LES and DES for complex geometries
Title: LES and DES for complex geometries
SNIC Project: SNIC 2020/5-605
Project Type: SNIC Medium Compute
Principal Investigator: Lars Davidson <lada@chalmers.se>
Affiliation: Chalmers tekniska högskola
Duration: 2021-01-01 – 2022-01-01
Classification: 20306
Homepage: http://www.tfd.chalmers.se/~lada/


The project will be used for several purposes: Multi-scale heterogeneous reaction systems: The project deals with modelling and simulations of catalyzed and non-catalyzed heterogeneous chemical reactions in gas-solid fluid flow systems at multiple levels of abstraction (molecular/nano-scale, coarse-grained/meso-scale, macro-scale). A number of different softwares, all currently installed and available on Hebbe, will be used. Laser-induced crystallization: We employ numerical simulations to investigate the evolution of a laser-induced bubble acting as a nucleation site for crystals. The volume of fluid (VOF) framework is used in combination with a model for phase change. We use a commercial software already available on Hebbe. Eulerian-Lagrangian simulations of bubbly flows: The project aims to characterize the turbulent flows generated by rising bubbles. An in-house software will be used. The code employs FFTW and openmpi libraries already available on SNIC and exhibits strong scaling as the number of MPI processes increases. Modeling fermentation bioreactors: This research aims at formulating, developing, and validating a theoretical model for mass transfer intensification through utilization of.CFD simulations are performed with commercial and open-source codes to establish flow patterns and mixing behaviors of the bioreactor, as well as a sub-grid scale model to understand further the details of gas-liquid interactions on microscales. Transients in water turbines: The project will employ rotating and morphing mesh techniques, together with highly resolved flow simulations and cavitation models, to study transients in water turbines. Intermittent renewable electric energy production forces the water turbines to constantly vary operating conditions and to start and stop frequently. This causes flow instabilities that deteriorate the machines. The aim is to understand and minimize these hazardous effects. Already installed OpenFOAM, and FOAM-extend, will be used. Vibrations in electric generator fan blades: The cooling air flow in axially cooled electric generators is often driven by fan blades mounted on the rotor. The fan blades occasionally break, causing great damage to the machines. The project will study the particular conditions at the fan blades of axially cooled machines, using highly resolved flow simulations. One- or two-way coupling to the structural dynamics will be included. Already installed OpenFOAM, and FOAM-extend, will be used. Counter-rotating axial pump-turbine: The electric grid needs to be able to store intermittent renewable energy produced when there is low demand of power, to be used when there is a high demand of power. The project will use highly resolved flow simulations to design and optimize pump-turbines to be used for very low head, using seawater, to be used in areas where commonly used pumped hydro is not feasible. The need for precision cooling has become inevitable with the increasing power density in auto-motive internal combustion engines (ICEs) as well as in batteri packages. Subcooled flow boiling offers immense potential for precision cooling. The primary challenges in extracting this potential are: understanding the complexities in the subcooled flow boiling phenomenon, especially in the complicated flow pas-sages of the ICE coolant jacket and battery package channels; and estimating the risk of encountering film boiling. The present study introduces a numerical model to estimate the wall heat flux in subcooled flow boiling and the model includes a mechanistic formulation to account for vapor bubble interaction. The formulation for vapor bubble interaction serves two purposes: blends two well-established models in literature (one in the isolated bubbles regime and other in the fully developed boiling regime) to estimate the wall heat flux; and provides information to limit boiling in order to not encounter film boiling. A new numerical model to estimate subcooled flow boiling heat flux is introduced. The commercial CFD code STAR-CCM+ is used in this work.