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. Stall characteristics and tip clearance effects in forward swept axial compressor rotors

    NASA Astrophysics Data System (ADS)

    Ramakrishna, P. V.; Govardhan, M.

    2009-03-01

    Tilting the blade sections to the flow direction (blade sweep) would increase the operating range of an axial compressor due to modifications in the pressure and velocity fields on the suction surface. On the other hand, blade tip gap, though finite, has great influence on the performance of a turbomachine. The present paper investigates the combined effect of these two factors on various flow characteristics in a low speed axial flow compressor. For this present study, nine computational domains were modeled; three rotor sweep configurations (0°, 20° and 30°) and for three different clearance levels for each rotor. Commercial CFD solver ANSYS CFX 11.0 is used for the simulations. Results indicated that tip chordline sweep is found to improve the stall margin of the compressor by modifying the suction surface boundary layer migration phenomenon. Diffusion Factor (DF) contours showed the severity of stalling with unswept rotor. For the swept rotors, the zones of high probable stall are less severe and they become less in size with increasing sweep. Increment in the tip gap is found to gradually affect the performance of unswept rotor, while the effect is very high for the two swept rotors for the earlier increments. As a minimum clearance is unavoidable, swept rotors suffer relatively higher deviation from the idealistic behavior than the unswept rotor due to tip clearance.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. Experimental and numerical investigation of a shock wave within a swept shrouded propfan rotor

    SciTech Connect

    Helming, K.

    1996-01-01

    Laser velocity measurements are conducted in a swept propfan rotor in order to investigate the local transonic flow region on the suction surface at high subsonic inlet Mach numbers. The velocity measurements are accompanied by a three-dimensional Navier-Stokes calculation for a selected operating point. The good agreement between computed and measured flow field gives some confidence to study the local three-dimensional passage shock on the suction surface by using the numerical procedure. Apart from the computed three-dimensional shock, structure is investigated in detail. By considering streamlines, it is concluded whether the shock wave is normal or oblique. The results are compared with the one-dimensional shock conditions.

  10. 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.

  11. 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.

  12. 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.

  13. The Effect of Area Variation on Wave Rotor Elements

    NASA Technical Reports Server (NTRS)

    Wilson, Jack

    1997-01-01

    The effect of varying the cross-sectional flow area of the passages of a wave rotor is examined by means of the method of characteristics. An idealized expansion wave, an idealized inlet port, and an idealized compression stage are considered. It is found that area variation does not have a very significant effect on the expansion wave, nor on the compression stage. For the expansion wave, increasing the passage area in the flow direction has the same effect as a diffuser, so that the flow emerges at a lower velocity than it would for the constant area case. This could be advantageous. The inlet is strongly affected by the area variation, as it changes the strength of the hammer shock wave, thereby changing the pressure behind it. In this case, reduction in the passage area in the flow direction leads to increased pressure. However, this result is dependent on the assumption that the inlet conditions remain constant with area variation. This may not be the case.

  14. Forward sweep, low noise rotor blade

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F. (Inventor)

    1994-01-01

    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 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.

  15. Shock Characteristics Measured Upstream of Both a Forward-Swept and an Aft-Swept Fan

    NASA Technical Reports Server (NTRS)

    Podboy, Gary G.; Krupar, Martin J.; Sutliff, Daniel L.; Horvath, Csaba

    2007-01-01

    Three different types of diagnostic data-blade surface flow visualization, shroud unsteady pressure, and laser Doppler velocimeter (LDV)--were obtained on 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 transonic tip speeds. Flow visualization data are presented for the forward-swept fan operating at 13831 rpm(sub c), and for the aft-swept fan operating at 12500 and 13831 rpm(sub c) (corresponding to tip rotational Mach numbers of 1.07 and 1.19, respectively). The flow visualization data identify where the shocks occur on the suction side of the rotor blades. These data show that at the takeoff speed, 13831 rpm(sub c), the shocks occurring in the tip region of the forward-swept fan are further downstream in the blade passage than with the aft-swept fan. Shroud unsteady pressure measurements were acquired using a linear array of 15 equally-spaced pressure transducers extending from two tip axial chords upstream to 0.8 tip axial chords downstream of the static position of the tip leading edge of each rotor. Such data are presented for each fan operating at one subsonic and five transonic tip speeds. The unsteady pressure data show relatively strong detached shocks propagating upstream of the aft-swept rotor at the three lowest transonic tip speeds, and weak, oblique pressure disturbances attached to the tip of the aft-swept fan at the two highest transonic tip speeds. The unsteady pressure measurements made with the forward-swept fan do not show strong shocks propagating upstream of that rotor at any of the tested speeds. A comparison of the forward-swept and aft-swept shroud unsteady pressure measurements indicates that at any given transonic speed the pressure disturbance just upstream of the tip of the forward-swept fan is much weaker than that of the aft-swept fan. The LDV data suggest that at 12500 and 13831 rpm(sub c), the forward-swept fan swallowed the

  16. 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.

  17. 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

  18. 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.

  19. Optimization of stall regulated rotors

    SciTech Connect

    Fuglsang, P.L.; Madsen, H.A.

    1995-09-01

    The present work deals with the optimization of stall regulated rotors for wind turbines. Two different optimization methods are presented. The first method is a single design point optimization procedure, whereas the second is a multi pointed optimization technique which is founded on a general optimization algorithm. The use of an optimization algorithm offers the possibility to treat complex optimization problems concerning the entire rotor geometry. The two methods are compared through design of a 20 kW rotor showing good agreement. By use of the optimization algorithm, different aspects of modern wind turbine design layout are investigated. The improvement of the annual energy production by optimizing the airfoil characteristics in addition to the blade chord and twist has been found marginal compared to a case where a standard NACA 634x airfoil family is used. The optimal ratio of swept area to rated power is found depending strongly on the value of the specified maximum loads. Optimization of rotors to specific wind regimes has not been found favorable. In general, the results show that the optimization algorithm is an useful aid to the design.

  20. 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.

  1. Lifting surface theory for a helicopter rotor in forward flight

    NASA Technical Reports Server (NTRS)

    Tai, H.; Runyan, H. L.

    1985-01-01

    A lifting surface theory was 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 vortex lattice procedure. Calculations demonstrating the application of the method are given in terms of the lift distribution on a single rotor, a two-bladed rotor, and a rotor with swept-forward and swept-back tips. In addition, the lift on a rotor which is vibrating in a pitching mode at 4/rev is given. Compressibility effects and interference effects for a two-bladed rotor are discussed.

  2. Lifting surface theory for a helicopter rotor in forward flight

    NASA Technical Reports Server (NTRS)

    Tai, H.; Runyan, H. L.

    1984-01-01

    A lifting surface theory was 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 vortex lattice procedure. Calculations demonstrating the application of the method are given in terms of the lift distribution on a single rotor, a two-bladed rotor, and a rotor with swept-forward and swept-back tips. In addition, the lift on a rotor which is vibrating in a pitching mode at 4/rev is given. Compressibility effects and interference effects for a two-bladed rotor are discussed.

  3. 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.

  4. 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.

  5. 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.

  6. Calculation of blade-vortex interaction airloads on helicopter rotors

    NASA Technical Reports Server (NTRS)

    Johnson, Wayne

    1989-01-01

    Two alternative approaches area developed to calculate blade-vortex interaction airloads on helicopter rotors, second-order lifting-line theory and a lifting-surface theory correction. The common approach of using a larger vortex core radius to account for lifting-surface effects is quantified. The second-order lifting-line theory also improves the modeling of low aspect-ratio blades yawed flow, and swept tips. Calculated results are compared with wind-tunnel measurements of lateral flapping, and with flight test measurements of blade section lift on SA349/2 and H-34 helicopter rotors. The tip vortex core radius required for good correlation with the flight test data is about a 20-percent chord, which is within the range of measured viscous core sizes for helicopter rotors.

  7. 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.

  8. Aerodynamic sweeping study and design for transonic compressor rotor blades

    NASA Astrophysics Data System (ADS)

    Chen, N. X.; Zhang, H. W.; Huang, W. G.

    2010-08-01

    The objective of the present paper is to study the sweep effect on the blade design performance of a transonic compressor rotor. The baseline to be modified and swept is a designed well efficient transonic single rotor compressor. The first part of the present study is concerning the sweep effect with straight leading edge. In this case fixing the hub section the swept blade is formed by tilting the leading edge with whole blade forwards and backwards axially. The second part is to use an optimization strategy with simple gradient-based optimum-searching method and multi-section blade parameterization technique to search and generate an optimal swept rotor with curved arbitrary leading edge. Its adiabatic efficiency is a little bit greater than that of the reference un-swept rotor.

  9. 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.

  10. Comparison of Neovascular Lesion Area Measurements From Different Swept-Source OCT Angiographic Scan Patterns in Age-Related Macular Degeneration.

    PubMed

    Zheng, Fang; Zhang, Qinqin; Motulsky, Elie H; de Oliveira Dias, João Rafael; Chen, Chieh-Li; Chu, Zhongdi; Miller, Andrew R; Feuer, William; Gregori, Giovanni; Kubach, Sophie; Durbin, Mary K; Wang, Ruikang K; Rosenfeld, Philip J

    2017-10-01

    We compared area measurements for the same neovascular lesions imaged using swept source optical coherence tomography angiography (SS-OCTA) and enlarging scan patterns. Patients with neovascular age-related macular degeneration were imaged using a 100-kHz SS-OCTA instrument (PLEX Elite 9000). The scanning protocols included the 3 × 3, 6 × 6, 9 × 9, and 12 × 12 mm fields of view. Two groups were studied. Group 1 included small lesions contained within the 3 \\( \\times \\) 3 mm scan, and Group 2 included larger lesions that were fully contained within the 6 \\( \\times \\) 6 mm scan. A total of 30 eyes of 26 patients were enrolled in Group 1 and 30 eyes of 25 patients were enrolled in Group 2. In Group 1, the automated mean lesion area measurements were 1.11 (SD = 0.78), 1.14 (SD = 0.80), and 1.27 (SD = 0.82) mm2 for the 3 \\( \\times \\) 3, 6 \\( \\times \\) 6, and 12 \\( \\times \\) 12 mm scans, respectively (ANOVA P < 0.001; post hoc comparisons, P = 0.184, 3 \\( \\times \\) 3 vs. 6 \\( \\times \\) 6 mm; P < 0.001 for the other two pairs). In Group 2, the automated mean lesion area measurements were 5.43 (SD = 2.56), 5.53 (SD = 2.48), and 5.49 (SD = 2.65) mm2 for the 6 \\( \\times \\) 6, 9 \\( \\times \\) 9, and 12 \\( \\times \\) 12 mm scans, respectively (ANOVA P = 0.435; post-hoc comparisons, P = 0.062, 6 \\( \\times \\) 6 vs. 9 \\( \\times \\) 9 mm; P = 0.553, 6 \\( \\times \\) 6 vs. 12 \\( \\times \\) 12 mm; P = 0.654, 9 \\( \\times \\) 9 vs. 12 \\( \\times \\) 12 mm). The similarity in lesion area measurements across different scan patterns suggests that SS-OCTA imaging can be used to follow quantitatively the enlargement of choroidal neovascularization as the disease progresses.

  11. 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.

  12. 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

  13. Effects of Diabetic Macular Edema on Repeatability of Retinal Nerve Fiber Layer Thickness Measurements at the Macular and Peripapillary Area Using Swept-Source Optical Coherence Tomography.

    PubMed

    Min, Jung Kee; Lee, Seunghwan; Kim, Ju Sung; Woo, Je Moon; Yang, Hyun Seung

    2017-02-01

    To investigate the repeatability of macular and peripapillary retinal nerve fiber layer (RNFL) thickness measurements made using swept-source optical coherence tomography (SS-OCT) and automated segmentation. Measurements were made in non-diabetic controls and in patients with diabetic retinopathy (DR) with or without diabetic macular edema (DME). A total of 131 eyes of 131 participants were included. Fifty-one eyes with DR had no DME (DME[-]), 45 eyes with DR had DME (DME[+]), and 35 eyes were healthy. Measurements of RNFL and full retinal thickness were simultaneously obtained with SS-OCT in the peripapillary area and in the nine Early Treatment Diabetic Retinopathy Study (ETDRS) subfields using the wide three-dimensional mode. All measurements were made twice on the same day by a single examiner to test intra-observer repeatability. Intraclass correlation coefficients (ICCs) and coefficients of repeatability were examined to evaluate repeatability. Average macular and temporal peripapillary RNFL thickness values were greater in the DME[+] group (36.4 ± 13.2 and 83.8 ± 19.4 µm, respectively) than in the control (27.4 ± 3.5 and 73.5 ± 11.4 µm, respectively) and DME[-] (27.9 ± 3.4 µm and 70.3 ± 11.3 µm, respectively) groups (both P < 0.001). The ICCs of average macular (control: 0.982, DME[-]: 0.913, and DME[+]: 0.970) and peripapillary (control: 0.972, DME[-]: 0.973, and DME[+]: 0.958) RNFL thickness measurements indicated good repeatability in all three study groups. Although the ICCs of average RNFL thickness measurements were relatively lower in eyes with DR than in healthy controls, the intra-observer repeatability of SS-OCT RNFL and full retinal thickness measurements is sufficiently reliable for them to be clinically useful.

  14. 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.

  15. Study on the Matching of the Wind Turbine Capacity and the Rotor Diameter in Inner Mongolia

    NASA Astrophysics Data System (ADS)

    Cao, Liang; Wu, Yong Zhong

    2017-05-01

    There are abundant wind resources in Inner Mongolia Autonomous Region and in order to develop the wind resources economically and reasonably, it is necessary to produce and promote wind turbine generators that fit the exploitation of the wind resources. The energy generated by the wind turbines is closely linked to the rotor swept area. If the rotor diameter doubles, the wind power will increase by four times. This paper, based on the actual wind resources, divided Inner Mongolia into different regions, and, in accordance with the present wind farm development in Inner Mongolia and the on-grid energy requirements, offered a scheme for the matching of the unit capacity and the rotor diameter in wind farms of some typical regions, which provides some scientific and theoretical references for the proper selection of the wind turbine generator parameters.

