wind tunnel

This paper presents a study of the impact of horizontal aperture separation in single-sided ventilation flows with two apertures (SS2). The study is based on wind tunnel measurements and dimensional analysis. The results show that the SS2 ventilation flow rate, scaled with incoming wind velocity and aperture area, depends on the incoming wind angle relative to the aperture façade, θ, and on the aperture separation scaled by building width, s′. For most wind angles, the ventilation flow increases as the square-root of s′.

Since the 1970s, many authors have discussed the impact of poor airtightness on building energy use, indoor air quality, building damage, or noise transmission. Nowadays, because poor airtightness affects significantly the energy performance of buildings, and even more significantly with low-energy targets, many countries include requirements for building airtightness in their national regulations or energy-efficiency programs. Building pressurization tests are increasingly used for compliance checks to energy performance requirements and may result in severe penalties.

This paper describes the effect of outward opening the sash of a window on local and overall wind pressures. Wind tunnel experiments were used for the purpose of evaluation. A centre-pivot roof window on a pitched roof in a modelled scaled building was used in the analysis of wind pressures. The wind pressures were defined in terms of wind pressure coefficients. Traditionally, wind pressure coefficients are extracted from the analysis of a sealed plane surface. These wind pressure coefficients are used to estimate the natural ventilation rate through windows/openings due to wind effect.

A model tunnel (approximately ten hydraulic diameters) with different designs of the tunnel mouth has been placed in a wind tunnel and has been subjected to the effects of external wind by varying the wind direction at the mouth of the tunnel. In the experimental oriented study pressures have been measured and the airflow has been made visible with smoke and by the sand erosion method (semolina). The relation between the flow ratio and the direction of the wind has been explored.

Natural ventilation of buildings is a design strategy for the passive cooling of buildings that can be considerably efficient if properly undertaken. In Brazil, as in many other developing countries, spontaneous (self build) housing is often of poor quality. Also, each of these dwellings has a negative impact on the neighbouring ones and on the impact on the urban environment. In the city of Campinas, Brazil, with its hot-humid climate, adequate ventilation is essential for thermal comfort.

Wind catcher systems have been employed in buildings in the Middle East for many centuries and they are known by different names in different parts of the region. Recently there has been an increase in the application of this approach for natural ventilation and passive cooling in the UK and other countries.

This paper reviews the current literature on discharge coefficients (CD) of openings and compares different studies for wind-driven cross-ventilation. Considerable variation of discharge coefficients with opening porosity, configuration (shape and location in the faade), wind angle and Reynolds number is shown. Consequently, the use of a constant CD value such as that given in textbooks or other sources might be an invalid simplification.

To accurately estimate the natural ventilation of outdoor spaces surrounded by low-rise buildings using a wind tunnel requires correct representation of the natural wind regime combined with appropriately scaled building models and testing method. Existing outdoor ventilation studies are largely based on wind speed and estimated air change rates. Wind speeds mainly influence: peoples comfort, safety in pedestrian areas, the heat transfer between outdoor surfaces and airflow, and evaporation from wet surfaces.

To evaluate the property of cross ventilation quantitatively, it is important that the calculated air flow field is compared with measurement. In this paper, the air flow field in the wind tunnel of the Building Research Institute of Japan (BRI) was calculated by CFD analysis using the standard k- e model, and the adequacy of the calculation was examined by comparison with measured values.

The mechanism of cross ventilation is dealt with in this paper. The results are obtained by a combination of wind tunnel studies and CFD predictions using a Reynolds stress model as the turbulence model. All buildings have been exposed to a uniform velocity field and therefore the reference flow rate for an opening is equal to the velocity multiplied by the opening area. The openings were located at or close to the position of the stagnation point on the corresponding sealed building.