scholarly journals Numerical 3D study on the influence of spanwise distribution of tubercles on wings for UAV applications

2019 ◽  
Vol 304 ◽  
pp. 02014
Author(s):  
Charalampos Papadopoulos ◽  
Vasilis Katsiadramis ◽  
Kyros Yakinthos
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Computational Study ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Number Range ◽  
Reynolds Number Range ◽  
Efficiency Increase ◽  
Sinusoidal Shape

In this work, a 3D numerical study on the influence of the spanwise distribution of tubercles for UAV applications is presented. The idea of using tubercles in aeronautics comes from the humpback whale (Megaptera novaeangliae) which has a characteristic flipper, with a spanwise scalloped leading edge, creating an almost sinusoidal shape, consisting of bumps called tubercles. Early experimental research showed a great potential in enhancing the 3D aerodynamic characteristics of a wing. Most of the existing experimental results concern infinite wings (2D) models and are accompanied with substantial loss in lift and increase in drag in pre–stall region. On the other hand, finite models (3D) have displayed a better overall aerodynamic performance (increased lift and moment, but also decreased drag). At a range of Reynolds number between 500,000 and 1,000,000 (based on the mean chord of the flipper), tubercles act as virtual fences, introducing a pair of counter rotating vortices that delays the stall of the flipper, a phenomenon that the whales use to perform sharp turns and catch their prey. The aforementioned Reynolds number range is the same as the operational Reynolds number for typical Unmanned Aerial Vehicles (UAV). To assess the influence of the tubercles installation on UAV wings, a full 3D computational study is carried-out, with the use of CFD tools that at a first phase are validated and calibrated with available in the literature experimental data. Then, computations are performed, for different spanwise tubercles distributions. The results show that there is a noticeable potential on controlling the flow on the wings of a UAV operating in a Reynolds number range between 500,000 and 1,000,000 (based on UAV’s wing mean chord), which can lead to an aerodynamic performance and efficiency increase.

Influence of tubercles’ spanwise distribution on swept wings for unmanned aerial vehicles

2020 ◽  
pp. 095441002091958
Author(s):  
Charalampos Papadopoulos ◽  
Vasilis Katsiadramis ◽  
Kyros Yakinthos
Keyword(s):  
Reynolds Number ◽  
Unmanned Aerial Vehicles ◽  
Numerical Study ◽  
Computational Study ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Number Range ◽  
Aerial Vehicles ◽  
Reynolds Number Range

In this work, a 3D numerical study on the influence of the spanwise distribution of tubercles on a unmanned aerial vehicle wing is presented. The idea of using tubercles in aeronautics comes from the humpback whale (Megaptera novaeangliae) which has a characteristic flipper, with a spanwise scalloped leading edge, creating an almost sinusoidal shape, consisting of bumps called tubercles. The whale uses this layout in order to achieve high underwater maneuverability. Early experimental research showed a great potential in enhancing the 3D aerodynamic characteristics of a wing. Most of the existing experimental results concern infinite wings (2D) models and are accompanied with substantial loss in lift and increase in drag in pre-stall region. On the other hand, 3D finite models have displayed a better overall aerodynamic performance (increased lift and moment, but also, decreased drag). At a range of Reynolds number between 500,000 and 1,000,000 (based on the mean chord of the flipper), tubercles act as virtual fences, introducing a pair of counter rotating vortices that delays the stall of the flipper, a phenomenon that the whales exploit to perform sharp turns and catch their prey. The aforementioned Reynolds number range is the same as the operational Reynolds number for typical unmanned aerial vehicles. To assess the influence of the tubercles installation on UAV wings, a full 3D computational study is carried-out with the use of CFD tools which at a first phase are validated and calibrated with the available literature experimental data. Then, computations are performed for different spanwise tubercles distributions. The results show that there is a noticeable potential on controlling the flow on the wings of a UAV operating in a Reynolds number range between 500,000 and 1,000,000 (based on UAV’s wing mean chord), which can lead to an aerodynamic performance and efficiency increase.

scholarly journals Lift Generation of an Elliptical Airfoil at a Reynolds Number of 1000

2019 ◽  
Vol 16 (2) ◽  
pp. 6738-6752
Author(s):  
S. Tobing
Keyword(s):  
Reynolds Number ◽  
Unsteady Aerodynamics ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Two Dimensional ◽  
Hovering Flight ◽  
Number Range ◽  
High Production ◽  
Passenger Aircraft ◽  
3D Wing

