Oil Weight Question?

[Huck BB62]

Originally Posted by evldave

I can't speak to the rest (it sounds reasonable), but Laminar Flow is actually the smooth flowing part in the middle of a stream of viscous fluid (whether it be oil or water or urine). The edge has many terms (boundary layer is one), but to clarify the Laminar Flow is the smooth flowing portion in the middle of the stream. (sorry, I spent years doing hydrology can't let a you get away with using incorrect terms)

Arrrgghhh, I quite agree as the term concerns hydrology, but not as the term is used in fluid systems. Laminar by it's very definition is "layers". In the context of a viscous fluid, lube oil, through a pipe or over a machined part, the term laminar is used thusly:

Consider the flow of oil as it passes a pipe's surface. The boundary layer is a very thin sheet of oil (as I explained earlier it's thicker as the oil's viscosity is increased) lying over the surface of the pipe, metal part, and anywhere the oil flows with velocity past a surface. Because oil has viscosity, this layer of oil tends to adhere to the pipe. As the oil moves past the pipe, the boundary layer at first flows smoothly over the relatively smooth surface of the pipe. Here the flow is called laminar and the boundary layer is a laminar boundary layer (this is where I incompletely used the term laminar).

As viscosity, or velocity of the oil is increased, this laminar layer or stagnantly thick layer of oil is increased, thusly hampering heat transfer due to the friction of the part against the flow of the oil itself.

The point at which the boundary layer changes from laminar to turbulent is called the transistion point. Where the boundary layer becomes turbulent, drag, due to friction, is relatively high.

This same exact usage of the laminar region is utilized in air craft design.

It's why a golf ball has dimples, to break up the laminar flow of air over the ball. A perfectly smooth golf ball goes only a fraction of the distance as a dimpled ball.

As oil applies to the inside of your engine and the reason higher viscosities can spell trouble:

http://www.cartage.org.lb/en/themes/...daryLayers.htm


I apologize for any confusion I may have caused. evldave is fundamentally correct.

Now we're all learned on it!

(I'm a certified tribologist, shame on me for not explaining it properly)