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

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.Ministerio de Economía y Competitividad | Ref. BIA2012-38676- C03-0

Smoothed Particle Hydrodynamics model for civil and coastal engineering applications

Smoothed Particle Hydrodynamics (SPH) is a Lagrangian meshless method applied successfully in the field of Computational Fluid Dynamics (CFD). Meshless methods have proven to give good results in problems involving free-surface flows. This technique can deal with complex geometries and flow discontinuities, but the serial implementation of most SPH codes makes almost impossible to face real-engineering problems. During the past years SPH codes have evolved using new powerful hardware like GPUs (Graphic Processing Units). DualSPHysics was developed to take advantage of GPU computing without losing the accuracy and reliability of previous SPH code, SPHysics, implemented in FORTRAN. This step forward opens a whole new range of applications but also presents a lot of new challenges. The aim of this work is to show the research carried out to adapt DualSPHysics to solve new complex engineering applications. The goal of this manuscript is to present the implementations carried out in the code and how DualSPHysics is a tool that can facilitate the design-job in various fields. Three different applications in the fields of coastal and civil engineering are presented in this work. The first one analyses a case of coastal protection. Climate change is forcing to reevaluate old coastal defences and to improve the design of new ones. DualSPHysics is used to study wave propagation and wave-structure interaction. The code is validated with analytical and experimental data showing reliability, accuracy and efficiency. This validation proves that the method is suitable to reproduce free-surface phenomena such as breaking waves, and fluid-structure interaction. The capabilities of DualSPHysics to reproduce wave-structure interaction are shown where wave heights and forces exerted onto objects of the coast are numerically computed. The case of study mimics a realistic promenade including the urban furniture with dimensions and geometries close to the real ones. The second study presents the implementation of moorings for floating structures. Each year more energy devices are placed in the sea to take advantage of unexploited resources like oil & gas, wind farms, WECs (Wave Energy Converters)- Most of these off-shore structures are moored to the sea bed because of the wave conditions. A new set of equations is implemented in DualSPHysics to cover the behaviour of moored floating bodies. Validation is provided for both floating bodies and moored lines showing good agreement with experiments and numerical data. Two different working cases are presented to show the capabilities of the code. The last application is related with civil engineering. The research focuses on how roads can experience runoff problems due to the intense rain discharge associated to severe storms. Two advanced tools are combined to analyse runoff phenomena in real terrains. UAV (Unmanned Aerial Vehicle) photogrammetry is used to obtain the geometry of the case and DualSPHysics model is applied to compute the trajectory of the water interacting with the complex geometry. The effectiveness of protective measures to palliate flood effects is also analysed. The amount of water arriving to the road is measured for different scenarios. The performance of the protective measure, a ditch, is observed to decrease when its depth is reduced.Ministerio de Economía y Competitividad | Ref. BIA2012-38676-C03-0