Extended Abstract (200K)P2.6
The influence of pulse-firing delays on sonic anemometer response characteristics
Morten Nielsen, Risų National Laboratory, Roskilde, Denmark; and S. E. Larsen
State-of-the-art sonic anemometers deduce the instantaneous wind vector and sound virtual temperature by transit times of sound pulses, travelling back and forth in three measurement paths. To eliminate cross-talk effects, the pulse firings have to be sequential. Therefore, the anemometer response is distorted when the frequency of turbulent perturbations approach that of the measurement cycle. Furthermore, the temperature response is distorted by the sound-path bending caused by the wind component perpendicular to the individual measurement path. Since pulse-timing distortions increase with frequency it is necessary to consider compensating effects of volumetric averaging along the measurement paths, together with the block-averaging and aliasing effects of the discrete sample strategy. The (co-)spectral response of all signals is modelled for the omnidirectional Solent R3 anemometer taking its special instrument geometry and pulse-firing rhythm into account. The pulse-firing sequence imply that the response depends on the instrument orientation relative to the wind direction. The temperature and heat-flux responses are improved relative to those of the preceding R2 version.
Poster Session 2, Observational Methods
Monday, 15 July 2002, 2:00 PM-2:00 PM
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