[immortality]

Hi
I have a as seems simple question.
can we expect that boundary layer be visible in the flow?
I have a flow in a tube like shock tube(but 2D).but I can't see the boundary layer.is it a trouble with mesh?I have set y+ around 30.or its not a rationale expectation?
thanks.

[wyldckat]

Hi Ehsan,

"See the boundary layer" in what sense?
Do you mean that you expect to see the U profile along a plot line in a cross-section of the tube?

Can you show an image of the profile you're seeing? Including a snapshot of the mesh?

Best regards,
Bruno

[immortality]

Hi
I want to know if the boundary layer has resolved well or not(it originated at all or not)

[wyldckat]

Caution: I might be wrong here, but the following is what I vaguely know on this topic!

I thought that the wall function is meant to compensate for not being possible to solve the boundary layer!?

In other words, isn't it this why there are wall functions in the first place? Namely because we cannot spend too much memory/computation time solving the boundary layer directly with an ultra fine mesh near the wall?

And that the reason why y+ is used as a reference is precisely so that we can use the wall function to sort-of replace the better estimated boundary layers? (The "log" and the "viscous" ones, I think...)

At least this is what I've understood from here:

• http://www.cfd-online.com/Wiki/Two_e...all_treatments
• http://www.cfd-online.com/Wiki/Near-..._models#FLUENT

Last but not least, if I'm not mistaken, the only way to figure out if the boundary layer is at least properly approximated, without experimental data, would be to rely on DNS modelling:

Originally Posted by http://www.openfoam.com/features/turbulence.php

Direct numerical simulation (DNS): Resolves all scales of turbulence by solving the Navier-Stokes equations numerically without any turbulence modelling. DNS simulations can be performed in OpenFOAM using the dnsFoam solver.

But I think this is seriously heavy in terms of computing power...