Numerical Simulation of Bubble Cluster Induced Flow by Three-Dimensional Vortex-in-Cell Method

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Bin Chen ◽  
Zhiwei Wang ◽  
Tomomi Uchiyama
Keyword(s):  
Void Fraction ◽  
Liquid Velocity ◽  
Peak Velocity ◽  
Three Dimensional ◽  
Terminal Velocity ◽  
Single Bubble ◽  
Bubble Cluster ◽  
Aggregation Effect ◽  
Cluster Distance ◽  
Induced Flow

The behavior of air bubble clusters rising in water and the induced flow field are numerically studied using a three-dimensional two-way coupling algorithm based on a vortex-in-cell (VIC) method. In this method, vortex elements are convected in the Lagrangian frame and the liquid velocity field is solved from the Poisson equation of potential on the Eulerian grid. Two-way coupling is implemented by introducing a vorticity source term induced by the gradient of void fraction. Present simulation results are favorably compared with the measured results of bubble plume, which verifies the validity of the proposed VIC method. The rising of a single bubble cluster as well as two tandem bubble clusters are simulated. The mechanism of the aggregation effect in the rising process of bubble cluster is revealed and the transient processes of the generation, rising, strengthening, and separation of a vortex ring structure with bubble clusters are illustrated and analyzed in detail. Due to the aggregation, the average rising velocity increases with void fraction and is larger than the terminal rising velocity of single bubble. For the two tandem bubble cluster cases, the aggregation effect is stronger for smaller initial cluster distance, and both the strength of the induced vortex structure and the average bubble rising velocity are larger. For the 20 mm cluster distance case, the peak velocity of the lower cluster is about 2.7 times that of the terminal velocity of the single bubble and the peak average velocity of two clusters is about 2 times larger. While for the 30 mm cluster distance case, both the peak velocity of the lower cluster and two clusters are about 1.7 times that of the terminal velocity of the single bubble.

scholarly journals Concentration and velocity statistics of inertial particles in upward and downward pipe flow

2017 ◽  
Vol 822 ◽  
pp. 640-663 ◽  
Author(s):  
J. L. G. Oliveira ◽  
C. W. M. van der Geld ◽  
J. G. M. Kuerten
Keyword(s):  
Liquid Velocity ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Stokes Number ◽  
Terminal Velocity ◽  
Point Particle ◽  
Inertial Particles ◽  
Carrier Fluid ◽  
Velocity Statistics ◽  
The Difference

Three-dimensional particle tracking velocimetry is applied to particle-laden turbulent pipe flows at a Reynolds number of 10 300, based on the bulk velocity and the pipe diameter, for developed fluid flow and not fully developed flow of inertial particles, which favours assessment of the radial migration of the inertial particles. Inertial particles with Stokes number ranging from 0.35 to 1.11, based on the particle relaxation time and the radial-dependent Kolmogorov time scale, and a ratio of the root-mean-square fluid velocity to the terminal velocity of order 1 have been used. Core peaking of the concentration of inertial particles in up-flow and wall peaking in down-flow have been found. The difference in mean particle and Eulerian mean liquid velocity is found to decrease to approximately zero near the wall in both flow directions. Although the carrier fluid has all of the characteristics of the corresponding turbulent single-phase flow, the Reynolds stress of the inertial particles is different near the wall in up-flow. These findings are explained from the preferential location of the inertial particles with the aid of direct numerical simulations with the point-particle approach.

A Mechanistic Model for Predicting Subcooled Boiling Flow

2003 ◽  
Author(s):  
G. H. Yeoh ◽  
J. Y. Tu
Keyword(s):  
Void Fraction ◽  
Liquid Velocity ◽  
Fluid Model ◽  
Mechanistic Model ◽  
Three Dimensional ◽  
Annular Channel ◽  
Heat Fluxes ◽  
Group Model ◽  
Subcooled Boiling ◽  
Boiling Flow

Population balance equations combined with a three-dimensional two-fluid model are employed to predict subcooled boiling flow at low pressure in a vertical annular channel. The MUSIG (MUltiple-SIze-Group) model implemented in CFX4.4 is extended to account for the wall nucleation and condensation in the subcooled boiling regime. Comparison of model predictions against local measurements is made for the void fraction, bubble Sauter diameter and gas and liquid velocities covering a range of different mass and heat fluxes and inlet subcoolings. Good agreement is achieved with the local radial void fraction, bubble Sauter diameter and liquid velocity profiles against measurements. However, significant weakness of the model is evidenced in the prediction of the vapor velocity. Work is in progress to circumvent the deficiency of the extended MUSIG model by the consideration of an algebraic slip model to account for bubble separation.

