Review of existing numerical methods and validation procedure available for bird strike modelling Review of existing numerical methods and validation procedure available for bird strike modelling 14th ICCES Conference, Jan , Miami, USA Marie-Anne Lavoie Augustin 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

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

EXPERIMENTAL EXPERIMENTAL DATA Most complete results: Wilbeck (1977) Gelatin with 10% porosity Density of 950 kg/m 3 Shape of projectile

EXPERIMENTAL DATA

Normalized Hugoniot Pressure ExperimentalAnalytical 116 m/s m/s m/s

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 0.50.5 m rigid square plate.

NUMERICAL BIRD MODELS - L agrangian 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 gr ( lbs) Fluid-structure interaction controlled through a node-to- surface contact between the bird and the target

RESULTS - Lagrangian

RESULTS - ALE

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)