Peak and Post-Peak Power Aerodynamics from Phase VI NASA Ames Wind Turbine Data

2005 ◽  
Vol 127 (2) ◽  
pp. 192-199 ◽  
Author(s):  
Brandon S. Gerber ◽  
James L. Tangler ◽  
Earl P. N. Duque ◽  
J. David Kocurek
Keyword(s):  
Performance Prediction ◽  
Peak Power ◽  
Tangential Force ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Wind Tunnel Test ◽  
Drag Coefficients ◽  
Force Coefficients ◽  
Lift And Drag ◽  
Blade Element

Constant speed/pitch rotor operation lacks adequate theory for predicting peak and post-peak power. The objective of this study was to identify and quantify how measured blade element performance characteristics from the Phase VI NASA Ames 24m×36m80ft×120ft wind tunnel test of a two-bladed, tapered, twisted rotor relate to the prediction of peak and post-peak rotor power. The performance prediction code, NREL’s Lifting Surface Prescribed Wake code (LSWT), was used to study the flow physics along the blade. Airfoil lift and drag coefficients along the blade were derived using the predicted angle of attack distribution from LSWT and Phase VI measured normal and tangential force coefficients. Through successive iterations, the local lift and drag coefficients were modified until agreement was achieved between the predicted and Phase VI measured normal and tangential force coefficients along the blade. This agreement corresponded to an LSWT angle of attack distribution and modified airfoil data table that reflected the measured three-dimensional aerodynamics. This effort identified five aerodynamic events important to the prediction of peak and post-peak power. The most intriguing event was a rapid increase in drag that corresponds with the occurrence of peak power. This is not currently modeled in engineering performance prediction methods.

Three-Dimensional Numerical Prediction of the Hydrodynamic Loads and Motions of Offshore Structures

2000 ◽  
Vol 122 (4) ◽  
pp. 294-300 ◽  
Author(s):  
Karl W. Schulz ◽  
Yannis Kallinderis
Keyword(s):  
Flow Structure ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Structural Response ◽  
Offshore Structures ◽  
Three Dimensions ◽  
Navier Stokes ◽  
Hydrodynamic Loads ◽  
Drag Coefficients ◽  
Lift And Drag

A generalized numerical method for solution of the incompressible Navier-Stokes equations in three-dimensions has been developed. This solution methodology allows for the accurate prediction of the hydrodynamic loads on offshore structures, which is then combined with a rigid body structural response to address the flow-structure coupling which is often present in offshore applications. Validation results using this method are first presented for fixed structures which compare the drag coefficients of sphere and cylinder geometries to experimental measurements over a range of subcritical Reynolds numbers. Additional fixed structure results are then presented which explore the influence of aspect ratio effects on the lift and drag coefficients of a bare circular cylinder. Finally, the spanwise flow variations between a fixed and freely vibrating cylindrical structure are compared to demonstrate the ability of the flow-structure method to correctly predict correlation length increases for a vibrating structure. [S0892-7219(00)00904-3]

scholarly journals Numerical investigation of the aerodynamic characteristics and attitude stability of a bio-inspired corrugated airfoil for MAV or UAV applications

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 4021 ◽  
Author(s):  
Hui Tang ◽  
Yulong Lei ◽  
Xingzhong Li ◽  
Yao Fu
Keyword(s):  
Reynolds Number ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Numerical Calculations ◽  
Spanwise Direction ◽  
Stable Range ◽  
Fluid Force ◽  
Attitude Stability ◽  
Lift And Drag

In this study, two-dimensional (2D) and three-dimensional (3D) numerical calculations were conducted to investigate the aerodynamic characteristics, especially the unsteady aerodynamic characteristics and attitude stability of a bio-inspired corrugated airfoil compared with a smooth-surfaced airfoil (NACA2408 airfoil) at the chord Reynolds number of 4000 to explore the potential applications of non-traditional, corrugated dragonfly airfoils for micro air vehicles (MAVs) or micro-sized unmanned aerial vehicles (UAVs) designs. Two problem settings were applied to our numerical calculations. First, the airfoil was fixed at a constant angle of attack to analyze the aerodynamic characteristics and the hydrodynamic moment. Second, the angle of attack of airfoils was passively changed by the fluid force to analyze the attitude stability. The current numerical solver for the flow field around an unsteady rotating airfoil was validated against the published numerical data. It was confirmed that the corrugated airfoil performs (in terms of the lift-to-drag ratio) much better than the profiled NACA2408 airfoil at low Reynolds number R e = 4000 in low angle of attack range of 0 ∘ – 6 ∘ , and performs as well at the angle of attack of 6 ∘ or more. At these low angles of attack, the corrugated airfoil experiences an increase in the pressure drag and decrease in shear drag due to recirculation zones inside the cavities formed by the pleats. Furthermore, the increase in the lift for the corrugated airfoil is due to the negative pressure produced at the valleys. It was found that the lift and drag in the 2D numerical calculation are strong fluctuating at a high angle of attacks. However, in 3D simulation, especially for a 3D corrugated airfoil with unevenness in the spanwise direction, smaller fluctuations and the smaller average value in the lift and drag were obtained than the results in 2D calculations. It was found that a 3D wing with irregularities in the spanwise direction could promote three-dimensional flow and can suppress lift fluctuations even at high angles of attack. For the attitude stability, the corrugated airfoil is statically more unstable near the angle of attack of 0 ∘ , has a narrower static stable range of the angle of attack, and has a larger amplitude of fluctuations of the angle of attack compared with the profiled NACA2408 airfoil. Based on the Routh–Hurwitz stability criterion, it was confirmed that the control systems of the angle of attack passively changed by the fluid force for both two airfoils are unstable systems.

