RANS Equation-Based Gas Cyclone Separator CFD Simulation: an Appropriate Time Step Size

Abstract

The present work answers a question for Reynolds-Averaged Navier-Stokes (RANS) equation-based gas cyclone separator computational fluid dynamics (CFD) simulation: “How small is the appropriate time step size?”. The gas cyclone separator CFD models were developed with appropriate near-wall grid sizes and the proper numerical scheme set suggested by our previous works. The quadratic pressure-strain Reynolds stress turbulence model was used. The mean velocity profiles simulated by time step sizes of 0.0001 s, 0.0005 s, 0.00075 s, and 0.001 s were compared to the reference experimental data. Moreover, the hit-rate validation and statistical analysis were assessed to achieve the guideline for specifying the proper time step size. The results revealed that the time step sizes of 0.0001 s and 0.0005 s provided better mean axial velocity prediction accuracy than others. From hit-rate validation and statistical analysis, it can be finally concluded that the time step size smaller than 1/1470 of the residence time is essential for predicting mean flow inside the gas cyclone separator.