Based on the method of characteristics, in this study an analytical solution for one-dimensional shallow-water equations is developed to simulate the instantaneous dam-break flows propagating down a triangular wet-bed channel. The internal relationships between the hydraulic properties associated with dam-break flow are investigated through comparisons with well-known analytical solutions for rectangular channels. Meanwhile, laboratory experiments are conducted in a prismatic, horizontal, and smooth flume with a triangular cross section. Nonintrusive digital image processing is applied to obtain water surface profiles and stage hydrographs. Results show that the dam-break flow propagation depends on the dimensionless parameter $h_d^{*}$ , defined as the ratio of initial tailwater depth over the reservoir head. $h_d^{*}$ has a significant effect on the dam-break wave in the downstream flooded area. For $h_d^{*}\le 0.4$ , the water surface profiles in the reservoir for different $h_d^{*}$ at a given time remain similar. For $h_d^{*}\ge 0.5$ , extra negative waves occur in the reservoir, leading to water surface undulations. Undular bores are generated at the dam site and propagate downstream. The time evolution of dam-break flows under three different reservoir heads is similar for the same $h_d^{*}$ . The inception of water surface profile change is earlier when the reservoir head is larger. The analytical model shows satisfactory agreement with the experimental results, though some errors exist between the analytical solution and measurements due to the formation of extra negative waves, a jet, and undular bores. The similarities and discrepancies between the hydraulics in the triangular and rectangular channels are identified analytically in terms of the profiles of water depth, velocity, discharge, bore height, and wave-front celerity with $h_d^{*}$ . The presented solution could be applied to predict the effect of wet-bed conditions on the dam-break wave in triangular channels, while laboratory measurement data could be used for validating analytical and numerical models.

The one-dimensional gravity wave model (GWM) is the result of ignoring the convection term in the Saint-Venant Equations (SVEs), and has the characteristics of fast numerical calculation and low stability requirements. To study its performances and limitations in 1D dam-break flood, this paper verifies the model using a dam-break experiment. The experiment was carried out in a large-scale flume with depth ratios (initial downstream water depth divided by upstream water depth) divided into 0 and 0.1~0.4. The data were collected by image processing technology, and the hydraulic parameters, such as water depth, flow discharge, and wave velocity, were selected for comparison. The experimental results show that the 1D GWM performs an area with constant hydraulic parameters, which is quite different from the experimental results in the dry downstream case. For a depth ratio of 0.1, the second weak discontinuity point, which is connected to the steady zone in the 1D GWM, moves upstream, which is contrary to the experimental situation. For depth ratios of 0.2~0.4, the moving velocity of the second weak discontinuity point is faster than the experimental value, while the velocity of the shock wave is slower. However, as the water depth ratio increases, the hydraulic parameters calculated by 1D GWM in the steady zone gradually approach the experimental value.

Multiphase flows are very important in industrial application. In present study, the force schemes in the pseudopotential LBM for two-phase flows have been compared in detail and the force schemes include Shan-Chen, EDM, MED, and Guo’s schemes. Numerical simulations confirm that all four schemes are consistent with the Laplace law. For Shan-Chen scheme, the smaller τ is, the smaller the surface tension is. However, for other schemes, τ has no effect on surface tension. When 0.6<τ≤1, the achieved density ratio will reduce as τ reduces. During this range of τ, the maximum density ratio of EDM scheme will be greater than that of other schemes. For a constant T, the curves of the maximum spurious currents (u′) has a minimum value which is corresponding to τ′ except for EDM schemes. In the region of τ′<τ≤1, u′ will reduce as τ decreases. On the other hand, in the area of τ≤τ′, u′ will increase as τ decreases. However, for EDM scheme, u′ will increase as τ increases.

A sudden dam failure is usually simulated by the rapid removal of a gate in laboratory tests and numerical simulations. The gate-opening time is often determined according to the Lauber and Hager instantaneous collapse criterion (referred to as the Lauber–Hager criterion), which is established for a rectangular open channel with a dry bed. However, this criterion is not suitable for non-rectangular channels or initial wet-bed conditions. In this study, the effect of the gate-opening time on the wave evolution is investigated by using the large eddy simulation (LES) model. The instantaneous dam-break, namely, a dam-break without a gate, is simulated for comparison. A gate-opening criterion for generating dam-break flow in a non-rectangular wet-bed channel is proposed in this study, which can be used as an extension of the Lauber–Hager criterion and provides a more comprehensive and reasonable estimate of the gate opening time.