scholarly journals Application of background pressure with kinematic criterion for free surface extension to suppress non-physical voids in the finite volume particle method

2019 ◽  
Author(s):  
Nathan Quinlan ◽  
Mohsen Hassanzadeh Moghimi
Keyword(s):  
Free Surface ◽  
Finite Volume ◽  
Particle Method ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Particle Methods ◽  
Positive Pressure ◽  
Absolute Pressure ◽  
Free Surfaces ◽  
Spatial Discretisation

Lagrangian particle methods such as smoothed particle hydrodynamics (SPH) and the finite volume particle method (FVPM) can suffer from non-physical voids in the spatial discretisation, due to the inability of numerical particles to deform as continuum fluid elements can. It is known that the situation can be improved for wall-bounded flows in SPH by adding a uniform background pressure to ensure positive absolute pressure everywhere. In this article, we investigate the application of background pressure in FVPM, and show that numerical voids grow under negative pressure and collapse under positive pressure. To use this technique in free-surface flow, however, the background pressure must be applied as an atmospheric pressure at the free surface. A kinematic criterion for free surface extension (KCFSE) to differentiate physical free surfaces from new numerical voids has been developed, supplementing the inherent capability of FVPM to identify free-surface particles robustly. The novel method enables background pressure to be applied at physical free surfaces and throughout the fluid, but not in non-physical voids, facilitating the suppression of such spurious voids. The KCFSE is validated for a translating square cylinder inside a rectangular numerical domain, with and without a free surface, and liquid in an oscillating rectangular tank.

scholarly journals A physically consistent particle method for high-viscous free-surface flow calculation

2021 ◽  
Author(s):  
Masahiro Kondo ◽  
Takahiro Fujiwara ◽  
Issei Masaie ◽  
Junichi Matsumoto
Keyword(s):  
Angular Momentum ◽  
Free Surface ◽  
Particle Method ◽  
Free Surface Flow ◽  
Momentum Conservation ◽  
Free Surface Flows ◽  
Surface Flow ◽  
Particle Methods ◽  
Surface Flows ◽  
Angular Momentum Conservation

AbstractParticle methods for high-viscous free-surface flows are of great use to capture flow behaviors which are intermediate between solid and liquid. In general, it is important for numerical methods to satisfy the fundamental laws of physics such as the conservation laws of mass and momentum and the thermodynamic laws. Especially, the angular momentum conservation is necessary to calculate rotational motion of high-viscous objects. However, most of the particle methods do not satisfy the physical laws in their spatially discretized system. The angular momentum conservation law is broken mostly because of the viscosity models, which may result in physically strange behavior when high-viscous free-surface flow is calculated. In this study, a physically consistent particle method for high-viscous free-surface flows is developed. The present method was verified, and its performance was shown with calculating flow in a rotating circular pipe, high-viscous Taylor–Couette flow, and offset collision of a high-viscous object.

scholarly journals A physically consistent particle method for incompressible fluid flow calculation

2020 ◽  
Author(s):  
Masahiro Kondo
Keyword(s):  
Mechanical Energy ◽  
Particle Method ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Particle Methods ◽  
Analytical Mechanics ◽  
Time Step ◽  
Consistent System ◽  
Energy Behavior ◽  
Dissipation Property

AbstractIn general, mechanical energy monotonically decreases in a physically consistent system, constructed with conservative force and dissipative force. This feature is important in designing a particle method, which is a discrete system approximating continuum fluid with particles. When the discretized system can be fit into a framework of analytical mechanics, it will be a physically consistent system which prevents instability like particle scattering along with unphysical mechanical energy increase. This is the case also in incompressible particle methods. However, most incompressible particle methods do not satisfy the physical consistency, and they need empirical relaxations to suppress the system instability due to the unphysical energy behavior. In this study, a new incompressible particle method with the physical consistency, moving particle full-implicit (MPFI) method, is developed, where the discretized interaction forces are related to an analytical mechanical framework for the systems with dissipation. Moreover, a new pressure evaluation technique based on the virial theorem is proposed for the system. Using the MPFI method, static pressure, droplet extension, standing wave and dam break calculations were conducted. The capability to predict pressure and motion of incompressible free surface flow was presented, and energy dissipation property depending on the particle size and time step width was studied through the calculations.

scholarly journals Sloshing Simulation of Single-Phase and Two-Phase SPH using DualSPHysics

