Analysis of ventilation flow in slot-ventilated enclosures by temporal forcing of the inlet jet.

Ventilation is of primary importance to obtain a healthy indoor environment in enclosures such as buildings, cars, airplanes, etc. However, mechanical ventilation consumes energy for heating/cooling of the inlet air and for fan operation. Increasing the ventilation efficiency is therefore very important. This project investigates the effect of temporal forcing of the inlet jet on the airflow and ventilation efficiency in an enclosure. Temporal forcing refers to imposing a controlled time variation to obtain a statistically instationary inlet flow. This differs from most existing ventilation systems, in which the inlet flow is stationary, at least at small time scales (e.g.<10 min.). A previous study on an impinging free jet has indicated that temporal forcing can substantially change the jet vortical structures and its mixing efficiency. In the present study, the effect of temporal forcing on enclosure airflow will be investigated, not only with the aim to increase the mixing efficiency of the jet, but, more importantly, also with the aim to break up airflow recirculation cells in the enclosure. The research is conducted using state-of-the-art experimental and numerical techniques for both a generic enclosure and more realistic enclosures. Higher ventilation efficiency by temporal forcing can have potentially very large benefits for the energy efficiency of ventilation systems, with large impacts in the building sector, but also in the airplane, naval and automobile sector.