Fluid simulations of nonlocal dissipative drift‐wave turbulence

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≫Lc or Lαlc≫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≂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 scali...