A Comparative Study on the Performance of CFD/LBM-DEM Coupling in Predicting Soil Fluidization

Coupling discrete element method (DEM) with computational fluid dynamics including Navier-Stokes theories (CFD-DEM) and Lattice Botlzmann method (LBM-DEM) has been used widely to model the response of soil foundation under increasing seepage flows; however, a comparison of these methods in predicting soil and fluid behaviours during fluidization has not been carried out in a rigorous way. The current paper will hence provide an evaluation on their performance by applying them to model a laboratory test where a sandy soil is subjected to fluidization process under increasing hydraulic gradient. A brief discussion about the differences in their theories and numerical algorithm is made before the DEM is used to simulate a representative soil element while NS-based CFD and LBM are used separately to model upward fluid flows. The mutual interactions between fluid and solid phases are carried out and update to each other through third-party platforms. The results show relatively similar hydraulic conductivity predicted by the two methods, which agrees well with the experimental data; however, the critical hydraulic gradient estimated by LBM-DEM coupling is found closer to the experimental value. The CFD-DEM coupling provides more stable computation through its averaged fluid variables, whereas LBM-DEM coupling can provide more detailed interactions between fluid and soil particles at micro-scale due to its high resolution. The study then suggests several conditions which can optimize the efficiency of using these methods in practical applications.