Science.gov

Sample records for rotor swept area

  1. Effects of a Forward-swept Front Rotor on the Flowfield of a Counterrotation Propeller

    NASA Technical Reports Server (NTRS)

    Nallasamy, M.; Podboy, Gary G.

    1994-01-01

    The effects of a forward-swept front rotor on the flowfield of a counterrotation model propeller at takeoff conditions at zero degree angle of attack are studied by solving the unsteady three-dimensional Euler equations. The configuration considered is an uneven blade count counterrotation model with twelve forward-swept blades on the fore rotor and ten aft-swept blades on the aft rotor. The flowfield is compared with that of a reference aft-swept counterrotation geometry and Laser Doppler Velocimeter (LDV) measurements. At the operating conditions considered, the forward-swept blade experiences a higher tip loading and produces a stronger tip vortex compared to the aft-swept blade, consistent with the LDV and acoustic measurements. Neither the solution nor the LDV data indicated the formation of a leading edge vortex. The predicted radial distribution of the circumferentially averaged axial velocity at the measurement station agreed very closely with LDV data, while crossflow velocities showed poor agreement. The discrepancy between prediction and LDV data of tangential and radial velocities is due in part to the insufficient mesh resolution in the region between the rotors and in the tip region to track the tip vortex. The vortex is diffused by the time it arrives at the measurement station. The uneven blade count configuration requires the solution to be carried out for six blade passages of the fore rotor and five passages of the aft rotor, thus making grid refinement prohibitive.

  2. Takeoff/approach noise for a model counterrotation propeller with a forward-swept upstream rotor

    NASA Technical Reports Server (NTRS)

    Woodward, Richard P.; Hall, David G.; Podboy, Gary G.; Jeracki, Robert J.

    1993-01-01

    A scale model of a counterrotating propeller with forward-swept blades in the forward rotor and aft-swept blades in the aft rotor (designated F39/A31) has been tested in the NASA Lewis 9- by 15-Foot Anechoic Wind Tunnel. This paper presents aeroacoustic results at a takeoff/approach condition of Mach 0.20. Laser Doppler Velocimeter results taken in a plane between the two rotors are also included to quantify the interaction flow field. The intention of the forward-swept design is to reduce the magnitude of the forward rotor tip vortex and/or wakes which impinge on the aft rotor, thus lowering the interaction tone levels.

  3. Takeoff/approach noise for a model counterrotation propeller with a forward-swept upstream rotor

    NASA Technical Reports Server (NTRS)

    Woodward, Richard P.; Hall, David G.; Podboy, Gary G.; Jeracki, Robert J.

    1993-01-01

    A scale model of a counterrotating propeller with forward-swept blades in the forward rotor and aft-swept blades in the aft rotor (designated F39/A31) has been tested in the NASA Lewis 9- by 15-Foot Anechoic Wind Tunnel. This paper presents aeroacoustic results at a takeoff/approach condition of Mach 0.20. Laser Doppler velocimeter results taken in a plane between the two rotors are also included to quantify the interaction flow field. The intention of the forward-swept design is to reduce the magnitude of the forward rotor tip vortex and/or wakes which impinge on the aft rotor, thus lowering the interaction tone levels. A reference model propeller (designated F31/A31), having aft-swept blades in both rotors, was also tested. Aeroelastic performance of the F39/A31 propeller was disappointing. The forward rotor tip region tended to untwist toward higher effective blade angles under load. The forward rotor also exhibited steady state blade flutter at speeds and loadings well below the design condition. The noise results, based on sideline acoustic data, show that the interaction tone levels were up to 8 dB higher with the forward-swept design compared to those for the reference propeller at similar operating conditions, with these tone level differences extending down to lower propeller speeds where flutter did not occur. These acoustic results are for a poorly-performing forward-swept propeller. It is quite possible that a properly-designed forward-swept propeller would exhibit substantial interaction tone level reductions.

  4. Comments on Frequency Swept Rotating Input Perturbation Techniques and Identification of the Fluid Force Models in Rotor/bearing/seal Systems and Fluid Handling Machines

    NASA Technical Reports Server (NTRS)

    Muszynska, Agnes; Bently, Donald E.

    1991-01-01

    Perturbation techniques used for identification of rotating system dynamic characteristics are described. A comparison between two periodic frequency-swept perturbation methods applied in identification of fluid forces of rotating machines is presented. The description of the fluid force model identified by inputting circular periodic frequency-swept force is given. This model is based on the existence and strength of the circumferential flow, most often generated by the shaft rotation. The application of the fluid force model in rotor dynamic analysis is presented. It is shown that the rotor stability is an entire rotating system property. Some areas for further research are discussed.

  5. Comparison of Tone Mode Measurements for a Forward Swept and Baseline Rotor Fan

    NASA Technical Reports Server (NTRS)

    Heidelberg, Laurence J.

    2003-01-01

    A forward swept fan, designated the Quite High Speed Fan (QHSF), was tested in the NASA Glenn 9- by 15-foot Low Speed Wind Tunnel to investigate its noise reduction relative to a baseline fan of the same aerodynamic performance. The design objective of the QHSF was a 6 dB reduction in Effective Perceived Noise Level relative to the baseline fan at the takeoff condition. The design noise reduction was to be a result of lower levels of multiple pure tone noise due to the forward swept rotor, and lower rotor/stator interaction tone noise from a leaned stator. Although the design 6 dB reduction was observed in far-field measurements, the induct mode measurements revealed the reasons for goals. All of the noise reduction was from the blade passing tone and its harmonics and most of this was unexpectedly from rotor/strut interaction modes. The reason for large differences in rotor/strut noise sources could not be determined with certainty. The reductions in the multiple pure tone noise for the forward swept rotor were not observed. this reduction were not the ones related to the design

  6. Aeroelasticity and structural optimization of composite helicopter rotor blades with swept tips

    NASA Technical Reports Server (NTRS)

    Yuan, K. A.; Friedmann, P. P.

    1995-01-01

    This report describes the development of an aeroelastic analysis capability for composite helicopter rotor blades with straight and swept tips, and its application to the simulation of helicopter vibration reduction through structural optimization. A new aeroelastic model is developed in this study which is suitable for composite rotor blades with swept tips in hover and in forward flight. The hingeless blade is modeled by beam type finite elements. A single finite element is used to model the swept tip. Arbitrary cross-sectional shape, generally anisotropic material behavior, transverse shears and out-of-plane warping are included in the blade model. The nonlinear equations of motion, derived using Hamilton's principle, are based on a moderate deflection theory. Composite blade cross-sectbnal properties are calculated by a separate linear, two-dimensional cross section analysis. The aerodynamic loads are obtained from quasi-steady, incompressible aerodynamics, based on an implicit formulation. The trim and steady state blade aeroelastic response are solved in a fully coupled manner. In forward flight, where the blade equations of motion are periodic, the coupled trim-aeroelastic response solution is obtained from the harmonic balance method. Subsequently, the periodic system is linearized about the steady state response, and its stability is determined from Floquet theory.

  7. Acoustic evaluation of a novel swept-rotor fan. [noise reduction in turbofan engines

    NASA Technical Reports Server (NTRS)

    Lucas, J. G.; Woodward, R. P.; Mackinnon, M. J.

    1978-01-01

    Inlet noise and aerodynamic performance are presented for a high tip speed fan designed with rotor blade leading edge sweep that gives a subsonic component of inlet Mach number normal to the edge at all radii. The intent of the design was to minimize the generation of rotor leading edge shock waves thereby minimizing multiple pure tone noise. Sound power level and spectral comparisons are made with several high-speed fans of conventional design. Results show multiple pure tone noise at levels below those of some of the other fans and this noise was initiated at a higher tip speed. Aerodynamic performance of the fan did not meet design goals for this first build which applied conventional design procedures to the swept fan geometry.

  8. Comparison of calculated and measured pressures on straight and swept-tip model rotor blades

    NASA Technical Reports Server (NTRS)

    Tauber, M. E.; Chang, I. C.; Caughey, D. A.; Phillipe, J. J.

    1983-01-01

    Using the quasi-steady, full potential code, ROT22, pressures were calculated on straight and swept tip model helicopter rotor blades at advance ratios of 0.40 and 0.45, and into the transonic tip speed range. The calculated pressures were compared with values measured in the tip regions of the model blades. Good agreement was found over a wide range of azimuth angles when the shocks on the blade were not too strong. However, strong shocks persisted longer than predicted by ROT22 when the blade was in the second quadrant. Since the unsteady flow effects present at high advance ratios primarily affect shock waves, the underprediction of shock strengths is attributed to the simplifying, quasi-steady, assumption made in ROT22.

  9. Swept sine testing of rotor-bearing system for damping estimation

    NASA Astrophysics Data System (ADS)

    Chandra, N. Harish; Sekhar, A. S.

    2014-01-01

    Many types of rotating components commonly operate above the first or second critical speed and they are subjected to run-ups and shutdowns frequently. The present study focuses on developing FRF of rotor bearing systems for damping estimation from swept-sine excitation. The principle of active vibration control states that with increase in angular acceleration, the amplitude of vibration due to unbalance will reduce and the FRF envelope will shift towards the right (or higher frequency). The frequency response function (FRF) estimated by tracking filters or Co-Quad analyzers was proved to induce an error into the FRF estimate. Using Fast Fourier Transform (FFT) algorithm and stationary wavelet transform (SWT) decomposition FRF distortion can be reduced. To obtain a theoretical clarity, the shifting of FRF envelope phenomenon is incorporated into conventional FRF expressions and validation is performed with the FRF estimated using the Fourier Transform approach. The half-power bandwidth method is employed to extract damping ratios from the FRF estimates. While deriving half-power points for both types of responses (acceleration and displacement), damping ratio (ζ) is estimated with different approximations like classical definition (neglecting damping ratio of order higher than 2), third order (neglecting damping ratios with order higher than 4) and exact (no assumptions on damping ratio). The use of stationary wavelet transform to denoise the noise corrupted FRF data is explained. Finally, experiments are performed on a test rotor excited with different sweep rates to estimate the damping ratio.

  10. Large-Area Atom Interferometry with Frequency-Swept Raman Adiabatic Passage.

    PubMed

    Kotru, Krish; Butts, David L; Kinast, Joseph M; Stoner, Richard E

    2015-09-04

    We demonstrate light-pulse atom interferometry with large-momentum-transfer atom optics based on stimulated Raman transitions and frequency-swept adiabatic rapid passage. Our atom optics have produced momentum splittings of up to 30 photon recoil momenta in an acceleration-sensitive interferometer for laser cooled atoms. We experimentally verify the enhancement of phase shift per unit acceleration and characterize interferometer contrast loss. By forgoing evaporative cooling and velocity selection, this method lowers the atom shot-noise-limited measurement uncertainty and enables large-area atom interferometry at higher data rates.

  11. Noninvasive characterisation of foot reflexology areas by swept source-optical coherence tomography in patients with low back pain.

    PubMed

    Dalal, Krishna; Elanchezhiyan, D; Das, Raunak; Dalal, Devjyoti; Pandey, Ravindra Mohan; Chatterjee, Subhamoy; Upadhyay, Ashish Datt; Maran, V Bharathi; Chatterjee, Jyotirmoy

    2013-01-01

    Objective. When exploring the scientific basis of reflexology techniques, elucidation of the surface and subsurface features of reflexology areas (RAs) is crucial. In this study, the subcutaneous features of RAs related to the lumbar vertebrae were evaluated by swept source-optical coherence tomography (SS-OCT) in subjects with and without low back pain (LBP). Methods. Volunteers without LBP (n = 6 (male : female = 1 : 1)) and subjects with LBP (n = 15 (male : female = 2 : 3)) were clinically examined in terms of skin colour (visual perception), localised tenderness (visual analogue scale) and structural as well as optical attributes as per SS-OCT. From each subject, 6 optical tomograms were recorded from equidistant transverse planes along the longitudinal axis of the RAs, and from each tomogram, 25 different spatial locations were considered for recording SS-OCT image attributes. The images were analysed with respect to the optical intensity distributions and thicknesses of different skin layers by using AxioVision Rel. 4.8.2 software. The SS-OCT images could be categorised into 4 pathological grades (i.e., 0, 1, 2, and 3) according to distinctness in the visible skin layers. Results. Three specific grades for abnormalities in SS-OCT images were identified considering gradual loss of distinctness and increase in luminosity of skin layers. Almost 90.05% subjects were of mixed type having predominance in certain grades. Conclusion. The skin SS-OCT system demonstrated a definite association of the surface features of healthy/unhealthy RAs with cutaneous features and the clinical status of the lumbar vertebrae.

  12. Noninvasive Characterisation of Foot Reflexology Areas by Swept Source-Optical Coherence Tomography in Patients with Low Back Pain

    PubMed Central

    Dalal, Krishna; Elanchezhiyan, D.; Das, Raunak; Dalal, Devjyoti; Pandey, Ravindra Mohan; Chatterjee, Subhamoy; Upadhyay, Ashish Datt; Maran, V. Bharathi; Chatterjee, Jyotirmoy

    2013-01-01

    Objective. When exploring the scientific basis of reflexology techniques, elucidation of the surface and subsurface features of reflexology areas (RAs) is crucial. In this study, the subcutaneous features of RAs related to the lumbar vertebrae were evaluated by swept source-optical coherence tomography (SS-OCT) in subjects with and without low back pain (LBP). Methods. Volunteers without LBP (n = 6 (male : female = 1 : 1)) and subjects with LBP (n = 15 (male : female = 2 : 3)) were clinically examined in terms of skin colour (visual perception), localised tenderness (visual analogue scale) and structural as well as optical attributes as per SS-OCT. From each subject, 6 optical tomograms were recorded from equidistant transverse planes along the longitudinal axis of the RAs, and from each tomogram, 25 different spatial locations were considered for recording SS-OCT image attributes. The images were analysed with respect to the optical intensity distributions and thicknesses of different skin layers by using AxioVision Rel. 4.8.2 software. The SS-OCT images could be categorised into 4 pathological grades (i.e., 0, 1, 2, and 3) according to distinctness in the visible skin layers. Results. Three specific grades for abnormalities in SS-OCT images were identified considering gradual loss of distinctness and increase in luminosity of skin layers. Almost 90.05% subjects were of mixed type having predominance in certain grades. Conclusion. The skin SS-OCT system demonstrated a definite association of the surface features of healthy/unhealthy RAs with cutaneous features and the clinical status of the lumbar vertebrae. PMID:23662156

  13. Using a collision model to design safer wind turbine rotors for birds

    SciTech Connect

    Tucker, V.A.

    1996-11-01

    A mathematical model for collisions between birds and propeller-type turbine rotors identifies the variables that can be manipulated to reduce the probability that birds will collide with the rotor. This study defines a safety index--the clearance power density--that allows rotors of different sizes and designs to be compared in terms of the amount of wind energy converted to electrical energy per bird collision. The collision model accounts for variations in wind speed during the year and shows that for model rotors with simple, one-dimensional blades, the safety index increases in proportion to rotor diameter, and variable speed rotors have higher safety indexes than constant speed rotors. The safety index can also be increased by enlarging the region near the center of the rotor hub where the blades move slowly enough for birds to avoid them. Painting the blades to make them more visible might have this effect. Model rotors with practical designs can have safety indexes an order of magnitude higher than those for model rotors typical of the constant speeds rotors in common use today. This finding suggests that redesigned rotors could have collision rates with birds perhaps an order of magnitude lower than today`s rotors, with no reduction in the production of wind power. The empirical data that exist for collisions between raptors, such as hawks and eagles, and rotors are consistent with the model: the numbers of raptor carcasses found beneath large variable speed rotors, relative to the numbers found under small constant speed rotors, are in the proportions predicted by the collision model rather than in proportion to the areas swept by the rotor blades. However, uncontrolled variables associated with these data prevent a stronger claim of support for the model.

  14. Effects of four inlet and outlet tip-annulus-area blockage configurations on the performance of an axial-flow fan rotor

    NASA Technical Reports Server (NTRS)

    Osborn, W. M.; Hager, R. D.

    1976-01-01

    An axial-flow fan rotor was tested with four configurations of tip-annulus-area blockage to speeds as high as 0.8 of design speed. The rotor performance with the four blockage configurations is compared with the unblocked rotor performance and with blockage configurations previously investigated. The blockage configurations enable the rotor to operate in a stable condition, to much lower flows than the unblocked rotor, with no evidence of rotating stall. The blockage configurations were effective in reducing rotor torque and weight flow but were accompanied by reductions in pressure ratio and efficiency.

  15. Wind-tunnel and Flight Investigations of the Use of Leading-Edge Area Suction for the Purpose of Increasing the Maximum Lift Coefficient of a 35 Degree Swept-Wing Airplane

    NASA Technical Reports Server (NTRS)

    Holzhauser, Curt A; Bray, Richard S

    1956-01-01

    An investigation was undertaken to determine the increase in maximum lift coefficient that could be obtained by applying area suction near the leading edge of a wing. This investigation was performed first with a 35 degree swept-wing model in the wind tunnel, and then with an operational 35 degree swept-wing airplane which was modified in accord with the wind-tunnel results. The wind-tunnel and flight tests indicated that the maximum lift coefficient was increased more than 50 percent by the use of area suction. Good agreement was obtained in the comparison of the wind-tunnel results with those measured in flight.

  16. Preliminary Structural Design Conceptualization for Composite Rotor for Verdant Power Water Current: Cooperative Research and Development Final Report, CRADA Number CRD-08-296

    SciTech Connect

    Hughes, S.

    2011-02-01

    The primary thrust of the CRADA will be to develop a new rotor design that will allow higher current flows (>4m/s), greater swept area (6-11m), and in the process, will maximize performance and energy capture.

  17. Forward sweep, low noise rotor blade

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F. (Inventor)

    1996-01-01

    A forward-swept, low-noise rotor blade includes an inboard section, an aft-swept section and a forward-swept outboard section. The rotor blade reduces the noise of rotorcraft, including both standard helicopters and advanced systems such as tiltrotors. The primary noise reduction feature is the forward sweep of the planform over a large portion of the outer blade radius. The rotor blade also includes an aft-swept section. The purpose of the aft-swept region is to provide a partial balance to pitching moments produced by the outboard forward-swept portion of the blade. The rotor blade has a constant chord width; or has a chord width which decreases linearly along the entire blade span; or combines constant and decreasing chord widths, wherein the blade is of constant chord width from the blade root to a certain location on the rotor blade, then decreases linearly to the blade tip thereafter. The noise source showing maximum noise reduction is blade-vortex interaction (BVI) noise. Also reduced are thickness, noise, high speed impulsive noise, cabin vibration and loading noise.

  18. Blade-to-Blade Variations in Shocks Upstream of Both a Forward-Swept and an Aft-Swept Fan

    NASA Technical Reports Server (NTRS)

    Podboy, Gary G.; Krupar, Martin J.

    2006-01-01

    Detailed laser Doppler velocimeter (LDV) flow field measurements were made upstream of two fans, one forward-swept and one aft-swept, in order to learn more about the shocks which propagate upstream of these rotors when they are operated at supersonic tip speeds. The blade-to-blade variations in the flows associated with these shocks are thought to be responsible for generating Multiple Pure Tone (MPT) noise. The measured blade-to-blade variations are documented in this report through a series of slideshows which show relative Mach number contours computed from the velocity measurements. Data are presented for the forward-swept fan operating at three speeds (corresponding to tip relative Mach numbers of 0.817, 1.074, and 1.189), and for the aft-swept fan operating at two (tip relative Mach numbers of 1.074 and 1.189). These LDV data illustrate how the perturbations in the upstream flow field created by the rotating blades vary with axial position, radial position and rotor speed. As expected, at the highest tested speed the forward-swept fan swallowed the shocks which occur in the tip region, whereas the aftswept fan did not. This resulted in a much smaller flow disturbance just upstream of the tip of the forward-swept fan. Nevertheless, further upstream the two fan flows were much more similar.

  19. Frequency comb swept lasers

    PubMed Central

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C.; Fujimoto, James G.

    2010-01-01

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a ~−1.2dB sensitivity roll off over ~3mm range, compared to conventional swept source and FDML lasers which have −10dB and −5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0–3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed. PMID:19997365

  20. Frequency comb swept lasers.

    PubMed

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C; Fujimoto, James G

    2009-11-09

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a approximately -1.2dB sensitivity roll off over approximately 3mm range, compared to conventional swept source and FDML lasers which have -10dB and -5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0-3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed.

  1. Compressible, unsteady lifting-surface theory for a helicopter rotor in forward flight

    NASA Technical Reports Server (NTRS)

    Runyan, H. L.; Tai, H.

    1985-01-01

    A lifting-surface theory has been developed for a helicopter rotor in forward flight for compressible and incompressible flow. The method utilizes the concept of the linearized acceleration potential and makes use of the doublet lattice procedure. Calculations demonstrating the application of the method are given in terms of the lift distribution on a one-bladed rotor, a two-bladed rotor, and a rotor with swept-forward and swept-back tips. Also, the lift on a rotor vibrating in a pitching mode at 4 per revolution is given. Compressibility effects and interference effects for a two-bladed rotor are discussed.

  2. A mathematical model of bird collisions with wind turbine rotors

    SciTech Connect

    Tucker, V.A.

    1996-11-01

    When a bird flies through the disk swept out by the blades of a wind turbine rotor, the probability of collision depends on the motions and dimensions of the bird and the blades. The collision model in this paper predicts the probability for birds that glide upwind, downwind, an across the wind past simple one-dimensional blades represented by straight lines, and upwind and downwind past more realistic three-dimensional blades with chord and twist. Probabilities vary over the surface of the disk, and in most cases, the tip of the blade is less likely to collide with a bird than parts of the blade nearer the hub. The mean probability may be found by integration over the disk area. The collision model identifies the rotor characteristics that could be altered to make turbines safer for birds.

  3. Swept Light Sources

    NASA Astrophysics Data System (ADS)

    Johnson, Bart; Atia, Walid; Kuznetsov, Mark; Cook, Christopher; Goldberg, Brian; Wells, Bill; Larson, Noble; McKenzie, Eric; Melendez, Carlos; Mallon, Ed; Woo, Seungbum; Murdza, Randal; Whitney, Peter; Flanders, Dale

    A 1060 nm OEM laser "engine", manufactured by Axsun Technologies, is described. It consists of a swept laser and control electronics coupled with a balanced receiver, k-clock, and a 550 MS/s data acquisition board. The laser's passive mode-locking behavior induced by the rapid wavelength sweep is discussed. As they pass though the gain medium, each pulse is shifted to longer wavelength due to the rise in refractive index associated with gain depletion. New, longer wavelengths, are thus created by nonlinear means rather than by building up anew from spontaneous emission. This nonlinear mechanism enables low noise operation and fast sweep rates. The so-called "coherence revival" phenomenon associated with interference between neighboring mode-locked pulses, is discussed. Typical laser and system data is shown, including k-clock frequency, trigger waveform, pulsed and average output powers and RIN. Receiver and DAQ board noise performance is quantified. The laser RIN is estimated to be lower than -150 dB/Hz. A typical shot-noise-limited sensitivity of 103 dB is achieved for 1.9 mW sample power. The engine is designed for ophthalmic imaging and retinal images from prototype commercial systems are presented.

  4. Design and fabrication of forward-swept counterrotation blade configuration for wind tunnel testing

    NASA Technical Reports Server (NTRS)

    Nichols, G. H.

    1994-01-01

    Work performed by GE Aircraft on advanced counterrotation blade configuration concepts for high speed turboprop system is described. Primary emphasis was placed on theoretically and experimentally evaluating the aerodynamic, aeromechanical, and acoustic performance of GE-defined counterrotating blade concepts. Several blade design concepts were considered. Feasibility studies were conducted to evaluate a forward-swept versus an aft-swept blade application and how the given blade design would affect interaction between rotors. Two blade designs were initially selected. Both designs involved in-depth aerodynamic, aeromechanical, mechanical, and acoustic analyses followed by the fabrication of forward-swept, forward rotor blade sets to be wind tunnel tested with an aft-swept, aft rotor blade set. A third blade set was later produced from a NASA design that was based on wind tunnel test results from the first two blade sets. This blade set had a stiffer outer ply material added to the original blade design, in order to reach the design point operating line. Detailed analyses, feasibility studies, and fabrication procedures for all blade sets are presented.

  5. Fast swept-volume distance for robust collision detection

    SciTech Connect

    Xavier, P.G.

    1997-04-01

    The need for collision detection arises in several robotics areas, including motion-planning, online collision avoidance, and simulation. At the heart of most current methods are algorithms for interference detection and/or distance computation. A few recent algorithms and implementations are very fast, but to use them for accurate collision detection, very small step sizes can be necessary, reducing their effective efficiency. We present a fast, implemented technique for doing exact distance computation and interference detection for translationally-swept bodies. For rotationally swept bodies, we adapt this technique to improve accuracy, for any given step size, in distance computation and interference detection. We present preliminary experiments that show that the combination of basic and swept-body calculations holds much promise for faster accurate collision detection.

  6. Effects of Swept Tips on V-22 Whirl Flutter and Loads

    NASA Technical Reports Server (NTRS)

    Acree, C. W., Jr.

    2005-01-01

    A CAMRAD II model of the V-22 Osprey tiltrotor was constructed for the purpose of analyzing the effects of blade design changes on whirl flutter. The model incorporated a dual load-path grip/yoke assembly, a swashplate coupled to the transmission case, and a drive train. A multiple-trailer free wake was used for loads calculations. The effects of rotor design changes on whirl-mode stability were calculated for swept blades and offset tip masses. A rotor with swept tips and inboard tuning masses was examined in detail to reveal the mechanisms by which these design changes affect stability and loads. Certain combinations of design features greatly increased whirl-mode stability, with (at worst) moderate increases to loads.

  7. Design Selection and Analysis of a Swept and Leaned Stator Concept

    NASA Technical Reports Server (NTRS)

    Envia, Edmane; Nallasamy, M.

    1998-01-01

    This report describes a theoretical design and analysis study of the benefits of vane sweep and lean for reducing rotor- stator interaction tone noise. It is shown that the kinematic relationship between the rotor wakes and stator vanes is the principal factor in determining the achievable noise reductions. Vane sweep and lean control rotor wake skewing as seen by the stator vanes and hence influence the number of wake intersections per vane. An increase in the number of intersections reduces noise levels. Hence, to reduce rotor-stator noise, van sweep and lean must be chosen in such a way as to increase wake intersections per vane. A simple design rule is thus proposed which requires a sweep configuration that puts the vane tip downstream of its root and a vane lean that is in the direction of the rotor rotation. A detailed comparison of the predicted and measured noise reductions for a swept and leaned stator is then carried out. Overall, these comparisons show that the predicted benefits of a swept and leaned stator are in good agreement, qualitative as well as quantitative, with the measured reductions for the fan speeds relevant to noise certification procedure. Furthermore, the results also demonstrate the validity of design criterion and the theoretical tools used in this study.

  8. Swept Frequency Laser Metrology System

    NASA Technical Reports Server (NTRS)

    Zhao, Feng (Inventor)

    2010-01-01

    A swept frequency laser ranging system having sub-micron accuracy that employs multiple common-path heterodyne interferometers, one coupled to a calibrated delay-line for use as an absolute reference for the ranging system. An exemplary embodiment uses two laser heterodyne interferometers to create two laser beams at two different frequencies to measure distance and motions of target(s). Heterodyne fringes generated from reflections off a reference fiducial X(sub R) and measurement (or target) fiducial X(sub M) are reflected back and are then detected by photodiodes. The measured phase changes Delta phi(sub R) and Delta phi (sub m) resulting from the laser frequency swept gives target position. The reference delay-line is the only absolute reference needed in the metrology system and this provides an ultra-stable reference and simple/economical system.

  9. HELIOS dual swept frequency radiometer

    NASA Technical Reports Server (NTRS)

    White, J. R.

    1975-01-01

    The HELIOS dual swept frequency radiometer, used in conjunction with a dipole antenna, was designed to measure electromagnetic radiation in space. An engineering prototype was fabricated and tested on the HELIOS spacecraft. Two prototypes and two flight units were fabricated and three of the four units were integrated into the HELIOS spacecraft. Two sets of ground support equipment were provided for checkout of the radiometer.

  10. A study of the noise radiation from four helicopter rotor blades. [tests in Ames 40 by 20 foot wind tunnel

    NASA Technical Reports Server (NTRS)

    Lee, A.; Mosher, M.

    1978-01-01

    Acoustic measurements were taken of a modern helicopter rotor with four blade tip shapes in the NASA Ames 40-by-80-Foot Wind Tunnel. The four tip shapes are: rectangular, swept, trapezoidal, and swept tapered in platform. Acoustic effects due to tip shape changes were studied based on the dBA level, peak noise pressure, and subjective rating. The swept tapered blade was found to be the quietest above an advancing tip Mach number of about 0.9, and the swept blade was the quietest at low speed. The measured high speed impulsive noise was compared with theoretical predictions based on thickness effects; good agreement was found.

  11. Tilt rotor aircraft aeroacoustics

    NASA Technical Reports Server (NTRS)

    George, Albert R.; Smith, Charles A.; Maisel, Martin D.; Brieger, John T.

    1989-01-01

    This paper studies the state of knowledge and the needed improvement in noise methodology and measurements for tilt rotor aircraft. Similarities and differences between tilt rotor aeroacoustic conditions and helicopter and propeller experience are identified. A discussion of the possible principal noise mechanisms throughout the flight envelope shows a need for further experimental and analytical investigations to develop an adequate understanding of the important sources and influencing factors. Existing experimental data from flight tests suggest terminal area noise reduction by operating within certain portions of the conversion flight envelope. Prediction methods are found to provide approximate indications only for low frequency harmonic and broadband noise for several of the tilt rotor's operating conditions. The acoustic effects of the hover case 'fountain' flow are pronounced and need further research. Impulsive noise and high frequency harmonic noise remain problems, as on helicopters, pending major improvements in wake, unsteady aerodynamics, and acoustics methodology.

  12. Molecular Rotors

    DTIC Science & Technology

    2006-10-31

    Zack Murray No Faith Jordan No Charles Hagerdorn No Elizabeth Baker, No Mathew Myers No Leah A. Edelman No William T. Gathright No Bill Bockrath No...ligand could impact the construction of rotor arrays. Consequently, VASP calculations were performed in collaboration with Dr. Jeffrey Reimers of

  13. A prediction of high-speed rotor noise

    NASA Technical Reports Server (NTRS)

    Purcell, Timothy W.

    1989-01-01

    A combined computational (CFD) and integral approach solves the acoustic pressure fields of two high-speed helicopter rotors. A CFD code supplies boundary data to a non-linear type of Kirchhoff integral formulation to find the far-field pressures. Direct calculations of pressures are given by the CFD code up to the sonic cylinder where the Kirchhoff method takes over. This paper shows predictions and measurements of High-Speed Impulsive (HSI) noise in hover for two different rotor geometries. One rotor has a conventional rectangular planform, while the other rotor is highly swept and tapered. The swept rotor analysis forms the majority of this paper. Test data from both rotors are shown and compared with predictions for a range of tip Mach numbers from .85 to .95 (including delocalization). The correlation with the near-field pressures from the straight bladed experiment is excellent and good to excellent correlation is seen for the far-field pressures from both experiments.

  14. Pressure Sensitive Paint Measurements on 15% Scale Rotor Blades in Hover

    NASA Technical Reports Server (NTRS)

    Wong, Oliver D.; Watkins, Anthony Neal; Ingram, JoAnne L.

    2005-01-01

    This paper describes a proof of concept test to examine the feasibility of using pressure sensitive paint (PSP) to measure the pressure distributions on a rotor in hover. The test apparatus consisted of the US Army 2-meter Rotor Test Stand (2MRTS) and 15% scale swept tip rotor blades. Two camera/rotor separations were examined: 0.76 and 1.35 radii. The outer 15% of each blade was painted with PSP. Intensity and lifetime based PSP measurement techniques were attempted. Data were collected from all blades at thrust coefficients ranging from 0.004 to 0.009.

  15. Separators for flywheel rotors

    DOEpatents

    Bender, D.A.; Kuklo, T.C.

    1998-07-07

    A separator forms a connection between the rotors of a concentric rotor assembly. This separator allows for the relatively free expansion of outer rotors away from inner rotors while providing a connection between the rotors that is strong enough to prevent disassembly. The rotor assembly includes at least two rotors referred to as inner and outer flywheel rings or rotors. This combination of inner flywheel ring, separator, and outer flywheel ring may be nested to include an arbitrary number of concentric rings. The separator may be a segmented or continuous ring that abuts the ends of the inner rotor and the inner bore of the outer rotor. It is supported against centrifugal loads by the outer rotor and is affixed to the outer rotor. The separator is allowed to slide with respect to the inner rotor. It is made of a material that has a modulus of elasticity that is lower than that of the rotors. 10 figs.

  16. Separators for flywheel rotors

    DOEpatents

    Bender, Donald A.; Kuklo, Thomas C.

    1998-01-01

    A separator forms a connection between the rotors of a concentric rotor assembly. This separator allows for the relatively free expansion of outer rotors away from inner rotors while providing a connection between the rotors that is strong enough to prevent disassembly. The rotor assembly includes at least two rotors referred to as inner and outer flywheel rings or rotors. This combination of inner flywheel ring, separator, and outer flywheel ring may be nested to include an arbitrary number of concentric rings. The separator may be a segmented or continuous ring that abuts the ends of the inner rotor and the inner bore of the outer rotor. It is supported against centrifugal loads by the outer rotor and is affixed to the outer rotor. The separator is allowed to slide with respect to the inner rotor. It is made of a material that has a modulus of elasticity that is lower than that of the rotors.

  17. Influence of vane sweep on rotor-stator interaction noise

    NASA Technical Reports Server (NTRS)

    Envia, Edmane; Kerschen, Edward J.

    1990-01-01

    The influence of vane sweep in rotor-stator interaction noise is investigated. In an analytical approach, the interaction of a convected gust representing the rotor viscous wake, with a cascade of cascade of finite span swept airfoils, representing the stator, is analyzed. The analysis is based on the solution of the exact linearized equations of motion. High frequency convected gusts for which noise generation is concentrated near the leading edge of airfoils is considered. In a preliminary study, the problem of an isolated finite span swept airfoil interacting with a convected gust is analyzed. Results indicate that sweep can substantially reduce the farfield noise levels for a single airfoil. Using the single airfoil model, an approximate solution to the problem of noise radiation from a cascade of finite span swept airfoils interacting with a convected gust is derived. A parametric study of noise generated by gust cascade interaction is carried out to assess the effectiveness of vane sweep in reducing rotor-stator interaction noise. The results show that sweep is beneficial in reducing noise levels. Rotor wake twist or circumferential lean substantially influences the effectiveness of vane sweep. The orientation of vane sweep must be chosen to enhance the natural phase lag caused by wake lean, in which case rather small sweep angles substantially reduce the noise levels.

  18. Influence of vane sweep on rotor-stator interaction noise

    NASA Astrophysics Data System (ADS)

    Envia, Edmane; Kerschen, Edward J.

    1990-12-01

    The influence of vane sweep in rotor-stator interaction noise is investigated. In an analytical approach, the interaction of a convected gust representing the rotor viscous wake, with a cascade of cascade of finite span swept airfoils, representing the stator, is analyzed. The analysis is based on the solution of the exact linearized equations of motion. High frequency convected gusts for which noise generation is concentrated near the leading edge of airfoils is considered. In a preliminary study, the problem of an isolated finite span swept airfoil interacting with a convected gust is analyzed. Results indicate that sweep can substantially reduce the farfield noise levels for a single airfoil. Using the single airfoil model, an approximate solution to the problem of noise radiation from a cascade of finite span swept airfoils interacting with a convected gust is derived. A parametric study of noise generated by gust cascade interaction is carried out to assess the effectiveness of vane sweep in reducing rotor-stator interaction noise. The results show that sweep is beneficial in reducing noise levels. Rotor wake twist or circumferential lean substantially influences the effectiveness of vane sweep. The orientation of vane sweep must be chosen to enhance the natural phase lag caused by wake lean, in which case rather small sweep angles substantially reduce the noise levels.

  19. Swept wing ice accretion modeling

    NASA Technical Reports Server (NTRS)

    Potapczuk, M. G.; Bidwell, C. S.

    1990-01-01

    An effort to develop a three-dimensional ice accretion modeling method is initiated. This first step toward creation of a complete aircraft icing simulation code builds on previously developed methods for calculating three-dimensional flowfields and particle trajectories combined with a two-dimensional ice accretion calculation along coordinate locations corresponding to streamlines. This work is intended as a demonstration of the types of calculations necessary to predict a three-dimensional ice accretion. Results of calculations using the 3D method for a MS-317 swept wing geometry are projected onto a 2D plane normal to the wing leading edge and compared to 2D results for the same geometry. These results indicate that the flowfield over the surface and the particle trajectories differed for the two calculations. This led to lower collection efficiencies, convective heat transfer coefficients, freezing fractions, and ultimately ice accumulation for the 3D calculation.

  20. Laser velocimeter measurements of the flow field generated by a forward-swept propfan during flutter

    NASA Technical Reports Server (NTRS)

    Podboy, Gary G.; Krupar, Martin J.

    1993-01-01

    Results are presented from an investigation to measure the flow field generated by a forward-swept propfan operating in flutter at a low forward velocity. For comparison to the flutter condition, flow field data are also presented for a slightly reduced rotational speed just below flutter. The forward-swept propfan was tested as the front rotor of a counterrotating pusher propeller. A laser Doppler velocimeter (LDV) was used to measure the velocity field in planes normal to the model centerline downstream of the rotor and in planes of constant radius within the blade passages at each operating condition. A comparison of the data taken at the two different operating conditions indicated that the mean, time-averaged flow about the blades did not change drastically as the propfan rotational speed was increased from the stable operating point to the flutter condition. No regions of flow separation could be identified in the data plots of the mean intrablade flow field. The data also indicate that the relative flow about the blades remained subsonic during flutter operation. The blades were found to have a higher than expected tip loading at both operating conditions. This is thought to have been caused by the outer blade sections twisting under load to higher than expected effective blade angles. This high tip loading resulted in strong vortices and a very nonuniform flow downstream of the tips of the forward-swept blades. This high tip loading may also have caused the blade flutter.

  1. Evaluation of a doubly-swept blade tip for rotorcraft noise reduction

    NASA Technical Reports Server (NTRS)

    Wake, Brian E.; Egolf, T. Alan

    1992-01-01

    A computational study was performed for a doubly-swept rotor blade tip to determine its benefit for high-speed impulsive (HSI) and blade-vortex interaction (BVI) noise. This design consists of aft and forward sweep. For the HSI-noise computations, unsteady Euler calculations were performed for several variations to a rotor blade geometry. A doubly-swept planform was predicted to increase the delocalizing Mach number to 0.94 (representative of a 200+ kt helicopter). For the BVI-noise problem, it had been hypothesized that the doubly-swept blade tip, by producing a leading-edge vortex, would reduce the tip-vortex effect on BVI noise. A procedure was used in which the tip vortex velocity profile computed by a Navier-Stokes solver was used to compute the inflow associated with BVI. This inflow was used by a Euler solver to compute the unsteady pressures for an acoustic analysis. The results of this study were inconclusive due to the difficulty in accurately predicting the viscous tip vortex downstream of the blade. Also, for the condition studied, no leading-edge vortex formed at the tip.

  2. Ultrasonic Resonance Spectroscopy of Composite Rings for Flywheel Rotors

    NASA Technical Reports Server (NTRS)

    Harmon, Laura M.; Baaklini, George Y.

    2001-01-01

    Flywheel energy storage devices comprising multilayered composite rotor systems are being studied extensively for utilization in the International Space Station. These composite material systems were investigated with a recently developed ultrasonic resonance spectroscopy technique. The system employs a swept frequency approach and performs a fast Fourier transform on the frequency spectrum of the response signal. In addition. the system allows for equalization of the frequency spectrum, providing all frequencies with equal amounts of energy to excite higher order resonant harmonics. Interpretation of the second fast Fourier transform, along with equalization of the frequency spectrum, offers greater assurance in acquiring and analyzing the fundamental frequency, or spectrum resonance spacing. The range of frequencies swept in a pitch-catch mode was varied up to 8 MHz, depending on the material and geometry of the component. Single and multilayered material samples, with and without known defects, were evaluated to determine how the constituents of a composite material system affect the resonant frequency. Amplitude and frequency changes in the spectrum and spectrum resonance spacing domains were examined from ultrasonic responses of a flat composite coupon, thin composite rings, and thick composite rings. Also, the ultrasonic spectroscopy responses from areas with an intentional delamination and a foreign material insert, similar to defects that may occur during manufacturing malfunctions, were compared with those from defect-free areas in thin composite rings. A thick composite ring with varying thickness was tested to investigate the full-thickness resonant frequency and any possible bulk interfacial bond issues. Finally, the effect on the frequency response of naturally occurring single and clustered voids in a composite ring was established.

  3. Swept Impact Seismic Technique (SIST)

    USGS Publications Warehouse

    Park, C.B.; Miller, R.D.; Steeples, D.W.; Black, R.A.

    1996-01-01

    A coded seismic technique is developed that can result in a higher signal-to-noise ratio than a conventional single-pulse method does. The technique is cost-effective and time-efficient and therefore well suited for shallow-reflection surveys where high resolution and cost-effectiveness are critical. A low-power impact source transmits a few to several hundred high-frequency broad-band seismic pulses during several seconds of recording time according to a deterministic coding scheme. The coding scheme consists of a time-encoded impact sequence in which the rate of impact (cycles/s) changes linearly with time providing a broad range of impact rates. Impact times used during the decoding process are recorded on one channel of the seismograph. The coding concept combines the vibroseis swept-frequency and the Mini-Sosie random impact concepts. The swept-frequency concept greatly improves the suppression of correlation noise with much fewer impacts than normally used in the Mini-Sosie technique. The impact concept makes the technique simple and efficient in generating high-resolution seismic data especially in the presence of noise. The transfer function of the impact sequence simulates a low-cut filter with the cutoff frequency the same as the lowest impact rate. This property can be used to attenuate low-frequency ground-roll noise without using an analog low-cut filter or a spatial source (or receiver) array as is necessary with a conventional single-pulse method. Because of the discontinuous coding scheme, the decoding process is accomplished by a "shift-and-stacking" method that is much simpler and quicker than cross-correlation. The simplicity of the coding allows the mechanical design of the source to remain simple. Several different types of mechanical systems could be adapted to generate a linear impact sweep. In addition, the simplicity of the coding also allows the technique to be used with conventional acquisition systems, with only minor modifications.

  4. Numerical simulation of swept-wing flows

    NASA Technical Reports Server (NTRS)

    Reed, Helen L.

    1991-01-01

    The transition process characteristics of flows over swept wings were computationally modelled. The crossflow instability and crossflow/T-S wave interaction are analyzed through the numerical solution of the full three dimensional Navier-Stokes equations including unsteadiness, curvature, and sweep. The leading-edge region of a swept wing is considered in a three-dimensional spatial simulation with random disturbances as the initial conditions.

  5. Coherence properties of short cavity swept lasers

    PubMed Central

    Johnson, Bart; Atia, Walid; Kuznetsov, Mark; Goldberg, Brian D.; Whitney, Peter; Flanders, Dale C.

    2017-01-01

    It has been shown theoretically and experimentally that short cavity swept lasers are passively mode locked. We develop a mathematical model of these lasers and the light field solutions are used to predict the coherence length and coherence revival behavior. The calculations compare favorably with data from a 990–1100 nm laser swept at 100 kHz suitable for optical coherence tomography applications. PMID:28271002

  6. Preform spar cap for a wind turbine rotor blade

    DOEpatents

    Livingston, Jamie T.; Driver, Howard D.; van Breugel, Sjef; Jenkins, Thomas B.; Bakhuis, Jan Willem; Billen, Andrew J.; Riahi, Amir

    2011-07-12

    A spar cap for a wind turbine rotor blade. The spar cap may include multiple preform components. The multiple preform components may be planar sheets having a swept shape with a first end and a second end. The multiple preform components may be joined by mating the first end of a first preform component to the second end of a next preform component, forming the spar cap.

  7. V/STOL tilt rotor aircraft study: Wind tunnel tests of a full scale hingeless prop/rotor designed for the Boeing Model 222 tilt rotor aircraft

    NASA Technical Reports Server (NTRS)

    Magee, J. P.; Alexander, H. R.

    1973-01-01

    The rotor system designed for the Boeing Model 222 tilt rotor aircraft is a soft-in-plane hingeless rotor design, 26 feet in diameter. This rotor has completed two test programs in the NASA Ames 40' X 80' wind tunnel. The first test was a windmilling rotor test on two dynamic wing test stands. The rotor was tested up to an advance ratio equivalence of 400 knots. The second test used the NASA powered propeller test rig and data were obtained in hover, transition and low speed cruise flight. Test data were obtained in the areas of wing-rotor dynamics, rotor loads, stability and control, feedback controls, and performance to meet the test objectives. These data are presented.

  8. Prediction of sand particle trajectories and sand erosion damage on helicopter rotor blades

    NASA Astrophysics Data System (ADS)

    Shin, Bong Gun

    agreement with the experimental data. Next, second computational validation for flow around the SC1095 airfoil for various turbulence models were performed in order to select a suitable turbulence model. These results concluded that numerical results with k -- o SST model have a reasonably best accuracy. Relative inflow conditions to the blade section of helicopter rotor blades are highly dependent upon rotor blade geometric conditions and helicopter rotor operational conditions. Therefore, in this dissertation, 3D erosion simulations for four different rotating blades with uniform airfoil profile (SC1095) were performed in order to understand the details of erosion mechanism. These results indicate that erosion patterns including maximum erosion rate position and the extent of erosion damaged area on the blade section were highly dependent upon a spanwise twist distribution. It is found that the magnitude of erosion damage on the blade section is affected by not a spanwise twist but a swept tip. Next, in this dissertation, UH-60A helicopter rotor blades rotating in the computational domain for various collective pitch angles and climb velocities were simulated. These results indicate that overall erosion characteristics for helicopter rotor blades can be considered to be not dependent upon these operational parameters though there is a little difference in the magnitude of erosion damage and the maximum erosion rate position. These results concluded that a hover condition can be chosen as a reference operational condition for predicting erosion characteristics or for investigating erosion reduction methods. The final phase of this research is a generalization for particle trajectories and erosion characteristics on 3D helicopter rotor blades in order to reduce very expensive erosion computational cost. The generalized results show that aerodynamic and erosion characteristics for a 3D rotor blade can be predicted by using the 2D airfoil results for corresponding relative

  9. On Cup Anemometer Rotor Aerodynamics

    PubMed Central

    Pindado, Santiago; Pérez, Javier; Avila-Sanchez, Sergio

    2012-01-01

    The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup. PMID:22778638

  10. On cup anemometer rotor aerodynamics.

    PubMed

    Pindado, Santiago; Pérez, Javier; Avila-Sanchez, Sergio

    2012-01-01

    The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup.

  11. Transonic flow analysis for rotors. Part 1: Three-dimensional quasi-steady, full-potential calculation

    NASA Technical Reports Server (NTRS)

    Chang, I. C.

    1984-01-01

    A new computer program is presented for calculating the quasi-steady transonic flow past a helicopter rotor blade in hover as well as in forward flight. The program is based on the full potential equations in a blade attached frame of reference and is capable of treating a very general class of rotor blade geometries. Computed results show good agreement with available experimental data for both straight and swept tip blade geometries.

  12. Halbach Magnetic Rotor Development

    NASA Technical Reports Server (NTRS)

    Gallo, Christopher A.

    2008-01-01

    The NASA John H. Glenn Research Center has a wealth of experience in Halbach array technology through the Fundamental Aeronautics Program. The goals of the program include improving aircraft efficiency, reliability, and safety. The concept of a Halbach magnetically levitated electric aircraft motor will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels, increase efficiency and reliability, reduce maintenance and decrease operating noise levels. Experimental hardware systems were developed in the GRC Engineering Development Division to validate the basic principles described herein and the theoretical work that was performed. A number of Halbach Magnetic rotors have been developed and tested under this program. A separate test hardware setup was developed to characterize each of the rotors. A second hardware setup was developed to test the levitation characteristics of the rotors. Each system focused around a unique Halbach array rotor. Each rotor required original design and fabrication techniques. A 4 in. diameter rotor was developed to test the radial levitation effects for use as a magnetic bearing. To show scalability from the 4 in. rotor, a 1 in. rotor was developed to also test radial levitation effects. The next rotor to be developed was 20 in. in diameter again to show scalability from the 4 in. rotor. An axial rotor was developed to determine the force that could be generated to position the rotor axially while it is rotating. With both radial and axial magnetic bearings, the rotor would be completely suspended magnetically. The purpose of this report is to document the development of a series of Halbach magnetic rotors to be used in testing. The design, fabrication and assembly of the rotors will be discussed as well as the hardware developed to test the rotors.

  13. Open Rotor Development

    NASA Technical Reports Server (NTRS)

    Van Zante, Dale E.; Rizzi, Stephen A.

    2016-01-01

    The ERA project executed a comprehensive test program for Open Rotor aerodynamic and acoustic performance. System studies used the data to estimate the fuel burn savings and acoustic margin for an aircraft system with open rotor propulsion. The acoustic measurements were used to produce an auralization that compares the legacy blades to the current generation of open rotor designs.

  14. A review of research in rotor loads

    NASA Technical Reports Server (NTRS)

    Bousman, William G.; Mantay, Wayne R.

    1988-01-01

    The research accomplished in the area of rotor loads over the last 13 to 14 years is reviewed. The start of the period examined is defined by the 1973 AGARD Milan conference and the 1974 hypothetical rotor comparison. The major emphasis of the review is research performed by the U.S. Army and NASA at their laboratories and/or by the industry under government contract. For the purpose of this review, two main topics are addressed: rotor loads prediction and means of rotor loads reduction. A limited discussion of research in gust loads and maneuver loads is included. In the area of rotor loads predictions, the major problem areas are reviewed including dynamic stall, wake induced flows, blade tip effects, fuselage induced effects, blade structural modeling, hub impedance, and solution methods. It is concluded that the capability to predict rotor loads has not significantly improved in this time frame. Future progress will require more extensive correlation of measurements and predictions to better understand the causes of the problems, and a recognition that differences between theory and measurement have multiple sources, yet must be treated as a whole. There is a need for high-quality data to support future research in rotor loads, but the resulting data base must not be seen as an end in itself. It will be useful only if it is integrated into firm long-range plans for the use of the data.

  15. The advantages of a swept source optical coherence tomography system in the evaluation of occlusal disorders

    NASA Astrophysics Data System (ADS)

    Marcauteanu, Corina; Bradu, Adrian; Sinescu, Cosmin; Topala, Florin Ionel; Negrutiu, Meda Lavinia; Duma, Virgil Florin; Podoleanu, Adrian Gh.

    2014-01-01

    Occlusal disorders are characterized by multiple dental and periodontal signs. Some of these are reversible (such as excessive tooth mobility, fremitus, tooth pain, migration of teeth in the absence of periodontitis), some are not (pathological occlusal/incisal wear, abfractions, enamel cracks, tooth fractures, gingival recessions). In this paper we prove the advantages of a fast swept source OCT system in the diagnosis of pathological incisal wear, a key sign of the occlusal disorders. On 15 extracted frontal teeth four levels of pathological incisal wear facets were artificially created. After every level of induced defect, OCT scanning was performed. B scans were acquired and 3D reconstructions were generated. A swept source OCT instrument is used in this study. The swept source is has a central wavelength of 1050 nm and a sweeping rate of 100 kHz. A depth resolution determined by the swept source of 12 μm in air was experimentally measured. The pathological incisal wear is qualitatively observed on the B-scans as 2D images and 3D reconstructions (volumes). For quantitative evaluations of volumes, we used the Image J software. Our swept source OCT system has several advantages, including the ability to measure (in air) a minimal volume of 2352 μm3 and to collect high resolution volumetric images in 2.5 s. By calculating the areas of the amount of lost tissue corresponding to each difference of B-scans, the final volumes of incisal wear were obtained. This swept source OCT method is very useful for the dynamic evaluation of pathological incisal wear.

  16. Analysis of a System to Prevent Helicopter Rotor Blade-Airframe Strikes

    DTIC Science & Technology

    1989-05-01

    airframe are particularly vulnerable: the tail boom, canopy and, in the case of the underslung, teetoring rotor, the rotor shaft. This latter case is...but they do occur. Three areas of the airframe are particularly vulnerable: the tail boom, canopy and, in the case of the underslung, teetoring rotor...particular vulnerable, the tail boom, canopy and, in the case of the underslung, teetoring rotor, the rotor shaft. This latter case, known as "mast

  17. Flow Measurements and Multiple Pure Tone Noise From a Forward Swept Fan

    NASA Technical Reports Server (NTRS)

    Weir, Donald S.; Podboy, Gary G.

    2005-01-01

    A forward-swept fan, designated the Quiet High Speed Fan (QHSF), was tested in the NASA Glenn 9- by 15-foot Low Speed Wind Tunnel to investigate its noise reduction relative to a baseline fan of the same aerodynamic performance. The objective of the Quiet High Speed Fan was a 6-dB reduction in the Effective Perceived Noise Level relative to the baseline fan at the takeoff condition. The intent of the Quiet High Speed Fan design was to provide both a multiple pure tone noise reduction from the forward sweep of the fan rotor and a rotor-stator interaction blade passing tone noise reduction from a leaned stator. The tunnel noise data indicted that the Quiet High Speed Fan was quieter than the baseline fan for a significant portion of the operating line and was 6 dB quieter near the takeoff condition. Although reductions in the multiple pure tones were observed, the vast majority of the EPNdB reduction was a result of the reduction in the blade passing tone and its harmonics. Laser Doppler Velocimetry (LDV) and shroud unsteady pressure measurement data were obtained upstream of the QHSF and baseline rotors to improve the understanding of the shocks which propagate upstream of the two fans when they are operated at high speeds. The flow phenomena that produce multiple pure tone noise is discussed and compared to measurements of the fan acoustic inlet modes and the far field noise signature of the fan.

