How to make a UDF to repeat itself ???

magnounibo · November 30, 2009, 11:13

Hi everybody,

I would like UDF to repeat itself adjusting a variable until it reaches a specific (under a tolerance) value.

I'm using VOF multiphase model to simulate transient vapor bubble growing in a superheated liquid, mass and energy sources are given by UDF.

At each time step, Fluent calculates mass and energy rates through my DEFINE_SOURCE UDFs. Then it put this value inside energy and continuity equations and solves them to compute fields of temperature and other variables.

This is the basis.

Then, before a new time step is computed, I would like to control that calculated temperature at the liquid-vapor interface is at the saturation temperature, if negative I want Fluent to restart mass and energy sources calculation and go on until saturation temperature at the interface is matched.

So, it's like an iterative procedure in which at each time step UDF has to be repeated until a precise value becomes under a determinate tolerance.
My problem is that I don't know how to write an UDF that does this work.

Can anybody help me???

Thank in advance

Mirco

liurengtong123 · June 25, 2010, 07:44

Hi, i have the same question like you ,i want to know if you know how to solve it.
Big thanks!!!!

qwerty753 · June 30, 2010, 06:39

I have the same problem about BC at imposed heat flux.
I want to control a parameter unitil the first time step and restart this time step if my tollerance criterium isn't satisfied.
How to write in UDF?
Thank

liurengtong123 · July 2, 2010, 04:33

is there someone can solve this problem ? I need your help!!!

qwerty753 · July 11, 2010, 06:16

Have anyone an idea?

pranab_jha · July 26, 2011, 17:15

Hi guys, this might be too late. But I think this problem can be solved using a UDM (user defined memory) location. You can store the value from one iteration in the UDM and then in the next time-step, you can compare the new value against the old value (stored in the UDM).

November 30, 2009, 11:13	How to make a UDF to repeat itself ???	#1
magnounibo New Member Mirco Magnini Join Date: Apr 2009 Location: Bologna, Italy Posts: 14 Rep Power: 17	Hi everybody, I would like UDF to repeat itself adjusting a variable until it reaches a specific (under a tolerance) value. I'm using VOF multiphase model to simulate transient vapor bubble growing in a superheated liquid, mass and energy sources are given by UDF. At each time step, Fluent calculates mass and energy rates through my DEFINE_SOURCE UDFs. Then it put this value inside energy and continuity equations and solves them to compute fields of temperature and other variables. This is the basis. Then, before a new time step is computed, I would like to control that calculated temperature at the liquid-vapor interface is at the saturation temperature, if negative I want Fluent to restart mass and energy sources calculation and go on until saturation temperature at the interface is matched. So, it's like an iterative procedure in which at each time step UDF has to be repeated until a precise value becomes under a determinate tolerance. My problem is that I don't know how to write an UDF that does this work. Can anybody help me??? Thank in advance Mirco

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June 25, 2010, 07:44		#2
liurengtong123 New Member Rengtong Liu Join Date: May 2010 Posts: 15 Rep Power: 16	Hi, i have the same question like you ,i want to know if you know how to solve it. Big thanks!!!!

June 30, 2010, 06:39		#3
qwerty753 New Member qwerty753 Join Date: May 2009 Posts: 16 Rep Power: 17	I have the same problem about BC at imposed heat flux. I want to control a parameter unitil the first time step and restart this time step if my tollerance criterium isn't satisfied. How to write in UDF? Thank

July 2, 2010, 04:33		#4
liurengtong123 New Member Rengtong Liu Join Date: May 2010 Posts: 15 Rep Power: 16	is there someone can solve this problem ? I need your help!!!

July 11, 2010, 06:16		#5
qwerty753 New Member qwerty753 Join Date: May 2009 Posts: 16 Rep Power: 17	Have anyone an idea?

July 26, 2011, 17:15		#6
pranab_jha Member Pranab N Jha Join Date: Nov 2009 Location: Houston, TX Posts: 86 Rep Power: 17	Hi guys, this might be too late. But I think this problem can be solved using a UDM (user defined memory) location. You can store the value from one iteration in the UDM and then in the next time-step, you can compare the new value against the old value (stored in the UDM).