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)