i want to simulate the impact of different objects on wave propagation in the free field. A bit like in the "Impedant Sphere" tutorial, only with more complex geometries and from different angles. I also have alpha values as the absorption coefficient of different materials. I'm working with custom boundary conditions.
By studying the PDFs and the forum i got the formula for converting alpha values to Z and from the correlation between gamma and lambda lambda = -gamma(Z/(j rho omega)) i theoretically can get all the values i need.
What confuses me, is the choice of setting re_gamma = -1.0 in the "Impedant Sphere" Tutorial.
My approach would have been setting re_lambda = 1 (Neumann Condition) and calculating the gamma-values from there on, but the results are a bit weird and apparently that's not the way to do it. I tried to 'rebuild' the tutorial with my own aproach for comparsion, but yeah... results don't seem to be right.
Am i missing something or just generally mixing up different problems?
I want to use Acousto for my bachelor thesis, so i'm thankful for every hint.
Anton
Last edit: Anton Hoyer 2021-01-05
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thank you for interest in Acousto. The approach used in the user manual (Section 4.2.3) and in the Tutorials Book (Section 2.5) differ on the physical meaning of the unknown function. In the Useer Manual is the velocity potential, whereas for the impedent sphere tutorial is the pressure. Which approach are you using ?
Umberto
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I figured that out. By substituting 2.5 into 2.3 and comparing with 2.4 i get an equation to calculate gamma/lambda. Quick question: is there a minus sign missing in 2.6? Because the gamma file in the ImpedSphere_PlaneWave folder declares re_gamma = -1.
I attached some screenshots, so maybe you get an idea what went wrong.
As a reference the solution from the tutorial (picture 1). Then the rebuild with the same values of gamma and lambda, only with gmsh-geometry and custombc=2 (picture 2) and finally my first try with lambda=1 and corresponding gamma value (picture 3). The total field on the surface in picture 3 and the resulting solution definitely isn't right, but i don't know why.
Hello,
i want to simulate the impact of different objects on wave propagation in the free field. A bit like in the "Impedant Sphere" tutorial, only with more complex geometries and from different angles. I also have alpha values as the absorption coefficient of different materials. I'm working with custom boundary conditions.
By studying the PDFs and the forum i got the formula for converting alpha values to Z and from the correlation between gamma and lambda lambda = -gamma(Z/(j rho omega)) i theoretically can get all the values i need.
What confuses me, is the choice of setting re_gamma = -1.0 in the "Impedant Sphere" Tutorial.
My approach would have been setting re_lambda = 1 (Neumann Condition) and calculating the gamma-values from there on, but the results are a bit weird and apparently that's not the way to do it. I tried to 'rebuild' the tutorial with my own aproach for comparsion, but yeah... results don't seem to be right.
Am i missing something or just generally mixing up different problems?
I want to use Acousto for my bachelor thesis, so i'm thankful for every hint.
Anton
Last edit: Anton Hoyer 2021-01-05
Dear Anton,
thank you for interest in Acousto. The approach used in the user manual (Section 4.2.3) and in the Tutorials Book (Section 2.5) differ on the physical meaning of the unknown function. In the Useer Manual is the velocity potential, whereas for the impedent sphere tutorial is the pressure. Which approach are you using ?
Umberto
Hello Umberto,
thanks for your quick reply!
I'm using the approach based on pressure.
Anton
OK, thank you. Before going on I just want to be sure that you are not, in fact, misled by a typo before Eq. 2.6.
The line before should read "Substituting into Eq. 2.3 and comparing with 2.4".
Clearer now ?
I figured that out. By substituting 2.5 into 2.3 and comparing with 2.4 i get an equation to calculate gamma/lambda. Quick question: is there a minus sign missing in 2.6? Because the gamma file in the ImpedSphere_PlaneWave folder declares re_gamma = -1.
I attached some screenshots, so maybe you get an idea what went wrong.
As a reference the solution from the tutorial (picture 1). Then the rebuild with the same values of gamma and lambda, only with gmsh-geometry and custombc=2 (picture 2) and finally my first try with lambda=1 and corresponding gamma value (picture 3). The total field on the surface in picture 3 and the resulting solution definitely isn't right, but i don't know why.
Thanks for your help!
Last edit: Anton Hoyer 2021-01-07