sediment concentration values, with the monthly input flow rate considered as input and the mean concentration of suspended sediments considered as output. It should be noted that various regression methods, including linear, exponential, GPR, and SVR, have been used to model the relationship between input flow rate and suspended sediment. Each of these methods has unique features and advantages and has been selected based on the type of data and the problem at hand. By combining these methods, a comprehensive and accurate model for predicting the concentration of suspended sediments based on the input flow rate between two semi-wells has been developed, which can contribute to a better understanding of the behavior of suspended sediments and the factors affecting them.

As the results indicate, the concentration of suspended sediments is low during wet years and increases with the increase in input flow rates into the reservoirs. Eventually, the phenomenon of 120-day winds in early May stabilizes the concentration of suspended sediments. This is due to the fact that the input flow rate from semi-well 1 is higher than other points, resulting in a higher concentration of suspended sediments in this semi-well. This is because the input flow rate directly affects the production and movement of suspended sediments in the lake. With an increase in the input flow rate, the two main factors affecting the production of suspended sediments, namely the water current velocity and the energy of sinusoidal waves, also increase. This increase in water current velocity and energy of sinusoidal waves improves the conditions for the production and accumulation of suspended sediments in this point. Therefore, the concentration of suspended sediments in Chah-Nimeh 1 is generally higher than other points in the lake. This figure shows that the retrieval values of suspended sediments using the physical method based on Sentinel-2 satellite imagery are accurate and reliable. This finding indicates that water turbidity data can be used to validate the retrieval values of suspended sediments from other methods. To investigate the effect of input flow rate on suspended sediments in more detail, a time profile of monthly volume input flow rates in millions of cubic meters versus the average concentration of suspended sediments in Chah-Nimeh 1 in milligrams per cubic meter has been studied. With these figures, it can be observed that the concentration of suspended sediments in the lakes is highly influenced by the input flow rate, and it increases with an increase in input flow rate. Additionally, in other months of the year, the amount of suspended sediments has been somewhat constant and accompanied by slight changes. Therefore, it can be concluded that the amount of suspended sediments in the lakes is strongly influenced by the input flow rate, and it increases with an increase in input flow rate. We developed a model for establishing the relationship between input flow rate and the average concentration of suspended sediments using regression methods and monthly input flow rate and average concentration of suspended sediments in semi-well 1 data. As the results show, the GPR model has achieved acceptable results and has been used as the optimal model.

This study used Sentinel-2 satellite imagery to estimate suspended sediment parameters in lakes and reservoirs. A strong correlation was found between the volume of input flow rates and the average concentration of suspended sediments, particularly in Chah-Nimeh 1. A regression-based model was developed to estimate the overall concentration of suspended sediments. This study can provide helpful information for managing water resources and aquatic ecosystems.

In this research, a rotary gate has been used along with a rectangular-semi circular transition in order to measure and control the flow. The hydraulic efficiency of this type of transition and gate has been investigated using factors such as the level of the water level of the approaching flow and the opening angle of the gate, which is effective on the geometric location of the transition wall. The depth measurement of the flow from the upstream of the gate to its downstream was done by a depth gauge with an accuracy of 0.1 mm. The flow rate passing through the rotary gate is also estimated based on the stage-discharge curve and basic hydraulic equations, as well as three angle separation methods, data aggregation method and break point method. to check and calculate the error values in each discharge estimation method, indexes such as: average relative error index (Error), root mean square error (RMSE), standard error (SE) and normal root mean square error (NRMSE) were used. The analysis of the results obtained using the statistical indicators of the three methods mentioned above shows that all three methods have high and acceptable accuracy. In the method of using all the data and the breaking point method, the discharge is calculated by having the depth of flow at upstream, the radius and opening of the gate. Since relatively short calculations are performed in these two methods, it is sufficient for initial estimates. The results showed that the method of using each angle seems more accurate because the number of calculations in it is more. The error percentage index for the separation method is 1.30%, in the aggregated data method it is 3.29% and the breaking point method is 3.98%.Therefore, according to the results of this research, it can be seen that by using this gate and the design and construction of transition in rectangular channels, it is possible to measure the flow in irrigation and drainage networks with very good accuracy. Investigating the amount of energy loss due to the hydraulic jump of the flow after the gate shows that the amount of energy loss decreases with the increase of the opening angle.