http://www.k-wave.org/forum/topic/temperature-changes-with-grid-size Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 00:26:43 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/temperature-changes-with-grid-size#post-8115 Thu, 08 Apr 2021 19:15:53 +0000 Alexander 8115@http://www.k-wave.org/forum/ <p>Hi Dr. Treeby,</p> <p>I can confirm I used a fixed number of elements with:</p> <p><code></code>`<br /> ring = makeCartCircle(radius, 256);<br /> [source.p_mask, order_index,reorder_index]= cart2grid(kgrid, ring);<br /> <code></code>`</p> <p><a href="https://waynestateprod-my.sharepoint.com/:f:/g/personal/eu7209_wayne_edu/Et6Pvc10AstKmGzRdtM-KJsBcNYd4TW9l1P59UEWsQqLPA?e=4Sufmu" rel="nofollow">https://waynestateprod-my.sharepoint.com/:f:/g/personal/eu7209_wayne_edu/Et6Pvc10AstKmGzRdtM-KJsBcNYd4TW9l1P59UEWsQqLPA?e=4Sufmu</a></p> <p>^ In slides 10+11 you can see how the pressure waveform changes with Nx &amp; Ny. Slide 11 shows the dirichlet BC and while the waveforms aren't exactly the same with changing Nx/y, they are closer than with the default BC. </p> http://www.k-wave.org/forum/topic/temperature-changes-with-grid-size#post-8105 Thu, 25 Mar 2021 17:49:23 +0000 Bradley Treeby 8105@http://www.k-wave.org/forum/ <p>Hi Alexander,</p> <p>Are you using an equal number of point sources in each case? A difference will arise in this case because of the scaling of the source. There are a few forum posts discussing this. I found <a href="http://www.k-wave.org/forum/topic/using-sourcep-to-specify-pressure-distribution#post-4181">this one</a> but I recall there being others.</p> <p>Dirichlet will give you a different problem as all of the sources will also act as scatterers.</p> <p>Hope that helps,</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/temperature-changes-with-grid-size#post-8090 Fri, 19 Mar 2021 16:29:52 +0000 Alexander 8090@http://www.k-wave.org/forum/ <p>I've updated the slides again. I recalled from another post I made (<a href="http://www.k-wave.org/forum/topic/input-pressure-signal-vs-sensor-pressure-signal" rel="nofollow">http://www.k-wave.org/forum/topic/input-pressure-signal-vs-sensor-pressure-signal</a>) that we have to use dirichlet BC to get a specific pressure distribution. This doesn't seem to 100% solve the issue of pressure (and therefore temperature) varying with grid size, but it is an improvement. </p> <p>Is there a recommended way of doing this that avoids these varying pressure/temp issues? or is dirichlet the answer? </p> http://www.k-wave.org/forum/topic/temperature-changes-with-grid-size#post-8089 Fri, 19 Mar 2021 15:46:48 +0000 Alexander 8089@http://www.k-wave.org/forum/ <p>Another update, I've plotted the time trace of the pressure at the focus (slide 10). It would appear as Nx/y increases and dx/y decreases (in order for the physical space to stay the same size) the pressure at the center decreases. Is this expected? </p> <p>So if we increase the fineness of the grid would the element size have to increase as well? If so I don't 100% understand why this is the case. </p> http://www.k-wave.org/forum/topic/temperature-changes-with-grid-size#post-8088 Thu, 18 Mar 2021 19:36:40 +0000 Alexander 8088@http://www.k-wave.org/forum/ <p>Turns out the t_end for Nx/y=256 and Nx/y=512 aren't exactly the same in kgrid.t_array. So I updated the slides in the link to show the raw pressure field @ t=50usec (slide 9). </p> http://www.k-wave.org/forum/topic/temperature-changes-with-grid-size#post-8087 Thu, 18 Mar 2021 19:23:03 +0000 Alexander 8087@http://www.k-wave.org/forum/ <p>I've updated the slides in the above link. It looks like the raw pressure field isn't the same for the last recorded field (@ t_end). Seeing as t_end is the same for all simulations and the waveform is the same I would expect the pressure field to be the same as well. </p> <p>I thought this was an issue with createCWSignals(...), so I switched to a sine wave for slides 7&amp;8 with no improvement. </p> http://www.k-wave.org/forum/topic/temperature-changes-with-grid-size#post-8086 Thu, 18 Mar 2021 18:15:01 +0000 Alexander 8086@http://www.k-wave.org/forum/ <p>I came across an issue running thermal sims with a ring transducer. It would appear that if I change only Nx/Ny that my temperature (T1 and T2) changes. It may be an issue with how extractAmpPhase(...) is working/ how Q is being calculated. But I just took the default example and changed it to use a ring array. </p> <p>Note: When I change Nx/Ny I also change dx/dy so the grid is the same size in [mm]. Also a pdf of the results and the code can be see at the link below. </p> <p><a href="https://waynestateprod-my.sharepoint.com/:f:/g/personal/eu7209_wayne_edu/Et6Pvc10AstKmGzRdtM-KJsBcNYd4TW9l1P59UEWsQqLPA?e=nRqyJZ" rel="nofollow">https://waynestateprod-my.sharepoint.com/:f:/g/personal/eu7209_wayne_edu/Et6Pvc10AstKmGzRdtM-KJsBcNYd4TW9l1P59UEWsQqLPA?e=nRqyJZ</a> </p>