Experimental Investigation of the Aerodynamics and Flowfield of a NACA 0015 Airfoil Over a Wavy Ground

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
T. Lee ◽  
V. Tremblay-Dionne
Keyword(s):  
Lift Coefficient ◽  
Ground Effect ◽  
Lower Surface ◽  
Moment Coefficient ◽  
Aerodynamic Properties ◽  
Image Velocimetry ◽  
Ground Distance ◽  
Almost All ◽  
Naca 0015 ◽  
The Impact

The aerodynamic properties and flowfield of a NACA 0015 airfoil over a wavy ground were investigated experimentally via surface pressure and particle image velocimetry (PIV) measurements. Flat-surface results were also obtained to be served as a comparison. For the wavy ground, there exhibited a cyclic variation in the sectional lift coefficient Cl over an entire wavelength. The maximum Cl observed at the wave peak (produced by the wavy ground-induced RAM pressure) and minimum Cl occurred at the wave valley (resulting from the unusual suction pressure developed on the airfoil's lower surface due to the converging-diverging flow passage developed underneath it) reduced with increasing ground distance. By contrast, the pitching-moment coefficient showed an opposite trend to the variation in Cl and had an almost all-negative value. Meanwhile, two peak values in the drag coefficient over each wavelength were observed. The wavy ground effect-produced gains in the mean Cl and lift-to-drag ratio were at the expense of longitudinal stability. Additional measurements considering different wavelengths and amplitudes are needed to further quantify the impact of wavy ground on wing-in-ground effect (WIG) airfoils and wings.

scholarly journals Experimental Investigation of the Ground Effect of WIG Craft—NEW1 Model

Proceedings ◽  
2020 ◽  
Vol 39 (1) ◽  
pp. 17
Author(s):  
Sakornsin ◽  
Thipyopas ◽  
Atipan
Keyword(s):  
Lift Coefficient ◽  
Ground Surface ◽  
Ground Effect ◽  
Aerodynamic Characteristics ◽  
Scale Model ◽  
Negative Slope ◽  
Stream Velocity ◽  
Longitudinal Stability ◽  
Moment Coefficient ◽  
The Moment

Navy Experimental Wing-in-Ground-Effect (WIG) craft namely as NEW1, is the first version of 2-seated WIG craft which has been designed and developed by Royal Thai Navy since 2017. This experimental research is a part of the NEW1 project which aims to investigate the aerodynamic characteristics and aspects of the flow passing through the WIG craft model when in ground effect. In the experiment, the WIG craft—NEW1 of 1:15 scale model is tested in a close circuit wind tunnel of 1 m × 1 m test section at Kasetsart University. The tests are conducted at the free stream velocity of 40 m/s or Reynolds number of 280,000, at angles of attack ranging from −9° to 21°, and at the wing to ground distances ranging from 5.0 C to 0.3 C. The measurement of 6-DoF of forces and moments and pressure distributions on the ground surface underneath the WIG craft model are made during the tests. The results show that the ground has significant effects on the aerodynamic characteristics of the WIG craft model when the wing to ground distance is less than its mean chord. It was found that when the model move from 5.0 C (out of ground effect) to 0.3 C, the lift coefficient increases up to 15.7%, the drag coefficient decreases up to 5.6%, and the lift to drag ratio increases 33.4%. The proximity of the model to the ground also affects the longitudinal stability of the model. The moment coefficient curves against angle of attack has negative slope for both in and out of ground effect indicating favorable longitudinal stability. However, it was found that the aerodynamic center move further aft toward the trailing edge when the model move closer to the ground.

scholarly journals Sensitivity analysis of the effect of wind characteristics and turbine properties on wind turbine loads

2019 ◽  
Vol 4 (3) ◽  
pp. 479-513 ◽  
Author(s):  
Amy N. Robertson ◽  
Kelsey Shaler ◽  
Latha Sethuraman ◽  
Jason Jonkman
Keyword(s):  
Sensitivity Analysis ◽  
Wind Turbine ◽  
Lift Coefficient ◽  
International Electrotechnical Commission ◽  
Individual Parameter ◽  
Aerodynamic Properties ◽  
Fatigue Loads ◽  
Sensitive Parameters ◽  
The Impact ◽  
Inflow Conditions

