This two-part paper investigates key parameters that may affect the pressurewaveform predicted by the classical theory ofwater-hammer. Shortcomings in the prediction of pressure wave attenuation, s...

This two-part paper investigates parameters that may significantly affect water-hammer wave attenuation, shape and timing. Possible sources that may affect the waveform predicted by classical water...

A number of different methods that use signal processing of fluid transients (water hammer waves) for fault detection in pipes have been proposed in the past two decades. However, most of them focus solely on the detection of discrete deterioration, such as leaks or discrete blockages. Few studies have been conducted on the detection of distributed deterioration, such as extended sections of corrosion and extended blockages. This is despite the fact that they commonly exist and can have a severe negative impact on the operation of pipelines. The research reported here proposes a method of detecting distributed deterioration by investigating the time-domain water hammer response trace from a single pipe with a deteriorated section. Through wave analysis using a step pressure input, a theoretical square-shaped perturbation is found to exist in the transient pressure trace as a result of distributed deterioration. The hydraulic impedance of this section can be derived from the magnitude of the refle...

Improved one-dimensional (1D) models—compared to previous work by the authors—are proposed which are able to predict the velocity, length, and position of the liquid column in the rapid emptying and filling of a pipeline. The models include driving pressure and gravity, skin friction and local drag, and holdup at the tail and gas intrusion at the front of the liquid column. Analytical and numerical results are validated against each other, and against experimental data from a large-scale laboratory setup.

To simulate transient cavitating pipe flow, the discrete gas cavity model (DGCM) is combined with first-order and second-order finite-volume method (FVM) Godunov-type schemes. The earlier discrete vapor cavity model (DVCM) and DGCM based on the method of characteristics (MOC) are known to produce unrealistic pressure spikes. The new FVM-DGCM extends the previously developed FVM-DVCM through the introduction of a very small amount of free gas at the middle of each computation cell. Importantly, a pressure adjustment procedure is proposed to establish the relation between the cavity and the halves of the reach. Predictions of FVM-DGCM are compared with those of FVM-DVCM and MOC-DGCM and with experimental data. Results show that the proposed model reproduces the experimental pressure histories considerably better than the other two models. In particular, it produces fewer spikes, but—as in the old models—the first pressure peak due to cavity collapse is predicted much better than the subsequent peaks. The second-order FVM-DGCM is found to be accurate and robust, even for Courant numbers significantly less than 1.