Pressure Wave Analysis Of Transient Flow In Pipe Distribution Systems

Low or negative pressure transients (also called surge or water hammer) create temporary opportunities for external chemical and microbial contaminants at higher pressure to enter the water distribution system, creating potential health hazard and potential weakening of distribution pipes, leading to failure. This study investigates how such events as power outages, pump shutdowns, valve operations, main flushing, firefighting, and main breaks can create significant rapid, temporary drops in system pressure. The report offers useful recommendations for using surge models to optimally locate pressure monitors and to minimize the occurrence and impact from low- and negative-pressure transients.

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An analysis is presented of the effect of longitudinal pressure pulsations or vibrations on the velocity distribution in laminar or turbulent fully developed pipe flow. Specifically, the Reynolds equations are formulated in a noninertial reference frame so that the influence of pressure pulsations, vibrations, or a combined pressure and vibrational oscillation can be obtained from a single solution. For axisymmetric developed flow of a constant property (incompressible) fluid, the radial and circumferential momentum equations can be solved and the axial momentum equation is linearized so that the velocity field can be obtained as the sum of a steady and a time-dependent component. By obtaining a solution for the case where the pressure (or amplitude of vibration) varies sinusoidally, one obtains the solution for disturbances of arbitrary waveform through a Fourier series expansion of the disturbance. Results are presented that show that the velocity field is dependent upon the mean flow Reynolds number, a vibrational Reynolds number, and the amplitude of the forcing function. In general, the fluid response to differing waveforms is similar to that obtained for simple harmonic oscillations with respect to the various parameters explored.

Examining a range of case studies involving different types of systems and the types of surge suppression equipment which may be suited to each, this practical book provides an indepth analysis of actual systems, with emphasis on the type of hydraulic transient behaviour to be expected in each kind of configuration.