k-Wave User Forum » Topic: Nonlinear effect using K-Wave

k-Wave User Forum » Topic: Nonlinear effect using K-Wave http://www.k-wave.org/forum/topic/nonlinear-effect-using-k-wave Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 01:32:21 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php bencox on "Nonlinear effect using K-Wave" http://www.k-wave.org/forum/topic/nonlinear-effect-using-k-wave#post-4929 Mon, 05 Jan 2015 11:50:46 +0000 bencox 4929@http://www.k-wave.org/forum/ Hi ak714, I'm not sure what you're trying to do. Half of your elements have a different amplitude to the other half, but the frequency is the same. If you want to generate nonlinear acoustic effects you will need the amplitudes to be large, eg. 0.5e6 Pa or more. Ben ak714 on "Nonlinear effect using K-Wave" http://www.k-wave.org/forum/topic/nonlinear-effect-using-k-wave#post-4919 Tue, 23 Dec 2014 08:47:29 +0000 ak714 4919@http://www.k-wave.org/forum/ Hi I'm working with k-wave First I did a Delay & sum image reconstruction with Phased Array in 2D simulation so i want to adopt a nonlinear effects with this Phased array make a half of transducers in array was exictied in different frequency and make a nonlinear effect at focal points but when i did in nonlinear examples it doesn't work so I wonder what is the problem here it is my code clear all; % ========================================================================= % DEFINE SIMULATION PROPERTIES % ========================================================================= % define the properties used in the simulation p0 = 7*10^6; % source pressure [Pa] c0 = 1500; % sound speed [m/s] rho0 = 1000; % density [kg/m^3] alpha_0 = 0.25; % absorption coefficient [dB/(MHz^2 cm)] sigma = 1; % shock parameter source_freq = 1e6; % frequency [Hz] points_per_wavelength = 50; % number of grid points per wavelength at f0 wavelength_separation = 15; % separation between the source and detector pml_size = 64; % PML size CFL = 0.25; % % compute corresponding grid spacing dx = c0/(points_per_wavelength*source_freq); % [m] dy = c0/(points_per_wavelength*source_freq); % compute corresponding grid size Nx = wavelength_separation*points_per_wavelength + 20; Ny = wavelength_separation*points_per_wavelength + 20; % ========================================================================= % RUN SIMULATION % ========================================================================= % create the computational grid kgrid = makeGrid(Nx, dx, Ny, dy ); % assign the properties of the propagation medium medium.sound_speed = ones(Nx,Ny)*c0; medium.density = ones(Nx,Ny)*rho0; medium.alpha_power = 2; medium.alpha_coeff = alpha_0; medium.alpha_mode = 'no_dispersion'; % extract the maximum frequency supported by the grid f_max = min(min(medium.sound_speed))/(2*dx); % [Hz] Num_T = 128; % define a single source element source.p_mask = zeros(Nx,Ny); source.p_mask(Nx,Ny/2-Num_T+2:+2:Ny/2+Num_T) = 1; % define a single sensor position an integer number of wavelengths away sensor.mask = zeros(Nx, Ny); sensor.mask(Nx/2,Ny/2)=1; x_px = wavelength_separation*points_per_wavelength; x = x_px*dx; % compute the nonlinearity coefficient required to give the correct shock % parameter mach_num = p0/(rho0*c0.^2); k = 2*pi*source_freq/c0; BonA = 2*(sigma/(mach_num*k*x) - 1); medium.BonA = BonA; display_mask = source.p_mask; % set the simulation options input_args = {'PMLInside', false, 'PMLSize', [pml_size,pml_size], 'PMLAlpha', 1.5,'DisplayMask', display_mask... ,'RecordMovie', true, 'MovieType', 'image', 'MovieName', 'Non_linear'}; % compute points per temporal period points_per_period = round(points_per_wavelength / CFL); % compute corresponding time spacing dt = 1/(points_per_period*source_freq); focus_X=Nx/2*dx; focus_Y=0; for i=1:1:Num_T/2 tone_burst_offset(1,i+Num_T/2)=(sqrt(focus_X^2+focus_Y^2)-sqrt(((2*i-1)*dy-focus_Y)^2+focus_X^2))/1500/dt ; end for i=-1:-1:-Num_T/2 tone_burst_offset(1,i+Num_T/2+1)=(sqrt(focus_X^2+focus_Y^2)-sqrt(((2*i+1)*dy-focus_Y)^2+focus_X^2))/1500/dt ; end Min=min(tone_burst_offset(1,:)); for i=1:1:Num_T tone_burst_offset(1,i)= tone_burst_offset(1,i)-Min; end tone_burst_freq = source_freq*1; % [Hz] tone_burst_cycles = 10; source.p = toneBurst(1/dt, tone_burst_freq, tone_burst_cycles, 'SignalOffset', tone_burst_offset) source.p = (p0./(1500*1000)).*source.p; source_lf = toneBurst(1/dt, tone_burst_freq+10^5, tone_burst_cycles, 'SignalOffset', tone_burst_offset); source_lf = (p0./(1500*1000)).*source.p*2; for a=1:Num_T/2 for b=1:length(source.p) source.p(a,b) = source_lf(a,b); end end % create the time array using an integer number of points per period t_end = Nx*dx/1500; kgrid.t_array = 0:dt:t_end; % create the source term, offset by dt/2 so there is a point that lands on the axis % source.p = p0*sin(2*pi*source_freq*(kgrid.t_array)); % run the simulation sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor, input_args{:}); plot(sensor_data) save 'data_set' [f, sensor_data_as] = spect(sensor_data(1, :), 1/dt); figure; [f_sc, scale, prefix] = scaleSI(max(f(:))); plot(scale*f, sensor_data_as, 'k-'); ylabel('Amplitude Spectrum'); xlabel(['Frequency [' prefix 'Hz]']); legend('Original Time Series', 'Filtered Time Series'); set(gca, 'XLim', [0 1]);