Arbitrary Lagrangian–Eulerian simulations of highly electrically charged micro-droplet Coulomb explosion deformation pathways

2016 ◽  
Vol 07 (03) ◽  
pp. 1650016 ◽  
Author(s):  
Alastair Radcliffe
Keyword(s):  
Coulomb Explosion ◽  
Reconstruction Technique ◽  
Charged Droplet ◽  
Arbitrary Lagrangian Eulerian ◽  
Droplet Deformation ◽  
Finite Element Scheme ◽  
Deformation Dynamics ◽  
Ale Methods ◽  
Electrically Charged ◽  
Symmetric Finite Element

Numerical simulation results of the Coulomb explosion pathways of cooled water and heated glycol droplets electrically charged to the critical Rayleigh limit are presented, calculated using an axi-symmetric finite element scheme previously used for the same problem [Radcliffe A. J., Non-conforming finite elements for axisymmetric charged droplet deformation dynamics and Coulomb explosions, Int. J. Num. Meth. Fluids 71:249–268, (2013), doi:10.1002/fld.3667.] which has been adapted to use arbitrary Lagrangian–Eulerian (ALE) methods and a novel tip reconstruction technique in order to greatly improve its accuracy in matching available experimental data.

scholarly journals A linear-elasticity-based mesh moving method with no cycle-to-cycle accumulated distortion

2021 ◽  
Author(s):  
Patrícia Tonon ◽  
Rodolfo André Kuche Sanches ◽  
Kenji Takizawa ◽  
Tayfun E. Tezduyar
Keyword(s):  
Linear Elasticity ◽  
Solid Surfaces ◽  
Moving Mesh ◽  
Test Case ◽  
Half Cycle ◽  
Arbitrary Lagrangian Eulerian ◽  
Interface Motion ◽  
Mesh Motion ◽  
Ale Methods ◽  
Moving Mesh Methods

AbstractGood mesh moving methods are always part of what makes moving-mesh methods good in computation of flow problems with moving boundaries and interfaces, including fluid–structure interaction. Moving-mesh methods, such as the space–time (ST) and arbitrary Lagrangian–Eulerian (ALE) methods, enable mesh-resolution control near solid surfaces and thus high-resolution representation of the boundary layers. Mesh moving based on linear elasticity and mesh-Jacobian-based stiffening (MJBS) has been in use with the ST and ALE methods since 1992. In the MJBS, the objective is to stiffen the smaller elements, which are typically placed near solid surfaces, more than the larger ones, and this is accomplished by altering the way we account for the Jacobian of the transformation from the element domain to the physical domain. In computing the mesh motion between time levels $$t_n$$ t n and $$t_{n+1}$$ t n + 1 with the linear-elasticity equations, the most common option is to compute the displacement from the configuration at $$t_n$$ t n . While this option works well for most problems, because the method is path-dependent, it involves cycle-to-cycle accumulated mesh distortion. The back-cycle-based mesh moving (BCBMM) method, introduced recently with two versions, can remedy that. In the BCBMM, there is no cycle-to-cycle accumulated distortion. In this article, for the first time, we present mesh moving test computations with the BCBMM. We also introduce a version we call “half-cycle-based mesh moving” (HCBMM) method, and that is for computations where the boundary or interface motion in the second half of the cycle consists of just reversing the steps in the first half and we want the mesh to behave the same way. We present detailed 2D and 3D test computations with finite element meshes, using as the test case the mesh motion associated with wing pitching. The computations show that all versions of the BCBMM perform well, with no cycle-to-cycle accumulated distortion, and with the HCBMM, as the wing in the second half of the cycle just reverses its motion steps in the first half, the mesh behaves the same way.

scholarly journals Cylindrically and non-cylindrically symmetric expansion dynamics of tin microdroplets after ultrashort laser pulse impact

2021 ◽  
Vol 127 (2) ◽  
Author(s):  
Tiago de Faria Pinto ◽  
Jan Mathijssen ◽  
Randy Meijer ◽  
Hao Zhang ◽  
Alex Bayerle ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Droplet Deformation ◽  
Cylindrically Symmetric ◽  
Linearly Polarized ◽  
Particle Hydrodynamics ◽  
Deformation Dynamics ◽  
Smoothed Particle ◽  
Asymmetric Shock

