Usually, any code performing electromagnetic calculations requires,
as a part of the input, a target model.
In order for a model to be acceptable
to a particular computational software, it must satisfy a set of specific
requirements determined by the design and algorithms of this software.
Some computational systems include components for building target models,
and some assume that the models, in suitable format, must be supplied by
DOVA was conceived and designed to utilize already existing
Such models may be available from an aircraft manufacturer
or a commercial vendor. They may have also been generated with the use
of scanning technology or built with one of the many commercially
available design packages.
Typically, aircraft or other platform models are created by computer
aided design (CAD) software systems which let the user output a representation
of the model in some electronic format, usually, specific for the utilized
In order to exchange information between different CAD systems,
various translators/converters have been developed.
Such translators are
supposed to make a representation developed by one system readable by another
However, such a translation/conversion can be a very complex process
and certain information in this process may be lost or distorted.
as a general rule, it is a good practice to examine the model for consistency
and absence of defects.
In order to make this task easier for the DOVA
user, we identified several very basic requirements that models intended
to be analyzed with DOVA should satisfy.
The following list, broken into two groups, describes these requirements.
The first group consists of requirements that
must be satisfied in order for DOVA to begin and complete execution of
all computational procedures. These requirements are as follows:
The aircraft surface should consist of planar
triangular facets (triangles).
Any pair of surface triangles should either have
no points in common, or have only one common edge, or a common vertex.
Overlaps are not allowed.
Each edge of a surface triangle should be shared
by exactly two triangles.
The aircraft surface must be connected, that is,
on such surface it should be possible to connect any two points with a
continuous curve lying completely on the surface.
The aircraft surface is oriented by the outward
Interior parts, such as chairs, internal walls,
devices, etc. should be removed.
Engine inlets should be closed.
Let l(e) denote the length of an edge e
(the specific units of length are not important). m = min l(e)
and M = max l(e), where the min and max are taken over all
edges on the surface. It is desirable that M/m < 20 and m
Let a(T) and A(T) denote, respectively,
the smallest and the largest angle (in degrees) in a triangle T. Let p
= min a(T) and P = max A(T), where the min and max
are taken over all surface triangles. It is desirable that p > 5
degrees and P < 175 degrees.
A large number of currently available CAD files representing realistic
platform models have the potential of being utilized for electromagnetic
simulations and analyses, possibly after some preprocessing. Model verification
and necessary preprocessing can be accomplished with Matis' specially developed
The second group includes the requirements
8 and 9 below. These are the requirements under which performance of DOVA
is expected to be most efficient in terms of speed and robustness. They
have been developed experimentally, primarily, by testing various components
of DOVA on SGI computers and PC workstations, and from our experience
with other software packages that perform geometric calculations.
Read about GeomFix,
a ToolBox for Evaluating and Fixing Geometry of Surface Models.