CFD investigation of air flow around a simple obstacle with single heating wall

ABSTRACT

Established within the framework of the European Commission Training and Mobility of Researchers Programme (TMR) the primary objective of the ATREUS project (http://aix.meng.auth.gr/atreus/) is to bring together current knowledge on parameters determining the microclimatic environment of urban areas and to further expand and use this knowledge in the optimization of heating and ventilation of buildings. While thermal effects are important in a narrow region close to the heated wall, they may also have influence on the local flow field and pollutant dispersion. To date numerical studies concerning the influence of thermal effects within a street canyon due to solar radiation show varying degrees of modification to the classic isothermal flow regimes. A combined numerical-field study using the Computation Fluid Dynamics (CFD) code CHENSI within TRAPOS project (http://www2.dmu.dk/AtmosphericEnvironment/trapos/main.htm) reported the numerical model overestimates the thermal effects on the canyon airflow, predicting two counter-rotating vortices when only one recirculation vortex was observed in the field. Model-scale wind tunnel investigations show further inconsistency with the numerical predictions but are in themselves limited in their scope of study to either for 2D cavities and or full-heated cylindrical building with square cross-section. The aim of the current work is to provide information to enhance the understanding of the flow phenomena and flow perturbations due to wall heating within the vicinity of a building.

A three-dimensional numerical simulation (using CFD code CHENSI) of airflow around simple obstacle with vertical wall heating is presented in this study. The two turbulence models, the standard k-e model and Chen&Kim, are employed to predict the flow field and thermal effects. The wind tunnel experimental data with low wind speed conditions, which has been provided by the Meteorological Institute, University of Hamburg, have been compared with model results. The scenario is unique in that a model has been constructed to represent an isolated building (a cube) where only one of its vertical faces is heated i.e. simulating the influence of the sun heating one wall of a building. The intercomparison for isothermal case showed good agreement in terms of the gross features of the mean flow, although some detailed differences were observed. Different ratios of buoyancy to inertia forces have been applied to investigate perturbations on the flow due to thermal effects. The work appears to improve model's results by optimisation of the boundary conditions.