Question about transient result output

Anna Tian · June 29, 2013, 11:30

Hi

I'd like to only record the history of one expression (could be done by monitor) and have a result that I can restart from. Which output option shall I choose at CFX-pre 'Output control'?

ghorrocks · June 30, 2013, 08:32

I do not understand your question. Have you got a monitor point which you want the data to continue after a restart? You control this in the solver manager settings.

Anna Tian · June 30, 2013, 09:50

Quote:

Originally Posted by ghorrocks

I do not understand your question. Have you got a monitor point which you want the data to continue after a restart? You control this in the solver manager settings.

I mean: how to set up so that I can have transient simulation with the full solution of the last time step saved?

And also if I want to continue the simulation in the future, i can also restart from the last time step.

ghorrocks · June 30, 2013, 10:12

Doesn't a normal stop of a transient run give you a result file with a full solution which can be used for a restart?

Anna Tian · June 30, 2013, 10:38

Quote:

Originally Posted by ghorrocks

Doesn't a normal stop of a transient run give you a result file with a full solution which can be used for a restart?

Yes. It can. But it occupy too much of my disk space. How to reduce the size of the file?

ghorrocks · June 30, 2013, 10:49

Have you looked at the results file options? You can control the compression and which variables get written. This can make the results file much smaller.

Hard drives are cheap, sounds like you need to buy another one. It is not worth your while fiddling with compression and making files smaller when you can buy lots of hard drive space for so little cash.

Anna Tian · June 30, 2013, 10:53

Quote:

Originally Posted by ghorrocks

Have you looked at the results file options? You can control the compression and which variables get written. This can make the results file much smaller.

Hard drives are cheap, sounds like you need to buy another one. It is not worth your while fiddling with compression and making files smaller when you can buy lots of hard drive space for so little cash.

I checked it but confused about which option shall I choose. I don't need the solution in the middle. I only need the solution at the last time step. Which option shall I choose?

ghorrocks · June 30, 2013, 19:55

It is under the results tab in the output control object.

singer1812 · July 2, 2013, 15:11

Typically when running large transients, I will use Output Trn Results at step time steps (every xx seconds) and use the option of selected variables (those that I am usually most interested in). This will create alot of small results files that cant be used as a restart, but are useful in post processing.

I also use Output Trn Results Option Standard at larger time steps (for example 50*xx seconds), which can be used for restarts. This limits the large data set (you can increase the 50 to what ever you are comfortable with).

In addition to that I use Backup Option of Essential at every yy step interval (dont confuse this with time [s]). This file can be used for restarts in case of crashes and what not. This file gets over written with every backup so it will not take up much diskspace.

Anna Tian · July 4, 2013, 13:21

Quote:

Originally Posted by singer1812

Typically when running large transients, I will use Output Trn Results at step time steps (every xx seconds) and use the option of selected variables (those that I am usually most interested in). This will create alot of small results files that cant be used as a restart, but are useful in post processing.

I also use Output Trn Results Option Standard at larger time steps (for example 50*xx seconds), which can be used for restarts. This limits the large data set (you can increase the 50 to what ever you are comfortable with).

In addition to that I use Backup Option of Essential at every yy step interval (dont confuse this with time [s]). This file can be used for restarts in case of crashes and what not. This file gets over written with every backup so it will not take up much diskspace.

May I suppose that if I set the timestep interval as 1000, the disk space will be saved by 999/1000 and I can still restart from a solution among the last 1000 time steps?

singer1812 · July 5, 2013, 12:32

You will only be able to restart the solution (From the Backup) at the backup time step, which includes no other ones prior.

If you need a restart at an arbitrary time, you will need to do that from the transient results. If diskspace is a concern, use smallest as the choice, but that can still chew up alot of diskspace. It also might not be a totally clean restart depending on what physics you have going on.

June 29, 2013, 11:30	Question about transient result output	#1
Anna Tian Senior Member Meimei Wang Join Date: Jul 2012 Posts: 494 Rep Power: 16	Hi I'd like to only record the history of one expression (could be done by monitor) and have a result that I can restart from. Which output option shall I choose at CFX-pre 'Output control'? __________________ Best regards, Meimei

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Transient simulations: how to tell its converged (I've read the FAQ & user guides!)	JuPa	CFX	12	March 27, 2020 18:24
A question about starting computation from an acquired result	jennyrui2008	OpenFOAM Running, Solving & CFD	0	January 8, 2009 22:39
A question of starting computation from an acquired result	jennyrui2008	OpenFOAM Running, Solving & CFD	0	January 8, 2009 22:38
Output transient file to csv	Ben	CFX	3	September 23, 2008 09:17
how to output the static pressure of transient	Fred	FLUENT	0	January 11, 2006 03:27

June 30, 2013, 08:32		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	I do not understand your question. Have you got a monitor point which you want the data to continue after a restart? You control this in the solver manager settings.

June 30, 2013, 10:12		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Doesn't a normal stop of a transient run give you a result file with a full solution which can be used for a restart?

June 30, 2013, 10:49		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Have you looked at the results file options? You can control the compression and which variables get written. This can make the results file much smaller. Hard drives are cheap, sounds like you need to buy another one. It is not worth your while fiddling with compression and making files smaller when you can buy lots of hard drive space for so little cash.

June 30, 2013, 19:55		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	It is under the results tab in the output control object.

July 2, 2013, 15:11		#9
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 21	Typically when running large transients, I will use Output Trn Results at step time steps (every xx seconds) and use the option of selected variables (those that I am usually most interested in). This will create alot of small results files that cant be used as a restart, but are useful in post processing. I also use Output Trn Results Option Standard at larger time steps (for example 50*xx seconds), which can be used for restarts. This limits the large data set (you can increase the 50 to what ever you are comfortable with). In addition to that I use Backup Option of Essential at every yy step interval (dont confuse this with time [s]). This file can be used for restarts in case of crashes and what not. This file gets over written with every backup so it will not take up much diskspace.

July 5, 2013, 12:32		#11
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 21	You will only be able to restart the solution (From the Backup) at the backup time step, which includes no other ones prior. If you need a restart at an arbitrary time, you will need to do that from the transient results. If diskspace is a concern, use smallest as the choice, but that can still chew up alot of diskspace. It also might not be a totally clean restart depending on what physics you have going on.