Abstract
This study presents a methodology for the characterization of biofouling growth over surfaces exposed to hydrodynamic shear stresses. The aim is to mimic conditions over tidal turbine blades. A dedicated marine test platform has been designed using a twin-blade vertical axis impeller. Samples are mounted radially over the symmetrical impeller surfaces to be exposed to stresses which increase continuously from root to tip. The useful stress test range varies from 50 Pa to 250 Pa at design rotational speed. Hydrodynamic conditions over the impeller surface were assessed from computational fluid dynamics simulations, with a transitional Reynolds Averaged Navier Stokes k-ω SST model and a transient sliding mesh method to account for hull-impeller interaction. Results have shown that the flow remains attached over the impeller surface. Non-destructive field microscopy and image analysis utilizing the FIJI and WEKA platform provided quantitative information on biofouling evolution. A comparison between samples immersed statically for 37 weeks with those exposed to flow-induced stresses showed significant differences. Static samples developed biofouling faster and exhibited greater species diversity. Below a threshold stress of approximately 100 Pa, dynamic samples were dominated by hard-shell macrofouling, especially barnacles, while higher-stress regions were primarily colonized by biofilms and slime.