This may seem a bit strange,i advise you slove the case you upload again.

Yes i'm using double precision...
Your results at the number of iterations you indicate aren't the same of mine... I don't know why!
Changing URF of pression from 0.3 to 0.1 i have the result i want, but is it a correct method?
And what means to decrease URF?
Excuse for my bad knowledge... :(

Maybe it is completely wrong approach, but what happens if you try to use transient solver?

Why i have to use a transient solver if the problem is steady?

I'm didn't say you have to, I said that maybe something unexpected happens if it breaks so early. I don't know ;)

I repost the former question:
Changing URF of pression from 0.3 to 0.1 i have the result i want, but is it a correct method?
And what means to decrease URF?

Does anyone know it?

i was about to ask you to reduce mom urf little bit. Or reducing pressure urf would help but might not be the case always.


urf of pressure results in slower update of pressure.
pressure_new = pressure_old + urf * change in pressure.

anyway the main reason of your problem is your grid. it is not refined enough to handle fast change that is coming in flow direction. If this situation happens the gradient of u,v,w varries very fast. And often breaking local maxima minima. When you use second order scheme there is a contribution of this term in momentum equation. If your gradients are false this term might be shooting up and down. By reducing pressure unerrelaxation the change due to pressure change is restricted (which is main change per iteration) and behaviour of second order contribution is controled better.

for steady state using low urf is no cheating. Its just a way to get converged solution.

A few years later, which is the solution to this problem? I encounter the same difficulties and I did all the above things proposed..

Achillieas, I don't think it is an unusual experience to get crappier convergence when switch to a less robust discretisation scheme but I don't think it is something special with a pipe expansion (as the testimonies above afirm) . Therefore I would advise you to do as in every case - describe as much as possible about your case, display the mesh and ask for help.