CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   Main CFD Forum (http://www.cfd-online.com/Forums/main/)
-   -   Re. to my Radial jet with FIDAP and a new question (http://www.cfd-online.com/Forums/main/1482-re-my-radial-jet-fidap-new-question.html)

Dr. Ahmed Hassaneen October 31, 1999 20:59

Re. to my Radial jet with FIDAP and a new question
 
1.I want to reply to myself for my last message. The reason for FIDAP to doesn't solve for the RESTART command is the fact that I was adding a new degree of freedom (FREE) in the RESTART execytion which is not allowed in FIDAP for the RESTART job. 2. I have a new problem which is: I do have a repeated message of having a (pivot) in the equations from 130 to 2100 or so. It is a huge number of pivots. What shoul I do in this case and does it affect the solution.

Eric Grald November 8, 1999 13:54

Re: Re. to my Radial jet with FIDAP and a new question
 
Dear Dr. Hassaneen,

Regarding your restart problem, you should use the READ restart rather than the EXECUTION restart. With READ restart, you can select any field from the old results database. For example, the commands

ICNODE(VELOCITY,READ,ALL) ICNODE(SURFACE,READ,ALL)

will restart the calculation by using the velocities and free surface locations from the old results database.

Regarding the warning messages about the small pivots, please read note (1) of the PRESSURE command documentation (on page 3-49 of the FIPREP users manual). You should set the value of MIXED small enough so that you only see about 10 small pivot warnings per iteration.

Eric

Ahmed Hassaneen November 8, 1999 15:53

Re: Re. to my Radial jet with FIDAP and a new question and another question
 
Thanks for the reply. You are right, we should use READ RESTART instead of EXECUTION(RESTART) as long as we are adding a new degree of freedom. But if we are solving for the same degrees of freedom we can use the Execution(RESTART). The pivots is less than 10 per iteration but it seemed too large because the solution monitors display it for each timestip and each iteration. Thanks for your help

Paul November 12, 1999 10:13

Re: Re. to my Radial jet with FIDAP and a new question
 
If you want to get rid of your pivot messages switch to a a completely iterative solution method. I change your solver to SEGREGATED. Also remeber to change to the CGS and CR methods

CGS=150 CR=150

However it would be advisable to increase the tolerance criteria to 1e-6 +

Regards

Paul

Ahmed Hassaneen November 12, 1999 12:57

Re: Re. to my Radial jet with FIDAP and a new question
 
Dear Paul, Thanks for your suggestions. In fact I'm no longer having these pivots. The reason for these pivots was the solution of the FREE SURFACE. The position of the actual FREE SURFACE was almost infinite, That is why it was giving me these pivots. With that infinite FREE SURFACE position I think the velocity and pressure were almost ZERO. Thanks Regards =Ahmed=


All times are GMT -4. The time now is 10:46.