k-Wave User Forum » Topic: Problems in nonlinear simulation
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Bradley Treeby on "Problems in nonlinear simulation"
http://www.k-wave.org/forum/topic/problems-in-nonlinear-simulation#post-7758
Thu, 20 Aug 2020 12:02:55 +0000Bradley Treeby7758@http://www.k-wave.org/forum/<p>Hi Jack,</p>
<p>The waves will decay due to both geometric spreading and acoustic absorption. The former will depend on the shape of your source (e.g., point source vs large piston source), and the latter on the medium properties and acoustic frequency.</p>
<p>One point to check in your code if you think something is wrong: make sure the source and sensor points are not within the perfectly matched layer.</p>
<p>Brad.
</p>jackYANG on "Problems in nonlinear simulation"
http://www.k-wave.org/forum/topic/problems-in-nonlinear-simulation#post-7757
Thu, 20 Aug 2020 02:47:14 +0000jackYANG7757@http://www.k-wave.org/forum/<p>Hi brad,<br />
Thank you for your recommended articles,maybe I still do not fully understand, please forgive my ignorance.In k-Wave,the coupled governing equations can also be combined to give a modified form of the Westervelt equation valid for heterogeneous media with power law absorption?The penultimate formula in III B?Or is it the first time that I asked the above formula to calculate the sound pressureIn addition, why does the sound pressure decay so quickly in both two - and three-dimensional simulations?Even if it decays at 1/ distance.This gives me an incorrect sound pressure gain.Is there any way to prevent the attenuation of my sound pressure source signal from being so serious? Now basically my source signal will attenuate by 10,000 times after passing 2cm (for example, from 1MPa to 100Pa), but I want to simulate the nonlinear sound wave focusing, so I must ensure that the sound pressure signals at the focus position are large enough.Thank you for your patience.<br />
jackYANG
</p>Bradley Treeby on "Problems in nonlinear simulation"
http://www.k-wave.org/forum/topic/problems-in-nonlinear-simulation#post-7743
Wed, 19 Aug 2020 14:42:56 +0000Bradley Treeby7743@http://www.k-wave.org/forum/<p>Hi Jack,</p>
<p>All the details are given in <a href="http://www.k-wave.org/papers/2012-Treeby-JASA.pdf">this paper</a>.</p>
<p>Hope that helps,</p>
<p>Brad.
</p>jackYANG on "Problems in nonlinear simulation"
http://www.k-wave.org/forum/topic/problems-in-nonlinear-simulation#post-7720
Tue, 04 Aug 2020 15:06:15 +0000jackYANG7720@http://www.k-wave.org/forum/<p>Hi brad and guys,<br />
Recently, I have been working on the function kspaceFirstOrder3D, which has a calculation method for nonlinear attenuation sound pressure.But I'm a little confused, it doesn't seem to include the Laplace operator.I want to confirm this formula for calculating the sound pressure in the program:<br />
p = c0.^2 .* (...(rhox + rhoy + rhoz) ...+ absorb_tau .* real(ifftn( absorb_nabla1 .* fftn(rho0 .* (duxdx + duydy + duzdz)) ))...- absorb_eta .* real(ifftn( absorb_nabla2 .* fftn(rhox + rhoy + rhoz) ))...+ medium.BonA .*(rhox + rhoy + rhoz).^2 ./ (2 .* rho0) ...);<br />
Is the formula the same as eq(2.7) in K-wave_user_manual_1.1?Does it lose the term Lρ?It would be even better if you could explain every item in the program.In fact, I've been wondering how accurately Kwave calculates the sound pressure, and how the sound pressure decays so quickly with distance, even if the attenuation is not set in water,it may be that I don't understand deeply enough. I hope you can help me.Thank you.
</p>