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A finite element discretization of the standard parabolic equation in generalized boundary fitting coordinates

Kampanis, Nikolaos A, Delis Anargyros, Antonopoulou D.C., Kozyrakis G.

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URI: http://purl.tuc.gr/dl/dias/CE246EDE-494C-4EEC-AACD-F2C861FC874C
Year 2013
Type of Item Peer-Reviewed Journal Publication
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Bibliographic Citation N. A. Kampanis, A. I. Delis, D. C. Antonopoulou and G. Kozyrakis, "A finite element discretization of the standard parabolic equation in generalized boundary fitting coordinates," Appl. Num. Math., vol. 67, pp. 152-166, May 2013. doi:10.1016/j.apnum.2011.05.005 https://doi.org/10.1016/j.apnum.2011.05.005
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Summary

A simplified, but quantitatively reliable approximation of atmospheric sound propagation is given by the standard parabolic equation. The waveguide is a cylindrically symmetric, unbounded, domain with an irregular lower boundary. The associated initial-boundary value problem uses a mixed-type boundary condition along the lower boundary and a nonlocal, absorbing boundary condition of the DtN (or NtD) type, applied on an artificial upper boundary. Exterior wave fields of a constant index of refraction and a linear, when squared (as function of height) one, are considered. The physical, complex waveguide reduces to an orthogonal computational domain by the means of a numerical transformation to generalized coordinates, fitting the lower, irregular boundary. The technique presented is of practical interest for its proper handling of complex ground topographies; it is interfaced with a mesh generator and processes the topographic data retrieved from a geographic information system, hence the transformation of coordinates is computed numerically. The transformed initial-boundary value problem (on the orthogonal computational domain) is discretized by the Crank–Nicolson in time and a continuous, piecewise linear finite element method in space. The propagation of cylindrically symmetric sound waves over a complex terrain, emitted to the atmosphere by a harmonic source, has been studied. The effectiveness of the numerical method introduced, is exploited on several test cases.

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