The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Hyung Jin Sung - One of the best experts on this subject based on the ideXlab platform.
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influence of a large eddy breakup device on the Frictional Drag in a turbulent boundary layer
Physics of Fluids, 2017Co-Authors: Joonseok Kim, Min Yoon, Junsun Ahn, Jinyul Hwang, Hyung Jin SungAbstract:A direct numerical simulation of a spatially developing turbulent boundary layer with a large-eddy breakup (LEBU) device was performed to investigate the influence of the LEBU device on the near-wall turbulence and Frictional Drag. The LEBU device, which is thin and rectangular in shape, was located at 80% of the boundary layer thickness (δ). The LEBU device reduced the skin-friction coefficient (Cf) up to 17%. The breakdown of the outer structures passing through the LEBU device reduced the energy of the long wavelength motions (λz+>200) along the wall-normal direction. The reduction of Cf mainly arose from the contribution of the Reynolds shear stress by the difference in the spatial coherence of the outer high- and low-speed structures. We investigated the relationship between the large-scale motions and the velocity–vorticity correlations (vωz and −wωy), which directly contribute to Cf. The contributions of vωz and −wωy accounted for 80% of the total Cf reduction. The amount of the Cf reduction induce...
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Contribution of velocity-vorticity correlations to the Frictional Drag in wall-bounded turbulent flows
Physics of Fluids, 2016Co-Authors: Min Yoon, Junsun Ahn, Jinyul Hwang, Hyung Jin SungAbstract:The relationship between the Frictional Drag and the velocity-vorticity correlations in wall-bounded turbulent flows is derived from the mean vorticity equation. A formula for the skin friction coefficient is proposed and evaluated with regards to three canonical wall-bounded flows: turbulent boundary layer, turbulent channel flow, and turbulent pipe flow. The Frictional Drag encompasses four terms: advective vorticity transport, vortex stretching, viscous, and inhomogeneous terms. Drag-reduced channel flow with the slip condition is used to test the reliability of the formula. The advective vorticity transport and vortex stretching terms are found to dominate the contributions to the Frictional Drag.
Carlos A. Ramírez - One of the best experts on this subject based on the ideXlab platform.
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Summary of Frictional Drag coefficient relationships for spheres: Evolving solution strategies applied to an old problem
Chemical Engineering Science, 2017Co-Authors: Carlos A. RamírezAbstract:Abstract In 1851 Stokes reported his analytical solution for the kinetic force (form Drag plus Frictional Drag) exerted by an unbounded fluid on a steadily falling sphere under very slow or creeping flow conditions. This so called Stokes’ law was improved in the early 20th Century by several authors, who included diverse approximations to the inertia term neglected by Stokes in the Navier-Stokes equation describing Newtonian fluid motion around the sphere. Lapple and Shepherd (1940) followed this fundamental theoretical work with a landmark plot relating the experimental Frictional Drag coefficient f (directly proportional to the magnitude of the kinetic force) to the sphere diameter-based Reynolds number (Re) for 0.1 ≤ Re ≤ 3.0E+06. Researchers quickly realized that Stokes’ law (valid for Re
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summary of Frictional Drag coefficient relationships for spheres evolving solution strategies applied to an old problem
Chemical Engineering Science, 2017Co-Authors: Carlos A. RamírezAbstract:In 1851 Stokes reported his analytical solution for the kinetic force (form Drag plus Frictional Drag) exerted by an unbounded fluid on a steadily falling sphere under very slow or creeping flow conditions. This so called Stokes’ law was improved in the early 20th Century by several authors, who included diverse approximations to the inertia term neglected by Stokes in the Navier-Stokes equation describing Newtonian fluid motion around the sphere. Lapple and Shepherd (1940) followed this fundamental theoretical work with a landmark plot relating the experimental Frictional Drag coefficient f (directly proportional to the magnitude of the kinetic force) to the sphere diameter-based Reynolds number (Re) for 0.1 ≤ Re ≤ 3.0E+06. Researchers quickly realized that Stokes’ law (valid for Re < 0.1) was insufficient to explain the data over the entire span of Re, giving rise to new solution methodologies to predict f(Re). This communication gives a chronological listing of well-known f(Re) relationships, providing insights on the rationale and strategies used in their development. The modern chemical engineer can therefore readily assess the evolution of this problem and realize the remaining research gaps in the field of fluid flow around submerged spheres.
Min Yoon - One of the best experts on this subject based on the ideXlab platform.
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influence of a large eddy breakup device on the Frictional Drag in a turbulent boundary layer
Physics of Fluids, 2017Co-Authors: Joonseok Kim, Min Yoon, Junsun Ahn, Jinyul Hwang, Hyung Jin SungAbstract:A direct numerical simulation of a spatially developing turbulent boundary layer with a large-eddy breakup (LEBU) device was performed to investigate the influence of the LEBU device on the near-wall turbulence and Frictional Drag. The LEBU device, which is thin and rectangular in shape, was located at 80% of the boundary layer thickness (δ). The LEBU device reduced the skin-friction coefficient (Cf) up to 17%. The breakdown of the outer structures passing through the LEBU device reduced the energy of the long wavelength motions (λz+>200) along the wall-normal direction. The reduction of Cf mainly arose from the contribution of the Reynolds shear stress by the difference in the spatial coherence of the outer high- and low-speed structures. We investigated the relationship between the large-scale motions and the velocity–vorticity correlations (vωz and −wωy), which directly contribute to Cf. The contributions of vωz and −wωy accounted for 80% of the total Cf reduction. The amount of the Cf reduction induce...
