17 research outputs found
Integral SPH: Connecting the partition of unit to accurate gradient estimation
AYA2017-86274-P Del enfriamiento a las explosiones: la física de los objetos compactosPostprint (published version
Integral smoothed particle hydrodynamics with an improved partition of unit and a better track of contact discontinuities
The correct evaluation of gradients is at the cornerstone of the smoothed
particle hydrodynamics (SPH) technique. Using an integral approach to estimate
gradients has proven to enhance accuracy substantially. Such approach retains
the Lagrangian structure of SPH equations and is fully conservative. In this
paper we study, among other things, the connection between the choice of the
volume elements (VEs), which enters in the SPH summations, and the accuracy in
the gradient estimation within the integral approach scheme (ISPH). A new kind
of VEs are proposed which improve the partition of unit and are fully
compatible with the Lagrangian formulation of SPH, including the grad-h
corrections. Using analytic considerations, simple static toy models in 1D, and
a few full 3D test cases, we show that any improvement in the partition of unit
also leads to a better calculation of gradients when the integral approach is
used jointly. Additionally, we propose a simple-to-implement variant of the
ISPH scheme which is more adequate to handle sharp density contrasts.Comment: 29 pages, 17 figures, submitted to Journal of Computational Physic
Simulating Hydrodynamics in Cosmology with CRK-HACC
We introduce CRK-HACC, an extension of the Hardware/Hybrid Accelerated
Cosmology Code (HACC), to resolve gas hydrodynamics in large-scale structure
formation simulations of the universe. The new framework couples the HACC
gravitational N-body solver with a modern smoothed particle hydrodynamics (SPH)
approach called CRKSPH. onservative
eproducing ernel
utilizes smoothing functions that exactly interpolate
linear fields while manifestly preserving conservation laws (momentum, mass,
and energy). The CRKSPH method has been incorporated to accurately model
baryonic effects in cosmology simulations - an important addition targeting the
generation of precise synthetic sky predictions for upcoming observational
surveys. CRK-HACC inherits the codesign strategies of the HACC solver and is
built to run on modern GPU-accelerated supercomputers. In this work, we
summarize the primary solver components and present a number of standard
validation tests to demonstrate code accuracy, including idealized hydrodynamic
and cosmological setups, as well as self-similarity measurements
Approaching the exascale simulation of subsonic turbulence with smoothed particle hydrodynamics
The candidate will work in collaboration with the SPH-EXA and SKAO-Switzerland projects.Turbulence is key to many astrophysical and cosmological scenarios. Hence, a correct depiction of it in numerical simulations is of capital importance. Kolmogorov's theory states that in the subsonic regime the energy associated with the scale of the turbulent structures follows the power law � ∝ � −5∕3 , where � is the wave-number. Smoothed Particle Hydrodynamics simulations have traditionally shown difficulties building up a Kolmogorov-like turbulent cascade. The main reason for this can be traced back to the errors in gradient evaluation when standard SPH methods are used, jointly with over-viscous behavior from traditional artificial viscosity formulations. These problems can be tackled nowa- days with modern implementations of the gradient evaluation that are much more accurate, and also using adaptive switches and artificial viscosity cleaners that reduce dissipation where and when needed. With the goal of testing this new implementation, as well as the performance of the new state- of-the-art SPH-EXA code, a set of turbulence simulations have been carried out, that represent the most accurate and highest resolution SPH-based turbulence simulations to date. The combination of the high scalability of SPH-EXA with the use of upgraded hydrodynamics has shown a sizeable improvement in the results of the subsonic turbulence simulation