Aerodynamic performance investigation of sweptback wings with bio-inspired leading-edge tubercles

2021 ◽  
Author(s):  
V. T. Gopinathan ◽  
J. Bruce Ralphin Rose
Keyword(s):  
Flow Control ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Laminar Separation ◽  
Flow Separation Control ◽  
Pressure Distributions ◽  
Lifting Surfaces ◽  
Naca 0015

The aerodynamic behavior of sweptback wing configurations with bio-inspired humpback whale (HW) leading-edge (LE) tubercles has been investigated through computational and experimental techniques. Specifically, the aerodynamic performance of tubercled wings with symmetric (NACA 0015) and cambered (NACA 4415) airfoils is validated against the baseline model at various angles of attack ([Formula: see text]. The [Formula: see text]/[Formula: see text] ratio of the HW flipper is strategically reduced to 0.15 for ascertaining the flow control potential of the bio-inspired wings with sweptback configuration. It is a novel effort to quantify the effect of the leading-edge protuberances on stall delay, flow separation control and distribution of streamline vortices at unique [Formula: see text]/[Formula: see text] ratio outside the thickness range of HW flipper morphology. Four tapered sweptback wing models (Baseline A, Baseline B, HUMP 0015, HUMP 4415) are used with the amplitude-to-wavelength ([Formula: see text] ratio of 0.24 and Reynolds number about [Formula: see text]. The chordwise pressure distributions are recorded at the peak, mid and trough regions of the tubercled wings through a detailed wind tunnel testing and validated with numerical analysis. Additionally, the flow characteristics over the bio-inspired surfaces have been qualitatively analyzed through the laser flow visualization (LFV) technique to reveal the influence of laminar separation bubbles (LSBs). The essential aerodynamic characteristics such as boundary layer trip delay, vortex mixing, stall delay, and flow control at different AoA are addressed through consistent experimental data. As the sweptback configuration is a primary choice for airplane wings, the improved aerodynamic characteristics of the tubercled wings can be effectively utilized for the design of novel lifting surfaces, hydroplanes and wind turbines in the near future.

scholarly journals A large-eddy simulation on a deep-stalled aerofoil with a wavy leading edge

2017 ◽  
Vol 813 ◽  
pp. 23-52 ◽  
Author(s):  
Rafael Pérez-Torró ◽  
Jae Wook Kim
Keyword(s):  
Vortex Shedding ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Domain Size ◽  
Aerodynamic Characteristics ◽  
Streamwise Vortices ◽  
Aerodynamic Forces ◽  
Laminar Separation ◽  
Eddy Simulation ◽  
Large Eddy

A numerical investigation on the stalled flow characteristics of a NACA0021 aerofoil with a sinusoidal wavy leading edge (WLE) at chord-based Reynolds number $Re_{\infty }=1.2\times 10^{5}$ and angle of attack $\unicode[STIX]{x1D6FC}=20^{\circ }$ is presented in this paper. It is observed that laminar separation bubbles (LSBs) form at the trough areas of the WLE in a collocated fashion rather than uniformly/periodically distributed over the span. It is found that the distribution of LSBs and their influence on the aerodynamic forces is strongly dependent on the spanwise domain size of the simulation, i.e. the wavenumber of the WLE used. The creation of a pair of counter-rotating streamwise vortices from the WLE and their evolution as an interface/buffer between the LSBs and the adjacent fully separated shear layers are discussed in detail. The current simulation results confirm that an increased lift and a decreased drag are achieved by using the WLEs compared to the straight leading edge (SLE) case, as observed in previous experiments. Additionally, the WLE cases exhibit a significantly reduced level of unsteady fluctuations in aerodynamic forces at the frequency of periodic vortex shedding. The beneficial aerodynamic characteristics of the WLE cases are attributed to the following three major events observed in the current simulations: (i) the appearance of a large low-pressure zone near the leading edge created by the LSBs; (ii) the reattachment of flow behind the LSBs resulting in a decreased volume of the rear wake; and, (iii) the deterioration of von-Kármán (periodic) vortex shedding due to the breakdown of spanwise coherent structures.

scholarly journals Active Flow Control over a NACA23012 Airfoil using Hybrid Jet

2021 ◽  
Vol 71 (6) ◽  
pp. 721-729
Author(s):  
Deepak Kumar Singh ◽  
Anuj Jain ◽  
Akshoy Ranjan Paul
Keyword(s):  
Flow Control ◽  
Flow Separation ◽  
Active Flow Control ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Flow Separation Control ◽  
Blowing Ratio ◽  
Maximum Improvement ◽  
Stall Angle

