Effect of gradient production on scalar fluctuations in decaying grid turbulence

A generalized form of Yaglom's equation, in which the effect of turbulent production of temperature fluctuations is taken into account, is derived. The modified Yaglom equation (which extends the work of Danaila et al. [J. Fluid Mech. 391, 359 (1999)] to incorporate the effects of decay and production) is compared with experimental data. The flow under consideration is decaying grid turbulence with an imposed mean temperature gradient (Mydlarski and Warhaft [J. Fluid Mech. 358, 135 (1998)]). The agreement between theory and experiment is good and the effects of nonhomogeneities in the flow are small.