http://www.k-wave.org/forum/topic/back-propagation-of-nonlinear-waves Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 23:09:19 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/back-propagation-of-nonlinear-waves#post-8608 Fri, 09 Sep 2022 09:48:33 +0000 bencox 8608@http://www.k-wave.org/forum/ <p>Hi ahmedsallam,</p> <p>The harmonic generation is the frequency-domain manifestation of the wave steepening. Time-reversing the waves, ie. using time series recorded over many points covering a surface as sources and inputting them in time-reversed order, will undo the steepening and so will undo the harmonic generation. </p> <p>There are some time-reversal examples in k-Wave for photoacoustic sources, eg. <a href="http://www.k-wave.org/documentation/example_pr_2D_tr_circular_sensor.php">http://www.k-wave.org/documentation/example_pr_2D_tr_circular_sensor.php</a> which could be made nonlinear by setting a value for <code>medium.BonA</code> and making the initial pressure amplitude high enough.</p> <p>Best wishes<br /> Ben </p> http://www.k-wave.org/forum/topic/back-propagation-of-nonlinear-waves#post-8597 Tue, 23 Aug 2022 17:22:09 +0000 ahmedsallam 8597@http://www.k-wave.org/forum/ <p>Thanks for the reply Dr. Cox,</p> <p>How would you go about reversing the effect of harmonic generation in terms of the K-wave environment and functions? Are there any provided examples that could be useful in this direction? (I couldn't find any myself)</p> <p>Appreciate it! </p> http://www.k-wave.org/forum/topic/back-propagation-of-nonlinear-waves#post-8595 Tue, 23 Aug 2022 16:27:17 +0000 bencox 8595@http://www.k-wave.org/forum/ <p>Hi ahmedsaliam, </p> <p>Great question. Theoretically you can backpropagate nonlinearly steepened waves, so long as they haven't reached the point at which they have formed a shock, as then information loss occurs. In practice, the absorption needs to be considered. For purposes such as these, you can reverse the absorption to that it acts to amplify the signal, by using <code>medium.alpha_sign = [-1 1]</code>, which puts a negative sign in front of the absorption term but leaves the dispersion alone.</p> <p>Best wishes<br /> Ben </p> http://www.k-wave.org/forum/topic/back-propagation-of-nonlinear-waves#post-8591 Wed, 03 Aug 2022 01:31:46 +0000 ahmedsallam 8591@http://www.k-wave.org/forum/ <p>Hello,</p> <p>First of all thank you so much for this useful toolbox. </p> <p>I was wondering if k-wave has the capability to back propagate nonlinear waves for source identification and similar applications? Is it possible to reverse the harmonic generation phenomenon and end up with a single harmonic time signal at the source surface?</p> <p>Thanks, </p>