Investigation On The Electromagnetic Scattering From Electrical Large Size Rough (sea) Surface And Parallel Acceleration Technique

Research on electromagnetic(EM)scattering of three-dimensional(3-D)sea surface is of great interest in both civilian and military applications.And there still exists many problems about EM scattering from 3-D electrical large size sea surface.Firstly,the increase of incident frequency will arise a huge computational burden,therefore how to realize the fast EM scattering modeling and keep a good computational accuracy is still a great challenge.Secondly,overturning wave crest is a kind of nonlinear sea wave,while the problems is that there isn't an efficient modeling method to construct profiles of the sea wave in the overturning wave crest zone.Thirdly,sea spikes is a key point in the study of sea clutter.Besides,further investigation should be carried on the physical mechanism of the sea spikes.Breaking wave is considered as a main reason to the sea spikes,which always occurred in the overturning wave crest zone.However,the profiles of overturning vary during the generation process,which makes it more complicated.In addition,the desert terrain is a special rough surface,whose scattering characteristics is of great importance to the prediction of sand storm as well as control and prevents from the sand.The main works focus on the study of scattering characteristics from the 3-D electrical large size sea surface and parallel accelerated technique,including the construction of an accelerated scattering model of the 3-D electrical large scale sea surface and 3-D local sea surface with overturning wave crest,which is with emphasis on the fast computation of characteristic analysis as well as the physical mechanism of sea spikes.Meanwhile,the barchan is simulated,and the corresponding scattering characteristics is also studied.The main works are as followed: 1.An accelerated ray tracing method based on two-scale model(TSM-RT)is proposed for the analysis of scattering characteristics from 3-D electrical large size sea surface.Compared with the traditional accelerated ray tracing method,the number of initial rays and intersections between rays and facets are decreased efficiently in the TSM-RT method,hence the computational time is also decreased,further improving the efficiency of performance.2.An parallelized TSM-RT method based on CUDA is improved according to the features of TSM-RT method and GPU framework.Each ray is traced independently,then a GPU thread can represent a ray,and all rays are traced for parallel computing.Due to the great parallel computational capability of GPU,the computational time is dramatically decreased.Moreover,the asynchronous transfer and shared memory are used to further improve the speedup factors.The parallelized TSM-RT method is utilized to calculate the scattering problems from 3-D electrical large size sea surface,and the influence of block size,stream number and optimization techniques on the computational time is discussed.3.An 3-D time-varying overturning wave crest model is constructed based on the corresponding 2-D model,whose length and height are related to the wind speed.A 3-D local sea surface with overturning wave crest model is further modeled by combing the overturning wave crest with sea surface,and this model is a basic model to describe the profiles of overturning wave crest zone.Meanwhile,the back scattering characteristics of the 3-D local sea surface with overturning wave crest with different wind speed and overturning wave crests are calculated by the Integral Equation Model(IEM).Beside,the physical mechanism of sea spikes is also discussed.4.An improved 3-D local sea surface with overturning wave crest model is presented.The small roughness of the 3-D overturning wave crest model is modulated by the variation of the sea surface in the surf zone and assume that the sine wave is utilized to model the boundary between sea surface and overturning wave crest.Then a parallel IEM based on CUDA is proposed to accelerate the computational efficiency.The back scattering characteristics of the improved 3-D local sea surface with overturning wave crest is analyzed and the influence of sea surface size on the scattering results is discussed.5.Desert terrain is modeled,and a single barchan is simulated on the basis of wind-blown theory.Then IEM is adopted to analyze the scattering characteristics of the barchan,as well as the influence of the geometric structure of different slopes on the scattering results.