Experimental and numerical study of miscible Faraday instability

2009 ◽  
Vol 628 ◽  
pp. 43-55 ◽  
Author(s):  
F. ZOUESHTIAGH ◽  
S. AMIROUDINE ◽  
R. NARAYANAN
Keyword(s):  
Numerical Model ◽  
High Speed ◽  
Numerical Study ◽  
Stable Configuration ◽  
Rectangular Cell ◽  
Diffuse Interfaces ◽  
Faraday Instability ◽  
Miscible Liquids ◽  
Set Up ◽  
Nonlinear Numerical Model

A study of the Faraday instability of diffuse interfaces between pairs of miscible liquids of different densities, by means of experiments and by a nonlinear numerical model, is presented. The experimental set-up consisted of a rectangular cell in which the lighter liquid was placed above the denser one. The cell in this initially stable configuration was then subjected to vertical vibrations. The subsequent behaviour of the ‘interface’ between the two liquids was observed with a high-speed camera. This study shows that above a certain acceleration threshold an instability developed at the interface. The amplitude of the instability grew during the experiments which then led to the mixing of the liquids. The instability finally disappeared once the two liquids were fully mixed over a volume, considerably larger than the initial diffuse region. The results of a companion two-dimensional nonlinear numerical model that employs a finite volume method show very good agreement with the experiments. A physical explanation of the instability and the observations are advanced.

scholarly journals CMT-Based Wire Arc Additive Manufacturing Using 316L Stainless Steel: Effect of Heat Accumulation on the Multi-Layer Deposits

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 278 ◽  
Author(s):  
Seung Hwan Lee
Keyword(s):  
Additive Manufacturing ◽  
Numerical Model ◽  
Heat Source ◽  
Cooling Rate ◽  
High Speed ◽  
Numerical Study ◽  
Transient Behavior ◽  
Heat Accumulation ◽  
Cmt Welding ◽  
Wire Arc Additive Manufacturing

CMT welding sources are garnering attention as alternative heat sources for wire arc additive manufacturing because of their low-heat input. A comprehensive experimental and numerical study on the multi-layer deposition of STS316L was performed to investigate effect of heat accumulation during the deposition. The numerical model which is appropriate for WAMM was developed considering the characteristics of the CMT heat source for the first time. Using a high-speed camera, the transient behavior of the CMT arc was investigated, and applied to the heat source of the numerical model. The model was then used to analyze 10-layered deposits of STS316L, fabricated using CMT-based WAAM. During deposition, the temperature is measured using a pyrometer to analyze the microstructure, after which the cooling rate of each layer is estimated. The measured and simulated SDAS were compared. Based on the comparison, a guideline for the equation regarding the SDAS size and cooling rate was suggested.

Simulation of a Full-Scale CO2 Fracture Propagation Test

2018 ◽  
Author(s):  
Gaute Gruben ◽  
Stephane Dumoulin ◽  
Håkon Nordhagen ◽  
Morten Hammer ◽  
Svend T. Munkejord
Keyword(s):  
Fluid Dynamics ◽  
Numerical Model ◽  
Numerical Study ◽  
Crack Opening ◽  
Fracture Propagation ◽  
Full Scale ◽  
Coupling Scheme ◽  
Outer Diameter ◽  
Fe Model ◽  
Set Up

In this study, we present results from a numerical model of a full-scale fracture propagation test where the pipe sections are filled with impure, dense liquid-phase carbon dioxide. All the pipe sections had a 24″ outer diameter and a diameter/thickness ratio of ∼32. A near symmetric telescopic set-up with increasing toughness in the West and East directions was applied. Due to the near symmetric conditions in both set-up and results, only the East direction is modelled in the numerical study. The numerical model is built in the framework of the commercial finite element (FE) software LS-DYNA. The fluid dynamics is solved using an in-house computational fluid dynamics (CFD) solver which is coupled with the FE solver through a user-defined loading subroutine. As part of the coupling scheme, the FE model sends the crack opening profile to the CFD solver which returns the pressure from the fluid. The pipeline is discretized by shell elements, while the backfill is represented by the smoothed-particle hydrodynamics (SPH) method. The steel pipe is described by the J2 constitutive model and an energy-based fracture criterion, while the Mohr-Coulomb material model is applied for the backfill material. The CFD solver applies a one-dimensional homogeneous equilibrium model where the thermodynamic properties of the CO2 are represented by the Peng-Robinson equation-of-state (EOS). The results from the simulations in terms of crack velocity and pressure agree well with the experimental data for the low and medium toughness pipe sections, while a conservative prediction is given for the high-toughness section. Further work for strengthening the reliability of the model to predict the arrest vs. no-arrest boundary of a running ductile fracture is addressed.