  18. The development of CFD methods for rotor applications

    NASA Technical Reports Server (NTRS)

    Caradonna, F. X.; Mccroskey, W. J.

    1988-01-01

    The optimum design of the advancing helicopter rotor for high-speed forward flight always involves a tradeoff between transonic and stall limitations. However, the preoccupation of the rotor industry was primarily concerned with stall until well into the 1970s. This emphasis on stall resulted from the prevalent use of low-solidity rotors with rather outdated airfoil sections. The use of cambered airfoil sections and higher-solidity rotors substantially reduced stall and revealed the advancing transonic flow to be a more persistent limitation to high-speed rotor performance. Work in this area was spurred not only by operational necessity but also by the development of a tool for the prediction of these flows (the method of computational fluid dynamics). The development of computational fluid dynamics for these rotor problems was a major Army and NASA achievement. This work is now being extended to other rotor flow problems. The developments are outlined.

  19. Flywheel rotor and containment technology development

    SciTech Connect

    Kulkarni, S.V.

    1981-08-11

    The goals of the project are: to develop an economical and practical composite flywheel having an energy density of 88 Wh/kg at failure, an operational energy density of 44 to 55 Wh/kg, and an energy storage capacity of approximately 1 kWh; to determine the suitability of various manufacturing processes for low-cost rotor fabrication; to investigate flywheel and flywheel-systems dynamics; to test and evaluate prototype rotors for use in transportation and stationary applications; and to develop a fail-safe, lightweight, and low-cost flywheel containment. The following tasks have been accomplished: evaluation and selection of 1-kWh, first-generation, advanced flywheel rotor designs for subsequent development towards the DOE-established energy density goal of 88 Wh/kg at burst; completion of an advanced design concept for a flywheel primary containment structure, capable of containing the failure of a 1-kWh flywheel rotor and targeted for vehicular applications; non-destructive inspection and burst testing of approximately twenty (20) prototype rotors, and initiation of cyclic testing; completion of various activities in the areas of rotor manufacturing processes, dynamic analyses and composite materials design data generation; and initiation of an economic feasibility study to establish a rational costing methodology for composite rotors and containment.

  20. Rotor control system

    NASA Technical Reports Server (NTRS)

    Bradford, Michael P. (Inventor); Maciolek, Joseph R. (Inventor)

    1987-01-01

    A helicopter rotor control system (13) including a stop azimuth controller (32) for establishing the value of a deceleration command (15') to a deceleration controller (23), a transition azimuth predictor (41) and a position reference generator (55), which are effective during the last revolution of said rotor (14) to establish a correction indication (38) to adjust the deceleration command (15') to ensure that one of the rotor blades (27) stops at a predetermined angular position.

  1. Interaction of a swept shock wave and a supersonic wake

    NASA Astrophysics Data System (ADS)

    He, G.; Zhao, Y. X.; Zhou, J.

    2017-03-01

    The interaction of a swept shock wave and a supersonic wake has been studied. The swept shock wave is generated by a swept compression sidewall, and the supersonic wake is generated by a wake generator. The flow field is visualized with the nanoparticle-based planar laser scattering method, and a supplementary numerical simulation is conducted by solving the Reynolds-averaged Navier-Stokes equations. The results show that the pressure rise induced by the swept shock wave can propagate upstream in the wake, which makes the location where vortices are generated move upstream, thickens the laminar section of the wake, and enlarges the generated vortices. The wake is swept away from the swept compression sidewall by the pressure gradient of the swept shock wave. This pressure gradient is not aligned with the density gradient of the supersonic wake, so the baroclinic torque generates streamwise vorticity and changes the distribution of the spanwise vorticity. The wake shock is curved, so the flow downstream of it is non-uniform, leaving the swept shock wave being distorted. A three-dimensional Mach disk structure is generated when the wake shock interacts with the swept shock wave.

  2. Computational Study of Flow Interactions in Coaxial Rotors

    NASA Technical Reports Server (NTRS)

    Yoon, Seokkwan; Lee, Henry C.; Pulliam, Thomas H.

    2016-01-01

    account for multiple real-world constraints up front in design nor possible to know what performance is possible with a given design. Since unmanned vehicles are sized and optimized for the particular mission, a modern low-fidelity conceptual design and sizing tool that has been used for the design of large helicopters can be used for design of small coaxial rotorcraft. However, unlike most helicopters with single main rotor, the interactions between the upper and lower rotors emerge as an important factor to consider in design because an increase in performance of a multi-rotor system is not proportional to the number of rotors. Interference losses and differences in thrusts between the upper and lower rotors were investigated by theoretical methods as well as a computational fluid dynamics (CFD) method using the Reynolds-Averaged Navier-Stokes (RANS) equations. In this work, hybrid turbulence models are used to investigate the physics of interactions between coaxial rotors and a fuselage that are not well understood. Present study covers not only small-scale drones but also large-scale coaxial rotors for heavy-lifting missions. Considering the recently proposed FAA drone rules that require the flight only in visual line-of-sight, a large multirotor might be used as an airborne carrier for launch and recovery of unmanned aircraft systems with a human operator onboard. For applications to civil operations, their aerodynamic performance and noise levels need to be assessed. Noise is one of the largest limiting factors to rotorcraft operations in urban area. Since the high-frequency noise of multi-rotors may increase the annoyance, noise may turn out to be a key issue that must be addressed for market acceptability. One of the objectives of the present work is to study the effects of inter-rotor spacing and collectives on the performance, efficiency, and acoustics of coaxial rotor systems.

  3. High performance forward swept wing aircraft

    NASA Technical Reports Server (NTRS)

    Koenig, David G. (Inventor); Aoyagi, Kiyoshi (Inventor); Dudley, Michael R. (Inventor); Schmidt, Susan B. (Inventor)

    1988-01-01

    A high performance aircraft capable of subsonic, transonic and supersonic speeds employs a forward swept wing planform and at least one first and second solution ejector located on the inboard section of the wing. A high degree of flow control on the inboard sections of the wing is achieved along with improved maneuverability and control of pitch, roll and yaw. Lift loss is delayed to higher angles of attack than in conventional aircraft. In one embodiment the ejectors may be advantageously positioned spanwise on the wing while the ductwork is kept to a minimum.

  4. Multiphoton Raman Atom Optics with Frequency-Swept Adiabatic Passage

    NASA Astrophysics Data System (ADS)

    Kotru, Krish; Butts, David; Kinast, Joseph; Stoner, Richard

    2016-05-01

    Light-pulse atom interferometry is a promising candidate for future inertial navigators, gravitational wave detectors, and measurements of fundamental physical constants. The sensitivity of this technique, however, is often limited by the small momentum separations created between interfering atom wave packets (typically ~ 2 ℏk) . We address this issue using light-pulse atom optics derived from stimulated Raman transitions and frequency-swept adiabatic rapid passage (ARP). In experiments, these Raman ARP atom optics have generated up to 30 ℏk photon recoil momenta in an acceleration-sensitive atom interferometer, thereby enhancing the phase shift per unit acceleration by a factor of 15. Since this approach forgoes evaporative cooling and velocity selection, it could enable large-area atom interferometry at higher data rates, while also lowering the atom shot-noise-limited measurement uncertainty.

  5. Optimal energy growth in swept Hiemenz flow

    NASA Astrophysics Data System (ADS)

    Guegan, Alan; Huerre, Patrick; Schmid, Peter

    2006-11-01

    It has been shown in Gu'egan, Schmid & Huerre 2006 that the kinetic energy of optimal G"ortler-H"ammerlin (GH) perturbations in swept Hiemenz flow can be transiently amplified by two orders of magnitude at Reynolds numbers ranging from 400 to 1000 and spanwise wavenumbers from 0.1 to 0.5. In this configuration an array of counter-rotating chordwise vortices is compressed by the spanwise shear, as in the well-known Orr mechanism. We show that stronger transient growth can be achieved when the GH assumption is relaxed. In this case the optimal initial perturbation consists in vorticity sheets stacked in the chordwise direction, at a small angle from the symmetry plane of the base flow. Although the spatial structure of the GH perturbations is lost, wall-normal-spanwise plane cuts show that the amplification mechanism is mostly unchanged. The GH assumption thus provides a reasonably good estimate for transient energy amplification levels in swept Hiemenz flow. Extension of this analysis to the spatial growth problem is under way and preliminary results will be shown.

  6. Flexible rotor dynamics analysis

    NASA Technical Reports Server (NTRS)

    Shen, F. A.

    1973-01-01

    A digital computer program was developed to analyze the general nonaxisymmetric and nonsynchronous transient and steady-state rotor dynamic performance of a bending- and shear-wise flexible rotor-bearing system under various operating conditions. The effects of rotor material mechanical hysteresis, rotor torsion flexibility, transverse effects of rotor axial and torsional loading and the anisotropic, in-phase and out-of-phase bearing stiffness and damping force and moment coefficients were included in the program to broaden its capability. An optimum solution method was found and incorporated in the computer program. Computer simulation of experimental data was made and qualitative agreements observed. The mathematical formulations, computer program verification, test data simulation, and user instruction was presented and discussed.

  7. Aeroelastic Tailoring with Composites Applied to Forward Swept Wings

    DTIC Science & Technology

    1981-11-01

    wings a viable configo.-tion option for high perfotmance aircraft. Forward swept wings have an inherent -.endency to encounter a static aeroelastic...configuration option for high performance aircraft. Forward swept wings have an inherent tendency to encounter a static aeroelastic instability ialled divergence...conventional and super- critical airfoils. ....... ..................... 19 12 Static methods for subcritical divergence dynamic pressure projection. (a

  8. Effect of AFT Rotor on the Inter-Rotor Flow of an Open Rotor Propulsion System

    NASA Technical Reports Server (NTRS)

    Slaboch, Paul E.; Stephens, David B.; Van Zante, Dale E.

    2016-01-01

    The effects of the aft rotor on the inter-rotor flow field of an open rotor propulsion rig were examined. A Particle Image Velocimetry (PIV) dataset that was acquired phase locked to the front rotor position has been phase averaged based on the relative phase angle between the forward and aft rotors. The aft rotor phase was determined by feature tracking in raw PIV images through an image processing algorithm. The effect of the aft rotor potential field on the inter-rotor flow were analyzed and shown to be in good agreement with Computational Fluid Dynamics (CFD) simulations. It was shown that the aft rotor had no substantial effect on the position of the forward rotor tip vortex but did have a small effect on the circulation strength of the vortex when the rotors were highly loaded.

  9. Blade-Pitch Control for Quieting Tilt-Rotor Aircraft

    NASA Technical Reports Server (NTRS)

    Betzina, Mark D.; Nguyen, Khanh Q.

    2004-01-01

    A method of reducing the noise generated by a tilt-rotor aircraft during descent involves active control of the blade pitch of the rotors. This method is related to prior such noise-reduction methods, of a type denoted generally as higher-harmonic control (HHC), in which the blade pitch is made to oscillate at a harmonic of the frequency of rotation of the rotor. A tilt-rotor aircraft is so named because mounted at its wing tips are motors that can be pivoted to enable the aircraft to take off and land like a helicopter or to fly like a propeller airplane. When the aircraft is operating in its helicopter mode, the rotors generate more thrust per unit rotor-disk area than helicopter rotors do, thus producing more blade-vortex interaction (BVI) noise. BVI is a major source of noise produced by helicopters and tilt-rotor aircraft during descent: When a rotor descends into its own wake, the interaction of each blade with the blade-tip vortices generated previously gives rise to large air-pressure fluctuations. These pressure fluctuations radiate as distinct, impulsive noise. In general, the pitch angle of the rotor blades of a tilt-rotor aircraft is controlled by use of a swash plate connected to the rotor blades by pitch links. In both prior HHC methods and the present method, HHC control signals are fed as input to swash-plate control actuators, causing the rotor-blade pitch to oscillate. The amplitude, frequency, and phase of the control signal can be chosen to minimize BVI noise.

  10. Tilt rotor hover aeroacoustics

    NASA Technical Reports Server (NTRS)

    Coffen, Charles David

    1992-01-01

    The methodology, results, and conclusions of a study of tilt rotor hover aeroacoustics and aerodynamics are presented. Flow visualization and hot wire velocity measurement were performed on a 1/12-scale model of the XV-15 Tilt Rotor Aircraft in hover. The wing and fuselage below the rotor cause a complex recirculating flow. Results indicate the physical dimensions and details of the flow including the relative unsteadiness and turbulence characteristics of the flow. Discrete frequency harmonic thickness and the loading noise mechanism were predicted using WOPWOP for the standard metal blades and the Advanced Technology Blades. The recirculating flow created by the wing below the rotor is a primary sound mechanism for a hovering tilt rotor. The effects of dynamic blade response should be included for fountain flow conditions which produce impulsive blade loading. Broadband noise mechanisms were studied using Amiet's method with azimuthally varying turbulence characteristics derived from the measurements. The recirculating fountain flow with high turbulence levels in the recirculating zone is the dominant source of broadband noise for a hovering rotor. It is shown that tilt rotor hover aeroacoustic noise mechanisms are now understood. Noise predictions can be made based on reasonably accurate aerodynamic models developed here.

  11. Open Rotor Aeroacoustic Modelling

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    2012-01-01

    Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.

  12. Open Rotor Aeroacoustic Modeling

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    2012-01-01

    Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.

  13. W-Band Frequency-Swept EPR

    PubMed Central

    Hyde, James S.; Strangeway, Robert A.; Camenisch, Theodore G.; Ratke, Joseph J.; Froncisz, Wojciech

    2010-01-01

    This paper describes a novel experiment on nitroxide radical spin labels using a multiarm EPR W-band bridge with a loop-gap resonator (LGR). We demonstrate EPR spectroscopy of spin labels by linear sweep of the microwave frequency across the spectrum. The high bandwidth of the LGR, about 1 GHz between 3 dB points of the microwave resonance, makes this new experiment possible. A frequency-tunable yttrium iron garnet (YIG) oscillator provides sweep rates as high as 1.8 × 105 GHz/s, which corresponds to 6.3 kT/s in magnetic field-sweep units over a 44 MHz range. Two experimental domains were identified. In the first, linear frequency sweep rates were relatively slow, and pure absorption and pure dispersion spectra were obtained. This appears to be a practical mode of operation at the present level of technological development. The main advantage is the elimination of sinusoidal magnetic field modulation. In the second mode, the frequency is swept rapidly across a portion of the spectrum, and then the frequency sweep is stopped for a readout period; FID signals from a swept line oscillate at a frequency that is the difference between the spectral position of the line in frequency units and the readout position. If there is more than one line, oscillations are superimposed. The sweep rates using the YIG oscillator were too slow, and the portion of the spectrum too narrow to achieve the full EPR equivalent of Fourier transform (FT) NMR. The paper discusses technical advances required to reach this goal. The hypothesis that trapezoidal frequency sweep is an enabling technology for FT EPR is supported by this study. PMID:20462775

  14. Reducing rotor weight

    SciTech Connect

    Cheney, M.C.

    1997-12-31

    The cost of energy for renewables has gained greater significance in recent years due to the drop in price in some competing energy sources, particularly natural gas. In pursuit of lower manufacturing costs for wind turbine systems, work was conducted to explore an innovative rotor designed to reduce weight and cost over conventional rotor systems. Trade-off studies were conducted to measure the influence of number of blades, stiffness, and manufacturing method on COE. The study showed that increasing number of blades at constant solidity significantly reduced rotor weight and that manufacturing the blades using pultrusion technology produced the lowest cost per pound. Under contracts with the National Renewable Energy Laboratory and the California Energy Commission, a 400 kW (33m diameter) turbine was designed employing this technology. The project included tests of an 80 kW (15.5m diameter) dynamically scaled rotor which demonstrated the viability of the design.

  15. Open Rotor Spin Test

    NASA Video Gallery

    An open rotor, also known as a high-speed propeller, is tested in a wind tunnel. The propeller moves much more quickly than a standard propeller, and the blades of the propeller are shaped differen...

  16. Downstream influence of swept slot injection in hypersonic turbulent flow

    NASA Technical Reports Server (NTRS)

    Hefner, J. N.; Cary, A. M., Jr.; Bushnell, D. B.

    1977-01-01

    Results of an experimental and numerical investigation of tangential swept slot injection into a thick turbulent boundary layer at Mach 6 are presented. Film cooling effectiveness, skin friction, and flow structure downstream of the swept slot injection were investigated. The data were compared with that for unswept slots, and it was found that cooling effectiveness and skin friction reductions are not significantly affected by sweeping the slot.

  17. Effects of planform geometry on hover performance of a 2-meter-diameter model of a four-bladed rotor

    NASA Technical Reports Server (NTRS)

    Phelps, A. E., III; Althoff, S. L.

    1986-01-01

    Hover tests were conducted on three small scale rotors to evaluate the effects of blade planform taper on rotor hover performance. Tests were conducted on a rectangular swept-tip configuration, on a configuration with a 3 to 1 taper over the outboard 20 percent of the span, and on a configuration with a 5 to 1 taper over the outboard 20 percent of the blade span. The investigation covered a range of thrust coefficients from 0 to 0.0075 and a range of tip speeds from 300 to 600 ft/sec. The tests showed that both tapered configurations had better hover performance than the swept-tip rectangular configuration and that the 3 to 1 taper configuration was better than the 5 to 1 taper configuration. The test results were compared with predictions made with a prescribed wake analysis, a momentum analysis, and a simplified free wake analysis.

  18. Impulse radar with swept range gate

    DOEpatents

    McEwan, Thomas E.

    1998-09-08

    A radar range finder and hidden object locator is based on ultra-wide band radar with a high resolution swept range gate. The device generates an equivalent time amplitude scan with a typical range of 4 inches to 20 feet, and an analog range resolution as limited by a jitter of on the order of 0.01 inches. A differential sampling receiver is employed to effectively eliminate ringing and other aberrations induced in the receiver by the near proximity of the transmit antenna (10), so a background subtraction is not needed, simplifying the circuitry while improving performance. Techniques are used to reduce clutter in the receive signal, such as decoupling the receive (24) and transmit cavities (22) by placing a space between them, using conductive or radiative damping elements on the cavities, and using terminating plates on the sides of the openings. The antennas can be arranged in a side-by-side parallel spaced apart configuration or in a coplanar opposed configuration which significantly reduces main bang coupling.

  19. Impulse radar with swept range gate

    DOEpatents

    McEwan, T.E.

    1998-09-08

    A radar range finder and hidden object locator is based on ultra-wide band radar with a high resolution swept range gate. The device generates an equivalent time amplitude scan with a typical range of 4 inches to 20 feet, and an analog range resolution as limited by a jitter of on the order of 0.01 inches. A differential sampling receiver is employed to effectively eliminate ringing and other aberrations induced in the receiver by the near proximity of the transmit antenna, so a background subtraction is not needed, simplifying the circuitry while improving performance. Techniques are used to reduce clutter in the receive signal, such as decoupling the receive and transmit cavities by placing a space between them, using conductive or radiative damping elements on the cavities, and using terminating plates on the sides of the openings. The antennas can be arranged in a side-by-side parallel spaced apart configuration or in a coplanar opposed configuration which significantly reduces main bang coupling. 25 figs.

  20. An investigation of rotor harmonic noise by the use of small scale wind tunnel models

    NASA Technical Reports Server (NTRS)

    Sternfeld, H., Jr.; Schaffer, E. G.

    1982-01-01

    Noise measurements of small scale helicopter rotor models were compared with noise measurements of full scale helicopters to determine what information about the full scale helicopters could be derived from noise measurements of small scale helicopter models. Comparisons were made of the discrete frequency (rotational) noise for 4 pairs of tests. Areas covered were tip speed effects, isolated rotor, tandem rotor, and main rotor/tail rotor interaction. Results show good comparison of noise trends with configuration and test condition changes, and good comparison of absolute noise measurements with the corrections used except for the isolated rotor case. Noise measurements of the isolated rotor show a great deal of scatter reflecting the fact that the rotor in hover is basically unstable.

  1. Rotor balancing apparatus and system

    NASA Technical Reports Server (NTRS)

    Lyman, Frank (Inventor); Lyman, Joseph (Inventor)

    1976-01-01

    Rotor balancing apparatus and a system comprising balance probes for measuring unbalance at the ends of a magnetically suspended rotor are disclosed. Each balance probe comprises a photocell which is located in relationship to the magnetically suspended rotor such that unbalance of the rotor changes the amount of light recorded by each photocell. The signal from each photocell is electrically amplified and displayed by a suitable device, such as an oscilloscope.

  2. Helicopter tail rotor noise analyses

    NASA Technical Reports Server (NTRS)

    George, A. R.; Chou, S. T.

    1986-01-01

    A study was made of helicopter tail rotor noise, particularly that due to interactions with the main rotor tip vortices, and with the fuselage separation mean wake. The tail rotor blade-main rotor tip vortex interaction is modelled as an airfoil of infinite span cutting through a moving vortex. The vortex and the geometry information required by the analyses are obtained through a free wake geometry analysis of the main rotor. The acoustic pressure-time histories for the tail rotor blade-vortex interactions are then calculated. These acoustic results are compared to tail rotor loading and thickness noise, and are found to be significant to the overall tail rotor noise generation. Under most helicopter operating conditions, large acoustic pressure fluctuations can be generated due to a series of skewed main rotor tip vortices passing through the tail rotor disk. The noise generation depends strongly upon the helicopter operating conditions and the location of the tail rotor relative to the main rotor.

  3. Wave rotor demonstrator engine assessment

    NASA Technical Reports Server (NTRS)

    Snyder, Philip H.

    1996-01-01

    The objective of the program was to determine a wave rotor demonstrator engine concept using the Allison 250 series engine. The results of the NASA LERC wave rotor effort were used as a basis for the wave rotor design. A wave rotor topped gas turbine engine was identified which incorporates five basic requirements of a successful demonstrator engine. Predicted performance maps of the wave rotor cycle were used along with maps of existing gas turbine hardware in a design point study. The effects of wave rotor topping on the engine cycle and the subsequent need to rematch compressor and turbine sections in the topped engine were addressed. Comparison of performance of the resulting engine is made on the basis of wave rotor topped engine versus an appropriate baseline engine using common shaft compressor hardware. The topped engine design clearly demonstrates an impressive improvement in shaft horsepower (+11.4%) and SFC (-22%). Off design part power engine performance for the wave rotor topped engine was similarly improved including that at engine idle conditions. Operation of the engine at off design was closely examined with wave rotor operation at less than design burner outlet temperatures and rotor speeds. Challenges identified in the development of a demonstrator engine are discussed. A preliminary design was made of the demonstrator engine including wave rotor to engine transition ducts. Program cost and schedule for a wave rotor demonstrator engine fabrication and test program were developed.

  4. Stimulus frequency otoacoustic emissions evoked by swept tones.

    PubMed

    Chen, Shixiong; Deng, Jun; Bian, Lin; Li, Guanglin

    2013-12-01

    Otoacoustic emissions (OAEs) are soft sounds generated by the cochlea and the measurements of OAEs are useful in detecting cochlear damages. Stimulus frequency otoacoustic emissions (SFOAEs) are evoked by one single tone and they are the most frequency specific in probing functional status of the cochlea than other types of OAEs. However, SFOAEs are currently restricted to research only because of the difficulty and low efficiency of their measurements. To solve these problems, an efficient method of using swept tones to measure SFOAEs was proposed in this study. The swept tones had time-varying frequencies and therefore could efficiently measure SFOAEs over a wide frequency range with a resolution dependent on the sweep rate. A three-interval paradigm and a tracking filter were used to separate the swept-tone SFOAEs from background noises. The reliability of the swept-tone SFOAEs was examined by a repeated-measure design, and the accuracy was evaluated by the comparison with a standard method using pure tones as the stimuli. The pilot results of this study showed that SFOAEs could be measured successfully using swept tones in human ears with normal hearing. The amplitude and phase of the swept-tone SFOAEs were highly reproducible in the repeated measures, and were nearly equivalent to SFOAEs evoked by pure tones under various signal conditions. These findings suggest that the proposed swept-tone SFOAEs could be a useful method in estimating the cochlear functions and developing an efficient approach of OAE measurements to help with accurate hearing diagnoses in the clinic.

  5. Influence of rubbing on rotor dynamics, part 1

    NASA Technical Reports Server (NTRS)

    Muszynska, Agnes; Bently, Donald E.; Franklin, Wesley D.; Hayashida, Robert D.; Kingsley, Lori M.; Curry, Arthur E.

    1989-01-01

    The results of analytical and experimental research on rotor-to-stationary element rubbing in rotating machines are presented. A characterization of physical phenomena associated with rubbing, as well as a literature survey on the subject of rub is given. The experimental results were obtained from two rubbing rotor rigs: one, which dynamically simulates the space shuttle main engine high pressure fuel turbopump (HPFTP), and the second one, much simpler, a two-mode rotor rig, designed for more generic studies on rotor-to-stator rubbing. Two areas were studied: generic rotor-to-stator rub-related dynamic phenomena affecting rotating machine behavior and applications to the space shuttle HPFTP. An outline of application of dynamic stiffness methodology for identification of rotor/bearing system modal parameters is given. The mathematical model of rotor/bearing/seal system under rub condition is given. The computer program was developed to calculate rotor responses. Compared with experimental results the computed results prove an adequacy of the model.

  6. CFD modeling and analysis of rotor wake in hover interacting with a ground plane

    NASA Astrophysics Data System (ADS)

    Kalra, Tarandeep Singh

    The action of the rotor wake on loose sediment on the ground is primarily responsible for inducing the rotorcraft brownout phenomenon. Therefore, any simulation of brownout must be capable of accurately predicting the velocity field induced by the rotor when it is operating in ground effect. This work attempts to use a compressible, structured, overset Reynolds-Averaged Navier-Stokes (RANS) based solver to simulate hovering rotors in ground effect (IGE) to demonstrate the capability of the code to provide accurate tip vortex flow field predictions, and provide a good understanding of the ground-wake interactions. The computations are performed for a micro-scale rotor (0.086m radius, aspect ratio of 4.387 operating at a tip Mach number of 0.08 and Reynolds number of 32,500) and a sub-scale rotor (0.408m radius, aspect ratio of 9.132 operating at a tip Mach number of 0.24 and Reynolds number of 250,000) in order to compare to experimental measurements. The micro-scale rotor has a rectangular tip shape and is simulated three rotor heights: 1.5R, 1.0R and 0.5R above ground (R = Rotor radius). The sub-scale rotor is simulated at one particular rotor height (i.e. 1R) but with four different tip shapes: rectangular, swept, BERP-like and slotted tip. Various mesh placement strategies are devised to efficiently capture the path of the tip vortices for both regimes. The micro-scale rotor simulations are performed using the Spalart Allmaras (S-A) turbulence model. The examination of the IGE tip vortex flow field suggests high degree of instabilities close to the ground. In addition, the induced velocities arising from the proximity of the rotor tip vortices causes flow separation at the ground. The sub-scale rotor simulations show a smeared out flow field even at early wake ages due to excessive turbulence levels. The distance function in the S-A turbulence model is modified using the Delayed Detached Eddy Simulation (DDES) approach and a correction to length scaling is

  7. Aerodynamic Classification of Swept-Wing Ice Accretion

    NASA Technical Reports Server (NTRS)

    Broeren, Andy; Diebold, Jeff; Bragg, Mike

    2013-01-01

    The continued design, certification and safe operation of swept-wing airplanes in icing conditions rely on the advancement of computational and experimental simulation methods for higher fidelity results over an increasing range of aircraft configurations and performance, and icing conditions. The current state-of-the-art in icing aerodynamics is mainly built upon a comprehensive understanding of two-dimensional geometries that does not currently exist for fundamentally three-dimensional geometries such as swept wings. The purpose of this report is to describe what is known of iced-swept-wing aerodynamics and to identify the type of research that is required to improve the current understanding. Following the method used in a previous review of iced-airfoil aerodynamics, this report proposes a classification of swept-wing ice accretion into four groups based upon unique flowfield attributes. These four groups are: ice roughness, horn ice, streamwise ice, and spanwise-ridge ice. For all of the proposed ice-shape classifications, relatively little is known about the three-dimensional flowfield and even less about the effect of Reynolds number and Mach number on these flowfields. The classifications and supporting data presented in this report can serve as a starting point as new research explores swept-wing aerodynamics with ice shapes. As further results are available, it is expected that these classifications will need to be updated and revised.

  8. Dual mode-locked swept sources for SS-OCT

    NASA Astrophysics Data System (ADS)

    Stancu, Radu F.; Podoleanu, Adrian G.

    2016-03-01

    A novel dual-mode-locking mechanism was developed in order to tune an akinetic swept source (AKSS) based on dispersive cavity at a repetition rate close to, but slightly different from the inverse of the cavity roundtrip. Several optical source configurations emitting in the 1060 nm or 1550 nm wavelength region were developed, characterized and tested in OCT applications. For the 1550 nm swept source employing a Faraday rotating mirror in a dispersive cavity, sweeping rates in the range of MHz were achieved, from 782 kHz to up to 5 times this value, with proportional decrease in the tuning bandwidth. Linewidths smaller than 60 pm and output powers exceeding a few mW were measured. The 1060 nm swept source implemented was used to generate OCT images of a pressure sensitive adhesive.

  9. Acoustic test of a model rotor and tail rotor: Results for the isolated rotors and combined configuration

    NASA Technical Reports Server (NTRS)

    Martin, R. M.; Burley, C. L.; Elliott, J. W.

    1989-01-01

    Acoustic data from a model scale main rotor and tail rotor experiment in the NASA Langley 14 by 22 Foot Subsonic Tunnel are presented for the main rotor and trail rotor in isolation and for the two rotors operating together. Results for the isolated main rotor show the importance of the rotor flapping conditions on mid-frequency noise content. High levels of main rotor retreating side blade-vortex interaction noise are shown to radiate downstream of the model. The isolated tail rotor noise results show the dominance of harmonic noise in the thrusting direction. The occurrence of tail rotor broadband noise is seen by the broadening of the tail rotor harmonics and is attributed to fuselage wake turbulence. The combined main and tail rotor data are presented to show the dominance of each rotor's different noise sources at different directivity locations.

  10. Swept-Wing Ice Accretion Characterization and Aerodynamics

    NASA Technical Reports Server (NTRS)

    Broeren, Andy P.; Potapczuk, Mark G.; Riley, James T.; Villedieu, Philippe; Moens, Frederic; Bragg, Michael B.

    2013-01-01

    NASA, FAA, ONERA, the University of Illinois and Boeing have embarked on a significant, collaborative research effort to address the technical challenges associated with icing on large-scale, three-dimensional swept wings. The overall goal is to improve the fidelity of experimental and computational simulation methods for swept-wing ice accretion formation and resulting aerodynamic effect. A seven-phase research effort has been designed that incorporates ice-accretion and aerodynamic experiments and computational simulations. As the baseline, full-scale, swept-wing-reference geometry, this research will utilize the 65 percent scale Common Research Model configuration. Ice-accretion testing will be conducted in the NASA Icing Research Tunnel for three hybrid swept-wing models representing the 20, 64 and 83 percent semispan stations of the baseline-reference wing. Threedimensional measurement techniques are being developed and validated to document the experimental ice-accretion geometries. Artificial ice shapes of varying geometric fidelity will be developed for aerodynamic testing over a large Reynolds number range in the ONERA F1 pressurized wind tunnel and in a smaller-scale atmospheric wind tunnel. Concurrent research will be conducted to explore and further develop the use of computational simulation tools for ice accretion and aerodynamics on swept wings. The combined results of this research effort will result in an improved understanding of the ice formation and aerodynamic effects on swept wings. The purpose of this paper is to describe this research effort in more detail and report on the current results and status to date.

  11. Swept-Wing Ice Accretion Characterization and Aerodynamics

    NASA Technical Reports Server (NTRS)

    Broeren, Andy P.; Potapczuk, Mark G.; Riley, James T.; Villedieu, Philippe; Moens, Frederic; Bragg, Michael B.

    2013-01-01

    NASA, FAA, ONERA, the University of Illinois and Boeing have embarked on a significant, collaborative research effort to address the technical challenges associated with icing on large-scale, three-dimensional swept wings. The overall goal is to improve the fidelity of experimental and computational simulation methods for swept-wing ice accretion formation and resulting aerodynamic effect. A seven-phase research effort has been designed that incorporates ice-accretion and aerodynamic experiments and computational simulations. As the baseline, full-scale, swept-wing-reference geometry, this research will utilize the 65% scale Common Research Model configuration. Ice-accretion testing will be conducted in the NASA Icing Research Tunnel for three hybrid swept-wing models representing the 20%, 64% and 83% semispan stations of the baseline-reference wing. Three-dimensional measurement techniques are being developed and validated to document the experimental ice-accretion geometries. Artificial ice shapes of varying geometric fidelity will be developed for aerodynamic testing over a large Reynolds number range in the ONERA F1 pressurized wind tunnel and in a smaller-scale atmospheric wind tunnel. Concurrent research will be conducted to explore and further develop the use of computational simulation tools for ice accretion and aerodynamics on swept wings. The combined results of this research effort will result in an improved understanding of the ice formation and aerodynamic effects on swept wings. The purpose of this paper is to describe this research effort in more detail and report on the current results and status to date. 1

  12. Aerodynamic Evaluation of Two Compact Radial-Inflow Turbine Rotors

    NASA Technical Reports Server (NTRS)

    Simonyi, P. Susan; Roelke, Richard J.; Stabe, Roy G.; Nowlin, Brentley C.; Dicicco, Danielle

    1995-01-01

    The aerodynamic evaluation of two highly loaded compact radial turbine rotors was conducted at the NASA Lewis Research Center Small Engine Component Test Facility (SECTF). The experimental results were used for proof-of-concept, for modeling radial inflow turbine rotors, and for providing data for code verification. Two rotors were designed to have a shorter axial length, up to a 10-percent reduced diameter, a lighter weight, and equal or higher efficiencies with those of conventional radial inflow turbine rotors. Three configurations were tested: rotor 1, having a 40-percent shorter axial length, with the design stator (stator 1); rotor 1 with the design stator vanes closed down (stator 2); and rotor 2, slightly shorter axially and having higher loading, with stator 2. The stator had 36 vanes and the rotors each had 14 solid blades. Although presently uncooled, the rotor blades were designed for thicknesses which would allow cooling passages to be added. The overall stage performance measurements and the rotor and stator exit flow field surveys were obtained. Measurements of steady state temperatures, pressures, mass flow rates, flow angles, and output power were made at various operating conditions. Data were obtained at corrected speeds of 80, 90, 100, 110, and 120 percent of design over a range of equivalent inlet-to-exit pressure ratios of 3.5, 4.0, 4.5, and 5.0, the maximum pressure ratio achieved. The test showed that the configuration of rotor 1 with stator 1 running at the design pressure ratio produced a flow rate which was 5.6 percent higher than expected. This result indicated the need to close down the stator flow area to reduce the flow. The flow area reduction was accomplished by restaggering the vanes. Rotor 1 was retested with the closed-down stator vanes and achieved the correct mass flow. Rotor 2 was tested only with the restaggered vanes. The test results of the three turbine configurations were nearly identical. Although the measured

  13. Current Experimental Basis for Modeling Ice Accretions on Swept Wings

    NASA Technical Reports Server (NTRS)

    Vargas, Mario

    2005-01-01

    This work presents a review of the experimental basis for modeling ice accretions on swept wings. Experimental work related to ice accretion physics on swept wings conducted between 1954 and 2004 is reviewed. Proposed models or explanations of scallop formations are singled out and discussed. Special emphasis is placed on reviewing the work done to determine the basic macroscopic mechanisms of scallop formation. The role of feather growth and its connection to scallop growth is discussed. Conceptual steps in modeling scallop formations are presented. Research elements needed for modeling are discussed.

  14. Fiber-based swept-source terahertz radar.

    PubMed

    Huang, Yu-Wei; Tseng, Tzu-Fang; Kuo, Chung-Chiu; Hwang, Yuh-Jing; Sun, Chi-Kuang

    2010-05-01

    We demonstrate an all-terahertz swept-source imaging radar operated at room temperature by using terahertz fibers for radiation delivery and with a terahertz-fiber directional coupler acting as a Michelson interferometer. By taking advantage of the high water reflection contrast in the low terahertz regime and by electrically sweeping at a high speed a terahertz source combined with a fast rotating mirror, we obtained the living object's distance information with a high image frame rate. Our experiment showed that this fiber-based swept-source terahertz radar could be used in real time to locate concealed moving live objects with high stability.

  15. Acoustic predictions using measured pressures from a model rotor in the DNW

    NASA Technical Reports Server (NTRS)

    Visintainer, Joseph A.; Burley, Casey L.; Marcolini, Michael A.; Liu, Sandy R.

    1991-01-01

    A contemporary design, 4-bladed United Technologies model rotor with pressure-instrumented blades was tested in the Duits-Nederslandse Windtunnel. Simultaneous acoustic and pressure measurements were made for a wide range of operating conditions. Microphones were optimally positioned at a number of locations in the flow forward of the rotor to measure rotor thickness noise, high-speed impulsive noise (both in the rotor plane), and blade-vortex interaction noise (forward and 25 deg below the rotor plane). The blade surface pressure data are used as aerodynamic input to WOPWOP, which is a state-of-the-art rotor noise prediction program that predicts rotor thickness and loading noise. The predicted results using WOPWOP are compared to the measured noise levels for cases where either thickness noise, blade-vortex interaction noise, or high-speed impulsive noise is the dominant noise mechanism. The comparisons show regions of good agreement, as well as areas where further improvement is necessary.

  16. Extension of Goldstein's circulation function for optimal rotors with hub

    NASA Astrophysics Data System (ADS)

    Okulov, V. L.; Sørensen, J. N.; Shen, W. Z.

    2016-09-01

    The aerodynamic interaction or interference between rotor blades and hub body is usually very complicated, but some useful simplifications can be made by considering the hub with an infinite cylinder. Various attempts to find the optimum distribution of circulation by the lifting vortex lines method have been previously proposed to describe the blade interaction with the hub modeled by the infinite cylinder. In this case, the ideal distribution of bound circulation on the rotor blades is such that the shed vortex system in the hub-area is a set of helicoidal vortex sheets moving uniformly as if rigid, exactly as in the case where there is no influence of the streamtube deformations by the central hub-body. In the present investigation, we consider a more specific problem of the rotor-hub interaction where the initial flow streamtubes and the rotor slipstream submitted strong deformations at the nose-area of the semi-infinite hub.

  17. Variable camber rotor study

    NASA Technical Reports Server (NTRS)

    Dadone, L.; Cowan, J.; Mchugh, F. J.

    1982-01-01

    Deployment of variable camber concepts on helicopter rotors was analytically assessed. It was determined that variable camber extended the operating range of helicopters provided that the correct compromise can be obtained between performance/loads gains and mechanical complexity. A number of variable camber concepts were reviewed on a two dimensional basis to determine the usefulness of leading edge, trailing edge and overall camber variation schemes. The most powerful method to vary camber was through the trailing edge flaps undergoing relatively small motions (-5 deg to +15 deg). The aerodynamic characteristics of the NASA/Ames A-1 airfoil with 35% and 50% plain trailing edge flaps were determined by means of current subcritical and transonic airfoil design methods and used by rotor performance and loads analysis codes. The most promising variable camber schedule reviewed was a configuration with a 35% plain flap deployment in an on/off mode near the tip of a blade. Preliminary results show approximately 11% reduction in power is possible at 192 knots and a rotor thrust coefficient of 0.09. The potential demonstrated indicates a significant potential for expanding the operating envelope of the helicopter. Further investigation into improving the power saving and defining the improvement in the operational envelope of the helicopter is recommended.

  18. Polygonal shaft hole rotor

    DOEpatents

    Hussey, John H.; Rose, John Scott; Meystrik, Jeffrey J.; White, Kent Lee

    2001-01-23

    A laminated rotor for an induction motor has a plurality of ferro-magnetic laminations mounted axially on a rotor shaft. Each of the plurality of laminations has a central aperture in the shape of a polygon with sides of equal length. The laminations are alternatingly rotated 180.degree. from one another so that the straight sides of the polygon shaped apertures are misaligned. As a circular rotor shaft is press fit into a stack of laminations, the point of maximum interference occurs at the midpoints of the sides of the polygon (i.e., at the smallest radius of the central apertures of the laminations). Because the laminates are alternatingly rotated, the laminate material at the points of maximum interference yields relatively easily into the vertices (i.e., the greatest radius of the central aperture) of the polygonal central aperture of the next lamination as the shaft is inserted into the stack of laminations. Because of this yielding process, the amount of force required to insert the shaft is reduced, and a tighter fit is achieved.

  19. Single rotor turbine engine

    DOEpatents

    Platts, David A.

    2002-01-01

    There has been invented a turbine engine with a single rotor which cools the engine, functions as a radial compressor, pushes air through the engine to the ignition point, and acts as an axial turbine for powering the compressor. The invention engine is designed to use a simple scheme of conventional passage shapes to provide both a radial and axial flow pattern through the single rotor, thereby allowing the radial intake air flow to cool the turbine blades and turbine exhaust gases in an axial flow to be used for energy transfer. In an alternative embodiment, an electric generator is incorporated in the engine to specifically adapt the invention for power generation. Magnets are embedded in the exhaust face of the single rotor proximate to a ring of stationary magnetic cores with windings to provide for the generation of electricity. In this alternative embodiment, the turbine is a radial inflow turbine rather than an axial turbine as used in the first embodiment. Radial inflow passages of conventional design are interleaved with radial compressor passages to allow the intake air to cool the turbine blades.

  20. Swept-source anatomic optical coherence elastography of porcine trachea

    NASA Astrophysics Data System (ADS)

    Bu, Ruofei; Price, Hillel; Mitran, Sorin; Zdanski, Carlton; Oldenburg, Amy L.

    2016-02-01

    Quantitative endoscopic imaging is at the vanguard of novel techniques in the assessment upper airway obstruction. Anatomic optical coherence tomography (aOCT) has the potential to provide the geometry of the airway lumen with high-resolution and in 4 dimensions. By coupling aOCT with measurements of pressure, optical coherence elastography (OCE) can be performed to characterize airway wall stiffness. This can aid in identifying regions of dynamic collapse as well as informing computational fluid dynamics modeling to aid in surgical decision-making. Toward this end, here we report on an anatomic optical coherence tomography (aOCT) system powered by a wavelength-swept laser source. The system employs a fiber-optic catheter with outer diameter of 0.82 mm deployed via the bore of a commercial, flexible bronchoscope. Helical scans are performed to measure the airway geometry and to quantify the cross-sectional-area (CSA) of the airway. We report on a preliminary validation of aOCT for elastography, in which aOCT-derived CSA was obtained as a function of pressure to estimate airway wall compliance. Experiments performed on a Latex rubber tube resulted in a compliance measurement of 0.68+/-0.02 mm2/cmH2O, with R2=0.98 over the pressure range from 10 to 40 cmH2O. Next, ex vivo porcine trachea was studied, resulting in a measured compliance from 1.06+/-0.12 to 3.34+/-0.44 mm2/cmH2O, (R2>0.81). The linearity of the data confirms the elastic nature of the airway. The compliance values are within the same order-of-magnitude as previous measurements of human upper airways, suggesting that this system is capable of assessing airway wall compliance in future human studies.

  1. Icing Analysis of a Swept NACA 0012 Wing Using LEWICE3D Version 3.48

    NASA Technical Reports Server (NTRS)

    Bidwell, Colin S.

    2014-01-01

    Icing calculations were performed for a NACA 0012 swept wing tip using LEWICE3D Version 3.48 coupled with the ANSYS CFX flow solver. The calculated ice shapes were compared to experimental data generated in the NASA Glenn Icing Research Tunnel (IRT). The IRT tests were designed to test the performance of the LEWICE3D ice void density model which was developed to improve the prediction of swept wing ice shapes. Icing tests were performed for a range of temperatures at two different droplet inertia parameters and two different sweep angles. The predicted mass agreed well with the experiment with an average difference of 12%. The LEWICE3D ice void density model under-predicted void density by an average of 30% for the large inertia parameter cases and by 63% for the small inertia parameter cases. This under-prediction in void density resulted in an over-prediction of ice area by an average of 115%. The LEWICE3D ice void density model produced a larger average area difference with experiment than the standard LEWICE density model, which doesn't account for the voids in the swept wing ice shape, (115% and 75% respectively) but it produced ice shapes which were deemed more appropriate because they were conservative (larger than experiment). Major contributors to the overly conservative ice shape predictions were deficiencies in the leading edge heat transfer and the sensitivity of the void ice density model to the particle inertia parameter. The scallop features present on the ice shapes were thought to generate interstitial flow and horse shoe vortices which enhance the leading edge heat transfer. A set of changes to improve the leading edge heat transfer and the void density model were tested. The changes improved the ice shape predictions considerably. More work needs to be done to evaluate the performance of these modifications for a wider range of geometries and icing conditions

  2. Icing Analysis of a Swept NACA 0012 Wing Using LEWICE3D Version 3.48

    NASA Technical Reports Server (NTRS)

    Bidwell, Colin S.

    2014-01-01

    Icing calculations were performed for a NACA 0012 swept wing tip using LEWICE3D Version 3.48 coupled with the ANSYS CFX flow solver. The calculated ice shapes were compared to experimental data generated in the NASA Glenn Icing Research Tunnel (IRT). The IRT tests were designed to test the performance of the LEWICE3D ice void density model which was developed to improve the prediction of swept wing ice shapes. Icing tests were performed for a range of temperatures at two different droplet inertia parameters and two different sweep angles. The predicted mass agreed well with the experiment with an average difference of 12%. The LEWICE3D ice void density model under-predicted void density by an average of 30% for the large inertia parameter cases and by 63% for the small inertia parameter cases. This under-prediction in void density resulted in an over-prediction of ice area by an average of 115%. The LEWICE3D ice void density model produced a larger average area difference with experiment than the standard LEWICE density model, which doesn't account for the voids in the swept wing ice shape, (115% and 75% respectively) but it produced ice shapes which were deemed more appropriate because they were conservative (larger than experiment). Major contributors to the overly conservative ice shape predictions were deficiencies in the leading edge heat transfer and the sensitivity of the void ice density model to the particle inertia parameter. The scallop features present on the ice shapes were thought to generate interstitial flow and horse shoe vortices which enhance the leading edge heat transfer. A set of changes to improve the leading edge heat transfer and the void density model were tested. The changes improved the ice shape predictions considerably. More work needs to be done to evaluate the performance of these modifications for a wider range of geometries and icing conditions.

  3. Flutter analysis of highly swept delta wings by conventional methods

    NASA Technical Reports Server (NTRS)

    Gibbons, M. D.; Soistmann, D. L.; Bennett, R. M.

    1988-01-01

    The flutter boundaries of six thin highly-swept delta-platform wings have been calculated. Comparisons are made between experimental data and results using several aerodynamic methods. The aerodynamic methods used include a subsonic and supersonic kernel function, second order piston theory, and a transonic small disturbance code. The dynamic equations of motion are solved using analytically calculated mode shapes and frequencies.

  4. Homopolar motor with dual rotors

    DOEpatents

    Hsu, J.S.

    1998-12-01

    A homopolar motor has a field rotor mounted on a frame for rotation in a first rotational direction and for producing an electromagnetic field, and an armature rotor mounted for rotation on said frame within said electromagnetic field and in a second rotational direction counter to said first rotational direction of said field rotor. The two rotors are coupled through a 1:1 gearing mechanism, so as to travel at the same speed but in opposite directions. This doubles the output voltage and output power, as compared to a motor in which only the armature is rotated. Several embodiments are disclosed. 7 figs.

  5. Homopolar motor with dual rotors

    DOEpatents

    Hsu, John S.

    1998-01-01

    A homopolar motor (10) has a field rotor (15) mounted on a frame (11) for rotation in a first rotational direction and for producing an electromagnetic field, and an armature rotor (17) mounted for rotation on said frame (11) within said electromagnetic field and in a second rotational direction counter to said first rotational direction of said field rotor (15). The two rotors (15, 17) are coupled through a 1:1 gearing mechanism (19), so as to travel at the same speed but in opposite directions. This doubles the output voltage and output power, as compared to a motor in which only the armature is rotated. Several embodiments are disclosed.

  6. 14 CFR 29.921 - Rotor brake.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.921 Rotor brake. If there is a means to control the rotation of the rotor drive system independently of the engine, any limitations...

  7. Development of flexible rotor balancing criteria

    NASA Technical Reports Server (NTRS)

    Walter, W. W.; Rieger, N. F.

    1979-01-01

    Several studies in which analytical procedures were used to obtain balancing criteria for flexible rotors are described. General response data for a uniform rotor in damped flexible supports were first obtained for plain cylindrical bearings, tilting pad bearings, axial groove bearings, and partial arc bearings. These data formed the basis for the flexible rotor balance criteria presented. A procedure by which a practical rotor in bearings could be reduced to an equivalent uniform rotor was developed and tested. It was found that the equivalent rotor response always exceeded to practical rotor response by more than sixty percent for the cases tested. The equivalent rotor procedure was then tested against six practical rotor configurations for which data was available. It was found that the equivalent rotor method offered a procedure by which balance criteria could be selected for practical flexible rotors, using the charts given for the uniform rotor.

  8. 14 CFR 27.921 - Rotor brake.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.921 Rotor brake. If there is a means to control the rotation of the rotor drive system independently of the engine, any limitations...

  9. Euler solutions to nonlinear acoustics of non-lifting hovering rotor blades

    NASA Technical Reports Server (NTRS)

    Baeder, J. D.

    1991-01-01

    For the first time a computational fluid dynamics (CFD) method is used to calculate directly the high-speed impulsive (HSI) noise of a non-lifting hovering rotor blade out to a distance of over three rotor radii. In order to accurately propagate the acoustic wave in a stable and efficient manner, an implicit upwind-biased Euler method is solved on a grid with points clustered along the line of propagation. A detailed validation of the code is performed for a rectangular rotor blade at tip Mach numbers ranging from 0.88 to 0.92. The agreement with experiment is excellent at both the sonic cylinder and at 2.18 rotor radii. The agreement at 3.09 rotor radii is still very good, showing improvements over the results from the best previous method. Grid sensitivity studies indicate that with special attention to the location of the boundaries a grid with approximately 60,000 points is adequate. This results in a computational time of approximately 40 minutes on a Cray-XMP. The practicality of the method to calculate HSI noise is demonstrated by expanding the scope of the investigation to examine the rectangular blade as well as a highly swept and tapered blade over a tip Mach number range of 0.80 to 0.95. Comparisons with experimental data are excellent and the advantages of planform modifications are clearly evident. New insight is gained into the mechanisms of nonlinear propagation and the minimum distance at which a valid comparison of different rotors can be made: approximately two rotor radii from the center of rotation.

  10. Aerodynamic Classification of Swept-Wing Ice Accretion

    NASA Technical Reports Server (NTRS)

    Diebold, Jeff M.; Broeren, Andy P.; Bragg, Michael B.

    2013-01-01

    The continued design, certification and safe operation of swept-wing airplanes in icing conditions rely on the advancement of computational and experimental simulation methods for higher fidelity results over an increasing range of aircraft configurations and performance, and icing conditions. The current stateof- the-art in icing aerodynamics is mainly built upon a comprehensive understanding of two-dimensional geometries that does not currently exist for fundamentally three-dimensional geometries such as swept wings. The purpose of this report is to describe what is known of iced-swept-wing aerodynamics and to identify the type of research that is required to improve the current understanding. Following the method used in a previous review of iced-airfoil aerodynamics, this report proposes a classification of swept-wing ice accretion into four groups based upon unique flowfield attributes. These four groups are: ice roughness, horn ice, streamwise ice and spanwise-ridge ice. In the case of horn ice it is shown that a further subclassification of "nominally 3D" or "highly 3D" horn ice may be necessary. For all of the proposed ice-shape classifications, relatively little is known about the three-dimensional flowfield and even less about the effect of Reynolds number and Mach number on these flowfields. The classifications and supporting data presented in this report can serve as a starting point as new research explores swept-wing aerodynamics with ice shapes. As further results are available, it is expected that these classifications will need to be updated and revised.

  11. Aerodynamic Classification of Swept-Wing Ice Accretion

    NASA Technical Reports Server (NTRS)

    Diebold, Jeff M.; Broeren, Andy P.; Bragg, Michael B.

    2013-01-01

    The continued design, certification and safe operation of swept-wing airplanes in icing conditions rely on the advancement of computational and experimental simulation methods for higher fidelity results over an increasing range of aircraft configurations and performance, and icing conditions. The current state-of-the-art in icing aerodynamics is mainly built upon a comprehensive understanding of two-dimensional geometries that does not currently exist for fundamentally three-dimensional geometries such as swept wings. The purpose of this report is to describe what is known of iced-swept-wing aerodynamics and to identify the type of research that is required to improve the current understanding. Following the method used in a previous review of iced-airfoil aerodynamics, this report proposes a classification of swept-wing ice accretion into four groups based upon unique flowfield attributes. These four groups are: ice roughness, horn ice, streamwise ice and spanwise-ridge ice. In the case of horn ice it is shown that a further subclassification of nominally 3D or highly 3D horn ice may be necessary. For all of the proposed ice-shape classifications, relatively little is known about the three-dimensional flowfield and even less about the effect of Reynolds number and Mach number on these flowfields. The classifications and supporting data presented in this report can serve as a starting point as new research explores swept-wing aerodynamics with ice shapes. As further results are available, it is expected that these classifications will need to be updated and revised.

