Wind Environment Assessments of a High Density Urban District Using CFD Tool

Abstract

The urban expansion of Dalian city over the past 60 years from approximately 50 km2 to 500 km2 has been characterized by a high-density downtown morphological pattern, while the urban wind speed per year has trended downward. To evaluate natural ventilation performance in the high-density downtown area of Dalian, an in situ wind environmental survey was performed, and the results were used as a reference to configure CFD numerical simulation boundary conditions. The results indicate that urban edifices, such as enclosed city blocks, strip apartments in rows and, especially, high-rise buildings with large podium bulk, were unfavourable to natural ventilation and could reduce the mean wind speed by up to 78% relative to the approaching speed. The natural ventilation performance of different building morphologies were further evaluated via CFD simulations, which indicated such strategies as using ventilation paths, hybrid buildings with different heights, and increasing building height while decreasing their land coverage could improve the urban ventilation performance. Increasing the building height and reducing land coverage was one of the most efficient strategies and increased wind velocities up to 2.4 times the real case. Green land significantly cooled and humidified its surroundings, particularly the downwind spaces.