Mathematical modelling of shallow flows: closure models drawn from grain-scale mechanics of sediment transport and flow hydrodynamics

Canadian Journal of Civil Engineering 36(10) 1605–16Mathematical modelling of river processes is, nowadays, a key element in river engineering and planning. River modelling tools should rest on conceptual models drawn from mechanics of sediment transport, river mechanics, and river hydrodynamics. The objectives of the present work are (i) to describe conceptual models of sediment transport, deduced from grain-scale mechanics of sediment transport and turbulent flow hydrodynamics, and (ii) to present solutions to specific river morphology problems. The conceptual models described are applicable to the morphologic evolution of rivers subjected to the transport of poorly sorted sediment mixtures at low shear stresses and to geomorphic flows featuring intense sediment transport at high shear stresses. In common, these applications share the fact that sediment transport and flow resistance depend, essentially, on grain-scale phenomena. The idealized flow structures are presented and discussed. Numerical solutions for equilibrium and nonequilibrium sediment transport are presented and compared with laboratory and field data

Geomorphic dam-break flows. Part I: conceptual model

Proceedings of the Institution of Civil Engineers - Water Management 163 Issue WM6This paper presents a one-dimensional conceptual model for simulating geomorphic dam-break flows. The model is based on conservation laws drawn from continuum mixture theory that are integrated over the flow depth,assuming that the f10w is composed of two transport layers. Closure equations were derived from the review and reanalysis of previous studies on granular flow,debris f10w and sheet flow. The sediment transport is modelled assuming capacity regime. The c10sure equation coefficients are estimated based on a large set of experiments available in the literature. The validity of the model is discussed by computing the most relevant dimensionless parameters. The model is expected to simulate adequately the friction at the wave front and the sheet flow throughout the wave profile. Ultimately, although the problem incorporates complex phenomena,the model can be easily implemented by practising engineers for simulating one- dimensional geomorphic dam-break flows. The implementation and the verification of the adequacy of the model for simulating these flows are presented in a 'companion paper

Geomorphic dam-break flows. Part I: conceptual model

Proceedings of the Institution of Civil Engineers - Water Management 163 Issue WM6This paper presents a one-dimensional conceptual model for simulating geomorphic dam-break flows. The model is based on conservation laws drawn from continuum mixture theory that are integrated over the flow depth,assuming that the f10w is composed of two transport layers. Closure equations were derived from the review and reanalysis of previous studies on granular flow,debris f10w and sheet flow. The sediment transport is modelled assuming capacity regime. The c10sure equation coefficients are estimated based on a large set of experiments available in the literature. The validity of the model is discussed by computing the most relevant dimensionless parameters. The model is expected to simulate adequately the friction at the wave front and the sheet flow throughout the wave profile. Ultimately, although the problem incorporates complex phenomena,the model can be easily implemented by practising engineers for simulating one- dimensional geomorphic dam-break flows. The implementation and the verification of the adequacy of the model for simulating these flows are presented in a 'companion paper

Geomorphic dam-break flows. Part II: numerical simulation

Proceedings of the Institution of Civil Engineers - Water Management 163 Issue WM