The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Shu-san Hsiau - One of the best experts on this subject based on the ideXlab platform.
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Convection Cells and segregation in a vibrated granular bed
AIChE Journal, 2002Co-Authors: Shu-san Hsiau, Pai‐chei Wang, Chi-hwang TaiAbstract:Granular materials may be circulated in a container with two symmetric Convection Cells under external vertical vibration conditions. Effects of the container geometry on the Convection strength and segregation process are studied experimentally. First, the wall tilted outward angles are changed to observe the direction of the Convection roll and Convection strength. The strength of the normal Convection rolls decreases by increasing the wall angles of the container from 0° (vertical walls). The Convection rolls become reversed when the wall tilted outward angles are greater than a transition angle. The wall roughness and vibration velocity amplitude are also changed to investigate their influences on the Convection cell strength. The segregation of a larger disk induced by the Convection Cells of smaller disks shows that the normal Convection rolls induce the upward motion of the larger disk, and the reverse Convection rolls result in the downward motion of the larger disk. The separation velocity increases linearly with the Convection flow rate.
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simulation study of the Convection Cells in a vibrated granular bed
Chemical Engineering Science, 2000Co-Authors: Shiechen Yang, Shu-san HsiauAbstract:The discrete element method (DEM) is employed to study the Convection Cells of glass beads in a two-dimensional vibrated granular bed. The flow pattern and velocity vectors are consistent with the former experimental results. The solid fractions and the granular temperatures are studied with different vibration acceleration and vibration velocity. A power-law relation exists between the Convection flow rate and the dimensionless vibration velocity. The mass flow rate was found to increase with the bed velocity in a power-law relation, J∝V2.3b, and decrease with the bed velocity in a power-law relation, J∝V−0.4b, with a fixed vibration acceleration.
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Granular Convection Cells in a vertical shaker
Powder Technology, 2000Co-Authors: Shu-san Hsiau, C.h ChenAbstract:Granular materials exhibit convective motions in a confined box under external vibration. Particles move upward in the center and flow downward along the side walls. This paper experimentally studies the phenomena of Convection Cells in a two-dimensional box with 3-mm glass beads under different vibration intensities. Using image processing technology and particle tracking method, the velocity fields of the convective granular beds were measured and analyzed at different vibration conditions. The vertical and horizontal velocity profiles at different locations were investigated. The Convection cell centers could be determined from the velocity profiles. The Convection flow rate was calculated and had a power law dependence on the amplitude of the vibration velocity.
Jeffrey V Turner - One of the best experts on this subject based on the ideXlab platform.
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density dependent surface water groundwater interaction and nutrient discharge in the swan canning estuary
Hydrological Processes, 2001Co-Authors: Anthony J Smith, Jeffrey V TurnerAbstract:Salinity in the Swan–Canning Estuary, Western Australia, varies seasonally from freshwater conditions in winter up to the salinity of seawater in summer. Field observations show that the resulting seasonal density contrasts between the estuary and the adjacent fresh groundwater system are sufficient to drive mixed-Convection Cells that give rise to circulation of river water in the aquifer. In this study, we examine the role of steady density-driven Convection as a mechanism that contributes to the exchange of dissolved nutrients, particularly ammonium, between the Swan–Canning Estuary and the local groundwater system. We present results from two-dimensional (section) and three-dimensional density-coupled flow and mass transport modelling, in comparison with Glover's abrupt-interface solution for saltwater intrusion. The modelling is focused on developing an understanding of the physical processes that influence the long-term or mean convective behaviour of groundwater beneath the estuary. It is shown that the convective stability depends fundamentally on the interplay between two factors: (1) the downward destabilizing buoyancy effect of density contrasts between the estuary and aquifer; and (2) the upward stabilizing influence of regional groundwater discharge. The structure of Convection Cells beneath the estuary and recirculation rates of estuary water within the groundwater system are shown to be related to a flow-modified Rayleigh number that depends critically on the aquifer anisotropy and estuary meander pattern. The recirculation of estuary water by these mechanisms is responsible for transport of high concentrations of ammonium, observed in pore fluids in the estuary bed sediments, into groundwater and its eventual return to the estuary. Copyright © 2001 John Wiley & Sons, Ltd.
