A Generalisable LES–Lagrangian Particle Framework for Ember Storm Simulation at the Wildland-Urban Interface

Embers have been identified as the leading cause of house loss in previous fire events. Near the wildland-urban interface (WUI), areas where structures and developments meet wildland, embers pose a greater risk as small ember particles can flow over roads and terrain into properties, increasing the likelihood of structure damage. Much of the existing literature treats embers as 'ballistic' in nature, where the embers get entrained into the air and travel significant distance while airborne. In contrast, 'ember storms' are characterised by the embers sliding across the ground and being repeatedly lofted into the air. Although recent computational works have provided significant insight into ember transport, the current models do not capture the near-ground behaviour and transportation of embers, and the entrainment (the process through which near-ground particles are introduced into the flow) of embers from the ground, both of which are key factors in ember storms. This thesis presents the development of a generalisable computational framework that couples large-eddy simulation (LES) with Lagrangian particle tracking to simulate ember storm dynamics with high spatial and temporal resolution. The framework is implemented using Nek5000, a high-fidelity spectral element solver, and is designed for reuse in a broad range of particle-laden turbulent flow problems. The phenomenological model captures both airborne ember transport and near-surface phenomena such as ground entrainment and repeated particle lifting, which are critical for accurately representing ember storms. Using the framework, a series of parametric studies are conducted to evaluate the effects of wind speed, building spacing, and particle properties on ember behaviour. The results highlight how flow–structure interactions influence ember transport. By improving the physical realism of ember storm modelling, this framework enhances understanding of ember dynamics at the WUI. It provides a useful tool for investigating ember transport mechanisms, with potential to inform the development of improved mitigation strategies in fire-prone regions.