Simulation of random wave overtopping by a WCSPH model

In this work the Weakly Compressible SPH-based (WCSPH) model DualSPHysics has been validated and applied to study the random wave overtopping of dike-promenade layout in shallow water conditions. Data from physical model tests carried out in a small-scale wave flume have been used for model validation. The results have been compared in terms of water surface elevation, mean discharges and individual overtopping volumes distribution. The selected geometrical layout is representative of the coastal area of Premià de Mar, in Catalonia (Spain). This stretch of the coast presents both railways and a bike path very close to the shore and therefore exposed to possible sea storms. For the first time an SPH-based model has been employed to reproduce long-lasting wave overtopping tests, made of time series of 1000 irregular waves, which are representative of real sea states. The density diffusion scheme and the modified Dynamic Boundary Conditions have been applied in the present simulations. By employing standard setup for SPH modelling of wave-structure interaction problems of a very long duration, stable simulations and accurate results have been attained

Boundary conditions generated by dynamic particles in SPH methods

Smoothed Particle Hydrodynamics is a purely Lagrangian method that can be applied to a wide variety of fields. The foundation and properties of the so called dynamic boundary particles (DBPs) are described in this paper. These boundary particles share the same equations of continuity and state as the moving particles placed inside the domain, although their positions and velocities remain unaltered in time or are externally prescribed. Theoretical and numerical calculations were carried out to study the collision between a moving particle and a boundary particle. The boundaries were observed to behave in an elastic manner in absence of viscosity. They allow the fluid particles to approach till a critical distance depending on the energy of the incident particle. In addition, a dam break confined in a box was used to check the validity of the approach. The good agreement between experiments and numerical results shows the reliability of DBPs

Modeling dam break behavior over a wet bed by a SPH technique

Dam break evolution over dry and wet beds is analyzed with a smoothed particle hydrodynamics model. The model is shown to accurately fit both experimental dam break profiles and the measured velocities. In addition, the model allows one to study different propagation regimes during the dam break evolution. In particular, different dissipation mechanisms were identified: bottom friction and wave breaking. Although breaking dominates over wet beds at the beginning of the movement, bottom friction becomes the main dissipation mechanism in the long run

Study of the bed velocity induced by twin propellers

Twin propellers without a rudder were studied using a physical model with a fixed clearance distance and three different rotating velocities. Experimental results were compared with results from theoretical expressions developed over the past 50 years for the efflux velocity, axial velocity, and maximum bed velocity. It was found that the efflux velocity equations overestimated the experimental results, whereas the computed axial velocities matched the experimental data reasonably well. However, when maximum bed velocity expressions were compared with experimental results, only one method was found to behave better; overestimation resulted if a quadratic superposition of single jets was used.Peer ReviewedPostprint (published version

Efficient response of an onshore Oscillating Water Column Wave Energy Converter using a one-phase SPH model coupled with a multiphysics library

In this paper the numerical modelling of an Oscillating Water Column (OWC) Wave Energy Converter (WEC) is studied using DualSPHysics, a software that applies the Smoothed Particle Hydrodynamics (SPH) method. SPH is a Lagrangian meshless method used in a growing range of applications within the field of Computational Fluid Dynamics (CFD). The power take-off (PTO) system of the OWC WEC is numerically modelled by adding a force on a plate floating on top of the free surface inside the OWC chamber. That force is implemented in the multiphysics library Project Chrono, which avoids the need of simulating the air phase that is computationally expensive in the SPH methods. Validation is carried out with experimental data received from the Korea Research Institute of Ship and Ocean Engineering (KRISO) and Ocean Energy Systems (OES) of the International Energy Agency (IEA) Task 10. The numerical and experimental water surface elevation at the centre of the OWC WEC chamber and the airflow speed through the orifice are compared for different wave conditions and different PTO systems (different orifice diameters at the top part of the chamber of the OWC WEC). Results show that DualSPHysics is a valid tool to model an OWC WEC with and without PTO system, even though no air phase is included.Research Foundation - Flanders | Ref. 1SC5421NXunta de Galicia | Ref. ED431C 2021/44Agencia Estatal de Investigación | Ref. IJCI-2017-3259

Study of the bed velocity induced by twin propellers

Twin propellers without a rudder were studied using a physical model with a fixed clearance distance and three different rotating velocities. Experimental results were compared with results from theoretical expressions developed over the past 50 years for the efflux velocity, axial velocity, and maximum bed velocity. It was found that the efflux velocity equations overestimated the experimental results, whereas the computed axial velocities matched the experimental data reasonably well. However, when maximum bed velocity expressions were compared with experimental results, only one method was found to behave better; overestimation resulted if a quadratic superposition of single jets was used.Ministerio de Economía y Competitividad | Ref. TRA2015-70473-

