Influence of Stratification and Inflow Conditions on CO₂ Transport in Wind Turbine Wakes

Carbon dioxide (CO₂) emissions from diffuse sources such as vehicles and aircraft remain difficult to eliminate and continue to drive global warming. Direct Air Capture (DAC) offers a promising mitigation strategy, but its effectiveness is constrained by the low ambient concentration of CO₂ in the atmosphere. Increasing this local concentration, even modestly, could improve the efficiency and economic viability of DAC systems. Previous studies (Pulletikurthi et al., 2024 JRSE) have shown that wind turbines significantly modifiy scalar transport through enhanced turbulent mixing. In this study, we investigate how scalar mixing in the wake of a horizontal axis wind turbine is influenced by atmospheric stratification and upstream CO₂ distributions, with a focus on identifying flow conditions that may lead to local modulation of CO₂ concentration. We employ large eddy simulations (LES) coupled with an actuator disk model (ADM) to examine the evolution of passive scalars that represent CO₂ as they are transported through turbine wakes in thermally stratified atmospheric boundary layers. Several CO2 distributions, uniform, logarithmic, and empirical, are studied in order to assess how different inflow profiles with turbine-induced turbulence. Special attention is given to the influence of both stable and unstable stratification on wake development, vertical mixing, and scalar transport behavior. We analyze scalar fluxes and the structure of mixing in the near and far wake in response to variations in atmospheric stability and background scalar gradients. The objective is to understand how wake dynamics are coupled with environmental conditions to reshape scalar fields and influence local concentration patterns. These insights aim to inform future strategies for integrating wind energy infrastructure with DAC systems by identifying atmospheric and operational regimes where scalar accumulation is possible.