Wind tunnel tests on a large astronomical telescope

Abstract The paper describes the methodology of the wind tunnel test program for the evaluation of wind loads on a new 8-metre class astronomical telescope, designed to be operated in open air. The objective of the tests was to determine the static and dynamic wind loads on the telescope structure and the primary mirror. Since these loads affect the normal performance of the telescope, a greater accuracy is needed than it is generally the case with structures dimensioned for ultimate wind loads. The aimed accuracy is achieved by a program combining experimental and computational models, which includes full and model scale tests of the telescope bars, a detailed computer model for the telescope structure including member shadowing and static and dynamic tests for azimuth and altitude forces and moments. Because of resonance problems in the mounting of the model an original method was applied to derive the aerodynamic admittance from the force spectra measurements on the model.