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Technical Studies: Wind Loading: Structure Functions

The following structure functions have been calculated from the Gemini South wind test data from measured pressures on the surface of the dummy primary mirror. The pressure "structure function" is defined as:

D(rho) = <|P(r+rho)-P(r)|2>

It is a measure of how the amplitude of pressure differences from one point to another on the mirror surface varies as a function of the separation between the measurement points.

The file number encodes the conditions of the test. The first three numbers in the name indicate the azimuth orientation of the dome slit relative to the incoming wind direction. The next two numbers indicate the zenith angle of the telescope, and the final two letters indicate the status of the large vents on the side of the Gemini enclosure, the first letter indicating the upwind vent gate. So, for example, 04530oc indicates the telescope was pointing 45 degrees away from the wind in azimuth, was at a zenith angle of 30 degrees (elevation of 60 degrees), the upwind vent gate was open and the downwind vent gate was closed.

List of Structure Functions

Ruth A. Kneale / / June 8, 2001