Core assumptions behind Bernoulli’s equation (inviscid, steady, along a streamline) Which set of statements best reflects the assumptions under which Bernoulli’s equation applies?

Difficulty: Easy

Correct Answer: All of the above

Explanation:


Introduction / Context:
Bernoulli’s equation is derived from the mechanical energy balance for steady, incompressible, inviscid flow along a streamline with no pumps/turbines and only gravity as a body force. Recognizing its assumptions prevents misuse in diffusers, across valves, or in highly viscous flows.


Given Data / Assumptions:

  • Steady flow (no local acceleration).
  • Incompressible fluid of constant density.
  • Negligible viscosity (inviscid), hence no dissipation between sections.
  • Body force is gravity only; no shaft work added or removed.
  • Uniform section-wise velocity is an engineering approximation used when applying average velocity with a kinetic energy correction factor near 1.


Concept / Approach:

Bernoulli states p/γ + v^2/(2 g) + z = constant along a streamline for the above conditions. In practice, a kinetic energy correction factor may be used if velocity is non-uniform; the “uniform velocity” statement reflects that simplified use without correction factors.


Step-by-Step Solution:

Identify inviscid assumption ⇒ no head loss.Restrict body forces to gravity ⇒ potential head term z.Steady, incompressible ⇒ no density/time variations.Uniform velocity (or correction factor near unity) allows use of average velocity in v^2/(2 g).


Verification / Alternative check:

Compare with the full energy equation including head loss and pump/turbine head; Bernoulli is the special case with h_L = 0 and h_pump = h_turbine = 0.


Why Other Options Are Wrong:

Options (a), (b), and (c) individually are partial statements; the correct comprehensive assumption set is captured by “All of the above”.


Common Pitfalls:

Applying Bernoulli across components with significant losses or work exchange; ignoring the need for correction factors when velocity is highly non-uniform.


Final Answer:

All of the above

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