The open‑source Lagrangian particle model LAPMOD now incorporates the building downwash effect in its algorithm with PRIME2. Designed with odour in mind, it treats downwash at the particle level for point, area and volume sources, removes the need for BPIP preprocessing, and avoids the unrealistic “constant concentration” cavities that can appear with older schemes.
Odour impacts are dominated by what happens in the first few tens to hundreds of metres from the source. In this near field, buildings can force plumes downwards, enhance turbulence and create recirculation zones that strongly affect ground‑level concentrations at nearby receptors. If a dispersion model gets the building wake wrong, it can easily under‑ or over‑estimate the very concentrations that determine whether neighbours complain or not. That makes the choice of downwash scheme critical for odour assessments around wastewater treatment plants, composting facilities, food processing sites and other installations with complex layouts.
