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The influence of bacteria-based biofouling on the wall friction and velocity distribution of hydropower pipes

conference contribution
posted on 2023-05-23, 07:17 authored by Perkins, SCT, Alan HendersonAlan Henderson, Walker, JM, Li, XL

Algae biofouling such as the freshwater diatoms Gomphonema tarraleahae and Tabellaria flucculosa have been investigated thoroughly in open channel flows. Their presence has been shown to cause a significant increase in the local skin friction coefficient, the overall drag coefficient and can produce reductions in flow capacity of up to 10%.

This present study extends previous work to investigate bacteria based biofouling that forms on the inside walls of pipelines and machinery that are not exposed to sunlight. The effect of biofouling on a 1:5m long internally painted pipe section was investigated. The pipe section was first installed in a hydropower scheme for an extended period to allow the growth of flow conditioned biofilms at an average flow velocity of 1:3 m/s. It was then returned to the laboratory and tested at 15 different flow rates corresponding to a range of Reynolds numbers from ReD = 0.9 x 105 - 3.9 x 105. At each flow rate the head loss of the fouled pipe was measured as well as the complete velocity profile at the downstream end of the pipe to ensure the full effect of the biofouling was captured. These results were used to evaluate the pipe friction factor and sand equivalent surface roughness, which could then be compared to values predicted by the Colebrook-White Equation.

Trends in the experimentally determined values of pipe friction factor with varying Reynolds number are significantly different from those predicted by the Colebrook-White Equation. Initially the friction factor increases gradually, before a sharp increase is observed at ReD = 1.53x10 5. Following this spike, the friction factor decreases rapidly compared to theoretical plots. The friction factor of a 3:5 m clean pipe was also tested simultaneously, which closely matched the expected prediction for a hydraulically smooth pipe flow.

Experimental velocity profiles show significant deviations from the theoretical prediction of flow through a rough pipe with a higher maximum velocity observed in the centre of the pipe but a lower velocity in the near wall region. All experimental values of velocity are lower than those predicted for hydraulically smooth pipe flow.

History

Publication title

Proceedings of the 18th Australasian Fluid Mechanics Conference

Volume

USB

Editors

PA Brandner and BW Pearce

Pagination

1-4

ISBN

9780646583730

Department/School

School of Engineering

Publisher

Australasian Fluid Mechanics Society

Place of publication

Launceston, Tasmania, Australia

Event title

18th Australasian Fluid Mechanics Conference

Event Venue

Launceston, Tasmania, Australia

Date of Event (Start Date)

2012-12-03

Date of Event (End Date)

2012-12-07

Rights statement

Copyright 2012 Leishman Associates

Repository Status

  • Restricted

Socio-economic Objectives

Hydro-electric energy

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    University Of Tasmania

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