Passive scalar intermittency in compressible flow

A compressible generalization of the Kraichnan model [Phys. Rev. Lett. 72, 1016 (1994)] of passive scalar advection is considered. The dynamical role of compressibility on the intermittency of the scalar statistics is investi gated for the direct cascade regime. Simple physical arguments suggest that an enhanced intermittency should appear for increasing compressibility, du e to the slowing down of Lagrangian trajectory separations. This is confirm ed by a numerical study of the dependence of intermittency exponents on the degree of compressibility, by a Lagrangian method for calculating simultan eous N-point tracer correlations. [S1063-651X(99)51008-8].