A Study on the Induced Liquid Velocity in Plumes by Tiny Bubbles

2007 ◽  
Author(s):  
Xiaobo Gong ◽  
Shu Takagi ◽  
Yoichiro Matsumoto
Keyword(s):  
Mass Transfer ◽  
Residence Time ◽  
Liquid Velocity ◽  
Bubble Diameter ◽  
Terminal Velocity ◽  
Transfer Efficiency ◽  
Single Bubble ◽  
Bubble Plume ◽  
Mass Transfer Efficiency ◽  
Bubble Plumes

The effect of the bubble-induced liquid velocity on the mass transfer performance in the bubble plume is analyzed quantitatively with numerical simulations. A two-way coupling Eulerian-Lagrangian approach is used in the modeling of the bubble plumes with mass transfer. The dissolution of oxygen in bubble plumes with the initial bubble diameters from 100μm to 1mm is simulated. The results show that when a single bubble generator is used with the gas flux rate equals 10−8 cubic meter per second, for the plume with 100μm bubbles inside a 0.1m height cubic tank the maximum of the bubble-induced liquid velocity is over 10 times larger than the bubble’s terminal velocity, and the averaged residence time of bubbles in the plume is around one-tenth of the rising period estimated with the terminal velocity of a single bubble. The result suggests that for bubble plumes in a shallow bulk of water, the benefits of using smaller bubbles for high mass transfer efficiency will be overestimated without considering the reduction of the residence time of bubbles because of the bubble-induced liquid velocity. The present simulation shows that the dissolution efficiency of oxygen for the bubble plume with 100μm bubbles in 0.1m tank is around 1/2 of the theoretical value estimated with a single bubble rising with negligible diameter shrink. Compared with a plume in a 0.1m tank, the shrink of bubble diameter and the scattering of bubbles from the center of plume during their rising in a 0.4m tank attenuate the reduction of the averaged residence time because of the acceleration process as shown in a 0.1m tank. The effect of bubble-induced liquid velocity on the mass transfer efficiency for plumes with initial bubble diameter smaller than 160μm does not present obviously in a 0.4m tank as it does in the shorter tank.

scholarly journals Tephra4D: A Python-Based Model for High-Resolution Tephra Transport and Deposition Simulations—Applications at Sakurajima Volcano, Japan

Atmosphere ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 331
Author(s):  
Kosei Takishita ◽  
Alexandros P. Poulidis ◽  
Masato Iguchi
Keyword(s):  
Scale Effects ◽  
Three Dimensional ◽  
Particle Diameter ◽  
Terminal Velocity ◽  
Diameter Distribution ◽  
Velocity Variation ◽  
Small Scale ◽  
Modified Model ◽  
Sakurajima Volcano ◽  
Ash Transport

Vulcanian eruptions (short-lived explosions consisting of a rising thermal) occur daily in volcanoes around the world. Such small-scale eruptions represent a challenge in numerical modeling due to local-scale effects, such as the volcano’s topography impact on atmospheric circulation and near-vent plume dynamics, that need to be accounted for. In an effort to improve the applicability of Tephra2, a commonly-used advection-diffusion model, in the case of vulcanian eruptions, a number of key modifications were carried out: (i) the ability to solve the equations over bending plume, (ii) temporally-evolving three-dimensional meteorological fields, (iii) the replacement of the particle diameter distribution with observed particle terminal velocity distribution which provides a simple way to account for the settling velocity variation due to particle shape and density. We verified the advantage of our modified model (Tephra4D) in the tephra dispersion from vulcanian eruptions by comparing the calculations and disdrometer observations of tephra sedimentation from four eruptions at Sakurajima volcano, Japan. The simulations of the eruptions show that Tephra4D is useful for eruptions in which small-scale movement contributes significantly to ash transport mainly due to the consideration for orographic winds in advection.

Finite state induced flow models. II - Three-dimensional rotor disk

1995 ◽  
Vol 32 (2) ◽  
pp. 323-333 ◽  
Author(s):  
David A. Peters ◽  
Cheng Jian He
Keyword(s):  
Three Dimensional ◽  
Flow Models ◽  
Finite State ◽  
Rotor Disk ◽  
Induced Flow

Preliminary results of numerical simulation of submarine landslide-generated waves

2021 ◽  
Author(s):  
Ramtin Sabeti ◽  
Mohammad Heidarzadeh
Keyword(s):  
Numerical Simulation ◽  
Numerical Modelling ◽  
Numerical Solutions ◽  
Numerical Technique ◽  
Source Region ◽  
Three Dimensional ◽  
Terminal Velocity ◽  
Sensitivity Analyses ◽  
Physical Experiments ◽  
Set Up

<p>Landslide-generated waves have been major threats to coastal areas and have led to destruction and casualties. Their importance is undisputed, most recently demonstrated by the 2018 Anak Krakatau tsunami, causing several hundred fatalities. The accurate prediction of the maximum initial amplitude of landslide waves (<em>η<sub>max</sub></em>) around the source region is a vital hazard indicator for coastal impact assessment. Laboratory experiments, analytical solutions and numerical modelling are three major methods to investigate the (<em>η<sub>max</sub></em>). However, the numerical modelling approach provides a more flexible and cost- and time-efficient tool. This research presents a numerical simulation of tsunamis due to rigid landslides with consideration of submerged conditions. In particular, this simulation focuses on studying the effect of landslide parameters on <em>η<sub>max</sub>.</em> Results of simulations are compared with our conducted physical experiments at the Brunel University London (UK) to validate the numerical model.</p><p>We employ the fully three-dimensional computational fluid dynamics package, FLOW-3D Hydro for modelling the landslide-generated waves. This software benefit from the Volume of Fluid Method (VOF) as the numerical technique for tracking and locating the free surface. The geometry of the simulation is set up according to the wave tank of physical experiments (i.e. 0.26 m wide, 0.50 m deep and 4.0 m). In order to calibrate the simulation model based on the laboratory measurements, the friction coefficient between solid block and incline is changed to 0.41; likewise, the terminal velocity of the landslide is set to 0.87 m/s. Good agreement between the numerical solutions and the experimental results is found. Sensitivity analyses of landslide parameters (e.g. slide volume, water depth, etc.) on <em>η<sub>max </sub></em>are performed. Dimensionless parameters are employed to study the sensitivity of the initial landslide waves to various landslide parameters.</p>

