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Item Stress tensor symmetry preserving model applied to the 2-D viscoelastic flow of a biofilm(Montana State University - Bozeman, College of Letters & Science, 2016) Kanewske, Daniel Bert; Chairperson, Graduate Committee: Tianyu ZhangThe symmetry of the numeric representation of the stress tensor has been shown to be important for maintaining stability, in the sense of Hadamard, of the numeric method. Also, the viscoelastic behavior of biofilms is well documented. A 2D model for the viscoelastic flow of a biofilm using a modified Navier-Stokes equation (NSE) with a novel elastic stress term are presented. The elastic stress is modeled using a numeric stress tensor symmetry preserving scheme that is based on the numeric solution to the Lie derivative and its equivalent counterpart in the form of a symmetric matrix Riccati differential equation (SMRDE). In addition, a coupled advection equation (AE) is applied to the biofilm volume fraction. Solutions to the NSE and AE are found by applying the finite element method (FEM) to the Eulerian-Lagrangian method (ELM). The ELM is solved by first determining the 'characteristic foot' for each Gaussian quadrature point and node point in the mesh. The advection equation is solved using a modified Galerkin Least Squares (GLS) method. Computations are made using the Trilinos iterative sparse matrix solver library called AztexOO which has built in matrix preconditioners and support for parallel processing. The resulting model is used to predict the deformation of a biofilm in a 2D channel. In addition, the accompanying distribution of the pressure and stresses over the evolving velocity field is presented.Item Parametric study of cyclic loading effects on the creep behavior of polymers and polymer based composites(Montana State University - Bozeman, College of Engineering, 2000) Schumacher, Shane ChristianItem Material characterization of poly (vinylidene fluoride) : a thin film piezoelectric polymer(Montana State University - Bozeman, College of Engineering, 1997) Holloway, Frank ConlyItem A three dimensional finite element model of biofilm subjected to fluid flow and its application to predicting detachment potential(Montana State University - Bozeman, College of Engineering, 2006) Gammelgard, Peter Norman; Chairperson, Graduate Committee: Brett TowlerMicrobial 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.Item Quantifying the viscoelastic properties of treated and untreated Pseudomonas aeruginosa and Staphylococcus epidermidis biofilms using a rheological creep analysis(Montana State University - Bozeman, College of Engineering, 2008) Sutton, Michael Philip; Chairperson, Graduate Committee: Warren L. JonesMicrobial biofilms are quite difficult to kill and control, and present many problems to industry and medicine. The ability to alter the mechanical properties of biofilms could aid in the control of biofilm. The goal of this research project was to develop techniques for measuring the mechanical properties of biofilms so that the effects of chemical treatments could be assessed. Constitutive material models were developed and applied to assist in this effort to quantify the effects. Biofilms are viscoelastic in nature, therefore, rheological testing techniques were utilized for this research. Creep testing was performed on a parallel plate rheometer to determine biofilm mechanical properties. The rheometer is a mechanical device that can accurately measure and apply shear stress and strain on viscoelastic samples. The Burger material model closely approximated material behavior of most chemical treatments. This model was used for determining constitutive properties. Pseudomonas aeruginosa (FRD1) and Staphylococcus epidermidis colony biofilms were used for testing. Several treatment methods were used to investigate their effect on biofilm mechanical properties. As a source of different cations, solutions of NaCl, FeCl3, AlCl3, MgCl2, CaCl2, FeCl2 were used for testing. Multivalent cation treatments stiffened the FRD1 biofilm, but weakened the S. epidermidis. Urea treatments weakened both biofilm species. Glutaraldehyde treatments weakened the FRD1 biofilm, but had little effect on the S. epidermidis. Several treatments - EDTA, Barquat, chlorine, antibiotics (rifampin, and ciprofloxacin) - weakened biofilms of both species. The effect of the same chemical treatment between the two species of biofilm sometimes had nearly opposite effects on the biofilms mechanical properties. This research illustrated that it is possible to alter the mechanical properties of biofilm through chemical addition. Further, there are significant differences between the ways that the material properties of biofilms of different species of bacteria will be affected by a chemical treatment. Finally, it was observed that the 4-parameter Burger model for constitutive mechanical properties of biofilms fit the vast majority of the collected data, so that this model proves useful in comparing properties of biofilms grown or treated under various conditions.