Direct Numerical Simulation of the First Stages of a Plunging Breaker Using a Level Set Method

2009 ◽  
Author(s):  
Pablo Go´mez ◽  
Claudio Zanzi ◽  
Julia´n Palacios ◽  
Joaqui´n Lo´pez ◽  
Julio Herna´ndez
Keyword(s):  
Level Set Method ◽  
Level Set ◽  
Stokes Equations ◽  
Numerical Study ◽  
Local Level ◽  
Wave Crest ◽  
Small Scale ◽  
Breaking Wave ◽  
Mass Force ◽  
The Impact

A numerical study of wave breaking in shallow water is presented. The jet formed at the wave crest and the subsequent splash-up phenomenon resulting from the impact of the jet on the liquid surface are analyzed. The wave is assumed to be generated by an accelerated piston in an open channel containing liquid. The two-dimensional, incompressible, unsteady Navier-Stokes equations are solved using a local level set method to treat the interface evolution [Go´mez et al., Int. J. Numer. Meth. Engng, 63, pp. 1478–1512, 2005], which permits to analyze the combined air-liquid flow. Viscous and capillary effects are retained. The level set transport and reinitialization equations are solved in a narrow band around the interface using an adaptive refined grid. Two different approaches are considered to take into account the relative movement between the piston and the end wall of the channel. The first one uses a fixed grid and introduces a mass force per unit mass equal to the piston acceleration, and the second one is based on using a moving grid, which is compressed as the piston moves forward, and an arbitrary Lagrangian-Eulerian method. The numerical results obtained for the evolution of the wave shape during the breaking process, particularly the evolution of the plunging jet, the air cavity and the complex flow resulting from the impact of the plunging jet, are compared with experimental visualization results obtained for a small-scale breaking wave, for which the breaking process is strongly influenced by surface tension. A good degree of agreement was observed between both types of results during the first stages of the breaking process.

Numerical Simulation of Breaking Waves Using a Level Set Method

2002 ◽  
Author(s):  
Pablo Go´mez ◽  
Julio Herna´ndez ◽  
Joaqui´n Lo´pez ◽  
Fe´lix Faura
Keyword(s):  
Free Surface ◽  
Level Set Method ◽  
Level Set ◽  
Stokes Equations ◽  
Numerical Study ◽  
Operating Conditions ◽  
Breaking Wave ◽  
Level Set Function ◽  
Set Function ◽  
The Impact

A numerical study of the initial stages of wave breaking processes in shallow water is presented. The waves considered are assumed to be generated by moving a piston in a two-dimensional channel, and may appear, for example, in the injection chamber of a high-pressure die casting machine under operating conditions far from the optimal. A numerical model based on a finite-difference discretization of the Navier-Stokes equations in a Cartesian grid and a second-order approximate projection method has been developed and used to carry out the simulations. The evolution of the free surface is described using a level set method, with a reinitialization procedure of the level set function which uses a local grid refinement near the free surface. The ability of different algorithms to improve mass conservation in the reinitialization step of the level set function has been tested in a time-reversed single vortex flow. The results for the breaking wave profiles show the flow characteristics after the impact of the first plunging jet onto the wave’s forward face and during the subsequent splash-up.

Influence of Wave Shape on the Impact of Shallow-Water Waves on Vertical Walls

2006 ◽  
Author(s):  
Claudio Zanzi ◽  
Pablo Go´mez ◽  
Julia´n Palacios ◽  
Joaqui´n Lo´pez ◽  
Julio Herna´ndez
Keyword(s):  
Shallow Water ◽  
Level Set ◽  
Water Waves ◽  
High Speed ◽  
Numerical Study ◽  
Local Level ◽  
Wave Shape ◽  
Shallow Water Waves ◽  
Vertical Walls ◽  
The Impact

A numerical study of the impact of shallow-water waves on vertical walls is presented. The air-liquid flow was simulated using a code for incompressible viscous flow, based on a local level set algorithm and a second-order approximate projection method. The level set transport and reinitialization equations were solved in a narrow band around the interface using an adaptive refined grid. The wave is assumed to be generated by a plunger which is accelerated in an open channel containing water. An arbitrary Lagrangian-Eulerian method was used to take into account the relative movement between the plunger and the end wall of the channel. The evolution of the free surface was visualized using a laser light sheet and a high-speed camera, with a sampling frequency of 1000 Hz. Several simulations were carried out to investigate the influence of the shape of the wave approaching the wall on the relevant quantities associated with the impact. The wave shape just before the impact was changed varying the total length of the channel. The results are compared with experimental results and with results obtained by other authors.

