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1

An aerodynamic comparison of blown and mechanical high lift airfoils  

NASA Technical Reports Server (NTRS)

Short takeoff and landing (STOL) performance utilizing a circulation control airfoil was successfully demonstrated on the A-6 CCW (circulation control wing). Controlled flight at speeds as slow as 67 knots was demonstrated. Takeoff ground run and liftoff speed reductions in excess of 40 and 20 percent respectively were achieved. Landing ground roll and approach speeds were similarly reduced. The technology demonstrated was intended to be useable on modern high performance aircraft. STOL performance would be achieved through the combination of a 2-D vectored nozzle and a circulation control type of high lift system. The primary objective of this demonstration was to attain A-6 CCW magnitude reductions in takeoff and landing flight speed and ground distance requirements using practical bleed flow rates from a modern turbofan engine for the blown flap system. Also, cruise performance could not be reduced by the wing high lift system. The A-6 was again selected as the optimum demonstration vehicle. The procedure and findings of the study to select the optimum high lift wing design are documented. Some findings of a supercritical airfoil and a comparison of 2-D and 3-D results are also described.

Carr, John E.

1987-01-01

2

Parametric Investigation of a High-Lift Airfoil at High Reynolds Numbers  

Microsoft Academic Search

A new two-dimensional, three-element, advanced high-lift research airfoil has been tested in the NASA Langley Research CenterŐs Low-Turbulence Pressure Tunnel at a chord Reynolds number up to 1.6 x 10 7. The components of this high-lift airfoil have been designed using a incompressible computational code (INS2D). The design was to provide high maximum-lift values while maintaining attached flow on the

John C. Lin; Chet J. Dominik

1997-01-01

3

Design of high lift airfoils with a Stratford distribution by the Eppler method  

NASA Technical Reports Server (NTRS)

Airfoils having a Stratford pressure distribution, which has zero skin friction in the pressure recovery area, were investigated in an effort to develop high lift airfoils. The Eppler program, an inverse conformal mapping technique where the x and y coordinates of the airfoil are developed from a given velocity distribution, was used.

Thomson, W. G.

1975-01-01

4

Parametric Investigation of a High-Lift Airfoil at High Reynolds Numbers  

NASA Technical Reports Server (NTRS)

A new two-dimensional, three-element, advanced high-lift research airfoil has been tested in the NASA Langley Research Center s Low-Turbulence Pressure Tunnel at a chord Reynolds number up to 1.6 x 107. The components of this high-lift airfoil have been designed using a incompressible computational code (INS2D). The design was to provide high maximum-lift values while maintaining attached flow on the single-segment flap at landing conditions. The performance of the new NASA research airfoil is compared to a similar reference high-lift airfoil. On the new high-lift airfoil the effects of Reynolds number on slat and flap rigging have been studied experimentally, as well as the Mach number effects. The performance trend of the high-lift design is comparable to that predicted by INS2D over much of the angle-of-attack range. However, the code did not accurately predict the airfoil performance or the configuration-based trends near maximum lift where the compressibility effect could play a major role.

Lin, John C.; Dominik, Chet J.

1997-01-01

5

Pneumatic Spoiler Controls Airfoil Lift  

NASA Technical Reports Server (NTRS)

Air ejection from leading edge of airfoil used for controlled decrease of lift. Pneumatic-spoiler principle developed for equalizing lift on helicopter rotor blades. Also used to enhance aerodynamic control of short-fuselage or rudderless aircraft such as "flying-wing" airplanes. Leading-edge injection increases maneuverability of such high-performance fixed-wing aircraft as fighters.

Hunter, D.; Krauss, T.

1991-01-01

6

Icing Test Results on an Advanced Two-Dimensional High-Lift Multi-Element Airfoil  

NASA Technical Reports Server (NTRS)

An experimental study has been conducted to investigate ice accretions on a high-lift, multi-element airfoil in the Icing Research Tunnel at the NASA Lewis Research Center. The airfoil is representative of an advanced transport wing design. The experimental work was conducted as part of a cooperative program between McDonnell Douglas Aerospace and the NASA Lewis Research Center to improve current understanding of ice accretion characteristics on the multi-element airfoil. The experimental effort also provided ice shapes for future aerodynamic tests at flight Reynolds numbers to ascertain high-lift performance effects. Ice shapes documented for a landing configuration over a variety of icing conditions are presented along with analyses.

Shin, Jaiwon; Wilcox, Peter; Chin, Vincent; Sheldon, David

1994-01-01

7

High-Lift Optimization Design Using Neural Networks on a Multi-Element Airfoil  

NASA Technical Reports Server (NTRS)

The high-lift performance of a multi-element airfoil was optimized by using neural-net predictions that were trained using a computational data set. The numerical data was generated using a two-dimensional, incompressible, Navier-Stokes algorithm with the Spalart-Allmaras turbulence model. Because it is difficult to predict maximum lift for high-lift systems, an empirically-based maximum lift criteria was used in this study to determine both the maximum lift and the angle at which it occurs. Multiple input, single output networks were trained using the NASA Ames variation of the Levenberg-Marquardt algorithm for each of the aerodynamic coefficients (lift, drag, and moment). The artificial neural networks were integrated with a gradient-based optimizer. Using independent numerical simulations and experimental data for this high-lift configuration, it was shown that this design process successfully optimized flap deflection, gap, overlap, and angle of attack to maximize lift. Once the neural networks were trained and integrated with the optimizer, minimal additional computer resources were required to perform optimization runs with different initial conditions and parameters. Applying the neural networks within the high-lift rigging optimization process reduced the amount of computational time and resources by 83% compared with traditional gradient-based optimization procedures for multiple optimization runs.

Greenman, Roxana M.; Roth, Karlin R.; Smith, Charles A. (Technical Monitor)

1998-01-01

8

Computational Investigation of Separation Control for High-Lift Airfoil Flows  

Microsoft Academic Search

This paper gives an overview of numerical flow control investigations for high-lift airfoil flows carried out by the authors.\\u000a Two configurations at stall conditions, a generic two-element setup with single flap and a second configurationwith slat and\\u000a flap of more practical relevance are investigated by simulations based on the Reynolds-averaged Navier-Stokes equations and\\u000a eddy-viscosity turbulence models. For both cases flow

Markus Schatz; Bert Günther; Frank Thiele

9

Numerical and experimental study of blowing jet on a high lift airfoil  

NASA Astrophysics Data System (ADS)

Active manipulation of separated flows over airfoils at moderate and high angles of attack in order to improve efficiency or performance has been the focus of a number of numerical and experimental investigations for many years. One of the main methods used in active flow control is the usage of blowing devices with constant and pulsed blowing. Through CFD simulation over a 2D high-lift airfoil, this study is trying to highlight the impact of pulsed blowing over its aerodynamic characteristics. The available wind tunnel data from INCAS low speed facility are also beneficial for the validation of the numerical analysis. This study intends to analyze the impact of the blowing jet velocity and slot geometry on the efficiency of an active flow control.

Bobonea, A.; Pricop, M. V.

2013-10-01

10

Design and test of a natural laminar flow/large Reynolds number airfoil with a high design cruise lift coefficient  

NASA Technical Reports Server (NTRS)

Research activity on an airfoil designed for a large airplane capable of very long endurance times at a low Mach number of 0.22 is examined. Airplane mission objectives and design optimization resulted in requirements for a very high design lift coefficient and a large amount of laminar flow at high Reynolds number to increase the lift/drag ratio and reduce the loiter lift coefficient. Natural laminar flow was selected instead of distributed mechanical suction for the measurement technique. A design lift coefficient of 1.5 was identified as the highest which could be achieved with a large extent of laminar flow. A single element airfoil was designed using an inverse boundary layer solution and inverse airfoil design computer codes to create an airfoil section that would achieve performance goals. The design process and results, including airfoil shape, pressure distributions, and aerodynamic characteristics are presented. A two dimensional wind tunnel model was constructed and tested in a NASA Low Turbulence Pressure Tunnel which enabled testing at full scale design Reynolds number. A comparison is made between theoretical and measured results to establish accuracy and quality of the airfoil design technique.

Kolesar, C. E.

1987-01-01

11

High-lift airfoil trailing edge separation control using a single dielectric barrier discharge plasma actuator  

NASA Astrophysics Data System (ADS)

Control of flow separation from the deflected flap of a high-lift airfoil up to Reynolds numbers of 240,000 (15 m/s) is explored using a single dielectric barrier discharge (DBD) plasma actuator near the flap shoulder. Results show that the plasma discharge can increase or reduce the size of the time-averaged separated region over the flap depending on the frequency of actuation. High-frequency actuation, referred to here as quasi-steady forcing, slightly delays separation while lengthening and flattening the separated region without drastically increasing the measured lift. The actuator is found to be most effective for increasing lift when operated in an unsteady fashion at the natural oscillation frequency of the trailing edge flow field. Results indicate that the primary control mechanism in this configuration is an enhancement of the natural vortex shedding that promotes further momentum transfer between the freestream and separated region. Based on these results, different modulation waveforms for creating unsteady DBD plasma-induced flows are investigated in an effort to improve control authority. Subsequent measurements show that modulation using duty cycles of 50-70% generates stronger velocity perturbations than sinusoidal modulation in quiescent conditions at the expense of an increased power requirement. Investigation of these modulation waveforms for trailing edge separation control similarly shows that additional increases in lift can be obtained. The dependence of these results on the actuator carrier and modulation frequencies is discussed in detail.

Little, Jesse; Nishihara, Munetake; Adamovich, Igor; Samimy, Mo

2010-03-01

12

Turbulence modeling for high-lift multi-element airfoil configurations  

NASA Astrophysics Data System (ADS)

This study provides a detailed comparison of two turbulence closures for aerodynamic flows around high-lift airfoils; the first based on turbulent viscosity and the second on the algebraic Reynolds-stress approximation. A detailed analysis of their derivation helps shed light on their inherent limitations in predicting complex flow phenomena such as confluent boundary layers and flow separation found in typical take-off and landing conditions. Amongst the turbulent viscosity models coded and studied are the Spalart-Allmaras, Baldwin-Barth, Wilcox k - o and Menter's Shear Stress Transport model. A parameter study based on different pressure-strain correlations and dissipation models (or near-wall treatment) is included when studying the algebraic Reynolds-stress models for both the explicit (EARSM) and the more traditional or implicit (IARSM) forms. One of each of the following categories: one-equation, two-equation, IARSM and EARSM is selected and compared on several low-speed high-lift configurations. Comparisons to experimental data for both mean flow and turbulence quantities are provided for all cases studied. Results are generally very promising and of sufficient accuracy for engineering interest. Overall, the study indicates that for flows around low-speed high-lift airfoils, the algebraic Reynolds-stress construct does not represent a higher level of description than the eddy viscosity models since it fails to improve on accuracy. The basic underlying assumption of weak-equilibrium in algebraic Reynolds-stress models is outperformed by well calibrated eddy-viscosity models.

Godin, Philippe

13

Multi-element airfoil optimization for maximum lift at high Reynolds numbers  

NASA Technical Reports Server (NTRS)

An experimental study has been performed to assess the maximum lift capability of a supercritical multielement airfoil representative of an advanced transport aircraft wing. The airfoil model was designed with a leading-edge slat and single or two-segment trailing-edge flaps. Optimization work was performed at various slat/flap deflections as well as gap/overhang positions. Landing configurations and the attainment of maximum lift coefficients of 4.5 with single-element flaps and 5.0 with two-segment flaps was emphasized. Test results showed a relatively linear variation of the optimum gap/overhang positioning of the slat versus slat deflection, considerable differences in optimum rigging between single and double segment flaps, and large Reynolds number effects on multielement airfoil optimization.

Valarezo, Walter O.; Dominik, Chet J.; Mcghee, Robert J.; Goodman, Wesley L.; Paschal, Keith B.

1991-01-01

14

A study of high-lift airfoils at high Reynolds numbers in the Langley low-turbulence pressure tunnel  

NASA Technical Reports Server (NTRS)

An experimental study was conducted in the Langley Low Turbulence Pressure Tunnel to determine the effects of Reynolds number and Mach number on the two-dimensional aerodynamic performance of two supercritical type airfoils, one equipped with a conventional flap system and the other with an advanced high lift flap system. The conventional flap system consisted of a leading edge slat and a double slotted, trailing edge flap with a small chord vane and a large chord aft flap. The advanced flap system consisted of a leading edge slat and a double slotted, trailing edge flap with a large chord vane and a small chord aft flap. Both models were tested with all elements nested to form the cruise airfoil and with the leading edge slat and with a single or double slotted, trailing edge flap deflected to form the high lift airfoils. The experimental tests were conducted through a Reynolds number range from 2.8 to 20.9 x 1,000,000 and a Mach number range from 0.10 to 0.35. Lift and pitching moment data were obtained. Summaries of the test results obtained are presented and comparisons are made between the observed aerodynamic performance trends for both models. The results showing the effect of leading edge frost and glaze ice formation is given.

Morgan, Harry L., Jr.; Ferris, James C.; Mcghee, Robert J.

1987-01-01

15

Measuring Lift with the Wright Airfoils  

ERIC Educational Resources Information Center

In this laboratory or demonstration exercise, we mount a small airfoil with its long axis vertical at one end of a nearly frictionless rotating platform. Air from a leaf blower produces a sidewise lift force L on the airfoil and a drag force D in the direction of the air flow (Fig. 1). The rotating platform is kept in equilibrium by adding weights…

Heavers, Richard M.; Soleymanloo, Arianne

2011-01-01

16

Measuring Lift with the Wright Airfoils  

NASA Astrophysics Data System (ADS)

In this laboratory or demonstration exercise, we mount a small airfoil with its long axis vertical at one end of a nearly frictionless rotating platform. Air from a leaf blower2 produces a sidewise lift force L on the airfoil and a drag force D in the direction of the air flow (Fig. 1). The rotating platform is kept in equilibrium by adding weights (the measured values of L) to the lower end of a string passing over a pulley and connected to the other end of the rotating platform (Fig. 2). Our homemade airfoils are similar to those tested by the Wright brothers in 1901. From our lift plots in Fig. 3, we can draw the same conclusions as the Wrights about the influence of an airfoil's curvature and shape on lift.

Heavers, Richard M.; Soleymanloo, Arianne

2011-11-01

17

The effect of heavy rain on an airfoil at high lift  

NASA Technical Reports Server (NTRS)

No serious studies of the relationship of heavy rain to aircraft safety were made until 1981 when it was suggested that the torrential rain which often occurs at the time of severe wind shear might substantially increase the danger to aircraft operating at slow speeds and high lift in the vicinity of airports. While these data were not published until early 1983, appropriate measures were taken by NASA to study the effect of heavy rain on the lift of wings typical of commercial aircraft. One of the aspects of these tests that seemed confirmed by the data was the existence of a velocity effect on the lift data. The data seemed to indicate that when all the normal non-dimensional aerodynamic parameters were used to sort out the data, the effect of velocity was not accounted for, as it usually is, by the effect of dynamic pressure. Indeed, the measured lift coefficients at high lift indicated a dropoff in lift coefficient for the same free-stream water content as velocity was increased. indicated a drop-off in lift coefficient for the same free-stream water content as velocity was increased.

Donaldson, Coleman DUP.; Sullivan, Roger D.

1987-01-01

18

Comparative Results from a CFD Challenge Over a 2D Three-Element High-Lift Airfoil  

NASA Technical Reports Server (NTRS)

A high-lift workshop was held in May of 1993 at NASA Langley Research Center. A major part of the workshop centered on a blind test of various computational fluid dynamics (CFD) methods in which the flow about a two- dimensional (2D) three-element airfoil was computed without prior knowledge of the experimental data. The results of this 'blind' test revealed: (1) The Reynolds Averaged Navier-Stokes (RANS) methods generally showed less variability among codes than did potential/Euler solvers coupled with boundary-layer solution techniques. However, some of the coupled methods still provided excellent predictions. (2) Drag prediction using coupled methods agreed more closely with experiment than the RANS methods. Lift was more accurately predicted than drag for both methods. (3) The CFD methods did well in predicting lift and drag changes due to changes in Reynolds number, however, they did not perform as well when predicting lift and drag increments due to changing flap gap, (4) Pressures and skin friction compared favorably with experiment for most of the codes. (5) There was a large variability in most of the velocity profile predictions. Computational results predict a stronger siat wake than measured suggesting a missing component in turbulence modeling, perhaps curvature effects.

Klausmeyer, Steven M.; Lin, John C.

1997-01-01

19

CFD Validation for High-Lift Devices: Three-Element Airfoil  

Microsoft Academic Search

In this study, the accuracy of structured and unstructured mesh CFD codes in simulating the flow around a three-element high-lift configuration (slat, main wing, and flap) is assessed, and mesh dependency and effect of turbulence models are studied. In the first part of the study, the results of two structured mesh CFD codes and an unstructured mesh CFD code using

Mitsuhiro Murayama; Zhong Lei; Junichi Mukai; Kazuomi Yamamoto

2006-01-01

20

PARAMETRIC INVESTIGATION OF A HIGH-LIFT AIRFOIL AT HIGH REYNOLDS NUMBERS John C. Lin* NASA Langley Research Center, Hampton, VA 23681-0001 and Chet J. Dominik McDonnell Douglas Aerospace, Long Bea  

E-print Network

A new two-dimensional, three-element, advanced high-lift research airfoil has been tested in the NASA Langley Research CenterŐs Low-Turbulence Pressure Tunnel at a chord Reynolds number up to 1.6 x 10 7 . The components of this high-lift airfoil have been designed using a incompressible computational code (INS2D). The design was to provide high maximum-lift values while maintaining attached flow on the single-segment flap at landing conditions. The performance of the new NASA research airfoil is compared to a similar reference high-lift airfoil. On the new high-lift airfoil the effects of Reynolds number on slat and flap rigging have been studied experimentally, as well as the Mach number effects. The performance trend of the high-lift design is comparable to that predicted by INS2D over much of the angle-of-attack range. However, the code did not accurately predict the airfoil performance or the configuration-based trends near maximum lift where the compressibility effect could play ...

Ch Ca; John C. Lin; Chet J. Dominik

1997-01-01

21

An Experimntal Investigation of the 30P30N Multi-Element High-Lift Airfoil  

NASA Technical Reports Server (NTRS)

High-lift devices often generate an unsteady flow field producing both broadband and tonal noise which radiates from the aircraft. In particular, the leading edge slat is often a dominant contributor to the noise signature. An experimental study of a simplified unswept high-lift configuration, the 30P30N, has been conducted to understand and identify the various flow-induced noise sources around the slat. Closed-wall wind tunnel tests are performed in the Florida State Aeroacoustic Tunnel (FSAT) to characterize the slat cove flow field using a combination of surface and off-body measurements. Mean surface pressures compare well with numerical predictions for the free-air configuration. Consistent with previous measurements and computations for 2D high-lift configurations, the frequency spectra of unsteady surface pressures on the slat surface display several narrowband peaks that decrease in strength as the angle of attack is increased. At positive angles of attack, there are four prominent peaks. The three higher frequency peaks correspond, approximately, to a harmonic sequence related to a feedback resonance involving unstable disturbances in the slat cove shear layer. The Strouhal numbers associated with these three peaks are nearly insensitive to the range of flow speeds (41-58 m/s) and the angles of attack tested (3-8.5 degrees). The first narrow-band peak has an order of magnitude lower frequency than the remaining peaks and displays noticeable sensitivity to the angle of attack. Stereoscopic particle image velocimetry (SPIV) measurements provide supplementary information about the shear layer characteristics and turbulence statistics that may be used for validating numerical simulations.

Pascioni, Kyle A.; Cattafesta, Louis N.; Choudhari, Meelan M.

2014-01-01

22

High fidelity numerical simulation of airfoil thickness and kinematics effects on flapping airfoil propulsion  

E-print Network

High fidelity numerical simulation of airfoil thickness and kinematics effects on flapping airfoil online 17 July 2013 Keywords: Flapping airfoil Airfoil thickness Kinematics High order Navier-digit airfoils. Airfoil thickness and kinematics effects on the flapping airfoil propulsion

Hu, Hui

23

Experimental and computational investigation of lift-enhancing tabs on a multi-element airfoil  

NASA Technical Reports Server (NTRS)

An experimental and computational investigation of the effect of lift enhancing tabs on a two-element airfoil was conducted. The objective of the study was to develop an understanding of the flow physics associated with lift enhancing tabs on a multi-element airfoil. A NACA 63(sub 2)-215 ModB airfoil with a 30 percent chord Fowler flap was tested in the NASA Ames 7 by 10 foot wind tunnel. Lift enhancing tabs of various heights were tested on both the main element and the flap for a variety of flap riggings. Computations of the flow over the two-element airfoil were performed using the two-dimensional incompressible Navier-Stokes code INS2D-UP. The computer results predict all of the trends in the experimental data quite well. When the flow over the flap upper surface is attached, tabs mounted at the main element trailing edge (cove tabs) produce very little change in lift. At high flap deflections. however, the flow over the flap is separated and cove tabs produce large increases in lift and corresponding reductions in drag by eliminating the separated flow. Cove tabs permit high flap deflection angles to be achieved and reduce the sensitivity of the airfoil lift to the size of the flap gap. Tabs attached to the flap training edge (flap tabs) are effective at increasing lift without significantly increasing drag. A combination of a cove tab and a flap tab increased the airfoil lift coefficient by 11 percent relative to the highest lift tab coefficient achieved by any baseline configuration at an angle of attack of zero percent and the maximum lift coefficient was increased by more than 3 percent. A simple analytic model based on potential flow was developed to provide a more detailed understanding of how lift enhancing tabs work. The tabs were modeled by a point vortex at the training edge. Sensitivity relationships were derived which provide a mathematical basis for explaining the effects of lift enhancing tabs on a multi-element airfoil. Results of the modeling effort indicate that the dominant effects of the tabs on the pressure distribution of each element of the airfoil can be captured with a potential flow model for cases with no flow separation.

Ashby, Dale

1996-01-01

24

Analysis of transonic flow over lifting and oscillating airfoils  

NASA Technical Reports Server (NTRS)

Finite element procedures are presented for the numerical solution of transonic flow over lifting and oscillating airfoils based on small disturbance theory. The algorithm is simple and effective in handling the mixed flow problem and, for airfoil in free air, treats the entire flow domain by making use of the far field asymptotic solution. Numerical results are presented and compared with experimental data and those obtained by finite difference relaxation techniques.

Chan, S. T. K.; Brashears, M. R.

1976-01-01

25

AIAA Paper 2005-1260 High Performance Airfoil Using Co-Flow Jet Flow  

E-print Network

airfoil to exceed the inviscid limit of maximum lift coefficient due to the high jet velocity inducingAIAA Paper 2005-1260 High Performance Airfoil Using Co-Flow Jet Flow Control Ge-Cheng Zha Dept the superior performance of co-flow jet(CFJ) airfoil to dramatically increase lift, stall margin, and drag

Zha, Gecheng

26

Acoustic radiation from lifting airfoils in compressible subsonic flow  

NASA Technical Reports Server (NTRS)

The far field acoustic radiation from a lifting airfoil in a three-dimensional gust is studied. The acoustic pressure is calculated using the Kirchhoff method, instead of using the classical acoustic analogy approach due to Lighthill. The pressure on the Kirchhoff surface is calculated using an existing numerical solution of the unsteady flow field. The far field acoustic pressure is calculated in terms of these values using Kirchhoff's formula. The method is validated against existing semi-analytical results for a flat plate. The method is then used to study the problem of an airfoil in a harmonic three-dimensional gust, for a wide range of Mach numbers. The effect of variation of the airfoil thickness and angle of attack on the acoustic far field is studied. The changes in the mechanism of sound generation and propagation due to the presence of steady loading and non-uniform mean flow are also studied.

Atassi, Hafiz M.; Subramaniam, Shankar; Scott, James R.

1990-01-01

27

Acoustic radiation from lifting airfoils in compressible subsonic flow  

NASA Technical Reports Server (NTRS)

The far field acoustic radiation from a lifting airfoil in a three-dimensional gust is studied. The acoustic pressure is calculated using the Kirchhoff method, instead of using the classical acoustic analogy approach due to Lighthill. The pressure on the Kirchhoff surface is calculated using an existing numerical solution of the unsteady flow field. The far field acoustic pressure is calculated in terms of these values using Kirchhoff's formula. The method is validated against existing semi-analytical results for a flat plate. The method is then used to study the problem of an airfoil in a harmonic three-dimensional gust, for a wide range of Mach numbers. The effect of variation of the airfoil thickness and angle of attack on the acoustic far field is studied. The changes in the mechanism of sound generation and propagation due to the presence of steady loading and nonuniform mean flow are also studied.

Atassi, Hafiz M.; Subramaniam, Shankar; Scott, James R.

1990-01-01

28

Impact of Airfoils on Aerodynamic Optimization of Heavy Lift Rotorcraft  

NASA Technical Reports Server (NTRS)

Rotor airfoils were developed for two large tiltrotor designs, the Large Civil Tilt Rotor (LCTR) and the Military Heavy Tilt Rotor (MHTR). The LCTR was the most promising of several rotorcraft concepts produced by the NASA Heavy Lift Rotorcraft Systems Investigation. It was designed to carry 120 passengers for 1200 nm, with performance of 350 knots cruise at 30,000 ft altitude. A parallel design, the MHTR, had a notional mission of 40,000 Ib payload, 500 nm range, and 300 knots cruise at 4000 ft, 95 F. Both aircraft were sized by the RC code developed by the U. S. Army Aeroflightdynamics Directorate (AFDD). The rotors were then optimized using the CAMRAD II comprehensive analysis code. Rotor airfoils were designed for each aircraft, and their effects on performance analyzed by CAMRAD II. Airfoil design criteria are discussed for each rotor. Twist and taper optimization are presented in detail for each rotor, with discussions of performance improvements provided by the new airfoils, compared to current technology airfoils. Effects of stall delay and blade flexibility on performance are also included.

Acree, Cecil W., Jr.; Martin Preston B.; Romander, Ethan A.

2006-01-01

29

Compressible flows with periodic vortical disturbances around lifting airfoils. Ph.D. Thesis - Notre Dame Univ.  

NASA Technical Reports Server (NTRS)

A numerical method is developed for solving periodic, three-dimensional, vortical flows around lifting airfoils in subsonic flow. The first-order method that is presented fully accounts for the distortion effects of the nonuniform mean flow on the convected upstream vortical disturbances. The unsteady velocity is split into a vortical component which is a known function of the upstream flow conditions and the Lagrangian coordinates of the mean flow, and an irrotational field whose potential satisfies a nonconstant-coefficient, inhomogeneous, convective wave equation. Using an elliptic coordinate transformation, the unsteady boundary value problem is solved in the frequency domain on grids which are determined as a function of the Mach number and reduced frequency. The numerical scheme is validated through extensive comparisons with known solutions to unsteady vortical flow problems. In general, it is seen that the agreement between the numerical and analytical results is very good for reduced frequencies ranging from 0 to 4, and for Mach numbers ranging from .1 to .8. Numerical results are also presented for a wide variety of flow configurations for the purpose of determining the effects of airfoil thickness, angle of attack, camber, and Mach number on the unsteady lift and moment of airfoils subjected to periodic vortical gusts. It is seen that each of these parameters can have a significant effect on the unsteady airfoil response to the incident disturbances, and that the effect depends strongly upon the reduced frequency and the dimensionality of the gust. For a one-dimensional (transverse) or two-dimensional (transverse and longitudinal) gust, the results indicate that airfoil thickness increases the unsteady lift and moment at the low reduced frequencies but decreases it at the high reduced frequencies. The results show that an increase in airfoil Mach number leads to a significant increase in the unsteady lift and moment for the low reduced frequencies, but a significant decrease for the high reduced frequencies.

Scott, James R.

1991-01-01

30

Optimal boundary control problems related to high-lift configurations  

E-print Network

Optimal boundary control problems related to high-lift configurations Christian John, Bernd R problems related to the aerodynamic optimiza- tion of flows around airfoils in high-lift configurations, 25]. Our paper deals with two problems, both related to high-lift configurations, where the lift

Tröltzsch, Fredi

31

Airfoils  

NSDL National Science Digital Library

In this experiment, learners discover how an airfoil creates lift. Learners use simple materials to build an airfoil and test it at different angles to investigate Bernoulli's principle. This activity guide includes questions for drawing conclusions, extensions, and an answer key.

Ricles, Shannon; Locke, Dan; Livingston, John

2013-01-30

32

Enhancement of Lift and Drag Characteristics of an Oscillating Airfoil in Deep Dynamic Stall Using Plasma  

E-print Network

1 Enhancement of Lift and Drag Characteristics of an Oscillating Airfoil in Deep Dynamic Stall 32611-6300 The two dimensional flow past an oscillating NACA 0012 airfoil at Re = 1.35 x 105 control over such an oscillating airfoil is theoretically predicted. Simulation results without plasma

Roy, Subrata

33

Experimental Study of Slat Noise from 30P30N Three-Element High-Lift Airfoil in JAXA Hard-Wall Low-Speed Wind Tunnel  

NASA Technical Reports Server (NTRS)

Aeroacoustic measurements associated with noise radiation from the leading edge slat of the canonical, unswept 30P30N three-element high-lift airfoil configuration have been obtained in a 2 m x 2 m hard-wall wind tunnel at the Japan Aerospace Exploration Agency (JAXA). Performed as part of a collaborative effort on airframe noise between JAXA and the National Aeronautics and Space Administration (NASA), the model geometry and majority of instrumentation details are identical to a NASA model with the exception of a larger span. For an angle of attack up to 10 degrees, the mean surface Cp distributions agree well with free-air computational fluid dynamics predictions corresponding to a corrected angle of attack. After employing suitable acoustic treatment for the brackets and end-wall effects, an approximately 2D noise source map is obtained from microphone array measurements, thus supporting the feasibility of generating a measurement database that can be used for comparison with free-air numerical simulations. Both surface pressure spectra obtained via KuliteTM transducers and the acoustic spectra derived from microphone array measurements display a mixture of a broad band component and narrow-band peaks (NBPs), both of which are most intense at the lower angles of attack and become progressively weaker as the angle of attack is increased. The NBPs exhibit a substantially higher spanwise coherence in comparison to the broadband portion of the spectrum and, hence, confirm the trends observed in previous numerical simulations. Somewhat surprisingly, measurements show that the presence of trip dots between the stagnation point and slat cusp enhances the NBP levels rather than mitigating them as found in a previous experiment.

Murayama, Mitsuhiro; Nakakita, Kazuyuki; Yamamoto, Kazuomi; Ura, Hiroki; Ito, Yasushi; Choudhari, Meelan M.

2014-01-01

34

Effects of Airfoil Thickness and Maximum Lift Coefficient on Roughness Sensitivity: 1997--1998  

SciTech Connect

A matrix of airfoils has been developed to determine the effects of airfoil thickness and the maximum lift to leading-edge roughness. The matrix consists of three natural-laminar-flow airfoils, the S901, S902, and S903, for wind turbine applications. The airfoils have been designed and analyzed theoretically and verified experimentally in the Pennsylvania State University low-speed, low-turbulence wind tunnel. The effect of roughness on the maximum life increases with increasing airfoil thickness and decreases slightly with increasing maximum lift. Comparisons of the theoretical and experimental results generally show good agreement.

Somers, D. M.

2005-01-01

35

Wind tunnel tests of two airfoils for wind turbines operating at high reynolds numbers  

SciTech Connect

The objectives of this study were to verify the predictions of the Eppler Airfoil Design and Analysis Code for Reynolds numbers up to 6 x 106 and to acquire the section characteristics of two airfoils being considered for large, megawatt-size wind turbines. One airfoil, the S825, was designed to achieve a high maximum lift coefficient suitable for variable-speed machines. The other airfoil, the S827, was designed to achieve a low maximum lift coefficient suitable for stall-regulated machines. Both airfoils were tested in the NASA Langley Low-Turbulence Pressure Tunnel (LTPT) for smooth, fixed-transition, and rough surface conditions at Reynolds numbers of 1, 2, 3, 4, and 6 x 106. The results show the maximum lift coefficient of both airfoils is substantially underpredicted for Reynolds numbers over 3 x 106 and emphasized the difficulty of designing low-lift airfoils for high Reynolds numbers.

Sommers, D.; Tangler, J.

2000-06-29

36

Optimization of an Advanced Design Three-Element Airfoil at High Reynolds Numbers  

NASA Technical Reports Server (NTRS)

New high-lift components have been designed for a three-element advanced high-lift research airfoil using a state-of-the-art computational method. The new components were designed with the aim to provide high maximum-lift values while maintaining attached flow on the single-segment flap at approach conditions. This three-element airfoil has been tested in the NASA Langley Low-Turbulence Pressure Tunnel at chord Reynolds number up to 16 million. The performance of the NASA research airfoil is compared to a reference advanced high-lift research airfoil. Effects of Reynolds number on slat and flap rigging have been studied experimentally. The performance trend of this new high-lift design is comparable to that predicted by the computational method over much of the angle of attack range. Nevertheless, the method did not accurately predict the airfoil performance or the configuration-based trends near maximum lift.

Lin, John C.; Dominik, Chet J.

1995-01-01

37

Investigation of a bio-inspired lift-enhancing effector on a 2D airfoil.  

PubMed

A flap mounted on the upper surface of an airfoil, called a 'lift-enhancing effector', has been shown in wind tunnel tests to have a similar function to a bird's covert feathers, which rise off the wing's surface in response to separated flows. The effector, fabricated from a thin Mylar sheet, is allowed to rotate freely about its leading edge. The tests were performed in the NCSU subsonic wind tunnel at a chord Reynolds number of 4 × 10(5). The maximum lift coefficient with the effector was the same as that for the clean airfoil, but was maintained over an angle-of-attack range from 12° to almost 20°, resulting in a very gentle stall behavior. To better understand the aerodynamics and to estimate the deployment angle of the free-moving effector, fixed-angle effectors fabricated out of stiff wood were also tested. A progressive increase in the stall angle of attack with increasing effector angle was observed, with diminishing returns beyond the effector angle of 60°. Drag tests on both the free-moving and fixed effectors showed a marked improvement in drag at high angles of attack. Oil flow visualization on the airfoil with and without the fixed-angle effectors proved that the effector causes the separation point to move aft on the airfoil, as compared to the clean airfoil. This is thought to be the main mechanism by which an effector improves both lift and drag. A comparison of the fixed-effector results with those from the free-effector tests shows that the free effector's deployment angle is between 30° and 45°. When operating at and beyond the clean airfoil's stall angle, the free effector automatically deploys to progressively higher angles with increasing angles of attack. This slows down the rapid upstream movement of the separation point and avoids the severe reduction in the lift coefficient and an increase in the drag coefficient that are seen on the clean airfoil at the onset of stall. Thus, the effector postpones the stall by 4-8° and makes the stall behavior more gentle. The benefits of using the effector could include care-free operations at high angles of attack during perching and maneuvering flight, especially in gusty conditions. PMID:22498691

Johnston, Joe; Gopalarathnam, Ashok

2012-09-01

38

Aeroacoustic interaction of a distributed vortex with a lifting Joukowski airfoil  

Microsoft Academic Search

A first principles computational aeroacoustics calculation of the flow and noise fields produced by the interaction of a distributed vortex with a lifting Joukowski airfoil is accomplished at the Reynolds number of 200. The case considered is that where the circulations of the vortex and the airfoil are of opposite sign, corresponding to blade vortex interaction on the retreating side

J. C. Hardin; S. L. Lamkin

1984-01-01

39

High lift selected concepts  

NASA Technical Reports Server (NTRS)

The benefits to high lift system maximum life and, alternatively, to high lift system complexity, of applying analytic design and analysis techniques to the design of high lift sections for flight conditions were determined and two high lift sections were designed to flight conditions. The influence of the high lift section on the sizing and economics of a specific energy efficient transport (EET) was clarified using a computerized sizing technique and an existing advanced airplane design data base. The impact of the best design resulting from the design applications studies on EET sizing and economics were evaluated. Flap technology trade studies, climb and descent studies, and augmented stability studies are included along with a description of the baseline high lift system geometry, a calculation of lift and pitching moment when separation is present, and an inverse boundary layer technique for pressure distribution synthesis and optimization.

Henderson, M. L.

1979-01-01

40

Experimental and Computational Investigation of Lift-Enhancing Tabs on a Multi-Element Airfoil  

NASA Technical Reports Server (NTRS)

An experimental and computational investigation of the effect of lift-enhancing tabs on a two-element airfoil has been conducted. The objective of the study was to develop an understanding of the flow physics associated with lift-enhancing tabs on a multi-element airfoil. An NACA 63(2)-215 ModB airfoil with a 30% chord fowler flap was tested in the NASA Ames 7- by 10-Foot Wind Tunnel. Lift-enhancing tabs of various heights were tested on both the main element and the flap for a variety of flap riggings. A combination of tabs located at the main element and flap trailing edges increased the airfoil lift coefficient by 11% relative to the highest lift coefficient achieved by any baseline configuration at an angle of attack of 0 deg, and C(sub 1max) was increased by 3%. Computations of the flow over the two-element airfoil were performed using the two-dimensional incompressible Navier-Stokes code INS2D-UP. The computed results predicted all of the trends observed in the experimental data quite well. In addition, a simple analytic model based on potential flow was developed to provide a more detailed understanding of how lift-enhancing tabs work. The tabs were modeled by a point vortex at the air-foil or flap trailing edge. Sensitivity relationships were derived which provide a mathematical basis for explaining the effects of lift-enhancing tabs on a multi-element airfoil. Results of the modeling effort indicate that the dominant effects of the tabs on the pressure distribution of each element of the airfoil can be captured with a potential flow model for cases with no flow separation.

Ashby, Dale L.

1996-01-01

41

High lift aerodynamics  

NASA Technical Reports Server (NTRS)

The current program is aimed at providing a physical picture of the flow physics and quantitative turbulence data of the interaction of a high Reynolds number wake with a flap element. The impact of high lift on aircraft performance is studied for a 150 passenger transport aircraft with the goal of designing optimum high lift systems with minimum complexity.

Sullivan, John; Schneider, Steve; Campbell, Bryan; Bucci, Greg; Boone, Rod; Torgerson, Shad; Erausquin, Rick; Knauer, Chad

1994-01-01

42

Numerical solutions of the linearized Euler equations for unsteady vortical flows around lifting airfoils  

NASA Technical Reports Server (NTRS)

A linearized unsteady aerodynamic analysis is presented for unsteady, subsonic vortical flows around lifting airfoils. The analysis fully accounts for the distortion effects of the nonuniform mean flow on the imposed vortical disturbances. A frequency domain numerical scheme which implements this linearized approach is described, and numerical results are presented for a large variety of flow configurations. The results demonstrate the effects of airfoil thickness, angle of attack, camber, and Mach number on the unsteady lift and moment of airfoils subjected to periodic vortical gusts. The results show that mean flow distortion can have a very strong effect on the airfoil unsteady response, and that the effect depends strongly upon the reduced frequency, Mach number, and gust wave numbers.

Scott, James R.; Atassi, Hafiz M.

1990-01-01

43

High-Rate Artificial Lift  

Microsoft Academic Search

This paper summarizes the major considerations in the selection, design, installation, operation, or repair of high-rate artificial-lift systems. The major types of artificial lift - sucker-rod pumps, gas-lift systems, electrical submersible pumps, hydraulic pumps and jets, and hydraulic turbine-driven pumps - will be discussed. An extensive bibliography of artificial-lift papers is included.

Joe Clegg

1988-01-01

44

High-rate artificial lift  

SciTech Connect

This paper summarizes the major considerations in the selection, design, installation, operation, or repair of high-rate artificial-lift systems. The major types of artificial lift - sucker-rod pumps, gas-lift systems, electrical submersible pumps, hydraulic pumps and jets, and hydraulic turbine-driven pumps - will be discussed. An extensive bibliography of artificial-lift papers is included.

Clegg, J.D.

1988-03-01

45

High Lift Flight Tunnel  

NASA Technical Reports Server (NTRS)

Concept for new generation of wind tunnel, in which the model is moved thru the test medium, instead of the medium flowing over a static model. Offers potentially greater accuracy of test data. Intended to address the low-speed/ high lift arena.

1998-01-01

46

Aeroacoustic interaction of a distributed vortex with a lifting Joukowski airfoil  

NASA Technical Reports Server (NTRS)

A first principles computational aeroacoustics calculation of the flow and noise fields produced by the interaction of a distributed vortex with a lifting Joukowski airfoil is accomplished at the Reynolds number of 200. The case considered is that where the circulations of the vortex and the airfoil are of opposite sign, corresponding to blade vortex interaction on the retreating side of a single helicopter rotor. The results show that the flow is unsteady, even in the absence of the incoming vortex, resulting in trailing edge noise generation. After the vortex is input, it initially experiences a quite rapid apparent diffusion rate produced by stretching in the airfoil velocity gradients. Consideration of the effects of finite vortex size and viscosity causes the noise radiation during the encounter to be much less impulsive than predicted by previous analyses.

Hardin, J. C.; Lamkin, S. L.

1984-01-01

47

Experimental Study of Lift-Enhancing Tabs on a Two-Element Airfoil  

NASA Technical Reports Server (NTRS)

The results of a wind-tunnel test are presented for a two-dimensional NASA 63(sub 2)-215 Mod B airfoil with a 30% chord single-slotted flap. The use of lift-enhancing tabs (similar to Gurney flaps) on the lower surface near the trailing edge of both elements was investigated on four nap configurations. A combination of vortex generators on the flap and lift-enhancing tabs was also investigated. Measurements of surface-pressure distributions and wake profiles were used to determine the aerodynamic performance of each configuration. By reducing flow separation on the flap, a lift-enhancing tab at the main-element trailing edge increased the maximum lift by 10.3% for the 42-deg flap case. The tab had a lesser effect at a moderate flap deflection (32 deg) and adversely affected the performance at the smallest flap deflection (22 deg). A tab located near the flap trailing edge produced an additional lift increment for all flap deflections. The application of vortex generators to the flap eliminated lift-curve hysteresis and reduced flow separation on two configurations with large flap deflections (greater than 40 deg). A maximum-lift coefficient of 3.32 (17% above the optimum baseline) was achieved with the combination of lift-enhancing tabs on both elements and vortex generators on the flap.

Storms, Bruce L.; Ross, James C.

1995-01-01

48

High lift wake investigation  

NASA Technical Reports Server (NTRS)

The behavior of wakes in adverse pressure gradients is critical to the performance of high-lift systems for transport aircraft. Wake deceleration is known to lead to sudden thickening and the onset of reversed flow; this 'wake bursting' phenomenon can occur while surface flows remain attached. Although known to be important for high-lift systems, few studies of such decelerated wakes exist. In this study, the wake of a flat plate has been subjected to an adverse pressure gradient in a two-dimensional diffuser, whose panels were forced to remain attached by use of slot blowing. Pitot probe surveys, L.D.V. measurements, and flow visualization have been used to investigate the physics of this decelerated wake, through the onset of reversed flow.

Sullivan, J. P.; Schneider, S. P.; Hoffenberg, R.

1996-01-01

49

Low-speed aerodynamic characteristics of an airfoil optimized for maximum lift coefficient  

NASA Technical Reports Server (NTRS)

An investigation has been conducted in the Langley low-turbulence pressure tunnel to determine the two-dimensional characteristics of an airfoil optimized for maximum lift coefficient. The design maximum lift coefficient was 2.1 at a Reynolds number of 9.7 million. The airfoil with a smooth surface and with surface roughness was tested at angles of attack from 6 deg to 26 deg, Reynolds numbers (based on airfoil chord) from 2.0 million to 12.9 million, and Mach numbers from 0.10 to 0.35. The experimental results are compared with values predicted by theory. The experimental pressure distributions observed at angles of attack up to at least 12 deg were similar to the theoretical values except for a slight increase in the experimental upper-surface pressure coefficients forward of 26 percent chord and a more severe gradient just behind the minimum-pressure-coefficient location. The maximum lift coefficients were measured with the model surface smooth and, depending on test conditions, varied from 1.5 to 1.6 whereas the design value was 2.1.

Bingham, G. J.; Chen, A. W.

1972-01-01

50

AIAA 20004741 Two-dimensional High-Lift  

E-print Network

, the necessary aerodynamic gradient in- formation is obtained with large computational savings over traditional-to-point matched multi-block grid system and the Message Passing Interface (MPI) parallel solution methodology are used as design variables. The prediction of high-lift flows around a baseline three-element airfoil

Kim, Sangho

51

High-Lift Flow Physics Experiment With MDA 3-Element Model  

NASA Technical Reports Server (NTRS)

MDA 3-element high-lift airfoil model installed in the Basic Aerodynamics Research Tunnel. Configuration to b e used for particle imaging velocimetry (PIV) and Laser Velocimetry (LV) measurements. In building 1214.

1997-01-01

52

Large-eddy simulation of an airfoil at maximum lift  

NASA Astrophysics Data System (ADS)

In many complex flows, large-eddy simulation is difficult due to the simultaneous presence of a variety of flow features, often with quite different resolution requirements. A structured-grid approach to this problem would be forced to carry the resolution requirements of the finest region throughout the entire domain making the number of points required impractical. An unstructured-grid method can place points based on local resolution requirements resulting in a large reduction in the number of points required. For this reason, unstructured-grid large-eddy simulation techniques have been developed using the finite element method to solve the compressible Navier-Stokes equations with a dynamic model of the subgrid-scale stresses. Results will be presented for flow over a NACA 4412 airfoil at 12^circ angle of attack at a chord Reynolds number of 1.64× 10^6. In particular, the results will address the effect of the wind tunnel walls and transition strip used in the experiment of Wadcock (1987).

Jansen, Kenneth

1996-11-01

53

Theoretical investigations of high lift aerodynamics  

NASA Technical Reports Server (NTRS)

A program which generates a coordinate system for a two element airfoil with the mesh points concentrated in areas of significant vorticity, i.e., boundary layer and wake is operational. The 'imbedded' grid method developed allows a transition from the scale of the main airfoil to the scale of the flap. This requirement is essential for the modeling of viscous flows over the flap and slat of a multielement airfoil. An airfoil mounted in a 2-D wind tunnel was formulated. The program is ready for a fine grid and a large number of planes to explore the characteristics of a Navier-Stokes solver in a quasi-3D case. The program was converted to a form suitable for the STAR computer. Runs were made to map a three dimensional flow field for a wall airfoil intersection with and without lift.

Bennett, G.; Thompson, J.

1983-01-01

54

Adaptation of the Theodorsen theory to the representation of an airfoil as a combination of a lifting line and a thickness distribution  

NASA Technical Reports Server (NTRS)

The theory provides a direct method for resolving an airfoil into a lifting line and a thickness distribution as well as a means of synthesizing thickness and lift components into a resultant airfoil and computing its aerodynamic characteristics. Specific applications of the technique are discussed.

Barger, R. L.

