The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform
Philipp Schlatter - One of the best experts on this subject based on the ideXlab platform.
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Particle transport in turbulent curved pipe flow
Journal of Fluid Mechanics, 2016Co-Authors: Azad Noorani, Gaetano Sardina, Luca Brandt, Philipp SchlatterAbstract:Direct numerical simulations (DNS) of particle-laden turbulent flow in straight, mildly curved and strongly bent pipes are performed in which the solid phase is modelled as small heavy spherical particles. A total of seven populations of dilute particles with different Stokes numbers, one-way coupled with their carrier phase, are simulated. The objective is to examine the effect of the curvature on micro-particle transport and accumulation. It is shown that even a slight non-zero curvature in the flow configuration strongly impact the particle concentration map such that the concentration of inertial particles with bulk Stokes number 0.45 (based on bulk velocity and pipe radius) at the inner-Bend Wall of mildly curved pipe becomes 12.8 times larger than that in the viscous sublayer of the straight pipe. Near-Wall helicoidal particle streaks are observed in the curved configurations with their inclination varying with the strength of the secondary motion of the carrier phase. A reflection layer, as previously observed in particle laden turbulent S-shaped channels, is also apparent in the strongly curved pipe with heavy particles. In addition, depending on the curvature, the central regions of the mean Dean vortices appear to be completely depleted of particles, as observed also in the partially re-laminarised region at the inner Bend. The turbophoretic drift of the particles is shown to be affected by weak and strong secondary motions of the carrier phase and geometry-induced centrifugal forces. The first and second-order moments of the velocity and acceleration of the particulate phase in the same configurations are addressed in a companion paper by the same authors. The current data-set will be useful for modelling particles advected in Wall-bounded turbulent flows where the effects of the curvature are not negligible.
Xiang Jialiang - One of the best experts on this subject based on the ideXlab platform.
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Data from: Relationship between wear formation and large-particle motion in a pipe Bend
2019Co-Authors: Zhang Hebing, Lin Zhe, He Zhaohui, Xiang Jialiang, Su XianghuiAbstract:Fine and large particles flowing through a Bend in a pipe move differently and therefore erode the pipe differently. The present paper simulates solid–liquid two-phase flow containing large particles in a Bend and analyzes the relationship between the wear formation and particle motion. Wear experiments are carried out using 3-mm glass bead particles at a mass concentration of 1%–15%. At the same time, the flow field and the motion of the granular system are obtained in computational fluid dynamics–discrete element method simulation. The wear formation mechanism is revealed by comparing experiments with numerical simulations. The wear rate of the Wall surface increases with the mass concentration, while the marginal growth rate decreases as the mass concentration increases. As the mass concentration increases to a certain value, the degree of wear reaches a maximum and remains unchanged subsequently because of the formation of a particle barrier along the Bend Wall. The particles near the Wall region will bouncing forward because of the periodic disturbance flow around particles. The impacting of mass bouncing particles makes the formation of the erosion ripple on the test sheet
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Relationship between wear formation and large-particle motion in a pipe Bend.
Royal Society open science, 2019Co-Authors: Zhang Hebing, Lin Zhe, Xiang JialiangAbstract:Fine and large particles flowing through a Bend in a pipe move differently and therefore erode the pipe differently. This paper simulates solid-liquid two-phase flow containing large particles in a Bend and analyses the relationship between the wear formation and particle motion. Wear experiments are carried out using 3-mm glass bead particles at a mass concentration of 1-15%. At the same time, the flow field and the motion of the granular system are obtained in computational fluid dynamics-discrete element method simulation. The wear formation mechanism is revealed by comparing experiments with numerical simulations. The wear rate of the Wall surface increases with the mass concentration, while the marginal growth rate decreases as the mass concentration increases. As the mass concentration increases to a certain value, the degree of wear reaches a maximum and remains unchanged subsequently because of the formation of a particle barrier along the Bend Wall. The particles near the Wall region will bounce forward because of the periodic disturbance flow around particles. The impact of mass bouncing particles causes the formation of the erosion ripple on the test sheet.
Anders Rasmuson - One of the best experts on this subject based on the ideXlab platform.
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Heat and Mass Transfer in U-Bend of a Pneumatic Conveying Dryer
Chemical Engineering Research & Design, 2008Co-Authors: Muslikhin Hidayat, Anders RasmusonAbstract:Abstract Computational fluid dynamics (CFD) modelling with the Eularian–Eularian formulation is used to describe the drying phenomena occurring in pneumatic conveying drying particularly in the U-Bend. Two user defined scalar equations (UDSs) are inserted into the solution to take into account the solid particle moisture content and the mass fraction of water in the gas phase, respectively. The drying kinetics cover the two periods of drying: the constant drying rate and the falling drying rate. The investigation emphasized influences of the parameters (solid loading ratio, gas velocity, Bend radius ratio, feed moisture content and geometry arrangement of a U-Bend) on the drying rate and moisture content. A validation of the drying model is accomplished by comparing calculation results with experimental data. In general, the drying rate decreases along the axial direction of pipe due to the decrease in driving force (the air humidity increases). The mass-weighted average drying rate shows a slight decrease in and just after the U-Bend, which is mainly due to the high accumulation of solid particles at the outer U-Bend Wall. Solid particles disperse and the slip velocities are high in the area after the U-Bend. This causes the mass-weighted average drying rate to slightly increase.
