The base program used here is the NVIDIA's oclParticles example provided in the NVIDIA_GPU_Computing_SDK package.
Here I made some changes on the boundaries of collisions, so it looks that there is a hole at the bottom of the box and the particles are coming out of the box.
All collisions between the particles are defined as previous, I didn't change that. The hole is a 0.25 length square.
Then, I change the positions of the particles to be at y=0 when they're coming out from the box through the hole. This result into a fountain like simulation.
The bottom of the box.
And the interaction of the fountain particles with a thrown sphere of particles.
I also made a circular hole of radius 0.5. This is how it looks like
As I mentioned before I did this just changing the collision's boundaries in the integration kernel of Particles.cl.