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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1945

High-Speed Wind-Tunnel Tests of Dive-Recovery Flaps of a 0.3-Scale Model of the P-47D Airplane

This report presents the results of tests of a 0.3-Scale Model of the Republic P-47D airplane equipped with several dive-recovery flaps. Results are presented showing the drag coefficient and pitching-moment coefficient produced by the various flaps. The results of computations made to predict the normal acceleration due to deflecting the flaps in a vertical dive, the lift coefficient of the tail required for balance, and the relative magnitudes of the various factors which contribute to the pitching-moment increment are also given.

William T Hamilton↗
NASA NTRS2016

Detached Eddy Simulation of Flap Side-Edge Flow

Detached Eddy Simulation (DES) of flap side-edge flow was performed with a wing and half-span flap configuration used in previous experimental and numerical studies. The focus of the study is the unsteady flow features responsible for the production of far-field noise. The simulation was performed at a Reynolds number (based on the main wing chord) of 3.7 million. Reynolds Averaged Navier-Stokes (RANS) simulations were performed as a precursor to the DES. The results of these precursor simulations match previous experimental and RANS results closely. Although the present DES simulations have not reached statistical stationary yet, some unsteady features of the developing flap side-edge flowfield are presented. In the final paper it is expected that statistically stationary results will be presented including comparisons of surface pressure spectra with experimental data.

Simulation↗
NASA NTRS2015

An Assessment of Flap and Main Landing Gear Noise Abatement Concepts

A detailed assessment of the acoustic performance of several noise reduction concepts for aircraft flaps and landing gear is presented. Consideration is given to the best performing concepts within the suite of technologies that were evaluated in the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel using an 18 percent scale, semi-span, high-fidelity Gulfstream aircraft model as a test bed. Microphone array measurements were obtained with the model in a landing configuration (flap deflected 39 degrees and the main landing gear deployed or retracted). The effectiveness of each concept over the range of pitch angles, speeds, and directivity angles tested is presented. Comparison of the acoustic spectra, obtained from integration of the beamform maps between the untreated baseline and treated configurations, clearly demonstrates that the flap and gear concepts maintain noise reduction benefits over the entire range of the directivity angles tested.

Khorrami, Mehdi R.↗
NASA NTRS2016

Computational Design of a Krueger Flap Targeting Conventional Slat Aerodynamics

In this study, we demonstrate the design of a Krueger flap as a substitute for a conventional slat in a high-lift system. This notional design, with the objective of matching equivalent-mission performance on aircraft approach, was required for a comparative aeroacoustic study with computational and experimental components. We generated a family of high-lift systems with Krueger flaps based on a set of design parameters. Then, we evaluated the high-lift systems using steady 2D RANS simulations to find a good match for the conventional slat, based on total lift coefficients in free-air. Finally, we evaluated the mean aerodynamics of the high-lift systems with Krueger flap and conventional slat as they were installed in an open-jet wind tunnel flow. The surface pressures predicted with the simulations agreed well with experimental results.

Computational↗
NASA NTRS2017

Wind Tunnel Investigation of Passive Porosity Applied to the Leading-Edge Extension and Leading-Edge Flaps on a Slender Wing at Subsonic Speed

A wind tunnel experiment was conducted in the NASA Langley Research Center 7- by 10-Foot High Speed Tunnel to determine the effects of passive surface porosity on the subsonic vortex flow interactions about a general research fighter configuration. Flow-through porosity was applied to the leading-edge extension, or LEX, and leading-edge flaps mounted to a 65deg cropped delta wing model as a potential vortex flow control technique at high angles of attack. All combinations of porous and nonporous LEX and flaps were investigated. Wing upper surface static pressure distributions and six-component forces and moments were obtained at a free-stream Mach number of 0.20 corresponding to a Reynolds number of 1.35(106) per foot, angles of attack up to 45deg, angles of sideslip of 0deg and +/-5deg, and leading-edge flap deflections of 0deg and 30deg.

Erickson, Gary E.↗
NASA NTRS2017

Assessment of a Conceptual Flap System Intended for Enhanced General Aviation Safety

A novel multielement trailing-edge flap system for light general aviation airplanes was conceived for enhanced safety during normal and emergency landings. The system is designed to significantly reduce stall speed, and thus approach speed, with the goal of reducing maneuveringflight accidents and enhancing pilot survivability in the event of an accident. The research objectives were to assess the aerodynamic performance characteristics of the system and to evaluate the extent to which it provided both increased lift and increased drag required for the low-speed landing goal. The flap system was applied to a model of a light general aviation, high-wing trainer and tested in the Langley 12- Foot Low-Speed Wind Tunnel. Data were obtained for several device deflection angles, and component combinations at a dynamic pressure of 4 pounds per square foot. The force and moment data supports the achievement of the desired increase in lift with substantially increased drag, all at relatively shallow angles of attack. The levels of lift and drag can be varied through device deflection angles and inboard/outboard differential deflections. As such, it appears that this flap system may provide an enabling technology to allow steep, controllable glide slopes for safe rapid descent to landing with reduced stall speed. However, a simple flat-plate lower surface spoiler (LSS) provided either similar or superior lift with little impact on pitch or drag as compared to the proposed system. Higher-fidelity studies are suggested prior to use of the proposed system.

