Comparing Estimation Methods Of Cross-spectra Between Wave And Current

Wave and current exist almost at the same time, and the influence of their interaction is extremely popular. Taking more focus on the wave-current interaction, we can explain the dynamic phenomena and its evolution process more accurately. As a statistical tool, cross-spectra can be used for the analysis of wave-current interaction in frequency domain. A good estimation method may not be perfect for any occasion, and its chosen should be depended on specific application. With the methods’ innovation of cross spectrum estimation and the improvement of the statistical theory, it is necessary to find a suitable method to analyze wave-current interaction precisely.Primary simulation has been done based on the theoretical model. Three methods, Welch, MTM and MVDR, are used in the tests in conditions of the changing of sample size^ subjects common frequency、amplitude coefficient, adding specific frequency, and increasing noise variance. The results show that the MVDR method is more capable for distinguishing adjacent cohere frequency with no pseudo peak, and has high frequency resolution and small deviation. Based on the wind-wave experiment data of Physical Oceanography Laboratory of the Ocean University of China, three pairs experiment data has been chosen to do the experiment by the above three methods. The results imply that coherence between wave and current on dominant frequency band is significant by the three methods. At high frequency band, estimated magnitude-squared coherence by MVDR method decays as wave spectra and current spectra, unlike the results from the other two methods which maintained at significant level, even at very high frequency band.It is showed that MVDR method is more reasonable to numerical simulation and wind-wave experiment. Then MVDR method is employed to further analysis of the wind-wave experiment data, comparing the shape of the single spectrum and the cross spectrum estimation, analyzing wave-current interaction in different depth and time delay between wave and current based on lead-lag model.