scholarly journals Improvement of Aerodynamic Performance of Cambered Airfoils Using Leading-Edge Slots

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Saman Beyhaghi ◽  
Ryoichi S. Amano
Keyword(s):  
Lift Coefficient ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Bottom Surface ◽  
Original Design ◽  
Local Pressure ◽  
Maximum Increase ◽  
Average Improvement ◽  
Length Width ◽  
Inlet Angle

Feasibility of increasing lift and decreasing drag by drilling narrow span-wide channels near the leading edge of NACA 4412 airfoils is investigated. It is proposed to drill two-segment slots that allow some of the incoming air to flow through them and then exit from the bottom surface of the airfoil. Such slots can result in an increased local pressure and thereby higher lift. Length, width, inlet angle, and exit angle of slots are varied to determine optimum configurations. Aerodynamic performance at different angles of attack (AoAs) and the chord-based Reynolds number of 1.6 × 106 is investigated. It is concluded that longer and narrower slots with exit streams more aligned with the air flowing below the airfoil can result in a higher lift. Also, in order to keep the slotted airfoils beneficial for AoAs greater than zero, it is proposed to (a) slightly lower the slot position with respect to the original design and (b) tilt up the first-leg by a few degrees. For the best design case considered, an average improvement of 8% is observed for lift coefficient over the entire range of AoA (with the maximum increase of 15% for AoA = 0), without any significant drag penalty.

scholarly journals Numerical Analysis of Wind Turbine Airfoil Aerodynamic Performance with Leading Edge Bump

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Majid Asli ◽  
Behnam Mashhadi Gholamali ◽  
Abolghasem Mesgarpour Tousi
Keyword(s):  
Wind Turbine ◽  
Control Method ◽  
Flow Behavior ◽  
Renewable Energy Sources ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Vortex Generator ◽  
Leading Edge ◽  
Suction Side ◽  
Aerodynamic Performance

Aerodynamic performance improvement of wind turbine blade is the key process to improve wind turbine performance in electricity generated and energy conversion in renewable energy sources concept. The flow behavior on wind turbine blades profile and the relevant phenomena like stall can be improved by some modifications. In the present paper, Humpback Whales flippers leading edge protuberances model as a novel passive stall control method was investigated on S809 as a thick airfoil. The airfoil was numerically analyzed by CFD method in Reynolds number of 106and aerodynamic coefficients in static angle of attacks were validated with the experimental data reported by Somers in NREL. Therefore, computational results for modified airfoil with sinusoidal wavy leading edge were presented. The results revealed that, at low angles of attacks before the stall region, lift coefficient decreases slightly rather than baseline model. However, the modified airfoil has a smooth stall trend while baseline airfoil lift coefficient decreases sharply due to the separation which occurred on suction side. According to the flow physics over the airfoils, leading edge bumps act as vortex generator so vortices containing high level of momentum make the flow remain attached to the surface of the airfoil at high angle of attack and prevent it from having a deep stall.

Analysing and Optimizing the Aerodynamic Performance of Wind Turbine Blades Using Injected-Air Jets at Variable Frequency and Amplitude for Flow Control

2005 ◽  
Vol 29 (4) ◽  
pp. 331-339 ◽  
Author(s):  
Liu Hong ◽  
Huo Fupeng ◽  
Chen Zuoyi
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Suction Surface ◽  
Air Jet

Optimum aerodynamic performance of a wind turbine blade demands that the angle of attack of the relative wind on the blade remains at its optimum value. For turbines operating at constant speed, a change in wind speed causes the angle of attack to change immediately and the aerodynamic performance to decrease. Even with variable speed rotors, intrinsic time delays and inertia have similar effects. Improving the efficiency of wind turbines under variable operating conditions is one of the most important areas of research in wind power technology. This paper presents findings of an experimental study in which an oscillating air jet located at the leading edge of the suction surface of an aerofoil was used to improve the aerodynamic performance. The mean air-mass flowing through the jet during each sinusoidal period of oscillation equalled zero; i.e. the jet both blew and sucked. Experiments investigated the effects of the frequency, momentum and location of the jet stream, and the profile of the turbine blade. The study shows significant increase in the lift coefficient, especially in the stall region, under certain conditions. These findings may have important implications for wind turbine technology.

