Characterization of drag mechanisms over biofilm

Soft biofilms can form at flow boundaries, producing increased friction drag and adversely affecting the performance of hydrodynamic systems. The underlying mechanisms of drag production in soft biofilms–such as the role played by compliance, vibration of streamers, and the contribution of form drag to overall resistance–are poorly understood. To examine the drag producing flow, flat plates covered in biofilms were studied in the Skin-Friction Flow Facility at the University of Michigan. Experiments evaluating the drag produced by the live biofilm were then compared to those of solid, 3D printed, rigid replicas to differentiate the measured drag forces and their components. High-resolution, 3D rigid replicas of select cases were generated via additive manufacturing using in situ measurements of the biofilm surface profile. These measurements were accurate to 50 µm as measured by a Micro-epsilon 2900-25 laser line scanner. The hydrodynamic performance of the biofilms, grown under flow on flat plates, was determined through pressure drop measurements as well as planar particle image velocimetry. Comparisons of the resistance curves for the rigid replicas and live biofilm will be discussed and flow measurements will be presented.