http://www.k-wave.org/forum/topic/2d-simulation-not-giving-expected-focal-gain Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 01:47:20 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/2d-simulation-not-giving-expected-focal-gain#post-6559 Thu, 16 Aug 2018 22:46:46 +0000 chuck_c 6559@http://www.k-wave.org/forum/ <p>Thanks for the good explanation. This is helpful and makes sense. </p> http://www.k-wave.org/forum/topic/2d-simulation-not-giving-expected-focal-gain#post-6558 Thu, 16 Aug 2018 21:14:06 +0000 bencox 6558@http://www.k-wave.org/forum/ <p>Hi Charles, </p> <p>In your 2D simulation you're modelling the focussing of (part of) a cylindrical wave, not (part of) a spherical wave. The 2D simulation can be thought of as modelling a 3D scenario in which everything is constant in the unmodelled dimension, so the curved source in 2D could be thought of as modelling a 3D source that is the shape of side of a cylinder, eg. shaped like guttering. So the focus will certainly be very different, yes.</p> <p>Best wishes,<br /> Ben </p> http://www.k-wave.org/forum/topic/2d-simulation-not-giving-expected-focal-gain#post-6537 Fri, 27 Jul 2018 19:39:48 +0000 chuck_c 6537@http://www.k-wave.org/forum/ <p>Hello,</p> <p>I am trying to simulate a spherical cap shaped piezoceramic transducer in 2D. I have characterized the physical transducer with a hydrophone, and my 3D simulations yield the expected pressure pattern and gain (ratio of max to source pressure) of 40. However, when I try to collapse the simulation to 2D for kspaceFirstOrder2D, I only get a gain of ~9. Is this behavior expected?</p> <p>Any input is helpful and appreciated.</p> <p>Thanks,<br /> Charles</p> <p>----------------------Begin code snippet---------------------<br /> clear all;</p> <p>% create the computational grid<br /> Nz = 256*2; % number of grid points in the z (row) direction7<br /> Nx = Nz; % number of grid points in the y (column) direction<br /> dx = 200e-6; % grid point spacing in the x direction [m]<br /> dz = dx; % grid point spacing in the y direction [m]</p> <p>medium.sound_speed = ones([Nx Nz])*1480; % m/s sound speed in water<br /> medium.density = ones([Nx Nz])*1e03; % kg/m^3 density of water</p> <p>kgrid = makeGrid(Nx, dx, Nz, dz);<br /> [kgrid.t_array, dt] = makeTime(kgrid, medium.sound_speed);</p> <p>Nt = length(kgrid.t_array);</p> <p>%%</p> <p>% first define transduce geometry and place elemental sources in the kgrid<br /> transducer_radius_m = (64e-03);<br /> transducer_height_m = (63.2 - 51.74)*1e-03;</p> <p>transducer_radius_pix = round( transducer_radius_m / dz );<br /> transducer_height_pix = round( transducer_height_m / dx );</p> <p>sphere = rot90(makeArc([Nx Nz], [Nx/2 10], transducer_radius_pix, transducer_radius_pix+1, [Nx/2 Nx/2]),-1);</p> <p>[sx, sy, sz] = size(sphere);</p> <p>source.p_mask = zeros(Nx,Nz);<br /> source.p_mask = sphere; </p> <p>%% source signal<br /> % transducer source parameters<br /> % define a time varying sinusoidal source<br /> source_freq = 1.1e6; % [Hz]<br /> source_mag = 1e6/40; % [Pa]<br /> source.p = source_mag*sin(2*pi*source_freq*kgrid.t_array);</p> <p>% filter the source to remove any high frequencies not supported by the grid<br /> source.p = filterTimeSeries(kgrid, medium, source.p);</p> <p>figure;<br /> plot( source_freq*kgrid.t_array, source.p );<br /> xlabel('# cycles (freq * time)');<br /> ylabel('Input pressure [Pa]');</p> <p>%% setup sensor and run simulation</p> <p>sensor.mask = ones(Nx,Nz);<br /> sensor.record = {'p_max'};</p> <p>input_args = {'PlotSim', true, 'DisplayMask', source.p_mask, 'DataCast', 'single', 'PMLInside', false, 'PlotPML', false};</p> <p>% run the simulation<br /> [sensor_data] = kspaceFirstOrder2D(kgrid, medium, source, sensor, input_args{:} );</p> <p>pmap = reshape(sensor_data.p_max(:), Nx, Nz);</p> <p>%% Image pressure map</p> <p>figure;<br /> imagesc(1e03*dx * (1:Nx), 1e03*dz*(1:Nz), transpose(pmap));<br /> xlabel('x [mm]');<br /> ylabel('z [mm]');<br /> pmap_single = gather(pmap);<br /> colormap(jet)<br /> colorbar;</p> <p>--------------------------------End Code Snippet----------------------------------- </p>