  This paper proposes a computational methodology for the integration of
Computer Aided Design (CAD) and the Finite Cell Method (FCM) for models with
"dirty geometries". FCM, being a fictitious domain approach based on higher
order finite elements, embeds the physical model into a fictitious domain,
which can be discretized without having to take into account the boundary of
the physical domain. The true geometry is captured by a precise numerical
integration of elements cut by the boundary. Thus, an effective Point
Membership Classification algorithm that determines the inside-outside state of
an integration point with respect to the physical domain is a core operation in
FCM. To treat also "dirty geometries", i.e. imprecise or flawed geometric
models, a combination of a segment-triangle intersection algorithm and a flood
fill algorithm being insensitive to most CAD model flaws is proposed to
identify the affiliation of the integration points. The present method thus
allows direct computations on geometrically and topologically flawed models.
The potential and merit for practical applications of the proposed method is
demonstrated by several numerical examples.
