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Base Vector System versus Rotated System
Posted Jul 24, 2012, 2:20 p.m. EDT 0 Replies
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Do you have any experience on rotating the material coordinate or rotating the geometric body in COMSOL 4.2? I am really confused about the setting of the Base Vector System. Here is my case study for the rotating coordinate and geometry.
1. I rotated the silicon (100) beam geometry to 45 degree in xy plane by setting the rotating angle in geometry. In this case, it means the material coordinate and the geometry will have a 45 degree difference and the eigen frequency for the extensional mode is around 21.29 MHz.
2. In another case, I used the rotated system under definition to rotate 45 degree by setting (0, 0, pi/4). Then I chose the rotated system for the material coordinate. The eigen frequency for the same mode is also 21.29 MHz which makes sense.
3. In the last case, I defined the based vector system under definition as x=[110], y=[-110], z=[001]. Then I chose the base vector system for the material coordinate. In my opinion, the eigen frequency of the same mode should be the same as the above two cases. However, the eigen frequency for the same mode in based vector system is 42.56 MHz. I really have no idea how this result happened.
Do you have any further suggestion on the base vector system as well as the global coordinate system?
I attached the base vector file herein for your reference. Any comment is appreciated.
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Hello Chih-Ming Lin
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