Abstract. Proper wind turbine design relies on the ability to accurately predict ultimate and fatigue loads of turbines. The load analysis process requires precise knowledge of the expected wind-inflow conditions as well as turbine structural and aerodynamic properties. However, uncertainty in most parameters is inevitable. It is therefore important to understand the impact such uncertainties have on the resulting loads. The goal of this work is to assess which input parameters have the greatest influence on turbine power, fatigue loads, and ultimate loads during normal turbine operation. An elementary effects sensitivity analysis is performed to identify the most sensitive parameters. Separate case studies are performed on (1) wind-inflow conditions and (2) turbine structural and aerodynamic properties, both cases using the National Renewable Energy Laboratory 5 MW baseline wind turbine. The Veers model was used to generate synthetic International Electrotechnical Commission (IEC) Kaimal turbulence spectrum inflow. The focus is on individual parameter sensitivity, though interactions between parameters are considered. The results of this work show that for wind-inflow conditions, turbulence in the primary wind direction and shear are the most sensitive parameters for turbine loads, which is expected. Secondary parameters of importance are identified as veer, u-direction integral length, and u components of the IEC coherence model, as well as the exponent. For the turbine properties, the most sensitive parameters are yaw misalignment and outboard lift coefficient distribution; secondary parameters of importance are inboard lift distribution, blade-twist distribution, and blade mass imbalance. This information can be used to help establish uncertainty bars around the predictions of engineering models during validation efforts, and provide insight to probabilistic design methods and site-suitability analyses.

scholarly journals Numerical Simulation on Aerodynamics of Multi-Element Airfoil with Drooped Spoiler in Ground Effect

2019 ◽  
Vol 37 (1) ◽  
pp. 167-176
Author(s):  
Jiang Liu ◽  
Junqiang Bai ◽  
Guozhu Gao ◽  
Min Chang ◽  
Nan Liu
Keyword(s):  
Lift Coefficient ◽  
Angle Of Attack ◽  
Ground Effect ◽  
Lower Surface ◽  
Navier Stokes ◽  
High Angle ◽  
High Angle Of Attack ◽  
Ride Height ◽  
Navier Stokes Equation ◽  
Sst Turbulence Model

By using the finite volume method and k-ω SST turbulence model to solve the Reynolds Average Navier-Stokes equation and using the slipping wall to simulate the relative movement of the ground, the ground effect on the aerodynamic characteristic of multi-element airfoil with drooped spoiler is investigated numerically, and the reason why the lift coefficient decreased in ground effect is analyzed. The results indicate that, with the reduction in ride height, the lift and the drag decrease and the lift-drag ratio increases for the multi-element airfoil; the amplitude of the reduction in the lift coefficient increases with the reduction in ride height and the increase in the angle of attack, the maximum of lift coefficient can be reduced by about 22%; with the effect of ground, the losses of suction at upper surface make the lift decrease, the increases of pressure at lower surface make the lift increase, the variation of the lift coefficient for the main wing caused by the former is more than three times that of the latter. Analyzing the reason why the lift coefficient decreases showed that:on the one hand, ground effect on the lift coefficient for clean airfoil is changed with the range of angle of attack. For the low-to-moderate angle of attack, the lift coefficient increases; for the high angle of attack, the lift coefficient decreases. But multi-element airfoil works in the takeoff and landing stage for the high angle of attack, which causes the reduction of the lift coefficient in ground effect. On the other hand, the increase of the lift coefficient caused by the deflection of spoiler decreases with the reduction in ride height and the maximum reduction can be about 50%, which illustrates that ground effect makes interaction of the front and back section for the multi-element airfoil weak, resulting in further decreasing the coefficient for the multi-element airfoil.

Experimental investigation of the aerodynamic characteristics of generic fan-in-wing configurations

2009 ◽  
Vol 113 (1139) ◽  
pp. 9-20 ◽  
Author(s):  
N. Thouault ◽  
C. Breitsamter ◽  
N. A. Adams ◽  
C. Gologan ◽  
J. Seifert
Keyword(s):  
Experimental Investigation ◽  
Lift Coefficient ◽  
Ground Effect ◽  
Aerodynamic Characteristics ◽  
Flow Visualisation ◽  
Force Measurements ◽  
Tunnel Model ◽  
Image Velocimetry ◽  
Flow Circulation ◽  
Stereo Particle Image Velocimetry

Abstract This experimental investigation concentrates on the aerodynamic behaviour of a generic fan-in-wing configuration. The effects of the fan(s) on the flow circulation in a short take-off and landing or a transition flight condition without ground effect are evaluated. A wind-tunnel model has been constructed and tested to quantify the aerodynamic effects. Force measurements, surface pressure measurements, stereo-particle image velocimetry and wool tufts flow visualisation are performed. Different fan-in-wing configurations with the fans rotating in the wing plane, one fan either at the rear or front part of the wing and two fans are compared to the closed wing without fans set as reference. A fan placed near the trailing edge improves significantly the lift coefficient due to a jet flap effect on the wing lower side combined with enhanced suction on the wing upper side. The jet exiting the nozzle rolls up in a counter rotating pair of vortices affecting significantly the wing behaviour. This experimental investigation constitutes also a useful database for further CFD comparison.

