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In this paper, a numerical wave flume with full functions of wave generation and absorption is proposed under the framework of Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH). In contrast to the conventional SPH numerical wave flumes using wave paddles and sponge layers, the wave generation and absorption in this paper are implemented using non-reflective open boundary conditions, which are capable of generating multiple types of waves, including solitary waves, linear and second-order regular waves. Passive and active wave absorption are available for transmitting incident waves and preventing secondary reflections. Steady or unsteady flows can also be defined during wave generation and absorption to set up numerical wave-flow flumes. The results on a series of validation cases indicate that this SPH numerical wave flume not only performs satisfactorily in conventional wave generation and absorption and nonlinear wave-structure interaction simulations but also has the following three advantages: 1) It avoids using the sponge layers to shorten the flumes, which improves the efficiency; 2) it keeps the mean water level steady and prevents water level shifting; and 3) it implements steady/unsteady flow and wave-flow interactions to model a wider range of hydrodynamic problems. [ABSTRACT FROM AUTHOR]

ABSTRACT Ni X.; Huang S.; Feng W., and Yao W., 2018. Numerical simulation of tidal bores using SPH method. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 951–956. Coconut Creek (Florida), ISSN 0749-0208. A tidal bore is a natural hydraulic phenomenon normally formed in funnel-shaped estuaries with large tidal ranges. Water levels and flow velocities change rapidly in both magnitude and direction when a tidal bore arrives. These strongly nonlinear water body movements have significant influences on scouring and deposition processes along the riverbed and produce hydrodynamic impacts on piers and dikes. In this paper, a mesh-free numerical method known as the smoothed particle hydrodynamics (SPH) method is used to implement a numerical model capable of handling complex free-surface flows and solve the Navier-Stokes equations with a large-eddy simulation. A tidal bore generation scheme suited for a mesh-free numerical method is also proposed based on the SPH open boundary technique. Various types of tidal bores, including undular bores, weakly breaking bores and breaking bores, are simulated and validated with measured data. The numerical results represent the evolutionary processes and hydrodynamic characteristics of tidal bores ranging from weak to strong intensities. The generation and evolution of dipole substructures in breaking tidal bores are also discussed. By studying the bed shear stresses and depth-averaged vorticities of the tidal bores, it can be concluded that the sediment incipience intensity grows nonlinearly in the second order with an increase in the tidal bore intensity, while the sediment transportation intensity grows linearly. [ABSTRACT FROM AUTHOR]

Balancing the trade-off between the simulation detail and the computational efficiency in a hydrodynamic numerical model is generally difficult, e.g., one can hardly find a single set of governing equations that is capable of efficiently describing the wave propagation processes from offshore to nearshore and accurately presenting the details of wave breaking and interacting with coastal structures simultaneously. To address this predicament, open boundary coupling schemes are proposed in this paper to hybridize a SWE (shallow water equations)-based SPH (Smoothed Particle Hydrodynamics) model with a NS (Navier-Stokes) equations-based SPH model. The NS-SPH model is used to present the nonlinear hydrodynamic features in the main study domains, while the remaining domains are simulated with the SWE-SPH model, which calculates much faster than the NS-SPH model. The hybrid SPH models are applied to simulate solitary wave propagation, steady flows over a bump, dam breaking waves and standing waves. The hybridization performance on the information transmitting, mass and energy conservation, simulation detail, computational accuracy, computational efficiency and computational convergence speed is fully validated and evaluated. The results indicate that the proposed open boundary coupling schemes are capable of improving the computational efficiency on the premise of computational accuracy and simulation detail. • A two-way open boundary coupling scheme is proposed for the hybridization of SPH models. • The one-way coupling scheme is modified with a nonreflective open boundary condition. • The coupling schemes improve computational efficiency on the premise of accuracy. [ABSTRACT FROM AUTHOR]