Instrumentation – orientation sensitivity of a Pitot tube If a Pitot tube is pointed upstream, downstream, or sideways in a flowing fluid, will it give the same reading in every case?

Introduction / Context:
A Pitot tube measures stagnation (total) pressure by bringing the flow to rest isentropically at the probe tip. Its reading depends critically on alignment with the flow direction. This question tests understanding of how orientation affects the measured pressure.

Given Data / Assumptions:

• Standard Pitot tube with an impact opening at the nose.
• Steady flow with a well-defined mean direction.
• Gauge measures stagnation pressure when correctly aligned.

Concept / Approach:
When the tube faces directly upstream (into the flow), the fluid at the tip stagnates and the measured pressure equals stagnation pressure p0 = p + ρ v^2/(2). If the tube faces sideways, the opening senses something close to static pressure; if it faces downstream, separated flow and low total pressure at the tip lead to erroneous, often near-static or even fluctuating readings.

Step-by-Step Reasoning:

Verification / Alternative check:
Prandtl Pitot-static probes incorporate separate ports: the nose port for stagnation, circumferential ports for static, highlighting the orientation dependence by design.

Why Other Options Are Wrong:

• True: contradicts basic operation; orientation matters.
• Other conditional options are irrelevant; the principle holds across Re and fluids, barring special multi-hole yaw-insensitive probes.

Common Pitfalls:
Assuming a Pitot tube alone gives velocity regardless of alignment; yaw errors must be corrected or minimized.

Final Answer:
False