Streamwise inhomogeneity of decaying grid turbulence

Accounting for the streamwise inhomogeneity of turbulence in Kolmogorov's e quation for the third-order moment of the velocity increment between two po ints allows compliance with two important classical results. These are retr ieved when the separation between the points either exceeds the integral le ngth scale or becomes comparable to the Kolmogorov length scale. In the con text of decaying grid turbulence, the results correspond to the mean turbul ent energy equation and the Batchelor-Townsend equation for the decay of th e mean-squared vorticity. Analogous results are obtained when the streamwis e inhomogeneity is included in Yaglom's equation. The form of the inhomogen eous 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].