Roughness effects of diatomaceous slime fouling on turbulent boundary layer hydrodynamics |
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Authors: | Elizabeth A K Murphy Michael P Schultz Karen A Flack Cecily N Steppe Matthew A Reidenbach |
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Institution: | 1. Department of Environmental Sciences, University of Virginia, Charlottesville, VA, USA;2. eam6vf@virginia.edu;4. Department of Naval Architecture and Ocean Engineering, United States Naval Academy, Annapolis, MD, USA;5. Department of Mechanical Engineering, United States Naval Academy, Annapolis, MD, USA;6. Department of Oceanography, United States Naval Academy, Annapolis, MD, USA;7. Department of Environmental Sciences, University of Virginia, Charlottesville, VA, USA https://orcid.org/0000-0002-5592-920X |
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Abstract: | AbstractBiofilm fouling significantly impacts ship performance. Here, the impact of biofilm on boundary layer structure at a ship-relevant, low Reynolds number was investigated. Boundary layer measurements were performed over slime-fouled plates using high resolution particle image velocimetry (PIV). The velocity profile over the biofilm showed a downward shift in the log-law region (ΔU+), resulting in an effective roughness height (ks) of 8.8?mm, significantly larger than the physical thickness of the biofilm (1.7?±?0.5?mm) and generating more than three times as much frictional drag as the smooth-wall. The skin-friction coefficient, Cf, of the biofilm was 9.0?×?10?3 compared with 2.9?×?10?3 for the smooth wall. The biofilm also enhances turbulent kinetic energy (tke) and Reynolds shear stress, which are more heterogeneous in the streamwise direction than smooth-wall flows. This suggests that biofilms increase drag due to high levels of momentum transport, likely resulting from protruding streamers and surface compliance. |
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Keywords: | Biofilm turbulence drag roughness PIV boundary layer |
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