  12. Integrated technology rotor/flight research rotor concept definition study

    NASA Technical Reports Server (NTRS)

    Carlson, R. G.; Beno, E. A.; Ulisnik, H. D.

    1983-01-01

    As part of the Integrated Technology Rotor/Flight Research Rotor (ITR/FRR) Program a number of advanced rotor system designs were conceived and investigated. From these, several were chosen that best meet the started ITR goals with emphasis on stability, reduced weight and hub drag, simplicity, low head moment stiffness, and adequate strength and fatigue life. It was concluded that obtaining low hub moment stiffness was difficult when only the blade flexibility of bearingless rotor blades is considered, unacceptably low fatigue life being the primary problem. Achieving a moderate hub moment stiffness somewhat higher than state of the art articulated rotors in production today is possible within the fatigue life constraint. Alternatively, low stiffness is possible when additional rotor elements, besides the blades themselves, provide part of the rotor flexibility. Two primary designs evolved as best meeting the general ITR requirements that presently exist. An I shaped flexbeam with an external torque tube can satisfy the general goals but would have either higher stiffness or reduced fatigue life. The elastic gimbal rotor can achieve a better combination of low stiffness and high fatigue life but would be a somewhat heavier design and possibly exhibit a higher risk of aeromechanical instability.

  13. Internal rotor friction instability

    NASA Technical Reports Server (NTRS)

    Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.

    1990-01-01

    The analytical developments and experimental investigations performed in assessing the effect of internal friction on rotor systems dynamic performance are documented. Analytical component models for axial splines, Curvic splines, and interference fit joints commonly found in modern high speed turbomachinery were developed. Rotor systems operating above a bending critical speed were shown to exhibit unstable subsynchronous vibrations at the first natural frequency. The effect of speed, bearing stiffness, joint stiffness, external damping, torque, and coefficient of friction, was evaluated. Testing included material coefficient of friction evaluations, component joint quantity and form of damping determinations, and rotordynamic stability assessments. Under conditions similar to those in the SSME turbopumps, material interfaces experienced a coefficient of friction of approx. 0.2 for lubricated and 0.8 for unlubricated conditions. The damping observed in the component joints displayed nearly linear behavior with increasing amplitude. Thus, the measured damping, as a function of amplitude, is not represented by either linear or Coulomb friction damper models. Rotordynamic testing of an axial spline joint under 5000 in.-lb of static torque, demonstrated the presence of an extremely severe instability when the rotor was operated above its first flexible natural frequency. The presence of this instability was predicted by nonlinear rotordynamic time-transient analysis using the nonlinear component model developed under this program. Corresponding rotordynamic testing of a shaft with an interference fit joint demonstrated the presence of subsynchronous vibrations at the first natural frequency. While subsynchronous vibrations were observed, they were bounded and significantly lower in amplitude than the synchronous vibrations.

  14. The large pursuit rotor.

    PubMed

    Williams, L R; Grbin, I R

    1976-09-01

    The question of whether certain phenomena that occur on the conventional rotary pursuit and other small apparatus also appear on a gross motor task was examined using a large pursuit rotor that required whole-body movements. College males (n=29) were given 90 10-sec trials over three consecutive days with 30 trials of continuous practice per day. The existence of reactive inhibition, reminiscence, and warmup decrement was confirmed, indicating that common mechanisms underlie both fine and gross bodily movements. In addition, the substantial amounts of learning and the high reliabilities for performance and learning indicated that the present apparatus has considerable potential for motor-learning research.

  15. Molecular Rotors as Switches

    PubMed Central

    Xue, Mei; Wang, Kang L.

    2012-01-01

    The use of a functional molecular unit acting as a state variable provides an attractive alternative for the next generations of nanoscale electronics. It may help overcome the limits of conventional MOSFETd due to their potential scalability, low-cost, low variability, and highly integratable characteristics as well as the capability to exploit bottom-up self-assembly processes. This bottom-up construction and the operation of nanoscale machines/devices, in which the molecular motion can be controlled to perform functions, have been studied for their functionalities. Being triggered by external stimuli such as light, electricity or chemical reagents, these devices have shown various functions including those of diodes, rectifiers, memories, resonant tunnel junctions and single settable molecular switches that can be electronically configured for logic gates. Molecule-specific electronic switching has also been reported for several of these device structures, including nanopores containing oligo(phenylene ethynylene) monolayers, and planar junctions incorporating rotaxane and catenane monolayers for the construction and operation of complex molecular machines. A specific electrically driven surface mounted molecular rotor is described in detail in this review. The rotor is comprised of a monolayer of redox-active ligated copper compounds sandwiched between a gold electrode and a highly-doped P+ Si. This electrically driven sandwich-type monolayer molecular rotor device showed an on/off ratio of approximately 104, a read window of about 2.5 V, and a retention time of greater than 104 s. The rotation speed of this type of molecular rotor has been reported to be in the picosecond timescale, which provides a potential of high switching speed applications. Current-voltage spectroscopy (I-V) revealed a temperature-dependent negative differential resistance (NDR) associated with the device. The analysis of the device I–V characteristics suggests the source of the

  16. New Approach to Ultrasonic Spectroscopy Applied to Flywheel Rotors

    NASA Technical Reports Server (NTRS)

    Harmon, Laura M.; Baaklini, George Y.

    2002-01-01

    Flywheel energy storage devices comprising multilayered composite rotor systems are being studied extensively for use in the International Space Station. A flywheel system includes the components necessary to store and discharge energy in a rotating mass. The rotor is the complete rotating assembly portion of the flywheel, which is composed primarily of a metallic hub and a composite rim. The rim may contain several concentric composite rings. This article summarizes current ultrasonic spectroscopy research of such composite rings and rims and a flat coupon, which was manufactured to mimic the manufacturing of the rings. Ultrasonic spectroscopy is a nondestructive evaluation (NDE) method for material characterization and defect detection. In the past, a wide bandwidth frequency spectrum created from a narrow ultrasonic signal was analyzed for amplitude and frequency changes. Tucker developed and patented a new approach to ultrasonic spectroscopy. The ultrasonic system employs a continuous swept-sine waveform and performs a fast Fourier transform on the frequency spectrum to create the spectrum resonance spacing domain, or fundamental resonant frequency. Ultrasonic responses from composite flywheel components were analyzed at Glenn to assess this NDE technique for the quality assurance of flywheel applications.

  17. Rotor Hover Performance and Flowfield Measurements with Untwisted and Highly-twisted Blades

    DTIC Science & Technology

    2010-09-01

    theory (also called annular disk momentum theory) helped fur- ther the understanding of rotor performance characteris- tics. Nomenclature A rotor disk area...observations when combined with simple blade element momentum theory (also called annular disk momentum theory) helped further the understanding of rotor...0.656 m, and (2) XV-15 like highly-twisted blade set that is made of 7 different airfoils , has a tip chord of 0.049 m, and has the same radius as that

  18. Dehumidification Performance of Humidity Control System with Double Ventilation Sorbent Rotor

    NASA Astrophysics Data System (ADS)

    Takaki, Sadao; Horibe, Akihiko; Haruki, Naoto; Nishina, Yuki; Inaba, Hideo

    The desiccant air-conditioning will be suitable for effective use of the exhaust heat. We have reported high dehumidification efficiency of the proposed system that is composed of a sorbent rotor and a refrigerating cycle. In this study, to improve the sorption efficiency of the rotor, the double ventilation rotor is proposed. After the processing air is dehumidified at the sorption area 1 of the rotor, the air is cooled and has higher relative humidity. And then, the air is blew into the sorption area 2 from the rotor opposite. The double ventilation characteristics on the influence of the division area of the rotor, the flow rate, the recovery temperature, and the temperature of the air cooler were investigated. As a result, the behavior of the double ventilation rotor is clarified and it is found that the quantity of dehumidification of the rotor is greater in the case of 1:1:2 (sorption(1): sorption(2): desorption ) division rate of the rotor than that of 1:1:1.

  19. Optimal design and performance analysis of an external circulation un-contact rotor pump

    NASA Astrophysics Data System (ADS)

    Su, H. S.; Yang, G. L.; Zhang, L. Q.; Fang, C. H.; Li, R. N.

    2013-12-01

    It's difficult to calculate the flow pulsation and efficiency of an un-contact rotor pump as there's a gap between the two rotors and internal leakage exists during the operation process. We analyze the primary cause that affects the volumetric efficiency of external circulation un-contact rotor pumps and discuss its gap leakage mechanisms. We establish the pump's 3d model, by using the calculation method and physical model provided from FLUENT software, and moving mesh grid and UDF technology are adopted in the unsteady flow field numerical simulation of the pump. Two rotors were set as rotating entities with fixed rotational speeds, while the boundary of the flow field calculation area changed as the rotors rotated, picking up each iterative step of the two rotors by the size of the moment and the outlet velocity through the function, and depositing them into the text file. The relationship between the two rotors' gap quantity, the rotor and the pump body's gap quantity, the transient flow characteristics and the pressure distribution of the pump's body were studied. The calculation results show that pump efficiency is the highest when the two rotors' minimum gap quantity is 0.17 millimetre, the rotor and the pump body's minimum axial gap quantity is 0.1 millimetre.

  20. Excitation of Crossflow Instabilities in a Swept Wing Boundary Layer

    NASA Technical Reports Server (NTRS)

    Carpenter, Mark H.; Choudhari, Meelan; Li, Fei; Streett, Craig L.; Chang, Chau-Lyan

    2010-01-01

    The problem of crossflow receptivity is considered in the context of a canonical 3D boundary layer (viz., the swept Hiemenz boundary layer) and a swept airfoil used recently in the SWIFT flight experiment performed at Texas A&M University. First, Hiemenz flow is used to analyze localized receptivity due to a spanwise periodic array of small amplitude roughness elements, with the goal of quantifying the effects of array size and location. Excitation of crossflow modes via nonlocalized but deterministic distribution of surface nonuniformity is also considered and contrasted with roughness induced acoustic excitation of Tollmien-Schlichting waves. Finally, roughness measurements on the SWIFT model are used to model the effects of random, spatially distributed roughness of sufficiently small amplitude with the eventual goal of enabling predictions of initial crossflow disturbance amplitudes as functions of surface roughness parameters.

  1. Swept-Wing Receptivity Studies Using Distributed Roughness

    NASA Technical Reports Server (NTRS)

    Saric, William S.

    1998-01-01

    This paper reviews the important recent progress in three-dimensional boundary-layer transition research. The review focuses on the crossflow instability that leads to transition on swept wings with a favorable pressure gradient. Following a brief overview of swept-wing instability mechanisms and the crossflow problem, a summary of the important findings of the 1990s is given. The discussion is presented from the experimental viewpoint, highlighting the ITAM work of Kachanov and co-workers, the DLR experiments of Bippes and co-workers, and the Arizona State University (ASU) investigations of Saric and co-workers. Where appropriate, relevant comparisons with CFD are drawn. The recent (last 18 months) research conducted by the ASU team is described in more detail in order to underscore the latest developments concerning nonlinear effects and transition control.

  2. Linear stability and control of swept Hiemenz flow

    NASA Astrophysics Data System (ADS)

    Guegan, Alan; Schmid, Peter; Huerre, Patrick

    2004-11-01

    Perturbations at the leading edge of swept wings may feed the downstream flow and trigger early boundary layer transition. Control strategies focusing on the leading edge boundary layer may provide significant improvement of flow stability over the wing surface. To this end, a gradient-based optimization algorithm is implemented to find the perturbations that experience the highest energy growth in swept Hiemenz flow over a finite time interval, under the Görtler-Hämmerlin assumption. A two-dimensional mechanism resembling the Orr-mechanism in the spanwise-wall-normal plane is shown to generate energy growth of up to three orders of magnitude for a Reynolds number Re=2000 and a spanwise wavenumber k=0.1. A similar algorithm is used to compute the wall-normal blowing/sucking sequence that most efficiently damps the energy amplification. The maximum energy is then found to decrease by more than 70%.

  3. Integrated technology rotor/flight research rotor hub concept definition

    NASA Technical Reports Server (NTRS)

    Dixon, P. G. C.

    1983-01-01

    Two variations of the helicopter bearingless main rotor hub concept are proposed as bases for further development in the preliminary design phase of the Integrated Technology Rotor/Flight Research Rotor (ITR/FRR) program. This selection was the result of an evaluation of three bearingless hub concepts and two articulated hub concepts with elastomeric bearings. The characteristics of each concept were evaluated by means of simplified methodology. These characteristics included the assessment of stability, vulnerability, weight, drag, cost, stiffness, fatigue life, maintainability, and reliability.

  4. Blade lock for a rotor disk and rotor blade assembly

    NASA Technical Reports Server (NTRS)

    Moore, Jerry H. (Inventor)

    1992-01-01

    A rotor disk 18 and rotor blade 26 assembly is disclosed having a blade lock 66 which retains the rotor blade against axial movement in an axially extending blade retention slot 58. Various construction details are developed which shield the dead rim region D.sub.d and shift at least a portion of the loads associated with the locking device from the dead rim. In one detailed embodiment, a projection 68 from the live rim D.sub.1 of the disk 18 is adapted by slots 86 to receive blade locks 66.

  5. Swept-source optical coherence tomography of lower limb wound healing with histopathological correlation

    NASA Astrophysics Data System (ADS)

    Barui, Ananya; Banerjee, Provas; Patra, Rusha; Das, Raunak Kumar; Dhara, Santanu; Dutta, Pranab K.; Chatterjee, Jyotirmoy

    2011-02-01

    Direct noninvasive visualization of wound bed with depth information is important to understand the tissue repair. We correlate skin swept-source-optical coherence tomography (OCT) with histopathological and immunohistochemical evaluation on traumatic lower limb wounds under honey dressing to compare and assess the tissue repair features acquired noninvasively and invasively. Analysis of optical biopsy identifies an uppermost brighter band for stratum corneum with region specific thickness (p < 0.0001) and gray-level intensity (p < 0.0001) variation. Below the stratum corneum, variation in optical intensities is remarkable in different regions of the wound bed. Correlation between OCT and microscopic observations are explored especially in respect to progressive growth and maturation of the epithelial and subepithelial components. Characteristic transition of uniform hypolucid band in OCT image for depigmented zone to wavy highly lucid band in the pigmented zone could be directly correlated with the microscopic findings. The transformation of prematured epithelium of depigmented area, with low expression of E-cadherin, to matured epithelium with higher E-cadherin expression in pigmented zone, implicated plausible change in their optical properties as depicted in OCT. This correlated evaluation of multimodal images demonstrates applicability of swept-source-OCT in wound research and importance of integrated approach in validation of new technology.

  6. Evaluation of Icing Scaling on Swept NACA 0012 Airfoil Models

    NASA Technical Reports Server (NTRS)

    Tsao, Jen-Ching; Lee, Sam

    2012-01-01

    Icing scaling tests in the NASA Glenn Icing Research Tunnel (IRT) were performed on swept wing models using existing recommended scaling methods that were originally developed for straight wing. Some needed modifications on the stagnation-point local collection efficiency (i.e., beta(sub 0) calculation and the corresponding convective heat transfer coefficient for swept NACA 0012 airfoil models have been studied and reported in 2009, and the correlations will be used in the current study. The reference tests used a 91.4-cm chord, 152.4-cm span, adjustable sweep airfoil model of NACA 0012 profile at velocities of 100 and 150 knot and MVD of 44 and 93 mm. Scale-to-reference model size ratio was 1:2.4. All tests were conducted at 0deg angle of attack (AoA) and 45deg sweep angle. Ice shape comparison results were presented for stagnation-point freezing fractions in the range of 0.4 to 1.0. Preliminary results showed that good scaling was achieved for the conditions test by using the modified scaling methods developed for swept wing icing.

  7. Absolute Instability in Swept Leading-Edge Boundary Layers

    NASA Astrophysics Data System (ADS)

    Lin, R.-S.; Li, F.; Malik, M. R.

    1997-11-01

    Absolute instabilities in the swept Hiemenz flow and flows over Poll's swept cylinder are studied. It is assumed that the span is infinite and the laminar flow field is subjected to a line impulsive excitation so that the spanwise wavenumber (β) is taken to be real, which is akin to the rotating disk study made by Lingwood.footnote Lingwood, R. J., J. Fluid Mech., 299, 17, 1995. We found that these flows can be absolutely unstable in the chordwise (x) direction. The pinch-point singularities formed by the coalescence of two distinct spatial branches can lie either below or above the real α-axis. The pinch points with a positive αi imply the existence of an unstable disturbance propagating against the mainstream, which has never been observed before. It is found that singularities of pinch type occur in a region very close to the leading edge, therefore the attachment-line Reynolds number is used to correlate the onset of absolute instability. The critical Reynolds number for absolute instability is found to be about R=540 compared to 583 for the attachment-line instability. Provided the non-linear behavior of this absolute instability is sufficient to trigger the laminar to turbulent transition, then it would cause a complete loss of laminar flow on a swept wing as does the attachment-line instability.

  8. NASA Open Rotor Noise Research

    NASA Technical Reports Server (NTRS)

    Envia, Ed

    2010-01-01

    Owing to their inherent fuel burn efficiency advantage compared with the current generation high bypass ratio turbofan engines, there is resurgent interest in developing open rotor propulsion systems for powering the next generation commercial aircraft. However, to make open rotor systems truly competitive, they must be made to be acoustically acceptable too. To address this challenge, NASA in collaboration with industry is exploring the design space for low-noise open rotor propulsion systems. The focus is on the system level assessment of the open rotors compared with other candidate concepts like the ultra high bypass ratio cycle engines. To that end there is an extensive research effort at NASA focused on component testing and diagnostics of the open rotor acoustic performance as well as assessment and improvement of open rotor noise prediction tools. In this presentation and overview of the current NASA research on open rotor noise will be provided. Two NASA projects, the Environmentally Responsible Aviation Project and the Subsonic Fixed Wing Project, have been funding this research effort.

  9. Boundary Layer Transition Detection on a Rotor Blade Using Rotating Mirror Thermography

    NASA Technical Reports Server (NTRS)

    Heineck, James T.; Schuelein, Erich; Raffel, Markus

    2014-01-01

    Laminar-to-turbulent transition on a rotor blade in hover has been imaged using an area-scan infrared camera. A new method for tracking a blade using a rotating mirror was employed. The mirror axis of rotation roughly corresponded to the rotor axis of rotation and the mirror rotational frequency is 1/2 that of the rotor. This permitted the use of cameras whose integration time was too long to prevent image blur due to the motion of the blade. This article will show the use of this method for a rotor blade at different collective pitch angles.

  10. Structural analysis of wind turbine rotors for NSF-NASA Mod-0 wind power system

    NASA Technical Reports Server (NTRS)

    Spera, D. A.

    1975-01-01

    Preliminary estimates of vibratory loads and stresses in hingeless and teetering rotors for the proposed 100-kW wind power system are presented. Stresses in the shank areas of the 19-m (62.5-ft) blades are given for static, rated, and overload conditions. The teetering rotor has substantial advantages over the hingeless rotor with respect to shank stresses, fatigue life, and tower loading. A teetering rotor will probably be required in order to achieve a long service life in a large wind turbine exposed to periodic overload conditions.

  11. Gas turbine rotor straightening -- Case history

    SciTech Connect

    Mazur, Z.; Kubiak, J.; Villela, A.; Orozco, J.

    1999-11-01

    Due to catastrophic damage, the turbine-compressor rotor of a gas turbine has been bent 0.62 mm. The in-situ repair process of rotor straightening is fully described. The repair process included the design of special fixtures for placing the rotor vertically and then hydraulically tensioning the rotor bolts for discs disassembling and run-out check by a special rotary equipment. After the repair process the rotor run-out fell within the design limits. Finally the rotor was put back into service. The approach to the in-house repair of the rotor bend has been successful and can be widely recommended for users of turbomachinery.

  12. Wind turbine rotor aileron

    DOEpatents

    Coleman, Clint; Kurth, William T.

    1994-06-14

    A wind turbine has a rotor with at least one blade which has an aileron which is adjusted by an actuator. A hinge has two portions, one for mounting a stationary hinge arm to the blade, the other for coupling to the aileron actuator. Several types of hinges can be used, along with different actuators. The aileron is designed so that it has a constant chord with a number of identical sub-assemblies. The leading edge of the aileron has at least one curved portion so that the aileron does not vent over a certain range of angles, but vents if the position is outside the range. A cyclic actuator can be mounted to the aileron to adjust the position periodically. Generally, the aileron will be adjusted over a range related to the rotational position of the blade. A method for operating the cyclic assembly is also described.

  13. Rotor component displacement measurement system

    DOEpatents

    Mercer, Gary D.; Li, Ming C.; Baum, Charles R.

    2003-05-27

    A measuring system for measuring axial displacement of a tube relative to an axially stationary component in a rotating rotor assembly includes at least one displacement sensor adapted to be located normal to a longitudinal axis of the tube; an insulated cable system adapted for passage through the rotor assembly; a rotatable proximitor module located axially beyond the rotor assembly to which the cables are connected; and a telemetry system operatively connected to the proximitor module for sampling signals from the proximitor module and forwarding data to a ground station.

  14. Test rig for investigations of force excited and synchrocoupling loaded rotor

    NASA Astrophysics Data System (ADS)

    Rauch, Adam

    1987-10-01

    The main topics of test rig based rotor investigations are: dynamic relations of a rotor bearing foundation system, shaft cracking, torsional simulation of rotor-generator hunting, flexural-torsional coupling of vibrations, and other areas of rotor dynamics including balancing, maintenance and modal analysis of a rotor. The present paper describes a general purpose rotor test rig capable of handling a great number of these areas. The test rig simulates a heavy, power-loaded rotor mounted on a flexible foundation. Five forms of excitation are provided: oscillating or impact torque, impact force, step force, bearing and foundation excitation. They can be combined if necessary. New research facilities offered by the rig are: external flexural force loading, driving torque loading by synchrocoupling with a full recovery of brake energy, bending release of rotor ends by pivoting, and multi-pulse impact force excitation. The most remarkable is the synchroaxle principle, called SAP for short, which is described in detail. Test rig features have been proved to be successful by research of shaft cracking and rotor-foundation vibrations. This presentation concerns only the general description, calculation and application aspects of the rig.

  15. Rotor assembly for a gas turbine engine

    SciTech Connect

    Antonellis, S. M.; Breunig, R. D.

    1985-07-02

    A rotor assembly for a gas turbine engine is disclosed. The rotor assembly includes a pair of axially spaced apart rotor disks such as the rotor disks. An inner air seal extends axially between the adjacent rotor disks. A member extends axially between the disks to join the disks together and is attached to the inner air seal at a mid span location to restrain the seal against outward movement.

  16. LAVA Applications to Open Rotors

    NASA Technical Reports Server (NTRS)

    Kiris, Cetin C.; Housman, Jeff; Barad, Mike; Brehm, Christoph

    2015-01-01

    Outline: LAVA (Launch Ascent Vehicle Aerodynamics); Introduction; Acoustics Related Applications; LAVA Applications to Open Rotor; Structured Overset Grids; Cartesian Grid with Immersed Boundary; High Speed Case; High Speed Case with Plate Low Speed Case.

  17. Feedback Control of Rotor Overspeed

    NASA Technical Reports Server (NTRS)

    Churchill, G. B.

    1984-01-01

    Feedback system for automatically governing helicopter rotor speed promises to lessen pilot's workload, enhance maneuverability, and protect airframe. With suitable modifications, concept applied to control speed of electrical generators, automotive engines and other machinery.

  18. Soft hub for bearingless rotors

    NASA Technical Reports Server (NTRS)

    Dixon, Peter G. C.

    1991-01-01

    Soft hub concepts which allow the direct replacement of articulated rotor systems by bearingless types without any change in controllability or need for reinforcement to the drive shaft and/or transmission/fuselage attachments of the helicopter were studied. Two concepts were analyzed and confirmed for functional and structural feasibility against a design criteria and specifications established for this effort. Both systems are gimballed about a thrust carrying universal elastomeric bearing. One concept includes a set of composite flexures for drive torque transmittal from the shaft to the rotor, and another set (which is changeable) to impart hub tilting stiffness to the rotor system as required to meet the helicopter application. The second concept uses a composite bellows flexure to drive the rotor and to augment the hub stiffness provided by the elastomeric bearing. Each concept was assessed for weight, drag, ROM cost, and number of parts and compared with the production BO-105 hub.

  19. Rehabilitation of creep-damaged high pressure turbine rotors

    SciTech Connect

    Puri, A.; Shuster, L.; Lam, T.

    1996-12-31

    The average age of TVA`s fossil fleet is approaching 40 years; a large segment of this population contains C grade turbine rotors manufactured in the 1950`s which have poor mechanical properties relative to forging of more recent vintage. The Westinghouse high temperature (HP) rotor fleet, consisting of sixteen (Frame 1606) 160 MW units and seven (Frame RT-2566) 250 MW units, are nearing the end of their creep life in the root attachment area of the control stage. TVA has evaluated the creep damage at the root attachment area of the control stages of these rotors and developed a cost effective strategy for rehabilitating the fleet without compromising unit reliability or efficiency. Economic evaluation of the various options did not favor the replacement of these rotors. This paper will focus on Root Cause Analysis (RCA) pertaining to the investigation of Side-Entry Curtis Stage blade root crack indications as well as the rehabilitation option(s) developed and execution of same for the Allen and Gallatin family of 250 MW HP Rotors.c

  20. Macroscopic balance model for wave rotors

    NASA Technical Reports Server (NTRS)

    Welch, Gerard E.

    1996-01-01

    A mathematical model for multi-port wave rotors is described. The wave processes that effect energy exchange within the rotor passage are modeled using one-dimensional gas dynamics. Macroscopic mass and energy balances relate volume-averaged thermodynamic properties in the rotor passage control volume to the mass, momentum, and energy fluxes at the ports. Loss models account for entropy production in boundary layers and in separating flows caused by blade-blockage, incidence, and gradual opening and closing of rotor passages. The mathematical model provides a basis for predicting design-point wave rotor performance, port timing, and machine size. Model predictions are evaluated through comparisons with CFD calculations and three-port wave rotor experimental data. A four-port wave rotor design example is provided to demonstrate model applicability. The modeling approach is amenable to wave rotor optimization studies and rapid assessment of the trade-offs associated with integrating wave rotors into gas turbine engine systems.

  1. Spatially Developing Secondary Instabilities in Compressible Swept Airfoil Boundary Layers

    NASA Technical Reports Server (NTRS)

    Li, Fei; Choudhari, Meelan M.

    2011-01-01

    Two-dimensional eigenvalue analysis is used on a massive scale to study spatial instabilities of compressible shear flows with two inhomogeneous directions. The main focus of the study is crossflow dominated swept-wing boundary layers although the methodology can also be applied to study other type of flows, such as the attachment-line flow. Certain unique aspects of formulating a spatial, two-dimensional eigenvalue problem for the secondary instability of finite amplitude crossflow vortices are discussed, namely, fixing the spatial growth direction unambiguously through a non-orthogonal formulation of the linearized disturbance equations. A primary test case used for parameter study corresponds to the low-speed, NLF-0415(b) airfoil configuration as tested in the ASU Unsteady Wind Tunnel, wherein a spanwise periodic array of roughness elements was placed near the leading edge in order to excite stationary crossflow modes with a specified fundamental wavelength. The two classes of flow conditions selected for this analysis include those for which the roughness array spacing corresponds to either the naturally dominant crossflow wavelength, or a subcritical wavelength that serves to reduce the growth of the naturally excited dominant crossflow modes. Numerical predictions are compared with the measured database, both as indirect validation for the spatial instability analysis and to provide a basis for comparison with a higher Reynolds number, supersonic swept-wing configuration. Application of the eigenvalue analysis to the supersonic configuration reveals that a broad spectrum of stationary crossflow modes can sustain sufficiently strong secondary instabilities as to potentially cause transition over this configuration. Implications of this finding for transition control in swept wing boundary layers are examined.

  2. Noninterference Systems Developed for Measuring and Monitoring Rotor Blade Vibrations

    NASA Technical Reports Server (NTRS)

    Kurkov, Anatole P.

    2003-01-01

    In the noninterference measurement of blade vibrations, a laser light beam is transmitted to the rotor blade tips through a single optical fiber, and the reflected light from the blade tips is collected by a receiving fiber-optic bundle and conducted to a photodetector. Transmitting and receiving fibers are integrated in an optical probe that is enclosed in a metal tube which also houses a miniature lens that focuses light on the blade tips. Vibratory blade amplitudes can be deduced from the measurement of the instantaneous time of arrival of the blades and the knowledge of the rotor speed. The in-house noninterference blade-vibration measurement system was developed in response to requirements to monitor blade vibrations in several tests where conventional strain gauges could not be installed or where there was a need to back up strain gauges should critical gauges fail during the test. These types of measurements are also performed in the aircraft engine industry using proprietary in-house technology. Two methods of measurement were developed for vibrations that are synchronous with a rotor shaft. One method requires only one sensor; however, it is necessary to continuously record the data while the rotor is being swept through the resonance. In the other method, typically four sensors are employed and the vibratory amplitude is deduced from the data by performing a least square fit to a harmonic function. This method does not require continuous recording of data through the resonance and, therefore, is better suited for monitoring. The single-probe method was tested in the Carl facility at the Wright- Patterson Air Force Base, and the multiple-probe method was tested in NASA Glenn Research Center's Spin Rig facility, which uses permanent magnets to excite synchronous vibrations. Representative results from this test are illustrated in the bar chart. Nonsynchronous vibrations were measured online during testing of the Quiet High Speed Fan in Glenn s 9- by 15-Foot

  3. Transition Flight Experiments on a Swept Wing with Suction

    NASA Technical Reports Server (NTRS)

    Maddalon, D. V.; Collier, F. S., Jr.; Montoya, L. C.; Putnam, R. J.

    1989-01-01

    Flight boundary-layer transition experiments were conducted on a 30 degree swept wing with a perforated leading-edge suction panel. The transition location on the panel was changed by systematically varying the location and amount of suction. Transition from laminar to turbulent flow was due to leading-edge turbulence contamination or crossflow disturbance growth and/or Tollmien-Schlichting disturbance growth, depending on flight condition and suction variation. Amplification factor correlations with transition location were made for various suction configurations using a state-of-the-art linear stability theory which accounts for body and streamline curvature and compressibility.

  4. Transition flight experiments on a swept wing with suction

    NASA Technical Reports Server (NTRS)

    Maddalon, D. V.; Collier, F. S., Jr.; Montoya, L. C.; Putnam, R. J.

    1989-01-01

    Flight boundary-layer transition experiments were conducted on a 30-degree swept wing with a perforated leading-edge suction panel. The transition location on the panel was changed by systematically varying the location and amount of suction. Transition from laminar to turbulent flow was due to leading-edge turbulence contamination or crossflow disturbance growth and/or Tollmien-Schlichting disturbance growth, depending on flight condition and suction variation. Amplification factor correlations with transition location were made for various suction configurations using a state-of-the-art linear stability theory which accounts for body and streamline curvature and compressibility.

  5. Transition Studies on a Swept-Wing Model

    NASA Technical Reports Server (NTRS)

    Saric, William S.

    1996-01-01

    The present investigation contributes to the understanding of boundary-layer stability and transition by providing detailed measurements of carefully-produced stationary crossflow vortices. It is clear that a successful prediction of transition in swept-wing flows must include an understanding of the detailed physics involved. Receptivity and nonlinear effects must not be ignored. Linear stability theory correctly predicts the expected wavelengths and mode shapes for stationary crossflow, but fails to predict the growth rates, even for low amplitudes. As new computational and analytical methods are developed to deal with three-dimensional boundary layers, the data provided by this experiment will serve as a useful benchmark for comparison.

  6. Fermions in Optical Lattices Swept across Feshbach Resonances

    SciTech Connect

    Diener, Roberto B.; Ho, T.-L.

    2006-01-13

    We point out that the recent experiments at ETH on fermions in optical lattices, where a band insulator evolves continuously into states occupying many bands as the system is swept adiabatically across Feshbach resonance, have implications on a wide range of fundamental issues in condensed matter. We derive the effective Hamiltonian of these systems, obtain expressions for their energies and band populations, and point out the increasing quantum entanglement of the ground state during the adiabatic sweep. Our results also explain why only specific regions in k space can be populated after the sweep as found at ETH.

  7. Swept frequency technique for dispersion measurement of microstrip lines

    NASA Technical Reports Server (NTRS)

    Lee, Richard Q.

    1987-01-01

    Microstrip lines used in microwave integrated circuits are dispersive. Because a microstrip line is an open structure, the dispersion can not be derived with pure TEM, TE, or TM mode analysis. Dispersion analysis has commonly been done using a spectral domain approach, and dispersion measurement has been made with high Q microstrip ring resonators. Since the dispersion of a microstrip line is fully characterized by the frequency dependent phase velocity of the line, dispersion measurement of microstrip lines requires the measurement of the line wavelength as a function of frequency. In this paper, a swept frequency technique for dispersion measurement is described.

  8. System for Controlling a Magnetically Levitated Rotor

    NASA Technical Reports Server (NTRS)

    Morrison, Carlos R. (Inventor)

    2006-01-01

    In a rotor assembly having a rotor supported for rotation by magnetic bearings, a processor controlled by software or firmware controls the generation of force vectors that position the rotor relative to its bearings in a "bounce" mode in which the rotor axis is displaced from the principal axis defined between the bearings and a "tilt" mode in which the rotor axis is tilted or inclined relative to the principal axis. Waveform driven perturbations are introduced to generate force vectors that excite the rotor in either the "bounce" or "tilt" modes.

  9. Research investigation of helicopter main rotor/tail rotor interaction noise

    NASA Technical Reports Server (NTRS)

    Fitzgerald, J.; Kohlhepp, F.

    1988-01-01

    Acoustic measurements were obtained in a Langley 14 x 22 foot Subsonic Wind Tunnel to study the aeroacoustic interaction of 1/5th scale main rotor, tail rotor, and fuselage models. An extensive aeroacoustic data base was acquired for main rotor, tail rotor, fuselage aerodynamic interaction for moderate forward speed flight conditions. The details of the rotor models, experimental design and procedure, aerodynamic and acoustic data acquisition and reduction are presented. The model was initially operated in trim for selected fuselage angle of attack, main rotor tip-path-plane angle, and main rotor thrust combinations. The effects of repositioning the tail rotor in the main rotor wake and the corresponding tail rotor countertorque requirements were determined. Each rotor was subsequently tested in isolation at the thrust and angle of attack combinations for trim. The acoustic data indicated that the noise was primarily dominated by the main rotor, especially for moderate speed main rotor blade-vortex interaction conditions. The tail rotor noise increased when the main rotor was removed indicating that tail rotor inflow was improved with the main rotor present.

  10. Turbomachinery rotor support with damping

    NASA Technical Reports Server (NTRS)

    Vonpragenau, George L. (Inventor)

    1990-01-01

    Damping seals, damping bearings, and a support sleeve are presented for the ball bearings of a high speed rotor. The ball bearings consist of a duplex set having the outer races packaged tightly within the sleeve while the sleeve provides a gap with a support member so that the bearings may float with the sleeve. The sleeve has a web extending radially between the pair of outer races and acts in conjunction with one or more springs to apply an axial preload to the outer races. The sleeves have a series of slits which provide the sleeve with a spring-like quality so that the spring acts to center the rotor upon which the bearings are mounted during start up and shut down. A damping seal or a damping bearing may be used in conjunction with the ball bearings and supporting sleeve, the damping seal and damping bearing having rotor portions including rigid outer surfaces mounted within the bore of a stator portion having triangular shaped pockets on the surface facing the rotor. Axial gates are provided between adjacent pockets in sections of the stator permitting fluid to flow with less resistance axially relative to the flow of fluids circumferentially between the rotor and the stator.

  11. Rotor assembly and assay method

    DOEpatents

    Burtis, Carl A.; Johnson, Wayne F.; Walker, William A.

    1993-01-01

    A rotor assembly for carrying out an assay includes a rotor body which is rotatable about an axis of rotation, and has a central chamber and first, second, third, fourth, fifth, and sixth chambers which are in communication with and radiate from the central chamber. The rotor assembly further includes a shuttle which is movable through the central chamber and insertable into any of the chambers, the shuttle including a reaction cup carrying an immobilized antigen or an antibody for transport among the chambers. A method for carrying out an assay using the rotor assembly includes moving the reaction cup among the six chambers by passing the cup through the central chamber between centrifugation steps in order to perform the steps of: separating plasma from blood cells, binding plasma antibody or antigen, washing, drying, binding enzyme conjugate, reacting with enzyme substrate and optically comparing the resulting reaction product with unreacted enzyme substrate solution. The movement of the reaction cup can be provided by attaching a magnet to the reaction cup and supplying a moving magnetic field to the rotor.

  12. Rotor assembly and assay method

    DOEpatents

    Burtis, C.A.; Johnson, W.F.; Walker, W.A.

    1993-09-07

    A rotor assembly for carrying out an assay includes a rotor body which is rotatable about an axis of rotation, and has a central chamber and first, second, third, fourth, fifth, and sixth chambers which are in communication with and radiate from the central chamber. The rotor assembly further includes a shuttle which is movable through the central chamber and insertable into any of the chambers, the shuttle including a reaction cup carrying an immobilized antigen or an antibody for transport among the chambers. A method for carrying out an assay using the rotor assembly includes moving the reaction cup among the six chambers by passing the cup through the central chamber between centrifugation steps in order to perform the steps of: separating plasma from blood cells, binding plasma antibody or antigen, washing, drying, binding enzyme conjugate, reacting with enzyme substrate and optically comparing the resulting reaction product with unreacted enzyme substrate solution. The movement of the reaction cup can be provided by attaching a magnet to the reaction cup and supplying a moving magnetic field to the rotor. 34 figures.

  13. Physical Mechanisms of Glaze Ice Scallop Formations on Swept Wings

    NASA Technical Reports Server (NTRS)

    Vargas, Mario; Reshotko, Eli

    1998-01-01

    An experiment was conducted to understand the physical mechanisms that lead to the formation of scallops on swept wings. Icing runs were performed on a NACA 0012 swept wing tip at 45 deg, 30 deg, and 15 deg sweep angles. A baseline case was chosen and direct measurements of scallop height and spacing, castings, video data and close-up photographic data were obtained. The results showed the scallops are made of glaze ice feathers that grow from roughness elements that have reached a minimum height and are located beyond a given distance from the attachment line. This distance depends on tunnel conditions and sweep angle, and is the critical parameter in the formation of scallops. It determines if complete scallops, incomplete scallops or no scallops are going to be formed. The mechanisms of growth for complete and incomplete scallops were identified. The effect of velocity, temperature and LWC on scallop formation was studied. The possibility that cross flow instability may be the physical mechanism that triggers the growth of roughness elements into glaze ice feathers is examined.

  14. Swept laser source based on acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Chen, Minghui; Li, Hao; Chen, Rong

    2014-12-01

    The design and development of the swept laser for optical coherence tomography is presented. It is manifested by a semiconductor optical amplifier, a fiber coupler, two fiber isolators, a semiconductor optical amplifier (SOA) and an acousto-optic tunable filter (AOTF) for frequency tuning within a unidirectional all-fiber ring cavity. Light output from the coupler is further amplified and spectral shaped by a booster SOA terminated at both ends with two isolators. The total loss in ring cavity is 8.2 dB. The gain SOA provides fiber-to-fiber small signal gain of 22.2 dB with saturation output power of 9.0 dBm. The developed laser source provides up to 100 kHz over a full-width wavelength tuning range of 140 nm at center wavelength of 1308 nm with an average power of 8 mW, yielding an axial resolution of 5.4 μm in air for OCT imaging. Theoretically, the measurement principle and the feasibility of the system are analyzed. Implementing the laser source in swept source based OCT (SS-OCT) system, real-time structural imaging of biological tissue is realized.

  15. Cooled variable nozzle radial turbine for rotor craft applications

    NASA Technical Reports Server (NTRS)

    Rogo, C.

    1981-01-01

    An advanced, small 2.27 kb/sec (5 lbs/sec), high temperature, variable area radial turbine was studied for a rotor craft application. Variable capacity cycles including single-shaft and free-turbine engine configurations were analyzed to define an optimum engine design configuration. Parametric optimizations were made on cooled and uncooled rotor configurations. A detailed structural and heat transfer analysis was conducted to provide a 4000-hour life HP turbine with material properties of the 1988 time frame. A pivoted vane and a moveable sidewall geometry were analyzed. Cooling and variable geometry penalties were included in the cycle analysis. A variable geometry free-turbine engine configuration with a design 1477K (2200 F) inlet temperature and a compressor pressure ratio of 16:1 was selected. An uncooled HP radial turbine rotor with a moveable sidewall nozzle showed the highest performance potential for a time weighted duty cycle.

  16. A general numerical model for wave rotor analysis

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel W.

    1992-01-01

    Wave rotors represent one of the promising technologies for achieving very high core temperatures and pressures in future gas turbine engines. Their operation depends upon unsteady gas dynamics and as such, their analysis is quite difficult. This report describes a numerical model which has been developed to perform such an analysis. Following a brief introduction, a summary of the wave rotor concept is given. The governing equations are then presented, along with a summary of the assumptions used to obtain them. Next, the numerical integration technique is described. This is an explicit finite volume technique based on the method of Roe. The discussion then focuses on the implementation of appropriate boundary conditions. Following this, some results are presented which first compare the numerical approximation to the governing differential equations and then compare the overall model to an actual wave rotor experiment. Finally, some concluding remarks are presented concerning the limitations of the simplifying assumptions and areas where the model may be improved.

  17. A general numerical model for wave rotor analysis

    NASA Astrophysics Data System (ADS)

    Paxson, Daniel W.

    1992-07-01

    Wave rotors represent one of the promising technologies for achieving very high core temperatures and pressures in future gas turbine engines. Their operation depends upon unsteady gas dynamics and as such, their analysis is quite difficult. This report describes a numerical model which has been developed to perform such an analysis. Following a brief introduction, a summary of the wave rotor concept is given. The governing equations are then presented, along with a summary of the assumptions used to obtain them. Next, the numerical integration technique is described. This is an explicit finite volume technique based on the method of Roe. The discussion then focuses on the implementation of appropriate boundary conditions. Following this, some results are presented which first compare the numerical approximation to the governing differential equations and then compare the overall model to an actual wave rotor experiment. Finally, some concluding remarks are presented concerning the limitations of the simplifying assumptions and areas where the model may be improved.

  18. Approximate relations and charts for low-speed stability derivatives of swept wings

    NASA Technical Reports Server (NTRS)

    Toll, Thomas A; Queijo, M J

    1948-01-01

    Contains derivations, based on a simplified theory, of approximate relations for low-speed stability derivatives of swept wings. Method accounts for the effects and, in most cases, taper ratio. Charts, based on the derived relations, are presented for the stability derivatives of untapered swept wings. Calculated values of the derivatives are compared with experimental results.

  19. Development of advanced stability theory suction prediction techniques for laminar flow control. [on swept wings

    NASA Technical Reports Server (NTRS)

    Srokowski, A. J.

    1978-01-01

    The problem of obtaining accurate estimates of suction requirements on swept laminar flow control wings was discussed. A fast accurate computer code developed to predict suction requirements by integrating disturbance amplification rates was described. Assumptions and approximations used in the present computer code are examined in light of flow conditions on the swept wing which may limit their validity.

  20. Rotor-to-stator Partial Rubbing and Its Effects on Rotor Dynamic Response

    NASA Technical Reports Server (NTRS)

    Muszynska, Agnes; Franklin, Wesley D.; Hayashida, Robert D.

    1991-01-01

    Results from experimental and analytical studies on rotor to stationary element partial rubbings at several locations and their effects on rotor dynamic responses are presented. The mathematical model of a rubbing rotor is given. The computer program provides numerical results which agree with experimentally obtained rotor responses.

  1. Rotor/Wing Interactions in Hover

    NASA Technical Reports Server (NTRS)

    Young, Larry A.; Derby, Michael R.

    2002-01-01

    Hover predictions of tiltrotor aircraft are hampered by the lack of accurate and computationally efficient models for rotor/wing interactional aerodynamics. This paper summarizes the development of an approximate, potential flow solution for the rotor-on-rotor and wing-on-rotor interactions. This analysis is based on actuator disk and vortex theory and the method of images. The analysis is applicable for out-of-ground-effect predictions. The analysis is particularly suited for aircraft preliminary design studies. Flow field predictions from this simple analytical model are validated against experimental data from previous studies. The paper concludes with an analytical assessment of the influence of rotor-on-rotor and wing-on-rotor interactions. This assessment examines the effect of rotor-to-wing offset distance, wing sweep, wing span, and flaperon incidence angle on tiltrotor inflow and performance.

  2. Open Rotor: New Option for Jet Engines

    NASA Video Gallery

    NASA's Dale Van Zante describes how the open rotor propulsion system will be tested in a wind tunnel at NASA's Glenn Research Center. Open rotor aircraft engines use high-speed propellers and are c...

  3. Rotor for centrifugal fast analyzers

    DOEpatents

    Lee, N.E.

    1984-01-01

    The invention is an improved photometric analyzer of the rotary cuvette type, the analyzer incorporating a multicuvette rotor of novel design. The rotor (a) is leaktight, (b) permits operation in the 90/sup 0/ and 180/sup 0/ excitation modes, (c) is compatible with extensively used Centrifugal Fast Analyzers, and (d) can be used thousands of times. The rotor includes an assembly comprising a top plate, a bottom plate, and a central plate, the rim of the central plate being formed with circumferentially spaced indentations. A uv-transmitting ring is sealably affixed to the indented rim to define with the indentations an array of cuvettes. The ring serves both as a sealing means and an end window for the cuvettes.

  4. Rotor for centrifugal fast analyzers

    DOEpatents

    Lee, Norman E.

    1985-01-01

    The invention is an improved photometric analyzer of the rotary cuvette type, the analyzer incorporating a multicuvette rotor of novel design. The rotor (a) is leaktight, (b) permits operation in the 90.degree. and 180.degree. excitation modes, (c) is compatible with extensively used Centrifugal Fast Analyzers, and (d) can be used thousands of times. The rotor includes an assembly comprising a top plate, a bottom plate, and a central plate, the rim of the central plate being formed with circumferentially spaced indentations. A UV-transmitting ring is sealably affixed to the indented rim to define with the indentations an array of cuvettes. The ring serves both as a sealing means and an end window for the cuvettes.

  5. Turbomachine rotor with improved cooling

    DOEpatents

    Hultgren, Kent Goran; McLaurin, Leroy Dixon; Bertsch, Oran Leroy; Lowe, Perry Eugene

    1998-01-01

    A gas turbine rotor has an essentially closed loop cooling air scheme in which cooling air drawn from the compressor discharge air that is supplied to the combustion chamber is further compressed, cooled, and then directed to the aft end of the turbine rotor. Downstream seal rings attached to the downstream face of each rotor disc direct the cooling air over the downstream disc face, thereby cooling it, and then to cooling air passages formed in the rotating blades. Upstream seal rings attached to the upstream face of each disc direct the heated cooling air away from the blade root while keeping the disc thermally isolated from the heated cooling air. From each upstream seal ring, the heated cooling air flows through passages in the upstream discs and is then combined and returned to the combustion chamber from which it was drawn.

  6. Turbomachine rotor with improved cooling

    DOEpatents

    Hultgren, K.G.; McLaurin, L.D.; Bertsch, O.L.; Lowe, P.E.

    1998-05-26

    A gas turbine rotor has an essentially closed loop cooling air scheme in which cooling air drawn from the compressor discharge air that is supplied to the combustion chamber is further compressed, cooled, and then directed to the aft end of the turbine rotor. Downstream seal rings attached to the downstream face of each rotor disc direct the cooling air over the downstream disc face, thereby cooling it, and then to cooling air passages formed in the rotating blades. Upstream seal rings attached to the upstream face of each disc direct the heated cooling air away from the blade root while keeping the disc thermally isolated from the heated cooling air. From each upstream seal ring, the heated cooling air flows through passages in the upstream discs and is then combined and returned to the combustion chamber from which it was drawn. 5 figs.

  7. Fan Noise Source Diagnostic Test: Rotor Alone Aerodynamic Performance Results

    NASA Technical Reports Server (NTRS)

    Hughes, Christopher E.; Jeracki, Robert J.; Woodward, Richard P.; Miller, Christopher J.

    2005-01-01

    The aerodynamic performance of an isolated fan or rotor alone model was measured in the NASA Glenn Research Center 9- by 15- Foot Low Speed Wind Tunnel as part of the Fan Broadband Source Diagnostic Test conducted at NASA Glenn. The Source Diagnostic Test was conducted to identify the noise sources within a wind tunnel scale model of a turbofan engine and quantify their contribution to the overall system noise level. The fan was part of a 1/5th scale model representation of the bypass stage of a current technology turbofan engine. For the rotor alone testing, the fan and nacelle, including the inlet, external cowl, and fixed area fan exit nozzle, were modeled in the test hardware; the internal outlet guide vanes located behind the fan were removed. Without the outlet guide vanes, the velocity at the nozzle exit changes significantly, thereby affecting the fan performance. As part of the investigation, variations in the fan nozzle area were tested in order to match as closely as possible the rotor alone performance with the fan performance obtained with the outlet guide vanes installed. The fan operating performance was determined using fixed pressure/temperature combination rakes and the corrected weight flow. The performance results indicate that a suitable nozzle exit was achieved to be able to closely match the rotor alone and fan/outlet guide vane configuration performance on the sea level operating line. A small shift in the slope of the sea level operating line was measured, which resulted in a slightly higher rotor alone fan pressure ratio at take-off conditions, matched fan performance at cutback conditions, and a slightly lower rotor alone fan pressure ratio at approach conditions. However, the small differences in fan performance at all fan conditions were considered too small to affect the fan acoustic performance.

  8. Wave Rotor Research and Technology Development

    NASA Technical Reports Server (NTRS)

    Welch, Gerard E.

    1998-01-01

    Wave rotor technology offers the potential to increase the performance of gas turbine engines significantly, within the constraints imposed by current material temperature limits. The wave rotor research at the NASA Lewis Research Center is a three-element effort: 1) Development of design and analysis tools to accurately predict the performance of wave rotor components; 2) Experiments to characterize component performance; 3) System integration studies to evaluate the effect of wave rotor topping on the gas turbine engine system.

  9. Rotor and bearing system for a turbomachine

    DOEpatents

    Lubell, Daniel; Weissert, Dennis

    2006-09-26

    A rotor and bearing system for a turbomachine. The turbomachine includes a drive shaft, an impeller positioned on the drive shaft, and a turbine positioned on the drive shaft proximate to the impeller. The bearing system comprises one gas journal bearing supporting the drive shaft between the impeller and the turbine. The area between the impeller and the turbine is an area of increased heat along the drive shaft in comparison to other locations along the drive shaft. The section of the drive shaft positioned between impeller and the turbine is also a section of the drive shaft that experiences increased stressed and load in the turbomachine. The inventive bearing machine system positions only one radial bearing in this area of increased stress and load.

  10. Rotor Design Options for Improving XV-15 Whirl-Flutter Stability Margins

    NASA Technical Reports Server (NTRS)

    Acree, C. W., Jr.; Peyran, R. J.; Johnson, Wayne

    2004-01-01

    Rotor design changes intended to improve tiltrotor whirl-flutter stability margins were analyzed. A baseline analytical model of the XV-15 was established, and then a thinner, composite wing was designed to be representative of a high-speed tiltrotor. The rotor blade design was modified to increase the stability speed margin for the thin-wing design. Small rearward offsets of the aerodynamic-center locus with respect to the blade elastic axis created large increases in the stability boundary. The effect was strongest for offsets at the outboard part of the blade, where an offset of the aerodynamic center by 10% of tip chord improved the stability margin by over 100 knots. Forward offsets of the blade center of gravity had similar but less pronounced effects. Equivalent results were seen for swept-tip blades. Appropriate combinations of sweep and pitch stiffness completely eliminated whirl flutter within the speed range examined; alternatively, they allowed large increases in pitch-flap coupling (delta-three) for a given stability margin. A limited investigation of the rotor loads in helicopter and airplane configuration showed only minor increases in loads.

  11. Routes to turbulence in the rotating disk boundary-layer of a rotor-stator cavity

    NASA Astrophysics Data System (ADS)

    Yim, Eunok; Serre, Eric; Martinand, Denis; Chomaz, Jean-Marc

    2016-11-01

    The rotating disk is an important classical problem, due to the similarities between the 3D boundary layers on a disk and a swept aircraft wing. It is nowadays admitted that a direct transition to turbulence may exist through a steep-fronted nonlinear global mode located at the boundary between the locally connectively and absolutely unstable regions (Pier 2003; Viaud et al. 2008, 2011; Imayama et al. 2014 and others). However, recent studies (Healey 2010; Harris et al. 2012; Imayama et al. 2013) suggest that there may be an alternative route starting at lower critical Reynolds number, based on convective travelling waves but this scenario is still not fully validated and proven. To better characterize such transition, direct numerical simulations are performed in a closed cylindrical rotor-stator cavity (without hub) up to Re = O (105) . All boundaries are no slip and for the stable region around the rotation axis prevents the disturbances coming from the very unstable stator boundary to disturb the rotor boundary layer. Different transition scenarii to turbulence are investigated when the rotor boundary layer is forced at different positions and forcing amplitude. The associated dynamics of coherent structures in various flow regions are also investigated when increasing Re .

