Annular flow dynamic characteristics of two inverse coaxial rotational cones

Dye liquid visualization and PIV experiments were conducted to reveal the influence of the Reynolds number (Re) and the presence of an end plate at the upper boundary on the annular flow dynamics characteristics of coaxial cones. The key flow information, such as the vorticity and velocity distributions, time-averaged flow field, and Reynolds stresses, were obtained by processing the velocity field. The Taylor vortex dynamics mechanism was studied based on the quantitative evaluation of the periodic vortex transformations. The experimental results showed that there was upward flow in the annulus at very low Reynolds numbers (Re = 107 and 160), and the annular flow transitioned from an upward to a downward pattern as Re (Re ≥ 214) increased. The first vortex was always separated by a negative vortex, B2, generated in the top right corner for Re = 214–642. A counterclockwise vortex under the free water surface always formed because the centrifugal force dominated at the water level, and there was always a fixed clockwise vortex under the upper cap because the dynamic pressure dominated at the non-slip wall surface for Re = 214–1925. The dominant convex outward or concave inward flow reflected the dominant motive source force. The total Reynolds stress increased with the increase in Re, and the magnitudes of the stresses were in the following order: radial normal stress > axial normal stress > shear stress.