Abstract
A Lagrangian numerical simulation technique to calculate concentration fluctuation fields by a non-buoyant plume in grid generated turbulence has been developed. Lagrangian velocities of the fluid particles in the downstream decaying turbulence are simulated by the summation of unsteady random Fourier modes. The distribution of wavenumbers are selected to estimate the effects of large scale structure well. Then, the backward diffusion technique of particle-pair is applied to the prediction of scalar statistics. Simulations of scalar fluctuation fields of a line source plume in a grid-generated turbulence have been made and the simulation results are compared with the experimental data. the present new model gives good predictions of the actual scalar fluctuation statistics.
