Lagrangian stochastic particle model simulations of turbulent dispersion around buildings

This paper describes a numerical modeling approach that can be used to provide estimates of air concentrations due to emissions at industrial sites or other sites where buildings may have an important impact on the dispersion patterns. The procedure consists of two sequential steps: (i) Prediction of mean flow and turbulence fields via a turbulent flow model; and, (ii) Employment of the calculated flow and turbulence fields to drive a Lagrangian stochastic particle model. Two flow scenarios are used as input to a Lagrangian model; the scenarios assume neutral atmospheric conditions and incoming winds that are from 270 and 240°. The problem configuration for the first calculation is based on an earlier transport and diffusion simulation that employed an existing particle-in-cell flux-gradient dispersion model. The second simulation is used to demonstrate the strong spatial variations that the concentration field exhibit within the highly complex separation zones of building wakes. The relationship between concentration levels and toxic load are discussed for the case of a chemical spill.