Does anyone have a down to earth explanation for kinematic viscosity and centistokes?

A Google search for centistokes brings up many hits, some plain definiyions, some not as plain.

And this helps me how? LOL

quote:

A unit of measurement for kinematic viscosity equal to the unit millimeters squared per second. The centistoke is the ratio of a liquid's absolute viscosity in centipoise to the density.

Try this one out of H&P magazines Glossary of Flud Power terms found in their Fluid Power Hand Book & Directory they used to print once a year.
Kinematic viscosity — absolute viscosity of a fluid divided by its density at the same temperature of measurement. It is the measure of a fluid’s resistance to flow under gravity..

You can see the whole Glossary in Chapter 4 of my basic training book at the Ebooks Link on the home page of this forum. Use the "Back to HydraulicsPneumatics.com" link at the bottom of this page.

No definition of centistokes in the Glossary that I could find.

Sorry to make you LOL, certainly not my intention.

OK, so I'm understanding it's the time it takes for x amount of oil with a y density to pass through a 1 mm orifice at 40° C. But what are the x and y values? Y represents a Poise, but I can't get a good definition on that online anywhere.

There is some info in the Vickers Industrial Hydraulics Manuals. There is a lot more in the latest Eaton book of the same title.

I have been loookking at some of the sites I frequent and found this info on Viscosity. See if it gives any better references.

http://www.engineeringtoolbox.com/technical-terms-fluid-mechanics-d_181.html

Scroll down to "Viscisity" May be worth something. I have not checked any of the references yet.

The more I try to learn this, the more jargon I come across that tries to explain it, confusing me even more. A Poise represents dynamic viscosity. Dynamic viscosity has something to do with shearing, but I've never figured out how you can shear a fluid.

Kinematic viscosity is dynamic viscosity divided by density. Being unable to understand dynamic viscosity leaves me unable to fully understand kinematic viscosity.

Even though I know kinematic viscosity is described in Centistokes, being 1mm²/sec (I haven't figured out why a volume measurement is expressed as a square function), for the life of me, I can't picture what's going on here...

Josh wrote:

quote:

Dynamic viscosity has something to do with shearing, but I've never figured out how you can shear a fluid.

See if this article is any help:

http://www.noria.com/Advanced_search.asp?generalsearch=shearing

If that link does not go diretly to the article then go to http://www.noria.com and type "shearing" in the Search space.



g

Josh,

What I understand from kinematic viscosity is that fluids are made up of molecules. so if molecules move from place to place, they do so in particular lane-systems or layers. each layer rubs against another layer i.e. each layer shears another layer. This frictional force is kinematic viscosity.

Kinematic Viscosity X density = dynamic viscosity (temperature dependent)

AKB

I have a pretty good understanding that kinematic viscosity is a factory of viscosity and density under gravity, but I still don't know what a centistoke is, or how it's measured.

Bud, that looks some some good reasources you link; I'll have to have a look when I get more time.

Here is a link to a dictionary on the NORIA site that has a definition of Kinematic Viscosity and a million other definitions on Oil and Lubrication.

http://www.noria.com/dictionary/default.asp?definitions...qxq222&alphasearch=K

I get the concept that it's a given amount of liquid at a given temperature flowing through a given diameter of tube from gravity. But what's 1mm²/sec? Volume is represented by cubics, not squares.

quote:

But what's 1mm²/sec? Volume is represented by cubics, not squares.

Your GUESS is as good as MINE. I would try the question on the NORIA site.

I have little knowledge of Hydraulic Fluids. Over the years I always defer to the manufacturers spec's. Primarily the PUMP MANUFACTURER. Never got in trouble that way