What does a simple pitot tube measure in a flowing fluid? Choose the most precise statement about the quantity indicated by a basic L-shaped pitot tube inserted into a pipe or duct stream.

Introduction / Context:
The pitot tube is among the simplest velocity probes used to survey velocity profiles in ducts, stacks, and aerodynamic testing. Understanding exactly what it measures avoids common mistakes when converting pressure readings to flow rates.

Given Data / Assumptions:

• “Simple pitot tube” means a single-hole, forward-facing probe that senses stagnation (total) pressure at its tip.
• Static pressure is obtained separately (e.g., wall tap or static ring), or assumed known.
• Flow is steady and incompressible at moderate speeds.

Concept / Approach:
The dynamic pressure q is q = p_total − p_static. For incompressible flow, q = 0.5 * ρ * v^2, so the local velocity v at the probe tip is v = sqrt(2q/ρ). Because the pitot senses conditions only at its small sensing point, it indicates point velocity, not the cross-sectional average. To compute volumetric flow, one must integrate the point velocity over the area (or apply a profile-based correction factor). Multiport probes and averaging pitot tubes exist, but a single-hole pitot is a point instrument.

Step-by-Step Solution:

Verification / Alternative check:
Velocity profile traverses using a pitot tube show different readings at different radial positions, confirming point measurement.

Why Other Options Are Wrong:

• Average / maximum velocity: Require traversing or specialized averaging probes.
• Static pressure only: A simple pitot measures total pressure; static must be supplied separately.
• Volumetric flow directly: Needs area integration; pitot alone cannot provide it without profiling.

Common Pitfalls:
Using a single centerline pitot reading as the average; always apply a profile correction or perform a full traverse.

Final Answer:
Point velocity (local flow speed at the probe tip)