Andrew F. Barton

Characterizing the roughness of freshwater biofilms using a photogrammetric methodology.

The physical roughness of a surface changes when freshwater biofilms colonize and grow on it and this has significant implications for surfaces enclosing water conveying systems such as pipelines and canals. Plates with surfaces initially artificially roughened with varying grit size were deployed in an open channel system and biofilms were allowed to grow on the exposed surface. The plates were retrieved at intervals in time and their surfaces mapped using close range photogrammetry. For a fine grit surface (0.5–4 mm particles), diatom-dominated biofilms initially grew between the roughness elements; they subsequently developed as a mat to create a physically smoother outer surface than the underlying rough surface. For a coarse grit surface (2–4 mm), biofilms colonized faster; in one instance, larger clumps of biofilm were observed as transverse ripples across the plate.

Verification of a Numerical Model for the Prediction of Low Slope Vertical Slot Fishway Hydraulics

Abstract A numerical model has been developed to predict the three-dimensional flow character within low slope vertical slot fishways (VSFs). The model solves the three dimensional Reynolds averaged Navier-Stokes equations, closed with the renormalised k-ॉ turbulence formulations. The model employs the volume of fluid method to deal with the free surface. Results are presented for velocities and surface elevations utilising two fishway designs from prototype and laboratory studies. The respective data from these studies are directly compared to the numerical model predictions forming the basis of verification. The model is shown to predict critical design velocities, slot flow characteristics, flow recirculation and water surface elevations well enough to be useful in low slope VSF design.

Design and Calibration of a Water Tunnel for Skin Friction Research

Abstract A new water tunnel facility has been designed for application in skin friction and boundary layer research. The closed loop, recirculating facility with working section 200 χ 600 χ 2400 mm and test surface 600 χ 1000 mm has been designed to operate at working section flow speeds of up to 2 ms-1 (Reynolds number based on test surface length 2.2 χ 106). A force balance enables the direct measurement of drag on test surfaces. Hot film, pitot and multi-hole pressure probes are used to investigate the near wall flow.

A Case Study of the Improvements Gained in Conduit Efficiency by Cleaning a Biofouled Pipeline

Abstract The hydraulic performance of pipelines can be significantly affected by the presence of biological growth on internal surfaces. The change in wall roughness brought about by biofilms has been studied by the use of headloss tests, pre-and post-cleaning, of a low pressure hilltop pipeline of a Hydro Tasmanian hydroelectric scheme. Results of the headloss tests show that improvements to hydraulic efficiency can be achieved from the cleaning of biofouling material, and that identifying the flow velocities at which hydraulically smooth, transitional or rough conditions occur can aid in optimising the operating characteristics of the conduit. Results show both reductions in headloss and improvements in power output at the powerstation at given flow rates. The data when plotted in the style of a Moody diagram shows that the friction law, roughened by biological growth, is observed to deviate from the Colebrook-White relationship, although the results are too narrow in Reynolds number to be conclusive. It was found that bacteria made up the majority of the biofilm biomass in the pipeline studied. Based on molecular analysis, members of the class Alphaproteobacteria were the most frequently detected followed by members of the phylum Chloroflexi. Chemical analyses found high levels of iron, manganese and aluminium in the biofilm.