Water Flow Characteristics Of Mountainous Branching River Sections And Method Of Determining The Width Of The Channel Regulation Line

There are a large number of branching rivers in the mountainous areas of southwest China.As a special river form,the topography of the riverbed and the characteristics of the water flow are significantly different from those of a single river,making the water flow conditions in the river section more complex and adversely affecting the navigation of ships and flooding.As the most important design parameter in the remediation project,the width of the channel remediation line directly determines the quality of the remediation project,so it is important to establish the calculation method of the width of the channel remediation line in the mountainous branching rivers.This paper uses a combination of theoretical analysis and numerical simulation to achieve the following results:(1)Through the numerical simulation of the two-dimensional water flow in the study river section,the variation rule between the diversion ratio and flow in the mountainous branching river section was derived: the diversion ratio and flow are logarithmically distributed,the influence of flow on the diversion ratio gradually decreases with the increase of flow,the diversion ratio curve tends to a certain value,the diversion ratio basically does not change,and flow is no longer the influencing factor of the change of the diversion ratio.(2)By analysing the flow velocities and water levels in the various divisions of the study river section,the characteristics of the flow in the mountainous branching river section are derived: the velocity gradient in the diversion zone is generally small,with a large velocity gradient at the inlet of the branching channel forming a high velocity zone and a low velocity stagnation zone near the river centre;the flow velocity in the diversion zone decreases along its course and drops to a minimum value near the river centre,with the velocity decrease increasing as the flow increases;the water level in the diversion zone changes slightly,with the water level at the inlet of the branching channel fluctuating.The water level in the diversion zone fluctuates,and the water level at the inlet of the channel fluctuates.The velocity characteristics of the branch channel in the diversion zone are mainly influenced by the morphology of the river core,with the velocity of the narrower side of the channel varying significantly in relation to the water surface ratio when the river core is close to the shore.The flow characteristics of the confluence area are basically the same as those of the diversion area.(3)The formula for calculating the width of the channel training line in the mountainous branch river section was constructed by introducing the flow ratio of the main branch river,combining the width of the flat beach,the average water depth,the specific drop of the riverbed and the average flow velocity,etc.The parameters of the established formula were derived by the least squares method,and the formula for calculating the width of the channel training line was compared with the hydraulics formula method and the flow-ratio-drop formula method through linear regression analysis,which showed that the established formula for calculating the width of the channel training line in the branch river section was more accurate.(4)The morphological characteristics and flow conditions of the branching river sections were used to determine the navigable branching channels in the study river section during the dry season.The design water level and regulation water level of the study section were determined,and the characteristics and applicability of each regulation water level determination method were derived.The width calculation formulae of the channel regulation line established in this paper were compared with the values calculated by the commonly used regulation line width formulae,showing that the formulae proposed in this paper can be used for the calculation of the regulation parameters of the study river section.(5)Based on the formula for calculating the width of the channel training line constructed in this paper,a channel training plan was developed for the branch branch channel section of the Yujiang River Bridge.The two-dimensional mathematical model of water flow was applied to analyse and predict the stability of the channel,and the numerical simulation results showed that the overall stability of the channel was good.The results of the numerical simulation show that the overall stability of the channel is good.