SPH Simulation of Green Water Flows on Ships Free to Heave and Pitch

International audienc

Simulations of Breaking Wave Impacts on a Rigid Wall at Two Different Scaleswith a Two-Phase Fluid Compressible SPH Model

International audienceAfter years of efforts, HydrOcean and Ecole Centrale Nantes, supported by GTT, succeeded in the development of anSPH software gathering all functionalities for relevant simulations of sloshing impacts on membrane containment systemsfor LNG carriers. Based on Riemann solvers, SPH-Flow deals with two compressible fluids (liquid and gas) that interact withthe impacted structure through a complete coupling. The liquid, the gas and the structure are modeled by different kindsof dedicated particles allowing sharp interfaces. An efficient parallelization scheme enables performing calculations with asufficiently high density of particles to capture adequately the sharp impact pressure pulses. The development of the bi-fluidversion led, in a first stage, to unstable solutions in the gaseous phase for pressures below the ullage pressure. This difficultywas presented at ISOPE-2010 and has been overcome since. Simulations of a unidirectional breaking wave impacting a rigidwall after propagating along a flume are presented in this paper. The physical phenomena involved in the last stage of theimpacts are scrutinized and compared with experimental results from the Sloshel project. A comparison between calculatedresults at full scale and at scale 1:6 is proposed. Conclusions about scaling in the context of wave impacts are given

Simulation of extreme wave impacts on a FLNG

International audienc

Simulation of Liquid Impacts With a Two-Phase Parallel SPH Model

International audienc

Dynamique fortement non linéaire de l'interface entre deux fluides non miscibles dans un réservoir fermé.14eme Journées de l'Hydrodynamique

National audienc

Simulations of Hydro-Elastic Impacts Using a Parallel SPH Model

International audienceThe work presented in this paper started with a PhD Thesis (GTT/ECN) (Deuff, 2007) dedicated to the development of a Smoothed Particle Hydrodynamics (SPH) solver able to simulate hydro-elastic impacts with strong fluid/structure coupling. Further developments have been made to integrate the fluid/structure SPH solver in an industrial SPH platform named SPHF low. These developments have mainly focused on the parallelisation of the fluid/structure solver and the implementation of solutions to avoid the so-called Tensile Instability. They enable the simulation of liquid impacts on complex structures such as MarkIII or NO96 containment systems. The paper first describes the theoretical core of the SPH fluid/structure solver. Various academic test cases are presented for validation of the recently implemented SPH structural model, such as the free vibration of a beam and wave propagation through a heterogeneous material. Recent developments on the parallelisation and solutions implemented to avoid Tensile Instability are described. The final validation case allows a comparison of the results of the fluid/structure SPH solver with analytical model results on a deformable beam wedge impacting the free surface at very high velocity

Highly nonlinear dynamics of theinterface between two non miscible fluidsin a closed tank.

International audienc

Interplay between crosslinking and ice nucleation controls the porous structure of freeze-dried hydrogel scaffolds

International audienc

Nextmuse - Deliverable D4.2 Intermediate report on efficient parallel SPH

The SPH method is based on a Lagrangian particle formalism which needs to deal with possibly strongly disordered particles, that is to say to deal with scattered data in the memory bank. In the past, computer scientists used to optimize their algorithms only in terms of arithmetic operations. Reducing the number of operations (divisions, multiplications...) implied reducing the elapsed CPU time in the same ratio. Nowadays, this assertion does not hold because arithmetic operations and memory accesses are both involved in code optimization. In certain pathological cases, memory access optimizations are 10 times more efficient than arithmetic optimizations. As a consequence, one must carefully look at the data organization within the solver and the way it is addressed. Moreover, data structures are a central part of a solver and a modification of them could greatly impact the whole program. Thus cache management aspects should be regarded as much as possible at beginning of optimization process and/or first solver implementation. In the next sections, simple test cases representative of meshless methods are presented. The first one is related to spatial locality and memory locality of data, and shows that the performances decrease when spatial and memory localities are not closely linked. The second one is an attempt to restore consistency between spatial and memory localities by using Peano-Hilbert curves algorithm

Nextmuse - Deliverable D3.1 Intermediate report on Fluid-Solid coupling for rigid body motions, and solid mechanics modelling

The principal and largest effort in the development of this task is dedicated to coupling of SPH solutions of fluid dynamics with rigid body motion. This topic is of great interest in several engineering application, including naval hydrodynamics problems, and represents a challenging task because the fluid and the structures are strongly coupled. For what concern the development of the coupling algorithm a model was studied by INSEAN and NUIG. The core procedure of the algorithm was designed both for SPH models with boundary particle method (see deliverable D1.1 for details) as well as for the FVPM variant (see deliverable D1.1).The latter was implemented at NUIG in the period M6-M12. This model has been tested on a cylinder constrained with springs in a channel flow for which no free-surface occurs For such a problem experimental data are available in literature. A good accordance between the numerical solver and the experiments was obtained. For what concern the SPH model the coupling algorithm will be implemented by INSEAN during the period M12-M18 in order to deal with free-surface flow interacting with rigid bodies. Specifically the method will be validated with the problem of a freely floating 2D ship section subjected to gravity wave system. Before dealing with the problems of gravity waves interacting with freely floating bodies great care has been given to the study of wave propagation. Indeed, a correct and accurate modeling of gravity waves is a crucial point for such simulations. In order to evaluate the accuracy of the SPH models in reproducing gravity wave propagations, 2D regular waves have been generated through a wave maker (both piston and flap have been considered) and a large number of simulations have been performed for steepness and height-to-depth ratio spreading from deep to shallow water. INSEAN took care of such study starting from the δ-SPH model described in deliverable D1.1. The SPH results have been compared with both experimental and numerical data. In the latter case, a BEM-MEL solver has been used. In fact, such a solver is one of the most appropriate scheme to describe the propagation of gravity waves since it is based on the potential theory. Specifically, we used the BEM-MEL code developed at INSEAN and experimental data performed at the INSEAN tanks. Beyond the test on regular waves, we also performed simulations with wave-packets. This is a quite stiff problem which involves high non-linear phenomena including breaking waves. For such a study, experimental data are available in literature. INSEAN during the period M12-M18 will continue the work simulating the dynamics of freely-moving rigid bodies in regular waves where the coupling algorithm will be implemented and validated through comparison with experimental data. Following the purpose given at TASK 3.1, a bibliography research has been performed in order to find experiments suitable for testing the SPH model in dealing with interactions between fluids and rigid bodies. Unfortunately this research did not provide sufficient detailed experimental data. Therefore the INSEAN database was examined and an experimental campaign regarding this topic was found. This campaign consisted in the analysis of a ship model excited by regular beam waves. Firstly the ship model was constrained and exiting forces, wave elevation and velocity field through PIV technique were measured. Then the same experiments were repeated leaving the ship model free to move in heave and roll motion. In this case the ship motion evolution was recorded. The experimental results are discussed in section 1.4 of the present report