MEASURING AVERAGE WIND SPEED
Abstract
An investigation was made of the transient response of rotating windmill and cup anemometers. In general, the experiments confirmed the contention that rotating anemometers indicate the average wind velocity as being higher or lower than the actual value, depending on the circumstances. The cause for this discrepancy is the difference in the effective aerodynamic moments during the acceleration and the deceleration of the rotor. The comparison of the transient response of cup and windmill anemometers showed that for the latter device the time constant of the transient process approximating the deceleration was four times greater than the time constant during the acceleration. For the cup anemometer this ratio was one to six. A comparative evaluation of the average wind velocity indication by a rotating cup anemometer using a restrained anemometer as a reference was also made. It was found that the rotating anemometer indicated higher average wind velocity for velocities up to 10-11 m/sec., and lower average wind velocity for higher values. The results of the investigation indicate that true results can be obtained only from a simultaneous study of the wind structure and the dynamic properties of the wind gages.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 02, 1969
- Accession Number
- AD0696229
Entities
People
- D. Ya. Surazhskii
- V. Yu. Torochkov
Organizations
- National Air and Space Intelligence Center