Effect of Roof Design Configurations onNatural Ventilation with an Obstacle Inside the Building Model

Abstract

Roof shape, roof angle, and internal obstacle are some of the factors that have a substantial impact on building's ventilation performance.However, previous roof ventilation studies havenot considered the influence of internal obstacle which canaffectthe overallbuilding’sventilation performance.Forthis study,CFD was used to studythe effect of roof design configurations on natural ventilation with an obstacle inside the building model. The numerical simulation was carried outbyusing steady RANS equation specifically the Standard k-ε with enhanced wall treatment. A total of 40simulationcases were carried out. The study considered two roof shapes mainly the sawtooth roof and the saltbox roof with varyingroof angle which were 10º, 20º,30º,and 40º. Internal obstacles with various height were further added into the simulation cases. Next, grid sensitivity analysis was carried out using Grid Convergence Index (GCI) and Factor of two of observations (FAC2) analysis was carried outas model verification methodto ensure a reliablesimulationresult. Based on the results, it is found that airflow characteristics such as wind speed, distributionof pressurecoefficient, and flowrate of an isolated building are strongly dependenton the roof shape and roof angle. Next, the dimensionless flowrate(DFR)is measured to be highest with largest roof angle while lowest with smaller roof angle. Furthermore, the DFR of a building with internal obstacle is lower than that without aninternal obstacledue to blockage of incoming air. Moreover, the results showthat the sawtooth roof outperforms the saltbox roof in terms of measured parameter.Finally, the study concluded that an isolated building with higher roof angle and without an internal obstacle leadsto the best dimensionless flowrate throughout the building.