Domain Decomposition Method Of Hybrid Finite-Element/Boundary-element Formulation For Electromagnetic Characteristics Of Complex Targets

With the improvement of computer capability,the modern electromagnetic simulation calculation target is developing from component level to system level,and complex aircraft whole aircraft system level simulation has been the key difficulty in engineering electromagnetic calculation.Whole aircraft system-level targets usually contain metal-medium composite structures,such as complex antenna arrays and large metal platforms.Such complex models are often very difficult to construct integrated meshes for electromagnetic calculations.System-level targets need to be optimized to adjust the local structure when facing repeated modeling and meshing problems,which is very time-consuming,reducing the manual intervention of electromagnetic calculation methods are of great interest.At the same time,the complex materials also develop from isotropic to anisotropic or artificial materials such as frequency-selective surfaces,which are difficult to handle efficiently by traditional computational methods.In the face of different application scenarios,electromagnetic computation has developed in the direction of customization,efficiency and accuracy.In this dissertation,a series of researches are carried out to address the scientific problems faced by the target in complex whole aircraft target EM simulation calculation such as integration mesh is difficult to generate,repeated adjustment of local structure is very timeconsuming,complex anisotropic medium metal composite structure is difficult to handle,and multi-scale calculation is difficult to converge.In this dissertation,based on the non-conformal domain decomposition method,the model which is difficult to generate the mesh integrally is divided into different subdomains,and different customized electromagnetic calculation methods are used for different subdomains to study.It enables the electromagnetic calculation to obtain efficient and accurate results.In response to numerical simulation examples that require local structural adjustments in engineering,resulting in time-consuming repetitive modeling,this dissertation investigates an embedded finite element domain decomposition method(EDDM)for simplifying repetitive modeling and partitioning.The EDDM to simplify repetitive modelling and dissection is developed by separating the local structure that needs repetitive modelling from the overall structure.The part that does not need to be modified in the whole problem is divided into background subdomain.The local structure that needs to be adjusted,replaced,moved and rotated is set as embedded subdomains.The embedded subdomains and background subdomain ensure the continuity of electric field and current through Robin transmission conditions,volume equivalent source,port equivalent source,etc.The wave equation and boundary conditions of each subdomain are determined according to the uniqueness theorem so that the solution results are consistent with the original physical problem.This method can effectively save mesh reconstruction time for problems that require local adjustment and multiple modeling.For the difficulty of integrated simulation of new electrically large anisotropic materials,this dissertation studies the anisotropic domain decomposition method(ADDM).This method starts from the anisotropic Maxwell equations and the constitutive equation of the medium.It modifies the wave equation in each subdomain into an anisotropic equation.The transmission conditions in different subdomains are derived again according to the difference between the anisotropic and mono-isotropic mediums.Anisotropic Robin transmission conditions,volume equivalent source and port equivalent source transmission conditions are obtained.Numerical examples show the method’s accuracy in dealing with anisotropic problems.In response to the simulation problem of increasing modeling time due to local adjustment of patch frequency selection surface in multi-layer media,this dissertation further proposes an embedded finite element domain decomposition method of inhomogeneous background(EDDM-IM)media based on the EDDM.The EDDM-IM studies the problem that the buffer region of the original EDDM cannot cross the interface of inhomogeneous layered media.Therefore,a simple buffer region method(SBRM)and a more advanced adaptive buffer region method(ABRM)are proposed.The ABRM allows the buffer region to exist in any inhomogeneous background medium by adding supplementary sources and modifying the coupling equation.Furthermore,an inheritance calculation method is proposed,which can save a lot of time in solving the multi-step embedded object rotation and translation problem by combining the ABRM.For the time-consuming problem of repetitive modeling of radiation and scattering in complex multi-scale models,this dissertation proposes a multi-domain and multisolver method(MDMSM).The MDMSM is a hybrid method based on the domain decomposition framework,which is compatible with the embedded and non-embedded FEM-DDM and the boundary element domain decomposition method(BEM-DDM).This method can flexibly select the appropriate partition and calculation methods for various solution scenarios.The subdomain solution is calculated by choosing the most suitable DDM for sub-coupling calculation,and different transmission conditions are used for calculation between different subdomains.In multi-step scene calculation,the proposed superimposed inheritance calculation method can be combined to save calculation time further.This dissertation applies it to the simulation of the embedded antenna array structure in complex multi-scale aircraft targets,and the practicability and effectiveness of the method are proved.