Hydrodynamic performance of fouling release surfaces

There is a requirement to develop an environmentally friendly alternative to traditional toxic antifouling ship hull coatings. Silicone fouling release coatings offer a promising alternative. These coatings may become fouled but if the adhesive strengths of the organisms to the surface are sufficiently low, the hydrodynamic forces generated when a ship is underway will cause the organisms to detach leaving a smooth surface. At present, little is known about the hydrodynamic performance of these coatings. This study examined the panel drag on fouling release surfaces of different barnacle shear adhesion strength with uniform cylinder patterns, uniform barnacle patterns and heterogeneous fouling communities. The purpose was to investigate the fouling release properties of antifouling coatings and their performance, with respect to panel drag, so predictions could be made at ship scale.; A through-hull hydrodynamic drag meter was designed, constructed and calibrated. The instrument was used to measure the drag, water velocity, and video record the surface of static immersion panels in the field. Coating performance was evaluated based on drag with respect to barnacle shear adhesion strength.; The concept of fouling release was visually documented and quantified through measurements in the reduction of panel drag. It was found that density effects of fouling elements can increase or decrease the likelihood of hydrodynamic release. Low barnacle shear adhesion strength was shown to produce lower drag penalties on silicone fouling release surfaces. Furthermore, it was demonstrated that lower barnacle shear adhesion strength resulted in lower U.S. Navy fouling ratings after hydrodynamic fouling release. This observation allowed the prediction that a silicone fouling release surface with barnacle shear adhesion strength of less than .02 MPa would be hydrodynamically clean of hard fouling with the fouling communities present at this study.; A modified ITTC 78 method and Granville's similarity-law method were used to scale drag data of heterogeneous fouling communities generated by this study. The analysis suggests that these methods may be used to predict ship resistance with low form fouling, however, they were found unsuitable to scale hard fouling. At 300 m ship scale, the best performing fouling release surface (BSA = .023 MPa) was predicted to have an increase in drag of 9% to 22% when fouled.