Knut Küllmer Andreas Krämer Supervisors Bonn-Rhein-Sieg University of Applied Sciences, Sankt Augustin Prof. Dr. Wolfgang Joppich In cooperation with the University of Siegen [email protected] Prof. Dr. Dirk Reith [email protected] Prof. Dr.-Ing. Holger Foysi The Lattice Boltzmann Method for Complex Flows on the Microscale Introduction The Lattice Boltzmann Method Liquid-vapor equilibrium A method for simulating the motions of gases and liquids (Computational Fluid Dynamics) (Static droplet) Fundamentally different from classical fluid simulations: particle-based description (BGK equation, particle distribution functions ݂௜ ) BGK ݂݀௜ ͳ ୣ୯ ࢞ǡ ‫ ݐ‬൅ ࢋ௜ ή ߘ݂௜ ‫ܠ‬ǡ ൌ െ ݂௜ ࢞ǡ ‫ ݐ‬െ ݂௜ ሺ࢞ǡ ‫ݐ‬ሻ ݀‫ݐ‬ ߬ Vapor phase: Liquid phase: Distinct strengths Efficient for parallel computing Easily solvable on regular lattice Particularly suited for complex flows (e.g. multiphase/multicomponent flow, complex shaped boundaries) Project 1: Droplet dynamics in microfluidic devices Motivation Droplet-based microfluidics as a vastly expanding industry with numerous biological, chemical, medical and technical applications Various assets make the Lattice Boltzmann Method a suitable tool for flows on the microscale Multiphase models are limited due to numerical deficiencies Goals Optimization of discretization schemes in a class of Lattice Boltzmann multiphase models to ensure a correct physical representation of a single component. The new discretizations reduce spurious velocities (undesired numerical artefact) and force the simulated liquid and vapor densities to match the values predicted by thermodynamic theory. An accurate representation of a single component is substantial for the simulation of multicomponent systems. Taylor-Green decaying vortex : Comparing simulation and reality Software Development Couette Flow: Error between simulation and reality Simulation of droplet dynamics in microfluidic devices (coalescence, deformation, interfacial tension, active manipulation) Optimization of the underlying algorithms (reduce numerical artefacts, increase robustness, increase accuracy) Project 2: Lubricant flow between rough surfaces Validation: Model problems Application: Real geometries Motivation Different finishing techniques (grinding, polishing, sandblastingflead to different surface shapes. Study their role in lubrication ՜ Simulation Classical simulation techniques do not behave well for complex-shaped (= realistic) surfaces ՜ Lattice Boltzmann: a promising alternative Goals To study how the shape of the surfaces affects the efficiency of lubrication in realistic geometries Development of a modular software package for the Lattice Boltzmann simulation on unstructured grids 0.1 mm Reducing friction is a pivotal part of energy-efficient engineering One principal goal of the PhD is to simulate lubricant flow over highly resolved geometries. But before a simulation tool can be applied to real-world problems, it has to proof that it calculates the right physics. Standard benchmarks are the Taylor-Green decaying vortex or the Couette flow between two moving walls. Coupled simulation of fluid and surface movements (Multiphysics) Prof. Dr.-Ing. Rainer Herpers [email protected] www.gi.h-brs.de Institute for Technology, Renewables and Energy-efficient Engineering (TREE)