k-Wave User Forum » Topic: Pressure antinode of reflected wave

k-Wave User Forum » Topic: Pressure antinode of reflected wave http://www.k-wave.org/forum/topic/pressure-antinode-of-reflected-wave Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 01:06:35 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php bencox on "Pressure antinode of reflected wave" http://www.k-wave.org/forum/topic/pressure-antinode-of-reflected-wave#post-7824 Mon, 14 Sep 2020 21:38:59 +0000 bencox 7824@http://www.k-wave.org/forum/ Hi Durant, I set <code>sensor.record = {'p_final'};</code>, ran your code, and plotted a slice through <code>sensor_data.p_final</code>. The spacing between the peaks was a wavelength. Best wishes, Ben kevin durant on "Pressure antinode of reflected wave" http://www.k-wave.org/forum/topic/pressure-antinode-of-reflected-wave#post-7764 Sat, 22 Aug 2020 08:44:01 +0000 kevin durant 7764@http://www.k-wave.org/forum/ Hi, Ben Sorry to disturb you again. My code for simulation is as following. clear; close all; % ========================================================================= % DEFINE THE K-WAVE GRID % ========================================================================= % physical properties of the transducer transducer.EleNum = 1; transducer.R = 5e-3; % diameter of aperture % set total number of grid points not including the PML Nx = 256; % [grid points/X] Ny = 256; % [grid points/Y] Nz = 512; % [grid points/Z] % set desired grid size in the x-direction not including the PML x = 25.6e-3; % [m] z = 51.2e-3; % [m] % calculate the spacing between the grid points dx = x/Nx; % [m] dy = dx; % [m] dz = z/Nz; % [m] % create the k-space grid kgrid = kWaveGrid(Nx, dx, Ny, dy, Nz, dz); % ========================================================================= % DEFINE THE MEDIUM PARAMETERS % ========================================================================= sound_speed_Water = 1500; medium.sound_speed = sound_speed_Water * ones(Nx, Ny, Nz); % [m/s] medium.density = 1000 * ones(Nx, Ny, Nz); % [kg/m^3] medium.alpha_coeff = 0; % assume no attenuation medium.alpha_power = 1; medium.alpha_mode = 'no_dispersion'; Freq = 1e6; %[Hz] Zg = ceil((transducer.R^2/sound_speed_Water * Freq + 2e-3)/ dz); %far-field distance ZIte = 40; % distance between second medium to far-field medium.sound_speed(:, :, Zg+ZIte:end) = 2000; % parameters of second medium medium.density(:, :, Zg+ZIte:end) = 1200; medium.alpha_coeff(:, :, Zg+ZIte:end) = 0; % ========================================================================= % DEFINE THE INPUT SIGNAL % ========================================================================= % create the time array kgrid.makeTime(medium.sound_speed); % define properties of the input signal source_mag = 2; % [Pa] source_freq = Freq; % [Hz] source.u_mask = zeros(Nx, Ny, Nz); % creat single circle flat transducer manually using grid points mask = zeros(Nx, Ny); p_ind = bsxfun(@plus, kgrid.x_vec.^2, kgrid.y_vec.^2'); mask(p_ind <= transducer.R^2) = 1; source.u_mask(:, :, 11) = mask; source.uz = source_mag * sin(2 * pi * source_freq * kgrid.t_array); source.ux = 0; source.uy = 0; % define a series of Cartesian points to collect the data sensor.mask = zeros(Nx, Ny, Nz); sensor.mask(Nx/2, :, :) = 1; sensor.record_start_index = ceil(numel(kgrid.t_array)/2); % define the field parameters to record sensor.record = {'p', 'p_max_all'}; input_args = {'DisplayMask', sensor.mask, 'DataCast', 'single', ... 'CartInterp', 'nearest', 'PMLSize', [10 10 10]}; % run the simulation sensor_data = kspaceFirstOrder3D(kgrid, medium, source, sensor, input_args{:}); Using that simulation, the distance between the sound pressure antinode are λ/4. Then I followed your suggestion to modify the transducer.R to 10e-3 and set 'PMLAlpha' to [2 2 0], [0 0 2] and [0 0 0], but the reflection wave is even more unexplainable. So,,, I wanna know if there is some problems in my simulation code or I misunderstand what you really mean? Thanks again. Best wishes. Durant bencox on "Pressure antinode of reflected wave" http://www.k-wave.org/forum/topic/pressure-antinode-of-reflected-wave#post-7756 Wed, 19 Aug 2020 22:37:51 +0000 bencox 7756@http://www.k-wave.org/forum/ Hi Durant, Is it a near-field effect due to the finite size of your source? As a check, you could try using a large-area planar source parallel to the interface, thereby ensuring the edge waves from the source are not affecting the field significantly. To do that, you may want to align the planar source with the grid and turn off the PML (by setting <code>PMLAlpha</code> in the relevant direction to zero) so that the extends periodically (by the periodic nature of the model) and is therefore truly planar. Best wishes, Ben kevin durant on "Pressure antinode of reflected wave" http://www.k-wave.org/forum/topic/pressure-antinode-of-reflected-wave#post-7748 Wed, 19 Aug 2020 15:11:36 +0000 kevin durant 7748@http://www.k-wave.org/forum/ Hi, Brad I used a 3D modle to simulate the ultrasound propagation in two tissue, where the impendence between the two tissue are dismatched. The transducer is circle with R = 5e-3m. Interface between the tissue is parallel to tansducer, located in front of the transducer approximately 20mm. So, the pressure field in the first tissue should be the superposition of reflected wave and incident wave. But why the distance between the sound pressure antinode are λ/4 rather than λ/2 ？ Is the λ/4 right, and I missed some information about the K-Wave? Thans, looking forward to your reply. Durant