http://www.k-wave.org/forum/topic/about-high-velocity-problem-using-example_tvsp_homogeneous_medium_monopolem Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 03:09:26 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/about-high-velocity-problem-using-example_tvsp_homogeneous_medium_monopolem#post-5718 Mon, 24 Oct 2016 09:46:41 +0000 Bradley Treeby 5718@http://www.k-wave.org/forum/ <p>Hi John,</p> <p>Can you post your code? It sounds like a classic instability.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/about-high-velocity-problem-using-example_tvsp_homogeneous_medium_monopolem#post-5709 Thu, 13 Oct 2016 21:00:07 +0000 uhultrasound 5709@http://www.k-wave.org/forum/ <p>Hi Brad,</p> <p>Thank you for your help. Sorry that I don't know how to upload pictures into the forum to show the problem. </p> <p>I inserted a Disc object in the medium using "makeDisc" function in the 2D example_tvsp_homogeneous_medium_monopole.m . I define the medium speed=1500m/s and the medium density=1000kg/m^3, and the Disc speed=6000m/s and the medium density=1500kg/m^3.</p> <p>source.p = source_mag*sin(2*pi*source_freq*kgrid.t_array); % sinusoidal wave<br /> sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor, input_args{:});<br /> sensor_data_record = sensor_data.p; % recorded data</p> <p>The problem is that I even use source_mag = 1e-12 for the source magnitude (extremely small magnitude), the resulting sensor_data.p data range from 10^-29 (1st data) to 10^9 (last data), the data is extremely large (i.e. 10^9). The wavefield display gradually shows the Disc shape in black, and then entire wavefield display turns to be black (I guess it may be because the sensor_data.p is too large).</p> <p>However, when the Disc speed is less than 6000m/s (e.g. 5000, 3000), everything looks normal. But when the Disc speed is greater than 6000m/s, this problem occurs.</p> <p>I was wondering if you know what the problem is for this kind of high-speed objects in the simulations?</p> <p>Many thanks,</p> <p>John </p>