Bumblebees cannot fly! That conclusion is likely to be drawn by scientists who analysed the insect using aerodynamics of stationary wings such as that of a passenger aircraft. Looking at the insect again using a newfound understanding of unsteady aerodynamics; it is clear why bumblebees can fly. Bumblebees utilise mechanisms behind unsteady aerodynamics such as leading-edge vortices (LEVs) formation, wake capture, and rapid end-of-stroke rotation to generate forces that enable the insect to fly. This study focuses on two-dimensional (2D) elliptical airfoil. Earlier works found the aerodynamic characteristics of an elliptical airfoil to differ greatly from a conventional airfoil, and that this airfoil shape could generate the counter-rotating vortices used by insects to generate lift. Therefore, this research aims to study the lift generation of a bumblebee-inspired elliptical airfoil in a normal hovering flight. This study focuses on hovering flight with the insect flies in a nearly stationary position, which explains the importance of lift generation to stay aloft. The motion of the elliptical airfoil is inspired by the flapping kinematics of bumblebees at a typical Reynolds number range of . It is found that the current two-dimensional model is capable of capturing the counter-rotating vortices and correlates the formation of these structures to a high production of lift. These results show that bumblebees utilise these counter-rotating vortices to generate lift enough to fly in hovering flight. This results also indicate that flapping 2D elliptical airfoils can be used to investigate their 3D wing counterparts, which translate to a reduced time and computing costs.

An Experimental and Numerical Study of Flow and Heat Transfer in Channels With Pin Fin-Dimple Combined Arrays of Different Configurations

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
Yu Rao ◽  
Chaoyi Wan ◽  
Shusheng Zang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Experimental Conditions ◽  
Number Range ◽  
Pin Fin ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Reynolds Number Range

An experimental and numerical study was conducted to investigate the flow and heat transfer characteristics in channels with pin fin-dimple combined arrays of different configurations, where dimples are located transversely or both transversely and streamwisely between the pin fins. The flow structure, friction factor, and heat transfer characteristics of the pin fin-dimple channels of different configurations have been obtained and compared with each other for the Reynolds number range of 8200–50,500. The experimental study showed that, compared to the pin fin channel, depending on the configurations of the pin fin-dimple combined arrays the pin fin-dimple channel can have distinctively further improved convective heat transfer performance by 8.0%–20.0%, whereas lower or slightly higher friction factors over the studied Reynolds number range. Furthermore, three-dimensional and steady-state conjugate computations have been carried out for similar experimental conditions. The numerical computations showed detailed characteristics of the distribution of the velocity and turbulence level in the flow, which revealed the underlying mechanisms for the pressure loss and heat transfer characteristics in the pin fin-dimple channels of different configurations.

scholarly journals Aerodynamic Characteristics of Different Airfoils under Varied Turbulence Intensities at Low Reynolds Numbers

2020 ◽  
Vol 10 (5) ◽  
pp. 1706 ◽  
Author(s):  
Yang Zhang ◽  
Zhou Zhou ◽  
Kelei Wang ◽  
Xu Li
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Flow Separation ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Jet Flow ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Low Reynolds Numbers ◽  
Low Reynolds

A numerical study was conducted on the influence of turbulence intensity and Reynolds number on the mean topology and transition characteristics of flow separation to provide better understanding of the unsteady jet flow of turboelectric distributed propulsion (TeDP) aircraft. By solving unsteady Reynolds averaged Navier-Stokes (URANS) equation based on C-type structural mesh and γ - Re ˜ θ t transition model, the aerodynamic characteristics of the NACA0012 airfoil at different turbulence intensities was calculated and compared with the experimental results, which verifies the reliability of the numerical method. Then, the effects of varied low Reynolds numbers and turbulence intensities on the aerodynamic performance of NACA0012 and SD7037 were investigated. The results show that higher turbulence intensity or Reynolds number leads to more stable airfoil aerodynamic performance, larger stalling angle, and earlier transition with a different mechanism. The generation and evolution of the laminar separation bubble (LSB) are closely related to Reynolds number, and it would change the effective shape of the airfoil, having a big influence on the airfoil’s aerodynamic characteristics. Compared with the symmetrical airfoil, the low-Reynolds-number airfoil can delay the occurrence of flow separation and produce more lift in the same conditions, which provides guidance for further airfoil design under TeDP jet flow.

scholarly journals Leading-Edge Roughness Affecting Diamond-Wing Aerodynamic Characteristics

Aerospace ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 98 ◽  
Author(s):  
Andrei Buzica ◽  
Lisa Debschütz ◽  
Florian Knoth ◽  
Christian Breitsamter
Keyword(s):  
Reynolds Number ◽  
Surface Pressure ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Coefficients ◽  
Number Range ◽  
Edge Roughness ◽  
Vortex Separation ◽  
Roughness Size

Diamond wing configurations for low signature vehicles have been studied in recent years. Yet, despite numerous research on highly swept, sharp edged wings, little research on aerodynamics of semi-slender wings with blunt leading-edges exists. This paper reports on the stall characteristics of the AVT-183 diamond wing configuration with variation of leading-edge roughness size and Reynolds number. Wind tunnel testing applying force and surface pressure measurements are conducted and the results presented and analysed. For the investigated Reynolds number range of 2.1 × 10 6 ≤ R e ≤ 2.7 × 10 6 there is no significant influence on the aerodynamic coefficients. However, leading-edge roughness height influences the vortex separation location. Trip dots produced the most downstream located vortex separation onset. Increasing the roughness size shifts the separation onset upstream. Prior to stall, global aerodynamic coefficients are little influenced by leading-edge roughness. In contrast, maximum lift and maximum angle of attack is reduced with increasing disturbance height. Surface pressure fluctuations show dominant broadband frequency peaks, distinctive for moderate sweep vortex breakdown. The experimental work presented here provides insights into the aerodynamic characteristics of diamond wings in a wide parameter space including a relevant angle of attack range up to post-stall.