scholarly journals Improving the aerodynamic performance of a cycloidal rotor through active compliant morphing

2017 ◽  
Vol 121 (1241) ◽  
pp. 901-915
Author(s):  
L. Ferrier ◽  
M. Vezza ◽  
H. Zare-Behtash
Keyword(s):  
Negative Impact ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Micro Air Vehicles ◽  
Aerodynamic Performance ◽  
Dynamic Stall ◽  
Marine Vehicles ◽  
Aerospace Applications ◽  
Naca 0015 ◽  
Air Vehicles

ABSTRACTCycloidal rotors are a novel form of propulsion system that can be adapted to various forms of transport such as air and marine vehicles, with a geometrical design differing significantly from the conventional screw propeller. Research on cycloidal rotor design began in the early 1930s and has developed throughout the years to the point where such devices now operate as propulsion systems for various aerospace applications such as micro air vehicles, unmanned air vehicles and compound helicopters. The majority of research conducted on the cycloidal rotor’s aerodynamic performance have not assessed mitigating the dynamic stall effect, which can have a negative impact on the rotor performance when the blades operate in the rotor retreating side. A solution has been proposed to mitigate the dynamic stall effect through employment of active, compliant leading-edge morphing. A review of the current state of the art in this area is presented. A two-dimensional, implicit unsteady numerical analysis was conducted using the commercial computational fluid dynamics software package STAR CCM+, on a two-bladed cycloidal rotor. An overset mesh technique, otherwise known as a chimera mesh, was used to apply complex transient motions to the simulations. Active, compliant leading-edge morphing is applied to an oscillating NACA 0015 aerofoil to attempt to mitigate the dynamic stall whilst maintaining the positive dynamic lift coefficient (Cl) contributions. It was verified that by applying a pulsed input leading-edge rotational morphing schedule, the leading-edge vortex does not fully form and the large flow separation is prevented. Further work in this investigation will focus on coupling the active, leading-edge motion to the cycloidal rotor model with the aim to maximise aerodynamic performance.

Development of a Mini Heat Sink Model With Homogeneous Heat Transfer Capability

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
J. F. Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Heating Surface ◽  
Bottom Surface ◽  
Cooling Power ◽  
Local Pressure ◽  
Pressure Drops ◽  
Transfer Capability ◽  
Length Width ◽  
Heat Transfer Capability

A model of mini heat sink with microchannels was developed to obtain homogeneous heat transfer capability. The channels are constructed in the form of eight triangular arrays based on a square substrate. Air is sucked from the periphery to the center of the substrate by a vacuum pump and heat transferred from the bottom surface of substrate can be removed by air flowing through channels. Corresponding to the given heat transfer power and the target temperature of substrate, the relationship among length, width and depth of channel was analytically established. By numerical simulation, local pressure drops at the joint of channels and air duct are first obtained and then the dimensions of each channel in a triangular array can be determined one by one. The investigation reveals that the widths of channels will vary with their depths, lengths and pressure differences between two ends. Since all channels are required for the same cooling power, the homogeneous heat transfer of heat sink can be realized. By assembling a certain number of heat sink units, the area of dissipation of heat sink can be enlarged and contoured to fit close to heating surface.

scholarly journals A Study on Aerodynamic Behavior of Subsonic UAVs' Wing Sections with Flaps

2020 ◽  
Vol vm02 (is01) ◽  
pp. 22-27
Author(s):  
Halil Yalcin Akdeniz
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Open Source Software ◽  
Lift Force ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Reynolds Numbers ◽  
Aerodynamic Performance ◽  
Performance Parameters ◽  
Original Design ◽  
Flap Design

