On Spiral Turbulent Flow in an Annular Concentric Channel

The paper presents the results of Newtonian-fluid spiral flow simulation in an annular channel. The simulation parameters were dimeters ratio of 0.5; Re = 100 ÷ 10,000 and dimensionless inner cylinder rotation rate χ = 0.2 ÷ 5. The turbulent flow regimes were simulated using URANS, a non-stationary statistical turbulence model. While simulation, the following flow regimes were detected: homogeneous flow without pronounced structures (Re = 100, χ≤3 and Re=300, χ≤0.5); flow with Gortler-type continuous spiral vortices near inner cylinder (Re = 300, χ=1 and Re = 1000 ÷ 10000, χ = 0.5); flow with Taylor-type vortices (Re = 100, χ≥3 and Re = 300, χ≥3); flow with small-scale Gortler-type vortices near both channel walls (Re ≥ 1000 and χ≥1). The spiral spin of Gortler-type vortices near the outer cylinder was co-directed with the rotation of the inner cylinder, while the vortices near the inner cylinder spin against the rotation. Formation of large Taylor-type vortex structures led to a decrease in the channel skin friction coefficient faRe. Gortler-type vortices interaction near the channel walls triggered the formation of small-scale structures increasing in the channel resistance as the Reynolds number and rotation speed grew.