k-Wave

1. PtL
   

   Member
   Joined: Apr '18
   Posts: 1

   clear variables;
   Nt=10240;
   dt=1e-4;
   Nx = 2048;
   dx = 1e-1; %when I change dx from 1e-1 to 1e-2, an unexpected sound appears
   kgrid = kWaveGrid(Nx, dx);
   medium.sound_speed =340; %[m/s]
   medium.density = 1.29; % [kg/m^3]
   source.p0=zeros(Nx,1);
   source.p_mask=zeros(Nx,1);
   source.p_mask(2,1)=1; % Define the real Sound Source's position
   m=zeros(Nx,1);
   m(100,1)=1;
   sensor.mask=m;
   kgrid.setTime(Nt, dt);
   source.p=100 * sin(2 * pi * 150 * kgrid.t_array);
   sensor_data = kspaceFirstOrder1D(kgrid, medium, source, sensor);

   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   My codes are above, when I change dx from 1e-1 to 1e-2, at the end of x-axis there will be an unexpected sound source which send a sound wave to the real sound source. Is this a bug or I have something wrong??

   Posted 2 years ago #

2. bencox
   

   Developer
   Joined: Mar '10
   Posts: 292

   Hi PtL,

   There are two main problems. First you have placed your source in the absorbing PML. To avoid this use source.p_mask(21,1)=1 as the PML is 20 grid points wide, or use the optional input pair 'PMLInside', false.

   Second, your time step is too long. Ideally the CFL number, the ratio of dt * sound speed / dx should be about 0.3. Setting the timesteps using kgrid.makeTime(medium.sound_speed) will sort that out.

   Also, you don't need the source.p0 line.

   Best wishes
   Ben

   Posted 2 years ago #

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