  16. Tilt Rotor Aircraft Aeroacoustics

    NASA Technical Reports Server (NTRS)

    George, Albert R.

    1996-01-01

    A fleet of civil tilt rotor transports offers a means of reducing airport congestion and point-to-point travel time. The speed, range, and fuel economy of these aircraft, along with their efficient use of vertiport area, make them good candidates for short-to-medium range civil transport. However, to be successfully integrated into the civilian community, the tilt rotor must be perceived as a quiet, safe, and economical mode of transportation that does not harm the environment. In particular, noise impact has been identified as a possible barrier to the civil tilt rotor. Along with rotor conversion-mode flight, and blade-vortex interaction noise during descent, hover mode is a noise problem for tilt rotor operations. In the present research, tilt rotor hover aeroacoustics have been studied analytically, experimentally, and computationally. Various papers on the subject were published as noted in the list of publications. More recently, experimental measurements were made on a 1/12.5 scale model of the XV-15 in hover and analyses of this data and extrapolations to full scale were also carried out. A dimensional analysis showed that the model was a good aeroacoustic approximation to the full-scale aircraft, and scale factors were derived to extrapolate the model measurements to the full-scale XV-15. The experimental measurements included helium bubble flow visualization, silk tuft flow visualization, 2-component hot wire anemometry, 7-hole pressure probe measurements, vorticity measurements, and outdoor far field acoustic measurements. The hot wire measurements were used to estimate the turbulence statistics of the flow field into the rotors, such as length scales, velocity scales, dissipation, and turbulence intermittency. Several different configurations of the model were tested: (1) standard configurations (single isolated rotor, two rotors without the aircraft, standard tilt rotor configuration); (2) flow control devices (the 'plate', the 'diagonal fences'); (3

  17. A Method for Determining Cloud-Droplet Impingement on Swept Wings

    NASA Technical Reports Server (NTRS)

    Dorsch, Robert G.; Brun, Rinaldo J.

    1953-01-01

    The general effect of wing sweep on cloud-droplet trajectories about swept wings of high aspect ratio moving at subsonic speeds is discussed. A method of computing droplet trajectories about yawed cylinders and swept wings is presented, and illustrative droplet trajectories are computed. A method of extending two-dimensional calculations of droplet impingement on nonswept wings to swept wings is presented. It is shown that the extent of impingement of cloud droplets on an airfoil surface, the total rate of collection of water, and the local rate of impingement per unit area of airfoil surface can be found for a swept wing from two-dimensional data for a nonswept wing. The impingement on a swept wing is obtained from impingement data for a nonswept airfoil section which is the same as the section in the normal plane of the swept wing by calculating all dimensionless parameters with respect to flow conditions in the normal plane of the swept wing.

  18. Forward-Swept Fan Flutter Calculated Using TURBO Code

    NASA Technical Reports Server (NTRS)

    Srivastava, Rakesh; Bakhle, Milind A.; Stefko, George L.

    2003-01-01

    Flutter, a self-excited dynamic instability arising because of fluid structure interaction, can be a significant design problem for rotor blades in gas turbines. Blade shapes influenced by noise-reduction requirements increase the likelihood of flutter in modern blade designs. Validated numerical methods provide designers an invaluable tool to calculate and avoid the flutter instability during the design phase. Toward this objective, a flutter analysis code, TURBO, was developed and validated by researchers from the NASA Glenn Research Center and other researchers working under grants and contracts with Glenn. The TURBO code, which is based on unsteady three-dimensional Reynolds-averaged Navier-Stokes equations was used to calculate the observed flutter of a forward-swept fan. The forward-swept experimental fan, designed to reduce noise, showed flutter at part-speed conditions during wind tunnel tests.

  19. 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.

  20. 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.

  1. Molecular Rotors

    DTIC Science & Technology

    2006-10-31

    Molecular Dipolar Rotors on Insulating Surfaces," Salamanca , Spain. Trends in Nanotechnology Conference. September 5-9, 2003 [86] Laura I. Clarke, Mary Beth...Horansky at the Trends in Nanotechnology Conference, Salamanca , Spain (September 5-9, 2003). [145] Michl, J. “Unusual Molecules: Artificial Surface...temperature and frequency for difluorophenylene rotor crystal. Figure JP6. Monte Carlo results for the local potential asymmetry at

  2. 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.

  3. 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.

  4. 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.

  5. Computation of transonic potential flow on helicopter rotor blades

    NASA Technical Reports Server (NTRS)

    Costes, M.; Jones, H. E.

    1987-01-01

    Two computer codes, the full-potential three-dimensional (FP3D) code and the full-potential rotor (FPR) code have recently been developed. Both of these codes solve the three-dimensional conservative formulation of the full potential equation. The FPR code was developed at the U.S. Army Aeroflightdynamics Directorate (AFDD) while the FP3D code was a joint development by ONERA and AFDD. Both of these codes were used to predict the nonlifting, unsteady flow over a rotor operating at high advance ratio and tip speed. Three different rotor tip planform shapes were studied: a rectangular tip, a 30 deg aft swept tip and a 30 deg forward swept tip. Results of these computations are compared to results obtained using an earlier small-disturbances code. Also, the lifting flow over a rectangular tip operating at a slightly different condition was computed. These results are also compared with the small disturbances computations and with experimental results.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  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. 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.

  16. 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.

  17. 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.

  18. The mid-infrared swept laser: life beyond OCT?

    NASA Astrophysics Data System (ADS)

    Childs, D. T. D.; Hogg, R. A.; Revin, D. G.; Rehman, I. U.; Cockburn, J. W.; Matcher, S. J.

    2015-03-01

    Near-infrared external cavity lasers with high tuning rates ("swept lasers") have come to dominate the field of nearinfrared low-coherence imaging of biological tissues. Compared with time-domain OCT, swept-source OCT a) replaces slow mechanical scanning of a bulky reference mirror with much faster tuning of a laser cavity filter element and b) provides a ×N (N being the number of axial pixels per A-scan) speed advantage with no loss of SNR. We will argue that this striking speed advantage has not yet been fully exploited within biophotonics but will next make its effects felt in the mid-infrared. This transformation is likely to be driven by recent advances in external cavity quantum cascade lasers, which are the mid-IR counterpart to the OCT swept-source. These mid-IR sources are rapidly emerging in the area of infrared spectroscopy. By noting a direct analogy between time-domain OCT and Fourier Transform Infrared (FTIR) spectroscopy we show analytically and via simulations that the mid-IR swept laser can acquire an infrared spectrum ×N (N being the number of spectral data points) faster than an FTIR instrument, using identical detected flux levels and identical receiver noise. A prototype external cavity mid-IR swept laser is demonstrated, offering a comparatively low sweep rate of 400 Hz over 60 cm-1 with 2 cm-1 linewidth, but which provides evidence that sweep rates of over a 100 kHz should be readily achievable simply by speeding up the cavity tuning element. Translating the knowledge and experience gained in near-IR OCT into mid-IR source development may result in sources offering significant benefits in certain spectroscopic applications.

  19. 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.

  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. Flutter of swept fan blades

    NASA Technical Reports Server (NTRS)

    Kielb, R. E.; Kaza, K. R. V.

    1984-01-01

    The effect of sweep on fan blade flutter is studied by applying the analytical methods developed for aeroelastic analysis of advance turboprops. Two methods are used. The first method utilizes an approximate structural model in which the blade is represented by a swept, nonuniform beam. The second method utilizes a finite element technique to conduct modal flutter analysis. For both methods the unsteady aerodynamic loads are calculated using two dimensional cascade theories which are modified to account for sweep. An advanced fan stage is analyzed with 0, 15 and 30 degrees of sweep. It is shown that sweep has a beneficial effect on predominantly torsional flutter and a detrimental effect on predominantly bending flutter. This detrimental effect is shown to be significantly destabilizing for 30 degrees of sweep.

  2. 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.

  3. 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.

  4. Benefits of Swept and Leaned Stators for Fan Noise Reduction

    NASA Technical Reports Server (NTRS)

    Woodward, Richard P.; Elliott, David M.; Hughes, Christopher E.; Berton, Jeffrey J.

    1998-01-01

    An advanced high bypass ratio fan model was tested in the NASA Lewis Research Center 9 x 15-Foot Low Speed Wind Tunnel. The primary focus of this test was to quantify the acoustic benefits and aerodynamic performance of sweep and lean in stator vane design. Three stator sets were used for this test series. A conventional radial stator was tested at two rotor-stator axial spacings. Additional stator sets incorporating sweep + lean, and sweep only were also tested. The hub axial location for the swept + lean, and sweep only stators corresponded to the location of the radial stator at the upstream rotor-stator spacing, while the tip axial location of these modified stators corresponded to the radial stator axial position at the downstream position. The acoustic results show significant reductions in both rotor-stator interaction noise and broadband noise beyond what could be achieved through increased axial spacing of the conventional, radial stator. Theoretical application of these results to acoustically quantify a fictitious 2-engine aircraft and flight path suggested that about 3 Effective Perceived Noise (EPN) dB could be achieved through incorporation of these modified stators. This reduction would represent a significant portion of the 6 EPNdB noise goal of the current NASA Advanced Subsonic Technology (AST) initiative relative to that of 1992 technology levels. A secondary result of this fan test was to demonstrate the ability of an acoustic barrier wall to block aft-radiated fan noise in the wind tunnel, thus revealing the acoustic structure of the residual inlet-radiated noise. This technology should prove valuable toward better understanding inlet liner design, or wherever it is desirable to eliminate aft-radiated noise from the fan acoustic signature.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  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. 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

  12. Wake model for helicopter rotors in high speed flight

    NASA Technical Reports Server (NTRS)

    Johnson, Wayne R.

    1988-01-01

    Two alternative approaches are developed to calculate blade-vortex interaction airloads on helicopter rotors: second order lifting-line theory, and a lifting surface theory correction. The common approach of using a larger vortex core radius to account for lifting-surface effects is quantified. The second order lifting-line theory also improves the modeling of yawed flow and swept tips. Calculated results are compared with wind tunnel measurements of lateral flapping, and with flight test measurements of blade section lift on SA349/2 and H-34 helicopter rotors. The tip vortex core radius required for good correlation with the flight test data is about 20 percent chord, which is within the range of measured viscous core sizes for helicopter rotors.

  13. 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.

  14. 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.

  15. Numerical simulation of swept-wing flows

    NASA Technical Reports Server (NTRS)

    Reed, Helen L.

    1991-01-01

    Efforts of the last six months to computationally model the transition process characteristics of flow over swept wings are described. Specifically, the crossflow instability and crossflow/Tollmien-Schlichting wave interactions are analyzed through the numerical solution of the full 3D Navier-Stokes equations including unsteadiness, curvature, and sweep. This approach is chosen because of the complexity of the problem and because it appears that linear stability theory is insufficient to explain the discrepancies between different experiments and between theory and experiment. The leading edge region of a swept wing is considered in a 3D spatial simulation with random disturbances as the initial conditions.

  16. 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.

  17. Helicopter tail rotor noise

    NASA Technical Reports Server (NTRS)

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

    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.

  18. Suction laminarization of highly swept supersonic laminar flow control wings

    NASA Technical Reports Server (NTRS)

    Pfenninger, W.; Vemuru, C. S.

    1988-01-01

    An evaluation is made of a suction-based method for the laminarization of highly-swept supersonic wings at cruise Mach numbers in the 2.0-2.5 range, in the interest of the reduction of wave drag due to lift. The laminar boundary layer development, as well as Tollmien-Schlichting and crossflow instabilities, have been analyzed for the case of an X66 supercritical airfoil at 60 and 72 deg sweep, for Mach numbers of 1.56 and 2.52, respectively. Strong suction is found to be needed at the front part of the upper surface and both the upper and lower rear pressure-rise areas.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Precipitation measurements on wind-swept slopes

    Treesearch

    Austin E. Helmers

    1954-01-01

    Precipitation catch for three calendar years is compared for four types of gage installation on a wind-swept south-facing slope with a 22° gradient at elevation 5500 ft. The 1950 precipitation catch by (1) weighing-recording gage with the orifice and an Alter type wind shield sloped parallel to the ground surface, (2) unshielded nonrecording gage with orifice sloped...

  6. 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.

  7. Implementation of swept synthetic aperture imaging

    NASA Astrophysics Data System (ADS)

    Bottenus, Nick; Jakovljevic, Marko; Boctor, Emad; Trahey, Gregg E.

    2015-03-01

    Ultrasound imaging of deep targets is limited by the resolution of current ultrasound systems based on the available aperture size. We propose a system to synthesize an extended effective aperture in order to improve resolution and target detectability at depth using a precisely-tracked transducer swept across the region of interest. A Field II simulation was performed to demonstrate the swept aperture approach in both the spatial and frequency domains. The adaptively beam-formed system was tested experimentally using a volumetric transducer and an ex vivo canine abdominal layer to evaluate the impact of clutter-generating tissue on the resulting point spread function. Resolution was improved by 73% using a 30.8 degree sweep despite the presence of varying aberration across the array with an amplitude on the order of 100 ns. Slight variations were observed in the magnitude and position of side lobes compared to the control case, but overall image quality was not significantly degraded as compared by a simulation based on the experimental point spread function. We conclude that the swept aperture imaging system may be a valuable tool for synthesizing large effective apertures using conventional ultrasound hardware.

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

    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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. The NYU inverse swept wing code

    NASA Technical Reports Server (NTRS)

    Bauer, F.; Garabedian, P.; Mcfadden, G.

