Review of existing numerical Review of existing numerical methods and validation procedure methods and validation procedure available for bird strike modellingavailable for bird strike modelling 14th ICCES Conference, Jan 3-8 2007, Miami, USA
Marie-Anne LavoieAugustin Gakwaya
- Laval University
David G. Zimcik M. Nejad Ensan
– NRC-IAR
• During the certification process, an aircraft must demonstrate its ability to land safely after being struck by a bird• Past experience has been to demonstrate this compliance
through full-scale test• Bird models are generally developed based on tests data
that are nearly 30 years old• Aim to summarize the steps involved in creating a bird
model
INTRODUCTION
INTRODUCTION
• THEORY of bird strikes and an analytical evaluation of the expected results
• EXPERIMENTAL DATA that are currently available
• Description of the three NUMERICAL BIRD MODELS one can use
• Analysis of the RESULTS
• Recommendations are made in the CONCLUSION regarding the best suitable method
THEORY
• High velocity bird impact hydrodynamic behavior
• Event is divided into two stages:
•Shock: Hugoniot pressure:
•Steady flow: Stagnation pressure:
• Equation of state 33
2210
221
CCCCP
vP
vvP
imstag
imshsh
EXPERIMENTAL EXPERIMENTAL DATA
Most complete results: Wilbeck (1977)
• Gelatin with 10% porosity• Density of 950 kg/m3
• Shape of projectile
EXPERIMENTAL DATA
EXPERIMENTAL DATA
Normalized Hugoniot Pressure
Experimental Analytical
116 m/s 3.5 14.9
197 m/s 7.8 12.0
253 m/s 3.4 10.5
EXPERIMENTAL DATA
Current work in bird testing
• Best practice tends to tweak numerical model to fit test data from impacted aeronautical structures;
• Down side of this general approach is that bird models are specific to their application;
• Industries which have financed recent bird strike tests are not willing to make their knowledge public.
NUMERICAL BIRD MODELS
• Early stages of bird impact simulations, the bird was represented by a pressure pulse on the structure. • Three main modelling methods are currently
available. They are:• the Lagrangian mesh; • the arbitrary Lagrangian-Euler (ALE) mesh;• the smooth particle hydrodynamics (SPH) method.
• 1 kg bird travelling at 116 m/s impacts on a 0.50.5 m rigid square plate.
NUMERICAL BIRD MODELS - Lagrangian
• 500 hexahedral elements
• Fluid-structure interaction controlled through contact between bird and target
NUMERICAL BIRD MODELS - ALE
• 19,000 hexahedral elements of equal length, width and height
• Fluid-structure interaction controlled through *constrained Lagrange in solid
NUMERICAL BIRD MODELS - SPH
• 4600 SPH particles each weighing 0.224 gr (0.0005 lbs)
• Fluid-structure interaction controlled through a node-to-surface contact between the bird and the target
RESULTS - Lagrangian
RESULTS - Lagrangian
RESULTS - ALE
RESULTS - ALE
RESULTS - SPH
RESULTS - SPH
CONCLUSION
• The comparison with the experimental data highlights the need for future bird calibration testing • The Lagrangian method is no longer suitable• ALE and SPH models compare well with the
analytical predictions• Currently, the ALE method is a standard approach
to bird impact modelling• The SPH method formulation works well and is still
developing• We are working on an improved version of SPH
method which will interact with a solid structure
ACKNOWLEGMENTS
• Laval University
• National Research Council of Canada (NRC)
• Consortium for Research and Innovation in Aerospace in Quebec (CRIAQ)