Identification of vortex pairs in aircraft wakes from sectional velocity data

Carmer, Carl F. v.; Konrath, Robert; Schröder, Andreas; Monnier, Jean-Claude

doi:10.1007/s00348-007-0450-8

Cited by 12 publications

(6 citation statements)

References 27 publications

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“…Zhou et al (1999) determined that vortices correspond to regions where the imaginary component of the complex eigenvalues is greater than zero, λ ci > 0. To improve the signal-to-noise ratio the imaginary part of the complex eigenvalue is typically squared λ 2 ci and is used as a threshold to identify vortices (Carmer et al 2008). Threshold levels help to differentiate between turbulent structures that exist within the free-stream flow and measurement noise.…”

Section: Identification Of Large-scale Wake Structuresmentioning

confidence: 99%

Flow topology in the wake of a cyclist and its effect on aerodynamic drag

et al. 2014

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Three-dimensional flows around a full-scale cyclist mannequin were investigated experimentally to explain the large variations in aerodynamic drag that are measured as the legs are positioned around the 360 • crank cycle. It is found that the dominant mechanism affecting drag is not the small variation in frontal surface area over the pedal stroke but rather due to large changes in the flow structure over the crank cycle. This is clearly shown by a series of detailed velocity field wake surveys and skin friction flow visualizations. Two characteristic flow regimes are identified, corresponding to symmetrical low-drag and asymmetrical high-drag regimes, in which the primary feature of the wake is shown to be a large trailing streamwise vortex pair, orientated asymmetrically in the centre plane of the mannequin. These primary flow structures in the wake are the dominant mechanism driving the variation in drag throughout the pedal stroke. Topological critical points have been identified on the suction surfaces of the mannequin's back and are discussed with velocity field measurements to elucidate the time-average flow topologies, showing the primary flow structures of the low-and high-drag flow regimes. The proposed flow topologies are then related to the measured surface pressures acting on the suction surface of the mannequin's back. These measurements show that most of the variation in drag is due to changes in the pressure distribution acting on the lower back, where the large-scale flow structures having the greatest impact on drag develop.

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Section: Identification Of Large-scale Wake Structuresmentioning

confidence: 99%

Flow topology in the wake of a cyclist and its effect on aerodynamic drag

et al. 2014

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“…42 Page 2 of 12 fields of view of typically 40 × 30 cm 2 (Carmer et al 2008;Lignarolo et al 2014 among others).…”

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confidence: 99%

On the use of helium-filled soap bubbles for large-scale tomographic PIV in wind tunnel experiments

et al. 2015

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tracing fidelity is controlled by the flow rates of helium, liquid soap and air in HFSB production. A characteristic time response, defined as the ratio of slip velocity and the fluid acceleration, is obtained. The feasibility of performing time-resolved tomographic PIV measurements over large volumes in aerodynamic wind tunnels is also studied. The flow past a 5-cm-diameter cylinder is measured over a volume of 20 × 20 × 12 cm 3 at a rate of 2 kHz. The achieved seeding density of <0.01 ppp enables resolving the Kármán vortices, whereas turbulent substructures cannot be captured.

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“…The velocity data were used to determine the vortex strength, size, and location at the PIV plane. To identify the vortex centre, the Q -function was employed (equation (1)), which is a local indicator of the rotation rate compared to the strain rate [ 26 ]. The advantage of this method over the vorticity parameter is that it can distinguish between rotational vortex flows, where Q < 0, and vortical shear layers, where Q becomes > 0.…”

Section: Cfd Methodologymentioning

confidence: 99%

Intake ground vortex characteristics

Mishra

MacManus

Murphy

2011

Proceedings of the Institution of Mechanical Engineers, Part G:

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The development of ground vortices when an intake operates in close proximity to the ground has been studied computationally for several configurations including front and rear quarter approaching flows as well as tailwind arrangements. The investigations have been conducted at model scale using a generic intake geometry. Reynolds Averaged Navier–Stokes calculations have been used and an initial validation of the computational model has been carried out against experimental data. The computational method has subsequently been applied to configurations that are difficult to test experimentally by including tailwind and rear quarter flows. The results, along with those from a previous compatible study of headwind and pure cross-wind configurations, have been used to assess the ground vortex behaviour under a broad range of velocity ratios and approaching wind angles. The characteristics provide insights on the influence of the size and strength of ground vortices on the overall quality of the flow ingested by the intake.

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Identification of vortex pairs in aircraft wakes from sectional velocity data

Cited by 12 publications

References 27 publications

Flow topology in the wake of a cyclist and its effect on aerodynamic drag

Flow topology in the wake of a cyclist and its effect on aerodynamic drag

On the use of helium-filled soap bubbles for large-scale tomographic PIV in wind tunnel experiments

Intake ground vortex characteristics

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