The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Kstar Team - One of the best experts on this subject based on the ideXlab platform.
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propagation dynamics associated with resonant magnetic Perturbation fields in high confinement mode plasmas inside the kstar tokamak
Physical Review Letters, 2017Co-Authors: W W Xiao, Y.m. Jeon, Y K Oh, George R. Tynan, S. W. Yoon, T E Evans, W.h. Ko, Kstar TeamAbstract:Author(s): Xiao, WW; Evans, TE; Tynan, GR; Yoon, SW; Jeon, YM; Ko, WH; Nam, YU; Oh, YK; KSTAR team | Abstract: The propagation dynamics of resonant magnetic Perturbation fields in KSTAR H-mode plasmas with injection of small edge Perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the Perturbation field first excites a plasma response on the q=3 magnetic surface and then propagates inward to the q=2 surface with a radially averaged propagation velocity of resonant magnetic Perturbations field equal to 32.5 m/ s. As a result, the Perturbation field brakes the toroidal rotation on the q=3 surface first causing a momentum transport Perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic Perturbations field is larger than the radial propagation velocity of the Perturbation in the toroidal rotation.
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propagation dynamics associated with resonant magnetic Perturbation fields in high confinement mode plasmas inside the kstar tokamak
Physical Review Letters, 2017Co-Authors: W W Xiao, Y.m. Jeon, George R. Tynan, S. W. Yoon, T E Evans, Y U Nam, Kstar TeamAbstract:The propagation dynamics of resonant magnetic Perturbation fields in KSTAR H-mode plasmas with injection of small edge Perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the Perturbation field first excites a plasma response on the q=3 magnetic surface and then propagates inward to the q=2 surface with a radially averaged propagation velocity of resonant magnetic Perturbations field equal to 32.5 m/ s. As a result, the Perturbation field brakes the toroidal rotation on the q=3 surface first causing a momentum transport Perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic Perturbations field is larger than the radial propagation velocity of the Perturbation in the toroidal rotation.
W W Xiao - One of the best experts on this subject based on the ideXlab platform.
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propagation dynamics associated with resonant magnetic Perturbation fields in high confinement mode plasmas inside the kstar tokamak
Physical Review Letters, 2017Co-Authors: W W Xiao, Y.m. Jeon, Y K Oh, George R. Tynan, S. W. Yoon, T E Evans, W.h. Ko, Kstar TeamAbstract:Author(s): Xiao, WW; Evans, TE; Tynan, GR; Yoon, SW; Jeon, YM; Ko, WH; Nam, YU; Oh, YK; KSTAR team | Abstract: The propagation dynamics of resonant magnetic Perturbation fields in KSTAR H-mode plasmas with injection of small edge Perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the Perturbation field first excites a plasma response on the q=3 magnetic surface and then propagates inward to the q=2 surface with a radially averaged propagation velocity of resonant magnetic Perturbations field equal to 32.5 m/ s. As a result, the Perturbation field brakes the toroidal rotation on the q=3 surface first causing a momentum transport Perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic Perturbations field is larger than the radial propagation velocity of the Perturbation in the toroidal rotation.
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propagation dynamics associated with resonant magnetic Perturbation fields in high confinement mode plasmas inside the kstar tokamak
Physical Review Letters, 2017Co-Authors: W W Xiao, Y.m. Jeon, George R. Tynan, S. W. Yoon, T E Evans, Y U Nam, Kstar TeamAbstract:The propagation dynamics of resonant magnetic Perturbation fields in KSTAR H-mode plasmas with injection of small edge Perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the Perturbation field first excites a plasma response on the q=3 magnetic surface and then propagates inward to the q=2 surface with a radially averaged propagation velocity of resonant magnetic Perturbations field equal to 32.5 m/ s. As a result, the Perturbation field brakes the toroidal rotation on the q=3 surface first causing a momentum transport Perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic Perturbations field is larger than the radial propagation velocity of the Perturbation in the toroidal rotation.
