10～60m/sの範囲の強風時における大気乱流のスペクトルとスケール

Abstract

This paper is mainly concerned with power spectra and scales of turbulence in strong winds in the range of 10-60m/s. The spectra and the scales were calculated with the method of maximum entropy spectral analysis. The spectra for both longitudinal and ver-tical velocities are represented well by the algebraic expression suggested by Fichtl and McVehil (1970) and Busch (1973). But the factor controlling peakedness and the peak wave number vary with mean wind speed for the longitudinal velocities. The peak wave number is not proportional to the height above the ground for the vertical velocities. A few kind of scales are dealt with and compared with each other. As the integral scales are overes-timated due to underestimates of high-frequency components of wind fluctuations, the meas-ured values were corrected. The ratio of integral scales to scales connected with spectral peaks agrees well with the theoretical result obtained from the algebraic expression of spectrum. The scales of the longitudinal velocities for over-sea winds increased with the mean wind velocities and were larger than those for over-land winds. The above experi-mental result shows that a similarity theory given as a function of a parameter nz/U does not hold true. The scales of the vertical velocity for a rough terrain were not proportional to height. It also means that the similarity theory is not consistent with the present data for the vertical velocity.