Lattice boltzmann simulations of viscoelastic fluids in biofabrication and adjacent characterization

This thesis provides a rigorous introduction into many concepts important to Lattice Boltzmann simulations for viscoelastic fluids. It does in fact provide the first such simulation, that is able to simulate realistic viscoelastic fluids. Many algorithms necessary to perform the Lattice Boltzmann simulations presented in this thesis are covered explicitly. This includes, the Lattice Boltzmann algorithm, the Immersed Boundary Method and a finite volume algorithm. Validations are provided for the algorithms. Instabilities and their mitigation are explored. The shuffling algorithm necessary for viscoelastic fluids, which was developed in this thesis is presented. Derivations are given for most theoretical concepts used in this thesis. Interpretations and definitions of important quantities are explored solely driven by usability and without regard for previous definitions. An altered derivation of the Reynolds number provides a better way to speed up the simulation using Reynolds scaling. A different definition of the Capillary number allows finding the relevant parameter range more easily. Defining the Weissenberg number for each fluid model allows for better comparisons between the models. Afterwards, parameters are extracted from real data using the theoretical concepts. These are the parameters used throughout the thesis. Applications from atomic force microscopy to bioprinting needles are discussed. The simulations are used to explain and quantify the altered tank-treading frequency, that can be observed in shear-flows. A rectangular Poiseuille flow is investigated to explore the visibility of the elastic effects in different deformation metric. Lookup tables are provided for Real-Time Deformability-Cytometry (RT-DC). RT-DC is also investigated to explore a curious local minimum of the deformation, which is present in current simulations but not in experimental data. Finally, channels used for evaluation of cells at constant extensional rate are explored. According to literature, these should be hyperbolic. However, this thesis demonstrates, that they are not, and provides adequate shapes for different fluids. All tools are provided for maximum reproducibility.