22.7.4. Viscous Sublayer in High Reynolds Number Flows

Try these first

1. 1.

   What is the viscous sublayer?

   Hint

   Think of where friction most affects the flow near surfaces.

2. 2.

   What does the Reynolds number indicate?

   Hint

   Recall the factor that determines whether flow is laminar or turbulent.

3. 3.

   What is the viscous sublayer?

   Hint

   Consider where viscous effects are most significant.

4. 4.

   True or False: The Moody chart is only useful for laminar flow.

   Hint

   Think about what flow types the chart encompasses.

5. 5.

   Given a pipe with a diameter of 0.5 m flowing at a Reynolds number of 400,000, calculate the wall shear stress if the fluid has a viscosity of 0.001 Pa.s.

   Hint

   Utilize wall shear stress formulas and the relationships from Nikuradse’s experiments.

6. 6.

   If the flow in a non-circular conduit reaches a Reynolds number of 3 million, how might the viscous sublayer behave differently than in a lower Reynolds flow? Describe the consequences.

   Hint

   Discuss the transitions observed in behavior as the Reynolds number increases.