Science.gov

Sample records for acoustic power flow

  1. Mobility power flow analysis of coupled plate structure subjected to mechanical and acoustic excitation

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1992-01-01

    The mobility power flow approach that was previously applied in the derivation of expressions for the vibrational power flow between coupled plate substructures forming an L configuration and subjected to mechanical loading is generalized. Using the generalized expressions, both point and distributed mechanical loads on one or both of the plates can be considered. The generalized approach is extended to deal with acoustic excitation of one of the plate substructures. In this case, the forces (acoustic pressures) acting on the structure are dependent on the response of the structure because of the scattered pressure component. The interaction between the plate structure and the acoustic fluid leads to the derivation of a corrected mode shape for the plates' normal surface velocity and also for the structure mobility functions. The determination of the scattered pressure components in the expressions for the power flow represents an additional component in the power flow balance for the source plate and the receiver plate. This component represents the radiated acoustical power from the plate structure. For a number of coupled plate substrates, the acoustic pressure generated by one substructure will interact with the motion of another substructure. That is, in the case of the L-shaped plate, acoustic interaction exists between the two plate substructures due to the generation of the acoustic waves by each of the substructures. An approach to deal with this phenomena is described.

  2. Mobility power flow analysis of an L-shaped plate structure subjected to acoustic excitation

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1989-01-01

    An analytical investigation based on the Mobility Power Flow method is presented for the determination of the vibrational response and power flow for two coupled flat plate structures in an L-shaped configuration, subjected to acoustical excitation. The principle of the mobility power flow method consists of dividing the global structure into a series of subsystems coupled together using mobility functions. Each separate subsystem is analyzed independently to determine the structural mobility functions for the junction and excitation locations. The mobility functions, together with the characteristics of the junction between the subsystems, are then used to determine the response of the global structure and the power flow. In the coupled plate structure considered here, mobility power flow expressions are derived for excitation by an incident acoustic plane wave. In this case, the forces (acoustic pressures) acting on the structure are dependent on the response of the structure because of the scattered pressure component. The interaction between the structure and the fluid leads to the derivation of a corrected mode shape for the plates' normal surface velocity and also for the structure mobility functions. The determination of the scattered pressure components in the expressions for the power flow represents an additional component in the power flow balance for the source plate and the receiver plate. This component represents the radiated acoustical power from the plate structure.

  3. Comparison of Comet Enflow and VA One Acoustic-to-Structure Power Flow Predictions

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.; Schiller, Noah H.; Cabell, Randolph H.

    2010-01-01

    Comet Enflow is a commercially available, high frequency vibroacoustic analysis software based on the Energy Finite Element Analysis (EFEA). In this method the same finite element mesh used for structural and acoustic analysis can be employed for the high frequency solutions. Comet Enflow is being validated for a floor-equipped composite cylinder by comparing the EFEA vibroacoustic response predictions with Statistical Energy Analysis (SEA) results from the commercial software program VA One from ESI Group. Early in this program a number of discrepancies became apparent in the Enflow predicted response for the power flow from an acoustic space to a structural subsystem. The power flow anomalies were studied for a simple cubic, a rectangular and a cylindrical structural model connected to an acoustic cavity. The current investigation focuses on three specific discrepancies between the Comet Enflow and the VA One predictions: the Enflow power transmission coefficient relative to the VA One coupling loss factor; the importance of the accuracy of the acoustic modal density formulation used within Enflow; and the recommended use of fast solvers in Comet Enflow. The frequency region of interest for this study covers the one-third octave bands with center frequencies from 16 Hz to 4000 Hz.

  4. Digital stroboscopic holographic interferometry for power flow measurements in acoustically driven membranes

    NASA Astrophysics Data System (ADS)

    Keustermans, William; Pires, Felipe; De Greef, Daniël; Vanlanduit, Steve J. A.; Dirckx, Joris J. J.

    2016-06-01

    Despite the importance of the eardrum and the ossicles in the hearing chain, it remains an open question how acoustical energy is transmitted between them. Identifying the transmission path at different frequencies could lead to valuable information for the domain of middle ear surgery. In this work a setup for stroboscopic holography is combined with an algorithm for power flow calculations. With our method we were able to accurately locate the power sources and sinks in a membrane. The setup enabled us to make amplitude maps of the out-of-plane displacement of a vibrating rubber membrane at subsequent instances of time within the vibration period. From these, the amplitude maps of the moments of force and velocities are calculated. The magnitude and phase maps are extracted from this amplitude data, and form the input for the power flow calculations. We present the algorithm used for the measurements and for the power flow calculations. Finite element models of a circular plate with a local energy source and sink allowed us to test and optimize this algorithm in a controlled way and without the present of noise, but will not be discussed below. At the setup an earphone was connected with a thin tube which was placed very close to the membrane so that sound impinges locally on the membrane, hereby acting as a local energy source. The energy sink was a little piece of foam carefully placed against the membrane. The laser pulses are fired at selected instants within the vibration period using a 30 mW HeNe continuous wave laser (red light, 632.8 nm) in combination with an acousto-optic modulator. A function generator controls the phase of these illumination pulses and the holograms are recorded using a CCD camera. We present the magnitude and phase maps as well as the power flow measurements on the rubber membrane. Calculation of the divergence of this power flow map provides a simple and fast way of identifying and locating an energy source or sink. In conclusion

  5. Acoustic concentration of particles in fluid flow

    DOEpatents

    Ward, Michael D.; Kaduchak, Gregory

    2010-11-23

    An apparatus for acoustic concentration of particles in a fluid flow includes a substantially acoustically transparent membrane and a vibration generator that define a fluid flow path therebetween. The fluid flow path is in fluid communication with a fluid source and a fluid outlet and the vibration generator is disposed adjacent the fluid flow path and is capable of producing an acoustic field in the fluid flow path. The acoustic field produces at least one pressure minima in the fluid flow path at a predetermined location within the fluid flow path and forces predetermined particles in the fluid flow path to the at least one pressure minima.

  6. Powered-Lift Aerodynamics and Acoustics. [conferences

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Powered lift technology is reviewed. Topics covered include: (1) high lift aerodynamics; (2) high speed and cruise aerodynamics; (3) acoustics; (4) propulsion aerodynamics and acoustics; (5) aerodynamic and acoustic loads; and (6) full-scale and flight research.

  7. The acoustics of turbulent flow

    NASA Astrophysics Data System (ADS)

    Rimskii-Korsakov, A. V.

    Papers are presented on such topics as the excitation of sound by small perturbations of entropy and vorticity in spatially nonuniform flows of a compressible ideal gas; the aeroacoustic characteristics of acoustically excited jets; the noise intensity and spectrum in a turbulent boundary layer on a flat plate; sound refraction in a turbulent shear flow; and the spectrum of spatial correlations of turbulent pressure pulsations at a wall at high Reynolds numbers. Consideration is also given to a comparative study of the acoustic fields of air and helium jets at subsonic outflow speeds; the effect of external boundary layer flow on jet-noise characteristics; wing-profile noise in turbulent flow; sound emission from an unsteady boundary layer; and the sound-field characteristics of a moving source (with application to aircraft-noise analysis). The effect of a sound field on coherent structures in turbulent flow, aerodynamic forces causing fan vibration and noise, and a silencer for a jet-aircraft powerplant are also examined. For individual items see A84-28803 to A84-28820

  8. Flow profiling of a surface-acoustic-wave nanopump

    NASA Astrophysics Data System (ADS)

    Guttenberg, Z.; Rathgeber, A.; Keller, S.; Rädler, J. O.; Wixforth, A.; Kostur, M.; Schindler, M.; Talkner, P.

    2004-11-01

    The flow profile in a capillary gap and the pumping efficiency of an acoustic micropump employing surface acoustic waves is investigated both experimentally and theoretically. Ultrasonic surface waves on a piezoelectric substrate strongly couple to a thin liquid layer and generate a quadrupolar streaming pattern within the fluid. We use fluorescence correlation spectroscopy and fluorescence microscopy as complementary tools to investigate the resulting flow profile. The velocity was found to depend on the applied power approximately linearly and to decrease with the inverse third power of the distance from the ultrasound generator on the chip. The found properties reveal acoustic streaming as a promising tool for the controlled agitation during microarray hybridization.

  9. Distribution of Acoustic Power Spectra for an Isolated Helicopter Fuselage

    NASA Astrophysics Data System (ADS)

    Kusyumov, A. N.; Mikhailov, S. A.; Garipova, L. I.; Batrakov, A. S.; Barakos, G.

    2016-03-01

    The broadband aerodynamic noise can be studied, assuming isotropic flow, turbulence and decay. Proudman's approach allows practical calculations of noise based on CFD solutions of RANS or URANS equations at the stage of post processing and analysis of the solution. Another aspect is the broadband acoustic spectrum and the distribution of acoustic power over a range of frequencies. The acoustic energy spectrum distribution in isotropic turbulence is non monotonic and has a maximum at a certain value of Strouhal number. In the present work the value of acoustic power peak frequency is determined using a prescribed form of acoustic energy spectrum distribution presented in papers by S. Sarkar and M. Y. Hussaini and by G. M. Lilley. CFD modelling of the flow around isolated helicopter fuselage model was considered using the HMB CFD code and the RANS equations.

  10. Quenching of acoustic bandgaps by flow noise

    NASA Astrophysics Data System (ADS)

    Elnady, T.; Elsabbagh, A.; Akl, W.; Mohamady, O.; Garcia-Chocano, V. M.; Torrent, D.; Cervera, F.; Sánchez-Dehesa, J.

    2009-03-01

    We report an experimental study of acoustic effects produced by wind impinging on noise barriers based on two-dimensional sonic crystals with square symmetry. We found that the attenuation strength of sonic-crystal bandgaps decreases for increasing values of flow speed. A quenching of the acoustic bandgap appears at a certain speed value that depends of the barrier filling ratio. For increasing values of flow speed, the data indicate that the barrier becomes a sound source because of its interaction with the wind. We conclude that flow noise should be taken into account in designing acoustic barriers based on sonic crystals.

  11. Low power acoustic harvesting of aerosols

    SciTech Connect

    Kaduchak, G.; Sinha, D. N.

    2001-01-01

    A new acoustic device for levitation and/or concentration of aerosols and sniall liquid/solid samples (up to several millimeters in diameter) in air has been developed. The device is inexpensive, low-power, and, in its simplest embodiment, does not require accurate alignmen1 of a resonant cavity. It is constructed from a cylindrical PZT tube of outside diameter D = 19.0 mm and thickness-to-radius ratio h/a - 0.03. The lowest-order breathing mode of the tube is tuned to match a resonant mode of the interior air-filled cylindrical cavity. A high Q cavity results that can be driven efficiently. An acoustic standing wave is created in the inteirior cavity of the cylindrical shell where particle concrmtration takes place at the nodal planes of the field. It is shown that drops of water in excess of 1 mm in diameter may be levitated against the force of gravity for approxirnately 100 mW of input electrical power. The main objective of the research is to implement this lowpower device to concentrate and harvest aerosols in a flowing system. Several different cavity geonietries iwe presented for efficient collection of 1 he conaartratetl aerosols. Concentraiion factors greater than 40 iue demonstrated for particles of size 0.7 1.1 in a flow volume of 50 L/minute.

  12. Nonlinear Acoustics Used To Reduce Leakage Flow

    NASA Technical Reports Server (NTRS)

    Daniels, Christopher C.; Steinetz, Bruce M.

    2004-01-01

    Leakage and wear are two fundamental problems in all traditional turbine seals that contribute to an engine's inefficiency. The solutions to seal leakage and wear conflict in the conventional design space. Reducing the clearance between the seal and rotating shaft reduces leakage but increases wear because of increased contact incidents. Increasing the clearance to reduce the contact between parts reduces wear but increases parasitic leakage. The goal of this effort is to develop a seal that restricts leakage flow using acoustic pressure while operating in a noncontacting manner, thereby increasing life. In 1996, Dr. Timothy Lucas announced his discovery of a method to produce shock-free high-amplitude pressure waves. For the first time, the formation of large acoustic pressures was possible using dissonant resonators. A pre-prototype acoustic seal developed at the NASA Glenn Research Center exploits this fundamental acoustic discovery: a specially shaped cavity oscillated at the contained fluid's resonant frequency produces high-amplitude acoustic pressure waves of a magnitude approaching those required of today's seals. While the original researchers are continuing their development of acoustic pumps, refrigeration compressors, and electronic thermal management systems using this technology, the goal of researchers at Glenn is to apply these acoustic principles to a revolutionary sealing device. When the acoustic resonator shape is optimized for the sealing device, the flow from a high-pressure cavity to a low-pressure cavity will be restricted by a series of high-amplitude standing pressure waves of higher pressure than the pressure to be sealed. Since the sealing resonator cavity will not touch the adjacent sealing structures, seal wear will be eliminated, improving system life. Under a cooperative agreement between Glenn and the Ohio Aerospace Institute (OAI), an acoustic-based pre-prototype seal was demonstrated for the first time. A pressurized cavity was

  13. Thermal acoustic interaction and flow phenomenon

    NASA Astrophysics Data System (ADS)

    Leung, E. W.; Baroth, E.; Chan, C. K.; Wang, T. G.

    1990-01-01

    In containerless science for material processing, the acoustic fields is used to levitate and to control the position of a heated or cooled sample. The interaction between the temperature and the acoustic fields leads to complicated fluid flow phenomena, resulting in the perturbation of the sample position and the heat transfer process. The physical mechanisms in this thermal-acoustic field were investigated using the technique of holographic interferometry and thermometry. Of particular interest was the heat transfer rate from the sample associated with the sound intensities, normal frequencies of the acoustic standing wave field, and gravitational effects. For metallic spheres with high thermal conductivity, the surface temperature was found to be uniform. The thermal flow phenomenon, which is associated with the circulating flow inside the resonant chamber, was recorded. The heat transfer coefficient at the sample surface was correlated with the acoustic and the gravitational parameters, based on the classical theory of convective heat transfer. These correlations can be used to predict the heat transfer from a spherical object in a zero-gravity environment.

  14. Acoustic propagation under tidally driven, stratified flow.

    PubMed

    Finette, Steven; Oba, Roger; Shen, Colin; Evans, Thomas

    2007-05-01

    Amplitude and phase variability in acoustic fields are simulated within a canonical shelf-break ocean environment using sound speed distributions computed from hydrodynamics. The submesoscale description of the space and time varying environment is physically consistent with tidal forcing of stratified flows over variable bathymetry and includes the generation, evolution and propagation of internal tides and solibores. For selected time periods, two-dimensional acoustic transmission examples are presented for which signal gain degradation is computed between 200 and 500 Hz on vertical arrays positioned both on the shelf and beyond the shelf break. Decorrelation of the field is dominated by the phase contribution and occurs over 2-3 min, with significant recorrelation often noted for selected frequency subbands. Detection range is also determined in this frequency band. Azimuth-time variations in the acoustic field are illustrated for 100 Hz sources by extending the acoustic simulations to three spatial dimensions. The azimuthal and temporal structure of both the depth-averaged transmission loss and temporal correlation of the acoustic fields under different environmental conditions are considered. Depth-averaged transmission loss varies up to 4 dB, depending on a combination of source depth, location relative to the slope and tidally induced volumetric changes in the sound speed distribution. PMID:17550157

  15. Mean Flow Augmented Acoustics in Rocket Systems

    NASA Technical Reports Server (NTRS)

    Fischbach, Sean

    2014-01-01

    Combustion instability in solid rocket motors and liquid engines has long been a subject of concern. Many rockets display violent fluctuations in pressure, velocity, and temperature originating from the complex interactions between the combustion process and gas dynamics. Recent advances in energy based modeling of combustion instabilities require accurate determination of acoustic frequencies and mode shapes. Of particular interest is the acoustic mean flow interactions within the converging section of a rocket nozzle, where gradients of pressure, density, and velocity become large. The expulsion of unsteady energy through the nozzle of a rocket is identified as the predominate source of acoustic damping for most rocket systems. Recently, an approach to address nozzle damping with mean flow effects was implemented by French [1]. This new approach extends the work originated by Sigman and Zinn [2] by solving the acoustic velocity potential equation (AVPE) formulated by perturbing the Euler equations [3]. The present study aims to implement the French model within the COMSOL Multiphysiscs framework and analyzes one of the author's presented test cases.

  16. Quasinormal acoustic oscillations in the Michel flow

    NASA Astrophysics Data System (ADS)

    Chaverra, Eliana; Morales, Manuel D.; Sarbach, Olivier

    2015-05-01

    We study spherical and nonspherical linear acoustic perturbations of the Michel flow, which describes the steady radial accretion of a perfect fluid into a nonrotating black hole. The dynamics of such perturbations are governed by a scalar wave equation on an effective curved background geometry determined by the acoustic metric, which is constructed from the spacetime metric and the particle density and four-velocity of the fluid. For the problem under consideration in this paper the acoustic metric has the same qualitative features as an asymptotically flat, static and spherically symmetric black hole, and thus it represents a natural astrophysical analogue black hole. As for the case of a scalar field propagating on a Schwarzschild background, we show that acoustic perturbations of the Michel flow exhibit quasinormal oscillations. Based on a new numerical method for determining the solutions of the radial mode equation, we compute the associated frequencies and analyze their dependency on the mass of the black hole, the radius of the sonic horizon and the angular momentum number. Our results for the fundamental frequencies are compared to those obtained from an independent numerical Cauchy evolution, finding good agreement between the two approaches. When the radius of the sonic horizon is large compared to the event horizon radius, we find that the quasinormal frequencies scale approximately like the surface gravity associated with the sonic horizon.

  17. Mean Flow Augmented Acoustics in Rocket Systems

    NASA Technical Reports Server (NTRS)

    Fischbach, Sean R.

    2014-01-01

    Oscillatory motion in solid rocket motors and liquid engines has long been a subject of concern. Many rockets display violent fluctuations in pressure, velocity, and temperature originating from the complex interactions between the combustion process and gas dynamics. The customary approach to modeling acoustic waves inside a rocket chamber is to apply the classical inhomogeneous wave equation to the combustion gas. The assumption of a linear, non-dissipative wave in a quiescent fluid remains valid while the acoustic amplitudes are small and local gas velocities stay below Mach 0.2. The converging section of a rocket nozzle, where gradients in pressure, density, and velocity become large, is a notable region where this approach is not applicable. The expulsion of unsteady energy through the nozzle of a rocket is identified as the predominate source of acoustic damping for most rocket systems. An accurate model of the acoustic behavior within this region where acoustic modes are influenced by the presence of a steady mean flow is required for reliable stability predictions. Recently, an approach to address nozzle damping with mean flow effects was implemented by French [1]. This new approach extends the work originated by Sigman and Zinn [2] by solving the acoustic velocity potential equation (AVPE) formulated by perturbing the Euler equations [3]. The acoustic velocity potential (psi) describing the acoustic wave motion in the presence of an inhomogeneous steady high-speed flow is defined by, (del squared)(psi) - (lambda/c)(exp 2)(psi) - M(dot)[M(dot)(del)(del(psi))] - 2(lambda(M/c) + (M(dot)del(M))(dot)del(psi)-2(lambda)(psi)[M(dot)del(1/c)]=0 (1) with M as the Mach vector, c as the speed of sound, and lambda as the complex eigenvalue. French apply the finite volume method to solve the steady flow field within the combustion chamber and nozzle with inviscid walls. The complex eigenvalues and eigenvector are determined with the use of the ARPACK eigensolver. The

  18. Acoustic streaming flows and sample rotation control

    NASA Astrophysics Data System (ADS)

    Trinh, Eugene

    1998-11-01

    Levitated drops in a gas can be driven into rotation by altering their surrounding convective environment. When these drops are placed in an acoustic resonant chamber, the symmetry characteristics of the steady streaming flows in the vicinity of the drops determine the rotational motion of the freely suspended fluid particles. Using ultrasonic standing waves around 22 kHz and millimeter-size electrostatically levitated drops, we have investigated the correlation between the convective flow characteristics and their rotational behavior. The results show that accurate control of the drop rotation axis and rate can be obtained by carefully modifying the symmetry characteristics of the chamber, and that the dominant mechanism for rotation drive is the drag exerted by the air flow over the drop surface. In addition, we found that the rotational acceleration depends on the drop viscosity, suggesting that this torque is initially strongly influenced by differential flows within the drop itself. [Work sponsored by NASA].

  19. Acoustic Flow Monitor System - User Manual

    USGS Publications Warehouse

    LaHusen, Richard

    2005-01-01

    INTRODUCTION The Acoustic Flow Monitor (AFM) is a portable system that was designed by the U.S. Geological Survey Cascades Volcano Observatory to detect and monitor debris flows associated with volcanoes. It has been successfully used internationally as part of real-time warning systems in valleys threatened by such flows (Brantley, 1990; Marcial and others, 1996; Lavigne and others, 2000). The AFM system has also been proven to be an effective tool for monitoring some non-volcanic debris flows. This manual is intended to serve as a basic guide for the installation, testing, and maintenance of AFM systems. An overview of how the system works, as well as instructions for installation and guidelines for testing, is included. Interpretation of data is not covered in this manual; rather, the user should refer to the references provided for published examples of AFM data.

  20. Time Reversal Acoustic in a flowing medium

    NASA Astrophysics Data System (ADS)

    Luong, Trung Dung; Arora, Manish; Hies, Thomas; Ohl, Claus-Dieter; Claus-Dieter Ohl grou Team; DHI Water; Environment (S) Pte. Ltd. Collaboration

    2013-11-01

    We explore the effect of flow on time reversal acoustics (TRA). Traditionally, TRA has been studied in static conditions, while a motion of the medium is expected to degrade the spatio-temporal focussing of the sound pulse. Here, we study the effect of the flow with a TRA system at 1MHz. A controlled flow is added between the emitter and receiver. Additional, a metallic plate is utilized to increases the numerical aperture of the emitting transducer. The impulse response of the non-flowing system, is recorded and time reversed. Then, the response of the hydrophone is recorded in presence and absence of the flow. It is found that the time reversed signal focuses on at the hydrophone in both the cases. In the absence of flow, the focus signal is observed to be shifted in the time domain. Furthermore, there is a drop in the peak-to-peak value of the focus signal in the presence of flow. For a flow rate of 3 cm/s (Re ~ 1000), a distinct shift in the time domain and a reduction of the peak is obtained. The results will be discussed and compared with numerical simulation of TRA under flow conditions.

  1. Convective Heat Transfer in Acoustic Streaming Flows

    NASA Astrophysics Data System (ADS)

    Gopinath, Ashok

    1992-01-01

    Convective heat transfer due to acoustic streaming has been studied in the absence of an imposed mean flow. The work is motivated by the need to design and control the thermal features of a suitable experimental rig for the containerless processing of materials by heat treatment of acoustically levitated alloy samples at near zero-gravity. First the problem of heat transfer from an isolated sphere (in a standing sound field) is explored in detail. The streaming Reynolds number, Rs, which characterizes the resulting steady flows, is determined from the acoustic signal. A scale analysis is used to ascertain the importance of buoyancy and viscous dissipation. The steady velocity and temperature fields are determined using asymptotic techniques and numerical methods for the limiting cases of Rs<<1 and Rsgg1. Working correlations for the average Nusselt number are obtained for a wide range of Prandtl numbers. A simple experiment is conducted to verify the predictions for the more relevant case of Rsgg1. The acoustic levitation chamber itself is modelled as a Kundt tube (supporting a plane axial standing sound wave) with insulated side-wall and isothermal end-walls. Analytical solution techniques are used to determine the steady fields close to the tube walls. For the steady recirculatory transport in the core, the numerical solver PHOENICS is adopted for the solution of the complete elliptic form of the governing equations. A study of the effects of a range of acoustic and geometric parameters on the flow and heat transfer is performed and Nusselt number correlations are obtained for air. PHOENICS is also used to study the effects of variable fluid properties and axial side-wall conduction (coupled with radiation). The role of normal/reduced gravity is assessed and suggestions made for terrestrial testing of the levitation apparatus. Finally, with the sample located at a node in the levitation chamber, the effect of the interaction of the streaming flows (on the sphere

  2. Acoustic signals generated in inclined granular flows

    NASA Astrophysics Data System (ADS)

    Tan, Danielle S.; Jenkins, James T.; Keast, Stephen C.; Sachse, Wolfgang H.

