470
B. Arizmendi et al.
15.2.4.4 Crystal Bouncing
The numerical replication of the crystal bouncing phenomenon is challenging.
Ice crystals bounce back on the surfaces of the aircraft and they do not adhere
to them. Ice crystal bouncing has a complicated physics due to factors such as
orientation, disintegration at extremely high velocities, and the circumstances post
crystal impact. Various experiments quantified the bouncing criterion for particles
impacting on wet surfaces [39]. Notably Davis et al. [40] identified that on a wet
surface the tangential velocity component of the impacting particle shows negligible
changes, while the losses in post-impact velocities are attributed to the significant
changes in the normal velocity.
15.2.5 Existing Research Methods for Ice Accretion
To date several methods are devised to help predict and understand the physics
of ice accretion. These ranging from experimental tests to numerical simulations.
Experimental tests which are performed either in-flight or in wind tunnels are
presented in the first subsection. Then, the numerical approaches will be presented
and described. Both approaches are complementary and often used in synergy to
address the complex ice accretion problem.
15.2.5.1 Flight Test and Wind Tunnel Experiments
The phenomenon of in-flight ice accretion requires further efforts to be fully understood. Physical replication of icing scenarios could increase the understanding on
the physics and could provide datasets for the validation of numerical models. Very
complete reviews of the research methodologies for aircraft icing were developed
by Kind et al. [41] and Bragg [42]. In this section we will focus on the available
experimental methodologies. Depending on the location of the experiments, they
are divided into ground tests and in-flight tests. Ground tests entail the use of wind
or icing tunnel which vary depending on the components being tested such as fixed
wings, engines, or propellers. This approach is convenient because it enables the
focus on the physics of certain specific parts and requires less time and cost than inflight testing. In addition, operating in-ground does not compromise the safety of the
flight crew or the aircraft. However, this leads to uncertainties that will be presented
later in the section. The main ground tests approaches described in literature [41]
are:
• Dry tests—These tests are performed in a regular wind tunnel. The expected or
critical ice shapes are simulated separately and then attached to the components
of interest. The objective is to understand the effects of the icing on the aircraft
performance and aerodynamics that is the performance degradation entailed if ice
B. Arizmendi et al.
15.2.4.4 Crystal Bouncing
The numerical replication of the crystal bouncing phenomenon is challenging.
Ice crystals bounce back on the surfaces of the aircraft and they do not adhere
to them. Ice crystal bouncing has a complicated physics due to factors such as
orientation, disintegration at extremely high velocities, and the circumstances post
crystal impact. Various experiments quantified the bouncing criterion for particles
impacting on wet surfaces [39]. Notably Davis et al. [40] identified that on a wet
surface the tangential velocity component of the impacting particle shows negligible
changes, while the losses in post-impact velocities are attributed to the significant
changes in the normal velocity.
15.2.5 Existing Research Methods for Ice Accretion
To date several methods are devised to help predict and understand the physics
of ice accretion. These ranging from experimental tests to numerical simulations.
Experimental tests which are performed either in-flight or in wind tunnels are
presented in the first subsection. Then, the numerical approaches will be presented
and described. Both approaches are complementary and often used in synergy to
address the complex ice accretion problem.
15.2.5.1 Flight Test and Wind Tunnel Experiments
The phenomenon of in-flight ice accretion requires further efforts to be fully understood. Physical replication of icing scenarios could increase the understanding on
the physics and could provide datasets for the validation of numerical models. Very
complete reviews of the research methodologies for aircraft icing were developed
by Kind et al. [41] and Bragg [42]. In this section we will focus on the available
experimental methodologies. Depending on the location of the experiments, they
are divided into ground tests and in-flight tests. Ground tests entail the use of wind
or icing tunnel which vary depending on the components being tested such as fixed
wings, engines, or propellers. This approach is convenient because it enables the
focus on the physics of certain specific parts and requires less time and cost than inflight testing. In addition, operating in-ground does not compromise the safety of the
flight crew or the aircraft. However, this leads to uncertainties that will be presented
later in the section. The main ground tests approaches described in literature [41]
are:
• Dry tests—These tests are performed in a regular wind tunnel. The expected or
critical ice shapes are simulated separately and then attached to the components
of interest. The objective is to understand the effects of the icing on the aircraft
performance and aerodynamics that is the performance degradation entailed if ice