Experiments on tip vortices interacting with downstream wings

Chen, Chen; Wang, Zhijin; Gursul, Ismet

doi:10.1007/s00348-018-2539-7

Cited by 19 publications

(15 citation statements)

References 50 publications

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“…However, their analysis is more focused on the steady aerodynamics that appear in formation flying of fixed-wing aircrafts, rather than in the unsteady impinging of vortices in a flapping wing. Recently, Chen et al [40] have characterized experimentally the flow structures generated by the interaction of the wing tip vortices of two wings with different vertical and spanwise offsets for the wing tips at Re = 5 • 10 3 . Similarly, McKenna and coworkers [41,42] have investigated the flow patterns formed by an impinging wing tip vortex upon the wing tip of an oscillating wing.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of flow over flapping wings in tandem: wingspan effects

Jurado,

Arranz,

Flores

et al. 2022

Preprint

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We report direct numerical simulations of a pair of wings in horizontal tandem configuration, to analyze the effect of their aspect ratio on the flow and the aerodynamic performance of the system. The wings are immersed in a uniform free-stream at Reynolds number Re = 1000, and they undergo heaving and pitching oscillation with Strouhal number St = 0.7. The aspect ratios of forewing and hindwing vary between 2 and 4. The aerodynamic performance of the system is dictated by the interaction between the trailing edge vortex (TEV) shed by the forewing and the induced leading edge vortex formed on the hindwing. The aerodynamic performance of the forewing is similar to that of an isolated wing irrespective of the aspect ratio of the hindwing, with a small modulating effect produced by the forewing-hindwing interactions. On the other hand, the aerodynamic performance of the hindwing is clearly affected by the interaction with the forewing's TEV. Tandem configurations with a larger aspect ratio on the forewing than on the hindwing result in a quasi-two-dimensional flow structure on the latter. This yields an 8% increase in the time-averaged thrust coefficient of the hindwing, with no change in its propulsive efficiency.

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Section: Introductionmentioning

confidence: 99%

Numerical simulation of flow over flapping wings in tandem: wingspan effects

Jurado,

Arranz,

Flores

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…However, it also plays a crucial and hazardous role on the traffic capacity, 4 aerodynamic noise 5 and safety of aircraft. 6 Motivated by these meaningful engineering problems, a large body of scientific researches have been undertaken to investigate the structure of wingtip vortex and its development from the near wake 7 to middle wake 8 and far wake. 9 Among these investigations, the effects of wing geometry parameters, 10 flow conditions, and winglet shapes, 11 as well as the inner interactions 12 or interactions with surrounding flow 13 are mostly focused.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on the structures and induced drag of wingtip vortices for different wingtip configurations

Cheng

Xiang

Liu

2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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As an effective method to reduce induced drag and the risk of wake encounter, the winglet has been an essential device and developed into diverse configurations. However, the structures and induced drag, as well as wandering features of the wingtip vortices ( WTVs) generated by these diverse winglet configurations are not well understood. Thus, the WTVs generated by four typical wingtip configurations, namely the rectangular wing with blended/raked/split winglet and without winglet (Model BL/ RA/ SP/NO for short), are investigated in this paper using particle image velocimetry technology. Comparing with an isolated primary wingtip vortex generated by Model NO, multiple vortices are twisted coherently after installing the winglets. In addition, the circulation evolution of WTVs demonstrates that the circulation for Model SP is the largest, while Model RA is the smallest. By tracking the instantaneous vortex center, the vortex wandering behavior is observed. The growth rate of wandering amplitude along with the streamwise location from the quickest to the slowest corresponds to Model SP, Model NO, Model BL, Model RA in sequence, implying that the WTVs generated by model SP exhibit the quickest mitigation. Considering that the induced drag scales as the lift to power 2, the induced drag and lift are estimated based on the wake integration method, and then the form factor λ, defined by [Formula: see text], is calculated to evaluate the aerodynamic performance. Comparing with the result of Model NO, the form factor decreases by 7.99%, 4.80%, and 2.60% for Model RA, Model BL, Model SP, respectively. In sum, Model RA and BL have a smaller induced drag coefficient but decay slower; while Model SP has a larger induced drag coefficient but decays quicker. An important implication of these results is that reducing the strength of WTVs and increasing the growth rate of vortex wandering amplitude can be the mutual requirements for designing new winglets.

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“…This topic is comprehensively reviewed by Gursul (2004). The effect of the leading-edge sweep-angle and Reynolds number on the development of axial velocity in the vortex core was conducted computationally by Chen et al (2018). It was ascertained that the Reynolds number has the most influence over the axial flow in trailing vortices behind a delta wing: for Re ≥ 10 5 , a jet-like axial velocity profile is most commonly observed behind a delta wing with sweep-angles of both 50 • and 76 • .…”

Section: Introductionmentioning

confidence: 99%

Spatial development of trailing vortices behind a delta wing, in and out of ground effect

Morris

Williamson

2020

Exp Fluids

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In this research, we study the dynamics of vortex pairs both in and out of ground effect. Trailing vortices are generated by towing a 75 • leading-edge sweep-angle delta wing in an XY-towing tank, at 15 • angle of attack. As the delta wing is towed, it generates a spatially developing vortex pair with the axial (streamwise) flow in the vortex cores. Particle image velocimetry is used to determine the transverse velocity field, and the vortex pair is found to be well-characterized by the superposition of two Lamb-Oseen vortices. The axial flow is captured using a longitudinal light sheet. To ensure we capture the vortex core, a technique is used wherein the light sheet is set such that it is slightly oblique to the length of the vortex. Using this technique allows the axial flow to be measured in the vortex core more than 20 chord-lengths downstream of the delta wing, capturing data at a resolution as close as 0.03 chord-lengths apart. This technique is unaffected by displacements of the vortex core, allowing us to analyze the axial flow profile both in and out of ground effect. A Gaussian velocity profile with a wake-like velocity deficit (flow upstream) is observed in the far-wake of the delta wing in both cases. We also trigger the long-wavelength instability (

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Experiments on tip vortices interacting with downstream wings

Cited by 19 publications

References 50 publications

Numerical simulation of flow over flapping wings in tandem: wingspan effects

Numerical simulation of flow over flapping wings in tandem: wingspan effects

Experimental investigation on the structures and induced drag of wingtip vortices for different wingtip configurations

Spatial development of trailing vortices behind a delta wing, in and out of ground effect

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