Normal Vortex Interaction with a Circular Cylinder

Abstract

Interaction of a columnar vortex with a long circular cylinder translated normal to the vortex axis is examined for the case where the cylinder diameter is much larger than the vortex core radius. The study focuses on understanding and quantifying the limitations of traditional vortex lament models arising from vortex-induced separation of the cylinder boundary layer and vortex core shape deformation. These limitations are examined over a wide range of values of the impact parameter, de ned as the ratio of the ambient normal velocity past the cylinder to the maximum vortex azimuthal velocity. Filament model predictions of vortex displacement are compared to experimental data both before and after vortex-induced boundary-layer separation. Experimental data are presented showing the importance of the ambient normal velocity to the cylinder in delaying vortex-induced boundary-layer separation, so that for cases with high impact parameter the ow is governed by inviscid effects even as the vortex moves quite close to the cylinder surface. The inviscid shape deformation of the vortex core is modest in the cases examined, even for close vortex-cylinder interaction, and is shown to have small effect on the surface pressure. The topology of secondary vorticity structures ejected from the cylinder boundary layer is examined using a two-color laserinduced uorescence technique and is found to be qualitatively different for cases with high and low values of the impact parameter.

Visualization of tornado-like vortex interacting with wide tornado-break wall

“…6d). The tornado vortex behavior during the interaction with a wall reveals very similar characteristics as a normal vortex interaction with a thick cylinder (Krishnamoorthy et al 1999), in which laboratory experiments showed substantial streamwise bending and spanwise displacement of a vortex during the impact.…”

“…In the orthogonal blade-vortex interaction and the cylinder-vortex interaction it was commonly observed that the translating vortex was influenced by the wall at some distance before the impact (Krishnamoorthy and Marshall 1998;Krishnamoorthy et al 1999). The cause was the boundary layer separation and ejection of secondary vortices from the body leading surface.…”

“…Another characteristic aspect of the vortex-cylinder interaction is the streamwise and lateral displacement of the vortex, in front of the cylinder. Affes and Conlisk (1993) explained this effect based on an invicid theory, which was later confirmed by laboratory experiments (Krishnamoorthy et al 1999). A detailed review of the research on the orthogonal blade-vortex interaction is provided by Coton et al (2004).…”

“…Among those interactions, an orthogonal vortex-cylinder interaction most closely corresponds to the problem studied in this paper. Krishnamoorthy et al (1999) demonstrated that during the vortex-cylinder interaction the vortex induces a boundary layer separation from the circular cylinder wall. The duration of this process is governed by an impact parameter that represents the ratio of the impact velocity to the maximum vortex tangential velocity.…”

Numerical Study of the Instability and Flow Transition in a Vortex-Ring/Wall Interaction

“…Moreover, it is observed from Figs. 2(d) and 2(e) that a series of loop-like vortices (Krishnamoorthy and Marshall 1998;Krishnamoorthy et al 1999;Gossler and Marshall 2001) and hair-pin vortices (Hon and Walker 1991;Adrian 2007;Liu and Chen 2011) wrapping around the vortex rings are formed. With the evolution of vortical structures, it is seen that the strength and number of the wrapping vortices are increased con-siderably as shown in Figs.…”