scholarly journals DEM Study on the Segregation of a Non-Spherical Intruder in a Vibrated Granular Bed

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 448
Author(s):  
Jinpeng Qiao ◽  
Kejun Dong ◽  
Chenlong Duan
Keyword(s):  
Aspect Ratio ◽  
Vibration Frequency ◽  
Vibration Amplitude ◽  
Granular Temperature ◽  
Equivalent Diameter ◽  
Granular Bed ◽  
Small Particles ◽  
Porosity Variation ◽  
Segregation Process ◽  
Prolate Shape

The segregation process of a single large intruder in a vibrated bed of small particles has been widely studied, but most previous studies focused on spherical intruders. In this work, the discrete element method was used to study the effects of vibration conditions and intruder shape on the dimensionless ascending velocity (va) of the intruder. The intruder was in a prolate shape with aspect ratio varied but its equivalent diameter fixed. Three equivalent diameters, namely volume-equivalent diameter, surface-area-equivalent diameter, and Sauter diameter, were used. It was found that va increases and then decreases with the rise of the dimensionless vibration amplitude (Ad) and the dimensionless vibration frequency (fd), and va increases with the decrease of the sphericity of the intruder (Φ). Moreover, the porosity variation in the vibrated bed and the granular temperature were analyzed, which can be linked to the change of va. It was further found that va can be uniformly correlated to Ad‧f 0.5 d, while the critical change of the response of va to Ad and fd occurs at Γ = 4.83, where Γ is the vibration intensity. Based on these findings, a piecewise equation was proposed to predict va as a function of Ad, fd, and Φ.

scholarly journals Vibration induced segregation of single large particles

2021 ◽  
Vol 249 ◽  
pp. 14006
Author(s):  
Dizhe Zhang ◽  
David Pinson ◽  
Zongyan Zhou
Keyword(s):  
Vibration Frequency ◽  
Vibration Amplitude ◽  
Initial Orientation ◽  
Size Ratio ◽  
Brazil Nut ◽  
Segregation Process ◽  
Large Particles ◽  
Vertical Segregation ◽  
Brazil Nut Effect ◽  
Time Required

The vibration-induced segregation (e.g., rising of one large intruder - so called Brazil Nut Effect (BNE)) is studied by discrete element method. Vibration frequency and amplitude are two dominating factors in the occurrence of BNE and a phase diagram is constructed. For fixed vibration amplitude, segregation only occurs when vibration frequency is within a certain range. Larger vibration amplitude can expand the range of vibration frequency for BNE. Size ratio and the intruder shape are studied under certain vibration conditions. Larger size ratio can enlarge the segregation intensity. The shape of the intruder influences the segregation process by the intruder′s orientation. Standing-like initial orientation can increase the time required for the intruder to reach the top while lying-like initial orientation cannot significantly affect the vertical segregation.

Modification of MnS inclusion by tellurium in 38MnVS6 micro-alloyed steel

2020 ◽  
Vol 117 (6) ◽  
pp. 615
Author(s):  
Ping Shen ◽  
Lei Zhou ◽  
Qiankun Yang ◽  
Zhiqi Zeng ◽  
Kenan Ai ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Aspect Ratio ◽  
Strong Influence ◽  
Experimental Results ◽  
Alloyed Steel ◽  
Equivalent Diameter ◽  
Small Aspect Ratio ◽  
Steel Quality ◽  
Eds Analysis ◽  
Micro Alloyed Steel

