Comparison of the Eulerian and Lagrangian approaches in studying the flow pattern and heat transfer in a separated axisymmetric turbulent gas–droplet flow

The Eulerian and Lagrangian approaches are used to perform a numerical study of the disperse phase dynamics, turbulence, and heat transfer in a turbulent gas–droplet flow in a tube with sudden expansion with the following ranges of two-phase flow parameters: initial droplet size $d_1= 0-200$ $\mu$m and mass fraction of droplets $M_{L1}=0-0.1$. The main difference between the Eulerian and Lagrangian approaches is the difference in the predictions of the droplet mass fraction: the Eulerian approach predicts a smaller value of $M_L$ both in the recirculation region and in the flow core (the difference reaches $15-20\%$). It is demonstrated that the disperse phase mass fraction calculated by the Lagrangian approach agrees better with measured data than the corresponding value predicted by the Eulerian approach.