I am working on an Air Blast Cannon for work and am having trouble finding the proper formulas to calibrate it. This Cannon needs to have a barrel with about a 4 inch bore. It will only be used to generate high speed air blasts, so it will not have a projectile. Are there any formulas or online calculators I can use to adjust the Air Reservoir pressures and volumes, relative to the the Barrel size, in order to zero in on my target air speed? I have found a few formulas that seem like they should work, but all of them require a projectile mass (which I don't have) and don't provide units, so I am unsure how to proceed. Additionally, these calculations don't have to be super precise, only accurate enough to give a rough idea on the materials I'll need to use. I am hoping you guys can provide formulas (with units preferably), useful website links, or even data from similar projects. I am looking forward to your responses. Thanks!