Numerical Simulation of Wind Loads on Antenna Structures
This contribution considers the modeling and simulation of the wind loads applied to a 35m deep space antenna. The performance of such large structures can be heavily affected by deformations due to wind effects. The aim of the investigation is the predic
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Abstract. This contribution considers the modeling and simulation of the wind loads applied to a 35m deep space antenna. The performance of such large structures can be heavily affected by deformations due to wind effects. The aim of the investigation is the prediction of the deformation of the antenna structure caused by wind loads. The presented work constitutes an example for the use of numerical simulation techniques to complex practical multi-physics problems by suitably coupling the numerical methodologies available for the fluid mechanics and structural mechanics subtasks.
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Introduction
For telemetry and telecommand operations of deep space and high elliptical orbit missions, in particular for Rosetta mission, the European Space Agency (ESA) is procuring a Deep Space SIX Band Antenna (DSA), presently under construction at the New Norcia site, nearby Perth. The antenna diameter for fulfilling the project requirements is 35 meters. The antenna, a dual reflector Cassegrain system, is of elevation over azimuth type, symmetric, with joke support by two elevation bearings. The mount is placed, with a large scale azimuth bearing, on top of a concrete tower. The baseline antenna radio frequency (RF) subsystem is including SIX-band receiving and transmitting capabilities. The antenna mechanics and structure is already designed and prepared for the future optional implementation of Ka-band receiving capabilities. The pointing requirements of large reflector antennas operating at X/Kaband frequencies are very demanding. This is due to the small beam width at these frequencies and the requirement to operate with full performance under environmental (wind load) conditions. By 'pointing requirements' is meant the accuracy with which the antenna RF-axis is aligned to the commanded, instantaneous pointing vector to the spacecraft. The examined variable is here the 'pointing error', which should not rise above two millidegree. The surface accuracy of the various reflectors is also a very important parameter, influencing both the phase error and the optical aberrations of the antenna aperture, which may result if not properly controlled in a dramatic deterioration of the antenna performance. By surface accuracy is meant e.g. for
M. Breuer et al. (eds.), High Performance Scientific and Engineering Computing © Springer-Verlag Berlin Heidelberg 2002
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Sieber, Droll, Schafer
the main reflector the deviation of the real surface from the ideally shaped parabolic surface optimized upon RF requirements. Here the RMS-value is the determining value, which shouldn't be higher than 2 millimeters. All kind of forces acting on the antenna have an effect on the pointing and on the surface accuracy. Therefore, the wind loads under which the antenna is operated playa very decisive role. The objective of the paper is to investigate the capabilities of computational fluid dynamics (CFD) to predict the wind load and the resulting RMS-value and pointing error with sufficient accuracy. Till nowadays it is common practice in antenna desig
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