An Improved Anemometer for Low-Level Winds. Phase I. Design Plan

摘要

A design plan has been developed for a sonic anemometer with a sonic path length of less than 1 ft and with high accuracy. The configuration of the sonic portion of the anemometer consists of a horizontal square array of four receivers placed symmetrically above a transmitter located on the vertical axis of symmetry. A fifth receiver is placed on this axis, either in the plane of the other four receivers or slightly above it. Over-all dimensions are less than 1 ft. Designs conceived for the small source of intense sound required include a hydraulically-driven radially-vibrating sphere, arrays of small tubes radiating from their open ends, and bimorph elements constructed of quartz or lead-zirconate disks. It is expected that spherical or hemispherical piezoelectric ceramics will be used as receivers. Theoretical and experimental studies led to the conclusion that the choice of sound transmission frequency for the sonic anemometer will be a compromise between the power-output-versus-frequency characteristics of the smallest transducers that are practicable, and the effects on sound propagation of wakes or atmospheric inhomogenieties in the sound path length. Phase measurements of continuously transmitted sound will provide the basis for measuring wind velocity components. (Author)