    1983-01-01

    An inverse swept wing code is described that is based on the widely used transonic flow program FLO22. The new code incorporates a free boundary algorithm permitting the pressure distribution to be prescribed over a portion of the wing surface. A special routine is included to calculate the wave drag, which can be minimized in its dependence on the pressure distribution. An alternate formulation of the boundary condition at infinity was introduced to enhance the speed and accuracy of the code. A FORTRAN listing of the code and a listing of a sample run are presented. There is also a user's manual as well as glossaries of input and output parameters.

  19. Nonlinear wave interactions in swept wing flows

    NASA Technical Reports Server (NTRS)

    Elhady, Nabil M.

    1988-01-01

    An analysis is presented which examines the modulation of different instability modes satisfying the triad resonance condition in time and space in a three-dimensional boundary layer flow. Detuning parameters are used for the wave numbers and the frequencies. The nonparallelism of the mean flow is taken into account in the analysis. At the leading-edge region of an infinite swept wing, different resonant triads are investigated that are comprised of travelling crossflow, vertical vorticity and Tollmein-Schlichting modes. The spatial evolution of the resonating triad components are studied.

  20. Structural response of a rotating bladed disk to rotor whirl

    NASA Technical Reports Server (NTRS)

    Crawley, E. F.

    1985-01-01

    A set of high speed rotating whirl experiments were performed in the vacuum of the MIT Blowdown Compressor Facility on the MIT Aeroelastic Rotor, which is structurally typical of a modern high bypass ratio turbofan stage. These tests identified the natural frequencies of whirl of the rotor system by forcing its response using an electromagnetic shaker whirl excitation system. The excitation was slowly swept in frequency at constant amplitude for several constant rotor speeds in both a forward and backward whirl direction. The natural frequencies of whirl determined by these experiments were compared to those predicted by an analytical 6 DOF model of a flexible blade-rigid disk-flexible shaft rotor. The model is also presented in terms of nondimensional parameters in order to assess the importance of the interation between the bladed disk dynamics and the shaft-disk dynamics. The correlation between the experimental and predicted natural frequencies is reasonable, given the uncertainty involved in determining the stiffness parameters of the system.

  1. 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.

  2. Imaging of noncarious cervical lesions by means of a fast swept source optical coherence tomography system

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    Non-carious cervical lesions (NCCL) are defined as the loss of tooth substance at the cemento-enamel junction and are caused by abrasion, erosion and/or occlusal overload. In this paper we proved that our fast swept source OCT system is a valuable tool to track the evolution of NCCL lesions in time. On several extracted bicuspids, four levels of NCCL were artificially created. After every level of induced lesion, OCT scanning was performed. B scans were acquired and 3D reconstructions were generated. The swept source OCT instrument used in this study has a central wavelength of 1050 nm, a sweeping range of 106 nm (measured at 10 dB), an average output power of 16 mW and a sweeping rate of 100 kHz. A depth resolution determined by the swept source of 12 μm in air was experimentally obtained. NCCL were measured on the B-scans as 2D images and 3D reconstructions (volumes). For quantitative evaluations of volumes, the Image J software was used. By calculating the areas of the amount of lost tissue corresponding to each difference of Bscans, the final volumes of NCCL were obtained. This swept source OCT method allows the dynamic diagnosis of NCCL in time.

  3. 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.

  4. 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

  5. Open Rotor Spin Test

    NASA Image and Video Library

    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...

  6. Single Rotor Turbine

    DOEpatents

    Platts, David A.

    2004-10-26

    A rotor for use in turbine applications has a centrifugal compressor having axially disposed spaced apart fins forming passages and an axial turbine having hollow turbine blades interleaved with the fins and through which fluid from the centrifugal compressor flows.

  7. 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.

  8. Rotor internal friction instability

    NASA Technical Reports Server (NTRS)

    Bently, D. E.; Muszynska, A.

    1985-01-01

    Two aspects of internal friction affecting stability of rotating machines are discussed. The first role of internal friction consists of decreasing the level of effective damping during rotor subsynchronous and backward precessional vibrations caused by some other instability mechanisms. The second role of internal frication consists of creating rotor instability, i.e., causing self-excited subsynchronous vibrations. Experimental test results document both of these aspects.

  9. Frequency-Swept Integrated Solid Effect.

    PubMed

    Can, Thach V; Weber, Ralph T; Walish, Joseph J; Swager, Timothy M; Griffin, Robert G

    2017-06-06

    The efficiency of continuous wave dynamic nuclear polarization (DNP) experiments decreases at the high magnetic fields used in contemporary high-resolution NMR applications. To recover the expected signal enhancements from DNP, we explored time domain experiments such as NOVEL which matches the electron Rabi frequency to the nuclear Larmor frequency to mediate polarization transfer. However, satisfying this matching condition at high frequencies is technically demanding. As an alternative we report here frequency-swept integrated solid effect (FS-ISE) experiments that allow low power sweeps of the exciting microwave frequencies to constructively integrate the negative and positive polarizations of the solid effect, thereby producing a polarization efficiency comparable to (±10 % difference) NOVEL. Finally, the microwave frequency modulation results in field profiles that exhibit new features that we coin the "stretched" solid effect. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. 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

  11. Wall pressure fluctuations beneath swept shock wave/boundary layer interactions

    NASA Technical Reports Server (NTRS)

    Garg, S.; Settles, G. S.

    1993-01-01

    An experimental research program providing basic knowledge and establishing a database on the fluctuating pressure loads produced on aerodynamic surfaces beneath 3D shock wave/boundary layer interactions is presented. A turbulent boundary layer on a flat plate is subjected to interactions with swept planar shock waves generated by sharp fins at angle of attack. Measurements are made for the first time in the aft areas of these interactions, showing fluctuating pressure levels as high as 160 dB.

  12. 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.

  13. Wind turbine rotor

    SciTech Connect

    Baskin, J. M.; Miller, G. E.; Wiesner, W.

    1985-12-10

    A fixed pitch wind turbine rotor is teeter mounted onto a low speed input shaft which is connected to the input of a step-up transmission. The output of the transmission is connected to a rotary pole amplitude modulated induction machine which is operable as a generator at a plurality of discreet speeds of rotation and is also operable as a startup motor for the rotor. A switch responsive to the rotational speed of the wind turbine rotor switches the generator from one speed of operation to the other. The rotor hub and the inner body portions of two blades which extend radially outwardly in opposite directions from the hub, are constructed from steel. The outer end portions of the blade are constructed from a lighter material, such as wood, and are both thinner and narrower than the remainder of the rotor. The outer end section of each blade includes a main body portion and a trailing edge portion which is hinge-connected to the main body portion. Each blade includes a centrifugal force operated positioning means which normally holds the drag brake section in a retracted position, but operates in response to a predetermined magnitude of centrifugal force to move the drag brake section into its deployed position. Each blade has an airfoil cross section and each blade has a plus twist inner portion adjacent the hub changing to first a zero twist and then a minus twist as it extends radially outwardly from the hub.

  14. Stall Precursor Study of High Frequency Data for Three High Speed, Swept Compressor Rotors.

    DTIC Science & Technology

    1994-12-01

    of Technology Air University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Aeronautical Engineering James F...than what I was writing helped steer me in the right direction on countless occasions. I would also like to acknowledge Dr. Bill Copenhaver and the...compressors such as by Sellin et al. [9], Puterbaugh and Copenhaver [10], and Copenhaver et al. [11] described the changes in shock structure and blade tip

  15. A Description of the Design of Highly Swept Propeller Blades

    NASA Technical Reports Server (NTRS)

    Whitcomb, Richard T

    1950-01-01

    A description of the two swept propellers investigated in the Langley 8-foot high-speed tunnel is presented, together with the discussions of the numerous assumptions and analyses on which the designs of these propellers are based. The blades are swept considerably along the entire blade radius and, in order to allow for reductions in the maximum stresses, are swept forward inboard and backward outboard. The blades have been designed on the basis of the blade-element method primarily to have subcritical efficiencies at the highest possible forward speed. The designs have been controlled primarily by the stresses in the blades. (author)

  16. 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.

  17. Rotor-vortex interaction noise

    NASA Technical Reports Server (NTRS)

    Schlinker, R. H.; Amiet, R. K.

    1983-01-01

    A theoretical and experimental study was conducted to develop a validated first principles analysis for predicting noise generated by helicopter main-rotor shed vortices interacting with the tail rotor. The generalized prediction procedure requires a knowledge of the incident vortex velocity field, rotor geometry, and rotor operating conditions. The analysis includes compressibility effects, chordwise and spanwise noncompactness, and treats oblique intersections with the blade planform. Assessment of the theory involved conducting a model rotor experiment which isolated the blade-vortex interaction noise from other rotor noise mechanisms. An isolated tip vortex, generated by an upstream semispan airfoil, was convected into the model tail rotor. Acoustic spectra, pressure signatures, and directivity were measured. Since assessment of the acoustic prediction required a knowledge of the vortex properties, blade-vortes intersection angle, intersection station, vortex stength, and vortex core radius were documented. Ingestion of the vortex by the rotor was experimentally observed to generate harmonic noise and impulsive waveforms.

  18. 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.

  19. 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.

  20. 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.

  1. Rotor mapping and ablation to treat atrial fibrillation.

    PubMed

    Zaman, Junaid A B; Peters, Nicholas S; Narayan, Sanjiv M

    2015-01-01

    Rotors have long been postulated to drive atrial fibrillation, but evidence has been limited to animal models. This changed recently with the demonstration using focal impulse and rotor modulation (FIRM) mapping that rotors act as human atrial fibrillation sources. This mechanistic approach to diagnosing the causes of atrial fibrillation in individual patients has been supported by substantially improved outcomes from FIRM-guided ablation, resulting in increased attention to rotors as therapeutic targets. In this review, we outline the pathophysiology of rotors in animal and in-silico studies of fibrillation, and how this motivated FIRM mapping in humans. We highlight the characteristics of rotors in human atrial fibrillation, now validated by several techniques, with discussion on similar and discrepant findings between techniques. The interventional approaches to eliminate atrial fibrillation rotors are explained and the ablation results in latest studies using FIRM are discussed. We propose that mapping localized sources for human atrial fibrillation, specifically rotors, is moving the field towards a unifying hypothesis that explains several otherwise contradictory observations in atrial fibrillation management. We conclude by suggesting areas of potential research that may reveal more about these critical sites and how these may lead to better and novel treatments for atrial fibrillation.

  2. 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.

  3. 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.

  4. 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

  5. Broadband rotor noise analyses

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    The various mechanisms which generate broadband noise on a range of rotors studied include load fluctuations due to inflow turbulence, due to turbulent boundary layers passing the blades' trailing edges, and due to tip vortex formation. Existing analyses are used and extensions to them are developed to make more accurate predictions of rotor noise spectra and to determine which mechanisms are important in which circumstances. Calculations based on the various prediction methods in existing experiments were compared. The present analyses are adequate to predict the spectra from a wide variety of experiments on fans, full scale and model scale helicopter rotors, wind turbines, and propellers to within about 5 to 10 dB. Better knowledge of the inflow turbulence improves the accuracy of the predictions. Results indicate that inflow turbulence noise depends strongly on ambient conditions and dominates at low frequencies. Trailing edge noise and tip vortex noise are important at higher frequencies if inflow turbulence is weak. Boundary layer trailing edge noise, important, for large sized rotors, increases slowly with angle of attack but not as rapidly as tip vortex noise.

  6. 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.

  7. 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.

  8. XV-15 tilt rotor

    NASA Technical Reports Server (NTRS)

    1980-01-01

    This photo shows the unique XV-15 Tiltrotor aircraft in vertical flight at the NASA Dryden Flight Research Center. The XV-15s, manufactured by Bell, were involved in limited research at NASA/Dryden in 1980 and 1981. The development of the XV-15 Tiltrotor research aircraft was initiated in 1973 with joint Army/NASA funding as a 'proof of concept', or 'technology demonstrator' program, with two aircraft being built by Bell Helicopter Textron (BHT) in 1977. NASA Ames Research Center, where most of the NASA research is conducted, continues to be in charge of the joint NASA/Army/Bell program. The aircraft are powered by twin Lycoming T-53 turboshaft engines that are connected by a cross-shaft and drive three-bladed, 25 ft diameter metal rotors (the size extensively tested in a wind tunnel). The engines and main transmissions are located in wingtip nacelles to minimize the operational loads on the cross-shaft system and, with the rotors, tilt as a single unit. For takeoff, the proprotors and their engines are used in the straight-up position where the thrust is directed downward. The XV-15 then climbs vertically into the air like a helicopter. In this VTOL mode, the vehicle can lift off and hover for approximately one hour. Once off the ground, the XV-15 has the ability to fly in one of two different modes. It can fly as a helicopter, in the partially converted airplane mode. The XV-15 can also then convert from the helicopter mode to the airplane mode. This is accomplished by continuous rotation of the proprotors from the helicopter rotor position to the conventional airplane propeller position. During the ten to fifteen second conversion period, the aircraft speed increases and lift is transferred from the rotors to the wing. To land, the proprotors are rotated up to the helicopter rotor position and flown as a helicopter to a vertical landing.

  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. 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

  11. 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.

  12. Welding of combustion turbine rotors and discs

    SciTech Connect

    Driver, T.L.; Amos, D.R.; Clark, R.E.

