The Experts below are selected from a list of 3369 Experts worldwide ranked by ideXlab platform
Hiroki Saito - One of the best experts on this subject based on the ideXlab platform.
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benard von karman Vortex Street in an exciton polariton superfluid
Physical Review B, 2012Co-Authors: Hiroki Saito, Tomohiko Aioi, Tsuyoshi KadokuraAbstract:The dynamics of an exciton-polariton superfluid resonantly injected into a semiconductor microcavity are investigated numerically. The results reveal that a B\'enard\char21{}von K\'arm\'an Vortex Street is generated in the wake behind an obstacle potential, in addition to the generation of quantized Vortex dipoles and dark solitons. The Vortex Street can be observed in the presence of a disorder potential in a realistic sample, and it can be observed even in time-integrated measurements.
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benard von karman Vortex Street in a bose einstein condensate
Physical Review Letters, 2010Co-Authors: Kazuki Sasaki, Naoya Suzuki, Hiroki SaitoAbstract:Vortex shedding from an obstacle potential moving in a Bose-Einstein condensate is investigated. Long-lived alternately aligned Vortex pairs are found to form in the wake, which is similar to the Benard-von Karman Vortex Street in classical viscous fluids. Various patterns of Vortex shedding are systematically studied and the drag force on the obstacle is calculated. It is shown that the phenomenon can be observed in a trapped system.
Yuren Shi - One of the best experts on this subject based on the ideXlab platform.
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benard von karman Vortex Street in a dipolar bose einstein condensate
Physica A-statistical Mechanics and Its Applications, 2021Co-Authors: Yongzhen Zhao, Yuren ShiAbstract:Abstract The Benard–von Karman Vortex Street in dipolar Bose–Einstein Condensate trapped by a harmonic potential is investigated numerically. The results show that when the velocity of the obstacle potential increases to a certain value and for a suitable potential width, the Vortex pairs released from the moving obstacle potential alternately will form a periodic anti-symmetric double-row in dipolar BEC, and forming a Benard-von Karman Vortex Street. The influence of the dipole interaction strength, the width and the velocity of the obstacle potential on the Vortex structure produced in the wake is also studied, and the structure of the phase diagram is obtained. The drag force on the obstacles potential is calculated, and the mechanical mechanism of Vortex pair is analyzed.
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benard von karman Vortex Street in a spin orbit coupled bose einstein condensate
Physical Review E, 2020Co-Authors: Xueying Yang, Na Tang, Zhikun Zhou, Lin Song, Juan Zhang, Yuren ShiAbstract:The dynamics of pseudo-spin-1/2 Bose-Einstein condensates with weak spin-orbit coupling through a moving obstacle potential are studied numerically. Four types of wakes are observed and the phase diagrams are determined for different spin-orbit coupling strengths. The conditions to form B\'enard--von K\'arm\'an Vortex Street are rather rigorous, and we investigate in detail the dynamical characteristics of the Vortex Streets. The two point vortices in a pair rotate around their center, and the angular velocity and their distance oscillate periodically. The oscillation intensifies with increasing spin-orbit coupling strengths, and it makes part of the Vortex pairs dissociate into separate vortices or combine into single ones and destroys the Vortex Street in the end. The width $b$ of the Street and the distance $l$ between two consecutive Vortex pairs of the same circulation are determined by the potential radius and its moving velocity, respectively. The $b/l$ ratios are independent of the spin-orbit coupling strength and fall in the range $0.19--0.27$, which is a little smaller than the stability criterion 0.28 for classical fluids. Proper $b/l$ ratios are necessary to form B\'enard--von K\'arm\'an Vortex Street, but the spin-orbit coupling strength affects the stability of the Street patterns. Finally, we propose a protocol to experimentally realize the Vortex Street in $^{87}\mathrm{Rb}$ spin-orbit-coupling Bose-Einstein condensates.
Yongil Shin - One of the best experts on this subject based on the ideXlab platform.
