I want to build a computer simulated wind tunnel. I have experience building physics simulators. I undersand that there are already some existing free wind tunnel simulators out there, but do they work at supersonic speeds? I want to predict the drag coefficient of various rockets and bullets at various speeds both sub and supersonic speeds. Can I do that with free existing software? If not how should I go about to code my own wind tunnel? I can create particle physics where each particle represents a mole or even a molecule. But I think molecules will be too many and a strain on the cpu. Would I need to give the particles an electrical charge so that they repel each other if too close due to electron - electron interaction? I can give the particles (representing moles) mass , velocity and momentum. I can also feed similar properties into the object in question. Once I work out the Drag coefficient for various bullets and rockets at various speeds I will add rockets and bullets into my "what if" simulator. I can then make a simple game out of it.