Author(s): Jessica Andrewartha; Jane Sargison; Kathryn Perkins; Greg Walker; Alan Henderson
Linked Author(s):
Keywords: Biofilm; Boundary layer; Hydropower; Laser Doppler Velocimetry; Turbulence
Abstract: Hydro Tasmania, a hydroelectric utility, operates approximately 170 km of open channels, some of which are subject to extensive biofilm growth by freshwater diatoms such as Gomphonema tarraleahae and Tabellaria flocculosa. A recirculating water tunnel equipped with a Laser Doppler Velocimetry system was used to obtain detailed measurements of the turbulent boundary layer for smooth, rough and biofouled surfaces. Test plates were placed in a hydroelectric canal for up to 12months to allow flow-conditioned freshwater biofilms to develop. The structure of the turbulent boundary layer is compared for smooth, artificially sand-grain roughened, and biofouled surfaces. The results indicate that the presence of biofilms at the wall only changes the structure of the boundary layer in the near-wall region, providing support for the wall similarity hypothesis for flows over freshwater biofilms. Significant increases in skin friction coefficient were measured for the biofouled surfaces.
Year: 2010