نشریه تحقیقات مهندسی سازه های آبیاری و زهکشی
سال هفدهم شماره 66 (بهار و تابستان 1395)

The cost of concrete gravity dams is more than other dams¡ Therefore in order to make the project more economical¡ optimization of dimensions with aim of reducing the volume of concrete used¡ becomes a necessity. In this study keeping in view the sustainability situation¡ dimensions of Koyna concrete gravity dam was developed and optimized by using Honey Bee Mating Optimization model in the Matlab software. The results show that the volume of concrete used in the construction of this dam is equal to 3633 m3 for existing dimensions¡ and Under optimal dimensions it declined to 3312.52 m3¡ which indicates a reduction of 8.82 percent in the objective function value (volume of concrete used in the construction of the dam). Therefore it can be concluded the reduced volume of concrete used for the construction of the dam makes a considerable saving on the costs of the project¡ and hence the project will be economical.

Flow resistance equations are a classical component of river hydraulic analysis, required for such applications as flood routing, prediction of flow depths and velocities in the design of floods conveyance structures, channel flood capacity estimation and the indirect estimation of flood discharges by the slope-area technique. In this research the effect of particle shape and bed slope of channel on Manning’s roughness coefficient have been investigated experimentally. To achieve this aim, two types of gravels (natural and crushed shapes) with three average gravel sizes (3.8, 4.66 and 6.53 cm), four bed slopes (0.004, 0.006, 0.008 and 0.01 percent) were used under different hydraulic conditions. The results showed that as the gravel size and bed slope increases or the relative submergence decreases, the Manning’s roughness coefficient (n) increases. Moreover, the results revealed that the average value of Manning’s roughness coefficient (n) of crushed gravels were by 2.7, 3.7, 3.8 and 5.9 percent more than natural gravels in the bed slopes of 0.004, 0.006, 0.008 and 0.01 percent, respectively. Also, the difference between the values of Manning’s roughness coefficients (n) for crushed and natural particles increased by decreasing relative submergence and increasing bed slope. In other words, the effect of particle shape on Manning’s roughness coefficient is applicable in steep slopes and low relative submergences (large-scale roughness).

Control of contaminant transport from surface pollutant resources such as landfills to groundwater is one of the most important challenges in environmental engineering. In this research a new technique was experimentally studied in order to control transportation of contaminants from surface pollutant to underground layers and groundwater. Therefore, a hydraulic barrier in the form of the clean sandy soil was placed in between two layers of clayey soil as a column test, and downward movement of contaminant from surface to a fresh water source located beneath column test was investigated. Contaminated source in the form of Cl-1 ions, under constant head was created and the hydraulic barrier was produced via fresh water injection wells, expanded in sandy layer. The results of this research revealed that providing injection wells with hydraulic barrier can reduce contaminant transport from surface to groundwater more than 90 percent. Furthermore, the results showed that the best performance of injection wells in the creation of hydraulic barrier happens while the hydraulic head in the wells and the level of contamination resource are being at the same level. It needs to be mentioned that the screen of injection well should be located at the middle of sandy layer.

Hydraulic jump has been used widely for dissipating excess energy downstream of hydraulic structures in irrigation and drainage networks. The characteristics of hydraulic jump in triangular sections have not been studied as much as those in rectangular, trapezoidal and circular sections. In this paper, the characteristics of hydraulic jump in a triangular channel with broad crested end sill is studied. The experiments are carried out in a laboratory flume of 9 m length, 0.5 m width and o.6 m height with glass side walls. Different flow discharges and sluice gate openings with issuing jet Froude number in the range of 2.5-12.5 was studied. The results showed that for a given Froude number, the required tail water depth for the triangular section is up to 70% lower than that in a rectangular section. Based on the regression analysis, several empirical equations are proposed for determining sequent depth ratio and dimensionless sill height as a function of inflow Froude number. The proposed equations can be used in designing controlled hydraulic jump in triangular sections were tail water is not adequate for a classic hydraulic jump.

In most of the countries in the world, even in the developed countries, surface irrigation is still one of the important irrigation methods in irrigated agriculture. It is estimated that more than 90 percent of the irrigated lands are irrigated with surface irrigation methods. Since determination of optimum field’s dimensions, including slope, inflow rate, and irrigation time, play an important role in enhancement of application efficiency and reduction of projects costs. Therefore, this research was conducted in the Ramshir irrigation and drainage network in the Khuzestan province (namely Velayate plan) with the objectives of determining fields’ dimensions, design and management parameters of border irrigation with closed-end regime and for achieving higher application efficiency and distribution uniformity. Using water advance and recession measurements along the border length and use of a comprehensive surface irrigation model, that is to say, WinSRFR-3.1 model, the soil infiltration parameters of the area were determined. Hence, the model was calibrated and the parameters of the best fitted infiltration equation, based on the Kostiakov-Lewis equation, was determined. Also by using the simulation part of the model, the dimensions and other design and management parameters of border irrigation, with closed-end regime cultivated with wheat crop, was determined. Based on results and with regards to proper application efficiency and distribution uniformity, the border design alternative of 7 m wide, 200 m length, and slopes of 0.005 to 0.001 m/m was a proper alternative for all ranges of selected inflow discharges (10-20 lit/s) and net irrigation depths of 50 to 90 mm. However, based on results, the design alternative of 200 m border length and longitudinal slope of 0.0005 m/m is the best alternative with regards to higher application efficiency. Moreover, the longitudinal slope of 0.0005 m/m is an ideal slope for all combinations of design alternatives with fair application efficiencies. Basically, the border length of 300 m and higher are not a suitable option for all selected slopes and low inflow rates of less than 10 lit/s. Finally, in the Ramshir irrigation and drainage network, if the field’s dimensions together with the other design and management parameters is set properly, achieving high application efficiency, even higher than 70 percent, in the border irrigation for many design alternatives is easily possible.

