Chapter 5

Chapter 5, Technical Studies

Appendix 5.5.B: Wind Loading

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Cases:

Animations

The dynamic wind measurements from three of the 116 tests are shown here as animations. These are relatively severe cases, with above median wind speed and fully open ventilation gates. For each test case, three animation plots are displayed as follows:

Upper left: wind pressure distribution (pressure range = ± 10 Pascals)
Upper right: mirror surface distortion map (range = ± 1.0 microns)
Lower row: resultant wind speed at each anemometer (range = 0 to 20 m/s)

The animations are the first 600 frames of the data (60 seconds at 10 samples per second). Regions in red on the wind pressure distribution represent positive values and in blue represent negative values. The optical surface distortions were calculated based on the wind pressure distribution by Finite Element Analysis. Regions in red on the surface distortion are higher than those in blue. The resultant wind speed was calculated at each of the five anemometer locations (+X, -X, -Y, M2, Dome) and animated as a gauge reading.

Average and RMS wind pressure and velocity

Data from each of the 116 five-minute wind tests has been reduced, and three cases are shown here. For each test case, three plots are displayed as follows:

Upper left: average Wind pressure distribution (pressure range = ± 5 Pascals)
Upper right: RMS Wind pressure distribution (pressure range = 0 - 3 Pascals)
Lower row: resultant wind speed (range = 0 to 20 m/s)

The data reduction is based on all 3000 samples from each test (300 seconds at 10 samples per second). At each of the 24 or 32 pressure sensor locations (depending on which test series the data are from) the temporal average pressure and temporal RMS pressure were calculated, then these data were interpolated and extrapolated by cubic spline fit to fill in the 8-meter diameter circle. Regions in red on the average wind pressure distribution represent positive values and in blue represent negative values.

The resultant wind speed was calculated at each of the five anemometer locations (+X, -X, -Y, M2, Dome). At each anemometer location, a temporal average resultant velocity was calculated from the measured three orthogonal wind components (U,V,W). The average resultant wind velocities are plotted for the five anemometer locations. Temporal averages of the individual velocity components have also been calculated. These velocity components (U,V,W) are parallel to the primary mirror axes (X,Y,Z) when the mirror is in zenith. In addition, the RMS resultant wind velocity (VRMS) has been calculated.

Additional cases

Data for additional cases are available on the web at NIO Technical Studies: Wind Loading.


March 2002