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Observation of von Kármán Vortex Street in an Atomic Superfluid Gas
'American Physical Society (APS)', 2018Co-Authors: Woo Jin Kwon, Joon Hyun Kim, Sang Won Seo, Yongil ShinAbstract:We report on the experimental observation of Vortex cluster shedding from a moving obstacle in an oblate atomic Bose-Einstein condensate. At low obstacle velocities v above a critical value, Vortex clusters consisting of two like-sign vortices are generated to form a regular configuration like a von Kármán Street, and as v is increased, the shedding pattern becomes irregular with many different kinds of Vortex clusters. In particular, we observe that the Stouhal number associated with the shedding frequency exhibits saturation behavior with increasing v. The regular-to-turbulent transition of the Vortex cluster shedding reveals remarkable similarities between a superfluid and a classical viscous fluid. Our work opens a new direction for experimental investigations of the superfluid Reynolds number characterizing universal superfluid hydrodynamics. © 2016 American Physical Society117171sciescopu
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observation of von karman Vortex Street in an atomic superfluid gas
Physical Review Letters, 2016Co-Authors: Woo Jin Kwon, Joon Hyun Kim, Sang Won Seo, Yongil ShinAbstract:We report on the experimental observation of Vortex cluster shedding from a moving obstacle in an oblate atomic Bose-Einstein condensate. At low obstacle velocities v above a critical value, Vortex clusters consisting of two like-sign vortices are generated to form a regular configuration like a von Karman Street, and as v is increased, the shedding pattern becomes irregular with many different kinds of Vortex clusters. In particular, we observe that the Stouhal number associated with the shedding frequency exhibits saturation behavior with increasing v. The regular-to-turbulent transition of the Vortex cluster shedding reveals remarkable similarities between a superfluid and a classical viscous fluid. Our work opens a new direction for experimental investigations of the superfluid Reynolds number characterizing universal superfluid hydrodynamics.
Degroote Joris - One of the best experts on this subject based on the ideXlab platform.
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Investigation of the gap Vortex Street in densely packed tube arrays in axial flow using CFD and experiments
International Centre for Numerical Methods in Engineering CIMNE, 2020Co-Authors: Dolfen Henri, Bertocchi F., Rohde M., Vierendeels Jan, Degroote Joris, Owen Roger, De Borst Rene, Reese Jason, Pearce ChrisAbstract:Axial flow in tube bundles with small pitch-to-diameter ratio, a geometry encountered in nuclear reactor cores and heat exchangers, often displays periodic fluctuations. A significant velocity discrepancy between the inter-cylinder gap and subchannel center originates from the difference in through-flow area, feeding an instability. As it is associated with velocity-shear, it is similar to the Kelvin-Helmholtz type and the term 'gap instability' is adopted. A Vortex Street arises and structural vibration of the cylinders might develop due to the fluctuating pressure. Numerical simulations of this phenomenon were performed. The computational domain was constructed to match the most important geometrical features of an experimental setup. The bundle consists of 7 steel tubes in triangular array, placed in a hexagonal conduit. A flexible segment made of silicone is embedded in the central tube, with both extremes clamped to the steel parts of the cylinder. In the experiment, data of the fluctuating velocity was gathered using laser Doppler anemometry measurements. As first step, a completely rigid structure was considered. Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations were used to test if this particular geometry also triggers the gap Vortex Street, which was the case. The phenomenon clearly appears as oscillations of the velocity components. Subsequently, fluid-structure interaction (FSI) simulations, taking into account the flexible part, allowed to assess the effect of the fluctuating flow field on the structure. A comparison between one-way and two-way coupled simulations was made.
