next up previous contents
Next: Measurements Up: Wind loading on Previous: Relationship between pressure

Wind tunnel measurements of the pressure/velocity field on the mirror


In the previous section we have found a general, if approximate relationship between the average rms of pressure fluctuations on a primary mirror and the optical aberrations caused by dynamic deformations. It is also of interest to establish correlations between the wind speed measured on the mirror and the pressure fluctuations so that the ventilation of the enclosure can be planned optimally.

In fact the wind has a twofold effect on the mirror: on the one hand it affects negatively the optical performance by deforming the mirror, on the other hand it has a positive effect as it decreases mirror seeinggif. We will present here some wind tunnel measurements taken for the VLT cylindrical enclosure.

Figure: Photograph of test model

Lorenzo Zago,, Sun Feb 26 22:57:31 GMT+0100 1995