Correcting Inflow Measurements From Wind Turbines Using a Lifting-Surface Code

2000 ◽  
Vol 122 (4) ◽  
pp. 196-202 ◽  
Author(s):  
J. Whale ◽  
C. J. Fisichella ◽  
M. S. Selig
Keyword(s):  
Angle Of Attack ◽  
Three Dimensional ◽  
Correction Method ◽  
Local Flow ◽  
Flow Angle ◽  
Lifting Surface ◽  
Surface Code ◽  
Turbine Design ◽  
The Relationship ◽  
Blade Element

In order to provide accurate blade element data for wind turbine design codes, measured three-dimensional (3D) field data must be corrected in terms of the (sectional) angle of attack. A 3D Lifting-Surface Inflow Correction Method (LSIM) has been developed with the aid of a vortex-panel code in order to calculate the relationship between measured local flow angle and angle of attack. The results show the advantages of using the 3D LSIM correction over 2D correction methods, particularly at the inboard sections of the blade where the local flow is affected by post-stall effects and the influence of the blade root. [S0199-6231(00)00604-3]

Relations of Lift and Drag Coefficients of Flow around Flat Plate

2014 ◽  
Vol 518 ◽  
pp. 161-164 ◽  
Author(s):  
Hai Bo Jiang ◽  
Yan Ru Li ◽  
Zhong Qing Cheng
Keyword(s):  
Flat Plate ◽  
Small Angle ◽  
Total Pressure ◽  
Angle Of Attack ◽  
Vertical Component ◽  
Horizontal Component ◽  
High Angle ◽  
High Angle Of Attack ◽  
Drag Coefficients ◽  
Lift And Drag

In this paper, when Reynolds number is within the range of 10000 to 1000000, the horizontal component of the total pressure of flow around flat plate at high angle of attack was regarded as lift of high angle of attack, and the vertical component was regarded as drag of high angle of attack. The horizontal component of total pressure at small angle of attack was regarded as shape drag, and the total drag coefficient at small angle of attack was considered to the sum of the shape drag and frictional drag at zero angle of attack. For the two states of large and small angle of attack, the application scopes of the formulas of lift and drag coefficients were given. Final, the relations of lift and drag coefficients were obtained by eliminating all angles of attack. Research results show that lift - drag curve of small angles of attack is parabola, and the lift - drag curve of high angles of attack is circle.

Numerical Study on Flap Style Rudder Hydrodynamic Characteristics With Different Connections

2016 ◽  
Author(s):  
Zhenwei Dong ◽  
Zhijian Xiao ◽  
Shiqi Gong ◽  
Zhiguo Zhang ◽  
Dakui Feng
Keyword(s):  
Numerical Study ◽  
Angle Of Attack ◽  
Large Angle ◽  
Hydrodynamic Characteristics ◽  
Computation Method ◽  
Suction Surface ◽  
Drag Coefficients ◽  
Flow Field Characteristics ◽  
The Difference ◽  
Lift And Drag

The flow field characteristics of 2-D flap style rudders with and without gap are analyzed through 4 models. To explore the influence of different filling styles, one flap rudder with gap and three flap rudders without gap are simulated from 0 to 30 degrees angle of attack with k-omega SST turbulence model. Validation is done by comparing the results with EFD data from reference and the mesh independence verification is also made. Then lift and drag coefficients are compared among four models. Pressure, velocity distributions are given to explain the difference on hydrodynamic characteristics among them. Unsteady computation method is used to investigate the fluctuation characteristics of drag coefficients at large angle of attack. Stream lines are shown to better understand the vortex system on the suction surface.

