Journal of Fluid Mechanics

Dependence of the non-stationary form of Yaglom’s equation on the Schmidt number

P. ORLANDI a1 and R. A. ANTONIA a2
a1 Departimento di Meccanica e Aeronautica, Universita Degli Studi di Roma ‘La Sapienza’, 00184 Rome, Italy
a2 Department of Mechanical Engineering, University of Newcastle, N.S.W. 2308, Australia


The dynamic equation for the second-order moment of a passive scalar increment is investigated in the context of DNS data for decaying isotropic turbulence at several values of the Schmidt number Sc, between 0.07 and 7. When the terms of the equation are normalized using Kolmogorov and Batchelor scales, approximate independence from Sc is achieved at sufficiently small rB (r is the separation across which the increment is estimated and ηB is the Batchelor length scale). The results imply approximate independence of the mixed velocity-scalar derivative skewness from Sc and underline the importance of the non-stationarity. At small rB, the contribution from the non-stationarity increases as Sc increases.

(Received August 7 2001)
(Revised September 26 2001)