    1995-12-31

    Weld repair of steam turbine rotors and discs by Westinghouse has been performed successfully and has proven itself in operation for the last 15 years. Since 1978, over 200 low pressure (LP) rotors and discs have been weld repaired using the Gas Tungsten Arc Welding (GTAW) process. This process yields properties equal to or better than the original rotor/disc forging for LP alloys. In 1987, the GTAW process was extended to include repair on high pressure (HP) rotor alloys. Since that time, over 45 high pressure and intermediate pressure (IP) rotors have been successfully weld repaired and returned to service. Recently, to meet the demand for repair of combustion turbine alloys, a development program was initiated to make a step increase in the current LP welding process and filler materials from 100--110 ksi weld metal yield strength (on LP alloys) to 140 ksi needed on many areas of a combustion turbine. The challenge to increase the strength by 30% could not be achieved at the expense of the other critical properties particularly toughness. This paper first reviews the successful LP and HP welding programs which were fundamental building blocks for welding combustion turbines. Secondly, the development and testing of a new filler material for welding combustion turbines is reviewed which demonstrated the ability to achieve approximately 135 ksi yield strength. This new program was implemented on lower stress areas of several production parts which are described in part three. The paper concludes with a summary of possible future work to achieve nominal yield strengths near 145 ksi.

  13. ROTOR END CAP

    DOEpatents

    Rushing, F.C.

    1959-02-01

    An improved end cap is described for the cylindrical rotor or bowl of a high-speed centrifugal separator adapted to permit free and efficient continuous counter current flow of gas therethrough for isotope separation. The end cap design provides for securely mounting the same to the hollow central shaft and external wall of the centrifuge. Passageways are incorporated and so arranged as to provide for continuous counter current flow of the light and heavy portions of the gas fed to the centrifuge.

  14. 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.

  15. 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.

  16. 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.

  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. 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.

  19. 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.

  20. 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.

  1. 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...

  2. 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...

  3. 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.

  4. The longitudinal stability of elastic swept wings at supersonic speed

    NASA Technical Reports Server (NTRS)

    Frick, C W; Chubb, R S

    1950-01-01

    The longitudinal stability characteristics of elastic swept wings of high aspect ratio experiencing bending and torsional deformations are calculated for supersonic speed by the application of linearized lifting-surface theory. A parabolic wing deflection curve is assumed and the analysis is simplified by a number of structural approximations. The method is thereby limited in application to wings of high aspect ratio for which the root effects are small. Expressions for the lift, pitching-moment, and span load distribution characteristics are derived in terms of the elastic properties of the wing; namely, the design stress, the modulus of elasticity, the shearing modulus, and the maximum design load factor. The analysis applies to wings with leading edges swept behind the Mach lines. In all cases, however, the trailing edge is sonic or supersonic. Application of the method of analysis to wings with leading edges swept ahead of the Mach lines is discussed.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. Euler solutions to nonlinear acoustics of non-lifting 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. 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.

  11. 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.

  12. 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.

  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. 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

  15. 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.

  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. 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.

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. Receptivity and Transition of Supersonic Boundary Layers Over Swept Wings

    NASA Technical Reports Server (NTRS)

    Balakumar, Ponnampalam; King, Rudolph A.

    2010-01-01

    The receptivity, stability, and transition of three-dimensional supersonic boundary layers over (1) a swept cylinder, (2) a swept wing with a sharp leading edge, and (3) a swept wing with a blunt leading edge are numerically investigated for a free-stream Mach number of 3. These computations are compared to an earlier experimental and computational study performed by Archambaud et al.1 The steady flow fields with and without roughness elements are obtained by solving the full Navier-Stokes equations. The N-factors computed in this study at the transition onset locations reported in Ref. 1 for flow over the swept cylinder are approximately 16.5 for traveling crossflow disturbances and 9 for stationary disturbances. The N-factors for the traveling crossflow are high based on our past experiences. However, they are comparatively smaller than those reported by Archambaud et al., who found N-factor values in the range of 20 to 25 for traveling disturbances and 13 to 20 for stationary disturbances. Similarly, the N-factors computed in this study for the traveling and stationary disturbances for the flow over the sharp wing are approximately 7 and 2.5, respectively, and for the flow over the blunt wing are 6.5 and 4.8, respectively. Using the envelope method, Archambaud et al. obtained values of approximately 8.0 and 4.0 for the sharp wing case and 16.0 and 12.0 for the blunt wing case.

  3. Electrofriction method of manufacturing squirrel cage rotors

    DOEpatents

    Hsu, John S.

    2005-04-12

    A method of making a squirrel cage rotor of copper material for use in AC or DC motors, includes forming a core with longitudinal slots, inserting bars of conductive material in the slots, with ends extending out of opposite ends of the core, and joining the end rings to the bars, wherein the conductive material of either the end rings or the bars is copper. Various methods of joining the end rings to the bars are disclosed including electrofriction welding, current pulse welding and brazing, transient liquid phase joining and casting. Pressure is also applied to the end rings to improve contact and reduce areas of small or uneven contact between the bar ends and the end rings. Rotors made with such methods are also disclosed.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 14 CFR 29.1509 - Rotor speed.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Rotor speed. 29.1509 Section 29.1509....1509 Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

  11. 14 CFR 27.1509 - Rotor speed.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Rotor speed. 27.1509 Section 27.1509... Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be established... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

  12. 14 CFR 27.1509 - Rotor speed.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor speed. 27.1509 Section 27.1509... Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be established... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

  13. 14 CFR 29.1509 - Rotor speed.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor speed. 29.1509 Section 29.1509....1509 Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

  14. 14 CFR 29.1509 - Rotor speed.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Rotor speed. 29.1509 Section 29.1509....1509 Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

  15. 14 CFR 27.1509 - Rotor speed.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Rotor speed. 27.1509 Section 27.1509... Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be established... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

  16. 14 CFR 27.1509 - Rotor speed.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Rotor speed. 27.1509 Section 27.1509... Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be established... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

  17. 14 CFR 29.1509 - Rotor speed.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Rotor speed. 29.1509 Section 29.1509....1509 Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

  18. 14 CFR 29.1509 - Rotor speed.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Rotor speed. 29.1509 Section 29.1509....1509 Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

  19. 14 CFR 27.1509 - Rotor speed.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Rotor speed. 27.1509 Section 27.1509... Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be established... minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater...

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Rotor blade assembly having internal loading features

    DOEpatents

    Soloway, Daniel David

    2017-05-16

    Rotor blade assemblies and wind turbines are provided. A rotor blade assembly includes a rotor blade having exterior surfaces defining a pressure side, a suction side, a leading edge and a trailing edge each extending between a tip and a root, the rotor blade defining a span and a chord, the exterior surfaces defining an interior of the rotor blade. The rotor blade assembly further includes a loading assembly, the loading assembly including a weight disposed within the interior and movable generally along the span of the rotor blade, the weight connected to a rotor blade component such that movement of the weight towards the tip causes application of a force to the rotor blade component by the weight. Centrifugal force due to rotation of the rotor blade biases the weight towards the tip.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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%.

  15. 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.

  16. Frequency multiplexed long range swept source optical coherence tomography

    PubMed Central

    Zurauskas, Mantas; Bradu, Adrian; Podoleanu, Adrian Gh.

    2013-01-01

    We present a novel swept source optical coherence tomography configuration, equipped with acousto-optic deflectors that can be used to simultaneously acquire multiple B-scans originating from different depths. The sensitivity range of the configuration is evaluated while acquiring five simultaneous B-scans. Then the configuration is employed to demonstrate long range B-scan imaging by combining two simultaneous B-scans from a mouse head sample. PMID:23760762

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Progress in rotor broadband noise research

    NASA Technical Reports Server (NTRS)

    Brooks, T. F.; Schlinker, R. H.

    1983-01-01

    The current status of research on various rotor broadband noise sources is reviewed. Theoretical modeling techniques which appear to have the most promise in the development of successful noise prediction capabilities are emphasized. The types of noise considered include: turbulence ingestion noise, blade self-noise due to turbulence passing the trailing edge, blade self-noise due to separated flow, and blade self-noise due to vortex shedding. Comparisons with experimental results are given, and present theoretical and experimental limitations are delineated to help identify areas of needed research.

  4. Rotor heating effects from geomagnetic induced currents

    SciTech Connect

    Gish, W.B.; Feero, W.E.; Rockefeller, G.D. )

    1994-04-01

    The heating effects at the end-ring connection areas of the rotor due to the harmonic current generation of a saturating unit transformer from geomagnetic induced currents (GIC) on the transmission system have been calculated from observed data and from EMTP studies sponsored by the Electric Power Research Institute. These calculations show that damage may occur during strong GIC storm activity. This damage can occur from unit transformer saturation or other transformers in the system near the generator. The possibility of damage should be monitored during strong GIC storms through the use of appropriate negative sequence current monitoring and alarms.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Open Rotor: New Option for Jet Engines

    NASA Image and Video Library

    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...

  15. 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.

  16. 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.

  17. 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.

  18. Quantum rotor in nanostructured superconductors

    PubMed Central

    Lin, Shi-Hsin; Milošević, M. V.; Covaci, L.; Jankó, B.; Peeters, F. M.

    2014-01-01

    Despite its apparent simplicity, the idealized model of a particle constrained to move on a circle has intriguing dynamic properties and immediate experimental relevance. While a rotor is rather easy to set up classically, the quantum regime is harder to realize and investigate. Here we demonstrate that the quantum dynamics of quasiparticles in certain classes of nanostructured superconductors can be mapped onto a quantum rotor. Furthermore, we provide a straightforward experimental procedure to convert this nanoscale superconducting rotor into a regular or inverted quantum pendulum with tunable gravitational field, inertia, and drive. We detail how these novel states can be detected via scanning tunneling spectroscopy. The proposed experiments will provide insights into quantum dynamics and quantum chaos. PMID:24686241

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Design of plywood and paper flywheel rotors

    NASA Astrophysics Data System (ADS)

    Erdman, A. G.; Hagen, D. L.; Gaff, S. A.

    1982-05-01

    Technical and economic design factors of cellulosic rotors are compared with conventional materials for stationary flywheel energy storage systems. Wood species, operation in a vacuum, assembly and costs of rotors are evaluated. Wound kraft paper, twine and plywood rotors are examined. Two hub attachments are designed. Support stiffness is shown to be constrained by the material strength, rotor configuration and speed ratio. Preliminary duration of load tests was performed on vacuum dried hexagonal birch plywood. Dynamic and static rotor hub fatigue equipment is designed. Moisture loss rates while vacuum drying plywood cylinders were measured, and the radial and axial diffusion coefficients were evaluated. Diffusion coefficients of epoxy coated plywood cylinders were also obtained. Economics of cellulosic and conventional rotors were examined. Plywood rotor manufacturing costs were evaluated. The optimum economic shape for laminated rotors is shown to be cylindrical. Vacuum container costs are parametrically derived and based on material properties and costs. Containment costs are significant and are included in comparisons. The optimum design stress and wound rotor configuration are calculated for seventeen examples. Plywood rotors appear to be marginally competitive with the steel hose wire or E glass rotors. High performance oriented kraft paper rotors potentially provide the lowest energy storage costs in stationary systems.

  5. Flywheels Would Compensate for Rotor Imbalance

    NASA Technical Reports Server (NTRS)

    Hrastar, J. A. S.

    1982-01-01

    Spinning flywheels within rotor can null imbalance forces in rotor. Flywheels axes are perpendicular to each other and to rotor axis. Feedback signals from accelerometers or strain gages in platform control flywheel speeds and rotation directions. Concept should be useful for compensating rotating bodies on Earth. For example, may be applied to large industrial centrifuge, particularly if balance changes during operation.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  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. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Swept-Wing Receptivity Studies Using Distributed Roughness

    NASA Technical Reports Server (NTRS)

    Saric, William S.

    1999-01-01

    Transition to turbulence in swept-wing flows has resisted correlation with linear theory because of its sensitivity to freestream conditions and 3-D roughness and because one of the principal instability modes quickly 'becomes nonlinear. In the face of such a formidable problem, two rather long-term fundamental efforts have been underway at DLR Gottinberg and Arizona State University that address swept-wing transition. These efforts have been recently reviewed by Bippes (1997) and Reibert and Saric (1997). Thus, the present work is a continuation of a series of studies on swept-wing boundary layers which have led to a better understanding of the transition process. In particular, we have taken advantage of the sensitivity to 3-D roughness and the modal nature of the instability in order to propose a particular control strategy. Complementing the two aforementioned reviews, general reviews of the swept-wing transition problem are found in Arnal (1997) and Kachanov (1996). Other recent reviews include Reshotko (t997), Crouch (1997), and Herbert (1997a,b). The failure of linear theory is discussed in Reed et al. (1996). The historical work is found in Reed and Sar-ic (1989). The basic idea is that the combination of sweep and chordwise pressure gradient within the boundary layer creates a velocity component perpendicular to the inviscid streamline. This crossflow profile is inflectional and exhibits both traveling and stationary unstable waves called crossflow vortices that are (approximately) aligned along the inviscid streamlines. Under conditions of low freestream turbulence levels, the dominant crossflow wave is stationary (Reibert and Saric t997) while moderate to high turbulence levels initiate dominant traveling waves (Dehle and Bippes 1996; Bippes 1997). 'Me mechanism is relatively insensitive to sound and 2-D surface roughness (Radeztsky et al. 1993) but very sensitive to 3-D roughness near the attachment line. We concentrate our work on low

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Assessment of choroidal topographic changes by swept source optical coherence tomography after photodynamic therapy for central serous chorioretinopathy.

