Understanding the drag of soft biofilms: A multidisciplinary experimental approach
University of Michigan
Abstract
Biofouling on naval vessels can cause increased drag, resulting in higher fuel consumption accompanied by additional emissions. Predicting the growth and drag of biofouling is essential for improved design and identifying an optimum cleaning schedule, among other things. However, understanding and predicting the drag of live biofouling, a complicated phenomenon with intricate interplay between biology, fluid dynamics, and material science, is challenging. Several factors, such as types and distributions of biological species, growth duration, characteristics of the resulting fouling morphology (presence of streamers, compliance, etc.), their distributions (coverage), and sloughing with time, can play a significant role in complicating laboratory experiments. The compunding of these factors can result in significant spread in drag and inferred roughness quantities needed for predicting drag reliably. In this presentation, findings from an interdisciplinary study on the growth and drag produced by soft live marine biofilms grown in natural seawater to understand the interplay between biology and hydrodynamics are presented. The effect of ambient conditions, mainly flow velocity and duration, on the growth, the biological composition quantified using DNA sequencing, coverage, and measured drag using a bespoke turbulent channel flow setup is discussed. Informed by the live fouling studies, an approach using artificial roughness elements is tested to understand the effect of heterogeneous roughness distribution on inferred roughness quantities commonly used in drag prediction models. The presentation will conclude by discussing important lessons learned and future work planned.
About the speaker
Dr. Harish Ganesh is an Associate Research Scientist in the Department of Naval Architecture and Marine Engineering at the University of Michigan, Ann Arbor. His research expertise lies in fluid dynamics, mainly in single and multiphase turbulent flows using experimental techniques involving X-rays, optical methods such as PIV and PTV, and skin-friction drag measurement, applied to problems of naval and societal interest. Dr. Ganesh’s research spans from tabletop turbidity current experiments to hydrodynamic cavitation studies in the world’s largest water tunnel. His current research interests include the understanding of the physics of cavitating flows encountered in naval and industrial contexts, turbid solid-liquid flows, drag reduction by superhydrophobic surfaces, and the growth and drag characteristics of soft biofilms in marine. He has published over 30 peer-reviewed journal and conference papers and serves regularly as a reviewer for several prestigious journals. Throughout his career, Dr. Ganesh has participated in and led several multidisciplinary, multi-team research projects, collaborating extensively with numerical modelers. As principal investigator (PI/co-PI), Dr. Ganesh has secured research funding from DARPA, ONR, Carlsberg breweries, to name a few, and coordinated multiple multi-university efforts for the Office of Naval Research (ONR).
