LOW-WAVE-NUMBER STATISTICS OF RANDOMLY ADVECTED PASSIVE SCALARS

A heuristic analysis of the decay of a passive scalar field, subject t o statistically steady random advection, predicts two low-wave-number spectral scaling regimes analogous to the similarity states previously identified by Chasnov [Phys. Fluids 6, 1036 (1994)]. Consequences of their predicted coexistence in a single flow are examined. The analysi s is limited to the idealized case of narrow band advection. To comple ment the analysis, and to extend the predictions to physically more re alistic advection processes, advection diffusion is simulated using a one-dimensional stochastic model. An experimental test of the predicti ons is proposed.