scholarly journals Numerical and Experimental Analyses of Three- Dimensional Unsteady Flow around a Micro-Pillar Subjected to Rotational Vibration

Micromachines ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 668 ◽  
Author(s):  
Kanji Kaneko ◽  
Takayuki Osawa ◽  
Yukinori Kametani ◽  
Takeshi Hayakawa ◽  
Yosuke Hasegawa ◽  
...  
Keyword(s):  
Flow Field ◽  
Moving Boundary ◽  
Three Dimensional ◽  
Steady Streaming ◽  
Micro Piv ◽  
Piv Measurement ◽  
Image Velocimetry ◽  
Measurement Tools ◽  
Rotational Vibration ◽  
Induced Flow

The steady streaming (SS) phenomenon is gaining increased attention in the microfluidics community, because it can generate net mass flow from zero-mean vibration. We developed numerical simulation and experimental measurement tools to analyze this vibration-induced flow, which has been challenging due to its unsteady nature. The validity of these analysis methods is confirmed by comparing the three-dimensional (3D) flow field and the resulting particle trajectories induced around a cylindrical micro-pillar under circular vibration. In the numerical modeling, we directly solved the flow in the Lagrangian frame so that the substrate with a micro-pillar becomes stationary, and the results were converted to a stationary Eulerian frame to compare with the experimental results. The present approach enables us to avoid the introduction of a moving boundary or infinitesimal perturbation approximation. The flow field obtained by the micron-resolution particle image velocimetry (micro-PIV) measurement supported the three-dimensionality observed in the numerical results, which could be important for controlling the mass transport and manipulating particulate objects in microfluidic systems.

Implementation of a Pressure Drop Model for the CFD Simulation of Clogged Containment Sump Strainers

2009 ◽  
Author(s):  
Alexander Grahn ◽  
Eckhard Krepper ◽  
Frank-Peter Weiß ◽  
So¨ren Alt ◽  
Wolfgang Ka¨stner ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Cfd Simulation ◽  
Liquid Velocity ◽  
Compaction Pressure ◽  
Three Dimensional ◽  
General Purpose ◽  
Extended Model ◽  
Fibrous Materials ◽  
Loss Of Coolant Accident ◽  
Cake Porosity

The present study aims at modelling the pressure drop of flows across growing cakes of compressible, fibrous materials which may form on the upstream side of containment sump strainers after a loss-of-coolant accident (LOCA). The model developed is based on the coupled solution of a differential equation for the change of the pressure drop in terms of superficial liquid velocity and local porosity of the fibre cake and a material equation that accounts for the compaction pressure dependent cake porosity. Details of its implementation into a general-purpose three-dimensional computational fluid dynamics code (CFD) are given. An extension to this basic model is presented, which simulates the time dependent clogging of the fibre cake due to capturing of suspended particles as they pass trough the cake. The extended model relies on empirical relations which model the change of pressure drop and removal efficiency in terms of particle deposit in the fibre cake.

An Investigation of the Variability in Human Performance during Manual Material Handling Activities

1994 ◽  
Vol 38 (10) ◽  
pp. 578-582
Author(s):  
Gary A. Mirka ◽  
Ann Baker
Keyword(s):  
Material Handling ◽  
Human Performance ◽  
Sagittal Plane ◽  
Coupling Effect ◽  
Peak Velocity ◽  
Three Dimensional ◽  
Biomechanical Model ◽  
Manual Material Handling ◽  
Symmetric Lifting ◽  
Dependent Position

The goal of this study was to quantify the variability of the three-dimensional kinematic and kinetic parameters describing the motion of the torso during the performance of sagittally symmetric lifting tasks. Subjects performed eight repetitions of simple lifting tasks described by three levels of coupling (poor, fair and good) and seven levels of load (4.5, 9, 13.5, 18, 22.5, 27 and 31.5 kg). The three-dimensional, time dependent position, velocity and acceleration of the lumbar spine were monitored using the Lumbar Motion Monitor. These measures were then input into a dynamic biomechanical model which calculated torque about the L5/S1 joint in the sagittal plane. The results of the kinematic analysis showed significant variability in the magnitude of the peak velocity and acceleration in the sagittal plane and also showed significant motion in the transverse and coronal planes. The kinetic analysis showed an increase in the variability of the peak dynamic torque with greater levels of load but no coupling effect.

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