How shear increments affect the flow production branching ratio in CSDX
Abstract
In this study, the coupling of turbulencedriven azimuthal and axial flows in a linear device absent magnetic shear (Controlled Shear Decorrelation Experiment) is investigated. In particular, we examine the apportionment of Reynolds power between azimuthal and axial flows, and how the azimuthal flow shear affects axial flow generation and saturation by drift wave turbulence. We study the response of the energy branching ratio, i.e., ratio of axial and azimuthal Reynolds powers, ${P}_{z}^{R}/{P}_{y}^{R}$, to incremental changes of azimuthal and axial flow shears. We show that increasing azimuthal flow shear decreases the energy branching ratio. When axial flow shear increases, this ratio first increases but then decreases to zero. The axial flow shear saturates below the threshold for parallel shear flow instability. The effects of azimuthal flow shear on the generation and saturation of intrinsic axial flows are analyzed. Azimuthal flow shear slows down the modulational growth of the seed axial flow shear, and thus reduces intrinsic axial flow production. Azimuthal flow shear reduces both the residual Reynolds stress (of axial flow, i.e., ${\Pi}_{xz}^{Res}$) and turbulent viscosity ( ${\chi}_{z}^{DW}$) by the same factor $<{v}_{y}>\text{'}{}^{2}{\Delta}_{x}^{2}{L}_{n}^{2}{\rho}_{s}^{2}{c}_{s}^{2}$, where Δ_{x} is the distance relative to the reference point where $<{v}_{y}>=0$ in the plasma frame. Therefore, the stationary state axial flow shear is not affected by azimuthal flow shear to leading order since $<{v}_{z}>\text{'}~{\Pi}_{xz}^{Res}/{\chi}_{z}^{DW}$.
 Authors:

 Univ. of California, San Diego, CA (United States)
 Publication Date:
 Research Org.:
 Univ. of California, San Diego, CA (United States)
 Sponsoring Org.:
 USDOE Office of Science (SC), Fusion Energy Sciences (FES)
 OSTI Identifier:
 1540215
 Alternate Identifier(s):
 OSTI ID: 1441049
 Grant/Contract Number:
 FG0204ER54738
 Resource Type:
 Accepted Manuscript
 Journal Name:
 Physics of Plasmas
 Additional Journal Information:
 Journal Volume: 25; Journal Issue: 6; Journal ID: ISSN 1070664X
 Publisher:
 American Institute of Physics (AIP)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Citation Formats
Li, J. C., and Diamond, P. H. How shear increments affect the flow production branching ratio in CSDX. United States: N. p., 2018.
Web. doi:10.1063/1.5033911.
Li, J. C., & Diamond, P. H. How shear increments affect the flow production branching ratio in CSDX. United States. https://doi.org/10.1063/1.5033911
Li, J. C., and Diamond, P. H. Thu .
"How shear increments affect the flow production branching ratio in CSDX". United States. https://doi.org/10.1063/1.5033911. https://www.osti.gov/servlets/purl/1540215.
@article{osti_1540215,
title = {How shear increments affect the flow production branching ratio in CSDX},
author = {Li, J. C. and Diamond, P. H.},
abstractNote = {In this study, the coupling of turbulencedriven azimuthal and axial flows in a linear device absent magnetic shear (Controlled Shear Decorrelation Experiment) is investigated. In particular, we examine the apportionment of Reynolds power between azimuthal and axial flows, and how the azimuthal flow shear affects axial flow generation and saturation by drift wave turbulence. We study the response of the energy branching ratio, i.e., ratio of axial and azimuthal Reynolds powers, PzR/PyR, to incremental changes of azimuthal and axial flow shears. We show that increasing azimuthal flow shear decreases the energy branching ratio. When axial flow shear increases, this ratio first increases but then decreases to zero. The axial flow shear saturates below the threshold for parallel shear flow instability. The effects of azimuthal flow shear on the generation and saturation of intrinsic axial flows are analyzed. Azimuthal flow shear slows down the modulational growth of the seed axial flow shear, and thus reduces intrinsic axial flow production. Azimuthal flow shear reduces both the residual Reynolds stress (of axial flow, i.e., ΠxzRes) and turbulent viscosity (χzDW) by the same factor <vy>'2Δx2Ln2ρs2cs2, where Δx is the distance relative to the reference point where <vy>=0 in the plasma frame. Therefore, the stationary state axial flow shear is not affected by azimuthal flow shear to leading order since <vz>'~ΠxzRes/χzDW.},
doi = {10.1063/1.5033911},
journal = {Physics of Plasmas},
number = 6,
volume = 25,
place = {United States},
year = {2018},
month = {6}
}
Web of Science
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Works referencing / citing this record:
Impurity transport driven by parallel velocity shear turbulence in hydrogen isotope plasmas
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 Guo, Weixin; Wang, Lu; Zhuang, Ge
 Nuclear Fusion, Vol. 59, Issue 7