Hi Muhammad,

you asked your question some time ago, but just in case you still need some help:

An example for a custom drag law is provided in the Fluent UDF manual (available here: http://148.204.81.206/Ansys/150/ANSYS%20Fluent%20UDF%20Manual.pdf on page 140). Another example from my own work is enclosed. I used this for a custom drag law in a 3D gas-liquid Euler-Euler simulation in Fluent14.0 and it worked for me. Once you've compiled the UDF in Fluent (I never use interpreted UDFs), it becomes selectable in the Phase Interaction dialog box. A detailed description is also provided in the above mentioned UDF manual on page 376ff. Let me know if you need more assistance.

Best regards,

Stephan

Hi,

If you are trying to define the drag coefficient for the transport in DPM, I think you should write a UDF.

Could you define the context of your problem? The Fluent version?

Best regards,

Alejandro

Hi Alejandro Claro Barrento,

I am using Eulerian-Eulerian Model. Yes, why not.. I can define the context of my problem.. But I did understand your question, " Fluent Version" ?  

Please, see the attachment.. I have to introduce this kind of formulation in a Eulerian framework while using ANSYS Fluent. 

Dear Muhammed, here the complete manual

orange.engr.ucdavis.edu/Documentation12.0/120/FLUENT/fludf.pdf

Franco

Dear Franco Concli,

Thank you very much for sending me this UDF Manual.. appreciated.. 

Dear Ali,

       you can read the udf mamual,and of your question,you can use DEFINE_EXCHANGE_PROPERTY macro.About c language,first you can read in the mamual,it has c basic.

Best regards

Fangfang

Dear Yacine BENGUERBA and Fangfang Sun... Thank you very much for pointing out the solution . . . . 

For my experience, I suggest reading the UDF manual and going over the examples. It has nice practical examples which are quite easy to understand.

Use tutorials and define UDFs only in presented cases from documentation.  I do not   use UDFs because in some cases UDFs are difficult to read/compile in Ansys. For some tutorials like Heave and Pitch Simulation of Ship hull moving through head sea waves the UDF ( in C++ from the tutorial) was almost impossible to use.

Dear Dr Ionut Cristian Scurtu,

Can you please send me this document, " Heave and Pitch Simulation of Ship hull moving through head sea waves"..

Thanks

Here is the document "Heave and Pitch Simulation of Ship hull moving through head sea waves"  and a short tutorial about creating an UDF code in fluent. Hope it will help. 

Thank you all to share with me informative and valuable documents..

You can have a look at Ansys Help Documents. In that document there is a introduction about  the base of C language which will be used in UDF

You can learn it by fluent help, which have a very detail introduction. In the first, you should find the right macro. And then you just need to follow its sample.

Hi Muhammad,

you asked your question some time ago, but just in case you still need some help:

An example for a custom drag law is provided in the Fluent UDF manual (available here: http://148.204.81.206/Ansys/150/ANSYS%20Fluent%20UDF%20Manual.pdf on page 140). Another example from my own work is enclosed. I used this for a custom drag law in a 3D gas-liquid Euler-Euler simulation in Fluent14.0 and it worked for me. Once you've compiled the UDF in Fluent (I never use interpreted UDFs), it becomes selectable in the Phase Interaction dialog box. A detailed description is also provided in the above mentioned UDF manual on page 376ff. Let me know if you need more assistance.

Best regards,

Stephan

Great !! thank you to share this drag Coeff. with me.. Is it (Schiller and Naumann, 1933) drag coefficient ??

Hi Muhammad,

Yes, I think in this case it's the correlation from Schiller&Naumann, but I have modified the Reynolds number, Re, in comparison to the standard drag law used in Fluent. Inside the UDF, Re is calculated with the molecular (laminar) and the turbulent viscosity whereas Fluent only uses the laminar viscosity.

Let me know if you need further help.

Best regards,

Stephan

You can write your UDF using one of the examples of the Ansys UDF Manual. The codes are written in C+ language. It is easier to implement the codes using Linux. If you'd use Windows or Mac, you have to install an emulator.

Vivien, you're absolutely right: the UDF compilation in Linux is very easy. Most Linux distributions have also the advantage to need less ressources to run the system so that the Fluent processes can run faster and more stable. However, it was straightforward for me to compile UDFs in Fluent on a Windows machine when Microsoft Visual Studio was installed on the PC (tested with ANSYS17.0 and MS Visual Studio 2005). There might be other burdens to switch to Linux for some people. Furthermore, the ANSYS Fluent support recommended to use Windows for the newest Fluent version to me - because of issues with graphics in some Linux distributions, but I never tested it by muself. 

Best,

Stephan

Dear Vivien Rossbach ..

Can I say the central idea of your suggestion is to use Linux without any emulator ( visual studio ) ?? because I also want to switch on Linux for easy compilation and run my simulation as fast as possible, but I am little confused as Stephan C. Kaiser mentioned.. Please guide..

Regards

Hi Muhammad,

Even thought you asked specifically Vivien, I might give the following comment: I've been using Fluent with Scientific Linux (which is based on Red Heat Linux, RHEL) for my PhD thesis some time ago and it worked perfectly fine with ANSYS versions 14.0 and 15.0. The Linux system typically comes with integrated compilers, which is the reason why you don't need third-party software, like MS Visual Studio for Windows, and you can install additional packages via official repositories using the package manager if some libraries are missing. This makes the compilation of UDFs in Fluent relatively easy and straightforward. Unfortunately, I can't share any experience using Linux with the newest ANSYS release. If you want to test it I suggest to have a look on the ANSYS support page first, because ANSYS does not support all Linux distributions. A list of supported systems can be found here: http://www.ansys.com/-/media/Ansys/corporate/files/pdf/solutions/it-professionals/platform-support/platform-support-by-application-171.pdf?la=en

Good luck.

Best,

Stephan

Dear Dr Stephan C. Kaiser,

Thank you for sharing your experience and expert opinion. In my computer Laboratory, we have PC cluster with OS is Linux. May be this system successfully compiled my UDF and minimize the time consuming cost. I am sure, I would ask more suggestions to you. 

Thanks and Regards

Hi Mohammed. Please refer to:

https://www.learncax.com/knowledge-base/blog/by-category/cfd/writing-a-user-defined-function-udf-in-ansys-fluent. Regards

check fluent tutorial

hi, everyone. i have written code for 2 simple equations and want to take the temperature from every iteration of simulation. Can anyone please inform me how to proceed next by looking at code of equations. thanks in advance.

thanks