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

Citation

Perkins, SCT and Henderson, AD and Walker, JM and Li, XL, The influence of bacteria based biofouling on the wall friction and velocity distribution of hydropower pipes, Proceedings of the 18th Australasian Fluid Mechanics Conference, 3-7 December, Launceston, Tasmania, Australia, pp. 1-4. ISBN 9780646583730 (2012) [Refereed Conference Paper]

Copyright Statement

Copyright 2012 Leishman Associates

Official URL: http://www.proceedings.com/17862.html

Abstract

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 = 1:53105. 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.

Item Details

Item Type:Refereed Conference Paper
Research Division:Engineering
Research Group:Maritime Engineering
Research Field:Maritime Engineering not elsewhere classified
Objective Division:Energy
Objective Group:Renewable Energy
Objective Field:Hydro-Electric Energy
Author:Perkins, SCT (Mr Sam Perkins)
Author:Henderson, AD (Dr Alan Henderson)
Author:Walker, JM (Dr Jessica Walker)
Author:Li, XL (Mrs Xiao Li)
ID Code:82577
Year Published:2012
Deposited By:NC Maritime Engineering and Hydrodynamics
Deposited On:2013-02-07
Last Modified:2015-05-15
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