Computational Study of Taper Effect of a Hydrofoil at Different Reynolds Numbers on the Length of Cavity and Lift and Drag Coefficients

2009 ◽  
Author(s):  
Mohammad J. Izadi ◽  
Mahdi Mirtorabi
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Cavity Length ◽  
Computational Study ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
High Reynolds ◽  
Lift And Drag

In this paper a cavitating flow around a three dimensional tapered hydrofoil in an incompressible fluid is modeled and studied. The variables in this study are the taper ratio, angle of attack and the Reynolds number. The taper ratio changes from 0.2 to 1, the angles of attack varies from −2 to 12 degrees and all these are computed at two Reynolds numbers (Re = 5.791·107 and Re = 1.99·108). The flow is assumed to be unsteady and isothermal. Coefficients of drag and lift and also the cavity length are computed numerically. Comparing the numerical results of five investigated models (five tapered hydrofoils) and the work done by Kermeen experimentally, it can be seen that the tapered hydrofoil in some cases gave better results, reducing the cavity length and improving the lift coefficient. At the low Reynolds number, the length of the cavity is calculated to be small in comparison with the length gained at the high Reynolds number, and therefore the change of the taper and the angles of attack did change the amount of the lift coefficient as much. For high Reynolds number, as the angle of attack increased, the tapering effect became more important and the best lift coefficient and minimum cavity length is obtained at a taper ratio of 0.4 for an averaged angles of attack.

Compressor Blade Modelling Under Highly Negative Incedence

2011 ◽  
Author(s):  
Pavlos K. Zachos ◽  
Cornelia Ruelke ◽  
Vassilios Pachidis ◽  
Riti Singh
Keyword(s):  
Incidence Angle ◽  
Tangential Force ◽  
Three Dimensional ◽  
Pressure Change ◽  
Compressor Blade ◽  
Blade Design ◽  
Aerodynamic Coefficients ◽  
Resource Saving ◽  
Blade Element ◽  
Blade Loss

This paper investigates performance prediction techniques for compressor blades operating under highly negative incidence angle which is typical during engine groundstarts or windmilling relights. Although this is a very frequently occurring situation during the life of an aero engine, turbomachinery components are rarely tested under those conditions in the sake of resource saving. However, performance engineers require some knowledge of generic blade loss coefficients under those conditions for the preliminary estimation of the groundstart or relight capability of the engine which is also linked to design decisions such as the volume of the combustion chamber. A blade element concept is employed to break a 3D compressor blade design down to a number of 2D cross sections and study them separately using a CFD derived 2D blade loss coefficient database. Several different ways to synthesize the 3D blade out of the 2D sections are herein presented based on different expressions of blade aerodynamic coefficients. An investigation based on the expressions of the aerodynamic coefficients is conducted in order to justify the applicability of the blade element theory at such off-design conditions. The most suitable parameter set to represent a three dimensional blade design by a number of radially stacked two dimensional profiles is identified. The analysis shows that the approach based on pressure change and tangential force coefficients can more adequately approximate the performance of the 3D blade and therefore can be safely employed for a preliminary off-design blade performance studies.

Parametric Study on Wing-Lambda-Shock Formation

2021 ◽  
Author(s):  
Sirikorn Chainok ◽  
Thanapol Rungroch ◽  
Pattarasuda Chairach ◽  
Prasert Prapamonthon ◽  
Soemsak Yooyen ◽  
...  
Keyword(s):  
Mach Number ◽  
Free Stream ◽  
Angle Of Attack ◽  
Shock Formation ◽  
Local Pressure ◽  
Drag Coefficients ◽  
Pressure Coefficients ◽  
Free Stream Mach Number ◽  
Lambda Shock ◽  
Lift And Drag

Abstract It is well-known that a wing is one of the most important parts of an aircraft as it is used to generate lift force. According to a wing moving at sufficiently high subsonic speeds, the flow speed on the wing’s upper surface can be supersonic due to acceleration through the curvature-created suction, thereby forming a shock wave in a lambda shape. Additionally, the lambda shock can interact with the boundary layer flow. These phenomena relate to disturbances in the flow field, including flow separation, thus causing undesirable effects on lift production. Hence, a better understanding of the phenomenon of wing-lambda-shock formation and its nature is essential. This study presents a numerical investigation of the lambda-shock formation on an ONERA M6 wing, which is known as a swept, semi-span wing with no twist, under parametric effects of angle-of-attack, and free-stream Mach number, which is increased up to the supersonic regime. The pressure coefficients obtained by simulations are validated by open data. Then, numerical results in terms of the local pressure coefficient, local Mach number, averaged lift and drag coefficients, and λ-shape characteristics based on Mach number and pressure coefficients are discussed under an investigated range of the parameters. Results show that the angle-of-attack and free-stream Mach number can affect the lambda shock formation on the wing upper surface physically. Specifically, an iso-sonic surface with lambda shock waves is disturbed when the angle-of-attack and free-stream Mach number vary in an investigated range. This also affects lift and drag coefficients of the wing.

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