http://www.k-wave.org/forum/topic/propagation-in-absorbing-media Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 01:17:20 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/propagation-in-absorbing-media#post-5993 Mon, 19 Jun 2017 20:38:47 +0000 Bradley Treeby 5993@http://www.k-wave.org/forum/ <p>Hi Mario,</p> <p>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 <code>Modelling Power Law Absorption Example</code> to use:</p> <pre><code>medium.alpha_coeff = 0.0005; medium.alpha_power = 2.9;</code></pre> <p>Everything looks as expected. You could try reducing the time step further to see if you can make the simulation stable.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/propagation-in-absorbing-media#post-5976 Tue, 06 Jun 2017 12:32:09 +0000 marioj 5976@http://www.k-wave.org/forum/ <p>Hello,</p> <p>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.</p> <p>The power law used is alpha=1,66e-3*f^2.99 [dB/cm/Mhz].</p> <p>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.<br /> 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).</p> <p>Thanks.<br /> Mário </p>