http://www.k-wave.org/forum/topic/ultrasound-propagation-in-droplets Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 22:34:45 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/ultrasound-propagation-in-droplets#post-8208 Fri, 11 Jun 2021 11:27:16 +0000 Bradley Treeby 8208@http://www.k-wave.org/forum/ <p>Hi Zeng,</p> <p>I don't know anything about your particular problem, but yes, you can model lots of small scatterers in k-Wave by perturbing the acoustic density / sound speed. Keep in mind that if you run your simulation in 2D, what you're actually modelling is scattering by infinite cylinders. </p> <p>Also, the code you posted uses a disc-shaped initial pressure. You will want to look at some of the other examples for how to create a monochromatic (single frequency) plane wave.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/ultrasound-propagation-in-droplets#post-8206 Fri, 11 Jun 2021 08:15:57 +0000 zengqw2021 8206@http://www.k-wave.org/forum/ <p>Hello,<br /> I have created a code as follows:</p> <p>% Based on Heterogeneous Propagation Medium Example</p> <p>clearvars;</p> <p>% =========================================================================<br /> % SIMULATION<br /> % =========================================================================</p> <p>% create the computational grid<br /> Nx = 512; % number of grid points in the x (row) direction<br /> Ny = Nx; % number of grid points in the y (column) direction<br /> dx = 1e-6; % grid point spacing in the x direction [m]<br /> dy = 1e-6; % grid point spacing in the y direction [m]<br /> kgrid = kWaveGrid(Nx, dx, Ny, dy);</p> <p>% define the properties of the propagation medium<br /> Air_speed = 330;<br /> Air_rho0 = 1;<br /> Air_BonA = 0.4;<br /> Air_absob = 2.0;</p> <p>source_f0 = 1.1e6; % source frequency [Hz]<br /> water_temp = 22;<br /> water_speed = waterSoundSpeed(water_temp);<br /> water_rho0 = waterDensity(water_temp);<br /> water_BonA = waterNonlinearity(water_temp);<br /> water_absob = waterAbsorption(source_f0 * 1e-6, water_temp);</p> <p>% reference sound speed<br /> medium.sound_speed_ref = Air_speed;<br /> % sound speed<br /> medium.sound_speed = Air_speed* ones(Nx, Ny);<br /> % sound density<br /> medium.density = Air_rho0 * ones(Nx, Ny);<br /> % nonlinearity<br /> medium.BonA = Air_BonA * ones(Nx, Ny);<br /> % absorption<br /> medium.alpha_coeff = Air_absob * ones(Nx, Ny);</p> <p>medium.alpha_power = 2.0;</p> <p>%========create water droplets disk===</p> <p>N= 10; %Number of water droplets<br /> drop_pos_x = randperm(Nx-10); % Center of particle position<br /> drop_pos_y = randperm(Nx-10); %</p> <p>for i=1:N<br /> % droplets geometry<br /> drop_radius = 5; %radius of droplet,grid point spacing<br /> cx = drop_pos_x(i);<br /> cy = drop_pos_y(i);<br /> drop_mask = makeDisc(Nx, Ny, cx, cy, drop_radius);</p> <p> % sound speed<br /> medium.sound_speed(drop_mask == 1) = water_speed;<br /> % sound density<br /> medium.density(drop_mask == 1) = water_rho0;<br /> % nonlinearity<br /> medium.BonA(drop_mask == 1) = water_BonA;<br /> % absorption<br /> medium.alpha_coeff(drop_mask == 1) = water_absob;</p> <p>end</p> <p>% create initial pressure distribution using makeDisc<br /> disc_magnitude = 5; % [Pa]<br /> disc_x_pos = Nx/2; % [grid points]<br /> disc_y_pos = Ny/2; % [grid points]<br /> disc_radius = 20; % [grid points]<br /> disc_1 = disc_magnitude * makeDisc(Nx, Ny, disc_x_pos, disc_y_pos, disc_radius);</p> <p>source.p0 = disc_1 ;<br /> init_p0 = source.p0;</p> <p>% define a centered Cartesian circular sensor<br /> sensor_radius = 2e-4; % [m]<br /> sensor_angle = 2*pi ; % [rad]<br /> sensor_pos = [0, 0]; % [m]<br /> num_sensor_points = 150;<br /> cart_sensor_mask = makeCartCircle(sensor_radius, num_sensor_points, sensor_pos, sensor_angle);<br /> % Cartesian sensors aren't support in the C++ code, convert it to a binary mask<br /> [grid_sensor_mask, order_index, reorder_index] = cart2grid(kgrid, cart_sensor_mask);<br /> sensor.mask = grid_sensor_mask;</p> <p>% create the time array<br /> t1=kgrid.makeTime(medium.sound_speed);</p> <p>% run the simulation with optional inputs for plotting the simulation<br /> % layout in addition to removing the PML from the display<br /> sensor_data = kspaceFirstOrder2DC(kgrid, medium, source, sensor, ...<br /> 'PlotLayout', false, 'PlotPML', false);</p> <p>Can the above code be used to analyze the simulated pressure amplitude for<br /> the scattering of a monochromatic plane wave by a sphere of micron-sized particles?<br /> Could anyone give me some suggestions? Thanks advance.<br /> Zeng </p> http://www.k-wave.org/forum/topic/ultrasound-propagation-in-droplets#post-8202 Thu, 10 Jun 2021 02:20:08 +0000 zengqw2021 8202@http://www.k-wave.org/forum/ <p>Hi everyone,<br /> Recently, I want to study the propagation of ultrasound in space filled with water droplets. In the paper "Nonlinear ultrasound simulation in an axisymmetric coordinate system using a k-space pseudospectral method", I find the case "D. Scattering of plane wave by a fluid sphere"simulation seems to be similar to this situation.Scattering of acoustic signals is the main consideration.<br /> I want to know if I can set many micron-sized particles in the medium properties by resetting the droplet density parameters to achieve my idea.<br /> I hope to receive your reply.<br /> Thanks.<br /> Zeng </p>