Numerical simulation of influence of transition section on continuously curved channel flow

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 models,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.