Learning Forum

[harry93]

Hello CFD clan,

I am working on patient specific geometry. I have the waveform (attached) , from which I want to create a UDF and use it as my inlet BC. In the waveform, I want to use mass inflow and time as parameters. I have tried using transient profile by creating .txt file but I want to explore more on UDF. Can anyone let me know, how can I use this waveform and create a UDF from this.

Thank you

[Rob]

DEFINE_PROFILE and there's an example in the UDF manual. You may find you need 2-3 polynomial equations to get a good fit on the above data, so IF will be needed. I'd also look up the C function "floor".

[harry93]

Hello rob,
How do I extract the polynomial equation for this sinusoidal waveform. Can you help me with some examples ?
Thank you

[aitor.amatriain]

You can take n points from the plot, and then obtain a polynomial of order n-1 after solving a linear system, but this doubt is not related to the use of ANSYS Fluent.

[Amine Ben Hadj Ali]

You can make a regression using Python or even using Excel and from there you might the polynomials. if you have the data as table data you might just it directly as Transient Table :)

[harry93]

Hello DrAmine,
In case of using UDF and transient table, which one gives the accurate results ? Does using transient table decrease the accuracy of my results ?

[Amine Ben Hadj Ali]

Both will depend on the number of data points and the time steps you are using. Transient Table is accurate enough if it does contain enough frames.

[harry93]

ok got it
Thank you so much DrAnime.

[Amine Ben Hadj Ali]

Welcome! But DrAnime does not sound healthy ! :)

[Rob]

You have been looking quite drawn lately.....

[harry93]

Haha.. Noted !