1975-01-01

55

Summary of Airfoil Data  

NASA Technical Reports Server (NTRS)

The historical development of NACA airfoils is briefly reviewed. New data are presented that permit the rapid calculation of the approximate pressure distributions for the older NACA four-digit and five-digit airfoils by the same methods used for the NACA 6-series airfoils. The general methods used to derive the basic thickness forms for NACA 6 and 7-series airfoils together with their corresponding pressure distributions are presented. Detail data necessary for the application of the airfoils to wing design are presented in supplementary figures placed at the end of the paper. The report includes an analysis of the lift, drag, pitching-moment, and critical-speed characteristics of the airfoils, together with a discussion of the effects of surface conditions. Available data on high-lift devices are presented. Problems associated with lateral-control devices, leading-edge air intakes, and interference are briefly discussed, together with aerodynamic problems of application. (author)

Abbott, Ira H; Von Doenhoff, Albert E; Stivers, Louis, Jr

1945-01-01

56

Maximum Mean Lift Coefficient Characteristics at Low Tip Mach Numbers of a Hovering Helicopter Rotor Having an NACA 64(1)A012 Airfoil Section  

NASA Technical Reports Server (NTRS)

An investigation has been conducted on the Langley helicopter test tower to determine experimentally the maximum mean lift-coefficient characteristics at low tip Mach number and a limited amount of drag- divergence data at high tip Mach number of a helicopter rotor having an NACA 64(1)AO12 airfoil section and 8 deg of linear washout. Data are presented for blade tip Mach numbers M(t) of 0.29 to 0.74 with corresponding values 6 6 of tip Reynolds number of 2.59 x 10(exp 6) and 6.58 x 10(exp 6). Comparisons are made between the data from the present rotor with results previously obtained from two other rotors: one having NACA 0012 airfoil sections and the other having an NACA 0009 airfoil tip section. At low tip Mach numbers, the maximum mean lift coefficient for the blade having the NACA 64(1)AO12 section was about 0.08 less than that obtained with the blade having the NACA 0009 tip section and 0.21 less than the value obtained with the blade having the NACA 0012 tip section. Blade maximum mean lift coefficient values were not obtained for Mach number values greater than 0.47 because of a blade failure encountered during the tests. The effective mean lift-curve slope required for predicting rotor thrust varied from 5.8 for the tip Mach nuniber range of 0.29 to 0.55 to a value of 6.65 for a tip Mach number of 0.71. The blade pitching-moment coefficients were small and relatively unaffected by changes in thrust coefficient and Mach number. In the instances in which stall was reached, the break in the blade pitching-moment curve was in a stable direction. The efficiency of the rotor decreased with an increase in tip speed. Expressed as figure of merit, at a tip Mach number of 0.29 the maximum value was about 0.74. Similar measurements made on another rotor having an NACA 0012 airfoil and with a rotor having an NACA 0009 tip section, showed a value of 0.75. Synthesized section lift and profile-drag characteristics for the rotor-blade airfoil section are presented as an aid in predicting the high-tip-speed performance of rotors having similar airfoils.

Powell, Robert D., Jr.

1959-01-01

57

Designing highlift airfoils using genetic algorithms D. Quagliarella, A. Vicini  

E-print Network

Designing high­lift airfoils using genetic algorithms D. Quagliarella, A. Vicini C.I.R.A., Centro layer flow field solver capable of working in high­lift conditions. Examples of unconstrained of multi­component airfoils for high lift applications, based on a multi­objective genetic algorithm

Coello, Carlos A. Coello

58

Ris-R-1065(EN) Airfoil Characteristics for Wind Turbines  

E-print Network

and that the maximum lift coefficient is high at the root compared to 2D airfoil characteristics. The use the correct qualitative be- haviour for airfoils subject to rotation. The method shows that lift is high of rotational and 3D ef- fects on rotors. Furthermore, the methods show high maximum lift coefficients

59

High-order lifting  

Microsoft Academic Search

The well-known technique of adic-lifting for linear-system solution is studied. Some new methods are developed and applied to get algorithms for the following problems over the ring of univariate polynomials with coefficients from a field: rational system-solving, integrality certification and determinant\\/Smith-form computation. All algorithms are Las Vegas probabilistic.

Arne Storjohann

2002-01-01

60

TWO-DIMENSIONAL AIRCRAFT HIGH LIFT SYSTEM DESIGN AND OPTIMIZATION  

Microsoft Academic Search

A two-dimensiona l aircraft high-lift system design and optimization method, which can be easily extended to three dimensions, is presented. The need for such a tool is assessed. The method uses a gradient based local optimizer. The aerodynamic performance is predicted using an Interactive Boundary Layer (IBL) approach. Methods to represent general multi-element airfoils by a set of design variables

Eric Besnard; Adeline Schmitz; Erwan Boscher; Nicolas Garcia; Tuncer Cebeci

61

Active Control of Flow Separation on a High-Lift System with Slotted Flap at High Reynolds Number  

NASA Technical Reports Server (NTRS)

The NASA Energy Efficient Transport (EET) airfoil was tested at NASA Langley's Low- Turbulence Pressure Tunnel (LTPT) to assess the effectiveness of distributed Active Flow Control (AFC) concepts on a high-lift system at flight scale Reynolds numbers for a medium-sized transport. The test results indicate presence of strong Reynolds number effects on the high-lift system with the AFC operational, implying the importance of flight-scale testing for implementation of such systems during design of future flight vehicles with AFC. This paper describes the wind tunnel test results obtained at the LTPT for the EET high-lift system for various AFC concepts examined on this airfoil.

Khodadoust, Abdollah; Washburn, Anthony

2007-01-01

62

Development of two supercritical airfoils with a thickness-to-chord ratio of 0.20 and design lift coefficients of 0.3 and 0.4  

NASA Technical Reports Server (NTRS)

Two supercritical airfoils were developed specifically for application to span distributed loading cargo aircraft. These airfoils have a thickness-to-chord ratio of 0.20 and design lift coefficients of 0.3 and 0.4, and were derived by modifying a recently developed supercritical airfoil having a thickness-to-chord ratio of 0.18 and a design lift coefficient of 0.5. The aerodynamic characteristics were calculated using a theoretical method which computes the flow field about an airfoil having supercritical surface velocities.

Jernell, L. S.

1976-01-01

63

A Systematic Investigation of Pressure Distributions at High Speeds over Five Representative NACA Low-Drag and Conventional Airfoil Sections  

NASA Technical Reports Server (NTRS)

Pressure distributions determined from high-speed wind-tunnel tests are presented for five NACA airfoil sections representative of both low-drag and conventional types. Section characteristics of lift, drag, and quarter-chord pitching moment are presented along with the measured pressure distributions for the NACA 65sub2-215 (a=0.5), 66sub2-215 (a=0.6), 0015, 23015, and 4415 airfoils for Mach numbers up to approximately 0.85. A critical study is made of the airfoil pressure distributions in an attempt to formulate a set of general criteria for defining the character of high speed flows over typical airfoil shapes. Comparisons are made of the relative characteristics of the low-drag and conventional airfoils investigated insofar as they would influence the high-speed performance and the high-speed stability and control characteristics of airplanes employing these wing sections.

Graham, Donald J; Nitzberg, Gerald E; Olson, Robert N

1945-01-01

64

Models of Lift and Drag Coefficients of Stalled and Unstalled Airfoils in Wind Turbines and Wind Tunnels  

NASA Technical Reports Server (NTRS)

Equations are developed with which to calculate lift and drag coefficients along the spans of torsionally-stiff rotating airfoils of the type used in wind turbine rotors and wind tunnel fans, at angles of attack in both the unstalled and stalled aerodynamic regimes. Explicit adjustments are made for the effects of aspect ratio (length to chord width) and airfoil thickness ratio. Calculated lift and drag parameters are compared to measured parameters for 55 airfoil data sets including 585 test points. Mean deviation was found to be -0.4 percent and standard deviation was 4.8 percent. When the proposed equations were applied to the calculation of power from a stall-controlled wind turbine tested in a NASA wind tunnel, mean deviation from 54 data points was -1.3 percent and standard deviation was 4.0 percent. Pressure-rise calculations for a large wind tunnel fan deviated by 2.7 percent (mean) and 4.4 percent (standard). The assumption that a single set of lift and drag coefficient equations can represent the stalled aerodynamic behavior of a wide variety of airfoils was found to be satisfactory.

Spera, David A.

2008-01-01

65

Summary of Airfoil Data  

NASA Technical Reports Server (NTRS)

Recent airfoil data for both flight and wind-tunnel tests have been collected and correlated insofar as possible. The flight data consist largely of drag measurements made by the wake-survey method. Most of the data on airfoil section characteristics were obtained in the Langley two-dimensional low-turbulence pressure tunnel. Detail data necessary for the application of NACA 6-serles airfoils to wing design are presented in supplementary figures, together with recent data for the NACA 24-, 44-, and 230-series airfoils. The general methods used to derive the basic thickness forms for NACA 6- and 7-series airfoils and their corresponding pressure distributions are presented. Data and methods are given for rapidly obtaining the approximate pressure distributions for NACA four-digit, five-digit, 6-, and 7-series airfoils. The report includes an analysis of the lift, drag, pitching-moment, and critical-speed characteristics of the airfoils, together with a discussion of the effects of surface conditions. Available data on high-lift devices are presented. Problems associated with lateral-control devices, leading-edge air intakes, and interference are briefly discussed. The data indicate that the effects of surface condition on the lift and drag characteristics are at least as large as the effects of the airfoil shape and must be considered in airfoil selection and the prediction of wing characteristics. Airfoils permitting extensive laminar flow, such as the NACA 6-series airfoils, have much lower drag coefficients at high speed and cruising lift coefficients than earlier types-of airfoils if, and only if, the wing surfaces are sufficiently smooth and fair. The NACA 6-series airfoils also have favorable critical-speed characteristics and do not appear to present unusual problems associated with the application of high-lift and lateral-control devices. Much of the data given in the NACA Advance Confidential Report entitled "Preliminary Low-Drag-Airfoil and Flap Data from Tests at Large Reynolds Number and Low Turbulence," by Eastman N. Jacobs, Ira R. Abbott, and Milton Davidson, March 1942 has been corrected and included in the present paper, which supersedes the previously published paper.

Stivers, Louis S.; Abbott, Ira H.; von Doenhoff, Albert E.

1945-01-01

66

Airfoil  

NASA Technical Reports Server (NTRS)

Although the method and apparatus of the present invention can be utilized to apply either a uniform or a nonuniform covering of material over many different workpieces, the apparatus (20) is advantageously utilized to apply a thermal barrier covering (64) to an airfoil (22) which is used in a turbine engine. The airfoil is held by a gripper assembly (86) while a spray gun (24) is effective to apply the covering over the airfoil. When a portion of the covering has been applied, a sensor (28) is utilized to detect the thickness of the covering. A control apparatus (32) compares the thickness of the covering of material which has been applied with the desired thickness and is subsequently effective to regulate the operation of the spray gun to adaptively apply a covering of a desired thickness with an accuracy of at least plus or minus 0.0015 of an inch (1.5 mils) despite unanticipated process variations.

Derkacs, Thomas (Inventor); Fetheroff, Charles W. (Inventor); Matay, Istvan M. (Inventor); Toth, Istvan J. (Inventor)

1983-01-01

67

Reversible airfoils for stopped rotors in high speed flight  

NASA Astrophysics Data System (ADS)

This study starts with the design of a reversible airfoil rib for stopped-rotor applications, where the sharp trailing-edge morphs into the rounded leading-edge, and vice-versa. A NACA0012 airfoil is approximated in a piecewise linear manner and straight, rigid outer profile links used to define the airfoil contour. The end points of the profile links connect to control links, each set on a central actuation rod via an offset. Chordwise motion of the actuation rod moves the control and the profile links and reverses the airfoil. The paper describes the design methodology and evolution of the final design, based on which two reversible airfoil ribs were fabricated and used to assemble a finite span reversible rotor/wing demonstrator. The profile links were connected by Aluminum strips running in the spanwise direction which provided stiffness as well as support for a pre-tensioned elastomeric skin. An inter-rib connector with a curved-front nose piece supports the leading-edge. The model functioned well and was able to reverse smoothly back-and-forth, on application and reversal of a voltage to the motor. Navier–Stokes CFD simulations (using the TURNS code) show that the drag coefficient of the reversible airfoil (which had a 13% maximum thickness due to the thickness of the profile links) was comparable to that of the NACA0013 airfoil. The drag of a 16% thick elliptical airfoil was, on average, about twice as large, while that of a NACA0012 in reverse flow was 4–5 times as large, even prior to stall. The maximum lift coefficient of the reversible airfoil was lower than the elliptical airfoil, but higher than the NACA0012 in reverse flow operation.

Niemiec, Robert; Jacobellis, George; Gandhi, Farhan

2014-10-01

68

Robust Airfoil Optimization in High Resolution Design Space  

NASA Technical Reports Server (NTRS)

The robust airfoil shape optimization is a direct method for drag reduction over a given range of operating conditions and has three advantages: (1) it prevents severe degradation in the off-design performance by using a smart descent direction in each optimization iteration, (2) it uses a large number of B-spline control points as design variables yet the resulting airfoil shape is fairly smooth, and (3) it allows the user to make a trade-off between the level of optimization and the amount of computing time consumed. The robust optimization method is demonstrated by solving a lift-constrained drag minimization problem for a two-dimensional airfoil in viscous flow with a large number of geometric design variables. Our experience with robust optimization indicates that our strategy produces reasonable airfoil shapes that are similar to the original airfoils, but these new shapes provide drag reduction over the specified range of Mach numbers. We have tested this strategy on a number of advanced airfoil models produced by knowledgeable aerodynamic design team members and found that our strategy produces airfoils better or equal to any designs produced by traditional design methods.

Li, Wu; Padula, Sharon L.

2003-01-01

69

TCA High Lift Preliminary Assessment  

NASA Technical Reports Server (NTRS)

This paper presents a TCA (Technology Concept Airplane) High lift Preliminary Assessment. The topics discussed are: 1) Model Description; 2) Data Repeatability; 3) Effect of Inboard L.E. (Leading Edge) Flap Span; 4) Comparison of 14'x22' TCA-1 With NTF (National Transonic Facility) Modified Ref. H; 5) Comparison of 14'x22' and NTF Ref. H Results; 6) Effect of Outboard Sealed Slat on TCA; 7) TCA Full Scale Build-ups; 8) Full Scale L/D Comparisons; 9) TCA Full Scale; and 10) Touchdown Lift Curves. This paper is in viewgraph form.

Wyatt, G. H.; Polito, R. C.; Yeh, D. T.; Elzey, M. E.; Tran, J. T.; Meredith, Paul T.

1999-01-01

70

Performance of Co-Flow Jet Airfoil with Variation of Mach Number A. Lefebvre  

E-print Network

to enhance lift, reduce drag, and increase stall margin with high Mach number up to 0.4 at low energy or no structural moving parts. When a high lift airfoil flow control technique is developed, three primary issues for a 15% thickness Co-Flow Jet (CFJ) airfoil performance enhancement, which includes the variation of lift

Zha, Gecheng

71

NREL airfoil families for HAWTs  

SciTech Connect

The development of special-purpose airfoils for horizontal-axis wind turbines (HAWTs) began in 1984 as a joint effort between the National Renewable Energy Laboratory (NREL), formerly the Solar Energy Research Institute (SERI), and Airfoils, Incorporated. Since that time nine airfoil families have been designed for various size rotors using the Eppler Airfoil Design and Analysis Code. A general performance requirement of the new airfoil families is that they exhibit a maximum lift coefficient (c{sub 1,max}) which is relatively insensitive to roughness effects. The airfoil families address the needs of stall-regulated, variable-pitch, and variable-rpm wind turbines. For stall-regulated rotors, better peak-power control is achieved through the design of tip airfoils that restrain the maximum lift coefficient. Restrained maximum lift coefficient allows the use of more swept disc area for a given generator size. Also, for stall-regulated rotors, tip airfoils with high thickness are used to accommodate overspeed control devices. For variable-pitch and variable-rpm rotors, tip airfoils having a high maximum lift coefficient lend themselves to lightweight blades with low solidity. Tip airfoils having low thickness result in less drag for blades having full-span pitch control. Annual energy improvements from the NREL airfoil families are projected to be 23% to 35% for stall-regulated turbines, 8% to 20% for variable-pitch turbines, and 8% to 10% for variable-rpm turbines. The improvement for stall-regulated turbines has been verified in field tests.

Tangler, J.L. [National Renewable Energy Lab., Golden, CO (United States); Somers, D.M. [Airfoils Incorporated, State College, PA (United States)

1995-12-31

72

NREL airfoil families for HAWTs  

SciTech Connect

The development of special-purpose airfoils for horizontal-axis wind turbines (HAWTs) began in 1984 as a joint effort between the National Renewable Energy Laboratory (NREL), formerly the Solar Energy Research Institute (SERI), and Airfoils, Incorporated. Since that time seven airfoil families have been designed for various size rotors using the Eppler Airfoil Design and Analysis Code. A general performance requirement of the new airfoil families is that they exhibit a maximum lift coefficient (c{sub l,max}) which is relatively insensitive to roughness effects. The airfoil families address the needs of stall-regulated, variable-pitch, and variable-rpm wind turbines. For stall-regulated rotors, better peak-power control is achieved through the design of tip airfoils that restrain the maximum lift coefficient. Restrained maximum lift coefficient allows the use of more swept disc area for a given generator size. Also, for stall-regulated rotors, tip airfoils with high thickness are used to accommodate overspeed control devices. For variable-pitch and variable-rpm rotors, tip airfoils having a high maximum lift coefficient lend themselves to lightweight blades with low solidity. Tip airfoils having low thickness result in less drag for blades having full-span pitch control. Annual energy improvements from the NREL airfoil families are projected to be 23% to 35% for stall-regulated turbines, 8% to 20% for variable-pitch turbines, and 8% to 10% for variable-rpm turbines. The improvement for stall-regulated turbines has been verified in field tests.

Tangler, J L [National Renewable Energy Lab., Golden, CO (United States); Somers, D M [Airfoils Inc., State College, PA (United States)

1995-01-01

73

S814 and S815 Airfoils: October 1991--July 1992  

SciTech Connect

Two thick laminar-flow airfoils for the root portion of a horizontal-axis wind turbine blade, the S814 and S815, have been designed and analyzed theoretically. For both airfoils, the primary objectives of high maximum lift, insensitive to roughness, and low profile drag have been achieved. The constraints on pitching moment and airfoil thicknesses have been satisfied.

Somers, D. M.

2004-12-01

74

S904 and S905 Airfoils: May 1998--January 1999  

SciTech Connect

A family of natural-laminar-flow airfoils, the S904 and S905, for cooling-tower fans has been designed and analyzed theoretically. The two primary objectives of high maximum lift, relatively insensitive to roughness, and low profile drag have been achieved. The constraint on the lift a zero angle of attack has not been satisfied. The constraints on the pitching moment and the airfoil thicknesses have essentially been satisfied. The airfoils should exhibit docile stalls.

Somers, D. M.

2005-01-01

75

Improved Representation of High-Lift Devices for a Multidisciplinary Conceptual Aircraft Design Process  

E-print Network

A methodology for improving the quality of high-lift-system performance prediction within a multidisciplinary conceptual design process is presented. The high-lift-system geometry is explicitly modeled and a multiple-lifting-line method is used to compute its aerodynamic characteristics. Computation times are acceptable for use in a conceptual design process. The results for several test cases show good agreement with wind-tunnel and/or high-fidelity numerical data. In addition, the method allows for further enhancement by using nonlinear airfoil polars for interpolation, improving drag prediction, and introducing some degree of nonlinear aerodynamic behavior. Nomenclature A = altitude A0 = numerical coefficient B0 = numerical coefficient CD = drag coefficient (3-D) CDi = induced drag coefficient (3-D) CD0 = zero-lift drag coefficient (3-D) Cd = section drag coefficient (2-D) CL = lift coefficient (3-D)

Christian Werner-spatz; Wolfgang Heinze; Peter Horst

76

HSR High-Lift Technology Overview  

NASA Technical Reports Server (NTRS)

High-lift system performance will have a large impact on airplane noise and weight. Successful completion of PCD1 activities provided greater understanding of aerodynamic characteristics and configuration features important to high-lift system performance including: 1) Reynolds number effects (Ref. H); 2) Propulsion/airframe integration effects; and 3) Planform effects, canard/3-surface, alternate high-lift concepts, etc. PCD2 plans are aimed at achieving technology development performance goals and increasing technology readiness level for Technology Concept.

Applin, Z. T.

1999-01-01

77

Cooled highly twisted airfoil for a gas turbine engine  

SciTech Connect

This patent describes a cooled highly twisted airfoil for use in a gas turbine engine. The airfoil has a first cooling air cavity adjacent a leading edge of the airfoil, and a second cooling air cavity, separated from the first cavity by a wall. The second cavity provides cooling air to the first cavity by means of cooling holes provided in the wall. The improvement is characterized by: the wall comprising an integrally formed, continuous warped wall, defined as a surface of revolution about an axis, the axis determined such that the axis intersects the plane of a section close to a desired centerline of a series of impingement holes aligned in opposition to the leading edge, whereby cooling air is directed relatively precisely to the leading edge of the highly twisted airfoil through the impingement holes.

Kildea, R.J.

1988-04-19

78

High-lift aerodynamics: Prospects and plans  

NASA Technical Reports Server (NTRS)

The emergence of high-lift aerodynamics is reviewed as one of the key technologies to the development of future subsonic transport aircraft. Airport congestion, community noise, economic competitiveness, and safety - the drivers that make high-lift an important technology - are discussed. Attention is given to the potentially synergistic integration of high-lift aerodynamics with two other advanced technologies: ultra-high bypass ratio turbofan engines and hybrid laminar flow control. A brief review of the ongoing high-lift research program at Ames Research Center is presented. Suggestions for future research directions are made with particular emphasis on the development and validation of computational codes and design methods. It is concluded that the technology of high-lift aerodynamics analysis and design should move boldly into the realm of high Reynolds number, three-dimensional flows.

Olson, Lawrence E.

1992-01-01

79

High-order simulations of low Reynolds number membrane airfoils under prescribed motion  

NASA Astrophysics Data System (ADS)

The aerodynamics and aeroelastic response of a membrane wing under prescribed motion are investigated using a high-order, two-dimensional Navier-Stokes solver coupled to a geometrically nonlinear membrane model. The impact of increasing Reynolds number on the vortex dynamics and unsteady aerodynamic loads is examined for moderate-amplitude plunge and combined pitch-plunge motions at low frequency. Simulation results are compared with classical thin airfoil theory and highlight the differences between rigid and flexible membrane airfoils undergoing small and moderate amplitude motions. The present study demonstrates the ability of lifting membrane surface flexibility to enhance thrust production and propulsive efficiency, which may inform the design of flapping wing membrane fliers.

Jaworski, Justin W.; Gordnier, Raymond E.

2012-05-01

80

Key Topics for High-Lift Research: A Joint Wind Tunnel/Flight Test Approach  

NASA Technical Reports Server (NTRS)

Future high-lift systems must achieve improved aerodynamic performance with simpler designs that involve fewer elements and reduced maintenance costs. To expeditiously achieve this, reliable CFD design tools are required. The development of useful CFD-based design tools for high lift systems requires increased attention to unresolved flow physics issues. The complex flow field over any multi-element airfoil may be broken down into certain generic component flows which are termed high-lift building block flows. In this report a broad spectrum of key flow field physics issues relevant to the design of improved high lift systems are considered. It is demonstrated that in-flight experiments utilizing the NASA Dryden Flight Test Fixture (which is essentially an instrumented ventral fin) carried on an F-15B support aircraft can provide a novel and cost effective method by which both Reynolds and Mach number effects associated with specific high lift building block flows can be investigated. These in-flight high lift building block flow experiments are most effective when performed in conjunction with coordinated ground based wind tunnel experiments in low speed facilities. For illustrative purposes three specific examples of in-flight high lift building block flow experiments capable of yielding a high payoff are described. The report concludes with a description of a joint wind tunnel/flight test approach to high lift aerodynamics research.

Fisher, David; Thomas, Flint O.; Nelson, Robert C.

1996-01-01

81

Flight Investigation at Mach Numbers from 0.6 to 1.7 to Determine Drag and Base Pressures on a Blunt Trailing-edge Airfoil and Drag of Diamond and Circular-arc Airfoils at Zero Lift  

NASA Technical Reports Server (NTRS)

Results of an exploratory free-flight investigation at zero lift of several rocket-powered drag-research models having rectangular 6-percent-thick wings are presented for a Mach number range of 0.6 to 1.7. Wings having diamond, circular-arc, and blunt-trailing-edge airfoil sections were tested. Pressures over the base of the blunt-trailing-edge airfoil were measured. The drags of all the models were measured and are compared with theory in this paper.

Morrow, John D; Katz, Ellis

1955-01-01

82

The Determination of the Geometries of Multiple-Element Airfoils Optimized for Maximum Lift Coefficient. Ph.D. Thesis - Illinois Univ., Urbana  

NASA Technical Reports Server (NTRS)

Optimum airfoils in the sense of maximum lift coefficient are obtained by a newly developed method. The maximum lift coefficient is achieved by requiring that the turbulent skin friction be zero in the pressure rise region on the upper surface. Under this constraint, the pressure distribution is optimized. The optimum pressure distribution consists of a uniform stagnation pressure on the lower surface, a uniform minimum pressure on the upper surface immediately downstream of the front stagnation point followed by a Stratford zero skin friction pressure rise. When multiple-element airfoils are under consideration, this optimum pressure distribution appears on every element. The parameters used to specify the pressure distribution on each element are the Reynolds number and the normalized trailing edge velocity. The newly developed method of design computes the velocity distribution on a given airfoil and modifies the airfoil contour in a systematic manner until the desired velocity distribution is achieved. There are no limitations on how many elements the airfoil to be designed can have.

Chen, A. W.

1971-01-01

83

Three-Dimensional Effects on Multi-Element High Lift Computations  

NASA Technical Reports Server (NTRS)

In an effort to discover the causes for disagreement between previous 2-D computations and nominally 2-D experiment for flow over the 3-clement McDonnell Douglas 30P-30N airfoil configuration at high lift, a combined experimental/CFD investigation is described. The experiment explores several different side-wall boundary layer control venting patterns, document's venting mass flow rates, and looks at corner surface flow patterns. The experimental angle of attack at maximum lift is found to be sensitive to the side wall venting pattern: a particular pattern increases the angle of attack at maximum lift by at least 2 deg. A significant amount of spanwise pressure variation is present at angles of attack near maximum lift. A CFD study using 3-D structured-grid computations, which includes the modeling of side-wall venting, is employed to investigate 3-D effects of the flow. Side-wall suction strength is found to affect the angle at which maximum lift is predicted. Maximum lift in the CFD is shown to be limited by the growth of all off-body corner flow vortex and consequent increase in spanwise pressure variation and decrease in circulation. The 3-D computations with and without wall venting predict similar trends to experiment at low angles of attack, but either stall too earl or else overpredict lift levels near maximum lift by as much as 5%. Unstructured-grid computations demonstrate that mounting brackets lower die the levels near maximum lift conditions.

Rumsey, Christopher L.; Lee-Rausch, Elizabeth M.; Watson, Ralph D.

2002-01-01

84

Lift enhancement and flow structure of airfoil with joint trailing-edge flap and Gurney flap  

Microsoft Academic Search

The impact of Gurney flaps (GF), of different heights and perforations, on the aerodynamic and wake characteristics of a NACA\\u000a 0015 airfoil equipped with a trailing-edge flap (TEF) was investigated experimentally at Re = 2.54 × 105. The addition of the Gurney flap to the TEF produced a further increase in the downward turning of the mean flow (increased\\u000a aft camber), leading to a

T. Lee; Y. Y. Su

2011-01-01

85

Optimization of Flow Past a Moving Deformable Airfoil using Spectral Difference Method  

E-print Network

Optimization of Flow Past a Moving Deformable Airfoil using Spectral Difference Method Kui Ou airfoil, both individually and in combination. The lift and thrust characteristics of the combined flapping airfoil motion of plunging, pitching and deforming are investigated using a high-fidelity flow

Jameson, Antony

86

Three-dimensional effects in multi-element high lift computations  

Microsoft Academic Search

In an effort to discover the causes for disagreement between previous two-dimensional (2-D) computations and nominally 2-D experiment for flow over the three-element McDonnell Douglas 30P-30N airfoil configuration at high lift, a combined experimental\\/CFD investigation is described. The experiment explores several different side-wall boundary layer control venting patterns, documents venting mass flow rates, and looks at corner surface flow patterns.

Christopher L Rumsey; Elizabeth M Lee-Rausch; Ralph D Watson

2003-01-01

87

Analysis of non-symmetrical flapping airfoils  

NASA Astrophysics Data System (ADS)

Simulations have been done to assess the lift, thrust and propulsive efficiency of different types of non-symmetrical airfoils under different flapping configurations. The variables involved are reduced frequency, Strouhal number, pitch amplitude and phase angle. In order to analyze the variables more efficiently, the design of experiments using the response surface methodology is applied. Results show that both the variables and shape of the airfoil have a profound effect on the lift, thrust, and efficiency. By using non-symmetrical airfoils, average lift coefficient as high as 2.23 can be obtained. The average thrust coefficient and efficiency also reach high values of 2.53 and 0.61, respectively. The lift production is highly dependent on the airfoil’s shape while thrust production is influenced more heavily by the variables. Efficiency falls somewhere in between. Two-factor interactions are found to exist among the variables. This shows that it is not sufficient to analyze each variable individually. Vorticity diagrams are analyzed to explain the results obtained. Overall, the S1020 airfoil is able to provide relatively good efficiency and at the same time generate high thrust and lift force. These results aid in the design of a better ornithopter’s wing.

Tay, W. B.; Lim, K. B.

2009-08-01

88

Study of High Lift Configurations  

NASA Technical Reports Server (NTRS)

This project focus on the implementation of the Warren-Hassan transition / turbulence model (Journal of Aircraft, Vol. 35, No. 5) into the NASA code CFL3D and its testing for multi-element airfoils in landing configuration at different angles of attack. The Warren-Hassan transition model solves an evolution equation for a kinetic energy characteristic of non-turbulent fluctuations. This is combined with an empirical estimate of the frequency of the most amplified first-mode disturbance to yield an expression for an eddy viscosity characteristic of non-turbulent fluctuations. This is combined with the k - zeta model for fully turbulent flow to yield a unified approach capable of predicting both transition onset and extent. Blending of the non-turbulent and turbulent components of the model is accomplished by an intermittency function based on the work of Dhawan and Narasimha (Journal of Fluid Mechanics, Vol. 3, No. 4).

Edward, Jack R.; Hassan, Hassan A.

2000-01-01

89

Wind tunnel test of the S814 thick root airfoil  

SciTech Connect

The objective of this wind-tunnel test was to verify the predictions of the Eppler Airfoil Design and Analysis Code for a very thick airfoil having a high maximum lift coefficient designed to be largely insensitive to leading-edge roughness effects. The 24 percent thick S814 airfoil was designed with these characteristics to accommodate aerodynamic and structural considerations for the root region of a wind-turbine blade. In addition, the airfoil`s maximum lift-to-drag ratio was designed to occur at a high lift coefficient. To accomplish the objective, a two-dimensional wind tunnel test of the S814 thick root airfoil was conducted in January 1994 in the low-turbulence wind tunnel of the Delft University of Technology Low Speed Laboratory, The Netherlands. Data were obtained with transition free and transition fixed for Reynolds numbers of 0.7, 1.0, 1.5, 2.0, and 3.0 {times} 10{sup 6}. For the design Reynolds number of 1.5 {times} 10{sup 6}, the maximum lift coefficient with transition free is 1.32, which satisfies the design specification. However, this value is significantly lower than the predicted maximum lift coefficient of almost 1.6. With transition fixed at the leading edge, the maximum lift coefficient is 1.22. The small difference in maximum lift coefficient between the transition-free and transition-fixed conditions demonstrates the airfoil`s minimal sensitivity to roughness effects. The S814 root airfoil was designed to complement existing NREL low maximum-lift-coefficient tip-region airfoils for rotor blades 10 to 15 meters in length.

Somers, D.M. [Airfoils, Inc., State College, PA (United States); Tangler, J.L. [National Renewable Energy Lab., Golden, CO (United States)

1996-11-01

90

High-fidelity modeling of airfoil interaction with upstream turbulence  

NASA Astrophysics Data System (ADS)

To supplement past research on low speed unsteady airfoil responses to upstream disturbances, this work proposes and investigates a method to generate a turbulent momentum source to be convected downstream and interact with an SD7003 airfoil in a high-fidelity numerical simulation. A perturbation velocity field is generated from a summation of Fourier harmonics and applied to the forcing function in the momentum terms of the Navier Stokes Equations. The result is a three-dimensional, divergence-free, convected turbulent gust with applied statistical parameters. A parametric study has been done in 2D and 3D comparing the resultant flow fields and airfoil interactions for various numerical and physical parameters.

Brodnick, Jacob

91

A split-recoupled-semidirect computational technique applied to transonic flow over lifting airfoils  

NASA Technical Reports Server (NTRS)

A new version of the semidirect iterative method eliminates significant restrictions of previous versions of the method. A semidirect method solves finite-difference equations by a rapid globally implicit iterative process driven by a fast direct elliptic solver. The new approach can treat complex systems of equations in an efficient 'correction form', and allows the use of general, nonorthogonal, boundary-fitted coordinate transformations. These features are expected to lead to significant practical applications with conservation-equation systems in either two or three dimensions. The present application to the full potential equations for steady transonic flow over an airfoil at angle of attack illustrates the utility of the technique.

Martin, E. D.

1978-01-01

92

Noise impact of advanced high lift systems  

NASA Technical Reports Server (NTRS)

The impact of advanced high lift systems on aircraft size, performance, direct operating cost and noise were evaluated for short-to-medium and medium-to-long range aircraft with high bypass ratio and very high bypass ratio engines. The benefit of advanced high lift systems in reducing noise was found to be less than 1 effective-perceived-noise decibel level (EPNdB) when the aircraft were sized to minimize takeoff gross weight. These aircraft did, however, have smaller wings and lower engine thrusts for the same mission than aircraft with conventional high lift systems. When the advanced high lift system was implemented without reducing wing size and simultaneously using lower flap angles that provide higher L/D at approach a cumulative noise reduction of as much as 4 EPNdB was obtained. Comparison of aircraft configurations that have similar approach speeds showed cumulative noise reduction of 2.6 EPNdB that is purely the result of incorporating advanced high lift system in the aircraft design.

Elmer, Kevin R.; Joshi, Mahendra C.

1995-01-01

93

Motion Kinematics vs. Angle of Attack Effects in High-Frequency Airfoil Pitch/Plunge  

E-print Network

Motion Kinematics vs. Angle of Attack Effects in High-Frequency Airfoil Pitch/Plunge Michael V. OL1 10,000 with a SD7003 airfoil spanning the test section, while computations were with a 2D immersed loads time history and evolution of vortex shedding, especially at the airfoil leading edge. This turns

94

Quiet airfoils for small and large wind turbines  

DOEpatents

Thick airfoil families with desirable aerodynamic performance with minimal airfoil induced noise. The airfoil families are suitable for a variety of wind turbine designs and are particularly well-suited for use with horizontal axis wind turbines (HAWTs) with constant or variable speed using pitch and/or stall control. In exemplary embodiments, a first family of three thick airfoils is provided for use with small wind turbines and second family of three thick airfoils is provided for use with very large machines, e.g., an airfoil defined for each of three blade radial stations or blade portions defined along the length of a blade. Each of the families is designed to provide a high maximum lift coefficient or high lift, to exhibit docile stalls, to be relatively insensitive to roughness, and to achieve a low profile drag.

Tangler, James L. (Boulder, CO); Somers, Dan L. (Port Matilda, PA)

2012-06-12

95

Two-Dimensional High-Lift Aerodynamic Optimization Using Neural Networks  

NASA Technical Reports Server (NTRS)

The high-lift performance of a multi-element airfoil was optimized by using neural-net predictions that were trained using a computational data set. The numerical data was generated using a two-dimensional, incompressible, Navier-Stokes algorithm with the Spalart-Allmaras turbulence model. Because it is difficult to predict maximum lift for high-lift systems, an empirically-based maximum lift criteria was used in this study to determine both the maximum lift and the angle at which it occurs. The 'pressure difference rule,' which states that the maximum lift condition corresponds to a certain pressure difference between the peak suction pressure and the pressure at the trailing edge of the element, was applied and verified with experimental observations for this configuration. Multiple input, single output networks were trained using the NASA Ames variation of the Levenberg-Marquardt algorithm for each of the aerodynamic coefficients (lift, drag and moment). The artificial neural networks were integrated with a gradient-based optimizer. Using independent numerical simulations and experimental data for this high-lift configuration, it was shown that this design process successfully optimized flap deflection, gap, overlap, and angle of attack to maximize lift. Once the neural nets were trained and integrated with the optimizer, minimal additional computer resources were required to perform optimization runs with different initial conditions and parameters. Applying the neural networks within the high-lift rigging optimization process reduced the amount of computational time and resources by 44% compared with traditional gradient-based optimization procedures for multiple optimization runs.

Greenman, Roxana M.

1998-01-01

96

Performance predictions of VAWTs with NLF airfoil blades  

SciTech Connect

The successful design of an efficient Vertical Axis Wind Turbine (VAWT) can be obtained only when appropriate airfoil sections have been selected. Most VAWTs currently operating worldwide use blades of symmetrical NACA airfoil series. As these blades were designed for aviation applications, Sandia National Laboratories developed a family of airfoils specifically designed for VAWTs in order to decrease the Cost of Energy (COE) of the VAWT (Berg, 1990). Objectives formulated for the blade profile were: modest values of maximum lift coefficient, low drag at low angle of attack, high drag at high angle of attack, sharp stall, and low thickness-to-chord ratio. These features are similar to those of Natural Laminar Flow airfoils (NLF) and gave birth to the SNLA airfoil series. This technical brief illustrates the benefits and losses resulting from using NLF airfoils on VAWT blades. To achieve this goal, the streamtube model of Paraschivoiu (1988) is used to predict the performance of VAWTs equipped with blades of various airfoil shapes. The airfoil shapes considered are the conventional airfoils NACA 0018 and NACA 0021, and the SNLA 0018/50 airfoil designed at Sandia. Furthermore, the potential benefit of reducing the airfoil drag is clearly illustrated by the presentation of the individual contributions of lift and drag to power.

Masson, C.; Leclerc, C.; Paraschivoiu, I. [Ecole Polytechnique, Montreal, Quebec (Canada)

1997-02-01

97

Modification of the Douglas Neumann program to improve the efficiency of predicting component interference and high lift characteristics  

NASA Technical Reports Server (NTRS)

The Douglas Neumann method for low-speed potential flow on arbitrary three-dimensional lifting bodies was modified by substituting the combined source and doublet surface paneling based on Green's identity for the original source panels. Numerical studies show improved accuracy and stability for thin lifting surfaces, permitting reduced panel number for high-lift devices and supercritical airfoil sections. The accuracy of flow in concave corners is improved. A method of airfoil section design for a given pressure distribution, based on Green's identity, was demonstrated. The program uses panels on the body surface with constant source strength and parabolic distribution of doublet strength, and a doublet sheet on the wake. The program is written for the CDC CYBER 175 computer. Results of calculations are presented for isolated bodies, wings, wing-body combinations, and internal flow.

Bristow, D. R.; Grose, G. G.

1978-01-01

98

14TH EUROPEAN TURBULENCE CONFERENCE, 1-4 SEPTEMBER 2013, LYON, FRANCE TANDEM AIRFOIL VORTEX INTERACTION IN DEEP-STALL  

E-print Network

14TH EUROPEAN TURBULENCE CONFERENCE, 1-4 SEPTEMBER 2013, LYON, FRANCE TANDEM AIRFOIL VORTEX regime which may occur in tandem airfoil configurations at high angle of attack. It results from a detached flow on the downstream airfoil and a drop of the lift, rendering the elevators ineffective

Boyer, Edmond

99

S825 and S826 Airfoils: 1994--1995  

SciTech Connect

A family of airfoils, the S825 and S826, for 20- to 40-meter, variable-speed and variable-pitch (toward feather), horizontal-axis wind turbines has been designed and analyzed theoretically. The two primary objectives of high maximum lift, insensitive to roughness, and low profile drag have been achieved. The constraints on the pitching moments and the airfoil thicknesses have been satisfied. The airfoils should exhibit docile stalls.

Somers, D. M.

2005-01-01

100

Porous airfoil and process  

NASA Technical Reports Server (NTRS)

A porous airfoil having venting cavities with contoured barrier walls, formed by a core piece, placed beneath a porous upper and lower surface area that stretches over the nominal chord of an airfoil is employed, to provide an airfoil configuration that becomes self-adaptive to very dissimilar flow conditions to thereby improve the lift and drag characteristics of the airfoil at both subcritical and supercritical conditions.

Hartwich, Peter M. (Inventor)

1992-01-01

101

Three-Dimensional Effects in Multi-Element High Lift Computations  

NASA Technical Reports Server (NTRS)

In an effort to discover the causes for disagreement between previous two-dimensional (2-D) computations and nominally 2-D experiment for flow over the three-element McDonnell Douglas 30P-30N airfoil configuration at high lift, a combined experimental/CFD investigation is described. The experiment explores several different side-wall boundary layer control venting patterns, documents venting mass flow rates, and looks at corner surface flow patterns. The experimental angle of attack at maximum lift is found to be sensitive to the side-wall venting pattern: a particular pattern increases the angle of attack at maximum lift by at least 2 deg. A significant amount of spanwise pressure variation is present at angles of attack near maximum lift. A CFD study using three-dimensional (3-D) structured-grid computations, which includes the modeling of side-wall venting, is employed to investigate 3-D effects on the flow. Side-wall suction strength is found to affect the angle at which maximum lift is predicted. Maximum lift in the CFD is shown to be limited by the growth of an off-body corner flow vortex and consequent increase in spanwise pressure variation and decrease in circulation. The 3-D computations with and without wall venting predict similar trends to experiment at low angles of attack, but either stall too early or else overpredict lift levels near maximum lift by as much as 5%. Unstructured-grid computations demonstrate that mounting brackets lower the lift levels near maximum lift conditions.

Rumsey, Christopher L.; LeeReusch, Elizabeth M.; Watson, Ralph D.

2003-01-01

102

High-order lifting and integrality certification  

Microsoft Academic Search

Reductions to polynomial matrix multiplication are given for some classical problems involving a nonsingular input matrix over the ring of univariate polynomials with coefficients from a field. High-order lifting is used to compute the determinant, the Smith form, and a rational system solution with about the same number of field operations as required to multiply together two matrices having the

Arne Storjohann

2003-01-01

103

Flatback airfoil wind tunnel experiment.  

SciTech Connect

A computational fluid dynamics study of thick wind turbine section shapes in the test section of the UC Davis wind tunnel at a chord Reynolds number of one million is presented. The goals of this study are to validate standard wind tunnel wall corrections for high solid blockage conditions and to reaffirm the favorable effect of a blunt trailing edge or flatback on the performance characteristics of a representative thick airfoil shape prior to building the wind tunnel models and conducting the experiment. The numerical simulations prove the standard wind tunnel corrections to be largely valid for the proposed test of 40% maximum thickness to chord ratio airfoils at a solid blockage ratio of 10%. Comparison of the computed lift characteristics of a sharp trailing edge baseline airfoil and derived flatback airfoils reaffirms the earlier observed trend of reduced sensitivity to surface contamination with increasing trailing edge thickness.

Mayda, Edward A. (University of California, Davis, CA); van Dam, C.P. (University of California, Davis, CA); Chao, David D. (University of California, Davis, CA); Berg, Dale E.

2008-04-01

104

Preliminary Investigation of Certain Laminar-Flow Airfoils for Application at High Speeds and Reynolds Numbers  

NASA Technical Reports Server (NTRS)

In order to extend the useful range of Reynolds numbers of airfoils designed to take advantage of the extensive laminar boundary layers possible in an air stream of low turbulence, tests were made of the NACA 2412-34 and 1412-34 sections in the NACA low-turbulence tunnel. Although the possible extent of the laminar boundary layer on these airfoils is not so great as for specially designed laminar-flow airfoils, it is greater than that for conventional airfoils, and is sufficiently extensive so that at Reynolds numbers above 11,000,000 the laminar region is expected to be limited by the permissible 'Reynolds number run' and not by laminar separation as is the case with conventional airfoils. Drag measurements by the wake-survey method and pressure-distribution measurements were made at several lift coefficients through a range of Reynolds numbers up to 11,400,000. The drag scale-effect curve for the NACA 1412-34 is extrapolated to a Reynolds number of 30,000,000 on the basis of theoretical calculations of the skin friction. Comparable skin-friction calculations were made for the NACA 23012. The results indicate that, for certain applications at moderate values of the Reynolds number, the NACA 1412-34 and 2412-34 airfoils offer some advantages over such conventional airfoils as the NACA 23012. The possibility of maintaining a more extensive laminar boundary layer on these airfoils should result in a small drag reduction, and the absence of pressure peaks allows higher speeds to be reached before the compressibility burble is encountered. At lower Reynold numbers, below about 10,000,000, these airfoils have higher drags than airfoils designed to operate with very extensive laminar boundary layers.

Jacobs, E.N.; Abbott, Ira H.; von Doenhoff, A.E.

1939-01-01

105

Advances in Pneumatic-Controlled High-Lift Systems Through Pulsed Blowing  

NASA Technical Reports Server (NTRS)

Circulation Control technologies have been around for 65 years, and have been successfully demonstrated in laboratories and flight vehicles alike. Yet there are few production aircraft flying today that implement these advances. Circulation Control techniques may have been overlooked due to perceived unfavorable trade offs of mass flow, pitching moment, cruise drag, noise, etc. Improvements in certain aspects of Circulation Control technology are the focus of this paper. This report will describe airfoil and blown high lift concepts that also address cruise drag reduction and reductions in mass flow through the use of pulsed pneumatic blowing on a Coanda surface. Pulsed concepts demonstrate significant reductions in mass flow requirements for Circulation Control, as well as cruise drag concepts that equal or exceed conventional airfoil systems.

Jones, Gregory S.; Englar, Robet J.

2003-01-01

106

A unified viscous theory of lift and drag of 2-D thin airfoils and 3-D thin wings  

NASA Technical Reports Server (NTRS)

A unified viscous theory of 2-D thin airfoils and 3-D thin wings is developed with numerical examples. The viscous theory of the load distribution is unique and tends to the classical inviscid result with Kutta condition in the high Reynolds number limit. A new theory of 2-D section induced drag is introduced with specific applications to three cases of interest: (1) constant angle of attack; (2) parabolic camber; and (3) a flapped airfoil. The first case is also extended to a profiled leading edge foil. The well-known drag due to absence of leading edge suction is derived from the viscous theory. It is independent of Reynolds number for zero thickness and varies inversely with the square root of the Reynolds number based on the leading edge radius for profiled sections. The role of turbulence in the section induced drag problem is discussed. A theory of minimum section induced drag is derived and applied. For low Reynolds number the minimum drag load tends to the constant angle of attack solution and for high Reynolds number to an approximation of the parabolic camber solution. The parabolic camber section induced drag is about 4 percent greater than the ideal minimum at high Reynolds number. Two new concepts, the viscous induced drag angle and the viscous induced separation potential are introduced. The separation potential is calculated for three 2-D cases and for a 3-D rectangular wing. The potential is calculated with input from a standard doublet lattice wing code without recourse to any boundary layer calculations. Separation is indicated in regions where it is observed experimentally. The classical induced drag is recovered in the 3-D high Reynolds number limit with an additional contribution that is Reynold number dependent. The 3-D viscous theory of minimum induced drag yields an equation for the optimal spanwise and chordwise load distribution. The design of optimal wing tip planforms and camber distributions is possible with the viscous 3-D wing theory.

Yates, John E.

1991-01-01

107

14 CFR 25.345 - High lift devices.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false High lift devices. 25.345 Section 25...and Gust Conditions § 25.345 High lift devices. (a) If wing...EAS). (c) If flaps or other high lift devices are to be used in en...

2012-01-01

108

AIAA 2003-3957 Optimization of High-Lift  

E-print Network

AIAA 2003-3957 Optimization of High-Lift Configurations Using a Newton­Krylov Algorithm Marian, VA, 20191-4344. #12;Optimization of High-Lift Configurations Using a Newton­Krylov Algorithm Marian examples reveal a number of difficulties for numerical optimization methods when applied to high-lift

Zingg, David W.

109

14 CFR 25.345 - High lift devices.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false High lift devices. 25.345 Section 25...and Gust Conditions § 25.345 High lift devices. (a) If wing...EAS). (c) If flaps or other high lift devices are to be used in en...

