Bird Strike - Project - 2
Objective: To perform the simulation of bird strike in aero engine model using LS-DYNA. This is a clasic nonlinear transient dynamic problem similar to car crash and mobile drop. while accurate modelling of the problem requires advanced techniques such as SPH, this problem can be solved using generic explicit solver.
PROCEDURE:
STEP 1: seperating the all parts and saved all other sub files in different name
for bird:
opened the given original file all the parts are deleted except bird
Assigning the material and section cards to the part keyword and images of material and section card as shown.
saved the file with different name.
for casing:
opened the given original file all the parts are deleted except casing
Assigning the material and section cards to the part keyword and images of material and section card as shown.
saved the file with different name.
for blades:
opened the given original file all the parts are deleted except blades.
Assigning the material and section cards to the part keyword and images of material and section card as shown.
saved the file with different name.
for hub:
opened the given original file all the parts are deleted except hub.
Assigning the material and section cards to the part keyword and images of material and section card as shown.
saved the file with different name.
STEP 2: Applying boundary condition in seperate file
Arresting all the DOF's of the casing using boundary_spc_set keyword.
initial velocity generation keyword is used for giving the velocity for bird part and angular velocity for blades as shown.
STEP 3: applying contact cards
contact automatic singles surface is used to define the contact between the blades as when the birds collides on the blades some blades may come in contact with each other so to define this we use this card.
contact automatic surface to surface is used to define the contact between the blades and casing and bird and blades.
contact tied surface is used to define the contact between the hub and blades.
STEP 4: Assigning the control cards and data base card in seperate file.
contol termination card is used to give the end time value.
control energy is used to reduce the hourglass effect .
control time step is used for mass scaling to reduce the simulation time as this simulation involves more time to solve.
Required output are obtained from data base keyword.
STEP 5: Include card is used to get all the files in one single major file.
In the new empty file all the include file are called into this major files
STEP 6: Renumbering the nodes, elements, part, material, section, curve, node set and contact.
Result and error:
When the simulation started the error occured due to because of the contact definition surface to surface node set should not be used as shown in below image.
Instead of node set ID the part ID is used to assign the contact and every other thing is good to rerun the model.
Mass scaling
Since the model is little bit complex so to run this model in normal system going to take more time so to reduce this we can use mass scaling
TSSFAC=0.9,DT2MS=-4.5e-5
TSSFAC=0.9,DT2MS=-9E-6
TSSFAC=0.9,DT2MS=-9.9E-6
TSSFAC=0.9,DT2MS=-9.8E-6
Since the mass scaling percentage as to be below 10% so this is the best DT2MS and TSSFAC values
Below image shows the glimpse of simulation carried out.
Below the image show the element used for the stress and strain calculation.
Below the image shows the Von misses stress of some of the blades element and we can see the variation of stress when the bird is hitting it reaches maximum.
Below images shows the variation of strain in the blade elements. when the bird hitted on the blades some of the element at the hitted region shows high strain but also the strain of each elements vary thats due to the amount of energy it observed.
Below image shows the variation of K.E, I.E and total energy. when the bird strikes on the blade the K.E of the bird decreases and I.E of the bird increases and total energy remains constant.
CONCLUSION:
The bird strike and aero engine model is built and simulation is carried according to the given objective and requirement. The result and simulation shows that it is almost similar to what is happening in the nature and the data is also relatable and make sense.