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A computational investigation of non-isothermal gas–solid flow in a U-Bend
Powder Technology, 2007Co-Authors: Muslikhin Hidayat, Anders RasmusonAbstract:Abstract The non-isothermal gas–solid flow through a U-Bend of a pneumatic conveying dryer system is calculated using the commercial CFD program Fluent 6.1. Steady-state, incompressible and non-isothermal gas–solid flows are employed to simulate the cases. Variables studied include: particle diameter, particle density, solid loading ratio, feed gas temperature, heat flux through the Wall, gas velocity and Bend radius ratio on heat transfer phenomena between gas and solid particles. Validation is done by comparing calculation results with the available experimental data provided by Baughn et al. [J.W. Baughn, H. Iacovides, D.C. Jackson, B.E. Launder, Local heat transfer measurements in turbulent flow around a 180° pipe Bend, Journal of Heat Transfer 109 (1) (1987) 43–48] and Depew and Farbar [C.A. Depew, L. Farbar, Heat transfer to pneumatically conveyed glass particles of fixed size, Journal of Heat Transfer 85 (1963) 164–172]. In general, data validations of both cases show good agreement. The gas temperature decreases and the solid temperature increases along the axial direction of the pipe due to transfer of heat from the gas phase to the solid phase. The gas temperature decreases significantly at the outer Bend Wall due to an accumulation of particles, which causes much more energy to be transferred from the gas to solid phases. At the inner Bend Wall, the gas temperature decreases slightly but the solid temperature increases significantly due to a low concentration of particles. A U-Bend significantly increases the local and area average Nu numbers, but not the mass average Nu number. The slip velocity and particle distribution are the major factors influencing the value of the mass average Nu number.
Azad Noorani - One of the best experts on this subject based on the ideXlab platform.
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Particle transport in turbulent curved pipe flow
Journal of Fluid Mechanics, 2016Co-Authors: Azad Noorani, Gaetano Sardina, Luca Brandt, Philipp SchlatterAbstract:Direct numerical simulations (DNS) of particle-laden turbulent flow in straight, mildly curved and strongly bent pipes are performed in which the solid phase is modelled as small heavy spherical particles. A total of seven populations of dilute particles with different Stokes numbers, one-way coupled with their carrier phase, are simulated. The objective is to examine the effect of the curvature on micro-particle transport and accumulation. It is shown that even a slight non-zero curvature in the flow configuration strongly impact the particle concentration map such that the concentration of inertial particles with bulk Stokes number 0.45 (based on bulk velocity and pipe radius) at the inner-Bend Wall of mildly curved pipe becomes 12.8 times larger than that in the viscous sublayer of the straight pipe. Near-Wall helicoidal particle streaks are observed in the curved configurations with their inclination varying with the strength of the secondary motion of the carrier phase. A reflection layer, as previously observed in particle laden turbulent S-shaped channels, is also apparent in the strongly curved pipe with heavy particles. In addition, depending on the curvature, the central regions of the mean Dean vortices appear to be completely depleted of particles, as observed also in the partially re-laminarised region at the inner Bend. The turbophoretic drift of the particles is shown to be affected by weak and strong secondary motions of the carrier phase and geometry-induced centrifugal forces. The first and second-order moments of the velocity and acceleration of the particulate phase in the same configurations are addressed in a companion paper by the same authors. The current data-set will be useful for modelling particles advected in Wall-bounded turbulent flows where the effects of the curvature are not negligible.
Muslikhin Hidayat - One of the best experts on this subject based on the ideXlab platform.
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Heat and Mass Transfer in U-Bend of a Pneumatic Conveying Dryer
Chemical Engineering Research & Design, 2008Co-Authors: Muslikhin Hidayat, Anders RasmusonAbstract:Abstract Computational fluid dynamics (CFD) modelling with the Eularian–Eularian formulation is used to describe the drying phenomena occurring in pneumatic conveying drying particularly in the U-Bend. Two user defined scalar equations (UDSs) are inserted into the solution to take into account the solid particle moisture content and the mass fraction of water in the gas phase, respectively. The drying kinetics cover the two periods of drying: the constant drying rate and the falling drying rate. The investigation emphasized influences of the parameters (solid loading ratio, gas velocity, Bend radius ratio, feed moisture content and geometry arrangement of a U-Bend) on the drying rate and moisture content. A validation of the drying model is accomplished by comparing calculation results with experimental data. In general, the drying rate decreases along the axial direction of pipe due to the decrease in driving force (the air humidity increases). The mass-weighted average drying rate shows a slight decrease in and just after the U-Bend, which is mainly due to the high accumulation of solid particles at the outer U-Bend Wall. Solid particles disperse and the slip velocities are high in the area after the U-Bend. This causes the mass-weighted average drying rate to slightly increase.
