http://www.k-wave.org/forum/topic/viscoelastic-medium-simulation Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 07:35:03 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/viscoelastic-medium-simulation#post-7602 Sat, 13 Jun 2020 12:57:37 +0000 Bradley Treeby 7602@http://www.k-wave.org/forum/ <p>You can use the <code>eta = ...</code> equation to first calculate the absorption coefficient in Np/( (rad/s)^2 m):</p> <p><code>alpha_coeff_shear_np = eta / (2 * rho0 .* medium.sound_speed_shear .^ 3)</code></p> <p>And then convert this to dB/(MHz^2 cm) for input to medium.alpha_coeff_shear:</p> <p><code>medium.alpha_coeff_shear = neper2db(alpha_coeff_shear_np, 2)</code></p> <p>Brad. </p> http://www.k-wave.org/forum/topic/viscoelastic-medium-simulation#post-7584 Mon, 08 Jun 2020 21:41:10 +0000 Lilys 7584@http://www.k-wave.org/forum/ <p>Hi,<br /> I am trying to simulate the wave propagation in a viscoelastic medium using "pstdElastic2D" function. I assume that the viscoelastic properties can be defined using "medium.alpha_coeff_shear". For a 4 MHz transducer, I am defining the "medium.alpha_coeff_shear" of the order of 1e7 to have a shear viscosity (eta) of 2.5 Pa.s based on the calculation of "eta" in the "pstdElastic2D" function, which is:<br /> <pre><code>eta = 2 * rho0 .* medium.sound_speed_shear .^ 3 .* db2neper(medium.alpha_coeff_shear, 2);</code></pre> <p>However, I don't see any change in the results if I don't define "medium.alpha_coeff_shear" at all (elastic medium). Could you please clarify how the viscoelastic properties can be defined and what the range of "medium.alpha_coeff_shear" should be for a 4 MHz transducer?<br /> Thanks in advance for your time and help.<br /> <pre><code>shear_modulus = 4e3; %[Pa] shear_viscosity = 2.5; %[Pa.s] medium.density = 1000; % [kg/m^3] medium.sound_speed_compression = 1540; %[m/s] medium.sound_speed_shear = sqrt(shear_modulus / medium.density); %[m/s] medium.alpha_coeff_shear = shear_viscosity / (2 * medium.density * medium.sound_speed_shear^3) * 8.7 / 100 * (2 * pi * 1e6)^2; %[dB/(MHz^2 cm)]</code></pre>