Learning Forum

[megm07]

Hi all,

ANSYS/Fluent/CFD beginner here. I'm trying to run a very simple laminar flow simulation of airflow in a microfluidic channel. I'm following There is one inlet with specified non-zero velocity and one outlet. There are no other setup errors- mesh check and quality are good and the initialization converges. When I try to run the calculation for 500 iterations, it 'completes' almost immediately without throwing any errors, and my residuals plot is just blank. Screenshots of residual plot and console output are below. Am I missing something simple here? Any assistance is much appreciated.

I was mostly following an official ANSYS Fluent tutorial to help me set up the simulation, with differences only in the materials and lack of viscous flow in my case.

 

 

[Rob]

What was the initial condition? The above tends to happen when there is no flow due to boundary conditions or model set up. 

[megm07]

I have an initial velocity that I calculated from the experimental flow rate, so I put this velocity in the velocity-inlet condition. For pressure-outlet, I didn't specify a gauge pressure, I just left it at 0. Are there more boundary conditions that I would need?

[Rob]

Are you running double precision? You may also need to turn the residual checks off (Advanced button in Residual panel) to force a couple of iterations. Initialise from the inlet too. 

[megm07]

I was already running double precision, but taking out the residual checks and using standard initialization from the inlet appears to have worked. Now I can see residuals and I'm able to view results within Fluent. Thanks so much for your help!