Numerical investigation of urban heat island effect in various urban forms

• Developed 3D porous media models for simulating various urban layouts. • Compare and analyse the urban heat island effect of three urban layouts. • Identified optimal urban layout for future city development based on simulation results. The urban heat island effect is a widespread phenomenon in major cities worldwide, exerting significant impacts on urban environments, human health, and energy consumption, thus attracting extensive research interest. The manifestation of the urban heat island effect varies across different urban forms. This study employs a three-dimensional porous media model to comprehensively analyze the urban heat island effect and the influence of wind speed on three typical urban layouts: single-centre, multi- centre, and grid. The results indicate: (1) The more dispersed the city centre, the weaker the urban heat island intensity, with differences in peak heat island intensity of up to 0.3 K among different urban forms. (2) Under favorable environmental wind conditions, higher wind speeds lead to weaker heat island intensity. At v=5 m/s, the grid-based heat island intensity decreases by 0.57 K. (3) With increasing building density, the urban heat island effect intensifies in all three types of cities, with the single- centre city exhibiting the largest increase in heat island intensity, up to 23.5%