Can Colombo Port City high-rise tower and podium morphology improve pollutant dispersion and urban ventilation?

A rapid increase in high-rise building clusters within developing cities has led to mounting environmental and climatic issues. This is especially highlighted in Asian cities where extreme tropical climates are accentuated by ad-hoc developments, that in turn create unfavourable urban environments. Traffic emissions and air pollution, directly and indirectly, effect the Urban Heat Island (UHI) factor. Studies show that urban ventilation is a key mechanism to ameliorate UHI, reduce pollution stagnation, improve air quality, and reduce dependence on energy-consuming systems, thereby enhancing future sustainability. A research gap on the effect of the morphology of high-rise towers, and tower and podium forms as clusters on air pollution dispersion was identified. A high-rise cluster in the proposed Port City in Colombo, Sri Lanka was identified, and possible building forms were designed based on guidelines given by the local authority. Simplified three-dimensional building clusters were simulated using Ansys Fluent and a RANS k-epsilon turbulence model. Results suggest the addition of a podium has minimal impact on pollution dispersion when compared with only a tower form. Block podiums were found to concentrate pollution within the podium height, while tiered podiums pushed street pollution upwards along the face of a podium. However, more uniform dispersion was seen in tiered podiums, reducing overall pollution concentrations within the study area. Overall, as per requirement and context, it is highlighted that podium forms can be designed to create better-ventilated urban spaces with good air quality, within a high-rise high-dense environment.