    2015-10-01

    Spontaneous avalanching in specific deserts produces a low-frequency sound known as "booming." This creates a puzzle, because avalanches down the face of a dune result in collisions between sand grains that occur at much higher frequencies. Reproducing this phenomenon in the laboratory permits a better understanding of the underlying mechanisms for the generation of such lower frequency acoustic emissions, which may also be relevant to other dry granular flows. Here we report measurements of low-frequency acoustical signals, produced by dried "sounding" sand (sand capable of booming in the desert) flowing down an inclined chute. The amplitude of the signal diminishes over time but reappears upon drying of the sand. We show that the presence of this sound in the experiments may provide supporting evidence for a previously published "waveguide" explanation for booming. Also, we propose a model based on kinetic theory for a sheared inclined flow in which the flowing layer exhibits "breathing" modes superimposed on steady shearing. The predicted oscillation frequency is of a similar order of magnitude as the measurements, indicating that small perturbations can sustain oscillations of a low frequency. However, the frequency is underestimated, which indicates that the stiffness has been underestimated. Also, the model predicts a discrete spectrum of frequencies, instead of the broadband spectrum measured experimentally.

  3. Internal Acoustics of a Pintle Valve with Supercritical Helium Flow

    NASA Technical Reports Server (NTRS)

    Fishbach, Sean R.; Davis, R. Benjamin

    2010-01-01

    Large amplitude flow unsteadiness is a common phenomenon within the high flow rate ducts and valves associated with propulsion systems. Boundary layer noise, shear layers and vortex shedding are a few of the many sources of flow oscillations. The presence of lightly damped acoustic modes can organize and amplify these sources of flow perturbation, causing undesirable loading of internal parts. The present study investigates the self-induced acoustic environment within a pintle valve subject to high Reynolds Number flow of helium gas. Experiments were conducted to measure the internal pressure oscillations of the Ares I Launch Abort System (LAS) Attitude Control Motor (ACM) valve. The AGM consists of a solid propellant gas generator with eight pintle valves attached to the aft end. The pintle valve is designed to deliver variable upstream conditions to an attache( converging diverging nozzle. In order to investigate the full range of operating conditions 28 separate tests were conducted with varying pintle position and upstream pressure. Helium gas was utilized in order to closely mimic the speed of sound of the gas generator exhaust, minimizing required scaling during data analysis. The recordec pressure measurements were interrogated to multiple ends. The development of root mean square (RMS) value! versus Reynolds Number and Pintle position are important to creating bounding unsteady load curves for valve internal parts. Spectral analysis was also performed, helping to identify power spectral densities (PSD) of acoustic natural frequencies and boundary layer noise. An interesting and unexpected result was the identification of an acoustic mode within the valve which does not respond until the valve was over 60% open. Further, the response amplitude around this mode can be as large or larger than those associated with lower frequency modes.

  4. Tests Of Shear-Flow Model For Acoustic Impedance

    NASA Technical Reports Server (NTRS)

    Parrot, Tony L.; Watson, Willie R.; Jones, Michael G.

    1992-01-01

    Tests described in report conducted to validate two-dimensional shear-flow analytical model for determination of acoustic impedance of acoustic liner in grazing-incidence, grazing-flow environment by use of infinite-waveguide method. Tests successful for both upstream and downstream propagations. Work has potential for utility in testing of engine ducts in commercial aircraft.

  5. Structural power flow measurement

    SciTech Connect

    Falter, K.J.; Keltie, R.F.

    1988-12-01

    Previous investigations of structural power flow through beam-like structures resulted in some unexplained anomalies in the calculated data. In order to develop structural power flow measurement as a viable technique for machine tool design, the causes of these anomalies needed to be found. Once found, techniques for eliminating the errors could be developed. Error sources were found in the experimental apparatus itself as well as in the instrumentation. Although flexural waves are the carriers of power in the experimental apparatus, at some frequencies longitudinal waves were excited which were picked up by the accelerometers and altered power measurements. Errors were found in the phase and gain response of the sensors and amplifiers used for measurement. A transfer function correction technique was employed to compensate for these instrumentation errors.

  6. Flow structure, performance and scaling of acoustic jets

    NASA Astrophysics Data System (ADS)

    Muller, Michael Oliver

    Acoustic jets are studied, with an emphasis on their flow structure, performance, and scaling. The ultimate goal is the development of a micromachined acoustic jet for propulsion of a micromachined airborne platform, as well as integrated cooling and pumping applications. Scaling suggests an increase in performance with decreasing size, motivating the use of micro-technology. Experimental studies are conducted at three different orders of magnitude in size, each closely following analytic expectations. The jet creates a periodic vortical structure, the details of which are a function of amplitude. At small actuation amplitude, but still well above the linear acoustic regime, the flow structure consists of individual vortex rings, propagating away from the nozzle, formed during the outstroke of the acoustic cavity. At large amplitude, a trail of vorticity forms between the periodic vortex rings. Approximately corresponding to these two flow regions are two performance regimes. At low amplitude, the jet thrust increases with the fourth power of the amplitude; and at large amplitude, the thrust equals the momentum flux ejected during the output stroke, and increases as the square of the amplitude. Resonance of the cavity, at Reynolds numbers greater than approximately 10, enhances the jet performance beyond the incompressible behavior. Gains of an order of magnitude in the jet velocity occur at Reynolds numbers of approximately 100, and the data suggest further gains with increasing Reynolds number. The smallest geometries tested are micromachined acoustic jets, manufactured using MEMS technology. The throat dimensions are 50 by 200 mum, and the overall device size is approximately 1 mm 2, with eight throats per device. Several jets are manufactured in an array, to suit any given application. The performance is very dependent on frequency, with a sharp peak at the system resonance, occurring at approximately 70 kHz (inaudible). The mean jet velocity of these devices

  7. An Investigation of Acoustic Wave Propagation in Mach 2 Flow

    NASA Astrophysics Data System (ADS)

    Nieberding, Zachary J.

    Hypersonic technology is the next advancement to enter the aerospace community; it is defined as the study of flight at speeds Mach 5 and higher where intense aerodynamic heating is prevalent. Hypersonic flight is achieved through use of scramjet engines, which intake air and compress it by means of shock waves and geometry design. The airflow is then directed through an isolator where it is further compressed, it is then delivered to the combustor at supersonic speeds. The combusted airflow and fuel mixture is then accelerated through a nozzle to achieve the hypersonic speeds. Unfortunately, scramjet engines can experience a phenomenon known as an inlet unstart, where the combustor produces pressures large enough to force the incoming airflow out of the inlet of the engine, resulting in a loss of acceleration and power. There have been several government-funded programs that look to prove the concept of the scramjet engine and also tackle this inlet unstart issue. The research conducted in this thesis is a fundamental approach towards controlling the unstart problem: it looks at the basic concept of sending a signal upstream through the boundary layer of a supersonic flow and being able to detect a characterizeable signal. Since conditions within and near the combustor are very harsh, hardware is unable to be installed in that area, so this testing will determine if a signal can be sent and if so, how far upstream can the signal be detected. This experimental approach utilizes several acoustic and mass injection sources to be evaluated over three test series in a Mach 2 continuous flow wind tunnel that will determine the success of the objective. The test series vary in that the conditions of the flow and the test objectives change. The research shows that a characterizeable signal can be transmitted upstream roughly 12 inches through the subsonic boundary layer of a supersonic cross flow. It is also shown that the signal attenuates as the distance between the

  8. Acoustic monitoring of power-plant valves

    NASA Astrophysics Data System (ADS)

    Allen, J. W.; Hartman, W. F.; Robinson, J. C.

    1982-06-01

    Advanced surveillance diagnostics were applied to key nuclear power plant valves to improve the availability of the power plant. Two types of valves were monitored: BWR three-stage, pilot-operated safety/relief valves and PWR feedwater control valves. Excessive leakage across the pilot-disc seat in BWR safety/relief valves can cause the second-stage pressure to reach the critical value that activates the valve, even though the set pressure was not exceeded. Acoustic emissions created by the leak noise were monitored and calibrated to indicate incipient activation of the safety/relief valve. Hydrodynamic, vibration, control and process signals from PWR feedwater control valves were monitored by a mini-computer based surveillance system. On-line analysis of these signals coupled with earlier analytic modelling identified: (1) cavitation, (2) changes in steam packaging tightness, (3) valve stem torquing, (4) transducer oscillations, and (5) peak vibration levels during power transients.

  9. Separation of acoustic waves in isentropic flow perturbations

    SciTech Connect

    Henke, Christian

    2015-04-15

    The present contribution investigates the mechanisms of sound generation and propagation in the case of highly-unsteady flows. Based on the linearisation of the isentropic Navier–Stokes equation around a new pathline-averaged base flow, it is demonstrated for the first time that flow perturbations of a non-uniform flow can be split into acoustic and vorticity modes, with the acoustic modes being independent of the vorticity modes. Therefore, we can propose this acoustic perturbation as a general definition of sound. As a consequence of the splitting result, we conclude that the present acoustic perturbation is propagated by the convective wave equation and fulfils Lighthill’s acoustic analogy. Moreover, we can define the deviations of the Navier–Stokes equation from the convective wave equation as “true” sound sources. In contrast to other authors, no assumptions on a slowly varying or irrotational flow are necessary. Using a symmetry argument for the conservation laws, an energy conservation result and a generalisation of the sound intensity are provided. - Highlights: • First splitting of non-uniform flows in acoustic and non-acoustic components. • These result leads to a generalisation of sound which is compatible with Lighthill’s acoustic analogy. • A closed equation for the generation and propagation of sound is given.

  10. Selectively manipulable acoustic-powered microswimmers

    PubMed Central

    Ahmed, Daniel; Lu, Mengqian; Nourhani, Amir; Lammert, Paul E.; Stratton, Zak; Muddana, Hari S.; Crespi, Vincent H.; Huang, Tony Jun

    2015-01-01

    Selective actuation of a single microswimmer from within a diverse group would be a first step toward collaborative guided action by a group of swimmers. Here we describe a new class of microswimmer that accomplishes this goal. Our swimmer design overcomes the commonly-held design paradigm that microswimmers must use non-reciprocal motion to achieve propulsion; instead, the swimmer is propelled by oscillatory motion of an air bubble trapped within the swimmer's polymer body. This oscillatory motion is driven by the application of a low-power acoustic field, which is biocompatible with biological samples and with the ambient liquid. This acoustically-powered microswimmer accomplishes controllable and rapid translational and rotational motion, even in highly viscous liquids (with viscosity 6,000 times higher than that of water). And by using a group of swimmers each with a unique bubble size (and resulting unique resonance frequencies), selective actuation of a single swimmer from among the group can be readily achieved. PMID:25993314

  11. Acoustic monitoring of power plant valves

    NASA Astrophysics Data System (ADS)

    Allen, J. W.; Hartman, W. F.; Robinson, J. C.

    1982-06-01

    Advanced surveillance diagnostics were applied to key nuclear power plant valves to improve the availability of the power plant. Two types of valves were monitored: boiling water reactor (BWR) three-stage, pilot-operated safety/relief valves and pressurized water reactor (PWR) feedwater control valves. Excessive leakage across the pilot-disc seat in BWR safety/relief valves can cause the second-stage pressure to reach the critical value that activates the valve, even though the set pressure was not exceeded. Acoustic emission created by the leak noise were monitored and calibrated to indicate incipient activation of the safety/relief valve. Hydrodynamic, vibration, control and process signals frm PWR feedwater control valves were monitored by a mini-computer based surveillance system.

  12. Preliminary study of the effect of the turbulent flow field around complex surfaces on their acoustic characteristics

    NASA Technical Reports Server (NTRS)

    Olsen, W. A.; Boldman, D.

    1978-01-01

    Fairly extensive measurements have been conducted of the turbulent flow around various surfaces as a basis for a study of the acoustic characteristics involved. In the experiments the flow from a nozzle was directed upon various two-dimensional surface configurations such as the three-flap model. A turbulent flow field description is given and an estimate of the acoustic characteristics is provided. The developed equations are based upon fundamental theories for simple configurations having simple flows. Qualitative estimates are obtained regarding the radiation pattern and the velocity power law. The effect of geometry and turbulent flow distribution on the acoustic emission from simple configurations are discussed.

  13. Numerical computation of steady-state acoustic disturbances in flow

    NASA Technical Reports Server (NTRS)

    Watson, W. R.; Myers, M. K.

    1992-01-01

    Two time domain methods for computing two dimensional steady-state acoustic disturbances propagating through internal subsonic viscous flow fields in the presence of variable area are investigated. The first method solves the Navier-Stokes equations for the combined steady and acoustic field together and subtracts the steady flow to obtain the acoustic field. The second method solves a system of perturbation equations to obtain the acoustic disturbances, making use of a separate steady flow computation as input to the system. In each case the periodic steady-state acoustic fluctuations are obtained numerically on a supercomputer using a second order unsplit explicit MacCormack predictor-corrector method. Results show that the first method is not very effective for computing acoustic disturbances of even moderate amplitude. It appears that more accurate steady flow algorithms are required for this method to succeed. On the other hand, linear and nonlinear acoustic disturbances extracted from the perturbation approach are shown to exhibit expected behavior for the problems considered. It is also found that inflow boundary conditions for an equivalent uniform duct can be successfully applied to a nonuniform duct to obtain steady-state acoustic disturbances.

  14. Echo-acoustic flow affects flight in bats.

    PubMed

    Kugler, Kathrin; Greiter, Wolfgang; Luksch, Harald; Firzlaff, Uwe; Wiegrebe, Lutz

    2016-06-15

    Flying animals need to react fast to rapid changes in their environment. Visually guided animals use optic flow, generated by their movement through structured environments. Nocturnal bats cannot make use of optic flow, but rely mostly on echolocation. Here, we show that bats exploit echo-acoustic flow to negotiate flight through narrow passages. Specifically, bats' flight between lateral structures is significantly affected by the echo-acoustic salience of those structures, independent of their physical distance. This is true even though echolocation, unlike vision, provides explicit distance cues. Moreover, the bats reduced the echolocation sound levels in stronger flow, probably to compensate for the increased summary target strength of the lateral reflectors. However, bats did not reduce flight velocity under stronger echo-acoustic flow. Our results demonstrate that sensory flow is a ubiquitous principle for flight guidance, independent of the fundamentally different peripheral representation of flow across the senses of vision and echolocation.

  15. Echo-acoustic flow affects flight in bats.

    PubMed

    Kugler, Kathrin; Greiter, Wolfgang; Luksch, Harald; Firzlaff, Uwe; Wiegrebe, Lutz

    2016-06-15

    Flying animals need to react fast to rapid changes in their environment. Visually guided animals use optic flow, generated by their movement through structured environments. Nocturnal bats cannot make use of optic flow, but rely mostly on echolocation. Here, we show that bats exploit echo-acoustic flow to negotiate flight through narrow passages. Specifically, bats' flight between lateral structures is significantly affected by the echo-acoustic salience of those structures, independent of their physical distance. This is true even though echolocation, unlike vision, provides explicit distance cues. Moreover, the bats reduced the echolocation sound levels in stronger flow, probably to compensate for the increased summary target strength of the lateral reflectors. However, bats did not reduce flight velocity under stronger echo-acoustic flow. Our results demonstrate that sensory flow is a ubiquitous principle for flight guidance, independent of the fundamentally different peripheral representation of flow across the senses of vision and echolocation. PMID:27045094

  16. Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics

    PubMed Central

    Travagliati, Marco; Shilton, Richie; Beltram, Fabio; Cecchini, Marco

    2013-01-01

    Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we present the fabrication protocol for a multilayered SAW acoustic counterflow device. The device is fabricated starting from a lithium niobate (LN) substrate onto which two interdigital transducers (IDTs) and appropriate markers are patterned. A polydimethylsiloxane (PDMS) channel cast on an SU8 master mold is finally bonded on the patterned substrate. Following the fabrication procedure, we show the techniques that allow the characterization and operation of the acoustic counterflow device in order to pump fluids through the PDMS channel grid. We finally present the procedure to visualize liquid flow in the channels. The protocol is used to show on-chip fluid pumping under different flow regimes such as laminar flow and more complicated dynamics characterized by vortices and particle accumulation domains. PMID:24022515

  17. Flow visualization of acoustic levitation experiment

    NASA Technical Reports Server (NTRS)

    Baroth, ED

    1987-01-01

    Acoustic levitation experiments for space applications were performed. Holographic interferometry is being used to study the heat transfer rates on a heated rod enclosed in a 6 cu in chamber. Acoustic waves at levels up to 150 db increased the heating rates to the rod by factors of three to four. High speed real time holographic interferometry was used to measure the boundary layer on the heated rod. Data reduction and digitization of the interferograms are being implemented.

  18. Effects of Flow Profile on Educed Acoustic Liner Impedance

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Watson, Willie r.; Nark, Douglas M.

    2010-01-01

    This paper presents results of an investigation of the effects of shear flow profile on impedance eduction processes employed at NASA Langley. Uniform and 1-D shear-flow propagation models are used to educe the acoustic impedance of three test liners based on aeroacoustic data acquired in the Langley Grazing Flow Impedance Tube, at source levels of 130, 140 and 150 dB, and at centerline Mach numbers of 0.0, 0.3 and 0.5. A ceramic tubular, calibration liner is used to evaluate the propagation models, as this liner is expected to be insensitive to SPL, grazing flow Mach number, and flow profile effects. The propagation models are then used to investigate the effects of shear flow profile on acoustic impedances educed for two conventional perforate-over-honeycomb liners. Results achieved with the uniform-flow models follow expected trends, but those educed with the 1-D shear-flow model do not, even for the calibration liner. However, when the flow profile used with the shear-flow model is varied to increase the Mach number gradient near the wall, results computed with the shear-flow model are well matched to those achieved with the uniform-flow model. This indicates the effects of flow profile on educed acoustic liner impedance are small, but more detailed investigations of the flow field throughout the duct are needed to better understand these effects.

  19. On acoustic wave generation in uniform shear flow

    NASA Astrophysics Data System (ADS)

    Gogoberidze, G.

    2016-07-01

    The linear dynamics of acoustic waves and vortices in uniform shear flow is studied. For flows with very low shear rates, the dynamics of perturbations is adiabatic and can be described by the WKB approximation. However, for flows with moderate and high shear rates the WKB approximation is not appropriate, and alternative analysis shows that two important phenomena occur: acoustic wave over-reflection and wave generation by vortices. The later phenomenon is a known linear mechanisms for sound generation in shear flows, a mechanism that is related to the continuous spectrum that arises in linear shear flow dynamics. A detailed analytical study of these phenomena is performed and the main quantitative and qualitative characteristics of the radiated acoustic field are obtained and analyzed.

  20. Flow Field and Acoustic Predictions for Three-Stream Jets

    NASA Technical Reports Server (NTRS)

    Simmons, Shaun Patrick; Henderson, Brenda S.; Khavaran, Abbas

    2014-01-01

    Computational fluid dynamics was used to analyze a three-stream nozzle parametric design space. The study varied bypass-to-core area ratio, tertiary-to-core area ratio and jet operating conditions. The flowfield solutions from the Reynolds-Averaged Navier-Stokes (RANS) code Overflow 2.2e were used to pre-screen experimental models for a future test in the Aero-Acoustic Propulsion Laboratory (AAPL) at the NASA Glenn Research Center (GRC). Flowfield solutions were considered in conjunction with the jet-noise-prediction code JeNo to screen the design concepts. A two-stream versus three-stream computation based on equal mass flow rates showed a reduction in peak turbulent kinetic energy (TKE) for the three-stream jet relative to that for the two-stream jet which resulted in reduced acoustic emission. Additional three-stream solutions were analyzed for salient flowfield features expected to impact farfield noise. As tertiary power settings were increased there was a corresponding near nozzle increase in shear rate that resulted in an increase in high frequency noise and a reduction in peak TKE. As tertiary-to-core area ratio was increased the tertiary potential core elongated and the peak TKE was reduced. The most noticeable change occurred as secondary-to-core area ratio was increased thickening the secondary potential core, elongating the primary potential core and reducing peak TKE. As forward flight Mach number was increased the jet plume region decreased and reduced peak TKE.

  1. Ducted fan acoustic radiation including the effects of nonuniform mean flow and acoustic treatment

    NASA Technical Reports Server (NTRS)

    Eversman, Walter; Roy, Indranil Danda

    1993-01-01

    Forward and aft acoustic propagation and radiation from a ducted fan is modeled using a finite element discretization of the acoustic field equations. The fan noise source is introduced as equivalent body forces representing distributed blade loading. The flow in and around the nacelle is assumed to be nonuniform, reflecting the effects of forward flight and flow into the inlet. Refraction due to the fan exit jet shear layer is not represented. Acoustic treatment on the inlet and exhaust duct surfaces provides a mechanism for attenuation. In a region enclosing the fan a pressure formulation is used with the assumption of locally uniform flow. Away from the fan a velocity potential formulation is used and the flow is assumed nonuniform but irrotational. A procedure is developed for matching the two regions by making use of local duct modal amplitudes as transition state variables and determining the amplitudes by enforcing natural boundary conditions at the interface between adjacent regions in which pressure and velocity potential are used. Simple models of rotor alone and rotor/exit guide vane generated noise are used to demonstrate the calculation of the radiated acoustic field and to show the effect of acoustic treatment. The model has been used to assess the success of four techniques for acoustic lining optimization in reducing far field noise.

  2. Lattice Boltzmann formulation for flows with acoustic porous media

    NASA Astrophysics Data System (ADS)

    Sun, Chenghai; Pérot, Franck; Zhang, Raoyang; Lew, Phoi-Tack; Mann, Adrien; Gupta, Vinit; Freed, David M.; Staroselsky, Ilya; Chen, Hudong

    2015-10-01

    Porous materials are commonly used in various industrial systems such as ducts, HVAC, hoods, mufflers, in order to introduce acoustic absorption and to reduce the radiated acoustics levels. For problems involving flow-induced noise mechanisms and explicit interactions between turbulent source regions, numerical approaches remain a challenging task involving, on the one hand, the coupling between unsteady flow calculations and acoustics simulations and, on the other hand, the development of advanced and sensitive numerical schemes. In this paper, acoustic materials are explicitly modeled in lattice Boltzmann simulations using equivalent fluid regions having arbitrary porosity and resistivity. Numerical simulations are compared to analytical derivations as well as experiments and semi-empirical models to validate the approach.

  3. Separation of acoustic waves in isentropic flow perturbations

    NASA Astrophysics Data System (ADS)

    Henke, Christian

    2015-04-01

    The present contribution investigates the mechanisms of sound generation and propagation in the case of highly-unsteady flows. Based on the linearisation of the isentropic Navier-Stokes equation around a new pathline-averaged base flow, it is demonstrated for the first time that flow perturbations of a non-uniform flow can be split into acoustic and vorticity modes, with the acoustic modes being independent of the vorticity modes. Therefore, we can propose this acoustic perturbation as a general definition of sound. As a consequence of the splitting result, we conclude that the present acoustic perturbation is propagated by the convective wave equation and fulfils Lighthill's acoustic analogy. Moreover, we can define the deviations of the Navier-Stokes equation from the convective wave equation as "true" sound sources. In contrast to other authors, no assumptions on a slowly varying or irrotational flow are necessary. Using a symmetry argument for the conservation laws, an energy conservation result and a generalisation of the sound intensity are provided.

  4. Aeroacoustics of volcanic jets: Acoustic power estimation and jet velocity dependence

    NASA Astrophysics Data System (ADS)

    Matoza, Robin S.; Fee, David; Neilsen, Tracianne B.; Gee, Kent L.; Ogden, Darcy E.

    2013-12-01

    A fundamental goal of volcano acoustics is to relate observed infrasonic signals to the eruptive processes generating them. A link between acoustic power Πacoustic analogy theory). We reexamine this approach in the context of the current understanding of jet noise, using data from a laboratory jet, a full-scale military jet aircraft, and a full-scale rocket motor. Accurate estimates of Πacoustic field experiments. Typical volcano acoustic data better represent point measurements of acoustic intensity Iflows, velocity-scaling laws currently proposed for acoustic intensity differ from those for acoustic power and are of the form Iflows are more complex than the pure air laboratory case, which suggests that we do not currently know how the exponent nθ varies for a volcanic jet flow. This indicates that the formulation of Woulff and McGetchin (1976) can lead to large errors when inferring eruption parameters from acoustic data and thus requires modification. Quantitative integration of field, numerical, and laboratory studies within a modern aeroacoustics framework will lead to a more accurate relationship between volcanic infrasound and eruption parameters.

