[Back]

Ch. Lechner, H.C. Kuhlmann:
"Direct numerical simulation of particles located close to/at a solid wall in a shear flow";
Talk: The 8th Euromech Fluid Mechanics Conference (EFMC8), Bad Reichenhall; 2010-09-13 - 2010-09-16.

We report on our current progress in developing a code to be applied in
the context of the cleaning of wafer surfaces by hydromechanical forces.
Our goal is to study the detachment of (submicron) particles, exposed to a
shear flow, from a wall by means of a direct numerical simulation.
The particles are treated as rigid bodies with a two-way
interaction with the fluid.

Our software is based on
OpenFOAM\footnote{http://www.opencfd.co.uk/openfoam/}.
Following Uhlmann\footnote{Uhlmann,
\emph{J. Comput. Phys.}, \bf{209} 448, (2005).}
and Taira and Colonius\footnote{Taira and Colonius, \emph{J. Comput. Phys.},
\bf{225} 2118, (2007).}
we implement an immersed boundary method with direct forcing.
The interpolation between the fixed Eulerian grid and the Lagrangian
forcing points is performed with the regularized delta function introduced
by Peskin\footnote{Peskin, \emph{Acta Numerica}, \bf{11} 479,
(2002).}. For the time being we implemented this
approach in 2D using OpenFOAM's standard solver {\tt icoFoam} to
solve the incompressible Navier-Stokes equations. The coupling
between the particle and the fluid is explicit. To validate the
implementation we present results on standard benchmark tests of 2D
laminar flow around a cylinder for one-way and full coupling.
As a first step towards the simulation of the detachment of a
particle from a wall we investigate the behaviour of the above
numerical method for a particle that is located close to a wall.
For the simulation of particles that are attached to the wall we
implement a soft contact model allowing
for a small overlap between the particle and the wall, which is
counteracted by an elastic restoring force.
Thereby deformation and a finite contact area
can be included in the model despite of the assumption that the particles
are rigid (see e.g. Tomas\footnote{Tomas, \emph{Chem. Eng. Sci.}, \bf{62}, 1997
(2007)}). We expose the circular particle to a linear
shear flow.