نشریه پژوهش های مهندسی آب ایران
سال دوم شماره 2 (پیاپی 3، تابستان 1401)

This paper aims to develop a robust and efficient method for modeling the performance of steel jacket platforms under parameter uncertainties. For this purpose, a combined approach using Linear Simulation (LS) and the improved Grey Wolf Optimization algorithm was developed. First, the performance of the developed model was evaluated on benchmark functions, and then, the probability of failure of the steel jacket structure due to wave loads was calculated. The results showed that the highest probability of platform failure occurred under wave impact with an angle of 315 degrees, a height of 12.2 meters, and a period of 11 seconds, with a probability of 1E-5. This indicates a high level of safety for the designed platform. The results showed that the proposed model has suitable accuracy and can calculate the safety level of various offshore structures with acceptable precision.

River have always played a significant role in human’s life in a way that development of agriculture , desire for industrialization and urbanization could not have been possible without rivers . Since 1950 s the construction of structures, water control and convergence structures, bridges and structures crossing the rivers increased, and as a consequence the flow regime , sediment and the trend of rivers topographic and morphological changes altered greatly . Bank erosion play an important role in the alluvial river and its bed load concentration , while it is also considered on of the human threats in river engineering . Another phenomenon that causes changes in sediment transport rates is flooding, which naturally increases with erosion and increasing flow velocity, erosion power of the river, and in addition, sedimentation rates in lower slope areas will increase. For this purpose, bank erosion of river and hydraulic changes during flood was investigated by using CCHE2D ( National Center for Computational Hydroscience and Engineering, two dimensional ) model.

In this study the morphological change of river’s bed and bank was studied.The study area is about 4 km. The change mentioned are due to flood with 25 years return period which were studied in unsteady flow. Two-dimensional depth averaged CCHE-Mesh software was used for meshing and construction of the study area topography and CCHE2D model was used to simulate hydrodynamic , sediment transport and bank erosion . And CCHE has the ability to simulate one, two and three-dimensional flow in aquatic zones , especially natural rivers in steady and unsteady state . In addition , simulation of flow Hydrodynamics in alluvial streams and rivers , simulation of sediment transport in non-uniform sediment distribution mode , investigation of changes and retreats of riverbanks are among the model capabilities . Furthermore the possibility of the right bank erosion and change in flows direction due to the walls breaking was also studied. In this research, by using the model, the sensitivity of the flow characteristics namely water depth and flow velocity and sediment transport and result of bank erosion , in the River, are investigated in respect to the various Manning's roughness coefficient and three turbulent models i.e. two zero equation eddy viscosity models,depth averaged parabolic model , depth averaged mixing length model and k - e standard model that is based on two equation eddy viscosity models.

The novelty of this study is to investigate the bank erosion and the possibility of failure of the river bank wall in the study area in the flood with a 25 years return period in unsteady state. The results of erosion and sedimentation at different coefficients of manning and three different eddy viscosity models indicate that the overall erosion and sedimentation process is almost same for all of these different conditions, but there is a significant difference in their values and the amount of them . Finally, by comparing the erosion process that occurred in study area, the mixing length eddy viscosity model yielded the closest response, followed by simulations. In unsteady hydrograph of water level there is no significant change in the ratio of change in resistance coefficient . with change of about 50 percent , this coefficient of water level changes only about 10 percent and since the depth of river in the river for 25 returns is about It is one meter,It means that changes of about 10 cm is negligible. The results indicated the erosion of right bank of river after rail way near hole is happen. This erosion may result in the destruction of bank and lead the rivers flow to hole (in 25 years return period flood, for unsteady flow, erosion prevailed over sedimentation). Furthermore the high speed of flow in chute domain result in demolition of it’s structure. In bridge, extreme erosion may cause bridge to collapse. Also considerable erosion happen after Chute, in stilling basin and river bed . The velocity of about 12 m / s in the stilling basin is beyond the tolerance of the concrete structure and is likely to be eroded and destroyed.

Finally, in flood with 25 years return period after erosion and fracture of the coastal wall of River, part of the water flow diverts to the hole, initially causing water to enter in the hole , also cause the flow lines to reduce and this means to increase velocity and more erosion in bed and banks of river. A breakdown point that decreases the water level reduces the flow depth, increases the speed and ultimately increases the erosion and flooding power of the flood stream. In addition to the river bed and banks,the structure such as the chute is also damaged due to the high velocity of the flow when the flood passes over it.

The main purpose of this study was to investigate the uniformity of sediment transporting flows into bilateral intakes on both sides of a spillway and compare it with a single intake either in outer or inner bend. The results indicated that most of the sediment deposition is towards the inner-bend intake. In the case of a single intake structure, the comparative results with the bilateral intakes indicated that both the water inflow rate and sediment entrainment increase in the case of a single intake located on the outer bend. In the case of a single intake on the inner bend, the water inflow rate decreases, but the inward-sediment load increases. It is necessary to use both the intake sill and sluice way to control the sediments entering the intakes, especially for the inner-bend intake.

The catchment area of Qarasu river is always exposed to floods. To prevent possible damages, factors affecting the occurrence of floods in this area should be investigated. In this research, the dependence between the two main flood variables of peak flow and volume was determined during a statistical period of 41 years using copula functions. The results showed that the most suitable marginal distributions for both variables are Log-normal and Weibull, respectively. moreover, normal copula function is the most capable function to depict the structure of dependence between them, according to goodness of fit tests. Finally, applying the selected copula illustrated that the joint return periods in the state {or} is less than the joint return periods in the {and} and single variable state.

The most important factor in reducing leakage in water supply networks is pressure management, and the best solution to achieve this aim is to put in Pressure Reducing Valves(PRVs). On the opposite hand, due to the fact that the excess pressure in the target nodes of the network is wasted by PRVs, the importance of replacing equipment such as PATs(Pump As Turbines), which, in addition to reducing leakage in the network, increases the excess pressure in the network to produce hydro-electric energy as It is important to apply renewable and environmentally friendly energy. In this article, after entering the initial information of the 25-node network, optimization of the number and position of PATs is done with the Genetic Algorithm. For this purpose, a new objective function is introduced with the simultaneous approach of "pressure management in a water supply network, electricity generation from renewable sources and reducing the effect of greenhouse gases as a result of replacing renewable energy instead of energy produced by power plants (such as fossil fuels power plants)".

Pressurized irrigation is employed to enhance water efficiency and expand cultivated areas within limited water resources, but it results in a substantial rise in energy consumption within the agricultural sector. Consequently, the need to conserve water and energy arises as a critical requirement for pressurized irrigation. One effective approach to address this issue is the implementation of energy audits, which identify opportunities for energy savings within irrigation systems. However, there is a scarcity of studies that examine energy audits specifically in irrigation systems. Thus, the objective of this research is to present a methodology for conducting energy audits in sprinkle irrigation systems, encompassing all three defined levels of analysis. Additionally, the proposed methodology is applied to two case studies. It is worth noting that due to insufficient data monitoring in energy management and sprinkle irrigation systems, a comprehensive energy audit could not be fully executed. Nonetheless, conducting a preliminary audit can still elucidate the causes of energy losses and facilitate future planning for higher-level energy audits.