Modeling of Fabric Impact With High Speed Imaging and Nickel-Chromium Wires Validation

2011 ◽  
Vol 78 (5) ◽  
Author(s):  
Sidney Chocron ◽  
Trenton Kirchdoerfer ◽  
Nikki King ◽  
Christopher J. Freitas
Keyword(s):  
Numerical Simulations ◽  
High Speed ◽  
Numerical Models ◽  
Single Layer ◽  
Diagnostic Techniques ◽  
High Speed Photography ◽  
High Speed Imaging ◽  
Nickel Chromium ◽  
Validation Set ◽  
The Waves

Ballistic tests were performed on single-yarn, single-layer and ten-layer targets of Kevlar® KM2 (600 and 850 denier), Dyneema® SK-65 and PBO® (500 denier). The objective was to develop data for validation of numerical models so, multiple diagnostic techniques were used: (1) ultra-high speed photography, (2) high-speed video and (3) nickel-chromium wire technique. These techniques allowed thorough validation of the numerical models through five different paths. The first validation set was at the yarn level, where the transverse wave propagation obtained with analytical and numerical simulations was compared to that obtained in the experiments. The second validation path was at the single-layer level: the propagation of the pyramidal wave observed with the high speed camera was compared to the numerical simulations. The third validation consisted of comparing, for the targets with ten layers, the pyramid apex and diagonal positions from tests and simulations. The fourth validation, which is probably the most relevant, consisted of comparing the numerical and experimental ballistic limits. Finally for the fifth validation set, nickel-chromium wires were used to record electronically the waves propagating in the fabrics. It is shown that for the three materials the waves recorded during the tests match well the waves predicted by the numerical model.

Dynamics of Droplet Motion Induced by Electrowetting

2016 ◽  
Author(s):  
Yi Lu ◽  
Aritra Sur ◽  
Dong Liu ◽  
Carmen Pascente ◽  
Paul Ruchhoeft
Keyword(s):  
Contact Angle ◽  
High Speed ◽  
Numerical Models ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
High Speed Photography ◽  
Droplet Dynamics ◽  
Droplet Shape ◽  
Moving Contact Line ◽  
Moving Contact

Electrowetting has drawn significant interests due to the potential applications in electronic displays, lab-on-a-chip devices and electro-optical switches, etc. Current understanding of electrowetting-induced droplet dynamics is hindered by the inadequacy of available numerical and theoretical models in properly handling the dynamic contact angle at the moving contact line. A combined numerical and experimental approach was employed in this work to study the spatiotemporal responses of a droplet subject to EW with both direct current and alternating current actuating signals. The time evolution of the droplet shape was measured using high-speed photography. Computational fluid dynamics models were developed by using the Volume of Fluid-Continuous Surface Force method in conjunction with a selected dynamic contact angle model. It was found that the numerical models were able to accurately predict the key parameters of the electrowetting-induced droplet dynamics.

scholarly journals Hydrodynamic regime drives flow reversals in suction feeding larval fishes during early ontogeny

2019 ◽  
Author(s):  
Krishnamoorthy Krishnan ◽  
Asif Shahriar Nafi ◽  
Roi Gurka ◽  
Roi Holzman
Keyword(s):  
Numerical Simulations ◽  
High Speed ◽  
Prey Capture ◽  
Sparus Aurata ◽  
Larval Fish ◽  
Fish Larvae ◽  
Numerical Models ◽  
Hydrodynamic Regime ◽  
Suction Feeding ◽  
Larval Fishes

AbstractFish larvae are the smallest self-sustaining vertebrates. As such, they face multiple challenge that stem from their minute size, and from the hydrodynamic regime in which they dwell. This regime of intermediate Reynolds numbers (Re) was shown to affect the swimming of larval fish and impede their ability to capture prey. Numerical simulations indicate that the flow fields external to the mouth in younger larvae result in shallower spatial gradients, limiting the force exerted on the prey. However, observations on feeding larvae suggest that failures in prey capture can also occur during prey transport, although the mechanism causing these failures is unclear. We combine high-speed videography and numerical simulations to investigate the hydrodynamic mechanisms that impede prey transport in larval fishes. Detailed kinematics of the expanding mouth during prey capture by larval Sparus aurata were used to parameterize age-specific numerical models of the flows inside the mouth. These models reveal that, for small larvae that slowly expand their mouth, not all the fluid that enters the mouth cavity is expelled through the gills, resulting in flow reversal at the mouth orifice. This efflux at the mouth orifice was highest in the younger ages, but was also high (>8%) in slow strikes produced by larger fish. Our modeling explains the observations of “in-and-out” events in larval fish, where prey enters the mouth but is not swallowed. It further highlights the importance of prey transport as an integral part in determining suction feeding success.

