Picture a Ø160mm duct 10m in length, open at each end. Then I install an in-line fan at one end so that it blows into the duct and just let it run at full power. How can I determine what the air flow will be? I startet thinking about it and was just surprised that I didn't know how to approach it as I'm doing duct sizing and such pretty much every day. The fan has a capacity diagram, and the operating point will be somewhere along the outline close to maximum flow, but where exactly? Do I need to assume some pressure drop in order to get anywhere?