Simulating the urban wind-induced risks under typhoon conditions using ELES model

Tropical cyclones are becoming increasingly frequent and intense. In urban areas, the risks induced by strong winds can be amplified due to the alteration of urban airflow caused by complex urban structures. Understanding the impact of urban morphology and approaching wind conditions on urban wind environments is of great importance for enhancing urban resilience to climate change and mitigating the catastrophic effects of tropical cyclones. To address this, the present study employs Embedded Large Eddy Simulation (ELES) model to simulate the flow field within a realistic urban building complex, analyzing the probability density function of pedestrian-level wind (PLW) environments and the associated wind-induced risks. Results reveal that PLW conditions deteriorate significantly with increasing upstream terrain roughness, given a fixed reference wind speed under typhoon conditions. Specifically, normalized time-averaged and gust velocities at pedestrian level can reach up to 1.0 and 2.0, respectively, for an upstream terrain roughness length of 0.30 m, compared to 0.5 and 1.0 for a roughness length of 0.01 m. In contrast, building morphology shows limited influence on PLW under typhoon conditions, even when the average building height is halved.  These findings offer valuable insights for climate-adaptive urban design and the development of sustainable cities capable of withstanding the impacts of tropical cyclones.