Three-dimensional flow characteristics around a finite wall-mounted conical cylinder

This paper presents the numerical results of three-dimensional flow characteristics around a finite wall-mounted conical cylinder with an aspect ratio fixed at AR = 4 and the end diameter ratio (D1/D2) ranging from 0.5 to 1.0 at a low Reynolds number, Re = 50–500. The flow characteristics are discussed in terms of time-averaged streamlines, distribution of singular points, topological structures, three-dimensional mean streamwise vortices, and instantaneous spanwise vortices. Compared to an infinite height configuration, the downwash flow caused by the free-end suppresses the formation of the Kármán vortex street in the wake. The critical Reynolds number for horseshoe vortex formation exhibits a significant dependence on D1/D2, decreasing to Re = 150 when D1/D2 = 0.5. Two distinct topological patterns are identified in the time-averaged streamline behind the cylinder. Three flow patterns above the free-end of the finite conical cylinder are demonstrated, providing additional insights into flow structures on free-end surfaces. The stable Quadrupole, Sextupole, and Octupole types of time-averaged streamwise vortices are compared across different Re and D1/D2. Furthermore, this work not only reconciles the time-averaged and instantaneous interpretations with the solenoidal condition of the vorticity field but also clarifies the fundamental mechanisms behind the topological transition from hairpin to braid vortices driven by strain rate.