  5. Use of acoustic monitoring system for debris flow discharge evaluation

    NASA Astrophysics Data System (ADS)

    Galgaro, A. G.; Tecca, P. R.; Genevois, R.; Deganutti, A. M.

    2003-04-01

    In 1997 an automated system for monitoring of debris flows has been installed in the Acquabona channel Dolomites, Italy. Induction geophones, with a specific frequency of 10 Hz, measure the amplitude of vertical ground vibrations generated by the passage of a flowing mass along the channel. Continuous acoustic logs and ultrasonic hydrograph recorded at the lower-channel measurement station for the debris flow of August 17, 1998, show a striking correspondence. This correspondence, already observed in different flow sites, is represented by the best fit between flow depth and flow sensor amplitude. Average front velocity for surges, calculated from the signal peak time shift and the distance between the sensors along the flow path, range between 2.00 and 7.7 m/s. As the ultrasonic sensor provides a way to measure the variation of the flow section area with the flow depth, the debris flow peak discharge may be estimated; obtained values of debris flow peak discharge range from 4 and 30 m3/s. Volumes were calculated by integrating instantaneous discharges through the hydrograph and by integrating the geophone log (acoustic flux). Volumes of 13700 m3 and 15500 m3 have been respectively obtained. The slight difference between the two values may result from the fact that acoustic records: i) are sensitive to the high frequencies, typical of the debris flow tails; ii) sum up the contributions sent by the whole flowing mass, while the ecometer detect the flow depth at every time at only one section. As a consequence the rising of the whole geophone log gives a higher value at the integration result. This only acoustic system can give a reasonably proxy for discharge and total volumes involved, which are among the most important parameters for debris flow hazard assessment and planning countermeasures. This methodology can be used in other debris flow sites if they are calibrated by the acoustic characterization of debris, obtained by both seismic surveys and SPT tests, and

  6. Locating groundwater flow in karst by acoustic emission surveys

    SciTech Connect

    Stokowski, S.J. Jr.; Clark, D.A.

    1985-01-01

    An acoustic emission survey of Newala Fm. (primarily dolomite) karst has helped to locate subsurface water flow. This survey was performed on the Rock Quarry Dome, Sevier County, Tennessee. A Dresser RS-4 recording seismograph, adjusted to provide a gain of 1000, collected acoustic emission data using Mark Products CN368 vertical geophones with 3-inch spikes. Data was collected for 5-15 second intervals. The geophones were laid out along traverses with 10, 20, or 30-ft spacing and covered with sand bags in locations of high ambient noise. Traverses were laid out: along and across lineaments known to correspond with groundwater flow in natural subsurface channels; across and along a joint-controlled sink suspected of directing groundwater flow; and across a shallow sinkhole located tangentially to the Little Pigeon River and suspected of capturing river water for the groundwater system. Acoustic emissions of channelized flowing groundwater have a characteristic erratic spiked spectral signature. These acoustic emission signatures increase in amplitude and number in the immediate vicinity of the vertical projection of channelized groundwater flow if it occurs within approximately 30 feet of the surface. If the groundwater flow occurs at greater depths the emissions may be offset from the projection of the actual flow, due to propagation of the signal along rock pinnacles or attenuation by residual soils.

  7. Acoustic module of the Acquabona (Italy) debris flow monitoring system

    NASA Astrophysics Data System (ADS)

    Galgaro, A.; Tecca, P. R.; Genevois, R.; Deganutti, A. M.

    2005-02-01

    Monitoring of debris flows aimed to the assessment of their physical parameters is very important both for theoretical and practical purposes. Peak discharge and total volume of debris flows are crucial for designing effective countermeasures in many populated mountain areas where losses of lives and property damage could be avoided. This study quantifies the relationship between flow depth, acoustic amplitude of debris flow induced ground vibrations and front velocity in the experimental catchment of Acquabona, Eastern Dolomites, Italy. The analysis of data brought about the results described in the following. Debris flow depth and amplitude of the flow-induced ground vibrations show a good positive correlation. Estimation of both mean front velocity and peak discharge can be simply obtained monitoring the ground vibrations, through geophones installed close to the flow channel; the total volume of debris flow can be so directly estimated from the integral of the ground vibrations using a regression line. The application of acoustic technique to debris flow monitoring seems to be of the outmost relevance in risk reduction policies and in the correct management of the territory. Moreover this estimation is possible in other catchments producing debris flows of similar characteristics by means of their acoustic characterisation through quick and simple field tests (Standard Penetration Tests and seismic refraction surveys).

  8. Achieving acoustic cloak by using compressible background flow

    NASA Astrophysics Data System (ADS)

    Zhang, Ruo-Yang; Zhao, Qing; Ge, Mo-Lin

    2016-08-01

    We propose a scheme of acoustic spherical cloaking by means of background irrotational flow in compressible fluid. The background flow forms a virtual curved spacetime and directs the sound waves to bypass the cloaked objects. To satisfy the laws of real fluid, we show that spatially distributed mass source and momentum source are necessary to supply. The propagation of sound waves in this system is studied via both geometric acoustics approximation and full wave approach. The analytic solution of sound fields is obtained for plane wave incidence. The results reveal the effect of phase retardation (or lead) in comparison with the ordinary transformation-acoustic cloak. In addition, the ability of cloaking is also evaluated for unideal background flows by analyzing the scattering cross section. Project supported by the National Natural Science Foundation of China (Grant Nos. 11475088 and 11275024) and the Fund from the Ministry of Science and Technology of China (Grant No. 2013YQ030595-3).

  9. Achieving acoustic cloak by using compressible background flow

    NASA Astrophysics Data System (ADS)

    Zhang, Ruo-Yang; Zhao, Qing; Ge, Mo-Lin

    2016-08-01

    We propose a scheme of acoustic spherical cloaking by means of background irrotational flow in compressible fluid. The background flow forms a virtual curved spacetime and directs the sound waves to bypass the cloaked objects. To satisfy the laws of real fluid, we show that spatially distributed mass source and momentum source are necessary to supply. The propagation of sound waves in this system is studied via both geometric acoustics approximation and full wave approach. The analytic solution of sound fields is obtained for plane wave incidence. The results reveal the effect of phase retardation (or lead) in comparison with the ordinary transformation-acoustic cloak. In addition, the ability of cloaking is also evaluated for unideal background flows by analyzing the scattering cross section. Project supported by the National Natural Science Foundation of China (Grant Nos. 11475088 and 11275024) and the Fund from the Ministry of Science and Technology of China (Grant No. 2013YQ030595-3).

  10. Aero-acoustics of Drag Generating Swirling Exhaust Flows

    NASA Technical Reports Server (NTRS)

    Shah, P. N.; Mobed, D.; Spakovszky, Z. S.; Brooks, T. F.; Humphreys, W. M. Jr.

    2007-01-01

    Aircraft on approach in high-drag and high-lift configuration create unsteady flow structures which inherently generate noise. For devices such as flaps, spoilers and the undercarriage there is a strong correlation between overall noise and drag such that, in the quest for quieter aircraft, one challenge is to generate drag at low noise levels. This paper presents a rigorous aero-acoustic assessment of a novel drag concept. The idea is that a swirling exhaust flow can yield a steady, and thus relatively quiet, streamwise vortex which is supported by a radial pressure gradient responsible for pressure drag. Flows with swirl are naturally limited by instabilities such as vortex breakdown. The paper presents a first aero-acoustic assessment of ram pressure driven swirling exhaust flows and their associated instabilities. The technical approach combines an in-depth aerodynamic analysis, plausibility arguments to qualitatively describe the nature of acoustic sources, and detailed, quantitative acoustic measurements using a medium aperture directional microphone array in combination with a previously established Deconvolution Approach for Mapping of Acoustic Sources (DAMAS). A model scale engine nacelle with stationary swirl vanes was designed and tested in the NASA Langley Quiet Flow Facility at a full-scale approach Mach number of 0.17. The analysis shows that the acoustic signature is comprised of quadrupole-type turbulent mixing noise of the swirling core flow and scattering noise from vane boundary layers and turbulent eddies of the burst vortex structure near sharp edges. The exposed edges are the nacelle and pylon trailing edge and the centerbody supporting the vanes. For the highest stable swirl angle setting a nacelle area based drag coefficient of 0.8 was achieved with a full-scale Overall Sound Pressure Level (OASPL) of about 40dBA at the ICAO approach certification point.

  11. Acoustic agglomeration of power plant fly ash. Final report

    SciTech Connect

    Reethof, G.; McDaniel, O.H.

    1982-01-01

    The work has shown that acoustic agglomeration at practical acoustic intensities and frequencies is technically and most likely economically viable. The following studies were performed with the listed results: The physics of acoustic agglomeration is complex particularly at the needed high acoustic intensities in the range of 150 to 160 dB and frequencies in the 2500 Hz range. The analytical model which we developed, although not including nonlinear acoustic efforts, agreed with the trends observed. We concentrated our efforts on clarifying the impact of high acoustic intensities on the generation of turbulence. Results from a special set of tests show that although some acoustically generated turbulence of sorts exists in the 150 to 170 dB range with acoustic streaming present, such turbulence will not be a significant factor in acoustic agglomeration compared to the dominant effect of the acoustic velocities at the fundamental frequency and its harmonics. Studies of the robustness of the agglomerated particles using the Anderson Mark III impactor as the source of the shear stresses on the particles show that the agglomerates should be able to withstand the rigors of flow through commercial cyclones without significant break-up. We designed and developed a 700/sup 0/F tubular agglomerator of 8'' internal diameter. The electrically heated system functioned well and provided very encouraging agglomeration results at acoustic levels in the 150 to 160 dB and 2000 to 3000 Hz ranges. We confirmed earlier results that an optimum frequency exists at about 2500 Hz and that larger dust loadings will give better results. Studies of the absorption of acoustic energy by various common gases as a function of temperature and humidity showed the need to pursue such an investigation for flue gas constituents in order to provide necessary data for the design of agglomerators. 65 references, 56 figures, 4 tables.

  12. Quasi-normal acoustic oscillations in the transonic Bondi flow

    NASA Astrophysics Data System (ADS)

    Chaverra, Eliana; Sarbach, Olivier

    2016-01-01

    We analyze the dynamics of nonspherical acoustic perturbations of the transonic Bondi flow, describing the steady radial accretion of a polytropic perfect fluid into a gravity center. The propagation of such perturbations can be described by a wave equation on the curved effective background geometry determined by the acoustic metric introduced by Unruh in the context of experimental black hole evaporation. We show that for the transonic Bondi flow, Unruh's acoustic metric describes an analogue black hole and that the acoustic perturbations undergo quasi-normal oscillations. The associated quasi-normal frequencies are computed and they are proven to scale like the surface gravity of the acoustic black hole. This provides an explanation for results given in an earlier work, where it was shown that the acoustic perturbations of a relativistic fluid accreted by a nonrotating black hole possess quasi-normal modes, and where it was found empirically that the associated frequencies scaled like the surface gravity of the analogue black hole in the limit where the radius of the sonic horizon is much larger than the Schwarzschild radius.

  13. Hydrothermal vent flow and turbulence measurements with acoustic scintillation instrumentation

    NASA Astrophysics Data System (ADS)

    di Iorio, D.; Xu, G.

    2009-12-01

    Acoustically derived measurements of hydrothermal vent flow and turbulence were obtained from the active black smoker Dante in the Main Endeavour vent field, using scintillation analysis from one-way transmissions. The scintillation transmitter and receiver array formed a 93 m acoustic path through the buoyant plume 20 m above the structure. The acoustic path was parallel to the valley sidewall where the M2 tidal currents are approximately aligned along ridge due to topographic steering by the valley walls and hence most of the plume displacement is expected to occur along the acoustic path. On one deployment, data were collected for 6.5 weeks and vertical velocities range from 0.1 to 0.2 m/s showing a strong dependence on the spring/neap tidal cycle. The refractive index fluctuations which can be paramaterized in terms of the root-mean-square temperature fluctuations also shows a strong tidal modulation during spring tide.

  14. An investigation of the influence of acoustic waves on the liquid flow through a porous material.

    PubMed

    Poesio, Pietro; Ooms, Gijs; Barake, Sander; van der Bas, Fred

    2002-05-01

    An experimental and theoretical investigation has been made of the influence of high-frequency acoustic waves on the flow of a liquid through a porous material. The experiments have been performed on Berea sandstone cores. Two acoustic horns were used with frequencies of 20 and 40 kHz, and with maximum power output of 2 and 0.7 kW, respectively. Also, a temperature measurement of the flowing liquid inside the core was made. A high external pressure was applied in order to avoid cavitation. The acoustic waves were found to produce a significant effect on the pressure gradient at constant liquid flow rate through the core samples. During the application of acoustic waves the pressure gradient inside the core decreases. This effect turned out to be due to the decrease of the liquid viscosity caused by an increase in liquid temperature as a result of the acoustic energy dissipation inside the porous material. Also, a theoretical model has been developed to calculate the dissipation effect on the viscosity and on the pressure gradient. The model predictions are in reasonable agreement with the experimental data.

  15. Acoustic Streaming in Microgravity: Flow Stability and Heat Transfer Enhancement

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.

    1999-01-01

    Experimental results are presented for drops and bubbles levitated in a liquid host, with particular attention given to the effect of shape oscillations and capillary waves on the local flow fields. Some preliminary results are also presented on the use of streaming flows for the control of evaporation rate and rotation of electrostatically levitated droplets in 1 g. The results demonstrate the potential for the technological application of acoustic methods to active control of forced convection in microgravity.

  16. Acoustical power amplification and damping by temperature gradients.

    PubMed

    Biwa, Tetsushi; Komatsu, Ryo; Yazaki, Taichi

    2011-01-01

    Ceperley proposed a concept of a traveling wave heat engine ["A pistonless Stirling engine-The traveling wave heat engine," J. Acoust. Soc. Am. 66, 1508-1513 (1979).] that provided a starting point of thermoacoustics today. This paper verifies experimentally his idea through observation of amplification and strong damping of a plane acoustic traveling wave as it passes through axial temperature gradients. The acoustic power gain is shown to obey a universal curve specified by a dimensionless parameter ωτα; ω is the angular frequency and τα is the relaxation time for the gas to thermally equilibrate with channel walls. As an application of his idea, a three-stage acoustic power amplifier is developed, which attains the gain up to 10 with a moderate temperature ratio of 2.3. PMID:21302995

  17. Acoustical power amplification and damping by temperature gradients.

    PubMed

    Biwa, Tetsushi; Komatsu, Ryo; Yazaki, Taichi

    2011-01-01

    Ceperley proposed a concept of a traveling wave heat engine ["A pistonless Stirling engine-The traveling wave heat engine," J. Acoust. Soc. Am. 66, 1508-1513 (1979).] that provided a starting point of thermoacoustics today. This paper verifies experimentally his idea through observation of amplification and strong damping of a plane acoustic traveling wave as it passes through axial temperature gradients. The acoustic power gain is shown to obey a universal curve specified by a dimensionless parameter ωτα; ω is the angular frequency and τα is the relaxation time for the gas to thermally equilibrate with channel walls. As an application of his idea, a three-stage acoustic power amplifier is developed, which attains the gain up to 10 with a moderate temperature ratio of 2.3.

  18. Acoustic cross-correlation flowmeter for solid-gas flow

    NASA Astrophysics Data System (ADS)

    Sheen, S. H.; Raptis, A. C.

    1984-05-01

    An apparatus for measuring particle velocity in a solid-gas flow within a pipe is described. It includes: first and second transmitting transducers for transmitting first and second ultrasonic signals into the pipe at first and second locations, respectively, along the pipe; an acoustic decoupler, positioned between said first and second transmitting transducers, for acoustically isolating said first and second signals from one another; first and second detecting transducers for detecting said first and second signals and for generating first and second detected signals; and means for cross-correlating said first and second output signals.

  19. Acoustic cross-correlation flowmeter for solid-gas flow

    DOEpatents

    Sheen, S.H.; Raptis, A.C.

    1984-05-14

    Apparatus for measuring particle velocity in a solid-gas flow within a pipe includes: first and second transmitting transducers for transmitting first and second ultrasonic signals into the pipe at first and second locations, respectively, along the pipe; an acoustic decoupler, positioned between said first and second transmitting transducers, for acoustically isolating said first and second signals from one another; first and second detecting transducers for detecting said first and second signals and for generating first and second detected signals; and means for cross-correlating said first and second output signals.

  20. Acoustic cross-correlation flowmeter for solid-gas flow

    DOEpatents

    Sheen, Shuh-Haw; Raptis, Apostolos C.

    1986-01-01

    Apparatus for measuring particle velocity in a solid-gas flow within a pipe includes: first and second transmitting transducers for transmitting first and second ultrasonic signals into the pipe at first and second locations, respectively, along the pipe; an acoustic decoupler, positioned between said first and second transmitting transducers, for acoustically isolating said first and second signals from one another; first and second detecting transducers for detecting said first and second signals and for generating first and second detected signals in response to said first and second detected signals; and means for cross-correlating said first and second output signals.

  1. Structural and acoustic noise produced by turbulent flow over an elastic trailing edge

    NASA Astrophysics Data System (ADS)

    Howe, M. S.

    1993-09-01

    An analysis is made of the sound and vibration produced by turbulent flow at low Mach number over the trailing edge of an elastic plate. General formulas are developed for the structural and acoustic edge-noise when the control surface is modeled by a semiinfinite thin elastic plate which can support bending waves. Numerical results are given for steel plates in air and in water. In the latter case it is shown that, when the frequency is smaller than the coincidence frequency, the bending wave power exceeds the total sound power generated at the edge by 20-40 dB, independently of the mean flow velocity, so that sound generated by secondary scattering may then be the dominant source of acoustic radiation.

  2. Flow velocity measurement with the nonlinear acoustic wave scattering

    NASA Astrophysics Data System (ADS)

    Didenkulov, Igor; Pronchatov-Rubtsov, Nikolay

    2015-10-01

    A problem of noninvasive measurement of liquid flow velocity arises in many practical applications. To this end the most often approach is the use of the linear Doppler technique. The Doppler frequency shift of signal scattered from the inhomogeneities distributed in a liquid relatively to the emitted frequency is proportional to the sound frequency and velocities of inhomogeneities. In the case of very slow flow one needs to use very high frequency sound. This approach fails in media with strong sound attenuation because acoustic wave attenuation increases with frequency and there is limit in increasing sound intensity, i.e. the cavitation threshold. Another approach which is considered in this paper is based on the method using the difference frequency Doppler Effect for flows with bubbles. This method is based on simultaneous action of two high-frequency primary acoustic waves with closed frequencies on bubbles and registration of the scattered by bubbles acoustic field at the difference frequency. The use of this method is interesting since the scattered difference frequency wave has much lower attenuation in a liquid. The theoretical consideration of the method is given in the paper. The experimental examples confirming the theoretical equations, as well as the ability of the method to be applied in medical diagnostics and in technical applications on measurement of flow velocities in liquids with strong sound attenuation is described. It is shown that the Doppler spectrum form depends on bubble concentration velocity distribution in the primary acoustic beams crossing zone that allows one to measure the flow velocity distribution.

  3. Flow velocity measurement with the nonlinear acoustic wave scattering

    SciTech Connect

    Didenkulov, Igor; Pronchatov-Rubtsov, Nikolay

    2015-10-28

    A problem of noninvasive measurement of liquid flow velocity arises in many practical applications. To this end the most often approach is the use of the linear Doppler technique. The Doppler frequency shift of signal scattered from the inhomogeneities distributed in a liquid relatively to the emitted frequency is proportional to the sound frequency and velocities of inhomogeneities. In the case of very slow flow one needs to use very high frequency sound. This approach fails in media with strong sound attenuation because acoustic wave attenuation increases with frequency and there is limit in increasing sound intensity, i.e. the cavitation threshold. Another approach which is considered in this paper is based on the method using the difference frequency Doppler Effect for flows with bubbles. This method is based on simultaneous action of two high-frequency primary acoustic waves with closed frequencies on bubbles and registration of the scattered by bubbles acoustic field at the difference frequency. The use of this method is interesting since the scattered difference frequency wave has much lower attenuation in a liquid. The theoretical consideration of the method is given in the paper. The experimental examples confirming the theoretical equations, as well as the ability of the method to be applied in medical diagnostics and in technical applications on measurement of flow velocities in liquids with strong sound attenuation is described. It is shown that the Doppler spectrum form depends on bubble concentration velocity distribution in the primary acoustic beams crossing zone that allows one to measure the flow velocity distribution.

  4. Flow induced dust acoustic shock waves in a complex plasma

    NASA Astrophysics Data System (ADS)

    Jaiswal, Surabhi; Bandyopadhyay, Pintu; Sen, Abhijit

    2015-11-01

    We report on experimental observations of particle flow induced large amplitude shock waves in a dusty plasma. These dust acoustic shocks (DAS) are observed for strongly supersonic flows and have been studied in a U-shaped Dusty Plasma Experimental (DPEx) device for charged kaolin dust in a background of Argon plasma. The strong flow of the dust fluid is induced by adjusting the pumping speed and neutral gas flow into the device. An isolated copper wire mounted on the cathode acts as a potential barrier to the flow of dust particles. A sudden change of the dust density near the potential hill is used to trigger the onset of high velocity dust acoustic shocks. The dynamics of the shocks are captured by fast video pictures of the structures that are illuminated by a laser sheet beam. The physical characteristics of the shock are delineated from a parametric scan of their dynamical properties over a range of plasma parameters and flow speeds. Details of these observations and a physical explanation based on model calculations will be presented.

  5. Acoustically-coupled flow-induced vibration of a computational vocal fold model

    PubMed Central

    Daily, David Jesse; Thomson, Scott L.

    2012-01-01

    The flow-induced vibration of synthetic vocal fold models has been previously observed to be acoustically-coupled with upstream flow supply tubes. This phenomenon was investigated using a finite element model that included flow–structure–acoustic interactions. The length of the upstream duct was varied to explore the coupling between model vibration and subglottal acoustics. Incompressible and slightly compressible flow models were tested. The slightly compressible model exhibited acoustic coupling between fluid and solid domains in a manner consistent with experimental observations, whereas the incompressible model did not, showing the slightly compressible approach to be suitable for simulating acoustically-coupled vocal fold model flow-induced vibration. PMID:23585700

  6. Linear coupling of acoustic and cyclotron waves in plasma flows

    SciTech Connect

    Rogava, Andria; Gogoberidze, Grigol

    2005-05-15

    It is found that in magnetized electrostatic plasma flows the velocity shear couples ion-acoustic waves with ion-cyclotron waves and leads, under favorable conditions, to their efficient reciprocal transformations. It is shown that in a two-dimensional setup this coupling has a remarkable feature: it is governed by equations that are mathematically equal to the ones describing coupling of sound waves with internal gravity waves [Rogava and Mahajan, Phys. Rev. E 55, 1185 (1997)] in neutral fluids. For flows with low shearing rates a fully analytic, quantitative description of the coupling efficiency, based on a noteworthy quantum-mechanical analogy, is given and transformation coefficients are calculated.

  7. Flow-structure-acoustic interaction in a human voice model.

    PubMed

    Becker, Stefan; Kniesburges, Stefan; Müller, Stefan; Delgado, Antonio; Link, Gerhard; Kaltenbacher, Manfred; Döllinger, Michael

    2009-03-01

    For the investigation of the physical processes of human phonation, inhomogeneous synthetic vocal folds were developed to represent the full fluid-structure-acoustic coupling. They consisted of polyurethane rubber with a stiffness in the range of human vocal folds and were mounted in a channel, shaped like the vocal tract in the supraglottal region. This test facility permitted extensive observations of flow-induced vocal fold vibrations, the periodic flow field, and the acoustic signals in the far field of the channel. Detailed measurements were performed applying particle-image velocimetry, a laser-scanning vibrometer, a microphone, unsteady pressure sensors, and a hot-wire probe, with the aim of identifying the physical mechanisms in human phonation. The results support the existence of the Coanda effect during phonation, with the flow attaching to one vocal fold and separating from the other. This behavior is not linked to one vocal fold and changes stochastically from cycle to cycle. The oscillating flow field generates a tonal sound. The broadband noise is presumed to be caused by the interaction of the asymmetric flow with the downstream-facing surfaces of the vocal folds, analogous to trailing-edge noise. PMID:19275292

  8. Correlation of combustor acoustic power levels inferred from internal fluctuating pressure measurements

    NASA Technical Reports Server (NTRS)

    Vonglahn, U. H.

