Dönüşümsel Elektromanyetik Yaklaşımı ile Dalgalı Deniz Yüzeyi ve Üzerindeki Cisimlerden Saçılma Probleminin Etkin Monte Carlo Simülasyonu

Dalgalı deniz yüzeyi üzerinde bulunan gemi ve aldatıcı gibi cisimlerden saçılan elektromanyetik alana (veya bu alandan türetilen radar kesit alanı parametresine) ait olan istatistiksel özellikler; dönüşümsel elektromanyetik, sonlu elemanlar yöntemi (SEY) ve Monte Carlo yaklaşımları kullanılarak elde edilmiştir. Deniz yüzeyi profili, bir rasgele süreç olarak modellenmiş ve bu sürece ait spektral güç yoğunluğu fonksiyonu kullanılarak deniz yüzeyi profili için örnek fonksiyonlar elde edilmiştir. Her örnek deniz yüzeyi profili için oluşturulan sınır değer problemi, dönüşümsel elektromanyetik yaklaşımına dayanan SEY ile çözülmüş ve bunun sonucunda hesaplanan elektromanyetik alandan radar kesit alanı için örnek fonksiyonları elde edilmiştir. Koordinat dönüşümüne dayanan dönüşümsel elektromanyetik yaklaşımı sayesinde, standart yaklaşımın aksine SEY ağı sadece bir kez yaratılmakta ve bu sayede simülasyon süresi büyük ölçüde azaltılabilmektedir. Bu amaçla, yüzeyin etrafında/üzerinde bir metamateryal katman tasarlanmakta ve katmanla yüzey arasındaki bölge hesaplama bölgesinden çıkarılmaktadır. Monte Carlo ile her bir yüzey için tek bir ağ kullanılmakta ve sadece metamateryal içindeki parametreler değiştirilmektedir.

Anahtar Kelimeler:

Elektromanyetik saçılma, dalgalı deniz yüzeyi, sonlu elemanlar yöntemi, Monte Carlo, dönüşümsel elektromanyetik, koordinat dönüşüm tekniği, metamalzeme

Efficient Monte Carlo Simulation of Scattering from Rough Sea Surfaces with Objects via Transformation Electromagnetics

Statistical properties of scattered fields (or radar cross section values) in electromagnetic scattering from objects (such as ship- and decoy-like objects) on or above random rough sea surfaces are predicted by using transformation electromagnetics, finite element method (FEM) and Monte Carlo technique. The rough sea surface is modeled as a random process and is randomly generated by using the Pierson-Moskowitz spectrum. For each realization of the sea surface, scattered fields and the radar cross section values are computed by combining the FEM and the transformation electromagnetics. The results of a number of realizations are aggregated to model the problem as a random process, and their mean and variance values are determined accordingly. The main purpose of the transformation electromagnetics approach used in this paper is to create a single mesh without repeating mesh generation at each step, and hence, to achieve a great reduction in computation time. A metamaterial medium is introduced above the rough surface, and the region between the surface and the medium is discarded from the computational domain. At each realization, only the material parameters are modified with respect to the geometry of surface without changing the mesh.

Keywords:

Electromagnetic scattering, rough sea surface, finite element method, Monte Carlo, transformation electromagnetics, coordinate transformation technique, metamaterials,

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