Strange velocity profile at the inlet for a flow inside a cylindrical pipe
 

Hi Foamers,

I've searched in the forum for some pieces of advice but I couldn't find all the details I wanted. So here is my problem:

I'm running simpleFoam in laminar mode to solve the simple case of a fluid going through a cylindrical pipe.
First I runned the solver for a pipe long enough to see the boundary layer fully developed and then I did the same with a smaller pipe to see if I get the same velocity profile.
In my case the boundary layer needs 5 meters to get fully developed, so the big pipe is 6m long and the small one 1m.
To run it faster I've considered a rectangular mesh in 2D.

My 0/U file:

inlet
{
type fixedValue;
value uniform (0.01 0 0);
}
outlet
{
type inletOutlet;
inletValue uniform (0 0 0);
value uniform (0 0 0);
}
wall
{
type fixedValue;
value uniform (0 0 0);
}

My 0/p file

inlet
{
type zeroGradient;
}
outlet
{
type fixedValue;
value uniform 0;
}
wall
{
type zeroGradient;
}

The problem is the velocity profile at the inlet as you can see above.

Attachment 14150

Attachment 14151

To my mind it's impossible to have an acceleration of the fluid close to the wall at the inlet...

Is there somebody who knows what's wrong with my boundary layer or who can give me some pieces of advice?

Cheers,

Michel