masud407 Support for the k-Wave MATLAB toolbox en-US Mon, 25 May 2026 09:30:46 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/how-to-implement-the-arf-induced-shear-wave-propagation#post-8784 Wed, 31 May 2023 01:13:09 +0000 masud407 8784@http://www.k-wave.org/forum/ <p>Hello @bth12, did you manage to solve the problem? Please let me know. </p> http://www.k-wave.org/forum/topic/shear-wave-displacements-induced-by-acoustic-radiation-force#post-8783 Wed, 31 May 2023 01:10:21 +0000 masud407 8783@http://www.k-wave.org/forum/ <p>Did anyone manage to simulate it? Please let me know as I need some help on it. </p> http://www.k-wave.org/forum/topic/shear-wave-displacements-induced-by-acoustic-radiation-force#post-8145 Wed, 05 May 2021 11:50:10 +0000 uuu81704 8145@http://www.k-wave.org/forum/ <p>Hello, bhaskara.chintada<br /> I am also following this paper and want to simulate shear waves induced by ARF.<br /> But I don't know how to do "use stress as input" in pstdElastic2D() in paragraph--3.3 of this paper.</p> <p>specifically, I don't know how to define the source of pstdElastic2D() to get the displacement.<br /> Could you share your method or code, please~ </p> http://www.k-wave.org/forum/topic/shear-wave-displacements-induced-by-acoustic-radiation-force#post-7146 Fri, 13 Dec 2019 18:55:30 +0000 bhaskara.chintada 7146@http://www.k-wave.org/forum/ <p>Hello, </p> <p>I am trying to simulate shear waves induced by acoustic radiation force using k-Wave toolbox as described in the article [1]. I am able to reproduce shear wave displacements profiles similar to the plots in Figures 5 &amp; 6 of [1]. The displacement profiles obtained at different propagation distances (i.e. at different Ny indices) when stresses are given as input to the solver pstdElastic2D() as described in [1] are shown in the figure available at <a href="https://polybox.ethz.ch/index.php/s/ztlYYumUxqQBNgZ" rel="nofollow">https://polybox.ethz.ch/index.php/s/ztlYYumUxqQBNgZ</a>. However, I am curious to know the possible reasons behind obtaining negative displacements in k-Wave as shear wave displacements induced by acoustic radiation force are usually positive similar to the shear wave displacement profiles obtained from FEM simulation and analytical solution as shown in the Figure 3 of [1]. Please feel free to comment your intuitions and suggestions regarding this observation. Thank you. </p> <p>[1] <a href="https://asa.scitation.org/doi/pdf/10.1121/2.0000398?class=pdf" rel="nofollow">https://asa.scitation.org/doi/pdf/10.1121/2.0000398?class=pdf</a> </p> http://www.k-wave.org/forum/topic/how-to-implement-the-arf-induced-shear-wave-propagation#post-7085 Fri, 18 Oct 2019 19:19:57 +0000 Bradley Treeby 7085@http://www.k-wave.org/forum/ <p>Hi bth012,</p> <p>According the article:</p> <p>"to get a volume force as input, we can therefore use an input velocity equal to <code>Fi * dxi / (2 * rho0 * c0)</code>. Finally, this input should be divided by the spatial step dz to ensure proper scaling of the delta function in the z direction."</p> <p>Hope that helps,</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/how-to-implement-the-arf-induced-shear-wave-propagation#post-7034 Fri, 06 Sep 2019 19:55:34 +0000 bth012 7034@http://www.k-wave.org/forum/ <p>How to implement the ARF input as a source for the shear wave propagation.<br /> Anybody solving this matter? </p> http://www.k-wave.org/forum/topic/how-to-implement-the-arf-induced-shear-wave-propagation#post-6998 Thu, 15 Aug 2019 22:33:57 +0000 bth012 6998@http://www.k-wave.org/forum/ <p>Hello,</p> <p>I would like to simulate the ARF induced shear wave propagation and compute the displacement. Now I am following some simulation in the article "https://asa.scitation.org/doi/pdf/10.1121/2.0000398"<br /> I have a question. How do I put the ARF data into "pstdElastic2D.m", as an input? This part has not been resolved for a long time.<br /> Could you please give me some comments about that?</p> <p>Thanks, </p> http://www.k-wave.org/forum/topic/instability-in-shear-wave-absorption-simulation#post-6939 Fri, 28 Jun 2019 11:07:46 +0000 genny_p 6939@http://www.k-wave.org/forum/ <p>Hi Brad,<br /> Thanks for the suggestion. The simulation seems to actually only be stable with longer time steps (sparser grid spacing and higher CFL number) and when I decrease the time step then the simulation becomes unstable (you can see this by changing the factors in the sample code I provided). I take it then this is not a result of a numerical instability. What other types of instabilities could be possible?