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Estimation of particle dynamics in 2-D fluidized beds using particle tracking velocimetry

Particuology 2015年第5期13卷 39-51页

作者： Thomas Hagemeier Christoph Roloff Andreas Buck Evangelos Tsotsas NaWiTec Thermal Process EngineeringOtto-von-Guericke University MagdeburgUniversitaetsplatz 239106 MagdeburgGermany Fluid Dynamics and Technical Flow Otto-von-Guericke University MagdeburgUniversitaetsplatz 239106 MagdeburgGermany

The experimental characterization of particle dynamics in fluidized beds is of great importance in fostering an understanding of solid phase motion and its effect on particle properties in granulation processes, Commonly used techniques such as particle image velocimetry rely on the cross-correlation of illumination intensity and averaging procedures. It is not possible to obtain single particle velocities with such techniques. Moreover, the estimated velocities may not accurately represent the local particle velocities in regions with high velocity gradients. Consequently, there is a need for devices and methods that are capable of acquiring individual particle velocities. This paper describes how particle tracking velocimetry can be adapted to dense particulate flows. The approach presented in this paper couples high-speed imaging with an innovative segmentation algorithm for particle detection, and employs the Voronoi method to solve the assignment problem usually encountered in densely seeded fows. Lagrangian particle tracks are obtained as primary information, and these serve as the basis for calculating sophisticated quantities such as the solid-phase flow field, granular temperature, and solid volume fraction. We show that the consistency of individual trajectories is sufficient to recognize collision events.

关键词： particle dynamics particle tracking velocimetry Pseudo-2D Fluidized bed

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A novel particle tracking velocimetry method for complex granular flow field

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Chinese Physics B 2020年第1期29卷 293-299页

作者： Bi-De Wang Jian Song Ran Li Ren Han Gang Zheng Hui Yang School of Optical-Electrical and Computer Engineering University of Shanghai for Science and TechnologyShanghai 200093China School of Medical Instrument and Food Engineering University of Shanghai for Science and TechnologyShanghai 200093China

particle tracking velocimetry(PTV)is one of the most commonly applied granular flow velocity measurement ***,traditional PTV methods may have issues such as high mismatching rates and a narrow measurement range when measuring granular flows with large bulk density and high-speed *** this study,a novel PTV method is introduced to solve these problems using an optical flow matching algorithm with two further processing *** first step involves displacement correction,which is used to solve the mismatching problem in the case of high stacking *** other step is trajectory splicing,which is used to solve the problem of a measurement range reduction in the case of high-speed contrast The hopper flow experimental results demonstrate superior performance of this proposed method in controlling the number of mismatched particles and better measuring efficiency in comparison with the traditional PTV method.

关键词： particle tracking velocimetry optical flow displacement correction trajectory splicing

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Ensuring adequate statistics in particle tracking experiments

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Particuology 2021年第6期19卷 43-54页

作者： C.R.K.Windows-Yule School of Chemical Engineering University of BirminghamEdgbastonBirmingham B152TTUnited Kingdom Institute for Multiscale Simulation Engineering of Advanced MaterialsFriedrich-Alexander Universitat Erlangen-NurnbergSchloBplatz 491054 ErlangenGermany

particle tracking techniques such as magnetic particle tracking,radioactive particle tracking and positron emission particle tracking are widely used in academia and industry to image the dynamics of particulate and multiphase *** techniques can provide detailed data concerning a range of important,whole-field quantities based only on the time-averaged dynamics of a small number of tracer ***,in order for this data to be reliable,the duration over which these time-averages are taken must be suitably ***,the‘minimum averaging time’required to produce good statistics depends sensitively on the system in question and,at present,cannot be determined a priori in advance of an *** this paper,we take a step toward resolving this issue,using discrete element method simulations of a simple vibroﬂuidised granular bed to develop a series of scaling laws relating said minimum averaging time to a variety of key system *** scaling laws developed may be used by future experimentalists to predict the required averaging time for each given system during an experimental campaign,thus improving both the efficiency with which particle tracking techniques may be applied,and the reliability of the data produced thereby.

