High-fidelity multiscale modelling of debris flows

Wider research context: Debris flows are major natural hazards in mountainous countries. Debris materials may consist of water, soils of fine particles, and large blocks such as boulders and logs. The distinct multiscale and multiphase nature, of debris flows has great influence on their flow dynamics, deposition behaviour, and impact property with protection structures. We will achieve high-fidelity modelling of debris flows by considering the water phase, fine soil phase, and large particles, which cannot be achieved within the single phase or discrete frameworks. The proposed numerical framework can provide large-scale high-fidelity modelling of debris flows considering all salient features including soil-water coupling, particle segregation, large impact force of boulders, and natural complex particle shapes. Thus, it has high potential for research and engineering practices in geohazards. Besides the outcome will have major impact for hydraulic and chemical engineering, where such two-phase mixtures play an important role. Objectives: The ultimate goal of this project is to develop an accurate, robust, and efficient multiscale numerical framework to provide high-fidelity three-dimensional simulations for debris flows considering all salient features, including multiphase soil-water coupling with a micropolar constitutive model for the soil, mixture large particle interaction, natural irregular particle shape, and size segregation. Methods: Firstly, centrifuge model tests will be performed to study the multiscale nature of debris material and establish database for validation. Secondly, for the continuous water-soil mixture, a multilayer SPH method will be developed based on the mixture theory together with a micropolar constitutive model. Thirdly, a surface mesh represented discrete element method will be developed to model large boulders with arbitrarily complex shapes (DEM). The coupling between SPH and DEM will be achieved for frictional contact and viscous effect between boulders and continuous water/soil phases. Advanced multi-GPU parallelization techniques will be employed to achieve high efficiency to enable high fidelity numerical simulations. Level of originality: (1) Centrifuge tests using transparent debris model materials, which can capture the true behaviors of debris flows under stress levels similar to field-scale flows. The transparent model materials allow the explicit tracking of large particles using optical measurements. (2) A novel and comprehensive multiscale numerical framework consisting of the multilayer SPH for soil-water mixture based on micropolar theory and SMR-DEM for the natural irregular particles. (3) The multi- GPU acceleration of the proposed multiscale numerical framework allows efficient high-fidelity modeling of large-scale debris flows. Primary researchers involved: One full-time Ph.D student, and one full-time Postdoctoral researcher will be recruited to work under supervision of the applicant.