Modelling alternate approaches for calculating friction head loss in water distribution pipelines

Campbell, Alexander (2017) Modelling alternate approaches for calculating friction head loss in water distribution pipelines. [USQ Project]


Abstract

The accurate estimation of frictional head loss is essential when designing water distribution pipelines to ensure system capacities and delivery pressures are determined with sufficient accuracy. A range of approaches are available to calculate frictional head losses including the Darcy-Weisbach, Hazen-Williams and Manning’s equation. The use of the physically based Darcy-Weisbach equation is generally regarded as the most accurate approach. However, this does not deter many practising engineers using the empirical Hazen William equation due to its history and ease of use. This paper explores the use of computer-based modelling systems and the appropriate use of the available equations and their consequences on head loss calculations if not used inappropriately.
The purpose of this paper is to highlight a common oversight during the design of water distribution networks. The introduction and increased use of computer-based modelling should have seen the end of the Hazen-Williams equations due to its limited range of usefulness. However, software engineers are giving the end user of distribution network software the ability to use the Hazen Williams equation still. This paper will look to explore the effect this is having on the calculated frictional headlosses.

Frictional headloss equations use a variety of parameters to calculate losses. These parameters will all affect the headloss in different ways. Excel was used to isolate and review the effect of changing individual parameters had on overall losses.

To explore the effect of differing frictional headloss equations further a real-world example of Oakey QLD, was modelled using EPANET 2.0. This software gives the user the ability to construct large water distribution networks that can then be easily manipulated to run comparative experiments. There are a range of variables that affect frictional headloss equations, these variables are, diameter, pipe roughness, pipe age, operating temperature, fluid, velocity and discharge. It is already known that changing variables will affect the outcome, the primary purpose of this experiment is to verify and quantify the difference in meters between each equation explored. From this exploration, formal recommendations can be made.

The experimentation has produced expected results; the Darcy-Weisbach equation has proven to be the best suited and most stable throughout the ranges of flow within water distribution networks. The surprising result was that the Hazen-Williams equation performers better than expected even through large diameter networks. This is in part due to the limitations on the design of distribution networks by design guidelines.

Further work is needed on cost analysis and Model development. The Hazen-Williams equation acts as a conservative estimation for frictional headloss within water distribution networks in Australia. It is for this reason that it is still prescribed in design manuals and standards.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Honours)(Civil)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 -)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 -)
Supervisors: Ballie, Justine
Date Deposited: 08 Sep 2021 05:36
Last Modified: 08 Sep 2021 05:36
URI: http://eprints.usq.edu.au/id/eprint/40784

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