    PubMed

    Razavi, Sam; Souied, Eric H; Cavallero, Edoardo; Weber, Michel; Querques, Giuseppe

    2014-04-01

    To investigate the relationship between choroidal thickness and angiographic abnormalities in central serous chorioretinopathy (CSC) eyes by swept-source optical coherence tomography (swept-OCT), before and after half-fluence photodynamic therapy (PDT). Prospective interventional case series. Consecutive patients presenting with treatment-naive active CSC underwent a complete ophthalmologic examination, including swept-OCT at study entry and at 7 days and 30 days after treatment with half-fluence PDT. The main outcome measures were changes in choroidal maps after PDT (mean ± SD) and the relationship between choroidal thickness and angiographic abnormalities. Of 12 patients (2 females, 10 males; mean age, 55.6 ± 14.0 years), 12 eyes were included. At study entry, mean choroidal thickness measured in the center of the fovea was significantly thicker in the study eyes as compared to the fellow eyes (420.7 ± 107.5 μm vs 349.2 ± 109.7 μm, respectively; P = 0.016). Mean choroidal thickness in the center of the fovea significantly decreased in the study eyes at both 7 days (380.2 ± 113 μm; P = 0.005) and 30 days after PDT (362.3 ± 111 μm; P = 0.002). A similar significant choroidal thinning was recorded in each early treatment of diabetic retinopathy study (ETDRS) applied to 3D swept-OCT maps. At each time point, mean choroidal thickness was significantly thicker in sectors with than in sectors without angiographic abnormalities (421 ± 102.4 μm vs 397.6 ± 96.5 μm, P = 0.002 at study entry; 381.2 ± 106.6 μm vs 364 ± 101.2 μm, P = 0.01 at day 7; 366.3 ± 103.2 μm vs 347.2 ± 99.6 μm at day 30). Using swept-OCT, we demonstrated that in active CSC, choroidal thickness is increased to a greater extent in areas characterized by angiographic abnormalities. This increased choroidal thickness may persist even after PDT. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. CHOROIDAL STRUCTURAL CHANGES AND VASCULARITY INDEX IN STARGARDT DISEASE ON SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY.

    PubMed

    Ratra, Dhanashree; Tan, Roy; Jaishankar, Durgasri; Khandelwal, Neha; Gupta, Arushi; Chhablani, Jay; Agrawal, Rupesh

    2017-10-06

    To evaluate structural changes in the choroid of patients with Stargardt disease using swept source optical coherence tomography scans. A retrospective comparison cohort study was conducted on 39 patients with Stargardt disease, and on 25 age and gender matched-healthy controls. Subfoveal choroidal thickness (SFCT) was computed from the swept source optical coherence tomography machine, and the scans were binarized into luminal area and stromal areas, which were then used to derive choroidal vascularity index (CVI). Choroidal vascularity index and SFCT were analyzed independently using linear mixed effects model. There was no significant difference in SFCT between the 2 groups (347.20 ± 13.61 μm in Stargardt disease vs. 333.09 ± 18.96 μm in the control group, P = 0.548). There was a significant decrease in the CVI among eyes with Stargardt disease as compared with the normal eyes (62.51 ± 0.25% vs. 65.45 ± 0.29%, P < 0.001). There was a negative association between visual acuity and CVI (correlation coefficient = -0.75, P < 0.001) and a positive association between visual acuity and SFCT (correlation coefficient = 0.21, P = 0.035). Choroidal vascularity index appears to be a more robust tool compared with SFCT for choroidal changes in Stargardt disease. Choroidal vascularity index can possibly be used as a surrogate marker for disease monitoring. A decrease in CVI was associated with a decrease in visual function in eyes with Stargardt disease.

  4. Bucket rotor wind-driven generator

    NASA Technical Reports Server (NTRS)

    Chang, H. H.; Mccracken, H.

    1973-01-01

    As compared with the ordinary propeller type rotor, the bucket rotor is limited in rotational speed since the tip rotor speed can never exceed the wind speed. However, it does not present the blade fatigue problem that the ordinary rotor has, and it perhaps causes less sight pollution. The deflector vanes also provide a venturi passage to capture greater wind flow. The bucket rotors can be strung together end-to-end up to thousands of feet long to produce large amounts of power.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. Swept Impinging Oblique Shock/Boundary-Layer Interactions

    NASA Astrophysics Data System (ADS)

    Little, Jesse; Threadgill, James; Stab, Ilona

    2016-11-01

    Oblique shock waves impinging on boundary layers are common flow features associated with high-speed flows around complex body geometries and through internal channel flows. The increasingly three-dimensional surface geometries of modern vehicles has led to a prevalence of complex shock/boundary-layer interactions. Sweep has been observed to vary the interaction structure, unsteadinesses, and similarity scalings. Sharp-fins and highly-swept ramps have been noted to induce a quasi-conical development of the interaction, in contrast to a quasi-cylindrical scaling observed in low-sweep interactions. However, swept impinging oblique shock cases have largely been overlooked, with evidence of only cylindrical similarities observed in hypersonic conditions. Flow deflection beyond the maximum turning angle has been proposed as the mechanism for conical interaction development but such behavior has not been established for the present configuration. This study examines the effect of sweep on the interaction induced by a 12.5° generator in Mach 2.3 flow using oil-flow, Schlieren and PIV. Results document the development of similarity scalings at various angles of sweep, and highlight the difficulty in replicating a quasi-infinite span conditions in a moderately sized wind tun Supported by the Air Force Office of Scientific Research (FA9550-15-1-0430) and Raytheon Missile Systems.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Observations of vascular structures within and posterior to sclera in eyes with pathologic myopia by swept-source optical coherence tomography.

    PubMed

    Ohno-Matsui, Kyoko; Akiba, Masahiro; Ishibashi, Tatsuro; Moriyama, Muka

    2012-10-19

    We examined the intrascleral and retrobulbar blood vessels in highly myopic eyes by swept-source optical coherence tomography (swept-source OCT). We included in the study 662 of 357 patients with pathologic myopia (spherical equivalent of myopic refractive error ≥ 8.00 diopters or axial length > 26.5 mm). A swept-source OCT system that uses a wavelength sweeping laser with A-scan repetition rate of 100,000 Hz and 1 μm wavelength was used. Radial scans along 12 meridians of 12 mm scan length centered on the fovea were made. Indocyanine green angiography (ICGA) also was performed to identify the intrascleral and retrobulbar vessels that were observed by swept-source OCT. Intrascleral and retrobulbar blood vessels were observed in the macular area of the highly myopic eyes. Linear hyporeflective structures running in the sclera were observed in 474 of the 662 myopic eyes, and ICGA confirmed that these structures were the long posterior ciliary arteries (LPCAs) or the short posterior ciliary arteries (SPCAs) whose entry sites into the eye were displaced toward the temporal edge of the posterior staphyloma in 50 eyes. In 36 of the 662 eyes (5.4%), cross sections of the blood vessels were seen coursing through the scleral layer. In 177 of these 443 eyes, the retrobulbar posterior ciliary arteries (PCAs) also were observed as a cluster of circular or curved hyporeflectant structures just posterior to the sclera. Swept-source OCT is a high-quality method to detect intrascleral and retroscleral blood vessels in the eyes with pathologic myopia. These findings and longitudinal studies of these vessels will help in investigating how they are altered in pathologic myopia, and how such alterations are related to the complications in the retina-choroid and optic nerve.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. Aeroelastic considerations for torsionally soft rotors

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    A research study was initiated to systematically determine the impact of selected blade tip geometric parameters on 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 six tip designs were tested on the torsionally soft blades. The designs incorporated a systemmatic variation in geometric parameters including 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. A track sensitivity study was also conducted at several advance ratios for both rotors. Based on the test results, tip parameter variations generated significant rotor performance and loads differences for both baseline and torsionally soft blades. Azimuthal variation of elastic twist generated by variations in the tip parameters strongly correlated with rotor performance and loads, but the magnitude of advancing blade elastic twist did not. In addition, fixed system vibratory loads and rotor track for potential conformable rotor candidates appears very sensitive to parametric rotor changes.

  3. 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.

  4. Energy potential of dual lead rotors for twin screw compressors

    NASA Astrophysics Data System (ADS)

    Utri, Matthias; Brümmer, Andreas

    2017-08-01

    The paper deals with a theoretical investigation into the ways in which fluid properties influence the optimal geometrical parameters of dry running twin screw compressors with uniform and dual lead rotors. Dual lead rotors possess two segments with different rotor leads in order to optimise the progression of chamber volume, clearance size and outlet area. Optimal geometry parameters are determined by means of a multi-chamber model simulation. Fluids are treated as an ideal gas and fluid properties are varied systematically in order to provide guidance on how the machine should be designed for a particular application. The optimal geometry parameters mainly depend on the speed of sound and isentropic exponent of the fluid, because they influence outlet throttling during discharge, and pressure progression due to volumetric compression. In particular, the values for the rotor wrap angle and the internal volume ratio need to be adjusted individually for each compressor application. The results reveal that dual lead compressors possess most potential for fluids with low speed of sound and isentropic exponent.

  5. 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.

  6. Improved computational treatment of transonic flow about swept wings

    NASA Technical Reports Server (NTRS)

    Ballhaus, W. F.; Bailey, F. R.; Frick, J.

    1976-01-01

    Relaxation solutions to classical three-dimensional small-disturbance (CSD) theory for transonic flow about lifting swept wings are reported. For such wings, the CSD theory was found to be a poor approximation to the full potential equation in regions of the flow field that are essentially two-dimensional in a plane normal to the sweep direction. The effect of this deficiency on the capture of embedded shock waves in terms of (1) the conditions under which shock waves can exist and (2) the relations they must satisfy when they do exist is emphasized. A modified small-disturbance (MSD) equation, derived by retaining two previously neglected terms, was proposed and shown to be a consistent approximation to the full potential equation over a wider range of sweep angles. The effect of these extra terms is demonstrated by comparing CSD, MSD, and experimental wing surface pressures.

  7. 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.

  8. 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.

  9. 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.

  10. Swept-frequency acoustic interferometry technique for noninvasive chemical diagnostics

    SciTech Connect

    Sinha, D.N.; Springer, K.N.; Han, Wei; Lizon, D.C.; Houlton, R.J.

    1997-02-01

    Swept-Frequency Acoustic Interferometry (SFAI) is a noninvasive fluid characterization technique currently being developed for chemical weapons treaty verification. The SFAI technique determines sound speed and sound attenuation in a fluid over a wide frequency range from outside a container (e.g., reactor vessel, tank, pipe, industrial containers etc.). From the frequency dependence of sound attenuation, fluid density can also be determined. These physical parameters. when combined together, can be used to identify a range of chemicals. This technique can be adapted for chemical diagnostic applications, particularly in process control where monitoring of acoustic properties of chemicals (liquids, mixtures, emulsions, suspensions, etc.) may provide appropriate feedback information. The SFAI theory is discussed and experimental techniques are presented. Examples of several novel applications of the SFAI technique are also presented.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Crossflow instability control on a swept-wing: Preliminary studies

    NASA Technical Reports Server (NTRS)

    Bridges, David H.

    1994-01-01

    The pressure distribution on a swept wing causes the streamlines at the edge of the boundary layer to be curved. This pressure gradient normal to the external streamline creates a velocity component normal to the external streamline within the boundary layer which is referred to as the crossflow velocity. Because the crossflow velocity profile perpendicular to the wing surface has an inflection point, the profile is unstable. The stationary instability mode takes the form of crossflow vortices. Under these conditions, the boundary layer on the wing is extremely unstable and transition to turbulent flow takes place much closer to the leading edge of the wing than it would on an unswept wing. Higher skin friction drag is associated with turbulent flow, and so better aircraft performance could be obtained if the crossflow could be eliminated One method of controlling crossflow that is being investigated is boundary-layer suction. An extensive airfoil suction experiment in the 8 feet Transonic Pressure Tunnel (TPT) at NASA Langley Research Center will begin late in 1994. Because of the size, complexity, and expense associated with this test, a number of 'risk-reduction' tests are currently being conducted. The 20 x 28 in. Shear Flow Control Tunnel at NASA Langley is being used for some of these tests. Prior to the summer of 1994, a flat plate with a swept leading edge was installed in the 20 x 28 in. tunnel, with a displacement body mounted on the tunnel ceiling that created a pressure distribution on the plate similar to the pressure distribution on a swept wing. The flow over the plate was investigated during the summer of 1994 using a laser Doppler velocimeter (LDV) system. The LDV measurements indicated the possible presence of multiple disturbance modes, a rarely-seen phenomena since, in most tests, one disturbance mode dominates. The possible existence of multiple disturbance modes in the flat plate boundary layer, however, means that the flow in the 20 x 28 in

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. Architecture of the flagellar rotor

    PubMed Central

    Paul, Koushik; Gonzalez-Bonet, Gabriela; Bilwes, Alexandrine M; Crane, Brian R; Blair, David

    2011-01-01

    Rotation and switching of the bacterial flagellum depends on a large rotor-mounted protein assembly composed of the proteins FliG, FliM and FliN, with FliG most directly involved in rotation. The crystal structure of a complex between the central domains of FliG and FliM, in conjunction with several biochemical and molecular-genetic experiments, reveals the arrangement of the FliG and FliM proteins in the rotor. A stoichiometric mismatch between FliG (26 subunits) and FliM (34 subunits) is explained in terms of two distinct positions for FliM: one where it binds the FliG central domain and another where it binds the FliG C-terminal domain. This architecture provides a structural framework for addressing the mechanisms of motor rotation and direction switching and for unifying the large body of data on motor performance. Recently proposed alternative models of rotor assembly, based on a subunit contact observed in crystals, are not supported by experiment. PMID:21673656

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. Effect of seals on rotor systems

    NASA Technical Reports Server (NTRS)

    Fleming, D. P.

    1982-01-01

    Seals can exert large forces on rotors. As an example, in turbopump ring seals film stiffness as high as 90 MN/m (500,000 lb/in) have been calculated. This stiffness is comparable to the stiffness of rotor support bearings; thus seals can play an important part in supporting and stabilizing rotor systems. The work done to determine forces generated in ring seals is reviewed. Working formulas are presented for seal stiffness and damping, and geometries to maximize stiffness are discussed. An example is described where a change in seal design stabilized a previously unstable rotor.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Insights into the nature and control of rotor noise

    NASA Technical Reports Server (NTRS)

    Pegg, R. J.

