spectral analysis

Electric fans used for cooling or local ventilation are common household appliances around the world, especially in developing countries. They offer many advantages such as low cost and energy savings, as well as easy implementation. However, the airflow from fans is often considered to be less comfortable than the sensations produced by natural winds. In order to avoid the draught induced by fans, and to investigate dynamic airflow characteristics of household fans, an anemometer was utilized to measure the corresponding time series of the air velocity.

A non isothermal horizontal jet issuing from a round nozzle distanced from a wall is investigated experimentally. We consider four cases: an isothermal jet, a hot air jet, a cold air jet interacting with the wall and a cold air jet falling down without reaching the wall. The jet expansion rates show two categories. These are (1) an isothermal jet and cold jet not adhering to the wall, with a vertical expansion rate higher than the lateral rate and (2) a non isothermal jet adhering to the wall, with a lateral expansion rate higher than the vertical one.