Learning Forum

[sim_learner]

Hello,

I'm currently trying to simulate a small flow through a pipe with varying diameters. I attempted to reduce the residuals in my steady-state simulation, but it didn't work as expected. Therefore, I switched to a transient simulation.

However, I'm encountering an issue with the total pressure values. In the transient simulation, the maximum total pressure at the inlet is 0.172 Pa, while in the steady-state simulation, it is only 0.069 Pa.

Here are the residuals:
Steady:

Transient:

 

Could you please advise on why these differences might be occurring and how to address them?

Thank you.

[sim_learner]

I guess my problem is that I´m working with a very low velocity of  2.546e-5 m/s.
I would appreciate any insights or suggestions you might have on how to improve convergence for simulations with such low velocities.

[Rob]

If the velocity is that low the initial solution may be very similar to the converged solution, so residuals won't drop very far: read up on why. Are you running double precision? How much mesh are you using (resolution not cell count)? Why such a low speed?