Time: 2018, April 10, 13:00

Who: Thomas Weinhart, Anthony Thornton, Irana Denissen, Yousef Shaheen, J. M. F. Tsang, LuJIng

Topic: Where is the contact point between two overlapping spheres of different size?

The issue is where should the contact point between two particles be? clearly, it should be in the overlapping volume, but where?

- mid-distance, c=p_i+n(r_i-1/2*delta))?

- closer to the boundary of the larger particle, c=p_i+n(r_i-r_i/(r_i+r_j)*delta))?

- somewhere else?

The former definition is the standard in several DEM/DPM codes. It causes problems:

- when particles start to overlap fully, i.e. the smaller particle is inside the larger, the contact point is not between the two particle COM's anymore.

- for particle collisions with a flat wall, the contact point is slightly inside the wall

We are discussing this since Santorini 2015, without coming to a conclusion. This time we said the following

- The real contact point is not only dependent on curvature but also on stiffness of the particles.

- is there existing literature on this topic that has already solved this problem?

- if not, we could model the contact of two elastic spheres and find out?

- What about non-spherical particles, is the location of the contact point a function of curvature?

To be discussed further

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