Abstract
Biofilm streamer motion under different flow conditions is important for a wide range of industries. The existing work has largely focused on experimental characterisations of these streamers, which is often time-consuming and expensive. To better understand the physics of biofilm streamer oscillation and their interactions in fluid flow, a computational fluid dynamics-discrete element methodmodel has been developed. The model was used to study the flow-induced oscillations and cohesive failure of single and multiple biofilm streamers. We have studied the effect of streamer length on the oscillation at varied flow rates. The predicted single biofilm streamer oscillations in various flow rates agreed well with experimental measurements. We have also investigated the effect of the spatial arrangement of streamers on interactions between two oscillating streamers in parallel and tandem arrangements. Furthermore, cohesive failure of streamers was studied in an accelerating fluid flow, which is important for slowing down biofilm-induced clogging.
Highlights
Biofilms are microorganisms attaching and growing on surfaces, embedded in their extracellular polymeric substances (EPS; Garrett et al, 2008; Walter et al, 2013)
Valiei et al (2012) fabricated a microfluidic device with an array of micro‐pillars to mimic a porous media and they found that biofilm streamers began to emerge between different pillars
At the considered flow velocities, it seemed that there were three stages of streamer oscillation characteristics predicted by computational fluid dynamics (CFD)–discrete element method (DEM) simulations: (1) Stage 1: biofilm streamer slightly vibrated at very low fluid flow velocity; (2) Stage 2: oscillation amplitude increased sharply when the velocity exceeds 0.1 m/s; (3) Stage 3: The increase of maximum amplitude of streamer tip slowed down when the velocity exceeds 0.15 m/s, which was very close to the transition point (0.2 m/s) found in experimental measurements (Stoodley et al, 1998)
Summary
Biofilms are microorganisms attaching and growing on surfaces, embedded in their extracellular polymeric substances (EPS; Garrett et al, 2008; Walter et al, 2013). The presence of biofilms is the major cause for infections of medical devices (Cao et al, 2018; Hall‐Stoodley & Stoodley, 2009) and the clogging of industrial flow system, such as biofouling in membrane system (Vrouwenvelder et al, 2010). The extracellular matrix can hold the cells together to develop filament‐like biofilm structures to resist the fluid shear force and suspended freely with fluid flow (Klapper et al, 2002) Such filamentous structures of biofilms are referred to biofilm streamers which are ubiquitous in porous media and can accelerate the biofilm‐induced clogging of medical stents and water purification filters (Drescher et al, 2013; Hassanpourfard et al, 2015; Marty et al, 2012). The interactions between biofilm streamers and fluid flow are important but remain elusive
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