Element-local level set method for three-dimensional dynamic crack growth

2009 ◽  
Vol 80 (12) ◽  
pp. 1520-1543 ◽  
Author(s):  
Qinglin Duan ◽  
Jeong-Hoon Song ◽  
Thomas Menouillard ◽  
Ted Belytschko
Keyword(s):  
Crack Growth ◽  
Level Set Method ◽  
Level Set ◽  
Local Level ◽  
Three Dimensional ◽  
Dynamic Crack ◽  
Dynamic Crack Growth ◽  
Local Level Set

scholarly journals Does eating local food reduce the environmental impact of food production and enhance consumer health?

2010 ◽  
Vol 69 (4) ◽  
pp. 582-591 ◽  
Author(s):  
Gareth Edwards-Jones
Keyword(s):  
Food System ◽  
Local Food ◽  
Local Level ◽  
Qualitative Assessment ◽  
Small Scale ◽  
Quantitative Evidence ◽  
Self Sufficiency ◽  
Non Local ◽  
The Uk ◽  
The Impact

The concept of local food has gained traction in the media, engaged consumers and offered farmers a new marketing tool. Positive claims about the benefits of local food are probably not harmful when made by small-scale producers at the local level; however, greater concern would arise should such claims be echoed in policy circles. This review examines the evidence base supporting claims about the environmental and health benefits of local food. The results do not offer any support for claims that local food is universally superior to non-local food in terms of its impact on the climate or the health of consumers. Indeed several examples are presented that demonstrate that local food can on occasions be inferior to non-local food. The analysis also considers the impact on greenhouse gas emissions of moving the UK towards self-sufficiency. Quantitative evidence is absent on the changes in overall emissions that would occur if the UK switched to self-sufficiency. A qualitative assessment suggests the emissions per item of food would probably be greater under a scenario of self-sufficiency than under the current food system. The review does not identify any generalisable or systematic benefits to the environment or human health that arise from the consumption of local food in preference to non-local food.

scholarly journals Efficient Local Level Set Method without Reinitialization and Its Appliance to Topology Optimization

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Wenhui Zhang ◽  
Yaoting Zhang
Keyword(s):  
Topology Optimization ◽  
Level Set Method ◽  
Level Set ◽  
Computational Efficiency ◽  
Numerical Stability ◽  
Local Level ◽  
Band Model ◽  
Numerical Process ◽  
Local Level Set ◽  
Narrow Band Model

The local level set method (LLSM) is higher than the LSMs with global models in computational efficiency, because of the use of narrow-band model. The computational efficiency of the LLSM can be further increased by avoiding the reinitialization procedure by introducing a distance regularized equation (DRE). The numerical stability of the DRE can be ensured by a proposed conditionally stable difference scheme under reverse diffusion constraints. Nevertheless, the proposed method possesses no mechanism to nucleate new holes in the material domain for two-dimensional structures, so that a bidirectional evolutionary algorithm based on discrete level set functions is combined with the LLSM to replace the numerical process of hole nucleation. Numerical examples are given to show high computational efficiency and numerical stability of this algorithm for topology optimization.

Evaluation of Length Scales and Meshing Requirements for Resolving Two-Phase Flow Regime Transitions Using the Level Set Method

2021 ◽  
Author(s):  
Matt Zimmer ◽  
Igor A Bolotnov
Keyword(s):  
Thin Films ◽  
Flow Regime ◽  
Level Set Method ◽  
Level Set ◽  
Two Phase Flow ◽  
Small Scale ◽  
Phase Flow ◽  
Two Phase ◽  
Interface Capturing ◽  
Regime Transitions

Abstract New criteria for fully resolving two-phase flow regime transitions using direct numerical simulation with the level set method for interface capturing are proposed. A series of flows chosen to capture small scale interface phenomena are simulated at different grid refinements. These cases include droplet deformation and breakup in a simple shear field, the thin film around a Taylor bubble, and the rise of a bubble towards a free surface. These cases cover the major small scale phenomena observed in two-phase flows: internal recirculation, interface curvature, interface snapping, flow of liquid in thin films, and drainage/snapping of thin films. The results from these simulations and their associated grid studies were used to develop new meshing requirements for simulation of two-phase flow using interface capturing methods, in particular the level set method. When applicable, the code used in this work, PHASTA, was compared to experiments in order to contribute to the ongoing validation process of the code. Results show that when the solver meets these criteria, with the exception of resolving the nanometer scale liquid film between coalescing bubbles, the code is capable of accurately simulating interface topology changes.