In 38MnVS6 steel, the morphology of sulfide inclusion has a strong influence on the fatigue life and machinability of the steel. In most cases, the MnS inclusions show strip morphology after rolling, which significantly affects the steel quality. Usually, the MnS inclusion with a spherical morphology is the best morphology for the steel quality. In the present work, tellurium was applied to 38MnVS6 micro-alloyed steel to control the MnS inclusion. Trace tellurium was added into 38MnVS6 steel and the effect of Te on the morphology, composition, size and distribution of MnS inclusions were investigated. Experimental results show that with the increase of Te content, the equivalent diameter and the aspect ratio of inclusion decrease strikingly, and the number of inclusions with small aspect ratio increases. The inclusions are dissociated and spherized. The SEM-EDS analysis indicates that the trace Te mainly dissolves in MnS inclusion. Once the MnS is saturated with Te, MnTe starts to generate and wraps MnS. The critical Te/S value for the formation of MnTe in the 38MnV6 steel is determined to be approximately 0.075. With the increase of Te/S ratio, the aspect ratio of MnS inclusion decreases and gradually reaches a constant level. The Te/S value in the 38MnVS6 steel corresponding to the change of aspect ratio from decreasing to constant ranges from 0.096 to 0.255. This is most likely to be caused by the saturation of Te in the MnS inclusion. After adding Te in the steel, rod-like MnS inclusion is modified to small inclusion and the smaller the MnS inclusion, the lower the aspect ratio.

Numerical Simulation of Flow and Heat Transfer in Rectangular Channel With Different Aspect Ratios

2016 ◽  
Author(s):  
Liu Wenhua ◽  
Mo Yang ◽  
Li Ling ◽  
Qiao Liang ◽  
Yuwen Zhang
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Aspect Ratio ◽  
Characteristic Length ◽  
Rectangular Channel ◽  
Equivalent Diameter ◽  
Correction Coefficient ◽  
Corner Region ◽  
Flow And Heat Transfer ◽  
Aspect Ratios

Turbulent flow and heat transfer in rectangular channel has an important significance in engineering. Conventional approach to caculate Nusselt number of rectangular channel approximately is to take the equivalent diameter as the characteristic length and use the classic circular channel turbulent heat transfer coefficient correlations. However, under these conditions, the caculation error of Nusselt number can reach to 14% and thus this approach can not substantially describe the variation of Nusselt number of rectangular cross-sections with different aspect ratios. Therefore, caculation by using equivalent diameter as the characteristic length in classic experiment formula needs to be corrected. Seven groups of rectangular channel models with different aspect ratios have been studied numerically in this paper. By using standard turbulence model, the flow and heat transfer law of air with varing properties has been studied in 4 different sets of conditions in Reynolds number. The simulation and experimental results are in good agreement. The simulation results show that with the increase of aspect ratio, the cross-sectional average Nusselt number increased, Nusselt number of circumferential wall distributed more evenly and the difference between the infinite plate channel and square channel went up to 25%. The effects of corner region and long\short sides on heat transfer have also been investigated in this paper. Results show that in rectangular channel, heat transfer in corner region is significantly weaker than it in other region. With the increase of aspect ratio, effect on the long side of heat transfer of the short side is gradually reduced, and then eventually eliminates completely in the infinite flat place. Based on the studies above, correction coefficient for rectangular channels with different aspect ratios has been proposed in this paper and the accuracy of the correction coefficient has been varified by numerical simulations. This can reflect the variation of Nusselt number under different aspect ratios more effectively and thus has current significance for project to calculate Nusselt number of heat transfer in rectangular channel.

scholarly journals Scaling of granular temperature in a vibrated granular bed

2011 ◽  
Vol 83 (3) ◽  
Author(s):  
V. Zivkovic ◽  
M. J. Biggs ◽  
D. H. Glass
Keyword(s):  
Granular Temperature ◽  
Granular Bed

scholarly journals Droplet Generation in a Flow-Focusing Microfluidic Device with External Mechanical Vibration

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 743
Author(s):  
Zhaoqin Yin ◽  
Zemin Huang ◽  
Xiaohui Lin ◽  
Xiaoyan Gao ◽  
Fubing Bao
Keyword(s):  
Microfluidic Device ◽  
Vibration Frequency ◽  
Linear Correlation ◽  
Vibration Amplitude ◽  
Mechanical Vibration ◽  
Droplet Generation ◽  
Flow Focusing ◽  
Generation Frequency ◽  
External Vibration ◽  
Shrinkage Process