    1978-01-01

    Combustion chamber acoustic power levels inferred from internal fluctuating pressure measurements are correlated with operating conditions and chamber geometries over a wide range. The variables include considerations of chamber design (can, annular, and reverse-flow annular) and size, number of fuel nozzles, burner staging and fuel split, airflow and heat release rates, and chamber inlet pressure and temperature levels. The correlated data include those obtained with combustion component development rigs as well as engines.

  9. Acoustic black hole in a stationary hydrodynamic flow of microcavity polaritons.

    PubMed

    Nguyen, H S; Gerace, D; Carusotto, I; Sanvitto, D; Galopin, E; Lemaître, A; Sagnes, I; Bloch, J; Amo, A

    2015-01-23

    We report an experimental study of superfluid hydrodynamic effects in a one-dimensional polariton fluid flowing along a laterally patterned semiconductor microcavity and hitting a micron-sized engineered defect. At high excitation power, superfluid propagation effects are observed in the polariton dynamics; in particular, a sharp acoustic horizon is formed at the defect position, separating regions of sub- and supersonic flow. Our experimental findings are quantitatively reproduced by theoretical calculations based on a generalized Gross-Pitaevskii equation. Promising perspectives to observe Hawking radiation via photon correlation measurements are illustrated.

  10. Acoustic Black Hole in a Stationary Hydrodynamic Flow of Microcavity Polaritons

    NASA Astrophysics Data System (ADS)

    Nguyen, H. S.; Gerace, D.; Carusotto, I.; Sanvitto, D.; Galopin, E.; Lemaître, A.; Sagnes, I.; Bloch, J.; Amo, A.

    2015-01-01

    We report an experimental study of superfluid hydrodynamic effects in a one-dimensional polariton fluid flowing along a laterally patterned semiconductor microcavity and hitting a micron-sized engineered defect. At high excitation power, superfluid propagation effects are observed in the polariton dynamics; in particular, a sharp acoustic horizon is formed at the defect position, separating regions of sub- and supersonic flow. Our experimental findings are quantitatively reproduced by theoretical calculations based on a generalized Gross-Pitaevskii equation. Promising perspectives to observe Hawking radiation via photon correlation measurements are illustrated.

  11. Fast Pressure-Sensitive Paint for Flow and Acoustic Diagnostics

    NASA Astrophysics Data System (ADS)

    Gregory, James W.; Sakaue, Hirotaka; Liu, Tianshu; Sullivan, John P.

    2014-01-01

    The development and capabilities of fast-responding pressure-sensitive paint (fast PSP) are reviewed within the context of recent applications to aerodynamic and acoustic investigations. PSP is an optical technique for determining surface pressure distributions by measuring changes in the intensity of emitted light, whereas fast PSP is an extension applicable to unsteady flows and acoustics. Most fast PSP formulations are based on the development of porous binders that allow for rapid oxygen diffusion and interaction with the chemical sensor. This article reviews the development of porous binders, the selection of luminophore molecules suitable for unsteady testing, dynamic calibrations of PSP, data-acquisition methods, and noteworthy applications for flow and acoustic diagnostics. Calibrations of the dynamic response of fast PSP show a flat frequency response to at least 6 kHz, with some paint formulations exceeding a response of 1 MHz. Various applications of fast PSP are discussed that highlight the capabilities of the technique, and concluding remarks highlight the need for the future development of fast PSP.

  12. Optimization and Control of Acoustic Liner Impedance with Bias Flow

    NASA Technical Reports Server (NTRS)

    Wood, Houston; Follet, Jesse

    2000-01-01

    Because communities are impacted by steady increases in aircraft traffic, aircraft noise continues to be a growing problem for the growth of commercial aviation. Research has focused on improving the design of specific high noise source areas of aircraft and on noise control measures to alleviate noise radiated from aircraft to the surrounding environment. Engine duct liners have long been a principal means of attenuating engine noise. The ability to control in-situ the acoustic impedance of a liner would provide a valuable tool to improve the performance of liners. The acoustic impedance of a liner is directly related to the sound absorption qualities of that liner. Increased attenuation rates, the ability to change liner acoustic impedance to match various operating conditions, or the ability to tune a liner to more precisely match design impedance represent some ways that in-situ impedance control could be useful. With this in mind, the research to be investigated will focus on improvements in the ability to control liner impedance using a mean flow through the liner which is referred to as bias flow.

  13. Frequency-Preserved Acoustic Diode Model with High Forward-Power-Transmission Rate

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Du, Zongliang; Sun, Zhi; Gao, Huajian; Guo, Xu

    2015-06-01

    The acoustic diode (AD) can provide brighter and clearer ultrasound images by eliminating acoustic disturbances caused by sound waves traveling in two directions at the same time and interfering with each other. Such an AD could give designers new flexibility in making ultrasonic sources like those used in medical imaging or nondestructive testing. However, current AD designs, based on nonlinear effects, only partially fill this role by converting sound to a new frequency and blocking any backward flow of the original frequency. In this work, an AD model that preserves the frequencies of acoustic waves and has a relatively high forward-power-transmission rate is proposed. Theoretical analysis indicates that the proposed AD has forward, reverse, and breakdown characteristics very similar to electrical diodes. The significant rectifying effect of the proposed AD is verified numerically through a one-dimensional example. Possible schemes for experimental realization of this model as well as more complex and efficient AD designs are also discussed.

  14. Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale

    SciTech Connect

    P. Oshkai; M. Geveci; D. Rockwell; M. Pollack

    2002-12-12

    Flow-acoustic interactions due to fully turbulent inflow past a shallow axisymmetric cavity mounted in a pipe are investigated using a technique of high-image-density particle image velocimetry in conjunction with unsteady pressure measurements. This imaging leads to patterns of velocity, vorticity, streamline topology, and hydrodynamic contributions to the acoustic power integral. Global instantaneous images, as well as time-averaged images, are evaluated to provide insight into the flow physics during tone generation. Emphasis is on the manner in which the streamwise length scale of the cavity alters the major features of the flow structure. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary to maintain a flow tone. In addition, combined image analysis and pressure measurements allow categorization of the instantaneous flow patterns that are associated with types of time traces and spectra of the fluctuating pressure. In contrast to consideration based solely on pressure spectra, it is demonstrated that locked-on tones may actually exhibit intermittent, non-phase-locked images, apparently due to low damping of the acoustic resonator. Locked-on flow tones (without modulation or intermittency), locked-on flow tones with modulation, and non-locked-on oscillations with short-term, highly coherent fluctuations are defined and represented by selected cases. Depending on which of,these regimes occur, the time-averaged Q (quality)-factor and the dimensionless peak pressure are substantially altered.

  15. Acoustic measurement of the Deepwater Horizon Macondo well flow rate.

    PubMed

    Camilli, Richard; Di Iorio, Daniela; Bowen, Andrew; Reddy, Christopher M; Techet, Alexandra H; Yoerger, Dana R; Whitcomb, Louis L; Seewald, Jeffrey S; Sylva, Sean P; Fenwick, Judith

    2012-12-11

    On May 31, 2010, a direct acoustic measurement method was used to quantify fluid leakage rate from the Deepwater Horizon Macondo well prior to removal of its broken riser. This method utilized an acoustic imaging sonar and acoustic Doppler sonar operating onboard a remotely operated vehicle for noncontact measurement of flow cross-section and velocity from the well's two leak sites. Over 2,500 sonar cross-sections and over 85,000 Doppler velocity measurements were recorded during the acquisition process. These data were then applied to turbulent jet and plume flow models to account for entrained water and calculate a combined hydrocarbon flow rate from the two leak sites at seafloor conditions. Based on the chemical composition of end-member samples collected from within the well, this bulk volumetric rate was then normalized to account for contributions from gases and condensates at initial leak source conditions. Results from this investigation indicate that on May 31, 2010, the well's oil flow rate was approximately 0.10 ± 0.017 m(3) s(-1) at seafloor conditions, or approximately 85 ± 15 kg s(-1) (7.4 ± 1.3 Gg d(-1)), equivalent to approximately 57,000 ± 9,800 barrels of oil per day at surface conditions. End-member chemical composition indicates that this oil release rate was accompanied by approximately an additional 24 ± 4.2 kg s(-1) (2.1 ± 0.37 Gg d(-1)) of natural gas (methane through pentanes), yielding a total hydrocarbon release rate of 110 ± 19 kg s(-1) (9.5 ± 1.6 Gg d(-1)).

  16. Observation of hydrothermal flows with acoustic video camera

    NASA Astrophysics Data System (ADS)

    Mochizuki, M.; Asada, A.; Tamaki, K.; Scientific Team Of Yk09-13 Leg 1

    2010-12-01

    To evaluate hydrothermal discharging and its diffusion process along the ocean ridge is necessary for understanding balance of mass and flux in the ocean, ecosystem around hydrothermal fields and so on. However, it has been difficult for us to measure hydrothermal activities without disturbance caused by observation platform ( submersible, ROV, AUV ). We wanted to have some observational method to observe hydrothermal discharging behavior as it was. DIDSON (Dual-Frequency IDentification SONar) is acoustic lens-based sonar. It has sufficiently high resolution and rapid refresh rate that it can substitute for optical system in turbid or dark water where optical systems fail. DIDSON operates at two frequencies, 1.8MHz or 1.1MHz, and forms 96 beams spaced 0.3° apart or 48 beams spaced 0.6° apart respectively. It images out to 12m at 1.8MHz and 40m at 1.1MHz. The transmit and receive beams are formed with acoustic lenses with rectangular apertures and made of polymethylpentene plastic and FC-70 liquid. This physical beam forming allows DIDSON to consume only 30W of power. DIDSON updates its image between 20 to 1 frames/s depending on the operating frequency and the maximum range imaged. It communicates its host using Ethernet. Institute of Industrial Science, University of Tokyo ( IIS ) has understood DIDSON’s superior performance and tried to find new method for utilization of it. The observation systems that IIS has ever developed based on DIDSON are waterside surveillance system, automatic measurement system for fish length, automatic system for fish counting, diagnosis system for deterioration of underwater structure and so on. A next challenge is to develop an observation method based on DIDSON for hydrothermal discharging from seafloor vent. We expected DIDSON to reveal whole image of hydrothermal plume as well as detail inside the plume. In October 2009, we conducted seafloor reconnaissance using a manned deep-sea submersible Shinkai6500 in Central Indian

  17. Concurrent identification of aero-acoustic scattering and noise sources at a flow duct singularity in low Mach number flow

    NASA Astrophysics Data System (ADS)

    Sovardi, Carlo; Jaensch, Stefan; Polifke, Wolfgang

    2016-09-01

    A numerical method to concurrently characterize both aeroacoustic scattering and noise sources at a duct singularity is presented. This approach combines Large Eddy Simulation (LES) with techniques of System Identification (SI): In a first step, a highly resolved LES with external broadband acoustic excitation is carried out. Subsequently, time series data extracted from the LES are post-processed by means of SI to model both acoustic propagation and noise generation. The present work studies the aero-acoustic characteristics of an orifice placed in a duct at low flow Mach numbers with the "LES-SI" method. Parametric SI based on the Box-Jenkins mathematical structure is employed, with a prediction error approach that utilizes correlation analysis of the output residuals to avoid overfitting. Uncertainties of model parameters due to the finite length of times series are quantified in terms of confidence intervals. Numerical results for acoustic scattering matrices and power spectral densities of broad-band noise are validated against experimental measurements over a wide range of frequencies below the cut-off frequency of the duct.

  18. Method of measuring reactive acoustic power density in a fluid

    DOEpatents

    Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1985-01-01

    A method for determining reactive acoustic power density level and its direction in a fluid using a single sensor is disclosed. In the preferred embodiment, an apparatus for conducting the method, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas.

  19. Method of measuring reactive acoustic power density in a fluid

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1985-09-03

    A method for determining reactive acoustic power density level and its direction in a fluid using a single sensor is disclosed. In the preferred embodiment, an apparatus for conducting the method, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas. 5 figs.

  20. Sound power flux measurements in strongly exited ducts with flow

    NASA Astrophysics Data System (ADS)

    Holland, Keith R.; Davies, Peter O. A. L.; van der Walt, Danie C.

    2002-12-01

    This contribution describes new robust procedures for the measurement of sound power flux at appropriate axial positions along a duct with flow, using pairs of flush wall mounted microphones, or pressure transducers. The technology includes the application of selective averaging, order tracking, and optimized sampling rate methods to identify the small fraction of the total fluctuating wave energy that is being propagated along the flow path in a reverberent, or highly reactive duct system. Such measurements can also be used to quantify the local acoustic characteristics that govern the generation, transfer, and propagation of wave energy in the system. Illustrative examples include the determination of the acoustic characteristics of individual silencing elements installed in IC engine intakes and exhausts both on the flow bench and during controlled acceleration or run down on a test bed, where the wave component spectral levels approached 170 dB.

  1. 2-D steering and propelling of acoustic bubble-powered microswimmers.

    PubMed

    Feng, Jian; Yuan, Junqi; Cho, Sung Kwon

    2016-06-21

    This paper describes bi-directional (linear and rotational) propelling and 2-D steering of acoustic bubble-powered microswimmers that are achieved in a centimeter-scale pool (beyond chip level scale). The core structure of a microswimmer is a microtube with one end open in which a gaseous bubble is trapped. The swimmer is propelled by microstreaming flows that are generated when the trapped bubble is oscillated by an external acoustic wave. The bubble oscillation and thus propelling force are highly dependent on the frequency of the acoustic wave and the bubble length. This dependence is experimentally studied by measuring the resonance behaviors of the testing pool and bubble using a laser Doppler vibrometer (LDV) and by evaluating the generated streaming flows. The key idea in the present 2-D steering is to utilize this dependence. Multiple bubbles with different lengths are mounted on a single microswimmer with a variety of arrangements. By controlling the frequency of the acoustic wave, only frequency-matched bubbles can strongly oscillate and generate strong propulsion. By arranging multiple bubbles of different lengths in parallel but with their openings opposite and switching the frequency of the acoustic wave, bi-directionally linear propelling motions are successfully achieved. The propelling forces are calculated by a CFD analysis using the Ansys Fluent® package. For bi-directional rotations, a similar method but with diagonal arrangement of bubbles on a rectangular swimmer is also applied. The rotation can be easily reversed when the frequency of the acoustic wave is switched. For 2-D steering, short bubbles are aligned perpendicular to long bubbles. It is successfully demonstrated that the microswimmer navigates through a T-junction channel under full control with and without carrying a payload. During the navigation, the frequency is the main control input to select and resonate targeted bubbles. All of these operations are achieved by a single

  2. 2-D steering and propelling of acoustic bubble-powered microswimmers.

    PubMed

    Feng, Jian; Yuan, Junqi; Cho, Sung Kwon

    2016-06-21

    This paper describes bi-directional (linear and rotational) propelling and 2-D steering of acoustic bubble-powered microswimmers that are achieved in a centimeter-scale pool (beyond chip level scale). The core structure of a microswimmer is a microtube with one end open in which a gaseous bubble is trapped. The swimmer is propelled by microstreaming flows that are generated when the trapped bubble is oscillated by an external acoustic wave. The bubble oscillation and thus propelling force are highly dependent on the frequency of the acoustic wave and the bubble length. This dependence is experimentally studied by measuring the resonance behaviors of the testing pool and bubble using a laser Doppler vibrometer (LDV) and by evaluating the generated streaming flows. The key idea in the present 2-D steering is to utilize this dependence. Multiple bubbles with different lengths are mounted on a single microswimmer with a variety of arrangements. By controlling the frequency of the acoustic wave, only frequency-matched bubbles can strongly oscillate and generate strong propulsion. By arranging multiple bubbles of different lengths in parallel but with their openings opposite and switching the frequency of the acoustic wave, bi-directionally linear propelling motions are successfully achieved. The propelling forces are calculated by a CFD analysis using the Ansys Fluent® package. For bi-directional rotations, a similar method but with diagonal arrangement of bubbles on a rectangular swimmer is also applied. The rotation can be easily reversed when the frequency of the acoustic wave is switched. For 2-D steering, short bubbles are aligned perpendicular to long bubbles. It is successfully demonstrated that the microswimmer navigates through a T-junction channel under full control with and without carrying a payload. During the navigation, the frequency is the main control input to select and resonate targeted bubbles. All of these operations are achieved by a single

  3. Measurement of ultrasonic power using an acoustically absorbing well.

    PubMed

    Sutton, Yvonne; Shaw, Adam; Zeqiri, Bajram

    2003-10-01

    This paper describes a quick and cost-effective method for constructing a radiation force balance for measuring ultrasonic output power. It utilises a target manufactured from a high-quality acoustical absorber material. The target geometry is in the form of a cup or well that is water-filled and placed directly on the pan of a top-loading chemical balance, thus overcoming the need for the traditional gantry arrangement found in the majority of commercially available balances. The face of the transducer is placed directly in the water contained within the well. This simplification reduces time spent in setting up a balance for measurement, and targets can be manufactured to any required geometry and used on any suitable top-loading balance to measure output power. Within this study, the performance of the absorbing well method was evaluated over the frequency range of 1 MHz to 5 MHz, for acoustic power levels up to 1 W. Power measurements on three transducers were compared with measurements made on the National Physical Laboratory (NPL) primary standard radiation force balance and good agreement is demonstrated between the two systems. At a power of 50 mW, using a chemical balance of resolution 0.1 mg, typical type A (random) uncertainties were +/- 2.0% when expressed at the 95% confidence level.

  4. Power cepstrum technique with application to model helicopter acoustic data

    NASA Technical Reports Server (NTRS)

    Martin, R. M.; Burley, C. L.

    1986-01-01

    The application of the power cepstrum to measured helicopter-rotor acoustic data is investigated. A previously applied correction to the reconstructed spectrum is shown to be incorrect. For an exact echoed signal, the amplitude of the cepstrum echo spike at the delay time is linearly related to the echo relative amplitude in the time domain. If the measured spectrum is not entirely from the source signal, the cepstrum will not yield the desired echo characteristics and a cepstral aliasing may occur because of the effective sample rate in the frequency domain. The spectral analysis bandwidth must be less than one-half the echo ripple frequency or cepstral aliasing can occur. The power cepstrum editing technique is a useful tool for removing some of the contamination because of acoustic reflections from measured rotor acoustic spectra. The cepstrum editing yields an improved estimate of the free field spectrum, but the correction process is limited by the lack of accurate knowledge of the echo transfer function. An alternate procedure, which does not require cepstral editing, is proposed which allows the complete correction of a contaminated spectrum through use of both the transfer function and delay time of the echo process.

  5. Klamath Falls: High-Power Acoustic Well Stimulation Technology

    SciTech Connect

    Black, Brian

    2006-07-24

    Acoustic well stimulation (AWS) technology uses high-power sonic waves from specific frequency spectra in an attempt to stimulate production in a damaged or low-production wellbore. AWS technology is one of the most promising technologies in the oil and gas industry, but it has proven difficult for the industry to develop an effective downhole prototype. This collaboration between Klamath Falls Inc. and the Rocky Mountain Oilfield Testing Center (RMOTC) included a series of tests using high-power ultrasonic tools to stimulate oil and gas production. Phase I testing was designed and implemented to verify tool functionality, power requirements, and capacity of high-power AWS tools. The purpose of Phase II testing was to validate the production response of wells with marginal production rates to AWS stimulation and to capture and identify any changes in the downhole environment after tool deployment. This final report presents methodology and results.

  6. Effect of acoustic flows on the structure of a constricted glow discharge in argon

    NASA Astrophysics Data System (ADS)

    Saifutdinov, A. I.; Fadeev, S. A.; Saifutdinova, A. A.; Kashapov, N. F.

    2015-11-01

    Numerical experiments on the effect of acoustic flows on the structure of a constricted glow discharge in argon have been performed in the hybrid approximation. The possibility of controlling the combustion regime of the glow discharge with an extended positive column at a high pressure by means of the formation of acoustic flows at the excitation of a standing acoustic wave has been demonstrated. In this case, the discharge transfers from the constricted combustion regime to the diffuse one and becomes stable.

  7. Power flow control using quadrature boosters

    NASA Astrophysics Data System (ADS)

    Sadanandan, Sandeep N.

    A power system that can be controlled within security constraints would be an advantage to power planners and real-time operators. Controlling flows can lessen reliability issues such as thermal limit violations, power stability problems, and/or voltage stability conditions. Control of flows can also mitigate market issues by reducing congestion on some lines and rerouting power to less loaded lines or onto preferable paths. In the traditional control of power flows, phase shifters are often used. More advanced methods include using Flexible AC Transmission System (FACTS) Controllers. Some examples include Thyristor Controlled Series Capacitors, Synchronous Series Static Compensators, and Unified Power Flow Controllers. Quadrature Boosters (QBs) have similar structures to phase-shifters, but allow for higher voltage magnitude during real power flow control. In comparison with other FACTS controllers QBs are not as complex and not as expensive. The present study proposes to use QBs to control power flows on a power system. With the inclusion of QBs, real power flows can be controlled to desired scheduled values. In this thesis, the linearized power flow equations used for power flow analysis were modified for the control problem. This included modifying the Jacobian matrix, the power error vector, and calculating the voltage injected by the quadrature booster for the scheduled real power flow. Two scenarios were examined using the proposed power flow control method. First, the power flow in a line in a 5-bus system was modified with a QB using the method developed in this thesis. Simulation was carried out using Matlab. Second, the method was applied to a 30-bus system and then to a 118-bus system using several QBs. In all the cases, the calculated values of the QB voltages led to desired power flows in the designated line.

  8. Selective breakup of lipid vesicles under acoustic microstreaming flow

    NASA Astrophysics Data System (ADS)

    Pommella, Angelo; Garbin, Valeria

    2014-11-01

    The dynamics of lipid vesicles under small deformation in simple shear flow is well characterized: complex behaviors such as tumbling, breathing, and tank-treading are observed depending on the viscosity contrast between inner and outer fluid, vesicle excess area, membrane viscosity, and bending modulus. In contrast, phenomena upon large deformation are still poorly understood, in particular vesicle breakup. Simple shear flow geometries do not allow to reach the large stresses necessary to cause vesicle breakup. We use the acoustic microstreaming flow generated by an oscillating microbubble to study the large deformation and breakup of giant unilamellar vesicles. The deformation is governed by a capillary number based on the membrane elasticity K : Ca = ηγ˙a / K where η is the viscosity of the outer fluid, a the vesicle radius, and γ˙ the shear rate. We explore the effect of the mechanical properties of the membrane, and demonstrated selective breakup of vesicles based on the difference in membrane elasticity. The results reveal the influence of membrane mechanical properties in shear-induced vesicle breakup and the possibility to control in a quantitative way the selectivity of the process, with potential applications in biomedical technologies. The authors acknowledge funding from EU/FP7 Grant Number 618333.

  9. Flow and acoustic features of a supersonic tapered nozzle

    NASA Astrophysics Data System (ADS)

    Gutmark, E.; Bowman, H. L.; Schadow, K. C.

    1992-05-01

    The acoustic and flow characteristics of a supersonic tapered jet were measured for free and shrouded flow configurations. Measurements were performed for a full range of pressure ratios including over- and underexpanded and design conditions. The supersonic tapered jet is issued from a converging-diverging nozzle with a 3∶1 rectangular slotted throat and a conical diverging section leading to a circular exit. The jet was compared to circular and rectangular supersonic jets operating at identical conditions. The distinct feature of the jet is the absence of screech tones in the entire range of operation. Its near-field pressure fluctuations have a wide band spectrum in the entire range of measurements, for Mach numbers of 1 to 2.5, for over- and underexpanded conditions. The free jet's spreading rate is nearly constant and similar to the rectangular jet, and in a shroud, the pressure drop it is inducing is linearly proportional to the primary jet Mach number. This behavior persisted in high adverse pressure gradients at overexpanded conditions, and with nozzle divergence angles of up to 35°, no inside flow separation was observed.

