ON HOW A JOINT INTERACTION OF 2 INNOCENT PARTNERS (SMOOTH ADVECTION AND LINEAR DAMPING) PRODUCES A STRONG INTERMITTENCY

Forced advection of passive scalar by a smooth d-dimensional incompres sible velocity in the presence of linear damping is studied. Acting se parately advection and damping do not lead to an essential intermitten cy of the steady scalar statistics, while being mixed together produce a very strong non-Gaussianity in the convective range: 2n-th moment o f scalar difference, ([theta(t;r) - theta(t;0)](2n)] is proportional t o r xi(2n,) xi(2n) = min{2n,root d(2)/4+2 alpha dn/[(d-1)D]- d/2}, whe re alpha/D measures the rate of the damping in the units of the stretc hing rate. The probability density function (PDF) of the scalar differ ence is also found. (C) 1998 American Institute of Physics. [S1070-663 1(98)02811-6].