Numerical Study of the Flow Behind a Rotary Oscillating Circular Cylinder

Abstract

A numerical study is performed of flow behind a rotationally oscillating circular cylinder in a uniform flow by solving the two-dimensional incompressible Navier-Stokes equations. The flow behavior in lock-on regime and the timing of vortex formation from the oscillating cylinder are studied. When the frequency of excitation of the cylinder is in the vicinity of the natural vortex formation frequency, a lock-on vortex formation regime appears. As the excitation frequency being increased relative to the natural frequency the initially formed vorticity concentration switches to the opposite side of the cylinder. The effects of oscillating frequency and amplitude on the vortex structures formed in the near wake of the cylinder are also investigated. Based on the present calculated results, some complicated vortex patterns are identified and are consistent with the previous experimental visualizations.

Vortex formation and force characteristics of a foil in the wake of a circular cylinder

“…8(b) at d ¼ 1 are a row of single vortices with negative rotation over a row of vortex-pairs; the vortex-pairs are induced to move downward because of the interaction with each of the vortices with opposite signs. The similar vortex structures were also found experimentally by Williamson and Roshko (1988) and Ongoren and Rockwell (1988) for approach flow past a transversely oscillating cylinder, and computationally by Lu and Dalton (1996), Lu and Sato (1996), Lu et al (1997) and Lu (2002) for flow past a rotary oscillating cylinder and past a transversely oscillating cylinder, respectively. Further, Fig.…”

Numerical analysis on the propulsive performance and vortex shedding of fish-like travelling wavy plate

“…As well studied, the e ects of a surface normal pressure gradient are evident as the ow over a rotationally oscillating cylinder, in which ow separation can be reduced as veriÿed experimentally by Tokumaru and Dimotakis [27], and numerically by Lu and Sato [28] and Lu [29]. Thus, as described above, the e ect of the surface normal pressure gradient when c¿1 approximately is a mechanism for the suppression of ow separation along the plate, in particular in the region of the crest.…”

“…The ow over the wavy wall is strongly a ected by surface normal pressure gradient and centrifugal force due to alternating convex and concave curvatures. The e ects of a surface normal pressure gradient are evident as the ow over a rotationally oscillating cylinder, in which ow separation can be reduced as observed experimentally by Tokumaru and Dimotakis [27], and numerically by Lu and Sato [28] and Lu [29]. Experiments were undertaken to investigate viscous ow past a travelling wavy wall.…”

Numeric Simulation on the Performance of an Undulating Fin in the Wake of a Periodic Oscillating Plate

“…The fin boundary is no longer a streamline and there are streamlines that emanate from the fin and end on the fin. Lu and Tokumaru have verified that the travelling wave motion of the fin tends to suppress flow separation along the fin surface by both numerical and experimental methods respectively [36–37].…”