A CFD study of wind assessment in urban topology with complex wind flow

This paper presents a CFD study on the air ventilation assessment (AVA) in urban topology with twisted wind profiles (TWP). At present, most AVAs were conducted through wind tunnel experiments, and conventional wind profile (CWP) with no deviation of wind direction along the heights was employed. However, in practice, the hilly terrain around cities such as Hong Kong results in twisted wind flow that wind directions vary along the heights. This paper presents an LES-based CFD model based on the best practice guidelines (BPGs). Two twisted wind profiles (TWP) were introduced, and six simulation cases were performed. The CFD predicted wind speeds were validated against wind tunnel measurements in the literature, and good agreement was achieved. With the aid of the CFD model, wind conditions over heights were investigated, and the effects of twisted wind were evaluated. The results indicated a significant influence of TWPs on the AVA's outcomes and the wind speeds' vertical distribution. In addition, with the CFD results, it is possible to investigate the wind-structure interactions in specific urban areas and provide a better understanding of the effects of buildings on the local wind conditions, which could be useful to the urban plan for sustainable cities.