scholarly journals Improved δ-SPH Scheme with Automatic and Adaptive Numerical Dissipation

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2858 ◽  
Author(s):  
Abdelkader Krimi ◽  
Luis Ramírez ◽  
Sofiane Khelladi ◽  
Fermín Navarrina ◽  
Michael Deligant ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Smoothed Particle Hydrodynamics ◽  
Numerical Scheme ◽  
Compressible Flows ◽  
Adaptive Method ◽  
Numerical Dissipation ◽  
Numerical Examples ◽  
Weakly Compressible ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

In this work we present a δ-Smoothed Particle Hydrodynamics (SPH) scheme for weakly compressible flows with automatic adaptive numerical dissipation. The resulting scheme is a meshless self-adaptive method, in which the introduced artificial dissipation is designed to increase the dissipation in zones where the flow is under-resolved by the numerical scheme, and to decrease it where dissipation is not required. The accuracy and robustness of the proposed methodology is tested by solving several numerical examples. Using the proposed scheme, we are able to recover the theoretical decay of kinetic energy, even where the flow is under-resolved in very coarse particle discretizations. Moreover, compared with the original δ-SPH scheme, the proposed method reduces the number of problem-dependent parameters.

scholarly journals Wave Propagation Studies in Numerical Wave Tanks with Weakly Compressible Smoothed Particle Hydrodynamics

2021 ◽  
Vol 9 (2) ◽  
pp. 233
Author(s):  
Samarpan Chakraborty ◽  
Balakumar Balachandran
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Kernel Functions ◽  
Numerical Dissipation ◽  
Processing Unit ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Weakly Compressible ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Numerical Wave

Generation and propagation of waves in a numerical wave tank constructed using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) are considered here. Numerical wave tank simulations have been carried out with implementations of different Wendland kernels in conjunction with different numerical dissipation schemes. The simulations were accelerated by using General Process Graphics Processing Unit (GPGPU) computing to utilize the massively parallel nature of the simulations and thus improve process efficiency. Numerical experiments with short domains have been carried out to validate the dissipation schemes used. The wave tank experiments consist of piston-type wavemakers and appropriate passive absorption arrangements to facilitate comparisons with theoretical predictions. The comparative performance of the different numerical wave tank experiments was carried out on the basis of the hydrostatic pressure and wave surface elevations. The effect of numerical dissipation with the different kernel functions was also studied on the basis of energy analysis. Finally, the observations and results were used to arrive at the best possible numerical set up for simulation of waves at medium and long distances of propagation, which can play a significant role in the study of extreme waves and energy localizations observed in oceans through such numerical wave tank simulations.

scholarly journals Review of smoothed particle hydrodynamics: towards converged Lagrangian flow modelling

2020 ◽  
Vol 476 (2241) ◽  
pp. 20190801
Author(s):  
Steven J. Lind ◽  
Benedict D. Rogers ◽  
Peter K. Stansby
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Graphics Processing Units ◽  
Wave Structure ◽  
Free Form ◽  
Mesh Free ◽  
Weakly Compressible ◽  
Particle Hydrodynamics ◽  
Massively Parallel Computing ◽  
Smoothed Particle ◽  
Graphics Processing

This paper presents a review of the progress of smoothed particle hydrodynamics (SPH) towards high-order converged simulations. As a mesh-free Lagrangian method suitable for complex flows with interfaces and multiple phases, SPH has developed considerably in the past decade. While original applications were in astrophysics, early engineering applications showed the versatility and robustness of the method without emphasis on accuracy and convergence. The early method was of weakly compressible form resulting in noisy pressures due to spurious pressure waves. This was effectively removed in the incompressible (divergence-free) form which followed; since then the weakly compressible form has been advanced, reducing pressure noise. Now numerical convergence studies are standard. While the method is computationally demanding on conventional processors, it is well suited to parallel processing on massively parallel computing and graphics processing units. Applications are diverse and encompass wave–structure interaction, geophysical flows due to landslides, nuclear sludge flows, welding, gearbox flows and many others. In the state of the art, convergence is typically between the first- and second-order theoretical limits. Recent advances are improving convergence to fourth order (and higher) and these will also be outlined. This can be necessary to resolve multi-scale aspects of turbulent flow.

scholarly journals The Role of Discs in the Collapse and Fragmentation of Prestellar Cores

2016 ◽  
Vol 33 ◽  
Author(s):  
O. Lomax ◽  
A. P. Whitworth ◽  
D. A. Hubber
Keyword(s):  
Kinetic Energy ◽  
Smoothed Particle Hydrodynamics ◽  
Low Mass Stars ◽  
Gravitational Instabilities ◽  
Disc Material ◽  
Prestellar Cores ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Low Mass

