CFD Online Logo CFD Online URL
Home > Forums > FLUENT

more than 3 piecewise polynomial

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   February 27, 2009, 03:35
Default more than 3 piecewise polynomial
Posts: n/a
I want to define a property which has more than 3 ranges of temperature. In fluent, for density if we choose piecewise polynomial then we can give maximum 3 ranges.

I want to use 5 ranges. then how could i input 2 more ranges. Can anyone help me with this?
  Reply With Quote

Old   February 27, 2009, 05:56
Default Re: more than 3 piecewise polynomial
sathees kannan
Posts: n/a
udf can do
  Reply With Quote

Old   March 2, 2009, 02:33
Default Re: more than 3 piecewise polynomial
Posts: n/a
i can use UDF for other properties. but not for Specific heat(Cp). For Cp i have 5 piece wise polynomial. So, kindly let me know how to use 5 piece wise polynomial or UDF to define Cp property.

Thank you.
  Reply With Quote

Old   March 2, 2009, 05:32
Default Re: more than 3 piecewise polynomial
sathees kannan
Posts: n/a
sorry, I have never used UDF for Cp. but, I tried something by creating User-Defined Database. There we can give UDF for Cp, but I don't have any idea about which UDF we can use. Follow the screen-shot, it may give some clue. Good Luck
  Reply With Quote

Old   March 3, 2009, 09:54
Default Re: more than 3 piecewise polynomial
Posts: n/a
thanks, Do u think in similar way i can write a UDF for electrical conductivity, which is going to be part of source term in UDS for my vector potential equation.

How can i add entalpy udf. as there is no listing of enthalpy in properties list.

  Reply With Quote

Old   March 12, 2009, 10:04
Default Re: In v12, use DEFINE_SPECIFIC_HEAT
Posts: n/a
See the udf.h for the prototype. Also, the enthalpy is required in the UDF. Compute the integral of Cp from T_ref to T and assign that to *h. Heat of formation is added outside the call.
  Reply With Quote

Old   January 13, 2014, 17:12
Default piecewise poynomial
Join Date: Jan 2014
Location: Turkey
Posts: 36
Rep Power: 5
thermal energy is on a distinguished road
hi friends,

ı simulate melting problem inside annulor geometry. ı use paraffin (melting range 56-58oC) as a phase change material. first, ı have boussinesq approximation. and also my material properties depends on temperature like Cp (spesific heat) and k (thermal conductivity). my problem here is that,

if ı use piecewisepolynomial for k and Cp (solid value and liquid value), ı have a convergence problem (figure attached). but if ı use constant value for Cp and k, ı have no problem and it is still converging (iteration going on)

what's the reason of this. what's wrong. thanks for help
Attached Images
File Type: jpg Ads?z.jpg (53.5 KB, 26 views)
thermal energy is offline   Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
About polynomial input of cp in Star CD 3.26 S.B.J. Siemens 1 July 11, 2012 16:16
Piecewise Rotation Lance LeBlanc FLUENT 0 November 18, 2008 04:12
UDF Format 8th Order Polynomial Jason FLUENT 2 June 24, 2007 13:21
Piecewise function to model time-dependant BC Ramses Galaz CFX 2 April 6, 2006 10:00
3-D PLIC (Piecewise-Linear Interface Construction) Chih-Wei Chiu Main CFD Forum 0 May 19, 2002 20:41

All times are GMT -4. The time now is 22:21.