1. Summary of Gemini Technical Report No. 1
Water Tunnel Tests on Enclosure Concepts by
Woon-yin Wong and Fred Forbes
July 1991

2. Scope of Work How do the vents ventilate the enclosure?
How can ground turbulence be kept from entering the enclosure?
How can the enclosure protect the telescope, particularly with a large number of vents?

3. Tests Performed January, 1990 September 1990
Effect of vents on 4 enclosures with different porosities
September 1990
Comparison of ventilation of 4 enclosures with similar porosities
Flow characteristics of the buildings at two different heights

4. Enclosure Data

5. Enclosure Models

6. Enclosure Models

7. Enclosure Models

8. Telescope Model

9. Acrylic Models – 1st Tests

10. Acrylic Models – 2nd Tests

11. Hemispherical Enclosure Vents closed – Facing Into Wind

12. Hemispherical Enclosure Vents Closed – 90° to Wind

13. Hemispherical Enclosure Vents Open – Illustration of Flushing of the Enclosure Volume

14. Conclusions
Hemispherical, octagonal, or rectangular enclosures may be properly vented to provide uniform flushing at all wind directions.
Flushing occurs in 40 to 70 seconds when outside wind speed is about 11 m/s.
Replacement of 50 to 100 dome volumes per hour.
Forced air ventilation is 10 to 12 dome volumes per hour (Keck Project).
CTIO test indicated a natural flushing efficiency of 2 to 3 times better than forced flushing.

15. Conclusions, Cont’d.
With low pier, ground turbulence layer is lifted as approaches building
Lift was maximum with hemispherical dome
On average, flow was lifted ~3 meters.
With tall foundations, flow split around foundation with little or no vertical flow component.