Which device is an open-channel flow measurement device?

Which device is an open-channel flow measurement device?

• A. Orifice plate
• B. Venturi meter
• C. Weir
• D. Magnetic flow meter

Answer: (C)

Open-channel flow measurement uses devices that relate discharge to the water depth in an open channel where there is a free surface. A weir fits this idea because it sits in an open channel and creates a known hydraulic head at its crest; discharge is determined from the water height over the weir using standard head-discharge relationships. This lets you measure flow without forcing the fluid through a sealed, pressure-driven path. The other devices are for closed conduits. An orifice plate and a Venturi meter rely on pressure differences created by constricting the flow inside a sealed pipe to infer flow rate. A magnetic flow meter measures flow by detecting voltage generated as a conductive liquid moves through a magnetic field, also inside a closed pipe.

Open-channel flow measurement uses devices that relate discharge to the water depth in an open channel where there is a free surface. A weir fits this idea because it sits in an open channel and creates a known hydraulic head at its crest; discharge is determined from the water height over the weir using standard head-discharge relationships. This lets you measure flow without forcing the fluid through a sealed, pressure-driven path.

The other devices are for closed conduits. An orifice plate and a Venturi meter rely on pressure differences created by constricting the flow inside a sealed pipe to infer flow rate. A magnetic flow meter measures flow by detecting voltage generated as a conductive liquid moves through a magnetic field, also inside a closed pipe.