Result of simple pipe flow

I am comparing simscale with other CFD softwares and i cannot accomplish this simulation. Simple pipe of 8 inches and 30 meters, 17000 kg/h of air at 115ºC (properties looked online). I do not know why but the results end up diverging. Please help

Project: Prueba 4 | SimScale Workbench

Hello fran_jcr_nob,

I noted that the flow velocity is a ~160 m/s which is higher than the suggested limit for incompressible flow which is set to mach 0.3.

In addition I noted that you have adjusted the relaxation factors, what was the reasoning behind this?

I’m test a setup with initial conditions closer to the expected result, so you can take a look at it here

Best regards

Hello Sebastian. Thank you in advance for your answers.

I am not sure what that “relaxation factor” is, i am sure that i didnt adjusted nor it is that way by default.
What does this factor change? How do you adjust this relaxation factor for the new simulation?

Hello Fran,

I see you can find more information on relaxation factors here:

For the new run I just reseted this to default.

Best regards

I am seeing your results for the same simulation I did. In this case the pressure plot follows the same problem. What we can do to solve it?

Hello again Sebastian.

I have been trying other models that might make this simulation easy and faster to solve. In this case we try a 16 inch pipe of 2 meters, with 29000 kg/h of flow at the outlet and a pressure at the inlet of 79330 Pa.
This make the fluid’s speed way lower than the other models but the pressure at the outlet still show a sinusoidal behaviour

As soon as you solve this please let me know cuz is really weird that a simple simulation like this can’t converge