The Experts below are selected from a list of 795 Experts worldwide ranked by ideXlab platform
Mohammad Azri Mohd Jaafar - One of the best experts on this subject based on the ideXlab platform.
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large eddy simulation and preliminary modeling of the flow downstream a variable geometry swirler for gas turbine combustors
International Communications in Heat and Mass Transfer, 2011Co-Authors: Yehia A. Eldrainy, Khalid M. Saqr, Hossam S. Aly, Tholudin Mat Lazim, Mohammad Azri Mohd JaafarAbstract:This work presents a novel swirler with variable blade configuration for gas turbine combustors and industrial burners. The flow dynamics downstream the swirler was explored using Large Eddy Simulation (LES). The resolved turbulence kinetic energy in the region where the flow exhibits the main flow phenomena was well above 80% of the total turbulent kinetic energy of the flow. It was evidently shown that the new swirler produces a central recirculation zone and a Rankine Vortex structure which are necessary for swirl flame stabilization. Two Reynolds-averaged NavierStokes (RANS) simulation cases utilizing the standard and realizable k-e turbulence models were also conducted for two objectives. The first is to demonstrate the validity of RANS/eddy-viscosity models in predicting the main characteristics of swirling flows with comparison to the LES results. The second objective is to comparatively investigate the flow features downstream the new swirler in both co-rotating and counter-rotating blade configurations. The results show that the counter-rotating configuration produces higher turbulence kinetic energy and more compact recirculation zone compared to the co-rotating configuration.
Yehia A. Eldrainy - One of the best experts on this subject based on the ideXlab platform.
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large eddy simulation and preliminary modeling of the flow downstream a variable geometry swirler for gas turbine combustors
International Communications in Heat and Mass Transfer, 2011Co-Authors: Yehia A. Eldrainy, Khalid M. Saqr, Hossam S. Aly, Tholudin Mat Lazim, Mohammad Azri Mohd JaafarAbstract:This work presents a novel swirler with variable blade configuration for gas turbine combustors and industrial burners. The flow dynamics downstream the swirler was explored using Large Eddy Simulation (LES). The resolved turbulence kinetic energy in the region where the flow exhibits the main flow phenomena was well above 80% of the total turbulent kinetic energy of the flow. It was evidently shown that the new swirler produces a central recirculation zone and a Rankine Vortex structure which are necessary for swirl flame stabilization. Two Reynolds-averaged NavierStokes (RANS) simulation cases utilizing the standard and realizable k-e turbulence models were also conducted for two objectives. The first is to demonstrate the validity of RANS/eddy-viscosity models in predicting the main characteristics of swirling flows with comparison to the LES results. The second objective is to comparatively investigate the flow features downstream the new swirler in both co-rotating and counter-rotating blade configurations. The results show that the counter-rotating configuration produces higher turbulence kinetic energy and more compact recirculation zone compared to the co-rotating configuration.
Bruce R White - One of the best experts on this subject based on the ideXlab platform.
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martian dust devils laboratory simulations of particle threshold
Journal of Geophysical Research, 2003Co-Authors: R Greeley, M R Balme, James D Iversen, S M Metzger, Robert Mickelson, Jim Phoreman, Bruce R WhiteAbstract:[1] An apparatus has been fabricated to simulate terrestrial and Martian dust devils. Comparisons of surface pressure profiles through the Vortex core generated in the apparatus with both those in natural dust devils on Earth and those inferred for Mars are similar and are consistent with theoretical Rankine Vortex models. Experiments to determine particle threshold under Earth ambient atmospheric pressures show that sand (particles > 60 μm in diameter) threshold is analogous to normal boundary-layer shear, in which the rotating winds of the Vortex generate surface shear and hence lift. Lower-pressure experiments down to ∼65 mbar follow this trend for sand-sized particles. However, smaller particles (i.e., dust) and all particles at very low pressures (∼10–60 mbar) appear to be subjected to an additional lift function interpreted to result from the strong decrease in atmospheric pressure centered beneath the Vortex core. Initial results suggest that the wind speeds required for the entrainment of grains ∼2 μm in diameter (i.e., Martian dust sizes) are about half those required for entrainment by boundary layer winds on both Earth and Mars.
Joshua Wurman - One of the best experts on this subject based on the ideXlab platform.
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doppler radar derived wind field of five tornado events with application to engineering simulations
Engineering Structures, 2017Co-Authors: Maryam Refan, Joshua Wurman, Horia Hangan, Karen KosibaAbstract:Abstract Doppler radar data corresponding to five tornado events are analyzed using the Ground-Based Velocity Track Display method and the three-dimensional velocity field of nine volumetric samples is extracted. These samples are selected to cover a range of wind speeds (between 36 m/s and 64 m/s) and Vortex structures representative of EF0 to EF3 tornadoes in a first attempt to generate a tornado wind field database. Tangential velocity profiles, swirl ratios and Vortex structures, i.e. single-celled or two-celled Vortex, are determined for each of these volumetric samples. Among the nine volumetric samples, two show single-celled characteristics, Vortex breakdown bubble is evident in one and four demonstrate two-celled Vortex characteristics. The radial profiles of the tangential velocity are in good agreement with a modified Rankine Vortex model. The variation of maximum tangential velocities with height is very different when compared to the velocity variation in typical atmospheric boundary layer flows. The swirl ratios of the tornado volumetric samples are computed using the flow rate through the updrafts and the maximum circulation in the flows.
