## Fluids

#### User Define Real Gas Model (UDRGM)

• Cfdman
Subscriber
Hi guys,nWe are going to simulate the stream of a gas over a switchgear (the physiks of the problem is not important for you)nWe have our own data (table) for this gas. The ponit is that, for this gas Cp (specific heat) is changing with Temperature and Pressure both. For this purpose I should use UDRGM of Fluent, I studied also the manuel of Fluent but I could not get the Idea of using for my case.nThe problem is that: I I am looking to define Cp while having different thermodynamics lookup tables giving me Cp as temp and pressure varies. Is there any template of code available for doing so or else any method through which I could calculate the coefficients for the real gas models from the data of the thermodynamic table. Actually I have my own Data (tables) and I want to read them. Can I use UDRGM of Fluent so that I can use my own Data?nSorry, that I explained too much, I just wanted to explain my problem clearly.nn
• DrAmine
Ansys Employee
Thinking loud about writing your own Real Gas Property Table.nFor UDRGM you need to create a bilinear interpolation to get correct Cp from a table you can read (C programming) and parse it for UDRGM UDF.nWhat is your fluid?.Not an easy step.n
• Cfdman
Subscriber
Thanks for your reply.nOur fluid is Sulfur hexafluoride (SF6).nYes we created a bilinear interpolation in C for Cp, right now my question is:nWhat kind of equations should we use for computing Entropy, Enthalpy? ideal Gas Equations or the other state equations like Redlich-Kwong Equation of State? n
• DrAmine
Ansys Employee
Material Properties should be consistent: that is what I can say and this will make the whole thing complex.nnI recommend using SF6 RefProp which is available with Fluent. You create a RGP table for that and use that table for Fluent runs.n