ANSYS simulation of LIGO
ITM
Frequency shifts with time
(dynamic surface heating)
Simulation parameters
•
•
•
•
•
2D axysimmetrical model
Absorbed power in the coating: 10mW
Waist of the gaussian heating beam: 3.4 cm
Radiation into space @ 295K
Coating modeling included in the simulation
We chose 295K because the measured
temperature into Virgo towers is (22.0±0.1)°C
Modal analisys results
•2D axysimmetrical with coating, T=295K:
– f0=14459.5199 Hz breathing mode
– f0=9521.6059 Hz drum mode
•2D axysimmetrical with coating, T=300K:
– f0=14467.1918 Hz breathing mode
– f0=9526.46525 Hz drum mode
Difference with your simulation:
– (-14462.2638+14467.1918)/14465=8.5·10-5
– (-9523.18+9526.46525)/9524.8=8.6·10-5
We think this difference may be due to a non perfect
match of our elastic parameters and different
eigensolvers in Ansys and Comsol.
Thermal-modal analisys
steady state
• 10mW absorbed into coating T=295K:
– Δf/f0_breath=1.534·10-6
– Δf/f0_drum=1.633·10-6
• 10mW absorbed into substrate T=295K :
– Δf/f0_breath=1.651·10-6
– Δf/f0_drum=1.614·10-6
• 10mW absorbed into coating T=300K:
– Δf/f0_breath=1.283·10-6
– Δf/f0_drum=1.324·10-6
• 10mW absorbed into substrate T=300K :
– Δf/f0_breath=1.380·10-6
– Δf/f0_drum=1.306·10-6
The differences with your results are of the order of 12-14%, these may be due
to the fact that we used different temperature dependances of the elastic
parameters. Anyway we cannot exclude that the temperature distribution
inside the ITM is different as calculated by Ansys and Comsol...
Time dependent solution
We read your data files. There are 121 points in both files, if sampled every 5 minutes,
it means the time span is 10 hours. If we plot them against time, they look ok.
Frequency shift of the breathing mode
0,025
But if we zoom the last hours....
0,02
0,02104
0,015
0,02102
0,01
0,021
0,005
0,02098
0
0
2
4
6
8
10
Time (hrs)
12
Shift (Hz)
Shift (Hz)
Frequency shift of the breathing mode
0,02096
0,02094
0,02092
Are we missing something?
0,0209
0,02088
4
5
6
7
Time (hrs)
8
9
10
Ansys data (T0=295K)
Freqency shifts for 10mW
absorbed in the coating
0,025
Shift (Hz)
0,02
0,015
0,01
Breathing Ansys
Drum Ansys
0,005
0
0
2
4
6
8
10
12
Time (hrs)
Next step will be the solution for 10 mW absorbed into the substrate.