The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform
M S Abdelhady - One of the best experts on this subject based on the ideXlab platform.
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force propagation speed in a bed of Particles due to an Incident Particle impact
Advanced Powder Technology, 2010Co-Authors: M S Abdelhady, Ccm Camilo Rindt, S Abdelhady, A A Van SteenhovenAbstract:The force propagation speed in granular matter is a very difficult property to be measured. A new technique has been developed to calculate the force propagation speed in granular matter based on measuring experimentally the contact time. The contact time for a Particle hitting a bed of Particles is estimated as the time taken for a Particle to strike a bed of Particles till the time of its ejection, and it is calculated using the discrete element method. The speed of force propagation in a bed of Particles is estimated by plotting the dependence of the path length of the contact force on the contact time and finding the gradient of such dependence. Such approach leads to accurate results if the impact speed is below the yield velocity, i.e. no plastic deformations. It is found that the force propagation speed in spherical granular matter is proportional to the impact speed of the Incident Particle, which is different from force propagation in continuum matter. It is also found that the propagation speed is dependent on the material and diameters ratio of the interacting Particles, but it is not dependent on the number of bed layers. The propagation speed in granular matter is normalized by dividing it by a reference propagation speed, i.e. the propagation speed at an impact speed of 1 m/s. It is found that the normalized propagation speed is independent of the material and diameter of the interacting Particles, but it is logarithmically proportional to the impact speed. The proportionality constant is equal to 0.16, which can be taken as a universal constant for force propagation in spherical granular matter.
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contact time of an Incident Particle hitting a 2d bed of Particles
Powder Technology, 2009Co-Authors: M S Abdelhady, Ccm Camilo Rindt, Van Aa Anton SteenhovenAbstract:Abstract Removal of Particles from fouling layers due to an Incident Particle impact is affected by the fluid fluctuations in industrial applications if the contact time is larger than the fluctuations time scales. The contact time is an important parameter when analysing the influence of the fluid structure interaction on a fouling process. The contact time for a Particle hitting a bed of Particles is defined as the time it takes for the Incident Particle to bounce off the bed. The contact time for a Particle hitting a bed of Particles arranged in a rectangular and a hexagonal array is measured experimentally and calculated numerically based on the discrete element method. The Incident Particle and the bed Particles are of the same size and material. It is found that the contact time is proportional to the number of bed layers in case of a rectangular bed array and independent of the number of bed layers in case of a hexagonal bed of Particles. The contact time is inversely proportional to the impact speed. The rebound speed of the Incident Particle is independent of the number of bed layers in case of a hexagonal arrangement of Particles and is exponentially dependent on the number of bed layers in case of a rectangular arrangement. A hexagonal bed of Particles acts as a massive Particle due to its large co-ordination number compared to a rectangular bed of Particles. The force propagation speed in granular matter could be calculated by plotting the path of the force as a function of the contact time and finding the gradient of this graph.
Ccm Camilo Rindt - One of the best experts on this subject based on the ideXlab platform.
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force propagation speed in a bed of Particles due to an Incident Particle impact
Advanced Powder Technology, 2010Co-Authors: M S Abdelhady, Ccm Camilo Rindt, S Abdelhady, A A Van SteenhovenAbstract:The force propagation speed in granular matter is a very difficult property to be measured. A new technique has been developed to calculate the force propagation speed in granular matter based on measuring experimentally the contact time. The contact time for a Particle hitting a bed of Particles is estimated as the time taken for a Particle to strike a bed of Particles till the time of its ejection, and it is calculated using the discrete element method. The speed of force propagation in a bed of Particles is estimated by plotting the dependence of the path length of the contact force on the contact time and finding the gradient of such dependence. Such approach leads to accurate results if the impact speed is below the yield velocity, i.e. no plastic deformations. It is found that the force propagation speed in spherical granular matter is proportional to the impact speed of the Incident Particle, which is different from force propagation in continuum matter. It is also found that the propagation speed is dependent on the material and diameters ratio of the interacting Particles, but it is not dependent on the number of bed layers. The propagation speed in granular matter is normalized by dividing it by a reference propagation speed, i.e. the propagation speed at an impact speed of 1 m/s. It is found that the normalized propagation speed is independent of the material and diameter of the interacting Particles, but it is logarithmically proportional to the impact speed. The proportionality constant is equal to 0.16, which can be taken as a universal constant for force propagation in spherical granular matter.
