when calculating Pabs_total by using Pabs analysis, do i need to run a 3D simulation?? or can i also use a 2D simulation?
If you are referring to absorbed power calculations in this direct:
We have examples for both 2D and 3D calculations. Both cases use the same pabs analysis groups. For 2D case, monitors will return data only for area inside the simulation region and results will have only one z-value. This is similar to as having only one mesh cell along the z-axis Thus, you can use pabs analysis group in 2D simulations without modifying it.
I think it will be a good practice to go over the calculations and compare 2D with 3D to learn more and make sure that I did not miss anything.
I hope I could answer your questions.