Large Eddy Simulation of Isothermal and Non-isothermal Turbulent Flows in Ventilated Rooms*

The focus of our work has been on understanding the physics of isothermal and buoyant turbulent flows in ventilated spaces, and on the location and extent of intermittent regions of low TKE, also known as dead-zones, that form in such spaces, and could become breeding grounds for airborne diseases. In classrooms, for instance, small aerosol particles that are released during normal breathing/speaking, could accumulate in these regions, and linger for much longer periods of time. If these aerosols were to contain a high viral density, the entire classroom could become infected. While increasing the air changes per hour (ACH), via natural ventilation (opening the windows) and forced ventilation (increasing airflow rate), is an effective means of flushing out airborne pathogens, it is a prohibitively expensive option for schools, especially in winter, when it is impossible to exploit natural ventilation to increase the ACH. Results from our resolved LES show that for a given ventilation pathway, incoming cool ventilated air (during warm weather) tends to reduce the extent of dead-zones, while incoming warm air (during colder weather) causes thermal stratification which increases the extent of these dead-zones. Our simulations also explore cost effective ways to improve air quality.