The Method of Characteristics Applied to the Sensitivity Analysis for Water Hammer Problems

Abstract

Water hammer is a transient situation in pipe flows that is created by a sudden change in velocity. This phenomenon can create large pressure fluctuations in pipes and often can present hazards in pipelines. Generally, water hammer is created by rapidly closing valves and by suddenly shutting off or starting pumps. It is one of most destructive hydrodynamic effects in pressurized pipelines. In this study, the governing equations of the water hammer phenomenon are numerically solved using MATLAB and then a sensitivity analysis is performed by changing variables such as pipe roughness, reservoir head, pipe diameter, pipe length and wave velocity. The numerical solution is based on the method of characteristics (MOC). Results show that with increasing pipe roughness, pressure fluctuations decrease. In addition, increasing the reservoir water level causes intensive negative and positive pressures in the pipe. Maximum and minimum pressures occur at the end of the pipe so that ending section of pipe is a critical zone for design. By increasing the pipe diameter, the pressure fluctuations would be smaller. The pressure fluctuation range can also be significantly decreased by using shorter pipe lengths. As the wave velocity increases, the pressure fluctuation range decreases.