ON THE TURBULENT TRANSPORT OF A PASSIVE SCALAR BY ANISOTROPIC TURBULENCE

The effect of anisotropic turbulence on the vertical transport of a tr acer in a fluid layer is investigated numerically. It is found that fo r a fixed vertical turbulence spectrum an increase in the intensity of horizontal turbulence reduces the efficiency of the vertical transpor t. The reduction factor is inversely proportional to the anisotropy (d efined as the ratio of horizontal to vertical rms velocities) for larg e Peclet numbers. This effect had been overlooked in studies of turbul ent particle transport in stratified media, where the reduction in ver tical transport coefficients was entirely attributed to vertical mode suppression by stratification. Our study is based on Gaussian velocity fields. (C) 1996 American Institute of Physics.