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Plane wave scattering by a rigid sphere

Posted Oct 24, 2011, 12:56 p.m. EDT Acoustics & Vibrations Version 4.2, Version 4.2a 2 Replies

Tiago Lobo
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Hi,

I'm trying to model a plane wave scattering by a rigid sphere. The problem is: the wave is travelling in the wrong direction. I set the e_r vector to (0,0,1), so result equation for the traveling wave should be: exp(-i*k*z). Them, the wave should be traveling from +z to -z. The result gives me a wave traveling from -z to +z.

thanks.
2 Replies Last Post Nov 29, 2011, 10:06 a.m. EST
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Hello Tiago Lobo

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Geoffrey Moss
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Posted: 1 decade ago Nov 29, 2011, 9:29 a.m. EST
I have seen similar strange behavior. I believe it has to do with the way they formulate the pressure fields (total vs scattered) and propagate the wave. A Kludgy workaround is to change your vector to (0,0,-1). Unless the 'source' of your wave is not at (0,0,0), then your phasing will be unaffected, and the wave will travel in the correct direction.
I have seen similar strange behavior. I believe it has to do with the way they formulate the pressure fields (total vs scattered) and propagate the wave. A Kludgy workaround is to change your vector to (0,0,-1). Unless the 'source' of your wave is not at (0,0,0), then your phasing will be unaffected, and the wave will travel in the correct direction.
Tiago Lobo
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Posted: 1 decade ago Nov 29, 2011, 10:06 a.m. EST
Reading the documentation I found the reason for this strange behavior. Oddly, they define the time dependence as exp(i*w*t), instead of the usual exp(-i*w*t), which explains the difference.
To compare results using these 2 definitions you just have to take the conjugate of one of the answers. Put the wave to travel in the - direction will make the imaginary part be out of phase.
Reading the documentation I found the reason for this strange behavior. Oddly, they define the time dependence as exp(i*w*t), instead of the usual exp(-i*w*t), which explains the difference. To compare results using these 2 definitions you just have to take the conjugate of one of the answers. Put the wave to travel in the - direction will make the imaginary part be out of phase.

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