  10. Reversing pathologically increased EEG power by acoustic coordinated reset neuromodulation

    PubMed Central

    Adamchic, Ilya; Toth, Timea; Hauptmann, Christian; Tass, Peter Alexander

    2014-01-01

    Acoustic Coordinated Reset (CR) neuromodulation is a patterned stimulation with tones adjusted to the patient's dominant tinnitus frequency, which aims at desynchronizing pathological neuronal synchronization. In a recent proof-of-concept study, CR therapy, delivered 4–6 h/day more than 12 weeks, induced a significant clinical improvement along with a significant long-lasting decrease of pathological oscillatory power in the low frequency as well as γ band and an increase of the α power in a network of tinnitus-related brain areas. As yet, it remains unclear whether CR shifts the brain activity toward physiological levels or whether it induces clinically beneficial, but nonetheless abnormal electroencephalographic (EEG) patterns, for example excessively decreased δ and/or γ. Here, we compared the patients' spontaneous EEG data at baseline as well as after 12 weeks of CR therapy with the spontaneous EEG of healthy controls by means of Brain Electrical Source Analysis source montage and standardized low-resolution brain electromagnetic tomography techniques. The relationship between changes in EEG power and clinical scores was investigated using a partial least squares approach. In this way, we show that acoustic CR neuromodulation leads to a normalization of the oscillatory power in the tinnitus-related network of brain areas, most prominently in temporal regions. A positive association was found between the changes in tinnitus severity and the normalization of δ and γ power in the temporal, parietal, and cingulate cortical regions. Our findings demonstrate a widespread CR-induced normalization of EEG power, significantly associated with a reduction of tinnitus severity. PMID:23907785

  11. Development of acoustic flow instruments for solid/gas pipe flows

    SciTech Connect

    Sheen, S.H.; Raptis, A.C.

    1986-05-01

    Two nonintrusive acoustic flow sensing techniques are reported. One technique, passive in nature, simply measures the bandpassed acoustic noise level produced by particle/particle and particle/wall collisions. The noise levels, given in true RMS voltages or in autocorrelations, show a linear relationship to particle velocity but increase with solid concentration. Therefore, the passive technique requires calibration and a separate measure of solid concentration before it can be used to monitor the particle velocity. The second technique is based on the active cross-correlation principle. It measures particle velocity directly by correlating flow-related signatures at two sensing stations. The velocity data obtained by this technique are compared with measurements by a radioactive-particle time-of-flight (TOF) method. A multiplier of 1.53 is required to bring the acoustic data into agreement with the radioactive TOF result. The difference may originate from the difference in flow fields where particles are detected. The radioactive method senses particles mainly in the turbulent region and essentially measures average particle velocity across the pipe, while the acoustic technique detects particles near the pipe wall, and so measures the particle velocity in the viscous sublayer. Both techniques were tested in flows of limestone and air and 1-mm glass beads and air at the Argonne National Laboratory Solid/Gas Test Facility (SGFTF). The test matrix covered solid velocities of 20 to 30 m/s in a 2-in. pipe and solid-to-gas loading ratios of 6 to 22. 37 refs., 19 figs., 4 tabs.

  12. Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale

    SciTech Connect

    P Oshkai; M Geveci; D Rockwell; M Pollack

    2004-05-24

    Flow-acoustic interactions due to fully turbulent inflow past a shallow axisymmetric cavity mounted in a pipe, which give rise to flow tones, are investigated using a technique of high-image-density particle image velocimetry in conjunction with unsteady pressure measurements. This imaging leads to patterns of velocity, vorticity, streamline topology, and hydrodynamic contributions to the acoustic power integral. Global instantaneous images, as well as time-averaged images, are evaluated to provide insight into the flow physics during tone generation. Emphasis is on the manner in which the streamwise length scale of the cavity alters the major features of the flow structure. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary to maintain a flow tone. In addition, combined image analysis and pressure measurements allow categorization of the instantaneous flow patterns that are associated with types of time traces and spectra of the fluctuating pressure. In contrast to consideration based solely on pressure spectra, it is demonstrated that locked-on tones may actually exhibit intermittent, non-phase-locked images, apparently due to low damping of the acoustic resonator. Locked-on flow tones (without modulation or intermittency), locked-on flow tones with modulation, and non-locked-on oscillations with short-term, highly coherent fluctuations are defined and represented by selected cases. Depending on which of these regimes occur, the time-averaged Q (quality)-factor and the dimensionless peak pressure are substantially altered.

  13. Acoustic noise from tandem wind rotors of intelligent wind power unit

    NASA Astrophysics Data System (ADS)

    Kubo, Koichi; Mihara, Nobuhiko; Enishi, Akira; Kanemoto, Toshiaki

    2010-04-01

    The authors had invented the unique wind power unit composed of the large-sized front wind rotor, the small-sized rear wind rotor and the peculiar generator with the inner and the outer rotational armatures without the conventional stator. This unit is called "Intelligent Wind Power Unit" by the authors. The front and the rear wind rotors drive the inner and the outer armatures, respectively, while the rotational torque is counter-balanced between both armatures/wind rotors. This paper discusses experimentally the acoustic noise from the front and the rear wind rotors. The acoustic noise, in the counter-rotating operation, is induced mainly from the flow interaction between both rotors, and has the dominant power spectrum density at the frequency of the blade passing interaction. The noise is caused mainly from the turbulent fluctuation due to the flow separation on the blade, when the rear wind rotor stops or rotates in the same direction as the front wind rotor.

  14. An analysis of the acoustic energy in a flow duct with a vortex sheet

    NASA Astrophysics Data System (ADS)

    Boij, Susann

    2009-03-01

    Modelling the acoustic scattering and absorption at an area expansion in a flow duct requires the incorporation of the flow-acoustic interaction. One way to quantify the interaction is to study the energy in the incident and the scattered field respectively. If the interaction is strong, energy may be transferred between the acoustic and the main flow field. In particular, shear layers, that may be the result of the flow separation, are unstable to low frequency perturbations such as acoustic waves. The vortex sheet model is an analytical linear acoustic model, developed to study scattering of acoustic waves in duct with sharp edges including the interaction with primarily the separated flows that arise at sharp edges and corners. In the model the flow field at an area expansion in a duct is described as a jet issuing into the larger part of the duct. In this paper, the flow-acoustic interaction is described in terms of energy flow. The linear convective wave equation is solved for a two-dimensional, rectangular flow duct geometry. The resulting modes are classified as "hydrodynamic" and "acoustic" when separating the acoustic energy from the part of the energy arising from the steady flow field. In the downstream duct, the set of modes for this complex flow field are not orthogonal. For small Strouhal numbers, the plane wave and the two hydrodynamic waves are all plane, although propagating with different wave speeds. As the Strouhal numbers increases, the hydrodynamic modes changes to get a shape where the amplitude is concentrated near the vortex sheet. In an intermediate Strouhal number region, the mode shape of the first higher order mode is very similar to the damped hydrodynamic mode. A physical interpretation of this is that we have a strong coupling between the flow field and the acoustic field when the modes are non-orthogonal. Energy concepts for this duct configuration and mean flow profile are introduced. The energy is formulated such that the vortex

  15. Acoustic attenuation analysis program for ducts with mean flow

    NASA Technical Reports Server (NTRS)

    Kunze, R. K., Jr.

    1972-01-01

    A computerized acoustic attenuation prediction procedure has been developed to evaluate acoustically lined ducts for various geometric and environmental parameters. The analysis procedure is based on solutions to the acoustic wave equation, assuming uniform airflow on a duct cross section, combined with appropriate mathematical lining impedance models. The impedance models included in the analysis procedure are representative of either perforated sheet or porous polyimide impregnated fiberglass facing sheet coupled with a cellular backing space. Advantages and limitations of the analysis procedure are reviewed.

  16. Modified ion-acoustic solitary waves in plasmas with field-aligned shear flows

    SciTech Connect

    Saleem, H.; Haque, Q.

    2015-08-15

    The nonlinear dynamics of ion-acoustic waves is investigated in a plasma having field-aligned shear flow. A Korteweg-deVries-type nonlinear equation for a modified ion-acoustic wave is obtained which admits a single pulse soliton solution. The theoretical result has been applied to solar wind plasma at 1 AU for illustration.

  17. Modified ion-acoustic solitary waves in plasmas with field-aligned shear flows

    NASA Astrophysics Data System (ADS)

    Saleem, H.; Ali, S.; Haque, Q.

    2015-08-01

    The nonlinear dynamics of ion-acoustic waves is investigated in a plasma having field-aligned shear flow. A Koeteweg-deVries-type nonlinear equation for a modified ion-acoustic wave is obtained which admits a single pulse soliton solution. The theoretical result has been applied to solar wind plasma at 1 AU for illustration.

  18. A method to determine the acoustical properties of locally and nonlocally reacting duct liners in grazing flow

    NASA Technical Reports Server (NTRS)

    Succi, G.

    1982-01-01

    The acoustical properties of locally and nonlocally reacting acoustical liners in grazing flow are described. The effect of mean flow and shear flow are considered as well as the application to rigid and limp bulk reacting materials. The axial wavenumber of the least attenuated mode in a flow duct is measured. The acoustical properties of duct liners is then deduced from the measured axial wavenumber and known flow profile and boundary conditions. This method is a natural extension of impedance-like measurements.

  19. Distributed acoustic receptivity in laminar flow control configurations

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan

    1992-01-01

    A model problem related to distributed receptivity to free-stream acoustic waves in laminar flow control (LFC) configurations is studied, within the Orr-Sommerfield framework, by a suitable extension of the Goldstein-Ruban theory for receptivity due to localized disturbances on the airfoil surface. The results, thus, complement the earlier work on the receptivity produced by local variations in the surface suction and/or surface admittance. In particular, we show that the cumulative effect of the distributed receptivity can be substantially larger than that of a single, isolated suction strip or slot. Furthermore, even if the receptivity is spread out over very large distances, the most effective contributions come from a relatively short region in vicinity of the lower branch of the neutral stability curve. The length scale of this region is intermediate to that of the mean of these two length scales. Finally, it is found that the receptivity is effectively dominated by a narrow band of Fourier components from the wall-suction and admittance distributions, roughly corresponding to a detuning of less than ten percent with respect to the neutral instability wavenumber at the frequency under consideration. The results suggest that the drop-off in receptivity magnitudes away from the resonant wavenumber is nearly independent of the frequency parameter.

  20. Acoustic intensity near a high-powered military jet aircraft.

    PubMed

    Stout, Trevor A; Gee, Kent L; Neilsen, Tracianne B; Wall, Alan T; James, Michael M

    2015-07-01

    The spatial variation in vector acoustic intensity has been calculated between 100 and 3000 Hz near a high-performance military aircraft. With one engine of a tethered F-22A Raptor operating at military power, a tetrahedral intensity probe was moved to 27 locations in the geometric near and mid-fields to obtain the frequency-dependent intensity vector field. The angles of the maximum intensity region rotate from aft to sideline with increasing frequency, becoming less directional above 800 Hz. Between 100 and 400 Hz, which are principal radiation frequencies, the ray-traced dominant source region rapidly contracts and moves upstream, approaching nearly constant behavior by 1000 Hz. PMID:26233049

  1. Acoustic intensity near a high-powered military jet aircraft.

    PubMed

    Stout, Trevor A; Gee, Kent L; Neilsen, Tracianne B; Wall, Alan T; James, Michael M

    2015-07-01

    The spatial variation in vector acoustic intensity has been calculated between 100 and 3000 Hz near a high-performance military aircraft. With one engine of a tethered F-22A Raptor operating at military power, a tetrahedral intensity probe was moved to 27 locations in the geometric near and mid-fields to obtain the frequency-dependent intensity vector field. The angles of the maximum intensity region rotate from aft to sideline with increasing frequency, becoming less directional above 800 Hz. Between 100 and 400 Hz, which are principal radiation frequencies, the ray-traced dominant source region rapidly contracts and moves upstream, approaching nearly constant behavior by 1000 Hz.

  2. Determination of the acoustic source power levels of wind turbines

    NASA Astrophysics Data System (ADS)

    Debruijn, A.; Stam, W. J.; Dewolf, W. B.

    To facilitate Wind Energy Conversin System (WECS) licensing, it is recommended to obtain the immission-relevant sound power from the WECS, since this quantity fits into most recommendations for industrial installations. Measurements on small and medium-scale WECS show that rotor rotation speed is a more important parameter than the wind velocity with regard to the radiated noise. An acoustic telescope was used to identify noise sources on two medium-size wind turbines. The mechanical noise from the nacelle is mostly predominant but the trailing edge aerodynamic noise is not negligible. A prediction model for this type of noise, which leads to good agreement with experimental data was developed. A method to suppress turbulence signals around WECS is a set-up with twin microphones, using correlation techniques on both signals.

  3. Dynamics and acoustics of a cavitating Venturi flow using a homogeneous air-propylene glycol mixture

    NASA Astrophysics Data System (ADS)

    Navarrete, M.; Naude, J.; Mendez, F.; Godínez, F. A.

    2015-12-01

    Dynamics and acoustics generated in a cavitating Venturi tube are followed up as a function of the input power of a centrifugal pump. The pump of 5 hp with a modified impeller to produce uniform bubbly flow, pumps 70 liters of propylene glycol in a closed loop (with a water cooling system), in which the Venturi is arranged. The goal was to obtain correlations among acoustical emission, dynamics of the shock waves and the light emission from cavitation bubbles. The instrumentation includes: two piezoelectric transducers, a digital camera, a high-speed video camera, and photomultipliers. As results, we show the cavitation patterns as function of the pump power, and a graphical template of the distribution of the Venturi conditions as a function of the cavitation parameter. Our observations show for the first time the sudden formation of bubble clouds in the straight portion of the pipe after the diverging section of the Venturi. We assume that this is due to pre-existing of nuclei-cloud structures which suddenly grow up by the tensile tails of propagating shock waves (producing a sudden drop in pressure).

  4. The path to COVIS: A review of acoustic imaging of hydrothermal flow regimes

    NASA Astrophysics Data System (ADS)

    Bemis, Karen G.; Silver, Deborah; Xu, Guangyu; Light, Russ; Jackson, Darrell; Jones, Christopher; Ozer, Sedat; Liu, Li

    2015-11-01

    Acoustic imaging of hydrothermal flow regimes started with the incidental recognition of a plume on a routine sonar scan for obstacles in the path of the human-occupied submersible ALVIN. Developments in sonar engineering, acoustic data processing and scientific visualization have been combined to develop technology which can effectively capture the behavior of focused and diffuse hydrothermal discharge. This paper traces the development of these acoustic imaging techniques for hydrothermal flow regimes from their conception through to the development of the Cabled Observatory Vent Imaging Sonar (COVIS). COVIS has monitored such flow eight times a day for several years. Successful acoustic techniques for estimating plume entrainment, bending, vertical rise, volume flux, and heat flux are presented as is the state-of-the-art in diffuse flow detection.

  5. Separating underwater ambient noise from flow noise recorded on stereo acoustic tags attached to marine mammals.

    PubMed

    von Benda-Beckmann, Alexander M; Wensveen, Paul J; Samarra, Filipa I P; Beerens, S Peter; Miller, Patrick J O

    2016-08-01

    Sound-recording acoustic tags attached to marine animals are commonly used in behavioural studies. Measuring ambient noise is of interest to efforts to understand responses of marine mammals to anthropogenic underwater sound, or to assess their communication space. Noise of water flowing around the tag reflects the speed of the animal, but hinders ambient noise measurement. Here, we describe a correlation-based method for stereo acoustic tags to separate the relative contributions of flow and ambient noise. The uncorrelated part of the noise measured in digital acoustic recording tag (DTAG) recordings related well to swim speed of a humpback whale (Megaptera novaeangliae), thus providing a robust measure of flow noise over a wide frequency bandwidth. By removing measurements affected by flow noise, consistent ambient noise estimates were made for two killer whales (Orcinus orca) with DTAGs attached simultaneously. The method is applicable to any multi-channel acoustic tag, enabling application to a wide range of marine species. PMID:27229472

  6. Echo-acoustic flow dynamically modifies the cortical map of target range in bats.

    PubMed

    Bartenstein, Sophia K; Gerstenberg, Nadine; Vanderelst, Dieter; Peremans, Herbert; Firzlaff, Uwe

    2014-01-01

    Echolocating bats use the delay between their sonar emissions and the reflected echoes to measure target range, a crucial parameter for avoiding collisions or capturing prey. In many bat species, target range is represented as an orderly organized map of echo delay in the auditory cortex. Here we show that the map of target range in bats is dynamically modified by the continuously changing flow of acoustic information perceived during flight ('echo-acoustic flow'). Combining dynamic acoustic stimulation in virtual space with extracellular recordings, we found that neurons in the auditory cortex of the bat Phyllostomus discolor encode echo-acoustic flow information on the geometric relation between targets and the bat's flight trajectory, rather than echo delay per se. Specifically, the cortical representation of close-range targets is enlarged when the lateral passing distance of the target decreases. This flow-dependent enlargement of target representation may trigger adaptive behaviours such as vocal control or flight manoeuvres. PMID:25131175

  7. Separating underwater ambient noise from flow noise recorded on stereo acoustic tags attached to marine mammals.

    PubMed

    von Benda-Beckmann, Alexander M; Wensveen, Paul J; Samarra, Filipa I P; Beerens, S Peter; Miller, Patrick J O

    2016-08-01

    Sound-recording acoustic tags attached to marine animals are commonly used in behavioural studies. Measuring ambient noise is of interest to efforts to understand responses of marine mammals to anthropogenic underwater sound, or to assess their communication space. Noise of water flowing around the tag reflects the speed of the animal, but hinders ambient noise measurement. Here, we describe a correlation-based method for stereo acoustic tags to separate the relative contributions of flow and ambient noise. The uncorrelated part of the noise measured in digital acoustic recording tag (DTAG) recordings related well to swim speed of a humpback whale (Megaptera novaeangliae), thus providing a robust measure of flow noise over a wide frequency bandwidth. By removing measurements affected by flow noise, consistent ambient noise estimates were made for two killer whales (Orcinus orca) with DTAGs attached simultaneously. The method is applicable to any multi-channel acoustic tag, enabling application to a wide range of marine species.

  8. Echo-acoustic flow dynamically modifies the cortical map of target range in bats.

    PubMed

    Bartenstein, Sophia K; Gerstenberg, Nadine; Vanderelst, Dieter; Peremans, Herbert; Firzlaff, Uwe

    2014-01-01

    Echolocating bats use the delay between their sonar emissions and the reflected echoes to measure target range, a crucial parameter for avoiding collisions or capturing prey. In many bat species, target range is represented as an orderly organized map of echo delay in the auditory cortex. Here we show that the map of target range in bats is dynamically modified by the continuously changing flow of acoustic information perceived during flight ('echo-acoustic flow'). Combining dynamic acoustic stimulation in virtual space with extracellular recordings, we found that neurons in the auditory cortex of the bat Phyllostomus discolor encode echo-acoustic flow information on the geometric relation between targets and the bat's flight trajectory, rather than echo delay per se. Specifically, the cortical representation of close-range targets is enlarged when the lateral passing distance of the target decreases. This flow-dependent enlargement of target representation may trigger adaptive behaviours such as vocal control or flight manoeuvres.

  9. High-Power Piezoelectric Acoustic-Electric Power Feedthru for Metal Walls

    NASA Technical Reports Server (NTRS)

    Bao, Xiaoqi; Biederman, Will; Sherrit, Stewart; Badescu, Mircea; Bar-Cohen, Yoseph; Jones, Christopher; Aldrich, Jack; Chang, Zensheu

    2008-01-01

    Piezoelectric acoustic-electric power feed-through devices transfer electric power wirelessly through a solid wall by using acoustic waves. This approach allows for the removal of holes through structures. The technology is applicable to power supply for electric equipment inside sealed containers, vacuum or pressure vessels, etc where the holes on the wall are prohibitive or result in significant performance degrade or complex designs. In the author's previous work, 100-W electric power was transferred through a metal wall by a small, simple-structure piezoelectric device. To meet requirements of higher power applications, the feasibility to transfer kilowatts level power was investigated. Pre-stressed longitudinal piezoelectric feedthru devices were analyzed by finite element model. An equivalent circuit model was developed to predict the power transfer characteristics to different electric loads. Based on the analysis results, a prototype device was designed, fabricated and a demonstration of the transmission of electric power up to 1-kW was successfully conducted. The methods to minimize the plate wave excitation on the wall were also analyzed. Both model analysis and experimental results are presented in detail in this presentation.

  10. Progress in Acoustic Transmission of Power through Walls

    NASA Technical Reports Server (NTRS)

    Sherrit,Stewart; Coty, Benjamin; Bao, Xiaoqi; Bar-Cohen, Yoseph; Badescu, Mircea; Chang, Zensheu

    2008-01-01

    A document presents updated information on implementation of the wireless acoustic-electric feed-through (WAEF) concept, which was reported in Using Piezoelectric Devices To Transmit Power Through Walls (NPO-41157), NASA Tech Briefs, Vol. 32, No. 6 (June 2008), page 70. To recapitulate: In a basic WAEF setup, a transmitting piezoelectric transducer on one side of a wall is driven at resonance to excite ultrasonic vibrations in the wall. A receiving piezoelectric transducer on the opposite side of the wall converts the vibrations back to an ultrasonic AC electric signal, which is then detected and otherwise processed in a manner that depends on the modulation (if any) applied to the signal and whether the signal is used to transmit power, data, or both. The present document expands upon the previous information concerning underlying physical principles, advantages, and potential applications of WAEF. It discusses the design and construction of breadboard prototype piezoelectric transducers for WAEF. It goes on to present results of computational simulations of performance and results of laboratory tests of the prototypes. In one notable test, a 100-W light bulb was lit by WAEF to demonstrate the feasibility of powering a realistic load.

  11. Acoustic-televiewer and acoustic-waveform logs used to characterize deeply buried basalt flows, Hanford site, Benton County, Washington

    USGS Publications Warehouse

    Paillet, Frederick L.

    1985-01-01

    Acoustic-waveform and acoustic-televiewer logs were obtained for a 400-meter interval of deeply buried basalt flows in three boreholes, and over shorter intervals in two additional boreholes located on the U.S. Department of Energy 's Hanford site in Benton County, Washington. Borehole-wall breakouts were observed in the unaltered interiors of a large part of individual basalt flows; however, several of the flows in one of the five boreholes had almost no breakouts. The distribution of breakouts observed on the televiewer logs correlated closely with the incidence of core disking in some intervals, but the correlation was not always perfect, perhaps because of the differences in the specific fracture mechanisms involved. Borehole-wall breakouts were consistently located on the east and west sides of the boreholes. The orientation is consistent with previous estimates of the principal horizontal-stress field in south-central Washington, if breakouts are assumed to form along the azimuth of the least principal stress. The distribution of breakouts repeatedly indicated an interval of breakout-free rock at the top and bottom of flows. Because breakouts frequently terminate at major low-angle fractures, the data indicate that fracturing may have relieved some of the horizontal stresses near flow tops and bottoms. Unaltered and unfractured basalt appeared to have a uniform compressional velocity of 6.0 + or - 0.1 km/sec and a uniform shear velocity of 3.35 + or - 0.1 km/sec throughout flow interiors. Acoustics-waveform logs also indicated that borehole-wall breakouts did not affect acoustic propagation along the borehole; so fracturing associated with the formation of breakouts appeared to be confined to a thin annulus of stress concentration around the borehole. Televiewer logs obtained before and after hydraulic fracturing in these boreholes indicated the extent of induced fractures, and also indicated minor changes to pre-existing fractures that may have been inflated

  12. Output of acoustical sources. [effects of structural elements and background flow on immobile multipolar point radiation

    NASA Technical Reports Server (NTRS)

    Levine, H.

