r. daneshfaraz

Weirs play a crucial role in flood management and dam safety, accounting for a significant portion of the construction costs of dams. The selection of floods with long return periods for flood design is of utmost importance. However, in some cases, increasing the weir capacity by widening it may be impossible due to topographical limitations. One solution to enhance the flow capacity of weirs is the application of labyrinth weirs. These weirs increase the effective length of the weir crest within a given width, allowing for the passage of higher flow rates while maintaining similar hydraulic conditions. In this study, the hydraulic performance of labyrinth weirs is investigated using the Flow3D numerical model and laboratory data. Since laboratory experiments are time-consuming and costly, employing numerical simulations to achieve more accurate and reliable results for evaluating the hydraulic behavior of labyrinth weirs is prioritized. The results of the simulations indicate that the Flow3D software, utilizing statistical parameters such as R², DC, and RMSE, achieves values of (0.9805, 0.9725, and 0.0142), respectively. This demonstrates its capability to model the flow passing through weirs with high accuracy. The obtained values of the discharge coefficient in Flow3D show a high agreement with the laboratory data from Crookston. The approximate alignment of these results indicates the high accuracy of the numerical model. Additionally, in comparison to different discharges, the relative computational error observed for flow rates of 0.35, 0.6, and 0.44 (cubic meters per second) was approximately 0.5 percent, while for flow rates of 0.3, 0.4, and 0.57, the corresponding errors were 8, 6, and 4 percent, respectively. The results indicate that these tools can be effectively utilized in precise hydraulic analyses and the optimization of weir designs, irrigation systems, and fluid dynamics phenomena.

The use of sills with the gates leads to a reduction in the height of the gate. The sills affect the flow and change quantities, especially the discharge coefficient. In the present research, the discharge coefficient of the sluice gate is examined for the first presented theoretical relationship in a non-suppressed sill state to measure its performance using soft computing methods. For the models, 70% of the data were used for the training and the rest for the testing phases. The results of statistical indicators showed that in all SVM, KNN, GEP, and ANN models, the model with all input parameters was recognized as the superior model. In the SVM model, the results of various kernels showed that the Radial Basis Function kernel has better results in predicting the discharge coefficient compared to the Polynomial, Linear, and Sigmoid kernels. The results of the correlation coefficient (R), Root Mean Square Error (RMSE), mean percentage Relative Error (MRE%), and Kling Gupta Efficiency (KGE) in the test stage for the SVM model were 0.96, 0.018, 0.90, and 1.92%, respectively. The neighbor coefficient (K) results showed that in the K equal 2, the RMSE and MRE had a lower value and were close to the experimental results. In addition, in the KNN model, among distance criteria measures (Manhattan, Euclidean, Euclidean Squared, and Chebychev), the Manhattan criteria have a higher accuracy in predicting the discharge coefficient than the others. In the testing phase, this model's results were 0.97, 0.016, 0.96, and 1.70%. In addition, the results for the GEP model were 0.98, 0.019, 0.85, and 2.28%, respectively. In the present research, the ANN method is more accurate compared to SVM, GEP, and KNN models, so, for the ANN model, the KGE was in the very good range.

Flow hysteresis in a channel with a supercritical flow in the vicinity of a spindle-shaped bridge foundation (SSBF) with a change in flow rate has been investigated in a laboratory for the first time. Two spindle-shaped bridge foundations with diameters of 9 and 6.5 cm, which are placed at distances of 1.5 and 1 meter from the gate, have been used. The critical depth ranges between 0.027 and 0.0528 meters, and the used flow rates range from 250 to 600 liters/min. The flow regimes in the vicinity of the bridge foundations are classified based on the relative depths and Froude numbers created in sections B and C according based on the Froude number at the vena contracta. Sections B and C are near the bridge foundation and the flow passing through the center of the bridge foundation, respectively. The increase and subsequent decrease in velocity leads to different flow states. In some cases, two different behaviors can be seen from the flow with similar laboratory conditions. Hysteresis manifests in the range of Froude number 2.697~5.0. As the bridge foundations approach the valve, the hysteresis area becomes wider. Changes in the flow regime under the same conditions, called hysteresis, should be considered in designs. Also, with hysteresis, the relative residual energy and the downstream Froude number increased by 57.36% and 72.31%, respectively.

