wind pressure coefficient

Building energy simulation (BES) and Airflow network (AFN) programs generally incorporate wind pressure coefficients (Cp) estimated from secondary sources, namely data bases or analytical models. As these coefficients are influenced by a wide range of parameters, it is difficult to obtain reliable Cp data. This leads to uncertainties in BES-AFN models results, especially for naturally ventilated building studies, where air change rate which strongly depends on Cp, is a key value for thermal comfort and energy consumption results.

The ventilative cooling by natural ventilation is important technology for the buildings in urban area for the sake of energy saving and BCP (Business Continuity Plan). In fact, a large number of high-rise buildings in urban area in Japanese metropolises are equipped with natural ventilation apparatus such as openings and chimneys or shafts.

We conducted observations of wind velocity profiles above a high-density area in Tokyo, Japan, using a Doppler LIDAR system. Obtained data of the exponent index for the power law, which is commonly used to describe the wind velocity profile, displayed diurnal variation, decreasing in the daytime, which is expected in unstable atmospheric conditions. This paper provides information on the uncertainty in the calculated ventilation airflow rate due to the use of a constant value for the exponent index.

We conducted observations of wind velocity profiles above a high-density area in Tokyo, Japan, using a Doppler LIDAR system. Obtained data of the exponent index for the power law, which is commonly used to describe the wind velocity profile, displayed diurnal variation, decreasing in the daytime, which is expected in unstable atmospheric conditions. This paper provides information on the uncertainty in the calculated ventilation airflow rate due to the use of a constant value for the exponent index.

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.

Pressure coefficients (CP) are fundamental to calculate ventilation rates in buildings by the airflow network models (AFN). This paper deals with the use of CFD simulation to calculate Cp, and the use of those Cp values as input in building energy simulations (BES). The commercial package CFX was used to calculate CP for a 5-stories isolated building, typically found in social housing complexes in Brazil, The standard k-ε turbulence model was adopted.

The wind pressure coefficient is the basic driving force of wind-induced natural ventilation. The windvelocity along the building wall is also important for wind environment in balcony (veranda) or windowsand is the moment of inertia for the air flowing into rooms. These two values of the five-storiedapartment building with/without veranda were measured by wind tunnel test using scaled model. Theexperimental conditions are the faade type, the shape of veranda and wind direction.