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Analysis of the Gemini data

This study by Oleg Likhatchev from the University of Arizona explores pressure and velocity data analysis for the primary mirror, as well as buffeting forces on the secondary mirror of the Gemini Telescope. The research includes autocorrelation functions, power spectral densities, and spectral analysis of unsteady forces. It also discusses a semi-empirical theory for buffeting forces and compares static and dynamic pressure data.

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Analysis of the Gemini data

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  1. Analysis of the Gemini data By Oleg Likhatchev Aerospace and Mechanical Engineering Department University of Arizona

  2. Contents in Brief • Introduction: What can we learn from the Gemini data? • Pressure and velocity data analysis for the primary mirror: *Autocorrelation functions * Power Spectral Densities • Buffeting forces on thesecondary mirror: * Semi-empirical theory * Spectral analysis of unsteady forces on the secondary mirror

  3. The Gemini Telescope

  4. Pressure Sensors Layout +Y -X +X -Y

  5. Velocity Real Time Records c00030oo

  6. Pressure Real Time Records c00030oo

  7. c00030oo Velocity Autocorrelations at +X

  8. c00030oo Velocity Autocorrelations at -X

  9. c00030oo Pressure Autocorrelations <U>=5.81 m/s t=4.4 sec St=0.2 L=5.1 m <U>=1.78 m/s t=14 sec St=0.2 L=4.98 m

  10. Wind BuffetingQuasi-Steady Assumption

  11. Comparison of PSD’s for Static and Dynamic Pressures

  12. Pressure Sensor #7Velocity at –Xc00030oo <U>=5.81 m/s; f=0.8 Hz; St=0.2; L=1.45 m <U>=5.81 m/s; f=1.0 Hz; St=0.2; L=1.14 m

  13. Pressure Sensor #12Velocity at +Xc00030oo <U>=1.78 m/s; f=0.26 Hz; St=0.2; L=1.4 m

  14. Pressure Sensor #23Velocity at -Yc00030oo <U>=0.74 m/s; f=0.67 Hz; St=0.2; L=0.22 m

  15. Pressure PSD’s for Sensor #12(+X)Upwind Side of the Mirror 1Cases c04530oo and c04530co <U>=7.94 m/s L=1.2 m St=0.2 <U>=7.3 m/s L=1.2 m St=0.2

  16. Pressure PSD’s for Sensor #12(+X)Upwind Side of the Mirror 1Cases c04530oo and t04530oo <U>=7.94 m/s L=1.2 m St=0.2 <U>=7.3 m/s L=1.2 m St=0.2

  17. Buffeting Forces on theSecondary Mirror

  18. Buffeting Forces on a Rigid Circular Cylinder in Cross Flows(Water Tunnel Experiment, So & Savkar 1981 ) Lift Drag Strouhal Lift & Drag Re=1E+5 Buffeting Lift & Drag Re=2E+5 Re=3E+5

  19. Experimental Drag and Lift Coefficients

  20. Semi-empirical Theory of Buffeting Forces

  21. Buffeting Drag and Lift

  22. Buffeting Drag on the Second Mirror

  23. Unsteady Lift Due to Fluctuating Drag

  24. Buffeting ForcesCase c00030oo

  25. Buffeting ForcesCase c09030oo

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