Model for rotor tip vortex-airframe interaction. I - Theory

Affes, H.; Conlisk, A. T.

doi:10.2514/3.11924

Cited by 22 publications

(7 citation statements)

References 18 publications

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“…Computational estimates by Affes and Conlisk 10 indicate that signi cant inviscid deformation of the vortex core shape may occur as the vortexmoves close to the cylinderleadingedge. In this section, we examine the extent of core shape deformation and its effect on the cylinder surface pressure distribution by comparing predictions from a computation based on solution of the full Euler equations for a nite-corevortex with predictionsfrom the vortex lament model.…”

Section: Core Shape Deformationmentioning

confidence: 98%

Normal Vortex Interaction with a Circular Cylinder

1999

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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.

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Section: Core Shape Deformationmentioning

confidence: 98%

Normal Vortex Interaction with a Circular Cylinder

1999

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“…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).…”

Section: Introductionmentioning

confidence: 87%

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

Gorecki

Selvam

2014

J Vis

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A three-dimensional CFD model, based on large eddy simulation, is utilized to numerically simulate a perpendicular interaction between a traveling tornado-like vortex and a wide rigid wall. The tornado-like flow is modeled by the Rankine-Combined Vortex Model. The case, where the wall width is much larger than the tornado vortex core diameter is examined. The main goal of the paper is to improve the understanding of the dynamics of the tornado-wall interaction. The conclusions drawn in this study are supported by various visualizations. During the tornado impact, the structure of the tornado-like vortex is substantially mitigated by the wide wall. The low-level portion of the vortex is disturbed both in front of the wall and behind the wall. When the vortex is approaching the wall, the vortex-induced velocities cause a boundary layer separation from the leading face of the wall. The ejected, from the wall, vorticity patches wrap around the tornado-like vortex causing its weakening. Behind the wall the tornado vortex is subjected to the turbulent flow that further disrupts the tornado vortex structure. The tornado-like vortex mitigation results in a low wind speed region behind the tornado-break wall, where the wind velocities are reduced by more than 50 %.

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“…This is the third part of a series of papers on vortex/surface interaction. 2 ' 3 The objective is to identify and understand the primary features of the viscous flow on the airframe due to the impinging tip vortex. However, the difficulties associated with such a study are severe; it is well known from previous work that a primary feature of boundary layers induced by vortical structures is the development of a secondary eddy in the boundary layer on the airframe, which grows in time and is eventually ejected from the boundary layer.…”

Section: Introductionmentioning

confidence: 99%

Model for Rotor Tip Vortex-Airframe Interaction Part 3: Viscous Flow on Airframe

Affes

Xiao²,

Conlisk³

et al. 1998

AIAA Journal

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The behavior of vortex systems in the vicinity of solid surfaces is a matter of intense interest in rotorcraft aerodynamics, as well as in many other areas of fluid dynamics. We consider the viscous flow on a simplified model of a helicopter airframe due to a helicopter rotor tip vortex both experimentally and computationally. As the tip vortex approaches the airframe, the computational results predict the genesis of a region just upstream of the main vortex, characterized by reversed flow and rapid growth in size. The experiments clearly show evidence of such a region under the tip vortex in the region predicted by the computations and at roughly the same time. The secondary vorticity field in the computations is of a sign opposite to the vorticity associated with the tip vortex. Results for the streamline patterns and vorticity field during the genesis of the secondary eddy are presented and compared with experimental flow visualization results.

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Model for rotor tip vortex-airframe interaction. I - Theory

Cited by 22 publications

References 18 publications

Normal Vortex Interaction with a Circular Cylinder

Normal Vortex Interaction with a Circular Cylinder

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

Model for Rotor Tip Vortex-Airframe Interaction Part 3: Viscous Flow on Airframe

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