The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Xavier Obradors - One of the best experts on this subject based on the ideXlab platform.
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anisotropy and Strength of Vortex pinning centers in yba2cu3o7 x coated conductors
Applied Physics Letters, 2007Co-Authors: J Gutierrez, Teresa Puig, Xavier ObradorsAbstract:An experimental powerful methodology is proposed to evaluate and quantify the anisotropy and Strength of the different pinning contributions of YBa2Cu3O7−x coated conductors by combining angular dependent in-field critical current measurements in the whole temperature range. A clear separation between isotropic and anisotropic pinning centers and a further classification into weak and strong pinning centers are performed. These analyses envision to establish a correlation between defect microstructure and critical currents which is essential for artificial engineering high-performance nanostructured coated conductors.
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Anisotropy and Strength of Vortex pinning centers in YBa2Cu3O7−x coated conductors
Applied Physics Letters, 2007Co-Authors: J Gutierrez, Teresa Puig, Xavier ObradorsAbstract:An experimental powerful methodology is proposed to evaluate and quantify the anisotropy and Strength of the different pinning contributions of YBa2Cu3O7−x coated conductors by combining angular dependent in-field critical current measurements in the whole temperature range. A clear separation between isotropic and anisotropic pinning centers and a further classification into weak and strong pinning centers are performed. These analyses envision to establish a correlation between defect microstructure and critical currents which is essential for artificial engineering high-performance nanostructured coated conductors.
J Gutierrez - One of the best experts on this subject based on the ideXlab platform.
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anisotropy and Strength of Vortex pinning centers in yba2cu3o7 x coated conductors
Applied Physics Letters, 2007Co-Authors: J Gutierrez, Teresa Puig, Xavier ObradorsAbstract:An experimental powerful methodology is proposed to evaluate and quantify the anisotropy and Strength of the different pinning contributions of YBa2Cu3O7−x coated conductors by combining angular dependent in-field critical current measurements in the whole temperature range. A clear separation between isotropic and anisotropic pinning centers and a further classification into weak and strong pinning centers are performed. These analyses envision to establish a correlation between defect microstructure and critical currents which is essential for artificial engineering high-performance nanostructured coated conductors.
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Anisotropy and Strength of Vortex pinning centers in YBa2Cu3O7−x coated conductors
Applied Physics Letters, 2007Co-Authors: J Gutierrez, Teresa Puig, Xavier ObradorsAbstract:An experimental powerful methodology is proposed to evaluate and quantify the anisotropy and Strength of the different pinning contributions of YBa2Cu3O7−x coated conductors by combining angular dependent in-field critical current measurements in the whole temperature range. A clear separation between isotropic and anisotropic pinning centers and a further classification into weak and strong pinning centers are performed. These analyses envision to establish a correlation between defect microstructure and critical currents which is essential for artificial engineering high-performance nanostructured coated conductors.
Wolfgang Schröder - One of the best experts on this subject based on the ideXlab platform.
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direct particle fluid simulation of kolmogorov length scale size particles in decaying isotropic turbulence
Journal of Fluid Mechanics, 2017Co-Authors: Lennart Schneiders, Matthias Meinke, Wolfgang SchröderAbstract:The modulation of decaying isotropic turbulence by 45 000 spherical particles of Kolmogorov-length-scale size is studied using direct particle–fluid simulations, i.e. the flow field over each particle is fully resolved by direct numerical simulations of the conservation equations. A Cartesian cut-cell method is used by which the exchange of momentum and energy at the fluid–particle interfaces is strictly conserved. It is shown that the particles absorb energy from the large scales of the carrier flow while the small-scale turbulent motion is determined by the inertial particle dynamics. Whereas the viscous dissipation rate of the bulk flow is attenuated, the particles locally increase the level of dissipation due to the intense strain rate generated near the particle surfaces due to the crossing-trajectory effect. Analogously, the rotational motion of the particles decouples from the local fluid vorticity and strain-rate field at increasing particle inertia. The high level of dissipation is partially compensated by the transfer of momentum to the fluid via forces acting at the particle surfaces. The spectral analysis of the kinetic energy budget is supported by the average flow pattern about the particles showing a nearly universal strain-rate distribution. An analytical expression for the instantaneous rate of viscous dissipation induced by each particle is derived and subsequently verified numerically. Using this equation, the local balance of fluid kinetic energy around a particle of arbitrary shape can be precisely determined. It follows that two-way coupled point-particle models implicitly account for the particle-induced dissipation rate via the momentum-coupling terms; however, they disregard the actual length scales of the interaction. Finally, an analysis of the small-scale flow topology shows that the Strength of Vortex stretching in the bulk flow is mitigated due to the presence of the particles. This effect is associated with the energy conversion at small wavenumbers and the reduced level of dissipation at intermediate wavenumbers. Consequently, it damps the spectral flux of energy to the small scales.
