Bird Strike on Aero Engine

Bird-Strike

A Bird-strike sometimes called bird strike, bird ingestion (for an engine), bird hit or bird strike hazard (BASH) is a collision between an airborne animal (usually a bird or bat) and moving vehicle usually an aircraft.

Although it’s true that there is no way you can be completely sure of avoiding a bird strike. Bird strikes usually occur when aero-plane is flying at low altitudes. Therefore the most favorable condition for bird strike are during take-offs and landings ( or other related phases of the aero-planes. The reason for this is obvious, mostly birds are fly at low altitude, to there is greater risk of hitting an airborne animal.

What Happens during a Bird Strike?

Birds usually collide with any of the forward facing edge of the airplane, which includes the wing, nose cone, and the most common site is the jet engine. There have been cases of birds hitting the windshield or canopy of airbuses and fighter jets, which can result in the cracking of the surface of canopy or windshields. These cracks sometimes disrupt the air pressure inside the cabin and result in altitude loss or other flight related problems. The severity of damage done by the bird striking depends upon a few factors including speed difference, direction of impact and the weigh and size of birds.

Let take a perspective, consider a 5Kg bird hitting an airplane at relative velocity of 275kmph, can you figure out how much of an impact this translates into?

The most dangerous condition arises when birds hits the turbine and got caught in the engine, this event is refer to jet engine ingestion, since the bird is ingested by the engine.

After being struck in the engine, the bird can cause a disruption in the rotatory motion of the fan blades, result in partially or complete failure of engine, now what can a sudden failure on one such engine do to an airplane??? Flocks of birds are even more dangerous as they can have more severity impacts to the blades and engine of the gas turbine of the aero-plane.

So a bird strike are major threat to the aircraft structures, as a collision with bird during flight can lead to serious structural damage. Computational method has been used for more than 30 years for the bird proof design of such structure, being an efficient tool compared to the expensive physical certification tests with real birds. At the velocity of interest, the bird behave as soft body and flows in fluid like manner over the target structure, with the high deformation of the spreading material being a major challenge for finite element simulations.

Bird Strike (SPH Approach) [1]

Sample Results:?

Model time step is less than the contact time step (Hence it maintains the stability criteria)

Note: The ls dyna time step should not exceed the contact time step which is 2.659e-04 to avoid contact instability. If the step size is bigger than scale the penalty of offending surface

Maximum Effective Stress = 41.96 Mpa?

Maximum Impact Force = 0.789 KN (Considering Bird as very soft material)

We can fluctuate in the density and other parameters for larger impact force

Blade Failure

Bird strike simulation on aircraft structure have been performed and improved since the late 1970’s. A large variety of bird impactor geometries, material, masses, densities and modelling methods exist now days, there are three established techniques for numerical bird impactor modelling are used Lagrangian Eulerian, and SPH. The best approach depends upon the specific application, software package, computational resources and parameters setup.

References: https://www.researchgate.net/publication/258630574_Smooth_Particle_Hydrodynamic_Approach_for_Bird-Strike_Analysis_Using_LS-DYNA [1]