2013-01-01

110

Boeing 777 high lift control system  

Microsoft Academic Search

The Boeing 777 high lift control systems (HLCS), a state-of-the-art microprocessor-based system that provides fly-by-wire control, protection, and built-in-test and maintenance access functions for the leading edge slats and trailing edge flaps drive and actuation systems, is discussed. This system is designed to take advantage of technologically proven concepts as well as judicious application of new concepts in response to

J. Rea

1993-01-01

111

Trailing edge modifications for flatback airfoils.  

SciTech Connect

The adoption of blunt trailing edge airfoils (also called flatback airfoils) for the inboard region of large wind turbine blades has been proposed. Blunt trailing edge airfoils would not only provide a number of structural benefits, such as increased structural volume and ease of fabrication and handling, but they have also been found to improve the lift characteristics of thick airfoils. Therefore, the incorporation of blunt trailing edge airfoils would allow blade designers to more freely address the structural demands without having to sacrifice aerodynamic performance. These airfoils do have the disadvantage of generating high levels of drag as a result of the low-pressure steady or periodic flow in the near-wake of the blunt trailing edge. Although for rotors, the drag penalty appears secondary to the lift enhancement produced by the blunt trailing edge, high drag levels are of concern in terms of the negative effect on the torque and power generated by the rotor. Hence, devices are sought that mitigate the drag of these airfoils. This report summarizes the literature on bluff body vortex shedding and bluff body drag reduction devices and proposes four devices for further study in the wind tunnel.

Kahn, Daniel L. (University of California, Davis, CA); van Dam, C.P. (University of California, Davis, CA); Berg, Dale E.

2008-03-01

112

An experimental low Reynolds number comparison of a Wortmann FX67-K170 airfoil, a NACA 0012 airfoil and a NACA 64-210 airfoil in simulated heavy rain  

NASA Technical Reports Server (NTRS)

Wind tunnel experiments were conducted on Wortmann FX67-K170, NACA 0012, and NACA 64-210 airfoils at rain rates of 1000 mm/hr and Reynolds numbers of 310,000 to compare the aerodynamic performance degradation of the airfoils and to attempt to identify the various mechanisms which affect performance in heavy rain conditions. Lift and drag were measured in dry and wet conditions, a variety of flow visualization techniques were employed, and a computational code which predicted airfoil boundary layer behavior was used. At low angles of attack, the lift degradation in wet conditions varied significantly between the airfoils. The Wortmann section had the greatest overall lift degradation and the NACA 64-210 airfoil had the smallest. At high angles of attack, the NACA 64-210 and 0012 airfoils had improved aerodynamic performance in rain conditions due to an apparent reduction of the boundry layer separation. Performance degradation in heavy rain for all three airfoils at low angles of attack could be emulated by forced boundary layer transition near the leading edge. The secondary effect occurs at time scales consistent with top surface water runback times. The runback layer is thought to effectively alter the airfoil geometry. The severity of the performance degradation for the airfoils varied. The relative differences appeared to be related to the susceptibility of each airfoil to premature boundary layer transition.

Craig, Anthony P.; Hansman, R. John

1987-01-01

113

Viscous-flow analysis of a subsonic transport aircraft high-lift system and correlation with flight data  

NASA Technical Reports Server (NTRS)

High-lift system aerodynamics has been gaining attention in recent years. In an effort to improve aircraft performance, comprehensive studies of multi-element airfoil systems are being undertaken in wind-tunnel and flight experiments. Recent developments in Computational Fluid Dynamics (CFD) offer a relatively inexpensive alternative for studying complex viscous flows by numerically solving the Navier-Stokes (N-S) equations. Current limitations in computer resources restrict practical high-lift N-S computations to two dimensions, but CFD predictions can yield tremendous insight into flow structure, interactions between airfoil elements, and effects of changes in airfoil geometry or free-stream conditions. These codes are very accurate when compared to strictly 2D data provided by wind-tunnel testing, as will be shown here. Yet, additional challenges must be faced in the analysis of a production aircraft wing section, such as that of the NASA Langley Transport Systems Research Vehicle (TSRV). A primary issue is the sweep theory used to correlate 2D predictions with 3D flight results, accounting for sweep, taper, and finite wing effects. Other computational issues addressed here include the effects of surface roughness of the geometry, cove shape modeling, grid topology, and transition specification. The sensitivity of the flow to changing free-stream conditions is investigated. In addition, the effects of Gurney flaps on the aerodynamic characteristics of the airfoil system are predicted.

Potter, R. C.; Vandam, C. P.

1995-01-01

114

Close to real life. [solving for transonic flow about lifting airfoils using supercomputers  

NASA Technical Reports Server (NTRS)

NASA's Numerical Aerodynamic Simulation (NAS) facility for CFD modeling of highly complex aerodynamic flows employs as its basic hardware two Cray-2s, an ETA-10 Model Q, an Amdahl 5880 mainframe computer that furnishes both support processing and access to 300 Gbytes of disk storage, several minicomputers and superminicomputers, and a Thinking Machines 16,000-device 'connection machine' processor. NAS, which was the first supercomputer facility to standardize operating-system and communication software on all processors, has done important Space Shuttle aerodynamics simulations and will be critical to the configurational refinement of the National Aerospace Plane and its intergrated powerplant, which will involve complex, high temperature reactive gasdynamic computations.

Peterson, Victor L.; Bailey, F. Ron

1988-01-01

115

High-order accurate simulations of unsteady flow past plunging and pitching airfoils Chunlei Liang a,  

E-print Network

High-order accurate simulations of unsteady flow past plunging and pitching airfoils Chunlei Liang: Spectral difference method Plunging Pitching Micro Air Vehicle a b s t r a c t This paper presents simulations of unsteady flow past plunging and pitching airfoils using a high-order spectral difference (SD

Jameson, Antony

116

Design and experimental results for the S814 airfoil  

SciTech Connect

A 24-percent-thick airfoil, the S814, for the root region of a horizontal-axis wind-turbine blade has been designed and analyzed theoretically and verified experimentally in the low-turbulence wind tunnel of the Delft University of Technology Low Speed Laboratory, The Netherlands. The two primary objectives of high maximum lift, insensitive to roughness, and low profile drag have been achieved. The constraints on the pitching moment and the airfoil thickness have been satisfied. Comparisons of the theoretical and experimental results show good agreement with the exception of maximum lift which is overpredicted. Comparisons with other airfoils illustrate the higher maximum lift and the lower profile drag of the S814 airfoil, thus confirming the achievement of the objectives.

Somers, D.M. [Airfoils, Inc., State College, PA (United States)

1997-01-01

117

Status of the special-purpose airfoil families  

SciTech Connect

This work is directed at developing thin and thick airfoil families, for rotors with diameters of 10 to 30 m, that enhance energy output at low to medium wind speeds and provide more consistent operating characteristics with lower fatigue loads at high wind speeds. Performance is enhanced through the use of laminar flow, while more consistent rotor operating characteristics at high wind speeds are achieved by tailoring the airfoil such that the maximum lift coefficient C/sub 1,max/ is largely independent of roughness effects. Using the Eppler airfoil design code, two thin and one thick airfoil family were designed; each family has a root, outboard, and tip airfoil. Two-dimensional wind-tunnel tests were conducted to verify the predicted performance characteristics for both a thin and thick outboard airfoil from these families. Atmospheric tests on full-scale wind turbines will complete the verification process. 3 refs., 7 figs., 3 tabs.

Tangler, J.L.; Somers, D.M.

1987-12-01

118

Assessment of the aerodynamic characteristics of thick airfoils in high Reynolds and moderate Ma numbers using CFD modeling  

NASA Astrophysics Data System (ADS)

The aerodynamic characteristics of thick airfoils in high Reynolds number is assessed using two different CFD RANS solvers: the compressible MaPFlow and the incompressible CRES-flowNS-2D both equipped with the k-? SST turbulence model. Validation is carried out by comparing simulations against existing high Reynolds experimental data for the NACA 63-018 airfoil in the range of -10° to 20°. The use of two different solvers aims on one hand at increasing the credibility in the results and on the other at quantifying the compressibility effects. Convergence of steady simulations is achieved within a mean range of -10° to 14° which refers to attached or light stall conditions. Over this range the simulations from the two codes are in good agreement. As stall gets deeper, steady convergence ceases and the simulations must switch to unsteady. Lift and drag oscillations are produced which increase in amplitude as the angle of attack increases. Finally in post stall, the average CL is found to decrease up to ~24° or 32° for the FFA or the NACA 63-018 airfoils respectively, and then recover to higher values indicating a change in the unsteady features of the flow.

Prospathopoulos, John M.; Papadakis, Giorgos; Sieros, Giorgos; Voutsinas, Spyros G.; Chaviaropoulos, Takis K.; Diakakis, Kostas

2014-06-01

119

HSR High Lift Program and PCD2 Update  

NASA Technical Reports Server (NTRS)

The mission of High-Lift Technology is to develop technology allowing the design of practical high lift concepts for the High-Speed Civil Transport (HSCT) in order to: 1) operate safely and efficiently; and 2) reduce terminal control area and community noise. In fulfilling this mission, close and continuous coordination will be maintained with other High-Speed Research (HSR) technology elements in order to support optimization of the overall airplane (rather than just the high lift system).

Kemmerly, Guy T.; Coen, Peter; Meredith, Paul; Clark, Roger; Hahne, Dave; Smith, Brian

1999-01-01

120

Aerodynamic Characteristics of a Number of Modified NACA Four-Digit-Series Airfoil Sections  

NASA Technical Reports Server (NTRS)

Theoretical pressure distributions and measured lift, drag, and pitching moment characteristics at three values of Reynolds number are presented for a group of NACA four-digit-series airfoil sections modified for high-speed applications. The effectiveness of flaps applied to these airfoils and the effect of standard leading-edge roughness were also investigated at one value of Reynolds number. Results are also presented of tests of three conventional NACA four-digit-series airfoil sections.

Loftin, Laurence K., Jr.; Cohen, Kenneth G.

1947-01-01

121

S833, S834, and S835 Airfoils: November 2001--November 2002  

SciTech Connect

A family of quiet, thick, natural-laminar-flow airfoils, the S833, S834, and S835, for 1 - 3-meter-diameter, variable-speed/variable-pitch, horizontal-axis wind turbines has been designed and analyzed theoretically. The two primary objectives of high maximum lift, relatively insensitive to roughness, and low profile drag have been achieved. The airfoils should exhibit docile stalls, which meet the design goal. The constraints on the pitching moment and the airfoils thicknesses have been satisfied.

Somers, D. M.

2005-08-01

122

S830, S831, and S832 Airfoils: November 2001-November 2002  

SciTech Connect

A family of quiet, thick, natural-laminar-flow airfoils, the S830, S831, and S832, for 40 - 50-meter-diameter, variable-speed/variable-pitch, horizontal-axis wind turbines has been designed and analyzed theoretically. The two primary objectives of high maximum lift, relatively insensitive to roughness, and low profile drag have been achieved. The airfoils should exhibit docile stalls, which meet the design goal. The constraints on the pitching moment and the airfoils thicknesses have been satisfied.

Somers, D. M.

2005-08-01

123

Grid embedment as applied to viscous transonic airfoil flowfield analysis  

E-print Network

by applying it to a NACA 0012 airfoil and should be especially useful in the study of viscous interaction effects on airfoils in slightly supercritical flows. ACKNDNLEDGEMENTS The author wishes to express his appreciation to Dr. Leland Carlson... Surface Coupled Main-Embedded Grid Solution Procedure Highly Supercritical Inviscid Main-Embedded Grid Comparison Slightly Supercritical Inviscid Main-Embedded Grid Comparison High Lift Inviscid Main-Embedded Grid Comparison Completely Subcritical...

Reed, Christopher L.

2012-06-07

124

Shapes for rotating airfoils  

NASA Technical Reports Server (NTRS)

An airfoil which has particular application to the blade or blades of rotor aircraft and aircraft propellers is presented. The airfoil thickness distribution, camber and leading edge radius are shaped to locate the airfoil crest at a more aft position along the chord, and to increase the freestream Mach number at which sonic flow is attained at the airfoil crest. The reduced slope of the airfoil causes a reduction in velocity at the airfoil crest at lift coefficients from zero to the maximum lift coefficient. The leading edge radius is adjusted so that the maximum local Mach number at 1.25 percent chord and at the designed maximum lift coefficient is limited to about 0.48 when the Mach number normal to the leading edge is approximately 0.20. The lower surface leading edge radius is shaped so that the maximum local Mach number at the leading edge is limited to about 0.29 when the Mach number normal to the leading edge is approximately 0.20. The drag divergence Mach number associated with the airfoil is moved to a higher Mach number over a range of lift coefficients resulting in superior aircraft performance.

Bingham, G. J. (inventor)

1984-01-01

125

AFC-Enabled Simplified High-Lift System Integration Study  

NASA Technical Reports Server (NTRS)

The primary objective of this trade study report is to explore the potential of using Active Flow Control (AFC) for achieving lighter and mechanically simpler high-lift systems for transonic commercial transport aircraft. This assessment was conducted in four steps. First, based on the Common Research Model (CRM) outer mold line (OML) definition, two high-lift concepts were developed. One concept, representative of current production-type commercial transonic transports, features leading edge slats and slotted trailing edge flaps with Fowler motion. The other CRM-based design relies on drooped leading edges and simply hinged trailing edge flaps for high-lift generation. The relative high-lift performance of these two high-lift CRM variants is established using Computational Fluid Dynamics (CFD) solutions to the Reynolds-Averaged Navier-Stokes (RANS) equations for steady flow. These CFD assessments identify the high-lift performance that needs to be recovered through AFC to have the CRM variant with the lighter and mechanically simpler high-lift system match the performance of the conventional high-lift system. Conceptual design integration studies for the AFC-enhanced high-lift systems were conducted with a NASA Environmentally Responsible Aircraft (ERA) reference configuration, the so-called ERA-0003 concept. These design trades identify AFC performance targets that need to be met to produce economically feasible ERA-0003-like concepts with lighter and mechanically simpler high-lift designs that match the performance of conventional high-lift systems. Finally, technical challenges are identified associated with the application of AFC-enabled highlift systems to modern transonic commercial transports for future technology maturation efforts.

Hartwich, Peter M.; Dickey, Eric D.; Sclafani, Anthony J.; Camacho, Peter; Gonzales, Antonio B.; Lawson, Edward L.; Mairs, Ron Y.; Shmilovich, Arvin

2014-01-01

126

Aerodynamic characteristics of a propeller powered high lift semispan wing  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted on the engine/airframe integration aerodynamics for potential high-lift aircraft configurations. The model consisted of a semispan wing with a double-isolated flap system and a Krueger leading edge device. The advanced propeller and the powered nacelle were tested and aerodynamic characteristics of the combined system are presented. It was found that the lift coefficient of the powered wing could be increased by the propeller slipstream when the rotational speed was increased and high-lift devices were deployed. Moving the nacelle/propeller closer to the wing in the vertical direction indicated higher lift augmentation than a shift in the longitudinal direction. A pitch-down nacelle inclination enhanced the lift performance of the system much better than vertical and horizontal variation of the nacelle locations and showed that the powered wing can sustain higher angles of attack near maximum lift performance.

Takallu, M. A.; Gentry, G. L., Jr.

1992-01-01

127

Aerodynamic Characteristics of a Propeller-Powered High-Lift  

E-print Network

A small-scale semispan high-lift wing- ap system equipped under the wing with a turboprop engine assembly was tested in the Langley 14- by 22-Foot Subsonic Tunnel. Experimental data were obtained for various propeller rotational speeds, nacelle locations, and nacelle inclinations. To isolate the e ects of the high-lift system, data were obtained with and without the aps and leading-edge device. The e ects of the propeller slipstream on the overall longitudinal aerodynamic characteristics of the wing-propeller assembly were examined. Test results indicated that the lift coe cient of the wing could be increased by the propeller slipstream when the rotational speed was increased and high-lift devices were deployed. Decreasing the nacelle inclination (increased pitch down) enhanced the lift performance of the system much more than varying the vertical or horizontal location of the nacelle. Furthermore, decreasing the nacelle inclination led to higher lift curve slope values, which indicated that the powered wing could sustain higher angles of attack near maximum lift performance. Any lift augmentation was accompanied by a drag penalty due to the increased wing lift.

Semispan Wing; Garl L. Gentry; M. A. Takallu

128

EUROLIFT - advanced high lift aerodynamics for transport aircraft  

Microsoft Academic Search

The overall objective of the European High Lift Programme (EUROLIFT) is to reduce time and cost of the design process of high lift systems which will be reached by the development of more reliable computational and experimental design tools. This paper gives an overview of the EUROLIFT project and presents results of the first year.

Peter Thiede

2001-01-01

129

High-lift aerodynamics: Trends, trades, and options  

NASA Technical Reports Server (NTRS)

The trend toward the utilization of higher maximum lift coefficient with increased aircraft size and cruise velocities is discussed. The impact of this trend on the need for tradeoffs between cruise performance and takeoff, climb, and landing performance is examined. Theoretical methods for the analysis of the two-dimensional characteristics of flap systems are described and compared with experimental data. Four powered-lift concepts are described to outline some of the options currently being developed. Two jet-flap theories are described which provide analytical methods for estimation of the three-dimensional aerodynamic high-lift performance characteristics of powered lift systems.

Margason, R. J.; Morgan, H. L., Jr.

1975-01-01

130

Application of Excitation from Multiple Locations on a Simplified High-Lift System  

NASA Technical Reports Server (NTRS)

A series of active flow control experiments were recently conducted on a simplified high-lift system. The purpose of the experiments was to explore the prospects of eliminating all but simply hinged leading and trailing edge flaps, while controlling separation on the supercritical airfoil using multiple periodic excitation slots. Excitation was provided by three. independently controlled, self-contained, piezoelectric actuators. Low frequency excitation was generated through amplitude modulation of the high frequency carrier wave, the actuators' resonant frequencies. It was demonstrated, for the first time, that pulsed modulated signal from two neighboring slots interact favorably to increase lift. Phase sensitivity at the low frequency was measured, even though the excitation was synthesized from the high-frequency carrier wave. The measurements were performed at low Reynolds numbers and included mean and unsteady surface pressures, surface hot-films, wake pressures and particle image velocimetry. A modest (6%) increase in maximum lift (compared to the optimal baseline) was obtained due t o the activation of two of the three actuators.

Melton, LaTunia Pack; Yao, Chung-Sheng; Seifert, Avi

2004-01-01

131

Sound radiation from real airfoils in turbulence  

NASA Astrophysics Data System (ADS)

Leading edge noise measurements and calculations have been made on a three airfoils immersed in turbulence. The airfoils included variations in chord, thickness and camber and the measurements encompass integral scale to chord ratios from 9 to 40 percent as well as 4:1 ratios of leading edge radius and airfoil thickness to integral scale. Angle of attack is found to have a strong effect on the airfoil response function but for the most part only a small effect on leading edge noise because of the averaging effect of the isotropic turbulence spectrum. Angle of attack effects can therefore be significant in non-isotropic turbulence and dependent on airfoil shape. It is found that thicker airfoils generate significantly less noise at high frequencies but that this effect is not determined solely by the leading edge radius or overall thickness. Camber effects appear likely to be small. Angle of attack effects on the response function of a strongly cambered airfoil are shown to be centered on zero angle of attack, rather than the zero lift angle of attack.

Devenport, William J.; Staubs, Joshua K.; Glegg, Stewart A. L.

2010-08-01

132

Impulsive Start of a Symmetric Airfoil at High Angle of Attack  

NASA Technical Reports Server (NTRS)

The fluid dynamic phenomena following the impulsive start of a NACA 0015 airfoil were studied by using a time accurate solution of the incompressible laminar Navier-Stokes equations. Angle of attack was set at 10 deg to simulate steady-state poststall conditions at a Reynolds number of 1.2 x 10(exp 4). The calculation revealed that large initial lift values can be obtained, immediately following the impulsive start, when a trapped vortex develops above the airfoil. Before the buildup of this trapped vortex and immediately after the airfoil was set into motion, the fluid is attached to the airfoil's surface and flows around the trailing edge, demonstrating the delay in the buildup of the classical Kutta condition. The transient of this effect is quite short and is followed by an attached How event that leads to the trapped vortex that has a longer duration. The just described initial phenomenon eventually transits into a fully developed separated flow pattern identifiable by an alternating, periodic vortex shedding.

Katz, Joseph; Yon, Steven; Rogers, Stuart E.

1996-01-01

133

Unsteady flow structure and vorticity convection over the airfoil oscillating at high reduced frequency  

Microsoft Academic Search

Unsteady vortex structures and vorticity convection over the airfoil (NACA 0012), oscillating in the uniform inflow, are studied by flow visualization and velocity measurements. The airfoil, pivoting at one-third of the chord, oscillates periodically near the static stalling angle of attack (AOA) at high reduced-frequency. The phase-triggering and modified phase-averaged techniques are employed to reconstruct the pseudo instantaneous velocity field

Cheng-Hsiung Kuo; J. K. Hsieh

2001-01-01

134

Design and experimental results for a flapped natural-laminar-flow airfoil for general aviation applications  

NASA Technical Reports Server (NTRS)

A flapped natural laminar flow airfoil for general aviation applications, the NLF(1)-0215F, has been designed and analyzed theoretically and verified experimentally in the Langley Low Turbulence Pressure Tunnel. The basic objective of combining the high maximum lift of the NASA low speed airfoils with the low cruise drag of the NACA 6 series airfoils has been achieved. The safety requirement that the maximum lift coefficient not be significantly affected with transition fixed near the leading edge has also been met. Comparisons of the theoretical and experimental results show generally good agreement.

Somers, D. M.

1981-01-01

135

An Exploratory Investigation of a Slotted, Natural-Laminar-Flow Airfoil  

NASA Technical Reports Server (NTRS)

A 15-percent-thick, slotted, natural-laminar-flow (SNLF) airfoil, the S103, for general aviation applications has been designed and analyzed theoretically and verified experimentally in the Langley Low-Turbulence Pressure Tunnel. The two primary objectives of high maximum lift and low profile drag have been achieved. The constraints on the pitching moment and the airfoil thickness have been satisfied. The airfoil exhibits a rapid stall, which does not meet the design goal. Comparisons of the theoretical and experimental results show good agreement. Comparison with the baseline, NASA NLF(1)-0215F airfoil confirms the achievement of the objectives.

Somers, Dan M.

2012-01-01

136

Wind tunnel tests of an NACA 23021 airfoil equipped with a slotted extensible and a plain extensible flap  

NASA Technical Reports Server (NTRS)

An investigation has been made in the NACA 7- by 10-foot wind tunnel of a large chord NACA 23021 airfoil equipped with two arrangements of a completely extended 15 percent chord extensible flap. One of the flaps had a faired juncture, without a gap; the other was provided with a slot between the trailing edge of the airfoil and the nose of the flap. The results showed that the basic airfoil gave the lowest profile-drag coefficients over the low lift range, the airfoil with the plain extensible flap gave the lowest profile-drag coefficients over the moderate lift range, and the airfoil with the slotted extensible flap gave the lowest profile-drag coefficients over the high lift range. The airfoil with the slotted extensible flap had the same maximum lift at a flap deflection of 25 degrees as the airfoil with the plain extensible flap had at a flap deflection of 60 degrees. The results of comparisons of the airfoil pitching-moment coefficients obtained with the two types of flap are dependent upon the basis chosen for comparison. Complete aerodynamic section characteristics are presented for the various flap deflections for both flap arrangements in the completely extended portion.

Swanson, Robert S; Harris, Thomas A

1940-01-01

137

Airfoils for wind turbine  

SciTech Connect

Airfoils for the tip and mid-span regions of a wind turbine blade have upper surface and lower surface shapes and contours between a leading edge and a trailing edge that minimize roughness effects of the airfoil and provide maximum lift coefficients that are largely insensitive to roughness effects. The airfoil in one embodiment is shaped and contoured to have a thickness in a range of about fourteen to seventeen percent, a Reynolds number in a range of about 1,500,000 to 2,000,000, and a maximum lift coefficient in a range of about 1.4 to 1.5. In another embodiment, the airfoil is shaped and contoured to have a thickness in a range of about fourteen percent to sixteen percent, a Reynolds number in a range of about 1,500,000 to 3,000,000, and a maximum lift coefficient in a range of about 0.7 to 1.5. Another embodiment of the airfoil is shaped and contoured to have a Reynolds in a range of about 1,500,000 to 4,000,000, and a maximum lift coefficient in a range of about 1.0 to 1.5.

Tangler, J.L.; Somers, D.M.

2000-05-30

138

Airfoil Design and Rotorcraft Performance  

NASA Technical Reports Server (NTRS)

The relationship between global performance of a typical helicopter and the airfoil environment, as represented by the airfoil angles of attack and Mach number, has been examined using the comprehensive analysis CAMRAD II. A general correspondence is observed between global performance parameters, such as rotor L/D, and airfoil performance parameters, such as airfoil L/D, the drag bucket boundaries, and the divergence Mach number. Effects of design parameters such as blade twist and rotor speed variation have been examined and, in most cases, improvements observed in global performance are also observed in terms of airfoil performance. The relations observed between global Performance and the airfoil environment suggests that the emphasis in airfoil design should be for good L/D, while the maximum lift coefficient performance is less important.

Bousman, William G.

2003-01-01

139

The Effectiveness at High Speeds of a 20-Percent-chord Plain Trailing-edge Flap on the NACA 65-210 Airfoil Section  

NASA Technical Reports Server (NTRS)

An analysis has been made of the lift-control effectiveness of a 20-percent-chord plain trailing-edge flap on the NACA 65-210 airfoil section from section lift-coefficient data obtained at Mach numbers from 0.3 to 0.875. In addition, the effectiveness of the plain flap as a lift-control device has been compared with the corresponding effectiveness of both a spoiler and a dive-recovery flag on the INCA 65-210 airfoil section.

Stivers, Louis S., Jr.

1947-01-01

140

Wind Tunnel Tests of Wind Turbine Airfoils at High Reynolds Numbers  

NASA Astrophysics Data System (ADS)

Wind tunnel tests have been performed to measure the two-dimensional aerodynamic characteristics of two different airfoil families at high Reynolds numbers (from 3 to 12 millions) in the DNW High Pressure Wind Tunnel in Gottingen (HDG), Germany. Also, tests at a Reynolds number of 3 millions have been performed in the Low-Speed Low- Turbulence Wind Tunnel of Delft University, The Netherlands. The airfoils tested belong to two wind turbine dedicated families: the TU-Delft DU family and the ACCIONA Windpower AWA family that was designed in collaboration with CENER. Reynolds number effects on airfoil performance have been obtained in the range of 3 to 12 millions. The availability of data from two different wind tunnels has brought the opportunity to cross compare the results from the two facilities.

Llorente, E.; Gorostidi, A.; Jacobs, M.; Timmer, W. A.; Munduate, X.; Pires, O.

2014-06-01

141

The effects of sound on the boundary layer of an airfoil at high angles of attack  

E-print Network

THE EFFECTS OF SOUND ON THE BOUNDARY LAYER OF AN AIRFOIL AT HIGH ANGLES OF ATTACK A Thesis By THOMAS IRA HUTCHINSON S, rhr?tted to the Graduate School of the Agrtcultu, al and Mechanical College of Texas in partial f, . lfrllr:, cnt... of the requirements for the degree of MASTER OF SCIENCE January 1963 Mai"" Subject: Acrcspace Engrneering THE EFFECTS OF SOUND ON THE BOUNDARY LAYER OF AN AIRFOIL AT HIGH ANGLES OF ATTACK A Thesis THOMAS IRA HUTCHINSON Approved as to style and content by...

Hutchinson, Thomas Ira

2012-06-07

142

Optimized Natural-Laminar-Flow Airfoils and D. W. Zingg  

E-print Network

Optimized Natural-Laminar-Flow Airfoils J. Driver and D. W. Zingg University of Toronto Institute-averaged Navier-Stokes equations. The algorithm is applied to the design of airfoils with maximum lift-drag ratio natural-laminar-flow airfoils. In particular, the optimization algorithm is able to design an airfoil

Zingg, David W.

143

Airfoil flutter model suspension system  

NASA Technical Reports Server (NTRS)

A wind tunnel suspension system for testing flutter models under various loads and at various angles of attack is described. The invention comprises a mounting bracket assembly affixing the suspension system to the wind tunnel, a drag-link assembly and a compound spring arrangement comprises a plunge spring working in opposition to a compressive spring so as to provide a high stiffness to trim out steady state loads and simultaneously a low stiffness to dynamic loads. By this arrangement an airfoil may be tested for oscillatory response in both plunge and pitch modes while being held under high lifting loads in a wind tunnel.

Reed, Wilmer H. (inventor)

1987-01-01

144

Viscous single and multicomponent airfoil design with genetic algorithms  

Microsoft Academic Search

An optimization procedure aimed at the design of multicomponent airfoils for high-lift applications is described. The procedure is based on a multiobjective genetic algorithm; two flow solvers have been coupled with the genetic algorithm: a viscous–inviscid interaction method, based on an Euler flow solver and an integral boundary layer routine, and a method based on a full potential flow solver.

D Quagliarella; A Vicini

2001-01-01

145

Computational design and analysis of flatback airfoil wind tunnel experiment.  

SciTech Connect

A computational fluid dynamics study of thick wind turbine section shapes in the test section of the UC Davis wind tunnel at a chord Reynolds number of one million is presented. The goals of this study are to validate standard wind tunnel wall corrections for high solid blockage conditions and to reaffirm the favorable effect of a blunt trailing edge or flatback on the performance characteristics of a representative thick airfoil shape prior to building the wind tunnel models and conducting the experiment. The numerical simulations prove the standard wind tunnel corrections to be largely valid for the proposed test of 40% maximum thickness to chord ratio airfoils at a solid blockage ratio of 10%. Comparison of the computed lift characteristics of a sharp trailing edge baseline airfoil and derived flatback airfoils reaffirms the earlier observed trend of reduced sensitivity to surface contamination with increasing trailing edge thickness.

Mayda, Edward A. (University of California, Davis, CA); van Dam, C.P. (University of California, Davis, CA); Chao, David D. (University of California, Davis, CA); Berg, Dale E.

2008-03-01

146

Wind tunnel research comparing lateral control devices, particularly at high angles of attack X : various control devices on a wing with a fixed auxiliary airfoil  

NASA Technical Reports Server (NTRS)

Results are given of a series of systemic tests comparing lateral control devices with particular reference to their effectiveness at high angles of attack. These tests were made with two sizes of ordinary ailerons and different sizes of spoilers on a Clark Y wing model having a narrow auxiliary airfoil fixed ahead and above the leading edge, the chords of the main and auxiliary airfoils being parallel. In addition, the auxiliary airfoil itself was given angular deflection. The purpose was to provide rolling moments for lateral control. The tests were made in a 7 by 10 foot wind tunnel. They included both force and rotation tests to show the effect of the devices on the lift and drag characteristics of the wing and on the lateral stability characteristics, as well as lateral control. They showed that none of the aileron arrangements tried would give rolling control of an assumed satisfactory value at all angles of attack up to the stall. However, they would give satisfactory values, but at the expense of abnormally high deflections and very heavy hinge moments. The most effective combination of ailerons and spoilers gave satisfactory values of rolling moment at angles of attack below the stall, and the values did not fall off as rapidly above the stall as with ailerons alone. With an arrangement of this type having the proper relative proportions and linkage, it should be possible to obtain reasonably satisfactory yawing moments and control forces. Deflecting one-half of the auxiliary airfoil downward for the purpose of control gave strong favorable yawing moments at all angles of attack, but gave very small rolling moments at the low angles of attack.

Weick, Fred E; Noyes, Richard W

1933-01-01

147

Airfoil family design for large offshore wind turbine blades  

NASA Astrophysics Data System (ADS)

Wind turbine blades size has scaled-up during last years due to wind turbine platform increase especially for offshore applications. The EOLIA project 2007-2010 (Spanish Goverment funded project) was focused on the design of large offshore wind turbines for deep waters. The project was managed by ACCIONA Energia and the wind turbine technology was designed by ACCIONA Windpower. The project included the design of a wind turbine airfoil family especially conceived for large offshore wind turbine blades, in the order of 5MW machine. Large offshore wind turbines suffer high extreme loads due to their size, in addition the lack of noise restrictions allow higher tip speeds. Consequently, the airfoils presented in this work are designed for high Reynolds numbers with the main goal of reducing blade loads and mantainig power production. The new airfoil family was designed in collaboration with CENER (Spanish National Renewable Energy Centre). The airfoil family was designed using a evolutionary algorithm based optimization tool with different objectives, both aerodynamic and structural, coupled with an airfoil geometry generation tool. Force coefficients of the designed airfoil were obtained using the panel code XFOIL in which the boundary layer/inviscid flow coupling is ineracted via surface transpiration model. The desing methodology includes a novel technique to define the objective functions based on normalizing the functions using weight parameters created from data of airfoils used as reference. Four airfoils have been designed, here three of them will be presented, with relative thickness of 18%, 21%, 25%, which have been verified with the in-house CFD code, Wind Multi Block WMB, and later validated with wind tunnel experiments. Some of the objectives for the designed airfoils concern the aerodynamic behavior (high efficiency and lift, high tangential coefficient, insensitivity to rough conditions, etc.), others concern the geometry (good for structural design, compatibility for the different airfoil family members, etc.) and with the ultimate objective that the airfoils will reduce the blade loads. In this paper the whole airfoil design process and the main characteristics of the airfoil family are described. Some force coefficients for the design Reynolds number are also presented. The new designed airfoils have been studied with computational calculations (panel method code and CFD) and also in a wind tunnel experimental campaign. Some of these results will be also presented in this paper.

Méndez, B.; Munduate, X.; San Miguel, U.

2014-06-01

148

Overview of NASA HSR high-lift program  

NASA Technical Reports Server (NTRS)

The viewgraphs and discussion of the NASA High-Speed Research (HSR) Program being conducted to develop the technologies essential for the successful U.S. development of a commercial supersonic air transport in the 2005 timeframe are provided. The HSR program is being conducted in two phases, with the first phase stressing technology to ensure environmental acceptability and the second phase stressing technology to make the vehicle economically viable (in contrast to the current Concorde design). During Phase 1 of the program, a key element of the environmental emphases is minimization of community noise through effective engine nozzle noise suppression technology and through improving the performance of high-lift systems. An overview of the current Phase 1 High-Lift Program, directed at technology for community noise reduction, is presented. The total target for takeoff engine noise reduction to meet expected regulations is believed to be about 20 EPNdB. The high-lift research is stressing the exploration of innovative high-lift concepts and advanced flight operations procedures to achieve a substantial (approximately 6 EPNdB) reduction in community noise to supplement the reductions expected from engine nozzle noise suppression concepts; primary concern is focused on the takeoff and climbout operations where very high engine power settings are used. Significant reductions in aerodynamic drag in this regime will allow substantial reductions in the required engine thrust levels and therefore reductions in the noise generated.

Gilbert, William P.

1992-01-01

149

Noise exposure reduction of advanced high-lift systems  

NASA Technical Reports Server (NTRS)

The purpose of NASA Contract NAS1-20090 Task 3 was to investigate the potential for noise reduction that would result from improving the high-lift performance of conventional subsonic transports. The study showed that an increase in lift-to-drag ratio of 15 percent would reduce certification noise levels by about 2 EPNdB on approach, 1.5 EPNdB on cutback, and zero EPNdB on sideline. In most cases, noise contour areas would be reduced by 10 to 20 percent.

Haffner, Stephen W.

1995-01-01

150

AIAA 20020844 Design Optimization of HighLift  

E-print Network

gradient in- formation is obtained with large computational savings over traditional finite solver, FLO103-MB, a point-to-point matched multi-block grid system and the Message Passing Interface positioning, and angle of attack are used as design variables. The prediction of high-lift flows around

Jameson, Antony

151

High-lift generation and power requirements of insect flight  

Microsoft Academic Search

Recently, much progress has been made in revealing aerodynamic force mechanisms and predicting power requirements in insect flight. In this article, we review the research works in the past 10 years. We first summarize the kinematics of the flapping wing. Next we explore the unsteady high-lift mechanisms. Then we discuss the power requirements of hovering and forward flight in some

Mao Sun

2005-01-01

152

Low speed aerodynamic characteristics of NACA 6716 and NACA 4416 airfoils with 35 percent-chord single-slotted flaps. [low turbulence pressure tunnel tests to determine two dimensional lift and pitching moment characteristics  

NASA Technical Reports Server (NTRS)

An investigation was conducted in a low-turbulence pressure tunnel to determine the two-dimensional lift and pitching-moment characteristics of an NACA 6716 and an NACA 4416 airfoil with 35-percent-chord single-slotted flaps. Both models were tested with flaps deflected from 0 deg to 45 deg, at angles of attack from minus 6 deg to several degrees past stall, at Reynolds numbers from 3.0 million to 13.8 million, and primarily at a Mach number of 0.23. Tests were also made to determine the effect of several slot entry shapes on performance.

Bingham, G. J.; Noonan, K. W.

1974-01-01

153

High School Redesign Gets Presidential Lift  

ERIC Educational Resources Information Center

President Barack Obama applauded high school redesign efforts in his State of the Union address and encouraged districts to look to successful models for inspiration. Last week, he followed up with a request in his fiscal 2014 budget proposal for a new, $300 million competitive-grant program. Recognition is widespread that high schools need to…

Adams, Caralee J.

2013-01-01

154

Numerical analysis of active chordwise flexibility on the performance of non-symmetrical flapping airfoils  

NASA Astrophysics Data System (ADS)

This paper investigates the effect of active chordwise flexing on the lift, thrust and propulsive efficiency of three types of airfoils. The factors studied are the flexing center location, standard two-sided flexing as well as a type of single-sided flexing. The airfoils are simulated to flap with four configurations, and the effects of flexing under these configurations are investigated. Results show that flexing is not necessarily beneficial for the performance of the airfoils. However, with the correct parameters, efficiency is as high as 0.76 by placing the flexing centre at the trailing edge. The average thrust coefficient is more than twice as high, from 1.63 to 3.57 with flapping and flexing under the right conditions. Moreover, the single-sided flexing also gives an average lift coefficient as high as 4.61 for the S1020 airfoil. The shape of the airfoil does alter the effect of flexing too. Deviating the flexing phase angle away from 90° does not give a significant improvement to the airfoil’s performance. These results greatly enhance the design of a better performing ornithopter wing.

Tay, W. B.; Lim, K. B.

2010-01-01

155

Wind-tunnel test of the S814 thick root airfoil  

SciTech Connect

The objective of this wind-tunnel test was to verify the predictions of the Eppler Airfoil Design and Analysis Code for a very thick airfoil having a high maximum lift coefficient (c{sub 1,max} designed to be largely insensitive to leading edge roughness effects. The 24-percent-thick S814 airfoil was designed with these characteristics to accommodate aerodynamic and structural considerations for the root region of a wind-turbine blade. In addition, the airfoil`s maximum lift-to-drag ratio was designed to occur it a high lift coefficient. To accomplish the objective, a two-dimensional wind-tunnel test of the S814 thick root airfog was conducted in January 1994 in the low-turbulence wind tunnel of the Delft University of Technology Low Speed Laboratory. Data were obtained for transition-free and transition-fixed conditions at Reynolds numbers of 0.7, 1.0, 1.5, 2.0, and 3.0 {times} 10{sup 6}. For the design Reynolds numbers of 1.5 {times} l0{sup 6}, the transition-free c{sub 1,max} is 1.3 which satisfies the design specification. However, this value is significantly lower than the predicted c{sub 1,max} of almost l.6. With transition-fixed at the is 1.2. The difference in c{sub 1,max} between the transition-free and transition-fixed conditions demonstrates the airfoil`s minimal sensitivity to roughness effects. The S814 root airfoil was designed to complement existing NREL low c{sub 1,max} tip-region airfoils for rotor blades 10 to 15 meters in length.

Somers, D.M. [Airfoils, Inc., State College, VA (United States); Tangler, J.L. [National Renewable Energy Lab., Golden, CO (United States)

1995-01-01

156

Control of Separation on the Flap of a Three-Element High-Lift Configuration  

E-print Network

Control of Separation on the Flap of a Three-Element High-Lift Configuration B. G¨unther and Frank of the control of the flow over the flap of a three-element high-lift configuration by means of periodic of incorporating complex, heavy and expensive multi-element high lift devices, single flaps without slats

Andrzejak, Artur

157

DESIGN OPTIMIZATION OF HIGH-LIFT CONFIGURATIONS USING A VISCOUS ADJOINT-BASED METHOD  

E-print Network

' $ DESIGN OPTIMIZATION OF HIGH-LIFT CONFIGURATIONS USING A VISCOUS ADJOINT-BASED METHOD Sangho Kim · Objectives · Description of Continuous Adjoint Method · Viscous Aerodynamic Sensitivity Accuracy Study · High-Lift System Design · Conclusions and Future Work & % #12;' $ High­Lift System Configuration

Kim, Sangho

158

Design Optimization of MultiElement HighLift Configurations Using a Viscous Continuous Adjoint Method  

E-print Network

Design Optimization of Multi­Element High­Lift Configurations Using a Viscous Continuous Adjoint An adjoint-based Navier-Stokes design and optimization method for two-dimensional multi-element high-lift is obtained with large computational savings over traditional finite-difference methods. The high-lift

Kim, Sangho

159

Transition measurement and analysis on a swept wing in high lift configuration  

Microsoft Academic Search

In the framework of the European Research Program EUROLIFT (European High Lift Program), the ONERA experimental contribution is a basic experiment to study the transition phenomenon on a swept model equipped with a slat and a flap in high lift configuration. In preparation for the tests, the 3D high lift configuration has been computed at ONERA with a Navier Stokes

A. Séraudie; J. Perraud; F. Moens

2003-01-01

160

High-lift generation and power requirements of insect flight  

NASA Astrophysics Data System (ADS)

Recently, much progress has been made in revealing aerodynamic force mechanisms and predicting power requirements in insect flight. In this article, we review the research works in the past 10 years. We first summarize the kinematics of the flapping wing. Next we explore the unsteady high-lift mechanisms. Then we discuss the power requirements of hovering and forward flight in some insects. Finally, we mention recent studies on dragonfly flight.

Sun, Mao

2005-07-01

161

Prediction of high lift: review of present CFD capability  

Microsoft Academic Search

A survey is conducted of CFD methods applied to the computation of high-lift multi-element configurations over the last 10–15 years. Both 2-D and 3-D configurations are covered. The review is organized by configuration, in an effort to glean useful insights with respect to particular successes or failings of CFD methods as a whole. In general, for both 2-D and 3-D

Christopher L. Rumsey; Susan X. Ying

2002-01-01

162

LES of High-Reynolds-Number Coanda Flow Separating from a Rounded Trailing Edge of a Circulation Control Airfoil  

NASA Technical Reports Server (NTRS)

This slide presentation reviews the Large Eddy Simulation of a high reynolds number Coanda flow that is separated from a round trailing edge of a ciruclation control airfoil. The objectives of the study are: (1) To investigate detailed physics (flow structures and statistics) of the fully turbulent Coanda jet applied to a CC airfoil, by using LES (2) To compare LES and RANS results to figure out how to improve the performance of existing RANS models for this type of flow.

Nichino, Takafumi; Hahn, Seonghyeon; Shariff, Karim

2010-01-01

163

Lift enhancement by trapped vortex  

NASA Technical Reports Server (NTRS)

The viewgraphs and discussion of lift enhancement by trapped vortex are provided. Efforts are continuously being made to find simple ways to convert wings of aircraft from an efficient cruise configuration to one that develops the high lift needed during landing and takeoff. The high-lift configurations studied here consist of conventional airfoils with a trapped vortex over the upper surface. The vortex is trapped by one or two vertical fences that serve as barriers to the oncoming stream and as reflection planes for the vortex and the sink that form a separation bubble on top of the airfoil. Since the full three-dimensional unsteady flow problem over the wing of an aircraft is so complicated that it is hard to get an understanding of the principles that govern the vortex trapping process, the analysis is restricted here to the flow field illustrated in the first slide. It is assumed that the flow field between the two end plates approximates a streamwise strip of the flow over a wing. The flow between the endplates and about the airfoil consists of a spanwise vortex located between the suction orifices in the endplates. The spanwise fence or spoiler located near the nose of the airfoil serves to form a separated flow region and a shear layer. The vorticity in the shear layer is concentrated into the vortex by withdrawal of fluid at the suction orifices. As the strength of the vortex increases with time, it eventually dominates the flow in the separated region so that a shear or vertical layer is no longer shed from the tip of the fence. At that point, the vortex strength is fixed and its location is such that all of the velocity contributions at its center sum to zero thereby making it an equilibrium point for the vortex. The results of a theoretical analysis of such an idealized flow field are described.

Rossow, Vernon J.

1992-01-01

164

Design and validation of a high-lift low-pressure turbine blade  

NASA Astrophysics Data System (ADS)

This dissertation is a design and validation study of the high-lift low-pressure turbine (LPT) blade designated L2F. High-lift LPTs offer the promise of reducing the blade count in modern gas turbine engines. Decreasing the blade count can reduce development and maintenance costs and the weight of the engine, but care must be taken in order to maintain turbine section performance with fewer blades. For an equivalent amount of work extracted, lower blade counts increase blade loading in the LPT section. The high-lift LPT presented herein allows 38% fewer blades with a Zweifel loading coefficient of 1.59 and maintains the same inlet and outlet blade metal angles of conventional geometries in service today while providing an improved low-Reynolds number characteristic. The computational design method utilizes the Turbine Design and Analysis System (TDAAS) developed by John Clark of the Air Force Research Laboratory. TDAAS integrates several government-funded design utilities including airfoil and grid generation capability with a Reynolds-Averaged Navier-Stokes flow solver into a single, menu-driven, Matlab-based system. Transition modeling is achieved with the recently developed model of Praisner and Clark, and this study validates the use of the model for design purposes outside of the Pratt & Whitney (P&W) design system where they were created. Turbulence modeling is achieved with the Baldwin and Lomax zero-equation model. The experimental validation consists of testing the front-loaded L2F along with a previously designed, mid-loaded blade (L1M) in a linear turbine cascade in a low-speed wind tunnel over a range of Reynolds numbers at 3.3% freestream turbulence. Hot-wire anemometry and pressure measurements elucidate these comparisons, while a shear and stress sensitive film (S3F) also helps describe the flow in areas of interest. S3F can provide all 3 components of stress on a surface in a single measurement, and these tests extend the operational envelope of the technique to low speed air environments where small dynamic pressures and curved surfaces preclude the use of more traditional global measurement methods. Results are compared between the L1M and L2F geometries along with previous data taken in the same wind tunnel at identical flow conditions for the P&W Pack B geometry.

McQuilling, Mark Wayne

165

Controlled transitory stall on a pitching airfoil using pulsed actuation  

NASA Astrophysics Data System (ADS)

Transitory separation control of a static and pitching 2-D airfoil is investigated in wind tunnel experiments using pulsed actuation on time scales that are an order of magnitude shorter than the characteristic convective time scale T conv. Actuation is provided by momentary [O(0.05 T conv)] pulsed jets that are generated by a spanwise array of combustion-based actuators integrated in the center segment of the airfoil. The flow field in the center plane above the airfoil and in its near wake is computed from high-resolution PIV measurements in multiple overlapping cross-stream frames that are obtained phase-locked to the actuation and allow for tracking of vorticity concentrations. A single actuation pulse leads to a strong transitory increase in the circulation about the airfoil that is manifested by a partial collapse of the separated flow domain and is accompanied by the shedding of a large-scale clockwise vortex, and the attachment and accumulation of the surface vorticity layer behind it. The slow relaxation of the flow following termination of pulsed actuation returns the airfoil to full stall within 10 T conv. It is shown that repetition of actuation pulses within T conv can increase the streamwise extent of the attached flow domain, and the trapped vorticity leads to a substantial increase in the peak transitory circulation before the flow separates again when the actuation is terminated. The coupling of the pulsed actuation to the airfoil's motion enhances the actuation's control authority. Single pulse can significantly increase the lift over most of the oscillation cycle both at post-stall and at angles of attack that are below stall. Several actuation pulses distributed during the pitch oscillation cycle can momentarily extend the accumulation of vorticity and thus increase the transitory and cycle-averaged lift, and improve the airfoil's pitch stability.

