Is it possible to simulate US wave propagation in the medium with Spherical or Cylindrical boundary conditions?
Thank you
k-Wave
A MATLAB toolbox for the time-domain
simulation of acoustic wave fields
Spherical or Cylindrical boundary condition
(8 posts) (4 voices)-
Posted 11 years ago #
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Hi beta439,
Do you mean imposing general impedance boundary conditions, as in defining a boundary or object within the medium by enforcing a particular relationship between the pressure and particle velocity (rather than a change in sound speed and density)? If so, unfortunately this is not possible with the current release. If you mean imposing a spherical or cylindrical shaped source as a boundary condition, this is possible by setting
source.p_modeto'dirichlet'and creating your source mask to be the desired shape.Hope that answers your question!
Brad.
Posted 11 years ago # -
Dear Brad,
Thank you for your reply. I wanted to change the shape of the computational domain in order to simulate wave propagation in the tube with partially reflecting boundary condition. As I understood, the toolbox uses PML boundary condition and it is possible to change the PML properties such as size and alpha by which we can change the absorption property but I do not know how to change the shape of the boundary (computational domain).
Thanks again.
Posted 11 years ago # -
The computation is always performed using a regular Cartesian grid, so it's not possible to change the shape of the boundary directly. Also, the spatial gradients are computed using the Fourier spectral method, so if you adjust the PML, rather than just getting a partial reflection (as you would with FDTD), some of the wave will also "wrap" around the domain, appearing at the opposite side.
One way to simulate propagation in a tube with partially reflecting boundaries might be to define a tube or cylinder through the middle of the domain when you define the material properties. You could then adjust the ratio of the impedance inside and outside the tube to get the reflection coefficient you desire. If you leave the PML as is, the waves that are transmitted outside the tube will propagate off into free space.
Posted 11 years ago # -
Thank you Brad. I will model it this way.
Posted 11 years ago # -
Posted 10 years ago #
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Dear Brad,
I am simulating an array of transducers over human head and I need to change the boundry condition to spherical. In other words, I require that transducers only transmit in the radial direction toward centre of the sphere and no wave is propagated outside.
This necessitates to place them inside a spherical surface of PML which prohibits them from transmitting / radiating toward outside.I wonder if such modification of PML is possible or there is an alternative solution.
Kind regards,
MaryamPosted 7 years ago # -
Hi Maryam,
Why does the PML need to be spherical? If the medium is homogeneous on the outside of the array, the waves will propagate outwards and be absorbed when they reach the edge of the domain. This will be the same as if the PML surrounded the transducer. If you are worried about visualisation, you could mask out the outward travelling waves in your plots.
Brad.
Posted 7 years ago #
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