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Research Article Wind Field of a Nonmesocyclone Anticyclonic Tornado Crossing the Hong Kong International Airport
2016Co-Authors: Karen Kosiba, Paul Robinson, P. W. Chan, Joshua WurmanAbstract:Copyright © 2014 Karen A. Kosiba et al.This is an open access article distributed under theCreativeCommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A nonmesocyclone tornado traversed the Hong Kong International Airport on September 6, 2004 directly impacting a surface weather station. This allowed for 1-second 10-meter above ground level (AGL) wind observations through the core of the tornado. Integration of these 10-meter AGL wind data with Ground-Based Velocity Track (GBVTD) wind retrievals derived from LIDAR data provided a time history of the three-dimensional wind field of the tornado. These data indicate a progressive decrease in radial inflow with time and little to no radial inflow near the time the tornado crosses the surface weather station. Anemometer observations suggest that the tangential winds approximate a modified-Rankine Vortex outside the radius of maximum winds, suggesting that frictionally induced radial inflow was confined below 10mAGL. The radial-height distribution of angular momentum depicts an increase in low-level angular momentum just prior to the tornado reaching its maximum intensity. 1
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Wind Field of a Nonmesocyclone Anticyclonic Tornado Crossing the Hong Kong International Airport
Hindawi Limited, 2014Co-Authors: Karen Kosiba, Paul Robinson, P. W. Chan, Joshua WurmanAbstract:A nonmesocyclone tornado traversed the Hong Kong International Airport on September 6, 2004 directly impacting a surface weather station. This allowed for 1-second 10-meter above ground level (AGL) wind observations through the core of the tornado. Integration of these 10-meter AGL wind data with Ground-Based Velocity Track (GBVTD) wind retrievals derived from LIDAR data provided a time history of the three-dimensional wind field of the tornado. These data indicate a progressive decrease in radial inflow with time and little to no radial inflow near the time the tornado crosses the surface weather station. Anemometer observations suggest that the tangential winds approximate a modified-Rankine Vortex outside the radius of maximum winds, suggesting that frictionally induced radial inflow was confined below 10 m AGL. The radial-height distribution of angular momentum depicts an increase in low-level angular momentum just prior to the tornado reaching its maximum intensity
Karen Kosiba - One of the best experts on this subject based on the ideXlab platform.
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doppler radar derived wind field of five tornado events with application to engineering simulations
Engineering Structures, 2017Co-Authors: Maryam Refan, Joshua Wurman, Horia Hangan, Karen KosibaAbstract:Abstract Doppler radar data corresponding to five tornado events are analyzed using the Ground-Based Velocity Track Display method and the three-dimensional velocity field of nine volumetric samples is extracted. These samples are selected to cover a range of wind speeds (between 36 m/s and 64 m/s) and Vortex structures representative of EF0 to EF3 tornadoes in a first attempt to generate a tornado wind field database. Tangential velocity profiles, swirl ratios and Vortex structures, i.e. single-celled or two-celled Vortex, are determined for each of these volumetric samples. Among the nine volumetric samples, two show single-celled characteristics, Vortex breakdown bubble is evident in one and four demonstrate two-celled Vortex characteristics. The radial profiles of the tangential velocity are in good agreement with a modified Rankine Vortex model. The variation of maximum tangential velocities with height is very different when compared to the velocity variation in typical atmospheric boundary layer flows. The swirl ratios of the tornado volumetric samples are computed using the flow rate through the updrafts and the maximum circulation in the flows.
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Research Article Wind Field of a Nonmesocyclone Anticyclonic Tornado Crossing the Hong Kong International Airport
2016Co-Authors: Karen Kosiba, Paul Robinson, P. W. Chan, Joshua WurmanAbstract:Copyright © 2014 Karen A. Kosiba et al.This is an open access article distributed under theCreativeCommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A nonmesocyclone tornado traversed the Hong Kong International Airport on September 6, 2004 directly impacting a surface weather station. This allowed for 1-second 10-meter above ground level (AGL) wind observations through the core of the tornado. Integration of these 10-meter AGL wind data with Ground-Based Velocity Track (GBVTD) wind retrievals derived from LIDAR data provided a time history of the three-dimensional wind field of the tornado. These data indicate a progressive decrease in radial inflow with time and little to no radial inflow near the time the tornado crosses the surface weather station. Anemometer observations suggest that the tangential winds approximate a modified-Rankine Vortex outside the radius of maximum winds, suggesting that frictionally induced radial inflow was confined below 10mAGL. The radial-height distribution of angular momentum depicts an increase in low-level angular momentum just prior to the tornado reaching its maximum intensity. 1
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Wind Field of a Nonmesocyclone Anticyclonic Tornado Crossing the Hong Kong International Airport
Hindawi Limited, 2014Co-Authors: Karen Kosiba, Paul Robinson, P. W. Chan, Joshua WurmanAbstract:A nonmesocyclone tornado traversed the Hong Kong International Airport on September 6, 2004 directly impacting a surface weather station. This allowed for 1-second 10-meter above ground level (AGL) wind observations through the core of the tornado. Integration of these 10-meter AGL wind data with Ground-Based Velocity Track (GBVTD) wind retrievals derived from LIDAR data provided a time history of the three-dimensional wind field of the tornado. These data indicate a progressive decrease in radial inflow with time and little to no radial inflow near the time the tornado crosses the surface weather station. Anemometer observations suggest that the tangential winds approximate a modified-Rankine Vortex outside the radius of maximum winds, suggesting that frictionally induced radial inflow was confined below 10 m AGL. The radial-height distribution of angular momentum depicts an increase in low-level angular momentum just prior to the tornado reaching its maximum intensity