Woo, George T. K.; Glezer, Ari

2013-06-01

166

Root region airfoil for wind turbine  

DOEpatents

A thick airfoil is described for the root region of the blade of a wind turbine. The airfoil has a thickness in a range from 24%--26% and a Reynolds number in a range from 1,000,000 to 1,800,000. The airfoil has a maximum lift coefficient of 1.4--1.6 that has minimum sensitivity to roughness effects. 3 Figs.

Tangler, J.L.; Somers, D.M.

1995-05-23

167

INVERSE DESIGN OF AIRFOILS BASED ON A NOVEL FORMULATION  

E-print Network

-1- INVERSE DESIGN OF AIRFOILS BASED ON A NOVEL FORMULATION OF THE ANT COLONY OPTIMIZATION METHOD airfoils and to demonstrate its effectiveness. Since such an optimization method is in need of evaluation shaped airfoils or other components of lift producing or energy consuming/producing devices are often

Fainekos, Georgios E.

168

Airfoil structure  

DOEpatents

Past airfoil configurations have been used to improve aerodynamic performance and engine efficiencies. The present airfoil configuration further increases component life and reduces maintenance by reducing internal stress within the airfoil itself. The airfoil includes a chord and a span. Each of the chord and the span has a bow being summed to form a generally ``C`` configuration of the airfoil. The generally ``C`` configuration includes a compound bow in which internal stresses resulting from a thermal temperature gradient are reduced. The structural configuration reduces internal stresses resulting from thermal expansion. 6 figs.

Frey, G.A.; Twardochleb, C.Z.

1998-01-13

169

Airfoil structure  

DOEpatents

Past airfoil configurations have been used to improve aerodynamic performance and engine efficiencies. The present airfoil configuration further increases component life and reduces maintenance by reducing internal stress within the airfoil itself. The airfoil includes a chord and a span. Each of the chord and the span has a bow being summed to form a generally "C" configuration of the airfoil. The generally "C" configuration includes a compound bow in which internal stresses resulting from a thermal temperature gradient are reduced. The structural configuration reduces internal stresses resulting from thermal expansion.

Frey, Gary A. (Poway, CA); Twardochleb, Christopher Z. (Alpine, CA)

1998-01-01

170

Systematic Airfoil Tests in the Large Wind Tunnel of the DVL  

NASA Technical Reports Server (NTRS)

The present report is a description of systematic tests at maximum lift on airfoils with and without split flap and of profile drag at low lift. In order to obtain an opinion as to the suitability of the airfoils with flaps, the maximum-lift measurements were repeated on airfoils with split flaps. The profile drag at low lift was arrived at by direct weighing and momentum measurements and, since the profiles were of unusual depth, extended to large Reynolds numbers.

Doetsch, H; Kramer, M

1938-01-01

171

Gurney flap—Lift enhancement, mechanisms and applications  

NASA Astrophysics Data System (ADS)

Since its invention by a race car driver Dan Gurney in 1960s, the Gurney flap has been used to enhance the aerodynamics performance of subsonic and supercritical airfoils, high-lift devices and delta wings. In order to take stock of recent research and development of Gurney flap, we have carried out a review of the characteristics and mechanisms of lift enhancement by the Gurney flap and its applications. Optimum design of the Gurney flap is also summarized in this paper. For the Gurney flap to be effective, it should be mounted at the trailing edge perpendicular to the chord line of airfoil or wing. The flap height must be of the order of local boundary layer thickness. For subsonic airfoils, an additional Gurney flap increases the pressure on the upstream surface of the Gurney flap, which increases the total pressure of the lower surface. At the same time, a long wake downstream of the flap containing a pair of counter-rotating vortices can delay or eliminate the flow separation near the trailing edge on the upper surface. Correspondingly, the total suction on the airfoil is increased. For supercritical airfoils, the lift enhancement of the Gurney flap mainly comes from its ability to shift the shock on the upper surface in the downstream. Applications of the Gurney flap to modern aircraft design are also discussed in this review.

Wang, J. J.; Li, Y. C.; Choi, K.-S.

2008-01-01

172

Preliminary Investigation of the Effect of Compressibility on the Maximum Lift Coefficient, Special Report  

NASA Technical Reports Server (NTRS)

Preliminary data are presented on the variation of the maximum lift coefficient with Mach number. The data were obtained from tests in the 8-foot high-speed tunnel of three NACA 16-series airfoils of 1-foot chord. Measurements consisted primarily of pressure-distribution measurements in order to illustrate the nature of the phenomena. It was found that the maximum lift coefficient of airfoils is markedly affected by compressibility even at Mach numbers as low as 0.2. At high Mach numbers pronounced decrease of the maximum lift coefficient was found. The magnitude of the effects of compressibility on the maximum lift coefficient and the low speeds at which these effects first appear indicate clearly that consideration of the take-off thrust for propellers will give results seriously in error if these considerations are based on the usual low-speed maximum-lift-coefficient data generally used.

Stack, John; Fedziuk, Henry A.; Cleary, Harold E.

1943-01-01

173

On the Use of Surface Porosity to Reduce Unsteady Lift  

NASA Technical Reports Server (NTRS)

An innovative application of existing technology is proposed for attenuating the effects of transient phenomena, such as rotor-stator and rotor-strut interactions, linked to noise and fatigue failure in turbomachinery environments. A computational study was designed to assess the potential of passive porosity technology as a mechanism for alleviating interaction effects by reducing the unsteady lift developed on a stator airfoil subject to wake impingement. The study involved a typical high bypass fan Stator airfoil (solid baseline and several porous configurations), immersed in a free field and exposed to the effects of a transversely moving wake. It was found that, for the airfoil under consideration, the magnitude of the unsteady lift could be reduced more than 18% without incurring significant performance losses.

Tinetti, Ana F.; Kelly, Jeffrey J.; Bauer, Steven X. S.; Thomas, Russell H.

2001-01-01

174

Design of a Slotted, Natural-Laminar-Flow Airfoil for Business-Jet Applications  

NASA Technical Reports Server (NTRS)

A 14-percent-thick, slotted, natural-laminar-flow airfoil, the S204, for light business-jet applications has been designed and analyzed theoretically. The two primary objectives of high maximum lift, relatively insensitive to roughness, and low profile drag have been achieved. The drag-divergence Mach number is predicted to be greater than 0.70.

Somers, Dan M.

2012-01-01

175

Numerical Simulation of Pitching Airfoil Performance Enhancement Using Co-Flow Jet Flow Control  

E-print Network

helicopter blade using its pump as the only source of power. Due to the removal of dynamic stall, CFJ airfoil is able to remove the sharp moment drop at high angle of attack. Nomenclature CFJ Co-flow jet AoA Angle the balance of lift between advancing and retreating side of the rotor disk. The AoA is minimum

Zha, Gecheng

176

High-order Method for Modeling of Aerodynamics of Flapping Wings: Airfoil-Gust Interaction  

NASA Astrophysics Data System (ADS)

The use of Micro Air Vehicles (MAV) with flapping wing motion has received considerable attention in the recent years due to their great potential in military and commercial applications. A number of analytical, experimental, and computational studies have been performed to investigate the aerodynamic performance of MAV. However, most of these studies have been performed under idealized operating conditions. Hence, there is a lack of detailed knowledge on the operation of MAV in complex flow environments including flights in wind gust and near obstacles. The current numerical study investigates the performance of a rigid MAV in the presence of periodic gust for two different kinematic motions: plunge and pitch. Two-dimensional rigid airfoils are taken as prototypes of MAVs wings. The gust is assumed to be sinusoidal and modeled as a source term in the Navier-Stokes equations to avoid the implementation of special boundary conditions. The investigation showed a significant drop in the average lift force for the plunging motion in the presence of the gust compared to the pitching motion.

Gopalan, Harish; Povitsky, Alex

2011-11-01

177

Leading-edge singularities in thin-airfoil theory  

NASA Technical Reports Server (NTRS)

If the thin airfoil theory is applied to an airfoil having a rounded leading edge, a certain error will arise in the determination of the pressure distribution around the nose. It is shown that the evaluation of the drag of such a blunt nosed airfoil by the thin airfoil theory requires the addition of a leading edge force, analogous to the leading edge thrust of the lifting airfoil. The method of calculation is illustrated by application to: (1) The Joukowski airfoil in subsonic flow; and (2) the thin elliptic cone in supersonic flow. A general formula for the edge force is provided which is applicable to a variety of wing forms.

Jones, R. T.

1976-01-01

178

A new airfoil design concept  

NASA Technical Reports Server (NTRS)

The present airfoil design concept is based on utilizing unconventional geometry characteristics near the airfoil trailing edge which include a finite trailing edge thickness, strongly divergent trailing edge upper and lower surfaces, and high surface curvature on the lower surface at or near the lower surface trailing edge. This paper presents computational analyses of airfoils and a wing utilizing the concept, airfoil validation wind tunnel test results of several configurations, and wing-validation wind tunnel test results for a complete wing design. In addition to validating the concept, the airfoil and wing testing provided additional detailed data to better understand the aerodynamic advantage of such an unconventional trailing edge configuration. It is demonstrated that the concept represents a significant step in airfoil technology beyond that achieved with the Supercritical Airfoil. This concept provides the aerodynamicist an additional degree of design freedom and flexibility previously unrecognized.

Henne, P. A.; Gregg, R. D.

1989-01-01

179

A critical assessment of UH-60 main rotor blade airfoil data  

NASA Technical Reports Server (NTRS)

Many current comprehensive rotorcraft analyses employ lifting-line methods that require main rotor blade airfoil data, typically obtained from wind tunnel tests. In order to effectively evaluate these lifting-line methods, it is of the utmost importance to ensure that the airfoil section data are free of inaccuracies. A critical assessment of the SC1095 and SC1094R8 airfoil data used on the UH-60 main rotor blade was performed for that reason. Nine sources of wind tunnel data were examined, all of which contain SC1095 data and four of which also contain SC1094R8 data. Findings indicate that the most accurate data were generated in 1982 at the 11-Foot Wind Tunnel Facility at NASA Ames Research Center and in 1985 at the 6-inch by 22-inch transonic wind tunnel facility at Ohio State University. It has not been determined if data from these two sources are sufficiently accurate for their use in comprehensive rotorcraft analytical models of the UH-60. It is recommended that new airfoil tables be created for both airfoils using the existing data. Additional wind tunnel experimentation is also recommended to provide high quality data for correlation with these new airfoil tables.

Totah, Joseph

1993-01-01

180

A critical assessment of UH-60 main rotor blade airfoil data  

NASA Technical Reports Server (NTRS)

Many current comprehensive rotorcraft analyses employ lifting-line methods that require main rotor blade airfoil data, typically obtained from wind tunnel tests. In order to effectively evaluate these lifting-line methods, it is of the utmost importance to ensure that the airfoil section data are free of inaccuracies. A critical assessment of the SC1095 and SC1094R8 airfoil data used on the UH-60 main rotor blade was performed for that reason. Nine sources of wind tunnel data were examined, all of which contain SC1095 data and four of which also contain SC1094R8 data. Findings indicate that the most accurate data were generated in 1982 at the 11-Foot Wind Tunnel Facility at NASA Ames Research Center and in 1985 at the 6-inch-by-22-inch transonic wind tunnel facility at Ohio State University. It has not been determined if data from these two sources are sufficiently accurate for their use in comprehensive rotorcraft analytical models of the UH-60. It is recommended that new airfoil tables be created for both airfoils using the existing data. Additional wind tunnel experimentation is also recommended to provide high quality data for correlation with these new airfoil tables.

Totah, Joseph

1993-01-01

181

A study on high subsonic airfoil flows in relatively high Reynolds number by using OpenFOAM  

NASA Astrophysics Data System (ADS)

In the present study, numerical calculations of the flow-field around the airfoil model are performed by using the OpenFOAM in high subsonic flows. The airfoil model is NACA 64A010. The maximum thickness is 10 % of the chord length. The SonicFOAM and the RhoCentralFOAM are selected as the solver in high subsonic flows. The grid point is 158,000 and the Mach numbers are 0.277 and 0.569 respectively. The CFD data are compared with the experimental data performed by the cryogenic wind tunnel in the past. The results are as follows. The numerical results of the pressure coefficient distribution on the model surface calculated by the SonicFOAM solver showed good agreement with the experimental data measured by the cryogenic wind tunnel. And the data calculated by the SonicFOAM have the capability for the quantitative comparison of the experimental data at low angle of attack.

Nakao, Shinichiro; Kashitani, Masashi; Miyaguni, Takeshi; Yamaguchi, Yutaka

2014-04-01

182

Low-speed aerodynamic characteristics of a 14-percent-thick NASA phase 2 supercritical airfoil designed for a lift coefficient of 0.7  

NASA Technical Reports Server (NTRS)

The low speed aerodynamic characteristics of a 14 percent thick supercritical airfoil are documented. The wind tunnel test was conducted in the Low Turbulence Pressure Tunnel. The effects of varying chord Reynolds number from 2,000,000 to 18,000,000 at a Mach number of 0.15 and the effects of varying Mach number from 0.10 to 0.32 at a Reynolds number of 6,000,000 are included.

Harris, C. D.; Mcghee, R. J.; Allison, D. O.

1980-01-01

183

Airfoil Dynamic Stall and Rotorcraft Maneuverability  

NASA Technical Reports Server (NTRS)

The loading of an airfoil during dynamic stall is examined in terms of the augmented lift and the associated penalties in pitching moment and drag. It is shown that once stall occurs and a leading-edge vortex is shed from the airfoil there is a unique relationship between the augmented lift, the negative pitching moment, and the increase in drag. This relationship, referred to here as the dynamic stall function, shows limited sensitivity to effects such as the airfoil section profile and Mach number, and appears to be independent of such parameters as Reynolds number, reduced frequency, and blade sweep. For single-element airfoils there is little that can be done to improve rotorcraft maneuverability except to provide good static C(l(max)) characteristics and the chord or blade number that is required to provide the necessary rotor thrust. However, multi-element airfoils or airfoils with variable geometry features can provide augmented lift in some cases that exceeds that available from a single-element airfoil. The dynamic stall function is shown to be a useful tool for the evaluation of both measured and calculated dynamic stall characteristics of single element, multi-element, and variable geometry airfoils.

Bousman, William G.

2000-01-01

184

Nonlinear Analysis of Airfoil High-Intensity Gust Response Using a High-Order Prefactored Compact Code  

NASA Technical Reports Server (NTRS)

The nonlinear response of symmetric and loaded airfoils to an impinging vortical gust is investigated in the parametric space of gust dimension, intensity, and frequency. The study, which was designed to investigate the validity limits for a linear analysis, is implemented by applying a nonlinear high-order prefactored compact code and comparing results with linear solutions from the GUST3D frequency-domain solver. Both the unsteady aerodynamic and acoustic gust responses are examined.

Crivellini, A.; Golubev, V.; Mankbadi, R.; Scott, J. R.; Hixon, R.; Povinelli, L.; Kiraly, L. James (Technical Monitor)

2002-01-01

185

Aerodynamics of High-Lift Configuration Civil Aircraft Model in JAXA  

Microsoft Academic Search

This paper presents basic aerodynamics and stall characteristics of the high-lift configuration aircraft model JSM (JAXA Standard Model). During research process of developing high-lift system design method, wind tunnel testing at JAXA 6.5m by 5.5m low-speed wind tunnel and Navier-Stokes computation on unstructured hybrid mesh were performed for a realistic configuration aircraft model equipped with high-lift devices, fuselage, nacelle-pylon, slat

Yuzuru Yokokawa; Mitsuhiro Murayama; Takeshi Ito; Kazuomi Yamamoto

2007-01-01

186

Dynamic Stall Measurements and Computations for a VR-12 Airfoil with a Variable Droop Leading Edge  

NASA Technical Reports Server (NTRS)

High density-altitude operations of helicopters with advanced performance and maneuver capabilities have lead to fundamental research on active high-lift system concepts for rotor blades. The requirement for this type of system was to improve the sectional lift-to-drag ratio by alleviating dynamic stall on the retreating blade while simultaneously reducing the transonic drag rise of the advancing blade. Both measured and computational results showed that a Variable Droop Leading Edge (VDLE) airfoil is a viable concept for application to a rotor high-lift system. Results are presented for a series of 2D compressible dynamic stall wind tunnel tests with supporting CFD results for selected test cases. These measurements and computations show a dramatic decrease in the drag and pitching moment associated with severe dynamic stall when the VDLE concept is applied to the Boeing VR-12 airfoil. Test results also show an elimination of the negative pitch damping observed in the baseline moment hysteresis curves.

Martin, P. B.; McAlister, K. W.; Chandrasekhara, M. S.; Geissler, W.

2003-01-01

187

Aerodynamic behaviour of NREL S826 airfoil at Re=100,000  

NASA Astrophysics Data System (ADS)

This paper presents wind tunnel measurements of the NREL S826 airfoil at Reynolds number Re = 100,000 for angles of attack in a range of -10° to 25° the corresponding Large Eddy Simulation (LES) for selected angles of attack. The measurements have been performed at the low speed wind tunnel located at Fluid Mechanics laboratory of the Technical University of Denmark (DTU). Lift coefficient is obtained from the forge gauge measurements while the drag is measured according to the integration of the wake profiles downstream of the airfoil. The pressure distribution is measured by a set of pressure taps on the airfoil surface. The lift and drag polars are obtained from the LES computations using DTU's inhouse CFD solver, EllipSys3D, and good agreement is found between the measurement and the simulations. At high angles of attack, the numerical computations tend to over-predict the lift coefficients, however, there is a better agreement between the drag measurements and computations. It is concluded that LES computations are able to capture the lift and drag polars as well as the pressure distribution around the airfoil with an acceptable accuracy.

Sarlak, H.; Mikkelsen, R.; Sarmast, S.; Sřrensen, J. N.

2014-06-01

188

Influence of airfoil thickness on sound generated by high-frequency gust interactions  

NASA Technical Reports Server (NTRS)

The sound radiated by interaction of a short wavelength gust with a symmetric thin airfoil is analyzed. The theory is based on a linearization of the Euler equations about the subsonic mean flow past the airfoil. The sound generation mechanism is found to be concentrated in a local region surrounding the parabolic nose of the airfoil; the size of this local region scales on the gust wavelength. At low Mach numbers, moderate values of airfoil thickness decrease the sound power, while at higher Mach numbers the sound power tends to increase with airfoil thickness. Airfoil thickness produces dramatic changes in the far field directivity. Both the sound power and the directivity are strong functions of the gust orientation.

Tsai, C. T.; Kerschen, E. J.

1992-01-01

189

Recent progress in the analysis of iced airfoils and wings  

NASA Technical Reports Server (NTRS)

Recent work on the analysis of iced airfoils and wings is described. Ice shapes for multielement airfoils and wings are computed using an extension of the LEWICE code that was developed for single airfoils. The aerodynamic properties of the iced wing are determined with an interactive scheme in which the solutions of the inviscid flow equations are obtained from a panel method and the solutions of the viscous flow equations are obtained from an inverse three-dimensional finite-difference boundary-layer method. A new interaction law is used to couple the inviscid and viscous flow solutions. The newly developed LEWICE multielement code is amplified to a high-lift configuration to calculate the ice shapes on the slat and on the main airfoil and on a four-element airfoil. The application of the LEWICE wing code to the calculation of ice shapes on a MS-317 swept wing shows good agreement with measurements. The interactive boundary-layer method is applied to a tapered iced wing in order to study the effect of icing on the aerodynamic properties of the wing at several angles of attack.

Cebeci, Tuncer; Chen, Hsun H.; Kaups, Kalle; Schimke, Sue

1992-01-01

190

Three-dimensional aerodynamic analysis of a subsonic transport high-lift configuration and comparisons with wind-tunnel test results  

NASA Technical Reports Server (NTRS)

The sizing and efficiency of an aircraft is largely determined by the performance of its high-lift system. Subsonic civil transports most often use deployable multi-element airfoils to achieve the maximum-lift requirements for landing, as well as the high lift-to-drag ratios for take-off. However, these systems produce very complex flow fields which are not fully understood by the scientific community. In order to compete in today's market place, aircraft manufacturers will have to design better high-lift systems. Therefore, a more thorough understanding of the flows associated with these systems is desired. Flight and wind-tunnel experiments have been conducted on NASA Langley's B737-100 research aircraft to obtain detailed full-scale flow measurements on a multi-element high-lift system at various flight conditions. As part of this effort, computational aerodynamic tools are being used to provide preliminary flow-field information for instrumentation development, and to provide additional insight during the data analysis and interpretation process. The purpose of this paper is to demonstrate the ability and usefulness of a three-dimensional low-order potential flow solver, PMARC, by comparing computational results with data obtained from 1/8 scale wind-tunnel tests. Overall, correlation of experimental and computational data reveals that the panel method is able to predict reasonably well the pressures of the aircraft's multi-element wing at several spanwise stations. PMARC's versatility and usefulness is also demonstrated by accurately predicting inviscid three-dimensional flow features for several intricate geometrical regions.

Edge, D. Christian; Perkins, John N.

1995-01-01

191

Aerodynamic characteristics of a propeller-powered high-lift semispan wing  

NASA Technical Reports Server (NTRS)

A small-scale semispan high-lift wing-flap system equipped under the wing with a turboprop engine assembly was tested in the LaRC 14- by 22-Foot Subsonic Tunnel. Experimental data were obtained for various propeller rotational speeds, nacelle locations, and nacelle inclinations. To isolate the effects of the high lift system, data were obtained with and without the flaps and leading-edge device. The effects of the propeller slipstream on the overall longitudinal aerodynamic characteristics of the wing-propeller assembly were examined. Test results indicated that the lift coefficient of the wing could be increased by the propeller slipstream when the rotational speed was increased and high-lift devices were deployed. Decreasing the nacelle inclination (increased pitch down) enhanced the lift performance of the system much more than varying the vertical or horizontal location of the nacelle. Furthermore, decreasing the nacelle inclination led to higher lift curve slope values, which indicated that the powered wing could sustain higher angles of attack near maximum lift performance. Any lift augmentation was accompanied by a drag penalty due to the increased wing lift.

Gentry, Garl L., Jr.; Takallu, M. A.; Applin, Zachary T.

1994-01-01

192

Design Optimization of High-Lift Configurations Using a Viscous Continuous Adjoint Method  

Microsoft Academic Search

this paper addresses the validity ofthis design methodology for the problem of high-liftdesign. Traditionally, high-lift designs have been realizedby careful wind tunnel testing. This approach isboth expensive and challenging due to the extremelycomplex nature of the flow interactions that appear.CFD analyses have recently been incorporated to thehigh-lift design process

Sangho Kim; Juan J. Alonso; Antony Jameson

2002-01-01

193

Semi-Empirical Formulas of Drag/Lift Coefficients for High Speed Rigid Body  

E-print Network

1 Semi-Empirical Formulas of Drag/Lift Coefficients for High Speed Rigid Body Manoeuvring in Water, California, USA Abstract Falling of rigid body through water column with high speed is investigated and orientation of the bomb-like rigid bodies. Using the experimental data a semi-empirical formulas for the drag/lift

Chu, Peter C.

194

Prediction of High-Lift Flows Using Turbulent Closure Models  

Microsoft Academic Search

The flow over two different multi-element airfoil configurations is computed using linear eddy viscosityturbulence models and a nonlinear explicit algebraic stress model. A subset of recently-measuredtransition locations using hot film on a McDonnell Douglas configuration is presented, and theeffect of transition location on the computed solutions is explored. Deficiencies in wake profile computationsare found to be attributable in large part

Christopher L. Rumsey; Thomas B. Gatski; Susan X. Ying; Arild Bertelrud

1998-01-01

195

Experiments in High-Lift for High-Speed Civil Transports  

NASA Technical Reports Server (NTRS)

The lecture will present experimental work pertaining to HSCT high-lift aerodynamic testing. The effects of Reynolds number and test techniques will be discussed. The performance of attached-flow and leading-edge vortex-control high-lift devices will also be presented. All of the aerodynamic data presented will be from experiments performed prior to the HSR program. The subject of airframe noise testing and its relevance to highlift testing will be discussed but no quantitative data will be presented.

Ross, James C.; Olson, Lawrence E. (Technical Monitor)

1995-01-01

196

Investigation of CAST-10-2/DOA 2 airfoil in NAE high Reynolds number two-dimensional test facility  

NASA Technical Reports Server (NTRS)

A common airfoil model with the CAST 10-2/DOA-2 profile and 228 mm (9 inches) chord length was tested. The tests performed in NAE covered the Mach numbers from 0.3 to 0.8 and Reynolds numbers from 10 to 30 million. The model was tested with transition free and with transition fixed at 5 percent chord for both the upper and the lower surfaces. The data obtained were analyzed for the effects of Reynolds number, transition fixing and Mach number. The role of the boundary layer on the displacement effect, the interaction with the shock wave and the trailing edge separation are examined. The results are summarized as follows: (1) the airfoil performance depends strongly on Reynolds number and transition fixing; (2) with transition fixed, the aerodynamic quantities such as lift, pitching moment and drag show a monotonic variation with Reynolds number; (3) with transition free, the aerodynamic quantities vary less regularly with Reynolds number and a slight parametric dependency is shown. The weak dependency is due to the compensatory effect of the forward shift of the transition position and the thinning of the turbulent boundary layer as Reynolds number increases; (4) the shock Mach number and the shock position are weakly dependent on Reynolds number; and (5) the long extent of the laminar boundary layer at transonic speeds reduces the drag appreciably at low Reynolds numbers. The drag bucket around the design Mach number can be observed below Reynolds number 15 million.

Chan, Y. Y.

1989-01-01

197

Forehead lift  

MedlinePLUS

... In most people, the cut for the forehead lift is under the hairline. If you have a high or receding hairline , you may be able to ... can form. Permanent hair loss after a forehead lift is rare. Medical ... to form excessive scars Uncontrolled high blood pressure

198

Flow structure and performance of a flexible plunging airfoil  

NASA Astrophysics Data System (ADS)

An investigation was performed with the intent of characterizing the effect of flexibility on a plunging airfoil, over a parameter space applicable to birds and flapping MAVs. The kinematics of the motion was determined using of a high speed camera, and the deformations and strains involved in the motion were examined. The vortex dynamics associated with the plunging motion were mapped out using particle image velocimetry (PIV), and categorized according to the behavior of the leading edge vortex (LEV). The development and shedding process of the LEVs was also studied, along with their flow trajectories. Results of the flexible airfoils were compared to similar cases performed with a rigid airfoil, so as to determine the effects caused by flexibility. Aerodynamic loads of the airfoils were also measured using a force sensor, and the recorded thrust, lift and power coefficients were analyzed for dependencies, as was the overall propulsive efficiency. Thrust and power coefficients were found to scale with the Strouhal number defined by the trialing edge amplitude, causing the data of the flexible airfoils to collapse down to a single curve. The lift coefficient was likewise found to scale with trailing edge Strouhal number; however, its data tended to collapse down to a linear relationship. On the other hand, the wake classification and the propulsive efficiency were more successfully scaled by the reduced frequency of the motion. The circulation of the LEV was determined in each case and the resulting data was scaled using a parameter developed for this specific study, which provided significant collapse of the data throughout the entire parameter space tested.

Akkala, James Marcus

199

Efficient simulation of incompressible viscous flow over multi-element airfoils  

NASA Technical Reports Server (NTRS)

The incompressible, viscous, turbulent flow over single and multi-element airfoils is numerically simulated in an efficient manner by solving the incompressible Navier-Stokes equations. The solution algorithm employs the method of pseudo compressibility and utilizes an upwind differencing scheme for the convective fluxes, and an implicit line-relaxation scheme. The motivation for this work includes interest in studying high-lift take-off and landing configurations of various aircraft. In particular, accurate computation of lift and drag at various angles of attack up to stall is desired. Two different turbulence models are tested in computing the flow over an NACA 4412 airfoil; an accurate prediction of stall is obtained. The approach used for multi-element airfoils involves the use of multiple zones of structured grids fitted to each element. Two different approaches are compared; a patched system of grids, and an overlaid Chimera system of grids. Computational results are presented for two-element, three-element, and four-element airfoil configurations. Excellent agreement with experimental surface pressure coefficients is seen. The code converges in less than 200 iterations, requiring on the order of one minute of CPU time on a CRAY YMP per element in the airfoil configuration.

Rogers, Stuart E.; Wiltberger, N. Lyn; Kwak, Dochan

1993-01-01

200

Efficient simulation of incompressible viscous flow over multi-element airfoils  

NASA Technical Reports Server (NTRS)

The incompressible, viscous, turbulent flow over single and multi-element airfoils is numerically simulated in an efficient manner by solving the incompressible Navier-Stokes equations. The computer code uses the method of pseudo-compressibility with an upwind-differencing scheme for the convective fluxes and an implicit line-relaxation solution algorithm. The motivation for this work includes interest in studying the high-lift take-off and landing configurations of various aircraft. In particular, accurate computation of lift and drag at various angles of attack, up to stall, is desired. Two different turbulence models are tested in computing the flow over an NACA 4412 airfoil; an accurate prediction of stall is obtained. The approach used for multi-element airfoils involves the use of multiple zones of structured grids fitted to each element. Two different approaches are compared: a patched system of grids, and an overlaid Chimera system of grids. Computational results are presented for two-element, three-element, and four-element airfoil configurations. Excellent agreement with experimental surface pressure coefficients is seen. The code converges in less than 200 iterations, requiring on the order of one minute of CPU time (on a CRAY YMP) per element in the airfoil configuration.

Rogers, Stuart E.; Wiltberger, N. Lyn; Kwak, Dochan

1992-01-01

201

Dynamic airfoil stall investigations  

NASA Technical Reports Server (NTRS)

Experimental and computational investigations of the dynamic stall phenomenon continue to attract the attention of various research groups in the major aeronautical research laboratories. There are two reasons for this continued research interest. First, the occurrence of dynamic stall on the retreating blade of helicopters imposes a severe performance limitation and thus suggests to search for ways to delay the onset of dynamic stall. Second, the lift enhancement prior to dynamic stall presents an opportunity to achieve enhanced maneuverability of fighter aircraft. A description of the major parameters affecting dynamic stall and lift and an evaluation of research efforts prior to 1988 has been given by Carr. In this paper the authors' recent progress in the development of experimental and computational methods to analyze the dynamic stall phenomena occurring on NACA 0112 airfoils is reviewed. First, the major experimental and computational approaches and results are summarized. This is followed by an assessment of our results and an outlook toward the future.

Platzer, M. F.; Chandrasekhara, M. S.; Ekaterinaris, J. A.; Carr, L. W.

1992-01-01

202

A direct-inverse method for transonic and separated flows about airfoils  

NASA Technical Reports Server (NTRS)

A direct-inverse technique and computer program called TAMSEP that can be used for the analysis of the flow about airfoils at subsonic and low transonic freestream velocities is presented. The method is based upon a direct-inverse nonconservative full potential inviscid method, a Thwaites laminar boundary layer technique, and the Barnwell turbulent momentum integral scheme; and it is formulated using Cartesian coordinates. Since the method utilizes inverse boundary conditions in regions of separated flow, it is suitable for predicting the flow field about airfoils having trailing edge separated flow under high lift conditions. Comparisons with experimental data indicate that the method should be a useful tool for applied aerodynamic analyses.

Carlson, Leland A.

1990-01-01

203

Overview of Fundamental High-Lift Research for Transport Aircraft at NASA  

NASA Technical Reports Server (NTRS)

NASA has had a long history in fundamental and applied high lift research. Current programs provide a focus on the validation of technologies and tools that will enable extremely short take off and landing coupled with efficient cruise performance, simple flaps with flow control for improved effectiveness, circulation control wing concepts, some exploration into new aircraft concepts, and partnership with Air Force Research Lab in mobility. Transport high-lift development testing will shift more toward mid and high Rn facilities at least until the question: "How much Rn is required" is answered. This viewgraph presentation provides an overview of High-Lift research at NASA.

Leavitt, L. D.; Washburn, A. E.; Wahls, R. A.

2007-01-01

204

High Lift Force with 275 Hz Wing Beat in MFI  

E-print Network

aims to create a 25 mm (wingtip to wingtip) flapping wing micro air vehicle inspired by the aerodynamics of insect flight. A key challenge is generating appropriate wing trajectories. Previous work [1] showed a lift of 506 µN at 160 Hz using feedforward control. In this paper, refinements to the MFI design including those in [2] increased wing beat frequency to 275 Hz and lift to 1400 µN using pure sinusoidal drive for a fixed benchtop experiment. We show through simplified aerodynamic models that not only do sinusoidal actuator drives produce close to maximal lift, but significantly improved wing trajectories due to non-sinusoidal actuator drives are practically unobtainable due to actuator limitations. I.

E. Steltz; S. Avadhanula; R. S. Fearing

205

Effects of grit roughness and pitch oscillations on the S810 airfoil  

SciTech Connect

An S810 airfoil model was tested in The Ohio State University Aeronautical and Astronautical Research Laboratory 3 x 5 subsonic wind tunnel under steady state and unsteady conditions. The test defined baseline conditions for steady state angles of attack from -20{degrees} to +40{degrees} and examined unsteady behavior by oscillating the model about its pitch axis for three mean angles, three frequencies, and two amplitudes. For all cases, Reynolds numbers of 0.75, 1, 1.25, and 1.5 million were used. In addition, the above conditions were repeated after the application of leading edge grit roughness (LEGR) to determine contamination effects on the airfoil performance. Baseline steady state results of the S810 testing showed a maximum lift coefficient of 1.15 at 15.2{degrees}angle of attack. The application of LEGR reduced the maximum lift coefficient by 12% and increased the 0.0085 minimum drag coefficient value by 88%. The zero lift pitching moment of -0.0286 showed a 16% reduction in magnitude to -0.0241 with LEGR applied. Data were also obtained for two pitch oscillation amplitudes: {plus_minus}5.5{degrees} and {plus_minus}10{degrees}. The larger amplitude consistently gave a higher maximum lift coefficient than the smaller amplitude and both sets of unsteady maximum lift coefficients were greater than the steady state values. Stall was delayed on the airfoil while the angle of attack was increasing, thereby causing an increase in maximum lift coefficient. A hysteresis behavior was exhibited for all the unsteady test cases. The hysteresis loops were larger for the higher reduced frequencies and for the larger amplitude oscillations. In addition to the hysteresis behavior, an unusual feature of these data were a sudden increase in the lift coefficient where the onset of stall was expected. As in the steady case, the effect of LEGR in the unsteady case was to reduce the lift coefficient at high angles of attack.

Ramsay, R.R.; Hoffman, M.J.; Gregorek, G.M. [Ohio State Univ., Columbus, OH (United States)

1996-01-01

206

Computational Fluid Dynamic simulation of airfoils in unsteady low Reynolds number flows  

NASA Astrophysics Data System (ADS)

The inherent complexity of low Reynolds number (LRN) flows and their respective viscous vortical patterns demand an accurate solution method to achieve the desired accuracy. This complicated flow field needs even more robust methods when the flow is unsteady. The flow field of unsteady airfoils and wings in LRN regime is challenging to solve and Computational Fluid Dynamics (CFD) simulations stand out as solid solution techniques in this area. This thesis is motivated by an existing rotating-flapping mechanism, whose kinematics components can be broken into pitching, plunging and a novel figure-of-eight-like flapping motion of its blades and each blade's cross section. The focus is on two-dimensional low Reynolds number (LRN) flows using Computational Fluid Dynamics (CFD) and a Finite Volume Method (FVM). As one of the targets is to simulate a pair of blades, and consequently a pair of airfoils, a mesh motion library is developed to perform rotational and translational motions of multi-body configurations. The library and its sub-routines are tested on pairs of pitching, plunging and flapping airfoils, where the moving mesh problem is performed with a significant gain in the computational time compared to other moving mesh techniques such as Laplacian smoothing algorithm. The simulations of a single airfoil under harmonic and the novel figure-of-eight-like flapping motions, respectively, are conducted within 67% and 80% time it took to obtain a steady solution using the Laplace smoothing mesh motion algorithm, while the calculated force coefficients were in reasonably close agreement. Flow fields of single unsteady airfoils under pitching, plunging and figure-of-eight flapping motions are also simulated in this thesis accompanied with extensive parametric studies. The simulations of the considered figure-of-eight flapping pattern shows that its highly inclined asymmetrical kinematics results in higher vertical lift coefficients than the existing flapping patterns in the literature, useful for stable hovering flight. The studies over paired-airfoils arrangements under pitching and plunging and the figure-of-eight flapping motion show that the airfoil-airfoil interaction affects the fluid forces noticeably. The multi-plunging analysis, for example, reveals that the maximum lift coefficient is higher than that of a single plunging airfoil, while minimum drag coefficient is lower, showing the favorable effect of airfoil-airfoil interaction in the studied multi-plunging cases.

Amiralaei, Mohammadreza

207

Aerodynamic investigations of noise-reducing high-lift systems for passenger transport aircraft.  

E-print Network

?? This diploma thesis captures the three-dimensional implementation of noise-reducing high-liftsystems. A parametric CAD model is developed for the FNG aircraft and different high-lift configurationsare… (more)

Hövelmann, Andreas

2011-01-01

208

High lift force with 275 Hz wing beat in MFI  

Microsoft Academic Search

Abstract—The Micromechanical,Flying Insect (MFI) project aims to create a 25 mm,(wingtip to wingtip) flapping wing micro air vehicle inspired by the aerodynamics,of insect flight. A key challenge is generating,appropriate,wing,trajectories. Previous work,[1] showed,a lift of 506 µN at 160 Hz using feedforward control. In this paper, refinements to the MFI design including those in [2] increased,wing,beat frequency,to 275 Hz and,lift to

Erik Steltz; Srinath Avadhanula; Ronald S. Fearing

2007-01-01

209

HIGH LIFT DEVICES When an aircraft is landing or taking off, specially high  

E-print Network

. · Delay the flow separation by controlling the behavior of the boundary layer. High Lift Device (I;2013/6/3 5 SEPARATION CONTROL AERODYNAMICS (W6-1-1) · Prevent or delay the flow separation by controlling-2-1) > SKIN FRICTION DRAG REDUCTION (I) (i) Laminar flow technology to postpone the transition from laminar

Leu, Tzong-Shyng "Jeremy"

210

The trailing edge of a pitching airfoil at high reduced frequencies  

NASA Technical Reports Server (NTRS)

Trailing edge flows are visualized for a pitching airfoil. The validity of the quasi-steady and an extension to an unsteady Kutta condition are examined. A new dynamic similarity parameter is proposed.

Poling, D. R.; Telionis, D. P.

1985-01-01

211

Lock-On to a High-Lift State with Oscillatory Forcing in a Three-Dimensional Wake Flow  

E-print Network

Lock-On to a High-Lift State with Oscillatory Forcing in a Three-Dimensional Wake Flow Kunihiko locks onto period-one and period-two high-lift states. Discussions of the ongoing work on stabilizing separated flow about these periodic high-lift states are offered. 1 Introduction Recent research efforts

Dabiri, John O.

212

NDT&E International 40 (2007) 555565 Lift-off effect in high-frequency eddy current conductivity spectroscopy  

E-print Network

NDT&E International 40 (2007) 555­565 Lift-off effect in high-frequency eddy current conductivity-off, the so-called lift-off curve, highly nonlinear, which makes it difficult to achieve accurate eddy current Elsevier Ltd. All rights reserved. Keywords: Eddy current; Conductivity; Lift-off; High frequency

Nagy, Peter B.

213

Parameter study of simplified dragonfly airfoil geometry at Reynolds number of 6000.  

PubMed

Aerodynamic study of a simplified Dragonfly airfoil in gliding flight at Reynolds numbers below 10,000 is motivated by both pure scientific interest and technological applications. At these Reynolds numbers, the natural insect flight could provide inspiration for technology development of Micro UAV's and more. Insect wings are typically characterized by corrugated airfoils. The present study follows a fundamental flow physics study (Levy and Seifert, 2009), that revealed the importance of flow separation from the first corrugation, the roll-up of the separated shear layer to discrete vortices and their role in promoting flow reattachment to the aft arc, as the leading mechanism enabling high-lift, low drag performance of the Dragonfly gliding flight. This paper describes the effect of systematic airfoil geometry variations on the aerodynamic properties of a simplified Dragonfly airfoil at Reynolds number of 6000. The parameter study includes a detailed analysis of small variations of the nominal geometry, such as corrugation placement or height, rear arc and trailing edge shape. Numerical simulations using the 2D laminar Navier-Stokes equations revealed that the flow accelerating over the first corrugation slope is followed by an unsteady pressure recovery, combined with vortex shedding. The latter allows the reattachment of the flow over the rear arc. Also, the drag values are directly linked to the vortices' magnitude. This parametric study shows that geometric variations which reduce the vortices' amplitude, as reduction of the rear cavity depth or the reduction of the rear arc and trailing edge curvature, will reduce the drag values. Other changes will extend the flow reattachment over the rear arc for a larger mean lift coefficients range; such as the negative deflection of the forward flat plate. These changes consequently reduce the drag values at higher mean lift coefficients. The detailed geometry study enabled the definition of a corrugated airfoil geometry with enhanced aerodynamic properties, such as range and endurance factors, as compared to the nominal airfoil studied in the literature. PMID:20673771

Levy, David-Elie; Seifert, Avraham

2010-10-21

214

Development of a large-scale, outdoor, ground-based test capability for evaluating the effect of rain on airfoil lift  

NASA Technical Reports Server (NTRS)

A large-scale, outdoor, ground-based test capability for acquiring aerodynamic data in a simulated rain environment was developed at the Langley Aircraft Landing Dynamics Facility (ALDF) to assess the effect of heavy rain on airfoil performance. The ALDF test carriage was modified to transport a 10-ft-chord NACA 64210 wing section along a 3000-ft track at full-scale aircraft approach speeds. An overhead rain simulation system was constructed along a 525-ft section of the track with the capability of producing simulated rain fields of 2, 10, 30, and 40 in/hr. The facility modifications, the aerodynamic testing and rain simulation capability, the design and calibration of the rain simulation system, and the operational procedures developed to minimize the effect of wind on the simulated rain field and aerodynamic data are described in detail. The data acquisition and reduction processes are also presented along with sample force data illustrating the environmental effects on data accuracy and repeatability for the 'rain-off' test condition.

Bezos, Gaudy M.; Campbell, Bryan A.

1993-01-01

215

Numerical investigation of multi-element airfoils  

NASA Technical Reports Server (NTRS)

The flow over multi-element airfoils with flat-plate lift-enhancing tabs was numerically investigated. Tabs ranging in height from 0.25 percent to 1.25 percent of the reference airfoil chord were studied near the trailing edge of the main-element. This two-dimensional numerical simulation employed an incompressible Navier-Stokes solver on a structured, embedded grid topology. New grid refinements were used to improve the accuracy of the solution near the overlapping grid boundaries. The effects of various tabs were studied at a constant Reynolds number on a two-element airfoil with a slotted flap. Both computed and measured results indicated that a tab in the main-element cove improved the maximum lift and lift-to-drag ratio relative to the baseline airfoil without a tab. Computed streamlines revealed that the additional turning caused by the tab may reduce the amount of separated flow on the flap. A three-element airfoil was also studied over a range of Reynolds numbers. For the optimized flap rigging, the computed and measured Reynolds number effects were similar. When the flap was moved from the optimum position, numerical results indicated that a tab may help to reoptimize the airfoil to within 1 percent of the optimum flap case.

Cummings, Russell M.

1993-01-01

216

Assessment of computational issues associated with analysis of high-lift systems  

NASA Technical Reports Server (NTRS)

Thin-layer Navier-Stokes calculations for wing-fuselage configurations from subsonic to hypersonic flow regimes are now possible. However, efficient, accurate solutions for using these codes for two- and three-dimensional high-lift systems have yet to be realized. A brief overview of salient experimental and computational research is presented. An assessment of the state-of-the-art relative to high-lift system analysis and identification of issues related to grid generation and flow physics which are crucial for computational success in this area are also provided. Research in support of the high-lift elements of NASA's High Speed Research and Advanced Subsonic Transport Programs which addresses some of the computational issues is presented. Finally, fruitful areas of concentrated research are identified to accelerate overall progress for high lift system analysis and design.

Balasubramanian, R.; Jones, Kenneth M.; Waggoner, Edgar G.

1992-01-01

217

S829 Airfoil; Period of Performance: 1994--1995  

SciTech Connect

A 16%-thick, natural-laminar-flow airfoil, the S829, for the tip region of 20- to 40-meter-diameter, stall-regulated, horizontal-axis wind turbines has been designed and analyzed theoretically. The two primary objectives of restrained maximum lift, insensitive to roughness, and low profile drag have been achieved. The constraints on the pitching moment and the airfoil thickness have been satisfied. The airfoil should exhibit a docile stall.

Somers, D. M.

2005-01-01

218

High Lift Force with 275 Hz Wing Beat in MFI E. Steltz, S. Avadhanula, and R.S. Fearing  

E-print Network

High Lift Force with 275 Hz Wing Beat in MFI E. Steltz, S. Avadhanula, and R.S. Fearing Department from honeybees to increase the lift force of the structure. Honeybee flight is characterized by high trajectories. Previous work [1] showed a lift of 506 µN at 160 Hz using feedforward control. In this paper

Fearing, Ron

219

Experimental Investigation of Jet Mixing of a Co-Flow Jet Airfoil  

E-print Network

Experimental Investigation of Jet Mixing of a Co-Flow Jet Airfoil B. P. E. Dano, D. Kirk and G The jet mixing of a co-flow jet (CFJ) airfoil is investigated to understand the mechanism of lift and aerodynamic forces measurements are used to reveal the insight of the CFJ airfoil mixing process. At low Ao

Zha, Gecheng

220

Experimental testing using a remotely operated flap with a 2D high lift model  

NASA Technical Reports Server (NTRS)

The problem of efficient wind tunnel testing for multi-element airfoils was first addressed by the author during a previous ASEE fellowship. A modern three element model with internal actuators to position a flap in two degrees of freedom was designed and later built. Some preliminary testing proved that the approach was viable. The purpose of this summer's work was to fully develop experimental methods including efficient data acquisition. The final goal is to develop dense data sets for both lift and drag measurements as a function of flap position for both take-off and landing configurations. The model has a span of 36 in. and chord of 18 in. and is currently being fitted for a 3 ft. x 4 ft. low speed wind tunnel. The flap was reworked to allow all pressure taps to function after initial tests showed two blocked ports. The serial method of obtaining pressures from the surface taps was found to be exceedingly slow so a new method using 12 pressure transducers and a 12 port parallel scanning valve were developed. A new automated data acquisition and control algorithm was developed using LabView software and a PC platform. Flow two-dimensionality is currently under investigation with boundary layer control by blowing; this was previously omitted for initial testing. By the end of the summer a detailed data set (uncorrected) consisting of lift coefficient versus flap position for the landing configuration should be available.

