Pitot tube orientation effect If a Pitot tube is inserted with its nose facing downstream (away from the oncoming flow), how does the liquid column in the tube respond compared with the static level?

Introduction / Context:
A Pitot tube measures stagnation (total) pressure when its opening faces directly into the flow. Orientation errors change what pressure is communicated to the tube, affecting the indicated head and thus the inferred velocity.

Given Data / Assumptions:

• Incompressible, steady flow.
• Pitot tube connected to a manometer referencing static level.
• Tip oriented downstream instead of upstream.

Concept / Approach:

With the tip facing upstream, the local dynamic pressure converts to a rise corresponding to stagnation pressure p_0 = p + ½ ρ v^2. If reversed to face downstream, the tube senses a pressure below static because the opening is in a separated wake with lower total pressure. The manometer column therefore falls relative to the static level.

Step-by-Step Solution:

Verification / Alternative check:

Wind-tunnel and pipe-flow practice confirm that a reversed Pitot registers sub-static pressure, sometimes approaching the suction in the wake, giving a depressed column.

Why Other Options Are Wrong:

(b) suggests no change, which is not what is observed; (c) is the normal upstream-facing behavior; (d) is unnecessary; (e) is not representative of steady readings.

Common Pitfalls:

Assuming Pitot works the same regardless of orientation; ignoring wake effects behind the probe.

Final Answer:

falls in the tube to a depth