Numerical and Experimental Study of Multiphase Transient Core-Annular Flow Patterns in a Spouted Bed

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Ling Zhou ◽  
Chen Han ◽  
Ling Bai ◽  
Weidong Shi ◽  
Ramesh Agarwal
Keyword(s):  
Numerical Simulations ◽  
Flow Pattern ◽  
High Speed ◽  
Annular Flow ◽  
Fluid Phase ◽  
Flow Patterns ◽  
Spouted Bed ◽  
High Speed Imaging ◽  
Spouted Beds ◽  
Number Of Particles

Abstract Dense solid–gas bubbling systems with combined fluid-particle motion are among one of the most extensively used fluidization forms used in the chemical industry. Therefore, it is important to have a good understanding of the hydrodynamic behavior of bubbles. In this paper, both the experiment and numerical simulations are used to investigate the flow patterns in a spouted bed. For numerical simulations, the bidirectional coupling simulations using computational fluid dynamics (CFD) with discrete element method (DEM) are conducted. The results show that the simulations can accurately predict the bubbles morphology compared with the experimental results. When the number of particles is 30,000, only a single core-annular flow pattern appears. When the number of particles is increased to 36,500, the single bubble in the spouted bed transitions into two and a double core-annular flow pattern emerges. As the number of particles is increased to 43,000, a complex multicore-annular flow pattern appears. These flow patterns are also observed in the experiments using high-speed imaging camera. This paper analyzes and explains the causes of these flow phenomena from the dynamic characteristics of particle phase and fluid phase. These results have great significance in providing guidance for optimization of dense phase bubbling spouted beds.

Dynamic Measurements of Micro-Meter Particle Detachment on Glass Surfaces

2012 ◽  
Author(s):  
Asmaa Sadek Kassab ◽  
Victor M. Ugaz ◽  
Maria D. King ◽  
Yassin A. Hassan
Keyword(s):  
High Speed ◽  
Single Layer ◽  
Dynamic Measurements ◽  
Complex Motion ◽  
Short Term ◽  
High Speed Imaging ◽  
Increasing Trend ◽  
Different Types ◽  
Glass Surfaces ◽  
Initial Movement

This work presents a high resolution study of the condition under which a transient fluid flow causes spherical glass beads particles of 10–100 μm in size to detach from glass surfaces. The general approach is to conduct well-controlled experiments, to observe individual microparticle motion in short term resuspension, within a period up to 5s, and to focus on the basic detachment mechanisms of the resuspended particles to fully understand and quantify the behavior of particles immediately before liftoff. Particle tracking obtained from high-speed imaging of individual particle with 4000 frames/s, reveal three different types of motion: rolling/bouncing, immediate liftoff (where the particle showed immediate liftoff without any initial rolling/bouncing) and complex motion where particles travel with rolling/bouncing motion on the surface for a certain distance before liftoff. The longer it will take the particle to start its initial movement the more rapid is the liftoff once motion is initiated. The majority of particle trajectories from the glass substrate were parallel to the surface with complex motion, covering 25% of the total distance traveled in rolling/bouncing motion before liftoff. Additionally, Single layer detachment showed that the detachment percentage initially follow an exponentially increasing trend for a period of ∼ 1s, followed by a plateau phase for a period of 5s.

Preferentially Filled Foam Core Corrugated Steel Sandwich Structures for Improved Blast Performance

2015 ◽  
Vol 82 (6) ◽  
Author(s):  
Murat Yazici ◽  
Jefferson Wright ◽  
Damien Bertin ◽  
Arun Shukla
Keyword(s):  
Shock Tube ◽  
High Speed ◽  
Numerical Models ◽  
Front Face ◽  
High Speed Photography ◽  
Back Face ◽  
Foam Filling ◽  
Shock Impact ◽  
Foam Filled ◽  
Blast Performance

The mechanisms by which different morphologies of preferentially foam filled corrugated panels deform under planar blast loading, transmit shock, and absorb energy are investigated experimentally and numerically for the purpose of mitigating back-face deflection (BFD). Six foam filling configurations were fabricated and subjected to shock wave loading generated by a shock tube. Shock tube experimental results obtained from high-speed photography were used to validate the numerical models. The validated numerical model was further used to analyze 24 different core configurations. The experimental and numerical results show that soft/hard arrangements (front to back) are the most effective for blast resistivity as determined by the smallest BFDs. The number of foam filled layers in each specimen affected the amount of front-face deflections (FFDs), but did relatively little to alter BFDs, and results do not support alternating foam filling layers as a valid method to attenuate shock impact.

scholarly journals Behavior of Beam-to-Column Connections with Angles. Part 2-Numerical Analysis

2016 ◽  
Vol 6 (1) ◽  
pp. 35-40
Author(s):  
M. Ghindea ◽  
A. Cătărig ◽  
R. Ballok
Keyword(s):  
Numerical Simulations ◽  
Deformation Process ◽  
High Speed ◽  
Rotation Curve ◽  
Numerical Models ◽  
Experimental Tests ◽  
3D Models ◽  
Experimental Investigations ◽  
Software Packages ◽  
Parametric Studies

