Two-way coupled numerical simulation between outdoor thermal environment and PM_2.5 in urban blocks

While recent studies have explored the influence of outdoor thermal environment parameters on the dispersion of fine particulate matter (PM_2.5), or conversely the impact of PM_2.5 on urban thermal balance, integrated models that quantify the bidirectional feedback mechanisms between these factors are rarely discussed. This research developed a two-way coupled (TWC) numerical model that integrates the thermal environment and PM_2.5 in urban blocks. The proposed model establishes the two-way interactions by coupling momentum exchange between PM_2.5 and airflow speed using the discrete phase model (DPM) and the coupling heat balance between PM_2.5 concentration and thermal radiation using the discrete ordinates (DO) model. The simulation results of the TWC model, validated against actual measurement data, yielded average coefficients of determination (R²) of 0.81 for air temperature, 0.73 for wind speed, and 0.79 for PM_2.5 concentration. To evaluate the effectiveness of our model, we also constructed two "one-way coupled" models, which consider the unidirectional influence, and the traditional uncoupled model that neglects these interactions. Numerical simulation results indicated that the TWC model reduced the root mean square error (RMSE) of air temperature, wind speed, and PM_2.5 concentration by 0.12 °C (0.28 %),0.02 m/s (89.67 %),2.74 μg/m³ (24.22 %) compared to the non-coupled model, respectively. © 2025 Elsevier Ltd.