Turbulent Flow: Density Viscosity Paradox?

[justadream]

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Why is turbulent flow more likely at high density but low viscosity?

I thought density and viscosity are generally associated with each other.

I got this from: TBR Bio I page 143 #26

 

[Cawolf]

In fluids we had to calculate the Reynold's number of a fluid in motion - the higher the number the more likely the fluid is to be turbulent (some number depending on the path of flow).

Re = (density)(velocity)(Diameter of Tube)/(viscosity)

This means that turbulence is less likely and viscosity increases and more likely at high density.

I just remember how changes in these variables effect turbulence.

 

[Cawolf]

It is important to note that these are very different quantities.

Density is mass/volume and viscosity is N s/m^2 = (Pa)(s)

This quantity describes the force of friction between the layers of the fluid - imagine motor oil and water flowing down a pipe - the water is more "fluid" and will become chaotic at some speed, while the oil is highly bound to neighboring layers and is more "stable".

Density increases the turbulence because turbulence occurs due to kinetic energy causing eddy forces in the fluid layers - more mass per volume will give you more energy.