Please help

Dear Sir,
I am Rahul Prakash, a final year undergraduate in Chemical Engg Dept, Indian Institute of Technology, Bombay. As a part of my final year project, I'm trying to simulate the two-way interaction of metal nanoparticles (dispersed in water) and the water itself.
Basically, I want to move the particles as per Brownian motion and find the resulting effect in the fluid which is stationary and no other force is acting on it.
Please tell me how should I go about it.

Thanks and Regards
Rahul