Three-dimensional vortex interactions with a stationary blade

1999 ◽  
Vol 103 (1030) ◽  
pp. 579-588 ◽  
Author(s):  
C. J. Doolan ◽  
F. N. Coton ◽  
R. A. McD. Galbraith
Keyword(s):  
Three Dimensional ◽  
Lower Surface ◽  
Impulsive Loading ◽  
Axial Component ◽  
Core Flow ◽  
Vortex Interactions ◽  
Rapid Changes ◽  
Naca 0015 ◽  
And Control ◽  
The Impact

Abstract Surface pressure measurements were obtained during a three-dimensional vortex interaction with a NACA 0015 aerofoil. The upper and lower surfaces of the blade experienced different aerodynamic loads which appear to be controlled by the impact of the vortex axial core flow on the blade surface. On the upper surface of the blade, where the vortex core flow was away from the aerofoil, the interaction was characterised by the generation of a suction peak. On the lower surface, where the axial component was towards the blade, a pressure pulse developed and seemed to be influenced by the vortex approach angle. These features resulted in rapid changes in normal force and quarter chord pitching moment during the interaction. This impulsive loading of the blade may provide some explanation for sound generation and control degradation problems associated with the tail rotor of helicopters.

An analytic solution for two- and three-dimensional wings in ground effect

1970 ◽  
Vol 41 (4) ◽  
pp. 769-792 ◽  
Author(s):  
Sheila E. Widnall ◽  
Timothy M. Barrows
Keyword(s):  
Analytic Solution ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Ground Effect ◽  
Flow Region ◽  
Lower Surface ◽  
Surface Pressure Distribution ◽  
Lifting Surface ◽  
Source Sink ◽  
Confined Channel

The method of matched asymptotic expansions is applied to the problem of a wing of finite span in very close proximity to the ground. The general lifting surface problem is shown to be a direct problem, represented by a source-sink distribution on the upper surface of the wing and wake, with concentrated sources around the leading and side edges plus a separate confined channel flow region under the wing and wake. The two-dimensional flat plate airfoil is examined in detail and results for upper and lower surface pressure distribution and lift coefficient are compared with a numerical solution. A simple analytic solution is obtained for a flat wing with a straight trailing edge which has minimum induced drag. To lowest order, this optimally loaded wing has an elliptical planform and a lift distribution which is linear along the chord, resulting in a parabolic spanwise lift distribution. An expression for the lift coefficient at small clearance and angle of attack, valid for moderate aspect ratio, is derived. The analytic results show reasonable agreement when compared with numerical results from lifting surface theory.

scholarly journals Sensitivity of Uncertainty in Wind Characteristics and Wind Turbine Properties on Wind Turbine Extreme and Fatigue Loads

2019 ◽  
Author(s):  
Amy N. Robertson ◽  
Kelsey Shaler ◽  
Latha Sethuraman ◽  
Jason Jonkman
Keyword(s):  
Wind Turbine ◽  
Lift Coefficient ◽  
Individual Parameter ◽  
Aerodynamic Properties ◽  
Precise Knowledge ◽  
Fatigue Loads ◽  
Sensitive Parameters ◽  
The Impact ◽  
T Distribution ◽  
Inflow Conditions

Abstract. Wind turbine design relies on the ability to accurately predict turbine ultimate and fatigue loads. The loads analysis process requires precise knowledge of the expected wind-inflow conditions as well as turbine structural and aerodynamic properties. However, uncertainty in most parameters is inevitable. It is therefore important to understand the impact such uncertainties have on the resulting loads. The goal of this work is to assess which input parameters have the greatest influence on turbine power, fatigue loads, and ultimate loads during normal turbine operation. An Elementary Effects (EE) sensitivity analysis is performed to identify the most sensitive parameters. Separate case studies are performed on (1) wind-inflow conditions and (2) turbine structural and aerodynamic properties, both using the National Renewable Energy Laboratory (NREL) 5-MW baseline wind turbine. The focus is on individual parameter sensitivity, though interactions between parameters are considered. The results of this work show that for wind-inflow conditions, turbulence in the primary wind direction and shear are the most sensitivity parameters for turbine loads, which is expected. Secondary parameters of importance are identified as veer, u-direction integral length, and components of the IEC coherence model (au and bu), as well as the exponent (γ). For the turbine properties, the most sensitive parameters are yaw misalignment (θ) and outboard lift coefficient (Cl,t) distribution. This information can be used to help establish error bars around the predictions of engineering models during validation efforts, and provide insight to probabilistic design methods and site-suitability analyses.

