Effects of an upstream triangular plate on the wing-body junction flow

Théberge, M.-A.; Ekmekci, Alis

doi:10.1063/1.5000733

Cited by 5 publications

(4 citation statements)

References 33 publications

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“…Even though the proposed mechanisms for it show some differences, all observations agree the disappearance of the PHV mainly occurs in the region very close to the cylinder surface. The turbulent HV system triggers the local scour process in front of vertical piers on a flat loose bed by significantly amplifying the bed shear stress in this region [6,8,14]. The amplification of the bed shear stress is tightly related to the vertical position, size, and strength of the HVs as its magnitude is determined directly by the wall-normal gradient of the streamwise velocity, ∂U/∂y, induced by the HVs at the bed surface.…”

Section: Disappearance Of Phvmentioning

confidence: 99%

“…Depending on the regime of the approaching flow at the location of the cylinder, the horseshoe vortex (HV) system appears as a laminar or turbulent system, respectively [7]. The turbulent HV system oscillates randomly in front of the cylinder, inducing highly elevated means and fluctuations in bed shear stress [8]. Therefore, a full understanding of the evolution of the turbulent HV system is necessary for understanding, predicting, and controlling the initial stage of the local scour in front of cylinders.…”

Section: Introductionmentioning

confidence: 99%

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Evolution of Turbulent Horseshoe Vortex System in Front of a Vertical Circular Cylinder in Open Channel

Chen

Yang

2019

Water

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A turbulent horseshoe vortex (HV) system around a wall-mounted cylinder in open channel is characterized by random variations in vortex features and an abundance of vortex interactions. The turbulent HV system is responsible for initiating the local scour process in front of the cylinder. The evolution of the turbulent HV system is investigated statistically and quantitatively with time-resolved particle image velocimetry. The cylinder Reynolds numbers of the flow are 8600, 10,200, and 13,600, respectively. A novel vortex tracking method was proposed to obtain the variations in position, size, and strength of the primary HV (PHV) which dominates the system most of the time. Relationships between the various features of the PHV during its evolutionary process were obtained through correlation analyses. Results show that the dimensionless mean lifespan of the PHV is about 5.0. Statistically, the downstream movement of the PHV toward the cylinder is accompanied with its bed-approaching movement and decreasing in size, and the opposite is true. The circulation strength of the PHV decreases and increases dramatically in the region downstream of its time-averaged position when the PHV approaches and departs from the cylinder, respectively. Meanwhile, mechanisms responsible for the generation, movement, variation, and disappearance of the PHV are re-investigated and enriched based on its interactions with vortices in the separation region and structures in the incoming flow. The obtained change trends of the features of the PHV and the underlying mechanisms for its evolution are valuable for predicting and controlling the initial stage of the local scour in front of cylinders.

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Section: Disappearance Of Phvmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evolution of Turbulent Horseshoe Vortex System in Front of a Vertical Circular Cylinder in Open Channel

Chen

Yang

2019

Water

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“…These vortices include a bound vortex that encircles the small cylinder and two trailing vortices extending from the bound vortex into the wake region. The number of Hs and their oscillation frequency can vary depending on the regime, significantly affecting the wall shear stress 38 . Therefore, gaining a comprehensive understanding of the turbulent H-system is crucial for comprehending, predicting, and controlling the local dynamics in front of cylinders.…”

Section: Resultsmentioning

confidence: 99%

Direct numerical simulation of the turbulent flow around a Flettner rotor

Massaro,

Karp,

Jansson

et al. 2024

Sci Rep

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The three-dimensional turbulent flow around a Flettner rotor, i.e. an engine-driven rotating cylinder in an atmospheric boundary layer, is studied via direct numerical simulations (DNS) for three different rotation speeds ($$\alpha$$ α ). This technology offers a sustainable alternative mainly for marine propulsion, underscoring the critical importance of comprehending the characteristics of such flow. In this study, we evaluate the aerodynamic loads produced by the rotor of height h, with a specific focus on the changes in lift and drag force along the vertical axis of the cylinder. Correspondingly, we observe that vortex shedding is inhibited at the highest $$\alpha$$ α values investigated. However, in the case of intermediate $$\alpha$$ α , vortices continue to be shed in the upper section of the cylinder ($$y/h>0.3$$ y / h > 0.3 ). As the cylinder begins to rotate, a large-scale motion becomes apparent on the high-pressure side, close to the bottom wall. We offer both a qualitative and quantitative description of this motion, outlining its impact on the wake deflection. This finding is significant as it influences the rotor wake to an extent of approximately one hundred diameters downstream. In practical applications, this phenomenon could influence the performance of subsequent boats and have an impact on the cylinder drag, affecting its fuel consumption. This fundamental study, which investigates a limited yet significant (for DNS) Reynolds number and explores various spinning ratios, provides valuable insights into the complex flow around a Flettner rotor. The simulations were performed using a modern GPU-based spectral element method, leveraging the power of modern supercomputers towards fundamental engineering problems.

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“…The most studied and used solutions are the leading-edge fairing and the whole-body fairing. The former alters the shape of the wing nose in order to reduce the adverse pressure gradient generated by the leading edge, thus suppressing the onset of the horseshoe vortex [14][15][16][17][18][19]. The latter consists in wrapping the entire junction area with a fairing designed to suppress flow separation.…”

Section: Introductionmentioning

confidence: 99%

A Review of Numerical and Experimental Studies of the Anti-Fairing

Belligoli

Dwight

Eitelberg

et al. 2020

Aiaa Aviation 2020 Forum

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An anti-fairing is a concave deformation of the wall around a wing-body junction that can decrease the aerodynamic drag through the activation of a propulsive force generated by the interaction of the curved concave shape and the high-pressure region in proximity of the wing leading-edge. Although this mechanism is well understood, the dynamics of the interaction between the anti-fairing and the junction flow remain largely unexplored. This work brings together all the numerical and experimental studies of the anti-fairing to investigate its effect on turbulent quantities and the robustness of its design to changes to the incoming flow parameters, and to estimate the drag change with respect to a normal wing/flat-plate configuration. It is found that the interaction of the streamwise pressure gradient generated by the anti-fairing with the incoming boundary layer substantially reduces the shear responsible for viscous drag. Furthermore, no significant influence of the incoming boundary layer thickness on the antifairing performance is observed. However, a direct drag measurement with a force balance casts some doubts on the possibility to achieve large drag reductions.

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Effects of an upstream triangular plate on the wing-body junction flow

Cited by 5 publications

References 33 publications

Evolution of Turbulent Horseshoe Vortex System in Front of a Vertical Circular Cylinder in Open Channel

Evolution of Turbulent Horseshoe Vortex System in Front of a Vertical Circular Cylinder in Open Channel

Direct numerical simulation of the turbulent flow around a Flettner rotor

A Review of Numerical and Experimental Studies of the Anti-Fairing

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