Landman, Drew

1995-01-01

221

Prediction of High-Lift Flows using Turbulent Closure Models  

NASA Technical Reports Server (NTRS)

The flow over two different multi-element airfoil configurations is computed using linear eddy viscosity turbulence models and a nonlinear explicit algebraic stress model. A subset of recently-measured transition locations using hot film on a McDonnell Douglas configuration is presented, and the effect of transition location on the computed solutions is explored. Deficiencies in wake profile computations are found to be attributable in large part to poor boundary layer prediction on the generating element, and not necessarily inadequate turbulence modeling in the wake. Using measured transition locations for the main element improves the prediction of its boundary layer thickness, skin friction, and wake profile shape. However, using measured transition locations on the slat still yields poor slat wake predictions. The computation of the slat flow field represents a key roadblock to successful predictions of multi-element flows. In general, the nonlinear explicit algebraic stress turbulence model gives very similar results to the linear eddy viscosity models.

Rumsey, Christopher L.; Gatski, Thomas B.; Ying, Susan X.; Bertelrud, Arild

1997-01-01

222

High-precision position control of a heavy-lift manipulator in a dynamic environment  

E-print Network

This thesis considers the control of a heavy-lift serial manipulator operating on the deck of a large ocean vessel. This application presents a unique challenge for high- precision control because the system must contend ...

Garretson, Justin R. (Justin Richard)

2005-01-01

223

S822 and S823 Airfoils: October 1992--December 1993  

SciTech Connect

A family of thick airfoils for 3- to 10-meter, stall-regulated, horizontal-axis wind turbines, the S822 and S823, has been designed and analyzed theoretically. The primary objectives of restrained maximum lift, insensitive to roughness, and low profile have been achieved. The constraints on the pitching moments and airfoil thicknesses have been satisfied.

Somers, D. M.

2005-01-01

224

Design and validation of a high-lift low-pressure turbine blade  

Microsoft Academic Search

This dissertation is a design and validation study of the high-lift low-pressure turbine (LPT) blade designated L2F. High-lift LPTs offer the promise of reducing the blade count in modern gas turbine engines. Decreasing the blade count can reduce development and maintenance costs and the weight of the engine, but care must be taken in order to maintain turbine section performance

Mark Wayne McQuilling

2007-01-01

225

Aerodynamic Characteristics of a Propeller-Powered High-Lift Semispan Wing  

Microsoft Academic Search

A smal l-scale semispan high-lift wing-flap system equipped underthe wing with a turboprop engine assemb ly was tested in the Langley14- by 22-Foot Subsonic Tunnel. Experimental data were obtainedfor various propeller rotational speeds, nacelle locations, and nacelleinclinations. To isolate the effects of the high-lift system, data wereobtained with and without the flaps and leading-edge device. The effectsof the propeller slipstream

Garl L. Gentry; M. A. Takallu; Propeller-powered High-lift; Semispan Wing

1992-01-01

226

Identification of airfoil characteristics for optimum wind turbine performance / b  

E-print Network

6. The effect of camber on turbine performance, 18 7. The effect of maximum lift on turbine performance. . . . . . 19 Combined effect of both maximum lift and camber on turbine performance. 20 9. Elimination of twist effects. 21 10. Operating...) airfoil angle of attack airfoil twist angle angle between W and plane of rotation, ($ = u + 8) local solidity, ratio of segment area to total area swept out by rotor INTRODUCTION Haximum power output over a wide range of operating conditions...

Miller, Leonard Scott

2012-06-07

227

Effects of grit roughness and pitch oscillations on the NACA 4415 airfoil  

SciTech Connect

A NACA 4415 airfoil model was tested in The Ohio State University Aeronautical and Astronautical Research Laboratory 3 x 5 subsonic wind tunnel under steady state and unsteady conditions. The test defined baseline conditions for steady state angles of attack from {minus}10{degree} to +40{degree} and examined unsteady behavior by oscillating the model about its pitch axis for three mean angles, three frequencies, and two amplitudes. For all cases, Reynolds numbers of 0.75, 1, 1.25, and 1.5 million were used. In addition, these were repeated after the application of leading edge grit roughness (LEGR) to determine contamination effects on the airfoil performance. Steady state results of the NACA 4415 testing at Reynolds number of 1.25 million showed a baseline maximum lift coefficient of 1.30 at 12.3{degree} angle of attack. The application of LEGR reduced the maximum lift coefficient by 20% and increased the 0.0090 minimum drag coefficient value by 62%. The zero lift pitching moment of {minus}0.0967 showed a 13% reduction in magnitude to {minus}0.0842 with LEGR applied. Data were also obtained for two pitch oscillation amplitudes: {+-}5.5{degree} and {+-}10{degree}. The larger amplitude consistently gave a higher maximum lift coefficient than the smaller amplitude, and both unsteady maximum lift coefficients were greater than the steady state values. Stall is delayed on the airfoil while the angle of attack is increasing, thereby causing an increase in maximum lift coefficient. A hysteresis behavior was exhibited for all the unsteady test cases. The hysteresis loops were larger for the higher reduced frequencies and for the larger amplitude oscillations. As in the steady case, the effect of LEGR in the unsteady case was to reduce the lift coefficient at high angles of attack. In addition, with LEGR, the hysteresis behavior persisted into lower angles of attack than for the clean case.

Hoffmann, M.J.; Reuss Ramsay, R.; Gregorek, G.M. [Ohio State Univ., Columbus, OH (United States)

1996-07-01

228

Demonstration of a Low-Lift Heat Pump for High-Power Spacecraft Thermal Control  

Microsoft Academic Search

This paper describes the development and demonstration of a prototype low-lift heat pump for high-power spacecraft thermal control The low-lift heat pump was designed to provide 25 kW of cooling at 303 K and transport this waste heat to a radiator for heat rejection. To accomplish this, a demonstration heat pump with an evaporation temperature of 298 K and a

Lawrence R. Grzyll

2006-01-01

229

Lifting-based invertible motion adaptive transform (LIMAT) framework for highly scalable video compression  

Microsoft Academic Search

We propose a new framework for highly scalable video compression, using a lifting-based invertible motion adaptive transform (LIMAT). We use motion-compensated lifting steps to implement the temporal wavelet transform, which preserves invertibility, regardless of the motion model. By contrast, the invertibility requirement has restricted previous approaches to either block-based or global motion compensation. We show that the proposed framework effectively

Andrew Secker; David S. Taubman

2003-01-01

230

Reynolds-averaged Navier-Stokes investigation of high-lift low-pressure turbine blade aerodynamics at low Reynolds number  

NASA Astrophysics Data System (ADS)

Design trends for the low-pressure turbine (LPT) section of modern gas turbine engines include increasing the loading per airfoil, which promises a decreased airfoil count resulting in reduced manufacturing and operating costs. Accurate Reynolds-Averaged Navier-Stokes predictions of separated boundary layers and transition to turbulence are needed, as the lack of an economical and reliable computational model has contributed to this high-lift concept not reaching its full potential. Presented here for what is believed to be the first time applied to low-Re computations of high-lift linear cascade simulations is the Abe-Kondoh-Nagano (AKN) linear low-Re two-equation turbulence model which utilizes the Kolmogorov velocity scale for improved predictions of separated boundary layers. A second turbulence model investigated is the Kato-Launder modified version of the AKN, denoted MPAKN, which damps turbulent production in highly strained regions of flow. Fully Laminar solutions have also been calculated in an effort to elucidate the transitional quality of the turbulence model solutions. Time accurate simulations of three modern high-lift blades at a Reynolds number of 25,000 are compared to experimental data and higher-order computations in order to judge the accuracy of the results, where it is shown that the RANS simulations with highly refined grids can produce both quantitatively and qualitatively similar separation behavior as found in experiments. In particular, the MPAKN model is shown to predict the correct boundary layer behavior for all three blades, and evidence of transition is found through inspection of the components of the Reynolds Stress Tensor, spectral analysis, and the turbulence production parameter. Unfortunately, definitively stating that transition is occurring becomes an uncertain task, as similar evidence of the transition process is found in the Laminar predictions. This reveals that boundary layer reattachment may be a result of laminar vortex shedding interaction with the blade surface, or that application of Laminar solvers with highly refined grids may be valid for investigations of transitional flow. It is recommended that this be studied in the future along with further studies of the turbulence models presented, which have proved to be worthy of additional study in the present application.

Arko, Bryan M.

231

Transonic Flow Past a Symmetrical Airfoil at High Angle of Attack  

NASA Technical Reports Server (NTRS)

The results of an experimental investigation of shock-induced stall and leading-edge stall on a 64A010 airfoil section are presented. Advanced nonintrusive techniques - laser velocimetry and holographic interferometry - were used in characterizing the inviscid and viscous flow regions. The measurements include Mach contours of the inviscid now regions, and mean velocity, flow direction, and Reynolds shear stress profiles in the separated regions. The experimental observations of this study are relevant to efforts to improve surface-pressure prediction methods for airfoils at or near stall.

Johnson, D. A.; Bachalo, W. D.; Owen, F. K.

1981-01-01

232

Design and Experimental Results for the S825 Airfoil; Period of Performance: 1998-1999  

SciTech Connect

A 17%-thick, natural-laminar-flow airfoil, the S825, for the 75% blade radial station of 20- to 40-meter, variable-speed and variable-pitch (toward feather), horizontal-axis wind turbines has been designed and analyzed theoretically and verified experimentally in the NASA Langley Low-Turbulence Pressure Tunnel. The two primary objectives of high maximum lift, relatively insensitive to roughness and low-profile drag have been achieved. The airfoil exhibits a rapid, trailing-edge stall, which does not meet the design goal of a docile stall. The constraints on the pitching moment and the airfoil thickness have been satisfied. Comparisons of the theoretical and experimental results generally show good agreement.

Somers, D. M.

2005-01-01

233

Prediction of longitudinal aerodynamic characteristics of STOL configurations with externally blown high lift devices  

NASA Technical Reports Server (NTRS)

A theoretical method has been developed to predict the longitudinal aerodynamic characteristics of engine-wing-flap combinations with externally blown flaps (EBF) and upper surface blowing (USB) high lift devices. Potential flow models of the lifting surfaces and the jet wake are combined to calculate the induced interference of the engine wakes on the lifting surfaces. The engine wakes may be circular, elliptic, or rectangular cross-sectional jets, and the lifting surfaces are comprised of a wing with multiple-slotted trailing-edge flaps or a deflected trailing-edge Coanda surface. Results are presented showing comparisons of measured and predicted forces, pitching moments, span-load distributions, and flow fields.

Mendenhall, M. R.; Spangler, S. B.

1976-01-01

234

Design and experimental results for the S805 airfoil  

SciTech Connect

An airfoil for horizontal-axis wind-turbine applications, the S805, has been designed and analyzed theoretically and verified experimentally in the low-turbulence wind tunnel of the Delft University of Technology Low Speed Laboratory, The Netherlands. The two primary objectives of restrained maximum lift, insensitive to roughness, and low profile drag have been achieved. The airfoil also exhibits a docile stall. Comparisons of the theoretical and experimental results show good agreement. Comparisons with other airfoils illustrate the restrained maximum lift coefficient as well as the lower profile-drag coefficients, thus confirming the achievement of the primary objectives.

Somers, D.M. [Airfoils, Inc., State College, PA (United States)

1997-01-01

235

Design and experimental results for the S809 airfoil  

SciTech Connect

A 21-percent-thick, laminar-flow airfoil, the S809, for horizontal-axis wind-turbine applications, has been designed and analyzed theoretically and verified experimentally in the low-turbulence wind tunnel of the Delft University of Technology Low Speed Laboratory, The Netherlands. The two primary objectives of restrained maximum lift, insensitive to roughness, and low profile drag have been achieved. The airfoil also exhibits a docile stall. Comparisons of the theoretical and experimental results show good agreement. Comparisons with other airfoils illustrate the restrained maximum lift coefficient as well as the lower profile-drag coefficients, thus confirming the achievement of the primary objectives.

Somers, D.M. [Airfoils, Inc., State College, PA (United States)] [Airfoils, Inc., State College, PA (United States)

1997-01-01

236

Large-eddy simulation of flow around an airfoil on a structured mesh  

NASA Technical Reports Server (NTRS)

The diversity of flow characteristics encountered in a flow over an airfoil near maximum lift taxes the presently available statistical turbulence models. This work describes our first attempt to apply the technique of large-eddy simulation to a flow of aeronautical interest. The challenge for this simulation comes from the high Reynolds number of the flow as well as the variety of flow regimes encountered, including a thin laminar boundary layer at the nose, transition, boundary layer growth under adverse pressure gradient, incipient separation near the trailing edge, and merging of two shear layers at the trailing edge. The flow configuration chosen is a NACA 4412 airfoil near maximum lift. The corresponding angle of attack was determined independently by Wadcock (1987) and Hastings & Williams (1984, 1987) to be close to 12 deg. The simulation matches the chord Reynolds number U(sub infinity)c/v = 1.64 x 10(exp 6) of Wadcock's experiment.

Kaltenbach, Hans-Jakob; Choi, Haecheon

1995-01-01

237

Design Methodology for Multi-Element High-Lift Systems on Subsonic Civil Transport Aircraft  

NASA Technical Reports Server (NTRS)

The choice of a high-lift system is crucial in the preliminary design process of a subsonic civil transport aircraft. Its purpose is to increase the allowable aircraft weight or decrease the aircraft's wing area for a given takeoff and landing performance. However, the implementation of a high-lift system into a design must be done carefully, for it can improve the aerodynamic performance of an aircraft but may also drastically increase the aircraft empty weight. If designed properly, a high-lift system can improve the cost effectiveness of an aircraft by increasing the payload weight for a given takeoff and landing performance. This is why the design methodology for a high-lift system should incorporate aerodynamic performance, weight, and cost. The airframe industry has experienced rapid technological growth in recent years which has led to significant advances in high-lift systems. For this reason many existing design methodologies have become obsolete since they are based on outdated low Reynolds number wind-tunnel data and can no longer accurately predict the aerodynamic characteristics or weight of current multi-element wings. Therefore, a new design methodology has been created that reflects current aerodynamic, weight, and cost data and provides enough flexibility to allow incorporation of new data when it becomes available.

Pepper, R. S.; vanDam, C. P.

1996-01-01

238

Active Control of Flow Separation Over an Airfoil  

NASA Technical Reports Server (NTRS)

Designing an aircraft without conventional control surfaces is of interest to aerospace community. In this direction, smart actuator devices such as synthetic jets have been proposed to provide aircraft maneuverability instead of control surfaces. In this article, a numerical study is performed to investigate the effects of unsteady suction and blowing on airfoils. The unsteady suction and blowing is introduced at the leading edge of the airfoil in the form of tangential jet. Numerical solutions are obtained using Reynolds-Averaged viscous compressible Navier-Stokes equations. Unsteady suction and blowing is investigated as a means of separation control to obtain lift on airfoils. The effect of blowing coefficients on lift and drag is investigated. The numerical simulations are compared with experiments from the Tel-Aviv University (TAU). These results indicate that unsteady suction and blowing can be used as a means of separation control to generate lift on airfoils.

Ravindran, S. S.

1999-01-01

239

Airfoil self-noise and prediction  

NASA Technical Reports Server (NTRS)

A prediction method is developed for the self-generated noise of an airfoil blade encountering smooth flow. The prediction methods for the individual self-noise mechanisms are semiempirical and are based on previous theoretical studies and data obtained from tests of two- and three-dimensional airfoil blade sections. The self-noise mechanisms are due to specific boundary-layer phenomena, that is, the boundary-layer turbulence passing the trailing edge, separated-boundary-layer and stalled flow over an airfoil, vortex shedding due to laminar boundary layer instabilities, vortex shedding from blunt trailing edges, and the turbulent vortex flow existing near the tip of lifting blades. The predictions are compared successfully with published data from three self-noise studies of different airfoil shapes. An application of the prediction method is reported for a large scale-model helicopter rotor, and the predictions compared well with experimental broadband noise measurements. A computer code of the method is given.

Brooks, Thomas F.; Pope, D. Stuart; Marcolini, Michael A.

1989-01-01

240

Airfoil self-noise and prediction  

NASA Astrophysics Data System (ADS)

A prediction method is developed for the self-generated noise of an airfoil blade encountering smooth flow. The prediction methods for the individual self-noise mechanisms are semiempirical and are based on previous theoretical studies and data obtained from tests of two- and three-dimensional airfoil blade sections. The self-noise mechanisms are due to specific boundary-layer phenomena, that is, the boundary-layer turbulence passing the trailing edge, separated-boundary-layer and stalled flow over an airfoil, vortex shedding due to laminar boundary layer instabilities, vortex shedding from blunt trailing edges, and the turbulent vortex flow existing near the tip of lifting blades. The predictions are compared successfully with published data from three self-noise studies of different airfoil shapes. An application of the prediction method is reported for a large scale-model helicopter rotor, and the predictions compared well with experimental broadband noise measurements. A computer code of the method is given.

Brooks, Thomas F.; Pope, D. Stuart; Marcolini, Michael A.

1989-07-01

241

Overview and Summary of the Second AIAA High Lift Prediction Workshop  

NASA Technical Reports Server (NTRS)

The second AIAA CFD High-Lift Prediction Workshop was held in San Diego, California, in June 2013. The goals of the workshop continued in the tradition of the first high-lift workshop: to assess the numerical prediction capability of current-generation computational fluid dynamics (CFD) technology for swept, medium/high-aspect-ratio wings in landing/takeoff (high-lift) configurations. This workshop analyzed the flow over the DLR-F11 model in landing configuration at two different Reynolds numbers. Twenty-six participants submitted a total of 48 data sets of CFD results. A variety of grid systems (both structured and unstructured) were used. Trends due to grid density and Reynolds number were analyzed, and effects of support brackets were also included. This paper analyzes the combined results from all workshop participants. Comparisons with experimental data are made. A statistical summary of the CFD results is also included.

Rumsey, Christopher L.; Slotnick, Jeffrey P.

2014-01-01

242

Shape optimization of single- and two-element airfoils on multiblock grids  

NASA Technical Reports Server (NTRS)

A multiblock, discrete sensitivity analysis method is used to couple a direct optimization method and a flow analysis method. The domain is divided into smaller subdomains for which the sensitivities are obtained separately. Then, an effective sensitivity equation is solved to complete the coupling of all the sensitivity information. The flow analysis is based on the thin-layer Navier-Stokes equations solved by an implicit, upwind-biased, finite-volume method. The method of feasible directions is used for the present gradient-based optimization approach. First, a transonic airfoil is optimized to investigate the behavior of the method in highly nonlinear flows as well as the effect of different blocking strategies on the procedure. A supercritical airfoil is produced from an initially symmetric airfoil with multiblocking affecting the path but not the final shape. Secondly, a two-element airfoil is shape optimized in subsonic flow to demonstrate the present method's capability of shaping aerodynamically interfering elements simultaneously. For a very low and a very high Reynolds number cases, the shape of the main airfoil and the flap are optimized to yield improved lift-to-drag ratios.

Lacasse, James M.; Baysal, Oktay

1995-01-01

243

Scale Effect on Clark Y Airfoil Characteristics from NACA Full-Scale Wind-Tunnel Tests  

NASA Technical Reports Server (NTRS)

This report presents the results of wind tunnel tests conducted to determine the aerodynamic characteristics of the Clark Y airfoil over a large range of Reynolds numbers. Three airfoils of aspect ratio 6 and with 4, 6, and 8 foot chords were tested at velocities between 25 and 118 miles per hour, and the characteristics were obtained for Reynolds numbers (based on the airfoil chord) in the range between 1,000,000 and 9,000,000 at the low angles of attack, and between 1,000,000 and 6,000,000 at maximum lift. With increasing Reynolds number the airfoil characteristics are affected in the following manner: the drag at zero lift decreases, the maximum lift increases, the slope of the lift curve increases, the angle of zero lift occurs at smaller negative angles, and the pitching moment at zero lift does not change appreciably.

Silverstein, Abe

1935-01-01

244

Laminar-flow airfoil  

NASA Technical Reports Server (NTRS)

An airfoil having a fore airfoil element, an aft airfoil element, and a slot region in between them. These elements induce laminar flow over substantially all of the fore airfoil element and also provide for laminar flow in at least a portion of the slot region. The method of the invention is one for inducing natural laminar flow over an airfoil. In the method, a fore airfoil element, having a leading and trailing edge, and an aft airfoil element define a slot region. Natural laminar flow is induced over substantially all of the fore airfoil element, by inducing the pressures on both surfaces of the fore airfoil element to decrease to a location proximate the trailing edge of the fore airfoil element using pressures created by the aft airfoil element.

Somers, Dan M. (Inventor)

2005-01-01

245

CFD Computations for a Generic High-Lift Configuration Using TetrUSS  

NASA Technical Reports Server (NTRS)

Assessment of the accuracy of computational results for a generic high-lift trapezoidal wing with a single slotted flap and slat is presented. The paper is closely aligned with the focus of the 1st AIAA CFD High Lift Prediction Workshop (HiLiftPW-1) which was to assess the accuracy of CFD methods for multi-element high-lift configurations. The unstructured grid Reynolds-Averaged Navier-Stokes solver TetrUSS/USM3D is used for the computational results. USM3D results are obtained assuming fully turbulent flow using the Spalart-Allmaras (SA) and Shear Stress Transport (SST) turbulence models. Computed solutions have been obtained at seven different angles-of-attack ranging from 6 -37 . Three grids providing progressively higher grid resolution are used to quantify the effect of grid resolution on the lift, drag, pitching moment, surface pressure and stall angle. SA results, as compared to SST results, exhibit better agreement with the measured data. However, both turbulence models under-predict upper surface pressures near the wing tip region.

Pandya, Mohagna J.; Abdol-Hamid, Khaled S.; Parlette, Edward B.

2011-01-01

246

Large-scale Parallel Unstructured Mesh Computations for 3D High-lift Analysis  

NASA Technical Reports Server (NTRS)

A complete "geometry to drag-polar" analysis capability for the three-dimensional high-lift configurations is described. The approach is based on the use of unstructured meshes in order to enable rapid turnaround for complicated geometries that arise in high-lift configurations. Special attention is devoted to creating a capability for enabling analyses on highly resolved grids. Unstructured meshes of several million vertices are initially generated on a work-station, and subsequently refined on a supercomputer. The flow is solved on these refined meshes on large parallel computers using an unstructured agglomeration multigrid algorithm. Good prediction of lift and drag throughout the range of incidences is demonstrated on a transport take-off configuration using up to 24.7 million grid points. The feasibility of using this approach in a production environment on existing parallel machines is demonstrated, as well as the scalability of the solver on machines using up to 1450 processors.

Mavriplis, Dimitri J.; Pirzadeh, S.

1999-01-01

247

3-D High-Lift Flow-Physics Experiment - Transition Measurements  

NASA Technical Reports Server (NTRS)

An analysis of the flow state on a trapezoidal wing model from the NASA 3-D High Lift Flow Physics Experiment is presented. The objective of the experiment was to characterize the flow over a non-proprietary semi-span three-element high-lift configuration to aid in assessing the state of the art in the computation of three-dimensional high-lift flows. Surface pressures and hot-film sensors are used to determine the flow conditions on the slat, main, and flap. The locations of the attachments lines and the values of the attachment line Reynolds number are estimated based on the model surface pressures. Data from the hot-films are used to determine if the flow is laminar, transitional, or turbulent by examining the hot-film time histories, statistics, and frequency spectra.

McGinley, Catherine B.; Jenkins, Luther N.; Watson, Ralph D.; Bertelrud, Arild

2005-01-01

248

Large-Scale Parallel Unstructured Mesh Computations for 3D High-Lift Analysis  

NASA Technical Reports Server (NTRS)

A complete "geometry to drag-polar" analysis capability for three-dimensional high-lift configurations is described. The approach is based on the use of unstructured meshes in order to enable rapid turnaround for complicated geometries which arise in high-lift con gurations. Special attention is devoted to creating a capability for enabling analyses on highly resolved grids. Unstructured meshes of several million vertices are initially generated on a work-station, and subsequently refined on a supercomputer. The flow is solved on these refined meshes on large parallel computers using an unstructured agglomeration multigrid algorithm. Good prediction of lift and drag throughout the range of incidences is demonstrated on a transport take-off configuration using up to 24.7 million grid points. The feasibility of using this approach in a production environment on existing parallel machines is demonstrated, as well as the scalability of the solver on machines using up to 1450 processors.

Mavriplis, D. J.; Pirzadeh, S.

1999-01-01

249

Unstructured Grid Generation for Complex 3D High-Lift Configurations  

NASA Technical Reports Server (NTRS)

The application of an unstructured grid methodology on a three-dimensional high-lift configuration is presented. The focus of this paper is on the grid generation aspect of an integrated effort for the development of an unstructured-grid computational fluid dynamics (CFD) capability at the NASA Langley Research Center. The meshing approach is based on tetrahedral grids generated by the advancing-front and the advancing-layers procedures. The capability of the method for solving high-lift problems is demonstrated on an aircraft model referred to as the energy efficient transport configuration. The grid generation issues, including the pros and cons of the present approach, are discussed in relation to the high-lift problems. Limited viscous flow results are presented to demonstrate the viability of the generated grids. A corresponding Navier-Stokes solution capability, along with further computations on the present grid, is presented in a companion SAE paper.

Pirzadeh, Shahyar Z.

1999-01-01

250

Large-Scale Parallel Unstructured Mesh Computations for 3D High-Lift Analysis  

NASA Technical Reports Server (NTRS)

A complete "geometry to drag-polar" analysis capability for three-dimensional high-lift configurations is described. The approach is based on the use of unstructured meshes in order to enable rapid turnaround for complicated geometries which arise in high-lift configurations. Special attention is devoted to creating a capability for enabling analyses on highly resolved grids. Unstructured meshes of several million vertices are initially generated on a work-station, and subsequently refined on a supercomputer. The flow is solved on these refined meshes on large parallel computers using an unstructured agglomeration multigrid algorithm. Good prediction of lift and drag throughout the range of incidences is demonstrated on a transport take-off configuration using up to 24.7 million grid points. The feasibility of using this approach in a production environment on existing parallel machines is demonstrated, as well as the scalability of the solver on machines using up to 1450 processors.

Mavriplis, D. J.; Pirzadeh, S.

1999-01-01

251

Effects of a trapped vortex cell on a thick wing airfoil  

NASA Astrophysics Data System (ADS)

The effects of a trapped vortex cell (TVC) on the aerodynamic performance of a NACA0024 wing model were investigated experimentally at Re = 106 and 6.67× 105. The static pressure distributions around the model and the wake velocity profiles were measured to obtain lift and drag coefficients, for both the clean airfoil and the controlled configurations. Suction was applied in the cavity region to stabilize the trapped vortex. For comparison, a classical boundary layer suction configuration was also tested. The drag coefficient curve of the TVC-controlled airfoil showed sharp discontinuities and bifurcative behavior, generating two drag modes. A strong influence of the angle of attack, the suction rate and the Reynolds number on the drag coefficient was observed. With respect to the clean airfoil, the control led to a drag reduction only if the suction was high enough. Compared to the classical boundary layer suction configuration, the drag reduction was higher for the same amount of suction only in a specific range of incidence, i.e., ? = -2° to ? = 6° and only for the higher Reynolds number. For all the other conditions, the classical boundary layer suction configuration gave better drag performances. Moderate increments of lift were observed for the TVC-controlled airfoil at low incidence, while a 20% lift enhancement was observed in the stall region with respect to the baseline. However, the same lift increments were also observed for the classical boundary layer suction configuration. Pressure fluctuation measurements in the cavity region suggested a very complex interaction of several flow features. The two drag modes were characterized by typical unsteady phenomena observed in rectangular cavity flows, namely the shear layer mode and the wake mode.

Lasagna, Davide; Donelli, Raffaele; de Gregorio, Fabrizio; Iuso, Gaetano

2011-11-01

252

Aerodynamic Effects Caused by Icing of an Unswept NACA 65A004 Airfoil  

NASA Technical Reports Server (NTRS)

The effects of ice formations on the section lift, drag, and pitching-moment coefficients of an unswept NACA 65A004 airfoil section of 6-foot chord were studied.. The magnitude of the aerodynamic penalties was primarily a function of the shape and size of the ice formation near the leading edge of the airfoil. The exact size and shape of the ice formations were determined photographically and found to be complex functions of the operating and icing conditions. In general, icing of the airfoil at angles of attack less than 40 caused large increases in section drag coefficients (as much as 350 percent in 8 minutes of heavy glaze icing), reductions in section lift coefficients (up to 13 percent), and changes in the pitching-moment coefficient from diving toward climbing moments. At angles of attack greater than 40 the aerodynamic characteristics depended mainly on the ice type. The section drag coefficients generally were reduced by the addition of rime ice (by as much as 45 percent in 8 minutes of icing). In glaze icing, however, the drag increased at these angles of attack. The section lift coefficients were variably affected by rime-ice formations; however, in glaze icing, lift increases at high angles of attack amounted to as much as 9 percent for an icing time of 8 minutes. Pitching-moment-coefficient changes in icing conditions were somewhat erratic and depended on the icing condition. Rotation of the iced airfoil to angles of attack other than that at which icing occurred caused sufficiently large changes in the pitching-moment coefficient that, in flight, rapid corrections in trim might be required in order to avoid a hazardous situation.

Gray, Vernon H.; vonGlahn, Uwe H.

1958-01-01

253

1999 NASA High-Speed Research Program Aerodynamic Performance Workshop. Volume 2; High Lift  

NASA Technical Reports Server (NTRS)

The High-Speed Research Program sponsored the NASA High-Speed Research Program Aerodynamic Performance Review on February 8-12, 1999 in Anaheim, California. The review was designed to bring together NASA and industry High-Speed Civil Transport (HSCT) Aerodynamic Performance technology development participants in areas of: Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization) and High-Lift. The review objectives were to: (1) report the progress and status of HSCT aerodynamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among the scientist and engineers working HSCT aerodynamics. The HSR AP Technical Review was held simultaneously with the annual review of the following airframe technology areas: Materials and Structures, Environmental Impact, Flight Deck, and Technology Integration Thus, a fourth objective of the Review was to promote synergy between the Aerodynamic Performance technology area and the other technology areas within the airframe element of the HSR Program. This Volume 2/Part 1 publication presents the High-Lift Configuration Development session.

Hahne, David E. (Editor)

1999-01-01

254

High lift function of the pteroid bone and forewing of pterosaurs  

PubMed Central

The pteroid bone is a rod-like element found only in pterosaurs, the flying reptiles of the Mesozoic. It articulated at the wrist, and supported a membranous forewing in front of the inner part of the wing spar. The function of this bone, particularly its orientation, has been much debated. It is widely believed that it pointed towards the body, and that the forewing was relatively narrow. An alternative hypothesis states that it was directed forwards during flight, resulting in a much broader forewing that acted as a leading edge flap. We tested scale models in a wind tunnel to determine the aerodynamic consequences of these conflicting hypotheses, and found that performance is greatly improved if the pteroid is directed forwards: the lift?:?drag ratios are superior and the maximum lift is exceptionally high in comparison with conventional aerofoils. This high lift capability may have enabled even the largest pterosaurs to take off and land without difficulty. PMID:16519243

Wilkinson, Matthew T; Unwin, David M; Ellington, Charles P

2005-01-01

255

Advanced modelling of bird strike on high lift devices using hybrid Eulerian–Lagrangian formulation  

Microsoft Academic Search

The work presented in this paper deals with application of explicit finite element analyses in order to predict bird strike induced impact damage on high lift devices of typical large transport aircraft. The hybrid Eulerian–Lagrangian finite element formulation has been applied as to efficiently model the impact of a highly deformable object on an inboard flap structural model. As structural

I. Smojver; D. Ivan?evi?

256

1998 NASA High-Speed Research Program Aerodynamic Performance Workshop. Volume 2; High Lift  

NASA Technical Reports Server (NTRS)

NASA's High-Speed Research Program sponsored the 1998 Aerodynamic Performance Technical Review on February 9-13, in Los Angeles, California. The review was designed to bring together NASA and industry High-Speed Civil Transport (HSCT) Aerodynamic Performance technology development participants in areas of Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization), High-Lift, and Flight Controls. The review objectives were to (1) report the progress and status of HSCT aerodynamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among the scientists and engineers working HSCT aerodynamics. In particular, single- and multi-point optimized HSCT configurations, HSCT high-lift system performance predictions, and HSCT simulation results were presented along with executive summaries for all the Aerodynamic Performance technology areas. The HSR Aerodynamic Performance Technical Review was held simultaneously with the annual review of the following airframe technology areas: Materials and Structures, Environmental Impact, Flight Deck, and Technology Integration. Thus, a fourth objective of the Review was to promote synergy between the Aerodynamic Performance technology area and the other technology areas of the HSR Program.

McMillin, S. Naomi (Editor)

1999-01-01

257

1999 NASA High-Speed Research Program Aerodynamic Performance Workshop. Volume 2; High Lift  

NASA Technical Reports Server (NTRS)

NASA's High-Speed Research Program sponsored the 1999 Aerodynamic Performance Technical Review on February 8-12, 1999 in Anaheim, California. The review was designed to bring together NASA and industry High-Speed Civil Transport (HSCT) Aerodynamic Performance technology development participants in the areas of Configuration Aerodynamics (transonic and supersonic cruise drag prediction and minimization), High Lift, and Flight Controls. The review objectives were to (1) report the progress and status of HSCT aerodynamic performance technology development; (2) disseminate this technology within the appropriate technical communities; and (3) promote synergy among die scientists and engineers working on HSCT aerodynamics. In particular, single and midpoint optimized HSCT configurations, HSCT high-lift system performance predictions, and HSCT simulation results were presented, along with executive summaries for all the Aerodynamic Performance technology areas. The HSR Aerodynamic Performance Technical Review was held simultaneously with the annual review of the following airframe technology areas: Materials and Structures, Environmental Impact, Flight Deck, and Technology Integration. Thus, a fourth objective of the Review was to promote synergy between the Aerodynamic Performance technology area and the other technology areas of the HSR Program. This Volume 2/Part 2 publication covers the tools and methods development session.

Hahne, David E. (Editor)

1999-01-01

258

American Institute of Aeronautics and Astronautics Stall Suppression of a Low-Reynolds-Number Airfoil with a  

E-print Network

-Reynolds-Number Airfoil with a Dynamic Burst Control Plate Travis Grager,1 Alric Rothmayer,2 and Hui Hu3 ( ) Department to investigate the use of a dynamic burst control plate to suppress stall on a NACA 0012 airfoil by preventing burst control plate and increase the lift performance of the airfoil. Nomenclature AR = aspect ratio (b

Hu, Hui

259

An isolated high step-up forward\\/flyback active-clamp converter with output voltage lift  

Microsoft Academic Search

This paper presents an isolated high step-up forward\\/flyback active-clamp converter with output voltage lift. In order to obtain high step-up voltage gain, the output voltage lift is adopted. The characteristics of the output voltage lift are similar to the forward converter in the charging mode and the flyback converter in the discharging mode. The active-clamp circuit is employed to recycle

P. H. Kuo; T. J. Liang; K. C. Tseng; J. F. Chen; S. M. Chen

2010-01-01

260

Simplified dragonfly airfoil aerodynamics at Reynolds numbers below 8000  

NASA Astrophysics Data System (ADS)

Effective aerodynamics at Reynolds numbers lower than 10 000 is of great technological interest and a fundamental scientific challenge. The current study covers a Reynolds number range of 2000-8000. At these Reynolds numbers, natural insect flight could provide inspiration for technology development. Insect wings are commonly characterized by corrugated airfoils. In particular, the airfoil of the dragonfly, which is able to glide, can be used for two-dimensional aerodynamic study of fixed rigid wings. In this study, a simplified dragonfly airfoil is numerically analyzed in a steady free-stream flow. The aerodynamic performance (such as mean and fluctuating lift and drag), are first compared to a "traditional" low Reynolds number airfoil: the Eppler-E61. The numerical results demonstrate superior performances of the corrugated airfoil. A series of low-speed wind and water tunnel experiments were performed on the corrugated airfoil, to validate the numerical results. The findings indicate quantitative agreement with the mean wake velocity profiles and shedding frequencies while validating the two dimensionality of the flow. A flow physics numerical study was performed in order to understand the underlying mechanism of corrugated airfoils at these Reynolds numbers. Airfoil shapes based on the flow field characteristics of the corrugated airfoil were built and analyzed. Their performances were compared to those of the corrugated airfoil, stressing the advantages of the latter. It was found that the flow which separates from the corrugations and forms spanwise vortices intermittently reattaches to the aft-upper arc region of the airfoil. This mechanism is responsible for the relatively low intensity of the vortices in the airfoil wake, reducing the drag and increasing the flight performances of this kind of corrugated airfoil as compared to traditional low Reynolds number airfoils such as the Eppler E-61.

Levy, David-Elie; Seifert, Avraham

2009-07-01

261

Non-monotonic hydrodynamic lift force on highly-extended polymers near surfaces  

E-print Network

The hydrodynamic lift force that polymers experience near boundaries is known to be a crucial element when considering rheological flows of dilute polymer solutions. Here we develop theory to describe the hydrodynamic lift force on extended polymers flowing near flat surfaces. The lift force is shown to display a non-monotonic character increasing linearly with the distance to the wall $Z$ in the near-surface regime defined as $Zlift force displays a maximum, and for $Z>L$ we recover the well known far-field result in which the force decays as $Z^{-2}$. Our analytical theory has important implications in understanding adsorption, desorption, and depletion layers of highly extended objects in flow.

Charles E Sing; Alfredo Alexander-Katz

2011-03-17

262

Gas lifting a major oil field in Argentina with high CO{sub 2} content associated gas  

SciTech Connect

The El Trapial Field in the Neuquen Province of Central Argentina produces more than 55,000 BOPD after 4 years of operation. The associated gas produced at El Trapial contains as much as 75% CO{sub 2}. Immediately after the discovery of the field, a study indicated that gas lift would meet environmental concerns and be an attractive economical alternative for producing the field. The study also concluded that the high CO{sub 2} fraction gas dissolved in the oil could be used satisfactorily for gas lift purposes. A plan was implemented at that time to design and construct the production facilities around gas lift as the primary artificial lift method. This paper addresses special precautions required for design of the production and gas lift facilities to gas lift successfully with high acid content associated gas. Also discussed is Petrolera Argentina San Jorge`s experience with such a system at El Trapial during the first 2 years of operation.

Blann, J.R.; Laville, G.M.

1997-02-01

263

Transition Documentation on a Three-Element High-Lift Configuration at High Reynolds Numbers: Analysis  

NASA Technical Reports Server (NTRS)

A 2-D high-lift system experiment was conducted in August of 1996 in the Low Turbulence Pressure Tunnel at NASA Langley Research Center, Hampton, VA. The purpose of the experiment was to obtain transition measurements on a three element high-lift system for CFD code validation studies. A transition database has been created using the data from this experiment. The present report contains the analysis of the surface hot film data in terms of the transition locations on the three elements. It also includes relevant information regarding the pressure loads and distributions and the wakes behind the model to aid in the interpretation of the transition data. For some of the configurations the current pressure data has been compared with previous wind tunnel entries of the same model. The methodology used to determine the regions of transitional flow is outlined and each configuration tested has been analyzed. A discussion of interference effects, repeatability, and three-dimensional effects on the data is included.

Bertelrud, Arild; Anders, J. B. (Technical Monitor)

2002-01-01

264

Mechanical Design of High Lift Systems for High Aspect Ratio Swept Wings  

NASA Technical Reports Server (NTRS)

The NASA Ames Research Center is working to develop a methodology for the optimization and design of the high lift system for future subsonic airliners with the involvement of two partners. Aerodynamic analysis methods for two dimensional and three dimensional wing performance with flaps and slats deployed are being developed through a grant with the aeronautical department of the University of California Davis, and a flap and slat mechanism design procedure is being developed through a contract with PKCR, Inc., of Seattle, WA. This report documents the work that has been completed in the contract with PKCR on mechanism design. Flap mechanism designs have been completed for seven (7) different mechanisms with a total of twelve (12) different layouts all for a common single slotted flap configuration. The seven mechanisms are as follows: Simple Hinge, Upside Down/Upright Four Bar Linkage (two layouts), Upside Down Four Bar Linkages (three versions), Airbus A330/340 Link/Track Mechanism, Airbus A320 Link/Track Mechanism (two layouts), Boeing Link/Track Mechanism (two layouts), and Boeing 767 Hinged Beam Four Bar Linkage. In addition, a single layout has been made to investigate the growth potential from a single slotted flap to a vane/main double slotted flap using the Boeing Link/Track Mechanism. All layouts show Fowler motion and gap progression of the flap from stowed to a fully deployed position, and evaluations based on spanwise continuity, fairing size and number, complexity, reliability and maintainability and weight as well as Fowler motion and gap progression are presented. For slat design, the options have been limited to mechanisms for a shallow leading edge slat. Three (3) different layouts are presented for maximum slat angles of 20 deg, 15 deg and 1O deg all mechanized with a rack and pinion drive similar to that on the Boeing 757 airplane. Based on the work of Ljungstroem in Sweden, this type of slat design appears to shift the lift curve so that higher lift is achieved with the deployed slat with no increase in angle of attack. The layouts demonstrate that these slat systems can be designed with no need for slave links, and an experimental test program is outlined to experimentally validate the lift characteristics of the shallow slat.

Rudolph, Peter K. C.

1998-01-01

265

Wind tunnel wall interference in V/STOL and high lift testing: A selected, annotated bibliography  

NASA Technical Reports Server (NTRS)

This bibliography, with abstracts, consists of 260 citations of interest to persons involved in correcting aerodynamic data, from high lift or V/STOL type configurations, for the interference arising from the wind tunnel test section walls. It provides references which may be useful in correcting high lift data from wind tunnel to free air conditions. References are included which deal with the simulation of ground effect, since it could be viewed as having interference from three tunnel walls. The references could be used to design tests from the standpoint of model size and ground effect simulation, or to determine the available testing envelope with consideration of the problem of flow breakdown. The arrangement of the citations is chronological by date of publication in the case of reports or books, and by date of presentation in the case of papers. Included are some documents of historical interest in the development of high lift testing techniques and wall interference correction methods. Subject, corporate source, and author indices, by citation numbers, have been provided to assist the users. The appendix includes citations of some books and documents which may not deal directly with high lift or V/STOL wall interference, but include additional information which may be helpful.

Tuttle, M. H.; Mineck, R. E.; Cole, K. L.

1986-01-01

266

Two-axis hydraulic joint for high speed, heavy lift robotic operations  

SciTech Connect

A hydraulically driven universal joint was developed for a heavy lift, high speed nuclear waste remediation application. Each axis is driven by a simple hydraulic cylinder controlled by a jet pipe servovalve. Servovalve behavior is controlled by a force feedback control system, which damps the hydraulic resonance. A prototype single joint robot was built and tested. A two joint robot is under construction.

Vaughn, M.R.; Robinett, R.D.; Phelan, J.R.; VanZuiden, D.M.

1994-04-01

267

Endwall Loss and Mixing Analysis of a High Lift Low Pressure Turbine Cascade (Preprint).  

National Technical Information Service (NTIS)

A high lift LPT profile designated L2A is used as a test bed for studying the origin of endwall mixing loss and the role of vortical structures in loss development. It is shown analytically and experimentally that the mixing forces within the endwall wake...

M. E. Lyall, P. I. King, R. Sondergaard

2012-01-01

268

Analysis of a jet-controlled high-lift hydrofoil with a flap  

Microsoft Academic Search

A jet-controlled high-lift hydrofoil with a flap is investigated using both experimental and computational methods. Experiments were carried out in a cavitation tunnel to measure forces and moment acting on the hydrofoil, and surface pressure distribution. The measured data show the feasibility of such a device for marine applications. Computational studies have also been carried out in parallel with the

S. H. Rhee; S.-E. Kim; H. Ahn; J. Oh; H. Kim

2003-01-01

269

The aerodynamic design of multi-element high-lift systems for transport airplanes  

Microsoft Academic Search

High-lift systems have a major influence on the sizing, economics, and safety of most transport airplane configurations. The combination of complexity in flow physics, geometry, and system support and actuation has historically led to a lengthy and experiment intensive development process. However, during the recent past engineering design has changed significantly as a result of rapid developments in computational hardware

C. P. van Dam

2002-01-01

270

Force interaction of high pressure glow discharge with fluid flow for active separation control  

E-print Network

discharge DBD at high pressure to inhibit phenomena such as stall on airfoils, thus improving their liftForce interaction of high pressure glow discharge with fluid flow for active separation control modeling to lift limitations in the current understanding of the actuation mechanism. The present effort

Roy, Subrata

271

Ambulatory High Resolution Manometry, Lower Esophageal Sphincter Lift and Transient Lower Esophageal Sphincter Relaxation  

PubMed Central

Introduction Lower esophageal sphincter (LES) lift seen on high resolution manometry (HRM) is a possible surrogate marker of the longitudinal muscle contraction of the esophagus. Recent studies suggest that longitudinal muscle contraction of the esophagus induces LES relaxation. Aim Our goal was to determine, 1) the feasibility of prolonged ambulatory HRM and 2) to detect LES lift with LES relaxation using ambulatory HRM color isobaric contour plots. Methods In vitro validation studies were performed to determine the accuracy of HRM technique in detecting axial movement of the LES. Eight healthy normal volunteers were studied using a custom designed HRM catheter and a 16 channel data recorder, in the ambulatory setting of subject’s home environment. Color HRM plots were analyzed to determine the LES lift during swallow-induced LES relaxation as well as during complete and incomplete transient LES relaxations. Results Satisfactory recordings were obtained for 16 hours in all subjects. LES lift was small (2 mm) in association with swallow-induced LES relaxation. LES lift could not be measured during complete transient LES relaxations (TLESR) because the LES is not identified on the HRM color isobaric contour plot once it is fully relaxed. On the other hand, LES lift, mean 7.6 ± 1.4 mm, range 6–12 mm was seen with incomplete TLESRs (n = 80). Conclusions Our study demonstrates the feasibility of prolonged ambulatory HRM recordings. Similar to a complete TLESR, longitudinal muscle contraction of the distal esophagus occurs during incomplete TLESRs, which can be detected by the HRM. Using prolonged ambulatory HRM, future studies may investigate the temporal correlation between abnormal longitudinal muscle contraction and esophageal symptoms. PMID:22074595

Mittal, Ravinder K.; Karstens, Anna; Leslie, Eric; Babaei, Arash; Bhargava, Valmik

2011-01-01

272

Simulation of the cross-flow fan and application to a propulsive airfoil concept  

NASA Astrophysics Data System (ADS)

A concept of embedding a cross-flow fan into a wing for lift enhancement and thrust production is proposed. The design places a cross-flow fan near the trailing edge of the wing. Flow is drawn in from the suction surface, energized, and expelled out the trailing edge. The commercial CFD software Fluent is used to perform both 2D and 3D calculations for validation of an isolated cross-flow fan and housing against experimental data, with good correlation found in terms of both global performance and local flow field data. CFD results are used to identify regions of high loss, as well as make recommendations in regard to the temporal and spatial accuracy of collected data. Parametric studies demonstrate fan performance and flow field sensitivities to various cross-flow fan housing parameters. The effect of vortex cavities, clearance gap, and blade shape are investigated. A new inline housing geometry is developed and integrated within a modified Gottingen 570 airfoil. Unsteady sliding mesh calculations are used to visualize the flow field, and calculate fan performance and airfoil lift coefficient. The results of the CFD work show that the jet leaving the fan fills up the wake behind the airfoil, while the suction effect produced by the fan virtually eliminates flow separation at high angle of attack, yielding very high lift coefficients. A system level analysis demonstrates the benefits of using an embedded cross-flow fan for distributed aircraft propulsion. The goal of the system analysis is to investigate the tradeoffs between various design parameters, and provide a basis for preliminary cross-flow fan airfoil design.

