How Does Changing Mass Flow Rate or Diameter Affect Reynolds Number?

[cheertcc101]

The question gives this ..

The Reynolds number, Re, is a dimensionless group which characterizes the intensity of a flow. For large Re, a flow is turbulent; for small Re , it is laminar. For pipe flow, Re=u(density)D/mu, where D is pipe diameter and mu is dynamic viscosity.

It asks ..

If D and mu are fixed, what is the effect of increasing mass flow rate on Re?
and
If mass flow rate and mu are fixed, what is the effect of increasing D on Re?

Any help is appreciated,

Thanks!

 

[FredGarvin]

First of all, while Re is used to characterize the type of flow, it is a ratio of forces in a flowing fluid. It is a ratio of the inertial forces to the viscous forces.

Start by looking at what defines the mass flow rate...$$\dot{m}=\rho*A*V$$

You'll also need to look at the fact that area is $$A=\frac{1}{4}\pi*D^2$$