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contact time of an Incident Particle hitting a 2d bed of Particles
Powder Technology, 2009Co-Authors: M S Abdelhady, Ccm Camilo Rindt, Van Aa Anton SteenhovenAbstract:Abstract Removal of Particles from fouling layers due to an Incident Particle impact is affected by the fluid fluctuations in industrial applications if the contact time is larger than the fluctuations time scales. The contact time is an important parameter when analysing the influence of the fluid structure interaction on a fouling process. The contact time for a Particle hitting a bed of Particles is defined as the time it takes for the Incident Particle to bounce off the bed. The contact time for a Particle hitting a bed of Particles arranged in a rectangular and a hexagonal array is measured experimentally and calculated numerically based on the discrete element method. The Incident Particle and the bed Particles are of the same size and material. It is found that the contact time is proportional to the number of bed layers in case of a rectangular bed array and independent of the number of bed layers in case of a hexagonal bed of Particles. The contact time is inversely proportional to the impact speed. The rebound speed of the Incident Particle is independent of the number of bed layers in case of a hexagonal arrangement of Particles and is exponentially dependent on the number of bed layers in case of a rectangular arrangement. A hexagonal bed of Particles acts as a massive Particle due to its large co-ordination number compared to a rectangular bed of Particles. The force propagation speed in granular matter could be calculated by plotting the path of the force as a function of the contact time and finding the gradient of this graph.
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Influence of sintering on the growth rate of particulate fouling layers
International Journal of Heat and Mass Transfer, 2006Co-Authors: M.s. Abd-elhady, Ccm Camilo Rindt, Jg Johan Wijers, Sh Stef Clevers, Tng Adriaans, Van Aa Anton SteenhovenAbstract:This article addresses the question; why the gas-side temperature affects the rate of particulate fouling of heat exchangers? An experiment was carried out in a gas-cooler of a full-scale biomass gasifier to investigate the influence of the gas-side temperature on the strength, structure and growth rate of particulate fouling layers. It is observed that the particulate fouling rate in the gas cooler decreases with sintering, which is a function of the gas-side temperature. Detailed impaction experiments are carried out to investigate the influence of sintering on the removal of Particles from a particulate fouling layer due to an Incident Particle impact as well as the sticking of an Incident Particle to a particulate fouling layer. Sintering of a fouling layer lowers significantly the ability of an Incident Particle to stick to the fouling layer or to remove Particles out of the layer. However, Particles that are still able to deposit on the sintered fouling layer will not sinter immediately, and can be removed due to the Incident Particles impact. The removal of newly deposited Particles on a fouling layer due to Incident Particles becomes easier as sintering of the fouling layer takes place. Accordingly, it may be stated that sintering reduces the fouling rate of heat exchangers by lowering the deposition of new Particles and increasing the removal rate of newly deposited Particles. This explains why the growth rate of particulate fouling layers decreases with the gas-side temperature.
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Modelling the impaction of a micron Particle with a powdery layer
Powder Technology, 2006Co-Authors: M.s. Abd-elhady, Ccm Camilo Rindt, Jg Johan Wijers, Van Aa Anton SteenhovenAbstract:The interaction of an incoming micron Particle with already deposited Particles is an important factor in particulate fouling of heat exchangers. A numerical model was developed based on the discrete element method to simulate this interaction. The contact forces between the colliding Particles are based on the concept of contact mechanics, which takes plastic deformation of Particles into consideration. The numerical model predicts the critical sticking and removal velocities, which are important parameters in determining the fouling rate of heat exchangers. Very detailed information of the bed dynamics can be extracted from the numerical model. It appears that the time required for a Particle to be ejected out of a bed of Particles due to an Incident Particle impact is proportional to the interacting Particles diameter and to the square root of the number of bed layers. The maximum indentation in an Incident Particle hitting a bed of Particles is proven theoretically and numerically to be directly proportional to the velocity and diameter of the Incident Particle if plastic deformation occurs. Experiments were carried out in a vacuumed column to validate the numerical model. In the experiments, Incident Particles dropped onto a bed of Particles and the sticking, bouncing and removal behaviour were measured as a function of the Incident Particle impact speed. Both the numerics and the experiments showed that there are velocity regimes at which the Incident Particle sticks, bounces off or removes Particles from the bed of Particles. The regimes overlap due to the impact angle effect. The numerical model predictions regarding the critical sticking and removal velocities are in agreement with the measured values.
