Understanding the influence of street network designs on pedestrian ventilation in high-density urban areas: A wind tunnel study (14619121) (1 Oct 21 - 30 Sep 24)
• Researchers: NG Yan Yung, TSE Kam Tim
• Funding Amount: HK$1,179,833
• Funding source: Research Grants Council - General Research Fund

In a sub-tropical and high-density city such as Hong Kong, streets (i.e. roads and linear pedestrian open spaces) usually act as major breezeways. Careful designs of street networks are important for three main reasons:
(1) air infiltration into urban areas relies on street networks since building sites tend to be largely occupied, and have low permeability;
(2) streets are outdoor activity spaces, where sufficient ventilation is required for the comfort of pedestrians during hot and humid summers;
(3) street networks are usually planned prior to buildings and mistakes are hard to amend afterwards.

Although many studies have been conducted on regular (i.e. orthogonal) street networks, limited studies have parametrized the irregular morphological features of street networks, such as street orientation angles, in neighborhood and city scales. In fact, irregular street networks commonly exist in high-density Asian cities. However, the lack of relevant research results in
an inadequate understanding of street designs for better urban wind.

To better understand urban wind in complex built environments, it is important to parametrize the influences of urban morphological features, including irregular street networks, on urban wind. The insight will help to guide how roads and pedestrian open spaces should be better designed and linked to provide a more comfortable urban living environment.

This proposed study aims to: (1) collate a better categorical understanding of the typical urban morphological features of street networks in Hong Kong’s high-density urban areas; (2) using an existing wind tunnel benchmarking dataset in Hong Kong, develop regression models and urban maps to correlate pedestrian level wind velocity ratios with selected street-related
parameters on the basis of both neighbourhood-grids and fine resolution street-segments; (3) based on the above findings, conduct further wind tunnel parametric studies to quantify how different potential urban street design strategies benefit the pedestrian level wind; and (4) transfer the knowledge from the scientific findings to update the existing urban design
guidelines in Hong Kong.

Expected deliverables include (A) developing scientific models to correlate complex urban features with urban wind performance, establishing pedestrian level wind maps for Hong Kong’s high-density areas in both neighborhood and fine resolutions for planners’ visualization and quantification, (B) suggesting guidelines on the key urban features for better urban wind to be incorporated into “Hong Kong Planning Standards and Guidelines – Ch 11 Urban Design – Air Ventilation Assessment”. The guidelines will also be of reference value to planners and policy makers of other tropical-high-density cities.