k-Wave

1. Karthik Nagabhushana
   

   Member
   Joined: Apr '20
   Posts: 6

   Hi,

   I am currently trying to model imaging with a spherically focused transducer. Compared to the conventional 3D representation (kspaceFirstOrder3DC), I have found the axisymmetric representation (kspaceFirstOrderAS) to be extremely useful in terms of compute time and memory requirements for large grid sizes (>1024^3).

   However, one constraint in the axisymmetric representation is that the full range of acoustic power law is not supported (or medium.alpha_power is set to 2). Is this a fundamental limitation of the axisymmetric approach? If not, do you have plans in the future to support the acoustic power law?

   Thanks in advance

   Regards
   Karthik

   Posted 3 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,640

   Hi Karthik,

   >> Is this a fundamental limitation of the axisymmetric approach?

   In short, yes. It's because the generalisation of the Laplacian in cylindrical coordinates to the equivalent fractional version is not straightforward to solve.

   If your frequency content is centred around a particular frequency, you can get approximately the right absorption behaviour by adjusting the values of alpha_coeff so that you get the same absorption at that frequency, e.g.,

   alpha_coeff_adjusted * f^2 = alpha_coeff * f^y

   No current plans to extend the code to support power law absorption I'm afraid.

   Hope that helps,

   Brad

   Posted 3 years ago #

3. Karthik Nagabhushana
   

   Member
   Joined: Apr '20
   Posts: 6

   Hi Professor Treeby,

   Thanks for your comment.

   Thanks for suggesting an approximate workaround as well; I will try to use the axisymmetric simulations in a piecewise f^2 manner.

   Karthik

   Posted 3 years ago #

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