  12. Quad-rotor flight path energy optimization

    NASA Astrophysics Data System (ADS)

    Kemper, Edward

    Quad-Rotor unmanned areal vehicles (UAVs) have been a popular area of research and development in the last decade, especially with the advent of affordable microcontrollers like the MSP 430 and the Raspberry Pi. Path-Energy Optimization is an area that is well developed for linear systems. In this thesis, this idea of path-energy optimization is extended to the nonlinear model of the Quad-rotor UAV. The classical optimization technique is adapted to the nonlinear model that is derived for the problem at hand, coming up with a set of partial differential equations and boundary value conditions to solve these equations. Then, different techniques to implement energy optimization algorithms are tested using simulations in Python. First, a purely nonlinear approach is used. This method is shown to be computationally intensive, with no practical solution available in a reasonable amount of time. Second, heuristic techniques to minimize the energy of the flight path are tested, using Ziegler-Nichols' proportional integral derivative (PID) controller tuning technique. Finally, a brute force look-up table based PID controller is used. Simulation results of the heuristic method show that both reliable control of the system and path-energy optimization are achieved in a reasonable amount of time.

  13. Hi-Q Rotor - Low Wind Speed Technology

    SciTech Connect

    Todd E. Mills; Judy Tatum

    2010-01-11

    The project objective was to optimize the performance of the Hi-Q Rotor. Early research funded by the California Energy Commission indicated the design might be advantageous over state-of-the-art turbines for collecting wind energy in low wind conditions. The Hi-Q Rotor is a new kind of rotor targeted for harvesting wind in Class 2, 3, and 4 sites, and has application in areas that are closer to cities, or 'load centers.' An advantage of the Hi-Q Rotor is that the rotor has non-conventional blade tips, producing less turbulence, and is quieter than standard wind turbine blades which is critical to the low-wind populated urban sites. Unlike state-of-the-art propeller type blades, the Hi-Q Rotor has six blades connected by end caps. In this phase of the research funded by DOE's Inventions and Innovation Program, the goal was to improve the current design by building a series of theoretical and numeric models, and composite prototypes to determine a best of class device. Development of the rotor was performed by aeronautical engineering and design firm, DARcorporation. From this investigation, an optimized design was determined and an 8-foot diameter, full-scale rotor was built and mounted using a Bergey LX-1 generator and furling system which were adapted to support the rotor. The Hi-Q Rotor was then tested side-by-side against the state-of-the-art Bergey XL-1 at the Alternative Energy Institute's Wind Test Center at West Texas State University for six weeks, and real time measurements of power generated were collected and compared. Early wind tunnel testing showed that the cut-in-speed of the Hi-Q rotor is much lower than a conventional tested HAWT enabling the Hi-Q Wind Turbine to begin collecting energy before a conventional HAWT has started spinning. Also, torque at low wind speeds for the Hi-Q Wind Turbine is higher than the tested conventional HAWT and enabled the wind turbine to generate power at lower wind speeds. Based on the data collected, the results of

  14. Filter type rotor for multistation photometer

    DOEpatents

    Shumate, II, Starling E.

    1977-07-12

    A filter type rotor for a multistation photometer is provided. The rotor design combines the principle of cross-flow filtration with centrifugal sedimentation so that these occur simultaneously as a first stage of processing for suspension type fluids in an analytical type instrument. The rotor is particularly useful in whole-blood analysis.

  15. Rotor Losses in a Switched Reluctance Motor - Analysis and Reduction Methods

    NASA Astrophysics Data System (ADS)

    Schweighofer, B.; Recheis, M.; Fulmek, P.; Wegleiter, H.

    2013-01-01

    Due to the increasing hybridization and electrification of vehicles, flywheel energy storage devices are an important area of research. In automotive application besides the weight criteria, some additionally constrains, such as size, efficiency and especially cost have to be fulfilled. Therefore typically a compact design, in which the rotor of the needed electrical machine simultaneously acts as storage mass is chosen. Since the machine is running in vacuum and the rotor can dissipate its heat only by means of thermal radiation or through the bearings if conventional bearings are used, the rotor losses play a vital role. In this work the rotor losses of a switched reluctance machine are analyzed in detail and a method to reduce the rotor losses is proposed.

  16. Assessment of Anterior Segment Measurements with Swept Source Optical Coherence Tomography before and after Ab Interno Trabeculotomy (Trabectome) Surgery

    PubMed Central

    Huang, Ping

    2016-01-01

    Purpose. To compare the changes of anterior segment parameters, assessed by swept source anterior segment optical coherence tomography (AS-OCT) after combined Trabectome-cataract surgery and Trabectome-only surgery in open angle glaucoma patients. Methods. Thirty-eight eyes of 24 patients with open angle glaucoma were scanned with swept source AS-OCT before and 4 weeks after combined Trabectome-cataract or Trabectome-only surgery. Intraocular pressure, number of medications, and AS-OCT parameters, such as angle opening distance at 500 and 750 μm from the scleral spur (AOD500 and AOD750), trabecular-iris space area at 500 and 750 mm2 (TISA500, TISA750), angle recess area at 500 and 750 mm2 (ARA500, ARA750), trabecular iris angle (TIA), anterior chamber depth (ACD), anterior chamber width (ACW), and anterior chamber volume (ACV), were obtained before the surgery. These parameters were compared to evaluate whether the outcome of the surgery differed among the patients after the surgery. The width of the trabecular cleft was also measured for both groups. Results. The reduction of IOP and number of medications was found to be statistically significant in both groups (p < 0.001). ACD, ACV, and angle parameters such as AOD 500/750, TISA 500/750, ARA 500/750, and TIA500 showed significantly greater changes from the preoperative values to postoperative 1st month values in combined Trabectome-cataract surgery group (p < 0.05), whereas Trabectome-only group did not show statistically significant difference (p > 0.05). There was no statistically significant difference between two groups for the width of the trabecular cleft (p = 0.7). Conclusion. Anterior chamber angle parameters measured with swept source AS-OCT may be useful for evaluating glaucoma patients before and after Trabectome surgery with or without cataract surgery. PMID:27795855

  17. Structural Considerations of a 20MW Multi-Rotor Wind Energy System

    NASA Astrophysics Data System (ADS)

    Jamieson, P.; Branney, M.

    2014-12-01

    The drive to upscale offshore wind turbines relates especially to possiblereductions in O&M and electrical interconnection costs per MW of installed capacity.Even with best current technologies, designs with rated capacity above about 3 MW are less cost effective exfactory per rated MW(turbine system costs) than smaller machines.Very large offshore wind turbines are thereforejustifiedprimarily by overall offshore project economics. Furthermore, continuing progress in materials and structures has been essential to avoid severe penalties in the power/mass ratio of large multi-MW machines.The multi-rotor concept employs many small rotors to maximise energy capture area withminimum systemvolume. Previous work has indicated that this can enablea very large reduction in the total weight and cost of rotors and drive trains compared to an equivalent large single rotor system.Thus the multi rotor concept may enable rated capacities of 20 MW or more at a single maintenancesite. Establishing the cost benefit of a multi rotor system requires examination of solutions for the support structure and yawing, ensuring aerodynamic losses from rotor interaction are not significant and that overall logistics, with much increased part count (more reliable components) and less consequence of single failuresare favourable. This paper addresses the viability of a support structure in respect of structural concept and likely weight as one necessary step in exploring the potential of the multi rotor concept.

  18. High-efficiency approach for fabricating MTE rotor by micro-EDM and micro-extrusion

    NASA Astrophysics Data System (ADS)

    Geng, Xuesong; Chi, Guanxin; Wang, Yukui; Wang, Zhenlong

    2014-07-01

    Micro-gas turbine engine (MTE) rotor is an important indicator of its property, therefore, the manufacturing technology of the microminiature rotor has become a hot area of research at home and abroad. At present, the main manufacturing technologies of the MTE rotor are directed forming fabrication technologies. However, these technologies have a series of problems, such as complex processing technology high manufacturing cost, and low processing efficiency, and so on. This paper takes advantage of micro electric discharge machining (micro-EDM) in the field of microminiature molds manufacturing, organizes many processing technologies of micro-EDM reasonably to improve processing accuracy, presents an integrated micro-EDM technology and its process flow to fabricate MTE rotor die, and conducts a series of experiments to verify efficiency of this integrated micro-EDM. The experiments results show that the MTE rotor die has sharp outline and ensure the good consistency of MTE rotor blades. Meanwhile, the MTE rotor die is applied to micro extrusion equipment, and technologies of micro-EDM and micro forming machining are combined based on the idea of the molds manufacturing, so the MTE rotor with higher aspect ratio and better consistency of blades can be manufactured efficiently. This research presents an integrated micro-EDM technology and its process flow, which promotes the practical process of MTE effectively.

  19. Ultrasonic Resonance Spectroscopy of Composite Rims for Flywheel Rotors

    NASA Technical Reports Server (NTRS)

    Harmon, Laura M.; Baaklini, George Y.

    2002-01-01

    Flywheel energy storage devices comprising multilayered composite rotor systems are being studied extensively for utilization in the International Space Station. These composite material systems were investigated with a recently developed ultrasonic resonance spectroscopy technique. The ultrasonic system employs a continuous swept-sine waveform and performs a fast Fourier transform (FFT) on the frequency response spectrum. In addition, the system is capable of equalizing the amount of energy at each frequency. Equalization of the frequency spectrum, along with interpretation of the second FFT, aids in the evaluation of the fundamental frequency. The frequency responses from multilayered material samples, with and without known defects, were analyzed to assess the capabilities and limitations of this nondestructive evaluation technique for material characterization and defect detection. Amplitude and frequency changes were studied from ultrasonic responses of thick composite rings and a multiring composite rim. A composite ring varying in thickness was evaluated to investigate the full thickness resonance. The frequency response characteristics from naturally occurring voids in a composite ring were investigated. Ultrasonic responses were compared from regions with and without machined voids in a composite ring and a multiring composite rim. Finally, ultrasonic responses from the multiring composite rim were compared before and after proof spin testing to 63,000 rpm.

  20. Previous Open Rotor Research in the US

    NASA Technical Reports Server (NTRS)

    VanZante, Dale

    2011-01-01

    Previous Open Rotor noise experience in the United States, current Open Rotor noise research in the United States and current NASA prediction methods activities were presented at a European Union (EU) X-Noise seminar. The invited attendees from EU industries, research establishments and universities discussed prospects for reducing Open Rotor noise and reviewed all technology programs, past and present, dedicated to Open Rotor engine concepts. This workshop was particularly timely because the Committee on Aviation Environmental Protection (CAEP) plans to involve Independent Experts in late 2011 in assessing the noise of future low-carbon technologies including the open rotor.

  1. Advanced Rotor Blade Materials Evaluation

    DTIC Science & Technology

    2014-07-23

    helicopter rotor blade erosion resistant treatments that had been supplied in response to a US Navy BAA Program. The Navy Program was meant to improve the...earlier ONR BAA Program had been concluded and while this specific program was active. This program was one of the drivers behind the need to

  2. Numerical calculation of the transonic flow past a swept wing

    NASA Technical Reports Server (NTRS)

    Jameson, A.; Caughey, D. A.

    1977-01-01

    A numerical method is presented for analyzing the transonic potential flow past a lifting, swept wing. A finite difference approximation to the full potential equation is solved in a coordinate system which is nearly conformally mapped from the physical space in planes parallel to the symmetry plane, and reduces the wing surface to a portion of one boundary of the computational grid. A coordinate invariant, rotated difference scheme is used, and the difference equations are solved by relaxation. The method is capable of treating wings of arbitrary planform and dihedral, although approximations in treating the tips and vortex sheet make its accuracy suspect for wings of small aspect ratio. Comparisons of calculated results with experimental data are shown for examples of both conventional and supercritical transport wings. Agreement is good for both types, but it was found necessary to account for the displacement effect of the boundary layer for the supercritical wing, presumably because of its greater sensitivity to changes in effective geometry.

  3. Unified Formulation of the Aeroelasticity of Swept Lifting Surfaces

    NASA Technical Reports Server (NTRS)

    Silva, Walter; Marzocca, Piergiovanni; Librescu, Liviu

    2001-01-01

    An unified approach for dealing with stability and aeroelastic response to time-dependent pressure pulses of swept wings in an incompressible flow is developed. To this end the indicial function concept in time and frequency domains, enabling one to derive the proper unsteady aerodynamic loads is used. Results regarding stability in the frequency and time domains, and subcritical aeroelastic response to arbitrary time-dependent external excitation obtained via the direct use of the unsteady aerodynamic derivatives for 3-D wings are supplied. Closed form expressions for unsteady aerodynamic derivatives using this unified approach have been derived and used to illustrate their application to flutter and aeroelastic response to blast and sonic-boom signatures. In this context, an original representation of the aeroelastic response in the phase space was presented and pertinent conclusions on the implications of some basic parameters have been outlined.

  4. Crossflow Stability and Transition Experiments in Swept-Wing Flow

    NASA Technical Reports Server (NTRS)

    Dagenhart, J. Ray; Saric, William S.

    1999-01-01

    An experimental examination of crossflow instability and transition on a 45deg swept wing was conducted in the Arizona State University Unsteady Wind Tunnel. The stationary-vortex pattern and transition location are visualized by using both sublimating chemical and liquid-crystal coatings. Extensive hot-wire measurements were obtained at several measurement stations across a single vortex track. The mean and travelling wave disturbances were measured simultaneously. Stationary crossflow disturbance profiles were determined by subtracting either a reference or a span-averaged velocity profile from the mean velocity data. Mean, stationary crossflow, and traveling wave velocity data were presented as local boundary layer profiles and contour plots across a single stationary crossflow vortex track. Disturbance mode profiles and growth rates were determined. The experimental data are compared with predictions from linear stability theory.

  5. Transition Flight Experiments on a Swept Wing With Suction

    NASA Technical Reports Server (NTRS)

    Maddalon, D. V.; Collier, F. S., Jr.; Montoya, L. C.; Land, C. K.

    1989-01-01

    Flight experiments were conducted on a 30 degree swept wing with a perforated leading edge by systematically varying the location and amount of suction over a range of Mach number and Reynolds number. Suction was varied chordwise ahead of the front spar from either the front or rear direction by sealing spanwise perforated strips. Transition from laminar to turbulent flow was due to leading edge turbulence contamination or crossflow disturbance growth and/or Tollmien-Schlichting disturbance growth-depending on the test configuration, flight condition, and suction location. A state-of-the-art linear stability theory which accounts for body and streamline curvature and compressibility was used to study the boundary layer stability as suction location and magnitude varied. N-factor correlations with transition location were made for various suction configurations.

  6. Transition flight experiments on a swept wing with suction

    NASA Technical Reports Server (NTRS)

    Maddalon, D. V.; Land, C. K.; Collier, F. S.; Montoya, L. C.

    1989-01-01

    Flight experiments were conducted on a 30 degree swept wing with a perforated leading edge by systematically varying the location and amount of suction over a range of Mach number and Reynolds number. Suction was varied chordwise ahead of the front spar from either the front or rear direction by sealing spanwise perforated strips. Transition from laminar to turbulent flow was due to leading edge turbulence contamination or crossflow disturbance growth and/or Tollmien-Schlichting disturbance growth, depending on the test configuration, flight condition, and suction location. A state-of-the-art linear stability theory which accounts for body and streamline curvature and compressibility was used to study the boundary layer stability as suction location and magnitude varied. N-factor correlations with transition location were made for various suction configurations.

  7. An Analysis of Wave Interactions in Swept-Wing Flows

    NASA Technical Reports Server (NTRS)

    Reed, H. L.

    1984-01-01

    Crossflow instabilities dominate disturbance growth in the leading-edge region of swept wings. Streamwise vortices in a boundary layer strongly influence the behavior of other disturbances. Amplification of crossflow vortices near the leading edge produces a residual spanwise nonuniformity in the mid-chord regions where Tollmien-Schlichting (T-S) waves are strongly amplified. Should the T-S wave undergo double-exponential growth because of this effect, the usual transition prediction methods would fail. The crossflow/Tollmien-Schlichting wave interaction was modeled as a secondary instability. The effects of suction are included, and different stability criteria are examined. The results are applied to laminar flow control wings characteristic of energy-efficient aircraft designs.

  8. Evolution Of Traveling Crossflow Modes Over A Swept Flat Plate

    NASA Astrophysics Data System (ADS)

    Kurian, Thomas; Fransson, Jens H. M.; Alfredsson, P. Henrik

    An experimental investigation has been carried out to examine the growth of traveling crossflow instabilities over a swept flat plate mimicking the Falkner Skan-Cooke boundary layer. Different turbulence generating grids were placed upstream of the leading edge to vary incoming parameters. Hot-wire measurements were taken for one component of velocity and compared with linear PSE analysis. These showed a decrease in the growth rate for increasing turbulence intensity, which was most likely cause by nonlinear effects. Streamwise correlation measurements were also taken. All the cases except one triggered the same spanwise integral length scale inside the boundary layer. Receptivity coefficients are needed to do the PSE calculations and to see the need for nonlinear PSE.

  9. Ice Accretions on a Swept GLC-305 Airfoil

    NASA Technical Reports Server (NTRS)

    Vargas, Mario; Papadakis, Michael; Potapczuk, Mark; Addy, Harold; Sheldon, David; Giriunas, Julius

    2002-01-01

    An experiment was conducted in the Icing Research Tunnel (IRT) at NASA Glenn Research Center to obtain castings of ice accretions formed on a 28 deg. swept GLC-305 airfoil that is representative of a modern business aircraft wing. Because of the complexity of the casting process, the airfoil was designed with three removable leading edges covering the whole span. Ice accretions were obtained at six icing conditions. After the ice was accreted, the leading edges were detached from the airfoil and moved to a cold room. Molds of the ice accretions were obtained, and from them, urethane castings were fabricated. This experiment is the icing test of a two-part experiment to study the aerodynamic effects of ice accretions.

  10. Development of fast FBG interrogator with wavelength-swept laser

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tatsuya; Shinoda, Yukitaka

    2015-05-01

    The objective of this research is the construction of a structural health monitoring system that uses fiber Bragg grating (FBG) to determine the health of structures. We develop fast FBG interrogator for real-time measurement of the reflected wavelength of a multipoint FBG to monitor the broadband vibration of a structure. This FBG interrogator, which combines a wavelength-swept laser and a real-time measurement system is capable of measuring wavelength within a standard deviation of 2×10-3 nm or less. We have demonstrated that the FBG interrogator is able to measure vibration that has a resonance frequency of 440 Hz at intervals of 0.1 ms with a multipoint FBG.

  11. Measuremants in the wake of an infinite swept airfoil

    NASA Technical Reports Server (NTRS)

    Novak, C. J.; Ramaprian, B. R.

    1982-01-01

    This is a report of the measurements in the trailing edge region as well as in the report of the developing wake behind a swept NACA 0012 airfoil at zero incidence and a sweep angle of 30 degrees. The measurements include both the mean and turbulent flow properties. The mean flow velocities, flow inclination and static pressure are measured using a calibrated three-hole yaw probe. The measurements of all the relevant Reynolds stress components in the wake are made using a tri-axial hot-wire probe and a digital data processing technique developed by the authors. The development of the three dimensional near-wake into a nearly two dimensional far-wake is discussed in the light of the experimental data. A complete set of wake data along with the data on the initial boundary layer in the trailing edge region of the airfoil are tabulated in an appendix to the report.

  12. Automatic scaling of HF swept-frequency backscatter ionograms

    NASA Astrophysics Data System (ADS)

    Song, Huan; Hu, Yaogai; Jiang, Chunhua; Zhou, Chen; Zhao, Zhengyu

    2015-05-01

    This paper describes a method for automatically scaling HF swept-frequency backscatter ionograms, which can be applied to a low-power oblique backscatter sounding system. Based on the information of vertical echo in the ionogram, propagation mode is recognized from the amplitude differences between E layer and F layer echoes. Points on the leading edge are extracted by using minimum group path delay theory. The spurious points are removed by using residual analysis. A multiple linear polynomial was adopted to fit the extracted leading edge points. Smooth fitting curves can then be obtained. Automatic scaling results from 362 ionograms show that the proposed method can efficiently recognize propagation modes and extract leading edge curves by taking full advantages of echo characteristics and echo amplitudes in the ionograms. This novel method can be applied into real-time backscatter ionogram scaling, which facilitates the extensive usage of oblique backscatter soundings.

  13. Analytical study of vortex flaps on highly swept delta wings

    NASA Technical Reports Server (NTRS)

    Frink, N. T.

    1982-01-01

    This paper highlights some current results from ongoing analytical studies of vortex flaps on highly swept delta wings. A brief discussion of the vortex flow analysis tools is given along with comparisons of the theories to vortex flap force and pressure data. Theoretical trends in surface pressure distribution for both angle-of-attack variation and flap deflection are correctly predicted by Free Vortex Sheet theory. Also shown are some interesting calculations for attached-flow and vortex-flow flap hinge moments that indicate flaps utilizing vortex flow may generate less hinge moment than attached flow flaps. Finally, trailing-edge flap effects on leading-edge flap thrust potential are investigated and theory-experiment comparisons made.

  14. Optimal spatial disturbances along the swept attachment line

    NASA Astrophysics Data System (ADS)

    Guegan, Alan; Schmid, Peter; Huerre, Patrick

    2007-11-01

    Optimal spatial perturbations are described in the context of swept Hiemenz flow. The two parameters are the Reynolds number Re based on the flow stretching rate and spanwise sweep velocity, and the width L of the chordwise energy weight that defines the region of interest around the attachment line. At Reynolds numbers Re˜500 typically found in commercial aircrafts optimal spatial disturbances take the shape of counter-rotating spanwise vortices. Energy is amplified by the so-called lift-up mechanism in the spanwise direction. Amplification is stronger at higher Reynolds numbers but is mostly unchanged as L increases, although more counter-rotating spanwise vortices are observed. A physical interpretation is suggested that accounts for the shape of the perturbations and energy amplification scalings with L and the Reynolds number Re.

  15. Swept Source OCT Angiography of Neovascular Macular Telangiectasia Type 2

    PubMed Central

    Zhang, Qinqin; Wang, Ruikang K.; Chen, Chieh-Li; Legarreta, Andrew D.; Durbin, Mary K.; An, Lin; Sharma, Utkarsh; Stetson, Paul F.; Legarreta, John E.; Roisman, Luiz; Gregori, Giovanni; Rosenfeld, Philip J.

    2015-01-01

    Objective To image subretinal neovascularization in proliferative macular telangiectasia type 2 (MacTel2) using swept source optical coherence tomography based microangiography (OMAG). Study Design Patients with MacTel2 were enrolled in a prospective, observational study known as the MacTel Project and evaluated using a high-speed 1050nm swept-source OCT (SS-OCT) prototype system. The OMAG algorithm generated en face flow images from three retinal layers, as well as the region bounded by the outer retina and Bruch’s membrane, the choriocapillaris, and the remaining choroidal vasculature. The en face OMAG images were compared to images from fluorescein angiography (FA) and indocyanine green angiography (ICGA). Results Three eyes with neovascular MacTel2 were imaged. The neovascularization was best identified from the en face OMAG images that included a layer between the outer retinal boundary and Bruch’s membrane. OMAG images identified these abnormal vessels better than FA and were comparable to the images obtained using ICGA. In all three cases, OMAG identified choroidal vessels communicating with the neovascularization, and these choroidal vessels were evident in the two cases with ICGA imaging. In one case, monthly injections of bevacizumab reduced the microvascular complexity of the neovascularization, as well as the telangiectatic changes within the retinal microvasculature. In another case, less frequent bevacizumab therapy was associated with growth of the subretinal neovascular complex. Conclusions OMAG imaging provided detailed, depth-resolved information about subretinal neovascularization in MacTel2 eyes demonstrating superiority to FA imaging and similarities to ICGA imaging for documenting the retinal microvascular changes, the size and extent of the neovascular complex, the communications between the neovascular complex and the choroidal circulation, and the response to monthly bevacizumab therapy. PMID:26457402

  16. Optimal energy growth and optimal control in swept Hiemenz flow

    NASA Astrophysics Data System (ADS)

    Guégan, Alan; Schmid, Peter J.; Huerre, Patrick

    2006-11-01

    The objective of the study is first to examine the optimal transient growth of Görtler Hämmerlin perturbations in swept Hiemenz flow. This configuration constitutes a model of the flow in the attachment-line boundary layer at the leading-edge of swept wings. The optimal blowing and suction at the wall which minimizes the energy of the optimal perturbations is then determined. An adjoint-based optimization procedure applicable to both problems is devised, which relies on the maximization or minimization of a suitable objective functional. The variational analysis is carried out in the framework of the set of linear partial differential equations governing the chordwise and wall-normal velocity fluctuations. Energy amplifications of up to three orders of magnitude are achieved at low spanwise wavenumbers (k {˜} 0.1) and large sweep Reynolds number (textit{Re} {˜} 2000). Optimal perturbations consist of spanwise travelling chordwise vortices, with a vorticity distribution which is inclined against the sweep. Transient growth arises from the tilting of the vorticity distribution by the spanwise shear via a two-dimensional Orr mechanism acting in the basic flow dividing plane. Two distinct regimes have been identified: for k {≤sssim} 0.25, vortex dipoles are formed which induce large spanwise perturbation velocities; for k {gtrsim} 0.25, dipoles are not observed and only the Orr mechanism remains active. The optimal wall blowing control yields for instance an 80% decrease of the maximum perturbation kinetic energy reached by optimal disturbances at textit{Re} {=} 550 and k {=} 0.25. The optimal wall blowing pattern consists of spanwise travelling waves which follow the naturally occurring vortices and qualitatively act in the same manner as a more simple constant gain feedback control strategy.

  17. Advances in tilt rotor noise prediction

    NASA Technical Reports Server (NTRS)

    George, A. R.; Coffen, C. D.; Ringler, T. D.

    1992-01-01

    The two most serious tilt rotor external noise problems, hover noise and blade-vortex interaction noise, are studied. The results of flow visualization and inflow velocity measurements document a complex, recirculating highly unsteady and turbulent flow due to the rotor-wing-body interactions characteristic of tilt rotors. The wing under the rotor is found to obstruct the inflow, causing a deficit in the inflow velocities over the inboard region of the rotor. Discrete frequency harmonic thickness and loading noise mechanisms in hover are examined by first modeling tilt rotor hover aerodynamics and then applying various noise prediction methods using the WOPWOP code. The analysis indicates that the partial ground plane created by the wing below the rotor results in a primary sound source for hover.

  18. Fuselage upwash effects on RSRA rotor systems

    NASA Technical Reports Server (NTRS)

    Cowan, J.; Dadone, L.

    1985-01-01

    The effects of RSRA fuselage configurations on rotor performance and loads have been quantified analytically by means of currently available potential flow and rotor analysis. Four configurations of the Rotor Systems Research Aircraft (RSRA) were considered in this study. They were: (1) fuselage alone (conventional helicopter); (2) fuselage with auxiliary propulsion; (3) fuselage with wings (auxiliary lift); and (4) fuselage with both auxiliary lift propulsion. The rotor system investigated was identical to a CH-47D front rotor except that it had four instead of three blades. Two scaled-down versions of the same rotor were also analyzed to determine the effect of rotor scale on the fuselage upwash effects. The flight conditions considered for the upwash study are discussed. The potential flow models for the RSRA configuration, with and without the wings and the auxiliary propulsion system, are presented. The results of fuselage/wing/propulsion system upwash on performance and loads are also presented.

  19. Clearance flow-generated transverse forces at the rotors of thermal turbomachines. Ph.D. Thesis - Technische Univ., 1975

    NASA Technical Reports Server (NTRS)

    Urlichs, K.

    1983-01-01

    Self-excited rotor whirl represents a serious hazard in the operation of turbomachines. The reported investigation has, therefore, the objective to measure the lateral forces acting on the rotor and to determine the characteristic pressure distribution in the rotor clearance area. A description is presented of an approach for calculating the leakage flow in the case of an eccentric rotor position on the basis of empirical loss coefficients. The results are reported of an experimental investigation with a turbine stage, taking into account a variation of the clearance characteristics. The pressure data measured are consistent with the theoretical considerations.

  20. A swept wing panel in a low speed flexible walled test section

    NASA Technical Reports Server (NTRS)

    Goodyer, M. J.

    1987-01-01

    The testing of two-dimensional airfoil sections in adaptive wall tunnels is relatively widespread and has become routine at all speeds up to transonic. In contrast, the experience with the three-dimensional testing of swept panels in adaptive wall test sections is very limited, except for some activity in the 1940's at NPL, London. The current interest in testing swept wing panels led to the work covered by this report, which describes the design of an adaptive-wall swept-wing test section for a low speed wind tunnel and gives test results for a wing panel swept at 40 deg. The test section has rigid flat sidewalls supporting the panel, and features flexible top and bottom wall with ribs swept at the same angle as the wing. When streamlined, the walls form waves swept at the same angle as the wing. The C sub L (-) curve for the swept wing, determined from its pressure distributions taken with the walls streamlined, compare well with reference data which was taken on the same model, unswept, in a test section deep enough to avoid wall interference.

  1. Polarization-maintaining buffered Fourier domain mode-locked swept source for optical coherence tomography.

    PubMed

    Zhang, Jun; Jing, Joe; Wang, Pinghe; Chen, Zhongping

    2011-12-15

    A polarization-maintaining buffered Fourier domain mode-locked (FDML) swept source with a center wavelength of 1300 nm is demonstrated. The scanning rate of the buffered FDML swept source is doubled without sacrificing the output power of the swept source by combining two orthogonally polarized outputs with a polarization beam combiner. The stability of the swept source is improved because the polarization state of the laser beam inside the laser cavity is maintained without the use of any polarization controllers. The swept source is capable of an edge-to-edge tuning range of more than 150 nm and a FWHM range of 95 nm at a 102 kHz sweeping rate and with an average power of 12 mW. A swept source optical coherence tomography (SSOCT) system is developed utilizing this buffered FDML swept source. The axial resolution of the SSOCT system is measured to be 9.4 µm in air. The sensitivity of the SSOCT system is 107.5 dB at a depth of 0.25 mm with a 6 dB roll-off at a depth of 2.25 mm.

  2. Investigation of the Flow Physics Driving Stall-Side Flutter in Advanced Forward Swept Fan Designs

    NASA Technical Reports Server (NTRS)

    Sanders, Albert J.; Liu, Jong S.; Panovsky, Josef; Bakhle, Milind A.; Stefko, George; Srivastava, Rakesh

    2003-01-01

    Flutter-free operation of advanced transonic fan designs continues to be a challenging task for the designers of aircraft engines. In order to meet the demands of increased performance and lighter weight, these modern fan designs usually feature low-aspect ratio shroudless rotor blade designs that make the task of achieving adequate flutter margin even more challenging for the aeroelastician. This is especially true for advanced forward swept designs that encompass an entirely new design space compared to previous experience. Fortunately, advances in unsteady computational fluid dynamic (CFD) techniques over the past decade now provide an analysis capability that can be used to quantitatively assess the aeroelastic characteristics of these next generation fans during the design cycle. For aeroelastic applications, Mississippi State University and NASA Glenn Research Center have developed the CFD code TURBO-AE. This code is a time-accurate three-dimensional Euler/Navier-Stokes unsteady flow solver developed for axial-flow turbomachinery that can model multiple blade rows undergoing harmonic oscillations with arbitrary interblade phase angles, i.e., nodal diameter patterns. Details of the code can be found in Chen et al. (1993, 1994), Bakhle et al. (1997, 1998), and Srivastava et al. (1999). To assess aeroelastic stability, the work-per-cycle from TURBO-AE is converted to the critical damping ratio since this value is more physically meaningful, with both the unsteady normal pressure and viscous shear forces included in the work-per-cycle calculation. If the total damping (aerodynamic plus mechanical) is negative, then the blade is unstable since it extracts energy from the flow field over the vibration cycle. TURBO-AE is an integral part of an aeroelastic design system being developed at Honeywell Engines, Systems & Services for flutter and forced response predictions, with test cases from development rig and engine tests being used to validate its predictive

  3. Dynamic approximate entropy electroanatomic maps detect rotors in a simulated atrial fibrillation model.

    PubMed

    Ugarte, Juan P; Orozco-Duque, Andrés; Tobón, Catalina; Kremen, Vaclav; Novak, Daniel; Saiz, Javier; Oesterlein, Tobias; Schmitt, Clauss; Luik, Armin; Bustamante, John

    2014-01-01

    There is evidence that rotors could be drivers that maintain atrial fibrillation. Complex fractionated atrial electrograms have been located in rotor tip areas. However, the concept of electrogram fractionation, defined using time intervals, is still controversial as a tool for locating target sites for ablation. We hypothesize that the fractionation phenomenon is better described using non-linear dynamic measures, such as approximate entropy, and that this tool could be used for locating the rotor tip. The aim of this work has been to determine the relationship between approximate entropy and fractionated electrograms, and to develop a new tool for rotor mapping based on fractionation levels. Two episodes of chronic atrial fibrillation were simulated in a 3D human atrial model, in which rotors were observed. Dynamic approximate entropy maps were calculated using unipolar electrogram signals generated over the whole surface of the 3D atrial model. In addition, we optimized the approximate entropy calculation using two real multi-center databases of fractionated electrogram signals, labeled in 4 levels of fractionation. We found that the values of approximate entropy and the levels of fractionation are positively correlated. This allows the dynamic approximate entropy maps to localize the tips from stable and meandering rotors. Furthermore, we assessed the optimized approximate entropy using bipolar electrograms generated over a vicinity enclosing a rotor, achieving rotor detection. Our results suggest that high approximate entropy values are able to detect a high level of fractionation and to locate rotor tips in simulated atrial fibrillation episodes. We suggest that dynamic approximate entropy maps could become a tool for atrial fibrillation rotor mapping.

  4. Investigation of rotor blade element airloads for a teetering rotor in the blade stall regime

    NASA Technical Reports Server (NTRS)

    Dadone, L. U.; Fukushima, T.

    1974-01-01

    A model of a teetering rotor was tested in a low speed wind tunnel. Blade element airloads measured on an articulated model rotor were compared with the teetering rotor and showed that the teetering rotor is subjected to less extensive flow separation. Retreating blade stall was studied. Results show that stall, under the influence of unsteady aerodynamic effects, consists of four separate stall events, each associated with a vortex shed from the leading edge and sweeping over the upper surface of the rotor blade. Current rotor performance prediction methodology was evaluated through computer simulation.

  5. Pre-design study for a modern four-bladed rotor for the Rotor System Research Aircraft (RSRA). [integrating the YAH-64 main rotor

    NASA Technical Reports Server (NTRS)

    Hughes, C. W.; Logan, A. H.

    1981-01-01

    Various candidate rotor systems were compared in an effort to select a modern four-bladed rotor for the RSRA. The YAH-64 rotor system was chosen as the candidate rotor system for further development for the RSRA. The process used to select the rotor system, studies conducted to mate the rotor with the RSRA and provide parametric variability, and the development plan which would be used to implement these studies are presented. Drawings are included.

  6. A Survey of Theoretical and Experimental Coaxial Rotor Aerodynamic Research

    NASA Technical Reports Server (NTRS)

    Coleman, Colin P.

    1997-01-01

    The recent appearance of the Kamov Ka-50 helicopter and the application of coaxial rotors to unmanned aerial vehicles have renewed international interest in the coaxial rotor configuration. This report addresses the aerodynamic issues peculiar to coaxial rotors by surveying American, Russian, Japanese, British, and German research. (Herein, 'coaxial rotors' refers to helicopter, not propeller, rotors. The intermeshing rotor system was not investigated.) Issues addressed are separation distance, load sharing between rotors, wake structure, solidity effects, swirl recovery, and the effects of having no tail rotor. A general summary of the coaxial rotor configuration explores the configuration's advantages and applications.

  7. Morphometric measurement of Schlemm's canal in normal human eye using anterior segment swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Shi, Guohua; Wang, Fei; Li, Xiqi; Lu, Jing; Ding, Zhihua; Sun, Xinghuai; Jiang, Chunhui; Zhang, Yudong

    2012-01-01

    We have used anterior segment swept source optical coherence tomography to measure Schlemm's canal (SC) morphometric values in the living human eye. Fifty healthy volunteers with 100 normal eyes were measured in the nasal and temporal side. Comparison with the published SC morphometric values of histologic sections proves the reliability of our results. The statistical results show that there are no significant differences between nasal and temporal SC with respect to their diameter, perimeter, and area in our study (diameter: t=0.122, p=0.903; perimeter: t=-0.003, p=0.998; area: t=-1.169, p=0.244); further, no significant differences in SC morphometric values are found between oculus sinister and oculus dexter (diameter: t=0.943, p=0.35; perimeter: t=1.346, p=0.18; area: t=1.501, p=0.135).

  8. Integrated aerodynamic/dynamic optimization of helicopter rotor blades

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Aditi; Walsh, Joanne L.; Riley, Michael F.

    1989-01-01

    An integrated aerodynamic/dynamic optimization procedure is used to minimize blade weight and 4 per rev vertical hub shear for a rotor blade in forward flight. The coupling of aerodynamics and dynamics is accomplished through the inclusion of airloads which vary with the design variables during the optimization process. Both single and multiple objective functions are used in the optimization formulation. The Global Criteria Approach is used to formulate the multiple objective optimization and results are compared with those obtained by using single objective function formulations. Constraints are imposed on natural frequencies, autorotational inertia, and centrifugal stress. The program CAMRAD is used for the blade aerodynamic and dynamic analyses, and the program CONMIN is used for the optimization. Since the spanwise and the azimuthal variations of loading are responsible for most rotor vibration and noise, the vertical airload distributions on the blade, before and after optimization, are compared. The total power required by the rotor to produce the same amount of thrust for a given area is also calculated before and after optimization. Results indicate that integrated optimization can significantly reduce the blade weight, the hub shear and the amplitude of the vertical airload distributions on the blade and the total power required by the rotor.

  9. Rotor blade vortex interaction noise

    NASA Astrophysics Data System (ADS)

    Yu, Yung H.

    2000-02-01

    Blade-vortex interaction noise-generated by helicopter main rotor blades is one of the most severe noise problems and is very important both in military applications and community acceptance of rotorcraft. Research over the decades has substantially improved physical understanding of noise-generating mechanisms, and various design concepts have been investigated to control noise radiation using advanced blade planform shapes and active blade control techniques. The important parameters to control rotor blade-vortex interaction noise and vibration have been identified: blade tip vortex structures and its trajectory, blade aeroelastic deformation, and airloads. Several blade tip design concepts have been investigated for diffusing tip vortices and also for reducing noise. However, these tip shapes have not been able to substantially reduce blade-vortex interaction noise without degradation of rotor performance. Meanwhile, blade root control techniques, such as higher-harmonic pitch control (HHC) and individual blade control (IBC) concepts, have been extensively investigated for noise and vibration reduction. The HHC technique has proved the substantial blade-vortex interaction noise reduction, up to 6 dB, while vibration and low-frequency noise have been increased. Tests with IBC techniques have shown the simultaneous reduction of rotor noise and vibratory loads with 2/rev pitch control inputs. Recently, active blade control concepts with smart structures have been investigated with the emphasis on active blade twist and trailing edge flap. Smart structures technologies are very promising, but further advancements are needed to meet all the requirements of rotorcraft applications in frequency, force, and displacement.

  10. Rotor blades for turbine engines

    DOEpatents

    Piersall, Matthew R; Potter, Brian D

    2013-02-12

    A tip shroud that includes a plurality of damping fins, each damping fin including a substantially non-radially-aligned surface that is configured to make contact with a tip shroud of a neighboring rotor blade. At least one damping fin may include a leading edge damping fin and at least one damping fin may include a trailing edge damping fin. The leading edge damping fin may be configured to correspond to the trailing edge damping fin.

  11. Analysis of Low-Speed Stall Aerodynamics of a Swept Wing with Laminar-Flow Glove

    NASA Technical Reports Server (NTRS)

    Bui, Trong

    2013-01-01

    This is the presentation related to the paper of the same name describing Reynolds Averaged Navier Stokes (RANS) computational Fluid Dynamics (CFD) analysis of low speed stall aerodynamics of a swept wing with a laminar flow wing glove.

  12. A study of rotor broadband noise mechanisms and helicopter tail rotor noise

    NASA Technical Reports Server (NTRS)

    Chou, Shau-Tak Rudy

    1990-01-01

    The rotor broadband noise mechanisms considered are the following: (1) lift fluctuation due to turbulence ingestion; (2) boundary layer/trailing edge interaction; (3) tip vortex formation; and (4) turbulent vortex shedding from blunt trailing edge. Predictions show good agreement with available experimental data. The study shows that inflow turbulence is the most important broadband noise source for typical helicopters' main rotors at low- and mid-frequencies. Due to the size difference, isolated helicopter tail rotor broadband noise is not important compared to the much louder main rotor broadband noise. However, the inflow turbulence noise from a tail rotor can be very significant because it is operating in a highly turbulent environment, ingesting wakes from upstream components of the helicopter. The study indicates that the main rotor turbulent wake is the most important source of tail rotor broadband noise. The harmonic noise due to ingestion of main rotor tip vortices is studied.

  13. Swept source OCT imaging of human anterior segment at 200 kHz

    NASA Astrophysics Data System (ADS)

    Karnowski, Karol; Gora, Michalina; Kaluzny, Bartlomiej; Huber, Robert; Szkulmowski, Maciej; Kowalczyk, Andrzej; Wojtkowski, Maciej

    2009-02-01

    We present applicability of the high speed swept-source optical coherence tomography for in vivo imaging of the anterior segment of the human eye. Three dimensional imaging of the cornea with reduced motion artifacts is possible by using swept source with Fourier domain mode locking operating at 200kHz with 1300nm central wavelength. High imaging speeds allow for assessment of anterior and posterior corneal topography and generation of thickness and elevation maps.

  14. On the stability of an infinite swept attachment line boundary layer

    NASA Technical Reports Server (NTRS)

    Hall, P.; Malik, M. R.; Poll, D. I. A.

    1984-01-01

    The instability of an infinite swept attachment line boundary layer is considered in the linear regime. The basic three dimensional flow is shown to be susceptible to travelling wave disturbances which propagate along the attachment line. The effect of suction on the instability is discussed and the results suggest that the attachment in boundary layer on a swept wing can be significantly stabilized by extremely small amounts of suction. The results obtained are in excellent agreement with the available experimental observations.

  15. On the stability of an infinite swept attachment line boundary layer

    NASA Technical Reports Server (NTRS)

    Hall, P.; Mallik, M. R.; Poll, D. I. A.

    1984-01-01

    The instability of an infinite swept attachment line boundary layer is considered in the linear regime. The basic three dimensional flow is shown to be susceptible to travelling wave disturbances which propagate along the attachment line. The effect of suction on the instability is discussed and the results suggest that the attachment line boundary layer on a swept wing can be significantly stabilized by extremely small amounts of suction. The results obtained are in excellent agreement with the available experimental observations.

  16. An unsteady rotor/fuselage interaction method

    NASA Technical Reports Server (NTRS)

    Egolf, T. Alan; Lorber, Peter F.

    1987-01-01

    An analytical method has been developed to treat unsteady helicopter rotor, wake, and fuselage interaction aerodynamics. An existing lifting line/prescribed wake rotor analysis and a source panel fuselage analysis were modified to predict vibratory fuselage airloads. The analyses were coupled through the induced flow velocities of the rotor and wake on the fuselage and the fuselage on the rotor. A prescribed displacement technique was used to distort the rotor wake about the fuselage. Sensitivity studies were performed to determine the influence of wake and body geometry on the computed airloads. Predicted and measured mean and unsteady pressures on a cylindrical body in the wake of a two-bladed rotor were compared. Initial results show good qualitative agreement.

  17. Parametric tip effects for conformable rotor applications

    NASA Technical Reports Server (NTRS)

    Mantay, W. R.; Yeager, W. T., Jr.

    1983-01-01

    A research study was initiated to systematically determine the impact of selected blade tip geometric parameters on aeroelasticity conformable rotor performance and loads characteristics. The model articulated rotors included baseline and torsionally soft blades with interchangeable tips. Seven blade tip designs were evaluated on the baseline rotor and three tip designs were tested on the torsionally soft blades. The designs incorporated a systematic variation in three geometric parameters: sweep, taper, and anhedral. The rotors were evaluated in the NASA Langley Transonic Dynamics Tunnel at several advance ratios, lift and propulsive force values, and tip Mach numbers. Based on the test results, tip parameter variations generated significant rotor performance and loads difference for both baseline and torsionally soft blades. Azimuthal variation of elastic twist generated by the tip parameters strongly correlated with rotor performance and loads, but the magnitude of advancing blade elastic twist did not correlate.

  18. A 1987 progress report of manufacturing techniques for Gravity Probe B gyroscope rotors

    NASA Technical Reports Server (NTRS)

    Taylor, Roy A.; White, ED; Reed, William J.

    1987-01-01

    The significant improvements in the manufacture of Gravity Probe B gyroscope rotors developed since the publication of the last report on this project are presented. The improvements include the polishing machine structure, rough laps, finishing/polishing laps, lapping procedure, measurement techniques, and a summary of the manufacturing status. These six areas represent significant improvements in the manufacture of the gyroscope rotors to meet flight requirements.

  19. Performance and Environmental Assessment of an Advanced Aircraft with Open Rotor Propulsion

    NASA Technical Reports Server (NTRS)

    Guynn, Mark D.; Berton, Jeffrey J.; Haller, William J.; Hendricks, Eric S.; Tong, Michael T.

    2012-01-01

    Application of high speed, advanced turboprops, or "propfans," to transonic transport aircraft received significant attention during the 1970s and 1980s when fuel efficiency was the driving focus of aeronautical research. Unfortunately, after fuel prices declined sharply there was no longer sufficient motivation to continue maturing this technology. Recent volatility in fuel prices and increasing concern for aviation s environmental impact, however, have renewed interest in unducted, open rotor propulsion. Because of the renewed interest in open rotor propulsion, the lack of publicly available up-to-date studies assessing its benefits, and NASA s focus on reducing fuel consumption, a preliminary aircraft system level study on open rotor propulsion was initiated to inform decisions concerning research in this area. New analysis processes were established to assess the characteristics of open rotor aircraft. These processes were then used to assess the performance, noise, and emissions characteristics of an advanced, single-aisle aircraft using open rotor propulsion. The results of this initial study indicate open rotor engines have the potential to provide significant reductions in fuel consumption and landing-takeoff cycle NOX emissions. Noise analysis of the study configuration indicates that an open rotor aircraft in the single-aisle class would be able to meet current noise regulations with margin.

  20. Rotor fatigue monitoring data acquisition system

    NASA Technical Reports Server (NTRS)

    Smith, Scott M.

    1993-01-01

    The 40 by 80 Foot Wind Tunnel of the National Full Scale Aerodynamics Complex (NFAC) had a requirement to monitor rotor fatigue during a test. This test subjected various rotor components to stress levels higher than their structural fatigue limits. A data acquisition system was developed to monitor the cumulative fatigue damage of rotor components using National Instruments hardware and LabVIEW software. A full description of the data acquisition system including its configuration and salient features, is presented in this paper.

  1. Eigenvalues and stability problems of rotors

    NASA Technical Reports Server (NTRS)

    Walczyk, Z.

    1985-01-01

    The essential theoretical results of the application of a developed transfer matrix method to the free transverse vibration of a rotor are shown. Gyroscopic and shear effects, rotary inertia, and external and internal damping as well as the influence of sleeve bearings and rotor supports are taken into consideration. The eigenvalues of the motion equations of the rotor are searched by using a modified determinant method.

  2. Inertial dynamics of a general purpose rotor

    NASA Technical Reports Server (NTRS)

    Duval, R. W.

    1979-01-01

    The inertial dynamics of a fully articulated stiff rotor blade are derived with emphasis on equations that facilitate an organized programming approach for simulation applications. The model for the derivation includes hinge offset and six degrees of freedom for the rotor shaft. Results are compared with the flapping and lead-lag equations currently used in the Rotor Systems Research Aircraft simulation model and differences are analyzed.

  3. Flywheel Rotor Safe-Life Technology

    NASA Technical Reports Server (NTRS)

    Ratner, J. K. H.; Chang, J. B.; Christopher, D. A.; McLallin, Kerry L. (Technical Monitor)

    2002-01-01

    Since the 1960s, research has been conducted into the use of flywheels as energy storage systems. The-proposed applications include energy storage for hybrid and electric automobiles, attitude control and energy storage for satellites, and uninterruptible power supplies for hospitals and computer centers. For many years, however, the use of flywheels for space applications was restricted by the total weight of a system employing a metal rotor. With recent technological advances in the manufacturing of composite materials, however, lightweight composite rotors have begun to be proposed for such applications. Flywheels with composite rotors provide much higher power and energy storage capabilities than conventional chemical batteries. However, the failure of a high speed flywheel rotor could be a catastrophic event. For this reason, flywheel rotors are classified by the NASA Fracture Control Requirements Standard as fracture critical parts. Currently, there is no industry standard to certify a composite rotor for safe and reliable operation forth( required lifetime of the flywheel. Technical problems hindering the development of this standard include composite manufacturing inconsistencies, insufficient nondestructive evaluation (NDE) techniques for detecting defects and/or impact damage, lack of standard material test methods for characterizing composite rotor design allowables, and no unified proof (over-spin) test for flight rotors. As part of a flywheel rotor safe-life certification pro-ram funded b the government, a review of the state of the art in composite rotors is in progress. The goal of the review is to provide a clear picture of composite flywheel rotor technologies. The literature review has concentrated on the following topics concerning composites and composite rotors: durability (fatigue) and damage tolerance (safe-life) analysis/test methods, in-service NDE and health monitoring techniques, spin test methods/ procedures, and containment options

  4. In-flight lift-drag characteristics for a forward-swept wing aircraft and comparisons with contemporary aircraft)

    NASA Technical Reports Server (NTRS)

    Saltzman, Edwin J.; Hicks, John W.; Luke, Sue (Editor)

    1994-01-01

    Lift (L) and drag (D) characteristics have been obtained in flight for the X-29A airplane (a forward swept-wing demonstrator) for Mach numbers (M) from 0.4 to 1.3. Most of the data were obtained near an altitude of 30,000 ft. A representative Reynolds number for M = 0.9, and a pressure altitude of 30,000 ft, is 18.6 x 10(exp 6) based on the mean aerodynamic chord. The X-29A data (forward-swept wing) are compared with three high-performance fighter aircraft: the F-15C, F-16C, and F/A18. The lifting efficiency of the X-29A, as defined by the Oswald lifting efficiency factor, e, is about average for a cantilevered monoplane for M = 0.6 and angles of attack up to those required for maximum L/D. At M = 0.6 the level of L/D and e, as a function of load factor, for the X-29A was about the same as for the contemporary aircraft. The X-29A and its contemporaries have high transonic wave drag and equivalent parasite area compared with aircraft of the 1940's through 1960's.

  5. Swept frequency technique for dispersion measurement of microstrip lines

    NASA Technical Reports Server (NTRS)

    Lee, R. Q.

    1986-01-01

    Microstrip lines used in microwave integrated circuits are dispersive. Because a microstrip line is an open structure, the dispersion can not be derived with pure TEM, TE, or TM mode analysis. Dispersion analysis has commonly been done using a spectral domain approach, and dispersion measurement has been made with high Q microstrip ring resonators. Since the dispersion of a microstrip line is fully characterized by the frequency dependent phase velocity of the line, dispersion measurement of microstrip lines requires the measurement of the line wavelength as a function of frequency. In this paper, a swept frequency technique for dispersion measurement is described. The measurement was made using an automatic network analyzer with the microstrip line terminated in a short circuit. Experimental data for two microstrip lines on 10 and 30 mil Cuflon substrates were recorded over a frequency range of 2 to 20 GHz. Agreement with theoretical results computed by the spectral domain approach is good. Possible sources of error for the discrepancy are discussed.

  6. Laminar-turbulent transition delay on a swept wing

    NASA Astrophysics Data System (ADS)

    Borodulin, V. I.; Ivanov, A. V.; Kachanov, Y. S.; Hanifi, A.

    2016-10-01

    The paper describes the results of experiments on robustness of laminar-turbulent transition control on a swept-wing using distributed micro-sized roughness (DMSR) elements. These elements introduce controlled stationary vortices which are able to significantly modify the base flow and its stability characteristics. We have performed parametric study first varying height and period of the DMSR elements in order to find the most stabilizing effect on boundary later flow in compare to uncontrolled reference case without DMSR. Significant downstream shift of laminar-turbulent transition position due to application of DMSR is found and well documented with help of thermography. The robustness of this flow control method was studied by variation of the wind-tunnel flow quality introducing significant sound background or introducing enhanced turbulence level (applying turbulizing grids). The wind-tunnel tests performed with turbulence-generating grids (at enhanced turbulence levels) have shown that laminar-turbulent transition moves upstream in this case, while DMSR-elements loose their effectiveness for transition control (no matter in quiet sound conditions or at elevated sound background). The experiments on acoustic influence have shown that without DMSR acoustic does not effect transition location. However, in case then laminar-turbulent transition is delayed by presence of DMSR, an additional transition delay was observed when harmonic acoustic waves of certain frequency were excited.

