Adhesive force depending from impact velocity

Submitted by steve on Wed, 08/03/2011 - 09:20

I am trying to achieve an adhesive force which is higher when two particles crash with higher velocity.
My idea was to change gamma_n. Therefor I want to use the Hertz/history/stiffness model. By looking at the equations I noticed that the equations for gamman and gammat looks different from Hertz/history because they don't use Sn and St.
Now I am not quiet sure how to calculate gamma_n and gamma_t.
It would be nice to get a short advice. Thanks.

Forums:

steve | Wed, 08/03/2011 - 16:07

Hey Christoph,

thanks for your tip.
I had a look at the files and found the equation calculating Fn_coh in "pair_gran_hooke_history.cpp" but the manual says that you should use Hertzian Style for cohesion. I guess that it uses the same equation.
Anyway I don't know how to add the relative velocity to the equation.
It would be nice if you can give further advice.

Steve

ckloss's picture

ckloss | Wed, 08/03/2011 - 17:09

>>but the manual says that you should use Hertzian Style for cohesion
yes that's what is recommended for the current implementation.
However, whenever you develop your own model it is up to you ensure the validity of your implementation

>>Anyway I don't know how to add the relative velocity to the equation.
the code in pair_gran_hooke_history.cpp should be pretty self-explanatory if you have some experience in DEM and C++. If this is not the case, feel free to get yourself some good textbooks, see
node/38,
node/412)

or register for our courses here:
http://web678.public1.linz.at/media/other/flyer_course2.pdf

Cheers,
Christoph

steve | Thu, 08/04/2011 - 07:51

Thanks, I have basic knowledge in DEM and programming. But the challenge is to get the code to save the impact velocity/cohesion until the particles loose contact.
I wonder if anyone did something similar and could share the best way to do it?

ckloss's picture

ckloss | Thu, 08/04/2011 - 10:09

>>to save the impact velocity/cohesion until the particles loose contact
>>I wonder if anyone did something similar
have a look at how the shear history is used, you can use more history values and store the initial relative velocity there

Try to contact Jay warnett, user/2451, he has started some work related to contact history

Cheers,
Christoph