A time-dependent numerical simulation is performed to examine the flow separation control with the action of a hybrid jet (the combination of synthetic and continuous jets) over a NACA23012 airfoil. The unsteady Reynolds-averaged Navier–Stokes (URANS) simulation is performed with Spalart-Allmaras (SA) turbulence model to simulate the flow field around the airfoil to analyse the effect of the hybrid jet. A combined jet is placed at the point of flow separation on the upper surface of the airfoil which is located at the 12% of the chord length from the leading edge of the airfoil for a given flow configuration. Flow simulations are performed at a chord-based Reynolds number of 2.19 × 106 for the hybrid jet oscillating frequency of 0.159 at a blowing ratio of 3.0. The contribution of the continuous jet in the hybrid jet is evident by the flow control. Variation in the continuous jet velocity is studied, which improved the aerodynamic characteristics of the airfoil. The maximum improvement in lift to drag ratio is observed from 11.19 to 22.14 at an angle of attack of 22 degree. The stall angle also shows an enhancement from 18 degree to 20 degree.

Investigation on the effect of leading edge tubercles of sweptback wing at low reynolds number

2020 ◽  
Vol 21 (6) ◽  
pp. 621
Author(s):  
Veerapathiran Thangaraj Gopinathan ◽  
John Bruce Ralphin Rose ◽  
Mohanram Surya
Keyword(s):  
Leading Edge ◽  
Reynolds Numbers ◽  
Sweep Angle ◽  
Laminar Separation ◽  
Low Reynolds Numbers ◽  
Flow Energy ◽  
Airplane Wing ◽  
Low Reynolds ◽  
Naca 0015 ◽  
Wing Performance

Aerodynamic efficiency of an airplane wing can be improved either by increasing its lift generation tendency or by reducing the drag. Recently, Bio-inspired designs have been received greater attention for the geometric modifications of airplane wings. One of the bio-inspired designs contains sinusoidal Humpback Whale (HW) tubercles, i.e., protuberances exist at the wing leading edge (LE). The tubercles have excellent flow control characteristics at low Reynolds numbers. The present work describes about the effect of tubercles on swept back wing performance at various Angle of Attack (AoA). NACA 0015 and NACA 4415 airfoils are used for swept back wing design with sweep angle about 30°. The modified wings (HUMP 0015 A, HUMP 0015 B, HUMP 4415 A, HUMP 4415 B) are designed with two amplitude to wavelength ratios (η) of 0.1 & 0.24 for the performance analysis. It is a novel effort to analyze the tubercle vortices along the span that induce additional flow energy especially, behind the tubercles peak and trough region. Subsequently, Co-efficient of Lift (CL), Co-efficient of Drag (CD) and boundary layer pressure gradients also predicted for modified and baseline (smooth LE) models in the pre & post-stall regimes. It was observed that the tubercles increase the performance of swept back wings by the enhanced CL/CD ratio in the pre-stall AoA region. Interestingly, the flow separation region behind the centerline of tubercles and formation of Laminar Separation Bubbles (LSB) were asymmetric because of the sweep.

scholarly journals Flow Separation Control of Backward-Facing Step Airfoil NACA0015 by Blowing Technique

2019 ◽  
Vol 12 (1) ◽  
pp. 99-119
Author(s):  
Khuder N. Abed
Keyword(s):  
Flow Separation ◽  
Numerical Study ◽  
Leading Edge ◽  
Distribution Coefficients ◽  
Open Circuit ◽  
Experimental Investigations ◽  
Backward Facing Step ◽  
Ansys Fluent ◽  
Flow Separation Control ◽  
Naca 0015

The aim of this paper is to control the flow separation above backward-facing step (BFS) airfoil type NACA 0015 by blowing method. The flow field over airfoil has been studied both experimentally and computationally. The study was divided into two parts: a practical study through which NACA 0015 type with a backward -facing step (located at 44.4% c from leading edge) on the upper surface containing blowing holes parallel to the airfoil chord was used. The tests were done over two-dimensional airfoil in an open circuit suction subsonic wind tunnel with flow velocity 25m/s to obtain the pressure distribution coefficients. A numerical study was done by using ANSYS Fluent software version 16.0 on three models of NACA 0015, the first one has backward-facing step without blowing, the second with single blowing holes and the third have multi blowing holes technique. Both studies (experimental and numerical) were done at low Reynolds number (Re=4.4x105) and all models have chord length 0.27m.The experimental investigations and CFD simulations have been performed on the same geometry dimensions, it has been observed that the flow separation on the airfoil can be delayed by using  velocity blowing (30m/s) on the upper surface. The multi blowing holes with velocity improved the aerodynamics properties.The multi blowing holes and single blowing hole thesame effect onpressure distribution coefficients