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Investigation of the gap Vortex Street in densely packed tube arrays in axial flow using CFD and experiments
International Centre for Numerical Methods in Engineering CIMNE, 2020Co-Authors: Dolfen Henri, Bertocchi F., Rohde M., Vierendeels Jan, Degroote JorisAbstract:Axial flow in tube bundles with small pitch-to-diameter ratio, a geometry encountered in nuclear reactor cores and heat exchangers, often displays periodic fluctuations. A significant velocity discrepancy between the inter-cylinder gap and subchannel center originates from the difference in through-flow area, feeding an instability. As it is associated with velocity-shear, it is similar to the Kelvin-Helmholtz type and the term 'gap instability' is adopted. A Vortex Street arises and structural vibration of the cylinders might develop due to the fluctuating pressure. Numerical simulations of this phenomenon were performed. The computational domain was constructed to match the most important geometrical features of an experimental setup. The bundle consists of 7 steel tubes in triangular array, placed in a hexagonal conduit. A flexible segment made of silicone is embedded in the central tube, with both extremes clamped to the steel parts of the cylinder. In the experiment, data of the fluctuating velocity was gathered using laser Doppler anemometry measurements. As first step, a completely rigid structure was considered. Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations were used to test if this particular geometry also triggers the gap Vortex Street, which was the case. The phenomenon clearly appears as oscillations of the velocity components. Subsequently, fluid-structure interaction (FSI) simulations, taking into account the flexible part, allowed to assess the effect of the fluctuating flow field on the structure. A comparison between one-way and two-way coupled simulations was made.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.RST/Reactor Physics and Nuclear Material
Dolfen Henri - One of the best experts on this subject based on the ideXlab platform.
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Investigation of the gap Vortex Street in densely packed tube arrays in axial flow using CFD and experiments
International Centre for Numerical Methods in Engineering CIMNE, 2020Co-Authors: Dolfen Henri, Bertocchi F., Rohde M., Vierendeels Jan, Degroote Joris, Owen Roger, De Borst Rene, Reese Jason, Pearce ChrisAbstract:Axial flow in tube bundles with small pitch-to-diameter ratio, a geometry encountered in nuclear reactor cores and heat exchangers, often displays periodic fluctuations. A significant velocity discrepancy between the inter-cylinder gap and subchannel center originates from the difference in through-flow area, feeding an instability. As it is associated with velocity-shear, it is similar to the Kelvin-Helmholtz type and the term 'gap instability' is adopted. A Vortex Street arises and structural vibration of the cylinders might develop due to the fluctuating pressure. Numerical simulations of this phenomenon were performed. The computational domain was constructed to match the most important geometrical features of an experimental setup. The bundle consists of 7 steel tubes in triangular array, placed in a hexagonal conduit. A flexible segment made of silicone is embedded in the central tube, with both extremes clamped to the steel parts of the cylinder. In the experiment, data of the fluctuating velocity was gathered using laser Doppler anemometry measurements. As first step, a completely rigid structure was considered. Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations were used to test if this particular geometry also triggers the gap Vortex Street, which was the case. The phenomenon clearly appears as oscillations of the velocity components. Subsequently, fluid-structure interaction (FSI) simulations, taking into account the flexible part, allowed to assess the effect of the fluctuating flow field on the structure. A comparison between one-way and two-way coupled simulations was made.
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Investigation of the gap Vortex Street in densely packed tube arrays in axial flow using CFD and experiments
International Centre for Numerical Methods in Engineering CIMNE, 2020Co-Authors: Dolfen Henri, Bertocchi F., Rohde M., Vierendeels Jan, Degroote JorisAbstract:Axial flow in tube bundles with small pitch-to-diameter ratio, a geometry encountered in nuclear reactor cores and heat exchangers, often displays periodic fluctuations. A significant velocity discrepancy between the inter-cylinder gap and subchannel center originates from the difference in through-flow area, feeding an instability. As it is associated with velocity-shear, it is similar to the Kelvin-Helmholtz type and the term 'gap instability' is adopted. A Vortex Street arises and structural vibration of the cylinders might develop due to the fluctuating pressure. Numerical simulations of this phenomenon were performed. The computational domain was constructed to match the most important geometrical features of an experimental setup. The bundle consists of 7 steel tubes in triangular array, placed in a hexagonal conduit. A flexible segment made of silicone is embedded in the central tube, with both extremes clamped to the steel parts of the cylinder. In the experiment, data of the fluctuating velocity was gathered using laser Doppler anemometry measurements. As first step, a completely rigid structure was considered. Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations were used to test if this particular geometry also triggers the gap Vortex Street, which was the case. The phenomenon clearly appears as oscillations of the velocity components. Subsequently, fluid-structure interaction (FSI) simulations, taking into account the flexible part, allowed to assess the effect of the fluctuating flow field on the structure. A comparison between one-way and two-way coupled simulations was made.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.RST/Reactor Physics and Nuclear Material
