In this paper, after theoretical considerations, two ventilation openings are analysed : an opening with top-hinged flap and a wall inlet with central flap. The analysis shows that it is possible to split artificial resistance coefficients from literature into pure resistance and pure contraction coefficients .

This paper is built on the hypothesis that, as the heated area increases from a point source, a displacement flow is maintained until the heated area reaches a critical fraction of the floor area, after which there is a transition to mixing flow.This hypothesis is tested in a series of laboratory experiments with the investigation of thermal stratification and flow patterns produced by a range of area heat sources located on the floor of a naturally ventilated enclosure.

This paper develops a simple analytical model for the air flow inside a room with different discrete heating and cooling sources, established by combined localised and distributed heat input. Results from experiments are compared to simple theoretical models of the flow pattern.

In this paper, cross ventilation is evaluated by the multi zone network airflow simulation and using CFD. The distribution of indoor wind velocity by cross ventilation is influenced by the weather condition, the location of the building and the form of he building. This paper takes into account those three indexes and proposes a new evaluation method of natural cross ventilation performance

Investigation by means of CFD and small-scale laboratory experiments showed that flow bifurcations could occur in building spaces ventilated by buoyancy force with large opening ceiling.A theoretical model has been developed to determine the ceiling opening size at which the flow bifurcation occurs.The predictions were in good agreement with the experimental results obtained in this work.

The wind tunnel experiment is the major method for cross ventilation researches. Up to now no quantitative evaluation method nor standard has been produced. This research project is to develop the quantitative method to predict cross ventilation rate driven by wind. A specially designed wind tunnel is used in the project. Conventional wind tunnel experiment is carried out in parallel with scale models of building without openings.

CFD and fluid net models used for natural ventilation designs do not consider the impacts of fluctuating characteristics to the mean airflow rate. This paper presents first a correctional method for predicting mean airflow rate of natural ventilation when the average wind velocity is more important than velocity fluctuation. A correctional coefficient for airflow resistance of multi-zone models is deduced. This method is then applied to a big atrium of a naturally ventilated five floor laboratory.

Natural ventilation is often a highly unsteady phenomenon, therefore steady criteria, very helpful for mechanical systems, cannot be used. This paper presents ideas for evaluating transient flow situations. The theory of the air exchange efficiency is extended to transient flows.

Three flow regimes encountered in hybrid ventilation systems, depending on the external temperature along with the imposed heating and cooling loads, are investigated . A theoretical model is used and small-scale laboratory experiments are visualised. The transitions between those naturally ventilated flows may vary according the seasons.

This paper presents a procedure that allows to look at the influence of atmospheric turbulence in natural ventilation. This procedure uses wind time series. The results of the estimated turbulence influence on air change rates are compared with field measurements both from the references and from the tests conducted in real buildings in order to validate that procedure.