In this study, it is aimed to assess the aerodynamic and flight effects of the flap design on an airfoil. For this purpose, NACA 4415 type wing profile, which can also be used in unmanned aerial vehicles (UAVs), is selected. The original design and the +5-degree flapped design which has constant other design features are compared. Assessments are performed under constant Reynolds numbers and an angle of attack between 0-10 degrees with a 1-degree interval. Analyses are made using the open-source software XFLR5. For the flapped design is named NACA 4415-2, some basic aerodynamic performance parameters such as coefficient of drag (CD), coefficient of lift (CL) coefficient of pressure (Cp) maximum lift coefficient (Clmax) and minimum stall velocity (Vstall) have been observed. According to results, when the flap with 5o is added to the airfoil, it has been observed that the CL and Lift force of the original design of the airfoil increase significantly, CD of the airfoil increase partially, and the pressure coefficient tends to decrease significantly. Furthermore, it has been observed that while the minimum stall velocity has decreased, Clmax values increased.

The Effect of Intake and Exhaust on the Two-Dimensional Airfoil in a Distributed Propulsion System

2016 ◽  
Author(s):  
Yongsheng Wang ◽  
Ming Zhou ◽  
Quanyong Xu
Keyword(s):  
Lift Coefficient ◽  
Leading Edge ◽  
Jet Flow ◽  
Propulsion System ◽  
Two Dimensional ◽  
Original Design ◽  
Trailing Edge ◽  
Distributed Propulsion ◽  
Drag Ratio

A new distributed propulsion system in which micro-engines were embedded into the wings was proposed. To consider the effects of the intake and exhaust of the engines, the system was simplified as a two-dimensional airfoil with a surface ingestion and a trailing edge jet. The influence of the layout was comprehensively studied with CFD. Compared to the original design, the surface ingestion and trailing edge jet can increase the lift coefficient. The lift-drag ratio increases at smaller attack angles (< 3°) and decreases at greater attack angles (> 3°). The lift-drag ratio improvement with surface ingestion at the leading edge is mainly due to the drop in drag, while the increase with ingestion close to the trailing edge is primarily because of the augment of lift. Moreover, increasing the temperature of the jet flow can enlarge the range of the attack angles with a higher lift-drag ratio.

Alula-Inspired Leading Edge Device for Low Reynolds Number Flight

2016 ◽  
Author(s):  
Boris A. Mandadzhiev ◽  
Michael K. Lynch ◽  
Leonardo P. Chamorro ◽  
Aimy A. Wissa
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Tip Vortex ◽  
Relative Angle ◽  
Lift And Drag

Robust and predictable aerodynamic performance of unmanned aerial vehicles at the limits of their design envelope is critical for safety and mission adaptability. In order for a fixed wing aircraft to maintain the lift necessary for sustained flight at very low speeds and large angles of attack (AoA), the wing shape has to change. This is often achieved by using deployable aerodynamic surfaces, such as flaps or slats, from the wing leading or trailing edges. In nature, one such device is a feathered structure on birds’ wings called the alula. The span of the alula is 5% to 20% of the wing and is attached to the first digit of the wing. The goal of the current study is to understand the aerodynamic effects of the alula on wing performance. A series of wind tunnel experiments are performed to quantify the effect of various alula deployment parameters on the aerodynamic performance of a cambered airfoil (S1223). A full wind tunnel span wing, with a single alula located at the wing mid-span is tested under uniform low-turbulence flow at three Reynolds numbers, Re = 85,000, 106,00 and 146,000. An experimental matrix is developed to find the range of effectiveness of an alula-type device. The alula relative angle of attack measured measured from the mean chord of the airfoil is varied to modulate tip-vortex strength, while the alula deflection is varied to modulate the distance of the tip vortex to the wing surface. Lift and drag forces were measured using a six axis force transducer. The lift and drag coefficients showed the greatest sensitivity to the the alula relative angle of attack, increasing the normalized lift coefficient by as much as 80%. Improvements in lift are strongly correlated to higher alula angle, with β = 0° – 5°, while reduction in the drag coefficient is observed with higher alula tip deflection ratios and lower β angles. Results show that, as the wing angle of attack and Reynolds number are increased, the overall lift co-efficient improvement is diminished while the reduction in drag coefficient is higher.

