# Effect of Impact and Bearing Parameters on Bird Strike with Aero-Engine Fan Blades
## 3 Simulation of Bird Striking on a Rotating Fan
### Contact and Boundary Conditions  
The good handling of friction and impact problems at the interacting surfaces is one of the important advantages of LS-DYNA, and the accuracy of the simulation is determined by the definition of a contact interface. As a result, the selection of a suitable contact algorithm is crucial in modeling the interaction of the SPH particles and the FE elements accurately. The commonly used method for contact and sliding interface processing is the penalty method. To improve the accuracy of simulating the phenomenon of the blade being damaged during the impact, the contact type CONTACT_ERODING_NODES_TO_SURFACE was used in this research.  
The key bird ingestion parameters, including bird strike location, bird strike orientation, the rotational speed of the fan, and initial bird velocity, need to be based on realistic aero-engine operating conditions. The termination time was set to 6 ms, as at this time, the impact process is completed, and the obtained data can reflect the influence of bird impact. The time interval for outputs was set to 0.06 ms. The initial impact location of the bird was 1/2 of the blade height, the initial impact orientation of the bird was the head striking the fan, the rotational speed of the fan was set to 600 rad/s, the bird's initial velocity was set to 253 m/s. The bird's initial velocity was the initial relative speed of the bird and the engine, i.e., the ingestion speed. The elastic support parameters: the stiffness and the damping values were set to 10\({}^{8}\) N/m and 500 Ns/m, respectively.  
To study the effect of different impact parameters on the bird strike, different case scenarios of the above-mentioned parameters were chosen for simulation using the control variable method. The effect of bearings in bird strikes was also studied by giving different values of stiffness and damping to the elastic bearing.  
Three impact locations on the blade were chosen. Since the height of the bird is about 1/6 of the blade height, impact points were chosen to be at 1/6, 3/6 and 5/6 of the blade height, representing the root, the middle, and the tip locations of the blade, respectively (Figure 6).  
Figure 5: Fan pre-stress: the distribution of von Mises stress.  
Figure 7 shows the bird striking on the rotating fan from seven different impact orientations. Figure 7a shows the initial rotation of the bird model for \(90^{\circ}\), \(180^{\circ}\), and \(270^{\circ}\) around the Y axis. Figure 7b demonstrates the initial rotation of the bird model for \(45^{\circ}\), \(90^{\circ}\), and \(135^{\circ}\) around the Z axis. The seven considered impact orientations represent the head-, abdomen-, tail-, back-, and wing-first impacts.  
Referring to other examples [9; 19; 22], the rotational speed of the fan was set to three typical stage speeds of 600, 395, and 88 rad/s, corresponding to different operating phases. The ingestion speed of the bird corresponds to the experimental settings of Wilbeck [29], which was chosen to be 253, 225 and 118 m/s. According to the actual aero-engine rolling bearing stiffness and damping value ranges, the stiffness was set to \(10^{8}\), \(5\times 10^{7}\) and \(10^{7}\) N/m values, and the damping was set to 500, 5000, and 10,000 Ns/m values. Different case studies are listed in Table 5. The letter G stands for the control group, and letters L, O, V, R, S and D stand for impact location, impact orientation, initial bird velocity, rotational speed, support stiffness and support damping, respectively. The simulations for different bird collision parameter settings were performed using LS-DYNA.  
Figure 6: Three impact locations chosen for the bird model.  
Figure 7: Different impact orientations of the bird resulting from rotating the bird model around the (**a**) Y axis and (**b**) Z axis.