Brian F Farrell - One of the best experts on this subject based on the ideXlab platform.
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the mechanism by which nonlinearity sustains turbulence in plane couette flow
Journal of Physics: Conference Series, 2018Co-Authors: Mariosandreas Nikolaidis, Brian F Farrell, Petros J IoannouAbstract:Turbulence in wall-bounded shear flow results from a synergistic interaction between linear non-normality and nonlinearity in which non-normal growth of a subset of Perturbations configured to transfer energy from the externally forced component of the turbulent state to the Perturbation component maintains the Perturbation energy, while the subset of energy-transferring Perturbations is replenished by nonlinearity. Although it is accepted that both linear non-normality mediated energy transfer from the forced component of the mean flow and nonlinear interactions among Perturbations are required to maintain the turbulent state, the detailed physical mechanism by which these processes interact in maintaining turbulence has not been determined. In this work a statistical state dynamics based analysis is performed on turbulent Couette flow at R = 600 and a comparison to DNS is used to demonstrate that the Perturbation component in Couette flow turbulence is replenished by a non-normality mediated parametric growth process in which the fluctuating streamwise mean flow has been adjusted to marginal Lyapunov stability. It is further shown that the alternative mechanism in which the subspace of non-normally growing Perturbations is maintained directly by Perturbation-Perturbation nonlinearity does not contribute to maintaining the turbulent state. This work identifies parametric interaction between the fluctuating streamwise mean flow and the streamwise varying Perturbations to be the mechanism of the nonlinear interaction maintaining the Perturbation component of the turbulent state, and identifies the associated Lyapunov vectors with positive energetics as the structures of the Perturbation subspace supporting the turbulence.
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gravity waves in a horizontal shear flow part ii interaction between gravity waves and potential vorticity Perturbations
Journal of Physical Oceanography, 2009Co-Authors: Nikolaos A Bakas, Brian F FarrellAbstract:Interaction among potential vorticity Perturbations and propagating internal gravity waves in a horizontally sheared zonal flow is investigated. In the strong stratification limit, an initial vorticity Perturbation weakly excites two propagating gravity waves while the density component of the potential vorticity Perturbation is significantly amplified, potentially leading to convective collapse. If stratification is sufficiently weak, a strong coupling between vorticity Perturbations and gravity waves is found and spontaneous gravity wave generation occurs. This coupling can be traced to the nonnormal interaction between the potential vorticity and gravity wave manifolds in the weak stratification limit. Vorticity Perturbations amplify in energy due to downgradient Reynolds stress when their phase lines tilt against the shear and the large growth attained is transferred to propagating gravity waves. When the flow geometry is such that the excited gravity waves are confined in the vicinity of the vorticity Perturbation by their trapping levels, an overall convective collapse of this region can be anticipated. On the other hand, when the flow geometry permits wave propagation, significant gravity wave emission occurs.
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three dimensional optimal Perturbations in viscous shear flow
Physics of Fluids, 1992Co-Authors: Kathryn M. Butler, Brian F FarrellAbstract:Transition to turbulence in plane channel flow occurs even for conditions under which modes of the linearized dynamical system associated with the flow are stable. In this paper an attempt is made to understand this phenomena by finding the linear three‐dimensional Perturbations that gain the most energy in a given time period. A complete set of Perturbations, ordered by energy growth, is found using variational methods. The optimal Perturbations are not of modal form, and those which grow the most resemble streamwise vortices, which divert the mean flow energy into streaks of streamwise velocity and enable the energy of the Perturbation to grow by as much as three orders of magnitude. It is suggested that excitation of these Perturbations facilitates transition from laminar to turbulent flow. The variational method used to find the optimal Perturbations in a shear flow also allows construction of tight bounds on growth rate and determination of regions of absolute stability in which no Perturbation growth is possible.