Towards accelerating smoothed particle hydrodynamics simulations for free-surface flows on multi-GPU clusters

Starting from the single graphics processing unit (GPU) version of the Smoothed Particle Hydrodynamics (SPH) code DualSPHysics, a multi-GPU SPH program is developed for free-surface flows. The approach is based on a spatial decomposition technique, whereby different portions (sub-domains) of the physical system under study are assigned to different GPUs. Communication between devices is achieved with the use of Message Passing Interface (MPI) application programming interface (API) routines. The use of the sorting algorithm radix sort for inter-GPU particle migration and sub-domain “halo” building (which enables interaction between SPH particles of different sub-domains) is described in detail. With the resulting scheme it is possible, on the one hand, to carry out simulations that could also be performed on a single GPU, but they can now be performed even faster than on one of these devices alone. On the other hand, accelerated simulations can be performed with up to 32 million particles on the current architecture, which is beyond the limitations of a single GPU due to memory constraints. A study of weak and strong scaling behaviour, speedups and efficiency of the resulting program is presented including an investigation to elucidate the computational bottlenecks. Last, possibilities for reduction of the effects of overhead on computational efficiency in future versions of our scheme are discussed.Xunta de GaliciaEngineering and Physical Sciences Research Council (EPSRC)Research Councils UK (RCUK

Free-Surface Flow Simulations with Smoothed Particle Hydrodynamics Method using High-Performance Computing

Today, the use of modern high-performance computing (HPC) systems, such as clusters equipped with graphics processing units (GPUs), allows solving problems with resolutions unthinkable only a decade ago. The demand for high computational power is certainly an issue when simulating free-surface flows. However, taking the advantage of GPU’s parallel computing techniques, simulations involving up to 109 particles can be achieved. In this framework, this chapter shows some numerical results of typical coastal engineering problems obtained by means of the GPU-based computing servers maintained at the Environmental Physics Laboratory (EPhysLab) from Vigo University in Ourense (Spain) and the Tier-1 Galileo cluster of the Italian computing centre CINECA. The DualSPHysics free package based on smoothed particle hydrodynamics (SPH) technique was used for the purpose. SPH is a meshless particle method based on Lagrangian formulation by which the fluid domain is discretized as a collection of computing fluid particles. Speedup and efficiency of calculations are studied in terms of the initial interparticle distance and by coupling DualSPHysics with a NLSW wave propagation model. Water free-surface elevation, orbital velocities and wave forces are compared with results from experimental campaigns and theoretical solutions

A DEM approach for simulating flexible beam elements with the Project Chrono core module in DualSPHysics

This work presents a novel approach for simulating elastic beam elements in DualSPHysics leveraging functions made available by the coupling with the Project Chrono library. Such numerical frameworks, belonging to the Meshfree Particle Methods family, stand out for several features, like complex multiphase phenomena, moving boundaries, and high deformations which are handled with relative ease and reasonable numerical stability and reliability. Based on a co-rotating rigid element structure and lumped elasticity, a cogent mathematical formulation, relying on the Euler–Bernoulli beam theory for the structural discretization, is presented and applied to simulating two-dimensional flexible beams with the discrete elements method (DEM) formulation. Three test cases are presented to validate the smoothed particle hydrodynamics-based (SPH) structure model in both accuracy and stability, starting from an equilibrium test, to the dynamic response, and closing with a fluid–structure interaction simulation. This work proves that the developed theory can be used within a Lagrangian framework, using the features provided by a DEM solver, overtaking the initial limitations, and hence applying the results of static theories to complex dynamic problems.Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED481A-2021/337Ministerio de Ciencia, Innovación y Universidades | Ref. IJCI-2017-32592Agencia Estatal de Investigación | Ref. PID2020-113245RB-I0

GPUs, a new tool of acceleration in CFD: efficiency and reliability on smoothed particle hydrodynamics methods

Smoothed Particle Hydrodynamics (SPH) is a numerical method commonly used in Computational Fluid Dynamics (CFD) to simulate complex free-surface flows. Simulations with this mesh-free particle method far exceed the capacity of a single processor. In this paper, as part of a dual-functioning code for either central processing units (CPUs) or Graphics Processor Units (GPUs), a parallelisation using GPUs is presented. The GPU parallelisation technique uses the Compute Unified Device Architecture (CUDA) of nVidia devices. Simulations with more than one million particles on a single GPU card exhibit speedups of up to two orders of magnitude over using a single-core CPU. It is demonstrated that the code achieves different speedups with different CUDA-enabled GPUs. The numerical behaviour of the SPH code is validated with a standard benchmark test case of dam break flow impacting on an obstacle where good agreement with the experimental results is observed. Both the achieved speed-ups and the quantitative agreement with experiments suggest that CUDA-based GPU programming can be used in SPH methods with efficiency and reliability