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Density‐dependent surface water–groundwater interaction and nutrient discharge in the Swan–Canning Estuary
Hydrological Processes, 2001Co-Authors: Anthony J Smith, Jeffrey V TurnerAbstract:Salinity in the Swan–Canning Estuary, Western Australia, varies seasonally from freshwater conditions in winter up to the salinity of seawater in summer. Field observations show that the resulting seasonal density contrasts between the estuary and the adjacent fresh groundwater system are sufficient to drive mixed-Convection Cells that give rise to circulation of river water in the aquifer. In this study, we examine the role of steady density-driven Convection as a mechanism that contributes to the exchange of dissolved nutrients, particularly ammonium, between the Swan–Canning Estuary and the local groundwater system. We present results from two-dimensional (section) and three-dimensional density-coupled flow and mass transport modelling, in comparison with Glover's abrupt-interface solution for saltwater intrusion. The modelling is focused on developing an understanding of the physical processes that influence the long-term or mean convective behaviour of groundwater beneath the estuary. It is shown that the convective stability depends fundamentally on the interplay between two factors: (1) the downward destabilizing buoyancy effect of density contrasts between the estuary and aquifer; and (2) the upward stabilizing influence of regional groundwater discharge. The structure of Convection Cells beneath the estuary and recirculation rates of estuary water within the groundwater system are shown to be related to a flow-modified Rayleigh number that depends critically on the aquifer anisotropy and estuary meander pattern. The recirculation of estuary water by these mechanisms is responsible for transport of high concentrations of ammonium, observed in pore fluids in the estuary bed sediments, into groundwater and its eventual return to the estuary. Copyright © 2001 John Wiley & Sons, Ltd.
Anthony J Smith - One of the best experts on this subject based on the ideXlab platform.
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density dependent surface water groundwater interaction and nutrient discharge in the swan canning estuary
Hydrological Processes, 2001Co-Authors: Anthony J Smith, Jeffrey V TurnerAbstract:Salinity in the Swan–Canning Estuary, Western Australia, varies seasonally from freshwater conditions in winter up to the salinity of seawater in summer. Field observations show that the resulting seasonal density contrasts between the estuary and the adjacent fresh groundwater system are sufficient to drive mixed-Convection Cells that give rise to circulation of river water in the aquifer. In this study, we examine the role of steady density-driven Convection as a mechanism that contributes to the exchange of dissolved nutrients, particularly ammonium, between the Swan–Canning Estuary and the local groundwater system. We present results from two-dimensional (section) and three-dimensional density-coupled flow and mass transport modelling, in comparison with Glover's abrupt-interface solution for saltwater intrusion. The modelling is focused on developing an understanding of the physical processes that influence the long-term or mean convective behaviour of groundwater beneath the estuary. It is shown that the convective stability depends fundamentally on the interplay between two factors: (1) the downward destabilizing buoyancy effect of density contrasts between the estuary and aquifer; and (2) the upward stabilizing influence of regional groundwater discharge. The structure of Convection Cells beneath the estuary and recirculation rates of estuary water within the groundwater system are shown to be related to a flow-modified Rayleigh number that depends critically on the aquifer anisotropy and estuary meander pattern. The recirculation of estuary water by these mechanisms is responsible for transport of high concentrations of ammonium, observed in pore fluids in the estuary bed sediments, into groundwater and its eventual return to the estuary. Copyright © 2001 John Wiley & Sons, Ltd.
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Density‐dependent surface water–groundwater interaction and nutrient discharge in the Swan–Canning Estuary
Hydrological Processes, 2001Co-Authors: Anthony J Smith, Jeffrey V TurnerAbstract:Salinity in the Swan–Canning Estuary, Western Australia, varies seasonally from freshwater conditions in winter up to the salinity of seawater in summer. Field observations show that the resulting seasonal density contrasts between the estuary and the adjacent fresh groundwater system are sufficient to drive mixed-Convection Cells that give rise to circulation of river water in the aquifer. In this study, we examine the role of steady density-driven Convection as a mechanism that contributes to the exchange of dissolved nutrients, particularly ammonium, between the Swan–Canning Estuary and the local groundwater system. We present results from two-dimensional (section) and three-dimensional density-coupled flow and mass transport modelling, in comparison with Glover's abrupt-interface solution for saltwater intrusion. The modelling is focused on developing an understanding of the physical processes that influence the long-term or mean convective behaviour of groundwater beneath the estuary. It is shown that the convective stability depends fundamentally on the interplay between two factors: (1) the downward destabilizing buoyancy effect of density contrasts between the estuary and aquifer; and (2) the upward stabilizing influence of regional groundwater discharge. The structure of Convection Cells beneath the estuary and recirculation rates of estuary water within the groundwater system are shown to be related to a flow-modified Rayleigh number that depends critically on the aquifer anisotropy and estuary meander pattern. The recirculation of estuary water by these mechanisms is responsible for transport of high concentrations of ammonium, observed in pore fluids in the estuary bed sediments, into groundwater and its eventual return to the estuary. Copyright © 2001 John Wiley & Sons, Ltd.
