# How to define liquid viscosity using a temperature dependent polynomial – Fluent

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

December 10, 2022, 14:28
How to define liquid viscosity using a temperature dependent polynomial – Fluent
#1
New Member

Waru
Join Date: Apr 2022
Posts: 7
Rep Power: 4
Hi,

I'm trying to define the viscosity of a liquid as a temperature dependent polynomial function in Fluent.

I plotted the experiment data in Excel to get the trend line and polynomial equation. Pls, see "Excel poly.jpg" to see the experimental data and polynomial function.

When I tried to enter the coefficients in Fluent to define viscosity, I got a completely wrong graph. Pls, see "Fluent poly.png" to see the Fluent graph I got for the polynomial function.

Can you pls tell me what I have done wrong?

Best regards,
M
Attached Images
 Excel poly.jpg (62.5 KB, 17 views) Fluent poly.png (59.6 KB, 17 views)

December 10, 2022, 16:38
#2
Senior Member

Kareem
Join Date: Nov 2022
Location: New York
Posts: 119
Rep Power: 3
Quote:
 Originally Posted by modorous Hi, I'm trying to define the viscosity of a liquid as a temperature dependent polynomial function in Fluent. I plotted the experiment data in Excel to get the trend line and polynomial equation. Pls, see "Excel poly.jpg" to see the experimental data and polynomial function. When I tried to enter the coefficients in Fluent to define viscosity, I got a completely wrong graph. Pls, see "Fluent poly.png" to see the Fluent graph I got for the polynomial function. Can you pls tell me what I have done wrong? Thanks in advance. Best regards, M
Try increasing the significant figures in your trendline. Rounding error between .123456 and 5.6e-5 can be significant in a high order polynomial.
__________________

 December 11, 2022, 13:26 #3 New Member   Waru Join Date: Apr 2022 Posts: 7 Rep Power: 4 Thanks, Your suggestion helped. Increasing the significance of the coefficients helped. Thanks again.