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Direct particle–fluid simulation of Kolmogorov-length-scale size particles in decaying isotropic turbulence
Journal of Fluid Mechanics, 2017Co-Authors: Lennart Schneiders, Matthias Meinke, Wolfgang SchröderAbstract:The modulation of decaying isotropic turbulence by 45 000 spherical particles of Kolmogorov-length-scale size is studied using direct particle–fluid simulations, i.e. the flow field over each particle is fully resolved by direct numerical simulations of the conservation equations. A Cartesian cut-cell method is used by which the exchange of momentum and energy at the fluid–particle interfaces is strictly conserved. It is shown that the particles absorb energy from the large scales of the carrier flow while the small-scale turbulent motion is determined by the inertial particle dynamics. Whereas the viscous dissipation rate of the bulk flow is attenuated, the particles locally increase the level of dissipation due to the intense strain rate generated near the particle surfaces due to the crossing-trajectory effect. Analogously, the rotational motion of the particles decouples from the local fluid vorticity and strain-rate field at increasing particle inertia. The high level of dissipation is partially compensated by the transfer of momentum to the fluid via forces acting at the particle surfaces. The spectral analysis of the kinetic energy budget is supported by the average flow pattern about the particles showing a nearly universal strain-rate distribution. An analytical expression for the instantaneous rate of viscous dissipation induced by each particle is derived and subsequently verified numerically. Using this equation, the local balance of fluid kinetic energy around a particle of arbitrary shape can be precisely determined. It follows that two-way coupled point-particle models implicitly account for the particle-induced dissipation rate via the momentum-coupling terms; however, they disregard the actual length scales of the interaction. Finally, an analysis of the small-scale flow topology shows that the Strength of Vortex stretching in the bulk flow is mitigated due to the presence of the particles. This effect is associated with the energy conversion at small wavenumbers and the reduced level of dissipation at intermediate wavenumbers. Consequently, it damps the spectral flux of energy to the small scales.
S. Sekhavat - One of the best experts on this subject based on the ideXlab platform.
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High-reynolds number flow around coated symmetrical hydrofoil: effect of streamwise slip on drag force and Vortex structures
Journal of Marine Science and Technology, 2019Co-Authors: M. R. Rastan, S. Foshat, S. SekhavatAbstract:Effects of slip on the flow around a symmetrical hydrofoil with a blunt trailing-edge are numerically investigated at Reynolds numbers of $$Re=5 \times {10^6}$$ R e = 5 × 10 6 , $$12.5 \times {10^6}$$ 12.5 × 10 6 and $$25 \times {10^6}$$ 25 × 10 6 based on the free-stream velocity and chord length. The simulations are performed by applying a two-dimensional Unsteady Reynolds–Averaged Navier–Stokes (URANS) approach and SST k–ω turbulence model. Furthermore, the Navier boundary condition with different slip lengths ( $${L_{\text{s}}}=\;{\text{2}},{\text{ 35 and 7}}0$$ L s = 2 , 35 and 7 0 µm) is employed on the surfaces. The results indicate that the L _s has a considerable effect on the integral parameters and a moderate influence on the wake flow structure. As such, a massive drag reduction (up to 47%) is observed, and an increase of L _s causes the increase of both frictional and pressure drag reduction rate. It is shown that a noticeable drag reduction can be achieved when the non-dimensional slip length is larger than one. The increment of slip length also leads to increase the amplitude of force fluctuations and frequency of Vortex shedding; besides, the Strength of Vortex structures and the turbulence intensities are augmented.
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High-reynolds number flow around coated symmetrical hydrofoil: effect of streamwise slip on drag force and Vortex structures
Journal of Marine Science and Technology, 2018Co-Authors: M. R. Rastan, S. Foshat, S. SekhavatAbstract:Effects of slip on the flow around a symmetrical hydrofoil with a blunt trailing-edge are numerically investigated at Reynolds numbers of $$Re=5 \times {10^6}$$ , $$12.5 \times {10^6}$$ and $$25 \times {10^6}$$ based on the free-stream velocity and chord length. The simulations are performed by applying a two-dimensional Unsteady Reynolds–Averaged Navier–Stokes (URANS) approach and SST k–ω turbulence model. Furthermore, the Navier boundary condition with different slip lengths ( $${L_{\text{s}}}=\;{\text{2}},{\text{ 35 and 7}}0$$ µm) is employed on the surfaces. The results indicate that the Ls has a considerable effect on the integral parameters and a moderate influence on the wake flow structure. As such, a massive drag reduction (up to 47%) is observed, and an increase of Ls causes the increase of both frictional and pressure drag reduction rate. It is shown that a noticeable drag reduction can be achieved when the non-dimensional slip length is larger than one. The increment of slip length also leads to increase the amplitude of force fluctuations and frequency of Vortex shedding; besides, the Strength of Vortex structures and the turbulence intensities are augmented.
Teresa Puig - One of the best experts on this subject based on the ideXlab platform.
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anisotropy and Strength of Vortex pinning centers in yba2cu3o7 x coated conductors
Applied Physics Letters, 2007Co-Authors: J Gutierrez, Teresa Puig, Xavier ObradorsAbstract:An experimental powerful methodology is proposed to evaluate and quantify the anisotropy and Strength of the different pinning contributions of YBa2Cu3O7−x coated conductors by combining angular dependent in-field critical current measurements in the whole temperature range. A clear separation between isotropic and anisotropic pinning centers and a further classification into weak and strong pinning centers are performed. These analyses envision to establish a correlation between defect microstructure and critical currents which is essential for artificial engineering high-performance nanostructured coated conductors.
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Anisotropy and Strength of Vortex pinning centers in YBa2Cu3O7−x coated conductors
Applied Physics Letters, 2007Co-Authors: J Gutierrez, Teresa Puig, Xavier ObradorsAbstract:An experimental powerful methodology is proposed to evaluate and quantify the anisotropy and Strength of the different pinning contributions of YBa2Cu3O7−x coated conductors by combining angular dependent in-field critical current measurements in the whole temperature range. A clear separation between isotropic and anisotropic pinning centers and a further classification into weak and strong pinning centers are performed. These analyses envision to establish a correlation between defect microstructure and critical currents which is essential for artificial engineering high-performance nanostructured coated conductors.