Application of heat source for 1 second in a 3 seconds transient analysis

shahpar73 · June 23, 2016, 18:24

Hi
I want to run a transient heat transfer analysis for 3 seconds in which a heat flux on a boundary (in W m^-2) is to be switched on after 1s and then switched off after 2s. The purpose is to see how the surface cools down. How to set it in CFX-Pre.

ghorrocks · June 23, 2016, 19:51

Some options:

Use a CEL if function
heatflux = if(t>1[s],if(t<2[s],100[W],0[W]),0[W])

or

heatflux = step((t-1[s])/1[s])*step((2[s]-t)/1[s])*100[W]

or use a 1D interpolation function

shahpar73 · June 25, 2016, 08:08

Thanks Glenn. I really appreciate your help.
(1) In my case, the heat source is initialized from a "Profile data", lets say with the name "HeatSource". can I simply replace 100[W] with "HeatSource" in "step" function?
(2) "if" function is simple, so how to use "HeatSource" with "if".

ghorrocks · June 25, 2016, 08:42

I have never done that with profile data but I think you can do it. Give it a go and see if it works for you.

shahpar73 · September 3, 2016, 01:21

"if" function didn't work with profile data (may be I am not using it correctly); however, "step" function did work. The command is follow;

heatflux = step((t-1[s])/1[s])*step((2[s]-t)/1[s])*HeatFlux

Where HeatFlux is initialised as profile data and then defined as user function.

Thanks Glenn for the help.

ghorrocks · September 3, 2016, 08:00

I think the if function was introduced in ANSYS V15. If you have an older version you will only have the step function available.

June 23, 2016, 18:24	Application of heat source for 1 second in a 3 seconds transient analysis	#1
shahpar73 Member Shahid Parvez Join Date: Jul 2009 Location: Pakistan Posts: 38 Rep Power: 16	Hi I want to run a transient heat transfer analysis for 3 seconds in which a heat flux on a boundary (in W m^-2) is to be switched on after 1s and then switched off after 2s. The purpose is to see how the surface cools down. How to set it in CFX-Pre.

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June 23, 2016, 19:51		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Some options: Use a CEL if function heatflux = if(t>1[s],if(t<2[s],100[W],0[W]),0[W]) or heatflux = step((t-1[s])/1[s])step((2[s]-t)/1[s])100[W] or use a 1D interpolation function

June 25, 2016, 08:08		#3
shahpar73 Member Shahid Parvez Join Date: Jul 2009 Location: Pakistan Posts: 38 Rep Power: 16	Thanks Glenn. I really appreciate your help. (1) In my case, the heat source is initialized from a "Profile data", lets say with the name "HeatSource". can I simply replace 100[W] with "HeatSource" in "step" function? (2) "if" function is simple, so how to use "HeatSource" with "if".

June 25, 2016, 08:42		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	I have never done that with profile data but I think you can do it. Give it a go and see if it works for you.

September 3, 2016, 01:21		#5
shahpar73 Member Shahid Parvez Join Date: Jul 2009 Location: Pakistan Posts: 38 Rep Power: 16	"if" function didn't work with profile data (may be I am not using it correctly); however, "step" function did work. The command is follow; heatflux = step((t-1[s])/1[s])step((2[s]-t)/1[s])HeatFlux Where HeatFlux is initialised as profile data and then defined as user function. Thanks Glenn for the help.

September 3, 2016, 08:00		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	I think the if function was introduced in ANSYS V15. If you have an older version you will only have the step function available.