基于潮间带现场数据的底部切应力算法对比

底部切应力作为水动力和泥沙输移模型中的关键参数，对底床泥沙起动、侵蚀淤积速率的研究十分重要。目前基于现场实测流速数据计算底部切应力的理论方法有6种：LP mean法、LP max法、TKE法、TKEW法、RS法和ID法，这些方法都有其特定的适用条件。河口海岸浅水区域水流和波浪作用复杂，遴选合适的方法计算底部切应力非常重要。本文以江苏大丰斗龙港1个观测点(中值粒径为68.56 μm)和上海崇明东滩2个观测点(中值粒径分别为12.89 μm和45.02 μm)为例，利用声学三维高频流速仪ADV (Acoustic Doppler Velocimetry)和波潮仪(RBR wave)进行现场数据采集，分别用6种理论计算方法对底部切应力进行计算，结果表明：(1)LP mean法受到平均流速、仪器探头距离底部床面高度以及波浪强弱的影响，会低估底部切应力；(2)LP max法和TKE法在流速变化幅度较大、波浪作用明显的潮间带浅水环境会高估底部切应力；(3)TKEW法在TKE法的基础上进行了改进，更适用于波浪作用强烈的潮间带浅水环境底部切应力的计算；(4)RS法计算结果受到波浪影响会产生误差，存在较大波浪时，ID法计算结果比RS法计算结果更加可信，但是在水深条件不足时，ID法会高估底部切应力。

Comparison of methods for calculating bottom shear stress based on intertidal flat field data

As a key parameter in hydrodynamic and sediment transport models, bottom shear stress is very important to study the initiation and erosion rates of bottom sediment. At present, there are six theoretical methods for calculating bottom shear stress based on field measured flow velocity data: LP mean method, LP max method, TKE method, TKEW method, RS method and ID method, all of which have their specific applicable conditions. It is very important to select an appropriate method to calculate the bottom shear stress in the shallow water area of estuarine and coastal areas where the actions of current and wave are complex. In this study, one observation site at Dafeng Doulong Port, Jiangsu Province (median particle size: 68.56 μm) and two observation sites at Eastern Chongming Shoal, Shanghai (median particle size: 12.89 μm and 45.02 μm) were taken as examples. Field data were collected using Acoustic Doppler Velocimetry and wave measurement instrument (RBR wave), and the bottom shear stress was calculated by six theoretical methods. The results show that: (1) The LP mean method is affected by the average velocity, the distance from the probe to bed and the strength of waves, which underestimates the bottom shear stress and is not suitable for shallow water environment in intertidal flat; (2) LP max method and TKE method can overestimate shear stress in shallow water environment of intertidal flat where flow velocity varies greatly and wave action is obvious; (3) TKEW method was modified on the basis of TKE method, which is more suitable for solving the bottom shear stress under strong wave action; (4) The results of RS method are affected by waves, and the results of ID method are more reliable than those of RS method when large waves exist, but ID method will overestimate the bottom shear stress when water depth is insufficient.