斜压作用对河口落潮水流剖面的影响

Effect of baroclinic force on velocity profile of ebb flow in estuary

在咸淡水混合的河口由于水体密度在空间不均匀分布,水流受到斜压影响,其流速分布经常会偏离传统的对数分布。而常用的密度流分布基于常涡黏系数假定,无法用于瞬时流速剖面的拟合。基于水动力方程,得出考虑斜压影响下的湍流切应力分布,分析发现在斜压影响下的湍流切应力呈抛物线分布。在此基础上应用Prandtl混合长理论,提出考虑河口斜压影响的落潮水流流速剖面。通过比较数值模拟结果与实测资料,发现本文公式能很好地校正斜压引起流速剖面对于传统对数分布的偏差,提高拟合精度,得到更趋于合理的拟合参数。

Due to the uneven distribution of water density in space,the flow is affected by baroclinic force,and the velocity profile often deviates from the traditional logarithmic profile in saline-freshwater mixed estuaries.The well-known density flow profile,which is assumed constant eddy viscosity,cannot fit the instantaneous velocity profile.Based on the hydrodynamic equations,we obtain the profile of the turbulent shear stress,which indicates that the distribution of the shear stress is parabolic under the effect of baroclinic force.Then we derive the velocity profile of ebb flow influenced by the baroclinic force through Prandtl’s mixing theory.By comparison with numerical simulation results and experimental data,the proposed equation can correct the deviation between the classical logarithmic and the measurements,improve the fitting accuracy,and obtain the more reasonable fitting parameters.