Pressure drop in circular ventilation channels.
To size pipes or suction channels with circular section, also suitable for air or other compressed gases.
Pressure drop in rectangular ventilation channels.
Specific channels to non-circular section used in extraction systems, ventilation or conditioning.
It calculates the hydraulic diameter for a square or rectangular section in way to keep the same pressure drop.
If you do not have technical data about a fan, or the system is not realized yet but you need to know the motor power, you can obtain it here.
If you need the drag of an object into an air flow, or the reaction of an object due to an air flow, you can obtain it here.