New combinational active control strategy for improving aerodynamic characteristics of airfoil and rotor

2019 ◽  
Vol 234 (4) ◽  
pp. 977-996
Author(s):  
Yi-yang Ma ◽  
Qi-jun Zhao ◽  
Guo-qing Zhao
Keyword(s):  
Flow Control ◽  
Control Strategy ◽  
Active Flow Control ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Synthetic Jet ◽  
Dynamic Stall ◽  
Trailing Edge ◽  
Trailing Edge Flap ◽  
Cfd Method

In order to improve the aerodynamic characteristics of rotor, a new active flow control strategy by combining a synthetic jet actuator and a variable droop leading-edge or a trailing-edge flap has been proposed. Their control effects are numerically investigated by computational fluid dynamics (CFD) method. The validated results indicate that variable droop leading-edge and synthetic jet can suppress the formation of dynamic stall vortex and delay flow separation over rotor airfoil. Compared with the baseline state, Cdmax and Cmmax are significantly reduced. Furthermore, parametric analyses on dynamic stall control of airfoil by the combinational method are conducted, and it indicates that the aerodynamic characteristics of the oscillating rotor airfoil can be significantly improved when the non-dimensional frequency ( k*) of variable droop leading-edge is about 1.0. At last, simulations are conducted for the flow control of rotor by the combinational method. The numerical results indicate that large droop angle of variable droop leading-edge can better reduce the torque coefficient of rotor and the trailing-edge flap has the capability of increasing the thrust of rotor. Also, the synthetic jet could further improve the aerodynamic characteristics of rotor.

Research of the suction flow control on wings at low Reynolds numbers

2017 ◽  
Vol 232 (8) ◽  
pp. 1515-1528 ◽  
Author(s):  
Dongli Ma ◽  
Guanxiong Li ◽  
Muqing Yang ◽  
Shaoqi Wang
Keyword(s):  
Flow Control ◽  
Aerodynamic Force ◽  
Separation Bubble ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Flow State ◽  
Laminar Separation ◽  
Low Reynolds Numbers ◽  
Low Reynolds ◽  
Suction Flow

Laminar separation and transition have significant effects on aerodynamic characteristics of the wing under the condition of low Reynolds numbers. Using the flow control methods to delay and eliminate laminar separation has great significance. This study uses the method combined with water tunnel test and numerical calculation to research the effects of suction flow control on the flow state and aerodynamic force of the wing at low Reynolds numbers. The effects of suction flow rate and suction location on laminar separation, transition and aerodynamic performance of the wing are further researched. The results of the research show that, the suction can control laminar separation and transition effectively, when the suction holes are in the interior of the separation bubble, and close to the separation point, the suction has the best control effect. When the Reynolds number is Re = 3.0 × 105, the suction flow control can make the lift-to-drag ratio of the wing increase by 8.62%, and the aerodynamic characteristics of the wing are improved effectively.

Comparative Investigation of Laminar Separation Bubble on a Wing at Low Reynolds Number

2020 ◽  
Vol 12 (3) ◽  
Author(s):  
M.P. Uthra ◽  
A. Daniel Antony
Keyword(s):  
Reynolds Number ◽  
Separation Bubble ◽  
Low Reynolds Number ◽  
Flow Characteristics ◽  
Suction Side ◽  
Aerodynamic Performance ◽  
Laminar Separation Bubble ◽  
Laminar Separation ◽  
Low Reynolds ◽  
Air Vehicles

Most admirable and least known features of low Reynolds number flyers are their aerodynamics. Due to the advancements in low Reynolds number applications such as Micro Air vehicles (MAV), Unmanned Air Vehicles (UAV) and wind turbines, researchers’ concentrates on Low Reynolds number aerodynamics and its effect on aerodynamic performance. The Laminar Separation Bubble (LSB) plays a deteriorating role in affecting the aerodynamic performance of the wings. The parametric study has been performed to analyse the flow around cambered, uncambered wings with different chord and Reynolds number in order to understand the better flow characteristics, LSB and three dimensional flow structures. The computational results are compared with experimental results to show the exact location of LSB. The presence of LSB in all cases is evident and it also affects the aerodynamic characteristics of the wing. There is a strong formation of vortex in the suction side of the wing which impacts the LSB and transition. The vortex structures impact on the LSB is more and it also increases the strength of the LSB throughout the span wise direction.

