Linking a Lagrangian Particle Dispersion Model with Three-Dimensional Eulerian Wind Field Models

摘要

A slightly simplified form of Thomson's Lagrangian stochastic model (LSM) is presented for dispersion applications in three-dimensional (3D) flow fields. It is found that the Lagrangian velocity of a particle in 3D inhomogeneous Gaussian turbulence can be decomposed into the local Eulerian mean velocity UEi at the particle position and a velocity perturbation u_i. The Eulerian mean wind can be predicted by 3D wind field models, whereas the u_i is obtained from Thomson's model and depends on the turbulence field. The U_(Ei), u_i decomposition was used earlier in a two-dimensional particle model for a canopy (by Flesch and Wilson) and in models with 3D mean winds but with u_i based on LSM forms differing from that of Thomson. This note shows that theU_(Ei), u- decomposition is consistent with Thomson's LSM for general 3D flow fields and is a simpler solution that should lead to improved computational efficiency for dispersion applications.