HYDRODYNAMIC CONSEQUENCES OF BARNACLE COLONIZATION

The aim of this project was to study the hydrodynamic consequences of substratum colonization by barnacles. Replicas of individual barnacles and barnacle colonies, and living colonies were studied in a 5 m seaw ater flume using tracer dyes, macro video-photography and image digiti zation and in a small flume fitted with differential pressure sensors. Using replicas, colonization densities were manipulated to determine the dynamics of complex barnacle populations. These techniques enabled the quantification of drag, boundary layers and their interrelationsh ips with mean flow velocity and population density. These data show th at mean stream velocity affected the size and magnitude of the boundar y layer and that at higher velocities the flow over the height at whic h the cirri were operating was decreased proportionally greater than a t low mean stream velocities. The effect on flow velocity over the cir ri with increased boundary layer at higher mean stream velocities was assessed and an optimum mean stream velocity for flow over cirri ident ified. Density of barnacles was shown to have an effect on the flow ch aracteristics over the population, with flow changing from independent flow at low densities, through interactive flow to skimming flow at h igher densities. Drag was also shown to be affected by barnacle densit y. The economic impact of barnacle fouling on the world maritime fleet is estimated and discussed.