Flow measuring device that relies on fixed geometry to relate depth to discharge is a

Flow measuring device that relies on fixed geometry to relate depth to discharge is a

• A. Parshall Flume
• B. Orifice Plate
• C. Magnetic Meter
• D. Venturi

Answer: (A)

In open-channel flow measurement, a device with a fixed shape that establishes a known relationship between water depth and discharge is designed to give discharge directly from depth readings. A Parshall Flume has a precisely shaped throat and converging/diverging sections that create a documented, fixed relationship between the upstream depth (or depth over the throat) and the flow rate. By measuring the depth at a standard location, you can determine discharge from the established rating curve without needing differential pressure calculations. This makes it ideal for wastewater flow measurement in channels. The other devices operate on different principles: orifice plates and venturi meters infer flow from pressure losses in a closed conduit, not from depth in an open channel; magnetic meters measure flow velocity using a magnetic field, not depth-to-discharge conversion.

In open-channel flow measurement, a device with a fixed shape that establishes a known relationship between water depth and discharge is designed to give discharge directly from depth readings. A Parshall Flume has a precisely shaped throat and converging/diverging sections that create a documented, fixed relationship between the upstream depth (or depth over the throat) and the flow rate. By measuring the depth at a standard location, you can determine discharge from the established rating curve without needing differential pressure calculations. This makes it ideal for wastewater flow measurement in channels.

The other devices operate on different principles: orifice plates and venturi meters infer flow from pressure losses in a closed conduit, not from depth in an open channel; magnetic meters measure flow velocity using a magnetic field, not depth-to-discharge conversion.