Numerical analysis on the development of vortex structure in 90° pipe bend

摘要

In the present paper single-phase turbulent flow through 90° pipe bend with different curvature ratio (Rc/D) is numerically studied. Simulations are accomplished for turbulent flow conditions under high Reynolds number (Re) ranging from 1 × 10~5 to 10 × 10~5 and for three different curvature ratio conditions: 1) low curvature ratio (Rc/D = 1); 2) medium curvature ratio (Rc/D = 2 and 3); 3) high curvature ratio (Rc/D = 4 and 5). Numerical simulations are performed by solving unsteady Reynolds averaged Navier-Stokes (U-RANS) equations using k-e turbulence model. Development of a complex three-dimensional flow pattern with different vortices with their development in space is investigated through flow visualisation by numerical simulation. The numerical results indicate that with respect to both Reynolds number and curvature ratio, there is a complex change in flow pattern regarding the appearance, development and disappearance of several types of Dean vortices. In general, this paper provides numerical results on the development of different vortices and their evolution in space with a tentative map for 90° pipe bend with different Reynolds number and curvature ratios.