Continuity for incompressible steady flow in a pipe True or False: For an incompressible liquid flowing continuously through a pipe, the discharge (quantity per second) is different at different sections.

Difficulty: Easy

Correct Answer: False

Explanation:


Introduction:
The continuity equation is a cornerstone of fluid mechanics. For incompressible steady flow, it asserts constancy of volumetric flow rate along a streamline (and through any cross-section of a pipe), regardless of local changes in area and velocity.


Given Data / Assumptions:

  • Incompressible liquid (density constant).
  • Steady flow (no accumulation with time).
  • No leakage or branching between the two sections being compared.


Concept / Approach:
Continuity for incompressible steady flow: A1 * V1 = A2 * V2 = Q (constant). If the pipe diameter changes, velocity adjusts inversely with area to keep Q the same. Therefore, the statement that discharge is “different at different sections” is false.


Step-by-Step Solution:

1) Write continuity: Q = A * V for incompressible steady flow.2) Between any two sections, Q1 = A1 * V1 and Q2 = A2 * V2.3) With no sources/sinks, Q1 = Q2, hence discharge is the same.


Verification / Alternative check:
Measurement devices placed at different diameters show different velocities but the same volumetric flow rate when the system is closed and steady, validating continuity.


Why Other Options Are Wrong:

  • True: contradicts continuity.
  • Depends only on viscosity: viscosity affects losses and profiles, not mass conservation.
  • True only in laminar/turbulent: regime does not change mass conservation.


Common Pitfalls:
Confusing velocity changes with discharge changes. Remember that velocity can vary with area while Q remains constant.


Final Answer:
False

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