A meshless method is used to simulate free-surface fluid flows containing solid particles, motivated by the need to simulate river ice dynamics problems. A Smoothed Particle Hydrodynamics model (SPH), with an arbitrary Lagrangian-Eulerian formulation for the fluid phase, is two-way coupled with the Discrete Element Method (DEM) for the solid phase. Validation test cases include a bouncing sphere on a level surface, a collapse of a granular column, wedge entry into still water and solids of different densities falling into still water. The computed results using the SPH-DEM model agree quantitatively with the expected behaviour in the test cases. Numerical convergence is demonstrated for the wedge entry validation case. The SPH-DEM model is then used to simulate the stability of floating ice blocks approaching a stationary cover and ice accumulation upstream of an obstruction. The results show promise to serve as a useful quantitative engineering tool.

No abstract

Smoothed particle hydrodynamics (SPH) is known to be well adapted for the simulation of dynamic free surface flow. This paper examines the applicability of a weakly compressible SPH Arbitrary Lagrange Euler (ALE) method to the simulation of transient flows in hydraulic machines. The novelty of the approach is to use the properties of SPH-ALE in order to simulate rotor-stator interactions without a rotor-stator interface. Due to the ALE formalism, the particle velocity is a free parameter and can be chosen independently of the flow velocity. Instead of a rotor-stator interface, we have blocks of particles with different particle velocities. To validate the results, the flow field around a static airfoil and the pressure coefficient on the profile are compared with the results of an in-house Euler solver which is an inviscid finite volume code. Results of transient simulations prove the capability of the method to detect unsteady pressure waves and emphasize its applicability to study global phenomena in multistage machines.

<p>We have been investigating the variation of turbidity in the surface waters of Carpenter Reservoir, British Columbia, Canada. This long (~50 km) and narrow (~1 km) hydroelectric reservoir receives glacially-turbid meltwater, and there is concern that this turbidity limits light availability in the reservoir and, in turn, limits biological productivity. To address these concerns and to investigate the physical processes affecting turbidity, we use a combination of field observations, numerical simulations and analytical scaling arguments.</p> <p>Vertical profiles of temperature and turbidity indicate that during the summer stratified period, inflows plunge below the thermocline and travel along the bottom of the reservoir to the deep withdrawals. The load of glacial particles entering the reservoir is highest in summer. Yet, remarkably, turbidity in the epilimnion declines due to a combination of two processes: (1) thermal stratification isolates the epilimnion from plunging glacial inflows, and (2) suspended particles settle from the epilimnion to the hypolimnion. Nevertheless, profiles collected during strong winds indicate that episodic wind events can upwell turbid fluid from below the epilimnion into the surface waters. The upwelled water is then advected downstream, setting up a longitudinal turbidity gradient.</p> <p>Two-dimensional numerical simulations support the notion that wind-driven upwelling in summer contributes to a small turbidity flux into the epilimnion. The simulated thermocline deflections reveal waves with two dominant periods. The first period of approximately 4 days corresponds to the fundamental internal seiche, and the second period of 1 day corresponds to direct wind-forcing by diurnal winds. Changes in turbidity along the length of the epilimnion are determined by wind-driven fluxes at the upstream end of the epilimnion, longitudinal dispersion along the length of the epilimnion and particle settling out of the epilimnion.</p>