Reservoir sedimentation is always known as a serious problem for sustainable use of reservoirs and the main factor of reservoirs storage loss. One of the most common engineering techniques for preserving the reservoirs storage capacity is the periodical desilting of reservoirs by hydraulic flushing. Review of the literature shows that the pressurized flushing operation is currently accomplished with low efficiency. In this paper, the effect of PBC structure on the sediment removal efficiency during pressurized flushing operation was experimentally investigated. In this way, PBC structure with four relative length and four relative diameters were used in the reservoir. Non-cohesive sand particles with D50=0.36 mm were used as the deposited sediments in the reservoir. The results showed that by using the PBC structure with LPBC/Doutlet = 5.26andDPBC/Doutlet = 1.32, the flushing efficiency became 4.57 times more than that of reference test. By increasing the relative length of PBC structure, the maximum relative length and width of flushing cone increased, respectively, compared to the reference test while the variation of the maximum relative depth was negligible. In addition, all the geometric parameters of flushing cone hadtheir maximum values atDPBC/Doutlet = 1.32.

Differences in the flow properties in the main channel and flood plains causes, mass and momentum tensions between the both sections. The non-prismatic compound open channel cross section intensifies the mass and momentum transferring between the main channel and floodplains and has significant effect on the flow properties through the compound open channel. In this study the flow properties in the heterogeneous Roughness Non-Prismatic Compound Open Channel was assessed using the numerical and physical modeling. The physical modeling was conducted in the hydraulic laboratory center of Tehran University and numerical modeling was carried out using the Flow-3D as famous computation fluid dynamic tool (CFD).The results indicates that the Flow-3D is an effective tool for modeling the flow in the heterogeneous roughness non-prismatic compound open channel. During the CFD modeling it was found that the RNG turbulence model is more precise for simulation and modeling the flow properties. The results show that the heterogeneous roughness has significant effect on the flow characteristics such as velocity distribution and share stress gradient.

Bed topography downstream of the new hydraulic jump stilling basin (covered with six-legs elements) has been investigated in this study. Variation of maximum scour depth for different hydraulic conditions (Froude number ranged from 5.76 to 9.13) and three different sediment particle sizes was studied. The basin length, which was kept constant at all tests, was measured for maximum flow discharge. At this condition the maximum scour depth was measured which was found to be 61% less than that of maximum scour depth reported by other studies conducted for smooth bed basin. Increase of sediment particles from 0.95 mm to 2.23 can cause the scour depth to reduce by as much as 56%. In those tests which the jump length was less than the basin length, the scour depth was reduced significantly. For test with jump length to basin length ratio equal to 0.405, the scour depth shows reduction of 64% on an average. The upstream and downstream scour banks angles was measured for all tests which was to be equal to 6-24 degrees and 2-7 degrees respectively. The best fitted relation for dimensionless longitude bed profile also was obtained and presented.

The water surface profiles on spillway are important for design of free board and spillway training wall height. The engineers have used physical modeling to design these kinds of structures, Considering that the scale effect in the spillway modeling, leads to the different measured data between model and prototype, in this study, an experimental model based on Garmi-Chay Mianeh dam spillway was designed in three 1:100, 1:75, and 1:50 scales. Next, the water surface profile on spillway crest measured in seven discharges and compared with basic scale of (1:50), the percentage of water level difference on the crest calculated in two physical models with 1:100 and 1:75 scales. Results and observations revealed that in due to the effect of viscosity and surface tension the difference of water level in the scale of 1:100 and 1:75 was 18.4% and 15.6% respectively, relative to the base scale. The larger discharge, water level on spillway increases, leads to decrease viscosity and surface tension effects. For the difference in water level in the scale of 1:100 and 1:75 was 5.8% and 4.8% respectively relative to the base scale. In this study, viscosity and surface tension effects is stated with correction equation (K'), that was functions of Reynolds and Weber numbers. With the ogee spillway modeling the effect of viscosity in Reynolds numbers larger than 3.1*104 and the effect of tension surface in Weber numbers larger than 270 can be neglected and by extrapolation prototype results from model studies can be obtained.

Improving agricultural water productivity is one of the important objectives in irrigation canal networks. Accordingly, localizing and implementation of the modern operational technologies is essential. In order to deal with operation of main irrigation canal under inflow fluctuations, in the present study, the application of decentralized automatic control system, as the first step towards the canal automation is investigated. The Inflow fluctuations happen due to water scarcity in those irrigation networks located in the southern part of the watersheds. To this end, a decentralized PI Controller is designed to be applied for operation of mathematical model of the of Roodasht main irrigation canal. The deigned controller was tested by two normal and harsh unpredictable inflow fluctuation scenarios. The results of the simulation are evaluated by the operational performance evolution indices. The results indicate that the canal operational condition under the normal inflow fluctuations is reasonably controlled by the designed PI system. But in the case of harsh inflow fluctuations, the PI controller is not capable to handle the condition and the middle and downstream canal reaches are suffering from inappropriate water taking. Therefore it can be concluded that, application of the modern centralized controller would be recommended as a reliable options for operation of the main canal.