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 seawater flume using tracer dyes, macro video-photography and image digitization 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 interrelationships with mean flow velocity and population density. These data show that mean stream velocity affected the size and magnitude of the boundary layer and that at higher velocities the flow over the height at which the cirri were operating was decreased proportionally greater than at low mean stream velocities. The effect on flow velocity over the cirri with increased boundary layer at higher mean stream velocities was assessed and an optimum mean stream velocity for flow over cirri identified. Density of barnacles was shown to have an effect on the flow characteristics over the population, with flow changing from independent flow at low densities, through interactive flow to skimming flow at higher densities. Drag was also shown to be affected by barnacle density. The economic impact of barnacle fouling on the world maritime fleet is estimated and discussed.