k-Wave User Forum » Topic: Heterogeneous Ultrasound Simulation

k-Wave User Forum » Topic: Heterogeneous Ultrasound Simulation http://www.k-wave.org/forum/topic/heterogeneous-ultrasound-simulation Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 13:34:35 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php Bradley Treeby on "Heterogeneous Ultrasound Simulation" http://www.k-wave.org/forum/topic/heterogeneous-ultrasound-simulation#post-5828 Mon, 13 Feb 2017 09:53:29 +0000 Bradley Treeby 5828@http://www.k-wave.org/forum/ Hi Dennis, Yes, if you have very large density changes, then the tranmission coefficient may not be accurate. See Fig. 4 in <a href="http://bug.medphys.ucl.ac.uk/papers/2014-Robertson-IEEEIUS.pdf">this paper</a> for an illustration. I would suggest setting up a simple example in 1D with the same impedance mismatch, and then seeing how many points per wavelength are required until the reflection and transmission coefficients converge. I'm a bit confused about what you mean by the word net in your description? Brad. DennisGeisler on "Heterogeneous Ultrasound Simulation" http://www.k-wave.org/forum/topic/heterogeneous-ultrasound-simulation#post-5810 Fri, 06 Jan 2017 12:26:43 +0000 DennisGeisler 5810@http://www.k-wave.org/forum/ Hello everyone, i am student of mechanical engineering and my task is to simulate an ultrasound signal through wood. My goal is to find holes and delaminations. I have already found some Informations in this forum that maybe i will get a problem with an overestimated transmission. Is it possible that i will have this problems? Another problem is, that my net calculate stable values if i change the cfl number form 0,2 down to 0,01. But if i change my net, i am not able to get the same values of pressure, calculated with the same variables beside the net. Obviously that doesnt make sense. I dont have this problem if i calculate in air. Values in air are independent from cfl and netsize. I want to fit my result to measurements with the absorption terms. But as long as my values arent independent from net size, that doesnt works. I hope someone can help me with that. Best Regards Dennis Geisler My code: % scale geometry N=320; % Goal M=320; % Standard a=N/M; scale=1; pml_size= 30*a; % create the computational grid Nx = M*a; % number of grid points in the x (row) direction Ny = M*a; % number of grid points in the y (column) direction dx = 0.001/a; % grid point spacing in the x direction [m] dy = 0.001/a; % grid point spacing in the y direction [m] kgrid = makeGrid(Nx, dx, Ny, dy); % define the properties of the upper layer of the propagation medium medium.sound_speed = 343*ones(Nx, Ny); % [m/s] medium.density = 1*ones(Nx, Ny); % [kg/m^3] medium.alpha_coeff = 0.1328*ones(Nx, Nx); % [dB/(MHz^y cm)] % define the properties of the lower layer of the propagation medium medium.sound_speed(153*a:188*a, :) = 500 ; % [m/s] medium.density(153*a:188*a, :) = 700; % [kg/m^3] medium.alpha_coeff (153*a:188*a, :) =1; % [dB/(MHz^y cm)] medium.alpha_power =1; medium.alpha_mode ='no_dispersion'; % create the time array cfl = 0.05; % Courant-Friedrichs-Lewy number t_end = 0.002;% [s] % scale time c=0.1/cfl; kgrid.t_array = makeTime(kgrid, max(medium.sound_speed(:)), cfl, t_end); time_schwinger=kgrid.t_array(1,1:2000*a*c); % define a time varying sinusoidal source source_freq = 50000; % [Hz] amplitude = 60; % [Pa] source_mag = amplitude*[linspace(0,1,round(400*a*c)),ones(1,round(1200*a*c)), linspace(1,0,round(400*a*c))]; % [Pa] startpoint= [round((10+120+35+90+46/2)*a), round(Ny/2-(16+20)*a)]; angle=0.17; length=round(40*a); line = makeLine ( Nx,Ny, startpoint, angle, length); source.p_mask= line; quelle=sin(2*pi*source_freq*time_schwinger); source.p = source_mag.*quelle; % filter the source to remove high frequencies not supported by the grid %source.p = filterTimeSeries(kgrid, medium, source.p); % define a centered circular sensor sensor.mask = zeros(Nx,Ny); % sensor oberseite pos1=round(Ny*10/100); pos2=round(Ny*20/100); pos3=round(Ny*30/100); pos4=round(Ny*40/100); pos5=round(Ny*50/100); pos6=round(Ny*60/100); pos7=round(Ny*70/100); pos8=round(Ny*80/100); pos9=round(Ny*90/100); sensor.mask(60*a, pos1)=1; sensor.mask(60*a, pos2)=1; sensor.mask(60*a, pos3)=1; sensor.mask(60*a, pos4)=1; sensor.mask(60*a, pos5)=1; sensor.mask(60*a, pos6)=1; sensor.mask(60*a, pos7)=1; sensor.mask(60*a, pos8)=1; sensor.mask(60*a, pos9)=1; input_args = {'PMLSize', pml_size, }; % run the simulation sensor_data= kspaceFirstOrder2D(kgrid, medium, source, sensor, input_args{:}); % define the acoustic parameters to record sensor.record = {'p', 'p_final', 'I', 'I_avg' }; % ========================================================================= % VISUALISATION % =========================================================================