scholarly journals Effect of the opening and location ratio on the performance of an H-Darrieus VAWT

2021 ◽  
Author(s):  
Andres Felipe Burbano-Hernández ◽  
Diego Andres Hincapié Zuluaga ◽  
Jonathan Andrés Graciano-Uribe ◽  
Edwar Andrés Torres Lopéz
Keyword(s):  
Wind Turbines ◽  
Research Work ◽  
Vertical Axis ◽  
Lower Surface ◽  
Low Wind Speed ◽  
Opening Ratio ◽  
Cfd Method ◽  
Turbine Design ◽  
Naca 0015 ◽  
The Impact

Vertical axis wind turbines such as Darrieus turbines are a very interesting category of low wind speed domestic wind turbines. Further research work is needed to enhance their efficiency to fulfill the higher demand in small applications for power generation. The main objective of this work is to find a Darrieus turbine design to boost the starting capacity of the turbine through an opening located at the lower surface of the airfoil. We carried out a thorough CFD (Computational Fluid Dynamics) investigation to determine the impact of the opening position on the Darrieus rotor's output. This new type of airfoil uses a standard NACA 0015 profile and a profile with an opening on the lower surface of the profile. Different sizes of the opening in a symmetrical profile are evaluated through the CFD method to predict the Cp and CT of this H-Darrieus turbine design. Five sections were designed to describe the research of this new H-Darrieus rotor. Generally speaking, the results showed that the Cp decreases with the opening ratio, the desirable rotors with the lower surface opening ratio are 0.12 to 0.36 considering this with the low CpLP.

Experimental Study of Aerodynamics and Wingtip Vortex of a Rectangular Wing in Flat Ground Effect

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
A. Lu ◽  
V. Tremblay-Dionne ◽  
T. Lee
Keyword(s):  
Vortex Flow ◽  
Ground Surface ◽  
Ground Effect ◽  
Inviscid Flow ◽  
Tip Vortex ◽  
Vortex Strength ◽  
Induced Drag ◽  
Wingtip Vortex ◽  
Ground Distance ◽  
The Impact

The ground effect on the aerodynamics and tip vortex flow of a rectangular wing is investigated experimentally at Re = 2.71 × 105. The results show that there is a large lift increase with reducing ground distance. By contrast, only a small drag increase is observed in ground effect except in close ground proximity for which a great drag increase appears. The tip vortex also moves further outboard and upward with reducing ground distance. Near the ground, there is the presence of a corotating ground vortex (produced by the rolling up of the boundary layer developed on the ground surface), leading to an increased vortex strength. In extreme ground proximity, a counterrotating secondary vortex (SV) (induced by the crossflow of the tip vortex), relative to the tip vortex, appears which causes a reduced vortex strength and a lowered lift-induced drag, as well as a vortex rebound. The impact of ground effect on the vortex flow properties is also discussed. The lift-induced drag, computed based on the crossflow measurements via the Maskell wake integral method, in ground effect is also compared against the inviscid-flow predictions and wind tunnel total drag force measurements.

Thick Crescent Iced Sub-Conductors Spacing Influence on the Aerodynamic Properties

2013 ◽  
Vol 419 ◽  
pp. 62-66
Author(s):  
Li Jun Ma ◽  
Shu Ying Hao ◽  
Qi Chang Zhang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Wake Flow ◽  
Ice Thickness ◽  
Aerodynamic Coefficient ◽  
Coefficient Variation ◽  
Moment Coefficient ◽  
Aerodynamic Properties

Using computational fluid dynamics software FLUENT analysis and calculation the aerodynamic coefficient of the 28mm ice thickness crescent iced quad-bundle conductors under different spacing. Studies show that aerodynamic coefficient of downwind sub-conductors affected by wake-flow, with the upwind sub-conductors there is always a big difference. With different spacing values, quad-bundle iced conductors in the wake-flow of different effects. Upwind sub-conductors, spacing values have nothing to do with the aerodynamic coefficient. Downwind sub-conductors, drag coefficient in the larger change significantly, moment coefficient variation is relatively small. Sub-conductors spacing has no effect on the lift coefficient.

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