A modified calculation of particle buoyant forces in vibro-fluidized beds

Segregation of granular materials under vibration or flow conditions such as the Brazil nut effect has been well known, however, there is yet no consensus mechanisms to explain this phenomenon. This study attempts to investigate particle buoyant forces in the segregation process. To explain the difference of the segregation behavior for the large particle with different size, a modified calculation method of particle buoyant force is suggested for considering the effect of particle size ratio. A simple verification illustrates its validity.

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CYCLIC SEGREGATION STATE IN VERTICALLY VIBRATED BINARY GRANULAR MIXTURES

Modern Physics Letters B ◽

10.1142/s0217984914500201 ◽

2014 ◽

Vol 28 (03) ◽

pp. 1450020

Author(s):

QINGFAN SHI ◽

BEICHENG PAN ◽

CHANGHONG LU ◽

GANG SUN

Keyword(s):

Phase Diagram ◽

Atmospheric Pressure ◽

Air Flow ◽

Brazil Nut ◽

Positive Role ◽

Structure Changes ◽

Granular Mixtures ◽

Segregation Process ◽

Acceleration Amplitude ◽

Brazil Nut Effect

In this paper, the vertically vibrated binary granular mixtures at atmospheric pressure are studied experimentally. We find a nonstationary segregation state, of which the structure changes with time cyclically. The period of the cyclic segregation is measured and its variation with the vibration conditions is shown. The transition between the segregation states is also discussed, and a phase diagram on the plot of frequency against acceleration amplitude is given. In order to observe the effect of air flow in the segregation process, an alternative container with ventilated bottom is designed. Our experiments show that both regions of the Brazil nut segregation state and the cyclic segregation state shrink obviously by use of the latter container and disappear completely if the whole system is placed in vacuum. These results testify that the air pressure plays a positive role in both the Brazil nut effect and cyclic segregation.

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Vibration induced segregation of single large particles

EPJ Web of Conferences ◽

10.1051/epjconf/202124914006 ◽

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.

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Qualitative Observations of Dense Particle Motion in a Vibration-Excited Granular Bed

Volume 7: Engineering Education and Professional Development ◽

10.1115/imece2007-42306 ◽

2007 ◽

Cited By ~ 1

Author(s):

Timothy B. Morgan ◽

Theodore J. Heindel

Keyword(s):

Particle Motion ◽

Large Particle ◽

Granular Media ◽

Brazil Nut ◽

Dense Particle ◽

Brazil Nuts ◽

Bed Height ◽

X Ray Imaging ◽

Large Particles ◽

Brazil Nut Effect

The Brazil nut effect is a classic phenomenon in which larger objects typically migrate to the top of a bed of smaller granular media when exposed to vibration. An example of this phenomenon is finding Brazil nuts on the top of a can of mixed nuts. In this study, the Brazil nut problem is simulated by submerging a large particle in a bed of granular media and then subjecting the system to vibration. Stereoscopic X-ray imaging is used to visualize the large particle motion. These images are then compiled into movies where the particle motion may be tracked. Observations of the large particle motion are made under varying conditions of large particle material, vibration frequency, and bed height. Particle percolation, where smaller particles fill small voids beneath the large particles, is the dominate mechanism at higher vibration frequencies. However, as the frequency decreases, or as the disparity between the densities of the large and small particles decrease, the effects of convection become more pronounced.

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The water-enhanced Brazil nut effect

EPL (Europhysics Letters) ◽

10.1209/0295-5075/91/54001 ◽

2010 ◽

Vol 91 (5) ◽

pp. 54001 ◽

Cited By ~ 24

Author(s):

C. P. Clement ◽

H. A. Pacheco-Martinez ◽

M. R. Swift ◽

P. J. King

Keyword(s):

Brazil Nut ◽

Brazil Nut Effect

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A Horizontal Brazil-Nut Effect and Its Reverse

Physical Review Letters ◽

10.1103/physrevlett.95.028001 ◽

2005 ◽

Vol 95 (2) ◽

Cited By ~ 41

Author(s):

T. Schnautz ◽

R. Brito ◽

C. A. Kruelle ◽

I. Rehberg

Keyword(s):

Brazil Nut ◽

Brazil Nut Effect

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Total Pressure Correction of a Sub-Miniature Five-Hole Probe in Areas of Pressure Gradients

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation ◽

10.1115/gt2012-69280 ◽

2012 ◽

Author(s):

J. Town ◽

A. Akturk ◽

C. Camcı

Keyword(s):

Pressure Measurement ◽

Measurement Errors ◽

Total Pressure ◽

Pressure Gradients ◽

Pressure Data ◽

Flow Conditions ◽

Complex Flow ◽

Ducted Fan ◽

The Difference ◽

Best Fit

Five-hole probes, being a dependable and accurate aerodynamic tools, are excellent choices for measuring complex flow fields. However, total pressure gradients can induce measurement errors. The combined effect of the different flow conditions on the ports causes the measured total pressure to be prone to a greater error. This paper proposes a way to correct the total pressure measurement. The correction is based on the difference between the measured total pressure data of a Kiel probe and a sub-miniature prism-type five-hole probe. By comparing them in a ducted fan related flow field, a line of best fit was constructed. The line of best fit is dependent on the slope of the line in a total pressure versus span and difference in total pressure between the probes at the same location. A computer program, performs the comparison and creates the correction equation. The equation is subsequently applied to the five-hole probe total pressure measurement, and the other dependent values are adjusted. The validity of the correction is then tested by placing the Kiel probe and the five-hole probe in ducted fans with a variety of different tip clearances.

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Microbial Brazil nut effect

Soft Matter ◽

10.1039/d1sm01327k ◽

2021 ◽

Author(s):

Atul Srivastava ◽

Kenji Kikuchi ◽

Takuji Ishikawa

Keyword(s):

Granular Medium ◽

Brazil Nut ◽

Large Object ◽

Intuitive Process ◽

Brazil Nut Effect

The Brazil nut effect (BNE) is a counter-intuitive process of segregation of a large object inside a vibrated granular medium (GM), which has been studied widely by subjecting GMs to...

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Producing Steam by Spraying Water on a Heated Bed of Steel Spheres

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4050841 ◽

2021 ◽

pp. 1-42

Author(s):

D. Jordan Bouchard ◽

HengSheng Yang ◽

Sanjeev Chandra

Keyword(s):

Particle Size ◽

Thermal Mass ◽

Steam Generation ◽

Bed Porosity ◽

The Media ◽

Effect Of Particle Size ◽

The Difference ◽

Rate Of Evaporation ◽

A Minor ◽

Counter Current

Abstract Steam generators used in industrial baking ovens operate by pouring or spraying water on a preheated thermal mass. This paper presents a methodology to quantify the amount of steam generated from a thermal mass along with experiments to determine the effect of particle size and porosity on steam generation. Three sizes of steel spheres, 0.6 mm, 8 mm, and 16 mm in diameter, were used to construct porous media beds that were preheated in an oven after which water was sprayed onto them from a full-cone nozzle for a fixed duration. The weight of the heated bed and the impinging water were recorded during spraying. The difference in weight change when spraying on heated and unheated beds gave the rate of evaporation. Thermocouples were used to record the internal temperature of the bed. Steam generation rate increased with particle size while bed porosity had only a minor influence. The counter-current flow of steam within the media bed disrupts the downward flow of water enough to leave pockets of hot material, reducing steam production. To maximize steam generation the media size, material, and spray time should be matched to ensure the surfaces of particles remain above the boiling point of water during spraying.

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