wind tunnel

Natural ventilation is a commonly used principle when ventilation systems for buildings are designed.The ventilation can either be obtained by automatically controlled openings in the building envelope, orit can just be the simple action of opening a door or a window to let the fresh air in.

Conventional method to predict ventilation rate induced by wind is based on the orifice equationassociated with the discharge coefficient and wind pressure coefficient. In the cross-ventilationphenomena, however, this method has a problem due to the difficulty to predict resistance of thebuilding related with total pressure loss. In this paper, therefore, the stream tube caught by the inletopening is analyzed to investigate the pressure loss due to the transformation (and possiblyconvergence and divergence) of the stream tube.

To accurately estimate the natural wind driven ventilation potential of a specific low rise building in a densely shielded or built-up area under local wind conditions, it is necessary to have site wind frequency data, pressure coefficient data, details about the windward and leeward openings of the building and the data related to building design. This paper summarises the appropriate data and discusses how to obtain these in order to estimate the natural cross ventilation potential of such a low-rise building.

The use of a combined methodology of wind tunnel experiments and CFD simulations in order to study the potential of using active stack to enhance natural ventilation in residential apartments in Singapore is demonstrated in this paper. Comparison between the results obtained from the experiments and those from the simulations has been made.

The main aim of that study is to assess the status of natural ventilation in a typical four-room HDB (Housing and Development Board) flat in Singapore using scaled model in the wind tunnel and also to develop an effective passive or active stack system to enhance natural ventilation in the flat.

Wind pressure measurements corresponding to the various configurations of a detached houseshould be conducted by wind tunnel tests using a comparatively large geometric scale model because a building of extremely small size is targeted.

The authors recently reported the detailed experimental results on that the discharge coefficient of the openings exposed to the wind driven airflow clearly changes depending upon the windangle and consequent conditions. A full-scale building model in a wind tunnel has been used for theexperiment. In this paper, the mechanism of the change is discussed more deeply, and the predictionmethods of the discharge coefficient are tested by the new experimental results for different conditions of opening size and location.

In case of cross ventilation through the large opening, it is well known that the inflow directionat the opening is not normal to the opening. Authors proposed the simplified prediction method of theinflow direction at the inlet opening and the airflow rate simultaneously. It is also well known that the use of general discharged coefficient (CD) values is not suitable for the calculation of cross ventilation rate. First reason is that the simple connection of the pressure loss coefficient of an opening ( ?? as the reciprocal of square CD) in series under-estimates the airflow rate.

Airflow through openings in a cross ventilated building scale model was investigated in a windtunnel and by numerical predictions. Predictions for a wind direction perpendicular to the building showed an airflow pattern consisting of streamlines entering the room, that originated from approximately the same upstream area in the undisturbed boundary layer and a direction of the flow into the room dependent on opening location with velocity vectors pointing away from the stagnation point.

As particles in room air can cause lung diseases, it is important to study how they are transported and dispersed in buildings. This investigation numerically studied particle dispersion by using the Lagrangian approach. The turbulent airflow is solved by the RNG k-e model; and a discontinuous random walk (DRW) model is applied to account for the stochastic effect of particle movement in turbulent flow. The computed results agree reasonably well with the experimental data for particle dispersion in a wind tunnel.