Question

In laminar flow through pipes, the Reynolds number is typically less than what value?

• A. 500
• B. 1000
• C. 2000
• D. 4000

Hint:

Remember: Laminar flow → $Re<2000$.

Answer 1

The Correct Option is C

Concept: Reynolds number ($Re$) is used to determine the type of flow in a pipe.
Step 1: Definition of Reynolds number.
\[ Re = \frac{\rho v D}{\mu} \]
Step 2: Flow regimes.

• Laminar flow: $Re<2000$
• Transitional flow: $2000<Re<4000$
• Turbulent flow: $Re>4000$

Step 3: Evaluating the options.

• 500 $\rightarrow$ Too low (incorrect)
• 1000 $\rightarrow$ Possible but not standard limit (incorrect)
• 2000 $\rightarrow$ Standard upper limit for laminar flow (correct)
• 4000 $\rightarrow$ Turbulent range (incorrect)

Step 4: Conclusion.
Thus, laminar flow occurs when Reynolds number is less than 2000.