Instrument used to measure velocity of flow at a point Which device is classically used to determine the local flow speed in a pipe or open channel?

Introduction / Context:Hydraulic engineers employ various instruments to quantify flow. While Venturimeters and orifice meters infer discharge from pressure differences across constrictions, a Pitot tube directly senses local velocity through stagnation pressure.

Given Data / Assumptions:

• Steady, incompressible flow at the measurement location.
• Probe aligned with flow; calibration factor near unity.

Concept / Approach:The Pitot tube measures stagnation and static pressures, whose difference relates to the dynamic pressure. Using Bernoulli’s relation, the local velocity is obtained via V = C * sqrt(2 * (p_t − p_s) / rho). In contrast, Venturimeter and orifice meter provide section discharge Q; velocity is then Q/A and not strictly a point value.

Step-by-Step Solution:

Verification / Alternative check:Compare with a calibrated current meter (open channels) or with PIV/LDV in labs; results align within instrument uncertainty when properly used.

Why Other Options Are Wrong:Venturimeter and orifice meter measure discharge over a section, not point velocity. “Current meter only” ignores that a Pitot tube is the canonical point-velocity device. “None of these” is incorrect.

Common Pitfalls:Not correcting for velocity profile when converting point velocity to average velocity, and misalignment causing under-reading.

Final Answer:Pitot tube