  7. Effects of Suction on Swept-Wing Transition

    NASA Technical Reports Server (NTRS)

    Saric, William S.

    1998-01-01

    Stability experiments are conducted in the Arizona State University Unsteady Wind Tunnel on a 45 deg swept airfoil. The pressure gradient is designed to provide purely crossflow-dominated transition; that is, the boundary layer is subcritical to Tollmien-Schlichting disturbances. The airfoil surface is hand polished to a 0.25 microns rms finish. Under these conditions, stationary crossflow disturbances grow to nonuniform amplitude due to submicron surface irregularities near the leading edge. Uniform stationary crossflow waves are produced by controlling the initial conditions with spanwise arrays of micron-sized roughness elements near the attachment line. Hot-wire measurements provide detailed maps of the crossflow wave structure, and accurate spectral decompositions isolate individual-mode growth rates for the fundamental and harmonic disturbances. Roughness spacing, roughness height, and Reynolds number are varied to investigate the growth of all amplified wavelengths. The measurements show early nonlinear mode interaction causing amplitude saturation well before transition. Comparisons with nonlinear parabolized stability equations calculations show excellent agreement in both the disturbance amplitude and the mode-shape profiles.

  8. Design of helicopter rotors to noise constraints

    NASA Technical Reports Server (NTRS)

    Schaeffer, E. G.; Sternfeld, H., Jr.

    1978-01-01

    Results of the initial phase of a research project to study the design constraints on helicopter noise are presented. These include the calculation of nonimpulsive rotor harmonic and broadband hover noise spectra, over a wide range of rotor design variables and the sensitivity of perceived noise level (PNL) to changes in rotor design parameters. The prediction methodology used correlated well with measured whirl tower data. Application of the predictions to variations in rotor design showed tip speed and thrust as having the most effect on changing PNL.

  9. Rotor/wing aerodynamic interactions in hover

    NASA Technical Reports Server (NTRS)

    Felker, F. F.; Light, J. S.

    1986-01-01

    An experimental and theoretical investigation of rotor/wing aerodynamic interactions in hover is described. The experimental investigation consisted of both a large-scale and small-scale test. A 0.658-scale, V-22 rotor and wing was used in the large-scale test. Wind download, wing surface pressure, rotor performance, and rotor downwash data from the large-scale test are presented. A small-scale experiment was conducted to determine how changes in the rotor/wing geometry affected the aerodynamic interactions. These geometry variations included the distance between the rotor and wing, wing incidence angle, and configurations both with the rotor axis at the tip of the wing (tilt rotor configuration) and with the rotor axis at the center of the wing (compound helicopter configuration). A wing with boundary-layer control was also tested to evaluate the effect of leading and trailing edge upper surface blowing on the wing download. A computationally efficient, semi-empirical theory was developed to predict the download on the wing. Finally, correlations between the theoretical predictions and test data are presented.

  10. Prediction of helicopter rotor rotational noise

    NASA Astrophysics Data System (ADS)

    Xu, Guohua; Gao, Zheng

    1991-06-01

    Based on Farassat (1981) formulation 1A for subsonic time domain, a method is developed for predicting the rotor rotational noise, which is valid for arbitrary observer positions and all linear flight conditions. Without considering the elasticity of the blade, the retarded time equation and all of the integrands in the formulation 1A are derived and expressed as the proper form for numerical calculation. As examples, the noise calculation of the helicopter Z-8 rotor and 1/4 scale UH-1 rotor in hover are carried out. Discussions are presented on the influence of rotor parameters, such as the tip Mach number, the disk loading, and the blade airfoil.

  11. Rotor thermal stress monitoring in steam turbines

    NASA Astrophysics Data System (ADS)

    Antonín, Bouberle; Jan, Jakl; Jindřich, Liška

    2015-11-01

    One of the issues of steam turbines diagnostics is monitoring of rotor thermal stress that arises from nonuniform temperature field. The effort of steam turbine operator is to operate steam turbine in such conditions, that rotor thermal stress doesn't exceed the specified limits. If rotor thermal stress limits are exceeded for a long time during machine operation, the rotor fatigue life is shortened and this may lead to unexpected machine failure. Thermal stress plays important role during turbine cold startup, when occur the most significant differences of temperatures through rotor cross section. The temperature field can't be measured directly in the entire rotor cross section and standardly the temperature is measured by thermocouple mounted in stator part. From this reason method for numerical solution of partial differential equation of heat propagation through rotor cross section must be combined with method for calculation of temperature on rotor surface. In the first part of this article, the application of finite volume method for calculation of rotor thermal stress is described. The second part of article deals with optimal trend generation of thermal flux, that could be used for optimal machine loading.

  12. Dynamic Balancing Of Turbomachinery Shafts And Rotors

    NASA Technical Reports Server (NTRS)

    Verhoff, Vincent G.

    1993-01-01

    Method for dynamic balancing of turbomachinery shafts and rotors developed with view toward reducing time spent in balancing process. Improved method based on existing dynamic-balancing techniques and equipment, incorporating use of balancing arbor, which is mandrel duplicating mounting geometry and dynamic-balance properties of shaft balanced. Once shaft balanced, not necessary to disassemble machinery and/or shaft completely and rebalance shaft when replacing rotor on shaft. Instead, one balances replacement rotor on balancing arbor, then installs balanced rotor on shaft.

  13. Rotor Flapping Response to Active Control

    NASA Technical Reports Server (NTRS)

    Nguyen, Khanh; Johnson, Wayne

    2004-01-01

    Rotor active control using higher harmonic blade pitch has been proposed as a means to reduce both rotor radiated noise and airframe vibration and to enhance rotor performance. The higher harmonic input, however, can affect rotor thrust and cyclic flapping - the basic trim characteristics of the rotor. Some of the trim changes can negate the active control benefits. For example, wind tunnel test results of a full scale BO-105 rotor with individual-blade control indicate some rotor performance improvements, accompanied with changes in rotor trim, using two-per-rev blade pitch input. The observed performance benefits could therefore be a simple manifestation of the trim change rather than an efficient redistribution of the rotor airloads. More recently, the flight test of the BO-105 helicopter equip,ped with individual-blade-control actuators also reported trim changes whenever the two-per-rev blade pitch for noise reduction was activated. The pilot had to adjust the trim control to maintain the aircraft under a constant flight path. These two cases highlight the, importance of trim considerations in the application of active control to rotorcraft.

  14. High Speed Rotor Head Mounted Instrumentation System

    NASA Technical Reports Server (NTRS)

    Hee, Leonard; Reynolds, R. S. (Technical Monitor)

    1997-01-01

    NASA Ames Research Center has been investigating the air flow of a rotor blade on a UH-60 Blackhawk helicopter in-flight. This paper will address the hardware problems and solutions used to design and fabricate an instrumentation system on top of a UH-60 main rotor head. The instrumentation system consisted of 10 data systems operating in parallel and collected data from 370 sensors that are mounted in four rotor blades and on the rotating rotor head. The data was recorded on board the aircraft and simultaneously down linked to the ground station at 7.5 MHz.

  15. Macular Choroidal Thickness and Volume Measured by Swept-source Optical Coherence Tomography in Healthy Korean Children

    PubMed Central

    Lee, Jung Wook; Song, In Seok; Lee, Ju-hyang; Shin, Yong Un; Lim, Han Woong; Lee, Won June

    2016-01-01

    Purpose To evaluate the thickness and volume of the choroid in healthy Korean children using swept-source optical coherence tomography. Methods We examined 80 eyes of 40 healthy children and teenagers (<18 years) using swept-source optical coherence tomography with a tunable long-wavelength laser source. A volumetric macular scan protocol using the Early Treatment Diabetic Retinopathy Study grid was used to construct a choroidal thickness map. We also examined 44 eyes of 35 healthy adult volunteers (≥18 years) and compared adult measurements with the findings in children. Results The mean age of the children and teenagers was 9.47 ± 3.80 (4 to 17) vs. 55.04 ± 12.63 years (36 to 70 years) in the adult group (p < 0.001, Student's t-test). Regarding the Early Treatment Diabetic Retinopathy Study subfields, the inner temporal subfield was the thickest (247.96 µm). The inner and outer nasal choroid were thinner (p = 0.004, p = 0.002, respectively) than the surrounding areas. The mean choroidal volumes of the inner and outer nasal areas were smaller (p = 0.004, p = 0.003, respectively) than those of all the other areas in each circle. Among the nine subfields, all areas in the children, except the outer nasal subfield, were thicker than those in adults (p < 0.05). Regression analysis showed that age, axial length, and refractive error correlated with subfoveal choroidal thickness (p < 0.05). Conclusions Overall macular choroidal thickness and volume in children and teenagers were significantly greater than in adults. The nasal choroid was significantly thinner than the surrounding areas. The pediatric subfoveal choroid is prone to thinning with increasing age, axial length, and refractive error. These differences should be considered when choroidal thickness is evaluated in children with chorioretinal diseases. PMID:26865801

  16. Method for manufacturing a rotor having superconducting coils

    DOEpatents

    Driscoll, David I.; Shoykhet, Boris A.

    2001-01-01

    A method and apparatus for manufacturing a rotor for use with a rotating machine is provided that employs a superconducting coil on the rotor. An adhesive is applied to an outer surface of the rotor body, which may include a groove disposed within an outer surface of the rotor body. A superconducting coil is then mounted onto the rotor body such that the adhesive bonds the superconducting coil to the rotor body.

  17. Recent developments in the dynamics of advanced rotor systems

    NASA Technical Reports Server (NTRS)

    Johnson, W.

    1985-01-01

    The problems that were encountered in the dynamics of advanced rotor systems are described. The methods for analyzing these problems are discussed, as are past solutions of the problems. To begin, the basic dynamic problems of rotors are discussed: aeroelastic stability, rotor and airframe loads, and aircraft vibration. Next, advanced topics that are the subject of current research are described: vibration control, dynamic upflow, finite element analyses, and composite materials. Finally, the dynamics of various rotorcraft configurations are considered: hingeless rotors, bearingless rotors, rotors with circulation control, coupled rotor/engine dynamics, articulated rotors, and tilting proprotor aircraft.

  18. Simultaneous 1310/1550 dual-band swept laser source and fiber-based dual-band common-path swept source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Mao, Youxin; Chang, Shoude; Murdock, Erroll; Flueraru, Costel

    2011-08-01

    A simultaneous two wavelength band swept laser source and a fiber-based dual-band common-path swept source optical coherence tomography is reported. Simultaneous 1310/1550 dual-wavelength tuning is performed by using two fiber-ring cavities with corresponding optical semiconductor amplifier as their gain mediums and two narrowband optical filters with a single dual-window polygonal scanner. Measured average output powers of 60 mW and 27 mW have been achieved for 1310 and 1550 nm bands, respectively, while the two wavelengths were swept simultaneously from 1227 nm to 1387 nm for 1310 nm band and from 1519 nm to 1581 nm for 1550 nm band at an A-scan rate of 65 kHz. A broadband 1310/1550 wavelength-division multiplexing is used for coupling two wavelengths into a common-path single-mode GRIN-lensed fiber probe to form a dual-band common-path swept-source optical coherence tomography. Simultaneous OCT imaging at 1310 and 1550 nm is achieved by using a depth ratio correction method. This technique allows potentially for in vivo endoscopic high-speed functional OCT imaging with high quality spectroscopic contrast with low computational costs. On the other hand, the common path configuration is able to reject common mode noise and potentially implement high stability quantitative phase measurements.

  19. Experimental study of pressure and heating rate on a swept cylindrical leading edge resulting from swept shock wave interference. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Glass, Christopher E.

    1989-01-01

    The effects of cylindrical leading edge sweep on surface pressure and heat transfer rate for swept shock wave interference were investigated. Experimental tests were conducted in the Calspan 48-inch Hypersonic Shock Tunnel at a nominal Mach number of 8, nominal unit Reynolds number of 1.5 x 10 to the 6th power per foot, leading edge and incident shock generator sweep angles of 0, 15, and 30 deg, and incident shock generator angle-of-attack fixed at 12.5 deg. Detailed surface pressure and heat transfer rate on the cylindircal leading edge of a swept shock wave interference model were measured at the region of the maximum surface pressure and heat transfer rate. Results show that pressure and heat transfer rate on the cylindrical leading edge of the shock wave interference model were reduced as the sweep was increased over the range of tested parameters. Peak surface pressure and heat transfer rate on the cylinder were about 10 and 30 times the undisturbed flow stagnation point value, respectively, for the 0 deg sweep test. A comparison of the 15 and 30 deg swept results with the 0 deg swept results showed that peak pressure was reduced about 13 percent and 44 percent, respectively, and peak heat transfer rate was reduced about 7 percent and 27 percent, respectively.

  20. An experimental investigation of the effect of rotor tip shape on helicopter blade-slap noise. [in the langley v/stol wind tunnel

    NASA Technical Reports Server (NTRS)

    Hoad, D. R.

    1979-01-01

    The effect of tip-shape modification on blade-vortex interaction-induced helicopter blade-slap noise was investigated. The general rotor model system (GRMS) with a 3.148 m (10.33 ft) diameter, four-bladed fully articulated rotor was installed in the Langley V/STOL wind tunnel. The tunnel was operated in the open-throat configuration with treatment to improve the semi-anechoic characteristics of the test chamber. Based on previous investigation, four promising tips (ogee, sub-wing, 60 deg swept-tapered, and end-plate) were used along with a standard square tip as a baseline configuration. Aerodynamic and acoustical data concerning the relative applicability of the various tip configurations for blade-slap noise reduction are presented without analysis or discussion.

  1. Quantitative upper airway endoscopy with swept-source anatomical optical coherence tomography

    PubMed Central

    Wijesundara, Kushal; Zdanski, Carlton; Kimbell, Julia; Price, Hillel; Iftimia, Nicusor; Oldenburg, Amy L.

    2014-01-01

    Minimally invasive imaging of upper airway obstructions in children and adults is needed to improve clinical decision-making. Toward this goal, we demonstrate an anatomical optical coherence tomography (aOCT) system delivered via a small-bore, flexible endoscope to quantify the upper airway lumen geometry. Helical scans were obtained from a proximally-scanned fiber-optic catheter of 820 μm outer diameter and >2 mm focal length. Coupled with a long coherence length wavelength-swept light source, the system exhibited an SNR roll-off of < 10 dB over a 10 mm range. Operating at 10 rotations/s, the average accuracy of segmented cross-sectional areas was found to be −1.4 ± 1.0%. To demonstrate the capability of this system, aOCT was performed on a pediatric airway phantom and on ex vivo swine trachea. The ability for quantitative endoscopy afforded by this system can aid in diagnosis, medical and surgical decision making, and predictive modeling of upper airway obstructive disorders. PMID:24688814

  2. Assessment of cervical demineralization induced by Streptococcus mutans using swept-source optical coherence tomography

    PubMed Central

    Tezuka, Hiroki; Shimada, Yasushi; Matin, Khairul; Ikeda, Masaomi; Sadr, Alireza; Sumi, Yasunori; Tagami, Junji

    2016-01-01

    Abstract. Exposed root surfaces due to gingival recession are subject to biofilm stagnation that can result in caries formation. Cervical enamel and dentin demineralization induced by a cariogenic biofilm was evaluated using swept-source optical coherence tomography (SS-OCT). The cementoenamel junction (CEJ) sections of extracted human teeth were subjected to demineralization for 1, 2, or 3 weeks. A suspension of Streptococcus mutans was applied to form a cariogenic biofilm using an oral biofilm reactor. After incubation, demineralization was observed by SS-OCT. For the analysis of SS-OCT signal, the value of the area under the curve (AUC) of the signal profile was measured. Statistical analyses were performed with 95% level of confidence. Cervical demineralization was displayed as a bright zone in SS-OCT. The demineralization depth of dentin was significantly deeper than that of enamel (p<0.05). Enamel near the CEJ demonstrated a significant increase of AUC over the other enamel region after the demineralization. The gaps along the dentinoenamel junction were additionally observed in SS-OCT. SS-OCT was capable of monitoring the cervical demineralization induced by a cariogenic biofilm and is considered to be a promising modality for the diagnosis of cervical demineralization. PMID:27014718

  3. Swept-source OCT Angiography of the Retinal Vasculature using Intensity Differentiation Based OMAG Algorithms

    PubMed Central

    Huang, Yanping; Zhang, Qinqin; Thorell, Mariana Rossi; An, Lin; Durbin, Mary; Laron, Michal; Sharma, Utkarsh; Gregori, Giovanni; Rosenfeld, Philip J.; Wang, Ruikang K

    2014-01-01

    Background and Objective To demonstrate the feasibility of using a 1050 nm swept-source OCT (SS-OCT) system to achieve noninvasive retinal vasculature imaging in human eyes. Materials and Methods Volumetric datasets were acquired using a ZEISS 1 µm SS-OCT prototype that operated at an A-line rate of 100 kHz. A scanning protocol designed to allow for motion contrast processing, referred to as OCT angiography or optical microangiography (OMAG), was used to scan ~3 mm × 3 mm area in the central macular region of the retina within ~4.5 seconds. Intensity differentiation based OMAG algorithm was used to extract 3-D retinal functional microvasculature information. Results Intensity signal differentiation generated capillary-level resolution en face OMAG images of the retina. The parafoveal capillaries were clearly visible, thereby allowing visualization of the foveal avascular zone (FAZ) in normal subjects. Conclusion The capability of OMAG to produce retinal vascular images was demonstrated using the ZEISS 1 µm SS-OCT prototype. This technique can potentially have clinical value for studying retinal vasculature abnormalities. PMID:25230403

  4. Rotor fault condition monitoring techniques for squirrel-cage induction machine—A review

    NASA Astrophysics Data System (ADS)

    Mehrjou, Mohammad Rezazadeh; Mariun, Norman; Hamiruce Marhaban, Mohammad; Misron, Norhisam

    2011-11-01

    Nowadays, manufacturing companies are making great efforts to implement an effective machinery maintenance program, which provides incipient fault detection. The machine problem and its irregularity can be detected at an early stage by employing a suitable condition monitoring accompanied with powerful signal processing technique. Among various defects occurred in machines, rotor faults are of significant importance as they cause secondary failures that lead to a serious motor malfunction. Diagnosis of rotor failures has long been an important but complicated task in the area of motor faults detection. This paper intends to review and summarize the recent researches and developments performed in condition monitoring of the induction machine with the purpose of rotor faults detection. The aim of this article is to provide a broad outlook on rotor fault monitoring techniques for the researchers and engineers.

  5. Multiple piece turbine rotor blade

    DOEpatents

    Jones, Russell B; Fedock, John A

    2013-05-21

    A multiple piece turbine rotor blade with a shell having an airfoil shape and secured between a spar and a platform with the spar including a tip end piece. a snap ring fits around the spar and abuts against the spar tip end piece on a top side and abuts against a shell on the bottom side so that the centrifugal loads from the shell is passed through the snap ring and into the spar and not through a tip cap dovetail slot and projection structure.

  6. Parasite-Drag Measurements of Five Helicopter Rotor Hubs

    NASA Technical Reports Server (NTRS)

    Churchill, Gary B.; Harrington, Robert D.

    1959-01-01

    An investigation has been conducted in the Langley full-scale tunnel to determine the parasite drag of five production-type helicopter rotor hubs. Some simple fairing arrangements were attempted in an effort to reduce the hub drag. The results indicate that, within the range of the tests, changes in angle of attack, hub rotational speed, and forward speed generally had only a small effect on the equivalent flat-plate area representing parasite drag. The drag coefficients of the basic hubs, based on projected hub frontal area, increased with hub area and varied from 0.5 to 0.76 for the hubs tested.

  7. Blood Pump Having a Magnetically Suspended Rotor

    NASA Technical Reports Server (NTRS)

    Antaki, James F. (Inventor); Paden, Bradley (Inventor); Burgreen, Gregory (Inventor); Groom, Nelson J. (Inventor)

    2002-01-01

    A blood pump preferably has a magnetically suspended rotor that rotates within a housing. The rotor may rotate about a stator disposed within the housing. Radial magnetic bearings may be defined within the stator and the rotor in order to suspend the rotor. The radial magnetic bearings may be passive magnetic bearings that include permanent magnets disposed within the stator and the rotor or active magnetic bearings. The pump may further include an axial magnetic bearing that may be either a passive or an active magnetic bearing. A motor that drives the rotor may be disposed within the housing in order to more easily dissipate heat generated by the motor. A primary flow path is defined between the rotor and the stator, and a secondary flow path is defined between the stator and the rotor. Preferably, a substantial majority of blood passes through the primary flow path. The secondary flow path is large enough so that it provides adequate flushing of the secondary flow path while being small enough to permit efficient operation of the radial magnet bearings across the secondary flow path.

  8. Blood Pump Having a Magnetically Suspended Rotor

    NASA Technical Reports Server (NTRS)

    Antaki, James F. (Inventor); Paden, Bradley (Inventor); Burgreen, Gregory (Inventor); Groom, Nelson J. (Inventor)

    2001-01-01

    A blood pump preferably has a magnetically suspended rotor that rotates within a housing. The rotor may rotate about a stator disposed within the housing. Radial magnetic bearings may be defined within the stator and the rotor in order to suspend the rotor. The radial magnetic bearings may be passive magnetic bearings that include permanent magnets disposed within the stator and the rotor or active magnetic bearings. The pump may further include an axial magnetic bearing that may be either a passive or an active magnetic bearing. A motor that drives the rotor may be disposed within the housing in order to more easily dissipate heat generated by the motor. A primary flow path is defined between the rotor and the stator, and a secondary flow path is defined between the stator and the rotor. Preferably, a substantial majority of blood passes through the primary flow path. The secondary flow path is large enough so that it provides adequate flushing of the secondary flow path while being small enough to permit efficient operation of the radial magnet bearings across the secondary flow path.

  9. Pneumatic boot for helicopter rotor deicing

    NASA Technical Reports Server (NTRS)

    Blaha, B. J.; Evanich, P. L.

    1981-01-01

    Pneumatic deicer boots for helicopter rotor blades were tested. The tests were conducted in the 6 by 9 ft icing research tunnel on a stationary section of a UH-IH helicopter main rotor blade. The boots were effective in removing ice and in reducing aerodynamic drag due to ice.

  10. Total main rotor isolation system analysis

    NASA Technical Reports Server (NTRS)

    Sankewitsch, V.

    1981-01-01

    Requirements, preliminary design, and verification procedures for a total main rotor isolation system at n/rev are presented. The fuselage is isolated from the vibration inducing main rotor at one frequency in all degrees of freedom by four antiresonant isolation units. Effects of parametric variations on isolation system performance are evaluated.

  11. Prediction and reduction of rotor broadband noise

    NASA Technical Reports Server (NTRS)

    Hayden, R. E.; Aravamudan, K. S.

    1978-01-01

    Prediction techniques which can be or have been applied to subsonic rotors, and methods for designing helicopter rotors for reduced broadband noise generation are summarized. It is shown how detailed physical models of the noise source can be used to identify approaches to noise control.

  12. Balancing of Rigid and Flexible Rotors

    DTIC Science & Technology

    1986-01-01

    rotor conr- Igjurations that can be "dialed In" are shown at left. (Cour- tesy of’ Schenak Trebel Corporation.) ŕ 1,4 BALANJCING MACHINES ANI...anice, For all rigid rotors in any grado , the specific balance requirement for that grade should provide smooth operation. Tlhe grstde number represents

  13. Flapping inertia for selected rotor blades

    NASA Technical Reports Server (NTRS)

    Berry, John D.; May, Matthew J.

    1991-01-01

    Aerodynamics of helicopter rotor systems cannot be investigated without consideration for the dynamics of the rotor. One of the principal properties of the rotor which affects the rotor dynamics is the inertia of the rotor blade about its root attachment. Previous aerodynamic investigation have been performed on rotor blades with a variety of planforms to determine the performance differences due to blade planform. The blades tested for this investigation have been tested on the U.S. Army 2 meter rotor test system (2MRTS) in the NASA Langley 14 by 22 foot subsonic tunnel for hover performance. This investigation was intended to provide fundamental information on the flapping inertia of five rotor blades with differing planforms. The inertia of the bare cuff and the cuff with a blade extension were also measured for comparison with the inertia of the blades. Inertia was determined using a swing testing technique, using the period of oscillation to determine the effective flapping inertia. The effect of damping in the swing test was measured and described. A comparison of the flapping inertials for rectangular and tapered planform blades of approximately the same mass showed the tapered blades to have a lower inertia, as expected.

  14. Theoretical models of helicopter rotor noise

    NASA Technical Reports Server (NTRS)

    Hawkings, D. L.

    1978-01-01

    For low speed rotors, it is shown that unsteady load models are only partially successful in predicting experimental levels. A theoretical model is presented which leads to the concept of unsteady thickness noise. This gives better agreement with test results. For high speed rotors, it is argued that present models are incomplete and that other mechanisms are at work. Some possibilities are briefly discussed.

  15. Wave rotor-enhanced gas turbine engines

    NASA Technical Reports Server (NTRS)

    Welch, Gerard E.; Scott, Jones M.; Paxson, Daniel E.

    1995-01-01

    The benefits of wave rotor-topping in small (400 to 600 hp-class) and intermediate (3000 to 4000 hp-class) turboshaft engines, and large (80,000 to 100,000 lb(sub f)-class) high bypass ratio turbofan engines are evaluated. Wave rotor performance levels are calculated using a one-dimensional design/analysis code. Baseline and wave rotor-enhanced engine performance levels are obtained from a cycle deck in which the wave rotor is represented as a burner with pressure gain. Wave rotor-toppings is shown to significantly enhance the specific fuel consumption and specific power of small and intermediate size turboshaft engines. The specific fuel consumption of the wave rotor-enhanced large turbofan engine can be reduced while operating at significantly reduced turbine inlet temperature. The wave rotor-enhanced engine is shown to behave off-design like a conventional engine. Discussion concerning the impact of the wave rotor/gas turbine engine integration identifies tenable technical challenges.

  16. Computerized Analysis Of Helicopter-Rotor Aeroelasticity

    NASA Technical Reports Server (NTRS)

    Reddy, T. S. R.

    1988-01-01

    Analysis of aeroelastic stability of helicopter rotor automated. Symbolic-manipulation program, HESL, written in FORTRAN, used to aid in derivation of government equations of motion for elastic-bladed rotor. Operates both on expressions and matrices. By transferring some burden of algebraic manipulations from human analyst to computer, program reduces tedium analysis and conequent opportunity for errors.

  17. Rotor systems research aircraft simulation mathematical model

    NASA Technical Reports Server (NTRS)

    Houck, J. A.; Moore, F. L.; Howlett, J. J.; Pollock, K. S.; Browne, M. M.

    1977-01-01

    An analytical model developed for evaluating and verifying advanced rotor concepts is discussed. The model was used during in both open loop and real time man-in-the-loop simulation during the rotor systems research aircraft design. Future applications include: pilot training, preflight of test programs, and the evaluation of promising concepts before their implementation on the flight vehicle.

  18. An unsteady helicopter rotor: Fuselage interaction analysis

    NASA Technical Reports Server (NTRS)

    Lorber, Peter F.; Egolf, T. Alan

    1988-01-01

    A computational method was developed to treat unsteady aerodynamic interactions between a helicopter rotor, wake, and fuselage and between the main and tail rotors. An existing lifting line prescribed wake rotor analysis and a source panel fuselage analysis were coupled and modified to predict unsteady fuselage surface pressures and airloads. A prescribed displacement technique is used to position the rotor wake about the fuselage. Either a rigid blade or an aeroelastic blade analysis may be used to establish rotor operating conditions. Sensitivity studies were performed to determine the influence of the wake fuselage geometry on the computation. Results are presented that describe the induced velocities, pressures, and airloads on the fuselage and on the rotor. The ability to treat arbitrary geometries is demonstrated using a simulated helicopter fuselage. The computational results are compared with fuselage surface pressure measurements at several locations. No experimental data was available to validate the primary product of the analysis: the vibratory airloads on the entire fuselage. A main rotor-tail rotor interaction analysis is also described, along with some hover and forward flight.

  19. Radial-radial single rotor turbine

    SciTech Connect

    Platts, David A.

    2006-05-16

    A rotor for use in turbine applications has a radial compressor/pump having radially disposed spaced apart fins forming passages and a radial turbine having hollow turbine blades interleaved with the fins and through which fluid from the radial compressor/pump flows. The rotor can, in some applications, be used to produce electrical power.

  20. Computational Analysis of Multi-Rotor Flows

    NASA Technical Reports Server (NTRS)

    Yoon, Seokkwan; Lee, Henry C.; Pulliam, Thomas H.

    2016-01-01

    Interactional aerodynamics of multi-rotor flows has been studied for a quadcopter representing a generic quad tilt-rotor aircraft in hover. The objective of the present study is to investigate the effects of the separation distances between rotors, and also fuselage and wings on the performance and efficiency of multirotor systems. Three-dimensional unsteady Navier-Stokes equations are solved using a spatially 5th order accurate scheme, dual-time stepping, and the Detached Eddy Simulation turbulence model. The results show that the separation distances as well as the wings have significant effects on the vertical forces of quadroror systems in hover. Understanding interactions in multi-rotor flows would help improve the design of next generation multi-rotor drones.

  1. A CFD study of tilt rotor flowfields

    NASA Technical Reports Server (NTRS)

    Fejtek, Ian; Roberts, Leonard

    1989-01-01

    The download on the wing produced by the rotor wake of a tilt rotor vehicle in hover is of major concern because of its severe impact on payload-carrying capability. In a concerted effort to understand the fundamental fluid dynamics that cause this download, and to help find ways to reduce it, computational fluid dynamics (CFD) is employed to study this problem. The thin-layer Navier-Stokes equations are used to describe the flow, and an implicit, finite difference numerical algorithm is the method of solution. The methodology is developed to analyze the tilt rotor flowfield. Included are discussions of computations of an airfoil and wing in freestream flows at -90 degrees, a rotor alone, and wing/rotor interaction in two and three dimensions. Preliminary results demonstrate the feasibility and great potential of the present approach. Recommendations are made for both near-term and far-term improvements to the method.

  2. Substantially parallel flux uncluttered rotor machines

    SciTech Connect

    Hsu, John S.

    2012-12-11

    A permanent magnet-less and brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by polyphase alternating currents. An uncluttered rotor is positioned within the magnetic rotating field and is spaced apart from the stator. An excitation core is spaced apart from the stator and the uncluttered rotor and magnetically couples the uncluttered rotor. The brushless excitation source generates a magnet torque by inducing magnetic poles near an outer peripheral surface of the uncluttered rotor, and the stator currents also generate a reluctance torque by a reaction of the difference between the direct and quadrature magnetic paths of the uncluttered rotor. The system can be used either as a motor or a generator

  3. Open Rotor - Analysis of Diagnostic Data

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    2011-01-01

    NASA is researching open rotor propulsion as part of its technology research and development plan for addressing the subsonic transport aircraft noise, emission and fuel burn goals. The low-speed wind tunnel test for investigating the aerodynamic and acoustic performance of a benchmark blade set at the approach and takeoff conditions has recently concluded. A high-speed wind tunnel diagnostic test campaign has begun to investigate the performance of this benchmark open rotor blade set at the cruise condition. Databases from both speed regimes will comprise a comprehensive collection of benchmark open rotor data for use in assessing/validating aerodynamic and noise prediction tools (component & system level) as well as providing insights into the physics of open rotors to help guide the development of quieter open rotors.

  4. Vibration control of rotor shaft

    NASA Technical Reports Server (NTRS)

    Nonami, K.

    1985-01-01

    Suppression of flexural forced vibration or the self-excited vibration of a rotating shaft system not by passive elements but by active elements is described. The distinctive feature of this method is not to dissipate the vibration energy but to provide the force cancelling the vibration displacement and the vibration velocity through the bearing housing in rotation. Therefore the bearings of this kind are appropriately named Active Control Bearings. A simple rotor system having one disk at the center of the span on flexible supports is investigated in this paper. The actuators of the electrodynamic transducer are inserted in the sections of the bearing housing. First, applying the optimal regulator of optimal control theory, the flexural vibration control of the rotating shaft and the vibration control of support systems are performed by the optimal state feedback system using these actuators. Next, the quasi-modal control based on a modal analysis is applied to this rotor system. This quasi-modal control system is constructed by means of optimal velocity feedback loops. The differences between optimal control and quasi-modal control are discussed and their merits and demerits are made clear. Finally, the experiments are described concerning only the optimal regulator method.

  5. Characterization of Fourier domain mode-locked wavelength swept laser for optical coherence tomography imaging.

    PubMed

    Jeon, Min Yong; Zhang, Jun; Chen, Zhongping

    2008-03-17

    We present characteristics of a wavelength swept laser with a scanning fiber Fabry-Perot filter at 1300 nm. We investigate the dependence of the scanning frequencies in the swept laser. In conventional wavelength swept lasers, the relative intensity of the laser output decreases significantly as the scanning frequency increases. The peak wavelength of the output spectrum is red-shifted due to the nonlinear frequency downshifting in the semiconductor optical amplifier (SOA). In the Fourier domain mode-locked (FDML) wavelength swept laser, we investigate transient intensity profiles and the full width at half maximum in response to the injection currents and detuning of the scanning frequency. The degradation of the scanning range of the swept laser is caused by the deviation from the scanning frequency at 45.6 kHz. In addition, transient intensity profiles show significant asymmetric behavior in response to the detuned frequencies. Finally, the axial resolution and sensitivity as a function of imaging depth are analyzed for both forward and backward scans. With the FDML laser, the detection sensitivity up to 102 dB is achieved for the backward scans. The backward scans exhibit higher axial resolution and sensitivity than the forward scan.

  6. Forward-swept wing configuration designed for high maneuverability by use of a transonic computational method

    NASA Technical Reports Server (NTRS)

    Mann, M. J.; Mercer, C. E.

    1986-01-01

    A transonic computational analysis method and a transonic design procedure have been used to design the wing and the canard of a forward-swept-wing fighter configuration for good transonic maneuver performance. A model of this configuration was tested in the Langley 16-Foot Transonic Tunnel. Oil-flow photographs were obtained to examine the wind flow patterns at Mach numbers from 0.60 to 0.90. The transonic theory gave a reasonably good estimate of the wing pressure distributions at transonic maneuver conditions. Comparison of the forward-swept-wing configuration with an equivalent aft-swept-wing-configuration showed that, at a Mach number of 0.90 and a lift coefficient of 0.9, the two configurations have the same trimmed drag. The forward-swept wing configuration was also found to have trimmed drag levels at transonic maneuver conditions which are comparable to those of the HiMAT (highly maneuverable aircraft technology) configuration and the X-29 forward-swept-wing research configuration. The configuration of this study was also tested with a forebody strake.

  7. Associated factors for visibility and width of retrobulbar subarachnoid space on swept-source optical coherence tomography in high myopia

    PubMed Central

    Fan, Hua; Ma, Hongjie; Gao, Rulong; Ng, Danny Siu-Chun; Cheung, Carol Y.; Li, Shuangnong; Wu, Dezheng; Tang, Shibo

    2016-01-01

    Subarachnoid space (SAS) around optic nerve can be visible with swept-source optical coherence tomography (SS-OCT). However, the relevant factors for its visibility and width have not been reported. In this prospective study, 193 eyes with high myopia were evaluated by SS-OCT. The relationship between age, gender, axial length, optic disc area, parapapillary atrophy (PPA) area, peripapillary choroidal thickness with the visibility and width of SAS were assessed. The results showed that SAS was observed in 125 (64.8%) and not observed in 68 (35.2%) eyes. Visibility of SAS is associated with long axial length, high myopia, thin choroid, large PPA and large optic disc areas. Among these associations, PPA area was the only independent factor (b = 0.177, p < 0.001). The width of SAS was associated with thin choroid, long axial length, large optic disc area and large PPA area. Multivariant analysis showed that optic disc area and PPA area were independent factors for the width of SAS (b = 30.8, p = 0.016 and 16.2, p < 0.001 respectively). These results suggested that SAS was extended into the peripapillary region possibly due to extension of posterior sclera in high myopia. PMID:27827444

  8. Exhaust Plume Effects on Sonic Boom for a Delta Wing and a Swept Wing-Body Model

    NASA Technical Reports Server (NTRS)

    Castner, Raymond; Lake, Troy

    2012-01-01

    Supersonic travel is not allowed over populated areas due to the disturbance caused by the sonic boom. Research has been performed on sonic boom reduction and has included the contribution of the exhaust nozzle plume. Plume effect on sonic boom has progressed from the study of isolated nozzles to a study with four exhaust plumes integrated with a wing-body vehicle. This report provides a baseline analysis of the generic wing-body vehicle to demonstrate the effect of the nozzle exhaust on the near-field pressure profile. Reductions occurred in the peak-to-peak magnitude of the pressure profile for a swept wing-body vehicle. The exhaust plumes also had a favorable effect as the nozzles were moved outward along the wing-span.

  9. Experimental Investigation of Ice Accretion Effects on a Swept Wing

    NASA Technical Reports Server (NTRS)

    Papadakis, M.; Yeong, H. W.; Wong, S. C.; Vargas, M.; Potapczuk, M.

    2005-01-01

    An experimental investigation was conducted to study the effects of 2-, 5-, 10-, and 22.5-min ice accretions on the aerodynamic performance of a swept finite wing. The ice shapes tested included castings of ice accretions obtained from icing tests at the NASA Glenn Icing Research Tunnel (IRT) and simulated ice shapes obtained with the LEWICE 2.0 ice accretion code. The conditions used for the icing tests were selected to provide five glaze ice shapes with complete and incomplete scallop features and a small rime ice shape. The LEWICE ice shapes were defined for the same conditions as those used in the icing tests. All aerodynamic performance tests were conducted in the 7- x 10-ft Low-Speed Wind Tunnel Facility at Wichita State University. Six component force and moment measurements, aileron hinge moments, and surface pressures were obtained for a Reynolds number of 1.8 million based on mean aerodynamic chord and aileron deflections in the range of -15o to 20o. Tests were performed with the clean wing, six IRT ice shape castings, seven smooth LEWICE ice shapes, and seven rough LEWICE ice shapes. Roughness for the LEWICE ice shapes was simulated with 36-size grit. The experiments conducted showed that the glaze ice castings reduced the maximum lift coefficient of the clean wing by 11.5% to 93.6%, while the 5-min rime ice casting increased maximum lift by 3.4%. Minimum iced wing drag was 133% to 3533% greater with respect to the clean case. The drag of the iced wing near the clean wing stall angle of attack was 17% to 104% higher than that of the clean case. In general, the aileron remained effective in changing the lift of the clean and iced wings for all angles of attack and aileron deflections tested. Aileron hinge moments for the iced wing cases remained within the maximum and minimum limits defined by the clean wing hinge moments. Tests conducted with the LEWICE ice shapes showed that in general the trends in aerodynamic performance degradation of the wing with

  10. Structure Identification Within a Transitioning Swept-Wing Boundary Layer

    NASA Technical Reports Server (NTRS)

    Chapman, Keith; Glauser, Mark

    1996-01-01

    Extensive measurements are made in a transitioning swept-wing boundary layer using hot-film, hot-wire and cross-wire anemometry. The crossflow-dominated flow contains stationary vortices that breakdown near mid-chord. The most amplified vortex wavelength is forced by the use of artificial roughness elements near the leading edge. Two-component velocity and spanwise surface shear-stress correlation measurements are made at two constant chord locations, before and after transition. Streamwise surface shear stresses are also measured through the entire transition region. Correlation techniques are used to identify stationary structures in the laminar regime and coherent structures in the turbulent regime. Basic techniques include observation of the spatial correlations and the spatially distributed auto-spectra. The primary and secondary instability mechanisms are identified in the spectra in all measured fields. The primary mechanism is seen to grow, cause transition and produce large-scale turbulence. The secondary mechanism grows through the entire transition region and produces the small-scale turbulence. Advanced techniques use Linear Stochastic Estimation (LSE) and Proper Orthogonal Decomposition (POD) to identify the spatio-temporal evolutions of structures in the boundary layer. LSE is used to estimate the instantaneous velocity fields using temporal data from just two spatial locations and the spatial correlations. Reference locations are selected using maximum RMS values to provide the best available estimates. POD is used to objectively determine modes characteristic of the measured flow based on energy. The stationary vortices are identified in the first laminar modes of each velocity component and shear component. Experimental evidence suggests that neighboring vortices interact and produce large coherent structures with spanwise periodicity at double the stationary vortex wavelength. An objective transition region detection method is developed using

  11. Initial Assessment of Open Rotor Propulsion Applied to an Advanced Single-Aisle Aircraft

    NASA Technical Reports Server (NTRS)

    Guynn, Mark D.; Berton, Jeffrey J.; Hendricks, Eric S.; Tong, Michael T.; Haller, William J.; Thurman, Douglas R.

    2011-01-01

    Application of high speed, advanced turboprops, or propfans, to subsonic transport aircraft received significant attention and research in the 1970s and 1980s when fuel efficiency was the driving focus of aeronautical research. Recent volatility in fuel prices and concern for aviation s environmental impact have renewed interest in unducted, open rotor propulsion, and revived research by NASA and a number of engine manufacturers. Unfortunately, in the two decades that have passed since open rotor concepts were thoroughly investigated, NASA has lost experience and expertise in this technology area. This paper describes initial efforts to re-establish NASA s capability to assess aircraft designs with open rotor propulsion. Specifically, methodologies for aircraft-level sizing, performance analysis, and system-level noise analysis are described. Propulsion modeling techniques have been described in a previous paper. Initial results from application of these methods to an advanced single-aisle aircraft using open rotor engines based on historical blade designs are presented. These results indicate open rotor engines have the potential to provide large reductions in fuel consumption and emissions. Initial noise analysis indicates that current noise regulations can be met with old blade designs and modern, noiseoptimized blade designs are expected to result in even lower noise levels. Although an initial capability has been established and initial results obtained, additional development work is necessary to make NASA s open rotor system analysis capability on par with existing turbofan analysis capabilities.

  12. 14 CFR 27.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Equipment containing high energy rotors. 27... Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must be able to...

  13. 14 CFR 29.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Equipment containing high energy rotors. 29... § 29.1461 Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must...

  14. 14 CFR 25.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Equipment containing high energy rotors. 25... § 25.1461 Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must...

  15. 14 CFR 25.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Equipment containing high energy rotors. 25... § 25.1461 Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must...

  16. 14 CFR 27.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Equipment containing high energy rotors. 27... Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must be able to...

  17. 14 CFR 29.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Equipment containing high energy rotors. 29... § 29.1461 Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must...

  18. 14 CFR 27.547 - Main rotor structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... structure. (a) Each main rotor assembly (including rotor hubs and blades) must be designed as prescribed in this section. (b) (c) The main rotor structure must be designed to withstand the following loads... altitude. (d) The main rotor structure must be designed to withstand loads simulating— (1) For the...

  19. 14 CFR 29.661 - Rotor blade clearance.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure to... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Rotor blade clearance. 29.661 Section...

  20. 14 CFR 27.661 - Rotor blade clearance.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure to... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Rotor blade clearance. 27.661 Section...

  1. 14 CFR 29.661 - Rotor blade clearance.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure to... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Rotor blade clearance. 29.661 Section...

  2. 14 CFR 29.661 - Rotor blade clearance.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure to... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Rotor blade clearance. 29.661 Section...

  3. 14 CFR 29.547 - Main and tail rotor structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... autorotation. (d) The rotor structure must be designed to withstand loads simulating— (1) For the rotor blades... includes the rotor hub, blades, blade dampers, the pitch control mechanisms, and all other parts that rotate with the assembly. (b) Each rotor assembly must be designed as prescribed in this section and...

  4. 14 CFR 27.661 - Rotor blade clearance.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure to... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Rotor blade clearance. 27.661 Section...

  5. 14 CFR 27.547 - Main rotor structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... structure. (a) Each main rotor assembly (including rotor hubs and blades) must be designed as prescribed in this section. (b) (c) The main rotor structure must be designed to withstand the following loads... altitude. (d) The main rotor structure must be designed to withstand loads simulating— (1) For the...

  6. 14 CFR 27.661 - Rotor blade clearance.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure to... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor blade clearance. 27.661 Section...

  7. 14 CFR 29.547 - Main and tail rotor structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... autorotation. (d) The rotor structure must be designed to withstand loads simulating— (1) For the rotor blades... includes the rotor hub, blades, blade dampers, the pitch control mechanisms, and all other parts that rotate with the assembly. (b) Each rotor assembly must be designed as prescribed in this section and...

  8. 14 CFR 29.547 - Main and tail rotor structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... autorotation. (d) The rotor structure must be designed to withstand loads simulating— (1) For the rotor blades... includes the rotor hub, blades, blade dampers, the pitch control mechanisms, and all other parts that rotate with the assembly. (b) Each rotor assembly must be designed as prescribed in this section and...

  9. 14 CFR 29.547 - Main and tail rotor structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... autorotation. (d) The rotor structure must be designed to withstand loads simulating— (1) For the rotor blades... includes the rotor hub, blades, blade dampers, the pitch control mechanisms, and all other parts that rotate with the assembly. (b) Each rotor assembly must be designed as prescribed in this section and...

  10. 14 CFR 27.547 - Main rotor structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... structure. (a) Each main rotor assembly (including rotor hubs and blades) must be designed as prescribed in this section. (b) (c) The main rotor structure must be designed to withstand the following loads... altitude. (d) The main rotor structure must be designed to withstand loads simulating— (1) For the...

  11. 14 CFR 27.661 - Rotor blade clearance.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure to... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Rotor blade clearance. 27.661 Section...

  12. 14 CFR 29.547 - Main and tail rotor structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... autorotation. (d) The rotor structure must be designed to withstand loads simulating— (1) For the rotor blades... includes the rotor hub, blades, blade dampers, the pitch control mechanisms, and all other parts that rotate with the assembly. (b) Each rotor assembly must be designed as prescribed in this section and...

  13. 14 CFR 29.661 - Rotor blade clearance.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure to... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor blade clearance. 29.661 Section...

  14. 14 CFR 27.547 - Main rotor structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... structure. (a) Each main rotor assembly (including rotor hubs and blades) must be designed as prescribed in this section. (b) (c) The main rotor structure must be designed to withstand the following loads... altitude. (d) The main rotor structure must be designed to withstand loads simulating— (1) For the...

  15. 14 CFR 29.661 - Rotor blade clearance.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure to... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Rotor blade clearance. 29.661 Section...

  16. 14 CFR 27.661 - Rotor blade clearance.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure to... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Rotor blade clearance. 27.661 Section...

  17. 14 CFR 27.547 - Main rotor structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... structure. (a) Each main rotor assembly (including rotor hubs and blades) must be designed as prescribed in this section. (b) (c) The main rotor structure must be designed to withstand the following loads... altitude. (d) The main rotor structure must be designed to withstand loads simulating— (1) For the...

  18. 14 CFR 29.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Equipment containing high energy rotors. 29... § 29.1461 Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must...

  19. 14 CFR 25.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Equipment containing high energy rotors. 25... § 25.1461 Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must...

  20. 14 CFR 27.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Equipment containing high energy rotors. 27... Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must be able to...

  1. 14 CFR 29.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Equipment containing high energy rotors. 29... § 29.1461 Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must...

  2. 14 CFR 27.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Equipment containing high energy rotors. 27... Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must be able to...

  3. 14 CFR 25.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Equipment containing high energy rotors. 25... § 25.1461 Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must...

  4. 14 CFR 25.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Equipment containing high energy rotors. 25... § 25.1461 Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must...

  5. 14 CFR 27.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Equipment containing high energy rotors. 27... Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must be able to...

  6. 14 CFR 29.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Equipment containing high energy rotors. 29... § 29.1461 Equipment containing high energy rotors. (a) Equipment containing high energy rotors must meet paragraph (b), (c), or (d) of this section. (b) High energy rotors contained in equipment must...

  7. Flow Visualizations and Extended Thrust Time Histories of Rotor Vortex Wakes in Descent

    NASA Astrophysics Data System (ADS)

    Stack, James; Caradonna, Frank; Savas, Omer

    2003-11-01

    An experimental study is performed on a three-bladed rotor model in a water tow tank. The blade pitch and rotational velocity, the rotor plane angle of attack (descent angle), and the carriage speed are all varied in order to simulate a wide range of rotorcraft operating states, with the focus being on descent speeds and angles where the rotor is operating in or near vortex ring state an area in which there is currently very little available data. Circulation and blade Reynolds numbers are of order 10^5. Flow visualization is done by injecting air bubbles and fluorescent dye tangentially from the blade tips to mark the vortex core, showing the development of both short-wave (sinuous) and long-wave (leapfrogging) instabilities on the helical vortices in the wake. Strain gages are used to record transient loads, allowing a correlation between the rotor thrust performance and the development of the vortex wake. Test runs are performed for extended periods up to 500 rotor revolutions demonstrating the repeatability of the patterns of thrust variation. The data indicate that as the instabilities develop, adjacent vortices merge and form thick vortex rings, especially during descent. Periodic shedding of these rings from the wake associated with vortex ring state is observed, resulting in peak-to-peak thrust fluctuations of up to 95% of the mean and occurring at regular intervals of 2050 rotor revolutions, depending on flow parameters. Preliminary particle image velocimetry (PIV) data provide a quantitative measure of the entire rotor flow field for the case of a hovering rotor. The data yield additional information on the vortex filament instability, in particular the axial flow in the vortex cores.

  8. Full-Field Optical Coherence Tomography Using Galvo Filter-Based Wavelength Swept Laser

    PubMed Central

    Shirazi, Muhammad Faizan; Kim, Pilun; Jeon, Mansik; Kim, Jeehyun

    2016-01-01

    We report a wavelength swept laser-based full-field optical coherence tomography for measuring the surfaces and thicknesses of refractive and reflective samples. The system consists of a galvo filter–based wavelength swept laser and a simple Michelson interferometer. Combinations of the reflective and refractive samples are used to demonstrate the performance of the system. By synchronizing the camera with the source, the cross-sectional information of the samples can be seen after each sweep of the swept source. This system can be effective for the thickness measurement of optical thin films as well as for the depth investigation of samples in industrial applications. A resolution target with a glass cover slip and a step height standard target are imaged, showing the cross-sectional and topographical information of the samples. PMID:27869659

  9. Acousto-Optic-Based Wavelength-Comb-Swept Laser for Extended Displacement Measurements.

    PubMed

    Park, Nam Su; Chun, Soo Kyung; Han, Ga-Hee; Kim, Chang-Seok

    2017-03-31

    We demonstrate a novel wavelength-comb-swept laser based on two intra-cavity filters: an acousto-optic tunable filter (AOTF) and a Fabry-Pérot etalon filter. The AOTF is used for the tunable selection of the output wavelength with time and the etalon filter for the narrowing of the spectral linewidth to extend the coherence length. Compared to the conventional wavelength-swept laser, the acousto-optic-based wavelength-comb-swept laser (WCSL) can extend the measureable range of displacement measurements by decreasing the sensitivity roll-off of the point spread function. Because the AOTF contains no mechanical moving parts to select the output wavelength acousto-optically, the WCSL source has a high wavenumber (k) linearity of R² = 0.9999 to ensure equally spaced wavelength combs in the wavenumber domain.

  10. Numerical Analysis of Incipient Separation on 53 Deg Swept Diamond Wing

    NASA Technical Reports Server (NTRS)

    Frink, Neal T.

    2015-01-01

    A systematic analysis of incipient separation and subsequent vortex formation from moderately swept blunt leading edges is presented for a 53 deg swept diamond wing. This work contributes to a collective body of knowledge generated within the NATO/STO AVT-183 Task Group titled 'Reliable Prediction of Separated Flow Onset and Progression for Air and Sea Vehicles'. The objective is to extract insights from the experimentally measured and numerically computed flow fields that might enable turbulence experts to further improve their models for predicting swept blunt leading-edge flow separation. Details of vortex formation are inferred from numerical solutions after establishing a good correlation of the global flow field and surface pressure distributions between wind tunnel measurements and computed flow solutions. From this, significant and sometimes surprising insights into the nature of incipient separation and part-span vortex formation are derived from the wealth of information available in the computational solutions.

  11. Chromatic polarization effects of swept waveforms in FDML lasers and fiber spools.

    PubMed

    Wieser, Wolfgang; Palte, Gesa; Eigenwillig, Christoph M; Biedermann, Benjamin R; Pfeiffer, Tom; Huber, Robert

    2012-04-23

    We present detailed investigations of chromatic polarization effects, caused by fiber spools used in FDML lasers and buffering spools for rapidly wavelength swept lasers. We introduce a novel wavelength swept FDML laser source, specially tailored for polarization sensitive optical coherence tomography (OCT) which switches between two different linear polarization states separated by 45°, i.e. 90° on the Poincaré sphere. The polarization maintaining laser cavity itself generates a stable linear polarization state and uses an external buffering technique in order to provide alternating polarization states for successive wavelength sweeps. The design of the setup is based on a comprehensive analysis of the polarization output from FDML lasers, using a novel 150 MHz polarization analyzer. We investigate the fiber polarization properties related to swept source OCT for different fiber delay topologies and analyze the polarization state of different FDML laser sources.

