Hello Everyone(adsbygoogle = window.adsbygoogle || []).push({});

I am looking at equations of colliding particles in a granular gas and wondering how to calculate them.

We assume that the grains are identical perfect spheres (in R^3) of diameter D>0, (x,v) and (x-Dn,w) are their states before a collision, where n ε S^2 is the unit vector along the centre of both spheres, and x the position vector of the centre of the first sphere, e is the restitution coefficient which relates the normal components of the particle velocities before and after collision, the post collisional velocities (v*,w*) then are such that

(v*-w*)n = -e((v-w)n)

I was wondering how from this equation do we calculate the change of velocity for the colliding particles:

v* = v- 1/2(1+e)((v-w)n)n,

w* = w+ 1/2(1+e)((v-w)n)n

Many thanks to anyone that can help!

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Colliding Particles in Granular Material Flows

**Physics Forums | Science Articles, Homework Help, Discussion**