David Andersson presents his master’s thesis

Student: David Andersson
Main Supervisor: Tomas Johnson (FCC)
Examiner: Henrik Ström
Opponent: Adam Johansson

Abstract of thesis

Industrial spray paint applications are a multiscale, multiphysics and multiphase problem requiring large efforts for efficient and accurate modelling. Fraunhofer Chalmers Centre (FCC) has developed the tool “IBOFlow” for the purposes of both efficiency and accuracy and was used in this thesis.

The multiphase aspects combine a strong shaping airflow with the injection of fluid or powdered paint which is modelled using an Eulerian-Lagrangian framework with a two-way coupling between the phases. The multiphysics modelled are fluid dynamics, particle dynamics and electrostatic forces which are also coupled with each other. Lastly, and the focus of this thesis, is the modelling of the multiscale issue. The small temporal scales near the paint injection are currently modelled as compressible in a very resource demanding process which is separate from the large temporal scales. The small scales are subsequently imported as a boundary condition on a coarser simulation where the temporal scales extend to cover an entire paint job. Different desired finishing results require optimizations of the paint job where a multitude of compressible simulations are needed, making this a very costly process with respect to both time and resources.

This thesis has investigated the possibility of an incompressible simplification for the smaller temporal scales. The incompressible simplification was incrementally tested and validated for larger and larger fractions of the compressible simulation with the goal to reduce the number of required compressible simulations to one while also keeping sufficiently good accuracy.