New Aerodynamic Aspects of Aircraft De/Anti-icing fluids

This dissertation belongs to the research areas of aerodynamics and fluid dynamics. De/anti-icing fluids and so called cold soaked fuel frost (CSFF) are examined as aerodynamic contaminants originating during a ground stay of an airliner. The research consists mainly of experiments in a wind tunnel. Additionally, some CFD simulations are included to enhance the perception of the de/anti-icing fluid flow-off phenomena. The dissertation consists of four journal publications. The two first publications consider anti-icing fluid and CSFF as aerodynamic contaminations degrading performance of a wing and the two latter publications consider the de/anti-icing fluid flow-off phenomenon. In the two first publications two different wing section models are studied whereas the fluid flow-off phenomenon is studied on the surface of flat plate models. All wind tunnel tests are designed to simulate a take-off sequence of an airliner by accelerating the airflow from idle speed to 60 m/s which represents the lift-off speed of an airliner. In the first publication the contribution of the so-called secondary wave on the anti-icing fluid induced lift degradation of a wing section at the lift off and during initial climb of an airliner is considered. The effect of wing section slat geometry on the secondary wave is also studied. The second publication covers the first published experiments with authentic frost (CSFF) as an aerodynamic contamination over a wing surface instead of a fixed sandpaper type of roughness adopted in previous published studies. In the third and fourth publications de/anti-icing fluid flow-off phenomenon is studied. The concept of kinematic waves on the fluid surface when subjected to an accelerating airflow is demonstrated to explain the fluid transfer on a flat plate. The effect of fluid viscosity is addressed and a scaling law for fluid flow-off is developed. The scientific novelties included in this dissertation may be summarised as follows: (1) the contribution of secondary wave on the lift loss during takeoff and the effect of wing section and slat geometry on the secondary wave has been assessed, (2) the transient nature of CSFF as an aerodynamic contamination during takeoff has been demonstrated, (3) the role of wave motion on the surface of the de/anti-icing fluid layer subjected to an airflow has been clarified and simplified models have been formulated to understand the relation between kinematic waves and fluid transfer on the flat plate surface and (4) a scaling method has been developed for similarity in fluid flow-off between different scales and wind tunnel speed sequences.