    1980-01-01

    Acoustic radiation from a source, here viewed as an immobile point singularity with periodic strength and a given multipolar nature, is affected by the presence of nearly structural elements (e.g., rigid or impedance surfaces) as well as that of a background flow in the medium. An alternative to the conventional manner of calculating the net source output by integrating the energy flux over a distant control surface is described; this involves a direct evaluation of the secondary wavefunction at the position of the primary source and obviates the need for a (prospectively difficult) flux integration. Various full and half-planar surface configurations with an adjacent source are analyzed in detail, and the explicit results obtained, in particular, for the power factor of a dipole brings out a substantial rise in its output as the source nears the sharp edge of a half-plane.

  13. Effects of grazing flow on the steady-state flow resistance and acoustic impedance of thin porous-faced liners

    NASA Technical Reports Server (NTRS)

    Hersh, A. S.; Walker, B.

    1978-01-01

    The effects of grazing flow on the steady state flow resistance and acoustic impedance of seven Feltmetal and three Rigimesh thin porous faced liners were studied. The steady-state flow resistance of the ten specimens was measured using standard fluid mechanical experimental techniques. The acoustic impedance was measured using the two microphone method. The principal findings of the study are that the effects of grazing flow were measured and found to be small; small differences were measured between steady-state and acoustic resistance, and a semi-empirical model was derived that correlated the steady-state resistance data of the seven Feltmetal liners and the face sheet reactance of both the Feltmetal and Rigimesh liners.

  14. Flow-Structure-Acoustic Interaction Computational Modeling of Voice Production inside an Entire Airway

    NASA Astrophysics Data System (ADS)

    Jiang, Weili; Zheng, Xudong; Xue, Qian

    2015-11-01

    Human voice quality is directly determined by the interplay of dynamic behavior of glottal flow, vibratory characteristics of VFs and acoustic characteristics of upper airway. These multiphysics constituents are tightly coupled together and precisely coordinate to produce understandable sound. Despite many years' research effort, the direct relationships among the detailed flow features, VF vibration and aeroacoustics still remains elusive. This study utilizes a first-principle based, flow-structure-acoustics interaction computational modeling approach to study the process of voice production inside an entire human airway. In the current approach, a sharp interface immersed boundary method based incompressible flow solver is utilized to model the glottal flow; A finite element based solid mechanics solver is utilized to model the vocal vibration; A high-order immersed boundary method based acoustics solver is utilized to directly compute sound. These three solvers are fully coupled to mimic the complex flow-structure-acoustic interaction during voice production. The geometry of airway is reconstructed based on the in-vivo MRI measurement reported by Story et al. (1995) and a three-layer continuum based vocal fold model is taken from Titze and Talkin (1979). Results from these simulations will be presented and further analyzed to get new insight into the complex flow-structure-acoustic interaction during voice production. This study is expected to improve the understanding of fundamental physical mechanism of voice production and to help to build direct cause-effect relationship between biomechanics and voice sound.

  15. Overstability of acoustic waves in strongly magnetized anisotropic magnetohydrodynamic shear flows

    SciTech Connect

    Uchava, E. S.; Shergelashvili, B. M.; Tevzadze, A. G.; Poedts, S.

    2014-08-15

    We present a linear stability analysis of the perturbation modes in anisotropic magnetohydrodynamic (MHD) flows with velocity shear and strong magnetic field. Collisionless or weakly collisional plasma is described within the 16-momentum MHD fluid closure model that takes into account not only the effect of pressure anisotropy but also the effect of anisotropic heat fluxes. In this model, the low frequency acoustic wave is revealed into a standard acoustic mode and higher frequency fast thermo-acoustic and lower frequency slow thermo-acoustic waves. It is shown that thermo-acoustic waves become unstable and grow exponentially when the heat flux parameter exceeds some critical value. It seems that velocity shear makes thermo-acoustic waves overstable even at subcritical heat flux parameters. Thus, when the effect of heat fluxes is not profound acoustic waves will grow due to the velocity shear, while at supercritical heat fluxes the flow reveals compressible thermal instability. Anisotropic thermal instability should be also important in astrophysical environments, where it will limit the maximal value of magnetic field that a low density ionized anisotropic flow can sustain.

  16. Flow Duct Data for Validation of Acoustic Liner Codes for Impedance Eduction

    NASA Technical Reports Server (NTRS)

    Ahuja, K. K.; Munro, Scott; Gaeta, R. J., Jr.

    2000-01-01

    The objective of the study reported here was to acquire acoustic and flow data with hard and lined duct wall duct sections for validation of a liner prediction code being developed at NASA LaRC. Both the mean flowfield and acoustic flowfields were determined in a cross-plane of the rectangular duct. A flow duct facility with acoustic drivers connected to a rectangular (4.7 x 2.0 inch) source section and a linear acoustic liner mounted downstream of the source section was used in this study. The liner section was designed to allow liner materials to be placed on all 4 walls of the duct. The test liner was of the locally-reacting type and was made from a ceramic material. The material, consisting of a tubular structure, was provided by NASA LaRC. The liner was approximately 8.89 cm (3.5 inches) thick. For the current study, only the two "short" sides of the duct were lined with liner material. The other two sides were hard walls. Two especially built instrumentation sections were attached on either sides of the liner section to allow acoustic and flow measurements to be made upstream and downstream of the liner. The two instrumentation duct sections were built to allow measurement of acoustic and flow properties at planes perpendicular to flow upstream and downstream of the liner section. The instrumentation section was also designed to provide a streamwise gradient in acoustic (complex) pressure from which the acoustic particle velocity, needed for the model validation, can be computed. Flow measurements included pressure, temperature, and velocity profiles upstream of the liner section. The in-flow sound pressure levels and phases were obtained with a microphone probe equipped with a nose cone in two cross planes upstream of the liner and two cross plane downstream of the liner. In addition to the acoustic measurements at the cross planes. axial centerline acoustic data was acquired using an axially traversing microphone probe which was traversed from a location

  17. Acoustic streaming field structure. Part II. Examples that include boundary-driven flow.

    PubMed

    Bradley, Charles

    2012-01-01

    In this paper three simple acoustic streaming problems are presented and solved. The purpose of the paper is to demonstrate the use of a previously published streaming model by Bradley [J. Acoust. Soc. Am. 100(3), 1399-1408 (1996)] and illustrate, with concrete examples, some of the features of streaming flows that were predicted by the general model. In particular, the problems are intended to demonstrate cases in which the streaming field boundary condition at the face of the radiator has a nontrivial lateral dc velocity component. Such a boundary condition drives a steady solenoidal flow just like a laterally translating boundary drives Couette flow.

  18. The acoustic signature of bubbles fragmenting in sheared flow.

    PubMed

    Deane, Grant B; Stokes, M Dale

    2006-12-01

    Measurements of the sound of bubbles fragmenting in fluid shear are presented and analyzed. The frequency, amplitude, and decay rate of the acoustic emissions from 1.8-mm-radius bubbles fragmenting between opposed fluid jets have been determined. A broad band of frequencies (1.8 to 30 kHz) is observed with peak pressure amplitudes in the range of 0.03 to 2 Pa. While the peak pressure amplitudes show no significant scaling with frequency, the frequency dependence of the decay rates is consistent with the sum of thermal and acoustic radiation losses.

  19. Generalization and extension of the law of acoustic energy conservation in a nonuniform flow

    NASA Technical Reports Server (NTRS)

    Myers, M. K.

    1986-01-01

    An exact conservation equation is derived which generalizes the familiar acoustic energy equations. The new relation is valid for arbitrary disturbances to a viscous, compressible flow. It is suggested by a development of the acoustic energy equation by means of a regular perturbation expansion of the general energy equation of fluid mechanics. A perturbation energy density and flux are defined and identified as the exact physical quantities whose leading order perturbation representations are the usual acoustic energy density and flux. The conservation equation governing the perturbation energy quantities is shown to yield previously known results for several special cases.

  20. Structural-acoustic optimization of structures excited by turbulent boundary layer flow

    NASA Astrophysics Data System (ADS)

    Shepherd, Micah R.

    In order to reduce noise radiation of aircraft or marine panels, a general structural-acoustic optimization technique is presented. To compute the structural-acoustic response, a modal approach based on finite element / boundary element analysis is used which can easily incorporate fluid loading, added structures and static pre-loads. Simple deterministic or complex random forcing functions are included in the analysis by transforming their cross-spectral density matrices to modal space. Particular emphasis is placed in this dissertation on structures excited by the fluctuating pressures due to turbulent boundary layer (TBL) flow. An efficient frequency-spacing is also used to minimize evaluation time but ensure accuracy. The response from the structural-acoustic analysis is coupled to an evolutionary strategy with covariance matrix adaptation (CMA-ES) to find the best design for low noise and weight. CMA-ES, a stochastic optimizer with robust search properties, samples candidate solutions from a multi-variate normal distribution and adapts the covariance matrix to favor good solutions. The optimization procedure is validated by minimizing the sound radiated by a point-driven ribbed panel and comparing the optimization results to an exhaustive search of the design space. Structural-acoustic optimization is then performed on a curved marine panel with heavy fluid loading excited by slow TBL flow. A weighted combination of noise radiation and mass are minimized by changing the thickness of strips and patches of elements. An uncorrelated pressure approximation is used to estimate the modal force due to TBL flow thus reducing the evaluation time required to compute the objective function. The results show that the best noise reduction is achieved by minimizing the modal acceptance of energy by the panel. This is equivalent to pushing the structural modes away from the peak frequency range of the forcing function. Additionally, the Pareto trade-off curve between total

  1. Flow simulation and analysis of high-power flow batteries

    NASA Astrophysics Data System (ADS)

    Knudsen, E.; Albertus, P.; Cho, K. T.; Weber, A. Z.; Kojic, A.

    2015-12-01

    The cost of a flow battery system can be reduced by increasing its power density and thereby reducing its stack area. If per-pass utilizations are held constant, higher battery power densities can only be achieved using higher flow rates. Here, a 3D computational fluid dynamics model of a flow battery flow field and electrode is used to analyze the implications of increasing flow rates to high power density operating conditions. Interdigitated and serpentine designs, and cell sizes ranging from 10 cm2 to 400 cm2, are simulated. The results quantify the dependence of pressure loss on cell size and design, demonstrating that the details of the passages that distribute flow between individual channels and the inlet and outlet have a major impact on pressure losses in larger cells. Additionally, in-cell flow behavior is analyzed as a function of cell size and design. Flow structures are interrogated to show how and where electrode parameters influence pressure drops, and how regions where transport is slow are correlated with the presence of experimentally observed cell degradation.

  2. Unique flow transitions and particle collection switching phenomena in a microchannel induced by surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Tan, Ming K.; Yeo, Leslie Y.; Friend, James R.

    2010-12-01

    We present an experimental approach for controlled switching between uniform flow for pumping and vortical flow for mixing in a microchannel fabricated onto a piezoelectric substrate. For particle laden fluids, this arrangement permits a choice between transport and alignment of microparticles. Using surface acoustic waves with amplitudes beyond 1 nm, the transition from uniform to mixing flows occurs when the acoustic wavelength in the fluid is reduced to a dimension smaller than the channel width, i.e., λf≥Wch for uniform flow and λfflow. On the other hand, using relatively weak surface acoustic waves with amplitudes below 1 nm, particles in an initially homogeneous suspension agglomerate into equally spaced lines with a separation of λf/2. Switching the transducer between its fundamental resonant frequency f0 and its first harmonic frequency f1+˜2f0 causes a switch between uniform and mixing flow, while switching between large and small amplitude excitation allows one to choose whether to collect the particles in the flow along nodal lines parallel to the channel. These results are uniquely achieved without requiring the microfabrication of complex microchannel architectures and control schemes; the switching is simply achieved by adjusting two parameters: the acoustic excitation frequency and amplitude.

  3. Zonal Flow Velocimetry using Acoustic Modes in Experimental Models of a Planetary Core

    NASA Astrophysics Data System (ADS)

    Adams, M. M.; Mautino, A. R.; Stone, D.; Triana, S. A.; Lekic, V.; Lathrop, D. P.

    2015-12-01

    Rotating hydromagnetic experiments can serve as models of planetary cores, matching some of the dimensionless parameters relevant to planets. One challenge with such experiments is determining the flows present. The opacity of the fluids used in these experiments (e.g. liquid sodium) prevents direct flow visualization techniques from being employed. One method allowing determination of zonal flows in such experiments is acoustic mode velocimetry. In this technique, the rotational splittings of acoustic mode spectra are used to infer the azimuthal velocity profile of the flow. Here we present the use of this technique to study flows in experimental models of the Earth's core. Most of these results were obtained in a 60 cm diameter spherical Couette device, with a 20 cm diameter inner sphere, and using nitrogen gas as the working fluid. Turbulent flow is driven in the system via differential rotation of the outer shell and inner sphere. Acoustic modes are excited in the fluid volume using a speaker, and microphones are used to measure the frequencies and rotational splittings of the modes. We compare the observed splittings with those predicted by theory as a way of validating the method, and infer mean flows from these observations. We also present some preliminary results of acoustic studies in the 3 m diameter liquid sodium spherical Couette experiment. Finally, we discuss future prospects for this experimental technique.

  4. High-power piezoelectric acoustic-electric power feedthru for metal walls

    NASA Astrophysics Data System (ADS)

    Bao, Xiaoqi; Biederman, Will; Sherrit, Stewart; Badescu, Mircea; Bar-Cohen, Yoseph; Jones, Christopher; Aldrich, Jack; Chang, Zensheu

    2008-03-01

    Piezoelectric acoustic-electric power feed-through devices transfer electric power wirelessly through a solid wall using elastic waves. This approach allows for the elimination of the need for holes through structures for cabling or electrical feed-thrus . The technology supplies power to electric equipment inside sealed containers, vacuum or pressure vessels, etc where holes in the wall are prohibitive or may result in significant performance degradation or requires complex designs. In the our previous work, 100-W of electric power was transferred through a metal wall by a small, piezoelectric device with a simple-structure. To meet requirements of higher power applications, the feasibility to transfer kilowatts level power was investigated. Pre-stressed longitudinal piezoelectric feed-thru devices were analyzed by finite element modeling. An equivalent circuit model was developed to predict the characteristics of power transfer to different electric loads. Based on the analytical results, a prototype device was designed, fabricated and successfully demonstrated to transfer electric power at a level of 1-kW. Methods of minimizing plate wave excitation on the wall were also analyzed. Both model analysis and experimental results are presented in detail in this paper.

  5. Acoustic-loads research for powered-lift configurations

    NASA Technical Reports Server (NTRS)

    Schoenster, J. A.; Willis, C. M.; Schroeder, J. C.; Mixson, J. S.

    1976-01-01

    Data presented from large-scale model tests with jet engines having thrusts of 9 kN (2000 lb) and 36 kN (8000 lb) include acoustic loads for an externally blown wing and flap induced by a TF34 jet engine, an upper surface blown (USB) aircraft model in a wind tunnel, and two USB models in static tests. Comparisons of these results with results from acoustic loads studies on configurations of other sizes are made and the implications of these results on interior noise and acoustic fatigue are discussed.

  6. Effect of flow on the acoustic resonances of an open-ended duct

    NASA Technical Reports Server (NTRS)

    Ingard, U.; Singhal, V. K.

    1975-01-01

    The effect of flow on the acoustic resonances of an open-ended, hard-walled duct is analyzed. The flow produces acoustic losses both in the interior of the duct and at the ends. Unless the duct is very long, typically 100 times the diameter, the losses at the ends dominate. At flow Mach numbers in excess of 0.4 the losses are so large that axial duct resonances are almost completely suppressed. The plane-wave Green's function for the duct with flow is expressed in terms of the (experimentally determined) pressure reflection coefficients at the ends of the duct, and the flow dependence of the complex eigenfrequencies of the duct is obtained. Some observations concerning the noise produced by the flow in the duct are also reported.

  7. Flow reversal power limit for the HFBR

    SciTech Connect

    Cheng, Lap Y.; Tichler, P.R.

    1995-10-01

    The High Flux Beam Reactor (HFBR) undergoes a buoyancy-driven reversal of flow in the reactor core following certain postulated accidents. Uncertainties about the afterheat removal capability during the flow reversal has limited the reactor operating power to 30 MW. An experimental and analytical program to address these uncertainties is described in this report. The experiments were single channel flow reversal tests under a range of conditions. The analytical phase involved simulations of the tests to benchmark the physical models and development of a criterion for dryout. The criterion is then used in simulations of reactor accidents to determine a safe operating power level. It is concluded that the limit on the HFBR operating power with respect to the issue of flow reversal is in excess of 60 MW.

  8. Magnetic Amplifier for Power Flow Control

    SciTech Connect

    2012-02-24

    GENI Project: ORNL is developing an electromagnet-based, amplifier-like device that will allow for complete control over the flow of power within the electric grid. To date, complete control of power flow within the grid has been prohibitively expensive. ORNL’s controller could provide a reliable, cost-effective solution to this problem. The team is combining two types of pre-existing technologies to assist in flow control, culminating in a prototype iron-based magnetic amplifier. Ordinarily, such a device would require expensive superconductive wire, but the magnetic iron core of ORNL’s device could serve as a low-cost alternative that is equally adept at regulating power flow.

  9. Numerical and experimental investigation of the acoustic damping effect of single-layer perforated liners with joint bias-grazing flow

    NASA Astrophysics Data System (ADS)

    Zhao, Dan; Ang, Linus; Ji, C. Z.

    2015-04-01

    As one of the most commonly used acoustic dampers, perforated liners are receiving wide spread interest for reducing engine noise and stabilizing combustion systems. Generally, acoustic liner is a cylindrical sheet with perforated orifices fitted along the bounding wall of the combustor. In this work, the damping performances of seven single- and one double-layer perforated liners with different open area ratios are experimentally investigated. For this, a cold-flow pipe with a lined section is designed. Both grazing (mean flow through the pipe) and bias flows (air flow through the perforated holes) are applied and their flow rates are variable. The effects of the open area ratio η, the joint grazing-bias flow and the number of perforated layers on the liner's damping behavior are studied. It is shown experimentally that increasing the liner's open area ratio can increase its damping effect at higher frequency in terms of power absorption. In addition, increasing the grazing flow is shown to reduce the maximum acoustic power absorption, while the bias flow can increase the liners damping effect. Furthermore, the power absorption coefficient is varied periodically over forcing frequency. And the local maximum value is decreased with increased frequency. Comparison is then made between the performance of the single-layer liner and that of double-layer one. It is found that the double-layer liner can increase the damping effect at higher frequency range. In order to simulate the liner damping behavior, a time-domain numerical model is used. It is shown that the liner thickness needs to be considered to correct the predicted damping trend so that the estimated acoustic power absorption agrees well with the measured one over the interested frequency range.

  10. 76 FR 53437 - Free Flow Power Corporation; Northland Power Mississippi River LLC; Notice of Competing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-26

    ... Energy Regulatory Commission Free Flow Power Corporation; Northland Power Mississippi River LLC; Notice... Intervene, and Competing Applications August 18, 2011. On January 11, 2011, Free Flow Power Corporation (Free Flow) and Northland Power Mississippi River LLC (Northland) filed preliminary permit...

  11. An Evaluation of the Additional Acoustic Power Needed to Overcome the Effects of a Test-Article's Absorption During Reverberant Chamber Acoustic Testing of Spaceflight Hardware

    NASA Technical Reports Server (NTRS)

    Hozman, Aron D.; Hughes, William O.

    2014-01-01

    The exposure of a customer's aerospace test-article to a simulated acoustic launch environment is typically performed in a reverberant acoustic test chamber. The acoustic pre-test runs that will ensure that the sound pressure levels of this environment can indeed be met by a test facility are normally performed without a test-article dynamic simulator of representative acoustic absorption and size. If an acoustic test facility's available acoustic power capability becomes maximized with the test-article installed during the actual test then the customer's environment requirement may become compromised. In order to understand the risk of not achieving the customer's in-tolerance spectrum requirement with the test-article installed, an acoustic power margin evaluation as a function of frequency may be performed by the test facility. The method for this evaluation of acoustic power will be discussed in this paper. This method was recently applied at the NASA Glenn Research Center Plum Brook Station's Reverberant Acoustic Test Facility for the SpaceX Falcon 9 Payload Fairing acoustic test program.

  12. An Evaluation of the Additional Acoustic Power Needed to Overcome the Effects of a Test-Article's Absorption during Reverberant Chamber Acoustic Testing of Spaceflight Hardware

    NASA Technical Reports Server (NTRS)

    Hozman, Aron D.; Hughes, William O.

    2014-01-01

    The exposure of a customers aerospace test-article to a simulated acoustic launch environment is typically performed in a reverberant acoustic test chamber. The acoustic pre-test runs that will ensure that the sound pressure levels of this environment can indeed be met by a test facility are normally performed without a test-article dynamic simulator of representative acoustic absorption and size. If an acoustic test facilitys available acoustic power capability becomes maximized with the test-article installed during the actual test then the customers environment requirement may become compromised. In order to understand the risk of not achieving the customers in-tolerance spectrum requirement with the test-article installed, an acoustic power margin evaluation as a function of frequency may be performed by the test facility. The method for this evaluation of acoustic power will be discussed in this paper. This method was recently applied at the NASA Glenn Research Center Plum Brook Stations Reverberant Acoustic Test Facility for the SpaceX Falcon 9 Payload Fairing acoustic test program.

  13. Wall pressure fluctuations and acoustics in turbulent pipe flow

    NASA Astrophysics Data System (ADS)

    Daniels, M. A.; Lauchle, G. C.

    1986-09-01

    Measurements of the turbulent boundary layer (TBL) wall pressure spectrum and the facility's propagating acoustic field were conducted in the Boundary Layer Research Facility. Subminiature, piezoresistive-type pressure transducers were used. Detailed calibration of the pressure transducers was performed using a standing wave tube. Measured sensitivities of the transducers were within 0.5 dB of factory specifications and measured phase differences between individual transducers were insignificant. The TBL wall pressure spectrum was obtained using a novel signal-processing technique that allowed a minimization of both acoustic and vibration-induced noise. This technique uses pairs of transducer difference signals from an exisymmetric array of three flush-mounted pressure sensors and permits cancellation of the propagating acoustic and vibrationally induced pressure fields. A measurement involving the coherence function between these transducer signals was shown to validate the measured TBL wall pressure spectra and all assumptions used in developing the measurement technique. Non-dimensionalized spectra of the TBL fluctuating wall pressure measured in this investigation are compared to those measured previously. These comparisons substantiated a maximum, normalized transducer diameter for the complete resolution of the high-frequency part of the TBL wall pressure spectrum.

  14. Numerical Analysis of the Acoustic Field of Tip-Clearance Flow

    NASA Astrophysics Data System (ADS)

    Alavi Moghadam, S. M.; M. Meinke Team; W. Schröder Team

    2015-11-01

    Numerical simulations of the acoustic field generated by a shrouded axial fan are studied by a hybrid fluid-dynamics-acoustics method. In a first step, large-eddy simulations are performed to investigate the dynamics of tip clearance flow for various tip gap sizes and to determine the acoustic sources. The simulations are performed for a single blade out of five blades with periodic boundary conditions in the circumferential direction on a multi-block structured mesh with 1.4 ×108 grid points. The turbulent flow is simulated at a Reynolds number of 9.36 ×105 at undisturbed inflow condition and the results are compared with experimental data. The diameter and strength of the tip vortex increase with the tip gap size, while simultaneously the efficiency of the fan decreases. In a second step, the acoustic field on the near field is determined by solving the acoustic perturbation equations (APE) on a mesh for a single blade consisting of approx. 9.8 ×108 grid points. The overall agreement of the pressure spectrum and its directivity with measurements confirm the correct identification of the sound sources and accurate prediction of the acoustic duct propagation. The results show that the longer the tip gap size the higher the broadband noise level. Senior Scientist, Institute of Aerodynamics, RWTH Aachen University.

  15. Apparatus and method for acoustic monitoring of steam quality and flow

    DOEpatents

    Sinha, Dipen N.; Pantea, Cristian

    2016-09-13

    An apparatus and method for noninvasively monitoring steam quality and flow and in pipes or conduits bearing flowing steam, are described. By measuring the acoustic vibrations generated in steam-carrying conduits by the flowing steam either by direct contact with the pipe or remotely thereto, converting the measured acoustic vibrations into a frequency spectrum characteristic of the natural resonance vibrations of the pipe, and monitoring the amplitude and/or the frequency of one or more chosen resonance frequencies, changes in the steam quality in the pipe are determined. The steam flow rate and the steam quality are inversely related, and changes in the steam flow rate are calculated from changes in the steam quality once suitable calibration curves are obtained.

