The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform

Ko Okumura - One of the best experts on this subject based on the ideXlab platform.

  • High-Velocity Drag Friction in Granular Media near the Jamming Point
    Physical Review Letters, 2014
    Co-Authors: Yuka Takehara, Ko Okumura
    Abstract:

    Drag friction that acts on a disk in a two-dimensional granular medium is studied at High packing fractions. We concentrate on a High-Velocity Region, in which the dynamic component of the force, obtained as an average of a strongly fluctuating force, clearly scales with Velocity squared. We find that the total force composed of dynamic and static components, as well as its fluctuation, diverges with practically the same exponent as the packing fraction approaches the jamming point. To explain the critical behavior, we propose a simple theory equipped with a diverging length scale, which agrees well with the data and elucidates physical pictures for the divergence.

  • High-Velocity drag friction in dense granular media
    EPL, 2010
    Co-Authors: Yuka Takehara, Sachika Fujimoto, Ko Okumura
    Abstract:

    We study drag force acting on an obstacle in granular media, focusing on a High-Velocity Region where only a few direct studies are available. The granular media are two-dimensional and consist of small-sphere particles. A larger-disk obstacle moves in the medium at different constant speeds. The drag force is found to be proportional to the square of the Velocity. We explain the observed relations by developing original scaling arguments and by demonstrating a clear data collapse. As a result, we conclude that the friction we observed is physically different from a hydrodynamic inertial friction, which has been discussed in dilute granular flows and in impact experiments. The High-Velocity drag friction observed in this study may be attributed to another mechanism, where the formation of the dynamical force chains plays a crucial role.

Xiao Dong Chen - One of the best experts on this subject based on the ideXlab platform.

  • Airflow Characteristics of a Low Velocity Concurrent Pilot Scale Spray Drying Tower for Mono-disperse Particle Production
    2010
    Co-Authors: Sam Rogers, Cordelia Selomulya, Xiao Dong Chen
    Abstract:

    A pilot scale micro-fluidic-spray-dryer (MFJSD-II) utilizing a single-stream atomization to produce mono-disperse particles has been developed at Monash University. A unique feature of this unit is the use of relatively low air velocities in the range of 10-1-10-2 ms-1in comparison to conventional spray dryers. In this study, Computational Fluid Dynamics (CFD) simulations have revealed that the effects of natural convection, caused by heat loss from the wall, were significant in deflecting the flows of air from the central jet-side recirculation pattern, causing them to spread towards the wall. The flow patterns formed a layer of relatively High Velocity Region adjacent to the wall. The understanding of these flow patterns is crucial for future optimal design of low-Velocity spray dryer.

Xiao Chen - One of the best experts on this subject based on the ideXlab platform.

  • Numerical probing of a low Velocity concurrent pilot scale spray drying tower for mono-disperse particle production - Unusual characteristics and possible improvements
    Chemical Engineering and Processing, 2011
    Co-Authors: Samuel Rogers, Cordelia Selomulya, Xiao Chen
    Abstract:

    Abstract A pilot scale micro-fluidic-spray-dryer (MFJSD-II) utilizing a single-stream atomization to produce mono-disperse particles has been developed at Monash University. A unique feature of this unit is the use of relatively low air velocities in the range of 10 −1 –10 −2  m s −1 , which increases the residence time of the particles during the drying process, in comparison with conventional spray dryers. In this study, Computational Fluid Dynamics (CFD) simulation revealed that the effects of natural convection, caused by heat loss from the wall, were significant in deflecting the flows of air from the central jet-side recirculation pattern, causing them to spread towards the wall. The flow patterns formed a layer of relatively High Velocity Region adjacent to the wall. The understanding of these flow patterns would be crucial for future designs of low-Velocity spray dryers. The spreading of the central jet towards the wall also created recirculation Regions in the center of the tower, thus affecting the residence times particularly for smaller particles. More numerical simulations are required to optimize the design of the bottom bustle to be effectively used as a particle-separator.

