LIGGGHTS cohesion model minimum separation distance ratios

Submitted by mda156 on Thu, 11/05/2020 - 21:31

Hi,

I am simulating 2 and 3 sphere collisions of liquid coated spheres. We have surface tension set to 0 so there should be no capillary forces, and the collisions are linear/no tangential forces. We have experimental results of these collisions for two different particle materials as well and 2 different coating oil viscosities (3 and 10 MPa). We compared the results to both the Easo and Washino models. However, using the recommended "minSeparationDistanceRatio" of 1.01 the simulations do not match the results. Furthermore, in application I don't believe this ratio should be > 1. Here is the line from the code where it is used:

const double FviscN = stokesPreFactor*vn/std::max(minSeparationDistanceRatio,dist/rEff);

If the recommended 1.01 value is used the minimum would occur at a value larger than the effective radius. I used values of 0.15-0.4 for the minimum separation distance ratios to fit the simulated data to the experimental results. I believe, the recommended value should change for these models for high viscosity simulations.

Thanks,
Megan