This is the CFD-DEM simulation of a bubbling fluidized bed, as frequently used in many industries.
The video is comparing 3 simulations of a bubbling fluidized bed, using three different levels of coarse-graining. Coarse-graining is the modelling strategy to represent a multitude of real-world particles with one computational particle (a parcel). The fluid-particle and particle-particle interaction laws have to be adapted accordingly when following this strategy. The simulation on the left shows the original simulation (coarse graining = 1), the simulation in the middle shows a simulation with coarse graining = 1.5, the simulation on the right shows a simulation with coarse graining = 2.0. Note that coarse graining = 2.0 means that the computational parcel is twice the size of the original particle, meaning a speed-up of factor 2^3 = 8 in the simulation!