Kapal ◽  
2020 ◽  
Vol 17 (2) ◽  
pp. 50-57
Author(s):  
Andi Trimulyono ◽  
S Samuel ◽  
Muhammad Iqbal
Keyword(s):  
Free Surface ◽  
Pressure Sensors ◽  
Pressure Oscillation ◽  
Particle Method ◽  
Surface Flow ◽  
Particle Methods ◽  
Two Phase ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass

The sloshing phenomenon is one of the free surface flow that can endanger liquid cargo carriers such as ships. Sloshing is defined as the resonance of fluid inside a tank caused by external oscillation. When sloshing is close to the natural frequency of the tank it could endanger ships. Particle method has the advantages to be applied because sloshing is dealing with free surface. One of the particle methods is Smoothed Particle Hydrodynamics (SPH). In this study, compressible SPH was used as a result of the pressure oscillation, which exists because of the effect of density fluctuation as nature of weakly compressible SPH. To reduce pressure noise, a filtering method, Low Pass Filter,  was used to overcome pressure oscillation. Three pressure sensors were used in the sloshing experiment with a combination of motions and filling ratios. Only one pressure sensor located in the bottom was used to validate the numerical results. A set of SPH parameters were derived that fit for the sloshing problem. The SPH results show a good agreement with the experiment’s. The difference between SPH and experiment is under 1 % for sway, but a larger difference shows in roll. Low pass filter technique could reduce pressure noise, but comprehensive method needs to develop for general implementation.

scholarly journals Simulation of free-surface flow in a tank using the Navier-Stokes model and unstructured finite volume method

2005 ◽  
Vol 219 (3) ◽  
pp. 251-266 ◽  
Author(s):  
X Zhang ◽  
N M Sudharsan ◽  
R Ajaykumar ◽  
K Kumar
Keyword(s):  
Free Surface ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Free Surface Flow ◽  
Offshore Structures ◽  
Surface Flow ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Volume Method ◽  
Unstructured Finite Volume Method

Modelling free-surface flow has very important applications in many engineering areas such as oil transportation and offshore structures. Current research focuses on the modelling of free surface flow in a tank by solving the Navier-Stokes equation. An unstructured finite volume method is used to discretize the governing equations. The free surface is tracked by dynamically adapting the mesh and making it always surface conforming. A mesh-smoothing scheme based on the spring analogy is also implemented to ensure mesh quality throughout the computaiton. Studies are performed on the sloshing response of a liquid in an elastic container subjected to various excitation frequencies. Further investigations are also carried out on the critical frequency that leads to large deformation of the tank walls. Another numerical simulation involves the free-surface flow past as submerged obstacle placed in the tank to show the flow separation and vortices. All these cases demonstrate the capability of this numerical method in modelling complicated practical problems.

A new three-dimensional finite-volume non-hydrostatic shock-capturing model for free surface flow

2017 ◽  
Vol 29 (4) ◽  
pp. 552-566 ◽  
Author(s):  
Francesco Gallerano ◽  
Giovanni Cannata ◽  
Francesco Lasaponara ◽  
Chiara Petrelli
Keyword(s):  
Free Surface ◽  
Finite Volume ◽  
Three Dimensional ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Shock Capturing

scholarly journals Meshless particle modelling of free surface flow over spillways

2015 ◽  
Vol 18 (2) ◽  
pp. 354-370 ◽  
Author(s):  
Ehsan Jafari-Nodoushan ◽  
Khosrow Hosseini ◽  
Ahmad Shakibaeinia ◽  
Seyed-Farhad Mousavi
Keyword(s):  
Free Surface ◽  
Surface Profile ◽  
Particle Method ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Weakly Compressible ◽  
Wall Boundary Conditions ◽  
Free Surface Profile ◽  
Moving Particle ◽  
Lagrangian Particle Method

A meshless Lagrangian (particle) method based on the weakly compressible moving particle semi-implicit formulation (WC-MPS) is developed and analysed for simulation of flow over spillways. To improve the accuracy of the model for pressure and velocity calculation, some modifications are proposed and evaluated for the inflow and wall boundary conditions implementation methods. The final model is applied for simulation of flow over the 45° and 60° ogee spillways (with different inflow rates) and also shallow flow over a spillway-like curved bed channel. To evaluate the model, the numerical results of free surface profile and velocity and pressure field are compared with the available experimental measurements. Comparisons show the results’ accuracy of the developed model and proposed improvements. The results of this study will not only provide a reliable numerical tool for modelling of flow over spillways, but also provide an insight for better understating flow pattern over these hydraulic structures.

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