| The estuary of The Yangtse River is near to The East China Sea, it is not only the most important sea-route of Shanghai City (one of economy center of China), but also is the unique door and seaport of all the provinces along the River, its development influences not only on the local economy, but also on the development of Chinese economy in short, middle and long term. Therefore the study on the characteristics of ocean waves at the Yangtse River Estuary has important significance.From the situ-observation data of shallow and deep water regions at the coastal zone, it is shown statistically that the occurrency of the coupled ocean waves is more than those of the wind-induced waves and swell. The ratio of the coupled ocean waves at the Yangtse River Estuary (especially at shallow sea region)is nearby 70% of all the ocean waves, for instance at The Observation Station Dajishan. The structure of the frequency spectrums of the coupled ocean waves are complex and multiplex, the most of the spectrum types is of double or of multiple peak other than the special case of the single peak spectrum. Therefore, the research of the statistical characteristics of double peak spectrum will have the practical significance.In fact, the acquisition of the situ-observation data with the high resolution in time and space is mostly unable in the shoaling zone or surf zone and especially in The Yangtse River Estuary. In this zone, the ocean wave fields are complex and variable due to the influences such as geological, bottomed, shoaling, ocean-engineering factors and currents in coastal zone etc. So the lattice (multi-point) situ -observation is not applied and is not practised based on the economical and practical consideration. Hence, the numerical modeling is the practical and unique method for the acquisition of the statistical distribution of ocean waves with the high-resolution in the larger zone.The hydrological and meteorological situ-observation stations in The Yangtse River Estuary were established from 1955 years, a mass of data was acquired in thelast 40 years. A number of statistical and analytical works have been done by the institutions such as TheThird Shipping Affair Engineering And Relonnissanle Design Institue Of Ministry Of Communications, Hohai University, Yangize Valley Water Hudroprower Planning And Institule, Nanjing Hydraulic Research Institute and so on [25-30]. In 1993, the correlation analyses based on the data from the short-term situ-observation at near sea-route of The Yangtse River Estuary and the ship-stations were carried out to deduce the wave factors used in the engineering design.In period of the eighth five-year plan of China Government, correlated and statistical analyses were carried out by Nanjing Hydraulic Research Institute in terms of the situ-observation data of winds and waves and historical synoptic chart in order to the dredge of the sea-route of The Yangtse River Estuary, and empirical relations between wave and wind velocity and between wave and wind region. Furthermore, the values of wind velocities obtained from the situ-observation data of the ship-stations (50 , 25 ) are used to denote the wind velocities on the costal zone in the east of The Yangtse River Estuary and they are as the values of the wind velocities to deduce the wave factors in 20 meters deep. As the values of wave factors in period of reoccurrence were deduced for many significant propagating direction in The Yangtse River Estuary, the wave reflection -refraction modeling is employed in terms of the equations with the slowly varying topography, and the influence on the effects of the channel and shoaling is included in this model. At the same times, the effects of the bottom friction and wave breaking are also considered, but the local wind field and background flow are ignored.Statistical analysis and study of basic characteristics on wind and ocean wave in The Yangtse River Estuary are carried out to rich the knowledge of the ocean waves in The Yangtse River Estuary. The situ-observation data... |
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