  12. Characteristics of wind power on Savonius rotor using a guide-box tunnel

    SciTech Connect

    Irabu, Kunio; Roy, Jitendro Nath

    2007-11-15

    This study investigates to improve and adjust the output power of Savonius rotor under various wind power and suggests the method of prevention the rotor from strong wind disaster. In this study, as the appropriate device to achieve the purpose of it, a guide-box tunnel is employed. The guide-box tunnel is like a rectangular box as wind passage in which a test rotor is included. The area ratio between the inlet and exit of it is variable to adjust the inlet mass flow rate or input power. At first, the experiment was conducted to find the adequate configuration which would provide the best relative performance. The present experiment, however, does not include the test to retain the guide-box tunnel from the strong wind. The experiments include the static torque test of the fixed rotor at any phase angle and the dynamic torque test at rotation of them. Consequently, it was found that the maximum rotor rotational speed was achieved in the range of the guide-box area ratio between 0.3 and 0.7 and the value of the output power coefficient of the rotor with guide-box tunnel of the area ratio 0.43 increases about 1.5 times with three blades and 1.23 times with two blades greater than that without guide-box tunnel, respectively. It seemed that the performance of Savonius rotor within the guide-box tunnel is comparable enough with other methods for augmentation and control of the output. (author)

  13. Multiple piece turbine rotor blade

    SciTech Connect

    Kimmel, Keith D.; Plank, William L.

    2016-07-19

    A spar and shell turbine rotor blade with a spar and a tip cap formed as a single piece, the spar includes a bottom end with dovetail or fir tree slots that engage with slots on a top end of a root section, and a platform includes an opening on a top surface for insertion of the spar in which a shell made from an exotic high temperature resistant material is secured between the tip cap and the platform. The spar is tapered to form thinner walls at the tip end to further reduce the weight and therefore a pulling force due to blade rotation. The spar and tip cap piece is made from a NiAL material to further reduce the weight and the pulling force.

  14. Hydraulic Actuator System for Rotor Control

    NASA Technical Reports Server (NTRS)

    Ulbrich, Heinz; Althaus, Josef

    1991-01-01

    In the last ten years, several different types of actuators were developed and fabricated for active control of rotors. A special hydraulic actuator system capable of generating high forces to rotating shafts via conventional bearings is addressed. The actively controlled hydraulic force actuator features an electrohydraulic servo valve which can produce amplitudes and forces at high frequencies necessary for influencing rotor vibrations. The mathematical description will be given in detail. The experimental results verify the theoretical model. Simulations already indicate the usefulness of this compact device for application to a real rotor system.

  15. Internal Friction And Instabilities Of Rotors

    NASA Technical Reports Server (NTRS)

    Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.

    1992-01-01

    Report describes study of effects of internal friction on dynamics of rotors prompted by concern over instabilities in rotors of turbomachines. Theoretical and experimental studies described. Theoretical involved development of nonlinear mathematical models of internal friction in three joints found in turbomachinery - axial splines, Curvic(TM) splines, and interference fits between smooth cylindrical surfaces. Experimental included traction tests to determine the coefficients of friction of rotor alloys at various temperatures, bending-mode-vibration tests of shafts equipped with various joints and rotordynamic tests of shafts with axial-spline and interference-fit joints.

  16. Helicopter rotor induced velocities theory and experiment

    NASA Technical Reports Server (NTRS)

    Berry, John D.; Hoad, Danny R.; Elliott, Joe W.; Althoff, Susan L.

    1987-01-01

    An investigation has been performed to assess methods used for rotor inflow modeling. A key element of this assessment has been the recent acquisition of high quality experimental measurements of inflow velocities taken in the proximity of a lifting rotor in forward flight. Widely used rotor performance predictive methods are based on blade element strip theory coupled with an inflow model. The inflow prediction models assessed in this paper include the uniform inflow based on momentum, a skewed disk model, and two methods based on a vortex wake structure.

  17. Vacuum coupling of rotating superconducting rotor

    DOEpatents

    Shoykhet, Boris A.; Zhang, Burt Xudong; Driscoll, David Infante

    2003-12-02

    A rotating coupling allows a vacuum chamber in the rotor of a superconducting electric motor to be continually pumped out. The coupling consists of at least two concentric portions, one of which is allowed to rotate and the other of which is stationary. The coupling is located on the non-drive end of the rotor and is connected to a coolant supply and a vacuum pump. The coupling is smaller in diameter than the shaft of the rotor so that the shaft can be increased in diameter without having to increase the size of the vacuum seal.

  18. Discrete analog computing with rotor-routers.

    PubMed

    Propp, James

    2010-09-01

    Rotor-routing is a procedure for routing tokens through a network that can implement certain kinds of computation. These computations are inherently asynchronous (the order in which tokens are routed makes no difference) and distributed (information is spread throughout the system). It is also possible to efficiently check that a computation has been carried out correctly in less time than the computation itself required, provided one has a certificate that can itself be computed by the rotor-router network. Rotor-router networks can be viewed as both discrete analogs of continuous linear systems and deterministic analogs of stochastic processes.

  19. Molecular Rotors Built in Porous Materials.

    PubMed

    Comotti, Angiolina; Bracco, Silvia; Sozzani, Piero

    2016-09-20

    Molecules and materials can show dynamic structures in which the dominant mechanism is rotary motion. The single mobile elements are defined as "molecular rotors" and exhibit special properties (compared with their static counterparts), being able in perspective to greatly modulate the dielectric response and form the basis for molecular motors that are designed with the idea of making molecules perform a useful mechanical function. The construction of ordered rotary elements into a solid is a necessary feature for such design, because it enables the alignment of rotors and the fine-tuning of their steric and dipolar interactions. Crystal surfaces or bulk crystals are the most suitable to adapt rotors in 2D or 3D arrangements and engineer juxtaposition of the rotors in an ordered way. Nevertheless, it is only in recent times that materials showing porosity and remarkably low density have undergone tremendous development. The characteristics of large free volume combine well with the virtually unhindered motion of the molecular rotors built into their structure. Indeed, the molecular rotors are used as struts in porous covalent and supramolecular architectures, spanning both hybrid and fully organic materials. The modularity of the approach renders possible a variety of rotor geometrical arrangements in both robust frameworks stable up to 850 K and self-assembled molecular materials. A nanosecond (fast dynamics) motional regime can be achieved at temperatures lower than 240 K, enabling rotor arrays operating in the solid state even at low temperatures. Furthermore, in nanoporous materials, molecular rotors can interact with the diffusing chemical species, be they liquids, vapors, or gases. Through this chemical intervention, rotor speed can be modulated at will, enabling a new generation of rotor-containing materials sensitive to guests. In principle, an applied electric field can be the stimulus for chemical release from porous materials. The effort needed to

  20. AC conductivity of a niobium thin film in a swept magnetic field.

    PubMed

    Tsindlekht, M I; Genkin, V M; Gazi, S; Chromik, S

    2013-02-27

    We report results of measurements of the ac conductivity of a Nb superconducting thin film in a swept dc magnetic field. In the mixed state the swept dc field creates vortices at the film surface which pass through the film and form the observed ac conductivity. Vortex rate generation does not depend on the value of the dc field and there is a large plateau-like region of dc magnetic fields where the dissipation is approximately constant. A proposed phenomenological model describes quite well the main features of the ac response in these fields, including its dependency on the sweep rate, ac amplitude, frequency, and value of the second and third harmonics.

  1. Experimental transition and boundary-layer stability analysis for a slotted swept laminar flow control airfoil

    NASA Technical Reports Server (NTRS)

    Harvey, William D.; Harris, Charles D.; Brooks, Cuyler W., Jr.

    1989-01-01

    A swept, supercritical laminar flow control (LFC) airfoil designated NASA SCLFC(1)-0513F was tested at subsonic and transonic speeds in the NASA Langley eight-foot Transonic Pressure Tunnel. This paper examines Tollmien-Schlichting and crossflow disturbance amplification for this airfoil using the linear stability method. The design methodology using linear stability analysis is evaluated and the results of the incompressible and compressible methods are compared. Experimental data on the swept, supercritical LFC airfoil and reference wind tunnel and flight results are used to correlate and evaluate the N-factor method for transition prediction over a speed range M(infinity) from zero to one.

  2. Estimation of elastic parameters of ovarian tissue using phase stabilized swept source optical-coherence tomography

    NASA Astrophysics Data System (ADS)

    Nandy, Sreyankar; Wang, Tianheng; Salehi, Hassan; Sanders, Melinda; Brewer, Molly; Zhu, Quing

    2015-03-01

    We have estimated the micro-mechanical properties of ovarian tissue using phase-sensitive swept source optical coherence tomography. Ovary samples were mechanically excited by periodical vibration of an ultrasound transducer. The displacement and strain of the tissues were calculated during loading. Significant difference in strain was observed between the normal and malignant ovary groups, which indicates much softer and heterogeneous tissue structure for malignant ovaries. The initial results show that the phase sensitive swept source optical coherence elastography (OCE) can be an effective tool for characterization of stiffness and other micro-mechanical properties of normal and malignant ovarian tissue.

  3. Electrogasdynamic excitation of controlling disturbances near a swept wing leading edge

    NASA Astrophysics Data System (ADS)

    Chernyshev, Sergey; Kiselev, Andrey; Kuryachii, Aleksandr

    2016-10-01

    New design of multiple plasma actuator intended for the excitation of disturbances in boundary layer near a leading edge of a swept wing is proposed. The excited disturbances have to suppress the cross-flow-type instability modes provoking laminar-to-turbulent transition in usual conditions. Numerical modeling of the excitation of controlling disturbances by plasma actuator has been executed in stationary approximation for the case of infinite span swept wing at subsonic cruise flight conditions. Localized volumetric force and heat impact of actuator periodic along a wing span has been considered. Calculations have been executed for physical parameters of impact typical for surface dielectric barrier discharge.

  4. Precision assessment of biofluid viscosity measurements using molecular rotors.

    PubMed

    Akers, Walter J; Haidekker, Mark A

    2005-06-01

    Blood viscosity changes with many pathologic conditions, but its importance has not been fully investigated because the current methods of measurement are poorly suited for clinical applications. The use of viscosity-sensitive fluorescent molecular rotors to determine fluid viscosity in a nonmechanical manner has been investigated recently, but it is unknown how the precision of the fluorescence-based method compares to established mechanical viscometry. Human blood plasma viscosity was modulated with high-viscosity plasma expanders, dextran, pentastarch, and hetastarch. The samples were divided into a calibration and a test set. The relationship between fluorescence emission and viscosity was established using the calibration set. Viscosity of the test set was determined by fluorescence and by cone-and-plate viscometer, and the precision of both methods compared. Molecular rotor fluorescence intensity showed a power law relationship with solution viscosity. Mechanical measurements deviated from the theoretical viscosity value by less than 7.6%, while fluorescence-based measurements deviated by less than 6%. The average coefficient of variation was 6.9% (mechanical measurement) and 3.4% to 3.8% (fluorescence-based measurement, depending on the molecular rotor used). Fluorescence-based viscometry exhibits comparable precision to mechanical viscometry. Fluorescence viscometry does not apply shear and is therefore more practical for biofluids which have apparent non-Newtonian properties. In addition, fluorescence instrumentation makes very fast serial measurements possible, thus promising new areas of application in laboratory and clinical settings.

  5. Predesign study for a modern 4-bladed rotor for the NASA rotor systems research aircraft

    NASA Technical Reports Server (NTRS)

    Bishop, H. E.; Burkam, J. E.; Heminway, R. C.; Keys, C. N.; Smith, K. E.; Smith, J. H.; Staley, J. A.

    1981-01-01

    Trade-off study results and the rationale for the final selection of an existing modern four-bladed rotor system that can be adapted for installation on the Rotor Systems Research Aircraft (RSRA) are reported. The results of the detailed integration studies, parameter change studies, and instrumentation studies and the recommended plan for development and qualification of the rotor system is also given. Its parameter variants, integration on the RSRA, and support of ground and flight test programs are also discussed.

  6. Full Scale Rotor Aeroacoustic Predictions and the Link to Model Scale Rotor Data

    NASA Technical Reports Server (NTRS)

    Boyd, D. Douglas, Jr.; Burley, Casey L.; Conner, David A.

    2004-01-01

    The NASA Aeroacoustic Prediction System (NAPS) is used to establish a link between model-scale and full-scale rotor predictions and is partially validated against measured wind tunnel and flight aeroacoustic data. The prediction approach of NAPS couples a comprehensive rotorcraft analysis with acoustic source noise and propagation codes. The comprehensive analysis selected for this study is CAMRAD-II, which provides the performance/trim/wake solution for a given rotor or flight condition. The post-trim capabilities of CAMRAD-II are used to compute high-resolution sectional airloads for the acoustic tone noise analysis, WOPMOD. The tone noise is propagated to observers on the ground with the propagation code, RNM (Rotor Noise Model). Aeroacoustic predictions are made with NAPS for an isolated rotor and compared to results of the second Harmonic Aeroacoustic Rotor Test (HART-II) program, which tested a 40% dynamically and Mach-scaled BO-105 main rotor at the DNW. The NAPS is validated with comparisons for three rotor conditions: a baseline condition and two Higher Harmonic Control (HHC) conditions. To establish a link between model and full-scale rotor predictions, a full-scale BO-105 main rotor input deck for NAPS is created from the 40% scale rotor input deck. The full-scale isolated rotor predictions are then compared to the model predictions. The comparisons include aerodynamic loading, acoustic levels, and acoustic pressure time histories for each of the three conditions. With this link established, full-scale predictions are made for a range of descent flight conditions and compared with measured trends from the recent Rotorcraft Operational Noise Abatement Procedures (RONAP) flight test conducted by DLR and ONERA. Additionally, the effectiveness of two HHC conditions from the HART-II program is demonstrated for the full-scale rotor in flight.

  7. Improving the Accuracy of Wind Turbine Power Curve Validation by the Rotor Equivalent Wind Speed Concept

    NASA Astrophysics Data System (ADS)

    Scheurich, Frank; Enevoldsen, Peder B.; Paulsen, Henrik N.; Dickow, Kristoffer K.; Fiedel, Moritz; Loeven, Alex; Antoniou, Ioannis

    2016-09-01

    The measurement of the wind speed at hub height is part of the current IEC standard procedure for the power curve validation of wind turbines. The inherent assumption is thereby made that this measured hub height wind speed sufficiently represents the wind speed across the entire rotor area. It is very questionable, however, whether the hub height wind speed (HHWS) method is appropriate for rotor sizes of commercial state-of-the-art wind turbines. The rotor equivalent wind speed (REWS) concept, in which the wind velocities are measured at several different heights across the rotor area, is deemed to be better suited to represent the wind speed in power curve measurements and thus results in more accurate predictions of the annual energy production (AEP) of the turbine. The present paper compares the estimated AEP, based on HHWS power curves, of two different commercial wind turbines to the AEP that is based on REWS power curves. The REWS was determined by LiDAR measurements of the wind velocities at ten different heights across the rotor area. It is shown that a REWS power curve can, depending on the wind shear profile, result in higher, equal or lower AEP estimations compared to the AEP predicted by a HHWS power curve.

  8. HARP model rotor test at the DNW. [Hughes Advanced Rotor Program

    NASA Technical Reports Server (NTRS)

    Dawson, Seth; Jordan, David; Smith, Charles; Ekins, James; Silverthorn, Lou

    1989-01-01

    Data from a test of a dynamically scaled model of the Hughes Advanced Rotor Program (HARP) bearingless model main rotor and 369K tail rotor are reported. The history of the HARP program and its goals are reviewed, and the main and tail rotor models are described. The test facilities and instrumentation are described, and wind tunnel test data are presented on hover, forward flight performance, and blade-vortex interaction. Performance data, acoustic data, and dynamic data from near field/far field and shear layer studies are presented.

  9. Preliminary simulation of an advanced, hingless rotor XV-15 tilt-rotor aircraft

    NASA Technical Reports Server (NTRS)

    Mcveigh, M. A.

    1976-01-01

    The feasibility of the tilt-rotor concept was verified through investigation of the performance, stability and handling qualities of the XV-15 tilt rotor. The rotors were replaced by advanced-technology fiberglass/composite hingless rotors of larger diameter, combined with an advanced integrated fly-by-wire control system. A parametric simulation model of the HRXV-15 was developed, model was used to define acceptable preliminary ranges of primary and secondary control schedules as functions of the flight parameters, to evaluate performance, flying qualities and structural loads, and to have a Boeing-Vertol pilot conduct a simulated flight test evaluation of the aircraft.

  10. Wind turbine rotor hub and teeter joint

    DOEpatents

    Coleman, Clint; Kurth, William T.; Jankowski, Joseph

    1994-10-11

    A rotor hub is provided for coupling a wind turbine rotor blade and a shaft. The hub has a yoke with a body which is connected to the shaft, and extension portions which are connected to teeter bearing blocks, each of which has an aperture. The blocks are connected to a saddle which envelops the rotor blade by one or two shafts which pass through the apertures in the bearing blocks. The saddle and blade are separated by a rubber interface which provides for distribution of stress over a larger portion of the blade. Two teeter control mechanisms, which may include hydraulic pistons and springs, are connected to the rotor blade and to the yoke at extension portions. These control mechanisms provide end-of-stroke damping, braking, and stiffness based on the teeter angle and speed of the blade.

  11. Interlayer toughening of fiber composite flywheel rotors

    DOEpatents

    Groves, Scott E.; Deteresa, Steven J.

    1998-01-01

    An interlayer toughening mechanism to mitigate the growth of damage in fiber composite flywheel rotors for long application. The interlayer toughening mechanism may comprise one or more tough layers composed of high-elongation fibers, high-strength fibers arranged in a woven pattern at a range from 0.degree. to 90.degree. to the rotor axis and bound by a ductile matrix material which adheres to and is compatible with the materials used for the bulk of the rotor. The number and spacing of the tough interlayers is a function of the design requirements and expected lifetime of the rotor. The mechanism has particular application in uninterruptable power supplies, electrical power grid reservoirs, and compulsators for electric guns, as well as electromechanical batteries for vehicles.

  12. Using molecular rotors to probe gelation.

    PubMed

    Raeburn, Jaclyn; Chen, Lin; Awhida, Salmah; Deller, Robert C; Vatish, Manu; Gibson, Matthew I; Adams, Dave J

    2015-05-14

    A series of fluorescent probes, including a number of molecular rotors, have been used to follow the self-assembly of dipeptide-based low molecular weight gelators. We show that these probes can be used to gain an insight into the assembly process. Thioflavin T, a commonly used stain for β-sheets, appears to act as a molecular rotor in these gelling systems, with the fluorescence data closely matching that of other rotors. The molecular rotor was incorporated into an assay system with glucose oxidase to enable glucose-concentration specific gelation and hence generating a fluorescent output. Applying this system to urine from patients with various levels of glycosuria (a symptom of diabetes), it was found to provide excellent correlation with different clinical assessments of diabetes. This demonstrates a new concept in gelation-linked biosensing for a real clinical problem.

  13. Direct integration of transient rotor dynamics

    NASA Technical Reports Server (NTRS)

    Kascak, A. F.

    1980-01-01

    An implicit method was developed for integrating the equations of motion for a lumped mass model of a rotor dynamics system. As an aside, a closed form solution to the short bearing theory was also developed for a damper with arbitrary motion. The major conclusions are that the method is numerically stable and that the computation time is proportional to the number of elements in the rotor dynamics model rather than to the cube of the number. This computer code allowed the simulation of a complex rotor bearing system experiencing nonlinear transient motion and displayed the vast amount of results in an easily understood motion picture format - a 10 minute, 16 millimeter, color, sound motion picture supplement. An example problem with 19 mass elements in the rotor dynamics model took 0.7 second of central processing unit time per time step on an IBM 360-67 computer in a time sharing mode.

  14. Transonic aeroelasticity analysis for rotor blades

    NASA Technical Reports Server (NTRS)

    Chow, Chuen-Yen; Chang, I-Chung; Gea, Lie-Mine

    1989-01-01

    A numerical method is presented for calculating the unsteady transonic rotor flow with aeroelasticity effects. The blade structural dynamic equations based on beam theory were formulated by FEM and were solved in the time domain, instead of the frequency domain. For different combinations of precone, droop, and pitch, the correlations are very good in the first three flapping modes and the first twisting mode. However, the predicted frequencies are too high for the first lagging mode at high rotational speeds. This new structure code has been coupled into a transonic rotor flow code, TFAR2, to demonstrate the capability of treating elastic blades in transonic rotor flow calculations. The flow fields for a model-scale rotor in both hover and forward flight are calculated. Results show that the blade elasticity significantly affects the flow characteristics in forward flight.

  15. Transonic Aeroelasticity Analysis For Helicopter Rotor Blade

    NASA Technical Reports Server (NTRS)

    Chang, I-Chung; Gea, Lie-Mine; Chow, Chuen-Yen

    1991-01-01

    Numerical-simulation method for aeroelasticity analysis of helicopter rotor blade combines established techniques for analysis of aerodynamics and vibrations of blade. Application of method clearly shows elasticity of blade modifies flow and, consequently, aerodynamic loads on blade.

  16. Interlayer toughening of fiber composite flywheel rotors

    DOEpatents

    Groves, S.E.; Deteresa, S.J.

    1998-07-14

    An interlayer toughening mechanism is described to mitigate the growth of damage in fiber composite flywheel rotors for long application. The interlayer toughening mechanism may comprise one or more tough layers composed of high-elongation fibers, high-strength fibers arranged in a woven pattern at a range from 0{degree} to 90{degree} to the rotor axis and bound by a ductile matrix material which adheres to and is compatible with the materials used for the bulk of the rotor. The number and spacing of the tough interlayers is a function of the design requirements and expected lifetime of the rotor. The mechanism has particular application in uninterruptable power supplies, electrical power grid reservoirs, and compulsators for electric guns, as well as electromechanical batteries for vehicles. 2 figs.

  17. Potential acoustic benefits of circulation control rotors

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Cheeseman, I. C.

    1978-01-01

    The fundamental aeroacoustic mechanisms responsible for noise generation on a rotating blade are theoretically examined. Their contribution to the overall rotor sound pressure level is predicted. Results from a theory for airfoil trailing edge noise are presented. Modifications and extensions to other source theories are described where it is necessary to account for unique aspects of circulation control (CC) aerodynamics. The circulation control rotor (CCR), as embodied on an X-wing vertical takeoff and landing (VTOL) aircraft, is used as an example for computational purposes, although many of the theoretical results presented are generally applicable to other CC applications (such as low speed rotors, propellers, compressors, and fixed wing aircraft). Using the analytical models, it is shown that the utilization CC aerodynamics theoretically makes possible unprecedented advances in rotor noise reduction. For the X-wing VTOL these reductions appear to be feasible without incurring significant attendant performance and weight penalties.

  18. Soil moisture sensing via swept frequency based microwave sensors.

    PubMed

    Pelletier, Mathew G; Karthikeyan, Sundar; Green, Timothy R; Schwartz, Robert C; Wanjura, John D; Holt, Greg A

    2012-01-01

    There is a need for low-cost, high-accuracy measurement of water content in various materials. This study assesses the performance of a new microwave swept frequency domain instrument (SFI) that has promise to provide a low-cost, high-accuracy alternative to the traditional and more expensive time domain reflectometry (TDR). The technique obtains permittivity measurements of soils in the frequency domain utilizing a through transmission configuration, transmissometry, which provides a frequency domain transmissometry measurement (FDT). The measurement is comparable to time domain transmissometry (TDT) with the added advantage of also being able to separately quantify the real and imaginary portions of the complex permittivity so that the measured bulk permittivity is more accurate that the measurement TDR provides where the apparent permittivity is impacted by the signal loss, which can be significant in heavier soils. The experimental SFI was compared with a high-end 12 GHz TDR/TDT system across a range of soils at varying soil water contents and densities. As propagation delay is the fundamental measurement of interest to the well-established TDR or TDT technique; the first set of tests utilized precision propagation delay lines to test the accuracy of the SFI instrument's ability to resolve propagation delays across the expected range of delays that a soil probe would present when subjected to the expected range of soil types and soil moisture typical to an agronomic cropping system. The results of the precision-delay line testing suggests the instrument is capable of predicting propagation delays with a RMSE of +/-105 ps across the range of delays ranging from 0 to 12,000 ps with a coefficient of determination of r(2) = 0.998. The second phase of tests noted the rich history of TDR for prediction of soil moisture and leveraged this history by utilizing TDT measured with a high-end Hewlett Packard TDR/TDT instrument to directly benchmark the SFI instrument over

  19. Diagnosis of Dry Eye by Tear Meniscus Measurements Using Anterior Segment Swept Source Optical Coherence Tomography.

    PubMed

    Akiyama, Reina; Usui, Tomohiko; Yamagami, Satoru

    2015-11-01

    To evaluate the diagnostic power of tear meniscus measurements using anterior segment swept source optical coherence tomography (SS-OCT) for dry eye and suspected dry eye. Fifty subjects (27 men and 23 women; mean age 43.3 ± 13.7 years), comprising 26 eyes of 26 healthy subjects and 24 eyes of 24 patients with dry eye or suspected dry eye according to Japanese diagnostic criteria, were enrolled at The University of Tokyo Graduate School of Medicine. Subjects underwent SS-OCT, and the central upper and lower tear meniscus heights (TMHs) and areas (TMAs) and the lower tear meniscus volume (TMV) were examined. Intergrader variability and interimage variability, calculated using the pooled coefficient of variation and intraclass correlation coefficient, were used to assess repeatability of measurements in the dry eye group. To diagnose dry eye using tear meniscus measurements by SS-OCT, sensitivity, specificity, and cutoff values of optical coherence tomography (OCT) measurements were determined using receiver operating characteristic analysis. The TMH, TMA, and TMV measured by OCT were significantly lower in the dry eye group than in the control group (P < 0.001). Cutoff values of the lower TMH, TMA, and TMV were 191 μm, 12,360 μm, and 0.0473 mm, respectively. Intergrader repeatability and interimage repeatability, measured as the intraclass correlation coefficient, were >80% for all tear meniscus parameters, with acceptable repeatability. Significant correlations between tear meniscus measurements by OCT and vital staining scores, Schirmer test values, and tear film breakup time were observed (P < 0.05). SS-OCT is a noninvasive and practical method for quantitative evaluation of tear fluid and has the potential for detecting dry eye and suspected dry eye.

  20. Bistable devices for morphing rotor blades

    NASA Astrophysics Data System (ADS)

    Johnson, Terrence

    This dissertation presents two bistable concepts for morphing rotor blades. These concepts are simple and are composed of bistable devices that act as coupling structures between an actuator and the rotor blade. Bistable or "snap-through" mechanisms have two stable equilibrium states and are a novel way to achieve large actuation output stroke at relatively modest effort for gross rotor morphing applications. This is because in addition to the large actuation stroke associated with the snap-through (relative to conventional actuator/ amplification systems) coming at relatively low actuation effort, no locking is required in either equilibrium state (since they are both stable). The first concept that is presented in this dissertation is a that is composed of a bistable twisting device that twists the tip of helicopter rotor blades. This work examines the performance of the presented bistable twisting device for rotor morphing, specifically, blade tip twist under an aerodynamic lift load. The device is analyzed using finite element analysis to predict its load carrying capability and bistable behavior. The second concept that is presented is a concept that is composed of a bistable arch for rotor blade chord extension. The bistable arch is coupled to a thin flat plate that is supported by rollers. Increasing the chord of the rotor blade is expected to generate more lift-load and improve helicopter performance. In this work, a methodology is presented to design the bistable arches for chord morphing using the finite element analysis and pseudo-rigid body model method. This work also examines the effect of different arches, arch hinge size and shape, inertial loads and rigidity on arch performance. Finally, this work shows results from an experiment that was conducted to validate the developed numerical model and demonstrates how the arch can be actuated using a Nitinol Shape Memory Alloy (SMA) wire to extend the chord of a helicopter rotor blade.

  1. Tail Rotor Airfoils Stabilize Helicopters, Reduce Noise

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Founded by former Ames Research Center engineer Jim Van Horn, Van Horn Aviation of Tempe, Arizona, built upon a Langley Research Center airfoil design to create a high performance aftermarket tail rotor for the popular Bell 206 helicopter. The highly durable rotor has a lifetime twice that of the original equipment manufacturer blade, reduces noise by 40 percent, and displays enhanced performance at high altitudes. These improvements benefit helicopter performance for law enforcement, military training, wildfire and pipeline patrols, and emergency medical services.

  2. Finite-difference computations of rotor loads

    NASA Technical Reports Server (NTRS)

    Caradonna, F. X.; Tung, C.

    1985-01-01

    The current and future potential of finite difference methods for solving real rotor problems which now rely largely on empiricism are demonstrated. The demonstration consists of a simple means of combining existing finite-difference, integral, and comprehensive loads codes to predict real transonic rotor flows. These computations are performed for hover and high-advanced-ratio flight. Comparisons are made with experimental pressure data.

  3. Finite-difference computations of rotor loads

    NASA Technical Reports Server (NTRS)

    Caradonna, F. X.; Tung, C.

    1985-01-01

    This paper demonstrates the current and future potential of finite-difference methods for solving real rotor problems which now rely largely on empiricism. The demonstration consists of a simple means of combining existing finite-difference, integral, and comprehensive loads codes to predict real transonic rotor flows. These computations are performed for hover and high-advance-ratio flight. Comparisons are made with experimental pressure data.

  4. Spin stabilized magnetic levitation of horizontal rotors.

    SciTech Connect

    Romero, Louis Anthony

    2004-10-01

    In this paper we present an analysis of a new configuration for achieving spin stabilized magnetic levitation. In the classical configuration, the rotor spins about a vertical axis; and the spin stabilizes the lateral instability of the top in the magnetic field. In this new configuration the rotor spins about a horizontal axis; and the spin stabilizes the axial instability of the top in the magnetic field.

  5. Prediction of the Aero-Acoustic Performance of Open Rotors

    NASA Technical Reports Server (NTRS)

    VanZante, Dale; Envia, Edmane

    2014-01-01

    The rising cost of jet fuel has renewed interest in contrarotating open rotor propulsion systems. Contemporary design methods offer the potential to maintain the inherently high aerodynamic efficiency of open rotors while greatly reducing their noise output, something that was not feasible in the 1980's designs. The primary source mechanisms of open rotor noise generation are thought to be the front rotor wake and tip vortex interacting with the aft rotor. In this paper, advanced measurement techniques and high-fidelity prediction tools are used to gain insight into the relative importance of the contributions to the open rotor noise signature of the front rotor wake and rotor tip vortex. The measurements include three-dimensional particle image velocimetry of the intra-rotor flowfield and the acoustic field of a model-scale open rotor. The predictions provide the unsteady flowfield and the associated acoustic field. The results suggest that while the front rotor tip vortex can have a significant influence on the blade passing tone noise produced by the aft rotor, the front rotor wake plays the decisive role in the generation of the interaction noise produced as a result of the unsteady aerodynamic interaction of the two rotors. At operating conditions typical of takeoff and landing operations, the interaction noise level is easily on par with that generated by the individual rotors, and in some cases is even higher. This suggests that a comprehensive approach to reducing open rotor noise should include techniques for mitigating the wake of the front rotor as well as eliminating the interaction of the front rotor tip vortex with the aft rotor blade tip.

  6. Study of the feasibility aspects of flight testing an aeroelastically tailored forward swept research wing on a BQM-34F drone vehicle

    NASA Technical Reports Server (NTRS)

    Mourey, D. J.

    1979-01-01

    The aspects of flight testing an aeroelastically tailored forward swept research wing on a BQM-34F drone vehicle are examined. The geometry of a forward swept wing, which is incorporated into the BQM-34F to maintain satisfactory flight performance, stability, and control is defined. A preliminary design of the aeroelastically tailored forward swept wing is presented.

  7. VCSEL-based swept source for low-cost optical coherence tomography

    PubMed Central

    Moon, Sucbei; Choi, Eun Seo

    2017-01-01

    We present a novel wavelength-swept laser source for optical coherence tomography (OCT) which is based on the conventional laser diode technology of the vertical-cavity surface-emitting laser (VCSEL). In our self-heating sweep VCSEL (SS-VCSEL), a VCSEL device is simply driven by ramped pulses of currents in direct intensity modulation. The intrinsic property of VCSEL produces a frequency-swept output through the self-heating effect. By the injected current, the temperature of the active region is gradually increased in this effect. Consequently, it changes the wavelength of the laser output by itself. In this study, various characteristics of our SS-VCSEL were experimentally investigated for low-cost instrumentation of a swept source OCT system. A low-cost SS-VCSEL-based OCT system was demonstrated in this research that provided an axial resolution of 135 μm in air, sensitivity of −91 dB and a maximum imaging range longer than 10 cm when our source was operated at a sweep repetition rate of 5 kHz with an output power of 0.41 mW. Based on the experimental observations, we believe that our SS-VCSEL swept source can be an economic alternative in some of low-cost or long-range applications of OCT. PMID:28271006

  8. Optimizing swept-tone protocols for recording distortion-product otoacoustic emissions in adults and newborns.

    PubMed

    Abdala, Carolina; Luo, Ping; Shera, Christopher A

    2015-12-01

    Distortion-product otoacoustic emissions (DPOAEs), which are routinely used in the audiology clinic and research laboratory, are conventionally recorded with discrete tones presented sequentially across frequency. However, a more efficient technique sweeps tones smoothly across frequency and applies a least-squares-fitting (LSF) procedure to compute estimates of otoacoustic emission phase and amplitude. In this study, the optimal parameters (i.e., sweep rate and duration of the LSF analysis window) required to record and analyze swept-tone DPOAEs were tested and defined in 15 adults and 10 newborns. Results indicate that optimal recording of swept-tone DPOAEs requires use of an appropriate analysis bandwidth, defined as the range of frequencies included in each least squares fit model. To achieve this, the rate at which the tones are swept and the length of the LSF analysis window must be carefully considered and changed in concert. Additionally, the optimal analysis bandwidth must be adjusted to accommodate frequency-dependent latency shifts in the reflection-component of the DPOAE. Parametric guidelines established here are equally applicable to adults and newborns. However, elevated noise during newborn swept-tone DPOAE recordings warrants protocol adaptations to improve signal-to-noise ratio and response quality.

  9. Performance Characterization of Swept Ramp Obstacle Fields in Pulse Detonation Applications

    DTIC Science & Technology

    2010-03-01

    field of practical obstacle geometries. 15. NUMBER OF PAGES 97 14. SUBJECT TERMS Pulse Detonation , PDE , Transient Plasma Ignition, TPI, Swept... Detonation Transition NI - National Instruments NPS - Naval Postgraduate School PDC - Pulse Detonation Combustor PDE - Pulse Detonation Engine...with incredible grace. xvi THIS PAGE INTENTIONALLY LEFT BLANK 1 I. INTRODUCTION Pulse detonation engines ( PDE ) continue to be explored due to

  10. Optimum design of swept-forward high-aspect-ration graphite-epoxy wings

    NASA Technical Reports Server (NTRS)

    Shuart, Mark J.; Haftka, Raphael T.; Campbell, R. L.

    1989-01-01

    An analytical investigation of a swept-forward high-aspect-ratio graphite-epoxy transport wing is described. The objectives of this investigation are to illustrate an effective usage of the unique properties of composite materials by exploiting material tailoring and to demonstrate an integrated multidisciplinary approach for conducting this investigation.

  11. Optimizing swept-tone protocols for recording distortion-product otoacoustic emissions in adults and newborns

    PubMed Central

    Abdala, Carolina; Luo, Ping; Shera, Christopher A.

    2015-01-01

    Distortion-product otoacoustic emissions (DPOAEs), which are routinely used in the audiology clinic and research laboratory, are conventionally recorded with discrete tones presented sequentially across frequency. However, a more efficient technique sweeps tones smoothly across frequency and applies a least-squares-fitting (LSF) procedure to compute estimates of otoacoustic emission phase and amplitude. In this study, the optimal parameters (i.e., sweep rate and duration of the LSF analysis window) required to record and analyze swept-tone DPOAEs were tested and defined in 15 adults and 10 newborns. Results indicate that optimal recording of swept-tone DPOAEs requires use of an appropriate analysis bandwidth, defined as the range of frequencies included in each least squares fit model. To achieve this, the rate at which the tones are swept and the length of the LSF analysis window must be carefully considered and changed in concert. Additionally, the optimal analysis bandwidth must be adjusted to accommodate frequency-dependent latency shifts in the reflection-component of the DPOAE. Parametric guidelines established here are equally applicable to adults and newborns. However, elevated noise during newborn swept-tone DPOAE recordings warrants protocol adaptations to improve signal-to-noise ratio and response quality. PMID:26723333

  12. Full-scale S-76 rotor performance and loads at low speeds in the NASA Ames 80- by 120-Foot Wind Tunnel. Vol. 1

    NASA Technical Reports Server (NTRS)

    Shinoda, Patrick M.

    1996-01-01

    A full-scale helicopter rotor test was conducted in the NASA Ames 80- by 120-Foot Wind Tunnel with a four-bladed S-76 rotor system. Rotor performance and loads data were obtained over a wide range of rotor shaft angles-of-attack and thrust conditions at tunnel speeds ranging from 0 to 100 kt. The primary objectives of this test were (1) to acquire forward flight rotor performance and loads data for comparison with analytical results; (2) to acquire S-76 forward flight rotor performance data in the 80- by 120-Foot Wind Tunnel to compare with existing full-scale 40- by 80-Foot Wind Tunnel test data that were acquired in 1977; (3) to evaluate the acoustic capability of the 80- by 120- Foot Wind Tunnel for acquiring blade vortex interaction (BVI) noise in the low speed range and compare BVI noise with in-flight test data; and (4) to evaluate the capability of the 80- by 120-Foot Wind Tunnel test section as a hover facility. The secondary objectives were (1) to evaluate rotor inflow and wake effects (variations in tunnel speed, shaft angle, and thrust condition) on wind tunnel test section wall and floor pressures; (2) to establish the criteria for the definition of flow breakdown (condition where wall corrections are no longer valid) for this size rotor and wind tunnel cross-sectional area; and (3) to evaluate the wide-field shadowgraph technique for visualizing full-scale rotor wakes. This data base of rotor performance and loads can be used for analytical and experimental comparison studies for full-scale, four-bladed, fully articulated rotor systems. Rotor performance and structural loads data are presented in this report.

  13. Analysis of rotor vibratory loads using higher harmonic pitch control

    NASA Technical Reports Server (NTRS)

    Quackenbush, Todd R.; Bliss, Donald B.; Boschitsch, Alexander H.; Wachspress, Daniel A.

    1992-01-01

    Experimental studies of isolated rotors in forward flight have indicated that higher harmonic pitch control can reduce rotor noise. These tests also show that such pitch inputs can generate substantial vibratory loads. The modification is summarized of the RotorCRAFT (Computation of Rotor Aerodynamics in Forward flighT) analysis of isolated rotors to study the vibratory loading generated by high frequency pitch inputs. The original RotorCRAFT code was developed for use in the computation of such loading, and uses a highly refined rotor wake model to facilitate this task. The extended version of RotorCRAFT incorporates a variety of new features including: arbitrary periodic root pitch control; computation of blade stresses and hub loads; improved modeling of near wake unsteady effects; and preliminary implementation of a coupled prediction of rotor airloads and noise. Correlation studies are carried out with existing blade stress and vibratory hub load data to assess the performance of the extended code.

  14. Dynamics of High-Speed Rotors Supported in Sliding Bearings

    NASA Astrophysics Data System (ADS)

    Šimek, J.; Svoboda, R.

    The higher the operating speed, the more serious are problems with rotor stability. Three basic groups of rotors are analyzed and some methods of suppressing instability are shown. In the first group are classical elastic rotors supported in hydrodynamic bearings. Practically all high-speed rotors now run in tilting pad bearings, which are inherently stable, but in specific conditions even tiling pad bearings may not ensure rotor stability. The second group is composed of combustion engines turbocharger rotors, which are characteristic by heavy impellers at both overhung ends of elastic shaft. These rotors are in most cases supported in floating ring bearings, which bring special features to rotor behaviour. The third group of rotors with gas bearings exhibits special features.

  15. Higher harmonic control analysis for vibration reduction of helicopter rotor systems

    NASA Technical Reports Server (NTRS)

    Nguyen, Khanh Q.

    1994-01-01

    An advanced higher harmonic control (HHC) analysis has been developed and applied to investigate its effect on vibration reduction levels, blade and control system fatigue loads, rotor performance, and power requirements of servo-actuators. The analysis is based on a finite element method in space and time. A nonlinear time domain unsteady aerodynamic model, based on the indicial response formulation, is used to calculate the airloads. The rotor induced inflow is computed using a free wake model. The vehicle trim controls and blade steady responses are solved as one coupled solution using a modified Newton method. A linear frequency-domain quasi-steady transfer matrix is used to relate the harmonics of the vibratory hub loads to the harmonics of the HHC inputs. Optimal HHC is calculated from the minimization of the vibratory hub loads expressed in term of a quadratic performance index. Predicted vibratory hub shears are correlated with wind tunnel data. The fixed-gain HHC controller suppresses completely the vibratory hub shears for most of steady or quasi-steady flight conditions. HHC actuator amplitudes and power increase significantly at high forward speeds (above 100 knots). Due to the applied HHC, the blade torsional stresses and control loads are increased substantially. For flight conditions where the blades are stalled considerably, the HHC input-output model is quite nonlinear. For such cases, the adaptive-gain controller is effective in suppressing vibratory hub loads, even though HHC may actually increase stall areas on the rotor disk. The fixed-gain controller performs poorly for such flight conditions. Comparison study of different rotor systems indicates that a soft-inplane hingeless rotor requires less actuator power at high speeds (above 130 knots) than an articulated rotor, and a stiff-inplane hingeless rotor generally requires more actuator power than an articulated or a soft-inplane hingeless rotor. Parametric studies for a hingeless rotor

  16. High-speed high-sensitivity infrared spectroscopy using mid-infrared swept lasers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Childs, David T. D.; Groom, Kristian M.; Hogg, Richard A.; Revin, Dmitry G.; Cockburn, John W.; Rehman, Ihtesham U.; Matcher, Stephen J.

    2016-03-01

    Infrared spectroscopy is a highly attractive read-out technology for compositional analysis of biomedical specimens because of its unique combination of high molecular sensitivity without the need for exogenous labels. Traditional techniques such as FTIR and Raman have suffered from comparatively low speed and sensitivity however recent innovations are challenging this situation. Direct mid-IR spectroscopy is being speeded up by innovations such as MEMS-based FTIR instruments with very high mirror speeds and supercontinuum sources producing very high sample irradiation levels. Here we explore another possible method - external cavity quantum cascade lasers (EC-QCL's) with high cavity tuning speeds (mid-IR swept lasers). Swept lasers have been heavily developed in the near-infrared where they are used for non-destructive low-coherence imaging (OCT). We adapt these concepts in two ways. Firstly by combining mid-IR quantum cascade gain chips with external cavity designs adapted from OCT we achieve spectral acquisition rates approaching 1 kHz and demonstrate potential to reach 100 kHz. Secondly we show that mid-IR swept lasers share a fundamental sensitivity advantage with near-IR OCT swept lasers. This makes them potentially able to achieve the same spectral SNR as an FTIR instrument in a time x N shorter (N being the number of spectral points) under otherwise matched conditions. This effect is demonstrated using measurements of a PDMS sample. The combination of potentially very high spectral acquisition rates, fundamental SNR advantage and the use of low-cost detector systems could make mid-IR swept lasers a powerful technology for high-throughput biomedical spectroscopy.

  17. Wavelength-swept fiber laser based on acousto-optic tuning method

    NASA Astrophysics Data System (ADS)

    Chen, Ming-hui; Fan, Yun-ping; Zhang, Hao; Tao, Jian-feng; Zheng, Gang

    2016-10-01

    In this study, we have demonstrated a wavelength-swept fiber laser based on an acousto-optic tunable filter(AOTF) as a selective element and a semiconductor optical amplifier(SOA) as a gain medium in an internal fiber ring cavity. The light deriving from one port of the SOA goes through an optical isolator, the AOTF, a fiber coupler and a polarized controller successively, then it goes back to the other port of the SOA to form a ring cavity. The laser output is from another port of the fiber coupler. The laser made by this method is mainly used for swept-source optical coherence tomography(SS-OCT). The application of the SOA provides a sufficiently broad range and can ensure an increased axial resolution of SS-OCT. AOTF offers a wide tuning range, high switching speed and stable operation against vibration for the non-mechanical structure. The proposed wavelength-swept fiber laser ensures a high axial resolution of tomographic images and has a stable laser output. We have discussed the influence of the SOA injection current to the tuning range of the laser. In the SOA injection current of 280 mA, a continuous wavelength tuning range from 1295 to 1370 nm centered at a wavelength of 1330nm is obtained at the sweep rate of 1.06 kHz, and the power of the swept source was 1.14 mW. In addition, for quantitative characterization of the wavelength-swept performance with a AOTF, we have theoretically and experimentally analyzed the influence of the following controllable parameters: injection current, output power and sweeping frequency.

  18. Applying Pressure Sensitive Paint Technology to Rotor Blades

    NASA Technical Reports Server (NTRS)

    Watkins, A. Neal; Leighty, Bradley D.; Lipford, William E.; Goodman, Kyle Z.; Crafton, Jim; Gregory, James W.

    2014-01-01

    This report will present details of a Pressure Sensitive Paint (PSP) system for measuring global surface pressures on rotorcrtaft blades in simulated forward flight at the 14- by 22-Foot Subsonic Tunnel at the NASA Langley Research Center. The basics of the PSP method will be discussed and the modifications that were needed to extend this technology for use on rotor blades. Results from a series of tests will also be presented as well as several areas of improvement that have been identified and are currently being developed for future testing.

  19. The response of turbine engine rotors to interference rubs

    NASA Technical Reports Server (NTRS)

    Kascak, A. F.

    1980-01-01

    A method was developed for the direct integration of a rotor dynamics system experiencing a blade loss induced rotor rub. Both blade loss and rotor rub were simulated on a rotor typical of a small gas turbine. A small change in the coefficient of friction (from 0.1 to 0.2) caused the rotor to change from forward to backward whirl and to theoretically destroy itself in a few rotations. This method provides an analytical capability to study the susceptibility of rotors to rub induced backward whirl problems.

  20. Rotor blade structure and mounting for vertical axis wind machines

    SciTech Connect

    Lechner, W. L.

    1981-02-03

    A lightweight simplified economical and efficient sail or rotor blade for a vertical axis wind machine and simplified self-acting restraining means for the blade during rotor operation are disclosed. The rotor structure is characterized by ease of assembly and the absence of need for adjustment and frequent maintenance. Individual rotor blades are attached to vertical axis whips extending above and below horizontal rotor arms. The rotor is self-starting and turns in one direction only in response to wind coming from any direction on the compass.

  1. Important Scaling Parameters for Testing Model-Scale Helicopter Rotors

    NASA Technical Reports Server (NTRS)

    Singleton, Jeffrey D.; Yeager, William T., Jr.

    1998-01-01

    An investigation into the effects of aerodynamic and aeroelastic scaling parameters on model scale helicopter rotors has been conducted in the NASA Langley Transonic Dynamics Tunnel. The effect of varying Reynolds number, blade Lock number, and structural elasticity on rotor performance has been studied and the performance results are discussed herein for two different rotor blade sets at two rotor advance ratios. One set of rotor blades were rigid and the other set of blades were dynamically scaled to be representative of a main rotor design for a utility class helicopter. The investigation was con-densities permits the acquisition of data for several Reynolds and Lock number combinations.

  2. Overview of the Novel Intelligent JAXA Active Rotor Program

    NASA Technical Reports Server (NTRS)

    Saito, Shigeru; Kobiki, Noboru; Tanabe, Yasutada; Johnson, Wayne; Yamauchi, Gloria K.; Young, Larry A.

    2010-01-01

    The Novel Intelligent JAXA Active Rotor (NINJA Rotor) program is a cooperative effort between JAXA and NASA, involving a test of a JAXA pressure-instrumented, active-flap rotor in the 40- by 80-Foot Wind Tunnel at Ames Research Center. The objectives of the program are to obtain an experimental database of a rotor with active flaps and blade pressure instrumentation, and to use that data to develop analyses to predict the aerodynamic and aeroacoustic performance of rotors with active flaps. An overview of the program is presented, including a description of the rotor and preliminary pretest calculations.

  3. Rotor Wake Development During the First Revolution

    NASA Technical Reports Server (NTRS)

    McAlister, Kenneth W.

    2003-01-01

    The wake behind a two-bladed model rotor in light climb was measured using particle image velocimetry, with particular emphasis on the development of the trailing vortex during the first revolution of the rotor. The distribution of vorticity was distinguished from the slightly elliptical swirl pattern. Peculiar dynamics within the void region may explain why the peak vorticity appeared to shift away from the center as the vortex aged, suggesting the onset of instability. The swirl and axial velocities (which reached 44 and 12 percent of the rotor-tip speed, respectively) were found to be asymmetric relative to the vortex center. In particular, the axial flow was composed of two concentrated zones moving in opposite directions. The radial distribution of the circulation rapidly increased in magnitude until reaching a point just beyond the core radius, after which the rate of growth decreased significantly. The core-radius circulation increased slightly with wake age, but the large-radius circulation appeared to remain relatively constant. The radial distributions of swirl velocity and vorticity exhibit self-similar behaviors, especially within the core. The diameter of the vortex core was initially about 10 percent of the rotor-blade chord, but more than doubled its size after one revolution of the rotor. According to vortex models that approximate the measured data, the core-radius circulation was about 79 percent of the large-radius circulation, and the large-radius circulation was about 67 percent of the maximum bound circulation on the rotor blade. On average, about 53 percent of the maximum bound circulation resides within the vortex core during the first revolution of the rotor.

  4. Effects of aerodynamic interaction between main and tail rotors on helicopter hover performance and noise

    NASA Technical Reports Server (NTRS)

    Menger, R. P.; Wood, T. L.; Brieger, J. T.

    1983-01-01

    A model test was conducted to determine the effects of aerodynamic interaction between main rotor, tail rotor, and vertical fin on helicopter performance and noise in hover out of ground effect. The experimental data were obtained from hover tests performed with a .151 scale Model 222 main rotor, tail rotor and vertical fin. Of primary interest was the effect of location of the tail rotor with respect to the main rotor. Penalties on main rotor power due to interaction with the tail rotor ranged up to 3% depending upon tail rotor location and orientation. Penalties on tail rotor power due to fin blockage alone ranged up to 10% for pusher tail rotors and up to 50% for tractor tail rotors. The main rotor wake had only a second order effect on these tail rotor/fin interactions. Design charts are presented showing the penalties on main rotor power as a function of the relative location of the tail rotor.

  5. Ultrahigh speed 1050nm swept source/Fourier domain OCT retinal and anterior segment imaging at 100,000 to 400,000 axial scans per second.

    PubMed

    Potsaid, Benjamin; Baumann, Bernhard; Huang, David; Barry, Scott; Cable, Alex E; Schuman, Joel S; Duker, Jay S; Fujimoto, James G

    2010-09-13

    We demonstrate ultrahigh speed swept source/Fourier domain ophthalmic OCT imaging using a short cavity swept laser at 100,000 - 400,000 axial scan rates. Several design configurations illustrate tradeoffs in imaging speed, sensitivity, axial resolution, and imaging depth. Variable rate A/D optical clocking is used to acquire linear-in-k OCT fringe data at 100 kHz axial scan rate with 5.3 um axial resolution in tissue. Fixed rate sampling at 1 GSPS achieves a 7.5mm imaging range in tissue with 6.0 um axial resolution at 100 kHz axial scan rate. A 200 kHz axial scan rate with 5.3 um axial resolution over 4mm imaging range is achieved by buffering the laser sweep. Dual spot OCT using two parallel interferometers achieves 400 kHz axial scan rate, almost 2X faster than previous 1050 nm ophthalmic results and 20X faster than current commercial instruments. Superior sensitivity roll-off performance is shown. Imaging is demonstrated in the human retina and anterior segment. Wide field 12x12 mm data sets include the macula and optic nerve head. Small area, high density imaging shows individual cone photoreceptors. The 7.5 mm imaging range configuration can show the cornea, iris, and anterior lens in a single image. These improvements in imaging speed and depth range provide important advantages for ophthalmic imaging. The ability to rapidly acquire 3D-OCT data over a wide field of view promises to simplify examination protocols. The ability to image fine structures can provide detailed information on focal pathologies. The large imaging range and improved image penetration at 1050 m wavelengths promises to improve performance for instrumentation which images both the retina and anterior eye. These advantages suggest that swept source OCT at 1050 nm wavelengths will play an important role in future ophthalmic instrumentation.

  6. Rotor burst protection program: Statistics on aircraft gas turbine engine rotor failures that occurred in US commercial aviation during 1975

    NASA Technical Reports Server (NTRS)

    Delucia, R. A.; Mangano, G. J.

    1977-01-01

    Statistics on gas turbine rotor failures that have occurred in U.S. commercial aviation during 1975 are presented. The compiled data were analyzed to establish: (1) The incidence of rotor failures and the number of contained and uncontained rotor bursts; (2) The distribution of rotor bursts with respect to engine rotor component; i.e., fan, compressor or turbine; (3) The type of rotor fragment (disk, rim or blade) typically generated at burst; (4) The cause of failure; (5) The type of engines involved; and (6) The flight condition at the time of failure.

  7. A rotor optimization using regression analysis

    NASA Technical Reports Server (NTRS)

    Giansante, N.