An Experimental and Numerical Study of Dieless Water Jet Incremental Microforming

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Yi Shi ◽  
Weizhao Zhang ◽  
Jian Cao ◽  
Kornel F. Ehmann
Keyword(s):  
Numerical Model ◽  
Sheet Metal ◽  
Process Parameters ◽  
High Speed ◽  
Tool Path ◽  
Numerical Study ◽  
Single Point ◽  
Thin Sheet ◽  
Water Jet ◽  
Truncated Cone

Conventional single-point incremental forming (SPIF) is already in use for small batch prototyping and fabrication of customized parts from thin sheet metal blanks by inducing plastic deformation with a rigid round-tip tool. The major advantages of the SPIF process are its high flexibility and die-free nature. In lieu of employing a rigid tool to incrementally form the sheet metal, a high-speed water jet as an alternative was proposed as the forming tool. Since there is no tool-workpiece contact in this process, unlike in the traditional SPIF process, no lubricant and rotational motion of the tool are required to reduce friction. However, the geometry of the part formed by water jet incremental microforming (WJIMF) will no longer be controlled by the motion of the rigid tool. On the contrary, process parameters such as water jet pressure, stage motion speed, water jet diameter, blank thickness, and tool path design will determine the final shape of the workpiece. This paper experimentally studies the influence of the above-mentioned key process parameters on the geometry of a truncated cone shape and on the corresponding surface quality. A numerical model is proposed to predict the shape of the truncated cone part after WJIMF with given input process parameters. The results prove that the formed part's geometric properties predicted by the numerical model are in excellent agreement with the actually measured ones. Arrays of miniature dots, channels, two-level truncated cones, and letters were also successfully fabricated on stainless-steel foils to demonstrate WJIMF capabilities.

scholarly journals Experimental and Numerical Study of At-Rest Lateral Earth Pressure of Overconsolidated Sand

2011 ◽  
Vol 2011 ◽  
pp. 1-12 ◽  
Author(s):  
Magdi El-Emam
Keyword(s):  
Numerical Model ◽  
Numerical Study ◽  
Retaining Wall ◽  
Earth Pressure ◽  
System A ◽  
Lateral Earth Pressure ◽  
Backfill Soil ◽  
Load Cells ◽  
Set Up ◽  
Wall System

The paper presents a one-meter-height rigid facing panel, supported rigidly at the top and bottom to simulate nonyielding retaining wall system. A set of load cells is used to measure the horizontal force at the top and bottom of the facing panel, which is converted to equivalent horizontal earth pressure acting at the back of the wall. Another set of load cells is used to measure the vertical load at the bottom of the wall facing, both at the toe and the heel. Uniformly graded sand was used as backfill soil. The measured wall responses were used to calibrate a numerical model that used to predict additional wall parameters. Results indicated that the measured horizontal earth force is about three times the value calculated by classical at-rest earth pressure theory. In addition, the location of the resultant earth force is located closer to 0.4 H, which is higher compared to the theoretical value of H/3. The numerical model developed was able to predict the earth pressure distribution over the wall height. Test set up, instrumentation, soil properties, different measured responses, and numerical model procedures and results are presented together with the implication of the current results to the practical work.

