A partial flume is used to measure flow in an open channel and works by:

A partial flume is used to measure flow in an open channel and works by:

• A. Measuring pressure difference between upstream and downstream
• B. Measuring velocity with a moving vane
• C. Narrowing to a throat of fixed dimensions and then expanding again, with flow calculated from head difference before and at the throat
• D. Measuring the fluid's temperature gradient

Answer: (C)

A partial flume measures flow by creating a fixed constriction in the open channel and comparing the water levels (heads) at two points: upstream of the throat and at the throat itself. As the water is funneled through the narrow throat, it speeds up due to the reduced cross-sectional area, which lowers the pressure at the throat. The difference in hydraulic head between the upstream point and the throat is then related, through the known geometry and losses of the flume, to the discharge. Because the throat has fixed dimensions, this head difference maps to a specific flow rate via calibration, making the measurement reliable. This approach isn’t about measuring velocity with a moving vane, tracking temperature changes, or simply comparing pressures upstream and downstream; those don’t define how a partial flume determines flow.

A partial flume measures flow by creating a fixed constriction in the open channel and comparing the water levels (heads) at two points: upstream of the throat and at the throat itself. As the water is funneled through the narrow throat, it speeds up due to the reduced cross-sectional area, which lowers the pressure at the throat. The difference in hydraulic head between the upstream point and the throat is then related, through the known geometry and losses of the flume, to the discharge. Because the throat has fixed dimensions, this head difference maps to a specific flow rate via calibration, making the measurement reliable.

This approach isn’t about measuring velocity with a moving vane, tracking temperature changes, or simply comparing pressures upstream and downstream; those don’t define how a partial flume determines flow.