AbstractDisc fragmentation provides an important mechanism for producing low-mass stars in prestellar cores. Here, we describe smoothed particle hydrodynamics simulations which show how populations of prestellar cores evolve into stars. We find the observed masses and multiplicities of stars can be recovered under certain conditions.First, protostellar feedback from a star must be episodic. The continuous accretion of disc material on to a central protostar results in local temperatures which are too high for disc fragmentation. If, however, the accretion occurs in intense outbursts, separated by a downtime of ~ 104yr, gravitational instabilities can develop and the disc can fragment.Second, a significant amount of the cores’ internal kinetic energy should be in solenoidal turbulent modes. Cores with less than a third of their kinetic energy in solenoidal modes have insufficient angular momentum to form fragmenting discs. In the absence of discs, cores can fragment but results in a top-heavy distribution of masses with very few low-mass objects.

scholarly journals The Kelvin–Helmholtz instability and smoothed particle hydrodynamics

2019 ◽  
Vol 488 (4) ◽  
pp. 5210-5224 ◽  
Author(s):  
Terrence S Tricco
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Initial Conditions ◽  
Initial Density ◽  
Artificial Viscosity ◽  
Numerical Dissipation ◽  
Reference Solution ◽  
Helmholtz Instability ◽  
Non Linear ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

ABSTRACT We perform simulations of the Kelvin–Helmholtz instability using smoothed particle hydrodynamics (SPH). The instability is studied both in the linear and strongly non-linear regimes. The smooth, well-posed initial conditions of Lecoanet et al. (2016) are used, along with an explicit Navier–Stokes viscosity and thermal conductivity to enforce the evolution in the non-linear regime. We demonstrate convergence to the reference solution using SPH. The evolution of the vortex structures and the degree of mixing, as measured by a passive scalar ‘colour’ field, match the reference solution. Tests with an initial density contrast produce the correct qualitative behaviour. The $\mathcal {L}_2$ error of the SPH calculations decreases as the resolution is increased. The primary source of error is numerical dissipation arising from artificial viscosity, and tests with reduced artificial viscosity have reduced $\mathcal {L}_2$ error. A high-order smoothing kernel is needed in order to resolve the initial velocity amplitude of the seeded mode and inhibit excitation of spurious modes. We find that standard SPH with an artificial viscosity has no difficulty in correctly modelling the Kelvin–Helmholtz instability and yields convergent solutions.

scholarly journals An Efficient Sleepy Algorithm for Particle-Based Fluids

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Xiao Nie ◽  
Leiting Chen ◽  
Tao Xiang
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Flow Behavior ◽  
Visual Quality ◽  
Repulsive Force ◽  
Performance Gain ◽  
Weakly Compressible ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Fluid Particles ◽  
Computational Resources

We present a novel Smoothed Particle Hydrodynamics (SPH) based algorithm for efficiently simulating compressible and weakly compressible particle fluids. Prior particle-based methods simulate all fluid particles; however, in many cases some particles appearing to be at rest can be safely ignored without notably affecting the fluid flow behavior. To identify these particles, a novel sleepy strategy is introduced. By utilizing this strategy, only a portion of the fluid particles requires computational resources; thus an obvious performance gain can be achieved. In addition, in order to resolve unphysical clumping issue due to tensile instability in SPH based methods, a new artificial repulsive force is provided. We demonstrate that our approach can be easily integrated with existing SPH based methods to improve the efficiency without sacrificing visual quality.

A Modified Smoothed Particle Hydrodynamics Scheme to Model the Stationary and Moving Boundary Problems for Newtonian Fluid Flows

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Mohammad Sefid ◽  
Rouhollah Fatehi ◽  
Rahim Shamsoddini
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Moving Boundary ◽  
Fluid Flows ◽  
Boundary Problems ◽  
Driven Cavity ◽  
First Case ◽  
Weakly Compressible ◽  
Present Solution ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

A robust modified weakly compressible smoothed particle hydrodynamics (WCSPH) method based on a predictive corrective scheme is introduced to model the fluid flows engaged with stationary and moving boundary. In this paper, this model is explained and practically verified in three distinct laminar incompressible flow cases; the first case involves the lid driven cavity flow for two Reynolds numbers 400 and 1000. The second case is a flow generated by a moving block in the initially stationary fluid. The third case is flow around the stationary and transversely oscillating circular cylinder confined in a channel. These results in comparison with the standard benchmarks also confirm the good accuracy of the present solution algorithm.

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