Drag production mechanisms of filamentous biofilms.

Biofilms were grown on smooth acrylic surfaces for nominal incubation times of three, five, and ten weeks in a flow loop at the University of Michigan. The biofilm covered surfaces were exposed to the turbulent flow in a high-aspect ratio, fully developed channel flow facility at height-based Reynolds numbers from ≈ 5,000 to 30,000. Measurements of the pressure drop along each fouled upper surface revealed that the friction drag increased from approximately 10% to 400%.