I've been running some tests simulating a snowball hitting a wall. Most of the sim is working well now. I have high clumping values in the sim to create the look of the snow breaking up. The main issue I have is that after the snowball hits the wall, clumps of grains start to pick up speed, and often fly off at strange angles, sometimes even changing direction.

I'm guessing this is down to the high clumping values creating some sort of velocity feeback in the grains?

My main setting are:
Constraint Iterations: 120
Static Threshold: 1
Scale Kinetic: 1

Clumping:
Weight: 2
Stiffness: 40

Pop Solver
Max and Min substeps: 20