Numerical Study of Residual Stresses Induced by High Speed Milling Hardened SKD11 Steel

2015 ◽  
Vol 713-715 ◽  
pp. 2769-2774
Author(s):  
Y.C. Liu ◽  
De Weng Tang ◽  
S.L. Zou ◽  
Z.F. He ◽  
Yu Peng Xie
Keyword(s):  
Numerical Model ◽  
Residual Stresses ◽  
Thermal Load ◽  
High Speed ◽  
Mechanical Load ◽  
Numerical Study ◽  
High Speed Milling ◽  
Surface Residual Stresses ◽  
Continuous Feed ◽  
Tensile Surface

A thermo-mechanical numerical model for high speed milling hardened SKD11steel is developed to study the influences of mechanical load and thermal load on residual stresses for each feed. The residual stresses are predicted, which are induced by high speed milling hardened SKD11 steel. Based on a simplified two-dimension assumption, the continuous feed numerical model of high speed milling hardened SKD11 steel is developed. A modified Johnson–Cook (J-C) model considering the effect of phase transformation on flow stress is employed to model residual stresses. The results show that residual stresses dominate over the mechanical load and its impact becomes more and more significant for the posterior cut. The tensile surface residual stresses of posterior cut becomes larger than the previous cut but the work hardening thickness of posterior cut becomes thinner in the condition of this study.

Numerical Study on High-Speed Impact Between a Water Droplet and a Deformable Solid Surface

2012 ◽  
Author(s):  
Yongqiang Han ◽  
Yonghui Xie ◽  
Di Zhang
Keyword(s):  
Solid Surface ◽  
Water Droplet ◽  
High Speed ◽  
Numerical Study ◽  
Contact Radius ◽  
Deformable Solid ◽  
Theoretical Predictions ◽  
Steam Turbine Blade ◽  
Set Up ◽  
The Impact

In this study an axisymmetric model is set up to study the impact of a spherical water droplet with a planar deformable solid surface using the Lagrange-Euler coupling method which is based on a penalty formulation. The diameter and velocity of the droplet are 0.4 mm and 500 m/s respectively, while the solid is a kind of steam turbine blade material. The generated pressure distribution in the droplet and its variation with time, the formation of lateral jet, the deformation and stress distribution in the solid are obtained and investigated. It is shown that the compressibility of the droplet and the solid plays a significant role during the impact. The water-hammer pressure and the maximum contact edge pressure are calculated and in good agreement with the existing theoretical predictions. The calculated contact radius for shock departure is larger than that of the conventional theoretical prediction, which is analyzed and attributable to the radial motion of the liquid in the compressed region. The formation of the high-speed lateral jet is calculated and the time for the observable jetting is much later than that of the shock departure. This delay is discussed and the reason needs more research. The pressure of the contact edge region remains highest even after a considerable time of shock departure and lateral jetting. In the mean time, a saucer-shaped depression is generated in the center of the impact. The stress waves in solid move faster even before shock departure in the liquid. This causes disturbance of the solid surface before the high-speed lateral jetting and provides site for the scouring action of it, and subsequently may cause material damage and erosion.

scholarly journals Pullout simulation of post installed chemically bonded anchors in UHPFRC

2018 ◽  
Vol 199 ◽  
pp. 11007
Author(s):  
Fabien Delhomme ◽  
Michael Brun
Keyword(s):  
Numerical Model ◽  
High Performance ◽  
Failure Modes ◽  
Numerical Study ◽  
Design Stage ◽  
Embedment Depth ◽  
Concrete Damage ◽  
Pullout Failure ◽  
Set Up ◽  
Good Agreement

An experimental and numerical study was completed in order to examine the mechanical behaviour of post-installed bonded anchors in ultra-high performance fibre reinforced concrete with a compressive strength higher than 130 MPa. The aim was to analyse the failure mechanisms in static pullout tests and to suggest a simple numerical model, which can be employed in a design stage, to reproduce the global behaviour of the anchor. The experimental observations show that a combined pullout and concrete cone failure occurred for an embedment depth of 40 mm and a steel rod failure for an embedment depth of 100 mm. The numerical model was set up using Abaqus software, by adopting the concrete damage plastic model and a surface-based cohesive behaviour for the interface concrete-anchor. The obtained failure modes and ultimate loads are in good agreement with experimental results. A minimum embedment depth of 50 mm was assessed to prevent a pullout failure of the anchor.

