Spectral characteristics of wind-generated waves in labortaory are presented on the basis of a systematic measurement in a large-scale wind-wave channel and compared with those in the field. A marked characteristics o...Spectral characteristics of wind-generated waves in labortaory are presented on the basis of a systematic measurement in a large-scale wind-wave channel and compared with those in the field. A marked characteristics of the measured spetra is the existence of secondary spectrum-peak. The dependence of spectral peak-frequency, peak-value and zeroth-order moment on wind speed and fetch are presented and found roughly similar to those in the field represented by the JONSWAP spectrum, regardless of the differences in coefficient. The spectral slope beta at high-frequencies are found somewhat greater than those of field wind-waves in both cases of deep and shallow waters. Except for the low-frequency part, the spectral forms measured in different wind conditions are similar and fit for the JONSWAP spectrum with gamma = 6 and beta = 5.5. Some relevant problems are discussed.展开更多
Using the limit surface slope as a criterion of wave breaking, a simple model for estimating the spatial fraction of breaking surface of sea at an instant, which is regarded as the whitecap coverge in this paper, is a...Using the limit surface slope as a criterion of wave breaking, a simple model for estimating the spatial fraction of breaking surface of sea at an instant, which is regarded as the whitecap coverge in this paper, is analytically derived from the probability density of surface slope based on Gaussian statistics. The resulting fraction is found depending on the fourth moment of wave spectum, m(4), as well as the critical threshold of surface slope. By expressing the fourth moment in terms of the Neumann spectrum, a formula linking the fraction and wind speed for fully developed sea states is obtianed. Another formula relating the fraction to both wind speed and fetch (or duration) is achieved by expressing m, in terms of the Krylov spectrum and applying the empirical relationships used in the SMB ocean wave predicting technique. A comparison between these results and the field data of whitecap coverage collected by Monahan and O'Muircheartuigh shows an encouraging agreement.展开更多
基金This work was financially supported by the National Science Foundation of China(No.4967277)
文摘Spectral characteristics of wind-generated waves in labortaory are presented on the basis of a systematic measurement in a large-scale wind-wave channel and compared with those in the field. A marked characteristics of the measured spetra is the existence of secondary spectrum-peak. The dependence of spectral peak-frequency, peak-value and zeroth-order moment on wind speed and fetch are presented and found roughly similar to those in the field represented by the JONSWAP spectrum, regardless of the differences in coefficient. The spectral slope beta at high-frequencies are found somewhat greater than those of field wind-waves in both cases of deep and shallow waters. Except for the low-frequency part, the spectral forms measured in different wind conditions are similar and fit for the JONSWAP spectrum with gamma = 6 and beta = 5.5. Some relevant problems are discussed.
基金This work was financially supported by the National Science Foundation of China(No.49476270,49706067)
文摘Using the limit surface slope as a criterion of wave breaking, a simple model for estimating the spatial fraction of breaking surface of sea at an instant, which is regarded as the whitecap coverge in this paper, is analytically derived from the probability density of surface slope based on Gaussian statistics. The resulting fraction is found depending on the fourth moment of wave spectum, m(4), as well as the critical threshold of surface slope. By expressing the fourth moment in terms of the Neumann spectrum, a formula linking the fraction and wind speed for fully developed sea states is obtianed. Another formula relating the fraction to both wind speed and fetch (or duration) is achieved by expressing m, in terms of the Krylov spectrum and applying the empirical relationships used in the SMB ocean wave predicting technique. A comparison between these results and the field data of whitecap coverage collected by Monahan and O'Muircheartuigh shows an encouraging agreement.
