Abstract
Maxwell’s partial differential equations of electrodynamics formulated in the late
nineteenth century represent a fundamental unification of electric and magnetic fields,
predicting electromagnetic propagation phenomena. Up to now researchers worldwide
use computers ranging from simple desktop machines to massively parallel
supercomputing arrays to obtain solutions of these equations for the purpose of
investigating electromagnetic wave guiding, radiation and scattering.
Analytic solutions were, first, introduced. However, they are limited to specified
geometrical structures. Numerical solutions were, afterwards, developed to obtain
more accurate solutions to any type of structure. Finite difference time domain
(FDTD) technique is a direct numerical solution method for Maxwell’s time
dependent curl equations. This method employs no potentials. Rather, it is based upon
volumetric sampling of the unknown near-field distribution of fields within and
surrounding the structure of interest. The FDTD technique is a marching in time
procedure that simulates the continuous actual electromagnetic waves in a finite
spatial region by sampled data of numerical analogs propagating in a computer data
space. As the numerical wave propagates, the time is incremented taking into account
the characteristics of the modelled different regions. For simulation, where the
modelled region must extend to infinity, absorbing boundary conditions are employed
at the outer grid truncation planes which ideally permit all outgoing wave analogs to
exit the region with negligible reflection.
In this thesis, a lightning return stroke model is chosen to illustrate an
electrodynamic phenomenon. The lightning channel current is modelled by analytic
approximation in the form of Heidler function taking into account the speed of
propagation and the decreasing amplitude giving an accurate representation of the
phenomenon. Fields radiated by the channel are, then, simulated and calculated
through an FDTD domain code. Hybrid method is used to show the simplicity in
which the FDTD method can be implemented and manipulated with other methods.
Key words: Electrodynamics, Maxwell’s equations, FDTD, lightning strike, hybrid
solution.