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Contribution of velocity-vorticity correlations to the Frictional Drag in wall-bounded turbulent flows
Physics of Fluids, 2016Co-Authors: Min Yoon, Junsun Ahn, Jinyul Hwang, Hyung Jin SungAbstract:The relationship between the Frictional Drag and the velocity-vorticity correlations in wall-bounded turbulent flows is derived from the mean vorticity equation. A formula for the skin friction coefficient is proposed and evaluated with regards to three canonical wall-bounded flows: turbulent boundary layer, turbulent channel flow, and turbulent pipe flow. The Frictional Drag encompasses four terms: advective vorticity transport, vortex stretching, viscous, and inhomogeneous terms. Drag-reduced channel flow with the slip condition is used to test the reliability of the formula. The advective vorticity transport and vortex stretching terms are found to dominate the contributions to the Frictional Drag.
Jinyul Hwang - One of the best experts on this subject based on the ideXlab platform.
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influence of a large eddy breakup device on the Frictional Drag in a turbulent boundary layer
Physics of Fluids, 2017Co-Authors: Joonseok Kim, Min Yoon, Junsun Ahn, Jinyul Hwang, Hyung Jin SungAbstract:A direct numerical simulation of a spatially developing turbulent boundary layer with a large-eddy breakup (LEBU) device was performed to investigate the influence of the LEBU device on the near-wall turbulence and Frictional Drag. The LEBU device, which is thin and rectangular in shape, was located at 80% of the boundary layer thickness (δ). The LEBU device reduced the skin-friction coefficient (Cf) up to 17%. The breakdown of the outer structures passing through the LEBU device reduced the energy of the long wavelength motions (λz+>200) along the wall-normal direction. The reduction of Cf mainly arose from the contribution of the Reynolds shear stress by the difference in the spatial coherence of the outer high- and low-speed structures. We investigated the relationship between the large-scale motions and the velocity–vorticity correlations (vωz and −wωy), which directly contribute to Cf. The contributions of vωz and −wωy accounted for 80% of the total Cf reduction. The amount of the Cf reduction induce...
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Contribution of velocity-vorticity correlations to the Frictional Drag in wall-bounded turbulent flows
Physics of Fluids, 2016Co-Authors: Min Yoon, Junsun Ahn, Jinyul Hwang, Hyung Jin SungAbstract:The relationship between the Frictional Drag and the velocity-vorticity correlations in wall-bounded turbulent flows is derived from the mean vorticity equation. A formula for the skin friction coefficient is proposed and evaluated with regards to three canonical wall-bounded flows: turbulent boundary layer, turbulent channel flow, and turbulent pipe flow. The Frictional Drag encompasses four terms: advective vorticity transport, vortex stretching, viscous, and inhomogeneous terms. Drag-reduced channel flow with the slip condition is used to test the reliability of the formula. The advective vorticity transport and vortex stretching terms are found to dominate the contributions to the Frictional Drag.
Junsun Ahn - One of the best experts on this subject based on the ideXlab platform.
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influence of a large eddy breakup device on the Frictional Drag in a turbulent boundary layer
Physics of Fluids, 2017Co-Authors: Joonseok Kim, Min Yoon, Junsun Ahn, Jinyul Hwang, Hyung Jin SungAbstract:A direct numerical simulation of a spatially developing turbulent boundary layer with a large-eddy breakup (LEBU) device was performed to investigate the influence of the LEBU device on the near-wall turbulence and Frictional Drag. The LEBU device, which is thin and rectangular in shape, was located at 80% of the boundary layer thickness (δ). The LEBU device reduced the skin-friction coefficient (Cf) up to 17%. The breakdown of the outer structures passing through the LEBU device reduced the energy of the long wavelength motions (λz+>200) along the wall-normal direction. The reduction of Cf mainly arose from the contribution of the Reynolds shear stress by the difference in the spatial coherence of the outer high- and low-speed structures. We investigated the relationship between the large-scale motions and the velocity–vorticity correlations (vωz and −wωy), which directly contribute to Cf. The contributions of vωz and −wωy accounted for 80% of the total Cf reduction. The amount of the Cf reduction induce...
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Contribution of velocity-vorticity correlations to the Frictional Drag in wall-bounded turbulent flows
Physics of Fluids, 2016Co-Authors: Min Yoon, Junsun Ahn, Jinyul Hwang, Hyung Jin SungAbstract:The relationship between the Frictional Drag and the velocity-vorticity correlations in wall-bounded turbulent flows is derived from the mean vorticity equation. A formula for the skin friction coefficient is proposed and evaluated with regards to three canonical wall-bounded flows: turbulent boundary layer, turbulent channel flow, and turbulent pipe flow. The Frictional Drag encompasses four terms: advective vorticity transport, vortex stretching, viscous, and inhomogeneous terms. Drag-reduced channel flow with the slip condition is used to test the reliability of the formula. The advective vorticity transport and vortex stretching terms are found to dominate the contributions to the Frictional Drag.
