# UDF vs Custom field function

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 October 9, 2007, 05:06 UDF vs Custom field function #1 andrew Guest   Posts: n/a Hi colleague, I am currently writing up an equation that is to be input into fluent (for postprocessing)..i was wondering would i be able to fit this equation into the custom field function or should i write it in a udf and export it into fluent...using the custom field function would be a easier approach but i do not know the extend and how would the custom field function cope with the input of this equation...the equation that i would like to input in is:- Sp=miu/T*(dUi/dxj+dUj/dxi)dUi/dxj St=k(temperature_gradient)/T^2 thank you in advance...cheers regards andrew

 October 9, 2007, 09:07 Re: UDF vs Custom field function #2 Woo Meng Wai Guest   Posts: n/a Hi Andrew, I think in the custsom field function, you can the derivative of the velocities. However, there is no option for miu and temperature gradient. Not sure if you can implement this in the custom field function. Woo

 October 9, 2007, 10:51 Re: UDF vs Custom field function #3 andrew Guest   Posts: n/a hi Woo, Yes u have the derivative function for the velocity...how about the temperature derivatives (temperature gradient)? any ideas for it? i am not sure when u use the solve/set/expert function will actually work...ps advice..thank you in advance regards andrew

 October 9, 2007, 20:06 Re: UDF vs Custom field function #4 Woo Meng Wai Guest   Posts: n/a I think u have to advise me on this. I can't find the 'solve/set/advice function' Do you find this under the 'solve' tab? Woo [my fluent version 6.3.26

 October 10, 2007, 00:48 Re: UDF vs Custom field function #5 andrew Guest   Posts: n/a Hi woo, i am also using the same version of fluent... Just type it in fluent after the > u should be able to get them..firstly key in solve and if u enter u will see the set variable and then enter...u will see the expert...after that there is a few question on yes or no that u need to get it before u could get the derivatives function for dT/dx dT/dy and dT/dz...hope that u will be able to get them...cheers

 June 24, 2011, 10:53 derivative of the custom field function #6 New Member   osis Join Date: Jun 2011 Posts: 8 Rep Power: 14 is it possible to get the spatial derivative of the custom field function in fluent ?? or should I use UDF ?? thanks