scholarly journals Testing the effect of resolution on gravitational fragmentation with Lagrangian hydrodynamic schemes

2021 ◽  
Author(s):  
Yasuyoshi Yamamoto ◽  
Takashi Okamoto ◽  
Takayuki Saitoh
Keyword(s):  
Analytic Solution ◽  
Hydrodynamic Force ◽  
Fluid Element ◽  
Finite Mass ◽  
Numerical Resolution ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Definition Of ◽  
Self Gravity ◽  
Volume Method

Abstract To study the resolution required for simulating gravitational fragmentation with newly developed Lagrangian hydrodynamic schemes, Meshless Finite Volume method (MFV) and Meshless Finite Mass method (MFM), we have performed a number of simulations of the Jeans test and compared the results with both the expected analytic solution and results from the more standard Lagrangian approach: Smoothed Particle Hydrodynamics (SPH). We find that the different schemes converge to the analytic solution when the diameter of a fluid element is smaller than a quarter of the Jeans wavelength, λJ. Among the three schemes, SPH/MFV shows the fastest/slowest convergence to the analytic solution. Unlike the well-known behaviour of Eulerian schemes, none of the Lagrangian schemes investigated displays artificial fragmentation when the perturbation wavelength, λ, is shorter than λJ, even at low numerical resolution. For larger wavelengths (λ > λJ) the growth of the perturbation is delayed when it is not well resolved. Furthermore, with poor resolution, the fragmentation seen with the MFV scheme proceeds very differently compared to the converged solution. All these results suggest that, when unresolved, the ratio of the magnitude of hydrodynamic force to that of self-gravity at the sub-resolution scale is the largest/smallest in MFV/SPH, the reasons for which we discussed in detail. These tests are repeated to investigate the effect of kernels of higher-order than the fiducial cubic spline. Our results indicate that the standard deviation of the kernel is a more appropriate definition of the ‘size’ of a fluid element than its compact support radius.

scholarly journals Flow under long two-dimensional dam sluice gate using WSPH

2021 ◽  
Vol 31 (2) ◽  
pp. 98-111
Author(s):  
Juan Gabriel Monge Gapper ◽  
Alberto Serrano-Pacheco
Keyword(s):  
Numerical Method ◽  
Channel Length ◽  
High Ratio ◽  
Two Dimensional ◽  
Sluice Gate ◽  
Numerical Resolution ◽  
Particle Hydrodynamics ◽  
Two Dimensional Flow ◽  
Smoothed Particle ◽  
Long Channel

An application of the weakly compressible Smoothed Particle Hydrodynamics (WSPH) numerical method is presented here for the case of two-dimensional flow in a long channel with a partially open sluice gate. The results are compared with an analytical solution provided by shallow water equations (SWE) and available experimental data. Of particular interest is the application of this numerical method to a sluice gate case with a high ratio of channel length to depth, which tends to amplify the effects of the chosen numerical resolution. Good model congruence was observed even for relatively low vertical resolution, and the effects of the equations used to describe the boundary conditions were identified.

Simulation and experimental study on lubrication of high-speed reducer of electric vehicle

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fuchun Jia ◽  
Yulong Lei ◽  
Xianghuan Liu ◽  
Yao Fu ◽  
Jianlong Hu
Keyword(s):  
Flow Field ◽  
Electric Vehicle ◽  
High Speed ◽  
Content Type ◽  
Speed Reducer ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Novel Method ◽  
Set Up ◽  
Volume Method

Purpose The lubrication of the high-speed reducer of an electric vehicle is investigated. The specific contents include visualization of the flow field inside reducer, lubrication evaluation of bearings and efficiency experiment. Design/methodology/approach The flow field inside reducer at five working conditions: straight, uphill, downhill, left lean and right lean is simulated by smoothed particle hydrodynamics (SPH). According to the instantaneous number of particles through bearings, the lubrication states of bearings are evaluated. The test platform is set up to measure the efficiency of the reducer. Findings The flow field inside the reducer is obtained, the lubrication of bearings needs to be improved, the efficiency of the electric vehicle reducer meets the requirement. Originality/value The SPH method is used to simulate lubrication instead of using the traditional grid-based finite volume method. A novel method to evaluate the lubrication of bearings is proposed. The method and conclusions can guide electric vehicle reducer design.

scholarly journals Axisymmetric smoothed particle hydrodynamics with self-gravity

2009 ◽  
Vol 392 (1) ◽  
pp. 346-360 ◽  
Author(s):  
D. García-Senz ◽  
A. Relaño ◽  
R. M. Cabezón ◽  
E. Bravo
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Self Gravity

scholarly journals Simulation fragmentation of samples of rock at explosive loading

2020 ◽  
Vol 192 ◽  
pp. 01013
Author(s):  
Vitaly Trofimov ◽  
Ivan Shipovskii
Keyword(s):  
Digital Technology ◽  
Rock Properties ◽  
Expansion Velocity ◽  
Processing Plant ◽  
Sph Method ◽  
Simulation Based ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Definition Of ◽  
Holistic Vision

