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These wind tunnel tests were performed at the boundary layer wind
tunnel of the Danish Maritime Institute
as part of the test program
with the cylindrical enclosure selected for the VLT (cf. section
The model included the same complete enclosure with a fully modeled
telescope inside it at a scale of 1:64 (see
fig. ). The tests were run with
several venting configurations of the enclosure as described in
section 4.1.3 above and covered the
range of wind directions 0, 10, 20, 40, 90 and 180
in combination with telescope zenith angles of 10, 35 and 60.
Two types of measurements were performed:
Appendix includes sketches with the location of the
measurement points and tables with the means, minima, maxima
and rms of all pressure coefficients and wind speed measurements close
to the mirror surface measured.
The measured rms of the pressure coefficients are plotted in
fig. versus the azimuth with the wind direction
for different telescope altitudes and enclosure configurations.
- Measurements of the pressure difference between the upper and lower
faces of the primary mirror. Pressure taps were mounted on opposite sides
of the primary mirror at four symmetrical locations. The scanivalve setup
was such that instantaneous pressure differences were measured. These
instantaneous pressures were then expressed as coefficients
normalized by the reference external wind speed.
- Measurement of wind velocity close to the upper surface of the mirror,
by two single-wire hot-wire probes, respectively vertical and horizontal, located
about 10 mm (model scale) above the mirror surface.
Lorenzo Zago, email@example.com,
Sun Feb 26 22:57:31 GMT+0100 1995