</p> <p>Thanks,<br /> Genny </p> http://www.k-wave.org/forum/topic/instability-in-shear-wave-absorption-simulation#post-6894 Sat, 22 Jun 2019 20:18:49 +0000 Bradley Treeby 6894@http://www.k-wave.org/forum/ <p>Hi Genny,</p> <p>For the shear code, we don't have an out of the box function to test for stability with an absorbing medium. For the fluid code, we have an approximate way of checking for the stable time step size (see the <code>checkStability</code> function). It might be possible to find a relationship for the elastic code, but I haven't looked at it. If it is a numerical instability, then keep making the CFL smaller, it should eventually work. Let me know if it doesn't.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/instability-in-shear-wave-absorption-simulation#post-6851 Wed, 15 May 2019 12:05:54 +0000 genny_p 6851@http://www.k-wave.org/forum/ <p>Hi Brad, Ben, and the k-Wave community,</p> <p>As I mentioned at Photonics West, I am applying k-Wave to model scattering of planar shear waves in heterogeneous tissue, and so far the toolbox has been very easy to use and is working quite well for elastic scattering problems. I recently started trying to model shear wave absorption using the medium.alpha_coeff_shear factor to account for viscoelasticity. The results look quite reasonable for certain cases, but when I increase the absorption factor enough, the result seems to become unstable. I am using a value on the order of 3e6 dB/(MHz^2 cm), since this is around what we measure for shear wave absorption in tissue-mimicking phantoms with wave frequency on the order of 600 Hz, i.e. 1.08 dB/cm. You can see the instability forming in the example code below, where the edges of the plane wave start to increase with an amplitude much larger than the initial wave amplitude. </p> <p>I saw in the Modelling Power Law Absorption Example that you discuss numerical errors (<a href="http://www.k-wave.org/documentation/example_na_modelling_absorption.php#heading3)" rel="nofollow">http://www.k-wave.org/documentation/example_na_modelling_absorption.php#heading3)</a>, but there it is mentioned that the errors can be minimized by reducing the time step. I found the instability I see seems to worsen with a decreased time step (which I implemented by reducing the CFL number). The instability is also worse when I reduce the grid spacing (which in turn also reduced the time step). </p> <p>See the comments in my code below for the factors that influence the instability that I investigated. All the parameters used in the example code are typical for our experiments, except maybe the inital velocity u_0, but there doesn't seem to be any dependence of the instability on this value. This leads me to the following questions:</p> <p>1. Is this instability related to the numerical errors discussed in the Modelling Power Law Absorption Example?<br /> 2. Is there some relationship that tells me for which conditions (up to which absorption) the code works for before becoming unstable?<br /> 3. If I have a result that appears stable (i.e. with a low enough medium.alpha_coeff_shear value), how can I check whether the results are reliable, since when I decrease the grid size to check convergence the simulation then blows up?</p> <p>I would be grateful if someone had any insight to any of these questions.</p> <p>Thanks,<br /> Genny</p> <p>% -------------------------------------------------------------------------------------<br /> % Modified from Shear Waves And Critical Angle Reflection Example<br /> % Simplified code that shows instability during absorption of planar shear wave<br /> % Heterogeneities removed to focus on instability<br /> % Grid size cropped for quicker simulation<br /> % The parameters coded below result in an amplitude that appears to blow up<br /> % May 2019<br /> %<br /> % If one of the factors is changed to as decribed below (with all other parameters constant):<br /> % * decreasing alpha0_s1 to 2e6 the solution appears stable<br /> % * increasing alpha0_s1 to 4e6 the solution blows up more<br /> % * increasing t_end to 5000 the solution blows up more<br /> % * decreasing t_end to 2000 the solution appears stable<br /> % * decreasing cfl to 0.1 (decreases dt by a factor of 2) the solution blows up more<br /> % * increasing scale to 1.25 (decreases dx &amp; dt by a factor of 0.8) the solution blows up much more<br /> % * decreasing scale to 0.75 (increases dx &amp; dt by a factor of 