22 Influence Study of the Bird Shape on the Birdstrike …
275
Fig. 22.1 Common bird
shape, a cylinder shape;
b ellipsoid shape; c spherical
shape; d cylindrical with
hemispheres at both ends
FAR 25.571 stipulates that the weight of the bird impacts on the engine should be
1.8 kg. Therefore, the four bird sizes can be calculated based on their shapes, as seen
in Table 22.1. Table 22.1 indicates that the spherical bird has the largest diameter,
while the ellipsoidal bird has the largest length.
Four algorithms are mostly used in bird simulation, namely Lagrange algorithm,
Euler algorithm, ALE (Arbitrary Lagrange-Euler) algorithm and SPH (Smoothed
Particle Hydrodynamics) algorithm. The Lagrange algorithm is simple to calculate,
but its grid will be severely distorted under high-speed impact, and therefore the
calculation accuracy and efficiency will be significantly reduced. Euler algorithm
can ensure a regular grid, but the modeling is complex, and energy and quality
leakage will occur, causing inaccuracy. ALE algorithm combines the advantages
of Lagrange algorithm and Euler algorithm, but also retains the shortcomings of
both. The SPH algorithm is stable in calculation and there is no grid distortion. SPH
algorithm can simulate fluid sputtering easily, but it cannot show the stretching effect
between particles. Liu et al. [12] used a high-speed camera to study the response of
bird at different impact speeds and got conclusions. When the impact speed was
about 70 m/s, the bird body became massive fragments after impact, indicating that
a solid material model should be used at low speed. When the impact velocity was
120 m/s, the bird body became smaller fragments, indicating that a mixed model of
solid and fluid materials should be used for simulation at a medium impact velocity.
When the impact velocity was increased to 170 m/s, the bird body almost sputtered
in a fluid state, indicating that a fluid material model should be used under highspeed impact. In this paper, the birdstrike speed is 800 km/h, which is the cruising
speed of a general transportation aircraft. This speed has far exceeded 170 m/s, so
Table 22.1 Sizes and shapes
of the four birds
Bird shape
Diameter [mm] Length[mm]
Cylinder
106.449
212.899
Ellipsoids
121.854
243.708
Sphere
153.527
153.527
Cylindrical with hemispheres at
both ends
113.119
226.239
275
Fig. 22.1 Common bird
shape, a cylinder shape;
b ellipsoid shape; c spherical
shape; d cylindrical with
hemispheres at both ends
FAR 25.571 stipulates that the weight of the bird impacts on the engine should be
1.8 kg. Therefore, the four bird sizes can be calculated based on their shapes, as seen
in Table 22.1. Table 22.1 indicates that the spherical bird has the largest diameter,
while the ellipsoidal bird has the largest length.
Four algorithms are mostly used in bird simulation, namely Lagrange algorithm,
Euler algorithm, ALE (Arbitrary Lagrange-Euler) algorithm and SPH (Smoothed
Particle Hydrodynamics) algorithm. The Lagrange algorithm is simple to calculate,
but its grid will be severely distorted under high-speed impact, and therefore the
calculation accuracy and efficiency will be significantly reduced. Euler algorithm
can ensure a regular grid, but the modeling is complex, and energy and quality
leakage will occur, causing inaccuracy. ALE algorithm combines the advantages
of Lagrange algorithm and Euler algorithm, but also retains the shortcomings of
both. The SPH algorithm is stable in calculation and there is no grid distortion. SPH
algorithm can simulate fluid sputtering easily, but it cannot show the stretching effect
between particles. Liu et al. [12] used a high-speed camera to study the response of
bird at different impact speeds and got conclusions. When the impact speed was
about 70 m/s, the bird body became massive fragments after impact, indicating that
a solid material model should be used at low speed. When the impact velocity was
120 m/s, the bird body became smaller fragments, indicating that a mixed model of
solid and fluid materials should be used for simulation at a medium impact velocity.
When the impact velocity was increased to 170 m/s, the bird body almost sputtered
in a fluid state, indicating that a fluid material model should be used under highspeed impact. In this paper, the birdstrike speed is 800 km/h, which is the cruising
speed of a general transportation aircraft. This speed has far exceeded 170 m/s, so
Table 22.1 Sizes and shapes
of the four birds
Bird shape
Diameter [mm] Length[mm]
Cylinder
106.449
212.899
Ellipsoids
121.854
243.708
Sphere
153.527
153.527
Cylindrical with hemispheres at
both ends
113.119
226.239