Kummer, Joseph

273

Navier-Stokes simulations of WECS airfoil flowfields  

SciTech Connect

Sandia National Laboratories has initiated an effort to apply Computational Fluid Dynamics (CFD) to the study of WECS aerodynamics. Preliminary calculations are presented for the flow past a SAND 0018/50 airfoil. The flow solver used is F3D, an implicitly, finite-difference code which solves the Thin-Layer Navier-airfoil. The flow solver used is F3D, an implicit, finite-difference code which solves the Thin-Layer Navier-Stokes equations. 2D steady-state calculations are presented at various angles of attack, {alpha}. Sectional lift and drag coefficient, as well as surface pressure distributions, are compared with wind tunnel data, and exhibit reasonable agreement at low to moderate angles of attack. At high {alpha}, where the airfoil is stalled, a converged solution to the steady-state equations could not be obtained. The flowfield continued to change with successive iterations, which is consistent with the fact that the actual flow is inherently transient, and requires the solution of the full unsteady form of the equations.

Homicz, G.F. [Sandia National Lab., Albuquerque, NM (United States). Computational Fluid Dynamics Dept.

1994-06-01

274

Design optimization of transonic airfoils  

NASA Technical Reports Server (NTRS)

Numerical optimization procedures were considered for the design of airfoils in transonic flow based on the transonic small disturbance (TSD) and Euler equations. A sequential approximation optimization technique was implemented with an accurate approximation of the wave drag based on the Nixon's coordinate straining approach. A modification of the Euler surface boundary conditions was implemented in order to efficiently compute design sensitivities without remeshing the grid. Two effective design procedures producing converged designs in approximately 10 global iterations were developed: interchanging the role of the objective function and constraint and the direct lift maximization with move limits which were fixed absolute values of the design variables.

Joh, C.-Y.; Grossman, B.; Haftka, R. T.

1991-01-01

275

Shape Changing Airfoil  

NASA Technical Reports Server (NTRS)

Scoping of shape changing airfoil concepts including both aerodynamic analysis and materials-related technology assessment effort was performed. Three general categories of potential components were considered-fan blades, booster and compressor blades, and stator airfoils. Based on perceived contributions to improving engine efficiency, the fan blade was chosen as the primary application for a more detailed assessment. A high-level aerodynamic assessment using a GE90-90B Block 4 engine cycle and fan blade geometry indicates that blade camber changes of approximately +/-4deg would be sufficient to result in fan efficiency improvements nearing 1 percent. Constraints related to flight safety and failed mode operation suggest that use of the baseline blade shape with actuation to the optimum cruise condition during a portion of the cycle would be likely required. Application of these conditions to the QAT fan blade and engine cycle was estimated to result in an overall fan efficiency gain of 0.4 percent.

Ott, Eric A.

2005-01-01

276

Two experimental supercritical laminar-flow-control swept-wing airfoils  

NASA Technical Reports Server (NTRS)

Two supercritical laminar-flow-control airfoils were designed for a large-chord swept-wing experiment in the Langley 8-Foot Transonic Pressure Tunnel where suction was provided through most of the model surface for boundary-layer control. The first airfoil was derived from an existing full-chord laminar airfoil by extending the trailing edge and making changes in the two lower-surface concave regions. The second airfoil differed from the first one in that it was designed for testing without suction in the forward concave region of the lower surface. Differences between the first airfoil and the one from which it was derived as well as between the first and second airfoils are discussed. Airfoil coordinates and predicted pressure distributions for the design normal Mach number of 0.755 and section lift coefficient of 0.55 are given for the three airfoils.

Allison, Dennis O.; Dagenhart, J. Ray

1987-01-01

277

Navier-Stokes Analysis of a High Wing Transport High-Lift Configuration with Externally Blown Flaps  

NASA Technical Reports Server (NTRS)

Insights and lessons learned from the aerodynamic analysis of the High Wing Transport (HWT) high-lift configuration are presented. Three-dimensional Navier-Stokes CFD simulations using the OVERFLOW flow solver are compared with high Reynolds test data obtained in the NASA Ames 12 Foot Pressure Wind Tunnel (PWT) facility. Computational analysis of the baseline HWT high-lift configuration with and without Externally Blown Flap (EBF) jet effects is highlighted. Several additional aerodynamic investigations, such as nacelle strake effectiveness and wake vortex studies, are presented. Technical capabilities and shortcomings of the computational method are discussed and summarized.

Slotnick, Jeffrey P.; An, Michael Y.; Mysko, Stephen J.; Yeh, David T.; Rogers, Stuart E.; Roth, Karlin; Baker, M.David; Nash, S.

2000-01-01

278

Aerodynamic Analysis of Trailing Edge Enlarged Wind Turbine Airfoils  

NASA Astrophysics Data System (ADS)

The aerodynamic performance of blunt trailing edge airfoils generated from the DU- 91-W2-250, DU-97-W-300 and DU-96-W-350 airfoils by enlarging the thickness of trailing edge symmetrically from the location of maximum thickness to chord to the trailing edge were analyzed by using CFD and RFOIL methods at a chord Reynolds number of 3 × 106. The goal of this study is to analyze the aerodynamic performance of blunt trailing edge airfoils with different thicknesses of trailing edge and maximum thicknesses to chord. The steady results calculated by the fully turbulent k-? SST, transitional k-? SST model and RFOIL all show that with the increase of thickness of trailing edge, the linear region of lift is extended and the maximum lift also increases, the increase rate and amount of lift become limited gradually at low angles of attack, while the drag increases dramatically. For thicker airfoils with larger maximum thickness to chord length, the increment of lift is larger than that of relatively thinner airfoils when the thickness of blunt trailing edge is increased from 5% to 10% chord length. But too large lift can cause abrupt stall which is profitless for power output. The transient characteristics of blunt trailing edge airfoils are caused by blunt body vortices at low angles of attack, and by the combined effect of separation and blunt body vortices at large angles of attack. With the increase of thickness of blunt trailing edge, the vibration amplitudes of lift and drag curves increase. The transient calculations over-predict the lift at large angles of attack and drag at all angles of attack than the steady calculations which is likely to be caused by the artificial restriction of the flow in two dimensions.

Xu, Haoran; Shen, Wenzhong; Zhu, Weijun; Yang, Hua; Liu, Chao

2014-06-01

279

Robust, optimal subsonic airfoil shapes  

NASA Technical Reports Server (NTRS)

Method system, and product from application of the method, for design of a subsonic airfoil shape, beginning with an arbitrary initial airfoil shape and incorporating one or more constraints on the airfoil geometric parameters and flow characteristics. The resulting design is robust against variations in airfoil dimensions and local airfoil shape introduced in the airfoil manufacturing process. A perturbation procedure provides a class of airfoil shapes, beginning with an initial airfoil shape.

Rai, Man Mohan (Inventor)

2008-01-01

280

Grid-Adapted FUN3D Computations for the Second High Lift Prediction Workshop  

NASA Technical Reports Server (NTRS)

Contributions of the unstructured Reynolds-averaged Navier-Stokes code FUN3D to the 2nd AIAA CFD High Lift Prediction Workshop are described, and detailed comparisons are made with experimental data. Using workshop-supplied grids, results for the clean wing configuration are compared with results from the structured code CFL3D Using the same turbulence model, both codes compare reasonably well in terms of total forces and moments, and the maximum lift is similarly over-predicted for both codes compared to experiment. By including more representative geometry features such as slat and flap brackets and slat pressure tube bundles, FUN3D captures the general effects of the Reynolds number variation, but under-predicts maximum lift on workshop-supplied grids in comparison with the experimental data, due to excessive separation. However, when output-based, off-body grid adaptation in FUN3D is employed, results improve considerably. In particular, when the geometry includes both brackets and the pressure tube bundles, grid adaptation results in a more accurate prediction of lift near stall in comparison with the wind-tunnel data. Furthermore, a rotation-corrected turbulence model shows improved pressure predictions on the outboard span when using adapted grids.

Lee-Rausch, E. M.; Rumsey, C. L.; Park, M. A.

2014-01-01

281

MultiElement High-Lift Configuration Design Optimization Using Viscous Continuous Adjoint Method  

Microsoft Academic Search

An adjoint-based Navier-Stokes design and optimization method for two-dimensional multi-element high-lift configurations is derived and presented. The compressible Reynolds-averaged Navier-Stokes equations are used as a flow model together with the Spalart-Allmaras turbulence model to account for high Reynolds number effects. When a viscous continuous adjoint formulation is used, the necessary aerodynamic gradient information is obtained with large computational savings over

Sangho Kim; Juan J. Alonso; Antony Jameson

2004-01-01

282

Model and full scale high-lift wing wind tunnel experiments dedicated to airframe noise reduction  

Microsoft Academic Search

During landing approach, airframe noise has become a significant contributor to the overall radiated noise from commercial aircraft, when propelled by quiet high-bypass-ratio engines. The major sources of airframe noise are the landing gears and the wing high-lift devices (HLD). In view of European aviation industry to design and build a very large commercial aeroplane, the A3XX, a German National

Werner Dobrzynski; Burkhard Gehlhar; Heino Buchholz

2001-01-01

283

Assessment of Lift Augmentation Devices.  

National Technical Information Service (NTIS)

Contents: Aerodynamics of mechanical high-lift devices; Aerodynamics of pneumatic high-lift devices; Aerodynamics of variable sweep; Fundamental aspects of flow separation under high-lift conditions; Some notes on two-dimensional high-lift tests in wind-t...

1971-01-01

284

Summary of the First AIAA CFD High Lift Prediction Workshop (invited)  

NASA Technical Reports Server (NTRS)

The 1st AIAA CFD High Lift Prediction Workshop was held in Chicago in June 2010. The goals of the workshop included an assessment of the numerical prediction capability of current-generation CFD technology/ codes for swept, medium/high-aspect ratio wings in landing/take-off (high lift) configurations. 21 participants from 8 countries and 18 organizations, submitted a total of 39 datasets of CFD results. A variety of grid systems (both structured and unstructured) were used. Trends due to flap angle were analyzed, and effects of grid family, grid density, solver, and turbulence model were addressed. Some participants also assessed the effects of support brackets used to attach the flap and slat to the main wing. This invited paper describes the combined results from all workshop participants. Comparisons with experimental data are made. A statistical summary of the CFD results is also included.

Rumsey, C. L.; Long, M.; Stuever, R. A.; Wayman, T. R.

2011-01-01

285

Aero-Mechanical Design Methodology for Subsonic Civil Transport High-Lift Systems  

NASA Technical Reports Server (NTRS)

In today's highly competitive and economically driven commercial aviation market, the trend is to make aircraft systems simpler and to shorten their design cycle which reduces recurring, non-recurring and operating costs. One such system is the high-lift system. A methodology has been developed which merges aerodynamic data with kinematic analysis of the trailing-edge flap mechanism with minimum mechanism definition required. This methodology provides quick and accurate aerodynamic performance prediction for a given flap deployment mechanism early on in the high-lift system preliminary design stage. Sample analysis results for four different deployment mechanisms are presented as well as descriptions of the aerodynamic and mechanism data required for evaluation. Extensions to interactive design capabilities are also discussed.

vanDam, C. P.; Shaw, S. G.; VanderKam, J. C.; Brodeur, R. R.; Rudolph, P. K. C.; Kinney, D.

2000-01-01

286

Airfoil Shape Optimization for Transonic Flows of BetheZel'dovichThompson Fluids  

E-print Network

Airfoil Shape Optimization for Transonic Flows of Bethe­Zel'dovich­Thompson Fluids P. M. Congedo, France and P. Cinnella University of Lecce, 73100 Lecce, Italy High-performance airfoils for transonic on airfoils operating at high transonic speeds, due to a substantial increase in the airfoil critical Mach

Paris-Sud XI, Université de

287

Wind tunnel test results of heavy rain effects on airfoil performance  

NASA Technical Reports Server (NTRS)

The effects of simulated heavy rain on the aerodynamic characteristics of a NACA 64-210 airfoil section equipped with high-lift devices were investigated in the NASA Langley 14- by 22-Foot Subsonic Tunnel. The experiment was part of an on-going NASA program to determine the effect of heavy rain on airplane performance, and was directed at providing insight into scaling laws for subscale model testing of rain effects. The model used in the investigation had a chord of 2.5 feet, a span of 8.0 feet, and was mounted on the tunnel centerline between two large endplates. A water spray distribution system was located 10 chord lengths upstream of the model. The sensitivity of test results to partial-span coverage of the model in the simulated rain environment as compared to full-span coverage was also investigated. The lift and drag data obtained for the high-lift configuration show excellent repeatability of results compared to the previous data. Results obtained for various spray concentrations and tunnel speeds showed significant losses in maximum lift capability, a decrease in the angle of attack for maximum lift, and an increase in drag as the stimulated rain rate was increased. The test results also indicated that the data were not strongly affected by surface tension effects for the high-lift configuration.

Bezos, G. M.; Dunham, R. E., Jr.; Gentry, G. L., Jr.; Melson, W. Edward, Jr.

1987-01-01

288

A computational analysis of flow separation over five different airfoil geometries at high angles-of-attack  

NASA Technical Reports Server (NTRS)

The flux splitting method of Van Leer (1982) and an implicit, upwind-biased, finite-volume scheme of Rumsey (1985) for solving the two-dimensional Reynolds-averaged Navier-Stokes equations were applied to analyze five airfoil geometries (the NACA 0012, 12-percent Joukowski, NACA 4412, NACA 65-015, and LS1-0417 sections), at high angles of attack. The effect of grid density and grid extent on the Strouhal number of the unsteady flow was computed, as well as the effect of variations in Mach number, Reynolds number, and angle of attack. It was found, that past an angle of attack of 20 deg, Strouhal numbers were independent of angle of attack (at a constant value of 0.115), agreeing well with the experimental findings of Tyler (1931).

Rumsey, Christopher L.

1987-01-01

289

Determination of the theoretical pressure distribution for twenty airfoils  

NASA Technical Reports Server (NTRS)

This report gives the theoretical distribution of pressure at lift coefficients of 0, 0.5, 1.0, and 1.5 for 20 airfoils, calculated on the basis of a rigorous potential theory of arbitrary airfoils. It also provides tables from which the characteristics of the airfoils for any angle of attack in 2-dimensional potential flow are readily calculable. The theoretical values of the angles of zero lift, the lift and moment coefficients, and the ideal angles of attack are listed and some comparisons with experiment are indicated. The results presented may be of value in predicting structural loads and also in a correlation of theoretical pressure gradients with profile resistance.

Garrick, I E

1934-01-01

290

Options for Robust Airfoil Optimization under Uncertainty  

NASA Technical Reports Server (NTRS)

A robust optimization method is developed to overcome point-optimization at the sampled design points. This method combines the best features from several preliminary methods proposed by the authors and their colleagues. The robust airfoil shape optimization is a direct method for drag reduction over a given range of operating conditions and has three advantages: (1) it prevents severe degradation in the off-design performance by using a smart descent direction in each optimization iteration, (2) it uses a large number of spline control points as design variables yet the resulting airfoil shape does not need to be smoothed, and (3) it allows the user to make a tradeoff between the level of optimization and the amount of computing time consumed. For illustration purposes, the robust optimization method is used to solve a lift-constrained drag minimization problem for a two-dimensional (2-D) airfoil in Euler flow with 20 geometric design variables.

Padula, Sharon L.; Li, Wu

2002-01-01

291

Lower-body lift.  

PubMed

The lower-body lift, designed for patients with multiple lower-body contour deformities, uses a circumferential bikini-line incision to simultaneously lift relaxed trunk and thigh tissues. The author describes 2 lower-body lift procedures, focusing primarily on the high-lateral-tension abdominoplasty with transverse-thigh/buttock lift, which he developed in 1996. (Aesthetic Surg J 2001;21:355-370.). PMID:19331916

Lockwood, T E

2001-07-01

292

Characterization of the Effect of Wing Surface Instrumentation on UAV Airfoil Performance  

NASA Technical Reports Server (NTRS)

Recently proposed flight research at NASA Dryden Flight Research Center (DFRC) has prompted study into the aerodynamic effects of modifications made to the surfaces of laminar airfoils. The research is focused on the high-aspect ratio, laminar-flow type wings commonly found on UAVs and other aircraft with a high endurance requirement. A broad range of instrumentation possibilities, such as structural, pressure, and temperature sensing devices may require the alteration of the airfoil outer mold line as part of the installation process. This study attempts to characterize the effect of installing this additiona1 instrumentation on key airfoil performance factors, such as transition location, lift and drag curves, and stall point. In particular, the general case of an airfoil that is channeled in the spanwise direction is considered, and the impact on key performance characteristics is assessed. Particular attention is focused on exploring the limits of channel depth and low-Reynolds number on performance and stall characteristics. To quantify the effect of increased skin friction due to premature transition caused by protruding or recessed instrumentation, two simplified, conservative scenarios are used to consider two potential sources of diaturbance: A) that leading edge alterations would cause linearly expanding areas (triangles) of turbulent flow on both surfaces of the wing upstream of the natural transition point, and B) that a channel or bump on the upper surface would trip turbulent flow across the whole upper surface upstream of the natural transition point. A potentially more important consideration than the skin friction drag increment is the change in overall airfoil performance due to the installation of instrumentation along most of the wingspan. To quantify this effect, 2D CFD simulations of the flow over a representative mid-span airfoil section were conducted in order to assess the change in lift and drag curves for the airfoil in the presence of disturbed flow due to the installed instrumentation. A discussion as to the impact on high-altitude and low-speed operation of this and similar aircraft is provided.

Ratnayake, Nalin A.

2009-01-01

293

Aerodynamic, aeroacoustic, and aeroelastic investigations of airfoil-vortex interaction using large-eddy simulation  

NASA Astrophysics Data System (ADS)

In helicopters, vortices (generated at the tip of the rotor blades) interact with the next advancing blades during certain flight and manoeuvring conditions, generating undesirable levels of acoustic noise and vibration. These Blade-Vortex Interactions (BVIs), which may cause the most disturbing acoustic noise, normally occur in descent or high-speed forward flight. Acoustic noise characterization (and potential reduction) is one the areas generating intensive research interest to the rotorcraft industry. Since experimental investigations of BVI are extremely costly, some insights into the BVI or AVI (2-D Airfoil-Vortex Interaction) can be gained using Computational Fluid Dynamics (CFD) numerical simulations. Numerical simulation of BVI or AVI has been of interest to CFD for many years. There are still difficulties concerning an accurate numerical prediction of BVI. One of the main issues is the inherent dissipation of CFD turbulence models, which severely affects the preservation of the vortex characteristics. Moreover this is not an issue only for aerodynamic and aeroacoustic analysis but also for aeroelastic investigations as well, especially when the strong (two-way) aeroelastic coupling is of interest. The present investigation concentrates mainly on AVI simulations. The simulations are performed for Mach number, Ma = 0.3, resulting in a Reynolds number, Re = 1.3 x 106, which is based on the chord, c, of the airfoil (NACA0012). Extensive literature search has indicated that the present work represents the first comprehensive investigation of AVI using the LES numerical approach, in the rotorcraft research community. The major factor affecting the aerodynamic coefficients and aeroacoustic field as a result of airfoil-vortex interaction is observed to be the unsteady pressure generated at the location of the interaction. The present numerical results show that the aerodynamic coefficients (lift, moment, and drag) and aeroacoustic field are strongly dependent on the airfoil-vortex vertical miss-distance, airfoil angle of attack, vortex characteristics, and aeroelastic response of airfoil to airfoil-vortex interaction. A decay of airfoil-vortex interactions with the increase of vertical miss-distance and angle of attack was observed. Also, a decay of airfoil-vortex interactions is observed for the case of a flexible structure when compared with the case of a rigid structure. The decay of vortex core size produces a decrease in the aerodynamic coefficients.

Ilie, Marcel

294

A High-Lift Building Block Flow: Turbulent Boundary Layer Relaminarization A Final Report  

NASA Technical Reports Server (NTRS)

Experimental evidence exists which suggests turbulent boundary layer relaminarization may play an important role in the inverse Reynolds number effect in high-lift systems. An experimental investigation of turbulent boundary layer relaminarization has been undertaken at the University of Notre Dame's Hessert Center for Aerospace Research in cooperation with NASA Dryden Flight Research Center. A wind tunnel facility has been constructed at the Hessert Center and relaminarization achieved. Preliminary evidence suggests the current predictive tools available are inadequate at determining the onset of relaminarization. In addition, an in-flight relaminarization experiment for the NASA Dryden FTF-II has been designed to explore relaminarization at Mach and Reynolds numbers more typical of commercial high-lift systems.

Bourassa, Corey; Thomas, Flint O.; Nelson, Robert C.

2000-01-01

295

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, 4-7 January 2010, Orlando, Florida Feedback Control of High-Lift State  

E-print Network

-7 January 2010, Orlando, Florida Feedback Control of High-Lift State for A Low-Aspect-Ratio Wing Kunihiko by the existence of time-periodic high-lift states under open-loop control with periodic excitation, the extremum seeking algorithm is considered for designing feedback control to lock the flow onto such high-lift states

Dabiri, John O.

296

Control of Separation on the Flap of a Three-Element High-Lift Configuration  

Microsoft Academic Search

This paper describes a joint experimental and numerical investigation of the control of the flow over the flap of a three-element high-lift configuration by means of periodic excitation. At Reynolds numbers between 0.3 ? 106 and 1 ? 106 the flow is influenced by periodic blowing or periodic blowing\\/suction through slots near the flap leading edge. The delay of flow

B. Gunther; Frank Thiele; R. Petz; W. Nitsche; J. Sahner; T. Weinkaufk; H.-C. Hege

2007-01-01

297

Aerodynamic design of the high-lift-wing for a Megaliner aircraft  

Microsoft Academic Search

A ‘Megaliner’ aircraft configuration like the Airbus A380 will become a civil transport aircraft lager than all existing designs. Its wing had to be designed not only to give the required cruise performance but also to be compatible with the given airport infrastructure. The aerodynamic design of the high-lift system has to fulfil the resulting targets for the take-off and

Daniel Reckzeh

2003-01-01

298

A CFD Assessment of Several High-Lift Reference H Configuration Using Structured Grids  

NASA Technical Reports Server (NTRS)

The objective of this study is to calibrate a Navier-Stokes code for a high-lift Reference H configuration using structured grids. The outline of this presentation will first include a brief description of the grids used and the flow solver. Next the results will be presented in terms of convergence and resources used on the C-90. Predicted force and moment and surface pressure results are compared to experiment and off- and on-surface flow viz. is discussed.

Lessard, Wendy B.

1999-01-01

299

Profile-Drag Coefficients of Conventional and Low-Drag Airfoils as Obtained in Flight  

NASA Technical Reports Server (NTRS)

Results of flight tests indicate that profile-drag coefficients which were obtained with the low-drag airfoils were lower than with the conventional types over the range of light coefficients tested. For comparable conditions of the lift coefficient and Reynolds Number, the low-drag airfoils have profile-drag coefficients which may be 27 percent lower than the profile drag of the conventional airfoils tested. Detailed results are presented graphically.

Zalovcik, John A.

1944-01-01

300

S827 and S828 Airfoils; Period of Performance: 1994--1995  

SciTech Connect

A family of thick, natural-laminar-flow airfoils, the S827 and S828, for 40- to 50-meter, stall -regulated, horizontal-axis wind turbines has been designed and analyzed theoretically. The two primary objectives of restrained maximum lift, insensitive to roughness, and low profile drag have been achieved. The constraints on the pitching moments and the airfoil thicknesses have been satisfied. The airfoils should exhibit docile stalls.

Somers, D. M.

2005-01-01

301

FUN3D and CFL3D Computations for the First High Lift Prediction Workshop  

NASA Technical Reports Server (NTRS)

Two Reynolds-averaged Navier-Stokes codes were used to compute flow over the NASA Trapezoidal Wing at high lift conditions for the 1st AIAA CFD High Lift Prediction Workshop, held in Chicago in June 2010. The unstructured-grid code FUN3D and the structured-grid code CFL3D were applied to several different grid systems. The effects of code, grid system, turbulence model, viscous term treatment, and brackets were studied. The SST model on this configuration predicted lower lift than the Spalart-Allmaras model at high angles of attack; the Spalart-Allmaras model agreed better with experiment. Neglecting viscous cross-derivative terms caused poorer prediction in the wing tip vortex region. Output-based grid adaptation was applied to the unstructured-grid solutions. The adapted grids better resolved wake structures and reduced flap flow separation, which was also observed in uniform grid refinement studies. Limitations of the adaptation method as well as areas for future improvement were identified.

Park, Michael A.; Lee-Rausch, Elizabeth M.; Rumsey, Christopher L.

2011-01-01

302

Circulation Control by Steady and Pulsed Blowing for a Cambered Elliptical Airfoil.  

National Technical Information Service (NTIS)

An experimental investigation was performed on the effectiveness of circulation control in producing additional lift and preventing separation on a cambered elliptical airfoil section with a rounded trailing edge. Steady blowing and pulsed blowing from a ...

R. E. Walters, D. P. Myer, D. J. Holt

1972-01-01

303

Analytical study of a free-wing/free-trimmer concept. [for gust alleviation and high lift  

NASA Technical Reports Server (NTRS)

The free-wing/free-trimmer is a NASA-Conceived extension of the free-wing concept intended to permit the use of high-lift flaps. Wing pitching moments are balanced by a smaller, external surface attached by a boom or equivalent structure. The external trimmer is, itself, a miniature free wing, and pitch control of the wing-trimmer assembly is effected through a trailing-edge control tab on the trimmer surface. The longitudinal behavior of representative small free-wing/free-trimmer aircraft was analyzed. Aft-mounted trimmer surfaces are found to be superior to forward trimmers, although the permissible trimmer moment arm is limited, in both cases, by adverse dynamic effects. Aft-trimmer configurations provide excellent gust alleviation and meet fundamental stick-fixed stability criteria while exceeding the lift capabilities of pure free-wing configurations.

Porter, R. F.; Hall, D. W.; Brown, J. H., Jr.; Gregorek, G. M.

1978-01-01

304

S819, S820, and S821 Airfoils: October 1992--November 1993  

SciTech Connect

A family of thick airfoils for 10- to 20-meter, stall regulated, horizontal-axis wind turbines, the S819, S820, and S821, has been designed and analyzed theoretically. The primary objectives of restrained maximum lift, insensitive to roughness, and low profile drag have been achieved. The constraints on the pitching moments and airfoil thicknesses have been satisfied.

Somers, D. M.

2005-01-01

305

S816, S817, and S818 Airfoils: October 1991--July1992  

SciTech Connect

A family of thick laminar-flow airfoils for 30 to 40-meter horizontal-axis wind turbines, the S816, S817, and S818, has been designed and analyzed theoretically. The primary objectives of restrained maximum lift, insensitive to roughness, and low profile drag have been achieved. The constraints on the pitching moments and airfoil thicknesses have been satisfied.

Somers, D. M.

2004-12-01

306

AIAA Paper 2006-0102 Analysis of Jet Effects on Co-Flow Jet Airfoil  

E-print Network

are given. CFD solutions based on RANS model are used to provide the breakdowns of lift and drag with experiment as validation. The duct reaction forces are also validated by a 3D CFD calculation of the complete airfoil with jet ducts and wind tunnel wall. A comparative study of the jet effect on airfoil performance

Zha, Gecheng

307

Numerical Simulations of the Steady and Unsteady Aerodynamic Characteristics of a Circulation Control Wing Airfoil  

NASA Technical Reports Server (NTRS)

The aerodynamic characteristics of a Circulation Control Wing (CCW) airfoil have been numerically investigated, and comparisons with experimental data have been made. The configuration chosen was a supercritical airfoil with a 30 degree dual-radius CCW flap. Steady and pulsed jet calculations were performed. It was found that the use of steady jets, even at very small mass flow rates, yielded a lift coefficient that is comparable or superior to conventional high-lift systems. The attached flow over the flap also gave rise to lower drag coefficients, and high L/D ratios. Pulsed jets with a 50% duty cycle were also studied. It was found that they were effective in generating lift at lower reduced mass flow rates compared to a steady jet, provided the pulse frequency was sufficiently high. This benefit was attributable to the fact that the momentum coefficient of the pulsed jet, during the portions of the cycle when the jet was on, was typically twice as much as that of a steady jet.

Liu, Yi; Sankar, Lakshmi N.; Englar, Robert J.; Ahuja, Krishan K.

2003-01-01

308

An Approach to the Constrained Design of Natural Laminar Flow Airfoils  

NASA Technical Reports Server (NTRS)

A design method has been developed by which an airfoil with a substantial amount of natural laminar flow can be designed, while maintaining other aerodynamic and geometric constraints. After obtaining the initial airfoil's pressure distribution at the design lift coefficient using an Euler solver coupled with an integral turbulent boundary layer method, the calculations from a laminar boundary layer solver are used by a stability analysis code to obtain estimates of the transition location (using N-Factors) for the starting airfoil. A new design method then calculates a target pressure distribution that will increase the laminar flow toward the desired amount. An airfoil design method is then iteratively used to design an airfoil that possesses that target pressure distribution. The new airfoil's boundary layer stability characteristics are determined, and this iterative process continues until an airfoil is designed that meets the laminar flow requirement and as many of the other constraints as possible.

Green, Bradford E.

1997-01-01

309

Computational Simulations of a Three-Dimensional High-Lift Wing  

NASA Technical Reports Server (NTRS)

Highly resolved computational simulations of a three-dimensional high-lift wing are presented. The steady Reynolds Averaged Navier-Stokes computations are geared towards understanding the flow intricacies associated with inboard and outboard flap side edges. Both moderate and high flap deflections are simulated. Computed surface pressure fields accurately capture the footprint of vortices at flap side edges and are in excellent agreement with pressure sensitive paint measurements. The computations reveal that the outboard vortex possesses higher rotational velocities and lower core pressure than the inboard vortex and therefore is susceptible to severe vortex breakdown.

Khorrami, M. R.; Berkman, M. E.; Li, F.; Singer, B. A.

2002-01-01

310

Airfoil Thickness Effects on the Thrust Generation of Plunging Airfoils  

E-print Network

Airfoil Thickness Effects on the Thrust Generation of Plunging Airfoils Meilin Yu, Z. J. Wang to investigate the effects of airfoil thickness on the thrust generation of plunging airfoils and to assess the contributions of pressure and viscous forces in flapping propulsion. A series of NACA symmetric airfoils

Hu, Hui

311

The use of a panel code on high lift configurations of a swept forward wing  

NASA Technical Reports Server (NTRS)

A study was done on high lift configurations of a generic swept forward wing using a panel code prediction method. A survey was done of existing codes available at Ames, frow which the program VSAERO was chosen. The results of VSAERO were compared with data obtained from the Ames 7- by 10-foot wind tunnel. The results of the comparison in lift were good (within 3.5%). The comparison of the pressure coefficients was also good. The pitching moment coefficients obtained by VSAERO were not in good agreement with experiment. VSAERO's ability to predict drag is questionable and cannot be counted on for accurate trends. Further studies were done on the effects of a leading edge glove, canards, leading edge sweeps and various wing twists on spanwise loading and trim lift with encouraging results. An unsuccessful attempt was made to model spanwise blowing and boundary layer control on the trailing edge flap. The potential results of VSAERO were compared with experimental data of flap deflections with boundary layer control to check the first order effects.

Scheib, J. S.; Sandlin, D. R.

1985-01-01

312

VLSI architecture of low memory and high speed 2D lifting-based discrete wavelet transform for JPEG2000 applications  

Microsoft Academic Search

The paper presents a low memory and high speed VLSI architecture for 2D lifting-based lossless 5\\/3 filter discrete wavelet transform (DWT). The architecture is based on the proposed interlaced read scan algorithm (IRSA) and parallel scheme processing to achieve low memory size and high speed operation. The proposed lifting-based DWT architecture has the advantages of lower computational complexity, transforming signal

Jen-shiun Chiang; Chih-hsien Hsia; Hsin-jung Chen; Te-jung Lo

2005-01-01

313

An experimental study of a bio-inspired corrugated airfoil for micro air vehicle applications  

NASA Astrophysics Data System (ADS)

An experimental study was conducted to investigate the aerodynamic characteristics of a bio-inspired corrugated airfoil compared with a smooth-surfaced airfoil and a flat plate at the chord Reynolds number of Re C = 58,000-125,000 to explore the potential applications of such bio-inspired corrugated airfoils for micro air vehicle designs. In addition to measuring the aerodynamic lift and drag forces acting on the tested airfoils, a digital particle image velocimetry system was used to conduct detailed flowfield measurements to quantify the transient behavior of vortex and turbulent flow structures around the airfoils. The measurement result revealed clearly that the corrugated airfoil has better performance over the smooth-surfaced airfoil and the flat plate in providing higher lift and preventing large-scale flow separation and airfoil stall at low Reynolds numbers (Re C < 100,000). While aerodynamic performance of the smooth-surfaced airfoil and the flat plate would vary considerably with the changing of the chord Reynolds numbers, the aerodynamic performance of the corrugated airfoil was found to be almost insensitive to the Reynolds numbers. The detailed flow field measurements were correlated with the aerodynamic force measurement data to elucidate underlying physics to improve our understanding about how and why the corrugation feature found in dragonfly wings holds aerodynamic advantages for low Reynolds number flight applications.

Murphy, Jeffery T.; Hu, Hui

2010-08-01

314

Tornado lift  

E-print Network

It is shown that one of the causes for tornado is Tornado Lift. At increasing vortex diameter its kinetic energy decreases to keep the moment of momentum constant. A kinetic energy gradient of such vortex is Tornado Lift. Evaluation shows that contribution of Tornado Lift in air lifting in a tornado is comparable to buoyancy according to the order of magnitude.

Alexander Ivanchin

2010-02-06

315

Tornado lift  

E-print Network

It is shown that one of the causes for tornado is Tornado Lift. At increasing vortex diameter its kinetic energy decreases to keep the moment of momentum constant. A kinetic energy gradient of such vortex is Tornado Lift. Evaluation shows that contribution of Tornado Lift in air lifting in a tornado is comparable to buoyancy according to the order of magnitude.

Ivanchin, Alexander

2010-01-01

316

Techno-economic feasibility of high-temperature high-lift chemical heat pumps for upgrading industrial waste heat  

Microsoft Academic Search

This paper presents the results of a techno-economic feasibility study on two high-temperature high-lift chemical heat pumps for upgrading industrial waste heat. The study was set up in order to select the most promising heat pump concept for further development. First, a market study is performed to assess the amount of waste heat and the temperature dependence thereof. Based on

S. Spoelstra; W. G. Haije; J. W. Dijkstra

2002-01-01

317

Computational Analysis of Dual Radius Circulation Control Airfoils  

NASA Technical Reports Server (NTRS)

The goal of the work is to use multiple codes and multiple configurations to provide an assessment of the capability of RANS solvers to predict circulation control dual radius airfoil performance and also to identify key issues associated with the computational predictions of these configurations that can result in discrepancies in the predicted solutions. Solutions were obtained for the Georgia Tech Research Institute (GTRI) dual radius circulation control airfoil and the General Aviation Circulation Control (GACC) dual radius airfoil. For the GTRI-DR airfoil, two-dimensional structured and unstructured grid computations predicted the experimental trend in sectional lift variation with blowing coefficient very well. Good code to code comparisons between the chordwise surface pressure coefficients and the solution streamtraces also indicated that the detailed flow characteristics were matched between the computations. For the GACC-DR airfoil, two-dimensional structured and unstructured grid computations predicted the sectional lift and chordwise pressure distributions accurately at the no blowing condition. However at a moderate blowing coefficient, although the code to code variation was small, the differences between the computations and experiment were significant. Computations were made to investigate the sensitivity of the sectional lift and pressure distributions to some of the experimental and computational parameters, but none of these could entirely account for the differences in the experimental and computational results. Thus, CFD may indeed be adequate as a prediction tool for dual radius CC flows, but limited and difficult to obtain two-dimensional experimental data prevents a confident assessment at this time.

Lee-Rausch, E. M.; Vatsa, V. N.; Rumsey, C. L.

2006-01-01

318

Long lifetime and high-fidelity quantum memory of photonic polarization qubit by lifting zeeman degeneracy.  

PubMed

Long-lived and high-fidelity memory for a photonic polarization qubit (PPQ) is crucial for constructing quantum networks. We present a millisecond storage system based on electromagnetically induced transparency, in which a moderate magnetic field is applied on a cold-atom cloud to lift Zeeman degeneracy and, thus, the PPQ states are stored as two magnetic-field-insensitive spin waves. Especially, the influence of magnetic-field-sensitive spin waves on the storage performances is almost totally avoided. The measured average fidelities of the polarization states are 98.6% at 200???s and 78.4% at 4.5 ms, respectively. PMID:24483636

Xu, Zhongxiao; Wu, Yuelong; Tian, Long; Chen, Lirong; Zhang, Zhiying; Yan, Zhihui; Li, Shujing; Wang, Hai; Xie, Changde; Peng, Kunchi

2013-12-13

319

Long Lifetime and High-Fidelity Quantum Memory of Photonic Polarization Qubit by Lifting Zeeman Degeneracy  

NASA Astrophysics Data System (ADS)

Long-lived and high-fidelity memory for a photonic polarization qubit (PPQ) is crucial for constructing quantum networks. We present a millisecond storage system based on electromagnetically induced transparency, in which a moderate magnetic field is applied on a cold-atom cloud to lift Zeeman degeneracy and, thus, the PPQ states are stored as two magnetic-field-insensitive spin waves. Especially, the influence of magnetic-field-sensitive spin waves on the storage performances is almost totally avoided. The measured average fidelities of the polarization states are 98.6% at 200?s and 78.4% at 4.5 ms, respectively.

Xu, Zhongxiao; Wu, Yuelong; Tian, Long; Chen, Lirong; Zhang, Zhiying; Yan, Zhihui; Li, Shujing; Wang, Hai; Xie, Changde; Peng, Kunchi

2013-12-01

320

Long lifetime and high-fidelity quantum memory of photonic polarization qubit by lifting Zeeman degeneracy  

E-print Network

Long-lived and high-fidelity memory for photonic polarization qubit (PPQ) is crucial for constructing quantum networks. Here we present an EIT-based millisecond storage system in which a moderate magnetic field is applied on a cold-atom cloud to lift Zeeman degeneracy. PPQ states are stored as two magnetic-field-insensitive spin waves. Especially, the influence of magnetic-field-sensitive spin waves on the storage performances is almost totally avoided. The measured average fidelities of polarization states are 98.6% at 200 us and 78.4% at 4.5 ms, respectively.

Zhongxiao Xu; Yuelong Wu; Long Tian; Lirong Chen; Zhiying Zhang; Zhihui Yan; Shujing Li; Hai Wang; Changde Xie; Kunchi Peng

2013-06-18

321

Simulation of self-induced unsteady motion in the near wake of a Joukowski airfoil  

NASA Technical Reports Server (NTRS)

The unsteady Navier-Stokes analysis is shown to be capable of analyzing the massively separated, persistently unsteady flow in the post-stall regime of a Joukowski airfoil for an angle of attack as high as 53 degrees. The analysis has provided the detailed flow structure, showing the complex vortex interaction for this configuration. The aerodynamic coefficients for lift, drag, and moment were calculated. So far only the spatial structure of the vortex interaction was computed. It is now important to potentially use the large-scale vortex interactions, an additional energy source, to improve the aerodynamic performance.

Ghia, K. N.; Osswald, G. A.; Ghia, U.

1986-01-01

322

High Reynolds number tests of a Douglas DLBA 032 airfoil in the Langley 0.3-meter transonic cryogenic tunnel  

NASA Technical Reports Server (NTRS)

A wind-tunnel investigation of a Douglas advanced-technology airfoil was conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT). The temperature was varied from 227 K (409 R) to 100 K (180 R) at pressures ranging from about 159 kPa (1.57 atm) to about 514 kPa (5.07 atm). Mach number was varied from 0.50 to 0.78. These variables provided a Reynolds number range (based on airfoil chord) from 6.0 to 30.0 x 10 to the 6th power. This investigation was specifically designed to: (1) test a Douglas airfoil from moderately low to flight-equivalent Reynolds numbers, and (2) evaluate sidewall-boundary-layer effects on transonic airfoil performance characteristics by a systematic variation of Mach number, Reynolds number, and sidewall-boundary-layer removal. Data are included which demonstrate the effects of fixing transition, Mach number, Reynolds number, and sidewall-boundary-layer removal on the aerodynamic characteristics of the airfoil. Also included are remarks on model design and model structural integrity.

Johnson, Charles B.; Dress, David A.; Hill, Acquilla S.; Wilcox, Peter A.; Bui, Minh H.

1986-01-01

323

Theoretical and Experimental Data for a Number of NACA 6A-Series Airfoil Sections  

NASA Technical Reports Server (NTRS)

The NACA 6A-series airfoil sections were designed to eliminate the trailing-edge cusp which is characteristic of the NACA 6-series sections. Theoretical data are presented for NACA 6A-series basic thickness forms having the position of minimum pressure at 30-, 40-, and 50-percent chord and with thickness ratios varying from 6 percent to 15 percent. Also presented are data for a mean line designed to maintain straight sides on the cambered sections. The experimental results of a two dimensional wind tunnel investigation of the aerodynamic characteristics of five NACA 64A-series airfoil sections and two NACA 63A-series airfoil sections are presented. An analysis of these results, which were obtained at Reynolds numbers of 3 x 10(exp 6), 6 x 10(exp 6), and 9 x 10(exp 6), indicates that the section minimum drag and maximum lift characteristics of comparable NACA 6-series and 6A-series airfoil sections are essentially the same. The quarter-chord pitching-moment coefficients and angles of zero lift of NACA 6A-series airfoil sections are slightly more negative than those of corresponding NACA 6-series airfoil sections. The position of the aerodynamic center and the lift-curve slope of smooth NACA 6-series sections. The addition of standard leading-edge roughness causes the lift-curve slope of the newer sections to decrease with increasing airfoil thickness ratio.

Loftin, Laurence K., Jr.

1946-01-01

324

Gas lifting a major oil field in Argentina with high CO{sub 2} content associated gas  

SciTech Connect

The El Trapial Field in the Neuquen Province of Central Argentina produces more than 50,000 barrels of oil/day after only three years of operation. The associated gas produced at E1 Trapial contains as much as 75% CO{sub 2}. Immediately after the discovery of the field, a study indicated that gas lift would meet environmental concerns and be an attractive economical alternative for producing the field. The study also concluded that the high CO{sub 2} fraction gas dissolved in the oil could be used satisfactorily for gas lift purposes. A plan was implemented at that time to design and construct the production facilities around gas lift as the primary artificial lift method. This paper addresses special precautions required for design of the production and gas lift facilities to successfully gas lift with high acid content associated gas. Also discussed is Petrolera Argentina San Jorge`s experience with such a system at El Trapial during the first two years of operation.

Blann, J.R.; Laville, G.M.

1995-12-31

325

Process optimization of LIFT through visualization: towards high resolution metal circuit printing  

NASA Astrophysics Data System (ADS)

Laser induced forward transfer (LIFT) is a freeform, additive patterning technique capable of depositing high resolution metal structures. A laser pulse is used to generate small droplets from the donor material, defined by the spot size and energy of the pulse. Metallic as well as non-metallic materials can be patterned using this method. Being a contactless, additive and high resolution patterning technique, this method enables fabrication of multi-layer circuits, enabling bridge printing, thereby decreasing component spacing. Here we demonstrate copper droplet formation from a thin film donor. The investigation of the LIFT process is done via shadowgraphy and provides detailed insight on the droplet formation. Of particular importance is the interplay of the droplet jetting mechanism and the spacing between donor and receiving substrate on a stable printing process. Parameters such as the influence of laser fluence and donor thickness on the formation of droplets are discussed. An angle deviation analysis of the copper droplets during flight is carried out to estimate the pointing accuracy of the transfer. The possibility of understanding the droplet formation, could allow for stable droplets transferred with large gaps, simplifying the process for patterning continuous high-resolution conductive lines.

Giesbers, Merijn P.; Hoppenbrouwers, M. B.; Smits, E. C. P.; Mandamparambil, R.

2014-05-01

326

Navier-Stokes Simulation of Several High-Lift Reference H Configurations  

NASA Technical Reports Server (NTRS)

The subsonic flow field was numerically simulated around several High Speed Research Reference H configurations at various pitch and yaw angles. A sequence of structured-viscous grids were generated; the first grid modeled the wing-body high-lift geometry, and the second grid incorporated the nacelles and the horizontal tail. The third grid modeled the full-span geometry for sideslip calculations, and was obtained by mirroring a coarser version of the second grid. The CFL3D code, a Reynolds averaged, thin-layer Navier-Stokes flow solver for structural grids, was used for the flow solver and modeled the free-air Reference H high-lift configuration at wind tunnel conditions of Mach number 0.24 and Reynolds number of 1.4 x 10(exp 5) per in. Pitch sweeps were performed at angles of attack from 6 deg to 15 deg. Sideslip angle sweeps at 0 deg <= Beta <= +18 deg were performed at an angle of attack of 8 deg. The lateral and longitudinal performance characteristics were well predicted and very good force and moment comparisons were obtained. A very complex multiple vortical system develops at the higher angles of attack, and detailed postprocessing of the solutions provided a comprehensive three-dimensional understanding of the flow which helps to correlate and interpret the wind tunnel data.

Lessard, Wendy B.

1999-01-01

327

Unstructured Grid Viscous Flow Simulation Over High-Speed Research Technology Concept Airplane at High-Lift Conditions  

NASA Technical Reports Server (NTRS)

Numerical viscous solutions based on an unstructured grid methodology are presented for a candidate high-speed civil transport configuration, designated as the Technology Concept Airplane (TCA), within the High-Speed Research (HSR) program. The numerical results are obtained on a representative TCA high-lift configuration that consisted of the fuselage and the wing, with deflected full-span leading-edge and trailing-edge flaps. Typical on-and off-surface flow structures, computed at high-lift conditions appropriate for the takeoff and landing, indicated features that are generally plausible. Reasonable surface pressure correlations between the numerical results and the experimental data are obtained at free-stream Mach number M(sub infinity) = 0.25 and Reynolds number based on bar-c R(sub c) = 8 x 10(exp 6) for moderate angles of attack of 9.7 deg. and 13.5 deg. However, above and below this angle-of-attack range, the correlation between computed and measured pressure distributions starts to deteriorate over the examined angle-of-attack range. The predicted longitudinal aerodynamic characteristics are shown to correlate very well with existing experimental data across the examined angle-of-attack range. An excellent agreement is also obtained between the predicted lift-to-drag ratio and the experimental data over the examined range of flow conditions.

Ghaffari, Farhad

1999-01-01

328

Grid Sensitivity and Aerodynamic Optimization of Generic Airfoils  

NASA Technical Reports Server (NTRS)

An algorithm is developed to obtain the grid sensitivity with respect to design parameters for aerodynamic optimization. The procedure is advocating a novel (geometrical) parameterization using spline functions such as NURBS (Non-Uniform Rational B- Splines) for defining the airfoil geometry. An interactive algebraic grid generation technique is employed to generate C-type grids around airfoils. The grid sensitivity of the domain with respect to geometric design parameters has been obtained by direct differentiation of the grid equations. A hybrid approach is proposed for more geometrically complex configurations such as a wing or fuselage. The aerodynamic sensitivity coefficients are obtained by direct differentiation of the compressible two-dimensional thin-layer Navier-Stokes equations. An optimization package has been introduced into the algorithm in order to optimize the airfoil surface. Results demonstrate a substantially improved design due to maximized lift/drag ratio of the airfoil.

Sadrehaghighi, Ideen; Smith, Robert E.; Tiwari, Surendra N.

