Observation on wind turbulence characteristics and velocity spectra near the ground at the coastal region

Abstract

In this study, we carried out in situ observations and measured the wind characteristics and velocity spectra near the ground at the northeastern coast of Taiwan. Wind turbulence characteristics and three components of wind velocity spectra are obtained from analysis of data measured from July 1998 to June 1999 by using the ultrasonic anemometer mounted on a tower with a height of 26 m. The quadrant analysis technique is employed to investigate the contributions of stress components to the total Reynolds stress. Analysis of the observation data shows that the ratio of averaged values of longitudinal and vertical turbulence intensity, u 2 / U ̄ : w 2 / U ̄ is approximately 1:0.45. This is approximately close to the ratio 1:0.5, which was the averaged mean value calculated from many measurements of field data as indicated by Counihan. Observational results show that properly scaled longitudinal wind velocity spectrum is found to be in agreement with the Von Karman's form of spectrum equation. It also exhibited that properly scaled measured results of the lateral and vertical wind velocity spectra are approximately close to the predictions of the isotropic turbulence spectra equations.