Time Series Analyses of Concentration and Wind Fluctuations.

摘要

Analyses of concentration fluctuation C(f) spectra from boundary-layer smoke plume experiments as six separate locations show that the spectra from these experiments generally exhibit an inertial subrange at high frequencies with a slope of - 5/3 and indicate peak energy at a time period of about 50 to 100 s. These periods of peak energy are a factor of two to five less than those for the peak of the wind speed fluctuation (u' or v') spectra. A general spectral formula fits normalized spectra from the U.S. and Australia, where the frequency, n, is made dimensionless by multiplying by the plume dispersion parameter, (sigma (sub y)), and dividing by the wind speed, u. Peak energy occurs at a dimensionless frequency of (n sigma (sub y))/u equal to about 0.15. The Kolmogorov constraint in the inertial subrange is estimated from a set of averaged spectra. Cross-spectra indicate little relation between concentration and wind fluctuations. However, most of the correlation that exists is due to periods larger than about 10 or 20 s. Reprints. (JHD)