Automatic determination of coupling time step and region in unresolved DEM-CFD

When unresolved CFD-DEM is used in coupling calculation, both fluid flow field and particles dynamic both are in time and space domains solves. The coupling time step (coupling number) and coupling region (CFD solution domain) directly affect calculation accuracy and efficiency. Therefore, through real-time update of coupling conditions, establishment of CFD global as well as sub-domain solution technology, we proposed a calculation method for automatically determining the coupling time step and region. Our proposed strategy reduced the solution scale of the fluid domain during coupling, controlled coupling calculation accuracy, and improved calculation efficiency. The calculation revealed that maximum errors of displacement and velocity of single particle settling motion in a finite fluid were 6.2% and 7.1%, respectively, while maximum efficiency was improved by 44.4%. The maximum error reached 3.9%, when the velocity of particles in the pipe was 3.5 m/s. Computational efficiency increased by 26.1%. [Display omitted] •Establish the convergence conditions for the domain coupling solution•Establish CFD global or sub-domain solving algorithm•Establish a coupling algorithm for coupling time step and area determination•Single particle and multi-particle motion calculation examples for verification•Algorithm significantly improves CFD-DEM calculation accuracy and efficiency.