The demand for highly controllable droplet generation methods is very urgent in the medical, materials, and food industries. The droplet generation in a flow-focusing microfluidic device with external mechanical vibration, as a controllable droplet generation method, is experimentally studied. The effects of vibration frequency and acceleration amplitude on the droplet generation are characterized. The linear correlation between the droplet generation frequency and the external vibration frequency and the critical vibration amplitude corresponding to the imposing vibration frequency are observed. The droplet generation frequency with external mechanical vibration is affected by the natural generation frequency, vibration frequency, and vibration amplitude. The droplet generation frequency in a certain microfluidic device with external vibration is able to vary from the natural generation frequency to the imposed vibration frequency at different vibration conditions. The evolution of dispersed phase thread with vibration is remarkably different with the process without vibration. Distinct stages of expansion, shrinkage, and collapse are observed in the droplet formation with vibration, and the occurrence number of expansion–shrinkage process is relevant with the linear correlation coefficient.

scholarly journals A Stress-Strain Model for Unconfined Concrete in Compression considering the Size Effect

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Keun-Hyeok Yang ◽  
Yongjei Lee ◽  
Ju-Hyun Mun
Keyword(s):  
Compressive Strength ◽  
Aspect Ratio ◽  
Size Effect ◽  
Maximum Stress ◽  
Damage Zone ◽  
Peak Stress ◽  
Equivalent Diameter ◽  
Stress Strain ◽  
Compressive Strength Of Concrete ◽  
Strain Model

In this study, a stress-strain model for unconfined concrete with the consideration of the size effect was proposed. The compressive strength model that is based on the function of specimen width and aspect ratio was used for determining the maximum stress. In addition, in stress-strain relationship, a strain at the maximum stress was formulated as a function of compressive strength considering the size effect using the nonlinear regression analysis of data records compiled from a wide variety of specimens. The descending branch after the maximum stress was formulated with the consideration of the effect of decreasing area of fracture energy with the increase in equivalent diameter and aspect ratio of the specimen in the compression damage zone (CDZ) model. The key parameter for the slope of the descending branch was formulated as a function of equivalent diameter and aspect ratio of the specimen, concrete density, and compressive strength of concrete. Consequently, a rational stress-strain model for unconfined concrete was proposed. This model reflects trends that the maximum stress and strain at the peak stress decrease and the slope of the descending branch increases, when the equivalent diameter and aspect ratio of the specimen increase. The proposed model agrees well with the test results, irrespective of the compressive strength of concrete, concrete type, equivalent diameter, and aspect ratio of the specimen.

Thermal Performance Improvement of a Heat Sink With Piezoelectric Vibrating Fins

2010 ◽  
Author(s):  
Hee Seung Park ◽  
Sung Jin Kim
Keyword(s):  
Natural Frequency ◽  
Performance Improvement ◽  
Thermal Performance ◽  
Vibration Frequency ◽  
Heat Sink ◽  
Vibration Amplitude ◽  
Piezoelectric Actuators ◽  
Convection Heat ◽  
Heat Transfer Characteristics ◽  
Heat Sink Temperature

A heat sink with piezoelectric vibrating fins is developed through attaching piezoelectric actuators to the fins of a heat sink, and the heat transfer characteristics of the heat sink are experimentally investigated. Thermal performance improvement of the heat sink by the vibration of the fins is observed compared to the thermal performance of a natural convection heat sink with static fins under a fixed heat sink geometry condition. The thermal performance of the heat sink changes as the vibration amplitude of the fins or the vibration frequency of the fins changes. Particularly, if the vibration frequency of the fins matches up to the natural frequency of the fins, the vibration amplitude is significantly increased by resonance and the thermal performance also increases. The natural frequency of the fins changes with the heat sink temperature because the geometry of the fins changes and the properties of the fins change due to the temperature change.