    1976-01-01

    The dynamics of four important farfield rotating blade noise sources are summarized and techniques for noise reduction are discussed. These four noise areas include the role of unsteady blade surface loads on rotational noise, the effect of turbulent inflow on the radiated broadband noise of an airfoil, the influence of the trailing vortex on impulsive noise and tail rotor noise, and the effect of blade geometry on high-speed impulsive noise. These noise mechanisms occur to varying degrees on both helicopter rotors and propellers. Considerable theoretical work was done in the area of high-speed impulsive noise resulting from the geometry of the rotating blade system. Both model and full-scale experimental correlation of helicopter and propeller high-speed noise are presented. The effect of blade number and airfoil thickness distribution in reducing the high-speed noise is shown.

  9. 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.

  10. 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.

  11. V/STOL tilt rotor aircraft study. Volume 5: Definition of stowed rotor research aircraft

    NASA Technical Reports Server (NTRS)

    Soule, V. A.

    1973-01-01

    The results of a study of folding tilt rotor (stowed rotor) aircraft are presented. The effects of design cruise speed on the gross weight of a conceptual design stowed rotor aircraft are shown and a comparison is made with a conventional (non-folding) tilt rotor aircraft. A flight research stowed rotor design is presented. The program plans, including costs and schedules, are shown for the research aircraft development and a wind tunnel plan is presented for a full scale test of the aircraft.

  12. 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).

  13. 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.

  14. 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.

  15. Normal injection of helium from swept struts into ducted supersonic flow

    NASA Technical Reports Server (NTRS)

    Mcclinton, C. R.; Torrence, M. G.

    1975-01-01

    Recent design studies have shown that airframe-integrated scramjets should include instream mounted, swept-back strut fuel injectors to obtain short combustors. Because there was no data in the literature on mixing characteristics of swept strut fuel injectors, the present investigation was undertaken to provide such data. This investigation was made with two swept struts in a closed duct at Mach number of 4.4 and nominal jet-to-air mass flow ratio of 0.029 with helium used to simulate hydrogen fuel. The data is compared with flat plate mounted normal injector data to obtain the effect of swept struts on mixing. Three injector patterns were evaluated representing the range of hole spacing and jet-to-freestream dynamic pressure ratio of interest. Measured helium concentration, pitot pressure, and static pressure in the downstream mixing region are used to generate contour plots necessary to define the mixing region flow field and the mixing parameters.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Extended-Cavity Semiconductor Wavelength-Swept Laser for Biomedical Imaging.

    PubMed

    Yun, S H; Boudoux, C; Pierce, M C; de Boer, J F; Tearney, G J; Bouma, B E

    2004-01-01

    We demonstrate a compact high-power rapidly swept wavelength tunable laser source based on a semiconductor optical amplifier and an extended-cavity grating filter. The laser produces excellent output characteristics for biomedical imaging, exhibiting >4-mW average output power, <0.06-nm instantaneous linewidth, and >80-dB noise extinction with its center wavelength swept over 100 nm at 1310 nm at variable repetition rates up to 500 Hz.

  2. Extended-Cavity Semiconductor Wavelength-Swept Laser for Biomedical Imaging

    PubMed Central

    Yun, S. H.; Boudoux, C.; Pierce, M. C.; de Boer, J. F.; Tearney, G. J.; Bouma, B. E.

    2010-01-01

    We demonstrate a compact high-power rapidly swept wavelength tunable laser source based on a semiconductor optical amplifier and an extended-cavity grating filter. The laser produces excellent output characteristics for biomedical imaging, exhibiting >4-mW average output power, <0.06-nm instantaneous linewidth, and >80-dB noise extinction with its center wavelength swept over 100 nm at 1310 nm at variable repetition rates up to 500 Hz. PMID:20640193

  3. Variable-Tilt Helicopter Rotor Mast

    NASA Technical Reports Server (NTRS)

    Kelley, Henry L.

    1995-01-01

    Variable-tilt helicopter rotor mast proposed to improve helicopter performance and reduce vibration, especially at upper end of forward-speed range of helicopters. Achieved by use of universal coupling in main rotor mast or by tilting entire engine-and-transmission platform. Performance, energy efficiency, and safety enhanced.

  4. 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.

  5. 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.

  6. 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.

  7. 14 CFR 33.34 - Turbocharger rotors.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Turbocharger rotors. 33.34 Section 33.34... STANDARDS: AIRCRAFT ENGINES Design and Construction; Reciprocating Aircraft Engines § 33.34 Turbocharger rotors. Each turbocharger case must be designed and constructed to be able to contain fragments of a...

  8. 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.

  9. Calculating Flow Through A Helicopter Rotor

    NASA Technical Reports Server (NTRS)

    Kunz, Donald L.; Hodges, Dewey H.

    1991-01-01

    New method for calculating flow of air through and around helicopter rotor incorporated into General Rotorcraft Aeromechanical Stability Program (GRASP) (computer program for aeroelastic analysis). Flow about helicopter rotor represented by axisymmetric flow field in cylindrical region with actuator disk as source of flow.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  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. 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.

  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. 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.

  1. 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.

  2. Substantially parallel flux uncluttered rotor machines

    DOEpatents

    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. 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.

  4. 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.

  5. 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.

  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. 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.

  9. 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.

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

    PubMed

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

    2016-02-01

    To evaluate the thickness and volume of the choroid in healthy Korean children using swept-source optical coherence tomography. 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. 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). 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.

  11. 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

  12. 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.

  13. 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.

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  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 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. 14 CFR 27.547 - Main rotor structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Main rotor structure. 27.547 Section 27.547... 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...

  10. 14 CFR 27.547 - Main rotor structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Main rotor structure. 27.547 Section 27.547... 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...

  11. 14 CFR 27.547 - Main rotor structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Main rotor structure. 27.547 Section 27.547... 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...

  12. 14 CFR 27.661 - Rotor blade clearance.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Rotor blade clearance. 27.661 Section 27... 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...

  13. 14 CFR 27.661 - Rotor blade clearance.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor blade clearance. 27.661 Section 27... 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...

  14. 14 CFR 29.661 - Rotor blade clearance.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Rotor blade clearance. 29.661 Section 29... 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...

  15. 14 CFR 27.661 - Rotor blade clearance.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Rotor blade clearance. 27.661 Section 27... 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...

  16. 14 CFR 29.661 - Rotor blade clearance.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Rotor blade clearance. 29.661 Section 29... 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...

  17. 14 CFR 27.661 - Rotor blade clearance.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Rotor blade clearance. 27.661 Section 27... 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...

  18. 14 CFR 27.661 - Rotor blade clearance.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Rotor blade clearance. 27.661 Section 27... 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...

  19. 14 CFR 29.661 - Rotor blade clearance.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Rotor blade clearance. 29.661 Section 29... 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...

  20. 14 CFR 29.661 - Rotor blade clearance.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor blade clearance. 29.661 Section 29... 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...

  1. 14 CFR 29.661 - Rotor blade clearance.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Rotor blade clearance. 29.661 Section 29... 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...

  2. 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.

  3. Experimental evaluation of active and passive means of alleviating rotor impulsive noise in descent flight

    NASA Technical Reports Server (NTRS)

    Janakiram, D. S.

    1979-01-01

    A controlled wind tunnel test program was conducted on a model 2.14 m (7 ft) diameter teetering rotor to determine the effectiveness of blade tips such as the Ogee tip and the TAMI (Tip Air Mass Injection) tip in reducing the impulsive noise due to blade-vortex interaction in descent flight. In addition, a full rectangular tip which has the same span as the Ogee tip and an effective rectangular tip which has the same lifting area as the Ogee tip were also considered. The tests were conducted at two advance ratios (0.125 and 0.14) with various descent rates ranging from steady level flight to about 6 m/sec (20 ft/sec). A comparison of the performance of different rotors showed that for the same tip Mach number and thrust, the Ogee tip rotor absorbed more power than the full rectangular tip rotor, while the TAMI tip rotor absorbed more power than the effective tip rotor.

  4. 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.

  5. 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

  6. 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

  7. 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

  8. Swept source optical coherence tomography for quantitative and qualitative assessment of dental composite restorations

    NASA Astrophysics Data System (ADS)

    Sadr, Alireza; Shimada, Yasushi; Mayoral, Juan Ricardo; Hariri, Ilnaz; Bakhsh, Turki A.; Sumi, Yasunori; Tagami, Junji

    2011-03-01

    The aim of this work was to explore the utility of swept-source optical coherence tomography (SS-OCT) for quantitative evaluation of dental composite restorations. The system (Santec, Japan) with a center wavelength of around 1300 nm and axial resolution of 12 μm was used to record data during and after placement of light-cured composites. The Fresnel phenomenon at the interfacial defects resulted in brighter areas indicating gaps as small as a few micrometers. The gap extension at the interface was quantified and compared to the observation by confocal laser scanning microscope after trimming the specimen to the same cross-section. Also, video imaging of the composite during polymerization could provide information about real-time kinetics of contraction stress and resulting gaps, distinguishing them from those gaps resulting from poor adaptation of composite to the cavity prior to polymerization. Some samples were also subjected to a high resolution microfocus X-ray computed tomography (μCT) assessment; it was found that differentiation of smaller gaps from the radiolucent bonding layer was difficult with 3D μCT. Finally, a clinical imaging example using a newly developed dental SS-OCT system with an intra-oral scanning probe (Panasonic Healthcare, Japan) is presented. SS-OCT is a unique tool for clinical assessment and laboratory research on resin-based dental restorations. Supported by GCOE at TMDU and NCGG.

  9. Study of active rotor control for in-plane rotor noise reduction

    NASA Astrophysics Data System (ADS)

    Yang, Tianxiao

    This research consists of two parts: the main part of this research is the study of active rotor control for in-plane rotor noise reduction. The objective of this part of the research is to develop a methodology to find a loading solution that results in noise reduction at a single observer or over an area (at multiple observers), and propose potential active devices that may realize the loading solution to reduce in-plane noise. Another part of the research is the study of thickness noise prediction method, which aims to develop a new thickness noise prediction method able to provide fast and relatively accurate thickness noise prediction. In this research, a new thickness noise prediction method, called dual compact thickness noise model is developed. In this dual compact model, at each radial location, the airfoil is divided into two parts and the uniform pressure distribution is integrated on the front and rear part respectively. This generates two loading lines acting at different chordwise locations, and the loading noise generated by these two loading lines reproduces the acoustic signal of the normal thickness noise. The positions of the two loading lines are determined to be .... = 0.133 and .... = 0.867 in a baseline case by matching normal thickness noise and the dual compact result at an in-plane observer directly ahead of the rotor. The dual compact thickness noise model is validated through thickness noise computation for a wide variety of cases, in which different airfoils, blade planforms, and tip Mach numbers, are considered. The dual compact thickness noise result is in good agreement with normal thickness noise for each case. Additionally, the locations of the two loading lines are kept unchanged for all the cases. The computation time is significantly reduced by using the dual compact thickness noise model as compared to the normal thickness noise computation (typically 25 times faster). Finally, the accuracy of dual compact thickness noise

  10. Exploratory wind-tunnel investigation of the effect of the main rotor wake on tail rotor noise. [langley anechoic noise facility

    NASA Technical Reports Server (NTRS)

    Pegg, R. J.; Shidler, P. A.

    1978-01-01

    Approaches to minimizing the noise generated by the interaction of the tail rotor blades with the wake of the main rotor considered include repositioning of the tail rotor with respect to the main rotor, changes in the rotational direction of the tail rotor, and modification of the main rotor tip vortex. A variable geometry model was built which had the capability of varying tail rotor position relative to the main rotor as well as direction of tail rotor rotation. Acoustic data taken from the model in the Langley anechoic noise facility indicates interaction effects due to both main rotor shed vortex and the main rotor turbulence.

  11. 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)

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. V-22 Osprey Tilt-Rotor Aircraft

    DTIC Science & Technology

    2002-01-14

    Congressional Research Service ˜ The Library of Congress CRS Issue Brief for Congress Received through the CRS Web Order Code IB86103 V-22 Osprey ...00-00-2002 to 00-00-2002 4. TITLE AND SUBTITLE V-22 Osprey Tilt-Rotor Aircraft 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER...Congress V-22 Osprey Tilt-Rotor Aircraft SUMMARY The V-22 Osprey is a tilt-rotor aircraft that takes off and lands vertically like a heli- copter and

  18. V-22 Osprey Tilt-Rotor Aircraft

    DTIC Science & Technology

    2004-04-23

    Order Code RL31384 CRS Report for Congress V-22 Osprey Tilt-Rotor Aircraft Updated April 23, 2004 Christopher Bolkcom Specialist in National Defense...2004 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE V-22 Osprey Tilt-Rotor Aircraft 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 V-22 Osprey Tilt-Rotor Aircraft Summary The V-22 Osprey is a

  19. Rotor-Liquid-Fundament System's Oscillation

    NASA Astrophysics Data System (ADS)

    Kydyrbekuly, A.

    The work is devoted to research of oscillation and sustainability of stationary twirl of vertical flexible static dynamically out-of-balance rotor with cavity partly filled with liquid and set on relative frame fundament. The accounting of such factors like oscillation of fundament, liquid oscillation, influence of asymmetry of installation of a rotor on a shaft, anisotropism of shaft support and fundament, static and dynamic out-of-balance of a rotor, an external friction, an internal friction of a shaft, allows to settle an invoice more precisely kinematic and dynamic characteristics of system.

  20. 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.

