A Research Of Flow In Asymmetrical Bends

Most natural rivers have some local meandering river.The hydrodynamics in meandering river plays an important role about sediment transport,morphological evolution and scouring and silting on the river bed.Because of the influence of the curved river's morphology,flow in meander open channel is a complex spiral flow,this has significantly different with water in the straight flume.The generation of spiral flow can form lateral circulation and transverse slope of water surface,so the research of flow in bends has important significance.The plane form of natural meandering rivers is asymmetric,it has an important influence on bend flow.Most of existing research is about symmetrical bends,while the research of asymmetric bends is less.So it is necessary to carry out detailed studies about flow in asymmetrical bends.In this paper,three-dimensional numerical model is used to research the flow in Kinoshita-generated meandering bends.Taking into account the skewness and flatness coefficients,this paper sets up six models of asymmetric bends,analyzes the difference of flow in symmetric and the asymmetric bends and the influence of skewness and flatness coefficients from the aspects such as lateral and longitudinal velocity,flow dynamic axis,longitudinal average speed,circulation intensity.Through the comparative analysis of the results,the results show that the high velocity will occur near the convex bank at the apex of bend regardless of asymmetric and symmetrical bend and it is more concentrated in asymmetric bend.In addition,this phenomenon will be more obvious with the increase of skewness and flatness coefficients.longitudinal circulation will appear at the downstream apex with the increase of skewness and flatness coefficients.The small circulation will gradually disappear with skewness and flatness coefficients increasing,the transverse circulation distribution more uneven at the apex of bend.The distribution of bed shear stress in bend consistent with the distribution of longitudinal vertical mean velocity distribution,the high velocity area corresponds to the high shear stress.