The vertical drop is one of the most widely used hydraulic structures for dissipating the destructive energy of water. The purpose of this research is to investigate the effect of the two difference height, and five vertex angles of a triangular plan form vertical drop on energy dissipation and average velocity using the volume of fluid (VOF) method. The findings revealed that by decreasing vertex angle of the triangular plan form vertical drop, energy dissipation increases. The lowest relative depth of the pool occurs with this drop. In contrast, as the vertex angle of the triangular plan form vertical drop decreases, the average velocity at the foot of the drop increases and the maximum average velocity in the triangular plan form vertical drop with an angle of 60 degrees and a height of 0.2 m is higher than other models. The average downstream velocity also decreases by decreasing the angle  and this decrease is more intense in the center of the channel than on the sides.

The present study aimed to investigate and compare the laboratory results of energy dissipation and length of vertical Drops equipped with horizontal Screens with the results of standard stilling basins of type one, two, three and four simple vertical Drops. For this purpose, 64 different experiments were performed on vertical Drops equipped with a horizontal Screen at relative distances of 0, 0.25, 0.5, and 0.75 from the edge of Drops, with a porosity of 40 and 50% of the Screen and a height of 20 cm .The results showed that in all experiments and at a constant flow, increasing the distance of the Screen from the edge of Drops does not have much affect the energy dissipation of the current. On average, the downstream energy dissipation for the present study has increased by more than 20% compared to the simple vertical Drop, which can be an excellent alternative to the downstream stilling basin. Among the models of the present study, the most significant reduction in the relative length of the Drops was achieved by the vertical Drops model with a horizontal Screen with a relative distance of 0.75. On average, when using horizontal Screen at four relative distances from the edge of Drops, the relative length of the Drops is reduced by more than 73% compared to the vertical Drops equipped with a standard stilling basin.

In the last decade, the use of gabion structures in hydraulic engineering for stabilizing the structure due to its high density and weight has become widespread. Also, the material's roughness and porosity cause it to be used in energy dissipation and drainage projects. This study evaluates the relative energy dissipation of gabion structures downstream of the ogee spillway in the conditions of a submerged hydraulic jump. The evaluated parameters in this study were Froude number, gabion height, gabion thickness, and material diameter. The experiments were performed with three average diameters of 1.5, 2.2, and 3 cm for rock material, three gabion heights of 10 and 20 cm, and Max. The end sill heights were 10, 20, and 30 cm. The operated discharges were regulated from 20 to 40 l/s. The results showed that by decreasing the average diameter of gabion aggregates, the amount of relative energy dissipation increases in all tested models, so that in gabion with a 1.5 cm average diameter of aggregates, the amount of energy dissipation increased by 3.6% in comparison with using the diameter of 3cm for the average diameter of the material. Increasing the height of the gabion to the extent that the flow is entirely inward can have up to 33% more relative energy dissipation than the gabion with a height of 10 cm. Also, by increasing the diameter of the gabion from 10 cm to 30 cm, relative energy dissipation increases up to 15%.

Unpredictable settlement of earth dams has led researchers to develop new methods such as artificial neural networks, wavelet theory, fuzzy logic, and a combination of them. These methods do not require time-consuming analyses for estimation. In this research, the amount of settlement in rockfill dams with a central core has been estimated using artificial intelligence methods. The data of 35 rockfill dams with a central core were used to train and validate the models. The artificial neural network, wavelet transform model, and fuzzy-neural adaptive inference system are the proposed models which were used in the present study. According to the results, the best model for an artificial neural network had two hidden layers, the first layer of 18 neurons and the second layer of 7 neurons, with the Tansig-Tansig activation function, with a coefficient of determination R2=0.4969. The best model for the fuzzy-neural inference system had the ring function (Dsigmoid) as a membership function, with three membership functions and 142 repetitions with a coefficient of determination R2=0.2860. Also, combining wavelet-neural network conversion with the coif2 wavelet function due to the more adaptation this function has to the input variables, the better the performance, and this function, with a coefficient of determination R2=0.9447, had the highest accuracy compared to other models.

