Archives of Acoustics,

**25**, 3, pp. , 2000### Factors that influence the calculation of acoustic scattering by the method of source simulation

In this work the source simulation technique was used to

calculate the scattering of a plane wave by a cylinder with radial or elliptical

transverse section. The basic idea of the source simulation technique is to

replace the scattering (or radiating) body with a system of simple sources

located within the envelope of the scatterer (or radiator). The extent to which

the simulated field reproduces the original one depends on the degree of

correspondence between the simulated and the given boundary conditions.

Numerical simulations have shown that: 1) the shape of the auxiliary surface; 2)

the number of sources, and 3) the way the sources are distributed are the most

relevant parameters to ensure an accurate solution of the problem. In the case

of the single-layer method, the sources should not be positioned close to the

surface or to the center of the body, because the problem becomes

ill-conditioned. The auxiliary surface and the acatterer should be as similar as

possible in order to minimize the boundary error. With respect to the number of

sources (N), there are two opposite effects: 1) if (N) is too

small, the sound field is not reproduced accurately; 2) if (N) is too

large, the computing time increases and the solution accuracy decreases. The

method breaks down when the excitation frequency coincides with the

eigenfrequenciec - a narrow range of frequencies - of the space formed by the

auxiliary surface. As the auxiliary surface is frequently represented by simple

surfaces (cylinder, sphere), one can easily calculate the eigenfrequencies and

therefore avoid them.

calculate the scattering of a plane wave by a cylinder with radial or elliptical

transverse section. The basic idea of the source simulation technique is to

replace the scattering (or radiating) body with a system of simple sources

located within the envelope of the scatterer (or radiator). The extent to which

the simulated field reproduces the original one depends on the degree of

correspondence between the simulated and the given boundary conditions.

Numerical simulations have shown that: 1) the shape of the auxiliary surface; 2)

the number of sources, and 3) the way the sources are distributed are the most

relevant parameters to ensure an accurate solution of the problem. In the case

of the single-layer method, the sources should not be positioned close to the

surface or to the center of the body, because the problem becomes

ill-conditioned. The auxiliary surface and the acatterer should be as similar as

possible in order to minimize the boundary error. With respect to the number of

sources (N), there are two opposite effects: 1) if (N) is too

small, the sound field is not reproduced accurately; 2) if (N) is too

large, the computing time increases and the solution accuracy decreases. The

method breaks down when the excitation frequency coincides with the

eigenfrequenciec - a narrow range of frequencies - of the space formed by the

auxiliary surface. As the auxiliary surface is frequently represented by simple

surfaces (cylinder, sphere), one can easily calculate the eigenfrequencies and

therefore avoid them.

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