http://www.k-wave.org/forum/topic/power-law-absorption-in-axisymmetric-simulations Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 23:32:15 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/power-law-absorption-in-axisymmetric-simulations#post-7964 Sun, 29 Nov 2020 03:23:47 +0000 Karthik Nagabhushana 7964@http://www.k-wave.org/forum/ <p>Hi Professor Treeby, </p> <p>Thanks for your comment. </p> <p>Thanks for suggesting an approximate workaround as well; I will try to use the axisymmetric simulations in a piecewise f^2 manner. </p> <p>Karthik </p> http://www.k-wave.org/forum/topic/power-law-absorption-in-axisymmetric-simulations#post-7938 Thu, 26 Nov 2020 11:23:28 +0000 Bradley Treeby 7938@http://www.k-wave.org/forum/ <p>Hi Karthik,</p> <p>&gt;&gt; Is this a fundamental limitation of the axisymmetric approach?</p> <p>In short, yes. It's because the generalisation of the Laplacian in cylindrical coordinates to the equivalent fractional version is not straightforward to solve.</p> <p>If your frequency content is centred around a particular frequency, you can get approximately the right absorption behaviour by adjusting the values of <code>alpha_coeff</code> so that you get the same absorption at that frequency, e.g., </p> <p><code>alpha_coeff_adjusted * f^2 = alpha_coeff * f^y</code></p> <p>No current plans to extend the code to support power law absorption I'm afraid.</p> <p>Hope that helps,</p> <p>Brad </p> http://www.k-wave.org/forum/topic/power-law-absorption-in-axisymmetric-simulations#post-7912 Tue, 03 Nov 2020 02:31:11 +0000 Karthik Nagabhushana 7912@http://www.k-wave.org/forum/ <p>Hi, </p> <p>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 (&gt;1024^3). </p> <p>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? </p> <p>Thanks in advance </p> <p>Regards<br /> Karthik </p>