| The objective of this research is the three-dimensional modelling of fluid flows in geometry with small gaps based on the fictitious domain method. Small gaps play an important role in the mixing efficiency of agitation process used in the chemical reactors, and in the operation of single-screw and twin-screw extruders. The work is motivated by the need to improve the understanding of fluid flow and the optimization of process equipment design. There are many challenges in the numerical simulation of fluid flow in small gaps, particularly in the case of time-evolving topologies. First, fine meshes are required to account for the important scale differences between the geometrical dimensions, and they involve the solution of large algebraic systems, both leading to high computational cost. Also, the moving parts imply a transient geometry because of the changing volume of fluid with time and adequate numerical techniques must be developed.; In this work, a strategy based on the fictitious domain method and an efficient mesh partitioning method is used to model the fluid flow in geometry with small gaps and moving parts. The fictitious domain method requires only a single mesh to take into account the transient geometry, and the moving parts are described by a set of control points, on which the motion kinematics is imposed.; Two mesh refinement strategies were compared for the case of tetrahedral finite elements. (Abstract shortened by UMI.)... |
