Flow regimes – velocity and turbulence “Turbulent flow takes place at high velocities.” Do you agree with this general statement for internal flows in pipes?

Introduction:
Turbulence is characterized by chaotic, eddying motion and enhanced mixing. In internal flows, the transition from laminar to turbulent regimes is commonly correlated with increasing flow speed through the Reynolds number.

Given Data / Assumptions:

• Internal flow in a circular pipe.
• Reynolds number Re = (rho * V * D) / mu.
• Surface roughness and disturbances exist at realistic levels.

Concept / Approach:
For many engineering applications, laminar flow occurs at low Re, transitional at intermediate Re, and turbulent at sufficiently high Re. Since Re grows with velocity V, higher velocities favor turbulence. The simplified statement is broadly correct, though the precise threshold depends on geometry and disturbances.

Step-by-Step Solution:
1) Recognize that Re ∝ V; increasing V raises Re.2) Typical thresholds: laminar Re < ~2000; transitional ~2000–3000; turbulent ≥ ~3000–4000 (varies with source).3) Therefore, “high velocities” (yielding high Re) generally promote turbulence in pipes.

Verification / Alternative check:
Experimental observations show onset of puffs/slugs in the transitional band and fully developed turbulent spectra beyond the threshold, with friction factor following turbulent correlations (e.g., Colebrook).

Why Other Options Are Wrong:

• Disagree: ignores the Re–velocity relationship.
• Agree only for very viscous fluids: viscosity affects Re, but the statement is generally valid across fluids.
• Agree only when Reynolds number exceeds a threshold: while true in detail, the question seeks a general judgment; “Agree” captures the broad engineering rule.

Common Pitfalls:
Treating the velocity threshold as universal; thresholds vary with roughness, disturbances, and entrance effects.

Final Answer:
Agree