Performance of parallel FDTD method for shared- and distributed-memory architectures: Application tobioelectromagnetics

This work provides an in-depth computational performance study of the parallel finite-difference time-domain (FDTD) method. The parallelization is done at various levels including: shared- (OpenMP) and distributed- (MPI) memory paradigms and vectorization on three different architectures: Intel’s Knights Landing, Skylake and ARM’s Cavium ThunderX2. This study contributes to prove, in a systematic manner, the well-established claim within the Computational Electromagnetic community, that the main factor limiting FDTD performance, in realistic problems, is the memory bandwidth. Consequently a memory bandwidth threshold can be assessed depending on the problem size in order to attain optimal performance. Finally, the results of this study have been used to optimize the workload balancing of simulation of a bioelectromagnetic problem consisting in the exposure of a human model to a reverberation chamber-like environment

An Explicit Nodal Space-Time Discontinuous Galerkin Method for Maxwell’s Equations

A novel implicit nodal Space-Time Discontinuous Galerkin (STDG) method is proposed in this paper. An eigenvalue analysis is performed and compared with that for a DG scheme solved with a 4th-Order Runge-Kutta time integrator. We show that STDG offers a significant improvement of dissipative and dispersive properties and allows larger time steps, regardless of the spatial hp-refinement. A domain-decomposition technique is used to introduce an explicit formulation of the method in order to render it computationally efficient.This work is partially funded by the National Projects TEC2010-20841- C04-04, TEC2013-48414-C3-01, CSD2008-00068, P09-TIC-5327, P12-TIC- 1442, and from the GENIL excellence network

Efficient excitation of waveguides in Crank-Nicolson FDTD

In this paper, we present a procedure to calculate the discrete modes propagated with Crank-Nicolson FDTD in metallic waveguides. This procedure enables the correct excitation of this kind of waveguides at any resolution. The problem is reduced to solving an eigenvalue equation, which is performed, both in a closed form, for the usual rectangular waveguide, and numerically in the most general case, validated here with a ridged rectangular waveguide.The work described in this paper and the research leading to these results has received funding from the European Community's Seventh Framework Programme FP7/2007-2013, under grant agreement no 205294 (HIRF SE project), and from the Spanish National Projects TEC2010-20841-C04-04, TEC2007-66698-C04-02, CSD2008- 00068, DEX-530000-2008-105, and the Junta de Andalucia Projects TIC1541 and P09-TIC-5327

An analysis of the Leap-Frog Discontinuous Galerkin method for Maxwell equations

In this paper, we explore the accuracy limits of a Finite-Element Time-Domain 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 Time-Domain methods. A comparison with the Finite-Difference Time-Domain method, in terms of computational cost, is also includedThe work described in this paper and the research leading to these results has received funding from the European Community’s Seventh Framework Programme FP7/2007-2013, under grant agreement no 205294 (HIRF SE project), and from the Spanish National Projects TEC2010-20841-C04-04, CSD2008-00068, and the Junta de Andalucia Project P09-TIC-

Influence of Geometric Simplifications on Lightning Strike Simulations

This paper discusses the influence of simplifications in models used in the design of electromagnetic protection against indirect effects of lightning strikes. A real and complex test case such as the power plant of an A400M aircraft, simulated with the FDTD method, is chosen for this. The parameters studied are the inclusion/removal of installations, modification of electrical contacts, material properties, and changes in the cable characteristics. The simulations performed allow us to quantify the impact of different simplification approaches and, in consequence, to draw conclusions on the relative importance of different model features, being the most important ones to maintain the electrical contacts, to include installations and cables carrying high currents, to consider different materials, to respect the accurate cable routes or to take care of isolated equipment.This work has received funding from the Projects TEC2013-48414-C3-01, TEC2013-48414-C3-2-R, TEC2016-79214-C3-1-R, TEC2016-79214-C3-3-R, and TEC2015-68766-REDC (Spanish MINECO, EU FEDER), P12-TIC-1442 (J. de Andalucia, Spain), Alhambra-UGRFDTD (AIRBUS DS), and by the CSIRC alhambra.ugr.es supercomputing center

Efficient antenna modeling by DGTD

The work described in this article is partially funded by the Spanish National Projects TEC2013-48414-C3-01, CSD2008-00068, P09-TIC-5327, and P12-TIC-1442 and by the GENIL Excellence Network

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 im- proving 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.The work described in this letter and the research leading to these results has received support from the Projects TEC2013- 48414-C3-01 and TEC2015-68766-REDC (MINECO, Spain), P12-TIC-1442 (Junta de Andalucia, Spain), Alhambra-UGRFDTD (AIRBUS DS), and by the CSIRC alhambra.ugr.es supercomputing center

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 Leap-Frog Discontinuous Galerkin method, combined with a local time stepping algorithm, comparing it with the MoM and the (2,2) FDTD methods.The work described in this paper and the research leading to these results has received funding from the European Community’s Seventh Framework Programme FP7/2007-2013, under grant agreement no 205294 (HIRF SE project), and from the Spanish National Projects TEC2010-20841-C04-04, CSD2008-00068, and the Junta de Andalucia Project P09-TIC-

A hybrid Crank-Nicolson FDTD subgridding boundary condition for lossy thin-layer modelling

The inclusion of thin lossy, material layers, such as carbon based composites, is essential for many practical applications 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, and/or large computational costs. This work presents a novel technique for the modeling of thin-layer lossy materials in FDTD schemes which overcomes the instability problem at low computational cost. For this, a 1D-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 3D 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 low frequencies, and late time stability than existing techniques with low computational cost