Electromagnetic Characteristic Analysis of Hypersonic Vehicle Coated With Nonuniform Plasma Sheath Using DTS–LUSGS–FVTD Algorithm

The finite volume time domain (FVTD) method is proposed to accurately calculate the electromagnetic (EM) scattering of hypersonic vehicles coated with non-uniform plasma sheath. The plasma sheath in the actual flight environment is accurately established by solving the Navier–Stokes equations and combining appropriate thermochemical models. The radar cross section (RCS) of metal and uniform medium coated metal targets calculated by FVTD are in good agreement with those simulated by the software FEKO (MoM) and the Mie series. The calculated RCS of the vehicle under the reentry condition is consistent with the flight test data, too. The calculated electron number density distribution is consistent with the flight experiment results. The body fitted structure EM grid is adopted. The EM grid independence of the target coated with plasma sheath is studied. Then, the scattering and plasma EM parameters of the vehicle during the actual reentry are studied. The reentry altitude is from 78 to 55 km, and the reentry velocity is from 6406 to 6350 m/s. With the reentry altitude decreasing, the plasma angular frequency and collision frequency increased gradually. The scattering of different incident conditions and different wall catalytic conditions is analyzed in depth. This paper provides a valuable reference for vehicles' detection, recognition, and stealth during reentry flights.

A rigorous electromagnetic model is developed to predict the radiative properties of patterned silicon wafers. For nonplanar structures with a characteristic length close to the wavelength of incident radiation, Maxwell's equations must be used to describe the associated radiative interaction and they are solved by the unstructured finite volume time-domain (FVTD) method. The basic idea of the FVTD method is to cast the two Maxwell curl equations in a conservative form, and then treat the six scalar components of the electromagnetic fields as conserved quantities via a finite volume approach. In the die area, only one period of the structure is modeled due to its periodicity in geometry. To truncate a computational domain in an open space, the Mur boundary condition is applied to absorb outgoing waves. With the steady state time-harmonic electromagnetic fields known, the Poynting vector is used to calculate the radiative properties. To validate the present model, a wave scattering problem from a cylinder is first considered and the predicted results are found to be essentially identical to the analytical solution. After that, radiative interactions with a nonplanar structure and a patterned wafer consisting of the periphery and die area are investigated, and predicted reflectivities and absorptivities are found to match other available solutions very well, indicating that the present finite volume approach in the time domain is accurate to predict radiative interaction with microstructures.

The Finite Volume Time-Domain (FVTD) method flnds limited application in the simulation of electromagnetic scattering from electrically large scatterers because of the flne discretization required in terms of points-per-wavelength. An e-cient implementation of a higher-order FVTD method is proposed for electrically large, perfectly conducting scatterers. Higher-order and flne-grid accuracy are preserved, despite using only a flrst-order spatial accuracy and a coarse grid in substantial parts of the FVTD computational domain, by partially incorporating a time-domain Physical Optics (PO) approximation for the surface current. This can result in considerable savings in computational time while analyzing geometries containing electrically large, smooth sections using the FVTD method. The higher-order FVTD method in the present work is based on an Essentially Non-Oscillatory (ENO) reconstruction and results are presented for two-dimensional perfectly conducting scatterers subject to Transverse Magnetic (TM) or Transverse Electric (TE) illumination.

In this paper, the finite volume time domain (FVTD) semi-discrete formulation, discrete in the space and continuous in the time, is derived for the electromagnetic field simulation, starting from the Maxwell's equations. The time marching schemes that can be employed to turn this into discrete system of equations are presented. The discrete formulation is used to explain variations in FVTD methods e.g., methods which differ in spatial approximation. For a given problem, numerical methods anticipate the convergence of the solutions towards the reference (analytical) solution as the grid is refined. The convergence order for various FVTD methods is presented in different scenarios and compared with that of finite integration technique (FIT) and finite element method (FEM).