1995-01-01

329

Computational Analysis of Compressibility Effects on a High-Lift Wing  

NASA Technical Reports Server (NTRS)

The objective of this study was to investigate compressibility effects on a high-lift flowfield by simulating the flow about a three-dimensional multi-element wing. The computations were performed by solving both the incompressible and compressible Navier-Stokes equations (using the INS3D and OVERFLOW codes) on structured, overset grids. Turbulence was modeled via the one-equation, fully turbulent Spalart-Allmaras model. The computational results were validated with surface pressure measurements acquired at the NASA Ames 7- by 10-Foot Wind Tunnel. The geometry used for all computations consisted of an unswept wing in a landing configuration with a half-span flap and a three-quarter-span slat mounted inside a rectangular duct approximating the wind tunnel walls. The solutions were carefully examined to account for effects due to differences in algorithms. Compressibility effects were demonstrated by comparing surface particle traces, sectional pressure coefficient and boundary layer profile plots. It was found that small regions of compressibility near the slat and main-element leading edge can largely impact the flow. Even small compressibility regions can have significant global effects on the circulation and separation of each of the high-lift elements.

Baker, M. David; Nixon, David (Technical Monitor)

1999-01-01

330

Lift evaluation of a two-dimensional pitching flat plate X. Xia and K. Mohseni  

E-print Network

Lift evaluation of a two-dimensional pitching flat plate X. Xia and K. Mohseni Citation: Phys://pof.aip.org/authors #12;PHYSICS OF FLUIDS 25, 091901 (2013) Lift evaluation of a two-dimensional pitching flat plate X shown that a leading edge vortex (LEV) on an airfoil or wing can provide lift enhancement. In this paper

Mohseni, Kamran

331

Effect of In-Flight Ice Accretion on the Performance of a Multi-Element Airfoil  

NASA Technical Reports Server (NTRS)

The effects of potential in-flight ice accretion on the aerodynamic performance of a multi-element high-lift airfoil have been investigated at moderate-to-high Reynolds numbers. The investigation was conducted in the Low Turbulence Pressure Tunnel (LTPT) at NASA Langley Research Center. Simulated ice shapes obtained from earlier testing in the Icing Research Tunnel (IRT) at NASA Lewis Research Center were used on all three elements of the multi-element configuration. Incremental performance effects due to the ice accretion are presented for both smooth and rough ice accretions. Reynolds number effects on the measured performance characteristics were also assessed. The present results confirm the importance of avoiding any ice accretions on the forward element of a lifting configuration.

Khodadoust, Abdollah; Dominik, Chet; Shin, Jaiwon; Miller, Dean

1995-01-01

332

Nonlinear lift control at high speed and high angle of attack using vortex flow technology  

NASA Technical Reports Server (NTRS)

Nonlinear lift control at subsonic, transonic and low supersonic speeds owes its origin to the separated but organized vortical flows interacting with the wing upper surface. Since most of this flow originates near the wing or control-surface leading edge, a variety of devices has been studied experimentally which interact with and/or control this flow in order to gain a beneficial effect. The benefits (effects) originally studied were associated only with lift enhancement. Whereas, now the studied benefits encompass performance increase, attention to changes in trimmed conditions and longitudinal stability, improvements in lateral stability, and the attendant variation with changing Mach number. For those devices that can be theoretically modeled, state-of-the-art computer codes have been used for device design and/or analysis. Comparisons at design and off-design conditions are presented for validation purposes.

Lamar, John E.

1987-01-01

333

Eyelid lift  

MedlinePLUS

... lift to improve their appearance. This is called cosmetic or elective surgery. The eyelid lift may be done alone or ... Codere F, Tucker N. Cosmetic blepharoplasty and browplasty. In: ... Skin. 2nd ed . Philadelphia, PA: Elsevier Mosby; 2010:chap 39.

334

Aerodynamics of a Simple Three-Dimensional High-Lift System  

NASA Technical Reports Server (NTRS)

Experimental results are presented for a three-element high-lift system with a half-span flap and both a full- and three-quarter span slat. The simplified wing spanned the wind-tunnel test section with no wing sweep or wing tip. Full- and part-span slat configurations were tested to investigate the three-dimensional effects of a finite-span slat in a landing configuration. With a part-span slat, flow visualization and surface pressures revealed two vortices at the flap tip and one at the slat tip. Compared to the full-span slat case, the part-span slat configuration stalled at a lower angle of attack and yielded reduced lift at all angles of attack. At a representative approach attitude (10 deg), wake surveys indicated comparable induced drag for the full- and part-span slat configurations while the profile drag was more than doubled with a part-span slat. The vorticity contribution of the slat-tip vortex was minimal, suggesting that the vortex dissipates through viscous interaction with the main-element boundary layer. The addition of a lower-surface fence at the slat tip yielded two co-rotating vortices and partially alleviated the profile drag increase of the part-span slat.

Storms, Bruce; Ross, James C.; Takahashi, Timothy T.

1997-01-01

335

A Near-Term, High-Confidence Heavy Lift Launch Vehicle  

NASA Technical Reports Server (NTRS)

The use of well understood, legacy elements of the Space Shuttle system could yield a near-term, high-confidence Heavy Lift Launch Vehicle that offers significant performance, reliability, schedule, risk, cost, and work force transition benefits. A side-mount Shuttle-Derived Vehicle (SDV) concept has been defined that has major improvements over previous Shuttle-C concepts. This SDV is shown to carry crew plus large logistics payloads to the ISS, support an operationally efficient and cost effective program of lunar exploration, and offer the potential to support commercial launch operations. This paper provides the latest data and estimates on the configurations, performance, concept of operations, reliability and safety, development schedule, risks, costs, and work force transition opportunities for this optimized side-mount SDV concept. The results presented in this paper have been based on established models and fully validated analysis tools used by the Space Shuttle Program, and are consistent with similar analysis tools commonly used throughout the aerospace industry. While these results serve as a factual basis for comparisons with other launch system architectures, no such comparisons are presented in this paper. The authors welcome comparisons between this optimized SDV and other Heavy Lift Launch Vehicle concepts.

Rothschild, William J.; Talay, Theodore A.

2009-01-01

336

Tests of related forward-camber airfoils in the variable-density wind tunnel  

NASA Technical Reports Server (NTRS)

A recent investigation of numerous related airfoils indicated that positions of camber forward of the usual location resulted in an increase of the maximum lift. As an extension of this investigation, a series of forward-camber airfoils has been developed, the members of which show airfoil characteristics superior to those of the airfoils previously investigated. The primary object of this report is to present fully corrected results for airfoils in the useful range of shapes. With the data thus made available, an airplane designer may intelligently choose the best possible airfoil-section shape for a given application and may predict to a reasonable degree the aerodynamic characteristics to be expected in flight from the section shape chosen.

Jacobs, Eastman N; Pinkerton, Robert M; Greenberg, Harry

1937-01-01

337

A numerical study of the controlled flow tunnel for a high lift model  

NASA Technical Reports Server (NTRS)

A controlled flow tunnel employs active control of flow through the walls of the wind tunnel so that the model is in approximately free air conditions during the test. This improves the wind tunnel test environment, enhancing the validity of the experimentally obtained test data. This concept is applied to a three dimensional jet flapped wing with full span jet flap. It is shown that a special treatment is required for the high energy wake associated with this and other V/STOL models. An iterative numerical scheme is developed to describe the working of an actual controlled flow tunnel and comparisons are shown with other available results. It is shown that control need be exerted over only part of the tunnel walls to closely approximate free air flow conditions. It is concluded that such a tunnel is able to produce a nearly interference free test environment even with a high lift model in the tunnel.

Parikh, P. C.

1984-01-01

338

Navier-Stokes Computations and Experimental Comparisons for Multielement Airfoil Configurations  

NASA Technical Reports Server (NTRS)

A two-dimensional unstructured Navier-Stokes code is utilized for computing the flow around multielement airfoil configurations. Comparisons are shown for a landing configuration with an advanced-technology flap. Grid convergence studies are conducted to assess inaccuracies caused by inadequate grid resolution. Although adequate resolution is obtained for determining the pressure distributions, further refinement is needed to sufficiently resolve the velocity profiles at high angles of attack. For the advanced flap configuration, comparisons of pressure distributions and lift are made with experimental data. Here, two flap riggings and two Reynolds numbers are considered. In general, the trends caused by variations in these quantities are well predicted by the computations, although the angle of attack for maximum lift is overpredicted.

Anderson, W. Kyle; Bonhaus, Daryl L.; McGhee, Robert; Walker, Betty

1993-01-01

339

NREL Airfoil Families for HAWTs  

Microsoft Academic Search

The development of special-purpose airfoils for horizontal-axis wind turbines (HAWTs) began in 1984 as a joint effort between the National Renewable Energy Laboratory (NREL), formerly the Solar Energy Research Institute (SERI), and Airfoils, Incorporated. Since that time nine airfoil families have been designed for various size rotors using the Eppler Airfoil Design and Analysis Code. A general performance requirement of

J. L. Tangler; D. M. Somers

340

Rotating cylinder design as a lifting generator  

NASA Astrophysics Data System (ADS)

The airfoil shape of a wing has always been the design to generate lift. But few realized that a simple rotating cylinder can also create lift. However, the explanation and study of how a rotating cylinder creates lift are still complex. In remote area where it is difficult for air vehicle to access, the exploration and discovery of different configuration for design concept is rather important. Due to this reason, there is a need to think of a lift generator that can produce better lift (few fold better than conventional airfoil) at lower speed to take off in a short distance of time. This paper will explain the conditions and the design of such a wing using the rotating cylinder concept that will take off in a short time and requires little takeoff and landing strip. Spokes will be attached to the cylinder to force the surrounding air to rotate along with the cylinder. This will create a vortex that hastens the speed of the air on top of the cylinder and at the same time retarding the speed of air below the cylinder. From the results, the rougher surface cylinder produces more lift when rotating and also, higher speed rotation of the cylinder greatly changes the speed of the surrounding air, thus better lift.

Asrokin, Azharrudin; Rizal Ramly, Mohammad; Halim Ahmad, Abdul

2013-12-01

341

Two-dimensional high-lift aerodynamic optimization using neural networks  

Microsoft Academic Search

Artificial neural networks were successfully used to minimize the amount of data required to completely define the aerodynamics of a three-element airfoil. The ability of the neural nets to accurately predict the aerodynamic coefficients, for any flap deflection, gap, and overlap, was demonstrated for both computational and experimental training data sets. Multiple input, single output networks were trained using the

Roxana M. Greenman

1998-01-01

342

Aerodynamic sound of flow past an airfoil  

NASA Technical Reports Server (NTRS)

The long term objective of this project is to develop a computational method for predicting the noise of turbulence-airfoil interactions, particularly at the trailing edge. We seek to obtain the energy-containing features of the turbulent boundary layers and the near-wake using Navier-Stokes Simulation (LES or DNS), and then to calculate the far-field acoustic characteristics by means of acoustic analogy theories, using the simulation data as acoustic source functions. Two distinct types of noise can be emitted from airfoil trailing edges. The first, a tonal or narrowband sound caused by vortex shedding, is normally associated with blunt trailing edges, high angles of attack, or laminar flow airfoils. The second source is of broadband nature arising from the aeroacoustic scattering of turbulent eddies by the trailing edge. Due to its importance to airframe noise, rotor and propeller noise, etc., trailing edge noise has been the subject of extensive theoretical (e.g. Crighton & Leppington 1971; Howe 1978) as well as experimental investigations (e.g. Brooks & Hodgson 1981; Blake & Gershfeld 1988). A number of challenges exist concerning acoustic analogy based noise computations. These include the elimination of spurious sound caused by vortices crossing permeable computational boundaries in the wake, the treatment of noncompact source regions, and the accurate description of wave reflection by the solid surface and scattering near the edge. In addition, accurate turbulence statistics in the flow field are required for the evaluation of acoustic source functions. Major efforts to date have been focused on the first two challenges. To this end, a paradigm problem of laminar vortex shedding, generated by a two dimensional, uniform stream past a NACA0012 airfoil, is used to address the relevant numerical issues. Under the low Mach number approximation, the near-field flow quantities are obtained by solving the incompressible Navier-Stokes equations numerically at chord Reynolds number of 104. The far-field noise is computed using Curle's extension to the Lighthill analogy (Curle 1955). An effective method for separating the physical noise source from spurious boundary contributions is developed. This allows an accurate evaluation of the Reynolds stress volume quadrupoles, in addition to the more readily computable surface dipoles due to the unsteady lift and drag. The effect of noncompact source distribution on the far-field sound is assessed using an efficient integration scheme for the Curle integral, with full account of retarded-time variations. The numerical results confirm in quantitative terms that the far-field sound is dominated by the surface pressure dipoles at low Mach number. The techniques developed are applicable to a wide range of flows, including jets and mixing layers, where the Reynolds stress quadrupoles play a prominent or even dominant role in the overall sound generation.

Wang, Meng

1995-01-01

343

High freestream turbulence levels have been shown to greatly augment the heat transfer along a gas turbine airfoil, particularly for the first stage  

E-print Network

along a gas turbine airfoil, particularly for the first stage nozzle guide vane. For this study regions along a turbine vane. Introduction Accurate predictions of surface heat loads on an airfoil are made diffi- cult by the complex flow structure surrounding the airfoil. Boundary layers developing

Thole, Karen A.

344

Modeling and Grid Generation of Iced Airfoils  

NASA Technical Reports Server (NTRS)

SmaggIce Version 2.0 is a software toolkit for geometric modeling and grid generation for two-dimensional, singleand multi-element, clean and iced airfoils. A previous version of SmaggIce was described in Preparing and Analyzing Iced Airfoils, NASA Tech Briefs, Vol. 28, No. 8 (August 2004), page 32. To recapitulate: Ice shapes make it difficult to generate quality grids around airfoils, yet these grids are essential for predicting ice-induced complex flow. This software efficiently creates high-quality structured grids with tools that are uniquely tailored for various ice shapes. SmaggIce Version 2.0 significantly enhances the previous version primarily by adding the capability to generate grids for multi-element airfoils. This version of the software is an important step in streamlining the aeronautical analysis of ice airfoils using computational fluid dynamics (CFD) tools. The user may prepare the ice shape, define the flow domain, decompose it into blocks, generate grids, modify/divide/merge blocks, and control grid density and smoothness. All these steps may be performed efficiently even for the difficult glaze and rime ice shapes. Providing the means to generate highly controlled grids near rough ice, the software includes the creation of a wrap-around block (called the "viscous sublayer block"), which is a thin, C-type block around the wake line and iced airfoil. For multi-element airfoils, the software makes use of grids that wrap around and fill in the areas between the viscous sub-layer blocks for all elements that make up the airfoil. A scripting feature records the history of interactive steps, which can be edited and replayed later to produce other grids. Using this version of SmaggIce, ice shape handling and grid generation can become a practical engineering process, rather than a laborious research effort.

Vickerman, Mary B.; Baez, Marivell; Braun, Donald C.; Hackenberg, Anthony W.; Pennline, James A.; Schilling, Herbert W.

2007-01-01

345

Optimum configuration of high-lift aeromaneuvering orbital transfer vehicles in viscous flow  

NASA Technical Reports Server (NTRS)

The results of an analysis to determine the geometrical configuration of an aeroassisted transfer vehicle with a high lift-to-drag ratio (L/D) are described and the constraints imposed on this type of entry vehicle are considered. The aerodynamic characteristics of three configurations, a flat-plate delta wing, a truncated straight cone, and a truncated bent biconic are compared. The effect of viscosity is included in the analysis which examines the rounding of the sharp leading edges. It is shown that, under the constraints of carrying a given volume in the dead air region, the values of L/D are similar for each configuration and that a small blunt leading edge only slightly affects each vehicle's aerodynamic performance, causing less than a 5 percent drop in L/D. The truncated bent biconic is found to be the only configuration that provides the necessary stabilizing moments.

Davies, C. B.; Park, C.

1985-01-01

346

Automatic multi-block grid generation for high-lift configuration wings  

NASA Technical Reports Server (NTRS)

A new method for automatic multi-block grid generation is described. The method combines the Modified Advancing Front Method as a Predictor with an elliptic scheme as a corrector. It advances a collection of cells by one cell height in the outward direction using Modified Advancing Front Method, and then corrects newly-obtained cell positions by solving elliptic equations. This predictor-corrector type scheme is repeatedly applied until the field of interest is filled with hexahedral grid cells. Given the configuration surface grid, the scheme produces block layouts as well as grid cells with overall smoothness as its output. The present method saves human-time and reduces the burden on the user in generating grids for general 3-D configurations. It was used to generate multi-block grids for wings in their high-lift configuration.

Kim, Byoungsoo; Eberhardt, Scott

1995-01-01

347

Pig lift: A new artifical lift method  

SciTech Connect

Artificial lift of oil wells is a fairly broad subject. There are many different methods available but in a few cases none of them turns out to be a fit option. Some specific situation such as high viscosity or waxy oil, high gas-to-liquid ratio (GLR), horizontal and/or very deep well generate artificial lift problems that causes high reservoir back pressure, and, consequently, low production rates. Pig lift is a new novel artificial lift method developed to solve some of these problems. It uses a U-shaped double completion string in the wellbore, with a full bore bottom hole connector, and a surface piping and control system. This physical arrangement is put together to allow the cyclic and automated launching of a low density foam pig from the surface, pushing along with it the liquid phase accumulated into the tubing string. The method is, therefore, cyclic. High pressure gas is used to displace the pig. The system was successfully installed in five wells in Brazil, increasing the production flow rate significantly, as compared to conventional artificial lift methods. This paper presents the description of the pig lift method, and reports the results obtained in these field trials. Discussions of its technical and economical advantages and potential areas of application is also given.

Lima, P.C.R.

1996-12-31

348

Multiple piece turbine airfoil  

DOEpatents

A turbine airfoil, such as a rotor blade or a stator vane, for a gas turbine engine, the airfoil formed as a shell and spar construction with a plurality of dog bone struts each mounted within openings formed within the shell and spar to allow for relative motion between the spar and shell in the airfoil chordwise direction while also forming a seal between adjacent cooling channels. The struts provide the seal as well as prevent bulging of the shell from the spar due to the cooling air pressure.

Kimmel, Keith D (Jupiter, FL); Wilson, Jr., Jack W. (Palm Beach Gardens, FL)

2010-11-02

349

Piloted Simulation Study of the Effects of High-Lift Aerodynamics on the Takeoff Noise of a Representative High-Speed Civil Transport  

NASA Technical Reports Server (NTRS)

As part of an effort between NASA and private industry to reduce airport-community noise for high-speed civil transport (HSCT) concepts, a piloted simulation study was initiated for the purpose of predicting the noise reduction benefits that could result from improved low-speed high-lift aerodynamic performance for a typical HSCT configuration during takeoff and initial climb. Flight profile and engine information from the piloted simulation were coupled with the NASA Langley Aircraft Noise Prediction Program (ANOPP) to estimate jet engine noise and to propagate the resulting source noise to ground observer stations. A baseline aircraft configuration, which also incorporated different levels of projected improvements in low-speed high-lift aerodynamic performance, was simulated to investigate effects of increased lift and lift-to-drag ratio on takeoff noise levels. Simulated takeoff flights were performed with the pilots following a specified procedure in which either a single thrust cutback was performed at selected altitudes ranging from 400 to 2000 ft, or a multiple-cutback procedure was performed where thrust was reduced by a two-step process. Results show that improved low-speed high-lift aerodynamic performance provides at least a 4 to 6 dB reduction in effective perceived noise level at the FAA downrange flyover measurement station for either cutback procedure. However, improved low-speed high-lift aerodynamic performance reduced maximum sideline noise levels only when using the multiple-cutback procedures.

Glaab, Louis J.; Riley, Donald R.; Brandon, Jay M.; Person, Lee H., Jr.; Glaab, Patricia C.

1999-01-01

350

Aerodynamic loading on a cylinder behind an airfoil  

NASA Astrophysics Data System (ADS)

The interaction between the wake of a rotor blade and a downstream cylinder holds the key to the understanding and control of electronic cooling fan noise. In this paper, the aerodynamic characteristics of a circular cylinder are experimentally studied in the presence of an upstream NACA 4412 airfoil for the cylinder-diameter-based Reynolds numbers of Red=2,100 20,000, and the airfoil chord-length-based Reynolds numbers of Rec=14,700 140,000. Lift and drag fluctuations on the cylinder, and the longitudinal velocity fluctuations of the flow behind the cylinder were measured simultaneously using a load cell and two hot wires, respectively. Data analysis shows that unsteady forces on the cylinder increase significantly in the presence of the airfoil wake. The dependence of the forces on two parameters is investigated, that is, the lateral distance (T) between the airfoil and the cylinder, and the Reynolds number. The forces decline quickly as T increases. For Rec<60,000, the vortices shed from the upstream airfoil make a major contribution to the unsteady forces on the cylinder compared to the vortex shedding from the cylinder itself. For Rec>60,000, no vortices are generated from the airfoil, and the fluctuating forces on the cylinder are caused by its own vortex shedding.

Zhang, H. J.; Huang, L.; Zhou, Y.

2005-05-01

351

High-frequency microwave anti-/de-icing system for carbon-reinforced airfoil structures  

NASA Astrophysics Data System (ADS)

An aircraft may be subjected to icing for a variety of meteorological reasons during the flight. Ice formation on the plane and in particular on the aerodynamically carrying structures adversely affects the flight behaviour. Conventional de-icing methods for aluminum wings are characterised by a high energy consumption during the flight and slow ice melting due to thermal diffusion of the heat in the wing material. In addition to advanced turbines, novel materials and composites have to be used in order to reduce the weight and, hence, the fuel consumption. These composite materials have a far worse thermal conductivity than metals and undergo delamination when hot air systems, resistance or ohmic heating mats are used. In the paper, the unique advantages of a novel High Frequency Microwave Anti-/De-icing System for large future aircraft with carbon reinforced leading edge structures are presented.

Feher, Lambert; Thumm, Manfred

2001-08-01

352

Low-drag airfoils for transonic flow of dense gases  

Microsoft Academic Search

Low-drag airfoils for transonic flow of BZT gases are constructed through a nonlinear small-disturbance theory on this topic. This kind of transonic flow is characterized by the high nonlinearity of the fluid thermodynamic behavior that is closely coupled with its compressible flow dynamics. Utilizing BZT gases may result in low drag exerted on airfoils operating at high transonic speeds. This

Zvi Rusak; Chun-Wei Wang

2000-01-01

353

Low Reynolds Number Flow Dynamics of a Thin, Flat Airfoil with Elastically Mounted Leading Edge Actuator  

NASA Astrophysics Data System (ADS)

Direct numerical simulations are performed to investigate the effect of an elastically mounted leading edge actuator on the unsteady flow at high angles of attack over a flat, thin airfoil at Reynolds number of 14700 based on the chord length. The leading edge actuator is mounted with a torsion spring at one-third the chord length allowing dynamic variations in the effective angle of attack through flow-induced oscillations. The goal is to investigate potential benefits of flow induced flapping motion of the leading edge actuator to the lift and drag characteristics of thin airfoils. The structural model for the rigid actuator is based on a torsional spring-mounted compound pendulum. A fictitious-domain based finite volume approach [(Apte et al. (JCP 2009)] is used to compute this fluid-structure interaction problem on a fixed background mesh. It is shown that a lock-in region leading to limit cycle oscillations of the leading edge actuator can be achieved for certain spring parameters leading to improvements in mean lift-to-drag ratio.

Apte, Sourabh

2011-11-01

354

Suppression of dynamic stall with a leading-edge slat on a VR-7 airfoil  

NASA Technical Reports Server (NTRS)

The VR-7 airfoil was experimentally studied with and without a leading-edge slat at fixed angles of attack from 0 deg to 30 deg at Re = 200,000 and for unsteady pitching motions described by alpha equals alpha(sub m) + 10 deg(sin(wt)). The models were two dimensional, and the test was performed in a water tunnel at Ames Research Center. The unsteady conditions ranged over Re equals 100,000 to 250,000, k equals 0.001 to 0.2, and alpha(sub m) = 10 deg to 20 deg. Unsteady lift, drag, and pitching-moment measurements were obtained along with fluorescent-dye flow visualizations. The addition of the slat was found to delay the static-drag and static-moment stall by about 5 degrees and to eliminate completely the development of a dynamic-stall vortex during unsteady motions that reached angles as high as 25 degrees. In all of the unsteady cases studied, the slat caused a significant reduction in the force and moment hysteresis amplitudes. The reduced frequency was found to have the greatest effect on the results, whereas the Reynolds number had little effect on the behavior of either the basic or the slatted airfoil. The slat caused a slight drag penalty at low angles of attack, but generally increased the lift/drag ratio when averaged over the full cycle of oscillation.

Mcalister, K. W.; Tung, C.

1993-01-01

355

Transonic Airfoil Development  

NASA Technical Reports Server (NTRS)

This lecture consists of three parts, in which discussions are presented of the current state of development of transonic or supercritical airfoils designed for fully turbulent boundary layers on the surfaces, previous research on subcritical airfoils designed to achieve laminar boundary layers on all or parts of the surfaces, and current research on supercritical airfoils designed to achieve laminar boundary layers. In the first part the use of available two dimensional computer codes in the development of supercritical airfoils and the general trends in the design of such airfoils with turbulent boundary layers are discussed. The second part provides the necessary background on laminar boundary layer phenomena. The last part, which constitutes the major portion of the lecture, covers research by NASA on supercritical airfoils utilizing both decreasing pressure gradients and surface suction for stabilizing the laminar boundary layer. An investigation of the former has been recently conducted in fight using gloves on the wing panels of the U.S. Air Force F111 TACT airplane, research on the later is currently being conducted in a transonic wind tunnel which has been modified to greatly reduce the stream turbulence and noise levels in the tests section.

Whitcomb, R. T.

1983-01-01

356

Force control of heavy lift manipulators for high precision insertion tasks  

E-print Network

The inherent strength of robotic manipulators can be used to assist humans in performing heavy lifting tasks. These robots reduce manpower, reduce fatigue, and increase productivity. This thesis deals with the development ...

DiCicco, Matthew A. (Matthew Adam)

2005-01-01

357

Experimental results for the Eppler 387 airfoil at low Reynolds numbers in the Langley low-turbulence pressure tunnel  

NASA Technical Reports Server (NTRS)

Experimental results were obtained for an Eppler 387 airfoil in the Langley Low Turbulence Pressure Tunnel. The tests were conducted over a Mach number range from 0.03 to 0.13 and a chord Reynolds number range for 60,000 to 460,000. Lift and pitching moment data were obtained from airfoil surface pressure measurements and drag data for wake surveys. Oil flow visualization was used to determine laminar separation and turbulent reattachment locations. Comparisons of these results with data on the Eppler 387 airfoil from two other facilities as well as the Eppler airfoil code are included.

Mcghee, Robert J.; Walker, Betty S.; Millard, Betty F.

1988-01-01

358

Computing Aerodynamic Performance of a 2D Iced Airfoil: Blocking Topology and Grid Generation  

NASA Technical Reports Server (NTRS)

The ice accrued on airfoils can have enormously complicated shapes with multiple protruded horns and feathers. In this paper, several blocking topologies are proposed and evaluated on their ability to produce high-quality structured multi-block grid systems. A transition layer grid is introduced to ensure that jaggedness on the ice-surface geometry do not to propagate into the domain. This is important for grid-generation methods based on hyperbolic PDEs (Partial Differential Equations) and algebraic transfinite interpolation. A 'thick' wrap-around grid is introduced to ensure that grid lines clustered next to solid walls do not propagate as streaks of tightly packed grid lines into the interior of the domain along block boundaries. For ice shapes that are not too complicated, a method is presented for generating high-quality single-block grids. To demonstrate the usefulness of the methods developed, grids and CFD solutions were generated for two iced airfoils: the NLF0414 airfoil with and without the 623-ice shape and the B575/767 airfoil with and without the 145m-ice shape. To validate the computations, the computed lift coefficients as a function of angle of attack were compared with available experimental data. The ice shapes and the blocking topologies were prepared by NASA Glenn's SmaggIce software. The grid systems were generated by using a four-boundary method based on Hermite interpolation with controls on clustering, orthogonality next to walls, and C continuity across block boundaries. The flow was modeled by the ensemble-averaged compressible Navier-Stokes equations, closed by the shear-stress transport turbulence model in which the integration is to the wall. All solutions were generated by using the NPARC WIND code.

Chi, X.; Zhu, B.; Shih, T. I.-P.; Slater, J. W.; Addy, H. E.; Choo, Yung K.; Lee, Chi-Ming (Technical Monitor)

2002-01-01

359

Aerodynamic Characterization of a Thin, High-Performance Airfoil for Use in Ground Fluids Testing  

NASA Technical Reports Server (NTRS)

The FAA has worked with Transport Canada and others to develop allowance times for aircraft operating in ice-pellet precipitation. Wind-tunnel testing has been carried out to better understand the flowoff characteristics and resulting aerodynamic effects of anti-icing fluids contaminated with ice pellets using a thin, high-performance wing section at the National Research Council of Canada Propulsion and Icing Wind Tunnel. The objective of this paper is to characterize the aerodynamic behavior of this wing section in order to better understand the adverse aerodynamic effects of anti-icing fluids and ice-pellet contamination. Aerodynamic performance data, boundary-layer surveys and flow visualization were conducted at a Reynolds number of approximately 6.0×10(exp 6) and a Mach number of 0.12. The clean, baseline model exhibited leading-edge stall characteristics including a leading-edge laminar separation bubble and minimal or no separation on the trailing edge of the main element or flap. These results were consistent with expected 2-D aerodynamics and showed no anomalies that could adversely affect the evaluation of anti-icing fluids and ice-pellet contamination on the wing. Tests conducted with roughness and leading-edge flow disturbances helped to explain the aerodynamic impact of the anti-icing fluids and contamination. The stalling characteristics of the wing section with fluid and contamination appear to be driven at least partially by the effects of a secondary wave of fluid that forms near the leading edge as the wing is rotated in the simulated takeoff profile. These results have provided a much more complete understanding of the adverse aerodynamic effects of anti-icing fluids and ice-pellet contamination on this wing section. This is important since these results are used, in part, to develop the ice-pellet allowance times that are applicable to many different airplanes.

Broeren, Andy P.; Lee, Sam; Clark, Catherine

2013-01-01

360

Wind Tunnel Aerodynamic Characteristics of a Transport-type Airfoil in a Simulated Heavy Rain Environment  

NASA Technical Reports Server (NTRS)

The effects of simulated heavy rain on the aerodynamic characteristics of an NACA 64-210 airfoil section equipped with leading-and trailing-edge high-lift devices were investigated in the Langley 14- by 22-Foot Subsonic Tunnel. The model had a chord of 2.5 ft, a span of 8 ft, and was mounted on the tunnel centerline between two large endplates. Aerodynamic measurements in and out of the simulated rain environment were obtained for dynamic pressures of 30 and 50 psf and an angle-of-attack range of 0 to 20 degrees for the cruise configuration. The rain intensity was varied to produce liquid water contents ranging from 16 to 46 gm/cu m. The results obtained for various rain intensity levels and tunnel speeds showed significant losses in maximum lift capability and increases in drag for a given lift as the liquid water content was increased. The results obtained on the landing configuration also indicate a progressive decrease in the angle of attack at which maximum lift occurred and an increase in the slope of the pitching-moment curve as the liquid water content was increased. The sensitivity of test results to the effects of the water surface tension was also investigated. A chemical was introduced into the rain environment that reduced the surface tension of water by a factor of 2. The reduction in the surface tension of water did not significantly alter the level of performance losses for the landing configuration.

Bezos, Gaudy M.; Dunham, R. Earl, Jr.; Gentry, Garl L., Jr.; Melson, W. Edward, Jr.

1992-01-01

361

Predicted Aerodynamic Characteristics of a NACA 0015 Airfoil Having a 25% Integral-Type Trailing Edge Flap  

NASA Technical Reports Server (NTRS)

Using the two-dimensional ARC2D Navier-Stokes flow solver analyses were conducted to predict the sectional aerodynamic characteristics of the flapped NACA-0015 airfoil section. To facilitate the analyses and the generation of the computational grids, the airfoil with the deflected trailing edge flap was treated as a single element airfoil with no allowance for a gap between the flap's leading edge and the base of the forward portion of the airfoil. Generation of the O-type computational grids was accomplished using the HYGRID hyperbolic grid generation program. Results were obtained for a wide range of Mach numbers, angles of attack and flap deflections. The predicted sectional lift, drag and pitching moment values for the airfoil were then cast in tabular format (C81) to be used in lifting-line helicopter rotor aerodynamic performance calculations. Similar were also generated for the flap. Mathematical expressions providing the variation of the sectional lift and pitching moment coefficients for the airfoil and for the flap as a function of flap chord length and flap deflection angle were derived within the context of thin airfoil theory. The airfoil's sectional drag coefficient were derived using the ARC2D drag predictions for equivalent two dimensional flow conditions.

Hassan, Ahmed

1999-01-01

362

Oscillatory Behavior of an Arc Airfoil in Low-Speed Airflow  

NASA Astrophysics Data System (ADS)

A computational investigation is conducted to study the oscillatory behavior of an arc airfoil situated in low-speed airflow. The present work is relevant to situations where the conventional rigid airfoils do not apply, such as the flight of bats. The outcome of this study is also beneficial in the design of micro air vehicles with flexible wings. The computations are performed using a deforming mesh to accommodate the airfoil oscillations. An unsteady, spatially second-order algorithm is employed to capture the time-variations of the lift and drag coefficients. A key feature of the present work is the flow response to airfoil oscillations. Fast Fourier Transform was applied to various parameters of the flow. For certain values of angle of attack for the non-oscillating airfoil, the flow has a dominant frequency and a well-defined vortex shedding. For other values of angle of attack, the flow around the non-oscillating airfoil contains many frequencies and has complex vortical structures. However, the oscillating airfoil in all cases makes the flow field periodic with well-defined patterns of vortex shedding. In this work, the flux of vorticity from the airfoil surface into the airflow is computed and compared with the pressure gradient along the surface of the airfoil. Effects of oscillations on magnitude and behavior of aerodynamic forces are also studied.

Molki, Majid; Sattari, Negin

2011-11-01

363

Samus Counter Lifting Fixture  

SciTech Connect

A lifting fixture has been designed to handle the Samus counters. These counters are being removed from the D-zero area and will be transported off site for further use at another facility. This fixture is designed specifically for this particular application and will be transferred along with the counters. The future use of these counters may entail installation at a facility without access to a crane and therefore a lift fixture suitable for both crane and/or fork lift usage has been created The counters weigh approximately 3000 lbs. and have threaded rods extended through the counter at the top comers for lifting. When these counters were first handled/installed these rods were used in conjunction with appropriate slings and handled by crane. The rods are secured with nuts tightened against the face of the counter. The rod thread is M16 x 2({approx}.625-inch dia.) and extends 2-inch (on average) from the face of the counter. It is this cantilevered rod that the lift fixture engages with 'C' style plates at the four top comers. The strongback portion of the lift fixture is a steel rectangular tube 8-inch (vertical) x 4-inch x .25-inch wall, 130-inch long. 1.5-inch square bars are welded perpendicular to the long axis of the rectangular tube at the appropriate lift points and the 'C' plates are fastened to these bars with 3/4-10 high strength bolts -grade 8. Two short channel sections are positioned-welded-to the bottom of the rectangular tube on 40 feet centers, which are used as locators for fork lift tines. On the top are lifting eyes for sling/crane usage and are rated at 3500 lbs. safe working load each - vertical lift only.

Stredde, H.; /Fermilab

1998-05-27

364

Inverse lift: a signature of the elasticity of complex fluids?  

E-print Network

To understand the mechanics of a complex fluid such as a foam we propose a model experiment (a bidimensional flow around an obstacle) for which an external sollicitation is applied, and a local response is measured, simultaneously. We observe that an asymmetric obstacle (cambered airfoil profile) experiences a downards lift, opposite to the lift usually known (in a different context) in aerodynamics. Correlations of velocity, deformations and pressure fields yield a clear explanation of this inverse lift, involving the elasticity of the foam. We argue that such an inverse lift is likely common to complex fluids with elasticity.

Benjamin Dollet; Miguel Aubouy; Francois Graner

2004-11-25

365

Investigation of Co-Flow Jet Airfoil Mixing Mechanism Using Large Eddy Simulation  

E-print Network

Investigation of Co-Flow Jet Airfoil Mixing Mechanism Using Large Eddy Simulation Hong-Sik IM , Ge) to investigate Co-Flow Jet (CFJ) airfoil flows at high angle of attack (AOA). The standard Smagorinsky model coefficient(Cµ) is chosen as a parameter to control the jet flow of the CFJ airfoil. LES simulations were

Zha, Gecheng

366

IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY 1 Airborne Wind Energy Based on Dual Airfoils  

E-print Network

IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY 1 Airborne Wind Energy Based on Dual Airfoils Mario proposes to generate energy by flying a tethered airfoil across the wind flow at a high velocity. While airfoils with a shared tether can reduce overall system drag. While this technique may improve

367

Further Studies of Airfoils Supporting Non-Unique Solutions in Transonic Flow  

E-print Network

Further Studies of Airfoils Supporting Non-Unique Solutions in Transonic Flow Antony Jameson-unique solutions of the Euler equations were originally discussed by Jameson in 1991 ("Airfoil Admitting Non-Unique Solutions to the Euler Equations," AIAA Paper 1991-1625, June 1991) for several highly cambered airfoils

Jameson, Antony

368

Further Studies of Airfoils Supporting Non-unique Solutions in Transonic Flow  

E-print Network

Further Studies of Airfoils Supporting Non-unique Solutions in Transonic Flow Antony Jameson, John for several highly cambered airfoils which were the result of aggressive shape optimization. In 1999 Hafez and Guo found non-unique solutions for a symmetric parallel sided airfoil, and subsequently Kuzmin

Stanford University

369

Active Control of Flow around NACA 0015 Airfoil by Using DBD Plasma Actuator  

NASA Astrophysics Data System (ADS)

In this study, effect of plasma actuator on a flat plate and manipulation of flow separation on NACA0015 airfoil with plasma actuator at low Reynolds numbers were experimentally investigated. In the first section of the study, plasma actuator which consists of positive and grounded electrode couple and dielectric layer, located on a flat plate was actuated at different frequencies and peak to peak voltages in range of 3-5 kHz and 6-12 kV respectively. Theinduced air flow velocity on the surface of flat plate was measured by pitot tube at different locations behind the actuator. The influence of dielectricthickness and unsteady actuation with duty cycle was also examined. In the second section, the effect of plasma actuator on NACA0015 airfoil was studied atReynolds number 15000 and 30000. Four plasma actuators were placed at x/C = 0.1, 0.3, 0.5 and 0.9, and different electrode combinations were activated by sinusoidal signal. Flow visualizations were done when the attack angles were 0°, 5°, 10°, 15° and 20°. The results indicate that up to the 15° attack angle, the separated flow was reattached by plasma actuator at 12kV peak to peak voltage and 4 kHz frequency. However, 12 kVpp voltage was insufficient to reattach the flow at 20° angle of attack. The separated flow could be reattached by increasing the voltage up to 13 kV. Lift coefficient was also increased by the manipulated flow over the airfoil. Results showed that even high attack angles, the actuators can control the flow separation and prevent the airfoil from stall at low Reynolds numbers.

Akansu, Y. E.; Karakaya, F.; ?anl?soy, A.

2013-04-01

370

Patterning of epitaxial VO2 microstructures by a high-temperature lift-off process  

NASA Astrophysics Data System (ADS)

The growing field of oxide-electronics demands adequate fabrication methods that do not impair the material’s beneficial properties. To this end, we present a modified lift-off lithography method replacing the conventional polymer mask with an AlOx based mask. It can sustain the high-temperature and reactive gasses conditions commonly needed for oxide deposition, and is effectively wet-etched in dilute NaOH solutions. Here we demonstrate patterning of VO2 films. With its metal–insulator transition (MIT) near room temperature, it is attractive for various applications including sensors and transistors. But patterning is challenging since its properties are very sensitive to fabrication processes. We demonstrate patterning of 3 ?m wide VO2 electrodes and show they preserve the MIT magnitude and epitaxial growth of the non-patterned films. Some thinning of the VO2 is also observed. This process can be useful for patterning other materials that require harsh deposition conditions, and are resilient to low NaOH concentrations.

Yamin, Tony; Havdala, Tal; Sharoni, Amos

2014-12-01

371

Design and Experimental Results for the S827 Airfoil; Period of Performance: 1998--1999  

SciTech Connect

A 21%-thick, natural-laminar-flow airfoil, the S827, for the 75% blade radial station of 40- to 50-meter, stall-regulated, horizontal-axis wind turbines has been designed and analyzed theoretically and verified experimentally in the NASA Langley Low-Turbulence Pressure Tunnel. The primary objective of restrained maximum lift has not been achieved, although the maximum lift is relatively insensitive to roughness, which meets the design goal. The airfoil exhibits a relatively docile stall, which meets the design goal. The primary objective of low profile drag has been achieved. The constraints on the pitching moment and the airfoil thickness have been satisfied. Comparisons of the theoretical and experimental results generally show good agreement with the exception of maximum lift, which is significantly underpredicted.

Somers, D. M.

2005-01-01

372

Automated CFD for Generation of Airfoil Performance Tables  

NASA Technical Reports Server (NTRS)

A method of automated computational fluid dynamics (CFD) has been invented for the generation of performance tables for an object subject to fluid flow. The method is applicable to the generation of tables that summarize the effects of two-dimensional flows about airfoils and that are in a format known in the art as C81. (A C81 airfoil performance table is a text file that lists coefficients of lift, drag, and pitching moment of an airfoil as functions of angle of attack for a range of Mach numbers.) The method makes it possible to efficiently generate and tabulate data from simulations of flows for parameter values spanning all operational ranges of actual or potential interest. In so doing, the method also enables filling of gaps and resolution of inconsistencies in C81 tables generated previously from incomplete experimental data or from theoretical calculations that involved questionable assumptions.

Strawn, Roger; Mayda, E. Q.; vamDam, C. P.

2009-01-01

373

Airfoil Vibration Dampers program  

NASA Technical Reports Server (NTRS)

The Airfoil Vibration Damper program has consisted of an analysis phase and a testing phase. During the analysis phase, a state-of-the-art computer code was developed, which can be used to guide designers in the placement and sizing of friction dampers. The use of this computer code was demonstrated by performing representative analyses on turbine blades from the High Pressure Oxidizer Turbopump (HPOTP) and High Pressure Fuel Turbopump (HPFTP) of the Space Shuttle Main Engine (SSME). The testing phase of the program consisted of performing friction damping tests on two different cantilever beams. Data from these tests provided an empirical check on the accuracy of the computer code developed in the analysis phase. Results of the analysis and testing showed that the computer code can accurately predict the performance of friction dampers. In addition, a valuable set of friction damping data was generated, which can be used to aid in the design of friction dampers, as well as provide benchmark test cases for future code developers.

Cook, Robert M.

1991-01-01

374

Study of laminar separation bubble on low Reynolds number operating airfoils: RANS modelling by means of an high-accuracy solver and experimental verification  

NASA Astrophysics Data System (ADS)

This work is devoted to the Computational Fluid-Dynamics (CFD) simulation of laminar separation bubble (LSB) on low Reynolds number operating airfoils. This phenomenon is of large interest in several fields, such as wind energy, and it is characterised by slow recirculating flow at an almost constant pressure. Presently Reynolds Averaged Navier-Stokes (RANS) methods, due to their limited computational requests, are the more efficient and feasible CFD simulation tool for complex engineering applications involving LSBs. However adopting RANS methods for LSB prediction is very challenging since widely used models assume a fully turbulent regime. For this reason several transitional models for RANS equations based on further Partial Differential Equations (PDE) have been recently introduced in literature. Nevertheless in some cases they show questionable results. In this work RANS equations and the standard Spalart-Allmaras (SA) turbulence model are used to deal with LSB problems obtaining promising results. This innovative result is related to: (i) a particular behaviour of the SA equation; (ii) a particular implementation of SA equation; (iii) the use of a high-order discontinuous Galerkin (DG) solver. The effectiveness of the proposed approach is tested on different airfoils at several angles of attack and Reynolds numbers. Numerical results were verified with both experimental measurements performed at the open circuit subsonic wind tunnel of Universitŕ Politecnica delle Marche (UNIVPM) and literature data.

Crivellini, A.; D'Alessandro, V.; Di Benedetto, D.; Montelpare, S.; Ricci, R.

2014-04-01

375

Trends of Reynolds number effects on two-dimensional airfoil characteristics for helicopter rotor analyses  

NASA Technical Reports Server (NTRS)

The primary effects of Reynolds number on two dimensional airfoil characteristics are discussed. Results from an extensive literature search reveal the manner in which the minimum drag and maximum lift are affected by the Reynolds number. C sub d sub min and C sub l sub max are plotted versus Reynolds number for airfoils of various thickness and camber. From the trends observed in the airfoil data, universal scaling laws and easily implemented methods are developed to account for Reynolds number effects in helicopter rotor analyses.

Yamauchi, G. K.; Johnson, W.

1983-01-01

376

Wind-tunnel Investigation of High-lift and Stall-control Devices on a 37 Degree Sweptback Wing of Aspect Ratio 6 at High Reynolds Numbers  

NASA Technical Reports Server (NTRS)

Results are presented of an investigation in the Langley 19-foot pressure tunnel of the longitudinal characteristics of a semispan model wing having 37 degrees sweepback of the leading edge, an aspect ratio of 6, and NACA 641-212 airfoil section perpendicular to the 27-percent-chord line. Several types of stall-control devices including extensible round-nose leading-edge flaps, a leading-edge slat, and a drooped leading edge were investigated; partial- and full-span trailing-edge split and double slotted flaps were also tested. In addition, various combinations of the aforementioned leading- and trailing-edge flaps were investigated. The tests covered a range of Reynolds numbers between 2.00 x 10(6) and 9.35 x 10(6). The wing with or without trailing-edge splity of double slotted flap was longitudinally unstable near maximum lift due to tip stalling. The addition of an outboard half-span leading-edge flap or a leading-edge slat to the plain wing or wing with inboard half-span split flaps eliminated tip stalling and resulted in stable moment variations at the stall. The drooped leading edge, on the other hand, was only effective when used in conjunction with an upper-surface fence. The combination of an outboard leading-edge device and inboard half-span double slotted flap resulted in an undesirable loop in the pitching-moment curve near maximum lift in spite of an inboard stall. The loop is attributed to the section characteristics of the double slotted flap. Air-flow surveys behind the wing indicated that a suitably placed horizontal tail would eliminate the loop in the moment curve.

Koven, William; Graham, Robert R

1948-01-01

377

Robust, Optimal Subsonic Airfoil Shapes  

NASA Technical Reports Server (NTRS)

A method has been developed to create an airfoil robust enough to operate satisfactorily in different environments. This method determines a robust, optimal, subsonic airfoil shape, beginning with an arbitrary initial airfoil shape, and imposes the necessary constraints on the design. Also, this method is flexible and extendible to a larger class of requirements and changes in constraints imposed.

Rai, Man Mohan

2014-01-01

378

An Experimental Evaluation of Advanced Rotorcraft Airfoils in the NASA Ames Eleven-foot Transonic Wind Tunnel  

NASA Technical Reports Server (NTRS)

Five full scale rotorcraft airfoils were tested in the NASA Ames Eleven-Foot Transonic Wind Tunnel for full scale Reynolds numbers at Mach numbers from 0.3 to 1.07. The models, which spanned the tunnel from floor to ceiling, included two modern baseline airfoils, the SC1095 and SC1094 R8, which have been previously tested in other facilities. Three advanced transonic airfoils, designated the SSC-A09, SSC-A07, and SSC-B08, were tested to confirm predicted performance and provide confirmation of advanced airfoil design methods. The test showed that the eleven-foot tunnel is suited to two-dimensional airfoil testing. Maximum lift coefficients, drag coefficients, pitching moments, and pressure coefficient distributions are presented. The airfoil analysis codes agreed well with the data, with the Grumman GRUMFOIL code giving the best overall performance correlation.

Flemming, Robert J.