AbstractIn this work, the expansion dynamics of liquid tin micro-droplets irradiated by femtosecond laser pulses were investigated. The effects of laser pulse duration, energy, and polarization on ablation, cavitation, and spallation dynamics were studied using laser pulse durations ranging from 220 fs to 10 ps, with energies ranging from 1 to 5 mJ, for micro-droplets with an initial radius of 15 and 23 $$\upmu$$ μ m. Using linearly polarized laser pulses, cylindrically asymmetric shock waves were produced, leading to novel non-symmetric target shapes, the asymmetry of which was studied as a function of laser pulse parameters and droplet size. A good qualitative agreement was obtained between smoothed-particle hydrodynamics simulations and high-resolution stroboscopic experimental data of the droplet deformation dynamics.

Validation of an Improved Contact Method for Multi-Material Eulerian Hydrocodes in Three-Dimensions

2019 ◽  
Author(s):  
Kenneth C. Walls ◽  
David L. Littlefield
Keyword(s):  
Finite Element ◽  
Large Deformations ◽  
Three Dimensions ◽  
Contact Method ◽  
Arbitrary Lagrangian Eulerian ◽  
Aspect Ratios ◽  
Ale Methods ◽  
Lagrangian Finite Element ◽  
Multiple Materials ◽  
Natural Description

Abstract Realistic and accurate modeling of contact for problems involving large deformations and severe distortions presents a host of computational challenges. Due to their natural description of surfaces, Lagrangian finite element methods are traditionally used for problems involving sliding contact. However, problems such as those involving ballistic penetrations, blast-structure interactions, and vehicular crash dynamics, can result in elements developing large aspect ratios, twisting, or even inverting. For this reason, Eulerian, and by extension Arbitrary Lagrangian-Eulerian (ALE), methods have become popular. However, additional complexities arise when these methods permit multiple materials to occupy a single finite element.

Stability of an Electrically Charged Droplet

1962 ◽  
Vol 5 (5) ◽  
pp. 575 ◽  
Author(s):  
Gedalia Ailam (Volinez) ◽  
Isaiah Gallily
Keyword(s):  
Charged Droplet ◽  
Electrically Charged

Numerical Investigation of Flow Interference Effects in Fixed and Vibrating Tandem Square Columns Using Hybrid RANS-LES Models

2015 ◽  
Author(s):  
Harish Gopalan ◽  
Dominic Denver John Chandar ◽  
Narasimha Rao Pillamarri ◽  
Guan Mengzhao ◽  
Rajeev K. Jaiman ◽  
...  
Keyword(s):  
Solid Wall ◽  
Computational Cost ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Arbitrary Lagrangian Eulerian ◽  
High Reynolds Numbers ◽  
Flow Past ◽  
Ale Methods ◽  
High Reynolds ◽  
Flow Interference

Investigation of flow past tandem and side-by-side circular and square columns is of interest in offshore engineering. Flow past fixed and vibrating circular columns has received a lot of focus in the literature. However, the studies focused on square columns, especially at high Reynolds numbers are very limited due to the computational cost of large eddy simulation (LES). Unsteady Reynolds-averaged Navier-Stokes (URANS) methods are limited by their accuracy, especially for tandem columns in the wake interference regime (spacing to diameter ratio: L=D ∼ 3:0). Hybrid URANS-LES models (URANS near the solid-wall and LES away from the wall) can overcome the drawbacks of the traditional URANS methods and can provide a reasonable prediction of the flow physics at a fraction of the cost of LES without significantly sacrificing numerical accuracy. Arbitrary Lagrangian-Eulerian (ALE) methods fails when vibrating tandem bodies are in close proximity to each other or vibrate at high reduced velocities. Remeshing the domain can be expensive, especially at high Reynolds numbers (Re). Alternate strategies are necessary to efficiently simulation this problems. This study proposes the use of a non-linear URANS-LES model, coupled with an overset mesh method (for vibrating columns), for studying flow past tandem square columns. Simulations are performed at sub-critical Re to match the experimental Re. The initial results are encouraging for further investigation of fixed and vibrating tandem square column flow interference at high Reynolds numbers.