  1. Wideband frequency-swept excitation in pulsed EPR spectroscopy

    NASA Astrophysics Data System (ADS)

    Doll, Andrin; Jeschke, Gunnar

    2017-07-01

    Excitation of electron spins with monochromatic rectangular pulses is limited to bandwidths that are smaller than the spectral widths of most organic radicals and much smaller than the spectral widths of transition and rare earth metal ions. With frequency-swept pulses, bandwidths of up to 800 MHz have previously been attained for excitation and detection of spin packets at frequencies of about 9.6 GHz and bandwidths of up to 2.5 GHz in a polarization transfer experiment at frequencies of about 34 GHz. The remaining limitations, mainly due to resonator bandwidth and due to pulse length restrictions are discussed. Flip angles for state-space rotations on passage of a transition can generally be computed from the critical adiabaticity by the Landau-Zener-Stückelberg-Majorana expression. For hyperbolic secant pulses, the Demkov-Kunike model describes excitation for spin packets within and outside the sweep range. Well within the sweep range, the Bloch-Siegert phase shift is proportional to critical adiabaticity to a very good approximation. Because of the dependence of both flip angle and coherence phase on critical adiabaticity, it is advantageous to use pairs of amplitude and frequency modulation functions that provide such offset-independent adiabaticity. Compensation for the resonator response function should restore offset-independent adiabaticity. Whereas resonance offsets and Bloch-Siegert phase can be refocused at certain pulse length ratios, phase dispersion in coupled spin systems cannot generally be refocused. Based on the bandwidth limitations that arise from spin dynamics, requirements are derived for a spectrometer that achieves precise spin control over wide bands. The design of such a spectrometer and hardware characterization by EPR experiments are discussed.

  2. Multiple piece turbine rotor blade

    DOEpatents

    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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Characteristics of hingeless rotors with hub moment feedback controls including experimental rotor frequency response, Volume 1

    NASA Technical Reports Server (NTRS)

    Kuczynski, W. A.; Sissingh, G. J.

    1972-01-01

    Wind tunnel tests to determine the dynamic characteristics of hingeless rotors with hub moment feedback controls and to acquire experimental hingeless rotor transfer functions are discussed. Rotor transfer functions were calculated from data acquired during open loop frequency response tests. The transfer functions are linear and present the rotor longitudinal and lateral frequency responses to collective pitch, longitudinal cyclic pitch, and lateral cyclic pitch. The theoretical analysis was based on the rigid blade flapping model coupled with appropriate control system and cyclic pitch actuator equations of motion.

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

    PubMed Central

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

    2009-01-01

    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. PMID:18542467

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  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. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. Transonic Axial Splittered Rotor Tandem Stator Stage

    DTIC Science & Technology

    2016-12-01

    position relative to the design configuration. Numerical simulations were conducted of both hot and cold rotor shapes and compared. This study advanced...that of the cold shape results; however, the hot shape achieved a greater mass flow range. The procedure developed is easily implemented, utilizing a...negative 10 percent clocking position relative to the design configuration. Numerical simulations were conducted of both hot and cold rotor shapes and

  5. 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.

  6. 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.

  7. 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.

  8. Coupled rotor/airframe vibration prediction methods

    NASA Technical Reports Server (NTRS)

    Staley, J. A.; Sciarra, J. J.

    1974-01-01

    The problems of airframe structural dynamic representation and effects of coupled rotor/airframe vibration are discussed. Several finite element computer programs (including NASTRAN) and methods for idealization and computation of airframe natural modes and frequencies and forced response are reviewed. Methods for obtaining a simultaneous rotor and fuselage vibratory response, determining effectiveness of vibration control devices, and energy methods for structural optimization are also discussed. Application of these methods is shown for the vibration prediction of the model 347 helicopter.

  9. 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.

  10. 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.

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

    NASA Technical Reports Server (NTRS)

    Van Zante, Dale E.; 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.

  12. 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.

  13. Labyrinth seal forces on a whirling rotor

    NASA Technical Reports Server (NTRS)

    Wright, D. V.

    1983-01-01

    An experimental investigation of air labyrinth seal forces on a subsynchronously whirling model rotor is described and test results are given for diverging, converging, and straight two-strip seals. The effects of pressure drop, provide basic experimental data needed in the development of design methods for predicting and preventing self-excited whirl of turbine rotors and other machines having labyrinth seals. The total dynamic seal forces on the whirling model rotor are measured accurately by means of an active damping and stiffness system that is adjusted to obtain neutral whirl stability of the model rotor system. In addition, the whirling pressure pattern in the seal annulus is measured for a few test conditions and the corresponding pressure forces on the rotor are compared with the total measured forces. This comparison shows that either radial and axial pressure gradients in the seal annulus or drag forces on the rotor are significant. Comparisons made between the measured seal forces and theoretical results show that present theory is inadequate.

  14. Induced Power of the Helicopter Rotor

    NASA Technical Reports Server (NTRS)

    Ormiston, Robert A.

    2004-01-01

    A simplified rotor model was used to explore fundamental behavior of lifting rotor induced power at moderate and high advance ratios. Several rotor inflow theories, including dynamic inflow theory and prescribed-wake vortex theory, together with idealized notional airfoil stall models were employed. A number of unusual results were encountered at high advance ratios including trim control reversal and multiple trim solutions. Significant increases in rotor induced power (torque) above the ideal minimum were observed for moderately high advance ratio. Very high induced power was observed near and above unity advance ratio. The results were sensitive to the stall characteristics of the airfoil models used. An equivalent wing analysis was developed to determine induced power from Prandtl lifting line theory and help interpret the rotor induced power behavior in terms of the spanwise airload distribution. The equivalent wing approach was successful in capturing the principal variations of induced power for different configurations and operating conditions. The effects blade root cutout were found to have a significant effect on rotor trim and induced power at high advance ratios.

  15. Studies of a flat wake rotor theory

    NASA Technical Reports Server (NTRS)

    Curtiss, H. C., Jr.; Mckillip, R. M., Jr.

    1992-01-01

    A computer code was developed at Princeton University to calculate the velocity components in the flow field near a lifting rotor. The induced velocity components in the rotor flow field predicted by this theory are compared with experiment. It appears that on balance, this relatively simple theory gives a reasonable prediction of the average induced velocities in a rotor flow and is quite suitable for such applications as estimating the influence of the rotor wake on the tail surfaces of rotorcraft. The theory predicts that significant induced velocity components are present in all three flow directions in the wake at a lifting rotor. It should be noted , however, that there are a few experimental measurements of the longitudinal and lateral induced velocity components in the rotor wake. This theory, known as the flat wake theory, is essentially the rotary wing analog of Prandtl's lifting line theory. The theory is described in this report. Calculations based on the theory are presented and compared with a modern free wake theory.

  16. Labyrinth seal forces on a whirling rotor

    NASA Technical Reports Server (NTRS)

    Wright, D. V.

    1983-01-01

    An experimental investigation of air labyrinth seal forces on a subsynchronously whirling model rotor is described and test results are given for diverging, converging, and straight two-strip seals. The effects of pressure drop, back pressure, whirl direction, and whirl frequency are shown. These results provide basic experimental data needed in the development of design methods for predicting and preventing self-excited whirl of turbine rotors and other machines having labyrinth seals. The total dynamic seal forces on the whirling model rotor are measured accurately by means of a novel active damping and stiffness system that is adjusted to obtain neutral whirl stability of the model rotor system. In addition, the whirling pressure pattern in the seal annulus is measured for a few test conditions and the corresponding pressure forces on the rotor are compared with the total measured forces. This comparison shows that either radial and axial pressure gradients in the seal annulus or drag forces on the rotor are significant.

  17. Forces exciting generation roll at rotor vibrations when rotor-to-stator rubbing

    NASA Astrophysics Data System (ADS)

    Shatokhin, V. F.

    2017-07-01

    The consequences of emergencies of turbosets for different application are revealed, the cause of forced shutdown and even catastrophic destructions of which many researchers consider the rotor-to-stator rubbing and development—to a greater or lesser extent—of the phenomena of the rotor generation roll over the stator. The synchronous or asynchronous generation roll is determined by the rotor precession direction, coinciding or not coinciding with the self-rotation direction of the rotor. Asynchronous generation roll is the most dangerous form of the rotor-stator contact interaction with the vibrations with rubbing. The basic equations of rotor vibrations are presented: symmetric rotor fixed on two supports and that fixed on several supports after abrupt imbalance with and without rotor coming in contact with a flexible stator. The vibration process is considered as the rotor motion in a backlash with subsequent contact with the stator, loss of contact, or development of generation roll. The latter essentially depends on the properties of the "rotor-support-stator" dynamic system. The stator stiffness characteristic is specified in "force-deformation" coordinates that make it possible to take into account damping in the supports and power loss in the stator. The diagram of elastic-damping device was presented, which makes it possible to ensure a certain level of power loss at the stator displacements. The exciting forces promoting development of self-exciting vibrations of the rotor in the form of asynchronous generation roll were compared with the exciting forces of oil film of sliding bearings and forces of aerodynamic excitation in the turbine flow path and sealings. For the rotor systems of high and medium pressure of a 300 MW capacity turboset, the simulation results of the process of development of asynchronous generation roll at the vibrations with rubbing were revealed, and the basic characteristics of development of generation roll in a span between

  18. Aperiodicity Correction for Rotor Tip Vortex Measurements

    NASA Technical Reports Server (NTRS)

    Ramasamy, Manikandan; Paetzel, Ryan; Bhagwat, Mahendra J.

    2011-01-01

    The initial roll-up of a tip vortex trailing from a model-scale, hovering rotor was measured using particle image velocimetry. The unique feature of the measurements was that a microscope was attached to the camera to allow much higher spatial resolution than hitherto possible. This also posed some unique challenges. In particular, the existing methodologies to correct for aperiodicity in the tip vortex locations could not be easily extended to the present measurements. The difficulty stemmed from the inability to accurately determine the vortex center, which is a prerequisite for the correction procedure. A new method is proposed for determining the vortex center, as well as the vortex core properties, using a least-squares fit approach. This approach has the obvious advantage that the properties are derived from not just a few points near the vortex core, but from a much larger area of flow measurements. Results clearly demonstrate the advantage in the form of reduced variation in the estimated core properties, and also the self-consistent results obtained using three different aperiodicity correction methods.

  19. 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

  20. 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

  1. Amplified, frequency swept lasers for frequency domain reflectometry and OCT imaging: design and scaling principles.

    PubMed

    Huber, R; Wojtkowski, M; Taira, K; Fujimoto, J; Hsu, K

    2005-05-02

    We demonstrate a high-speed, frequency swept, 1300 nm laser source for frequency domain reflectometry and OCT with Fourier domain/swept-source detection. The laser uses a fiber coupled, semiconductor amplifier and a tunable fiber Fabry-Perot filter. We present scaling principles which predict the maximum frequency sweep speed and trade offs in output power, noise and instantaneous linewidth performance. The use of an amplification stage for increasing output power and for spectral shaping is discussed in detail. The laser generates ~45 mW instantaneous peak power at 20 kHz sweep rates with a tuning range of ~120 nm full width. In frequency domain reflectometry and OCT applications the frequency swept laser achieves 108 dB sensitivity and ~10 mum axial resolution in tissue. We also present a fast algorithm for real time calibration of the fringe signal to equally spaced sampling in frequency for high speed OCT image preview.

  2. 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.

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

    PubMed Central

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

    2017-01-01

    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. PMID:28362318

  4. 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.

  5. 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.

  6. 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

  7. Spectro-refractometry of individual microscopic objects using swept-source quantitative phase imaging.

    PubMed

    Jung, Jae-Hwang; Jang, Jaeduck; Park, Yongkeun

    2013-11-05

    We present a novel spectroscopic quantitative phase imaging technique with a wavelength swept-source, referred to as swept-source diffraction phase microscopy (ssDPM), for quantifying the optical dispersion of microscopic individual samples. Employing the swept-source and the principle of common-path interferometry, ssDPM measures the multispectral full-field quantitative phase imaging and spectroscopic microrefractometry of transparent microscopic samples in the visible spectrum with a wavelength range of 450-750 nm and a spectral resolution of less than 8 nm. With unprecedented precision and sensitivity, we demonstrate the quantitative spectroscopic microrefractometry of individual polystyrene beads, 30% bovine serum albumin solution, and healthy human red blood cells.

  8. 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.

  9. En face mode of swept-source optical coherence tomography in circumscribed choroidal haemangioma.

    PubMed

    Flores-Moreno, Ignacio; Caminal, Josep M; Arias-Barquet, Luis; Rubio-Caso, Marcos J; Catala-Mora, Jaume; Vidal-Martí, María; Muñoz-Blanco, Alex; Filloy, Alejandro; Ruiz-Moreno, José M; Duker, Jay S; Arruga, Jorge

    2016-03-01

    To describe the findings in circumscribed choroidal haemangioma (CCH) using en face swept-source optical coherence tomography (SS-OCT). En face images were obtained employing DRI-1 Atlantis OCT (Topcon, Tokyo, Japan), using a three-dimensional volumetric scan of 12×9 mm. Images were obtained from the retinal pigment epithelium to 1000 μm in depth of the tumour. Twenty-two eyes from 22 patients with the clinical diagnosis of CCH were included. In 20 eyes (90.9%), a characteristic pattern was visualised in the en face image across the vascular tumour. A multilobular pattern, similar to a honeycomb, with hyporeflective, confluent, oval or round areas corresponding with the lumen of the tumour vascular spaces, and hyper-reflective zones, which may represent the vessels walls and connective tissue of the tumour. Ten eyes (45.4%) showed a hyper-reflective halo surrounding the tumour. Seventeen tumours (77.2%) showed small diameter vessels at the inner zone and larger vessels in the outer area. Twelve patients (54.5%) had previously received treatment (photodynamic therapy, transpupillary thermotherapy, dexamethasone intravitreal implant or brachytherapy with ruthenium-106). No differences were found between treated and untreated patients in any of the measured parameters. En face SS-OCT is a rapid, non-invasive, high-resolution, technology, which allows a complementary study to cross-sectional scans in CCH. A characteristic multilobular pattern, with a hyper-reflective halo surrounding the tumour, was found in en face SS-OCT images. No morphological differences were found between naïve patients and patients who received previous treatment. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  10. 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.