Cordelia Selomulya - One of the best experts on this subject based on the ideXlab platform.

  • Numerical probing of a low Velocity concurrent pilot scale spray drying tower for mono-disperse particle production - Unusual characteristics and possible improvements
    Chemical Engineering and Processing, 2011
    Co-Authors: Samuel Rogers, Cordelia Selomulya, Xiao Chen
    Abstract:

    Abstract A pilot scale micro-fluidic-spray-dryer (MFJSD-II) utilizing a single-stream atomization to produce mono-disperse particles has been developed at Monash University. A unique feature of this unit is the use of relatively low air velocities in the range of 10 −1 –10 −2  m s −1 , which increases the residence time of the particles during the drying process, in comparison with conventional spray dryers. In this study, Computational Fluid Dynamics (CFD) simulation revealed that the effects of natural convection, caused by heat loss from the wall, were significant in deflecting the flows of air from the central jet-side recirculation pattern, causing them to spread towards the wall. The flow patterns formed a layer of relatively High Velocity Region adjacent to the wall. The understanding of these flow patterns would be crucial for future designs of low-Velocity spray dryers. The spreading of the central jet towards the wall also created recirculation Regions in the center of the tower, thus affecting the residence times particularly for smaller particles. More numerical simulations are required to optimize the design of the bottom bustle to be effectively used as a particle-separator.

  • Airflow Characteristics of a Low Velocity Concurrent Pilot Scale Spray Drying Tower for Mono-disperse Particle Production
    2010
    Co-Authors: Sam Rogers, Cordelia Selomulya, Xiao Dong Chen
    Abstract:

    A pilot scale micro-fluidic-spray-dryer (MFJSD-II) utilizing a single-stream atomization to produce mono-disperse particles has been developed at Monash University. A unique feature of this unit is the use of relatively low air velocities in the range of 10-1-10-2 ms-1in comparison to conventional spray dryers. In this study, Computational Fluid Dynamics (CFD) simulations have revealed that the effects of natural convection, caused by heat loss from the wall, were significant in deflecting the flows of air from the central jet-side recirculation pattern, causing them to spread towards the wall. The flow patterns formed a layer of relatively High Velocity Region adjacent to the wall. The understanding of these flow patterns is crucial for future optimal design of low-Velocity spray dryer.

Yuka Takehara - One of the best experts on this subject based on the ideXlab platform.

  • High-Velocity Drag Friction in Granular Media near the Jamming Point
    Physical Review Letters, 2014
    Co-Authors: Yuka Takehara, Ko Okumura
    Abstract:

    Drag friction that acts on a disk in a two-dimensional granular medium is studied at High packing fractions. We concentrate on a High-Velocity Region, in which the dynamic component of the force, obtained as an average of a strongly fluctuating force, clearly scales with Velocity squared. We find that the total force composed of dynamic and static components, as well as its fluctuation, diverges with practically the same exponent as the packing fraction approaches the jamming point. To explain the critical behavior, we propose a simple theory equipped with a diverging length scale, which agrees well with the data and elucidates physical pictures for the divergence.

  • High-Velocity drag friction in dense granular media
    EPL, 2010
    Co-Authors: Yuka Takehara, Sachika Fujimoto, Ko Okumura
    Abstract:

    We study drag force acting on an obstacle in granular media, focusing on a High-Velocity Region where only a few direct studies are available. The granular media are two-dimensional and consist of small-sphere particles. A larger-disk obstacle moves in the medium at different constant speeds. The drag force is found to be proportional to the square of the Velocity. We explain the observed relations by developing original scaling arguments and by demonstrating a clear data collapse. As a result, we conclude that the friction we observed is physically different from a hydrodynamic inertial friction, which has been discussed in dilute granular flows and in impact experiments. The High-Velocity drag friction observed in this study may be attributed to another mechanism, where the formation of the dynamical force chains plays a crucial role.