1984-01-01

379

Experimental Optimization Methods for Multi-Element Airfoils  

NASA Technical Reports Server (NTRS)

A modern three element airfoil model with a remotely activated flap was used to investigate optimum flap testing position using an automated optimization algorithm in wind tunnel tests. Detailed results for lift coefficient versus flap vertical and horizontal position are presented for two angles of attack: 8 and 14 degrees. An on-line first order optimizer is demonstrated which automatically seeks the optimum lift as a function of flap position. Future work with off-line optimization techniques is introduced and aerodynamic hysteresis effects due to flap movement with flow on are discussed.

Landman, Drew; Britcher, Colin P.

1996-01-01

380

Airfoil Pressure Distribution Investigation in the Variable Density Wind Tunnel  

NASA Technical Reports Server (NTRS)

Report presents the results of wind tunnel tests of pressure distribution measurements over one section each of six airfoils. Pressure distribution diagrams, as well as the integrated characteristics of the airfoils, are given for both a high and a low dynamic scale or, Reynolds number VL/V, for comparison with flight and other wind-tunnel tests, respectively. It is concluded that the scale effect is very important only at angles of attack near the burble. The distribution of pressure over an airfoil having a Joukowski section is compared with the theoretically derived distribution. A further study of the distribution of pressure over all of the airfoils resulted in the development of an approximate method of predicting the pressure distribution along the chord of any normal airfoil for all attitudes within the working range if the distribution at one attitude is known.

Jacobs, Eastman N; Stack, John; Pinkerton, Robert M

1931-01-01

381

A perfusion air-lift bioreactor for high density plant cell cultivation and secreted protein production  

Microsoft Academic Search

A new bioreactor design that allows continuous perfusion cultivation of plant cell suspensions is described in this paper. This design incorporates an internal cell settling zone with an external-loop air-lift bioreactor. The settling zone is created by inserting a baffle plate into the upper portion of the downcomer. Using this bioreactor, Anchusa officinalis suspension culture was cultivated to a cell

Wei Wen Su; Bing Jun He; Hua Liang; Sam Sun

1996-01-01

382

High-lift flow-physics flight experiments on a subsonic civil transport aircraft (B737-100)  

NASA Technical Reports Server (NTRS)

As part of the subsonic transport high-lift program, flight experiments are being conducted using NASA Langley's B737-100 to measure the flow characteristics of the multi-element high-lift system at full-scale high-Reynolds-number conditions. The instrumentation consists of hot-film anemometers to measure boundary-layer states, an infra-red camera to detect transition from laminar to turbulent flow, Preston tubes to measure wall shear stress, boundary-layer rakes to measure off-surface velocity profiles, and pressure orifices to measure surface pressure distributions. The initial phase of this research project was recently concluded with two flights on July 14. This phase consisted of a total of twenty flights over a period of about ten weeks. In the coming months the data obtained in this initial set of flight experiments will be analyzed and the results will be used to finalize the instrumentation layout for the next set of flight experiments scheduled for Winter and Spring of 1995. The main goal of these upcoming flights will be: (1) to measure more detailed surface pressure distributions across the wing for a range of flight conditions and flap settings; (2) to visualize the surface flows across the multi-element wing at high-lift conditions using fluorescent mini tufts; and (3) to measure in more detail the changes in boundary-layer state on the various flap elements as a result of changes in flight condition and flap deflection. These flight measured results are being correlated with experimental data measured in ground-based facilities as well as with computational data calculated with methods based on the Navier-Stokes equations or a reduced set of these equations. Also these results provide insight into the extent of laminar flow that exists on actual multi-element lifting surfaces at full-scale high-life conditions. Preliminary results indicate that depending on the deflection angle, the slat and flap elements have significant regions of laminar flow over a wide range of angles of attack. Boundary-layer transition mechanisms that were observed include attachment-line contamination on the slat and inflectional instability on the slat and fore flap. Also, the results agree fairly well with the predictions reported in a paper presented at last year's AIAA Fluid Dynamics Conference. The fact that extended regions of laminar flow are shown to exist on the various elements of the high-lift system raises the question what the effect is of loss of laminar flow as a result of insect contamiantion, rain or ice accumulation on high-life performance.

Vandam, Cornelis P.

1994-01-01

383

2-D Circulation Control Airfoil Benchmark Experiments Intended for CFD Code Validation  

NASA Technical Reports Server (NTRS)

A current NASA Research Announcement (NRA) project being conducted by Georgia Tech Research Institute (GTRI) personnel and NASA collaborators includes the development of Circulation Control (CC) blown airfoils to improve subsonic aircraft high-lift and cruise performance. The emphasis of this program is the development of CC active flow control concepts for both high-lift augmentation, drag control, and cruise efficiency. A collaboration in this project includes work by NASA research engineers, whereas CFD validation and flow physics experimental research are part of NASA s systematic approach to developing design and optimization tools for CC applications to fixed-wing aircraft. The design space for CESTOL type aircraft is focusing on geometries that depend on advanced flow control technologies that include Circulation Control aerodynamics. The ability to consistently predict advanced aircraft performance requires improvements in design tools to include these advanced concepts. Validation of these tools will be based on experimental methods applied to complex flows that go beyond conventional aircraft modeling techniques. This paper focuses on recent/ongoing benchmark high-lift experiments and CFD efforts intended to provide 2-D CFD validation data sets related to NASA s Cruise Efficient Short Take Off and Landing (CESTOL) study. Both the experimental data and related CFD predictions are discussed.

Englar, Robert J.; Jones, Gregory S.; Allan, Brian G.; Lin, Johb C.

2009-01-01

384

High Reynolds number tests of the cast 10-2/DOA 2 airfoil in the Langley 0.3-meter transonic cryogenic tunnel, phase 2  

NASA Technical Reports Server (NTRS)

Wind tunnel tests of an advanced technology airfoil, the CAST 10-2/DOA 2, were conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT). This was the third of a series of tests conducted in a cooperative airfoil research program between the National Aeronautics and Space Administration and the Deutsche Forschungsund Versuchsanstalt fur Luft- und Raumfahrt e. V. For these tests, temperature was varied from 270 K to 110 K at pressures from 1.5 to 5.75 atmospheres. Mach number was varied from 0.60 to 0.80, and the Reynolds number (based on airfoil chord) was varied from 2 to 20 million. The aerodynamic data for the 7.62 cm chord airfoil model used in these tests is presented without analysis. Descriptions of the 0.3-m TCT, the airfoil model, the test instrumentation, and the testing procedures are included.

Dress, D. A.; Stanewsky, E.; Mcguire, P. D.; Ray, E. J.

1984-01-01

385

High Reynolds number tests of the CAST 10-2/DOA 2 airfoil in the Langley 0.3-meter transonic cryogenic tunnel, phase 1  

NASA Technical Reports Server (NTRS)

A wind tunnel investigation of an advanced technology airfoil, the CAST 10-2/DOA 2, was conducted in the Langley 0.3 meter Transonic Cryogenic Tunnel (0.3 m TCT). This was the first of a series of tests conducted in a cooperative National Aeronautics and Space Administration (NASA) and the Deutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt e. V. (DFVLR) airfoil research program. Test temperature was varied from 280 K to 100 K to pressures from slightly above 1 to 5.8 atmospheres. Mach number was varied from 0.60 to 0.80, and the Reynolds number (based on airfoil chord) was varied from 4 x 10 to the 8th power to 45 x 10 to the 6th power. This report presents the experimental aerodynamic data obtained for the airfoil and includes descriptions of the airfoil model, the 0.3 m TCT, the test instrumentation, and the testing procedures.

Dress, D. A.; Mcguire, P. D.; Stanewsky, E.; Ray, E. J.

1983-01-01

386

Rime ice accretion and its effect on airfoil performance. Ph.D. Thesis. Final Report  

NASA Technical Reports Server (NTRS)

A methodology was developed to predict the growth of rime ice, and the resulting aerodynamic penalty on unprotected, subcritical, airfoil surfaces. The system of equations governing the trajectory of a water droplet in the airfoil flowfield is developed and a numerical solution is obtained to predict the mass flux of super cooled water droplets freezing on impact. A rime ice shape is predicted. The effect of time on the ice growth is modeled by a time-stepping procedure where the flowfield and droplet mass flux are updated periodically through the ice accretion process. Two similarity parameters, the trajectory similarity parameter and accumulation parameter, are found to govern the accretion of rime ice. In addition, an analytical solution is presented for Langmuir's classical modified inertia parameter. The aerodynamic evaluation of the effect of the ice accretion on airfoil performance is determined using an existing airfoil analysis code with empirical corrections. The change in maximum lift coefficient is found from an analysis of the new iced airfoil shape. The drag correction needed due to the severe surface roughness is formulated from existing iced airfoil and rough airfoil data. A small scale wind tunnel test was conducted to determine the change in airfoil performance due to a simulated rime ice shape.

Bragg, M. B.

1982-01-01

387

Oscillatory blowing airfoil  

NASA Technical Reports Server (NTRS)

10' NACA 0015 with 30% chord trailing edge flap deflected 20 degrees. Used in 0.3 Meter Transonic Cryogenic Tunnel, this airfoil has a 0.44 mm slot at 70% chord. Oscillatory blowing out of slot used for separation control. Howard Price appears in side view shot, in building 1145, Studio.

1997-01-01

388

Active Control of Separation From the Flap of a Supercritical Airfoil  

NASA Technical Reports Server (NTRS)

Active flow control in the form of periodic zero-mass-flux excitation was applied at several regions on the leading edge and trailing edge flaps of a simplified high-lift system t o delay flow separation. The NASA Energy Efficient Transport (EET) supercritical airfoil was equipped with a 15% chord simply hinged leading edge flap and a 25% chord simply hinged trailing edge flap. Detailed flow features were measured in an attempt to identify optimal actuator placement. The measurements included steady and unsteady model and tunnel wall pressures, wake surveys, arrays of surface hot-films, flow visualization, and particle image velocimetry (PIV). The current paper describes the application of active separation control at several locations on the deflected trailing edge flap. High frequency (F(+) approx.= 10) and low frequency amplitude modulation (F(+)AM approx.= 1) of the high frequency excitation were used for control. Preliminary efforts to combine leading and trailing edge flap excitations are also reported.

Melton, La Tunia Pack; Yao, Chung-Sheng; Seifert, Avi

2003-01-01

389

AEROELASTICITY OF AN AIRFOIL TEST RIG  

Microsoft Academic Search

This paper describes an aeroelastic model for an airfoil test rig which is based on the mode superposition method for structural systems and linear airfoil theory for describing the unsteady airfoil loading. The model is applied to the case of an airfoil undergoing rapid, small amplitude step-like maneuvers. The motivation for these tests was an interest in measuring airfoil indicial

G. M. Graham; J. E. Jenkins

1997-01-01

390

Airfoil longitudinal gust response in separated vs. attached flows  

NASA Astrophysics Data System (ADS)

Airfoil aerodynamic loads are expected to have quasi-steady, linear dependence on the history of input disturbances, provided that small-amplitude bounds are observed. We explore this assertion for the problem of periodic sinusoidal streamwise gusts, by comparing experiments on nominally 2D airfoils in temporally sinusoidal modulation of freestream speed in a wind tunnel vs. sinusoidal displacement of the airfoil in constant freestream in a water tunnel. In the wind tunnel, there is a streamwise unsteady pressure gradient causing a buoyancy force, while in the water tunnel one must subtract the inertial load of the test article. Both experiments have an added-mass contribution to aerodynamic force. Within measurement resolution, lift and drag, fluctuating and mean, were in good agreement between the two facilities. For incidence angle below static stall, small-disturbance theory was found to be in good agreement with measured lift history, regardless of oscillation frequency. The circulatory component of fluctuating drag was found to be independent of oscillation frequency. For larger incidence angles, there is marked departure between the measured lift history and that predicted from Greenberg's formula. Flow visualization shows coupling between bluff-body shedding and motion-induced shedding, identifiable with lift cancellation or augmentation, depending on the reduced frequency. Isolating the buoyancy effect in the wind tunnel and dynamic tares in the water tunnel, and theoretical calculation of apparent-mass in both cases, we arrive at good agreement in measured circulatory contribution between the two experiments whether the flow is attached or separated substantiating the linear superposition of the various constituents to total lift and drag, and supporting the idea that aerodynamic gust response can legitimately be studied in a steady freestream by oscillating the test article.

Granlund, K.; Monnier, B.; Ol, M.; Williams, D.

2014-02-01

391

Lift and drag in intruders moving through hydrostatic granular media at high speeds  

E-print Network

Recently, experiments showed that forces on intruders dragged horizontally through dense, hydrostatic granular packings mainly depend on the local surface orientation and can be seen as the sum of the forces exerted on small surface elements. In order to understand such forces more deeply, we perform 2D soft-sphere molecular dynamics simulation, on similar set up, of an intruder dragged through a 50-50 bi-disperse granular packing, with diameters 0.30 and 0.34 cm. We measure, for both circular and half-circle shapes, the forces parallel (drag) and perpendicular (lift) to the drag direction as functions of the drag speed, with V=10.3-309 cm/s, and intruder depths, with D=3.75-37.5 cm. The drag forces on an intruder monotonically increase with V and D, and are larger for the circle. However, the lift force does not depend monotonically on V and D, and this relationship is affected by the shape of the intruder. The vertical force was negative for the half-circle, but for a small range of V and D, we measure positive lift. We find no sign change for the lift on the circle, which is always positive. The explanation for the nonmonotonic dependence is related to the decrease in contacts on the intruder as V increases. This is qualitatively similar to supersonic flow detachment from an obstacle. The detachment picture is supported by simulation measurements of the velocity field around the intruder and force profiles measured on its surface.

Fabricio Q. Potiguar; Yang Ding

2013-06-25

392

Unsteady modes in the flowfield about an airfoil with a leading-edge horn-ice shape  

NASA Astrophysics Data System (ADS)

An analysis of unsteady modes present in the flowfield of an airfoil with a leading-edge horn-ice shape was performed in the current study. An NACA 0012 airfoil was tested in a subsonic wind tunnel at Re = 1.8 x 106. In addition to the clean configuration, the airfoil model was also tested with a set of boundary-layer trips, a two-dimensional extrusion of a horn-ice shape casting, and an array of simulated icing configurations created using simple geometries. Time-averaged and unsteady static pressure measurements were acquired about the airfoil surface, along with unsteady wake velocity and surface hot-film array measurements. Additionally, surface and off-body flow visualization techniques were used to visualize the airfoil flowfield. A technique was also developed to determine the unsteady shear-layer reattachment location of the ice-induced laminar separation bubble downstream of the horn-ice shape using the surface hot-film array measurements. The maximum amount of unsteadiness in the iced-airfoil flowfield was observed to increase with increasing angle of attack. For a fixed angle of attack prior to stall, a change in the feature height of the simulated ice shape led to a change in the distribution of flowfield unsteadiness, but did not change the maximum levels of unsteadiness present in the flowfield. The iced-airfoil flowfield unsteadiness was primarily associated with three different frequencies. The first was represented by an increase in spectral energy across a broad-band frequency range, and was observed just upstream of shear-layer reattachment as well as downstream of shear-layer reattachment. This increase in spectral energy was caused by the regular mode of unsteadiness due to vortical motion in the separated shear layer and vortex shedding from the separation bubble. The average Strouhal number of this regular mode corresponded to StL = 0.60, and the average vortex convection velocity was observed to be 0.45Uinfinity. These values were highly consistent with those reported elsewhere in the literature. The other two frequencies were much lower and were observed as narrow-band peaks in the spectral content of the acquired measurements that were primarily present in the region covered by the ice-induced separation bubble. The first was attributed to the shear-layer flapping phenomenon and was particularly dominant in the upstream portion of the separation bubble. The Strouhal number associated with this shear-layer flapping mode corresponded to St h = 0.0185, which was consistent with those reported in studies of separation bubbles about canonical geometries. The second frequency was lower than that of shear-layer flapping and was associated with a low-frequency mode of unsteadiness that can occur prior to static stall for airfoils of thin-airfoil stall type. This low-frequency mode was characterized by a low-frequency oscillation of the airfoil circulation, and it was clearly identified in the spectral content of the iced-airfoil lift coefficient. The resulting values of Strouhal number exhibited a dependence on the airfoil angle of attack and corresponded to a range that was consistent with the Strouhal number values reported in prior studies of the low-frequency mode in the literature. Using the method for determining the unsteady shear-layer reattachment location, the average time-dependent relationship between the reattachment location and the lift coefficient was calculated. It was discovered that at the low-frequency mode, the lift coefficient leads the shear-layer reattachment location by a phase of pi/2. This phase relationship occurred due to a feedback between the airfoil circulation and the separation bubble length. This improved understanding of the low-frequency mode in the iced-airfoil flowfield was utilized in a practical example to improve the predictive qualities of a hinge-moment-based stall prediction system. This improvement in the predictive qualities was performed by identifying the intermittent signature of the low-frequency mode in the wavelet transform of the hinge moment coeffic

Ansell, Phillip J.

393

Toward an adaptive variable-camber airfoil  

NASA Astrophysics Data System (ADS)

Performance capabilities of future "flight" vehicles will be significantly enhanced by the use of "smart" or adaptive structures. For example, advanced submarine stern configurations will require a variety of control surfaces to actively manage aftbody boundary layer flow, vorticity, propulsor inflow and intrapropulsor flow, as well as vehicle attitude. More specifically, real-time sensing of flow conditions over attitude control surfaces might be utilized to implement advanced camber control algorithms for increased lift without flow separation and improved tactical maneuvering performance with reduced acoustic signature. Thus, two necessary attributes of advanced control surfaces will be (1) integrated actuation to provide placement flexibility at remote locations with minimal structural interfacing and control interconnects, and (2) improved lift efficiency and associated flow characteristics using variable-camber control. The objective of this research effort was to develop a variable-camber airfoil, measure its performance in a wind tunnel, and assess the feasibility of implementing real-time camber optimization algorithms by using surface pressure readings. To begin, a numerical vortex blob method with integral boundary layer solvers was used to compare predicted lift performance between a variable-camber NACA 0012 airfoil fixed at 1/4 chord and its rigid full-flying baseline counterpart. Results at Re = 10,000,000 show a factor of two increase in maximum lift possible using variable-camber with a fixed wingbox. Subsequently, a 610 mm spanwise uniform test article, measuring 508 mm in chord and bilaterally capable of 18% camber at 21 degrees angle-of-attack, was developed using pneumatic actuation (with co-located servovalves, actuation cells, and displacement sensors) to control four discrete chordwise foil segments. Wind tunnel testing of the active and rigid 0012 foil sections (albeit limited to Re = 276,000 and associated dominance of laminar over turbulent flow separation) demonstrated an 80% increase in maximum lift possible with the variable-camber foil. Lastly, a camber optimization approach was identified and simulated using a Simplex algorithm to minimize error between prescribed and measured foil surface pressure distributions, thereby providing a means to control boundary layer development and its impact on flow transition and separation.

Maclean, Brian J.

394

Sinus Lift  

MedlinePLUS

... antibiotic and an antimicrobial mouthwash to help prevent infection. Most patients have only a little discomfort after a sinus-lift procedure. You will see the specialist after 7 to 10 days. He or she will evaluate the surgical site and remove stitches if they will not dissolve ...

395

Lift Off!  

NSDL National Science Digital Library

This activity (on page 2 of the PDF) is a full inquiry investigation into the engineering challenges of sending scientific sensors into space. Groups of learners will develop sensors to be deployed on model rockets to measure or indicate selected properties encountered during each rocketâs flight, test launching and modifying as necessary to gather data. Relates to linked video, DragonflyTV: Lift Off!

Twin Cities Public Television, Inc.

2005-01-01

396

Detailed measurements of the flowfield in the vicinity of an airfoil with glaze ice  

NASA Technical Reports Server (NTRS)

An experimental study has been conducted in the OSU subsonic tunnel to measure the characteristics of the separation bubble on an airfoil with glaze ice. A measured glaze ice accretion on a NACA 0012 airfoil was simulated in wood for this dry tunnel test. The 21 inch chord model was pressure belted and the ice shape internally tapped to obtain surface pressures, lift and moment coefficients. A wake survey probe was used to obtain airfoil drag. The separation bubble was explored by measuring the time averaged velocities using a split film probe. The probe was positioned using a computer controlled two-dimensional traversing system. In this paper, airfoil lift, drag, and moment coefficient data are compared for the airfoil with and without glaze ice. Velocity profiles in the separation bubble are presented for several chordwise stations at three angles of attack. The ice shape caused a severe lift and drag penalty. The velocity profiles show clearly the large bubble geometry, regions of reversed flow, and bubble reattachment.

Bragg, M. B.; Coirier, W. J.

1985-01-01

397

Experiments on heave/pitch limit-cycle oscillations of a supercritical airfoil close to the transonic dip  

NASA Astrophysics Data System (ADS)

Recent results from flutter experiments of the supercritical airfoil NLR 7301 at flow conditions near the transonic dip are presented. The airfoil was mounted with two degrees of freedom in an adaptive solid-wall wind tunnel, and boundary-layer transition was tripped. Two limit-cycle oscillation (LCO) test cases obtained in an adaptive test-section are proposed for comparison with numerical simulations. The results link the global aerodynamic force behavior to the observed LCOs and the identified transonic dip. The time lag of the lift response to the pitching motion of the airfoil appears to be responsible for the characteristic shape of the transonic dip. The amplitude limitation of the LCOs results from a slightly nonlinear dependency of lift and moment on the amplitude of the airfoil motion. LCOs can be controlled by relatively small forces, but amplitudes strongly depend on the damping of the aeroelastic system.

Dietz, G.; Schewe, G.; Mai, H.

2004-01-01

398

Plunger lift comes of age  

SciTech Connect

In the never-ending search to cut production costs while maintaining output and maximizing profits, operators are giving plunger lift a closer look. This is particularly true for marginal wells that might otherwise be shut in. Plunger lift is a cost-efficient method of artificially lifting low-liquid-volume oil wells that increase their profits. Some wells would have to be shut in if they remained on beam lit, due to high costs. With the plunger lift system, they are profitable. Field studies show plunger lift to be a cost-efficient, low-maintenance method of sustaining or improving output from low-volume wells. Not all wells are good candidates, so proper evaluation is essential. This paper reviews the optimal well environment for plunger lifts, their design, and cost benefit analysis.

Christian, J. [Amoco E and P, Andrews, TX (United States); Lea, J.F. [Amoco E and PTG, Tulsa, OK (United States); Bishop, B. [Enterra Lift Systems, Midland, TX (United States)

1995-11-01

399

Serrated-Planform Lifting-Surfaces  

NASA Technical Reports Server (NTRS)

A novel set of serrated-planform lifting surfaces produce unexpectedly high lift coefficients at moderate to high angles-of-attack. Each serration, or tooth, is designed to shed a vortex. The interaction of the vortices greatly enhances the lifting capability over an extremely large operating range. Variations of the invention use serrated-planform lifting surfaces in planes different than that of a primary lifting surface. In an alternate embodiment, the individual teeth are controllably retractable and deployable to provide for active control of the vortex system and hence lift coefficient. Differential lift on multiple serrated-planform lifting surfaces provides a means for vehicle control. The important aerodynamic advantages of the serrated-planform lifting surfaces are not limited to aircraft applications but can be used to establish desirable performance characteristics for missiles, land vehicles, and/or watercraft.

McGrath, Brian E. (Inventor); Wood, Richard M. (Inventor)

1999-01-01

400

Image Compression Techniques for High Resolution Satellite Imageries using Classical Lifting Scheme  

E-print Network

The properties of Wavelet Transform can be successfully applied for analysis and processing of non stationary signals e.g., speech and image processing, data compression and communications. Due to the growing number of applications in various areas, it is necessary to explore the hardware implementation options of the Discrete Wavelet Transform (DWT). The Wavelet Series is just a sampled version of Continuous Wavelet Transform (CWT) and its computation may consume significant amount of time and resources, depending on the required resolution. The Discrete Wavelet Transform (DWT), based on sub-band coding, is a fast computation technique of Wavelet Transform, easy to implement and reduces the computational time and resources. Wavelet Transform uses multi-resolution technique by which different frequencies are analyzed with different resolutions. The study of 2-D DWT architectures reveals that there are two schemes for implementing DWT, one is based on convolution and other is based on lifting scheme. In this paper detailed study of Lifting Scheme has been carried out. Different architectures have been studied and performance parameters such as PSNR and Compression Ratio are determined. After obtaining double precision value of the image of size 256*256 imagery in BMP format, discrete wavelet transforms techniques are applied to obtain the wavelet coefficients for calculating PSNR and Compression ratio. Inverse Discrete wavelet transform are applied to get back the reconstructed image. It is found that for both satellite Rural and Urban imageries, the lifting scheme is very useful for obtaining higher quality of reconstructed images while achieving better PSNR~29 and Compression Ratios ~8. I.

K Nagamani; Ag Ananth

401

High Reynolds number tests of the CAST-10-2/DOA 2 transonic airfoil at ambient and cryogenic temper ature conditions  

NASA Technical Reports Server (NTRS)

The transonic airfoil CAST 10-2/DOA 2 was investigated in several major transonic wind tunnels at Reynolds numbers ranging from Re=1.3 x 10(exp 6) to 45 x 10(exp 6) at ambient and cryogenic temperature conditions. The main objective was to study the degree and extent of the effects of Reynolds number on both the airfoil aerodynamic characteristics and the interference effects of various model-wind-tunnel systems. The initial analysis of the CAST 10-2 airfoil results revealed appreciable real Reynolds number effects on this airfoil and showed that wall interference can be significantly affected by changes in Reynolds number thus appearing as true Reynolds number effects.

Stanewsky, E.; Demurie, F.; Ray, Edward J.; Johnson, C. B.

1989-01-01

402

Unsteady Newton-Busemann flow theory. I - Airfoils  

NASA Technical Reports Server (NTRS)

Newtonian flow theory for unsteady flow at very high Mach numbers is completed by the addition of a centrifugal force correction to the impact pressures. The correction term is the unsteady counterpart of Busemann's centrifugal force correction to impact pressures in steady flow. For airfoils of arbitary shape, exact formulas for the unsteady pressure and stiffness and damping-in-pitch derivatives are obtained in closed form, which require only numerical quadratures of terms involving the airfoil shape. They are applicable to airfoils of arbitrary thickness having sharp or blunt leading edges. For wedges and thin airfoils these formulas are greatly simplified, and it is proved that the pitching motions of thin airfoils of convex shape and of wedges of arbitrary thickness are always dynamically stable according to Newton-Busemann theory. Leading-edge bluntness is shown to have a favorable effect on the dynamic stability; on the other hand, airfoils of concave shape tend toward dynamic instability over a range of axis positions if the surface curvature exceeds a certain limit. As a byproduct, it is also shown that a pressure formula recently given by Barron and Mandl for unsteady Newtonian flow over a pitching power-law shaped airfoil is erroneous and that their conclusion regarding the effect of pivot position on the dynamic stability is misleading.

Hui, W. H.; Tobak, M.

1981-01-01

403

Airfoil with nested cooling channels  

SciTech Connect

A turbine blade is described which consists of a root portion and wall means integral with the root portion defining an airfoil, the wall means including a pressure sidewall and a suction sidewall, joined together to define a forwardly located leading edge and rearwardly located trailing edge of the airfoil and spaced apart to define a spanwise and chordwise extending coolant cavity within the airfoil, and root portion including root passage means therethrough for receiving coolant fluid form outside the blade and for directing the fluid into the airfoil cavity.

Levengood, J.L.; Auxier, T.A.

1988-06-28

404

Numerical Simulations of Natural and Actuated Flow over a 3D, Low-Aspect-Ratio Airfoil  

E-print Network

Numerical Simulations of Natural and Actuated Flow over a 3D, Low-Aspect-Ratio Airfoil Guillaume A mean and unsteady lift and drag, the numerical simulations show good agreement with the experiments in the simulations. Both PIV measurements and transient numerical results indicate that this behavior is associated

Dabiri, John O.

405

Detection and estimation of the instantaneous flow topology on an airfoil using proper orthogonal decomposition  

Microsoft Academic Search

For the control of the lift distribution on a wing, the local flow state has to be known instantaneously, in particular, the location of critical points in the flow topology such as stagnation point, separation point and reattachment point. Unsteady CFD simulations are used to determine the flow field around a Naca 0018 airfoil at moderate Reynolds number. These simulations

Jurgen Seidel; Casey Fagley; Tom McLaughlin

2010-01-01

406

Control of vortex shedding on two-and three-dimensional airfoils  

E-print Network

on the control of separated flows over flat plates and airfoils at low Reynolds numbers associated with micro air: Vortex shedding, flow control, micro air vehicles, lift enhancement 1. Introduction Desirable features strategies for closed-loop flow and flight control utilizing actuation of leading-edge vortices. Keywords

Dabiri, John O.

407

The influence of laminar separation and transition on low Reynolds number airfoil hysteresis  

NASA Technical Reports Server (NTRS)

An experimental study of the Lissaman 7769 and Miley MO6-13-128 airfoils at low chord Reynolds numbers is presented. Although both airfoils perform well near their design Reynolds number of about 600,000, they each produce a different type of hysteresis loop in the lift and drag forces when operated below chord Reynolds numbers of 300,000. The type of hysteresis loop was found to depend upon the relative location of laminar separation and transition. The influence of disturbance environment and experimental procedure on the low Reynolds number airfoil boundary layer behavior is also presented. The use of potential flow solutions to help predict how a given airfoil will behave at low Reynolds numbers is also discussed.

Mueller, T. J.

1984-01-01

408

Vortex developments over steady and accelerated airfoils incorporating a trailing edge jet  

NASA Technical Reports Server (NTRS)

Computational and experimental studies are conducted to investigate the influence of a trailing edge jet on flow separation and subsequent vortex formation over steady and accelerated airfoils at high angles of attack. A computer code, employing the stream function-vorticity approach, is developed and utilized to conduct numerical experiments on the flow problem. To verify and economize such efforts, an experimental system is developed and incorporated into a subsonic wind tunnel where streamline and vortex flow visualization experiments are conducted. The study demonstrates the role of the trailing edge jet in controlling flow separation and subsequent vortex development for steady and accelerating flow at angles past the static stall angle of attack. The results suggest that the concept of the trailing edge jet may be utilized to control the characteristics of unsteady separated flows over lifting surfaces. This control possibility seems to be quite effective and could have a significant role in controlling unsteady separated flows.

Finaish, F.; Okong'o, N.; Frigerio, J.

1993-01-01

409

Supersonic, nonlinear, attached-flow wing design for high lift with experimental validation  

NASA Technical Reports Server (NTRS)

Results of the experimental validation are presented for the three dimensional cambered wing which was designed to achieve attached supercritical cross flow for lifting conditions typical of supersonic maneuver. The design point was a lift coefficient of 0.4 at Mach 1.62 and 12 deg angle of attack. Results from the nonlinear full potential method are presented to show the validity of the design process along with results from linear theory codes. Longitudinal force and moment data and static pressure data were obtained in the Langley Unitary Plan Wind Tunnel at Mach numbers of 1.58, 1.62, 1.66, 1.70, and 2.00 over an angle of attack range of 0 to 14 deg at a Reynolds number of 2.0 x 10 to the 6th power per foot. Oil flow photographs of the upper surface were obtained at M = 1.62 for alpha approx. = 8, 10, 12, and 14 deg.

Pittman, J. L.; Miller, D. S.; Mason, W. H.

1984-01-01

410

Upstream Boundary Layer Influence on Lifting Surface Trailing Edge Vortex Shedding at High Reynolds Number  

NASA Astrophysics Data System (ADS)

Prediction of lifting surface performance (such as lift, drag, vibration, and hydroacoustic noise) requires an understanding of the unsteady separated turbulent flow at the trailing edge. In this region, the separated shear layers may interact to form quasi-periodic vortical structures in the near wake (vortex shedding). Described are results from an experimental effort to identify and measure the major flow features in the near-wake of a hydrofoil at chord-based Reynolds numbers ranging from 0.5 to 60 million. The experiments were conducted at the US Navy's William B. Morgan Large Cavitation Channel with a two-dimensional, test-section-spanning hydrofoil (2.1 m chord, 3.0 m span). Two trailing edge shapes were investigated. Measurements include hydrofoil vibration, time-averaged and unsteady surface pressures, and LDV and PIV flow velocities. A correlation is demonstrated between the energy contained in the vortex shedding and the time-averaged shear of the boundary layers approaching the trailing edge. [Significant assistance provided by personnel from NSWC-CD. Sponsored by Code 333 of the Office of Naval Research.

Bourgoyne, Dwayne A.; Hamel, Joshua M.; Ceccio, Steven C.; Dowling, David R.

2002-11-01

411

Aerodynamic characteristics of an oscillating airfoil  

NASA Astrophysics Data System (ADS)

Results are reported from wind tunnel tests to study the effects of dynamic aerodynamics on the efficiency of a NACA 0018 airfoil used on a Darreius vertical axis wind turbine (VAWT). The topic is of interest because of uncontrolled pitching which occurs during operation and which produces stall, turbulence and separation effects that reduce efficiency. Present stream-tube theory and axial momentum models are not applicable in the unstable regimes. The wind tunnel tests were conducted with a 45 m/sec flow with an Re of 1.5 million. The situation mimicked typical wind turbine operational conditions. The airfoil was mounted on a hydraulic actuator to allow it to rotate about its quarter-chord location and to control the extent and frequency of oscillations. Data were also gathered on the performance in a steady flow for comparative purposes. Summary data are provided on the static and total pressures over a complete cycle of oscillation, and related to the angles of attack, time of onset of stall, and the lift and drag coefficients. The limitations of the study with regard to the absence of consideration of the flow acceleration experienced by an advancing blade are noted.

Wickens, R. H.

1986-03-01

412

Heavy Lifting  

NSDL National Science Digital Library

In this activity, learners work in NASA teams to build balloon-powered rockets using identical parts and compete to launch the greatest number of paper clips to "space" (the ceiling). The rockets learners build model the Ares V heavy lift launchers that carry heavy payloads into orbit. This lesson plan includes background information, tips, discussion questions and answers, and a "Mission Report" sheet for learners.

Shearer, Deborah A.; Gregory L. Vogt, Ed D.

2012-06-26

413

A two element laminar flow airfoil optimized for cruise. M.S. Thesis  

NASA Technical Reports Server (NTRS)

Numerical and experimental results are presented for a new two-element, fixed-geometry natural laminar flow airfoil optimized for cruise Reynolds numbers on the order of three million. The airfoil design consists of a primary element and an independent secondary element with a primary to secondary chord ratio of three to one. The airfoil was designed to improve the cruise lift-to-drag ratio while maintaining an appropriate landing capability when compared to conventional airfoils. The airfoil was numerically developed utilizing the NASA Langley Multi-Component Airfoil Analysis computer code running on a personal computer. Numerical results show a nearly 11.75 percent decrease in overall wing drag with no increase in stall speed at sailplane cruise conditions when compared to a wing based on an efficient single element airfoil. Section surface pressure, wake survey, transition location, and flow visualization results were obtained in the Texas A&M University Low Speed Wind Tunnel. Comparisons between the numerical and experimental data, the effects of the relative position and angle of the two elements, and Reynolds number variations from 8 x 10(exp 5) to 3 x 10(exp 6) for the optimum geometry case are presented.

Steen, Gregory Glen

1994-01-01

414

A LIFT SIMULATION A LIFT SIMULATION PROTOTYPE  

E-print Network

A LIFT SIMULATION A LIFT SIMULATION PROTOTYPE V C Galpin & S T Rock Computer Science Department University of the Witwatersrand, Johannesburg Wits 2050 South Africa #12;A LIFT SIMULATION 1 SUMMARY We present a simple simulation of lift (or elevator) operation that has been developed as a prototype

Galpin, Vashti

415

Aerothermodynamic heating and performance analysis of a high-lift aeromaneuvering AOTV concept  

NASA Astrophysics Data System (ADS)

The thermal-control requirements for design-optimized aeromaneuvering performance are determined for space-based applications and low-earth orbit sorties involving large, multiple plane-inclination changes. The leading-edge heating analysis is the most advanced developed for hypersonic-rarefied flow over lifting surfaces at incidence. The effects of leading-edge bluntness, low-density viscous phenomena, and finite-rate flow-field chemistry and surface catalysis are accounted for. The predicted aerothermodynamic heating characteristics are correlated with thermal-control and flight-performance capabilities. The mission payload capability for delivery, retrieval, and combined operations is determined for round-trip sorties extending to polar orbits. Recommendations are given for future design refinements. The results help to identify technology issues required to develop prototype operational systems.

Menees, G. P.; Brown, K. G.; Wilson, J. F.; Davies, C. B.

1985-06-01

416

Comparison of selected lift and sideslip characteristics of the Ayres Thrush S2R-800, winglets off and winglets on, to full-scale wind-tunnel data  

NASA Technical Reports Server (NTRS)

All calculations were done in the stability axes system. The winglets used were constructed of modified GA(w)-2 airfoils. Aerodynamic characteristics discussed include: angle of attack; lift-curve slope; side force; yawing moments; rolling moments.

Roskam, J.; Williams, M.

1981-01-01

417

Transition Documentation on a Three-Element High-Lift Configuration at High Reynolds Numbers--Database. [conducted in the Langley Low Turbulence Pressure Tunnel  

NASA Technical Reports Server (NTRS)

A 2-D (two dimensional) high-lift system experiment was conducted in August of 1996 in the Low Turbulence Pressure Tunnel at NASA Langley Research Center, Hampton, VA. The purpose of the experiment was to obtain transition measurements on a three element high-lift system for CFD (computational fluid dynamics) code validation studies. A transition database has been created using the data from this experiment. The present report details how the hot-film data and the related pressure data are organized in the database. Data processing codes to access the data in an efficient and reliable manner are described and limited examples are given on how to access the database and store acquired information.

Bertelrud, Arild; Johnson, Sherylene; Anders, J. B. (Technical Monitor)

2002-01-01

418

Experimental Study on the Wing Lift Characteristics of Biplane Micro Air Vehicle  

Microsoft Academic Search

This paper investigates wing aerodynamic characteristics used for bi-plane micro-air vehicles. Surface pressure distributions of two-dimensional biplane airfoils (4% cambered-plate airfoil) were measured at a chord Reynolds number of 6.4 × 104. Lift characteristics of three-dimensional biplane rectangular wings (aspect ratio of 3) were also measured at the same Reynolds number. It was indicated that the behaviors of laminar separation

Kohei Akiyama; Asei Tezuka; Yasuto Sunada; Kenichi Rinoie

2009-01-01

419

Wake structure of a deformable Joukowski airfoil  

Microsoft Academic Search

We examine the vortical wake structure shed from a deformable Joukowski airfoil in an unbounded volume of inviscid and incompressible fluid. The deformable airfoil is considered to model a flapping fish. The vortex shedding is accounted for using an unsteady point vortex model commonly referred to as the Brown–Michael model. The airfoil’s deformations and rotations are prescribed in terms of

Adam Ysasi; Eva Kanso; Paul K. Newton

2011-01-01

420

Bioinspired Corrugated Airfoil at Low Reynolds Numbers  

E-print Network

Bioinspired Corrugated Airfoil at Low Reynolds Numbers Hui Hu and Masatoshi Tamai Iowa State behavior around a bioinspired corrugated airfoil compared with a traditional streamlined airfoil and a flat of such bioinspired corrugated airfoils for micro air vehicle applications. The experiments were conducted in a low

Hu, Hui

421

Prediction of the Effect of Vortex Generators on Airfoil Performance  

NASA Astrophysics Data System (ADS)

Vortex Generators (VGs) are widely used by the wind turbine industry, to control the flow over blade sections. The present work describes a computational fluid dynamic procedure that can handle a geometrical resolved VG on an airfoil section. After describing the method, it is applied to two different airfoils at a Reynolds number of 3 million, the FFA- W3-301 and FFA-W3-360, respectively. The computations are compared with wind tunnel measurements from the Stuttgart Laminar Wind Tunnel with respect to lift and drag variation as function of angle of attack. Even though the method does not exactly capture the measured performance, it can be used to compare different VG setups qualitatively with respect to chord- wise position, inter and intra-spacing and inclination of the VGs already in the design phase.

Sřrensen, Niels N.; Zahle, F.; Bak, C.; Vronsky, T.

2014-06-01

422

Effect of oscillation frequency on wind turbine airfoil dynamic stall  

NASA Astrophysics Data System (ADS)

At the same oscillation amplitude, Reynolds Number, mean angle of attack, the dynamic stall characteristics of the NREL S809 airfoil undergoing sinusoidal pitch oscillations of different oscillation frequencies were investigated with modified k-? SST turbulence model of CFD solution for two-dimensional numerical simulation. The predicted lift, drag coefficients and moment coefficients were compared with the Ohio State University wind tunnel test results, which showed a good agreement. The birth, development and breaking off of eddies were analyzed through streamline distribution around airfoil and the influence of oscillation frequencies on dynamic stall characteristics was also described and analyzed in detail, which enrich the database of dynamic stall characteristics needed by the quantization of oscillation frequencies on dynamic characteristics and prove that sliding mesh method is reliable when dealing with dynamic stall problems.

Zhou, Z.; Li, C.; Nie, J. B.; Chen, Y.

2013-12-01

423

The effect of sound on the lift of an airfoil  

E-print Network

respective- ly R. N. Reynolds number based on chord length, V c Free stream velocity . none ft. . /sec. Chordwise co-ordinate Deviation in chordwise co-ordinate Section angle of attack Phase angle for alternating current degrees degrees 4P V... of attack and 13. 6 percent to 32. 9 percent at 2Q angle of attack in the range of speeds tested. I. I'NTRODUCTION During recent years, in the development of airer'aft capable of landing and taking off in short distances, re- newed emphasis has been...

Kitowski, John Victor

2012-06-07

424

Comparisons of two-dimensional shock-expansion theory with experimental aerodynamic data for delta-planform wings at high supersonic speeds  

NASA Technical Reports Server (NTRS)

An investigation has been conducted to explore the potential for optimizing airfoil shape at high supersonic speeds by utilizing the two-dimensional shock-expansion method. Theoretical and experimental force and moment coefficients are compared for four delta-planform semispan wings having a leading-edge sweep angle of 65 deg and incorporating modified diamond airfoils with a thickness-chord ratio of 0.06. The wings differ only in airfoil maximum-thickness position and camber. The experimental data are obtained at Mach numbers of 3.95 and 4.63 and at a Reynolds number of 9.84 million per meter. A relatively simple method is developed for predicting, in terms of lift-drag ratio, the optimum modified diamond airfoil at high supersonic and hypersonic speeds.

Jernell, L. S.

1974-01-01

425

Optical-velocimetry, wake measurements of lift and induced drag on a wing  

NASA Astrophysics Data System (ADS)

Particle Tracking Velocimetry was used, in a low-speed wind-tunnel study, to obtain simultaneous cross-flow velocity measurements in three planar regions downstream of an airfoil having a NACA 0015 profile. In order to measure both the total lift and induced drag, and their distributions on the airfoil, a wake integration technique based on the control volume approach was used. The airfoil model was tested in clean wing configuration and with a 3.33% Gurney flap attached to the trailing edge. The Gurney flap was found to increase the complexity of the wake and cause a systematic increase in lift and induced drag values. The changes in total lift and induced drag resulting from the fitting of a Gurney flap compared very favourably to investigations using traditional aerodynamic techniques demonstrating the validity of the method.

Grant, I.; McCutcheon, G.; McColgan, A. H.; Hurst, D.

2006-03-01

426

Analysing Performance of Lift Systems in PEPA  

E-print Network

to quite complex multi­lift systems, with a high degree of parallelism and non­determinism present (eAnalysing Performance of Lift Systems in PEPA Amani El­Rayes and Marta Kwiatkowska and Steven Minton \\Lambda Abstract We use the stochastic process algebra PEPA [8] to specify lift sys­ tems

Oxford, University of

427

Uncertainty Analysis for a Jet Flap Airfoil  

NASA Technical Reports Server (NTRS)

An analysis of variance (ANOVA) study was performed to quantify the potential uncertainties of lift and pitching moment coefficient calculations from a computational fluid dynamics code, relative to an experiment, for a jet flap airfoil configuration. Uncertainties due to a number of factors including grid density, angle of attack and jet flap blowing coefficient were examined. The ANOVA software produced a numerical model of the input coefficient data, as functions of the selected factors, to a user-specified order (linear, 2-factor interference, quadratic, or cubic). Residuals between the model and actual data were also produced at each of the input conditions, and uncertainty confidence intervals (in the form of Least Significant Differences or LSD) for experimental, computational, and combined experimental / computational data sets were computed. The LSD bars indicate the smallest resolvable differences in the functional values (lift or pitching moment coefficient) attributable solely to changes in independent variable, given just the input data points from selected data sets. The software also provided a collection of diagnostics which evaluate the suitability of the input data set for use within the ANOVA process, and which examine the behavior of the resultant data, possibly suggesting transformations which should be applied to the data to reduce the LSD. The results illustrate some of the key features of, and results from, the uncertainty analysis studies, including the use of both numerical (continuous) and categorical (discrete) factors, the effects of the number and range of the input data points, and the effects of the number of factors considered simultaneously.

Green, Lawrence L.; Cruz, Josue

2006-01-01

428

Wind-Tunnel Tests on Airfoil Boundary Layer Control Using a Backward-Opening Slot  

NASA Technical Reports Server (NTRS)

This report presents the results of an investigation to determine the effect of boundary layer control on the lift and drag of an airfoil. Boundary layer control was accomplished by means of a backward-opening slot in the upper surface of the hollow airfoil. Air was caused to flow through this slot by a pressure which was maintained inside the airfoil by a blower. Various slot locations, slot openings, and wing pressures were used. The tests were conducted in the 5-foot atmospheric wind tunnel of the Langley Memorial Aeronautical Laboratory. Under the test conditions, the maximum lift coefficient was increased about 96 per cent for one slot arrangement, and the minimum drag coefficient was decreased about 27 per cent for another, both being compared with the results obtained with the unslotted airfoil. It is believed from this investigation that the above effects may be increased by the use of larger slot openings, better slot locations, multiple slots, improved airfoil profiles, and trailing edge flaps.

Bamber, Millard J

1932-01-01

429

Method for forming a liquid cooled airfoil for a gas turbine  

DOEpatents

A method for forming a liquid cooled airfoil for a gas turbine is disclosed. A plurality of holes are formed at spaced locations in an oversized airfoil blank. A pre-formed composite liquid coolant tube is bonded into each of the holes. The composite tube includes an inner member formed of an anti-corrosive material and an outer member formed of a material exhibiting a high degree of thermal conductivity. After the coolant tubes have been bonded to the airfoil blank, the airfoil blank is machined to a desired shape, such that a portion of the outer member of each of the composite tubes is contiguous with the outer surface of the machined airfoil blank. Finally, an external skin is bonded to the exposed outer surface of both the machined airfoil blank and the composite tubes.

Grondahl, Clayton M. (Clifton Park, NY); Willmott, Leo C. (Ballston Spa, NY); Muth, Myron C. (Amsterdam, NY)

1981-01-01

430

Low-speed wind-tunnel results for symmetrical NASA LS(1)-0013 airfoil  

NASA Technical Reports Server (NTRS)

A wind-tunnel test has been conducted in the Langley Low-Turbulence Pressure Tunnel to evaluate the performance of a symmetrical NASA LS(1)-0013 airfoil which is a 13-percent-thick, low-speed airfoil. The airfoil contour was obtained from the thickness distribution of a 13-percent-thick, high-performance airfoil developed for general aviation airplanes. The tests were conducted at Mach numbers from 0.10 tp 0.37 over a Reynolds number range from about 0.6 to 12.0 X 10 to the 6th power. The angle of attack varied from about -8 to 20 degrees. The results indicate that the aerodynamic characteristics of the present airfoil are similar to, but slightly better than, those of the NACA 0012 airfoil.

Ferris, James C.; Mcghee, Robert J.; Barnwell, Richard W.

1987-01-01