Abstract:
Over the past few decades, aircraft icing has been the subject of numerous studies. Ice
accretion on an aircraft can damage its aerodynamic performance. It can also have a devastating
affect on structures such as high voltage pylons. The simulation of ice accretion
represents an important technological breakthrough in the understanding of ice behaviour
as well as an alternative to expensive experiments. Although numerical models will probably
never replace wind tunnel experiments, they continuously progress and benefit from
the latest advances in computing techniques. ICECREMO2 is a new generation model
and uses an unstructured grid approach. Unstructured meshes offer real advantages in
the generation of complex grid structures but also provide support for grid adaptivity.
Adaptivity consists in improving the resolution only in some aspects of the solution. It
offers the benefits of the high resolution without the computational overhead of classical
structured methods. Adaptive methods are usually more difficult to implement and the
application to the equation coupling water film and ice growth has never been investigated
before this work.
The mathematical model used in ICECREMO describes both the water film
flow and the
ice growth. This allows us to better predict glaze ice accretion when a runback water
film is present. The equation describing the thin film water
flow is a complex non-linear
fourth-order degenerate partial differential equation. To resolve complex features such
as a moving front, high resolution numerical methods are necessary. Such a numerical
scheme has been developed for this equation in a previous study on structured grid, and
has proven to be reliable. In this work Sweby's scheme has been reformulated in a finite
volume framework, an error estimator has been de ned for our adaptive mesh refinement
method and a grid refinement strategy has been implemented which follows the water film
front and keeps it under high resolution.
Finally, the impact of the improved resolution of the water film on the glaze ice growth
is investigated. Results obtained with first-order and high resolution methods have been
compared on different model problems under various conditions. At the end an extension
of the refinement strategy is proposed by defining error estimators with respect to the ice
layer and by combining it with a multi-step procedure.