1.3) the solution appears stable<br /> % * increasing cp1 to 3000 (decreases dt by a factor of 2) the solution blows up more<br /> % * decreasing cp1 to 750 (increases dt by a factor of 2) the solution appears stable<br /> % * increasing cs1 to 4.5 the solution blows up more<br /> % * decreasing cs1 to 3.5 the solution appears stable<br /> % * instability appears insensitive to frequency (300-1800 Hz tested)<br /> % * instability appears insensitive to u_0 (0.5 to 1000 tested)</p> <p>close all<br /> clearvars </p> <p>% define the medium properties for the outise material<br /> cp1 = 1500; % compressional wave speed [m/s]<br /> cs1 = 4.35; % shear wave speed [m/s]<br /> rho1 = 1000; % density [kg/m^3]<br /> alpha0_p1 = 0; % compressional absorption [dB/(MHz^2 cm)]<br /> alpha0_s1 = 3e6; % shear absorption [dB/(MHz^2 cm)] (measured approx 1.08 dB/cm at 600 Hz)</p> <p>% create the computational grid<br /> scale = 1; % grid spacing factor<br /> PML_size = 10; % [grid points]<br /> Nx = 40*scale ; % [grid points]<br /> Ny = 20*scale ; % [grid points]<br /> dx = 0.4e-3/scale; % [m]<br /> dy = 0.4e-3/scale; % [m]<br /> kgrid = kWaveGrid(Nx, dx, Ny, dy);</p> <p>% create the time array to run until wave passes through entire grid<br /> cfl = 0.2;<br /> t_end = 4500*1e-6;<br /> kgrid.makeTime(max([cp1 cs1]), cfl, t_end);</p> <p>% define the source<br /> source_freq = 600; % [Hz]<br /> u_0 = 500; % initial velocity<br /> source_mask = zeros(Nx, Ny);<br /> source_mask(:,1) = 1;<br /> source.u_mask = source_mask;<br /> source.ux = u_0 * sin(2 * pi * source_freq * kgrid.t_array);<br /> source.uy = 0 * sin(2 * pi * source_freq * kgrid.t_array);</p> <p>% define sensor<br /> sensor.record = {'u_max_all','u_min_all','u_final'};</p> <p>% define the medium properties<br /> clear medium<br /> medium.sound_speed_compression = cp1*ones(Nx, Ny);<br /> medium.sound_speed_shear = cs1*ones(Nx, Ny);<br /> medium.density = rho1*ones(Nx, Ny);<br /> medium.alpha_coeff_compression = alpha0_p1*ones(Nx, Ny);<br /> medium.alpha_coeff_shear = alpha0_s1*ones(Nx, Ny);</p> <p>% set the input arguments<br /> input_args = {'PMLSize', PML_size, 'PMLAlpha', 2, 'PlotPML', false, ...<br /> 'PMLInside', false, 'PlotScale', 'auto', ...<br /> 'DataCast', 'single'};</p> <p>% run the elastic simulation<br /> sensor_data_elastic = pstdElastic2D(kgrid, medium, source, sensor, input_args{:});</p> <p>% visualization</p> <p>ui = u_0*cp1/cs1; % initial velocity</p> <p>figure(1)<br /> subplot(2,2,1);<br /> imagesc(kgrid.y_vec*1e3, kgrid.x_vec*1e3, sensor_data_elastic.ux_max_all/ui); caxis([0 1.5])<br /> xlabel('y mm');ylabel('x mm');axis image;h = colorbar;ylabel(h, 'Normalized u_x');title('ux max all')<br /> subplot(2,2,2);<br /> imagesc(kgrid.y_vec*1e3, kgrid.x_vec*1e3, sensor_data_elastic.ux_final/ui); caxis([-1.5 1.5])<br /> xlabel('y mm');ylabel('x mm');axis image;h = colorbar;ylabel(h, 'Normalized u_x');title('ux final')<br /> subplot(2,2,3);<br /> imagesc(kgrid.y_vec*1e3, kgrid.x_vec*1e3, sensor_data_elastic.uy_max_all/ui); caxis([0 1.5])<br /> xlabel('y mm');ylabel('x mm');axis image;h = colorbar;ylabel(h, 'Normalized u_y');title('uy max all')<br /> subplot(2,2,4);<br /> imagesc(kgrid.y_vec*1e3, kgrid.x_vec*1e3, sensor_data_elastic.uy_final/ui); caxis([-1.5 1.5])<br /> xlabel('y mm');ylabel('x mm');axis image;h = colorbar;ylabel(h, 'Normalized u_y');title('uy final') </p> http://www.k-wave.org/forum/topic/explosive-source-in-a-layered-heterogeneous-medium#post-6040 Mon, 03 Jul 2017 20:39:38 +0000 mishka 6040@http://www.k-wave.org/forum/ <p>Hello,</p> <p>As a part of a project in my biomedical engineering masters degree studies, I need to run a simulation of explosion wave that propagates through a layered heterogeneous medium which consists of vinyl-nitrile foam and glycerin channels. The measurement is done right after the material.</p> <p>I downloaded the k-wave software for Matlab, it looks really professional and through, but I just can't understand what I need to do to perform my simulation.</p> <p>I attached slides that show my needs. I prefer simulating as shown in the first slide, but I think it's too complicated. So any of the other slides is also fine.</p> <p><a href="https://drive.google.com/open?id=0B1LAkTYOVkgyeFhDT2JHeDNlTkZ4VER3X045NVNVRHpNZ0ZF" rel="nofollow">https://drive.google.com/open?id=0B1LAkTYOVkgyeFhDT2JHeDNlTkZ4VER3X045NVNVRHpNZ0ZF</a></p> <p>I really need help because I don't know anyone who know how to use the software.</p> <p>Thank you,<br /> Moshe </p>