k-Wave

1. GreG
   

   Member
   Joined: Aug '14
   Posts: 3

   Hi,

   I tried to perform a 2 dimensions simulation (non homogeneous medium) and I got the following error message when i define the alpha_coeff, alpha_power and the medium density, (typically i was trying to simulate a part of a wall at audible frequencies) :

   Error using im2frame
   double-precision indexed CData values must be legal colormap indices: 1.0 <= value <=
   length(colormap)

   Error in kspaceFirstOrder2D (line 899)
   movie_frames(frame_index) = im2frame(p_plot, COLOR_MAP); %#ok<AGROW>

   Error in Grid_w_obstacles (line 157)
   sensor_data = kspaceFirstOrder2D(kgrid,medium,source,sensor,input_args{:});

   When i don't define alpha and (or) medium density the simulation works perfectly.

   Does anyone have an idea how to fix this issue ?

   Thanks a lot ,

   GreG.

   Posted 9 years ago #

2. bencox
   

   Developer
   Joined: Mar '10
   Posts: 292

   Hi GreG,

   When you watch the simulation does it look ok? I wonder if the simulation is blowing up and generating NaNs, perhaps because the absorption is too high. The simulations can become unstable for large values of absorption.

   Ben

   Posted 9 years ago #

3. GreG
   

   Member
   Joined: Aug '14
   Posts: 3

   Hi Ben,

   Thank you for your help.

   No, the simulation does not want to start. The process stops just before starting the time loop...
   It seems to be a display issue... I see briefly (less than 1 sec ) the wall displayed in greyscale, afterwards the error is generated.

   GreG.

   Posted 9 years ago #

4. bencox
   

   Developer
   Joined: Mar '10
   Posts: 292

   Hi GreG,

   What are your absorption values? Does it still fail if you make the absorption values very low?

   Ben

   Posted 9 years ago #

5. GreG
   

   Member
   Joined: Aug '14
   Posts: 3

   Hi Ben,

   I tried with very low absorption values (see here below) and it crashes also...

   medium.alpha_coeff = 1e-6; for air and for concrete
   medium.alpha_power = 1.1

   The problem seems to come from the concrete's density value.

   Typically i set the density value to 2000 (kg/m3) and the simulation failed, when i decreased the value by 10, the simulation worked.

   Do you have any explanation ?

   Thanks.

   Greg.

   Posted 9 years ago #

6. bencox
   

   Developer
   Joined: Mar '10
   Posts: 292

   Hi Greg,

   Can you post your code, or put in somewhere I can download it, so I can take a closer look?

   Thanks,
   Ben

   Posted 9 years ago #

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