Parastoo Yavari; Ali Akbar Akhtari; Arash Azari
Abstract
In the operation of water distribution networks in cities, leakage from pipes always causes problems for human health and for the environment. Leakage openings in pipes may exist in different shapes. Circular holes are common in corroded and punched pipes. In the leakage studies, the area of these openings ...
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In the operation of water distribution networks in cities, leakage from pipes always causes problems for human health and for the environment. Leakage openings in pipes may exist in different shapes. Circular holes are common in corroded and punched pipes. In the leakage studies, the area of these openings is usually assumed to be fixed and the leakage exponent is about 0.5. In this study, an analytical equation has been presented with two purposes. First, Examining the changes in the leak area and leakage exponent of circular holes. Second, providing an equation that contains more parameters than the general leakage equations. By using such an equation, the accuracy of leakage estimation is increased due to the direct involvement of the effective parameters. Also, for the possibility of modeling different leakage equations, including the present equation, a new hydraulic analysis model has been developed. This model tries to improve leakage modeling by including more capabilities than the existing hydraulic analysis models. Results showed that the leak area in circular holes is not fixed and changes due to different parameters. Comparison of the present equation and the orifice equation showed a significant difference which confirms that the orifice equation cannot be always used for circular leaks. In the study of leakage exponent, it was found that for polyethylene pipes, the leakage exponent is higher than value of 0.5 mentioned in the other studies and it can take different values depending on the leakage position in the network. Increasing the hole diameter did not affect the leakage exponent, but increased the leakage coefficient. On the other hand, for steel pipes, the leakage coefficient was fixed and the exponent remained around 0.5. Finally, the results showed the usefulness of the developed hydraulic analysis model for implementing the scenarios defined in this study.
Ayoob Moradi; Ali Akbar Akhtari; Arash Azari
Abstract
During the recent few decades, the use of various models has been regarded as a promising option to predict groundwater level (GWL) in any given region using a wide variety of data and relevant equations. The lack of trustworthy and comprehensive data is, nevertheless, one of the most significant obstacles ...
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During the recent few decades, the use of various models has been regarded as a promising option to predict groundwater level (GWL) in any given region using a wide variety of data and relevant equations. The lack of trustworthy and comprehensive data is, nevertheless, one of the most significant obstacles that must be overcome in order to analyze and anticipate the depletion of groundwater in the context of water management. Because of this, the implementation of artificial intelligence (AI) models that are able to predict the GWL with high accuracy using a reduced amount of data is unavoidable. In this work, the GWL variations of Lur plain were simulated using GMS model by utilizing the available data and maps. The accuracy of model was assessed at both phases i.e. validation and calibration. Following that, GA-ANN and ICA-ANN approaches, together with ELM, ORELM, and GMDH models, were used in order to fulfill the demand for too smaller volumes by AI procedures. According to the results, the ORELM output had the highest correlation with the observed information, which indicates that it is the most accurate model in this regard. The correlation coefficient for this model was 0.976. Because of this, instead of utilizing a complicated GMS model that needs a significant amount of data for the simulation, an ORELM model can be used to reliably forecast the GWL in the Lur plain. This simple model allows the researchers to accurately predict changes in GWL during rainy and non-rainy years compared to other complicated and time-consuming numerical models.
Salma Ajeel Fenjan; Ali Akbar Akhtari; Mohammad Hadi Tavana
Abstract
In this study, the performance of vertical and tilted crown weirs with different angles of the weir crest across the flow has been investigated using numerical and experimental models. Accordingly, various experiments are conducted on tilted crown sharp-crested weirs under different free-flow conditions. ...
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In this study, the performance of vertical and tilted crown weirs with different angles of the weir crest across the flow has been investigated using numerical and experimental models. Accordingly, various experiments are conducted on tilted crown sharp-crested weirs under different free-flow conditions. Moreover, computational fluid dynamic (CFD) modeling has been done using Fluent software to determine the best form of the discharge coefficient (Cd). In this study, the RNG model is used to define turbulence in the fluid flow and the two-phase volume of fluid (VOF) method is applied to define the interface of water-air in the flume. To verify the accuracy of the CFD model, the experimental data that was done in this research are used. Moreover, another goal of this research is to investigate the influence of the different angles of weir on hydraulic characteristics of flow such as pressure, velocity and Cd parameters. The results show that by increasing the weir crest angle across the flow (α), the Cd values are almost constant. Furthermore, the numerical results are in good agreement with the experimental models. As, the comparison of numerical and experimental data shows that the maximum absolute relative error (ARE) obtained are 2.8 %, which indicates the high accuracy of the CFD model. The vortex area with return velocity vectors can be seen in downstream of the weir and these vectors increase near the weir. In all velocity values, by decreasing the angle of weir to the flow direction, the Cd values increased and tends to a constant value while, the pressure values decreased. As for the velocity values in ranges of 0.05-0.23 m/s, the Cd value is ranged in 0.64-0.675. Finally, as the Reynolds and Froude number increase, the discharge coefficient decreases and tends to a constant number of 0.65 approximately.
Azadeh Gholami; Hossein Bonakdari; Ali Akbar Akhtari
Volume 3, Issue 1 , June 2016, , Pages 193-200
