A Comparison of Numerical Techniques for the Study of Lightning Indirect Effects

A comparison of various numerical tools and techniques was performed for calculating the lightning indirect effects to composite structures and internal systems. This paper is a summary of the initial comparison results. Detailed results of each technique considered are given in additional separate papers presented during this conference. The modeling considered current distributions over and within composite surfaces and the coupling of current and voltages to internal systems such as wire bundle cables and hydraulic and fuel tubes. The models were compared to each other and to measured data from low level swept continuous wave (LLCW) tests performed on two test fixtures. Other features of the codes such as run time, ease of use, computer requirements, availability of documentation and technical support, etc. are compared as well.

The EM analysis techniques that were compared included finite difference time domain (FDTD), finite difference frequency domain (FDFD), wire grid method-of-moments (MOM), boundary element method (BEM), a lumped element transmission line model, and a low frequency resistive-inductive method-of-moments model(MOM). The codes employed were a combination of Boeing in-house tools and commercially available software. Each code was run modeling two separate test fixtures using similar parameters including dimensions and material electrical properties. The first test fixture consisted of a 3-bladed graphite skin panel with an aluminum tube running between the blades. The second test fixture was the outboard section of a graphite composite wing-box with various tube and wire runs installed internally. The wing-box also had five apertures on one side. Comparisons of the results between the different model approaches and between selected test-point measurements are discussed.