Reaching the statistical steady state regime in two-fluid simulation of risers

Abstract

Two-fluid simulation of gas–solid flows in risers is very time-consuming and highly bounded by computational resources. Actual simulations are mostly performed applying either coarse meshes in small scale columns, or finer meshes in partial very small domains. In any case, simulations go through an initial transient stage and finally reach a statistical steady state regime over which analyses are performed. Despite the early transient stage is not of higher interest, its transient computation accounts for a very significant share of the total computing time in a simulation. In this work it is proposed to replace such transient computation by a steady state run. It is shown that such procedure allows to quickly overcome the early transient stage of a simulation so that a transient run may start straightly inside the statistical steady state regime. For an ordinary particular case, it is shown that the procedure can save as much as 8 calendar months of computing.