Investigation of rotor tip vortex interactions with a body

Bi, Naipei; Leishman, J. Gordon; Crouse, Gilbert L.

doi:10.2514/3.46430

Cited by 11 publications

(4 citation statements)

References 12 publications

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“…5 Several previousexperimentalstudies of vortex-cylinderinteraction have been performed that report information such as vortex trajectory prior to impact with the cylinder and surface pressure variation on the cylinder. 6 -9 Bi et al 7 note that tip vortex impingement on a cylinder causes large transient loads on the surface coupled with an adverse pressure gradient in the spanwise direction, suggesting separation of the boundary layer at the cylinder leading edge. Brand et al 9 note that interaction with a cylinder appears to induce breakdown of an impinging vortex and that following impingement the vortex breaks into two separate parts, which travel independently past the sides of the cylinder while a weak low-pressure region remains at the point of impingement.…”

Section: Introductionmentioning

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: Introductionmentioning

confidence: 98%

Normal Vortex Interaction with a Circular Cylinder

1999

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“…The present paper is concerned with boundary-layer separation and ejection of secondary vorticity induced by a vortex located near a circular cylinder, where the vortex axis is nominally orthogonal to the cylinder axis and the vortex core radius is much less than the cylinder diameter. This problem is particularly representative of rotorcraft aerodynamic problems, where impact of rotor tip vortices on the vehicle empennage, airframe and tail section during hover and low-speed flight causes strong impulsive forces and moments on the vehicle (Sheridan & Smith 1980;Bi & Leishman 1990;Bi, Leishman & Crouse 1993). Vortex-cylinder interaction is also important in problems such as turbulence-wall interaction in marine cable boundary layers (Neves, Moin & Moser 1994) and unsteady loading in an array of parallel cylinders owing to vortices shed from upstream cylinders, such as occurs in offshore platform risers, groups of tall buildings, and heat exchanger tube bundles (Rockwell 1998).…”

Section: Introductionmentioning

confidence: 99%

“…Several experimental studies of vortex-cylinder interaction have been performed that present results for surface pressure variation and vortex trajectory prior to impact with the cylinder. Bi & Leishman (1990) and Bi et al (1993) examine rotor tip-vortex interaction with a cylinder projecting from a body, modelling a helicopter with a long tail boom in low-speed flight. Trajectories of the tip vortices, located using the shadowgraph technique, are correlated with surface pressure variation, measured by an array of pressure taps along the cylindrical boom.…”

Section: Introductionmentioning

confidence: 99%

Simulation of normal vortex–cylinder interaction in a viscous fluid

Gossler

Marshall

2001

J. Fluid Mech.

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A computational study of three-dimensional vortex–cylinder interaction is reported for the case where the nominal orientation of the cylinder axis is normal to the vortex axis. The computations are performed using a new tetrahedral vorticity element method for incompressible viscous fluids, in which vorticity is interpolated using a tetrahedral mesh that is refit to the Lagrangian computational points at each timestep. Fast computation of the Biot-Savart integral for velocity is performed using a box-point multipole acceleration method for distant tetrahedra and Gaussian quadratures for nearby tetrahedra. A moving least-square method is used for differentiation, and a flux-based vorticity boundary condition algorithm is employed for satisfaction of the no-slip condition. The velocity induced by the primary vortex is obtained using a filament model and the Navier–Stokes computations focus on development of boundary-layer separation from the cylinder and the form and dynamics of the ejected secondary vorticity structure. As the secondary vorticity is drawn outward by the vortex-induced flow and wraps around the vortex, it has a substantial effect both on the essentially inviscid flow field external to the boundary layer and on the cylinder surface pressure field. Cases are examined with background free-stream velocity oriented in the positive and negative directions along the cylinder axis, with free-stream velocity normal to the cylinder axis, and with no free-stream velocity. Computations with no free-stream velocity and those with free-stream velocity tangent to the cylinder axis exhibit similar secondary vorticity structures, consisting of a vortex loop (or hairpin) that wraps around the primary vortex and is attached to the cylinder boundary layer at two points. Computations with free-stream velocity oriented normal to the cylinder axis exhibit secondary vorticity structure of a markedly different character, in which the secondary eddy remains close to the cylinder boundary and has a quasi-two-dimensional form for an extended time period.

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“…This interaction is interesting because its basic geometry can, under certain conditions, be similar to OBVI experienced by tail rotors. Both experimental [19][20][21] and computational studies [22] of this phenomenon have been conducted and significant advances have been made in the understanding of it. In particular, it has been established that the tip vortices deform significantly prior to impact on the vehicle surface and that the form of the pressure response at the surface varies considerably depending on relative location of the measurement point with respect to the point of impingement of the vortex core.…”

Section: Interactional Aerodynamicsmentioning

confidence: 99%

Helicopter tail rotor orthogonal blade vortex interaction

Coton

Marshall

Galbraith

et al. 2004

Progress in Aerospace Sciences

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The aerodynamic operating environment of the helicopter is particularly complex and, to some extent, dominated by the vortices trailed from the main and tail rotors. These vortices not only determine the form of the induced flow field but also interact with each other and with elements of the physical structure of the flight vehicle. Such interactions can have implications in terms of structural vibration, noise generation and flight performance. In this paper, the interaction of main rotor vortices with the helicopter tail rotor is considered and, in particular, the limiting case of the orthogonal interaction. The significance of the topic is introduced by highlighting the operational issues for helicopters arising from tail rotor interactions. The basic phenomenon is then described before experimental studies of the interaction are presented. Progress in numerical modelling is then considered and, finally, the prospects for future research in the area are discussed.

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Investigation of rotor tip vortex interactions with a body

Cited by 11 publications

References 12 publications

Normal Vortex Interaction with a Circular Cylinder

Normal Vortex Interaction with a Circular Cylinder

Simulation of normal vortex–cylinder interaction in a viscous fluid

Helicopter tail rotor orthogonal blade vortex interaction

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