Predicting contaminant dispersion using modified turbulent Schmidt numbers from different vortex structures

Air pollutant transmission has significant influences on indoor air quality (IAQ). It is crucial to study mechanisms involved with airborne contaminant dispersion indoors. However, relationship between pollutant diffusion coefficient and viscosity in enclosed spaces has not been fully understood. In this study, turbulent Schmidt number (Sc_t) was modified as a function of turbulent kinematic viscosity rather than a constant value to better simulate dispersion of airborne contaminant in two typical enclosed spaces: an aircraft cabin and an office room. An experiment for airborne contaminant transmission was conducted in an aircraft cabin mockup. Combining with experimental data in the office room with an under floor air distribution (UFAD) system from literature, Sc_t was modified based on airflow vortex structures. The performance of RNG k-ε model using the modified Sc_t was found to be obviously better than that using the default Sc_t value in both the two enclosed spaces. In addition, model applicability to different enclosed spaces was analyzed based on the airflow vibration frequency.