[Mathos]

Hi Guys!

I have been trying to simulate two stroke engine airflow through two domains.
One domain (covergent divergent nozze) is stationary and the other one (crankshaft inside volume) is rotating.
The simulation is working fine until these two domains disconnect.
Afterwards [Update failed for the Solution component in Fluid Flow (CFX). The solver failed with a non-zero exit code of : 2] error pops up with [overflow] condition.

Boundary conditions are that the outflow of rotating domain has velocity of 0.00122 kgs/s. Inlet of stationary venturi is 0 Pa.

Maybe someone has any idea what am I missing?
Please see picture attached.

Screenshot 2023-04-10 140541.png

Screenshot 2023-04-10 140701.jpg

Screenshot 2023-04-10 140912.jpg

[Opaque]

Not sure how you are coupling them, but the inlet cannot be disconnected from the outlet; otherwise, your boundary condition cannot communicate and the problem becomes ill-posed.

[Mathos]

Dear Opaque,

Thanks for the answer. Now it is clear why my simulation keeps crashing. I managed to make an expression for boundary condition of mass flow to become 0 on the time, when two domains get separated.

Now im running into another error [A wall has been placed at portion(s) of an OUTLET].

Maybe anyone could advise me if there is a possibility to create time dependent boundary condition change from "OUTLET" to "OPENING"? If yes, how can I do that?

Thanks again!

[Opaque]

Not possible via expressions, but you can configure the simulation

On the outline, right-click on Simulation and insert a new Analysis. You can then configure which one runs first, next, when to stop one, when to start the next, etc.

At this point, I advise reading the documentation for multi-configuration simulations.