Incorrect Cp Value when I used Piecewise-Polynomial Profile
 

I'm trying to use the Piecewise-Polynomal Profile to define Cp of Air, there are 8 temperatue ranges I need to specify. However, from the fourth temperature range, the curve in the dialog box deviates from the curve I plotted in MATLAB, and negative values appear. I have double checked the input values and found no errors. Any ideas?

Found the reason... The input value in FLUENT dialog box can only have less than 7 valid numbers, which leads to a huge rounding error.