Implementation and Validation of a Free Open Source 1D Water Hammer Code

Abstract

This paper presents a free code for calculating 1D hydraulic transients in liquid-filled piping. The transient of focus is the Water Hammer phenomenon which may arise due to e.g., sudden valve closure, pump start/stop etc. The method of solution of the system of partial differential equations given by the continuity and momentum balance is the Method of Characteristics (MOC). Various friction models ranging from steady-state and quasi steady-state to unsteady friction models including Convolution Based models (CB) as well as an Instantaneous Acceleration Based (IAB) model are implemented. Furthermore, two different models for modelling cavitation/column separation are implemented. Column separation may occur during low pressure pulses if the pressure decreases below the vapour pressure of the fluid. The code implementing the various models are compared to experiments from the literature. All experiments consist of an upstream reservoir, a straight pipe and a downstream valve.

Analysis of Unsteady Friction Models Used in Engineering Software for Water Hammer Analysis: Implementation Case in WANDA

“…Brunone and Vítkovský's friction models have been implemented by different authors who reported similar results of high accuracy than the previously implemented friction models [22,23,33]. Vardy and Brown's model provided the best damping and wave attenuation results compared to the previously mentioned models [22]. This is attributed to the high accuracy of the convolutional-based unsteady friction models.…”

“…Vítkovský's model provides slightly more accurate results than Brunone's as it has the sign correction term [32]. Brunone and Vítkovský's friction models have been implemented by different authors who reported similar results of high accuracy than the previously implemented friction models [22,23,33]. Vardy and Brown's model provided the best damping and wave attenuation results compared to the previously mentioned models [22].…”

“…The accuracy comparison was performed by comparing the simulated friction models' peaks and comparing it with the real measurement data. This means of comparison has been commonly applied in literature for comparing the accuracy of the friction models [21,22,30]. The summation of square error (SSE) demonstrated in Equation (13) has also been used to assist the error calculation.…”

“…This agrees with previous research that confirms that the Vardy and Brown unsteady friction model is the most accurate compared to the other implemented friction models. Jensen et al [22] showed that the Vardy and Brown friction model provided more accurate results than quasisteady and steady friction. In general, the convolutional-based models provide better estimation in terms of accuracy compared to other categories of unsteady friction models [20,21,27].…”

“…The models of Zielke, Vardy and Brown, and Trikha have similar results, where the maximum heads and wave shape are accurately predicted. Another comparison was performed by Jensen et al [22], who compared different models (steady, quasisteady, Brunone, Vardy and Brown, Zielke) with experimental data performed by Soares et al [23]. This study showed that Brunone's model provided better results over steady and quasisteady friction models.…”