Boundary layer vortex sheet evolution around an accelerating and rotating cylinder

Gehlert, Pascal; Babinsky, Holger

doi:10.1017/jfm.2021.121

Cited by 17 publications

(11 citation statements)

References 37 publications

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“…Missing data due to laser reflections close to the cylinder and plate surface are recovered by interpolating between the tracked cylinder and plate surface velocities and the external flowfield [14].…”

Section: Naca-0021 Wingmentioning

confidence: 99%

“…Here, the flowfield can be understood to be composed of a superposition of individual flow elements. As such, we model free vorticity as a collection of point vortices and the boundary layer as a superposition of individual vortex sheets [29,10,16,14], where the rate of change of each component of vorticity links to a force [19].…”

Section: Introductionmentioning

confidence: 99%

“…We note that similar to the approach used in previous studies [9,14], boundary layer vorticity is replaced by a vortex sheet γ b located on the body surface, as permitted by the potential flow framework and illustrated in figure 3. The first integral in equation 8 is performed over the cylinder surface B b , whilst the second acts on the area of the remaining flowfield.…”

mentioning

confidence: 99%

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Vortex Force Decomposition - Forces Associated with Individual Elements of a Vorticity Field

Gehlert

Andreu-Angulo

Babinsky

2023

Preprint

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The impulse theory used to calculate the force from a vorticity distribution in two-dimensional, incompressible flow, is re-cast with the aim of approximating, to a first order, the forces generated by a specific flow feature, such as a free vortex passing by an object. To achieve this, the force acting on the body is split up into several core contributions. The first component arises from the time variation of the body's boundary layer. The second is generated by the advection of any free vorticity located in the flowfield by the object's boundary layer vorticity. The final force contribution is due to new vorticity being shed. To test the theory, it is applied to two multi-body flowfields consisting of a circular cylinder and a flat plate wing at incidence in close proximity. Force balance measurements and planar particle image velocimetry data are simultaneously obtained at Reynolds numbers of 10 000 and 20 000. The forces acting on the cylinder are successfully recovered from the vorticity data using the derived formulation, verifying its accuracy. Subsequently, the proposed force formulation is used to create force heat maps that demonstrate how the location of a leading edge vortex affects its force contribution around a pitching NACA-0021 wing translating at a Reynolds number of 10 000.

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Section: Naca-0021 Wingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Vortex Force Decomposition - Forces Associated with Individual Elements of a Vorticity Field

Gehlert

Andreu-Angulo

Babinsky

2023

Preprint

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“…This complex representation of potential flows continues to be an integral part of the recent research in fluid mechanics, both for canonical [2][3][4][5][6] and applied [7][8][9][10][11][12] flows. In particular, the complex potential is used in both classical and modern monographs about vortex dynamics [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Stability of two-dimensional potential flows using bicomplex numbers

2022

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The use of the complex velocity potential and the complex velocity is widely disseminated in the study of two-dimensional incompressible potential flows. The advantages of working with complex analytical functions made this representation of the flow ubiquitous in the field of theoretical aerodynamics. However, this representation is not usually employed in linear stability studies, where the representation of the velocity as real vectors is preferred by most authors, in order to allow the representation of the perturbation as the complex exponential function. Some of the classical attempts to use the complex velocity potential in stability studies suffer from formal errors. In this work, we present a framework that reconciles these two complex representations using bicomplex numbers. This framework is applied to the stability of the von Kármán vortex street and a generalized formula is found. It is shown that the classical results of the symmetric and staggered von Kármán vortex streets are just particular cases of the generalized dynamical system in bicomplex formulation.

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“…Added mass force is a useful concept since it is easy to calculate and when acceleration rates are large, it captures the main unsteady force contribution [14,15]. Moreover, viewing the boundary layer vorticity as a superposition of individual vortex sheets, where the rate of change of each component links to a force, has been beneficial in understanding unsteady flows and provides an incentive to correctly identify these [7,16,17].…”

Section: Introductionmentioning

confidence: 99%