Streamwise inhomogeneity of decaying grid turbulence

Accounting for the streamwise inhomogeneity of turbulence in Kolmogorov's equation for the third-order moment of the velocity increment between two points allows compliance with two important classical results. These are retrieved when the separation between the points either exceeds the integral length scale or becomes comparable to the Kolmogorov length scale. In the context of decaying grid turbulence, the results correspond to the mean turbulent energy equation and the Batchelor-Townsend equation for the decay of the mean-squared vorticity. Analogous results are obtained when the streamwise inhomogeneity is included in Yaglom's equation. The form of the inhomogeneous term is illustrated and discussed in the context of measurements in a turbulent grid flow. (C) 2000 American Institute of Physics. [S1070-6631(00)50612-6].