Active botanical biofilters (ABBs) are engineered biosystems designed to eliminate indoor air pollutants. Nevertheless, their bio-aerodynamic study remains unexamined, leading to inaccurate predictions of airflow distribution affecting their operation. Plant complex biomass alters airflow distribution, producing a heterogeneous-turbulent flow. This study combined experimental and modelling approaches to characterise the aerodynamics of a full-scale ABB and provide engineering insights. Firstly, the ABB's components (substrate, roots, and foliage) were separately characterised in a wind tunnel, confirming an inertia-driven flow and yielding macroscopic parameters (Darcy permeability and Forchheimer drag). Those parameters were used to predict the aerodynamic performance of a full-scale ABB using a 3D RANS k−ω CFD model incorporating the Darcy-Forchheimer and Pedras-de-Lemos formulations. Results indicated that at operational Darcy velocities, the substrate medium provides most of the aerodynamic resistance and that inertial effects exist before plant biomass incorporation. Roots decreased permeability by 70% and increased the inertial drag coefficient by 14%, suggesting that plant biomass acts as a turbulence generator, potentially enhancing the convective mass transfer of pollutants. The CFD model was successfully validated against experimental data for predicting pressure drop (R 2 = 0.9946, RMSE = 3.53 Pa), demonstrating that the chosen formulation physically describes ABB's aerodynamics. Then, the framework could diagnose inefficiencies in current ABB designs due to short plenums, which were minimised by adding flow conditioning elements. The aerodynamic improvement was quantified, demonstrating CFD's potential to enable optimisation. A transferability matrix encompassing the current ABB configuration-specific findings and expected behaviours across ABBs was established for broader engineering applicability. • A validated 3D CFD model predicts botanical biofilter aerodynamic performance. • Roots decrease Darcy permeability by 70% and increase inertial drag by 14%. • Flow-conditioning elements reduce flow separation derived from short plenums. • Engineering insights are established for bio-aerodynamic biofilter scaling.
Alvarado-Alvarado et al. (Wed,) studied this question.