Dimensionless Quantiy.

[MolaKule]

This is a dimensionless quantity which expresses inertia and viscosity.

What is it and what are the four variables that determine this quantity?


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[Darwin1138]

Reynolds Number!!


mean velocity, characteristic linear dimension, dynamic viscosity and density

 

[NothingNew]

The dimensionless quantity which expresses inertia and viscosity is called the Reynolds Number. The four variables that determine this quantity are mean velocity, characteristic linear dimension, dynamic viscosity and density.

 

[A_Harman]

Yep, Reynolds number.
rho*v*d/mu
density*velocity*diameter/absolute viscosity

or you can cheat, and go with:
v*d/nu
velocity*diameter/kinematic viscosity

 

[MolaKule]

All answers were correct and good job.

Osborne Reynolds in 1883 realized that the nature of fluid flow depends on a dimensionless number, Re, subsequently named after him.

Flows with Re less than 2000 indicate the flow is laminar.

Flows with Re > 4000 indicate turbulent flow.

Flows with Re > 2000 and < than 4000 indicate a transition or "critical zone" between laminar and turbulent flow.

The human cell, for example, is subject to a Re of 10^-4.

A hydraulic oil of 100 cS flowing in a 1" pipe at 10 ft/s would have a Re of 774.

Both examples above indicate Laminar flow is occurring with low energy losses, so laminar flow is preferred over turbulent flow whenever possible.

There are situations in which turbulent flow is desired. One such case is when mixing is needed, such as in the combustor of gas turbine engines.

Since Darwin1138 presented the first correct answer, he walks away with the new 3-D Piston Cup Lapel Pin.

 

[erikadiaz]

Wow this is nice..