  16. Experimental Validation of Numerical Simulations for an Acoustic Liner in Grazing Flow

    NASA Technical Reports Server (NTRS)

    Tam, Christopher K. W.; Pastouchenko, Nikolai N.; Jones, Michael G.; Watson, Willie R.

    2013-01-01

    A coordinated experimental and numerical simulation effort is carried out to improve our understanding of the physics of acoustic liners in a grazing flow as well our computational aeroacoustics (CAA) method prediction capability. A numerical simulation code based on advanced CAA methods is developed. In a parallel effort, experiments are performed using the Grazing Flow Impedance Tube at the NASA Langley Research Center. In the experiment, a liner is installed in the upper wall of a rectangular flow duct with a 2 inch by 2.5 inch cross section. Spatial distribution of sound pressure levels and relative phases are measured on the wall opposite the liner in the presence of a Mach 0.3 grazing flow. The computer code is validated by comparing computed results with experimental measurements. Good agreements are found. The numerical simulation code is then used to investigate the physical properties of the acoustic liner. It is shown that an acoustic liner can produce self-noise in the presence of a grazing flow and that a feedback acoustic resonance mechanism is responsible for the generation of this liner self-noise. In addition, the same mechanism also creates additional liner drag. An estimate, based on numerical simulation data, indicates that for a resonant liner with a 10% open area ratio, the drag increase would be about 4% of the turbulent boundary layer drag over a flat wall.

  17. Applications of digital holography in visualized measurement of acoustic and flow fields

    NASA Astrophysics Data System (ADS)

    Zhao, Jianlin; Li, Enpu; Sun, Weiwei; Di, Jianglei

    2010-03-01

    Digital holography allows recording the hologram using digitally imaging devices such as CCD, and reconstructing the holographic image by numerically simulating the diffraction of the hologram. Its main advantages are by which one can directly obtain the complex amplitude distribution of the object field, so that more impersonally measure the detail information of the object field, such as the distribution of the refractive index changing in crystals induced by light irradiation, deformation of the object surface, particle distribution, as well as acoustic field, flow field and temperature distribution in air. In this paper, we summarize the principle and some of our experimental results on the applications of digital holography in visualized measurement of acoustic standing wave (acoustic levitation field), plasma plume and water flow (Karman vortex street) fields.

  18. Applications of digital holography in visualized measurement of acoustic and flow fields

    NASA Astrophysics Data System (ADS)

    Zhao, Jianlin; Li, Enpu; Sun, Weiwei; di, Jianglei

    2009-12-01

    Digital holography allows recording the hologram using digitally imaging devices such as CCD, and reconstructing the holographic image by numerically simulating the diffraction of the hologram. Its main advantages are by which one can directly obtain the complex amplitude distribution of the object field, so that more impersonally measure the detail information of the object field, such as the distribution of the refractive index changing in crystals induced by light irradiation, deformation of the object surface, particle distribution, as well as acoustic field, flow field and temperature distribution in air. In this paper, we summarize the principle and some of our experimental results on the applications of digital holography in visualized measurement of acoustic standing wave (acoustic levitation field), plasma plume and water flow (Karman vortex street) fields.

  19. Dust acoustic vortices in an inhomogeneous quantum magnetoplasma with dissipation and sheared dust flows

    NASA Astrophysics Data System (ADS)

    Masood, W.; Mirza, Arshad M.; Nargis, Shahida

    2008-10-01

    Linear and nonlinear properties of quantum dust acoustic waves are studied in a nonuniform, dissipative quantum plasma with sheared dust flow parallel to the ambient magnetic field, using the quantum hydrodynamic model. It is shown that the shear dust flow parallel to the external magnetic field can drive the quantum dust-acoustic wave unstable provided it has a negative slope. Stationary solutions of the nonlinear equations that govern the quantum dust-acoustic waves are also obtained. It is found that electrostatic monopolar, dipolar, and vortex street-type solutions can appear in such a plasma. It is observed that the inclusion of dust, quantum statistical, and Bohm potential terms significantly modify the scale lengths of these nonlinear structures. The relevance of the present investigation with regard to the dense astrophysical environments is also pointed out.

  20. Acoustics

    NASA Technical Reports Server (NTRS)

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

  1. A low order flow/acoustics interaction method for the prediction of sound propagation using 3D adaptive hybrid grids

    SciTech Connect

    Kallinderis, Yannis; Vitsas, Panagiotis A.; Menounou, Penelope

    2012-07-15

    A low-order flow/acoustics interaction method for the prediction of sound propagation and diffraction in unsteady subsonic compressible flow using adaptive 3-D hybrid grids is investigated. The total field is decomposed into the flow field described by the Euler equations, and the acoustics part described by the Nonlinear Perturbation Equations. The method is shown capable of predicting monopole sound propagation, while employment of acoustics-guided adapted grid refinement improves the accuracy of capturing the acoustic field. Interaction of sound with solid boundaries is also examined in terms of reflection, and diffraction. Sound propagation through an unsteady flow field is examined using static and dynamic flow/acoustics coupling demonstrating the importance of the latter.

  2. Comparison of acoustic and conventional flow measurement techniques at the Raccoon Mountain Pumped-Storage Plant: Final report

    SciTech Connect

    March, P.A.; Missimer, J.R.; Voss, A.; Pearson, H.S.

    1987-08-01

    The Electric Power Research Institute (EPRI) initiated a research project to evaluate the technical and economic feasibility of using the acoustic method of flow measurement in hydroelectric power plant efficiency tests. As a portion of this program, the Tennessee Valley Authority's (TVA) Raccoon Mountain Pumped-Storage Plant was chosen as one of the sites to be tested. The primary objective of the TVA test was to compare the measurements of the Ocean Research Engineering (ORE), acoustic flowmeter installed on Unit 1 to the Volumetric and Winter-Kennedy Techniques for flow measurement. The Winter-Kennedy Technique is the standard flow measurement technique used in the plant. The Volumetric Technique consisted of accurate measurement of the upper reservoir volume over specified time increments. For calibration, the upper reservoir was initially drained and as it was being filled, aerial photographs were taken to obtain contour lines which were correlated with simultaneous stage measurements. The photographs were used to compute the differential volume of the reservoir associated with a change in stage. Six performance tests were conducted on Unit 1. During the tests no other units were operated. Five tests were conducted in the generating mode and one test was conducted in the pumping mode. The uncertainty in the measurements using the Volumetric Technique is of the order of 0.5 percent for changes of stage elevation in excess of two feet. The flowrate measured by the ORE acoustic flowmeter was consistently of the order of 1.5 percent lower than the flowrate determined from the Volumetric Technique in both the generating and pumping modes. 3 refs., 32 figs., 14 tabs.

  3. Stabilized Acoustic Levitation of Dense Materials Using a High-Powered Siren

    NASA Technical Reports Server (NTRS)

    Gammell, P. M.; Croonquist, A.; Wang, T. G.

    1982-01-01

    Stabilized acoustic levitation and manipulation of dense (e.g., steel) objects of 1 cm diameter, using a high powered siren, was demonstrated in trials that investigated the harmonic content and spatial distribution of the acoustic field, as well as the effect of sample position and reflector geometries on the acoustic field. Although further optimization is possible, the most stable operation achieved is expected to be adequate for most containerless processing applications. Best stability was obtained with an open reflector system, using a flat lower reflector and a slightly concave upper one. Operation slightly below resonance enhances stability as this minimizes the second harmonic, which is suspected of being a particularly destabilizing influence.

  4. Acoustic intensity-based method for sound radiations in a uniform flow.

    PubMed

    Yu, Chao; Zhou, Zhengfang; Zhuang, Mei

    2009-11-01

    An acoustic intensity-based method (AIBM) is extended and verified for predicting sound radiation in a subsonic uniform flow. The method assumes that the acoustic propagation is governed by the modified Helmholtz equation on and outside of a control surface, which encloses all the noise sources and nonlinear effects. With acoustic pressure derivative and its co-located acoustic pressure as input from an open control surface, the unique solution of the modified Helmholtz equation is obtained by solving the least squares problem. The AIBM is coupled with near-field Computational Fluid Dynamics (CFD)/Computational Aeroacoustics (CAA) methods to predict sound radiation of model aeroacoustic problems. The effectiveness of this hybrid approach has been demonstrated by examples of both tonal and broadband noise. Since the AIBM method is stable and accurate based on the input acoustic data from an open surface in a radiated field, it is therefore advantageous for the far-field prediction of aerodynamics noise propagation when an acoustic input from a closed control surface, like the Ffowcs Williams-Hawkings surface, is not available [Philos. Trans. R. Soc. London, Ser. A 264, 321-342 (1969)]. PMID:19894800

  5. Acoustic Characterization of Axial Flow Left Ventricular Assist Device Operation In Vitro and In Vivo.

    PubMed

    Yost, Gardner L; Royston, Thomas J; Bhat, Geetha; Tatooles, Antone J

    2016-01-01

    The use of left ventricular assist devices (LVADs), implantable pumps used to supplement cardiac output, has become an increasingly common and effective treatment for advanced heart failure. Although modern continuous-flow LVADs improve quality of life and survival more than medical management of heart failure, device malfunction remains a common concern. Improved noninvasive methods for assessment of LVAD function are needed to detect device complications. An electronic stethoscope was used to record sounds from the HeartMate II axial flow pump in vitro and in vivo. The data were then uploaded to a computer and analyzed using two types of acoustic analysis software. Left ventricular assist device acoustics were quantified and were related to pump speed, acoustic environment, and inflow and outflow graft patency. Peak frequency values measured in vivo were found to correlate strongly with both predicted values and in vitro measurements (r > 0.999). Plots of the area under the acoustic spectrum curve, obtained by integrating over 50 Hz increments, showed strong correlations between in vivo and in vitro measurements (r > 0.966). Device thrombosis was found to be associated with reduced LVAD acoustic amplitude in two patients who underwent surgical device exchange.

  6. Acoustic Characterization of Axial Flow Left Ventricular Assist Device Operation In Vitro and In Vivo.

    PubMed

    Yost, Gardner L; Royston, Thomas J; Bhat, Geetha; Tatooles, Antone J

    2016-01-01

    The use of left ventricular assist devices (LVADs), implantable pumps used to supplement cardiac output, has become an increasingly common and effective treatment for advanced heart failure. Although modern continuous-flow LVADs improve quality of life and survival more than medical management of heart failure, device malfunction remains a common concern. Improved noninvasive methods for assessment of LVAD function are needed to detect device complications. An electronic stethoscope was used to record sounds from the HeartMate II axial flow pump in vitro and in vivo. The data were then uploaded to a computer and analyzed using two types of acoustic analysis software. Left ventricular assist device acoustics were quantified and were related to pump speed, acoustic environment, and inflow and outflow graft patency. Peak frequency values measured in vivo were found to correlate strongly with both predicted values and in vitro measurements (r > 0.999). Plots of the area under the acoustic spectrum curve, obtained by integrating over 50 Hz increments, showed strong correlations between in vivo and in vitro measurements (r > 0.966). Device thrombosis was found to be associated with reduced LVAD acoustic amplitude in two patients who underwent surgical device exchange. PMID:26536535

  7. Flow-excited acoustic resonances of coaxial side-branches in an annular duct

    NASA Astrophysics Data System (ADS)

    Arthurs, D.; Ziada, S.

    2009-01-01

    This paper investigates the aeroacoustic response of an annular duct with closed coaxial side-branches, and examines the effect of several passive countermeasures on the resonance intensity. The investigated geometry is inspired by the design of the Roll-Posts in the Rolls-Royce LiftSystem® engine, which is currently being developed for the Lockheed Martin Joint Strike Fighter (JSF®) aircraft. The effects of design parameters, such as diameter ratio, branch length ratio and thickness of the annular flow on the frequency and resonance intensity of the first acoustic mode are studied experimentally. Numerical simulations of the acoustic mode shapes and frequencies are also performed. The annular flow has been found to excite several acoustic modes, the strongest in all cases being the first acoustic mode, which consists of a quarter wavelength along the length of each branch. The ratios of the branch length and diameter, with respect to the main duct diameter, have been found to have strong effects on the frequency of the acoustic modes.

  8. Assessment of and Improvements to Acoustic Velocimetry in Flows in Core-like Geometries

    NASA Astrophysics Data System (ADS)

    Mautino, A. R.; Adams, M. M.; Stone, D.; Triana, S. A.; Lathrop, D. P.; Lekic, V.

    2015-12-01

    Rapidly rotating fluid flows are found in a wide variety of geophysical and astrophysical contexts, including the Earth's outer core. The dynamics of such flows can be studied experimentally at conditions inaccessible to computational modeling. However, accurately measuring the mean and time-varying flows noninvasively presents a technical challenge, particularly in opaque liquids. In this study, we tackle the problem of mapping zonal flow profiles in spherical Couette flows, shear flows in a core-like geometry. These rotating flows induce shifts and splittings in the spectrum of the acoustically resonant fluid-filled cavity. The azimuthal component of flow can be estimated from the spectra of the acoustic modes, using inversion procedures adapted from Helioseismology. Here, we present a technique for reconstructing the mean velocity field using modal analysis by way of the Finite Element Method, which is used to compute the forward model accurately, taking into account structural geometries associated with the experimental setups, such as shafts and axles. Accurate forward modeling is crucial for reliable mode identification, and we demonstrate that it allows us to identify many more modes than is possible when using the spherically symmetric approximation. We model flow geometry as a superposition of low order basis flow patterns, each of which affects mode frequency splittings and shifts through advection and Coriolis forces.

  9. Acoustic power measurement of high-intensity focused ultrasound transducer using a pressure sensor.

    PubMed

    Zhou, Yufeng

    2015-03-01

    The acoustic power of high-intensity focused ultrasound (HIFU) is an important parameter that should be measured prior to each treatment to guarantee effective and safe outcomes. A new calibration technique was developed that involves estimating the pressure distribution, calculating the acoustic power using an underwater pressure blast sensor, and compensating the contribution of harmonics to the acoustic power. The output of a clinical extracorporeal HIFU system (center frequency of ~1 MHz, p+ = 2.5-57.2 MPa, p(-) = -1.8 to -13.9 MPa, I(SPPA) = 513-22,940 W/cm(2), -6 dB size of 1.6 × 10 mm: lateral × axial) was measured using this approach and then compared with that obtained using a radiation force balance. Similarities were found between each method at acoustic power ranging from 18.2 W to 912 W with an electrical-to-acoustic conversion efficiency of ~42%. The proposed method has advantages of low weight, smaller size, high sensitivity, quick response, high signal-to-noise ratio (especially at low power output), robust performance, and easy operation of HIFU exposimetry measurement.

  10. Acoustic power measurement of high-intensity focused ultrasound transducer using a pressure sensor.

    PubMed

    Zhou, Yufeng

    2015-03-01

    The acoustic power of high-intensity focused ultrasound (HIFU) is an important parameter that should be measured prior to each treatment to guarantee effective and safe outcomes. A new calibration technique was developed that involves estimating the pressure distribution, calculating the acoustic power using an underwater pressure blast sensor, and compensating the contribution of harmonics to the acoustic power. The output of a clinical extracorporeal HIFU system (center frequency of ~1 MHz, p+ = 2.5-57.2 MPa, p(-) = -1.8 to -13.9 MPa, I(SPPA) = 513-22,940 W/cm(2), -6 dB size of 1.6 × 10 mm: lateral × axial) was measured using this approach and then compared with that obtained using a radiation force balance. Similarities were found between each method at acoustic power ranging from 18.2 W to 912 W with an electrical-to-acoustic conversion efficiency of ~42%. The proposed method has advantages of low weight, smaller size, high sensitivity, quick response, high signal-to-noise ratio (especially at low power output), robust performance, and easy operation of HIFU exposimetry measurement. PMID:25659300

  11. Acoustically Induced Streaming Flows near a Model Cod Otolith and their Potential Implications for Fish Hearing

    SciTech Connect

    Kotas, Charlotte W; Rogers, Peter; Yoda, Minami

    2011-01-01

    The ears of fishes are remarkable sensors for the small acoustic disturbances associated with underwater sound. For example, each ear of the Atlantic cod (Gadus morhua) has three dense bony bodies (otoliths) surrounded by fluid and tissue, and detects sounds at frequencies from 30 to 500 Hz. Atlantic cod have also been shown to localize sounds. However, how their ears perform these functions is not fully understood. Steady streaming, or time-independent, flows near a 350% scale model Atlantic cod otolith immersed in a viscous fluid were studied to determine if these fluid flows contain acoustically relevant information that could be detected by the ear s sensory hair cells. The otolith was oscillated sinusoidally at various orientations at frequencies of 8 24 Hz, corresponding to an actual frequency range of 280 830 Hz. Phaselocked particle pathline visualizations of the resulting flows give velocity, vorticity, and rate of strain fields over a single plane of this mainly two-dimensional flow. Although the streaming flows contain acoustically relevant information, the displacements due to these flows are likely too small to explain Atlantic cod hearing abilities near threshold. The results, however, may suggest a possible mechanism for detection of ultrasound in some fish species.

  12. Flow-excited acoustic resonance of a Helmholtz resonator: Discrete vortex model compared to experiments

    SciTech Connect

    Dai, Xiwen; Jing, Xiaodong Sun, Xiaofeng

    2015-05-15

    The acoustic resonance in a Helmholtz resonator excited by a low Mach number grazing flow is studied theoretically. The nonlinear numerical model is established by coupling the vortical motion at the cavity opening with the cavity acoustic mode through an explicit force balancing relation between the two sides of the opening. The vortical motion is modeled in the potential flow framework, in which the oscillating motion of the thin shear layer is described by an array of convected point vortices, and the unsteady vortex shedding is determined by the Kutta condition. The cavity acoustic mode is obtained from the one-dimensional acoustic propagation model, the time-domain equivalent of which is given by means of a broadband time-domain impedance model. The acoustic resistances due to radiation and viscous loss at the opening are also taken into account. The physical processes of the self-excited oscillations, at both resonance and off-resonance states, are simulated directly in the time domain. Results show that the shear layer exhibits a weak flapping motion at the off-resonance state, whereas it rolls up into large-scale vortex cores when resonances occur. Single and dual-vortex patterns are observed corresponding to the first and second hydrodynamic modes. The simulation also reveals different trajectories of the two vortices across the opening when the first and second hydrodynamic modes co-exist. The strong modulation of the shed vorticity by the acoustic feedback at the resonance state is demonstrated. The model overestimates the pressure pulsation amplitude by a factor 2, which is expected to be due to the turbulence of the flow which is not taken into account. The model neglects vortex shedding at the downstream and side edges of the cavity. This will also result in an overestimation of the pulsation amplitude.

  13. Flow-excited acoustic resonance of a Helmholtz resonator: Discrete vortex model compared to experiments

    NASA Astrophysics Data System (ADS)

    Dai, Xiwen; Jing, Xiaodong; Sun, Xiaofeng

    2015-05-01

    The acoustic resonance in a Helmholtz resonator excited by a low Mach number grazing flow is studied theoretically. The nonlinear numerical model is established by coupling the vortical motion at the cavity opening with the cavity acoustic mode through an explicit force balancing relation between the two sides of the opening. The vortical motion is modeled in the potential flow framework, in which the oscillating motion of the thin shear layer is described by an array of convected point vortices, and the unsteady vortex shedding is determined by the Kutta condition. The cavity acoustic mode is obtained from the one-dimensional acoustic propagation model, the time-domain equivalent of which is given by means of a broadband time-domain impedance model. The acoustic resistances due to radiation and viscous loss at the opening are also taken into account. The physical processes of the self-excited oscillations, at both resonance and off-resonance states, are simulated directly in the time domain. Results show that the shear layer exhibits a weak flapping motion at the off-resonance state, whereas it rolls up into large-scale vortex cores when resonances occur. Single and dual-vortex patterns are observed corresponding to the first and second hydrodynamic modes. The simulation also reveals different trajectories of the two vortices across the opening when the first and second hydrodynamic modes co-exist. The strong modulation of the shed vorticity by the acoustic feedback at the resonance state is demonstrated. The model overestimates the pressure pulsation amplitude by a factor 2, which is expected to be due to the turbulence of the flow which is not taken into account. The model neglects vortex shedding at the downstream and side edges of the cavity. This will also result in an overestimation of the pulsation amplitude.

  14. Determination of an equivalent pore size from acoustic flow measurements

    NASA Astrophysics Data System (ADS)

    Clark, Linde; Liu, Jin; Garrett, Steven

    2005-09-01

    The hydraulic radius, rh, is defined as the ratio of a channel's cross-sectional area to its perimeter. This parameter is important for specification of the performance of a porous medium that can be used as a regenerator in a Stirling engine or refrigerator. It is easy to calculate rh for pores of regular geometry, but difficult in more complex media. Two techniques which use oscillating flow to determine this parameter will be presented and compared. One technique extracts rh by finding the low velocity limit of the standard expression for viscous pressure drop in the Poiseuille flow regime. The other involves a plot of the nondimensional viscous flow resistance, Δpvis/Δxωρu, versus the reciprocal of the viscous penetration depth, 1/δν, in the laminar flow regime. When rh<δν, the flow behavior is frequency independent and the dynamics is characterized by rh only. When rh>δν, the flow resistance is frequency dependent and the dynamics is characterized by both rh and δν. It is possible to identify an effective hydraulic radius by equating it to the value of δν where that transition occurs. [Work supported by ONR.

  15. Velocity phase encoded MRI of gas flow in the acoustic boundary layer

    NASA Astrophysics Data System (ADS)

    Archibald, Geoffrey

    This thesis explores the use of magnetic resonance imaging (MRI) to study acoustic oscillations of a gas in a cylindrical tube. It describes experiments performed under conditions where the gas is in the Acoustic Viscous Boundary Layer and its flow is laminar. Velocity maps acquired at discrete phases of the acoustic oscillation are presented, and are compared with thermoacoustic theory. This represents the first time that such information has been obtained using MRI. An important component of the work reported in this thesis involves the design, construction, and characterization of an acousto-mechanical resonator (AMR). This device can drive oscillatory gas motion and impose density variations at rates that are compatible with MRI data acquisition. To date it has been operated at frequencies ranging from 0.7 Hz to 1.65 Hz and with peak gas displacement amplitudes of up to 2.5 cm. The AMR is based on a modular design intended to permit the study of acoustic flow through a variety of different structures and under a variety of different conditions. MRI experiments were performed on a mixture of thermally-polarized 3He and O2. The latter is used to increase the 3He longitudinal nuclear relaxation rate T1 --1 to a value comparable to the acoustic frequency. In turn, measurements of T1 --1 provide a means for determining the precise composition of the gas mixture. Velocity phase-encoding techniques were then used to map acoustic flow fields: A bipolar magnetic field gradient pulse inserted into the imaging sequence stores velocity information in the phase of the complex image data. The MRI pulse sequence is synchronized with the periodic motion of the gas so that the velocity measurement can be performed at discrete and well-defined phases of the acoustic cycle. These non-invasive flow imaging experiments provide information that is complementary to that which can be obtained from other gas velocity probes, and may lead to new opportunities in the study of acoustic

  16. Method and apparatus for acoustically monitoring the flow of suspended solid particulate matter

    DOEpatents

    Roach, Paul D.; Raptis, Apostolos C.

    1982-01-01

    A method and apparatus for monitoring char flow in a coal gasifier system cludes flow monitor circuits which measure acoustic attenuation caused by the presence of char in a char line and provide a char flow/no flow indication and an indication of relative char density. The flow monitor circuits compute the ratio of signals in two frequency bands, a first frequency band representative of background noise, and a second higher frequency band in which background noise is attenuated by the presence of char. Since the second frequency band contains higher frequencies, the ratio can be used to provide a flow/no flow indication. The second band can also be selected so that attenuation is monotonically related to particle concentration, providing a quantitative measure of char concentration.

