4- Conclusions
\label{conclusions}
A new wet particle collision technique i.e. Simplified Spring Collision
Method (SSCM), is developed in order to model collision of particles
with arbitrary shapes. The method defines an overlapping function based
on the distance from the particle interface which helps to find the
collision parameters. These include the collision point, degree of
overlapping, the local relative velocity and the local curvature at the
collision point. Moreover, SSCM by adjusting the spring stiffness
coefficient after the maximum overlapping happens, applies the collision
damping forces without using a dashpot. SSCM instead of using the
expensive lubrication forces, implements the restitution coefficient
obtained from the local relative velocity at the collision point.
Therefore, there is no need for extra grid refinement to solve the
lubrication forces during the collision which results in significant
saving in the computational costs.
SSCM was validated with the experiment and shown to be valid over a wide
range of Stokes numbers for the case of falling sphere. The study of the
effect of the collision course as the only unknown parameter shows that
for \(0.05D_{p}<\sigma<0.3D_{p}\), the error in the results is not
significant. The capability of the method also was tested for elliptical
and rectangular shapes. Furthermore, the accuracy of the tangential
component of SSCM was validated for a spherical particle exposed to the
shear flow. The accuracy method also was compared with the benchmarks
for the situation of two particles in the case of drafting, kissing and
tumbling. The results shows the overall agreement of the results.
However, there is an error in the velocity during the collision phase
due to the soft collision method and the diffuse nature of the
interface.