I am trying to build a low speed wind tunnel, and have a question. I understand that the contraction cone speeds up the air (proportional to the area ratio). What I am confused on is how does this "mechanical advantage" factor into sizing my fan / motor? I am planning on a tunnel with a velocity of 225 ft/s. That yields 33,000 cfm (for a 1.5' x 1.5' area). But if I build a 12:1 contraction cone, doesn't that help me downsize the fan/motor combo I need? Or does the 33,000 cfm number already represent this advantage of the contraction cone?