Alphonse C. Sterling - One of the best experts on this subject based on the ideXlab platform.
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On Making Magnetic-flux-rope Ω Loops for Solar Bipolar Magnetic Regions of All Sizes by Convection Cells
The Astrophysical Journal, 2020Co-Authors: Ronald L. Moore, Sanjiv K. Tiwari, Navdeep K. Panesar, Alphonse C. SterlingAbstract:We propose that the flux-rope $\Omega$ loop that emerges to become any bipolar magnetic region (BMR) is made by a Convection cell of the $\Omega$-loop's size from initially-horizontal magnetic field ingested through the cell's bottom. This idea is based on (1) observed characteristics of BMRs of all spans ($\sim$ 1000 km to $\sim$ 200,000 km), (2) a well-known simulation of the production of a BMR by a supergranule-size Convection cell from horizontal field placed at cell bottom, and (3) a well-known Convection-zone simulation. From the observations and simulations, we (1) infer that the strength of the field ingested by the biggest Convection Cells (giant Cells) to make the biggest BMR $\Omega$ loops is $\sim$ 10$^3$ G, (2) plausibly explain why the span and flux of the biggest observed BMRs are $\sim$ 200,000 km and $\sim$ 10$^{22}$ Mx, (3) suggest how giant Cells might also make "failed-BMR" $\Omega$ loops that populate the upper Convection zone with horizontal field, from which smaller Convection Cells make BMR $\Omega$ loops of their size, (4) suggest why sunspots observed in a sunspot cycle's declining phase tend to violate the hemispheric helicity rule, and (5) support a previously-proposed amended Babcock scenario for the sunspot cycle's dynamo process. Because the proposed Convection-based heuristic model for making a sunspot-BMR $\Omega$ loop avoids having $\sim$ 10$^5$ G field in the initial flux rope at the bottom of the Convection zone, it is an appealing alternative to the present magnetic-buoyancy-based standard scenario and warrants testing by high-enough-resolution giant-cell magnetoConvection simulations.
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On Making Magnetic-Flux-Rope $\Omega$ Loops for Solar Bipolar Magnetic Regions of All Sizes by Convection Cells.
arXiv: Solar and Stellar Astrophysics, 2020Co-Authors: Ronald L. Moore, Sanjiv K. Tiwari, Navdeep K. Panesar, Alphonse C. SterlingAbstract:We propose that the flux-rope $\Omega$ loop that emerges to become any bipolar magnetic region (BMR) is made by a Convection cell of the $\Omega$-loop's size from initially-horizontal magnetic field ingested through the cell's bottom. This idea is based on (1) observed characteristics of BMRs of all spans ($\sim$ 1000 km to $\sim$ 200,000 km), (2) a well-known simulation of the production of a BMR by a supergranule-size Convection cell from horizontal field placed at cell bottom, and (3) a well-known Convection-zone simulation. From the observations and simulations, we (1) infer that the strength of the field ingested by the biggest Convection Cells (giant Cells) to make the biggest BMR $\Omega$ loops is $\sim$ 10$^3$ G, (2) plausibly explain why the span and flux of the biggest observed BMRs are $\sim$ 200,000 km and $\sim$ 10$^{22}$ Mx, (3) suggest how giant Cells might also make "failed-BMR" $\Omega$ loops that populate the upper Convection zone with horizontal field, from which smaller Convection Cells make BMR $\Omega$ loops of their size, (4) suggest why sunspots observed in a sunspot cycle's declining phase tend to violate the hemispheric helicity rule, and (5) support a previously-proposed amended Babcock scenario for the sunspot cycle's dynamo process. Because the proposed Convection-based heuristic model for making a sunspot-BMR $\Omega$ loop avoids having $\sim$ 10$^5$ G field in the initial flux rope at the bottom of the Convection zone, it is an appealing alternative to the present magnetic-buoyancy-based standard scenario and warrants testing by high-enough-resolution giant-cell magnetoConvection simulations.
C.h Chen - One of the best experts on this subject based on the ideXlab platform.
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Granular Convection Cells in a vertical shaker
Powder Technology, 2000Co-Authors: Shu-san Hsiau, C.h ChenAbstract:Granular materials exhibit convective motions in a confined box under external vibration. Particles move upward in the center and flow downward along the side walls. This paper experimentally studies the phenomena of Convection Cells in a two-dimensional box with 3-mm glass beads under different vibration intensities. Using image processing technology and particle tracking method, the velocity fields of the convective granular beds were measured and analyzed at different vibration conditions. The vertical and horizontal velocity profiles at different locations were investigated. The Convection cell centers could be determined from the velocity profiles. The Convection flow rate was calculated and had a power law dependence on the amplitude of the vibration velocity.