Effect of pressure‐sensitive demand on surge analysis

Abstract

Traditional water distribution models solve the network problem by considering instantaneous demands lumped as nodal outflows. Such demand‐driven analysis assumes that demands are independent of pressures and can be met under all operating conditions. Under transient conditions, however, the resulting positive‐ or negative‐pressure surges can drastically alter the local pressures and affect the demand magnitude that can be extracted. A pressuresensitive demand representation is needed to assess the effect of pressure changes and produce more accurate transient results. A comparative study of demand formulations for surge analysis showed that the pressure‐insensitive demand assumption is intrinsically inaccurate and tends to overdesign surge protection devices. This overdesign results in unnecessary additional costs but does not necessarily ensure greater safety. The authors conclude that a pressure‐sensitive demand formulation should be used for surge analysis to adequately evaluate both system performance and the ultimate cost of system protection.

Lost in Optimisation of Water Distribution Systems? A Literature Review of System Design

“…7 nodes) [14], (2) real-world network (incl. 29 nodes) [248]. Objective (1) (7) ratio between diameter and height (real), (8) ratio between emergency volume and total volume (real).…”

Análisis transiente de la demanda de agua uniformemente distribuida

“…Otra desventaja relevante del algoritmo es que su funcionamiento óptimo depende de la discretización adoptada para la red, la cual debe ser establecida de forma tal que pueda cumplir con la condición de Courant y, dependiendo del caso, ésta debe ser tal que permita incorporar los nodos internos de interés dentro del análisis. Además, el algoritmo supone que la DUD es insensible a la presión en los nodos internos de las tuberías, lo cual puede llevar a sobreestimar (o subestimar) las condiciones transientes, con riesgo de afectar el dimensionamiento o funcionamiento de los artefactos supresores de ondas y, por ende, de los costos asociados (Jung et al, 2009). 26, 43-50…”

Transient Modeling of a Full-Scale Distribution System: Comparison with Field Data

“…Under transient conditions, the pressure may drop to or below zero, so that the demand in the actual system will not be met. Therefore, a pressure-sensitive demand formulation was utilized for all surge analyses, as recommended in Jung et al (2009a) and McInnis and Karney (1995).…”