# delta_n determination

Submitted by NSalloum on Wed, 01/09/2019 - 11:38

hello,

I was trying to find an approximate value of delta_n, i.e. overlap distance between the particles, so I thought about looking at the dump files I am getting and see how the value given for the diameter of each particle had changed with respect to the initial assigned diamter (i.e. radius in the input script).
But I have seen that most of the values over are more than the initial one, some are less, and some are of negative sign.

1- so may you please inform me what is the reason for that
2 -Is this the right way for getting the delta_n?
3- Is there another way for that?

best wishes,

### Forums:

richti83 | Thu, 01/10/2019 - 08:28

### What do you mean with "value

What do you mean with "value given for the diameter of each particle had changed" ? The diameter is normaly fixed, only the distance between the center of the particles changes
Than you can calculate delta_n=(R1+R2)-|(X1-X2)|.
As this is not a particle property but a contact property you can easily use compute pair/gran/local with output of delta

The output delta will output the overlap (sum of radii - distance between particle centers) in distance units .

example:
``` compute fc all pair/gran/local pos id force contactArea delta dump forcechain all local 100 post/fc*.dump c_fc[1] c_fc[2] c_fc[3] c_fc[4] c_fc[5] c_fc[6] c_fc[7] c_fc[8] c_fc[9] c_fc[10] c_fc[11] c_fc[12] c_fc[13] c_fc[14] #x1 y1 z1 x2 y2 z2 id1 id2 periodic fx fy fz A delta_n```

best
Christian.

NSalloum | Mon, 01/14/2019 - 11:49

### Paraview Visualization

thanks a lot Mr. Christian,

I didn't thought about that before.

I was also wondering if I can show some sort of visualization of some of the values I get using these commands in Paraview, so would it work ?

best wishes,

richti83 | Tue, 01/29/2019 - 10:53