Numerical Study of Transient Multiphase Slug Flow Through a Tube at High Velocity

2013 ◽  
Author(s):  
Carlton Adam ◽  
Hamid Hadim
Keyword(s):  
Numerical Model ◽  
High Speed ◽  
Numerical Study ◽  
Phase Changes ◽  
Dispersion Pattern ◽  
Liquid Slug ◽  
Gas Phases ◽  
Large Expansion ◽  
High Speed Cinematography ◽  
Turbulence Effects

A transient, two-dimensional computational fluid dynamics model is used to simulate the flow of a liquid slug through a pipe at high velocities. The slug is driven by a gas which enters the system at a constant pressure of 10 MPa. The gas accelerates the slug from rest through a distance of about 45 cm, after which the slug discharges into the open atmosphere. The interface between the two phases is initially uniform and flat, however as the flow develops, significant interphase mixing and deformation of the interface occurs. The simulation is ultimately used to predict the velocity and dispersion pattern of the liquid slug upon discharge into the atmosphere. The gas pressure and dispersion pattern over time are compared to experimental data collected via high-speed cinematography and piezoelectric pressure gauges. The numerical model predicts a slug exit velocity of 108 m/s which agrees reasonably well with empirical measurements. However, the numerical model fails to accurately predict the structure of the dispersion pattern of the exiting liquid, specifically in terms of the amount of mixing between the liquid and gas phases. To address these discrepancies between the model and the empirical data, a follow-on effort will be performed in an attempt to better capture the formation of the large expansion plume seen in the high-speed video. Specifically, phase changes in the liquid and gas will be addressed in the follow-on effort, as will turbulence effects on mixing at small scales.

scholarly journals Dynamical Studies and Numerical Study of the Pandemic Fractional COVID-19 Using the Caputo–Fabrizio Derivative

2021 ◽  
Author(s):  
Amr Mahdy ◽  
Y. A. Amer ◽  
E. S. M. Youssef ◽  
W. Adel
Keyword(s):  
Fixed Point ◽  
Numerical Model ◽  
Numerical Study ◽  
Models Of Care ◽  
Care Model ◽  
Significant Information ◽  
Proposed Model ◽  
Novel Virus ◽  
Set Up ◽  
Entire Number

Abstract In this document, we are in the process of solving and describing the engineering meaning of one of the most dangerous models that affect humans and that spreads at a tremendous speed between people. A Caputo–Fabrizio type partial request numerical model for the fractional Coronavirus model is introduced. The principal properties of the model are investigated. The presence and uniqueness of the answer for the proposed partial Coronavirus model are given through the fixed-point speculation. The mathematical propagations for the model are obtained by using explicit boundary regards. The non-number solicitation subordinate gives continuously versatile and more significant information about the multifaceted idea of the components of the proposed fractional budgetary models of care model than the entire number solicitation models set up beforehand. This new proposed model better may help to better understand the dynamic of this novel virus and may help to better control it.

Numerical Study on the Running Safety of High-Speed Train under the Cross Wind

2014 ◽  
Vol 694 ◽  
pp. 109-113
Author(s):  
Xiang Dong Chen ◽  
Yu Gong Xu
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Three Dimensional ◽  
Reduction Rate ◽  
Aerodynamic Characteristics ◽  
High Speed Train ◽  
Wheel Load ◽  
The Cross ◽  
Set Up ◽  
Train Safety

With the increasing speed, the crosswind effect is the more and more obvious. The three dimensional aerodynamic model of the high-speed train was set up to study the aerodynamic characteristics of the train under the cross wind. Based on the vehicle system dynamics, the couple model for dynamics of wind-train-rail systems was set up to study the train safety under the wind load. The derailment coefficient and reduction rate of wheel load were analyzed under the different train speed, different wind velocity. The results of this research can provide a theoretical basis for the high-speed train safety.

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