Abstract:
Flying an aircraft in icing conditions may seriously degrade its aerodynamical performance
and threaten the flight safety. Over the years, new technologies and improved
procedures have limited the potential risks caused by aircraft icing. Experimental
studies being very expensive, numerous computer codes have been developed to
simulate ice shapes and tackle the problem. Typically in these codes, a flow solution
and key icing parameters are evaluated around a clean un-iced geometry and
their values remain constant during the entire simulation. This approach may be
acceptable for short exposure times or when the ice shape only slightly deforms the
initial geometry. However, in other cases, the values of the icing parameters may
vary and the simulation will loose its accuracy: for large shapes, the presence of
the ice influences the surrounding airflow significantly, altering the value of icing
parameters and ultimately the ice accretion. Calculating more accurate ice shapes
therefore requires to periodically recompute the flow field around the body during
the simulation and determine updated values for icing parameters. This procedure,
known as multi-stepping, is investigated in this thesis and adapted to the new threedimensional
icing code ICECREMO2. Several multi-step algorithms are presented
and tested on cylinders and airfoils. When possible, the ice shapes simulated are
compared with experimental results.
The first multi-step calculations were generally performed manually. The user
had to perform a rather tedious work and inappropriate instructions could lead to
severe inaccuracies in the simulations. To avoid these difficulties, a fully automated
procedure will be developed including all stages of a multi-step computation. This
significantly reduces user interaction and the overall computing time.
The present research work forms part of the ICECREMO2 project. ICECREMO2
is a three-dimensional ice accretion and water flow code developed collaboratively
by Airbus UK, BAe Systems, Dunlop Aerospace, Rolls-Royce, GKN Westland Helicopters,
QinetiQ and Cranfield University under the auspices of the UK Department
of Trade and Industry.
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