A. Barreiro

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.

SPHysics - development of a free-surface fluid solver - Part 2: Efficiency and test cases

This paper, the second of a two-part series, analyses the efficiency of SPHysics and illustrates its capabilities by means of several test cases. Some intrinsic features of the SPH technique such as the use of link lists and the check for the limits are analysed here in detail. Numerical results are compared to experimental data for several cases studies: (i) Creation of waves by landslides, (ii) Dam-break propagation over wet beds and (iii) Wave-structure interaction. In addition, the capabilities of SPHysics to deal with realistic cases are depicted using the GPU version for several visual examples.

Integration of UAV photogrammetry and SPH modelling of fluids to study runoff on real terrains.

Roads can experience runoff problems due to the intense rain discharge associated to severe storms. Two advanced tools are combined to analyse the interaction of complex water flows with real terrains. UAV (Unmanned Aerial Vehicle) photogrammetry is employed to obtain accurate topographic information on small areas, typically on the order of a few hectares. The Smoothed Particle Hydrodynamics (SPH) technique is applied by means of the DualSPHysics model to compute the trajectory of the water flow during extreme rain events. The use of engineering solutions to palliate flood events is also analysed. The study case simulates how the collected water can flow into a close road and how precautionary measures can be effective to drain water under extreme conditions. The amount of water arriving at the road is calculated under different protection scenarios and the efficiency of a ditch is observed to decrease when sedimentation reduces its depth.

Parallel CPU/GPU Computing for Smoothed Particle Hydrodynamics Models

Smoothed Particle Hydrodynamics (SPH) is a numerical method particularly suitable to describe a variety of complex free-surface flows with large discontinuities. However, SPH simulations are computationally expensive and typical runtimes are too high to study real problems with high resolution. The proposed solution is the parallel computation to accelerate the SPH executions. This work introduces several high performance techniques applied to SPH to allow simulation of real problems at reasonable time. In this way, OpenMP was used to exploit all cores in the classical CPUs. On the other hand, CUDA language was used to take advantage of the high parallel computing power of GPUs (Graphics Processing Units). Finally, Message Passing Interface (MPI) was implemented to combine the power of several machines connected by network. These parallelization techniques are implemented in the code DualSPHysics and results are shown in terms of performance, efficiency and scalability using different CPU and GPU models.

Smoothed particle hydrodynamics applied in fluid structure interactions

The capabilities of SPH models to deal with complex scenarios involving real geometries and extreme events are shown for different applications. The model not only is able to capture the main features of complex flows, but also allows including objects that can move due to the force exerted by the fluid. This is of special interest to reproduce the flooding of coastal areas, where water can move cars, pieces of urban furniture or debris.

Smoothed Particle Hydrodynamics for Free-Surface Flows

A solver for free-surface flows (DualSPHysics) based on the Smoothed Particle Hydrodynamics (SPH) model is presented. The classical SPH formulation is described along with the governing equations, filters and corrections, boundary conditions and time stepping schemes. The reliability of the DualSPHysics model is discussed by comparing the numerical results with the experimental data for a benchmark test case. The applicability of the code is shown with some examples where wave propagation and wave-structure interaction are simulated.