Campbell, Bryan A.↗
NASA NTRS2015

Aerodynamic Load Analysis of a Variable Camber Continuous Trailing Edge Flap System on a Flexible Wing Aircraft

This paper presents an investigative aerodynamic analysis conducted on the novel control surface known as a Variable Camber Continuous Trailing Edge Flap (VCCTEF). The VCCTEF is modeled as a control effector on the NASA Generic Transport Model (GTM) where wing flexibility is considered. Aerodynamic modeling of the aircraft is conducted using vortex-lattice method (VLM), and an aeroelastic model of the aircraft that utilizes a coupled finite-element analysis (FEA) vortex-lattice solution is employed. VLM solutions are used to determine quasi-steady aerodynamic loading over the aeroelastic wing structures with VCCTEF. The load data is used to calculate aerodynamic sensitivities to control surface deployment and is also integrated to determine overall hinge moments. This analysis is conducted for different flight conditions, where control sensitivities compare the VCCTEF effectiveness against conventional control surfaces. Hinge moment results provide insight into aeroelastic wing loads, and worst case hinge moments for the VCCTEF can be estimated. Results show that the VCCTEF offers greater control authority than conventional ailerons at cruise, and nominal flap settings are determined for a low-speed take-off condition where the VCCTEF maintains comparable control effectiveness. Worst case hinge moment values are presented, where for a possible VCCTEF configuration, the stiff wing model demonstrates up to a 5.90 percent increase in flap hinge moment relative to a rigid model, and a reduced stiffness model demonstrates up to an 11.42 percent increase.

Aeroelasticity↗
NASA NTRSDate not supplied

Pterodactyl: Thermal Protection System Design Methodology for a Flap Control System

As interest in non-traditional entry vehicles continues to grow, the need for a Thermal Protection System (TPS) analysis approach that can account for entry solutions with changing geometry and complicated flow dynamics becomes invaluable. The NASA Space Technology Mission Directorate (STMD) Pterodactyl project aims to accomplish this through examination of a flap controlled Adaptable, Deployable Entry Placement Technology (ADEPT)-style Deployable Entry Vehicle (DEV). This paper details an improved methodology for modeling the aerothermodynamic environment and initial TPS design for a flap control system integrated with a symmetric DEV. Improvements include i) the addition of an anchoring process that uses an increased fidelity aerodynamic solution to anchor the aerothermal environment predictions and ii) increased surface resolution, for the 1D heat transfer analysis, to isolate the hottest area on the flap that will require the thickest TPS. It was found that the anchoring process provided an improved aerothermal environment prediction. Additionally, this analysis demonstrated that there is a need for increased surface resolution in the 1D thermal analysis since the predicted location of the hottest point was significantly different than the location identified using very coarse surface resolution.

Zane B Hays↗
NASA NTRSDate not supplied

Assessment of Control Algorithms for Mars Entry Vehicles With Flap-Based Trajectory Control Under Uncertainty

Flap-based steering systems on blunt-body entry vehicles may improve flight performance relative to heritage bank-angle steering systems. Successful implementation of articulating aerodynamic flaps on a hypersonic entry vehicle requires an active control system to map angle of attack and sidelip angle commands to flap deflection commands. Here, a successive-linearization model prective control algorithm, as a linear quadratic regulator, are formulated, designed, and assessed to address this multiple input multiple output control problem. These two control algorithms are assessed under uncertainty in Monte Carlo simulations for various control profiles and vehicle configurations. Results indicate that while both control algorithms provide successful command tracking under uncertainty, the model predictive controller provides a lower mean and integral error, as well as greater robustness, relative to the linear-quadratic regulator.

Daniel L Engel↗
NASA NTRSDate not supplied

Design of an Acoustic Shielding Flap Concept with Prediction and Validation

As part of a NATO task group, NASA has designed a noise reduction technology called a Shielding Flap for application to a hybrid wing body aircraft concept. The design drivers and objectives for this technology are outlined in this paper. Design parameters are defined, and recently-developed NASA software for prediction of acoustic scattering is used to investigate the expected performance of the technology for a range of parameter values. Detailed scattering computational results are presented for several simulated noise sources and for many variations of the shielding flap concept. A selection of computational results is compared with experimental data collected in the NASA Langley Quiet Flow Facility. Overall, the results indicate that the Shielding Flap has strong potential to reduce aft-radiated noise, which was a primary design objective, by shielding sound from the simulated sources while also shielding sound that is scattered from the main airframe.

