k-Wave

1. marioj
   

   Member
   Joined: Mar '17
   Posts: 8

   Hello,

   I am trying to model ultrasonic propagation in absorbing media (heterogenous material with scatters inside). The experimental attenuation obtained for physical samples have a power law absorption exponent slightly higher than 3, so I use as an approximation in the simulation the value of 2.99, due to limitations of k-wave.

   The power law used is alpha=1,66e-3*f^2.99 [dB/cm/Mhz].

   In k-wave using medium.alpha_coeff=1,66e-3 and medium.alpha_power=2.99 some instability problems appear (dark screen fields in all directions) using kspaceFirstOrder3D.
   In the my first simulation the time step used was 10^-9s and decreasing to 10^-10s do not solve the problem (in this last case CFL is approximately 0.03).

   Thanks.
   Mário

   Posted 7 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi Mario,

   I don't think it's an intrinsic problem, just that this value of absorption is still very high at high frequencies, which likely affects stability. For example, if you modify the Modelling Power Law Absorption Example to use:

   medium.alpha_coeff = 0.0005;
   medium.alpha_power = 2.9;

   Everything looks as expected. You could try reducing the time step further to see if you can make the simulation stable.

   Brad.

   Posted 7 years ago #

RSS feed for this topic

Reply

You must log in to post.