جستجوی مقالات مرتبط با کلیدواژه "water hammer" در نشریات گروه "مهندسی آب"

Using pressure reducing valves to reduce the pressure in water distribution systems to the minimum of required value is one of the most effective ways for leakage reduction. Valve opening/closing, switching a pump on/off and water consumption fluctuation by a large consumer cause transient flows. Interference between transient flow and a PRV with constant needle-valve setting may intensify pressure waves in WDS. Applying smart PRVs can limitpressure fluctuation. In this research, Input-output feedback linearization method has been used for smart PRV control. The results of this method have been compared with PRV with CNVS and proportional-integral-derivative controller. A theoretical network taken from references was used to evaluate the proposed methods. Network demands include normal consumers and an industrial large consumer. Water hammer caused by consumption variations, PRV with CNVS operation, IOFL method and PID controllers were modeled in Simulink. PRV outlet head fluctuation in PRV with CNVS is 18 to 28 m in PID controller and in IOFL method are 26 to 28 m. Also, the results showed that the IOFL method has smoother and less fluctuation than PID. Root-mean-square error for PRV outlet head in CNVS, PID controller and IOFL is 1.6, 0.32 and 0.28, respectively. Therefore, IOFL method has less error and better performance than PID. Also, this method has simpler computational operations by converting nonlinear system equations to linear equations.

This study was initiated to investigate the use of a porous structure in some parts of a pipeline to protect it against water hammer pressure wave. This study was inspired by the utilization of porous breakwaters which are commonly used to protect coastal areas. To fulfill the main objective of the study, different porous structures were installed in an experimental pipeline fed by a pump. The water hammer was induced by an upstream valve. The homogeneous porous structures were made up of spherical beads or broken rocks in different sizes and filled them in pipes with different lengths and subject them under different water hammer conditions. Results obtained from this study showed that during the first cycle of water hammer wave, the ratio of maximum pressure downstream of porous structure to the corresponding value in upstream is between 0.6 to 0.95, respectively. This pressure difference decreased drastically in next cycles. Generally, it can be conclude that an insignificant protection gained from a porous structure in downstream from water hammer; however, the overall pressure fluctuations in the pipe filled with a porous structure was less than a fully open pipe under the same discharge rates and the same water hammer condition. The results showed that porous structures in particular condition could be used to control pressure oscillations in piplines and it is proposed to consider practical aspects of this idea in future researches.

Optimization and modeling of the pressurized irrigation system in other to reduce their construction cost has attracted many scientists up to the present time. Optimization of these irrigation systems has often been conducted by using available commercial codes or toolbox's of conventional evolutionary algorithms combined with hydraulic models. Developed code that is based on genetic algorithm assigns an integer numeric to each available diameter. Then, by applying the cross-over, mutation and reinsertion with elitism approach on set of chromosomes optimum diameter of pipes are selected. Optimum diameters are sent to another subroutine that has been developed to simulating water hammer pressure in which maximum pressures due to water hammer phenomenon in all pipe are calculated. Then, calculated maximum pressures are sent to optimization subroutine again where constrains of working pressure are substituted by the bursting pressure constrains. Exchange of information between optimization and hammer models continues so that the calculated optimal diameters have not change. The results showed that optimized design by the present model reduces cost of implementation of pipelines of Ismailabad irrigation network from 825935.28$ to 730958.37$ which is equivalent to 11.5% of the cost of implementing of the pipelines.Also the results showed that by changing diameter of 3 pipes of 16 existing pipes we can control excess pressure of water hammer due to rapid closing of all valve at the end of pipelines during less than 1 second. In this case the cost of implementing of the pipelines increases 6.1% e.g. from 730958.37$ to 775511.5$.

Under transient flow condition, the behavior of water conveyance system varies according to their characteristics. In the present study, the pressure was measured using a fast and sensitive pressure gauge in Bukan and Piranshahr water conveyance system. The pressure simulation was conducted using Bentley Hammer software. The friction head loss was calculated by different methods. The results showed that Unsteady Vitkovsky method had minimum error comparing with other methods. Wave velocity increase had direct effect on maximum pressures while velocity decrease affected minimum pressures. In a shorter water conveyance system, the reduction of wave velocity had direct effect on maximum pressure. Destruction to the long conveyance system was more probable and maximum and minimum pressures occurred during the first period. Shorter conveyance system had more pressure fluctuations and the minimum pressure did not occur in the first period. Coincidence of periods happened at the beginning and continued untill the end of data recording in the longer conveyance system. However, as time passed by, such coincidence did not occure in shorter conveyance system.

Whenever and for any reason the velocity of the fluid ceases in the transfer line or water distribution networks, pressure waves will form in the pipe lines, which can produce a pressure several times more than a pressure pump’s output and lead to a great deal of tension on network’s components, which in turn will cause the water hammer phenomenon. Today, in every water transfer project, a detailed study on the water hammer phenomenon is essential, so that with a full recognition of this process’s adverse effects, the adequate measures would be taken to deal with it.This study uses Water Hammer V8i software to analyze the water hammer of Mehran city’s border terminal water conveyance pipe. The study was executed in 3 phases of simulation with protective equipment, without the protective equipment and with consultant’s recommended equipment. The results indicate that in the phase without the protective equipment, a great deal of negative pressure builds up along the water conveyance pipe line that needs to be controlled. In the next step, various combinations of Hydropneumatic tank and air valves were suggested. The results of several simulations showed that a 2 square meter Hydropneumatic tank and 3 fifty millimeter air valves will be capable of controlling the negative pressure along the pipe line.

In recent years، the optimal design of pipeline systems has become increasingly important in the water industry. In this study، the two methods of genetic algorithm and mathematical optimization were employed for the optimal design of pipeline systems with the objective of avoiding the water hammer effect caused by valve closure. The problem of optimal design of a pipeline system is a constrained one which should be converted to an unconstrained optimization problem using an external penalty function approach in the mathematical programming method. The quality of the optimal solution greatly depends on the value of the penalty factor that is calculated by the iterative method during the optimization procedure such that the computational effort is simultaneously minimized. The results obtained were used to compare the GA and mathematical optimization methods employed to determine their efficiency and capabilities for the problem under consideration. It was found that the mathematical optimization method exhibited a slightly better performance compared to the GA method.

Sudden changes in the boundary conditions of water transmission systems, such as sudden opening and closing of valves or abrupt on and off switching of pumps and turbines cause a transient flow called ‘water hammer’. In this study, comparisons were made between the effective parameters including pipeline material, on the one hand, and the equipment and tools available for reducing the effects of water hammer, on the other. For this purpose, a practical example of a water transmission line from a pumping station located near Shahid Shirdom Residential District to the upstream reservoir in Tehran was used for modeling by the Bentley Hammer XMV: 8 software. The results obtained for the different parameters and options were compared and it was revealed that, regarding the pipe material, GRP pipes reduced pressure by 49.1 Kpa compared to the Asbestos cement pipes and by 50.3 Kpa compared to the iron pipes. Comparison of the results for the protective systems indicated that the surge tank outperformed the other alternatives in controlling pressure such that maximum pressure was reduced by 3.9 bar when using surge tanks compared to the flywheel and by 5 bar compared to the check valve. Finally, it was found that the concurrent use of the surge tank and the flywheel would be the most ideal method for controlling the water hammer effects.