Chapter 9 - Finite-Volume Time Domain Method

In this work, the finite volume time domain semidiscrete formulation, discrete in the space and continuous in the time, is derived starting from the Maxwell's equations. This formulation is used to explain variations in finite volume time domain methods e.g., methods which differ in spatial approximation. The time marching schemes that can be employed to turn these semidiscrete formulations into discrete systems are presented. For a given problem, numerical methods anticipate the convergence of the solutions towards the reference (analytical) solution as the grid is refined. But the convergence rate or order depends on the details of the computational domain. The convergence order for various finite volume time domain methods is presented in different scenarios e.g., a computational domain with curved surface and a singularity in the field due to the geometry. It is a well known fact that the numerical solvers facilitate efficient design of passive microwave components by tendering the scattering parameters. Obtaining the scattering parameters using finite volume time methods is illustrated in this work along with the difficulties involved in the process. The solutions obtained for various applications e.g., a coaxial cable with a very high contrast of materials, are bidden against the solutions obtained from the finite integration technique and the finite element method. The development cycle of a finite volume time domain solver is portrayed. Various modules are explained in detail along with assorted libraries employed in the solver. The computational cost, more specifically the floating point operations for various finite volume time domain methods are limned. This work investigates the surmise of superior capabilities of finite volume time domain methods in the computational electromagnetics rigorously on both structured and unstructured grids.

Adapted from 'Computational Fluid Dynamics', Finite Volume Time Domain (FVTD) method is becoming increasingly popular in 'Computational Electromagnetics'. The focus of this paper is on the convergence analysis of different FVTD methods on tetrahedral and hexahedral meshes. Other aspects like implementation techniques, CPU time and memory are also furnished.

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This paper introduces a new generalized local time-step scheme to improve the computational efficiency of the Finite-Volume Time-Domain (FVTD) method. The new approach exploits the advantages of the FVTD method to use unstructured meshes (which allow inhomogeneity of cell densities) for large electromagnetic circuits with fine structural details and at the same time avoids the disadvantage of using a single time step determined by the smallest cell dimensions in the entire mesh. To illustrate this new scheme a large double-ridged horn antenna excited by a finely resolved coaxial feed is analyzed demonstrating a significant speed-up of the computation.

This paper is concerned with the numerical simulation for the electromagnetic (EM) scattering by a rough surface at a low grazing angle. First scattered electromagnetic fields are computed by the finite volume time domain (FVTD) method, second the field data in the time domain are converted to those in the spectral domain by the discrete Fourier transform (DFT), and finally far fields are computed by use of the Kirchhoff-Huygense theorem. The numerical results are compared with those obtained by other methods as well as with the experimental data.

Discontinuous Galerkin time domain (DGTD) offers attractive properties when it is applied to solve Maxwell's equations. The DGTD method is originated from the finite volume time domain (FVTD) and finite element method (FEM), and has the advantages of the two methods; furthermore, it is more flexible and accurate, and provides an embarrassingly parallel characteristic than FVTD and FEM. In this chapter, we introduce the basic concept of parallel DGTD method based on message passing interface (MPI) and graphics processing unit (GPU) based thread and memory access coalesced. The parallel DGTD method is then applied to solve the typical engineering problems. The numerical results demonstrate that the DGTD method is accurate and efficient for general electromagnetic problems.

Radio waves propagating through tunnels are strongly attenuated in the presence of discontinuities such as bends and branches. The useful structural modifications are requested to get better circumstances for radio waves in tunnels. In this paper, we propose several modifications arranged in a conventional T-junction of two-dimensional tunnels and analyze the transmission characteristics of radio waves by using the finite volume time domain (FVTD) method.

The presently well known Finite Volume Time Domain (FVTD) method is a powerful computational simulation technique in electromagnetism. Despite the fact that the temporal approach can be used for single-frequency as well as for wideband illumination studies, solving the Maxwell equations directly in the frequency domain is attractive (for example for RCS, problems with dispersive media, skin effect). In this paper, we propose a Frequency-Domain Finite Volume method based on the same scheme developed for the FVTD.

Finite Volume Time Domain modelling of microwave breakdown and plasma formation in a metallic aperture

In this paper an accurate analysis of two-dimensional (2D) Photonic Crystal (PhC) based multimode resonant cavities is carried out. The analysis is performed with a robust and accurate Finite Volume Time Domain (FVTD) technique. The analysis proves the ability of the FVTD method to extract different resonant modes from a multimode PhC resonant cavity with the use of appropriate source profiles. A detailed explanation on how the source is engineered and used to excite different modes is given. Furthermore, parameters such as resonant frequency and quality factor for each resonant mode are accurately calculated.