How to define a transient species source term?

aleisia · March 5, 2011, 22:59

In my transient analysis, I want to set my species source in a way like this:
turn it on for 1s, then switch it off. I guess there are two ways to do this, first is, to run the simulation to 1s (with a time interval ,say,0.01s) and stop it, change the BC to 0m/s and carry on.

Second is, write a udf source macro for my source, but I don't know how to, if you could share with me a good source code, I would be greatly indebted!

Also, I have some doubts about setting source term:
I set the surfaces as velocity inlet instead of setting the volume as fluid and a source term, because I don't know how to set UDF source terms. I actually tried to do that, and I can set it as source term and set the mass term as, say, 0.1kg/m^3s (choose CONSTANT) and species term as the same number 0.1kg/m^3s. I don't care much about the momentum input this release of substance brings along, so leave it alone. But according to what I found from other discussions, it seems that setting like this doesn't work, and I have to do it through UDF. I don't know if I'm getting this picture right, so you know, please tell me.

alastormoody11 · March 7, 2011, 01:55

Hi,

A simplistic strategy for writing your macro is to record a journal file in which you manually set the source term and use it as a base for writing your UDF.

My suggestion would be to access your physical time and then put the source term inside an if else setting so that it becomes 0 once your physical time exceeds 1s.

aleisia · March 7, 2011, 20:41

Quote:

Originally Posted by alastormoody11

Hi,

A simplistic strategy for writing your macro is to record a journal file in which you manually set the source term and use it as a base for writing your UDF.

My suggestion would be to access your physical time and then put the source term inside an if else setting so that it becomes 0 once your physical time exceeds 1s.

Hi, thanks for your reply. As I've no idea how to "record a journal file", do you know if there is mature set of source macro code for my situation? Of any tutorial besides the fluent udf manual?

Thanks!

alastormoody11 · March 7, 2011, 23:58

this is the first link that pops up after a google search for how to record a journal file in FLUENT:http://www.cfd-online.com/Wiki/Fluent_FAQ

Cant you even do a google search

I mean common

March 5, 2011, 22:59	How to define a transient species source term?	#1
aleisia Member Join Date: Mar 2011 Posts: 38 Rep Power: 15	In my transient analysis, I want to set my species source in a way like this: turn it on for 1s, then switch it off. I guess there are two ways to do this, first is, to run the simulation to 1s (with a time interval ,say,0.01s) and stop it, change the BC to 0m/s and carry on. Second is, write a udf source macro for my source, but I don't know how to, if you could share with me a good source code, I would be greatly indebted! Also, I have some doubts about setting source term: I set the surfaces as velocity inlet instead of setting the volume as fluid and a source term, because I don't know how to set UDF source terms. I actually tried to do that, and I can set it as source term and set the mass term as, say, 0.1kg/m^3s (choose CONSTANT) and species term as the same number 0.1kg/m^3s. I don't care much about the momentum input this release of substance brings along, so leave it alone. But according to what I found from other discussions, it seems that setting like this doesn't work, and I have to do it through UDF. I don't know if I'm getting this picture right, so you know, please tell me.

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March 7, 2011, 01:55		#2
alastormoody11 Senior Member Join Date: Jun 2009 Posts: 100 Rep Power: 17	Hi, A simplistic strategy for writing your macro is to record a journal file in which you manually set the source term and use it as a base for writing your UDF. My suggestion would be to access your physical time and then put the source term inside an if else setting so that it becomes 0 once your physical time exceeds 1s.

March 7, 2011, 23:58		#4
alastormoody11 Senior Member Join Date: Jun 2009 Posts: 100 Rep Power: 17	this is the first link that pops up after a google search for how to record a journal file in FLUENT:http://www.cfd-online.com/Wiki/Fluent_FAQ Cant you even do a google search I mean common