Particulate flows in a mixture of gas and liquid,i.e.gas-liquid-solid three-phase flows,are frequently encountered both in nature and industry.In such flows,complex interactions between multiple phases,i.e.particle-particle interactions,fluid-particle interactions and interfacial interactions(such as surface tension and particle wetting),play a crucial role.In literature,simulations of three-phase flows are some-times performed by incorporating interface capturing methods(e.g.VOF method)into the CFD-DEM coupling model.However,it is practically impossible to perform large(industrial)scale simulation because of the high computational cost.One of the strategies often employed to reduce the computational cost in CFD-DEM is to upscale particle size,which is applied mainly to particle single-phase and fluid-solid two-phase flows.The present work is focused on the scaled-up particle model for gas-liquid-solid three-phase flows.The interaction forces between multiple phases are scaled using the general criteria derived from the continuum assumption of particulate flow.A colour function based interface-capturing method with improved interface smoothness is developed,and the diffusion based coarse graining is employed to ensure sufficient space resolution in CFD even when particle size is increased.It is shown that the model developed is capable of predicting the both particles and fluid behaviour in the original system.