中文摘要：

通过分析不同长度的过渡段对连接连续弯曲河道后弯水流的影响，探讨航道整治工程设计中过渡段长度的确定依据。在模型试验资料验证的基础上，采用RNGκ-ε湍流模型和VOF方法处理自由水面的水气两相流数学模型，对连续弯道水流进行模拟计算。对比不同过渡段长度条件下后弯水流特征的变化情况，发现增加过渡段长度可以减弱前弯对后弯水流的影响。当相对过渡段长度大于一定数值后，后弯的特征水流情况保持稳定，增加过渡段长度所引起的减弱前弯水流对后弯水流影响的效应基本丧失。以后弯水流条件趋于稳定为特征定义临界过渡段长度，可作为航道尺度设计中过渡段长度取值的计算基础。

英文摘要：

The length of transition section is an important parameter of continuous meandering rivers, which has a profound influence on the flow regime in the second bend. Based on the experimental results from the physical mod- els, an air-water two-phase flow model is derived for flow simulation in the continuous bends. Both re-normalisation group （RNG） k-epsilon model and volume of fluid method （VOF） are used in the model derivation. Through inspec- ting various flow regimes due to different lengths of transition sections, it is found that the effect of flow in the front bend on the second bend can be weakened when the length of transition section increases. However, the flow in the second bend will be stabilized when the length exceeds a threshold value. The front bend has a neglectable influence on the flow in the second bend thereafter. Thus, a critical length of transition section can be defined, which can be used as the base value for the design of transition section in practical application.