Irregular material interfaces

[Hansen]

Dear FD Simulation team,

I am an end user of the FDSim3D code, as well as the FDSim2D program. Thanks for your time and effort devoted to developing and publishing the source code, which is efficient and architecture independent.
As to the 3D code, I am wondering whether I can ask a few questions:

1. In the example file CAN4, I noticed that the material interfaces are defined in the Mod_func.f90 file using functions. This is only feasible for regular or semi-regular interfaces. But for more general 3D cases, material interfaces are irregular, except the bedrock-halfspace interface. For the irregular interfaces, it is ineffective, if not impossible to define each interface using functions. I found that it may be feasible to define irregular interfaces using discrete geometrical data in the INTERFACE.DAT file, as is the case for the 2D code. If I can define the material interfaces in the INTERFACE.DAT file, then questions arise as to how to prepare the Mod_func.f90 file. Like the 2D code, can we using the parameter LAYER?

FUNCTION FUNC_RHO(X,Z,LAYER)
INTEGER , INTENT(IN) :: LAYER
REAL(WP), INTENT(IN) :: X,Z
REAL(WP) :: FUNC_RHO

IF ( LAYER == 1 ) THEN ! first layer (sediments)
FUNC_RHO = 2000._WP
ELSE IF ( LAYER == 2 ) THEN
FUNC_RHO = 2500._WP
ELSE ! bedrock
FUNC_RHO = 2500._WP
END IF

END FUNCTION FUNC_RHO

I am wondering whether you have an example for the irregular interface case?

2. Pertaining to the Perfectly Matched Layer (PML), end users need to set up a few parameters, like TPML (or TPML_X, TPML_Y, TPML_Z), R, TAU, POW, SF and WC. These parameters seem to affect the stability of a simulation significantly. After checking on the publications on the concept of PML and the book MKG2014, I still have no idea what R, TAU, POW, SF and WC are. Since, as you mentioned, the code cannot be treated as a black box, and 3D simulations are way more time-consuming than 2D cases, it is thus unfeasible to explore the impacts of all these parameters based on a trial and error approach. I am wondering whether you could provide me some references to these parameters so as to have a better understanding?

Really hope to hear from you.

Thank you very much.

Best regards

Hansen