Propulsion Airframe Aeroacoustics↗
NASA NTRS1942

Pressure-Distribution Measurements of a Model of a Davis Wing Section with Fowler Flap Submitted by Consolidated Aircraft Corporation

Wing pressure distribution diagrams for several angles of attack and flap deflections of 0 degrees, 20 degrees, and 40 degrees are presented. The normal force coefficients agree with lift coefficients obtained in previous test of the same model, except for the maximum lifts with flap deflection. Pressure distribution measurements were made at Reynolds Number of about 6,000,000.

PRESSURE DISTRIBUTION - AIRFOILS - DAVIS↗
DOE OSTI2022

Flap Endonuclease 1 Endonucleolytically Processes RNA to Resolve R-Loops through DNA Base Excision Repair

Flap endonuclease 1 (FEN1) is an essential enzyme that removes RNA primers and base lesions during DNA lagging strand maturation and long-patch base excision repair (BER). It plays a crucial role in maintaining genome stability and integrity. FEN1 is also implicated in RNA processing and biogenesis. A recent study from our group has shown that FEN1 is involved in trinucleotide repeat deletion by processing the RNA strand in R-loops through BER, further suggesting that the enzyme can modulate genome stability by facilitating the resolution of R-loops. However, it remains unknown how FEN1 can process RNA to resolve an R-loop. In this study, we examined the FEN1 cleavage activity on the RNA:DNA hybrid intermediates generated during DNA lagging strand processing and BER in R-loops. We found that both human and yeast FEN1 efficiently cleaved an RNA flap in the intermediates using its endonuclease activity. We further demonstrated that FEN1 was recruited to R-loops in normal human fibroblasts and senataxin-deficient (AOA2) fibroblasts, and its R-loop recruitment was significantly increased by oxidative DNA damage. We showed that FEN1 specifically employed its endonucleolytic cleavage activity to remove the RNA strand in an R-loop during BER. We found that FEN1 coordinated its DNA and RNA endonucleolytic cleavage activity with the 3'-5' exonuclease of APE1 to resolve the R-loop. Our results further suggest that FEN1 employed its unique tracking mechanism to endonucleolytically cleave the RNA strand in an R-loop by coordinating with other BER enzymes and cofactors during BER. Our study provides the first evidence that FEN1 endonucleolytic cleavage can result in the resolution of R-loops via the BER pathway, thereby maintaining genome integrity.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1966

Performance characteristics of a jet-flap rotor

Results of an experimental investigation of the characteristics of a jet-­flap rotor are presented and discussed. Comparisons of the rotor's force-­producing capabilities with those of a conventional rotor are made which show the jet-flap rotor to be operable well beyond standard rotor stall boundaries. Correlations are made between measured and calculated results which show generally goon agreement.

ROTOR BLADE↗
NASA NTRS1957

A Method for Predicting Lift Increments Due to Flap Deflection at Low Angles of Attack in Incompressible Flow

A method is presented for estimating the lift due to flap deflection at low angles of attack in incompressible flow. In this method provision is made for the use of incremental section-lift data for estimating the effectiveness of high-lift flaps. The method is applicable to swept wings of any aspect ratio or taper ratio. The present method differs from other current methods mainly in its ease of application and its more general application. Also included is a simplified method of estimating the lift-curve slope throughout the subsonic speed range.

WINGS, COMPLETE - TAPER AND TWIST↗
NASA NTRS1957

Wind-tunnel Investigation of External-flow Jet-augmented Double Slotted Flaps on a Rectangular Wing at an Angle of Attack of 0 Degree to High Momentum Coefficients

A wind-tunnel investigation has been made to determine the characteristics of external-flow jet-augmented double slotted flaps which appear suitable for application to airplanes with pod-mounted engines. The investigation included tests of the rectangular wing with an aspect ratio of 6 over a momentum-coefficient range from 0 to 28. Lift coefficients larger than the jet reaction in the lift direction were obtained with the external-flow jet-augmented double slotted flaps.

HIGH-LIFT DEVICES - COMPLETE WINGS↗
NASA NTRS1927

Flap Gear for Airplanes : A New Scheme in Which Variation is Automatic

A variable flap gear, which would function automatically and require no attention during flight appeared to be an attractive idea even in its early stages of development. The advantages of variable camber are described as well as the designs of these automatic flaps.

WING FLAPS, AUTOMATIC↗
NASA NTRS1946

Effect of Compressibility on the Pressure and Forces Acting on a Modified NACA 65,3-019 Airfoil Having A 0.20-Chord Flap

An investigation has been conducted in the Langley rectangular high-speed tunnel to determine the effect of compressibility on the pressure distribution for a modified NACA 65,3-019 airfoil having a 0.20-chord flap. The investigation was made for an angle-of-attack range extending from -2 to 12 deg at .20 flap deflections from 0 to -12 deg. Test data were obtained for Mach numbers from 0.28 to approximately 0.74. The results show that the effectiveness of the trailing-edge-type control surface rapidly decreased and approached zero as the Mach number increased above the critical value.

AIRFOILS-NACA 65,3-019 (MOD )-MOMENTS & ORDINATES ↗