Hi, I used a blower to flow air across an open duct through a nozzle. By using a gate valve, the mass flow rates were controlled. I took measurement in 3 different locations along the ducts. But, why by decreasing the mass flow rate, the air velocity was increased? It is just happend for the lower mass flow rates (downsizing the gate near to the bottom of surface)!!. but not when the gate is fully opened. I also wondering if someone could explain what should happen to the total pressure, dynamic pressure and static pressures when decreasing and increasing the mass flow rate? I'm really need someone to explain this simple physics. As I read more, I also confused more!! Thanks all.