scholarly journals A Comparison of Interface Growth Models Applied to Rayleigh–Taylor and Richtmyer–Meshkov Instabilities

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
J. Canfield ◽  
N. Denissen ◽  
M. Francois ◽  
R. Gore ◽  
R. Rauenzahn ◽  
...  
Keyword(s):  
Compressible Flow ◽  
Numerical Models ◽  
Transition To Turbulence ◽  
Analytical Models ◽  
Fluid Interfaces ◽  
Interface Model ◽  
Interface Position ◽  
Flow Solver ◽  
Interface Models ◽  
Interface Growth

Abstract Sophisticated numerical models that contain fluid interfaces rely upon interface evolution models to approximate the transition to turbulence near interfaces, in the presence of Rayleigh–Taylor (RTI) or Richtmyer–Meshkov (RMI) instability. Semi-analytical models have been developed in recent decades to predict the interface growth from an initial state into the nonlinear regime. Two of these models are considered in this study. They are the Goncharov and the z-models. Both of these interface models have strengths and weaknesses, which are examined here. Both of them have been implemented in the xRAGE compressible flow solver, which models fluid interfaces. The flow solver provides the fluids acceleration as a body force to the interface model. The purpose of such interface model is to evolve the early times of interface position as a subgrid model within a compressible flow simulation in order to then initialize a turbulence model. In this work, the interface models are assessed and compared for their evolution of RTI and RMI. The z-model performed better than the Goncharov model for all cases that were explored.

Homogenization of Composites with Extended General interfaces: Comprehensive Review and Unified Modeling

2021 ◽  
Author(s):  
Soheil Firooz ◽  
Paul Steinmann ◽  
Ali Javili
Keyword(s):  
Numerical Study ◽  
Finite Thickness ◽  
Heterogeneous Materials ◽  
Interface Model ◽  
Interface Position ◽  
Unified Modeling ◽  
Interface Models ◽  
Universal Interface ◽  
Underlying Mechanisms ◽  
Interface Parameters

Abstract Interphase regions that form in heterogeneous materials through various underlying mechanisms such as poor mechanical or chemical adherence, roughness, and coating, play a crucial role in the response of the medium. A well- established strategy to capture a finite-thickness interphase behavior is to replace it with a zero-thickness interface model characterized by its own displacement and/or traction jumps, resulting in different interface models. The contributions to date dealing with interfaces commonly assume that the interface is located in the middle of its corresponding interphase. We revisit this assumption and introduce a universal interface model, wherein a unifying approach to the homogenization of heterogeneous materials embedding interfaces between their constituents is developed. The proposed novel interface model is universal in the sense that it can recover any of the classical interface models. Next, via incorporating this universal interface model into homogenization, we develop bounds and estimates for the overall moduli of fiber-reinforced and particle-reinforced composites as functions of the interface position and properties. Furthermore, we elaborate on the computational implications of this interface model. Finally, we carry out a comprehensive numerical study to highlight the influence of interface position, stiffness ratio and interface parameters on the overall properties of composites, where an excellent agreement between the analytical and computational results is observed. The developed interface-enhanced homogenization framework also successfully captures size effects, which are immediately relevant to emerging applications of nano-composites due their pronounced interface effects at small scales.

scholarly journals Gaining a better understanding of the extrusion process in fused filament fabrication 3D printing: a review

2021 ◽  
Author(s):  
Bahaa Shaqour ◽  
Mohammad Abuabiah ◽  
Salameh Abdel-Fattah ◽  
Adel Juaidi ◽  
Ramez Abdallah ◽  
...  
Keyword(s):  
3D Printing ◽  
Numerical Models ◽  
Extrusion Process ◽  
Analytical Models ◽  
Limiting Factor ◽  
Fused Filament Fabrication ◽  
Promising Tool ◽  
Relevant Work ◽  
3D Printing Technique ◽  
Required Quality

AbstractAdditive manufacturing is a promising tool that has proved its value in various applications. Among its technologies, the fused filament fabrication 3D printing technique stands out with its potential to serve a wide variety of applications, ranging from simple educational purposes to industrial and medical applications. However, as many materials and composites can be utilized for this technique, the processability of these materials can be a limiting factor for producing products with the required quality and properties. Over the past few years, many researchers have attempted to better understand the melt extrusion process during 3D printing. Moreover, other research groups have focused on optimizing the process by adjusting the process parameters. These attempts were conducted using different methods, including proposing analytical models, establishing numerical models, or experimental techniques. This review highlights the most relevant work from recent years on fused filament fabrication 3D printing and discusses the future perspectives of this 3D printing technology.

