Question

The flow through a circular pipe is laminar. Now, the fluid through the pipe is replaced with a more viscous fluid and passed through the pipe again with the same velocity. What can we say about the nature of this flow?

(a) The flow will become turbulent

(b) The flow will be a transition flow

(c) The flow will remain laminar

(d) The Reynolds number of the earlier flow is required to answer this question

I got this question in an interview for internship.

Query is from Flow of Viscous Fluid Through Circular Pipes topic in division Viscous Flow & Turbulent Flow of Fluid Mechanics

Answer 1

Right option is (c) The flow will remain laminar

The explanation is: A flow through a circular pipe is said to be laminar when the Reynolds number is below 2100. A more viscous fluid would have a higher velocity coefficient, thus reducing the Reynolds number further at the same conditions. Hence, the Reynolds number will be well below 2100. Flow will remain laminar.