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How to define liquid viscosity using a temperature dependent polynomial Fluent

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Old   December 10, 2022, 14:28
Default How to define liquid viscosity using a temperature dependent polynomial Fluent
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Waru
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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
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File Type: png Fluent poly.png (59.6 KB, 17 views)
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Old   December 10, 2022, 16:38
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Quote:
Originally Posted by modorous View Post
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.
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Old   December 11, 2022, 13:26
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Thanks, Your suggestion helped.

Increasing the significance of the coefficients helped.

Thanks again.
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material properties, polynomial profiles, viscosity model

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