Research On Flow Characteristics Of Sharp Bend And Hydro-ice Dynamic Properties During The Multi-period

Ice cover is a common hydrological phenomenon in high latitude areas of the upper reaches of the Yellow River,which has a significant impact on drinking water projects and hydrological environment adjustment.Water and sediment characteristics are more typical under ice-cover conditions in sharp bends.To study the Hydro-Ice dynamic properties and material transport laws of curved rivers in various periods,and to solve engineering water transport and environmental problems,field experiments and numerical analysis methods are used.Continuous field experiments of the Shisifenzi reach in different periods,studied the flow characteristics of the open flow period and the frozen period;In addition,simulated the hydraulic characteristics of the bends under the condition of ice flow to explore the basic laws of the ice movement and hydraulic dynamic properties of the river under the coupling effect of Hydro-Ice;based on the measured river topography,utilized 3D and 2D simulation platforms to study the Hydro-Ice dynamic properties of the river in different periods.The research has important value for understanding the law of ice transportation in curves,improving the guarantee rate of water delivery during ice period,and the safety of water delivery during the frozen period.The main research results are as follows:(1)The main flow of the river approached the convex bank during the frozen period.resulting in a higher velocity of the convex bank and a more typical“parabolic distribution”of the hourly average velocity along the water depth during the frozen period in 2020.The main reason is that the flow is reduced(500m~3/s)and the serious blockage of a large number of ice on the concave bank of the curved top,which has changed the flow direction and distribution of the flow.(2)The vertical distribution of the velocity during the frozen period in 2019 is relatively even.The maximum flow velocity is at the relative water depth of 0.4 during the frozen period in 2020,indicated that the roughness of the ice is smaller than the riverbed.The velocity under the ice during the frozen period is less than that of the open flow period,and the longitudinal velocity during the frozen period is the same as that during the open flow period,along the flow direction,which is greater than the lateral and vertical velocity,while the lateral velocity direction is from the convex bank to the concave bank.It shows that the longitudinal velocity during the frozen period still accounts for a relatively large proportion.(3)The turbulence intensity during the frozen period in 2019 is evenly distributed along the water depth,the turbulence intensity along the water depth during the frozen period in2020 roughly obeys the"C"-shaped distribution.It presents a vertical distribution pattern different from that in the open flow period.The longitudinal and lateral turbulence intensity approximately equivalent during the frozen period,while the vertical distribution of turbulence intensity during the open flow period fluctuates greatly.(4)The simulation process of curved rivers ice movement shows that:the river ice mainly concentrates on the concave bank after turning the bend,and the accumulation is obvious,showing the characteristics of fewer convex banks and more concave banks;the ice stagnation area at the top of the bend is typical,and the low velocity area of the concave bank is more larger;the existence of ice increases the lateral circulation of the concave bank,which affects the development of the large circulation at the bottom of the convex bank;the water level of the ice flow on the curved top section is higher than that of the water flow,and the difference becomes smaller with the increase of the curvature;with the increase of curvature,the low velocity area and high turbulent kinetic energy area of the concave bank of the ice flow expand,and the mainstream area of the curved top section gradually shift to the convex bank.(5)The simulation reflects the change of the flow pattern in the bend,and reflects the general law of the change of the main flow of the bend.The FLOW-3D software has a small error in simulating the flow velocity during the open flow period;the RIVER-2D simulates a slightly larger error in the flow velocity during the frozen period,which has certain reference value for understanding the hydraulic dynamic properties of the Hydro-Ice flow during the frozen period.