Solvers for the Maxwell equations: application the determination of the radar signature of modern fighter aircraft

Pim Hooghiemstra

Site of the project:
National Aerospace Laboratory NLR
NLR Amsterdam
Anthony Fokkerweg 2
1059 CM Amsterdam

This master project has been the motivation of the poster for the celebration of our 50 year old applied mathethematical curriculum at the TU Delft.

start of the project: January 2007

In April 2007 the Interim Thesis has been appeared and a presentation has been given.

The Master project has been finished in October 2007 by the completion of the Masters Thesis and a final presentation has been given.

For working address etc. we refer to our alumnipage.

Summary of the master project:
Radar cross section prediction techniques are used to determine the radar signature of a military platform (for example an aircraft, ship or tank) when the radar signature can not be determined experimentally, because the platform is not available or for reasons of time and cost.

F16 Fighter Jet

For classic jet aircraft the radar cross section for forward observation angles is dominated by the contribution of the open ended cavity formed by the jet engine air intake and compres- sor fan. This cavity is characterized by its large depth (L/d > 3), curved centerline and nonuniform cross section, for which the scattering characteristics can not by analyzed by approximate high frequency methods. Jin et al. have published a numerical method based on a higher order finite element discretisation of the Maxwell equations, where the re- sulting linear system is solved by means of a frontal solution method. The method takes full advantage of the topology of the cavity scattering problem and has been successfully applied for the analysis of cavities of intermediate size. In van der Heul etal. an adaptation of their algorithm is discussed that can efficiently compute the electric field scattered by very large cavities, in particular the jet engine air intake cavity for X-band radar frequencies (10 GHz=0.03m).

Air intake and compressor

In this master thesis project a faster and more memory efficient method is looked after. Possibilities are faster direct solvers, parallel computing, domain decomposition, shifted preconditioners combined with Krylov subspace methods, etc.

Tetrahedral grid of a jet engine air intake

## Contact information: Kees Vuik

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