contact area calculation(wall-particle)

Submitted by clarence91 on Thu, 09/17/2015 - 03:58

Hello,

I found from the compute_pair_gran for wall-particle interaction CONTACT AREA is calculated as A=pi(r^2 - rsq);
While most of the research papers, calculate the maximum contact area(S) as:
S=1.36 k^(2/5) rho^(2/5) D^2 v_i^(4/5);
k is 1/Y_eff;

When I tried to compare my maximum contact area with LIGGGHTS, its not the same. Can any one help me?
Thank you.

Forums:

clarence91 | Thu, 09/17/2015 - 17:10

For my case, I am using vo=5m/s; E_wall = 2e9 Pa; E_particle=2e6 Pa; nu_wall=nu_particle=0.4; rho=890kg/m^3; D_particle=0.01m;
When I calculate with S=1.36 k^(2/5) rho^(2/5) D^2 v_i^(4/5); I get around 2.09e-5 m^2 as maximum contact area.
Whereas using LIGGGHTS, I get the maxmimum contact area as 3.44e-5 m^2. (ran a simulation)
May I know like, why is this difference?
I am following Hertzian formulation in both.

Thanks for your reply.

ckloss's picture

ckloss | Thu, 09/24/2015 - 10:05

Hi Clarence,

please do not be unpatient :-)

The reason for implementing the "geometric" version of the overlap calculation is that Hertz is not the only contact law - for that reason, the calculation was intended to be somewhat generic. But thatnks for the note, I'll add this hint to the documentation for the next release

If you want to have some different calculation, you can just change it in your local copy

Christoph

clarence91 | Sat, 09/26/2015 - 22:28

Thanks for your replies.

Considering hertzian model, maximum contact area between particle-wall or particle-particle is almost 50% more than what it should be with analytical.
For one of my reference case:
S_max = 2.09e-5 m^2 (analytical)
S_max = 3.44e-5m^2 (LIGGGHTS simulation)

Hope this is mentioned in the next release doc.
Thank you.