Calculation of turbulent gas-dispersion flows in channels with recirculation eddies

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

“…The droplets that entered the recirculation region, where the turbulent kinetic energy is smaller than in the shear layer, cannot leave the recirculation region. Accumulation of solid particles in the separation region of an isothermal two-phase flow was numerically demonstrated for the first time in [1]. The near-wall zone of the tube is almost free from particles owing to their evaporation (at small values of Stk) or their absence in the separation region (at large values of Stk).…”

“…We use axisymmetric Reynolds-averaged Navier-Stokes (RANS) equations written with due allowance for the influence of particles on transport processes in the gas. The gas turbulence is described by the model of Reynolds stress transfer [16] extended to the case with a disperse phase [1]. The use of this approach allowed us to avoid using the isotropic hypothesis of gas velocity fluctuations, which is, strictly speaking, inapplicable for separated flow calculations.…”

“…This model was developed for calculating separated single-phase flows behind a backward-facing step, but it was also used to describe separated axisymmetric flows [9]. The disperse phase velocity fluctuations are described by the differential model of Reynolds stress transfer; the temperature fluctuations and the turbulent heat flux are described by the models developed in [1,14]. The governing equations of the model and the numerical implementation of the method were considered in more detail in [9], where the numerical algorithm was also tested.…”

“…In engineering applications, two-phase flows with flow separation and recirculation are often used, for instance, for stabilizing the combustion of evaporating fuel particles owing to the formation of separation regions. Separated two-phase flows (see, e.g., [1][2][3][4][5][6][7][8][9]) are essentially anisotropic; the situation may be further aggravated by interphase heat and mass transfer, as well as by phase changes on the droplet surface. It is rather difficult to take into account and correctly describe all these factors that noticeably affect the flow pattern.…”

“…Separated turbulent two-phase flows were studied in [1,2,[4][5][6][7][8][9] with the use of the Eulerian approach [1, 4-6, 8, 9] and Lagrangian approach [2,5,7]. Comparisons of the results of these works with available measurements obtained in studying a two-phase flow in a tube with sudden expansion [2] and behind a backward-facing step [3] show that both approaches can be used for calculations and yield similar results.…”