Management of Natural Ventilation in High-Rise Building – a CFD Study

Abstract

The natural ventilation of a 7 floors office building was studied in terms of its openings’ discharge coefficient. A 2D, steady state, incompressible CFD model was developed using the FV method. The developed CFD model was validated against experimental data from wind tunnel measurements. Discharge coefficient is calculated for three elevations (ground floor, 4th and 7th floor) considering four combination of inclination angles 15o and 30o for windward and leeward openings. It was examined the dependence of discharge coefficient from: the wind velocity, the characteristics of the field where the building is situated (roughness length and atmospheric boundary layer thickness) considering four field types: a) Urban area (center and suburbs), b) Open field (classes 2 and 3). Two types of discharge coefficient was calculated, one based on the wind velocity at the opening, Cd, and one based on the wind velocity at the infinity, Cdw. The first varies between 0.54 to 0.7 but the second varies between 0.13 to 0.89 and it is considered more usable since it relates the buildings’ ventilation to the average wind velocity in the examined area, information available to the designer. Both are depended on the openings’ inclination angle, from the elevation of the examined floor, from the field roughness length around the building and from the wind turbulence intensity.