Modelling of interactions between dykes, inclined sheets and faults at Santorini volcano

2021 ◽  
Author(s):  
Kyriaki Drymoni ◽  
John Browning ◽  
Agust Gudmundsson
Keyword(s):  
Tensile Strength ◽  
Fault Zone ◽  
Numerical Models ◽  
Damage Zone ◽  
Sheet Thickness ◽  
Analytical Models ◽  
Energy Conditions ◽  
Dyke Swarm ◽  
Normal Faults ◽  
Santorini Volcano

<p>Dykes and inclined sheets are known occasionally to exploit faults as parts of their paths, but the conditions that allow this to happen are still not fully understood. Here we report field observations from a well-exposed dyke swarm of the Santorini volcano, Greece, that show dykes and inclined sheets deflected into faults and the results of analytical and numerical models to explain the conditions for deflection. The deflected dykes and sheets belong to a local swarm of 91 dyke/sheet segments that was emplaced in a highly heterogeneous and anisotropic host rock and partially cut by some regional faults and a series of historic caldera collapses, the caldera walls providing, excellent exposures of the structures. The numerical models focus on a normal-fault dipping 65° with a damage zone composed of parallel layers or zones of progressively more compliant rocks with increasing distance from the fault rupture plane. We model sheet-intrusions dipping from 0˚ to 90˚ and with overpressures of alternatively 1 MPa and 5 MPa, approaching the fault. We further tested the effects of changing (1) the sheet thickness, (2) the fault-zone thickness, (3) the fault-zone dip-dimension (height), and (4) the loading by, alternatively, regional extension and compression. We find that the stiffness of the fault core, where a compliant core characterises recently active fault zones, has pronounced effects on the orientation and magnitudes of the local stresses and, thereby, on the likelihood of dyke/sheet deflection into the fault zone. Similarly, the analytical models, focusing on the fault-zone tensile strength and energy conditions for dyke/sheet deflection, indicate that dykes/sheets are most likely to be deflected into and use steeply dipping recently active (zero tensile-strength) normal faults as parts of their paths.</p>

scholarly journals Modelling the high temperature oxidation of titanium alloys: review of analytical models and development of a new numerical tool PyTiOx

2020 ◽  
Vol 321 ◽  
pp. 06012
Author(s):  
C. Ciszak ◽  
D. Monceau ◽  
C. Desgranges
Keyword(s):  
Numerical Models ◽  
Ecological Impact ◽  
Operating Costs ◽  
Analytical Models ◽  
Temperature Oxidation ◽  
Ti Alloys ◽  
State Diffusion ◽  
First Results ◽  
Aeronautical Industry ◽  
Numerical Tool

In order to limit the ecological impact of air traffic and its operating costs, the aeronautical industry is looking for improving engines efficiencies and substitutes to high density Ni-based superalloys. Thus, a wider use of Ti-alloys operating at higher temperatures is one of the developed solutions. Being able to predict as accurately as possible the oxidation behavior of Ti-based components at high temperatures appears therefore crucial to improve their sizing and durability. Analytical models based on the solid-state diffusion laws can be found in the litterature. They are fairly accurate in most cases, but they reveal some intrinsic limitations in specific cases such as temperature transients or thin components. Numerical models were later developed to break down these limitations. First results from a new numerical tool called “PyTiOx” (still under development are presented here. They confirm the intrinsic limitations of analytical models. In the case of thin samples, the numerical model predicts an increase of scaling kinetic when metal becomes O-saturated, whereas analytical models do not.

scholarly journals Nonlinear processes in the bunched electron beams of high-power klystrons and the limits of analytical and one-dimensional numerical models applicability for their analysis.

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
V.Y. Rodyakin ◽  
◽  
V.M. Pikunov ◽  
V.N. Aksenov ◽  
◽  
...  
Keyword(s):  
Electron Beam ◽  
High Power ◽  
Numerical Models ◽  
Nonlinear Effects ◽  
Analytical Models ◽  
Modulation Amplitude ◽  
Two Dimensional ◽  
One Dimensional ◽  
Charge Parameter ◽  
Program Data

We present the results of a comparative theoretical analysis of the electron beam bunching in a single-stage klystron amplifier using analytical models, a one-dimensional disk program, and a two-dimensional program. Data on the influence of various one-dimensional and two-dimensional nonlinear effects on the efficiency of electron beam bunching at different values of the space charge parameter and the modulation amplitude are presented. The limits of applicability of analytical and one-dimensional numerical models for electron beam bunching analysis in high-power klystron amplifiers are found.

scholarly journals Nektar++: Design and implementation of an implicit, spectral/hp element, compressible flow solver using a Jacobian-free Newton Krylov approach

2021 ◽  
Vol 81 ◽  
pp. 351-372
Author(s):  
Zhen-Guo Yan ◽  
Yu Pan ◽  
Giacomo Castiglioni ◽  
Koen Hillewaert ◽  
Joaquim Peiró ◽  
...  
Keyword(s):  
Compressible Flow ◽  
Flow Solver ◽  
Design And Implementation

