Accurate solving of aeronautic EMC problems with Conform-FDTD method – CONFORME2

Aeronautic modeling is largely used by industrial group already at the design phase since two decades. It deals with different ElectroMagnetic Compatibility (EMC) qualifications for the lightning effects and High Intensity Radiating Field (HIRF). Various numerical methods are often needed to study whole structure complexity, cables topology, electronic system and communication antennas. The finite difference time domain method (FDTD) is a versatile approach able to carry out global simulation of an airplane including a complex topology of cable. Hence, hybridization is done between 3D finite difference solving, 1D thin oblique wire solving and lumped circuit element, the whole in a unique solver. Comparing to alternative approach such as the integral equation or the finite element, the FDTD method keeps the same order of computational and memory costs when the density or the complexity of a structure increases and, moreover, the cables treatment does not exhibit a sensible impact on these costs. This method is therefore very attractive for internal airplane problem. Besides, its frequency wideband solving and its temporal approach are major assets for EMC studies. The FDTD method can be parallelize with Message Passing Interface (MPI) allowing us to solve large problem by using thousands of cpus that is the case of XLIM solver TEMSI-FD used by Dassault Aviation since about eight years to study lightning and HIRF effects on their aircrafts.
The initial project called ANR ASTRID CONFORM solved the constraint of the staircasing inherent to the FDTD method by the development of conform meshing and solver. Various FDTD conform techniques have been studied leading to the realization of a general FDTD conform solver with cell multi-region. Moreover, the thin oblique wire formalism has been extended to none uniform Cartesian grid for the first time with the same ability and consistency as in a uniform grid. However, the extension of the wire formalism in conform cell don’t operate correctly despite a strong development on this approach for several reasons explained in this maturation project. That’s why we find this problematic in the core of this project with a new approach and with good hindsight to better progress in this complex problem of consistency in wire / conform cell coupling.
The maturation project CONFORME2 grows in TRL scale for all the problematic of modeling external and internal aircraft assemblies by proposing some original developments covering the conform FDTD solver, the conform meshing and software of pre- and post-processing inherent to the conform method. The aim is to take into account all the geometry complexity as well as the constitutive electromagnetic properties of materials (especially the finite conductivity) while the initial project focuses on perfectly conductive curved surface only. The operating validation of tools for EMC studies on aircraft will be carried out by Dassault Aviation that has large internal experience, many electromagnetic aircraft model and a database of results both on lightning effects and HIRF constraints.