Question

Water is flowing in a pipe. Which is the correct statement about the effect of an increase in the Reynolds number of the flow:

a.if the flow is laminar it cannot become turbulent if the wall is smooth.

b.if the flow is turbulent it could become laminar.

c.if the flow is laminar it could become turbulent.

d.if the flow is laminar it cannot become turbulent unless the wall is rough.

Answer 1

c.if the flow is laminar it could become turbulent.

Step-by-step explanation:

The Reynolds number (Re) is a dimensionless quantity used to help predict flow patterns in different fluid flow situations. At low Reynolds numbers of below 2300 flows tend to be dominated by laminar, while at high Reynolds numbers above 4000, turbulence results from differences in the fluid's speed and direction. In between these values is the transition region of flow.

In practice, fluid flow is generally chaotic, and very small changes to shape and surface roughness of bounding surfaces can result in very different flows.