stratified flow

Airborne transmissions take place as a transport of virus or bacteria via the aerosol flow in rooms. The distribution of aerosols tends to be evenly distributed if the flow in the room is fully mixed. The aerosols distribution will be different if the room air is stratified. A vertical temperature distribution may create stratified layers with either lower or higher concentrations of exhalation from the infected person.

An important element in the natural ventilation design procedure is the flow-pressure characteristics of a window with a given opening area. The flow in the room is another important element that is often ignored in the design phase due to lack of relevant information on the air movement. This paper shows the outcome of experiments with the room air distribution. The results show that the velocity distribution in the occupied zone can be described by a semi empirical model.

The article describes experiments with wall-mounted air terminal devices. The airflow from an air terminal device influences the occupants' thermal comfort and, therefore, it is important to develop an expression for the flow in the occupied zone. The velocity at the floor is influenced by the flow rate to the room, the temperature difference and the type of diffuser. The flow is stratified at Archimedes numbers larger than four. The article gives expressions for the velocity distribution close to the floor.