洞庭湖流速垂向分布特性

Properties of Vertical Distribution of Velocity in Dongtinghu Lake

根据洞庭湖不同测点的野外实测数据,结合测点的环境状况(有无水生植被),分析洞庭湖不同位置的流速垂向分布规律,发现底部无水生植物影响的主湖区与航道中心时均流速分布呈"J"形,采用对数律对流速剖面进行拟合,相关系数在0.95以上;在有水生植物分布的洲滩,时均流速的垂向分布偏离"J"形,具有明显的3层结构,且冠顶以上水流时均流速垂向分布满足对数律;受淹没水生植物影响,冠层内部的时均流速及切应力减小,有利于泥沙的沉积。

Based on the field measured data at sampling sites in Dongtinghu Lake,combined with the environmental conditions around samples,this paper analyzed the properties of vertical distribution of velocity at different locations in Dongtinghu Lake.The results indicate that for the main lake area without the influence of submerged vegetation,the time-averaged velocity profiles presented"J"shape,and according to the least squares fit with the classic logarithmic formula,their correlation coefficients were all greater than 0.95.For the floodplain with the presence of submerged aquatic vegetations,the time-averaged velocity distributions deviated from the"J"profiles.Three layers were appeared obviously and the velocity profile above the top of canopy followed the logarithmic forms.Affected by the submerged aquatic vegetation,the time-averaged velocity and shear stress of flow within the canopy were decreased,which was beneficial for the sediment deposition.