The main purpose of this study is to provide a method to increase energy dissipation on an inclined drop. Therefore, three types of rough elements with cylindrical, triangular and bat-shaped geometries are used on the inclined slope in the relative critical depth range of 0.128 to 0.36 and the effect of the geometry of these elements is examined using Flow 3D software. The results showed demonstrate that the downstream relative depth obtained from the numerical analysis is in good agreement with the laboratory results. The application of rough elements on the inclined drop increased the downstream relative depth and also the relative energy dissipation. The application of rough elements on the sloping surface of the drop significantly reduced the downstream Froude number, so that the Froude number in all models ranging from 4.7~7.5 to 1.45~3.36 also decreased compared to the plain drop. Bat-shaped elements are structurally smaller in size, so the use of these elements, in addition to dissipating more energy, is also economically viable.

The scour around the bridge piers is one of the main causes of bridge failure and the extraction of aggregates may aggravate this phenomenon. The present study comprehensively investigated the scour around the groups of bridge piers in the presence of aggregate extraction pits, using different discharges. The bridge piers roughened by gravel had been compared with the simple bridge piers; so, the results showed that the roughening caused the reduction of the scour depth. Scour depth change rate led to an increase in the equilibrium time. The results also showed that the reduction of the scour depth at the downstream groups of piers was more than that in the upstream. For the lowest discharge, the aggregate extraction pits had a considerable effect on the scour depth difference for the groups of piers in the downstream and upstream. On the other hand, the effects were decreased when the rate of discharge was increased. The experimental results obtained by the rough surface models showed that as the discharge was increased, the local scour was increased too; at the same time, the bed profile was posed at the low level. Generally, the scour depth of the groups of piers in the downstream of the extraction pit was more than that in the upstream. The results of the current research, therefore, demonstrated that the surface of the bridge pier roughened by gravel reduced the scour depth.

Sand mining from rivers is one of the biggest concerns in the science today. Certain principles and rules for choosing the right place for mining materials and the amount of this mining are missing in the design codes. Therefore, mining of river materials from sites with less potential and near structures has been occasionally seen. In the present study, it has been attempted to reinforce the structure to control the impact of the mining of material, which results in the increased scour by changing the flow pattern around the structure. The experiments were carried out in two simple and armed modes, in sand bed with a grain size of 0.78 mm, with a length of 4.25 meters, inside a canal of 13 meters in length and 1.2 meters in width. The extent of scouring along the longitudinal and transverse directions in different times from the start to the scouring equilibrium was investigated for all substrates under sub-critical flow conditions (range 0.5-0.25). The results showed that the use of a cable-protected method in the upstream pit led to 29.6% reduction in the maximum scour depth at the front and 34% reduction in the back of the pier; also, in the downstream of the pit, it reduced the maximum scour depth by 15% at the front of the pier. Therefore, the cable arrangement used at the piers surface, according to the current research method, resulted in a significant reduction in the depth and extent of scouring in the pier group of the bridge.

Inclined drop is one of the supercritical flow producers used in open channels to reduce slope and elevation of the ground. Given that the application of horizontal and vertical screen in the downstream of this drop as an energy dissipater can be effective in the n energy dissipation of flow, in the present study, 180 different experiments were performed to investigate the energy dissipation of flow. The results showed that the angle of the drop had no marginal impact on energy dissipation and the relative depth of downstream of inclined drop equipped with a vertical screen, but increasing the porosity of screen caused enhancement in both parameters. Also, for the inclined drop equipped with a horizontal screen, by increasing angle and decreasing the porosity of screen, the energy dissipation and relative depth of downstream were raised. Also, for inclined drop equipped with a horizontal screen, by increasing the angle and decreasing the porosity of screen, the energy dissipation and relative depth of downstream were enhanced. For a constant relative critical depth, the relative depth of downstream and the energy dissipation of the inclined drop equipped with a horizontal screen considered the function of the wetted length of screen and length of the drop. For vertical screen, it is only a function of screen porosity.