    1984-01-01

    The design and development of helicopter rotors is subject to the many design variables and their interactions that effect rotor operation. Until recently, selection of rotor design variables to achieve specified rotor operational qualities has been a costly, time consuming, repetitive task. For the past several years, Kaman Aerospace Corporation has successfully applied multiple linear regression analysis, coupled with optimization and sensitivity procedures, in the analytical design of rotor systems. It is concluded that approximating equations can be developed rapidly for a multiplicity of objective and constraint functions and optimizations can be performed in a rapid and cost effective manner; the number and/or range of design variables can be increased by expanding the data base and developing approximating functions to reflect the expanded design space; the order of the approximating equations can be expanded easily to improve correlation between analyzer results and the approximating equations; gradients of the approximating equations can be calculated easily and these gradients are smooth functions reducing the risk of numerical problems in the optimization; the use of approximating functions allows the problem to be started easily and rapidly from various initial designs to enhance the probability of finding a global optimum; and the approximating equations are independent of the analysis or optimization codes used.

  8. Boost pulverizer performance with new exhauster rotor

    SciTech Connect

    Lauber, J.A.

    1994-10-01

    Georgia Power Co.'s Jack McDonough station, near Atlanta, Ga, consists of two tangentially fired boilers rated 1.734-million lb/hr, each paired with a 265-MW turbine/generator. The plant's primary fuel is Eastern Bituminous coal, which is ground by five pulverizers. In April 1993, it first began evaluating a new high-efficiency rotor for the pulverizer exhausters, supplied by ABB C-E Services Inc. Windsor, Conn. McDonough was designed to burn coal with a Hardgrove Grindability Index (HGI) of 55 and is typically supplied fuel with an HGI of 45. Thus, the units must operate with all five pulverizers to obtain full load, although each was intended to generate full load using four pulverizers. Now that the plant is burning low-sulfur coal to comply with the clean Air Act Amendments of 1990, the increased hardness limits McDonough's full-load capabilities and will dramatically increase pulverizer maintenance. Management was left with two options: a complete pulverizer replacement or further modifications. (The mills had already been upgraded several years ago.) The introduction of high-efficiency rotors for the exhauster fans made the second option more attractive. Unfortunately, the vendor had no significant operating experience with the rotor design, still in the developmental stage. Therefore, the plant decided to install a test rotor at McDonough Unit 2. This article is a review of the rotor's basic theory of operation, test results, and wear characteristics experienced at the unit.

  9. Role of Rotors in the Ablative Therapy of Persistent Atrial Fibrillation

    PubMed Central

    Schricker, Amir A; Zaman, Junaid; Narayan, Sanjiv M

    2015-01-01

    Atrial fibrillation (AF) ablation is increasingly used to maintain sinus rhythm yet its results are sub-optimal, especially in patients with persistent AF or prior unsuccessful procedures. Attempts at improvement have often targeted substrates that sustain AF after it is triggered, yet those mechanisms are debated. Many studies now challenge the concept that AF is driven by self-sustaining disordered wavelets, showing instead that localised drivers (rotors) may drive disorder via a process known as fibrillatory conduction. Novel mapping using wide-area recordings, physiological filtering and phase analysis demonstrates rotors in human AF. Contact mapping with focal impulse and rotor modulation (FIRM) shows that localised ablation at sources can improve procedural success in many populations on long-term follow up and some newer approaches to rotor mapping are qualitatively similar. This review critically evaluates the data on rotor mapping and ablation, which advances our conceptual understanding of AF and holds the promise of substantially improving ablative outcomes in patients with persistent AF. PMID:26835100

  10. Calculation of rotor impedance for use in design analysis of helicopter airframe vibrations

    NASA Technical Reports Server (NTRS)

    Nygren, Kip P.

    1990-01-01

    Excessive vibration is one of the most prevalent technical obstacles encountered in the development of new rotorcraft. The inability to predict these vibrations is primarily due to deficiencies in analysis and simulation tools. The Langley Rotorcraft Structural Dynamics Program was instituted in 1984 to meet long term industry needs in the area of rotorcraft vibration prediction. As a part of the Langley program, this research endeavors to develop an efficient means of coupling the rotor to the airframe for preliminary design analysis of helicopter airframe vibrations. The main effort was to modify the existing computer program for modeling the dynamic and aerodynamic behavior of rotorcraft called DYSCO (DYnamic System COupler) to calculate the rotor impedance. DYSCO was recently developed for the U.S. Army and has proven to be adaptable for the inclusion of new solution methods. The solution procedure developed to use DYSCO for the calculation of rotor impedance is presented. Verification of the procedure by comparison with a known solution for a simple wind turbine model is about 75 percent completed, and initial results are encouraging. After the wind turbine impedance is confirmed, the verification effort will continue by comparison to solutions of a more sophisticated rotorcraft model. Future work includes determination of the sensitivity of the rotorcraft airframe vibrations to helicopter flight conditions and rotor modeling assumptions. When completed, this research will ascertain the feasibility and efficiency of the impedance matching method of rotor-airframe coupling for use in the analysis of airframe vibrations during the preliminary rotorcraft design process.

  11. Aerodynamic characteristics of the TARP (Toroidal Accelerator Rotor Platform) wind energy conversion system

    NASA Astrophysics Data System (ADS)

    Duffy, R. E.; Jaran, C.; Ungermann, C.

    1980-02-01

    Augmented wind energy conversion systems (WECS) are designed to increase the ambient wind velocity at the turbine blades. The Toroidal Accelerator Rotor Platform (TARP) is an augmenting structure for use with horizontal axis WECS. Its shape resembles that of a horizontally oriented wheel rim and is intended to be built into or retrofitted onto structures built for other purposes, which could increase the use of WECS in urban areas. Variations of the basic TARP structure, about three feet in diameter, were tested in a wind tunnel to determine the optimum design. The model system produced up to 4.5 times the power which the rotor and generator extracted without the TARP.

  12. Can shock waves on helicopter rotors generate noise? - A study of the quadrupole source

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Tadghighi, H.

    1990-01-01

    An analysis has previously established that local shock surfaces attached to helicopter rotor blades moving at high subsonic speeds are potent noise generators; in pursuit of this insight, a novel formulation is presented for the prediction of the noise of a deformable shock, whose area changes as a function of the azimuthal position of the blade. The derivation of this formulation has its basis in a mapping of the moving shock to a time-independent region. In virtue of this mapping, the implementation of the main result on a computer becomes straightforward enough for incorporation into the available rotor-noise prediction code. A problem illustrating the importance of rotor shocks in the generation of high-intensity noise is presented.

  13. Simulation of unsteady flows through stator and rotor blades of a gas turbine using the Chimera method

    NASA Technical Reports Server (NTRS)

    Nakamura, S.; Scott, J. N.

    1993-01-01

    A two-dimensional model to solve compressible Navier-Stokes equations for the flow through stator and rotor blades of a turbine is developed. The flow domains for the stator and rotor blades are coupled by the Chimera method that makes grid generation easy and enhances accuracy because the area of the grid that have high turning of grid lines or high skewness can be eliminated from the computational domain after the grids are generated. The results of flow computations show various important features of unsteady flows including the acoustic waves interacting with boundary layers, Karman vortex shedding from the trailing edge of the stator blades, pulsating incoming flow to a rotor blade from passing stator blades, and flow separation from both suction and pressure sides of the rotor blades.

  14. Laser balancing demonstration on a high-speed flexible rotor

    NASA Technical Reports Server (NTRS)

    Demuth, R. S.; Rio, R. A.; Fleming, D. P.

    1979-01-01

    This paper describes a flexible rotor system used for two-plane laser balancing and an experimental demonstration of the laser material removal method for balancing. A laboratory test rotor was modified to accept balancing corrections using a laser metal removal method while the rotor is at operating speed. The laser setup hardware required to balance the rotor using two correction planes is described. The test rig optical configuration and a neodymium glass laser were assembled and calibrated for material removal rates. Rotor amplitudes before and after balancing, trial and correction weights, rotor speed during operation of laser, and balancing time were documented. The rotor was balanced through the first bending critical speed using the laser material removal procedure to apply trial weights and correction weights without stopping the rotor.

  15. Tip Vortex and Wake Characteristics of a Counterrotating Open Rotor

    NASA Technical Reports Server (NTRS)

    VanZante, Dale E.; Wernet, Mark P.

    2012-01-01

    One of the primary noise sources for Open Rotor systems is the interaction of the forward rotor tip vortex and blade wake with the aft rotor. NASA has collaborated with General Electric on the testing of a new generation of low noise, counterrotating Open Rotor systems. Three-dimensional particle image velocimetry measurements were acquired in the intra-rotor gap of the Historical Baseline blade set. The velocity measurements are of sufficient resolution to characterize the tip vortex size and trajectory as well as the rotor wake decay and turbulence character. The tip clearance vortex trajectory is compared to results from previously developed models. Forward rotor wake velocity profiles are shown. Results are presented in a form as to assist numerical modeling of Open Rotor system aerodynamics and acoustics.

  16. Measurements of atmospheric turbulence effects on tail rotor acoustics

    NASA Technical Reports Server (NTRS)

    Hagen, Martin J.; Yamauchi, Gloria K.; Signor, David B.; Mosher, Marianne

    1994-01-01

    Results from an outdoor hover test of a full-scale Lynx tail rotor are presented. The investigation was designed to further the understanding of the acoustics of an isolated tail rotor hovering out-of-ground effect in atmospheric turbulence, without the effects of the main rotor wake or other helicopter components. Measurements include simultaneous rotor performance, noise, inflow, and far-field atmospheric turbulence. Results with grid-generated inflow turbulence are also presented. The effects of atmospheric turbulence ingestion on rotor noise are quantified. In contradiction to current theories, increasing rotor inflow and rotor thrust were found to increase turbulence ingestion noise. This is the final report of Task 13A--Helicopter Tail Rotor Noise, of the NASA/United Kingdom Defense Research Agency cooperative Aeronautics Research Program.

  17. NASA Now: Engineering Design: Tilt Rotors, Aircraft of the Future

    NASA Video Gallery

    Meet Carl Russell, a research aerospace engineer who is working on developing new innovations for air travel. Russell discusses how tilt rotors work, including a demonstration on how rotors use Ber...

  18. Estimation of dynamic rotor loads for the rotor systems research aircraft: Methodology development and validation

    NASA Technical Reports Server (NTRS)

    Duval, R. W.; Bahrami, M.

    1985-01-01

    The Rotor Systems Research Aircraft uses load cells to isolate the rotor/transmission systm from the fuselage. A mathematical model relating applied rotor loads and inertial loads of the rotor/transmission system to the load cell response is required to allow the load cells to be used to estimate rotor loads from flight data. Such a model is derived analytically by applying a force and moment balance to the isolated rotor/transmission system. The model is tested by comparing its estimated values of applied rotor loads with measured values obtained from a ground based shake test. Discrepancies in the comparison are used to isolate sources of unmodeled external loads. Once the structure of the mathematical model has been validated by comparison with experimental data, the parameters must be identified. Since the parameters may vary with flight condition it is desirable to identify the parameters directly from the flight data. A Maximum Likelihood identification algorithm is derived for this purpose and tested using a computer simulation of load cell data. The identification is found to converge within 10 samples. The rapid convergence facilitates tracking of time varying parameters of the load cell model in flight.

  19. Housing flexibility effects on rotor stability

    NASA Technical Reports Server (NTRS)

    Davis, L. B.; Wolfe, E. A.; Beatty, R. F.

    1985-01-01

    Preliminary rotordynamic evaluations are performed with a housing stiffness assumption that is typically determined only after the hardware is built. In addressing rotor stability, a rigid housing assumption was shown to predict an instability at a lower spin speed than a comparable flexible housing analysis. This rigid housing assumption therefore provides a conservative estimate of the stability threshold speed. A flexible housing appears to act as an energy absorber and dissipated some of the destabilizing force. The fact that a flexible housing is usually asymmetric and considerably heavier than the rotor was related to this apparent increase in rotor stability. Rigid housing analysis is proposed as a valuable screening criteria and may save time and money in construction of elaborate housing finite element models for linear stability analyses.

  20. Helicopter Rotor Blade With Free Tip

    NASA Technical Reports Server (NTRS)

    Stroub, Robert H.; Young, Larry; Cawthorne, Matthew; Keys, Charles

    1992-01-01

    Free-tip rotor blades improve fuel efficiency and performance characteristics of helicopters. Outermost portion of blade pivots independently with respect to inboard portion about pitch axis parallel to blade axis, located forward of aerodynamic center. Centrifugal force acts on tension/torsion strap and biases tip nose-up. Airstream turns tip nose-down, other torques cause tip to "weathervane" to intermediate angular position resulting in net lift. Reduces fluctuations in lift, with two effects: flapwise vibratory loads on blade and vibratory loads on pitch-control mechanism reduced; negative lift produced by advancing fixed tip eliminated, reducing power required to achieve same overall lift. Applies to tilt rotors and tail rotors as well.

  1. Evolution of Rotor Wake in Swirling Flow

    NASA Technical Reports Server (NTRS)

    El-Haldidi, Basman; Atassi, Hafiz; Envia, Edmane; Podboy, Gary

    2000-01-01

    A theory is presented for modeling the evolution of rotor wakes as a function of axial distance in swirling mean flows. The theory, which extends an earlier work to include arbitrary radial distributions of mean swirl, indicates that swirl can significantly alter the wake structure of the rotor especially at large downstream distances (i.e., for moderate to large rotor-stator spacings). Using measured wakes of a representative scale model fan stage to define the mean swirl and initial wake perturbations, the theory is used to predict the subsequent evolution of the wakes. The results indicate the sensitivity of the wake evolution to the initial profile and the need to have complete and consistent initial definition of both velocity and pressure perturbations.

  2. A Study of Coaxial Rotor Performance and Flow Field Characteristics

    DTIC Science & Technology

    2016-01-22

    opposite directions with a vertical separation distance equivalent to the separation between the upper and lower rotor of the coaxial system were simulated...lower rotor separately . Ramasamy provided a convenient summary of coaxial rotor hover perfor- mance measurements prior to 2013, including those surveyed 1...actual blades. Fig. 3. Performance of HC1 (Ref. 13) in hover compared with momentum theory, BEMT and RotUNS steady cal- culations. Rotor separation

  3. Active-Twist Rotor Control Applications for UAVs

    NASA Technical Reports Server (NTRS)

    Wilbur, Matthew L.; Wilkie, W. Keats

    2004-01-01

    The current state-of-the-art in active-twist rotor control is discussed using representative examples from analytical and experimental studies, and the application to rotary-wing UAVs is considered. Topics include vibration and noise reduction, rotor performance improvement, active blade tracking, stability augmentation, and rotor blade de-icing. A review of the current status of piezoelectric fiber composite actuator technology, the class of piezoelectric actuators implemented in active-twist rotor systems, is included.

  4. On aerodynamic design of the Savonius windmill rotor

    SciTech Connect

    Mojola, O.O.

    1982-08-01

    This paper examines under field conditions the performance characteristics of the Savonius windmill rotor. Test data were collected on the speed, torque and power of the rotor at a large number of wind speeds for each of seven values of the rotor overlap ratio. Field testing procedures are critically appraised and a unified approach is suggested. The performance data of the Savonius rotor are also fully discussed and design criteria established.

  5. User's Manual for Computer Program ROTOR. [to calculate tilt-rotor aircraft dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Yasue, M.

    1974-01-01

    A detailed description of a computer program to calculate tilt-rotor aircraft dynamic characteristics is presented. This program consists of two parts: (1) the natural frequencies and corresponding mode shapes of the rotor blade and wing are developed from structural data (mass distribution and stiffness distribution); and (2) the frequency response (to gust and blade pitch control inputs) and eigenvalues of the tilt-rotor dynamic system, based on the natural frequencies and mode shapes, are derived. Sample problems are included to assist the user.

  6. Numerical Study on the Effect of Swept Blade on the Aerodynamic Performance of Wind Turbine at High Tip Speed Ratio

    NASA Astrophysics Data System (ADS)

    Zuo, H. M.; Liu, C.; Yang, H.; Wang, F.

    2016-09-01

    The current situation is that the development of high speed wind energy saturates gradually, therefore, it is highly necessary to develop low speed wind energy. This paper, based on a specific straight blade and by using Isight, a kind of multidiscipline optimization software, which integrates ICEM (Integrated Computer Engineering and Manufacturing) and CFD (Computational Fluid Dynamics) software, optimizes the blade stacking line (the centers of airfoil from blade root to tip) and acquires the optimization swept blade shape. It is found that power coefficient Cp of swept blade is 3.2% higher than that of straight blade at the tip speed ratio of 9.82, that the thrust of swept blade receives is obviously less than that of straight blade. Inflow angle of attack and steam line on the suction of the swept and straight blade are also made a comparison.

  7. Discretely swept optical coherence tomography system using super-structure grating distributed Bragg reflector lasers at 1561-1639nm

    NASA Astrophysics Data System (ADS)

    Choi, D.; Yoshimura, R.; Hiro-Oka, H.; Furukawa, H.; Goto, A.; Satoh, N.; Igarashi, A.; Nakanishi, M.; Shimizu, K.; Ohbayashi, K.

    2012-01-01

    We have developed swept source optical coherence tomography (OCT) system with an optical comb swept source system. The swept source system comprised of two super-structured grating distributed Bragg reflector lasers covering a wavelength range from 1561-1693 nm. A method to scan these lasers to obtain an interference signal without stitching noises, which are inherent in these lasers, and to connect two lasers without concatenation noise is explained. Method to reduce optical aliasing noises in this optical comb swept laser OCT is explained and demonstrated based on the characteristic of the optical aliasing noises in this particular OCT system. By reduction of those noises, a sensitivity of 124 dB was realized. The A-scan rate, resolution and depth range were 3.1 kHz, 16 μm (in air) and 12 mm, respectively. Deep imaging penetration into tissue is demonstrated for two selected samples.

  8. Comprehensive analysis of helicopters with bearingless rotors

    NASA Technical Reports Server (NTRS)

    Murthy, V. R.

    1988-01-01

    A modified Galerkin method is developed to analyze the dynamic problems of multiple-load-path bearingless rotor blades. The development and selection of functions are quite parallel to CAMRAD procedures, greatly facilitating the implementation of the method into the CAMRAD program. A software is developed implementing the modified Galerkin method to determine free vibration characteristics of multiple-load-path rotor blades undergoing coupled flapwise bending, chordwise bending, twisting, and extensional motions. Results are in the process of being obtained by debugging the software.

  9. Superballistic wavepacket spreading in double kicked rotors

    NASA Astrophysics Data System (ADS)

    Fang, Ping; Wang, Jiao

    2016-08-01

    We investigate possible ways in which a quantum wavepacket spreads. We show that in a general class of double kicked rotor system, a wavepacket may undergo superballistic spreading; i.e., its variance increases as the cubic of time. The conditions for the observed superballistic spreading and two related characteristic time scales are studied. Our results suggest that the symmetry of the studied model and whether it is a Kolmogorov-Arnold-Moser system are crucial to its wavepacket spreading behavior. Our study also sheds new light on the exponential wavepacket spreading phenomenon previously observed in the double kicked rotor system.

  10. Analyses of Multishaft Rotor-Bearing Response

    NASA Technical Reports Server (NTRS)

    Nelson, H. D.; Meacham, W. L.

    1985-01-01

    Method works for linear and nonlinear systems. Finite-element-based computer program developed to analyze free and forced response of multishaft rotor-bearing systems. Acronym, ARDS, denotes Analysis of Rotor Dynamic Systems. Systems with nonlinear interconnection or support bearings or both analyzed by numerically integrating reduced set of coupledsystem equations. Linear systems analyzed in closed form for steady excitations and treated as equivalent to nonlinear systems for transient excitation. ARDS is FORTRAN program developed on an Amdahl 470 (similar to IBM 370).

  11. Rotor/bearing system dynamic stiffness measurements

    NASA Technical Reports Server (NTRS)

    Muszynska, A.

    1985-01-01

    Sweep perturbation testing as used in Modal Analysis when applied to a rotating machine has to take into consideration the machine dynamic state of equilibrium at its operational rotative speed. This stands in contrasts to a static equilibrium of nonrotating structures. The rotational energy has a significant influence on rotor dynamic characteristics. The best perturbing input for rotating machines is a forward or reverse rotating, circular force applied directly to the shaft. Determination of Dynamic Stiffness Characteristics of the rotor bearing system by nonsynchronous perturbation of a symmetric rotating shaft supported in one relatively rigid and one oil lubricated bearing.

  12. Simple theoretical models for composite rotor blades

    NASA Technical Reports Server (NTRS)

    Valisetty, R. R.; Rehfield, L. W.

    1984-01-01

    The development of theoretical rotor blade structural models for designs based upon composite construction is discussed. Care was exercised to include a member of nonclassical effects that previous experience indicated would be potentially important to account for. A model, representative of the size of a main rotor blade, is analyzed in order to assess the importance of various influences. The findings of this model study suggest that for the slenderness and closed cell construction considered, the refinements are of little importance and a classical type theory is adequate. The potential of elastic tailoring is dramatically demonstrated, so the generality of arbitrary ply layup in the cell wall is needed to exploit this opportunity.

  13. Variable diameter wind turbine rotor blades

    DOEpatents

    Jamieson, Peter McKeich; Hornzee-Jones, Chris; Moroz, Emilian M.; Blakemore, Ralph W.

    2005-12-06

    A system and method for changing wind turbine rotor diameters to meet changing wind speeds and control system loads is disclosed. The rotor blades on the wind turbine are able to adjust length by extensions nested within or containing the base blade. The blades can have more than one extension in a variety of configurations. A cable winching system, a hydraulic system, a pneumatic system, inflatable or elastic extensions, and a spring-loaded jack knife deployment are some of the methods of adjustment. The extension is also protected from lightning by a grounding system.

  14. Higher harmonic rotor blade pitch control

    NASA Technical Reports Server (NTRS)

    Ewans, J. R.

    1976-01-01

    Tests of a model 'Reverse Velocity Rotor' system at high advance ratios and with twice-per-revolution cyclic pitch control were made under joint Navy-NASA sponsorship in the NASA, Ames 12 ft. pressure tunnel. The results showed significant gains in rotor performance at all advance ratios by using twice-per-revolution control. Detailed design studies have been made of alternative methods of providing higher harmonic motion including four types of mechanical systems and an electro-hydraulic system. The relative advantages and disadvantages are evaluated on the basis of stiffness, weight, volume, reliability and maintainability.

  15. Hover performance tests of baseline metal and Advanced Technology Blade (ATB) rotor systems for the XV-15 tilt rotor aircraft

    NASA Technical Reports Server (NTRS)

    Bartie, K.; Alexander, H.; Mcveigh, M.; Lamon, S.; Bishop, H.

    1986-01-01

    Rotor hover performance data were obtained for two full-scale rotor systems designed for the XV-15 Tilt Rotor Research Aircraft. One rotor employed the rectangular planform metal blades (rotor solidity = 0.089) which were used on the initial flight configuration of the XV-15. The second rotor configuration examined the nonlinear taper, composite-construction, Advanced Technology Blade (ATB), (rotor solidity = 0.10) designed to replace the metal blades on the XV-15. Variations of the baseline ATB tip and cuff shapes were also tested. A new six-component rotor force and moment balance designed to obtain highly accurate data over a broad range of thrust and torque conditions is described. The test data are presented in nondimensional coefficient form for the performance results, and in dimensional form for the steady and alternating loads. Some wake and acoustic data are also shown.

  16. 14 CFR 23.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Equipment containing high energy rotors. 23... Equipment Miscellaneous Equipment § 23.1461 Equipment containing high energy rotors. (a) Equipment, such as Auxiliary Power Units (APU) and constant speed drive units, containing high energy rotors must...

  17. 14 CFR 23.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Equipment containing high energy rotors. 23... Equipment Miscellaneous Equipment § 23.1461 Equipment containing high energy rotors. (a) Equipment, such as Auxiliary Power Units (APU) and constant speed drive units, containing high energy rotors must...

  18. 14 CFR 29.411 - Ground clearance: tail rotor guard.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Ground clearance: tail rotor guard. 29.411 Section 29.411 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... System Loads § 29.411 Ground clearance: tail rotor guard. (a) It must be impossible for the tail rotor...

  19. 14 CFR 29.411 - Ground clearance: tail rotor guard.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Ground clearance: tail rotor guard. 29.411 Section 29.411 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... System Loads § 29.411 Ground clearance: tail rotor guard. (a) It must be impossible for the tail rotor...

  20. 14 CFR 29.411 - Ground clearance: tail rotor guard.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Ground clearance: tail rotor guard. 29.411 Section 29.411 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... System Loads § 29.411 Ground clearance: tail rotor guard. (a) It must be impossible for the tail rotor...

  1. 14 CFR 27.411 - Ground clearance: tail rotor guard.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Ground clearance: tail rotor guard. 27.411 Section 27.411 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... System Loads § 27.411 Ground clearance: tail rotor guard. (a) It must be impossible for the tail rotor...

  2. 14 CFR 27.411 - Ground clearance: tail rotor guard.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Ground clearance: tail rotor guard. 27.411 Section 27.411 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... System Loads § 27.411 Ground clearance: tail rotor guard. (a) It must be impossible for the tail rotor...

  3. 14 CFR 27.411 - Ground clearance: tail rotor guard.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Ground clearance: tail rotor guard. 27.411 Section 27.411 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... System Loads § 27.411 Ground clearance: tail rotor guard. (a) It must be impossible for the tail rotor...

  4. 14 CFR 29.411 - Ground clearance: tail rotor guard.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Ground clearance: tail rotor guard. 29.411 Section 29.411 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... System Loads § 29.411 Ground clearance: tail rotor guard. (a) It must be impossible for the tail rotor...

  5. 14 CFR 27.411 - Ground clearance: tail rotor guard.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Ground clearance: tail rotor guard. 27.411 Section 27.411 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... System Loads § 27.411 Ground clearance: tail rotor guard. (a) It must be impossible for the tail rotor...

  6. Development of a rotor wake-vortex model, volume 1

    NASA Technical Reports Server (NTRS)

    Majjigi, R. K.; Gliebe, P. R.

    1984-01-01

    Certain empirical rotor wake and turbulence relationships were developed using existing low speed rotor wave data. A tip vortex model was developed by replacing the annulus wall with a row of image vortices. An axisymmetric turbulence spectrum model, developed in the context of rotor inflow turbulence, was adapted to predicting the turbulence spectrum of the stator gust upwash.

  7. 14 CFR 29.411 - Ground clearance: tail rotor guard.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Ground clearance: tail rotor guard. 29.411 Section 29.411 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... System Loads § 29.411 Ground clearance: tail rotor guard. (a) It must be impossible for the tail rotor...

  8. Tarp rotor system thrust, yaw and load control

    SciTech Connect

    Weisbrich, A. L.

    1985-09-10

    Presented is a means for thrust and, hence, yaw and load control of a TARP twin rotor system by means of initiating a thrust differential between said rotors which, in turn, yaws the twin rotor assembly into a protected low flow velocity region about a TARP and alleviates load on said assembly.

  9. Helicopter tail rotor blade-vortex interaction noise

    NASA Technical Reports Server (NTRS)

    George, Albert R.; Chou, S.-T.

    1987-01-01

    A study is made of helicopter tail rotor noise, particularly that due to the interactions with main rotor tip vortices. Summarized here are present analysis, the computer codes, and the results of several test cases. Amiet's unsteady thin airfoil theory is used to calculate the acoustics of blade-vortex interaction. The noise source is modelled as a force dipole resulting from an airfoil of infinite span chopping through a skewed line vortex. To analyze the interactions between helicopter tail rotor and main rotor tip vortices, we developed a two-step approach: (1) the main rotor tip vortex system is obtained through a free wake geometry calculation of the main rotor using CAMRAD code; (2) acoustic analysis takes the results from the aerodynamic interaction analysis and calculates the farfield pressure signatures for the interactions. It is found that under a wide range of helicopter flight conditions, acoustic pressure fluctuations of significant magnitude can be generated by tail rotors due to a series of interactions with main rotor tip vortices. This noise mechanism depends strongly on the helicopter flight conditions and the relative location and phasing of the main and tail rotors. fluctuations of significant magnitude can be generated by tail rotors due to a series of interactions with main rotor tip vortices. This noise mechanism depends strongly upon the helicopter flight conditions and the relative location and phasing of the main and tail rotors.

  10. 14 CFR 23.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Equipment containing high energy rotors. 23... Equipment Miscellaneous Equipment § 23.1461 Equipment containing high energy rotors. (a) Equipment, such as Auxiliary Power Units (APU) and constant speed drive units, containing high energy rotors must...

  11. 14 CFR 23.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Equipment containing high energy rotors. 23... Equipment Miscellaneous Equipment § 23.1461 Equipment containing high energy rotors. (a) Equipment, such as Auxiliary Power Units (APU) and constant speed drive units, containing high energy rotors must...

  12. 14 CFR 23.1461 - Equipment containing high energy rotors.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Equipment containing high energy rotors. 23... Equipment Miscellaneous Equipment § 23.1461 Equipment containing high energy rotors. (a) Equipment, such as Auxiliary Power Units (APU) and constant speed drive units, containing high energy rotors must...

  13. Dovetail Rotor Construction For Permanent-Magnet Motors

    NASA Technical Reports Server (NTRS)

    Kintz, Lawrence J., Jr.; Puskas, William J.

    1988-01-01

    New way of mounting magnets in permanent-magnet, electronically commutated, brushless dc motors. Magnets wedge shaped, tapering toward center of rotor. Oppositely tapered pole pieces, electron-beam welded to rotor hub, retain magnets against centrifugal force generated by spinning rotor. To avoid excessively long electron-beam welds, pole pieces assembled in segments rather than single long bars.

  14. 76 FR 42020 - Airworthiness Standards; Rotor Overspeed Requirements

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-18

    ... ``extremely remote'' in Sec. 33.27(c); Exclusions of shaft sections from overspeed tests; Material properties... comment. Material Properties of Test Rotors Section 33.27(a)(1) proposed that test rotors used to... validated to prior overspeed test results of a similar rotor. The tool must be validated for each...

  15. Miniature swept source for point of care Optical Frequency Domain Imaging

    PubMed Central

    Goldberg, Brian D.; Nezam, S.M. Reza Motaghian; Jillella, Priyanka; Bouma, Brett E.; Tearney, Guillermo J.

    2009-01-01

    Point of care (POC) medical technologies require portable, small, robust instrumentation for practical implementation. In their current embodiment, optical frequency domain imaging (OFDI) systems employ large form-factor wavelength-swept lasers, making them impractical in the POC environment. Here, we describe a first step toward a POC OFDI system by demonstrating a miniaturized swept-wavelength source. The laser is based on a tunable optical filter using a reflection grating and a miniature resonant scanning mirror. The laser achieves 75 nm of bandwidth centered at 1340 nm, a 0.24 nm instantaneous line width, a 15.3 kHz repetition rate with 12 mW peak output power, and a 30.4 kHz A-line rate when utilizing forward and backward sweeps. The entire laser system is approximately the size of a deck of cards and can operate on battery power for at least one hour. PMID:19259202

  16. Experimental Evaluation of Stagnation Point Collection Efficiency of the NACA 0012 Swept Wing Tip

    NASA Technical Reports Server (NTRS)

    Tsao, Jen-Ching; Kreeger, Richard E.

    2010-01-01

    This paper presents the experimental work of a number of icing tests conducted in the Icing Research Tunnel at NASA Glenn Research Center to develop a test method for measuring the local collection efficiency of an impinging cloud at the leading edge of a NACA 0012 swept wing and with the data obtained to further calibrate a proposed correlation for such impingement efficiency calculation as a function of the modified inertia parameter and the sweep angle. The preliminary results showed that there could be some limitation of the test method due to the ice erosion problem when encountered, and also found that, for conditions free of such problem, the stagnation point collection efficiency measurement for sweep angles up to 45 could be well approximated by the proposed correlation. Further evaluation of this correlation is recommended in order to assess its applicability for swept-wing icing scaling analysis.

  17. NASA,FAA,ONERA Swept-Wing Icing and Aerodynamics: Summary of Research and Current Status

    NASA Technical Reports Server (NTRS)

    Broeren, Andy

    2015-01-01

    NASA, FAA, ONERA, and other partner organizations have embarked on a significant, collaborative research effort to address the technical challenges associated with icing on large scale, three-dimensional swept wings. These are extremely complex phenomena important to the design, certification and safe operation of small and large transport aircraft. There is increasing demand to balance trade-offs in aircraft efficiency, cost and noise that tend to compete directly with allowable performance degradations over an increasing range of icing conditions. Computational fluid dynamics codes have reached a level of maturity that they are being proposed by manufacturers for use in certification of aircraft for flight in icing. However, sufficient high-quality data to evaluate their performance on iced swept wings are not currently available in the public domain and significant knowledge gaps remain.

  18. The NASA Langley Laminar-Flow-Control (LFC) experiment on a swept, supercritical airfoil: Design overview

    NASA Technical Reports Server (NTRS)

    Harris, Charles D.; Harvey, William D.; Brooks, Cuyler W., Jr.

    1988-01-01

    A large-chord, swept, supercritical, laminar-flow-control (LFC) airfoil was designed and constructed and is currently undergoing tests in the Langley 8 ft Transonic Pressure Tunnel. The experiment was directed toward evaluating the compatibility of LFC and supercritical airfoils, validating prediction techniques, and generating a data base for future transport airfoil design as part of NASA's ongoing research program to significantly reduce drag and increase aircraft efficiency. Unique features of the airfoil included a high design Mach number with shock free flow and boundary layer control by suction. Special requirements for the experiment included modifications to the wind tunnel to achieve the necessary flow quality and contouring of the test section walls to simulate free air flow about a swept model at transonic speeds. Design of the airfoil with a slotted suction surface, the suction system, and modifications to the tunnel to meet test requirements are discussed.

  19. Corneal topography with high-speed swept source OCT in clinical examination

    PubMed Central

    Karnowski, Karol; Kaluzny, Bartlomiej J.; Szkulmowski, Maciej; Gora, Michalina; Wojtkowski, Maciej

    2011-01-01

    We present the applicability of high-speed swept source (SS) optical coherence tomography (OCT) for quantitative evaluation of the corneal topography. A high-speed OCT device of 108,000 lines/s permits dense 3D imaging of the anterior segment within a time period of less than one fourth of second, minimizing the influence of motion artifacts on final images and topographic analysis. The swept laser performance was specially adapted to meet imaging depth requirements. For the first time to our knowledge the results of a quantitative corneal analysis based on SS OCT for clinical pathologies such as keratoconus, a cornea with superficial postinfectious scar, and a cornea 5 months after penetrating keratoplasty are presented. Additionally, a comparison with widely used commercial systems, a Placido-based topographer and a Scheimpflug imaging-based topographer, is demonstrated. PMID:21991558

  20. Wideband detection of middle ear muscle activation using swept-tone distortion product otoacoustic emissions.

    PubMed

    Henin, Simon; Long, Glenis R; Thompson, Suzanne

    2014-07-01

    The measurement of efferent-induced suppression of otoacoustic emissions (OAEs) using contralateral acoustic stimulation (CAS) is complicated by potential contamination by the middle ear muscle reflex (MEMR), particularly at moderate to high CAS levels. When logarithmically sweeping primaries are used to measure distortion product otoacoustic emissions, the level and phase of the primaries at the entrance of the ear canal may be monitored simultaneously along with the OAEs elicited by the swept-tones. A method of detecting MEMR activation using swept-tones is presented in which the differences in the primaries in the ear canal with and without CAS are examined, permitting evaluation of MEMR effects over a broad frequency range. A range of CAS levels above and below expected contralateral acoustic reflex thresholds permitted evaluation of conditions with and without MEMR activation.

  1. Simple and versatile long range swept source for optical coherence tomography applications

    NASA Astrophysics Data System (ADS)

    Bräuer, Bastian; Lippok, Norman; Murdoch, Stuart G.; Vanholsbeeck, Frédérique

    2015-12-01

    We present a versatile long coherence length swept-source laser design for optical coherence tomography applications. This design consists of a polygonal spinning mirror and an optical gain chip in a modified Littman-Metcalf cavity. A narrowband intra-cavity filter is implemented through multiple passes off a diffraction grating set at grazing incidence. The key advantage of this design is that it can be readily adapted to any wavelength regions for which broadband gain chips are available. We demonstrate this by implementing sources at 1650 nm, 1550 nm, 1310 nm and 1050 nm. In particular, we present a 1310 nm swept source laser with 24 mm coherence length, 95 nm optical bandwidth, 2 kHz maximum sweep frequency and 7.5 mW average output power. These parameters make it a suitable source for the imaging of biological samples.

  2. Design aspects of long range supersonic LFC airplanes with highly swept wings. [laminar flow control

    NASA Technical Reports Server (NTRS)

    Pfenninger, W.; Vemuru, C. S.

    1990-01-01

    Studies on supersonic long-range LFC (laminar flow control) aircraft were performed with the aim of maximizing L/D and alleviating sonic boom during supersonic cruise. It is found that configurations with highly swept LFC wings of very high structural aspect ratio, with the sweep increasing toward the wing root and braced externally by wide chord laminarized struts, appear especially promising. In the supersonic cruise design condition the wing upper surface isobars are swept such that the flow in the direction normal to them is transonic with embedded supersonic zones and practically shock-free over most of the span, with M-perpendicular equal to the two-dimensional design values of advanced SC LFC airfoils, e.g., of the X-787 or X-6 type.

  3. Subcritical instability on the attachment-line of an infinite swept wing

    NASA Astrophysics Data System (ADS)

    Sengupta, T. K.; Dipankar, A.

    2005-04-01

    The leading-edge contamination (LEC) problem of an infinite swept wing is shown here as vortex-induced instability. The governing equation for receptivity is presented for LEC in terms of disturbance energy based on the Navier-Stokes equation. The unperturbed shear layer given by the swept Hiemenz boundary-layer solution is two-dimensional and an exact solution of incompressible the Navier-Stokes equation. Thus, the LEC problem is solved numerically by solving the full two-dimensional Navier-Stokes equation. The contamination at the attachment-line is shown by solving a receptivity to a convecting vortex moving outside the attachment-line boundary layer, which triggers subcritical spatio-temporal instability.

  4. Analysis, Synthesis, and Classification of Nonlinear Systems Using Synchronized Swept-Sine Method for Audio Effects

    NASA Astrophysics Data System (ADS)

    Novak, Antonin; Simon, Laurent; Lotton, Pierrick

    2010-12-01

    A new method of identification, based on an input synchronized exponential swept-sine signal, is used to analyze and synthesize nonlinear audio systems like overdrive pedals for guitar. Two different pedals are studied; the first one exhibiting a strong influence of the input signal level on its input/output law and the second one exhibiting a weak influence of this input signal level. The Synchronized Swept Sine method leads to a Generalized Polynomial Hammerstein model equivalent to the pedals under test. The behaviors of both pedals are illustrated through model-based resynthesized signals. Moreover, it is also shown that this method leads to a criterion allowing the classification of the nonlinear systems under test, according to the influence of the input signal levels on their input/output law.

  5. Extending a transonic small disturbance code to treat swept vertical surfaces

    NASA Technical Reports Server (NTRS)

    Gibbons, Michael D.

    1992-01-01

    A flexible-swept vertical surface capability has been developed and implemented within the CAP-TSD transonic small disturbance (TSD) code. The new capability required a modification to the TSD equation and a grid transformation for swept vertical surfaces. Modifications to the vertical surface boundary conditions allow it to be treated as a flexible surface. The new capability extends the range of problems which the code can treat. In order to assess the accuracy of the modifications, calculations were performed for a rectangular T-tail configuration and an AGARD T-tail configuration. Unsteady forces and moments are presented for the rectangular T-tail oscillating in yaw for a range of reduced frequencies. Comparisons are presented with linear theory and experiment. Steady and unsteady surface pressures are presented for the AGARD T-tail along with generalized aerodynamic forces. Comparisons are made with linear theory. The comparisons demonstrate the accuracy of the vertical surface modifications.

  6. Asymmetry Analysis of Macular Inner Retinal Layers for Glaucoma Diagnosis: Swept-Source Optical Coherence Tomography Study

    PubMed Central

    Lee, Sang-Yoon; Lee, Eun Kyoung; Park, Ki Ho; Kim, Dong Myung

    2016-01-01

    Purpose To report an asymmetry analysis of macular inner retinal layers using swept-source optical coherence tomography (OCT) and to evaluate the utility for glaucoma diagnosis. Design Observational, cross-sectional study. Participants Seventy normal healthy subjects and 62 glaucoma patients. Methods Three-dimensional scans were acquired from 70 normal subjects and 62 open angle glaucoma patients by swept-source OCT. The thickness of the retinal nerve fiber layer, ganglion cell-inner plexiform layer (GCIPL), ganglion cell complex, and total retina were calculated within a 6.2×6.2 mm macular area divided into a 31×31 grid of 200×200 μm superpixels. For each of the corresponding superpixels, the thickness differences between the subject eyes and contra-lateral eyes and between the upper and lower macula halves of the subject eyes were determined. The negative differences were displayed on a gray-scale asymmetry map. Black superpixels were defined as thickness decreases over the cut-off values. Results The negative inter-ocular and inter-hemisphere differences in GCIPL thickness (mean ± standard deviation) were -2.78 ± 0.97 μm and -3.43 ± 0.71 μm in the normal group and -4.26 ± 2.23 μm and -4.88 ± 1.46 μm in the glaucoma group. The overall extent of the four layers’ thickness decrease was larger in the glaucoma group than in the normal group (all Ps<0.05). The numbers of black superpixels on all of the asymmetry maps were larger in the glaucoma group than in the normal group (all Ps<0.05). The area under receiver operating characteristic curves of average negative thickness differences in macular inner layers for glaucoma diagnosis ranged from 0.748 to 0.894. Conclusions The asymmetry analysis of macular inner retinal layers showed significant differences between the normal and glaucoma groups. The diagnostic performance of the asymmetry analysis was comparable to that of previous methods. These findings suggest that the asymmetry analysis can be a

  7. Initiation Mechanisms of Low-loss Swept-ramp Obstacles for Deflagration to Detonation Transition in Pulse Detonation Combustors

    DTIC Science & Technology

    2009-12-01

    MECHANISMS OF LOW-LOSS SWEPT-RAMP OBSTACLES FOR DEFLAGRATION TO DETONATION TRANSITION IN PULSE DETONATION COMBUSTORS by Charles B. Myers IV...TITLE AND SUBTITLE Initiation Mechanisms of Low-loss Swept-ramp Obstacles for Deflagration to Detonation Transition in Pulse Detonation Combustors 6...DISTRIBUTION CODE A 13. ABSTRACT (maximum 200 words) In order to enhance the performance of pulse detonation combustors (PDCs), an efficient

  8. 115 kHz tuning repetition rate ultrahigh-speed wavelength-swept semiconductor laser.

    PubMed

    Oh, W Y; Yun, S H; Tearney, G J; Bouma, B E

    2005-12-01

    We demonstrate an ultrahigh-speed wavelength-swept semiconductor laser using a polygon-based wavelength scanning filter. With a polygon rotational speed of 900 revolutions per second, a continuous wavelength tuning rate of 9200 nm/ms and a tuning repetition rate of 115 kHz were achieved. The wavelength tuning range of the laser was 80 nm centered at 1325 nm, and the average polarized output power was 23 mW.

  9. Applications of Displacement Transfer Functions to Deformed Shape Predictions of the GIII Swept-Wing Structure

    NASA Technical Reports Server (NTRS)

    Lung, Shun-Fat; Ko, William L.

    2016-01-01

    The displacement transfer functions (DTFs) were applied to the GIII swept wing for the deformed shape prediction. The calculated deformed shapes are very close to the correlated finite element results as well as the measured data. The convergence study showed that using 17 strain stations, the wing-tip displacement prediction error was 1.6 percent, and that there is no need to use a large number of strain stations for G-III wing shape predictions.

  10. Three dimensional shear flow: Flow visualisation around a highly swept back and high incidence wing

    NASA Astrophysics Data System (ADS)

    Pailhas, G.

    1990-03-01

    A study to find a geometric profile position (sweep 60 degrees fixed, variable incidence) such that the vincinity of the wing body junction becomes a likely field for a horseshoe type turbulent motion, as found in the classical case of the straight wing, is presented. Cavitation flow visualizations by viscous coatings were carried out at incidences of 15, 20, 25, and 30 degrees. Results showed differences in the flows at the wing-body vicinity of differing swept back wings and straight wings.

  11. On the stability of the infinite swept attachment line boundary layer

    NASA Astrophysics Data System (ADS)

    Theofilis, V.; Duck, P. W.; Poll, D. I. A.

    A number of numerical schemes were employed in order to gain insight in the stability problem of the infinite swept attachment line boundary layer. The basic flow was taken to be the classical Hiemenz flow. A number of assumptions for the perturbation flow quantities were considered. In all cases a pseudo- spectral approach was used; the chordwise and spanwise directions were treated spectrally, while an implicit Crank-Nicolson scheme was used temporally. Extensive use of the FFT algorithm has been made.

  12. The stability of a three dimensional laminar boundary layer over a swept flat plate

    NASA Technical Reports Server (NTRS)

    Mueller, B.; Bippes, H.; Collier, F. S., Jr.

    1990-01-01

    The linear stability of the laminar boundary layer on a swept flat plate with an imposed favorable pressure gradient was studied utilizing a linear stability model which accounts for streamline curvature for three-dimensional incompressible flows. Calculations were performed for a leading-edge sweep angle of 45 degrees and freestream valocity of 19 m/s. Computed disturbance amplification rates and wavelengths for stationary crossflow vortices were compared with available experimental results.

  13. The stability of a three-dimensional laminar boundary layer on a swept flat plate

    NASA Technical Reports Server (NTRS)

    Collier, F. S., Jr.; Mueller, B.; Bippes, H.

    1990-01-01

    The linear stability of the laminar boundary layer on a swept flat plate with an imposed favorable pressure gradient was studied utilizing a linear stability model which accounts for streamline curvature for three-dimensional incompressible flows. Calculations were performed for an effective leading-edge sweep angle of 42.5 degrees and freestream velocity of 19 m/s. Computed disturbance amplification rates for the spectrum of amplified frequencies and wavelengths for stationary crossflow vortices were compared with experimental results.

  14. Separation attenuation in swept shock wave-boundary-layer interactions using different microvortex generator geometries

    NASA Astrophysics Data System (ADS)

    Martis, R. R.; Misra, A.

    2017-03-01

    A numerical study is conducted to determine the effectiveness of six different microvortex generator geometries in controlling swept shock wave/boundary-layer interactions. The geometries considered are base ramp, base ramp with declining angle of 45°, blunt ramp, split ramp, thick vanes, and ramped vanes. Microvortex generators with a gap were found to be better suited for delaying the separation. Thick vanes showed the largest delay in separation among the devices studied.

  15. Swept shock/boundary layer interaction experiments in support of CFD code validation

    NASA Technical Reports Server (NTRS)

    Settles, G. S.; Lee, Y.

    1990-01-01

    Research on the topic of shock wave/turbulent boundary layer interaction was carried out. Skin friction and surface pressure measurements in fin-induced, swept interactions were conducted, and heat transfer measurements in the same flows are planned. The skin friction data for a strong interaction case (Mach 4, fin-angles equal 16 and 20 degrees) were obtained, and their comparison with computational results was published. Surface pressure data for weak-to-strong fin interactions were also obtained.

  16. 28 MHz swept source at 1.0 μm for ultrafast quantitative phase imaging

    PubMed Central

    Wei, Xiaoming; Lau, Andy K. S.; Xu, Yiqing; Tsia, Kevin K.; Wong, Kenneth K. Y.

    2015-01-01

    Emerging high-throughput optical imaging modalities, in particular those providing phase information, necessitate a demanding speed regime (e.g. megahertz sweep rate) for those conventional swept sources; while an effective solution is yet to be demonstrated. We demonstrate a stable breathing laser as inertia-free swept source (BLISS) operating at a wavelength sweep rate of 28 MHz, particularly for the ultrafast interferometric imaging modality at 1.0 μm. Leveraging a tunable dispersion compensation element inside the laser cavity, the wavelength sweep range of BLISS can be tuned from ~10 nm to ~63 nm. It exhibits a good intensity stability, which is quantified by the ratio of standard deviation to the mean of the pulse intensity, i.e. 1.6%. Its excellent wavelength repeatability, <0.05% per sweep, enables the single-shot imaging at an ultrafast line-scan rate without averaging. To showcase its potential applications, it is applied to the ultrafast (28-MHz line-scan rate) interferometric time-stretch (iTS) microscope to provide quantitative morphological information on a biological specimen at a lateral resolution of 1.2 μm. This fiber-based inertia-free swept source is demonstrated to be robust and broadband, and can be applied to other established imaging modalities, such as optical coherence tomography (OCT), of which an axial resolution better than 12 μm can be achieved. PMID:26504636

  17. Modeling and numerical investigation of the inlet circumferential fluctuations of swept and bowed blades

    NASA Astrophysics Data System (ADS)

    Tang, Mingzhi; Jin, Donghai; Gui, Xingmin

    2017-02-01

    The circumferential fluctuation (CF) source terms induced by the inviscid blade force can affect the inlet distribution of flow parameters and radial equilibrium of swept and bowed blades. However, these phenomena cannot be adequately described by throughflow methods based on the axisymmetric assumption. A transport model for the CF stresses is proposed and correlated to the distribution of circulation to reflect the effect of the inviscid blade force. To investigate the effect of the inlet CFs on swept and bowed blades, the model is integrated into a throughflow model and applied to a series of cascades with different sweep and bow angles. For swept cascades, the CF source terms change the distributions of incidence angles, as well as the radial equilibrium at the inlet of the blade passage. And the influence is enhanced as the absolute value of the sweep angle increases. For bowed cascades, the distributions of incidence angles are also altered. For both cases, the model can offer a good prediction of the inlet CF source terms, and prove to exert a better prediction of blade design key parameters such as flow angles.

  18. Multiplexing of fiber-optic ultrasound sensors via swept frequency interferometry.

    PubMed

    Gabai, Haniel; Steinberg, Idan; Eyal, Avishay

    2015-07-27

    The use of fiber-optic sensors for ultrasound (US) detection has many advantages over conventional piezoelectric detectors. However, the issue of multiplexing remains a major challenge. Here, a novel approach for multiplexing fiber-optic based US sensors using swept frequency interferometry is introduced. Light from a coherent swept source propagates in an all-fiber interferometric network made of a reference arm and a parallel connection of N sensing arms. Each sensing arm comprises a short polyimide coated sensing section (~4cm), which is exposed to the US excitation, preceded by a delay of different length. When the instantaneous frequency of the laser is linearly swept, the receiver output contains N harmonic beat components which correspond to the various optical paths. Exposing the sensing sections to US excitation introduces phase modulation of the harmonic components. The US-induced signals can be separated in the frequency domain and be extracted from their carriers by common demodulation techniques. The method was demonstrated by multiplexing 4 sensing fibers and detecting microsecond US pulses which were generated by a 2.25MHz ultrasound transducer. The pulses were successfully measured by all sensing fibers without noticeable cross-talk.

  19. Measurement of frequency swept linearly with Fabry-Perot fiber interferometer

    NASA Astrophysics Data System (ADS)

    Luan, Zhu; Xu, Nan; Liu, De'an; Zhou, Yu; Liu, Liren

    2009-08-01

    Synthetic aperture imaging ladar (SAIL) used a series of pulses in which the optical frequency was swept linearly in time over a bandwidth greater than several gigahertz. The linearity of such broadly tunable sources is often poor which is leading to phase errors. Many methods are adopted to correct for quadratic and higher-order phase errors such as the reference channel or algorithm for unmatched channel of Aerospace and the reference interferometer of Naval Research Laboratory. If the real value of frequency swept quasi-linearly is measured another direct way to mitigate the waveform linearity problem can be developed. At first the frequency curve is measured with Fabry Perot fiber interferometer. Experiment and results are explained in detail in this paper. The quadratic and higher-order terms of frequency swept are calculated. They may be used to deduce the phase errors directly later. At the same time the wavefront is also measured by a Jamin shearing interferometer through the fringe analysis.

  20. Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation

    PubMed Central

    Siddiqui, Meena; Tozburun, Serhat; Zhang, Ellen Ziyi; Vakoc, Benjamin J.

