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-   -   Can Fluent start a simulation from a negative time (http://www.cfd-online.com/Forums/fluent/49874-can-fluent-start-simulation-negative-time.html)

Ted Chu November 23, 2008 16:06

Can Fluent start a simulation from a negative time
 
Hi all,

I am trying to do a simple 2D wave tank simulation. A solitary wave will be generated and propagate from left to right. I am using the DEFINE_CG_MOTION udf on the left wall (as a wavemaker). The velocity profile in the udf is a hyperbolic secant function varying with time. In order to have the left wall to follow the profile, the simulation needs to start from a negative time. I was just wondering if Fluent can start a simulation from a negative time?

Thanks..

Rogerio Fernandes Brito November 23, 2008 17:12

Re: Can Fluent start a simulation from a negative
 
I donīt think so!

http://rapidshare.de/files/40979319/0_wave.rar.html

Ted Chu November 23, 2008 17:43

Re: Can Fluent start a simulation from a negative
 
Thank you Rogerio. I already have this tutorial. It uses sine function which starts at time 0 to generate waves. Do you know how to use sech function which starts at a negative time in Fulent?? Or, is there another way to get around??

Rogerio Fernandes Brito November 23, 2008 18:18

Re: Can Fluent start a simulation from a negative
 
I will talk with others researchers about it, īcause iīm new in Fluent.

Best regards,

Rogerio.

Ted Chu November 23, 2008 20:58

Re: Can Fluent start a simulation from a negative
 
Thanks Rogerio.. At the mean time, can anyone else help??

CDE November 24, 2008 17:49

Re: Can Fluent start a simulation from a negative
 
You can set Fluent's flow time using the text command: (rpsetvar 'flow-time 0.0)

Replace 0.0 with the the flow-time you require. I have never tried using this with a negative time so I don't know if it will do what you require.

Ted Chu November 25, 2008 17:48

Re: Can Fluent start a simulation from a negative
 
Thanks.. I am trying it now, but I got this message saying INVALID COMMAND [rpsetvar]. Don't know why....

CDE November 25, 2008 23:30

Re: Can Fluent start a simulation from a negative
 
did you include the brackets when inputting the command?

copy the command below exactly

(rpsetvar 'flow-time 0.0)

Ted Chu November 26, 2008 08:00

Re: Can Fluent start a simulation from a negative
 
No, I did not include the brackets. I copied the command line into the console window, then got that message.

I just tried it again, but no luck still getting the invalid command rpsetvar.

I am using Fluent 6.3.26 on Windows. Thanks...

CDE November 26, 2008 17:00

Re: Can Fluent start a simulation from a negative
 
you need to include the brackets....it won't work without them. Its a scheme command

Ted Chu November 26, 2008 22:06

Re: Can Fluent start a simulation from a negative
 
Thanks a lot CDE!!! It worked. Yes, now I can start the simulation from a negative time.



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