Depreciation of kinetic energy of flow in the stilling basin is one of the most important topics considered by hydraulic engineers. Since hydraulic jump has known as one of the important factors to energy loss in the stilling basin, it is important to form and control it in the basin. The use of expanding section can be one of the ways to ensure the formation of a jump in the basin. This way in comparison to the prismatic channels, increased energy loss of current and reduced the secondary depth and the length of the hydraulic jump. On the other hand, given that the rough bed decreases the secondary depth and the jump length, in the present study, S-jump characteristics on non-continuous trapezoidal roughness elements at two relative roughness height of 1.15\leH/y1\le1.68 and 2.3\leH/y1\le3.37 in the non-prismatic channels were analyzed. The experiments were performed in a in the horizontal rectangular channel which is 30 cm wide, 45 cm deep and 5 m long. A total of 99 experiments were carried out in prismatic channels and non-prismatic channels with expanding ratios of 0.67, 0.5 and 0.33 and range of Froude numbers from 4 to 12. The results of present study show that the shear stress of rough non-prismatic channels in relative height of roughness elements of 1.15\leH/y1\le1.68 was about 11.12 times that on the smooth prismatic channels. Also, rough bed caused a 12 to 17 percent reduction in the conjugated depth and a 7 percent decrease in jump length in comparison to the smooth bed. For the relative height of 2.3\leH/y1\le3.37, the shear stress of a rough non-prismatic channels was 13.2 times that on smooth prismatic channel. The conjugated depth and length of jump in the rough expanding section decreased by 20-30\% and 13\% respectively. The rough non-prismatic channel at an expanding ratio of 0.33 in comparison to smooth prismatic channel caused 59.5\% reduction in the secondary depth and increased jump efficiency about 29\%.

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.

Investigation of the unsteady flow has an important role in water conveyance systems. In the present study water conveyance system including the storage tank, pumping station and pipeline was studied to investigate the maximum pressure due to occurrence of transient flow conditions. The transient condition was started by cutting the power of pumps and in a short time period, the change of flow condition was investigated in the supply collector. The friction losses in transient condition were calculated using Bentley Hammer software. In this process, four methods including steady, quasi steady, unsteady and unsteady Vitkovsky states were used. The pressure was measured by using a fast and sensitive pressure gauge and the observed results were compared with the simulation results and in this process the statistical methods were used. The results showed that there was not time correspondent between the period of cycles. The least amount of error for pressure, gained by method of unsteady Vitkovsky, is equal to 7.07m water at initial times and 11.79 m water in data logging period. For the maximum pressure values, maximum difference was obtained by use of unsteady method and the minimum difference by the two methods of steady and quasi steady methods. The maximum difference for the minimum pressure value was obtained for steady and unsteady Vitkovsky methods at initial and ulterior, respectively and its minimum difference was calculated for unsteady method. Increasing wave velocity had a direct effect on the maximum pressures and an inverse impact on the minimum pressures.

Water quality assessment of rivers, in order to insure human health and environmental sustainability, is one of the most important purposes of the physical and numerical models of solute transport in rivers. In this research, some tracer experiments were done and also the numerical model of OTIS was used to simulate solute transport. This model predicts the solute BT curve for a given hydraulic and geometrical parameters at downstream sections of river with respect to concentration of pollutant resource at upstream boundary condition. The experiments were conducted in a flume with length, width and depth of 12, 1.2 and 0.8m. Two longitudinal slopes of 0.004 and 0.007 and three discharges of 7.5, 11.5 and 15.5 (l/s) were selected for the experiments. A given mass of NACL solution was instantaneously injected into upstream of the flume and then the breakthrough curves were plotted based on the measured electric conductivity values along the centerline of the flume for the different sections at downstream of the injection point. To assessment the goodness of the simulated and observed BT curves, the statistical indices including the root mean square error (RMSE), Nash and Sutcliffe (NS) and mean absolute error (MAE) were extracted. With comparison of the observed BT curves with the numerical results (obtained with OTIS), the longitudinal dispersion coefficient values in different reach of flume were calculated. Analysis of the results showed that for a constant longitudinal slope and discharge, by increasing the distance from the injection location, the coefficient of dispersion was increased. Also, for constant slope, with enhancing the discharge rate, the dispersion coefficient was increased but for a given discharges, the dispersion coefficient was decreased with increasing the longitudinal -slope.

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