Editorial: Modelling and computational challenges in granular materials

Granularmaterials—conglomerates ofmacroscopic particles —are challenging systems to model. It is simply too costly to simulate the huge amount of particles in most systems in full detail. Even most intricate simulation methods, such as discrete particle simulations for modelling the full particle dynamics and direct numerical simulations to model a fluid flowing through the granular material, need to simplify particle properties, contact models and boundary conditions to become computationally feasible. Continuum methods efficiently simulate the bulk dynamics, based on simplified constitutive models that represent the granular materials efficiently, as effective media. However, the success of general constitutive relationships is still limited, because the inherent spatial and temporal scales of the particle dynamics are not well separated from the relevant macroscopic scales. Thus, the available constitutive models are based on simplifying assumptions that limit their range of applicability. The challenge for the modeller is therefore to choose the right method and scale to simulate a material efficiently and accurately: Is it better to use a discrete particle simulation, a probabilistic method, or a continuum approach? How can the results of different methods be compared with each other