Consider the flow of air and wale in pipes of the same diameter, at the same temperature, and at the same mean velocity. Which flow is more likely to be turbulent? Why?
The flow which likely to be more turbulent and reason for it.
Explanation of Solution
Flow type is determined by Reynold's number. It can be expressed as:
Here Reynolds number is
Reynolds is function of density and dynamic viscosity.
There is not a significant difference in dynamic viscosity of air and water but there is huge difference in density of these fluids.
Flow type is governed by kinematic viscosity. This is ratio of dynamic viscosity to density of fluid.
Write the expression for kinematic viscosity.
Here kinematic viscosity is
Substitute
Reynolds number is in reciprocal relation of kinematic viscosity.
This is higher in water comparison to air. So, water will be more turbulent.
The flow will be turbulent in case of water because of kinematic viscosity.
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Chapter 8 Solutions
Fluid Mechanics Fundamentals And Applications
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