The shedding of ice accreted on aircraft surfaces poses a serious threat to flight safety as it can
cause severe damage to downstream aircraft components such as aft-mounted engines. While there is
strong need for ice shedding simulation tools to support aircraft icing analysis and certification, currently
available ice shedding analysis methods may not predict ice fragment trajectory accurately due to the
inability to simulate the random nature of ice shedding events and the lack of experimental aerodynamic
data for ice fragments. In addition, most of the simulation tools have not been validated with experimental
trajectory data.
Both experimental and numerical investigations of shed ice trajectory were conducted as part of
the continuing development of an ice trajectory simulation tool at Wichita State University. The research
discussed in this thesis involved wind tunnel experiments conducted to obtain experimental aerodynamic
coefficients for simulated ice fragments, numerical ice trajectory analyses, Monte Carlo simulations to
evaluate the risk of ice fragment impact on critical aircraft components, and trajectory experiments
performed to validate the ice trajectory simulation tool.
Wind tunnel experiments were performed in the WSU 7-ft x 10-ft wind tunnel facility to obtain an
aerodynamic database of force and moment coefficients for a 12-inch square flat plate with 0.4-inch
thickness, a 10-inch diameter disk with 1-inch thickness and a 18-inch span glaze ice fragment with
symmetric horns computed with the LEWICE ice accretion code. The experiments were conducted at
airspeed of 160 mph with varying Euler angles (yaw, pitch and roll). The aerodynamic coefficients of the
three fragments tested demonstrated considerable sensitivity to fragment shape and orientation. The
experimental data were incorporated into the WSU trajectory analysis code developed.
The ice shedding analyses were conducted with two simulated ice fragments for a business jet
aircraft using the WSU trajectory code. The two simulated ice fragments include a disk and a glaze ice
fragment with symmetric horns released from the aircraft nose and from the antenna on the top of the
fuselage, respectively. Monte Carlo simulations were performed to compute probability maps of trajectory
footprints at the engine inlet plane. The analysis demonstrated the effect of the shed location, initial
fragment orientation and aircraft angle of attack on ice fragment trajectories. The results for Monte Carlo
simulations performed with the disk fragment showed that the fragment would have less than a 0.15%
chance of impacting the engine. For the glaze ice fragment, it was found that the probability of a collision
between the fragment and the engine was as high as 24.2%, depending on the aircraft’s pitch and yaw
angles.
Next, an experimental methodology was developed to obtain the trajectories of simulated ice
fragments released in a tunnel airstream for the validation of the ice fragment trajectory code. The tested
fragments were a 6-inch square flat plate with 0.4-inch thickness, a rectangular flat plate measuring 12-
inch long by 6-inch wide by 0.4-inch thick, a 12-inch span single horn glaze ice fragment and a 12-inch
span double horn symmetric glaze ice fragment. Experiments were performed at airspeed of 160 mph in
the WSU 7-ft x 10-ft wind tunnel facility. High-speed video cameras were employed to record the
fragment’s trajectories at 500 to 1,000 frames per second. The coordinates of a fragment’s trajectories
were determined from high speed images with the help of gridded vinyl sheets attached to one of the
wind tunnel side-walls and to the ceiling. The fragment trajectories showed considerable sensitivity to the
ice fragment shapes and their initial pitch angles at the moment of release. The flat plates with initial
pitch angle of 0° experienced considerable rotation as they moved downstream, while the flat plate with
initial pitch angle of 90° traveled downstream in a nearly straight path without rotation. Two cases of the
single horn glaze ice fragment were sensitive to initial orientation and exhibited oscillatory rotations with
respect to their spanwise axis. Two cases of the double horn symmetric glaze ice fragment resulted in
similar trajectories, however experienced considerably different speed.
Finally, the experimental trajectories were compared with analytical trajectories computed with
the WSU trajectory code. Good agreement was demonstrated between the experimental and computed
trajectories in most cases. However, the analytical results for the flat plate cases with significant rotations
were more than 10% different compared to the experimental data due to the effect of the plate large
rotation speed on the aerodynamic forces and moments acting on the plates. / Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering.
| Identifer | oai:union.ndltd.org:WICHITA/oai:soar.wichita.edu:10057/3639 |
| Date | 05 1900 |
| Creators | Shimoi, Koji |
| Contributors | Papadakis, Michael |
| Publisher | Wichita State University |
| Source Sets | Wichita State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
| Format | xix, 131 leaves, ill. |
| Rights | Copyright Koji Shimoi, 2010. All rights reserved |
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