A three dimensional finite element model of biofilm subjected to fluid flow and its application to predicting detachment potential
Gammelgard, Peter Norman.
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Microbial biofouling of wetted surfaces can adversely impact the hydrodynamic performance of pressurized conduits. These impacts are due, in part, to the viscoelastic material properties of biofilm. Of particular interest is the response of biofilm to changing hydrodynamic conditions and its effect on potential for biofilm removal. The goal of this research was two fold; 1) to develop a three dimensional numerical model, incorporating the viscoelastic material description of biofilm, to simulate the response of biofilm to varying hydrodynamic conditions and 2) use this model to identify behavioral characteristics of said biofilm which provide insight into effective removal procedures. Using a viscoelastic Burger fluid material description for biofilm, a numerical fluid-structure interface model was developed.The model was three-dimensional, allowed various sizes and shapes of biofilm to be defined, and was used in a parametric study to investigate biofilm behavior. The effect of the Burger material parameters and flow velocity were investigated. Additionally, the time scale over which microbial processes may influence biofilm material properties was identified and considered along with the results of the parametric study. Simulations revealed a consistent trend: biofilm clusters in flow channels undergo a transition from decreasing rates of deformation to increasing rates due to the interrelated effects of fluid-induced drag and cluster deformation. The results suggested that biofilm clusters which undergo a transition to accelerated deformation, in a time period shorter than that suggested to be influenced by microbial processes, are destined to eventual detachment. Identification of such behavior has significant impacts on biofilm removal methodology.