k-Wave

1. Ed Qu
   

   Member
   Joined: Feb '16
   Posts: 2

   Hi

   Our group wanted to integrate the algorithm for the acoustic dissipation and dispersion into our code for USCT simulation, but we encountered a problem during coding.

   The manual shows that the power index y can be defined between 0 and 3, except for 1; the grid (defined in 2.17e) includes the origin where k = 0. On the other hand, the first term on the right hand side of the equation (2.24) multiply the Fourier transform with k^(y-2). If we assume y < 2, this term will diverge at the origin.

   So far, we just simply define the value of Ld in (2.24) equal to 0 at the origin, but the stability of our program using this resolution is not good enough. The program will diverge in hundreds of steps if we define a large alpha and a y<2. Does anyone know how to resolve this problem?

   Thanks a lot.
   Sincerely,
   Ed

   Posted 8 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi Ed,

   Just to check - are using k-Wave for your simulations, or have you coded your own version?

   The absorption terms in k-Wave are defined in the function /private/kspaceFirstOrder_createAbsorptionVariables.m. The values for the absorption and dispersion terms are set to zero for k = 0.

   Keep in mind that when you add absorption, simulations using kspaceFirstOrderND are no longer unconditionally stable, even for a homogeneous medium. You will need to choose the time step to satisfy the appropriate stability criteria. In general, the time step will need to be reasonably small if the absorption values are very high. You can use the function checkStability to check the value of time step required.

   Hope that helps,

   Brad.

   Posted 8 years ago #

3. Ed Qu
   

   Member
   Joined: Feb '16
   Posts: 2

   Hi Dr. Treeby

   We found the file according to your reply. We have fixed the problem in our code. Thanks for your help!

   Sincerely,
   Ed

   Posted 8 years ago #

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