关键词： Granular particle tracking Positron emission particle tracking Radioactive particle tracking Magnetic particle tracking particle tracking velocimetry

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Scattering Characteristics of Liquid Droplets Spun Off from Rotating Disk Edge

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Journal of Thermal Science 2012年第1期21卷 42-48页

作者： Mizue MUNEKATA Akira NOGUCHI Jun NISHIYAMA Hiroaki KURISHIMA Hiroyuki YOSHIKAWA Dept. of Mech. System Eng. Kumamoto University 2-39-1 Kurokami Tokyo Electron Kyushu Ltd. Fukuhara

Scattering characteristics of liquid droplets spun off from a rotating disk edge are experimentally investigated. In the present research, aluminum disks are utilized and ethanol is employed for liquid. Scattering phenomena of the droplets are captured by the high-speed digital camera. Frequency distribution of the droplet diameter is evaluated from these images and distributions of horizontal flying velocity and angle of the droplets were measured by PTV. Liquid filaments are stretched outward from the stagnant liquid layer by centrifugal force and skew complicatedly by aerodynamic force. Some peaks appear in the distribution of the scattered droplet diameter and they are origi- nated from large terminal droplets and small droplets generated from filamentwise breakup. Most of the scattered droplets fly slightly inside in the tangential direction of the disk edge. The droplets spun off from the thin disk scatter widely compared with that from the thick one.

关键词： Rotating disk Scattering droplet Visualization particle tracking velocimetry

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Adaptive-optical 3D microscopy for microfluidic multiphase flows

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Light(Advanced Manufacturing) 2024年第3期5卷 105-119页

作者： Clemens Bilsing Erik Nützenadel Sebastian Burgmann Jürgen Czarske Lars Büttner Laboratory of Measurement and Sensor System Techniques TUD Dresden University of Technology01069 DresdenGermany Chair of Fluid Mechanics Bergische Universitát Wuppertal42119 WuppertalGermany BIOLAS Laboratory of Measurement and Sensor System Techniques01069 DresdenGermany

Measurements based on optical microscopy can be severely impaired if the access exhibits variations of the refractive *** the case of fluctuating liquid-gas boundaries,refraction introduces dynamical aberrations that increase the measurement *** is prevalent at multiphase flows(***,film flows)that occur in many technical applications as for example in coating and cleaning processes and the water management in fuel *** this paper,we present a novel approach based on adaptive optics for correcting the dynamical aberrations in real time and thus reducing the measurement *** shape of the fluctuating water-air interface is sampled with a reflecting light beam(Fresnel Guide Star)and a Hartmann-Shack sensor which makes it possible to correct its influence with a deformable mirror in a closed ***-dimensional flow measurements are achieved by using a double-helix point spread *** measure the flow inside a sessile,oscillating 50-μl droplet on an opaque gas diffusion layer for fuel cells and show that the temporally varying refraction at the droplet surface causes a systematic underestimation of the flow field magnitude corresponding to the first droplet eigenmode which plays a major role in their detachment *** demonstrate that the adaptive optics correction is able to reduce this systematic ***,the adaptive optics system can pave the way to a deeper understanding of water droplet formation and detachment which can help to improve the efficiency of fuels cells.

关键词： Double-Helix point spread function Adaptive optics particle tracking velocimetry Aberration correction Depth-resolving microscopy Closed-loop control

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Trajectory Analysis of particle Motions in Superfluid Helium-4 Using PTV Method

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Journal of Flow Control, Measurement & Visualization 2022年第2期10卷 76-85页

作者： Lizhu Chen Yoshiyuki Tsuji Department of Energy Engineering and Science Nagoya University Nagoya Japan

This paper describes the use of particle tracking velocimetry to analyze the Lagrangian acceleration of small particles in superfluid helium with varying time increments, . The probability density of acceleration exhibits Gaussian properties for , but displays a lognormal distribution for , where is the migration time characterizing the particle motion. The particle trajectories are well characterized by the Hurst exponent H. For smaller time scales than , the trajectories exhibit linear motion (), but have certain fractal properties with for time scales larger than .

关键词： Superfluid He II Counterflow particle tracking velocimetry

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