460
B. Arizmendi et al.
when flying through clouds is avoided. This kind of ice accretion might cause an
increase on the surface roughness or the generation of prominent ridges or horns in
the region of the leading edge or downstream [1].
Since the droplets are larger in size, inertia forces predominate to aerodynamic
ones and that make the droplets follow ballistic trajectories which increase the efficiency of water collection near the leading edge [12]. In addition, the impingement
point is aft the stagnation point and those can accumulate in unprotected areas. Large
droplets are associated with a larger amount of latent heat. If the supplied cooling
upon impact is not sufficient for complete freezing, a portion of the droplet will
remain in liquid state and will run back and freeze. This may generate glaze ice
ridges on the surface of the wing which might freeze in unprotected areas, and this
poses a hazard for the performance and safety of the aircraft [13].
The study of the ice accretion caused by SLD presents a challenge due to the
complicated physics which includes droplet shape and size changes, splashing,
bouncing, and gravity effects [6]. All these respects need to be considered in the
numerical modeling for accurate predictions. Furthermore, it is more likely that the
droplets partially freeze because the available cooling is lower than the released
latent heat of solidification. The liquid fraction runs downstream driven by the
airflow and generates complex shapes of challenging prediction [14].
15.2.1.3 Ice Crystals
As the flight altitude increases and the static temperature drops, the likelihood of
finding supercooled liquid droplets significantly decreases. Instead, ice crystals can
be encountered. Ice crystals do not present a major threat for the aerodynamic
performance of the aircraft, since the ice crystals bounce off the surface of the
aircraft and they do not attach to the airframe because they are removed by
aerodynamic forces. However, high densities of ice particles, which can present
diverse sizes are associated with engine power losses and damages [15]. Past studies
[16] reported that ice crystals melted due to relative higher temperatures attained
in the compressors and that water froze in static surfaces such as the compressor
second stage stator or the core of the engine. This icing type can cause obstruction
of the airflow which entails working under very different conditions to the designed
ones [17].
15.2.1.4 Snow
The presence of snow can also entail icing in man-made structures. Snow consists
of formations of ice crystals that precipitate from the clouds. Two different types
were identified in research, namely dry and wet snow. Dry snow is produced when
the water from the ice crystals is in a solid state at a very low temperature. The ice
crystals present very low adhesion forces among them and with surfaces. Therefore,
usually there is no ice accretion from dry snow [18]. Furthermore, the crystals
B. Arizmendi et al.
when flying through clouds is avoided. This kind of ice accretion might cause an
increase on the surface roughness or the generation of prominent ridges or horns in
the region of the leading edge or downstream [1].
Since the droplets are larger in size, inertia forces predominate to aerodynamic
ones and that make the droplets follow ballistic trajectories which increase the efficiency of water collection near the leading edge [12]. In addition, the impingement
point is aft the stagnation point and those can accumulate in unprotected areas. Large
droplets are associated with a larger amount of latent heat. If the supplied cooling
upon impact is not sufficient for complete freezing, a portion of the droplet will
remain in liquid state and will run back and freeze. This may generate glaze ice
ridges on the surface of the wing which might freeze in unprotected areas, and this
poses a hazard for the performance and safety of the aircraft [13].
The study of the ice accretion caused by SLD presents a challenge due to the
complicated physics which includes droplet shape and size changes, splashing,
bouncing, and gravity effects [6]. All these respects need to be considered in the
numerical modeling for accurate predictions. Furthermore, it is more likely that the
droplets partially freeze because the available cooling is lower than the released
latent heat of solidification. The liquid fraction runs downstream driven by the
airflow and generates complex shapes of challenging prediction [14].
15.2.1.3 Ice Crystals
As the flight altitude increases and the static temperature drops, the likelihood of
finding supercooled liquid droplets significantly decreases. Instead, ice crystals can
be encountered. Ice crystals do not present a major threat for the aerodynamic
performance of the aircraft, since the ice crystals bounce off the surface of the
aircraft and they do not attach to the airframe because they are removed by
aerodynamic forces. However, high densities of ice particles, which can present
diverse sizes are associated with engine power losses and damages [15]. Past studies
[16] reported that ice crystals melted due to relative higher temperatures attained
in the compressors and that water froze in static surfaces such as the compressor
second stage stator or the core of the engine. This icing type can cause obstruction
of the airflow which entails working under very different conditions to the designed
ones [17].
15.2.1.4 Snow
The presence of snow can also entail icing in man-made structures. Snow consists
of formations of ice crystals that precipitate from the clouds. Two different types
were identified in research, namely dry and wet snow. Dry snow is produced when
the water from the ice crystals is in a solid state at a very low temperature. The ice
crystals present very low adhesion forces among them and with surfaces. Therefore,
usually there is no ice accretion from dry snow [18]. Furthermore, the crystals