极浅水边界层的沉积环境效应  

Extremely Shallow Water Benthic Boundary Layer Processes and the Resultant Sedimentological and Morphological Characteristics

作　　者：高抒[1] 

机构地区：[1]南京大学海岸与海岛开发教育部重点实验室,南京210093

出　　处：《沉积学报》2010年第5期926-932,共7页Acta Sedimentologica Sinica

基　　金：国家自然科学基金重点项目"长江口邻近海区沉积动力过程对流域变化的响应"(批准号:40830853)资助

摘　　要：极浅水环境是水深远小于正常边界层厚度的环境,潮滩滩面和潮水沟就经常处于这种环境之中。来自江苏潮滩的观察资料表明,落潮后期滩面和潮水沟在薄层低速水流作用下可形成浅水波痕、平床和次级潮水沟形态,而边界层内的流速结构仍然得以维持,物质输运强度也与Von Krmn-Prandtl模型所定义的u100数值相一致。涨急时段中潮位附近形成的滩面涌潮是极浅水边界层的另一种动力学行为,它代表薄层高速水流作用下发生的底部边界层系统的崩溃,此时Von Krmn-Prandtl模型所刻画的流速结构不复存在。滩面涌潮高度是系统崩溃的临界水深,它可以定量地表示为Hb=4z0。极浅水边界层过程对潮滩沉积和地貌形成具有独特的作用。An extremely shallow water environment is defined as an environment where the water depth is much smaller than the thickness of a fully developed benthic boundary layer.The intertidal flat and tidal creeks represent examples of such environments.Observations from the Jiangsu coast show that,towards the end of an ebb tide phase,the bed surface and tidal creeks are subjected to water flows with a low speed（0.1 m/s in magnitude）and a very small water depth（1 cm in magnitude）.As a result,flat-topped ripples and plane bed are formed on the lower parts of the intertidal zone,whilst small-scale secondary creeks develop at the bottom of major creeks over the upper part of the intertidal zone.In these cases,the flow structure within the boundary appears to be maintained,with the u100 value derived being applicable to the calculation of sediment transport rates.Tidal surges occurring over the middle part of the intertidal flat are another type of behavior for the small flow depth boundary layer,representing destruction to the Von Kárm án-Prandtl flow structure;the height of the tidal surge is equivalent to the critical water depth associated with the system collapse,which can be expressed quantitatively as Hb=4 z0.Thus,the processes of the small flow depth boundary layer play a unique role in influencing the sedimentological and morphological patterns of intertidal flats.

关 键 词：极浅水边界层 潮滩 床面形态 滩面涌潮高度 沉积环境 江苏海岸 

分 类 号：P512.2[天文地球—地质学]