Measurements of Dimension and Morphology of Solid Particles Volume With Digital In-Line Holography

2019 ◽  
Author(s):  
Yijie Wang ◽  
Jun Chen
Keyword(s):  
Aspect Ratio ◽  
Solid Particles ◽  
Equivalent Diameter ◽  
Microscopic Images ◽  
Recorded Hologram ◽  
Accuracy Of Measurements ◽  
The Individual ◽  
Multi Phase ◽  
Individual Particles

Abstract Digital in-line holography (DIH) has been applied to measure the 3D position of objects in a variety of applications, including bubbles and droplets in multi-phase flows, tracking particles in turbulence flows, etc. In addition to the 3D position, the morphology and dimension of the individual particles can also be extracted from the recorded hologram. In this study, a lens-less digital in-line holography setup is applied to measure the morphology and size of three kinds of solid particles (Wollastonite Powder, Pearl Mica Powder and Solder Powder), whose sizes range from several to hundreds of micrometers. The statistics of equivalent diameter, aspect ratio and circularity are introduced to describe the morphology and dimension of each kind of particles. Microscopic images of the particles are taken to verify the accuracy of measurements with DIH. The results measured from DIH are in good agreements with results from microscopic images.

scholarly journals Modeling Transport and Deposition Efficiency of Oblate and Prolate Nano- and Micro-particles in a Virtual Model of the Human Airway

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Elise Holmstedt ◽  
Hans O. Åkerstedt ◽  
T. Staffan Lundström ◽  
Sofie M. Högberg
Keyword(s):  
Aspect Ratio ◽  
Statistical Study ◽  
Human Lung ◽  
Reynolds Numbers ◽  
Deposition Efficiency ◽  
Small Particles ◽  
Nonspherical Particle ◽  
Micro Particles ◽  
Prolate Spheroids ◽  
Modeling Transport

A model for the motion and deposition of oblate and prolate spheroids in the nano- and microscale was developed. The aim was to mimic the environment of the human lung, but the model is general and can be applied for different flows and geometries for small nonspherical particle Stokes and Reynolds numbers. A study of the motion and orientation of a single oblate and prolate particle has been done yielding that Brownian motion disturbs the Jeffery orbits for small particles. Prolate microparticles still display distinguishable orbits while oblate particles of the same size do not. A statistical study was done comparing the deposition efficiencies of oblate and prolate spheroids of different size and aspect ratio observing that smaller particles have higher deposition rate for lower aspect ratio while larger particles have higher deposition rates for large aspect ratio.

scholarly journals DESIGN OPTIMIZATION AND PERFORMANCE TEST OF MAGNETIC PICKUP FINGER SEED METERING DEVICE

2021 ◽  
pp. 137-144
Author(s):  
Fei Liu ◽  
Zhen Lin ◽  
Dapeng Li ◽  
Tao Zhang
Keyword(s):  
Vibration Frequency ◽  
Magnetic Induction ◽  
Vibration Amplitude ◽  
Magnetic Force ◽  
Performance Test ◽  
Simulation Software ◽  
National Standard ◽  
Design And Optimization ◽  
Seed Metering Device ◽  
Magnetic Induction Intensity

As the core part of precision seeder, the performance of pickup finger seed metering device directly affects the seeding quality. Aiming at the problem that the traditional pickup finger seed metering device can be easily affected by the performance of spring material, and the reliability of spring decreases with the increase of service time, a magnetic pickup finger seed metering device is designed to open and close the pickup finger by magnetic force, so as to improve the stability of seed metering performance. Through the design and optimization of permanent magnet structure, cam structure and seed taking pickup finger structure, the magnetic force distribution of ring magnet is analysed by using ANSYS Maxwell magnetic simulation software. Under the working speed of 3.9km/h, the vibration frequency, vibration amplitude and magnetic induction intensity were selected for orthogonal test. The experimental results show that the optimal combination of factors is vibration frequency 6Hz, vibration amplitude 3.1mm and magnetic induction intensity 316.34mT. Under the condition of the combination of operation parameters, the seed arrangement performance is 91.7% of the qualified rate, 6.2% of the replant rate and 2.1% of the missed rate, which meets the requirements of the national standard for the performance of the seeder. This study can provide a reference for the optimization of the structure and the improvement of the seed metering performance of the pickup finger seed metering device.

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