Closed-form expressions for the steady-state response of damped transmission line conductors considering their bending stiffness

2020 ◽  
Vol 26 (15-16) ◽  
pp. 1319-1329
Author(s):  
Marcelo A Ceballos ◽  
José E Stuardi
Keyword(s):  
Steady State ◽  
Transmission Line ◽  
Numerical Models ◽  
Mechanical Impedance ◽  
Steady State Solution ◽  
Bending Stiffness ◽  
Analytical Models ◽  
Dispersive Media ◽  
Overhead Transmission Line ◽  
Damper Design

This paper begins with a brief compilation of analytical models typically used to calculate the dynamic response of a conductor span belonging to an overhead transmission line, with a Stockbridge-type damper located near one of its ends. In most of analyses found in the literature, the calculation of the response is done through the superposition of waves that propagate in both longitudinal directions impinging and reflecting at the span ends and at the damper attachment points. The approach proposed in this paper allows obtaining the response as the steady-state solution of the governing differential equations providing suitable analytical expressions for conductors with bending stiffness, which are dispersive media for propagating waves. Using these analytical solutions, the influence of bending stiffness on the efficiency and on the optimal mechanical impedance of the damper, which are of great importance in damper design, can be described explicitly. At the same time, the proposed methodology avoids the need of numerical models or approximate formulas to calculate the bending strains in critical points of the conductor with a single damper.

UV disinfection of water: the need for UV reactor validation

2003 ◽  
Vol 3 (4) ◽  
pp. 293-300 ◽  
Author(s):  
Y.A. Lawryshyn ◽  
B. Cairns
Keyword(s):  
Legionella Pneumophila ◽  
Uv Light ◽  
Numerical Models ◽  
Operating Conditions ◽  
Analytical Models ◽  
Human Consumption ◽  
Average Dose ◽  
Reactor Performance ◽  
Uv Reactor ◽  
Bioassay Data

Disinfection by ultraviolet light (UV) has received wide endorsement as an important contribution to the multiple barrier approach for protection of public health. UV can be used both to disinfect wastewater discharged to the environment, and to disinfect that water when it is picked up again for human consumption. UV readily blocks infectivity by such chlorine-resistant pathogens as Cryptosporidium parvum, Giardia lamblia and Legionella pneumophila. Multiple disinfectant use is now being discussed to broaden the spectrum of pathogens that can be inactivated by using disinfectants in their most strategically advantageous dose and function. Optimizing multiple barrier strategies requires attention to validation of the concepts and technologies involved. UV technology validation ensures that the equipment can deliver the target UV design dose, and that the monitoring/control technology modulates the dose appropriately with changes in water quality or operating conditions. The bioassay approach for UV reactor validation is recommended over analytical and numerical models. Analytical models, which provide an average dose estimate, have been shown to be inadequate. Numerical models, which utilize Computational Fluid Dynamics (CFD) and UV light intensity models to predict reactor performance, can be accurate when used by skilled professionals but require significant validation and/or calibration against bioassay data.

Analytical and Numerical Prediction of Springback of SS/Al-Alloy Cladded Sheet in V-Bending

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Pankaj Kumar Sharma ◽  
Vijay Gautam ◽  
Atul Kumar Agrawal
Keyword(s):  
Analytical Model ◽  
Outer Layer ◽  
Numerical Models ◽  
Yield Criterion ◽  
Bending Moment ◽  
Analytical Models ◽  
Bend Angle ◽  
Radius Of Curvature ◽  
Al Alloy ◽  
First Case

Abstract The present work deals with the development of an analytical model incorporating the effects of anisotropy and strain hardening to predict the springback in V-bending of two-ply sheet metal using a punch profile radius of 15 mm and included a bend angle of 90 deg. In the analytical model, the total bending moment is determined from resulting bending stresses for two different layers arranged in parallel planes one above the other and a new radius of curvature after springback is determined by applying a negative bending moment. The two-ply sheet composed of layers of AA1050 and SS430 is characterized for its tensile properties to be used in analytical and numerical models for prediction of springback. To study the effect of each layer during bending operation, two possible cases of sheet placements during bending and springback are studied; i.e., in the first case, the inner layer is of AA1050 while the SS430 layer is the outer layer whereas in the second case it is opposite. In all the cases of springback experiments when the outer layer is of SS430, the springback values are higher than the values obtained with the specimens when the inner layer is of SS430. This could be attributed to the higher tensile strength of the stainless steel layer and the higher bending radius experienced by it. The springback behaviors are also analyzed by simulations using Hill's anisotropic yield criterion in abaqus software. The springback results obtained by simulations and analytical models are in good agreement in general; however, in some cases, discrepancy of more than 15% is observed in the analytical results when compared with the experimental results.

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