S. W. Yoon - One of the best experts on this subject based on the ideXlab platform.
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propagation dynamics associated with resonant magnetic Perturbation fields in high confinement mode plasmas inside the kstar tokamak
Physical Review Letters, 2017Co-Authors: W W Xiao, Y.m. Jeon, Y K Oh, George R. Tynan, S. W. Yoon, T E Evans, W.h. Ko, Kstar TeamAbstract:Author(s): Xiao, WW; Evans, TE; Tynan, GR; Yoon, SW; Jeon, YM; Ko, WH; Nam, YU; Oh, YK; KSTAR team | Abstract: The propagation dynamics of resonant magnetic Perturbation fields in KSTAR H-mode plasmas with injection of small edge Perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the Perturbation field first excites a plasma response on the q=3 magnetic surface and then propagates inward to the q=2 surface with a radially averaged propagation velocity of resonant magnetic Perturbations field equal to 32.5 m/ s. As a result, the Perturbation field brakes the toroidal rotation on the q=3 surface first causing a momentum transport Perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic Perturbations field is larger than the radial propagation velocity of the Perturbation in the toroidal rotation.
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propagation dynamics associated with resonant magnetic Perturbation fields in high confinement mode plasmas inside the kstar tokamak
Physical Review Letters, 2017Co-Authors: W W Xiao, Y.m. Jeon, George R. Tynan, S. W. Yoon, T E Evans, Y U Nam, Kstar TeamAbstract:The propagation dynamics of resonant magnetic Perturbation fields in KSTAR H-mode plasmas with injection of small edge Perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the Perturbation field first excites a plasma response on the q=3 magnetic surface and then propagates inward to the q=2 surface with a radially averaged propagation velocity of resonant magnetic Perturbations field equal to 32.5 m/ s. As a result, the Perturbation field brakes the toroidal rotation on the q=3 surface first causing a momentum transport Perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic Perturbations field is larger than the radial propagation velocity of the Perturbation in the toroidal rotation.
Y.m. Jeon - One of the best experts on this subject based on the ideXlab platform.
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propagation dynamics associated with resonant magnetic Perturbation fields in high confinement mode plasmas inside the kstar tokamak
Physical Review Letters, 2017Co-Authors: W W Xiao, Y.m. Jeon, Y K Oh, George R. Tynan, S. W. Yoon, T E Evans, W.h. Ko, Kstar TeamAbstract:Author(s): Xiao, WW; Evans, TE; Tynan, GR; Yoon, SW; Jeon, YM; Ko, WH; Nam, YU; Oh, YK; KSTAR team | Abstract: The propagation dynamics of resonant magnetic Perturbation fields in KSTAR H-mode plasmas with injection of small edge Perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the Perturbation field first excites a plasma response on the q=3 magnetic surface and then propagates inward to the q=2 surface with a radially averaged propagation velocity of resonant magnetic Perturbations field equal to 32.5 m/ s. As a result, the Perturbation field brakes the toroidal rotation on the q=3 surface first causing a momentum transport Perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic Perturbations field is larger than the radial propagation velocity of the Perturbation in the toroidal rotation.
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propagation dynamics associated with resonant magnetic Perturbation fields in high confinement mode plasmas inside the kstar tokamak
Physical Review Letters, 2017Co-Authors: W W Xiao, Y.m. Jeon, George R. Tynan, S. W. Yoon, T E Evans, Y U Nam, Kstar TeamAbstract:The propagation dynamics of resonant magnetic Perturbation fields in KSTAR H-mode plasmas with injection of small edge Perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the Perturbation field first excites a plasma response on the q=3 magnetic surface and then propagates inward to the q=2 surface with a radially averaged propagation velocity of resonant magnetic Perturbations field equal to 32.5 m/ s. As a result, the Perturbation field brakes the toroidal rotation on the q=3 surface first causing a momentum transport Perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic Perturbations field is larger than the radial propagation velocity of the Perturbation in the toroidal rotation.
