Injection of particle with various diameters
 

I have a circle surface for injection fluid and particles with various diameters. I want to inject most of the bigger diameter particles in the bottom segment of the circle but it's still distributed along the surfaces with the smaller ones.

I have seen the cfx documentation which talk about particle position, like injection with line weighting, point weighting, etc. But, it gives very brief explanation. So, I can't understand how to apply the std. deviation, which has to be input, to the distribution in the surface.

Could someone assist me to solve that case?

Thanks in advance