ISSN:
1089-7674
Source:
AIP Digital Archive
Topics:
Physics
Notes:
A two-dimensional [2d(x,y)] fluid code has been developed to explore nonlocal dissipative drift-wave turbulence and anomalous transport. In order to obtain steady-state turbulence, the y-averaged fluctuating density 〈n〉 has been forced to be zero in simulations, thus the difficulty of choosing proper sources and sinks in turbulence simulation codes has been avoided. If Ln(very-much-greater-than)Lc or Lαlc(very-much-greater-than)Lc, where Ln is the density gradient scale length, Lc the turbulence correlation length Lc, and Lαlc the adiabaticity-layer width, it has been shown that "local'' turbulence simulations give reasonable results. However, for Ln∼Lc, or Lαlc∼Lc "local'' turbulence codes are found to overestimate the flux. For a family of hyperbolic tangent background density profiles, n0(x)=nm−n1 tanh[(2x−Lx)/2Δn] with n1〈0.5nm, it has been demonstrated that the nonlocality of the turbulence leads to a transition from local gyro-Bohm (Dlocal(approximately-equal-to)7.6(Te/eB)[ρs/Ln(x)] [αlc(x)/0.01]−1/3), where αlc(x)=α(x)/κ(x)〈1, to nonlocal gyro-Bohm transport scaling [Dnonlocal(approximately-equal-to)7.6(Te/eB)(n1ρs/nmΔn) (αnlc/0.01)−1/3(Δn/40ρs)2/5 for αnlc(x)=α/κmax〈1, κ(x)=ρs/Ln(x) and α=k2(parallel)χe]. For the case Φ0(x)=−n0(x) with the model hyperbolic tangent density profiles n0(x), velocity shear increases the turbulence flux by 230% and the root-mean-square (RMS) fluctuating density by 36%. Otherwise, for Φ0(x)=n0(x), the turbulence flux is reduced by 71% and the RMS value of fluctuating density is decreased by 31% by velocity shear effects. © 1995 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.871420
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