Re: Assistance Needed with Adding Multiple Materials in GPR Simulation

[Antonis Giannopoulos]

It is easy to use more materials. As you can see in the example there is a #material: command. You just have to add more of these that describe the electrical properties of your materials. gprMax knows the properties of "free_space" which is vacuum and "pec" which is perfect electric conductor and you can use these directly to include voids and metallic objects respectively. 

Once you have your materials you use their IDs (names you have given them) in the object building commands like #box: or #cylinder: etc to build your model. The process of model building is like painting a canvas if your object building command covers an area build already with some properties the properties of the newer object override whatever is already there. In the beginning your model is empty space. So, the order of specifying object building commands is important.

It is very important to check your geometry and there are commands to help you do this and Paraview is easy to use to display the model.

If you get the spatial step the right size and the position of the sources and receivers then you will have a good model.

Here is a two-layer model of the simple example that has 5cm of sand on the top before it transitions to the half-space properties.

#title: A-scan from a metal cylinder buried in a dielectric half-space with 5cm dry sand on top
#domain: 0.240 0.210 0.002
#dx_dy_dz: 0.002 0.002 0.002
#time_window: 3e-9

#material: 6 0 1 0 half_space
#material: 4 0.001 1 0 dry_sand

#waveform: ricker 1 1.5e9 my_ricker
#hertzian_dipole: z 0.100 0.170 0 my_ricker
#rx: 0.140 0.170 0

#box: 0 0 0 0.240 0.170 0.002 half_space
#box: 0 0.120 0.240 0.170 0.002 dry_sand
#cylinder: 0.120 0.080 0 0.120 0.080 0.002 0.010 pec

#geometry_view: 0 0 0 0.240 0.210 0.002 0.002 0.002 0.002 cylinder_half_space n

Best of luck

Antonis 

On Friday 30 August 2024 at 16:38:41 UTC+1 mymi...@gmail.com wrote:

Hello, I am a bachelor's degree student who is starting to study GPR. I am a new user who does not understand much about the program. I need help. In the example of cylinder_Ascan_2D.in, there is only 1 underground material. But I want to add 2 or 3 materials that may be different materials. Is it possible? If it is possible, do you have an example for me to study? Thank you for all your advice or help.

[Antonis Giannopoulos]

Oops! There is a typo in the model ...

#title: A-scan from a metal cylinder buried in a dielectric half-space with 5cm dry sand on top
#domain: 0.240 0.210 0.002
#dx_dy_dz: 0.002 0.002 0.002
#time_window: 3e-9

#material: 6 0 1 0 half_space
#material: 4 0.001 1 0 dry_sand

#waveform: ricker 1 1.5e9 my_ricker
#hertzian_dipole: z 0.100 0.170 0 my_ricker
#rx: 0.140 0.170 0

#box: 0 0 0 0.240 0.170 0.002 half_space

#box: 0 0.120 0 0.240 0.170 0.002 dry_sand 

#cylinder: 0.120 0.080 0 0.120 0.080 0.002 0.010 pec

#geometry_view: 0 0 0 0.240 0.210 0.002 0.002 0.002 0.002 cylinder_half_space n

[SS MM]

Thx vey much sir