Lagrangian Measurements of Canopy Flow Statistics*

Air pollution in the environment is a major concern given the rise in population, and increasing trends of urban population density. Atmospheric turbulence causes dilution of pollutants in the environment. Thus, studying the fluid dynamics in the rough surface layer canopy flows is important for air pollution modeling, both for predictive and real-time emergency response applications.

We study the Lagrangian description of turbulence, measuring the velocity of moving flow tracers. Lagrangian statistics are key for most turbulent dispersion models, yet in the canopy flow they are lacking. Our goal is to provide direct Lagrangian measurements in a wind tunnel canopy flow model.

We preform Lagrangian measurements of the canopy flow modeled in a wind tunnel laboratory through the 3D-PTV method. To do so we use a unique real-time-image-processing system. A one of its kind dataset of Lagrangian measurements was gathered in this way, both inside and above the canopy layer. We use the dataset to investigate Lagrangian flow characteristics in the canopy model, deriving Lagrangian statistics directly for the first time. These results will aid to construct and validate dispersion models in the atmospheric surface layer.