Numerical Simulation of Swirl Decay in a Gas–Liquid Two-Phase Flow Generated by a Vane-Typed Swirler Inside a Horizontal Tube

Gas–liquid swirling flow has been widely used in industry, but its effective length in the horizontal tube is still unclear. The essence is lack of quantitative knowledge of decay characteristics in this flow. In this work, decay law of the horizontal gas–liquid swirling flow induced by a vane-typed swirler was investigated quantitatively by numerical simulation. The Eulerian-Eulerian multi-fluid model coupling with the RNG k-ε turbulence model were used to simulate the flow over the Reynolds number of air (Reg) range 4841.83 to 12715.36 and Reynolds number of water (Rel) range 5621.83 to 14079.46. The results show that phase distribution, velocity and pressure are significantly influenced by swirl decay. Absolute vortex flux decays to zero at z/D > 17, where z is the axial distance from the swirler outlet and D is the tube inner diameter. The decay model of swirl intensity was developed, and its calculated results show that swirl number Stp decays to 10% of the initial value S0 at around z/D = 6.5, and decays to 1% of the initial value S0 at z/D = 11 when Reg = 9681.95, Rel = 14079.46. Results not only enriching the theory of gas–liquid two-phase swirling flow but also providing theoretical support for the application of swirl flow in industry.