The purpose of this paper is to study the individual and combined effect of upstream planform curvature and difference in bed elevations at the tributary entrance to the confluence on the flow in the confluence hydrodynamics zone. To do this, flow at right-angled confluences with three planforms and four values of bed elevation discordance ratio (Δz T /h d ) is simulated using a threedimensional (3D) numerical model. Three confluence planforms include confluences with the (1) straight tributary canal (SC), (2) right bend (RB) and (3) left bend (LB) in the tributary. Four Δz T /h d values in the range [0.0, 0.5] include both concordant and discordant beds' confluences. Overall, nine cases with the straight main canal are considered. Special attention is paid to the flow deflection and flow separation zones since the former affects transfer of momentum from the tributary to the main canal and the latter affects transport capacity of the post-confluence channel. Comparison of the results reveals that the influence of RB in the tributary is practically negligible in comparison to the straight canal case. With the increasing difference in bed elevations between the tributary and main canals (Δz T ), the presence of LB strengthens 3D flow and the structure of the recirculation zone is destroyed.

The capability of the smoothed-particle hydrodynamics (SPH) method to model supercritical flow in circular pipe bends is considered. The standard SPH method, which makes use of dynamic boundary particles (DBP), is supplemented with the original algorithm for the treatment of open boundaries. The method is assessed through a comparison with measured free-surface profiles in a pipe bend, and already proposed regression curves for estimation of the flow-type in a pipe bend. The sensitivity of the model to different parameters is also evaluated. It is shown that an adequate choice of the artificial viscosity coefficient and the initial particle spacing can lead to correct presentation of the flow-type in a bend. Due to easiness of its implementation, the SPH method can be efficiently used in the design of circular conduits with supercritical flow in a bend, such as tunnel spillways, and bottom outlets of dams, or storm sewers.

No abstract

No abstract

The exchange discharge model (EDM) is the model that was developed for the estimation of a stagedischarge curve and flood routing in compound channels. It was thoroughly tested against experimental data in different compound channel layouts. However, there is a little evidence on its application in rivers. This paper studies EDM performance in estimating stage-discharge curve at two gauging stations on the same river with different hydraulic conditions and compares its results with the traditional, divided channel method (DCM). The contribution of momentum fluxes due to turbulence diffusion and mass exchange to the total energy loss are analysed. It is found that EDM parameter values (ψ t and ψ g ) depend on the hydraulic conditions at a gauging station. In the case of M1-type water surface profile, the ψ t -value increases and the effect of mass transfer is negligible. In the case of M2-type profile, the ψ t -value decreases and the momentum flux due to mass transfer becomes dominant. Nonetheless, the lower ψ t -value does not result in smaller additional loss due to turbulence diffusion, since the velocity difference between the main channel and the floodplain increases. Although the EDM and DCM provide approximately the same total discharge, EDM gives more realistic discharge distribution (main channel discharge is reduced and that on the floodplain is increased by 30-40% due to mass transfer caused by non-prismaticity of the channel).