Abstract Based on the results of experimental tests, presented in the first part of this paper, Part 1-Experimental Investigations (Ghindea M., Catarig A., Ballok R.) advanced numerical simulations were performed using FEM based software Abaqus. The recently arise of high speed computers and advanced FEM software packages allow to create and solve extensively detailed 3D models. The aim of this second part of the paper is to develop accurate FEM models for better approach of the studied beam-to-column connections. The paper presents the designed numerical models and the results for four bolted beam-to-column connections using top-and-seat and/or web angle cleats, in different configurations. The objective of this paper is to achieve functional numerical models which, by faithfully running, reproduce the experimental results. Thus, calibrating the numerical results with the experimental ones it can be perform then parametric studies, achieving reliable results for similar configurations of joints. The results obtained after numerical simulations were compared with experimental data. The behavior moment-rotation curve and the deformation process of the experimental captured specimens were virtually reproduced with minimum deviation.

scholarly journals Formation and rupture of gas film of antibubble

2020 ◽  
Vol 23 (1) ◽  
pp. 91-104
Author(s):  
Lichun Bai ◽  
Jinguang Sun ◽  
Zhijie Zeng ◽  
Yuhang Ma ◽  
Lixin Bai
Keyword(s):  
Liquid Film ◽  
High Speed ◽  
Liquid Surface ◽  
Single Layer ◽  
Liquid Films ◽  
Droplet Impact ◽  
Liquid Interface ◽  
High Speed Photography ◽  
Merging Process ◽  
The Impact

The formation and rupture of gas film in the process of formation, rupture and coalescence of antibubbles were investigated by high-speed photography. It was found that a gas film will appear and wrap a droplet when the droplet hit a layer of liquid film or foam before impacting the gas-liquid interface. The gas film may survive the impact on the gas-liquid interface and act as the gas film of an antibubble. A multilayer droplet will be formed when the droplet hits through several layer of liquid films, and a multilayer antibubble will be formed when the multilayer droplet impact a gas-liquid interface or a single layer of foam on the liquid surface. The way to generate antibubbles by liquid films will undergo the formation and rupture of gas films. The coalescence of two antibubbles, which shows a similar merging process of soap bubbles, also undergo the rupture and formation of gas films. The rupture of gas film of antibubble caused by aging and impact is also discussed.

An Experimental Study of Accelerated Cavitation Induced by Ultrasonics

1965 ◽  
Vol 87 (4) ◽  
pp. 967-976 ◽  
Author(s):  
F. Numachi
Keyword(s):  
Experimental Study ◽  
Frequency Spectrum ◽  
High Speed ◽  
Present Report ◽  
Ultrasonic Waves ◽  
High Speed Photography ◽  
Air Bubbles ◽  
The Waves

With a view to clarifying cavitation phenomena induced by ultrasonic waves, utilized recently in erosion tests, the frequency spectrum of the waves caused by cavitation was obtained, and the pattern of air bubbles produced were observed by high-speed photography. Some considerations also are given in the present report on the amount and form of erosion caused by cavitation.

scholarly journals Numerical and Experimental Study of the Interaction of a Spark-Generated Bubble and a Vertical Wall

2010 ◽  
Author(s):  
Arvind Jayaprakash ◽  
Georges Chahine ◽  
Chao-Tsung Hsiao
Keyword(s):  
Numerical Simulations ◽  
High Speed ◽  
Linear Time ◽  
Numerical Models ◽  
Vertical Wall ◽  
Bubble Collapse ◽  
Small Scale ◽  
Liquid Jet ◽  
Numerical Predictions ◽  
Jet Characteristics

An understanding of the fundamental mechanisms involved in the interaction between cavitation bubbles and structures is of importance for many applications involving cavitation erosion. Generally, the final stage of bubble collapse is associated with the formation of a high-speed reentrant liquid jet directed towards the solid surface. Local forces associated with the collapse of such bubbles can be very high and can exert significant loads on the materials. This formation and impact of liquid jet is an area of intense research. Under some conditions the presence of gravity and other nearby boundaries and free surfaces alters the jet direction and need to be understood, especially that in the laboratory, small scale tests in finite containers have these effects inherently present. In this work, experiments and numerical simulations of the interaction between a vertical wall and a bubble were carried out using Dynaflow’s three-dimensional code, 3DynaFS_Bem©, which models the unsteady dynamics of a liquid flow including the presence of highly non-linear time evolving gas-liquid interfaces. The numerical predictions were validated using scaled experiments carried out using spark generated bubbles. These spark bubble tests produced high fidelity test data that properly scale the fluid dynamics as long as the geometric non-dimensional parameters, gravity and time are properly scaled. The use of high speed cameras allowing framing rates as high as 50,000 frames per second to photograph the bubbles produced high quality observations of bubble dynamics including clear visualizations of reentrant jet formation inside the bubble. Such observations were very useful in developing and validating the numerical models. The cases studied showed very good correlation between the numerical simulations and the experimental observations and allowed development of predictive rules for the re-entrant jet characteristics, including jet angle and various definitions of the jet speed.

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