k-Wave User Forum » Topic: Issue with a source in elastic medium

k-Wave User Forum » Topic: Issue with a source in elastic medium http://www.k-wave.org/forum/topic/issue-with-a-source-in-elastic-medium Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 14:16:14 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php Bradley Treeby on "Issue with a source in elastic medium" http://www.k-wave.org/forum/topic/issue-with-a-source-in-elastic-medium#post-6838 Wed, 10 Apr 2019 13:32:20 +0000 Bradley Treeby 6838@http://www.k-wave.org/forum/ Hi Antoine, If you have a point source, it will propagate in all directions. If you imagine a line source as a row of point sources, some of the wave front will cancel out, but you are still left with the end points. These generate so-called edge waves, which propagate in the y-direction. You could increase the directionality of the source by using a velocity source. However, you cannot create a completely collimated source in one direction unless it's a plane wave. Hope that helps, Brad. Antoine Malrin on "Issue with a source in elastic medium" http://www.k-wave.org/forum/topic/issue-with-a-source-in-elastic-medium#post-6805 Thu, 28 Mar 2019 12:07:55 +0000 Antoine Malrin 6805@http://www.k-wave.org/forum/ Hello, I am new in k-wave and i tried to create a linear source with a time varying signal in an homogenous elastic medium. I want to simulate a compressional wave only (x direction). During the simulation, we can see appear à wave (in the y direction) in the source that i've not created and i can't explain where this wave comes from. Do you have an explanation please ? %% %% Test de sensor.record_start_index et verif des vitesses et temps de vol clear all close all %% On définit le maillage Nx = 600; % number of grid points in the x (row) direction Ny = 600; % number of grid points in the y (column) direction dx = 0.1e-3; % grid point spacing in the x direction [m] dy = 0.1e-3; % grid point spacing in the y direction [m] kgrid = kWaveGrid(Nx, dx, Ny, dy); %% Medium properties medium.sound_speed_compression = 1000*ones(Nx,Ny); % [m/s] medium.sound_speed_shear = 0*ones(Nx,Ny); % [m/s] medium.density = 1000*ones(Nx,Ny); % [kg/m^3] medium.alpha_coeff_compression = 0.1*ones(Nx,Ny); % [dB/(MHz^2 cm)] medium.alpha_coeff_shear = 0.00001; % [dB/(MHz^2 cm)] Nb_pt_par_lambda = 30; %% Vecteur temps cfl = 0.1; % Courant-Friedrichs-Lewy number t_end = 35e-6; % [s] kgrid.makeTime(max(medium.sound_speed_compression(:)), cfl, t_end); % Signal d'émission source_freq = 1e6; % [Hz] Nb_periode = 1.5; t = (0:kgrid.dt:Nb_periode/source_freq); magnitude = 400; % [Pa] % [Pa] w = zeros(1,size(kgrid.t_array,2)); w(1,1:size(t,2)) = hann(size(t,2)); source.sxx = magnitude * sin(2 * pi * source_freq * kgrid.t_array).*w; source.syy = 0; source.sxy = 0; %% Position emetteur x_pos = Nx/4; % [grid points] y_pos = Ny/2; % [grid points] source.s_mask = zeros(Nx,Ny); source.s_mask(x_pos,270:330) =1; %% Position recepteur D_E_R1 = round(0.02/dx); % distance emetteur/recepteur1 en terme d'échantillon D_R1_R2 = round(0.01/dx); Recep1_x = Nx/4 + D_E_R1; Recep1_y = y_pos ; Recep2_x = Recep1_x + D_R1_R2; Recep2_y = y_pos ; Recep_start1 = [Recep1_x Recep1_y]; Recep_start2 = [Recep2_x Recep2_y]; Recep_angle = 0; length = 10; SM1 = makeLine(Nx, Ny, Recep_start1, Recep_angle, length); % Le Premier point est le point le plus bas à gauche SM2 = makeLine(Nx, Ny, Recep_start2, Recep_angle, length); sensor_mask = SM1+SM2; % Map with E and R1-R2 figure imagesc(source.s_mask + sensor_mask) axis equal title('carte emetteur/recepteur') cartesian_pos_center = [Nx/2*dx, Ny/2*dy]; [x_SM1, y_SM1] = find(SM1>0); x_SM1 = x_SM1'; y_SM1 = y_SM1'; for i = 1:size(x_SM1,2) x_SM1(i) = x_SM1(i)*dx - cartesian_pos_center(1); y_SM1(i) = y_SM1(i)*dy - cartesian_pos_center(2); end [x_SM2, y_SM2] = find(SM2>0); x_SM2 = x_SM2'; y_SM2 = y_SM2'; for i = 1:size(x_SM2,2) x_SM2(i) = x_SM2(i)*dx - cartesian_pos_center(1); y_SM2(i) = y_SM2(i)*dy - cartesian_pos_center(2); end x_SM = [x_SM1, x_SM2]; y_SM = [y_SM1, y_SM2]; sensor.mask = [x_SM y_SM]; sensor.record = {'p', 'u','p_final'}; sensor.record_start_index = 1; % run the simulation sensor_data = pstdElastic2D(kgrid, medium, source, sensor ); for i=1:size(sensor_data.p,2) p_somme_R1(i) = mean(sensor_data.p(1:size(sensor_data.p,1)/2,i)); p_somme_R2(i) = mean(sensor_data.p(size(sensor_data.p,1)/2+1:end,i)); end figure plot(kgrid.t_array,p_somme_R1) hold on plot(kgrid.t_array,p_somme_R2,'r') hold off hhh = legend('R1','R2','R3'); xlabel('temps (s)') ylabel('Amplitude') title('signaux recus par chaque recepteur') sensor_data.p_final = sensor_data.p_final/max(max(sensor_data.p_final)); Thank you by advance for your answer. Antoine Malrin