# Variable Density Function

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 June 6, 2011, 12:51 Variable Density Function #1 New Member   Ryan Z. Davis Join Date: Mar 2010 Location: Idaho Falls, Idaho, United States Posts: 11 Rep Power: 9 Sponsored Links Hi all, I'm having trouble using the variable density function in FLUENT. I'm doing a simple differentially heated natural convection cavity (2D) and I'm defining density as a function of temperature. When I perform the simulation with air as the working fluid the density does not calculate correctly. During post processing I plot the data for temperature and density and when I perform hand calculations for density (based on the temperature given) I get a different density than what FLUENT calculates. Does FLUENT use any other factors when calculating the density of a fluid? Am I doing something incorrectly? The density function I use is given below. rho = (0.000013491 x (T^2)) - (0.0046555 x T) + 1.12881 Thanks, Ryan

 August 25, 2011, 14:16 #2 Member     NormalVector Join Date: Oct 2010 Posts: 72 Rep Power: 8 You may have already figured this problem out as it has been a few months since your post but I'll have a go at it: Make sure that you're entering the polynomial into FLUENT correctly. The boxes are for the coefficients increasing from 0. So, the first box is for the coefficient of T^0, the second for T^1, etc.

 Tags density udf, natural convection

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