Fully developed flow

AlephZero

What "fully developed" means here is:

If you take two sections through the wedge at different points in the flow, the flow profile is the same at each section. Also if you look at the flow at one pont at different times, it will be the same.

Most of the previous posts are about WHY the flow gets to be fully developed (or not) rather than what the consequences are.

From the second part of my definition, the flow is independent of t.

From the first definition, it follows that the v and w components must be zero everywhere. If there was a w velocity component to the left (say) at one point down the wedge, then "fully developed" means there would be the same velocity component left at EVERY point down the wedge, so all the water will finish up on one side, which is nonsense. The same applies to the v component.

So the velocity components v and w are 0. and the velocity does not depend on t or on x.

In other words, the general expression for the velocity is u(y,z).

AlephZero

No it doesn't reach a constant thickness. Look up the standard solution for flow over an infinite flat plate.

At least, thats what the standard theory says. It's usually safe to bet that CFD theories don't fit ALL the experimental facts, though.

Mitra

I still don't know if it is possible to have a “fully developed turbulent flow” over plate?

berkanozturk

Hello there, I would like to ask you a question.
I have two pipes which are parallely connected. I have a constant TOTAL FLOW which is divided into two.
Diameter1 > Diameter2 and now, when I increase Diameter1 (in order to decrease PRESSURE LOSS), my velocity is decreasing such that it will decrease (Velocity * Diameter) the Re in the first pipe.
My question is: I have steady state flow, fully developed, and laminar. Pipe lengths are equal and temperature is constant. Can I say that (given that Qtotal is constant and I am only changing D1) when I decrease pressure loss by increasing diameter, Re number is decreasing. So, shear stress distribution is decreasing as well!
or, when I increase reynolds number by decreasing Diameter 1, Pressure loss is increasing, and shear stress distribution is increasing?

I have a final presentation tomorrow morning. I am really confused about this result actually.

Hope somebody will answer.
berkan

banerjeerupak

how is fully developed flow related to the stream function of the flow?

banerjeerupak

Ψ=4y-((1/3) y^3)

This is the stream function i'm referring to here.