Experimental investigation of ground effects on aerodynamics of sinusoidal leading-edge wings

2020 ◽  
pp. 095440622097542
Author(s):  
AA Mehraban ◽  
MH Djavareshkian
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Wind Tunnel ◽  
Research Study ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Wide Range ◽  
Ground Effects

Sinusoidal leading-edge wings have attracted many considerations since they can delay the stall and enhance the maneuverability. The main contribution of this research study is to experimentally investigate effects of ground on aerodynamic performance of sinusoidal leading-edge wings. To this end, 6 tubercled wings with different amplitudes and wavelengths are fabricated and compared with the baseline wing which has smooth leading-edge. Proposed wings are tested in different distances from the ground in a wind tunnel lab for a wide range of angle of attack from 0° to 36° and low Reynolds number of 45,000. Results indicated that lift coefficient is improved when wings get close to the ground. Furthermore, increment of protuberance amplitude in the vicinity of the ground could efficiently prevent stalling particularly for shorter wavelength.

Aerodynamic Performance Improvement of a Wing Model Using an Array of Slotted Synthetic Jets

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Pramod Salunkhe ◽  
Yanhua Wu ◽  
Hui Tang
Keyword(s):  
Flow Separation ◽  
Performance Enhancement ◽  
Lift Coefficient ◽  
Power Spectra ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Synthetic Jets ◽  
Force Balance ◽  
Flow Separation Control ◽  
Wing Model

Abstract This work deals with the improvement in aerodynamic performance of a NACA0025 wing model using an array of slotted synthetic jets (SJs). A novel SJ actuator was designed and located at 30% of the chord from the leading edge (LE). Time-resolved particle image velocimetry (TR-PIV), force balance, static pressure distribution, and hotwire measurements were carried out in a subsonic wind tunnel to assess the performance enhancement due to the slotted SJ array. Initially, the SJ velocity was measured in quiescent flow condition at different actuation frequencies and amplifier voltages. Actuation at 1000 Hz and 200 V resulted in the highest blowing velocity of 10.5 m/s. Experiments were performed at various actuation frequencies, namely, 200, 600, and 1000 Hz. It was observed that actuation at 1000 Hz led to the highest increase in lift coefficient by 35.6% and reduction in average drag coefficient by 33%. TR-PIV measurements showed flow separation with flow reversal in the baseline case. After switching on the SJ array at 1000 Hz, the flow separation was completely eliminated. The momentum transfer from the highenergy primary flow to the retarding boundarylayer flow and actuation of SJ in a particular frequency range was observed to be the mechanisms for the flow separation control. Subsequently, fast Fourier transform (FFT) power spectra of hotwire data were computed from 40% to 80% of the chord. The FFT power spectra showed the successful stabilization of the flow field at the actuation of 1000 Hz.

Novel Tubercle Design for a Wind Turbine Blade Operating at Low Reynolds Number

2019 ◽  
Author(s):  
R. Deeksha ◽  
Mahesh K. Varpe
Keyword(s):  
Reynolds Number ◽  
Wind Turbine ◽  
Amplitude Ratio ◽  
Low Reynolds Number ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Operating Condition ◽  
Low Reynolds

Abstract Wind energy has become one of the vital sustainable energy resources and a leading contender to the renewable resources race. The need of extending the aerodynamic performance of a wind turbine paved the way for radical approaches in the design of wind turbine blades. One such promising technique is the adoption of passive flow controls like leading edge protuberance or tubercles. In this paper the aerodynamic performance of NACA0009 (baseline) superimposed with a leading edge protuberance is numerically investigated in the post-stall operating conditions. The investigation objective was to identify the optimum pitch to amplitude ratio of the protuberance in the post stall operating condition for a low Reynolds number of 5 × 104. Computational fluid dynamics computations were performed using κ-ω SST turbulence model. The optimum pitch to amplitude ratio was found to be 6 which enhanced the aerodynamic lift coefficient by 42% in the post stall operating condition. The lift is reduced at lower AOA but gets complement in the post stall operating conditions.

Sign in / Sign up

Export Citation Format

Share Document