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Removal of Particles from a powdery fouled surface due to impaction
2004Co-Authors: M.s. Abd-elhady, Ccm Camilo Rindt, Jg Johan Wijers, Van Aa Anton SteenhovenAbstract:Particulate fouling is defined as the unwanted deposition of Particles on heat exchange surfaces. The fouling layer reduces the heat transfer rate and leads to inefficient operation. The net fouling rate is the result of the difference between the deposition rate and the removal rate of Particles. One of the mechanisms that contribute to the removal of Particles from powdery fouled surfaces, is the collision of an Incident Particle with the fouled surface. In the present study, removal of Particles from powdery fouled surfaces due to an Incident Particle impact is studied numerically and experimentally. A numerical model is developed to study the interaction of an Incident Particle with a bed of Particles. The numerical model is based on the molecular dynamic theory of granular matter. The numerical model is tested for an Incident copper Particle hitting a bed of Particles at different impact speeds. The numerical results are verified experimentally. An experimental setup has been built to study the removal of Particles from powdery fouling layers due to an Incident Particle impact. It is shown that depending on the impact speed, zero, one, two or three Particles are ejected from the powdery layer. By comparing the numerical results with the experimental measurements it is shown that the numerical results fit in the measured range of impact mentioned above. The numerical model will be used further to characterize the removal of Particles from powdery fouling layers as function of Particle size, material, Incident Particle impact speed and the bed of Particles porosity.
Van Aa Anton Steenhoven - One of the best experts on this subject based on the ideXlab platform.
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contact time of an Incident Particle hitting a 2d bed of Particles
Powder Technology, 2009Co-Authors: M S Abdelhady, Ccm Camilo Rindt, Van Aa Anton SteenhovenAbstract:Abstract Removal of Particles from fouling layers due to an Incident Particle impact is affected by the fluid fluctuations in industrial applications if the contact time is larger than the fluctuations time scales. The contact time is an important parameter when analysing the influence of the fluid structure interaction on a fouling process. The contact time for a Particle hitting a bed of Particles is defined as the time it takes for the Incident Particle to bounce off the bed. The contact time for a Particle hitting a bed of Particles arranged in a rectangular and a hexagonal array is measured experimentally and calculated numerically based on the discrete element method. The Incident Particle and the bed Particles are of the same size and material. It is found that the contact time is proportional to the number of bed layers in case of a rectangular bed array and independent of the number of bed layers in case of a hexagonal bed of Particles. The contact time is inversely proportional to the impact speed. The rebound speed of the Incident Particle is independent of the number of bed layers in case of a hexagonal arrangement of Particles and is exponentially dependent on the number of bed layers in case of a rectangular arrangement. A hexagonal bed of Particles acts as a massive Particle due to its large co-ordination number compared to a rectangular bed of Particles. The force propagation speed in granular matter could be calculated by plotting the path of the force as a function of the contact time and finding the gradient of this graph.
Harry A. Atwater - One of the best experts on this subject based on the ideXlab platform.
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The role of Particle energy and pulsed Particle flux in physical vapor deposition and pulsed–laser deposition
Applied Physics Letters, 1999Co-Authors: Stefan G. Mayr, Marten Moske, Maggie E. Taylor, Konrad Samwer, Harry A. AtwaterAbstract:Surface morphology evolution of thin films generated by physical and pulsed-laser deposition depending on the Incident Particle energy and the pulse rate is investigated using a continuum growth model. The model includes curvature-induced surface diffusion, the Schwoebel barrier and surface atom displacement as main surface processes. The numerical solution of the model is in very good agreement with the results of kinetic Monte Carlo simulations, which also serve to estimate the continuum growth parameters, and with experimental results on thin Si films. The increase of the Incident Particle energy, starting from thermal energy, fundamentally influences the surface topography, changing from self-affine to self-organized morphology.
