porous media user defined function

Hi experts,

I was going through the release notes for 2022.1 version of acuSolve. I could see Porous Medium Effectiveness Type with user_function but could not find a type = user_function in the porosity_model tab in the acuSolve manual. The link is;

https://2022.help.altair.com/2022.1/hwcfdsolvers/acusolve/topics/acusolve/porosity_model_acusolve_com_ref.htm

Can someone tell me how to use Porous medium effectiveness type user_function and provide a sample code???

Thanks!!!