Transition and separation control in the leading edge region

2001 ◽  
Vol 105 (1049) ◽  
pp. 371-378
Author(s):  
P. W. C. Wong ◽  
M. Maina ◽  
A. M. Cobbin
Keyword(s):  
Parametric Study ◽  
Effective Means ◽  
Leading Edge ◽  
Peak Height ◽  
Edge Region ◽  
Military Aircraft ◽  
Laminar Separation ◽  
Pressure Distributions ◽  
Crossflow Instability ◽  
And Control

Abstract This paper describes an investigation of methods of controlling transition and separation in the leading edge region of military aircraft wings. For wings with the high leading edge sweep relevant to some military aircraft, if attachment line contamination can be prevented then transition is predominantly caused by crossflow instability close to the leading edge. The use of surface suction or cooling for suppressing these instabilities in order to delay transition, has been investigated in a parametric study. The placing of a short suction panel close to the leading edge has been found to be an effective means of controlling instability. Conversely, the level of cooling required to suppress crossflow instability may be too high for practical aircraft applications. The use of suction for preventing laminar separation for pressure distributions with a leading edge suction peak has also been included in the parametric study. The suction quantity required is strongly dependent on the peak height. The suction quantity that can be achieved in practice will limit the maximum peak height that can be attained without laminar separation. An investigation of leading edge stall and control has also been carried out. The analysis suggests that it is important to be able to identify whether the stall is due to laminar bubble bursting or turbulent re-separation, since different methods of controlling the stall may be required.

ANALYSIS OF THE EFFECTS OF MASS-INJECTION AT THE LEADING EDGE ON CAVITY FLOW CHARACTERISTICS

2009 ◽  
Vol 23 (03) ◽  
pp. 413-416 ◽  
Author(s):  
JI FEI WU ◽  
ZHAO LIN FAN ◽  
XIN FU LUO
Keyword(s):  
High Speed ◽  
Static Pressure ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Cavity Flow ◽  
Fluctuating Pressure ◽  
Pressure Distributions ◽  
Mass Injection ◽  
Varying Mass ◽  
Hole Number

An experimental investigation was conducted in a high speed wind tunnel to explore the effects of mass-injection on cavity flow characteristics. Detailed static-pressure and fluctuating pressure measurements were obtained at the cavity floor to enable the effects of the mass-injection at the leading edge to be determined. Results indicate that varying mass-injection hole number and the flux rate of mass-injection has no significant effect on cavity flow characteristics. However, mass-injection can reduce the cavity static pressure gradient when the cavity flow type is transitional-cavity flow. The study also indicates that Mach number can influence the effect of mass-injection on cavity fluctuating pressure distributions, and at supersonic speeds, mass-injection can suppress the cavity tones effectively.

scholarly journals Research on the forward flight performance of rotor based on variable-droop leading edge

2021 ◽  
Vol 39 (3) ◽  
pp. 668-674
Author(s):  
Congcong Li ◽  
Yongjie SHI ◽  
Guohua Xu ◽  
Xingliang Liu
Keyword(s):  
Flow Control ◽  
Control Method ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Integral Form ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Control Effect ◽  
Forward Flight ◽  
Force Coefficient

Aiming at the dynamic stall phenomenon of the retreating side of the rotor in forward flight, the existing flow control method of dynamic leading edge droop was applied to the flow control of forward-flying rotor at three-dimensional scale. A numerical simulation method based on variable droop leading edge is established in this paper. The seesaw rotor is taken as the research object, the moving overset mesh method and RBF grid deformation technology are used, the integral form of Reynolds average N-S equation is the main control equation. The influence of the dynamic leading edge at r/R=0.75~1 on the aerodynamic characteristics of the rotor when the forward ratio is 0.3 is investigated. It is found that variable droop leading edge on the retreating side can effectively inhibit the generation and development of separation vortices near the trailing edge, and has a significant effect on lifting lift coefficient and section normal force coefficient, reducing torque coefficient, and thus improving the equivalent lift-drag ratio of the rotor. In a certain range, the control effect is better with the increase of the droop amplitude under the leading edge.

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