Numerical investigations of airflow and heat transfer in traditional Balinese buildings
Traditional Balinese architecture is commonly related to culture and traditional reasoning. When subjected to several modem problems such as energy demand, pollution, and impact of urbanisation and tourism, traditional architecture becomes less attractive since the definitions behind traditional reasoning are not clear and can be interpreted in different ways. To understand this feature, the study of traditional Balinese architecture starts by using several key parameters such as wind engineering and heat transfer, as presented and used in several countries. The flow patterns around a cubic building have been studied by many researchers. The velocity profile at the model position and the local surface roughness are specific to each building model and cannot be estimated from general tests of a standard building shape, therefore specific velocity profiles and conditions are used in this particular study. The air flow around a cluster of traditional Balinese buildings is extremely complicated and difficult to determine by modelling an isolated building (via symmetric conditions) since the buildings are linked to each other. Full scale models of traditional buildings have been investigated by using CFD to predict the above aspects. Simulations using this method can be done more quickly and less expensively than with wind tunnel experiments, and are capable of delivering more detailed and comprehensive information about the flow structure. Two-dimensional models of traditional Balinese building arrangements are simulated by using a commercial code Fidap based on the finite element method to assess the effects of type of roof, fence and surface roughness. Three-dimensional models are simulated by using a commercial code CFX based on the finite volume method to verify some traditional definitions. A standard к-ε model is adopted because it needs less computational power and has achieved notable successes in calculating a wide variety of thin shear layer and recirculating flows without the need of adjustment of the model constants, but with the imposition of boundary conditions to reduce the over-prediction near windward edges. Adopting lower values of к and ε combined with multi-blocks is shown to reduce this over-estimation. For a cubic building, the results can be compared with several other turbulence models. It appears that traditional Balinese architecture has a strong and significant correlation with several engineering fields, therefore traditional communities can develop by considering the Tri Hita Karana concept in order to improve thermal comfort and reduce cooling loads, with corresponding energy savings.