Thanks stonecold, rmw and steamguy2. For anyone else following this thread, check out www.staticmixers.net - this site had all the information that I required at this stage.
I'm looking at mixing / blending / commingling two different sources of natural gas to give a homogeneous mixture with the 'right' physical composition.
As the commingled stream may not thourougly mix when combined, does anyone know of any equations, rules of thumb, or whatever, for designing...