V. Belyaev - One of the best experts on this subject based on the ideXlab platform.
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Diamond Detector Technology: Status and Perspectives
RAD Association Journal, 2018Co-Authors: D. Hits, L. Bäni, A. Alexopoulos, M. Artuso, F. Bachmair, M. Bartosik, H. Beck, V. Bellini, J. Beacham, V. BelyaevAbstract:The radiation tolerance of chemical vapor deposition (CVD) diamond against different Particle species and energies has been studied in beam tests and is presented. We also present beam test results on signal size as a function of Incident Particle rate in charged Particle detectors based on un-irradiated and irradiated poly-crystalline CVD diamond over a range of Particle fluxes from 2 kHz/cm2 to 20 MHz/cm2. The pulse height of the sensors was measured using readout electronics with a peaking time of 6 ns. In addition, the functionality of poly-crystalline CVD diamond 3D devices is demonstrated in beam tests and 3D diamond detectors are shown to be a promising technology for applications in future high rate/high intensity experiments.
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Diamond detectors for high energy physics experiments
2017Co-Authors: L. Bäni, A. Alexopoulos, M. Artuso, F. Bachmair, M. Bartosik, H. Beck, V. Bellini, V. Belyaev, J. Beacham, B. BenteleAbstract:Beam test results of the radiation tolerance study of chemical vapour deposition (CVD) diamond against different Particle species and energies is presented. We also present beam test results on the independence of signal size on Incident Particle rate in charged Particle detectors based on un-irradiated and irradiated poly-crystalline CVD diamond over a range of Particle fluxes from 2 kHz/cm2 to 10 MHz/cm2. The pulse height of the sensors was measured with readout electronics with a peaking time of 6 ns. In addition functionality of poly-crystalline CVD diamond 3D devices was demonstrated in beam tests and 3D diamond detectors are shown to be a promising technology for applications in future high luminosity experiments.
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Diamond Detector Technology: Status and Perspectives
2017Co-Authors: M. Reichmann, L. Bäni, A. Alexopoulos, M. Artuso, F. Bachmair, M. Bartosik, H. Beck, V. Bellini, J. Beacham, V. BelyaevAbstract:The planned upgrade of the LHC to the High-Luminosity-LHC will push the luminosity limits above the original design values. Since the current detectors will not be able to cope with this environment ATLAS and CMS are doing research to find more radiation tolerant technologies for their innermost tracking layers. Chemical Vapour Deposition (CVD) diamond is an excellent candidate for this purpose. Detectors out of this material are already established in the highest irradiation regimes for the beam condition monitors at LHC. The RD42 collaboration is leading an effort to use CVD diamonds also as sensor material for the future tracking detectors. The signal behaviour of highly irradiated diamonds is presented as well as the recent study of the signal dependence on Incident Particle flux. There is also a recent development towards 3D detectors and especially 3D detectors with a pixel readout based on diamond sensors.
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Diamond detector technology: status and perspectives
2016Co-Authors: Harris Kagan, L. Bäni, A. Alexopoulos, M. Artuso, F. Bachmair, M. Bartosik, V. Bellini, J. Beacham, H.p. Beck, V. BelyaevAbstract:The status of material development of polycrystalline chemical vapor deposition (CVD) diamond is presented. We also present beam test results on the independence of signal size on Incident Particle rate in charged Particle detectors based on un-irradiated and irradiated polycrystalline CVD diamond over a range of Particle fluxes from 2 kHz/cm2 to 10 MHz/cm2. The pulse height of the sensors was measured with readout electronics with a peaking time of 6 ns. In addition the first beam test results from 3D detectors made with poly-crystalline CVD diamond are presented. Finally the first analysis of LHC data from the ATLAS Diamond Beam Monitor (DBM) which is based on pixelated polycrystalline CVD diamond sensors bump-bonded to pixel readout electronics is shown.