Airfoil Section Characteristics at a Low Reynolds Number

1997 ◽  
Vol 119 (1) ◽  
pp. 129-135 ◽  
Author(s):  
Shigeru Sunada ◽  
Akitoshi Sakaguchi ◽  
Keiji Kawachi
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Flight Performance ◽  
High Reynolds ◽  
Shape Characteristics ◽  
Sharp Leading Edge

The aerodynamic characteristics of airfoils operating at Re = 4 × 103 were examined, varying the parameters related to the airfoil shape such as thickness, camber, and roughness. Airfoils with good aerodynamic performance at this Re have the following shape characteristics: (1) they are thinner than airfoils for higher Re numbers, (2) they have a sharp leading edge, and (3) they have a camber of about five percent with its maximum camber at about mid-chord. The characteristics of airfoils are strongly affected by leading edge vortices. The measured two-dimensional airfoil characteristics indicate that the planform, which greatly affects the flight performance of the three-dimensional wing at high Reynolds numbers, has little effect on the flight performance at this Reynolds number.

scholarly journals Numerical study on aerodynamic performance of waverider with a new bluntness method

2020 ◽  
pp. 095441002096841
Author(s):  
Zhipeng Qu ◽  
Houdi Xiao ◽  
Mingyun Lv ◽  
Guangli Li ◽  
Cui Kai
Keyword(s):  
Numerical Study ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
The Novel ◽  
High Lift ◽  
Wide Range ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Sharp Leading Edge

Abastrct The waverider is deemed the most promising configuration for hypersonic vehicle with its high lift-to-drag ratio at design conditions. However, considering the serious aero-heating protection, the sharp leading edge must be blunted. The existing traditional bluntness methods including the following two types: “reducing material method” and “adding material method”. Compared to the initial waverider, the volume will be smaller or larger using the traditional methods. With the fixed blunted radius, the volume and aerodynamic performance is determined. In this paper, a new bluntness method which is named “mixing material method” is developed. In this new method, a new parameter is introduced based on the traditional two bluntness methods. Under fixed blunted radius, the volume and aerodynamic performance can be changed within a wide range by adjusting the parameter. When the parameter is 0 and 1, the novel blunted method degenerated into the “reducing material method” and “adding material method” respectively. The influence of new parameter on the aerodynamic characteristics and volume are studied by numerical simulation. Results show that the volume, lift and lift-to-drag ratio increases with the increase of the parameter under the fixed blunt radius, but simultaneously, the drag will also increase. Therefore, considering the different requirements of the air-breathing hypersonic aircrafts for the balance of thrust and drag, lift and weight, a suitable bluntness parameter can be selected to achieve a balance. This research can provide reference for hypersonic waverider vehicle design.

scholarly journals Effect of Reynolds Number on a Plunging Airfoil

2020 ◽  
Author(s):  
Diana Carvalho Rodrigues ◽  
Emanuel António Rodrigues Camacho ◽  
Fernando Manuel da Silva Pereira Neves ◽  
André Resende Rodrigues Silva ◽  
Jorge Manuel Martins Barata
Keyword(s):  
Reynolds Number ◽  
New Technologies ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Number Range ◽  
Diffusion Effects ◽  
Speed Range ◽  
Nature Frequency ◽  
Edge Vortex ◽  
Effective Angle

Biomimetics is an area of science that studies the development of new technologies, whose source of inspiration is Nature. Unlike traditional aircraft, animals only have one structure to create both lift and thrust, and for Humans, although in the recent years the studies in this area increased, a long way must be made to achieve their capability. The present paper focuses on the effect of the Reynolds number on the wake configuration produced by a plunging airfoil. The experimental work was performed using an airstream, that was marked with smoke, with an oscillating airfoil NACA0012, whose dimensions are 44cm and 10cm of span and aerodynamic chord, respectively. The motion prescribed for the wing is harmonic, since it very well represents the type of motion seen in Nature. Frequency and amplitude were maintained, respectively, at 1.2Hz and 2.8cm, and the wind speed range from 0.25m/s to 1.00m/s, which represents a nondimensional amplitude of 0.28, a reduced frequencies of 3.02, 1.51 and 0.75, and a Strouhal number and a Reynolds number range of, 0.07 – 0.27 and 1,500 – 6,300, respectively. Results indicate that, with the increase of the Reynolds number, the convection effects become more predominant than diffusion effects, the curvature of the wakes and the maximum effective angle of attack decrease, and time and configuration of vortex shedding change. For Re = 1,500, St = 0.27, another relevant conclusion appears; the interaction of the leading-edge vortex with the trailing-edge vortex indicates an improvement of the aerodynamic performance of this system. Keywords: Biomimetics, Plunging, Airfoil, Vortices, Wakes

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