Research to improve the definition of rational parameters for blasting is becoming increasingly important and valuable. This is especially true in the era of digital technology, which allows miners to realize a holistic vision of optimizing the entire process - from the quarry to the receipt of the final product at the processing plant. The proposed computer simulation based on the Smoothed Particle Hydrodynamics (SPH) method in AUTODYN computer complex to optimize the explosion results by integrating the initial data - charge parameters and rock properties, is aimed at improving measures that reduce the total cost of drilling and blasting, increasing mining productivity and safety. The presented calculations make it possible to estimate the number of fragments and their initial expansion velocity for various explosives.

scholarly journals Phantom: A Smoothed Particle Hydrodynamics and Magnetohydrodynamics Code for Astrophysics

2018 ◽  
Vol 35 ◽  
Author(s):  
Daniel J. Price ◽  
James Wurster ◽  
Terrence S. Tricco ◽  
Chris Nixon ◽  
Stéven Toupin ◽  
...  
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
High Energy ◽  
Three Dimensions ◽  
High Energy Astrophysics ◽  
The Core ◽  
Particle Hydrodynamics ◽  
Galactic Potentials ◽  
Smoothed Particle ◽  
External Forces ◽  
Self Gravity

AbstractWe present Phantom, a fast, parallel, modular, and low-memory smoothed particle hydrodynamics and magnetohydrodynamics code developed over the last decade for astrophysical applications in three dimensions. The code has been developed with a focus on stellar, galactic, planetary, and high energy astrophysics, and has already been used widely for studies of accretion discs and turbulence, from the birth of planets to how black holes accrete. Here we describe and test the core algorithms as well as modules for magnetohydrodynamics, self-gravity, sink particles, dust–gas mixtures, H2 chemistry, physical viscosity, external forces including numerous galactic potentials, Lense–Thirring precession, Poynting–Robertson drag, and stochastic turbulent driving. Phantom is hereby made publicly available.

scholarly journals Toward understanding the origin of asteroid geometries

2018 ◽  
Vol 620 ◽  
pp. A167 ◽  
Author(s):  
K. Sugiura ◽  
H. Kobayashi ◽  
S. Inutsuka
Keyword(s):  
Major Axis ◽  
Impact Angle ◽  
Equal Mass ◽  
Low Velocity ◽  
Irregular Shapes ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Model Of Friction ◽  
Self Gravity ◽  
The Impact

More than a half of the asteroids in the main belt have irregular shapes with ratios of the minor to major axis lengths of less than 0.6. One of the mechanisms that create such shapes is collisions between asteroids. The relationship between the shapes of collisional outcomes and impact conditions such as impact velocities may provide information on the collisional environments and its evolutionary stages when those asteroids are created. In this study, we perform numerical simulations of collisional destruction of asteroids with radii 50 km and subsequent gravitational reaccumulation using smoothed-particle hydrodynamics for elastic dynamics with self-gravity, a model of rock fractures, and a model of friction in completely damaged rock. We systematically vary the impact velocity from 50 to 400 m s−1 and the impact angle from 5° to 45°. We investigate shapes of the largest remnants resulting from collisional simulations. As a result, various shapes (bilobed, spherical, flat, elongated, and hemispherical shapes) are formed through equal-mass and low-velocity (50−400 m s−1) impacts. We clarify a range of the impact angle and velocity to form each shape. Our results indicate that irregular shapes, especially flat shapes, of asteroids with diameters larger than 80 km are likely to be formed through similar-mass and low-velocity impacts, which are likely to occur in the primordial environment prior to the formation of Jupiter.

Unsteady Stokes Flow for a Vibrating Cantilever Under a Free-Surface

2014 ◽  
Author(s):  
Giovanni Di Ilio ◽  
Iskender Sahin ◽  
Angelantonio Tafuni
Keyword(s):  
Free Surface ◽  
Hydrodynamic Force ◽  
Rectangular Cross Section ◽  
Damping Coefficients ◽  
Particle Hydrodynamics ◽  
Unsteady Stokes Flow ◽  
Smoothed Particle ◽  
Parametric Studies ◽  
Stress Free Boundary ◽  
Quiescent Fluid

Vibration of a thin, rectangular-cross-section beam submerged in a viscous, quiescent fluid undergoing small amplitude oscillations is studied using a Boundary Element (BE) approach in which the free-surface is modeled through a stress-free boundary condition. The Stokes approximation is used where nonlinear convective terms are negligible and the problem is formulated in Fourier and Laplace transform space when appropriate. Results are expressed in terms of non-dimensional hydrodynamic force and its components, namely added mass and damping coefficients. Several parametric studies are conducted to evaluate the effects of depth of submergence, frequency and the amplitude of oscillations on the hydrodynamic functions. The results are compared with the classical solution for a vibrating lamina in an infinite fluid as the limit case and with a recent study using Smoothed Particle Hydrodynamics (SPH) analysis in the presence of a free-surface.

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