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A computational investigation of non-isothermal gas–solid flow in a U-Bend
Powder Technology, 2007Co-Authors: Muslikhin Hidayat, Anders RasmusonAbstract:Abstract The non-isothermal gas–solid flow through a U-Bend of a pneumatic conveying dryer system is calculated using the commercial CFD program Fluent 6.1. Steady-state, incompressible and non-isothermal gas–solid flows are employed to simulate the cases. Variables studied include: particle diameter, particle density, solid loading ratio, feed gas temperature, heat flux through the Wall, gas velocity and Bend radius ratio on heat transfer phenomena between gas and solid particles. Validation is done by comparing calculation results with the available experimental data provided by Baughn et al. [J.W. Baughn, H. Iacovides, D.C. Jackson, B.E. Launder, Local heat transfer measurements in turbulent flow around a 180° pipe Bend, Journal of Heat Transfer 109 (1) (1987) 43–48] and Depew and Farbar [C.A. Depew, L. Farbar, Heat transfer to pneumatically conveyed glass particles of fixed size, Journal of Heat Transfer 85 (1963) 164–172]. In general, data validations of both cases show good agreement. The gas temperature decreases and the solid temperature increases along the axial direction of the pipe due to transfer of heat from the gas phase to the solid phase. The gas temperature decreases significantly at the outer Bend Wall due to an accumulation of particles, which causes much more energy to be transferred from the gas to solid phases. At the inner Bend Wall, the gas temperature decreases slightly but the solid temperature increases significantly due to a low concentration of particles. A U-Bend significantly increases the local and area average Nu numbers, but not the mass average Nu number. The slip velocity and particle distribution are the major factors influencing the value of the mass average Nu number.
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Heat and Mass Transfer Effects in a U-Bend in Pneumatic Drying
2005Co-Authors: Muslikhin HidayatAbstract:Pneumatic conveying drying is a widely used process in many engineering applications. Due to the high velocity of the drying medium and the limited conveying distance, the drying times of theses dryers are typically short, in the order of seconds. Consequently, it is important to keep the suspended materials dispersed under good heat and mass transfer conditions in the system. However, the most effective drying takes place near the feed point (Perry et al. , 1997) and in the U-Bends (Fyhr and Rasmuson, 1997), where the velocity difference (slip) between gas and solid particles is the greatest. To improve the performance of pneumatic drying, better understanding of the gas and solid local conditions is important. The present study investigates the phenomena of pneumatic drying in a U-Bend. The investigation is divided into four steps, i.e. gas flow, gas-solid flow, non-isothermal gas-solid flow and non-isothermal gas-solid flow involving a mass transfer of moisture (a drying effect). The calculations of the first and the second steps use the commercial software Fluent 6.0 and the calculations of the third and the fourth steps use the commercial software Fluent 6.1. In the drying calculations, two UDSs are inserted into the solution to take into account the solid particle moisture content and the mass fraction of water in the gas phase, respectively. The moisture evaporation rate of solid particles and the humidification rate of gas are treated in the source terms of the corresponding UDS equations. The evaporation energy of moisture is treated in the source term of the solid energy equation. Each step is sequentially validated. Calculation results generally show good agreement with experimental data. However, experimental data show a faster dispersion of particles than calculation results. The gas and solid particles velocities are in the same ranges as those of the experiment data. The moisture content is somewhat slightly under-predicted. A major reason for this may be due to the absence of the cyclone in the simulation and another reason may be due to the lack of detailed modeling of the saw-dust properties. The effects of several important parameters are studied numerically. An increase in the solid loading ratio causes a decrease in the drying rate and an increasing gas velocity basically augments the drying rate. Different Bend radius ratios slightly alter the mass-weighted average values of the drying rate and moisture content in and after the U-Bend. Lower feed moisture content causes a lower drying rate and different positions along a U-Bend slightly affect drying behaviour. Due to curvature created by a U-Bend, solid particles experience centrifugal forces which cause solid particles to collide with the outer Bend Wall, thus causing solid particles to decelerate and accumulate in this region. Deceleration of solid particles causes an increase in the slip velocity between gas and solid particle, which is desired. However, accumulation of solid particles also causes undesired results, such as a decrease in the mass-weighted average values of the Nu number and the drying rate. The presence of a disperser in a U-Bend is needed to disperse the solid particles at the outer Bend Wall. Keywords: pneumatic conveying drying, U-Bend, computational fluid dynamics (CFD)