Numerical simulation of 2D hydraulic jumps using SPH method

A hydraulic jump that generally occurs in river or spillway is a rapid transition from supercritical to subcritical flow characterized by the development of large-scale turbulence, surface waves, energy dissipation and considerable air entrainment. The hydraulic jump is widely used as energy dissipaters in hydraulic engineering due to the high energy dissipation rate. In this study, a weakly compressible smoothed particle hydrodynamics model (WCSPH) is established to simulate the 2D hydraulic jump in open channel. To test the model, two hydraulic jump cases with different inflow Froude number are simulated. The comparison between numerical conjugate depths in the subcritical section with theoretical results show generally good agreement with theory. In addition, an aeration at the jump toe can be clearly observed in numerical results with only Single-phase flow. It is proved that SPH method has unique advantages dealing with the hydraulic jumps

On the non-slip boundary condition enforcement in SPH methods.

The implementation of boundary conditions is one of the points where the SPH methodology still has some work to do. The aim of the present work is to provide an in-depth analysis of the most representative mirroring techniques used in SPH to enforce boundary conditions (BC) along solid profiles. We specifically refer to dummy particles, ghost particles, and Takeda et al. [1] boundary integrals. A Pouseuille flow has been used as a example to gradually evaluate the accuracy of the different implementations. Our goal is to test the behavior of the second-order differential operator with the proposed boundary extensions when the smoothing length h and other dicretization parameters as dx/h tend simultaneously to zero. First, using a smoothed continuous approximation of the unidirectional Pouseuille problem, the evolution of the velocity profile has been studied focusing on the values of the velocity and the viscous shear at the boundaries, where the exact solution should be approximated as h decreases. Second, to evaluate the impact of the discretization of the problem, an Eulerian SPH discrete version of the former problem has been implemented and similar results have been monitored. Finally, for the sake of completeness, a 2D Lagrangian SPH implementation of the problem has been also studied to compare the consequences of the particle movemen

SPH simulation of free overfall in open channels with even and uneven bottom

The free overfall can be used as a simple and accurate device for flow measurement in open channels. In the past, the solution to this problem was found mainly through simplified theoretical expressions or on the basis of experimental data. In this paper, using the meshless smoothed particle hydrodynamics (SPH) method, the free overfall in open channels with even and uneven bottom is investigated. For the even bottom case, subcritical, critical and supercritical flows are simulated. For the uneven bottom case, supercritical flows with different Froude numbers are considered. The free surface profiles are predicted and compared with theoretical and experimental solutions in literature and good agreements are obtained. Keywords: SPH, free overfall, even and uneven bottom, subcritical flow, critical flow, supercritical flow

Modelling of the dispersed phase motion in free-surface flows with the two-fluid smoothed particle hydrodynamics approach

The sediment transport is an important problem in hydro-engineering. Accurate numerical modelling of this complex phenomenon remains a challenging task. In the present study we employ the Smoothed Particle Hydrodynamics (SPH) approach in the two-fluid formulation to compute the interactions between the carrier and dispersed phases. The main goal is to test this rather uncharted SPH variant for simple cases and to find problematic points that require further improvement. We present initial results of validation with experiment involving a vertical sheet of sand entering the water tank through free surface, as well as results from a simplified quasi-2D study of sedimentation

Particle methods parallel implementations by GP-GPU strategies

This paper outlines the problems found in the parallelization of SPH (Smoothed Particle Hydrodynamics) algorithms using Graphics Processing Units. Different results of some parallel GPU implementations in terms of the speed-up and the scalability compared to the CPU sequential codes are shown. The most problematic stage in the GPU-SPH algorithms is the one responsible for locating neighboring particles and building the vectors where this information is stored, since these specific algorithms raise many difficulties for a data-level parallelization. Because of the fact that the neighbor location using linked lists does not show enough data-level parallelism, two new approaches have been proposed to minimize bank conflicts in the writing and subsequent reading of the neighbor lists. The first strategy proposes an efficient coordination between CPU-GPU, using GPU algorithms for those stages that allow a straight forward parallelization, and sequential CPU algorithms for those instructions that involve some kind of vector reduction. This coordination provides a relatively orderly reading of the neighbor lists in the interactions stage, achieving a speed-up factor of x47 in this stage. However, since the construction of the neighbor lists is quite expensive, it is achieved an overall speed-up of x41. The second strategy seeks to maximize the use of the GPU in the neighbor’s location process by executing a specific vector sorting algorithm that allows some data-level parallelism. Although this strategy has succeeded in improving the speed-up on the stage of neighboring location, the global speed-up on the interactions stage falls, due to inefficient reading of the neighbor vectors. Some changes to these strategies are proposed, aimed at maximizing the computational load of the GPU and using the GPU texture-units, in order to reach the maximum speed-up for such codes. Different practical applications have been added to the mentioned GPU codes. First, the classical dam-break problem is studied. Second, the wave impact of the sloshing fluid contained in LNG vessel tanks is also simulated as a practical example of particle methods

Sph modelling of long-term sway-sloshing motion in a rectangular tank

This work aims to model long-term simulations of sway-sloshing motion in a partially filled rectangular tank with different water depths and enforced motion frequencies. The lateral motion frequency of the tank is chosen so as to coincide with the lowest theoretical natural frequency for the corresponding beam of the tank and initial depth of water reserve. A truly meshless method, Smoothed Particle Hydrodynamics (SPH) is used to discretize and solve the governing equations. It is shown that numerical results of the proposed SPH scheme are in good agreement with experimental and numerical findings of the literature