[jseamon1]

Hello All!

I am simulating flow through a circular tube with a diameter of about 300 microns and a length of 42 cm. I am using a stagnation pressure for the inlet and a pressure outlet of 0 Pa. As I have run the simulation, I noticed that the flow appears to accelerate randomly right before the outlet and I am trying to determine why. I have attached a picture (see outletFlow.png, note flow is going from right to left) to show what I am referring to at the outlet.

One thing that I think might be causing this is the fact that the pressure is not getting down to 0 Pa at the outlet despite that being a boundary condition (see pressureOut.png) does anyone have any thoughts on whether that might be true and how I might resolve that? Thank you all for your help!

[fluid23]

What other settings do you have on the pressure outlet, target mass flow perhaps?

[jseamon1]

Originally Posted by fluid23

What other settings do you have on the pressure outlet, target mass flow perhaps?

So I actually figured out the problem. Turned out to be a mesh problem. Right upstream of the outlet, there was a huge jump in mesh element size which caused the outlet acceleration (see oldMesh.png). I fixed the mesh and got a lot more reasonable results (see newMesh.png). Hope this is useful to someone in the future!

[fluid23]

That'll do it!