Pore fluid diffusion analysis 1

[jjt1980]

I've been teaching myself Abaqus for about 8 months now. I am creating a hollow cylinder that is fully saturated and has isotropic, elastic properties in Abaqus. I am loading the cylinder and analyzing the pore pressure and fluid velocity values. While running the analysis, I am getting the following message:

"There is zero VOL. FLUX everywhere in the model based on the default criterion. please check the value of the average VOL. FLUX during the current iteration to verify that the VOL. FLUX is small enough to be treated as zero. if not, please use the solution controls to reset the criterion for zero VOL. FLUX."

I am not sure where to perform this check and where the solution controls are. This project is academic and related to a Master's thesis.

 

[itsmoked]

I can't help you specifically but have you done your due diligence by pulling down and looking at every single possible tool window?

Also when you input aspects of the hollow cylinder were there any buttons that said "check here if zero blah blah"? I suspect this warning is because somewhere your low flow is being rounded to zero and possibly a division is about to occur.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jjt1980]

I need to take a look at all the tool windows as you said. No buttons that said zero blah blah. I may have to make the model from scratch again to see. What do you mean a division is about to occur? Thanks so much.

 

[jjt1980]

I guess you are referring to the boundary conditions in the "Initial" step. I do set a zero pore pressure BC at the inner surface of the hollow cylnider.

 

[itsmoked]

I 'mean' any program, worth a damn, will always check before any division for a zero denominator. In this case I suspect they throw a particular warning when they discover that your particular simulation somehow results in a divide by zero. It can be because rounding occurs, and hence a zero you might not be expecting, or you actually assign something to zero.

Their model can have many different separate calculations. If you need something not normally zero to be zero they may need to yank some entire calculation out of the calculation chain. They could've just tested your simulation and done it automatically. I suspect that they didn't and instead need you to manually signify this somehow. Hence: "[green]please use the solution controls to reset the criterion for zero[/green]".

A suggestion. Side step the issue. How can you really have zero pore pressure? Wouldn't even gravity produce some? Try a few small non zero values and see what happens.

Otherwise you need to find how to indicate to the program in the 'solution controls criteria' the use of zero.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jjt1980]

keith,

I am going to do my due diligence in looking at all the toolboxes. Thanks for your help!

Jeremy
CCNY
Biomedical Engineering