  11. 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.

  12. Epicardial rotors in panoramic optical maps of fibrillating swine ventricles.

    PubMed

    Kay, Matthew W; Rogers, Jack M

    2006-01-01

    It has been proposed that VF waves emanate from stable periodic sources (often called "mother rotors"). Our objective was to determine if stable rotors are consistently present on the epicardial surface of hearts comparable in size to human hearts. Using new optical mapping technology, we imaged VF from nearly the entire ventricular surface of 6 isolated swine hearts. Using newly developed pattern analysis algorithms, we identified and tracked VF wavefronts and phase singularities (PS). We introduce the notion of a compound rotor in which the rotor's central PS can change and describe an algorithm for automatically identifying such patterns. This prevents rotor lifetimes from being inappropriately abbreviated by wavefront fragmentation and collision events near the PS. We found that stable epicardial rotors were not consistently present during VF: only 1 of 17 VF episodes contained a compound rotor that lasted for the entire mapped interval of 4s. However, shorter-lived rotors were common; 12.2+/-3.3 compound rotors with lifetime>200 ms were visible on the epicardium at any given instant. We conclude that epicardial mother rotors do not drive VF in this experimental model; if mother rotors do exist, they are intramural or septal. This paucity of persistent rotors suggests that individual rotors will eventually terminate by themselves and therefore the continual formation of new rotors is critical for VF maintenance.

  13. 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

  14. The Effect of Rotor Tip Markings on Judgements of Rotor Sweep Extent

    DTIC Science & Technology

    2010-12-01

    displays, and to the experimental study of visual factors affecting pilot performance...research described in this report was to examine whether rotor tip markings would have any effect on the ability of helicopter pilots to judge the...helicopter rotor tips more visible to the pilot . The second aim was to determine whether increased visibility improves the judgement of the distance of

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Low-Reynolds Number Aerodynamics of an 8.9 Percent Scale Semispan Swept Wing for Assessment of Icing Effects

    NASA Technical Reports Server (NTRS)

    Broeren, Andy; Woodard, Brian; Diebold, Jeff; Moens, Frederic

    2017-01-01

    This paper presents the results of an experimental and computational study of low-Reynolds number swept wing aerodynamics. This work has been conducted in preparation for icing effects on a swept wing. A complete abstract will be written for the final paper.

  20. Aeropropulsive characteristics of twin nonaxisymmetric vectoring nozzles installed with forward-swept and aft-swept wings. [in the Langley 16 Foot Transonic Tunnel

    NASA Technical Reports Server (NTRS)

    Capone, F. J.

    1981-01-01

    An investigation was conducted in the Langley 16 Foot Transonic Tunnel to determine the aeropropulsive characteristics of a single expansion ramp nozzle (SERN) and a two dimensional convergent divergent nozzle (2-D C-D) installed with both an aft swept and a forward swept wing. The SERN was tested in both an upright and an inverted position. The effects of thrust vectoring at nozzle vector angles from -5 deg to 20 deg were studied. This investigation was conducted at Mach numbers from 0.40 to 1.20 and angles of attack from -2.0 deg to 16 deg. Nozzle pressure ratio was varied from 1.0 (jet off) to about 9.0. Reynolds number based on the wing mean geometric chord varied from about 3 million to 4.8 million, depending upon free stream number.

  1. Integrated Technology Rotor/Flight Research Rotor (ITR/FRR) concept definition study

    NASA Technical Reports Server (NTRS)

    Hughes, C. W.

    1983-01-01

    Studies were conducted by Hughes Helicopters, Inc. (HHI) for the Applied Technology Laboratory and Aeromechanics Laboratory, U.S. Army Research and Technology Laboratories (AVRADCOM) and the Ames Research Center, National Aeronautics and Space Administration (NASA). Results of predesign studies of advanced main rotor hubs, including bearingless designs, are presented in this report. In addition, the Government's rotor design goals and specifications were reviewed and evaluated. Hub concepts were designed and qualitatively evaluated in order to select the two most promising concepts for further development. Various flexure designs, control systems, and pitchcase designs were investigated during the initial phases of this study. The two designs selected for additional development were designated the V-strap and flat-strap cruciform hubs. These hubs were designed for a four bladed rotor and were sized for 18,400 pounds gross weight with the same diameter (62 feet) and solidity (23 inch chord) as the existing rotor on the Rotor Systems Research Aircraft (RSRA).

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. Soil Moisture Sensing via Swept Frequency Based Microwave Sensors

    PubMed Central

    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 r2 = 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

  11. 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.

  12. In Vivo Identification of the Posttrabecular Aqueous Outflow Pathway Using Swept-Source Optical Coherence Tomography.

    PubMed

    Uji, Akihito; Muraoka, Yuki; Yoshimura, Nagahisa

    2016-08-01

    The purpose of this study was to investigate a novel imaging technique to identify the continuous posttrabecular aqueous outflow pathway from a single B-scan, using swept-source optical coherence tomography (SS-OCT). Three-dimensional volume scans of the temporal or nasal side of the anterior segment area at the limbus were acquired from 11 eyes of 11 healthy subjects, using SS-OCT. The aqueous outflow pathway was identified using an en face OCT image and reconstructed images of the vasculature (vasculature map). Delineation of the whole aqueous outflow pathway in a single B-scan was accomplished by reslicing the volume scan. The posttrabecular aqueous outflow pathway was successfully identified in 10 eyes (90.9%). Combined with a flattening technique, the en face video and vasculature map showed a clear blood stream that could not be observed on a sequential stack of B-scans. In the en face images, the vessels were widely branched in the episclera venous plexus, perpendicularly penetrating the scleral stroma. Vessels running parallel to Schlemm's canal and the collector channels were observed in the deeper region of the sclera. The average longitudinal diameter of the vessel was 29.7 ± 6.6 μm at the episcleral venous plexus, and it was significantly larger than that in the deep scleral aqueous plexus (22.0 ± 4.8 μm; P = 0.0002). The continuous posttrabecular aqueous outflow pathway could be identified from a single B-scan and quantitatively analyzed using SS-OCT with en face imaging and volume scan reslicing.

  13. Swept-sine noise-induced damage as a hearing loss model for preclinical assays

    PubMed Central

    Sanz, Lorena; Murillo-Cuesta, Silvia; Cobo, Pedro; Cediel-Algovia, Rafael; Contreras, Julio; Rivera, Teresa; Varela-Nieto, Isabel; Avendaño, Carlos

    2015-01-01

    Mouse models are key tools for studying cochlear alterations in noise-induced hearing loss (NIHL) and for evaluating new therapies. Stimuli used to induce deafness in mice are usually white and octave band noises that include very low frequencies, considering the large mouse auditory range. We designed different sound stimuli, enriched in frequencies up to 20 kHz (“violet” noises) to examine their impact on hearing thresholds and cochlear cytoarchitecture after short exposure. In addition, we developed a cytocochleogram to quantitatively assess the ensuing structural degeneration and its functional correlation. Finally, we used this mouse model and cochleogram procedure to evaluate the potential therapeutic effect of transforming growth factor β1 (TGF-β1) inhibitors P17 and P144 on NIHL. CBA mice were exposed to violet swept-sine noise (VS) with different frequency ranges (2–20 or 9–13 kHz) and levels (105 or 120 dB SPL) for 30 min. Mice were evaluated by auditory brainstem response (ABR) and otoacoustic emission tests prior to and 2, 14 and 28 days after noise exposure. Cochlear pathology was assessed with gross histology; hair cell number was estimated by a stereological counting method. Our results indicate that functional and morphological changes induced by VS depend on the sound level and frequency composition. Partial hearing recovery followed the exposure to 105 dB SPL, whereas permanent cochlear damage resulted from the exposure to 120 dB SPL. Exposure to 9–13 kHz noise caused an auditory threshold shift (TS) in those frequencies that correlated with hair cell loss in the corresponding areas of the cochlea that were spotted on the cytocochleogram. In summary, we present mouse models of NIHL, which depending on the sound properties of the noise, cause different degrees of cochlear damage, and could therefore be used to study molecules which are potential players in hearing loss protection and repair. PMID:25762930

  14. 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.

  15. 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.

  16. 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.

  17. Performance investigation of the S-Rotors

    NASA Astrophysics Data System (ADS)

    Bhayo, B. A.; Al-Kayiem, H. H.; Yahaya, N. Z.

    2015-12-01

    This paper presents and discusses results from an experimental investigation of three models of wind S-rotors. Models 1 is modified from conventional Savonius rotor with a single stage and zero offsets zero overlaps; model 2 is three blade single stage wind rotor; and model 3 is double stage conventional Savonius rotor. The three models were designed, fabricated and characterized in terms of their coefficient of performance and dynamic torque coefficient. A special open wind simulator was designed for the test. The optimum parameters for the models were based on previous studies. The results showed that the model 1, model 2 and model 3 has the maximum power coefficient of 0.26, 0.17, and 0.21 at the correspondence tip speed ratio (TSR) of 0.42, 0.39 and 0.46, respectively. Model 1 is further optimized in terms of the aspect ratio resulting in improved power coefficient by 24%. The maximum dynamic torque coefficient of model 1, model 2 and model 3 was found as 0.81, 0.56 and 0.67 at the correspondence minimum TSR of 0.28, 0.21 and 0.17, respectively. It was noted that the all three models have high torque coefficient because the models were tested at higher applied torque on the rotors.

  18. 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.

  19. 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.

  20. Rotor instability due to loose rotating part

    NASA Technical Reports Server (NTRS)

    Muszynska, A.

    1985-01-01

    Loosening of a rotating part from its fixed position on the shaft or a part of the stator which comes loose and begins to turn with the rotor very frequently represents machinery malfunction. The loose part becomes involved in rotative motion mostly due to dry or fluid friction, and thus its motion is very erratic. The loose part can also move axially along the shaft. Detachment of the rotating part causes changes in the rotor balance state. Most often this results in higher unbalance. During steady-state operation the effect of a loose rotating part can manifest itself through heat vibration. It can be diagnosed by observing periodic changes of amplitude and phase of the synchronous response. During start-up (or shutdown) a loose rotating part carrying some amount of unbalance may manifest its dynamic action in the form of subsynchronous vibrations, very similar to those of other instabilities. The objective of this demonstration is to observe the effect of a loose rotating part (fixed, however, in the axial direction) under both steady-state (rotor constant speed) and transient (rotor start-up or shutdown) operation. The dynamic response depends very much on the amount of damping in the system: lubrication of the loose part/shaft surfaces and addition/elimination of aerodynamic drag blades, mounted on the loose disk, significantly change the rotor response.

  1. 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.

  2. 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

  3. 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.

  4. A Demonstration of the Principle of Aeroelastic Tailoring Applied to Forward Swept Wings

    DTIC Science & Technology

    1982-01-01

    simple wind tunnel test on a variable sweep cantilever wing model. Available analytical methods were used and were shown to accurately predict the... Cantilever Mount ........ 11 9 Wing Model in Fairing ....... .................. 11 10 Aluminum Plate Bending Stiffness Distribution ......... 16 11...accomplished by using the closed form solution for divergence dynamic pressure given in Bispling- hoff (Reference 1) for a uniform slender swept wing

  5. 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

  6. 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.

  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. 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.

  9. Nonlinear dynamics and health monitoring of 6-DOF breathing cracked Jeffcott rotor

    NASA Astrophysics Data System (ADS)

    Zhao, Jie; DeSmidt, Hans; Yao, Wei

    2015-04-01

    Jeffcott rotor is employed to study the nonlinear vibration characteristics of breathing cracked rotor system and explore the possibility of further damage identification. This paper is an extension work of prior study based on 4 degree-of-freedom Jeffcott rotor system. With consideration of disk tilting and gyroscopic effect, 6-dof EOM is derived and the crack model is established using SERR (strain energy release rate) in facture mechanics. Same as the prior work, the damaged stiffness matrix is updated by computing the instant crack closure line through Zero Stress Intensity Factor method. The breathing crack area is taken as a variable to analyze the breathing behavior in terms of eccentricity phase and shaft speed. Furthermore, the coupled vibration among lateral, torsional and longitudinal d.o.f is studied under torsional/axial excitation. The final part demonstrates the possibility of using vibration signal of damaged system for the crack diagnosis and health monitoring.

  10. 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.

  11. 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.

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

    NASA Image and Video Library

    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...

  13. Interaction between rotors of a counter rotating propeller

    NASA Technical Reports Server (NTRS)

    Chung, Jin-Deog; Hough, Joseph; Nagel, Robert T.

    1990-01-01

    Thermal anemometer measurements were obtained from a stationary hot film probe mounted between the forward and aft rotors of a model CRP. Data were obtained at several locations between rotors. To establish the rotor-rotor interaction flow mechanism, a method of conditional sampling has been developed which effectively fixes the forward rotor position in time or space and permits averaging the mean wake at any fixed rotor angular location. By 'fixing' the position of the forward blades, one can track the disturbance of the forward rotor as the rear rotor moves by. The decay and spreading of the forward blade wakes and the upstream propagation of the rear blade disturbance are shown along with the interaction of the flow disturbances from the two sets of blades.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  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. A Preliminary Feasibility Study for the Utilization of a Tilt-Rotor Aircraft (MV-22) for Logistical Support to the Military Outpost Along the Venezuelan Jungle Area Bordering Colombia

    DTIC Science & Technology

    1988-06-01

    Colombia . The lack of usable airutrip/landing sites in this area, precludes the use of conventional STOL aircraft, while the remote location restricts...TABLES I STAFF RECOMMENDATION OF THE AMERICAN COLLEGE OF SURGEON FOR AN EMERGENCY MEDICAL TRAUMA CENTER ...... 27 I II SIMULATION INPUT DATA...there has been incidents along the fluvial border with Colombia . Insurgents from this neighboring country have opened fire against cutters that patrol

  20. 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.