    2015-01-01

    We provide a framework for compensating errors within passive optical quadrature demodulation circuits used in swept-source optical coherence tomography (OCT). Quadrature demodulation allows for detection of both the real and imaginary components of an interference fringe, and this information separates signals from positive and negative depth spaces. To achieve a high extinction (∼60 dB) between these positive and negative signals, the demodulation error must be less than 0.1% in amplitude and phase. It is difficult to construct a system that achieves this low error across the wide spectral and RF bandwidths of high-speed swept-source systems. In a prior work, post-processing methods for removing residual spectral errors were described. Here, we identify the importance of a second class of errors originating in the RF domain, and present a comprehensive framework for compensating both spectral and RF errors. Using this framework, extinctions >60 dB are demonstrated. A stability analysis shows that calibration parameters associated with RF errors are accurate for many days, while those associated with spectral errors must be updated prior to each imaging session. Empirical procedures to derive both RF and spectral calibration parameters simultaneously and to update spectral calibration parameters are presented. These algorithms provide the basis for using passive optical quadrature demodulation circuits with high speed and wide-bandwidth swept-source OCT systems. PMID:25836784

  1. Clinical utility of anterior segment swept-source optical coherence tomography in glaucoma

    PubMed Central

    Angmo, Dewang; Nongpiur, Monisha E.; Sharma, Reetika; Sidhu, Talvir; Sihota, Ramanjit; Dada, Tanuj

    2016-01-01

    Optical coherence tomography (OCT), a noninvasive imaging modality that uses low-coherence light to obtain a high-resolution cross-section of biological structures, has evolved dramatically over the years. The Swept-source OCT (SS-OCT) makes use of a single detector with a rapidly tunable laser as a light source. The Casia SS-1000 OCT is a Fourier-domain, SS-OCT designed specifically for imaging the anterior segment. This system achieves high resolution imaging of 10΅m (Axial) and 30΅m (Transverse) and high speed scanning of 30,000 A-scans per second. With a substantial improvement in scan speed, the anterior chamber angles can be imaged 360 degrees in 128 cross sections (each with 512 A-scans) in about 2.4 seconds. We summarize the clinical applications of anterior segment SS-OCT in Glaucoma. Literature search: We searched PubMed and included Medline using the phrases anterior segment optical coherence tomography in ophthalmology, swept-source OCT, use of AS-OCT in glaucoma, use of swept-source AS-OCT in glaucoma, quantitative assessment of angle, filtering bleb in AS-OCT, comparison of AS-OCT with gonioscopy and comparison of AS-OCT with UBM. Search was made for articles dating 1990 to August 2015. PMID:27013821

  2. A spectrally accurate boundary-layer code for infinite swept wings

    NASA Astrophysics Data System (ADS)

    Pruett, C. David

    1994-12-01

    This report documents the development, validation, and application of a spectrally accurate boundary-layer code, WINGBL2, which has been designed specifically for use in stability analyses of swept-wing configurations. Currently, we consider only the quasi-three-dimensional case of an infinitely long wing of constant cross section. The effects of streamwise curvature, streamwise pressure gradient, and wall suction and/or blowing are taken into account in the governing equations and boundary conditions. The boundary-layer equations are formulated both for the attachment-line flow and for the evolving boundary layer. The boundary-layer equations are solved by marching in the direction perpendicular to the leading edge, for which high-order (up to fifth) backward differencing techniques are used. In the wall-normal direction, a spectral collocation method, based upon Chebyshev polynomial approximations, is exploited. The accuracy, efficiency, and user-friendliness of WINGBL2 make it well suited for applications to linear stability theory, parabolized stability equation methodology, direct numerical simulation, and large-eddy simulation. The method is validated against existing schemes for three test cases, including incompressible swept Hiemenz flow and Mach 2.4 flow over an airfoil swept at 70 deg to the free stream.

  3. A spectrally accurate boundary-layer code for infinite swept wings

    NASA Technical Reports Server (NTRS)

    Pruett, C. David

    1994-01-01

    This report documents the development, validation, and application of a spectrally accurate boundary-layer code, WINGBL2, which has been designed specifically for use in stability analyses of swept-wing configurations. Currently, we consider only the quasi-three-dimensional case of an infinitely long wing of constant cross section. The effects of streamwise curvature, streamwise pressure gradient, and wall suction and/or blowing are taken into account in the governing equations and boundary conditions. The boundary-layer equations are formulated both for the attachment-line flow and for the evolving boundary layer. The boundary-layer equations are solved by marching in the direction perpendicular to the leading edge, for which high-order (up to fifth) backward differencing techniques are used. In the wall-normal direction, a spectral collocation method, based upon Chebyshev polynomial approximations, is exploited. The accuracy, efficiency, and user-friendliness of WINGBL2 make it well suited for applications to linear stability theory, parabolized stability equation methodology, direct numerical simulation, and large-eddy simulation. The method is validated against existing schemes for three test cases, including incompressible swept Hiemenz flow and Mach 2.4 flow over an airfoil swept at 70 deg to the free stream.

  4. NASA/HAA Advanced Rotorcraft Technology and Tilt Rotor Workshop. Volume 7: Tilt Rotor Session

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The technical characteristics of the XV-15 aircraft were discussed. Program objectives, concept evaluation, tilt rotor experiments and civil market applications are presented. The XV-15 status and test schedule are also included.

  5. Response studies of rotors and rotor blades with application to aeroelastic tailoring

    NASA Technical Reports Server (NTRS)

    Friedmann, P. P.

    1982-01-01

    Various tools for the aeroelastic stability and response analysis of rotor blades in hover and forward flight were developed and incorporated in a comprehensive package capable of performing aeroelastic tailoring of rotor blades in forward flight. The results indicate that substantial vibration reductions, of order 15-40%, in the vibratory hub shears can be achieved by relatively small modifications of the initial design. Furthermore the optimized blade can be up to 20% lighter than the original design. Accomplishments are reported for the following tasks: (1) finite element modeling of rotary-wing aeroelastic problems in hover and forward flight; (2) development of numerical methods for calculating the aeroelastic response and stability of rotor blades in forward fight; (3) formulation of the helicopter air resonance problem in hover with active controls; and (4) optimum design of rotor blades for vibration reduction in forward flight.

  6. Effect of Rotor Diameter on the Thermal Stresses of a Turbine Rotor Model

    NASA Astrophysics Data System (ADS)

    Dávalos, J. O.; García, J. C.; Urquiza, G.; Castro-Gómez, L. L.; Rodríguez, J. A.; De Santiago, O.

    2016-04-01

    Thermal stresses in a simplified steam turbine rotor model during a cold startup are analyzed using finite element analysis (FEA). In order to validate the numerical model, an experimental array is developed in which a hollow cylinder is heated with hot air in the external surface. At the thick wall of the cylinder, temperature distribution is measured in real time, while at the same time an algorithm computes thermal stresses. Additional computational fluid dynamics (CFD) calculations are made to obtain magnitudes of velocity and pressure in order to compute convective heat transfer coefficient. The experimental results show good agreement with the FEA computations. To evaluate the effect of rotor diameter size, FEA computations with variation in external and internal diameters are performed. Results show that thermal stresses are proportional to rotor diameter size. Also, zones of higher stress concentration are found in the external and internal surfaces of the rotor.

  7. Rotor bore and turbine rotor wheel/spacer heat exchange flow circuit

    DOEpatents

    Caruso, Philip M.; Eldrid, Sacheverel Quentin; Ladhani, Azad A.; DeMania, Alan Richard; Palmer, Gene David; Wilson, Ian David; Rathbun, Lisa Shirley; Akin, Robert Craig

    2002-01-01

    In a turbine having closed-circuit steam-cooling passages about the rim of the rotor during steady-state operation, compressor discharge air is supplied to the rotor bore for passage radially outwardly into the wheel space cavities between the wheels and spacers. Communicating slots and channels in the spacers and wheels at circumferentially spaced positions enable egress of the compressor discharge air into the hot gas flow path. At turbine startup, cooling air flows through the closed-circuit steam passages to cool the outer rim of the rotor while compressor discharge air pre-warms the wheels and spacers. At steady-state, cooling steam is supplied in the closed-circuit steam-cooling passages and compressor discharge air is supplied through the bore and into the wheel space cavities to cool the rotor.

  8. Large-scale Advanced Prop-fan (LAP) static rotor test report

    NASA Technical Reports Server (NTRS)

    Degeorge, Charles L.; Turnberg, Jay E.; Wainauski, Harry S.

    1987-01-01

    Discussed is Static Rotor Testing of the SR-7L Large Scale Advanced Prop-Fan (LAP). The LAP is an advanced 9 foot diameter, 8 bladed propeller designed and built by Hamilton Standard under contract to the NASA Lewis Research Center. The Prop-Fan employs thin swept blades to provide efficient propulsion at flight speeds up to Mach .85. Static Testing was conducted on a 10,000 HP whirl rig at Wright Patterson Air Force Base. The test objectives were to investigate the Prop-Fan static aerodynamic and structural dynamic performance, determine the blade steady state stressers and deflections and to measure steady and unsteady pressures on the SR-7L blade surface. The measured performance of the LAP correlated well with analytical predictions at blade pitch angles below 30 deg. A stall buffet phenomenon was observed at blade pitch angles above 30 deg. This phenomenon manifested itself by elevated blade vibratory stress levels and lower than expected thrust produced and power absorbed by the Prop-Fan for a given speed and blade angle.

  9. Trailing Vortex Measurements in the Wake of a Hovering Rotor Blade with Various Tip Shapes

    NASA Technical Reports Server (NTRS)

    Martin, Preston B.; Leishman, J. Gordon

    2003-01-01

    This work examined the wake aerodynamics of a single helicopter rotor blade with several tip shapes operating on a hover test stand. Velocity field measurements were conducted using three-component laser Doppler velocimetry (LDV). The objective of these measurements was to document the vortex velocity profiles and then extract the core properties, such as the core radius, peak swirl velocity, and axial velocity. The measured test cases covered a wide range of wake-ages and several tip shapes, including rectangular, tapered, swept, and a subwing tip. One of the primary differences shown by the change in tip shape was the wake geometry. The effect of blade taper reduced the initial peak swirl velocity by a significant fraction. It appears that this is accomplished by decreasing the vortex strength for a given blade loading. The subwing measurements showed that the interaction and merging of the subwing and primary vortices created a less coherent vortical structure. A source of vortex core instability is shown to be the ratio of the peak swirl velocity to the axial velocity deficit. The results show that if there is a turbulence producing region of the vortex structure, it will be outside of the core boundary. The LDV measurements were supported by laser light-sheet flow visualization. The results provide several benchmark test cases for future validation of theoretical vortex models, numerical free-wake models, and computational fluid dynamics results.

  10. A generic approach for photogrammetric survey using a six-rotor unmanned aerial vehicle

    NASA Astrophysics Data System (ADS)

    Tahar, K. N.; Ahmad, A.; Akib, W. A. A. W. M.; Mohd, W. M. N. W.

    2014-02-01

    This paper discusses a rapid production of slope mapping using multi-rotor unmanned aerial vehicle (UAV). The objective of this study is to determine the accuracy of the photogrammetric results based on novel method of multi-rotor UAV images as well as to analyze the slope error distribution that are obtained from the UAV images. This study only concentrates on multi-rotor UAV which also known as Hexacopter. An operator can control the speed of multi-rotor UAV during flight mission. Several ground control points and checkpoints were established using Real Time Kinematic Global Positioning System (RTK- GPS) at the slope area. Ground control points were used in exterior orientation during image processing in sequence to transform image coordinates into local coordinate system. Checkpoints were established at the slope area for accuracy assessment. A digital camera, Sony NEX-5N was used for image acquisition of slope area from UAV platforms. The digital camera was mounted vertically at the bottom of UAV and captured the images at an altitude. All acquired images went through photogrammetric processing including interior orientation, exterior orientation and bundle adjustment using photogrammetric software. Photogrammetric results such as digital elevation model, and digital orthophoto including slope map were assessed. UAV is able to acquire data within short period of time with low budget compared to the previous methods such as satellite images and airborne laser scanner. Analysis on slope analysis and error distribution analysis are discussed in this paper to determine the quality of slope map in the area of interest. In summary, multi-rotor UAV is suited in slope mapping studies.

  11. Equivalence Between Squirrel Cage and Sheet Rotor Induction Motor

    NASA Astrophysics Data System (ADS)

    Dwivedi, Ankita; Singh, S. K.; Srivastava, R. K.

    2016-06-01

    Due to topological changes in dual stator induction motor and high cost of its fabrication, it is convenient to replace the squirrel cage rotor with a composite sheet rotor. For an experimental machine, the inner and outer stator stampings are normally available whereas the procurement of rotor stampings is quite cumbersome and is not always cost effective. In this paper, the equivalence between sheet/solid rotor induction motor and squirrel cage induction motor has been investigated using layer theory of electrical machines, so as to enable one to utilize sheet/solid rotor in dual port experimental machines.

  12. Calculated Hovering Helicopter Flight Dynamics with a Circulation Controlled Rotor

    NASA Technical Reports Server (NTRS)

    Johnson, W.; Chopra, I.

    1977-01-01

    The influence of the rotor blowing coefficient on the calculated roots of the longitudinal and lateral motion was examined for a range of values of the rotor lift and the blade flap frequency. The control characteristics of a helicopter with a circulation controlled rotor are discussed. The principal effect of the blowing is a reduction in the rotor speed stability derivative. Above a critical level of blowing coefficient, which depends on the flap frequency and rotor lift, negative speed stability is produced and the dynamic characteristics of the helicopter are radically altered.

  13. T700 power turbine rotor multiplane/multispeed balancing demonstration

    NASA Technical Reports Server (NTRS)

    Burgess, G.; Rio, R.

    1979-01-01

    Research was conducted to demonstrate the ability of influence coefficient based multispeed balancing to control rotor vibration through bending criticals. Rotor dynamic analyses were conducted of the General Electric T700 power turbine rotor. The information was used to generate expected rotor behavior for optimal considerations in designing a balance rig and a balance technique. The rotor was successfully balanced 9500 rpm. Uncontrollable coupling behavior prevented observations through the 16,000 rpm service speed. The balance technique is practical and with additional refinement it can meet production standards.

  14. Optical Shaft-Angle Encoder For Helicopter Rotor

    NASA Technical Reports Server (NTRS)

    Golub, Robert A.; Fitzpatrick, Fred; Dennis, Dale V.; Taylor, Bryant D.

    1993-01-01

    Angular position of helicopter rotor blade determined precisely. Accomplished by use of optical shaft-angle encoder called "256 Ring" on rotor swashplate. Each 360 degree rotation of helicopter main rotor broken down into 256 reflective segments. As rotor rotates, beam of light reflected in turn from each segment into optoelectronic system. One of 256 segments reflects larger pulse than others do. Position of rotor determined by counting number of pulses after this reference pulse. While swashplate mounting requirements unique to each type of helicopter, concept applicable to all types of rotorcraft.

  15. Test results from a dynamic model dynaflex rotor

    NASA Technical Reports Server (NTRS)

    Niebanck, C. F.; Goodman, R. K.

    1985-01-01

    A one-fifth scale dynamic model of the Sikorsky Dynaflex rotor was tested in hover and in forward flight conditions in a wind tunnel. The Dynaflex rotor features an advanced composite structure which flexes to provide a constant speed universal joint action. Testing concentrated on confirming that the stability and dynamic response of the rotor were satisfactory. Lift conditions of up to .11 Ct/sigma and advance ratios as high as .46 were reached. Vibratory loads were compared to those of articulated rotors. The Dynaflex rotor concept appears to be a practical concept from the standpoint of dynamic response and stability.

  16. On the flow field around a Savonius rotor

    NASA Astrophysics Data System (ADS)

    Bergeles, G.; Athanassiadis, N.

    A model of a two-bucket Savonius rotor windmill was constructed and tested in a wind tunnel. The flow field around the rotor was examined visually and also quantitatively with the use of a hot wire. The flow visualization revealed an upstream influence on the flow field up to 3 rotor diameters away and a strong downwash downstream. Hot wire measurements showed a large velocity deficit behind the rotor and a quick velocity recovery downstream due to strong mixing; the latter was associated with high levels of turbulence. Energy spectra revealed that all turbulence was concentrated in a single harmonic corresponding to twice the rotational speed of the rotor.

  17. Flywheel system using wire-wound rotor

    DOEpatents

    Chiao, Edward Young; Bender, Donald Arthur; Means, Andrew E.; Snyder, Philip K.

    2016-06-07

    A flywheel is described having a rotor constructed of wire wound onto a central form. The wire is prestressed, thus mitigating stresses that occur during operation. In another aspect, the flywheel incorporates a low-loss motor using electrically non-conducting permanent magnets.

  18. Eigenvalue assignment strategies in rotor systems

    NASA Technical Reports Server (NTRS)

    Youngblood, J. N.; Welzyn, K. J.

    1986-01-01

    The work done to establish the control and direction of effective eigenvalue excursions of lightly damped, speed dependent rotor systems using passive control is discussed. Both second order and sixth order bi-axis, quasi-linear, speed dependent generic models were investigated. In every case a single, bi-directional control bearing was used in a passive feedback stabilization loop to resist modal destabilization above the rotor critical speed. Assuming incomplete state measurement, sub-optimal control strategies were used to define the preferred location of the control bearing, the most effective measurement locations, and the best set of control gains to extend the speed range of stable operation. Speed dependent control gains were found by Powell's method to maximize the minimum modal damping ratio for the speed dependent linear model. An increase of 300 percent in stable speed operation was obtained for the sixth order linear system using passive control. Simulations were run to examine the effectiveness of the linear control law on nonlinear rotor models with bearing deadband. The maximum level of control effort (force) required by the control bearing to stabilize the rotor at speeds above the critical was determined for the models with bearing deadband.

  19. Modeling Aerodynamically Generated Sound of Helicopter Rotors

    NASA Technical Reports Server (NTRS)

    Brentner, Kenneth S.; Farassat, F.

    2002-01-01

    A great deal of progress has been made in the modeling of aerodynamically generated sound of rotors over the past decade. Although the modeling effort has focused on helicopter main rotors, the theory is generally valid for a wide range of rotor configurations. The Ffowcs Williams Hawkings (FW-H) equation has been the foundation for much of the development. The monopole and dipole source terms of the FW-H equation account for the thickness and loading noise, respectively. Bladevortex-interaction noise and broadband noise are important types of loading noise, hence much research has been directed toward the accurate modeling of these noise mechanisms. Both subsonic and supersonic quadrupole noise formulations have been developed for the prediction of high-speed impulsive noise. In an effort to eliminate the need to compute the quadrupole contribution, the FW-H equation has also been utilized on permeable surfaces surrounding all physical noise sources. Comparisons of the Kirchhoff formulation for moving surfaces with the FW-H equation have shown that the Kirchhoff formulation for moving surfaces can give erroneous results for aeroacoustic problems. Finally, significant progress has been made incorporating the rotor noise models into full vehicle noise prediction tools.

  20. The Evolution of Rotor and Blade Design

    SciTech Connect

    Tangler, J.

    2000-08-01

    The objective of this paper is to provide a historical perspective of the evolution of rotor and blade design during the last 20 years. This evolution is a balanced integration of economic, aerodynamic, structural dynamic, noise, and aesthetic considerations, which are known to be machine type and size dependent.

  1. Partial rotor-to-stator rub demonstration

    NASA Technical Reports Server (NTRS)

    Grissom, R.

    1985-01-01

    A rotor radial rub typically occurs in seals or at a blade tip or shroud when there is insufficient clearance, high vibration, or the shaft equilibrium position has been displaced to effectively limit the clearance (eccentricity). There are two extreme cases of radial rubs: full annular rub, when the rotor maintains continuous contact with the seal, etc.; and a partial rub, when the contact occurs during a fraction of the precession period. They both involve similar physical phenomena such as friction and modification of stiffness. In partial rubs with consecutive impacts, a significant average value of radial force is generated. This results in shaft average displacement in the direction opposite the rub location. The rotor rig demonstrates the characteristics of a partial lateral rub of varying severity and location. These characteristics include: (1) subharmonic components as a function of rotative speed/first balance resonance ratio and radial force; (2) higher harmonic content as a function of severity; (3) increased average rotor stiffness resulting in increased first balance resonance speed; and (4) change in overall orbital pattern as a sum of the unbalance response (1x) and subharmonic response (1nx).

  2. 14 CFR 27.1565 - Tail rotor.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Tail rotor. 27.1565 Section 27.1565 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... conditions. Rotorcraft Flight Manual and Approved Manual Material...

  3. 14 CFR 27.1565 - Tail rotor.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Tail rotor. 27.1565 Section 27.1565 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... conditions. Rotorcraft Flight Manual and Approved Manual Material...

  4. 14 CFR 27.1565 - Tail rotor.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Tail rotor. 27.1565 Section 27.1565 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... conditions. Rotorcraft Flight Manual and Approved Manual Material...

  5. A Model Rotor in Axial Flight

    NASA Technical Reports Server (NTRS)

    McAlister, K. W.; Huang, S. S.; Abrego, A. I.

    2001-01-01

    A model rotor was mounted horizontally in the settling chamber of a wind tunnel to obtain performance and wake structure data under low climb conditions. The immediate wake of the rotor was carefully surveyed using 3-component particle image velocimetry to define the velocity and vortical content of the flow, and used in a subsequent study to validate a theory for the separate determination of induced and profile drag. Measurements were obtained for two collective pitch angles intended to render a predominately induced drag state and another with a marked increase in profile drag. A majority of the azimuthally directed vorticity in the wake was found to be concentrated in the tip vortices. However, adjacent layers of inboard vorticity with opposite sense were clearly present. At low collective, the close proximity of the tip vortex from the previous blade caused the wake from the most recent blade passage to be distorted. The deficit velocity component that was directed along the azimuth of the rotor blade was never more that 15 percent of the rotor tip speed, and except for the region of the tip vortex, appeared to have totally disappeared form the wake left by the previous blade.

  6. Development of an Open Rotor Cycle Model in NPSS Using a Multi-Design Point Approach

    NASA Technical Reports Server (NTRS)

    Hendricks, Eric S.

    2011-01-01

    management scheme which schedules propeller blade angles with the freestream Mach number. Finally, sample open rotor performance results and areas for further model improvements are presented.

  7. Simulation of rotor blade element turbulence

    NASA Technical Reports Server (NTRS)

    Mcfarland, R. E.; Duisenberg, Ken

    1995-01-01

    A piloted, motion-based simulation of Sikorsky's Black Hawk helicopter was used as a platform for the investigation of rotorcraft responses to vertical turbulence. By using an innovative temporal and geometrical distribution algorithm that preserved the statistical characteristics of the turbulence over the rotor disc, stochastic velocity components were applied at each of twenty blade-element stations. This model was implemented on NASA Ames' Vertical Motion Simulator (VMS), and ten test pilots were used to establish that the model created realistic cues. The objectives of this research included the establishment of a simulation-technology basis for future investigation into real-time turbulence modeling. This goal was achieved; our extensive additions to the rotor model added less than a 10 percent computational overhead. Using a VAX 9000 computer the entire simulation required a cycle time of less than 12 msec. Pilot opinion during this simulation was generally quite favorable. For low speed flight the consensus was that SORBET (acronym for title) was better than the conventional body-fixed model, which was used for comparison purposes, and was determined to be too violent (like a washboard). For high speed flight the pilots could not identify differences between these models. These opinions were something of a surprise because only the vertical turbulence component on the rotor system was implemented in SORBET. Because of the finite-element distribution of the inputs, induced outputs were observed in all translational and rotational axes. Extensive post-simulation spectral analyses of the SORBET model suggest that proper rotorcraft turbulence modeling requires that vertical atmospheric disturbances not be superimposed at the vehicle center of gravity but, rather, be input into the rotor system, where the rotor-to-body transfer function severely attenuates high frequency rotorcraft responses.

  8. Dynamical localization of coupled relativistic kicked rotors

    NASA Astrophysics Data System (ADS)

    Rozenbaum, Efim B.; Galitski, Victor

    2017-02-01

    A periodically driven rotor is a prototypical model that exhibits a transition to chaos in the classical regime and dynamical localization (related to Anderson localization) in the quantum regime. In a recent work [Phys. Rev. B 94, 085120 (2016), 10.1103/PhysRevB.94.085120], A. C. Keser et al. considered a many-body generalization of coupled quantum kicked rotors, and showed that in the special integrable linear case, dynamical localization survives interactions. By analogy with many-body localization, the phenomenon was dubbed dynamical many-body localization. In the present work, we study nonintegrable models of single and coupled quantum relativistic kicked rotors (QRKRs) that bridge the gap between the conventional quadratic rotors and the integrable linear models. For a single QRKR, we supplement the recent analysis of the angular-momentum-space dynamics with a study of the spin dynamics. Our analysis of two and three coupled QRKRs along with the proved localization in the many-body linear model indicate that dynamical localization exists in few-body systems. Moreover, the relation between QRKR and linear rotor models implies that dynamical many-body localization can exist in generic, nonintegrable many-body systems. And localization can generally result from a complicated interplay between Anderson mechanism and limiting integrability, since the many-body linear model is a high-angular-momentum limit of many-body QRKRs. We also analyze the dynamics of two coupled QRKRs in the highly unusual superballistic regime and find that the resonance conditions are relaxed due to interactions. Finally, we propose experimental realizations of the QRKR model in cold atoms in optical lattices.

  9. The prediction of transonic loading on advancing helicopter rotors

    NASA Technical Reports Server (NTRS)

    Strawn, R. C.; Tung, C.

    1986-01-01

    Two different schemes are presented for including the effect of rotor wakes on the finie-difference prediction of rotor loads. The first formulation includes wake effects by means of a blade-surface inflow specification. This approach is sufficiently simple to permit coupling of a full-potential finite-difference rotor code to a comprehensive integral model for the rotor wake and blade motion. The coupling involves a transfer of appropriate loads and inflow data between the two computer codes. Results are compared with experimental data for two advancing rotor cases. The second rotor-wake modeling scheme is a split potential formulation for computing unsteady blade-vortex interactions. Discrete vortex fields are introduced into a three-dimensional, conservative, full-potential rotor code. Computer predictions are compared with two experimental blade-vortex interaction cases.

  10. The prediction of transonic loading advancing helicopter rotors

    NASA Technical Reports Server (NTRS)

    Strawn, R.; Tung, C.

    1986-01-01

    Two different schemes are presented for including the effect of rotor wakes on the finite-difference prediction of rotor loads. The first formulation includes wake effects by means of a blade-surface inflow specification. This approach is sufficiently simple to permit coupling of a full-potential finite-difference rotor code to a comprehensive integral model for the rotor wake and blade motion. The coupling involves a transfer of appropriate loads and inflow data between the two computer codes. Results are compared with experimental data for two advancing rotor cases. The second rotor wake modeling scheme in this paper is a split potential formulation for computing unsteady blade-vortex interactions. Discrete vortex fields are introduced into a three-dimensional, conservative, full-potential rotor code. Computer predictions are compared with two experimental blade-vortex interaction cases.

  11. Effects of ingested atmospheric turbulence on measured tail rotor acoustics

    NASA Technical Reports Server (NTRS)

    Signor, David B.; Yamauchi, Gloria K.; Mosher, Marianne; Hagen, Martin J.; George, Albert R.

    1992-01-01

    Results from an outdoor hover test of a full-scale Lynx tail rotor are presented. The investigation was designed to further the understanding of the acoustics of an isolated tail rotor hovering out-of-ground effect in atmospheric turbulence, without the effects of the main rotor wake or other helicopter components. Measurements include simultaneous rotor performance, noise, inflow, and far-field atmospheric turbulence. Results with grid-generated inflow turbulence are also presented. The effects of turbulence ingestion on rotor noise are quantified. Turbulence ingestion noise is found to be the dominant noise mechanism at locations near the rotor axis. At these locations, the sound radiated by the hovering rotor increases with both increasing atmospheric wind speed and ingested rms turbulent velocity.

  12. Optimum performance and potential flow field of hovering rotors

    NASA Technical Reports Server (NTRS)

    Wu, J. C.; Sigman, R. K.

    1975-01-01

    Rotor and propeller performance and induced potential flowfields were studied on the basis of a rotating actuator disk concept, with special emphasis on rotors hovering out of ground effect. A new theory for the optimum performance of rotors hovering OGE is developed and presented. An extended theory for the optimum performance of rotors and propellers in axial motion is also presented. Numerical results are presented for the optimum distributions of blade-bound circulation together with axial inflow and ultimate wake velocities for the hovering rotor over the range of thrust coefficient of interest in rotorcraft applications. Shapes of the stream tubes and of the velocities in the slipstream are obtained, using available methods, for optimum and off-optimum circulation distributions for rotors hovering in and out of ground effect. A number of explicit formulae useful in computing rotor and propeller induced flows are presented for stream functions and velocities due to distributions of circular vortices over axi-symmetric surfaces.

  13. Whirl and whip: Rotor/bearing stability problems

    NASA Technical Reports Server (NTRS)

    Muszynska, A.

    1985-01-01

    A mathematical model of a symmetric rotor supported by one rigid and one fluid lubricated bearing is proposed. The rotor model is represented by generalized (modal) parameters of its first bending mode. The rotational character of the bearing fluid force is taken into account. The model yields synchronous vibrations due to rotor unbalance as a particular solution of the equations of motion, rotor/bearing system natural frequencies and corresponding self-excited vibrations known as oil whirl and oil whip. The stability analysis yields rotative speed threshold of stability. The model also gives the evaluation of stability of the rotor synchronous vibrations. In the first balance resonance speed region two more thresholds of stability are yielded. The width of this stability region is directly related to the amount of rotor unbalance. The results of the analysis based on this model stand with very good agreement with field observations of rotor dynamic behavior and the experimental results.

  14. Utilization of rotor kinetic energy storage for hybrid vehicles

    SciTech Connect

    Hsu, John S.

    2011-05-03

    A power system for a motor vehicle having an internal combustion engine, the power system comprises an electric machine (12) further comprising a first excitation source (47), a permanent magnet rotor (28) and a magnetic coupling rotor (26) spaced from the permanent magnet rotor and at least one second excitation source (43), the magnetic coupling rotor (26) also including a flywheel having an inertial mass to store kinetic energy during an initial acceleration to an operating speed; and wherein the first excitation source is electrically connected to the second excitation source for power cycling such that the flywheel rotor (26) exerts torque on the permanent magnet rotor (28) to assist braking and acceleration of the permanent magnet rotor (28) and consequently, the vehicle. An axial gap machine and a radial gap machine are disclosed and methods of the invention are also disclosed.

  15. Icing research tunnel test of a model helicopter rotor

    NASA Technical Reports Server (NTRS)

    Miller, Thomas L.; Bond, Thomas H.

    1989-01-01

    An experimental program has been conducted in the NASA Lewis Research Center Icing Research Tunnel (IRT) in which an OH-58 tail rotor assembly was operated in a horizontal plane to simulate the action of a typical main rotor. Ice was accreted on the blades in a variety of rotor and tunnel operating conditions and documentation of the resulting shapes was performed. Rotor torque and vibration are presented as functions of time for several representative test runs, and the effects of various parametric variations on the blade ice shapes are shown. This OH-58 test was the first of its kind in the United States and will encourage additional model rotor icing tunnel testing. Although not a scaled representative of any actual full-scale main rotor system, this rig has produced torque and vibration data which will be useful in assessing the quality of existing rotor icing analyses.

  16. Optical Reflection Measurement System Using A Swept Modulation Frequency Technique

    NASA Astrophysics Data System (ADS)

    Braun, David M.; Leyde, Kent W.

    1989-03-01

    A measurement system has been developed capable of mea-suring reflected optical power as low as 0.0025% with a spot size diam-eter of 24 Am. One application for this system is the characterization of small-area photodetectors. The operation of the measurement system is simple, allowing the operator to quickly make multiple reflection measurements, and it does not require a darkroom. The measurement system merges a microscope, for visual alignment and focusing of the laser beam, with a lightwave component analyzer using modulation vec-tor error correction. A measurement comparison between the analyzer-based system and a power-meter-based system showed that each sys-tem can measure reflections as low as 0.0025%. However, the analyzer-based system offers the advantage of identifying the location and magnitude of system reflections. The system operates at a wavelength of 1310 nm.

  17. Integration of a wave rotor to an ultra-micro gas turbine (UmuGT)

    NASA Astrophysics Data System (ADS)

    Iancu, Florin

    2005-12-01

    Wave rotor technology has shown a significant potential for performance improvement of thermodynamic cycles. The wave rotor is an unsteady flow machine that utilizes shock waves to transfer energy from a high energy fluid to a low energy fluid, increasing both the temperature and the pressure of the low energy fluid. Used initially as a high pressure stage for a gas turbine locomotive engine, the wave rotor was commercialized only as a supercharging device for internal combustion engines, but recently there is a stronger research effort on implementing wave rotors as topping units or pressure gain combustors for gas turbines. At the same time, Ultra Micro Gas Turbines (UmuGT) are expected to be a next generation of power source for applications from propulsion to power generation, from aerospace industry to electronic industry. Starting in 1995, with the MIT "Micro Gas Turbine" project, the mechanical engineering research world has explored more and more the idea of "Power MEMS". Microfabricated turbomachinery like turbines, compressors, pumps, but also electric generators, heat exchangers, internal combustion engines and rocket engines have been on the focus list of researchers for the past 10 years. The reason is simple: the output power is proportional to the mass flow rate of the working fluid through the engine, or the cross-sectional area while the mass or volume of the engine is proportional to the cube of the characteristic length, thus the power density tends to increase at small scales (Power/Mass=L -1). This is the so-called "cube square law". This work investigates the possibilities of incorporating a wave rotor to an UmuGT and discusses the advantages of wave rotor as topping units for gas turbines, especially at microscale. Based on documented wave rotor efficiencies at larger scale and subsidized by both, a gasdynamic model that includes wall friction, and a CFD model, the wave rotor compression efficiency at microfabrication scale could be estimated

  18. Logarithmic intensity and speckle-based motion contrast methods for human retinal vasculature visualization using swept source optical coherence tomography

    PubMed Central

    Motaghiannezam, Reza; Fraser, Scott

    2012-01-01

    We formulate a theory to show that the statistics of OCT signal amplitude and intensity are highly dependent on the sample reflectivity strength, motion, and noise power. Our theoretical and experimental results depict the lack of speckle amplitude and intensity contrasts to differentiate regions of motion from static areas. Two logarithmic intensity-based contrasts, logarithmic intensity variance (LOGIV) and differential logarithmic intensity variance (DLOGIV), are proposed for serving as surrogate markers for motion with enhanced sensitivity. Our findings demonstrate a good agreement between the theoretical and experimental results for logarithmic intensity-based contrasts. Logarithmic intensity-based motion and speckle-based contrast methods are validated and compared for in vivo human retinal vasculature visualization using high-speed swept-source optical coherence tomography (SS-OCT) at 1060 nm. The vasculature was identified as regions of motion by creating LOGIV and DLOGIV tomograms: multiple B-scans were collected of individual slices through the retina and the variance of logarithmic intensities and differences of logarithmic intensities were calculated. Both methods captured the small vessels and the meshwork of capillaries associated with the inner retina in en face images over 4 mm2 in a normal subject. PMID:22435098

  19. Experimental study of main rotor tip geometry and tail rotor interactions in hover. Volume 2: Run log and tabulated data

    NASA Technical Reports Server (NTRS)

    Balch, D. T.; Lombardi, J.

    1985-01-01

    A model scale hover test was conducted in the Sikorsky Aircraft Model Rotor hover Facility to identify and quantify the impact of the tail rotor on the demonstrated advantages of advanced geometry tip configurations. The existence of mutual interference between hovering main rotor and a tail rotor was acknowledged in the test. The test was conducted using the Basic Model Test Rig and two scaled main rotor systems, one representing a 1/5.727 scale UH-60A BLACK HAWK and the others a 1/4.71 scale S-76. Eight alternate rotor tip configurations were tested, 3 on the BLACK HAWK rotor and 6 on the S-76 rotor. Four of these tips were then selected for testing in close proximity to an operating tail rotor (operating in both tractor and pusher modes) to determine if the performance advantages that could be obtained from the use of advanced geometry tips in a main rotor only environment would still exist in the more complex flow field involving a tail rotor. This volume contains the test run log and tabulated data.

  20. Acoustic testing of a 1.5 pressure ratio low tip speed fan with a serrated rotor (QEP fan B scale model). [reduction of engine noise

    NASA Technical Reports Server (NTRS)

    Kazin, S. B.; Paas, J. E.; Minzner, W. R.

    1973-01-01

    A scale model of the bypass flow region of a 1.5 pressure ratio, single stage, low tip speed fan was tested with a serrated rotor leading edge to determine its effects on noise generation. The serrated rotor was produced by cutting teeth into the leading edge of the nominal rotor blades. The effects of speed and exhaust nozzle area on the scale models noise characteristics were investigated with both the nominal rotor and serrated rotor. Acoustic results indicate the serrations reduced front quadrant PNL's at takeoff power. In particular, the 200 foot (61.0 m) sideline noise was reduced from 3 to 4 PNdb at 40 deg for nominal and large nozzle operation. However, the rear quadrant maximum sideline PNL's were increased 1.5 to 3 PNdb at approach thust and up to 2 PNdb at takeoff thust with these serrated rotor blades. The configuration with the serrated rotor produced the lowest maximum 200 foot (61.0 m) sideline PNL for any given thust when the large nozzle (116% of design area) was employed.

  1. Rotor-Fuselage Interaction: Analysis and Validation with Experiment

    NASA Technical Reports Server (NTRS)

    Berry, John D.; Bettschart, Nicolas

    1997-01-01

    The problem of rotor-fuselage aerodynamic interaction has to be considered in industry applications from various aspects. First, in order to increase helicopter speed and reduce operational costs, rotorcraft tend to be more and more compact, with a main rotor closer to the fuselage surface. This creates significant perturbations both on the main rotor and on the fuselage, including steady and unsteady effects due to blade and wake passage and perturbed inflow at the rotor disk. Furthermore,the main rotor wake affects the tail boom, empennage and anti-torque system. This has important consequences for helicopter control and vibrations at low speeds and also on tail rotor acoustics (main rotor wake-tail rotor interactions). This report describes the US Army-France MOD cooperative work on this problem from both the theoretical and experimental aspects. Using experimental 3D velocity field and fuselage surface pressure measurements, three codes that model the interactions of a helicopter rotor with a fuselage are compared. These comparisons demonstrate some of the strengths and weaknesses of current models for the combined rotor-fuselage analysis.

  2. Psychoacoustic Testing of Modulated Blade Spacing for Main Rotors

    NASA Technical Reports Server (NTRS)

    Edwards, Bryan; Booth, Earl R., Jr. (Technical Monitor)

    2002-01-01

    Psychoacoustic testing of simulated helicopter main rotor noise is described, and the subjective results are presented. The objective of these tests was to evaluate the potential acoustic benefits of main rotors with modulated (uneven) blade spacing. Sound simulations were prepared for six main rotor configurations. A baseline 4-blade main rotor with regular blade spacing was based on the Bell Model 427 helicopter. A 5-blade main rotor with regular spacing was designed to approximate the performance of the 427, but at reduced tipspeed. Four modulated rotors - one with "optimum" spacing and three alternate configurations - were derived from the 5 bladed regular spacing rotor. The sounds were played to 2 subjects at a time, with care being taken in the speaker selection and placement to ensure that the sounds were identical for each subject. A total of 40 subjects participated. For each rotor configuration, the listeners were asked to evaluate the sounds in terms of noisiness. The test results indicate little to no "annoyance" benefit for the modulated blade spacing. In general, the subjects preferred the sound of the 5-blade regular spaced rotor over any of the modulated ones. A conclusion is that modulated blade spacing is not a promising design feature to reduce the annoyance for helicopter main rotors.

  3. Rotor with Flattened Exit Pressure Profile

    NASA Technical Reports Server (NTRS)

    Baltas, Constantine (Inventor); Prasad, Dilip (Inventor); Gallagher, Edward J. (Inventor)

    2015-01-01

    A rotor blade comprises an airfoil extending radially from a root section to a tip section and axially from a leading edge to a trailing edge, the leading and trailing edges defining a curvature therebetween. The curvature determines a relative exit angle at a relative span height between the root section and the tip section, based on an incident flow velocity at the leading edge of the airfoil and a rotational velocity at the relative span height. In operation of the rotor blade, the relative exit angle determines a substantially flat exit pressure ratio profile for relative span heights from 75% to 95%, wherein the exit pressure ratio profile is constant within a tolerance of 10% of a maximum value of the exit pressure ratio profile.

  4. Design study of prestressed rotor spar concept

    NASA Technical Reports Server (NTRS)

    Gleich, D.

    1980-01-01

    Studies on the Bell Helicopter 540 Rotor System of the AH-1G helicopter were performed. The stiffness, mass and geometric configurations of the Bell blade were matched to give a dynamically similar prestressed composite blade. A multi-tube, prestressed composite spar blade configuration was designed for superior ballistic survivability at low life cycle cost. The composite spar prestresses, imparted during fabrication, are chosen to maintain compression in the high strength cryogenically stretchformed 304-L stainless steel liner and tension in the overwrapped HTS graphite fibers under operating loads. This prestressing results in greatly improved crack propagation and fatigue resistance as well as enhanced fiber stiffness properties. Advantages projected for the prestressed composite rotor spar concept include increased operational life and improved ballistic survivability at low life cycle cost.

  5. Helicopter rotor blade design for minimum vibration

    NASA Technical Reports Server (NTRS)

    Taylor, R. B.

    1984-01-01

    The importance of blade design parameters in rotor vibratory response and the design of a minimum vibration blade based upon this understanding are examined. Various design approaches are examined for a 4 bladed articulated rotor operating at a high speed flight condition. Blade modal shaping, frequency placement, structural and aerodynamic coupling, and intermodal cancellation are investigated to systematically identify and evaluate blade design parameters that influence blade airloads, blade modal response, hub loads, and fuselage vibration. The relative contributions of the various components of blade force excitation and response to the vibratory hub loads transmitted to the fuselage are determined in order to isolate primary candidates for vibration alleviation. A blade design is achieved which reduces the predicted fuselage vibration from the baseline blade by approximately one half. Blade designs are developed that offer significant reductions in vibration (and fatigue stresses) without resorting to special vibration alleviation devices, radical blade geometries, or weight penalties.

  6. Closed continuous-flow centrifuge rotor

    DOEpatents

    Breillatt, Jr., Julian P.; Remenyik, Carl J.; Sartory, Walter K.; Thacker, Louis H.; Penland, William Z.

    1976-01-01

    A blood separation centrifuge rotor having a generally parabolic core disposed concentrically and spaced apart within a housing having a similarly shaped cavity. Blood is introduced through a central inlet and into a central passageway enlarged downwardly to decrease the velocity of the entrant blood. Septa are disposed inside the central passageway to induce rotation of the entrant blood. A separation chamber is defined between the core and the housing wherein the whole blood is separated into red cell, white cell, and plasma zones. The zones are separated by annular splitter blades disposed within the separation chamber. The separated components are continuously removed through conduits communicating through a face seal to the outside of the rotor.

  7. Aerodynamic design of the National Rotor Testbed.

    SciTech Connect

    Kelley, Christopher Lee

    2015-10-01

    A new wind turbine blade has been designed for the National Rotor Testbed (NRT) project and for future experiments at the Scaled Wind Farm Technology (SWiFT) facility with a specific focus on scaled wakes. This report shows the aerodynamic design of new blades that can produce a wake that has similitude to utility scale blades despite the difference in size and location in the atmospheric boundary layer. Dimensionless quantities circulation, induction, thrust coefficient, and tip-speed-ratio were kept equal between rotor scales in region 2 of operation. The new NRT design matched the aerodynamic quantities of the most common wind turbine in the United States, the GE 1.5sle turbine with 37c model blades. The NRT blade design is presented along with its performance subject to the winds at SWiFT. The design requirements determined by the SWiFT experimental test campaign are shown to be met.

  8. Development of synchronous machines with HTS rotor

    NASA Astrophysics Data System (ADS)

    Kummeth, P.; Frank, M.; Nick, W.; Nerowski, G.; Neumueller, H.-W.

    2005-10-01

    Optimized design of synchronous machines can be achieved by use of HTS tape conductors. The introduction of an iron-free air-core stator winding and replacement of the rotor's copper windings by Bi-2223 tapes allows to develop very compact HTS machines with less than half the weight and volume, higher efficiency and excellent operational behavior compared to conventional devices. In consequence these rotating machines with HTS rotors become very attractive for ship drives, power generation and industrial applications. A 400 kW synchronous HTS machine was designed, manufactured and tested at Siemens. Main goal was to demonstrate the feasibility of basic concepts. Development of a 4 MVA synchronous HTS generator is currently under way.

  9. Design of rotors for improved structural life

    NASA Technical Reports Server (NTRS)

    Hill, J. T.

    1977-01-01

    Major rotor design criteria are discussed with particular emphasis on those aspects of rotor design that ensure long life component integrity. Dynamic considerations, that necessitate tuning of bladed disk and seal assemblies to avoid excessive vibratory stress at both design and off-design conditions are reviewed as well as low cycle fatigue considerations, which have resulted in detailed analysis procedures to establish part temperature and stress variation throughout an operating cycle and extensive specimen and component fatigue testing to establish safe cyclic operating limits. The frequency, size, and behavior of intrinsic material defects were investigated. Manufacturing process improvements, including the application of increasingly sophisticated inspection techniques and quality control procedures are reviewed in light of their impact on component durability.

  10. Vortex shedding by a Savonius rotor

    NASA Astrophysics Data System (ADS)

    Botrini, M.; Beguier, C.; Chauvin, A.; Brun, R.

    1984-05-01

    A series of flow visualizations was performed to characterize the wake vortices of a Savonius rotor. The trials were undertaken in an attempt to account for discrepancies between theoretical and experimentally-derived power coefficients. The Savonius examined was two-bladed with a center offset. All tests were made in a water tunnel. Dye injection provided the visualization, and average velocities and velocity fluctuations were measured using a laser Doppler anemometer. A system of three vortices was found to be periodically shed by the rotor. Flow velocity fluctuation intensity peaked as a vortex was shed. The vortex shedding alternated from blade to blade, so that one was shed from a blade moving upstream.

  11. Performance optimization of helicopter rotor blades

    NASA Technical Reports Server (NTRS)

    Walsh, Joanne L.

    1991-01-01

    As part of a center-wide activity at NASA Langley Research Center to develop multidisciplinary design procedures by accounting for discipline interactions, a performance design optimization procedure is developed. The procedure optimizes the aerodynamic performance of rotor blades by selecting the point of taper initiation, root chord, taper ratio, and maximum twist which minimize hover horsepower while not degrading forward flight performance. The procedure uses HOVT (a strip theory momentum analysis) to compute the horse power required for hover and the comprehensive helicopter analysis program CAMRAD to compute the horsepower required for forward flight and maneuver. The optimization algorithm consists of the general purpose optimization program CONMIN and approximate analyses. Sensitivity analyses consisting of derivatives of the objective function and constraints are carried out by forward finite differences. The procedure is applied to a test problem which is an analytical model of a wind tunnel model of a utility rotor blade.

  12. New twist to steering. [Magnus effect rotors

    SciTech Connect

    Borg, J.L.

    1980-06-01

    The new vessel steering system is based on The Magnus Effect which is defined in simplified terms; if a vertical cylinder immersed in water is rotated, it produces a force at right angles to the direction of the water flowing past it. The Magnus Effect rotor needs only sufficient torque to overcome bearing and surface friction forces, so that the power requirements are very low. Further energy savings are realized because the rotor can develop maximum turning force or can return to zero in a few seconds. Tests with these cylindrical rudders have been conducted to verify the hydrodynamic theory. This concept is in the preliminary stages of development. Results are expected soon from field testing on an 1800-hp pushboat working four barges on the Warrior and Tombigbee Rivers in Alabama and Mississippi.

  13. Chemical Ecology of Wave-Swept Shores: the Primacy of Contact Cues in Predation by Whelks.

    PubMed

    Ferrier, Graham A; Zimmer, Cheryl Ann; Zimmer, Richard K

    2016-12-01

    Wave-swept shores are valuable for developing and testing key ecological principles. A synthesis of research is nonetheless missing a critical component: the chemosensory basis for behavioral interactions that determine population- and community-wide attributes. Chemical signaling environments on wave-swept shores, given their intense, turbulent mixing and complex topographies, would be difficult or impossible to simulate in a laboratory setting. For this reason, appropriately scaled field studies are needed to advance understanding of chemical stimuli and their biotic effects. Here, we performed a field investigation to establish the relative roles of dissolved and contact cues in predation by whelks (Acanthinucella spirata) on barnacles (Balanus glandula), their preferred prey. Experiments tested responses of whelks to seawater drawn above dense prey patches (10,240-12,180 barnacles m(-2)) and also over adjacent sand flats (no prey present). There was no evidence of waterborne stimuli associated with prey, even when sea states were nearly tranquil. Field trials also tested faux prey, which were constructed from cleaned barnacle shells and flavored gels. Prospective contact cues were presented to whelks at concentrations typical of epidermal tissue and cuticle in live, intact barnacles. These compounds were highly effective inducers of attack behavior and feeding. Selective enzyme degradations showed that the bioactive material was proteinaceous. Moreover, whelks did not distinguish faux barnacles with a single, purified glycoprotein (named "MULTIFUNCin") from live counterparts. Combined field results thus demonstrate the importance of contact cues, and indicate little, if any, effect of waterborne cues on predation by whelks under native conditions. Our findings underscore the need for appropriately scaled field experiments, and highlight surface chemistry as a critical factor that drives trophic interactions on rocky, wave-swept shores.

  14. Simplified rotor load models and fatigue damage estimates for offshore wind turbines.

    PubMed

    Muskulus, M

    2015-02-28

    The aim of rotor load models is to characterize and generate the thrust loads acting on an offshore wind turbine. Ideally, the rotor simulation can be replaced by time series from a model with a few parameters and state variables only. Such models are used extensively in control system design and, as a potentially new application area, structural optimization of support structures. Different rotor load models are here evaluated for a jacket support structure in terms of fatigue lifetimes of relevant structural variables. All models were found to be lacking in accuracy, with differences of more than 20% in fatigue load estimates. The most accurate models were the use of an effective thrust coefficient determined from a regression analysis of dynamic thrust loads, and a novel stochastic model in state-space form. The stochastic model explicitly models the quasi-periodic components obtained from rotational sampling of turbulent fluctuations. Its state variables follow a mean-reverting Ornstein-Uhlenbeck process. Although promising, more work is needed on how to determine the parameters of the stochastic model and before accurate lifetime predictions can be obtained without comprehensive rotor simulations.

  15. Dynamic Tester For Rotor Seals And Bearings

    NASA Technical Reports Server (NTRS)

    Von Pragenau, George L.

    1991-01-01

    Simplified apparatus measures performance under vibration. Measures some of dynamic parameters of rotor seals and bearings. Tests damping seals, damping bearings, conventional seals, and conventional bearings. Used with variety of pumped liquids, from water to liquid oxygen or hydrogen. Designed to test bearings and seals of turbopumps, tester rotates shaft at high speed while liquid flows much as it would in real turbopump. Also measures deflections of components.

  16. Methyl rotor dependent vibrational interactions in toluene.

    PubMed

    Gascooke, Jason R; Lawrance, Warren D

    2013-04-07

    The methyl rotor dependence of a three state Fermi resonance in S1 toluene at ∼460 cm(-1) has been investigated using two-dimensional laser induced fluorescence. An earlier time-resolved study has shown the Fermi resonance levels to have different energy spacings at the two lowest methyl rotor states, m = 0 and 1 [J. A. Davies, A. M. Green, and K. L. Reid, Phys. Chem. Chem. Phys. 12, 9872 (2010)]. The overlapped m = 0 and 1 spectral features have been separated to provide direct spectral evidence for the m dependence of the resonance. The resonance has been probed at m = 3a(") 1 for the first time and found to be absent, providing further evidence for a large change in the interaction with m. Deperturbing the resonance at m = 0 and 1 reveals that the m dependence arises through differences in the separations of the "zero-order," locally coupled states. It is shown that this is the result of the local "zero-order" states being perturbed by long-range torsion-vibration coupling that shifts their energy by small amounts. The m dependence of the shifts arises from the Δm = ±3n (n = 1, 2, ...) coupling selection rule associated with torsion-rotation coupling in combination with the m(2) scaling of the rotor energies, which changes the ΔE for the interaction for each m. There is also an increase in the number of states that can couple to m = 1 compared with m = 0. Consideration of the magnitude of reported torsion-rotation coupling constants suggests that this effect is likely to be pervasive in molecules with methyl rotors.

  17. Open Rotor Research at NASA Glenn

    NASA Technical Reports Server (NTRS)

    VanZante, Dale E.

    2011-01-01

    A low-noise open rotor system is being tested in collaboration with General Electric and CFM International, a 50/50 joint company between Snecma and GE. Candidate technologies for lower noise will be investigated as well as installation effects such as pylon integration. The research program in both the low and high-speed wind tunnels is reviewed. Some detailed flowfield and acoustics measurements acquired for an internal NASA program are highlighted. The publically available research data is presented also.

  18. Flow Field Around a Hovering Rotor

    NASA Technical Reports Server (NTRS)

    Tung, C.; Low, S.

    1997-01-01

    A lifting surface hover code developed by the Analytical Method Inc. (AMI) was used to compute the average and unsteady velocity flow field of an isolated rotor without ground effect. The predicted velocity field compares well with experimental data obtained by hot-wire anemometry and by Laser Doppler Velocimetry. A subroutine 'DOWNWASH' was written to predict the velocity field at any given point in the wake for a given blade position.

  19. Ice Shapes on a Tail Rotor

    NASA Technical Reports Server (NTRS)

    Kreeger, Richard E.; Tsao, Jen-Ching

    2014-01-01

    Testing of a thermally-protected helicopter rotor in the Icing Research Tunnel (IRT) was completed. Data included inter-cycle and cold blade ice shapes. Accreted ice shapes were thoroughly documented, including tracing, scanning and photographing. This was the first time this scanning capability was used outside of NASA. This type of data has never been obtained for a rotorcraft before. This data will now be used to validate the latest generation of icing analysis tools.

  20. Multicyclic Controllable Twist Rotor Data Analysis

    NASA Technical Reports Server (NTRS)

    Wei, F. S.; Weisbrich, A. L.

    1979-01-01

    Rsults provide functional relationship between rotor performance, blade vibratory loads and dual control settings and indicate that multicyclic control produced significant reductions in blade flatwise bending moments and blade root actuator control loads. Higher harmonic terms of servo flap deflection were found to be most pronounced in flatwise bending moment, transmission vertical vibration and pitch link vibratory load equations. The existing test hardware represents a satisfactory configuration for demonstrating MCTR technology and defining a data base for additional wind tunnel testing.