Miguel Ruiz Cabello

HIRF Virtual Testing on the C-295 Aircraft: On the Application of a Pass/Fail Criterion and the FSV Method

In this paper, we show the application of numerical simulation for the virtual testing of a very complex system under high-intensity radiated fields (HIRF) conditions. Numerical results have been compared to measurements performed on a C-295 aircraft. The approach is based on the use of multiple tools for the preprocessing, computation, and postprocessing, all of them integrated under the same framework. This study is a part of the HIRF SE project, and the final step for the validation of the tools involved there, to introduce the use of simulation in the whole aircraft certification process in an HIRF environment. The main goal of the project is to provide the aeronautic industry with a numerical modeling computing framework, which could be used to predict the electromagnetic performance, and to carry out parametrical studies during the design phase, when changes are simpler and less costly. It could also lead in the future to a considerable reduction on the certification/qualification testing phase on air vehicles, to cross validate the results obtained from measurement and simulation providing best confidence in them, and to attain a more exhaustive analysis to achieve a higher level in the air vehicle safety.

A Leap-Frog Discontinuous Galerkin Time-Domain Method for HIRF Assessment

In this paper, we demonstrate the computational affordability and accuracy of a leap-frog discontinuous Galerkin (LFDG) time-domain method for high intensity radiated fields assessment in electromagnetic compatibility for aerospace. The conformal truncation of the computational domain is discussed and formulated in the LFDG context. Numerical validations are performed on challenging test cases, in comparison to measurements and to other numerical methods, demonstrating the accuracy, efficiency, and scalability of the algorithm.

On the Design of Aircraft Electrical Structure Networks

As part of the technology research engaged in the EU Clean Sky 1 project, we present in this paper an electrical structure network (ESN) designed to prevent the impact on an electronic equipment of unwanted voltage drops appearing when nonmetal composite materials are used for grounding. An iterative process has been followed to reach an optimal tradeoff solution meeting all the aircraft requirements: structural, safety, low weight, electrical, etc. Guidelines on the design of a low-impedance metal ESN, to minimize the inductive behavior of the power distribution network, are outlined in this paper. To this end, we employ the UGRFDTD simulation tool, combining finite-difference time domain to analyze the general EM problem, and a multiconductor transmission-line network to handle internal coupling between cables running along coinciding routes. The capability of this tool to create time-domain snapshots of surface currents is shown to provide a useful way to optimize the ESN, thanks to the insight gained on the physics of the problem.

An Analysis of the Leap-Frog Discontinuous Galerkin Method for Maxwell's Equations

In this paper, we explore the accuracy limits of a finite-element time-domain (TD) method applied to the Maxwell equations, based on a discontinuous Galerkin scheme in space, and a leap-frog temporal integration. The dispersion and dissipation properties of the method are investigated, as well as the anisotropy of the errors. The results of this novel analysis are represented in a practical and comprehensible manner, useful for the application of the method, and for the understanding of the behavior of the errors in discontinuous Gelerkin TD methods. A comparison with the finite-difference TD method, in terms of computational cost, is also included.

A Hybrid Crank–Nicolson FDTD Subgridding Boundary Condition for Lossy Thin-Layer Modeling

The inclusion of thin lossy material layers, such as carbon-based composites, is essential for many practical applications for modeling the propagation of electromagnetic energy through composite structures such as those found in vehicles and electronic equipment enclosures. Many existing schemes suffer problems of late time instability, inaccuracy at low frequency (LF), and/or large computational costs. This paper presents a novel technique for the modeling of thin-layer lossy materials in finite-difference time domain (FDTD) schemes, which overcomes the instability problem at low computational cost. For this, a 1-D subgrid is used for the spatial discretization of the thin-layer material. To overcome the additional time-step constraint posed by the reduction in the spatial cell size, a Crank–Nicolson time-integration scheme is used locally in the subgridded zone, and hybridized with the usual 3-D Yee-FDTD method, which is used for the rest of the computational domain. Several numerical experiments demonstrating the accuracy of this approach are shown and discussed. Results comparing the proposed technique with classical alternatives based on impedance boundary condition approaches are also presented. The new technique is shown to have better accuracy at LFs and late time stability than existing techniques with low computational cost.

DGTD for a Class of Low-Observable Targets: A Comparison With MoM and (2, 2) FDTD

The simulation of low-observable targets requires high accuracy, both in the geometrical discretization as well as in the numerical solution of the electromagnetic problem. In this letter, we employ the well-known NASA almond to illustrate the accuracy of the leapfrog discontinuous Galerkin method, combined with a local time-stepping algorithm, comparing it to the method of moments (MoM) and the (2, 2) finite-difference time-domain (FDTD) methods.

SIVA UAV: A Case Study for the EMC Analysis of Composite Air Vehicles

The increased use of carbon-fiber composites in unmanned aerial vehicles is a challenge for their EMC assessment by numerical solvers. For accurate and reliable simulations, numerical procedures should be tested not only for individual components, but also within the framework of complete systems. With this aim, this paper presents a benchmark test case based on experimental measurements coming from direct-current injection tests in the SIVA unmanned air vehicle, reproduced by a numerical finite-difference-time-domain solver that employs a new subgridding scheme to treat lossy composite thin panels. Validation was undertaken by applying the feature selective validation method, which quantifies the agreement between experimental and numerical data.

A New Efficient and Stable 3D Conformal FDTD

A novel conformal technique for the FDTD method, here referred to as Conformal Relaxed Dey-Mittra method, is proposed and assessed in this letter. This technique helps avoid local time-step restrictions caused by irregular cells, thereby improving the global stability criterion of the original Dey-Mittra method. The approach retains a second-order spatial convergence. A numerical experiment based on the NASA almond has been chosen to show the improvement in accuracy and computational performance of the proposed method.

Face centered anisotropic surface impedance boundary conditions in FDTD: Improved performance of staircased mesh for shielding problems

We present a new face centered approach to the collocation of the fields for the application of a surface impedance boundary condition (SIBC). This approach deals with the ambiguities in the surface normal that arise at the edges on stair-cased surfaces.. The accuracy of the new scheme is compared to edge based and conformal approaches using both planar sheet and spherical shell test cases. Stair-casing effects are evaluated and the face-centered scheme exhibits significantly less error than the edge based approach.

A new FDTD subgridding boundary condition for FDTD subcell lossy thin-layer modeling

In this work we present a novel algorithm based on a subgridding boundary condition, for the subcell treatment of conductive thin-layer in FDTD (SGBC). We show that this technique provides a robust late-time stability behavior, compared to classical impedance boundary condition (IBC) methods, with affordable computer requirements. The method is validated by means of high-frequency scattering problems as well as with low-frequency transfer impedance prediction of tubular shells.