فهرست مطالب mohamadreza jalili ghazizadeh

Side weirs are a type of hydraulic structures used for different purposes in water transition systems, water supply, flow diversion and flood control important. Side weir, is a key structure in transition of urban sewage; the advantage of this  structure in urban sewage is the pre treatment of the diverted flow due to side weir height which is in environmental engineering. The flow on these structures is spatially varied flow type with decreasing discharge. Spatially varied flow is a type of steady flow with decreasing or increasing discharge along the channel. To analyze this flow, its necessary to know the velocity distribution and the values of the  kinetic energy correction factor (α) and the momentum correction factor (β).However due to complexities concerned with this type of flow and experimental limitations there hasnchr('39')t been enough study on the velocity distribution  for this kind of flow . In this research the velocity distribution in a rectangular side weir has been investigated using a commercial software. Before performing the numerical analysis itchr('39')s necessary to check the softwarechr('39')s ability in modeling the  3D flow on the side weir. Experimental data of Jalili Ghazizadeh (1994) has been used for verification. In these experiments side weir lengths 20,30,45,75 (cm) and side weir heights 1, 10, 19 (cm) has been used while discharge in the main channel varied from 43 to 90 (lit/s). The simulation boundary conditions are volume flow rate discharge for upstream boundary,the "wall" for wall and "symmetry" boundary conditions for water surface. The only difference in boundary conditions for subcritical and supercritical flow is in downstream boundary condition which is "specified pressure" for supercritical flow and "specified velocity" for subcritical flow used respectively. Turbulence model is RNG in all simulations. Comparing the results shows that the software is capable of calculating  the discharge passing the rectangular side weir with a good accuracy for both subcritical and supercritical flows. Therefore, based on obtained results we can conclude that the commercial software is capable of simulating 3D flow on rectangular side weir and the results obtained from performing analysis with this software can be cited. Velocity distribution, correction factors for kinetic energy and momentum were studied in detail . In the case of subcritical flow on the side weirs, water in the main channel and downstream area of the side weir has been observed to seperate in the opposite direction of the main channels, there for it is important to study these areas. A noticeable point is that although large amounts of simulation points have (α) and (β) close to one, simulation results show that (α) and (β) can not be considered  equal to one for the  whole cases. The variation of (α) and (β) in side weirs length in this research were ascending. Based on existing simulation results, new equation between (α) and (β) for subcritical and supercritical flow and quantification of separating area were proposed. Results of this research can help side weir designers to have a better understanding of the complex 3D flow on side weirs.

One of the challenges facing water and wastewater companies around the world is water loss from water distribution networks following burst pipes and leakage, which imposes high economic, social and environmental costs on these companies. So, every year a large part of the budget of water and wastewater companies is allocated for the repair and rehabilitation of the pipe network. Therefore, knowing the frequency of burst pipes will help in estimating network leakages and selecting appropriate management strategies for dealing with these. Various factors affect the failure of water distribution pipes, one of the most important being water pressure. Therefore, the development of models to predict failure based on effective factors precisely is necessary to achieve optimal leakage management in water distribution networks. In the present study, using a developed model and analysis of pressure and burst field data in the urban water distribution network, the relationship between pressure and burst rate has been determined for a district of Tehran. The study area has 516 km of mains pipelines that include many types of material such as polyethylene, ductile iron, steel, PVC and asbestos cement. Both polyethylene and ductile iron pipes were selected for the investigation because they comprise 93 percent of the network length. After collecting and revising the statistics and information about the bursts and pressures recorded during the years 1386 to 1395, we have calculated the average zone point and the pressure index at this point and assigned it to the whole area. Finally, the pressure-burst relationship was presented individually for each material in the pipes. The prediction model of the failure consists of two parts, namely independent and dependent parts, through which the pressure parameter is linked through a power component to the failure rates. In this study, the maximum daily pressure at the average zone point was used as a pressure index in the pressure-burst relationship. The pressure-burst relationship for polyethylene and ductile iron based on maximum the daily pressure index is presented separately. In the relationships obtained for comparison, both the average of maximum daily pressure and the maximum of maximum daily pressure values were used. The results of this study showed that, in the dependent pressure part, the average of the maximum daily pressure index presents a more accurate result compared with the maximum value of the maximum daily pressure index and has a higher correlation coefficient. The reason for the inappropriateness of the maximum value of the maximum daily pressure can be temporary and non-permanent overload in one or more days of the year. As it may not really have caused a failure but has been involved in the calculation, this index does not have an accurate prediction of burst. Also, the relations are obtained for two conditions with a power pressure of 3 and an unknown situation, which indicates that, in the case of unknown power, higher correlation coefficients are obtained. Thus, for polyethylene the power is equal to 3 and the correlation coefficient = 0.97, while for ductile iron, the power was equal to 2.7 and the correlation coefficient = 0.99. According to the relationships obtained, it can be concluded that the pressure-burst model could predict the number of failure of main pipes in the water distribution networks well. The results also showed that pressure variations more often affect burst frequency in the polyethylene than the ductile iron pipes. The exponent of pressure in the failure prediction model also depends on the pipe material and is larger for polyethylene in comparison with ductile iron material, and the average for the maximum daily pressure index was a more accurate indicator in the failure prediction model. According to the results of this paper, we can improve pressure management and rehabilitation strategies for the reduction in burst frequency. By applying accurate pressure management and awareness of material susceptibility to burst, it is possible to reduce failure rate and, consequently, water loss.