| Dam failure is a low-probability,high-hazard social disaster.Earthen dams are widely used because they can be made locally,are highly adaptable to foundation deformation,and are simple to construct.However,the cohesive force between particles of bulk materials is weak,and the top of the dam is prone to overflow.In order to reduce the serious consequences caused by its breach,the dam breach process is simulated to reach a reference for theoretical calculations of the breach and practical engineering.This paper considers the breach in the case of diffuse top,and uses the fluid dynamics software Fluent to simulate the three-dimensional breach flow,and tries to introduce the dynamic grid technique for the development of the breach during the breach process.Combining the basic theories of hydraulics,geotechnics,and fluid mechanics,the RNG k-εturbulence model is used for transient calculations of the computational domain,and the VOF method is chosen for the free liquid surface treatment.The computational model is rate fixed with the large-scale dam-break test,and the errors of the shear stress-induced erosion rate,flow curve,and water level drop process line calculations are all within 5%,which proves the reliability of Fluent to study the dam-break water flow problem and This demonstrates the reliability and feasibility of Fluent’s study of dam failure flow problems.The dam-break process was set up for five inlet flow rates and ten moments of the breach size model combination of fifty conditions,mainly for the hydraulic characteristics of the earth dam breach to study the water surface line,flow velocity field,breach and dam body pressure,the shear stress on the breach,local head loss and other aspects of the different conditions in the dam-break process,the main findings of the study are as follows:(1)The maximum point pressure and shear stress applied at different inlet flow velocities and different breach sizes were obtained through simulation data processing.The relationship between the maximum point pressure and the width and flow velocity of the vent and the relationship between the maximum shear stress at the vent and the width and flow velocity of the vent.(2)The local head loss variation law and failure interval are obtained for different sections and different roughness at the time of dam failure.The local head loss failure interval is [106.65 m,126.65m] for Ks < 0.001 m and [116.65 m,126.65m] for Ks> 0.001 m.The local head loss decreases and then increases and then decreases again,and the failure interval decreases with the increase of roughness.(3)At the same breach size,as the inlet velocity increases,the pressure on the dam becomes negatively correlated,the shear stress on the dam increases,the water level on the headwater slope decreases less,the water level in the breach section of the earthen dam decreases more,the water level on the backwater slope decreases more or less the same as the slope of the backwater slope,and the flow rate through the breach and the flow rate downstream increases.(4)Under the same inlet velocity,the pressure and shear stress increases and then decreases with the increase of the breach,and the water level difference between upstream and downstream decreases.When the breach is too large,water fins are generated on both sides of the wall and impact the shore slope.The flow velocity through the breach and the flow downstream decreases.The overall flow velocity in front of the dam is relatively stable,and the flow velocity is in the upper and lower range of the inlet velocity,which is less affected by the change of the size of the breach.The flow velocity over the dam gradually increases,and the flow velocity at the toe of the backwater slope of the homogeneous earth dam gradually decreases with the increase of the breach. |
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