外文翻译---明渠中非恒定流和非均匀泥沙输移的二维数值模拟(节选)

have been reported (Holly and Rahuel 1990; and others). A fullycoupled model is usually more stable than a decoupled model.However, establishing a fully coupled model requires solving all the flowand sediment transport equations offlowproblem

may

reduce

simultaneously. The nonlinearity the

efficiency

of

sediment

transportsimulation,which can be mathematically simplified to a linear problem. Inaddition,the time scales of flow and channel morphodynamic processes maybedifferent, especially in the case where bed load is dominant.Thereforefully coupling the flow and sediment transport may not becost-effective. Following Wu (1991) and Wu and Vieira (2002), the present modeladopts a “semicoupling” procedure, in which the flow calculationis

decoupledfromsedimentcalculation,butthethreecomponentsofthesediment module (sediment transport, bed change, and bedmaterial sorting) are solved in a coupled fashion. This semicoupling procedureis very stable and efficient computationally.

Governing Equations and BoundaryConditions Governing Equations of Open-ChannelFlow

The depth-integrated continuity and momentum equationsofopen-channel floware

wheret=time; x and y=horizontal Cartesian coordinates; h=flow depth; U

andV=depth-averaged flow velocities in x and y directions;

?s=water

surface elevation; g=gravitational acceleration; r=density of flow;Txx, Txy, Tyx, andTyy=depth-averaged turbulent stresses;

shear stresses that are determinedby

;

and

, in which n=Manning’s

??bx and ??by=bed

roughness coefficient and w=bed angle with thehorizontal.

The turbulent shear stresses are determined by theBoussinesq’s assumption