Abstract

Field experiments on fluctuation velocity were carried out at different sites: section Xuliujing nearby estuary of Yangtze River, section Huanglingmia of middle of Yangtze River and the outlet of open diversion channel of Three Gorges Project with an Acoustic Doppler Current Profile (ADCP). And a number of data such as velocity of different discharge and different vertical line were obtained. Reynolds stress distribution along water depth in middle stream and near the bank was analyzed. On the basis of Prandtl’s mixing length, relationship between mixing length and water depth was researched, and the calculation method of Reynolds stress was discussed. The paper also presented the polynomial fitting method to calculating mixing length, then Reynolds stress was calculated by using the polynomial. The calculation results showed good agreement with the experiments.

Keywords: natural river, Prandtl’s mixing length, Reynolds stress, momentum transfer