An Internal Variable Update Procedure for the Treatment of Inelastic Material Behavior within an ALE-Description of Rolling Contact

2007 ◽  
Vol 9 ◽  
pp. 157-171 ◽  
Author(s):  
M. Ziefle ◽  
U. Nackenhorst
Keyword(s):  
Contact Problems ◽  
Internal Variable ◽  
Rolling Contact ◽  
Material Behavior ◽  
Internal Variables ◽  
Arbitrary Lagrangian Eulerian ◽  
Element Analysis ◽  
Integration Schemes ◽  
Inelastic Material ◽  
Ale Methods

Arbitrary Lagrangian Eulerian (ALE) methods provide a well established basis for the numerical analysis of rolling contact problems, the theoretical framework is well developed for elastic constitutive behavior. Special measures are necessary for the treatment of history dependent and explicitly time dependent material behavior within the relative–kinematic ALE– picture. In this presentation a fractional step approach is suggested for the integration of the evolution equation for internal variables. A Time–Discontinuous Galerkin (TDG) method is introduced for the numerical solution of the related advection equations. The advantage of TDG–methods in comparison with more traditional integration schemes is studied in detail. The practicability of the approach is demonstrated by the finite element analysis of rolling tires.

scholarly journals The Relation Between Ejection Mechanism and Ion Abundance in the Electric Double Layer of Drops

2021 ◽  
Author(s):  
Victor Kwan ◽  
Ryan O'Dwyer ◽  
David Laur ◽  
Jiahua Tan ◽  
Styliani Consta
Keyword(s):  
Surface Layer ◽  
Chemical Reactivity ◽  
Critical Role ◽  
Reaction Rates ◽  
Mass Spectrometry Data ◽  
Charged Droplet ◽  
Droplet Deformation ◽  
Ion Evaporation ◽  
Dynamics Simulations ◽  
Evaporation Mechanism

<div> Charged droplets have been associated with distinct chemical reactivity. It is assumed that the composition of the surface layer plays a critical role in enhancing the reaction rates in the droplets relative to their bulk counterparts. We use atomistic modeling to relate the localization of the ions in the surface layer to their ejection propensity. We find that<br>the ion ejection takes place via a two-stage process. Firstly, a conical protrusion emerges as a result of a global droplet deformation that is insensitive to the locations of single ions. The ions are subsequently ejected as they enter the conical regions. The study provides mechanistic insight into the<br> ion-evaporation mechanism, which can be used to revise the commonly used ion-evaporation models. We argue that atomistic molecular dynamics simulations of minute nano-drops, do not sufficiently distinguish the ion-evaporation mechanism from a Rayleigh fission. We explain mass spectrometry data on the charge state of small globular proteins and the existence of super-charged droplet states (above the Rayleigh limit) that have been detected in experiments. <br></div><div><br></div><div><br></div><div><br></div>

Impact Response of Sacrificial Cladding Structure with an Alporas Aluminum Foam Core Under Blast Loading

2020 ◽  
Vol 12 (08) ◽  
pp. 2050094
Author(s):  
Ibrahim Elnasri ◽  
Han Zhao
Keyword(s):  
Strain Rate ◽  
Aluminum Foam ◽  
Blast Loading ◽  
Front Propagation ◽  
Analytical Models ◽  
Core Material ◽  
Foam Core ◽  
Arbitrary Lagrangian Eulerian ◽  
Inertia Effects ◽  
Ale Methods

This paper presents numerical and analytical studies of the response of a sacrificial cladding structure with an Alporas aluminum foam core and a thick mild steel cover and rear plates under blast loading. A suitable numerical model in LS-DYNA based on the coupled Load Blast Enhanced/Multi-Material Arbitrary Lagrangian–Eulerian (LBE/MM-ALE) methods is selected and validated using the experimental data available in the literature. The shock front propagation and micro-inertia effects are responsible for the strength enhancement predicted in the virtual blast test. Two models with different decaying blast loading functions are examined to study the fluid–structure interaction (FSI) effect. The simulation results show that the FSI effect is negligible if the foam core is strain-rate insensitive. Further investigations should be conducted with analytical models if the core material of the sacrificial cladding structures exhibits a strong strain-rate effect (for example, Alporas foam).

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