NUMERICAL SIMULATION OF RAYLEIGH–TAYLOR INSTABILITY BASED ON AN IMPROVED PARTICLE LEVEL SET METHOD

2014 ◽  
Vol 11 (04) ◽  
pp. 1350094 ◽  
Author(s):  
HUI TIAN ◽  
GUOJUN LI ◽  
XIONGWEN ZHANG
Keyword(s):  
Level Set Method ◽  
Level Set ◽  
Stokes Equations ◽  
Density Ratio ◽  
Immiscible Fluids ◽  
Taylor Instability ◽  
Wide Range ◽  
Particle Level ◽  
Rayleigh Taylor Instability ◽  
Particle Level Set Method

An improved particle correction procedure for particle level set method is proposed and applied to the simulation of Rayleigh–Taylor instability (RTI) of the incompressible two-phase immiscible fluids. In the proposed method, an improved particle correction method is developed to deal with all the relative positions between escaped particles and cell corners, which can reduce the disturbance arising in the distance function correction process due to the non-normal direction movement of escaped particles. The improved method is validated through accurately capturing the moving interface of the Zalesak's disk. Furthermore, coupled with the projection method for solving the Navier–Stokes equations, the time-dependent evolution of the RTI interface over a wide range of Reynolds numbers, Atwood numbers and Weber numbers are numerically investigated. A good agreement between the present results and the existing analytical solutions is obtained and the accuracy of the proposed method is further verified. Moreover, the effects of control parameters including viscosity, density ratio, and surface tension coefficient on the evolution of RTI are analyzed in detail, and a critical Weber number for the development of RTI is found.

Numerical simulations of the humid atmosphere above a mountain

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Arthur Bousquet ◽  
Mickaël D. Chekroun ◽  
Youngjoon Hong ◽  
Roger M. Temam ◽  
Joseph Tribbia
Keyword(s):  
Boundary Conditions ◽  
Finite Volume ◽  
Compatibility Condition ◽  
Stokes Equations ◽  
Numerical Study ◽  
Taylor Series Expansion ◽  
Navier Stokes ◽  
Small Scale ◽  
Spatial Discretization ◽  
Humid Atmosphere

AbstractNew avenues are explored for the numerical study of the two dimensional inviscid hydrostatic primitive equations of the atmosphere with humidity and saturation, in presence of topography and subject to physically plausible boundary conditions for the system of equations. Flows above a mountain are classically treated by the so-called method of terrain following coordinate system. We avoid this discretization method which induces errors in the discretization of tangential derivatives near the topography. Instead we implement a first order finite volume method for the spatial discretization using the initial coordinates x and p. A compatibility condition similar to that related to the condition of incompressibility for the Navier- Stokes equations, is introduced. In that respect, a version of the projection method is considered to enforce the compatibility condition on the horizontal velocity field, which comes from the boundary conditions. For the spatial discretization, a modified Godunov type method that exploits the discrete finite-volume derivatives by using the so-called Taylor Series Expansion Scheme (TSES), is then designed to solve the equations. We report on numerical experiments using realistic parameters. Finally, the effects of a random small-scale forcing on the velocity equation is numerically investigated.

scholarly journals Numerical study of droplet deformation in shear flow using a conservative level-set method

2019 ◽  
Vol 207 ◽  
pp. 153-171 ◽  
Author(s):  
Ahmad Amani ◽  
Néstor Balcázar ◽  
Jesús Castro ◽  
Assensi Oliva
Keyword(s):  
Shear Flow ◽  
Level Set Method ◽  
Level Set ◽  
Numerical Study ◽  
Droplet Deformation ◽  
Conservative Level Set
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