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Numerical Modeling of Sediment Transport and Bed Evolution in Nonuniform Open-Channel Flows

Zerihun Yebegaeshet T.

Archives of Hydro-Engineering and Environmental Mechanics

2024

Vol. 71, nr 1

1--26

The shallow-water and multilayer hydrostatic models have been commonly used to analyze the problems of a sediment-laden, plane open-channel flow. The models are adequate to solve a quasi-hydrostatic flow problem, but their accuracy deteriorates as the effects of the vertical acceleration gain in significance. Herein, a higher-order numerical model for treating the problems of unsteady, plane open-channel flow over a movable bed is proposed. In this model, the flow hydrodynamics is governed by the depth-averaged Boussinesq-type equations, and the bed morphodynamics is determined by an Exner-type equation and additional equations describing the non-equilibrium transports of suspended load and bed load. A hybrid finite-volume and finite-difference scheme was used to discretize and solve the governing equations, yielding solutions that are in satisfactory agreement with the experimental data. Overall, the results of the proposed model for the temporal free-surface profile and bed evolution were fairly adequate. For the two particular cases considered, however, the quality of its results was moderately affected by the effects of the three-dimensional characteristics of the dam-break flow and the sliding of the dike body due to sub-surface flow. The results of this investigation highlight the importance of including a higher-order Boussinesq-type correction for refining sediment transport computations.

The pseudo-critical vapour-liquid flow

Downar-Zapolski P., Bilicki Z.

Archives of Thermodynamics

1998

Vol. 19, no 3/4

13-25

This paper investigates the influence of non-equilibrium evaporation on the properties of the critical flow of vapour-liquid mixture. As the non-equilibrium vapour generation is assumed to be dominant in a vapour-liquid flow, the Homogeneous Relaxation Model (HRM), with non-equilibrium mass transition, is selected and reduced to the equation for the linear pressure waves. Basing on this equation, the evolution of linear pressure wave in the non-equilibrium, two-phase mixture has been calculated. The conclusions coming from this calculations created a background for the concept of the pseudo-critical flow. A short description of the pseudo-critical flow regime is given and the main difference between the critical flow of equilibrium and non-equilibrium fluid are discussed. Finally, the remarks concerning a kind of relativity of the critical flow for non-equilibrium fluids are given.