using steady state result as initial condition for transient

s.amirzadeh · June 24, 2015, 02:49

hi, i want to use my steady state velocity results as initial condition for transient run,how can i do this?

Thomas MADELEINE · June 24, 2015, 04:20

if I understood correctly, you want to use the steady state solution of a case to initialize the transient one (not only the velocity but the whole solution)

then if your geometry is exactly the same (if not you can have some problems) when you start CFX-solver in order to launch your simulation, go to the second tab, select the initial condition. Then select in the folder file your previous .res

if I didn't understand correctly, please be more specific about which velocity (and why only velocity) and about where as initial condition.

s.amirzadeh · June 25, 2015, 01:13

thanks, you understood correctly,i have done that but my problem is that only the first time step uses the last solution result,
let me clarify it,in my case i'm using a force to reach the steady state velocities,then i want t add a heat flux to my geometry,so its transient now,but my force still exists and its same as steady state,
but when i run the transient case,only the firs time step has the steady state velocities and velocities in second time step and others become very small

s.amirzadeh · June 25, 2015, 03:09

and can anyone tell me how to fix this eror?

Lance · June 25, 2015, 03:24

You got an overflow, see FAQ
http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F

s.amirzadeh · June 26, 2015, 02:03

Quote:

Originally Posted by Lance

You got an overflow, see FAQ
http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F

thanks,that helped but my other problem still exists

ghorrocks · June 26, 2015, 07:05

Doesn't it just mean you need to run the force driving the flow and the heat flux together? And using the previous steady state run as an initial condition?

s.amirzadeh · June 27, 2015, 02:12

yes it dose but the problem is that initial condition only affects the the firs time step,and for other time steps velocities reach to lower velocities,i mean the steady state velocities disapear

ghorrocks · June 27, 2015, 06:17

Quote:

yes it dose but the problem is that initial condition only affects the the firs time step

That's why it is called an initial condition.

If the velocity changes then whatever is driving or retarding the velocities has changed. There is something in your steady model which is not in your transient model, and that is changing the velocity.

s.amirzadeh · June 28, 2015, 01:11

the difference between them is just i add a heat flux to the transient,noting else changes

ghorrocks · June 28, 2015, 02:34

Can you post an image of what you are modelling, some of the results you are asking about and your CCL.

June 24, 2015, 02:49	using steady state result as initial condition for transient	#1
s.amirzadeh New Member Join Date: Oct 2014 Posts: 23 Rep Power: 11	hi, i want to use my steady state velocity results as initial condition for transient run,how can i do this?

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June 24, 2015, 04:20		#2
Thomas MADELEINE Senior Member Thomas MADELEINE Join Date: Oct 2014 Posts: 126 Rep Power: 11	if I understood correctly, you want to use the steady state solution of a case to initialize the transient one (not only the velocity but the whole solution) then if your geometry is exactly the same (if not you can have some problems) when you start CFX-solver in order to launch your simulation, go to the second tab, select the initial condition. Then select in the folder file your previous .res if I didn't understand correctly, please be more specific about which velocity (and why only velocity) and about where as initial condition.

June 25, 2015, 01:13		#3
s.amirzadeh New Member Join Date: Oct 2014 Posts: 23 Rep Power: 11	thanks, you understood correctly,i have done that but my problem is that only the first time step uses the last solution result, let me clarify it,in my case i'm using a force to reach the steady state velocities,then i want t add a heat flux to my geometry,so its transient now,but my force still exists and its same as steady state, but when i run the transient case,only the firs time step has the steady state velocities and velocities in second time step and others become very small

June 25, 2015, 03:24		#5
Lance Senior Member Lance Join Date: Mar 2009 Posts: 669 Rep Power: 22	You got an overflow, see FAQ http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F

June 26, 2015, 07:05		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Doesn't it just mean you need to run the force driving the flow and the heat flux together? And using the previous steady state run as an initial condition?

June 27, 2015, 02:12		#8
s.amirzadeh New Member Join Date: Oct 2014 Posts: 23 Rep Power: 11	yes it dose but the problem is that initial condition only affects the the firs time step,and for other time steps velocities reach to lower velocities,i mean the steady state velocities disapear

June 28, 2015, 01:11		#10
s.amirzadeh New Member Join Date: Oct 2014 Posts: 23 Rep Power: 11	the difference between them is just i add a heat flux to the transient,noting else changes

June 28, 2015, 02:34		#11
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Can you post an image of what you are modelling, some of the results you are asking about and your CCL.