The Comparison of Viscous Force Approximations of Smoothed Particle Hydrodynamics in Poiseuille Flow Simulation

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Zhengang Liu ◽  
Zhenxia Liu
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Flow Simulation ◽  
Reynolds Numbers ◽  
Viscous Force ◽  
Numerical Instability ◽  
Viscous Stress ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Particle Approximation ◽  
Poiseuille Flows

Poiseuille flows at two Reynolds numbers (Re) 2.5 × 10−2 and 5.0 are simulated by two different smoothed particle hydrodynamics (SPH) schemes on regular and irregular initial particles' distributions. In the first scheme, the viscous stress is calculated directly by the basic SPH particle approximation, while in the second scheme, the viscous stress is calculated by the combination of SPH particle approximation and finite difference method (FDM). The main aims of this paper are (a) investigating the influences of two different schemes on simulations and reducing the numerical instability in simulating Poiseuille flows discovered by other researchers and (b) investigating whether the similar instability exists in other cases and comparing results with the two viscous stress approximations. For Re = 2.5 × 10−2, the simulation with the first scheme becomes instable after the flow approaches to steady-state. However, this instability could be reduced by the second scheme. For Re = 5.0, no instability for two schemes is found.

Research on Three-Dimensional Visualization System for Landslide and Mud-Rock Flows Based on Direct3D and SPH Methods

2014 ◽  
Vol 675-677 ◽  
pp. 1179-1183 ◽  
Author(s):  
Jian Gao ◽  
Qi Zhou ◽  
Ting Ting Meng
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Three Dimensional ◽  
Viscous Force ◽  
Disaster Prevention ◽  
Visualization System ◽  
Whole Process ◽  
3D Terrain ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Physical Forces

This paper converts DEM data to 3D terrain by using Direct3D technology, then, creates landslide on the 3D terrain ,and simulates landslides and mud-rock flows during the whole process in time by using Smoothed Particle Hydrodynamics methods. The landslide is abstracted to particle swarm of Direct3D in this simulation, each particle movements in the gravity, pressure and viscous force between particles and other physical forces so that implements three-dimensional and dynamic simulation of landslides and mud-rock flows. The extent of landslides and mud-rock effects is reached by estimating the real time location of particles, thus we can make early warning of the extent of landslides and mud-rock effects and provide technical support for disaster prevention and mitigation work..

Progress in Smoothed Particle Hydrodynamics to Simulate Bearing Chambers

2014 ◽  
Author(s):  
A. Ch. H. Kruisbrink ◽  
H. P. Morvan ◽  
F. R. Pearce
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Smoothed Particle Hydrodynamics ◽  
Flow Simulation ◽  
Two Phase ◽  
Surface And Interface ◽  
Physical Density ◽  
Model Complex ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

In this paper some novel Smoothed Particle Hydrodynamics (SPH) concepts are presented towards a feasibility study into the use of SPH for some aero-engine applications, e.g. for internal oil or fuel applications. A first challenge is to develop a capability to model complex wall geometries, associated with two-phase flows in gear boxes and bearing chambers for example. A demonstration is made of how such complex (for SPH) geometries can be built together with an outline of some of the wall boundary condition concepts used, including moving walls. This is an important feature for the application of SPH to engineering. Other boundary conditions are needed such as inlets, outlets and pressure boundaries, and a proper treatment of the free surface. These are outlined in the context of the proposed application. From an SPH flow simulation viewpoint, one of the challenges is to reduce the non-physical density variations arising from boundary conditions (at wall, free surface and interface), which are responsible for non-physical pressure variations and particle dynamics. The flow regimes found in the engineering systems outlined above involve droplets, filaments and films. It is therefore important to be able to handle the merging of fluids, as it is to model their interaction with another phase, which calls for appropriate multi-fluid and surface tension models. This paper introduces SPH, outlines a number of concepts listed above and presents some preliminary results towards the modeling of the KIT bearing chamber, as described by Kurz et al. [1]. This work builds on a number of numerical modeling communications made by the Nottingham team to SPHERIC, the ERCOFTAC Special Interest Group (SIG) for SPH.

scholarly journals The Effect of Iterative Procedures on the Robustness and Fidelity of Augmented Lagrangian SPH

Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 472
Author(s):  
Deniz Can Kolukisa ◽  
Murat Ozbulut ◽  
Mehmet Yildiz
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Augmented Lagrangian ◽  
Reynolds Numbers ◽  
Step Size ◽  
Time Step ◽  
Optimum Time ◽  
Time Step Size ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Spatial Derivatives

The Augmented Lagrangian Smoothed Particle Hydrodynamics (ALSPH) method is a novel incompressible Smoothed Particle Hydrodynamics (SPH) approach that solves Navier–Stokes equations by an iterative augmented Lagrangian scheme through enforcing the divergence-free coupling of velocity and pressure fields. This study aims to systematically investigate the time step size and the number of inner iteration parameters to boost the performance of the ALSPH method. Additionally, the effect of computing spatial derivatives with two alternative schemes on the accuracy of numerical results are also scrutinized. Namely, the first scheme computes spatial derivatives on the updated particle positions at each iteration, whereas the second one employs the updated pressure and velocity fields on the initial particle positions to compute the gradients and divergences throughout the iterations. These two schemes are implemented to the solution of a flow over a circular cylinder at Reynolds numbers of 200 in two dimensions. Initially, simulations are performed in order to determine the optimum time step sizes by utilizing a maximum number of five iterations per time step. Subsequently, the optimum number of inner iterations is investigated by employing the predetermined optimum time step size under the same flow conditions. Finally, the schemes are tested on the same flow problem with different Reynolds numbers using the best performing combination of the aforementioned parameters. It is observed that the ALSPH method can enable one to increase the time step size without deteriorating the numerical accuracy as a consequence of imposing larger ALSPH penalty terms in larger time step sizes, which, overall, leads to improved computational efficiency. When considering the hydrodynamic flow characteristics, it can be stated that two spatial derivative schemes perform very similarly. However, the results indicate that the derivative operation with the updated particle positions produces slightly lower velocity divergence magnitudes at larger time step sizes.

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