  17. Energy flow for electric power system deregulation

    NASA Astrophysics Data System (ADS)

    Lin, Chia-Hung

    Over the past few years, the electric power utility industry in North America and other countries has experienced a strong drive towards deregulation. People have considered the necessity of deregulation of electric utilities for higher energy efficiency and energy saving. The vertically integrated monopolistic industry is being transferred into a horizontally integrated competitive structure in some countries. Wheeling charges are a current high priority problem throughout the power industry, for independent power producers, as well as regulators. Nevertheless the present transmission pricing mechanism fails to be adjusted by a customer loading condition. Customer loading is dynamic, but the present wheeling charge method is fixed, not real-time. A real-time wheeling charge method is developed in this dissertation. This dissertation introduces a concept of a power flow network which can be used for the calculation of power contribution factors in a network. The contribution factor is defined as the ratio of the power contributed by a particular source to a line flow or bus load to the total output of the source. Generation, transmission, and distribution companies can employ contribution factors for the calculation of energy cost, wheeling charges, and loss compensation. Based on the concept of contribution factors, a proposed loss allocation method is developed in this dissertation. Besides, counterflow condition will be given a credit in the proposed loss allocation method. A simple 22-bus example was used for evaluating the contribution factors, proposed wheeling charge method, and loss allocation method.

  18. 77 FR 2288 - Free Flow Power Corporation and Northland Power Mississippi River LLC; Notice Announcing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-17

    ... Energy Regulatory Commission Free Flow Power Corporation and Northland Power Mississippi River LLC... by Free Flow Power Corporation for Project No. 12817-002, and Northland Power Mississippi River LLC.... Davis, Sr., Deputy Secretary. BILLING CODE 6717-01-P...

  19. Acoustic mapping of diffuse flow at a seafloor hydrothermal site: Monolith Vent, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Rona, P. A.; Jackson, D. R.; Wen, T.; Jones, C.; Mitsuzawa, K.; Bemis, K. G.; Dworski, J. G.

    Diffuse flow of hydrothermal solutions commonly occurs in patchy areas up to tens of meters in diameter in seafloor hydrothermal fields. It is recognized as a quantitatively significant component of thermal and chemical fluxes, yet is elusive to map. We report a new acoustic method to detect and map areas of diffuse flow using phase-coherent correlation techniques. The sonar system was modified to record phase information and mounted on DSV SEA CLIFF. The submersible occupied a stationary position on the seafloor and the transducer scanned the seafloor surrounding Monolith Vent, a sulfide edifice venting black smokers, at a nominal range of 17 m at a depth of 2249 m on the Juan de Fuca Ridge. Patchy areas of uncorrelated returns clearly stood out from a background of returns that exhibited ping-to-ping correlation. The areas of uncorrelated returns coincided with areas of diffuse flow as mapped by a video survey with the Navy's Advanced Tethered Vehicle (ATV). Correlated returns were backscattered from invariant seafloor. Uncorrelated returns were distorted by index of refraction inhomogeneities as they passed through diffuse flow between the seafloor and the transducer. The acoustic method presented can synoptically map areas of diffuse flow. When combined with standard in situ measurement and sampling methods the acoustic mapping will facilitate accurate determination of diffuse thermal and chemical fluxes in seafloor hydrothermal fields.

  20. Flow reversal power limit for the HFBR

    SciTech Connect

    Cheng, L.Y.; Tichler, P.R.

    1997-01-01

    The High Flux Beam Reactor (HFBR) is a pressurized heavy water moderated and cooled research reactor that began operation at 40 MW. The reactor was subsequently upgraded to 60 MW and operated at that level for several years. The reactor undergoes a buoyancy-driven reversal of flow in the reactor core following certain postulated accidents. Questions which were raised about the afterheat removal capability during the flow reversal transition led to a reactor shutdown and subsequent resumption of operation at a reduced power of 30 MW. An experimental and analytical program to address these questions is described in this report. The experiments were single channel flow reversal tests under a range of conditions. The analytical phase involved simulations of the tests to benchmark the physical models and development of a criterion for dryout. The criterion is then used in simulations of reactor accidents to determine a safe operating power level. It is concluded that the limit on the HFBR operating power with respect to the issue of flow reversal is in excess of 60 MW. Direct use of the experimental results and an understanding of the governing phenomenology supports this conclusion.

  1. Tracking Energy Flow Using a Volumetric Acoustic Intensity Imager (VAIM)

    NASA Technical Reports Server (NTRS)

    Klos, Jacob; Williams, Earl G.; Valdivia, Nicolas P.

    2006-01-01

    A new measurement device has been invented at the Naval Research Laboratory which images instantaneously the intensity vector throughout a three-dimensional volume nearly a meter on a side. The measurement device consists of a nearly transparent spherical array of 50 inexpensive microphones optimally positioned on an imaginary spherical surface of radius 0.2m. Front-end signal processing uses coherence analysis to produce multiple, phase-coherent holograms in the frequency domain each related to references located on suspect sound sources in an aircraft cabin. The analysis uses either SVD or Cholesky decomposition methods using ensemble averages of the cross-spectral density with the fixed references. The holograms are mathematically processed using spherical NAH (nearfield acoustical holography) to convert the measured pressure field into a vector intensity field in the volume of maximum radius 0.4 m centered on the sphere origin. The utility of this probe is evaluated in a detailed analysis of a recent in-flight experiment in cooperation with Boeing and NASA on NASA s Aries 757 aircraft. In this experiment the trim panels and insulation were removed over a section of the aircraft and the bare panels and windows were instrumented with accelerometers to use as references for the VAIM. Results show excellent success at locating and identifying the sources of interior noise in-flight in the frequency range of 0 to 1400 Hz. This work was supported by NASA and the Office of Naval Research.

  2. A Computational Study of the Flow Physics of Acoustic Liners

    NASA Technical Reports Server (NTRS)

    Tam, Christopher

    2006-01-01

    The present investigation is a continuation of a previous joint project between the Florida State University and the NASA Langley Research Center Liner Physics Team. In the previous project, a study of acoustic liners, in two dimensions, inside a normal incidence impedance tube was carried out. The study consisted of two parts. The NASA team was responsible for the experimental part of the project. This involved performing measurements in an impedance tube with a large aspect ratio slit resonator. The FSU team was responsible for the computation part of the project. This involved performing direct numerical simulation (DNS) of the NASA experiment in two dimensions using CAA methodology. It was agreed that upon completion of numerical simulation, the computed values of the liner impedance were to be sent to NASA for validation with experimental results. On following this procedure good agreements were found between numerical results and experimental measurements over a wide range of frequencies and sound-pressure-level. Broadband incident sound waves were also simulated numerically and measured experimentally. Overall, good agreements were also found.

  3. Acoustic geometry through perturbation of mass accretion rate: radial flow in static spacetimes

    NASA Astrophysics Data System (ADS)

    Ananda, Deepika B.; Bhattacharya, Sourav; Das, Tapas K.

    2015-09-01

    In this work we present an alternative derivation of the general relativistic acoustic analogue geometry by perturbing the mass accretion rate or flux of an ideal fluid flowing radially in a general static and spherically symmetric spacetime. To the best of our knowledge, this has so far been done in non-relativistic scenario. The resulting causal structure of the two dimensional acoustic geometry is qualitatively similar to that one derives via the perturbation of the velocity potential. Using this, we then briefly discuss the stability issues by studying the wave configurations generated by the perturbation of the mass accretion rate, and formally demonstrate the stability of the accretion process. This is in qualitative agreement with earlier results on stability, established via study of wave configurations generated by the perturbation of velocity potential, by using the acoustic geometry associated with it. We further discuss explicit examples of the Schwarzschild and Rindler spacetimes.

  4. An Evaluation of the Additional Acoustic Power Needed to Overcome the Effects of a Test-Articles Absorption During Reverberant Chamber Acoustic Testing of Spaceflight Hardware

    NASA Technical Reports Server (NTRS)

    Hozman, Aron D.; Hughes, William O.

    2014-01-01

    It is important to realize that some test-articles may have significant sound absorption that may challenge the acoustic power capabilities of a test facility. Therefore, to mitigate this risk of not being able to meet the customers target spectrum, it is prudent to demonstrate early-on an increased acoustic power capability which compensates for this test-article absorption. This paper describes a concise method to reduce this risk when testing aerospace test-articles which have significant absorption. This method was successfully applied during the SpaceX Falcon 9 Payload Fairing acoustic test program at the NASA Glenn Research Center Plum Brook Stations RATF.

  5. Isentropic acoustic propagation in a viscous fluid with uniform circular pipeline flow.

    PubMed

    Chen, Yong; Huang, Yiyong; Chen, Xiaoqian

    2013-10-01

    Isentropic wave propagation in a viscous fluid with a uniform mean flow confined by a rigid-walled circular pipeline is considered. A method based on the Fourier-Bessel theory, which is complete and orthogonal in Lebesgue space, is introduced to solve the convected acoustic equations. After validating the method's convergence, the cut-off frequency of wave modes is addressed. Furthermore, the effect of flow profile on wave attenuation is analyzed. Meanwhile, measurement performance of an ultrasonic flow meter based on wave propagation is numerically accounted.

  6. Isentropic acoustic propagation in a viscous fluid with uniform circular pipeline flow.

    PubMed

    Chen, Yong; Huang, Yiyong; Chen, Xiaoqian

    2013-10-01

    Isentropic wave propagation in a viscous fluid with a uniform mean flow confined by a rigid-walled circular pipeline is considered. A method based on the Fourier-Bessel theory, which is complete and orthogonal in Lebesgue space, is introduced to solve the convected acoustic equations. After validating the method's convergence, the cut-off frequency of wave modes is addressed. Furthermore, the effect of flow profile on wave attenuation is analyzed. Meanwhile, measurement performance of an ultrasonic flow meter based on wave propagation is numerically accounted. PMID:24116397

  7. Topologically protected one-way edge mode in networks of acoustic resonators with circulating air flow

    NASA Astrophysics Data System (ADS)

    Ni, Xu; He, Cheng; Sun, Xiao-Chen; Liu, Xiao-ping; Lu, Ming-Hui; Feng, Liang; Chen, Yan-Feng

    2015-05-01

    Recent explorations of topology in physical systems have led to a new paradigm of condensed matters characterized by topologically protected states and phase transition, for example, topologically protected photonic crystals enabled by magneto-optical effects. However, in other wave systems such as acoustics, topological states cannot be simply reproduced due to the absence of similar magnetics-related sound-matter interactions in naturally available materials. Here, we propose an acoustic topological structure by creating an effective gauge magnetic field for sound using circularly flowing air in the designed acoustic ring resonators. The created gauge magnetic field breaks the time-reversal symmetry, and therefore topological properties can be designed to be nontrivial with non-zero Chern numbers and thus to enable a topological sonic crystal, in which the topologically protected acoustic edge-state transport is observed, featuring robust one-way propagation characteristics against a variety of topological defects and impurities. Our results open a new venue to non-magnetic topological structures and promise a unique approach to effective manipulation of acoustic interfacial transport at will.

  8. Flow topology and acoustic emissions of trailing edge serrations at incidence

    NASA Astrophysics Data System (ADS)

    Arce León, Carlos; Ragni, Daniele; Pröbsting, Stefan; Scarano, Fulvio; Madsen, Jesper

    2016-05-01

    The flow past a NACA 0018 airfoil with sawtooth trailing edge serrations has been investigated using stereoscopic particle image velocimetry (PIV). The serration flap angle and airfoil incidence are varied in order to study the effect of secondary flow establishing between the suction and pressure sides of the serrations. The flow topology around the serrations is inferred from the analysis of time-averaged streamlines close to the airfoil surface and from the wall-normal flow velocity in between serrations. Additional PIV measurements with a plane in cross-flow highlight the formation of streamwise vortex pairs. The flow behavior is further characterized in terms of its turbulence statistics. Noise emissions are measured with an acoustic phased array in combination with beamforming. The serrations are found to be effective in reducing noise, and their application is studied for different degrees of airfoil incidence and serration flap angle.

  9. Optimal TCSC placement for optimal power flow

    NASA Astrophysics Data System (ADS)

    Lakdja, Fatiha; Zohra Gherbi, Fatima; Berber, Redouane; Boudjella, Houari

    2012-11-01

    Very few publications have been focused on the mathematical modeling of Flexible Alternating Current Transmission Systems (FACTS) -devices in optimal power flow analysis. A Thyristor Controlled Series Capacitors (TCSC) model has been proposed, and the model has been implemented in a successive QP. The mathematical models for TCSC have been established, and the Optimal Power Flow (OPF) problem with these FACTS-devices is solved by Newtons method. This article employs the Newton- based OPF-TCSC solver of MATLAB Simulator, thus it is essential to understand the development of OPF and the suitability of Newton-based algorithms for solving OPF-TCSC problem. The proposed concept was tested and validated with TCSC in twenty six-bus test system. Result shows that, when TCSC is used to relieve congestion in the system and the investment on TCSC can be recovered, with a new and original idea of integration.

  10. Characterization of acoustic droplet vaporization for control of bubble generation under flow conditions.

    PubMed

    Kang, Shih-Tsung; Huang, Yi-Luan; Yeh, Chih-Kuang

    2014-03-01

    This study investigated the manipulation of bubbles generated by acoustic droplet vaporization (ADV) under clinically relevant flow conditions. Optical microscopy and high-frequency ultrasound imaging were used to observe bubbles generated by 2-MHz ultrasound pulses at different time points after the onset of ADV. The dependence of the bubble population on droplet concentration, flow velocity, fluid viscosity and acoustic parameters, including acoustic pressure, pulse duration and pulse repetition frequency, was investigated. The results indicated that post-ADV bubble growth spontaneously driven by air permeation markedly affected the bubble population after insonation. The bubbles can grow to a stable equilibrium diameter as great as twice the original diameter in 0.5-1 s, as predicted by the theoretical calculation. The growth trend is independent of flow velocity, but dependent on fluid viscosity and droplet concentration, which directly influence the rate of gas uptake by bubbles and the rate of gas exchange across the wall of the semipermeable tube containing the bubbles and, hence, the gas content of the host medium. Varying the acoustic pressure does not markedly change the formation of bubbles as long as the ADV thresholds of most droplets are reached. Varying pulse duration and pulse repetition frequency markedly reduces the number of bubbles. Lengthening pulse duration favors the production of large bubbles, but reduces the total number of bubbles. Increasing the PRF interestingly provides superior performance in bubble disruption. These results also suggest that an ADV bubble population cannot be assessed simply on the basis of initial droplet size or enhancement of imaging contrast by the bubbles. Determining the optimal acoustic parameters requires careful consideration of their impact on the bubble population produced for different application scenarios.

  11. Acoustic monitoring of gas emissions from the seafloor. Part I: quantifying the volumetric flow of bubbles

    NASA Astrophysics Data System (ADS)

    Leblond, Isabelle; Scalabrin, Carla; Berger, Laurent

    2014-09-01

    Three decades of continuous ocean exploration have led us to identify subsurface fluid related processes as a key phenomenon in marine earth science research. The number of seep areas located on the seafloor has been constantly increasing with the use of multi-scale imagery techniques. Due to recent advances in transducer technology and computer processing, multibeam echosounders are now commonly used to detect submarine gas seeps escaping from the seafloor into the water column. A growing number of en- route surveys shows that sites of gas emissions escaping from the seafloor are much more numerous than previously thought. Estimating the temporal variability of the gas flow rate and volumes escaping from the seafloor has thus become a challenge of relevant interest which could be addressed by sea-floor continuous acoustic monitoring. Here, we investigate the feasibility of estimating the volumetric flow rates of gas emissions from horizontal backscattered acoustic signals. Different models based on the acoustic backscattering theory of bubbles are presented. The forward volume backscattering strength and the inversion volumetric flow rate solutions were validated with acoustic measurements from artificial gas flow rates generated in controlled sea-water tank experiments. A sensitivity analysis was carried out to investigate the behavior of the 120-kHz forward solution with respect to model input parameters (horizontal distance between transducer and bubble stream, bubble size distribution and ascent rate). The most sensitive parameter was found to be the distance of the bubble stream which can affect the volume backscattering strength by 20 dB within the horizontal range of 0-200 m. Results were used to derive the detection probability of a bubble stream for a given volume backscattering strength threshold according to different bubble flow rates and horizontal distance.

  12. Convection and fluidization in oscillatory granular flows: The role of acoustic streaming.

    PubMed

    Valverde, Jose Manuel

    2015-06-01

    Convection and fluidization phenomena in vibrated granular beds have attracted a strong interest from the physics community since the last decade of the past century. As early reported by Faraday, the convective flow of large inertia particles in vibrated beds exhibits enigmatic features such as frictional weakening and the unexpected influence of the interstitial gas. At sufficiently intense vibration intensities surface patterns appear bearing a stunning resemblance with the surface ripples (Faraday waves) observed for low-viscosity liquids, which suggests that the granular bed transits into a liquid-like fluidization regime despite the large inertia of the particles. In his 1831 seminal paper, Faraday described also the development of circulation air currents in the vicinity of vibrating plates. This phenomenon (acoustic streaming) is well known in acoustics and hydrodynamics and occurs whenever energy is dissipated by viscous losses at any oscillating boundary. The main argument of the present paper is that acoustic streaming might develop on the surface of the large inertia particles in the vibrated granular bed. As a consequence, the drag force on the particles subjected to an oscillatory viscous flow is notably enhanced. Thus, acoustic streaming could play an important role in enhancing convection and fluidization of vibrated granular beds, which has been overlooked in previous studies. The same mechanism might be relevant to geological events such as fluidization of landslides and soil liquefaction by earthquakes and sound waves. PMID:26123774

  13. Convection and fluidization in oscillatory granular flows: The role of acoustic streaming.

    PubMed

    Valverde, Jose Manuel

    2015-06-01

    Convection and fluidization phenomena in vibrated granular beds have attracted a strong interest from the physics community since the last decade of the past century. As early reported by Faraday, the convective flow of large inertia particles in vibrated beds exhibits enigmatic features such as frictional weakening and the unexpected influence of the interstitial gas. At sufficiently intense vibration intensities surface patterns appear bearing a stunning resemblance with the surface ripples (Faraday waves) observed for low-viscosity liquids, which suggests that the granular bed transits into a liquid-like fluidization regime despite the large inertia of the particles. In his 1831 seminal paper, Faraday described also the development of circulation air currents in the vicinity of vibrating plates. This phenomenon (acoustic streaming) is well known in acoustics and hydrodynamics and occurs whenever energy is dissipated by viscous losses at any oscillating boundary. The main argument of the present paper is that acoustic streaming might develop on the surface of the large inertia particles in the vibrated granular bed. As a consequence, the drag force on the particles subjected to an oscillatory viscous flow is notably enhanced. Thus, acoustic streaming could play an important role in enhancing convection and fluidization of vibrated granular beds, which has been overlooked in previous studies. The same mechanism might be relevant to geological events such as fluidization of landslides and soil liquefaction by earthquakes and sound waves.

  14. The Effects of Surfaces on the Aerodynamics and Acoustics of Jet Flows

    NASA Technical Reports Server (NTRS)

    Smith, Matthew J.; Miller, Steven A. E.

    2013-01-01

    Aircraft noise mitigation is an ongoing challenge for the aeronautics research community. In response to this challenge, low-noise aircraft concepts have been developed that exhibit situations where the jet exhaust interacts with an airframe surface. Jet flows interacting with nearby surfaces manifest a complex behavior in which acoustic and aerodynamic characteristics are altered. In this paper, the variation of the aerodynamics, acoustic source, and far-field acoustic intensity are examined as a large at plate is positioned relative to the nozzle exit. Steady Reynolds-Averaged Navier-Stokes solutions are examined to study the aerodynamic changes in the field-variables and turbulence statistics. The mixing noise model of Tam and Auriault is used to predict the noise produced by the jet. To validate both the aerodynamic and the noise prediction models, results are compared with Particle Image Velocimetry (PIV) and free-field acoustic data respectively. The variation of the aerodynamic quantities and noise source are examined by comparing predictions from various jet and at plate configurations with an isolated jet. To quantify the propulsion airframe aeroacoustic installation effects on the aerodynamic noise source, a non-dimensional number is formed that contains the flow-conditions and airframe installation parameters.

  15. Laminar flame and acoustic waves in two-dimensional flow

    SciTech Connect

    Zaytsev, M. L. Akkerman, V. B.

    2011-03-15

    The complete system of fluid dynamics equations describing the development of instability of a reaction front in a two-dimensional flow in reversed time are reduced to a closed system of equations of front dynamics by using Lagrangian variables and integrals of motion. The system can be used to analyze processes behind the front without solving the complete system of fluid dynamics and chemical kinetics equations. It is demonstrated how the gas density disturbances induced by the moving front can be described in the adiabatic approximation.

  16. Coherent structures in swirling flows and their role in acoustic combustion control

    NASA Astrophysics Data System (ADS)

    Paschereit, Christian Oliver; Gutmark, Ephraim; Weisenstein, Wolfgang

    1999-09-01

    Interaction between flow instabilities and acoustic resonant modes and their effect on heat release were investigated and controlled in an experimental low-emission swirl stabilized combustor. Acoustic boundary conditions of the combustor were modified to excite combustion instability at various axisymmetric and helical unstable modes in a fully premixed combustion. The combustion unstable modes were related to flow instabilities in the recirculating wakelike region on the combustor axis and the separating shear layer at the sudden expansion (dump plane). Flow field measurements were performed in a water tunnel using a simulated combustor configuration. The water tunnel tests demonstrated the existence of several modes of flow instabilities in a highly swirling flow, modes which were shown to affect the combustion process. Mean and turbulent characteristics of the internal and external swirling shear layers were measured and unstable flow modes were identified. Instability modes during combustion were visualized by phase locked images of OH chemiluminescence. The axisymmetric mode showed large variation of the heat release during one cycle, while the helical modes showed variations in the radial location of maximal heat release. Closed loop active control system was employed to suppress the thermoacoustic pressure oscillations and to reduce NOx emissions. Microphone and OH emission detection sensors monitored the combustion process and provided input to the control system. An acoustic source modulated the airflow and thus affected the mixing process and the combustion. Effective suppression of the pressure oscillations and the concomitant reduction of NOx emissions were associated with a reduced coherence of the flow structures which excited the thermoacoustic instability.

  17. Analysis of the STS-126 Flow Control Valve Structural-Acoustic Coupling Failure

    NASA Technical Reports Server (NTRS)

    Jones, Trevor M.; Larko, Jeffrey M.; McNelis, Mark E.

    2010-01-01

    During the Space Transportation System mission STS-126, one of the main engine's flow control valves incurred an unexpected failure. A section of the valve broke off during liftoff. It is theorized that an acoustic mode of the flowing fuel, coupled with a structural mode of the valve, causing a high cycle fatigue failure. This report documents the analysis efforts conducted in an attempt to verify this theory. Hand calculations, computational fluid dynamics, and finite element methods are all implemented and analyses are performed using steady-state methods in addition to transient analysis methods. The conclusion of the analyses is that there is a critical acoustic mode that aligns with a structural mode of the valve

  18. Flow and acoustic properties of low Reynolds number underexpanded supersonic jets

    NASA Technical Reports Server (NTRS)

    Hu, Tieh-Feng; Mclaughlin, D. K.

    1990-01-01

    An experimental program to investigate the flow and acoustic properties of model underexpanded supersonic jets was conducted. In particular, the role played by large-scale organized fluctuations in the flow evolution and acoustic production processes was examined in detail. The experimental conditions were chosen as low-Reynolds-number (Re = 8000) Mach 1.4 and 2.1 underexpanded jets exhausting from convergent nozzles. A consequence of performing the experiments at low Reynolds number is that the broadband shock-associated noise is suppressed. The focus of the present study is on the generation of noise by large-scale instabilities in the presence of strong shock cell structures. It is demonstrated that the production of screech is related to the modulation and decay of large-scale turbulence structures.

  19. Acoustic transmission matrix of a variable area duct or nozzle carrying a compressible subsonic flow

    NASA Technical Reports Server (NTRS)

    Miles, J. H.

    1980-01-01

    The differential equations governing the propagation of sound in a variable area duct or nozzle carrying a one dimensional subsonic compressible fluid flow are derived and put in state variable form using acoustic pressure and particle velocity as the state variables. The duct or nozzle is divided into a number of regions. The region size is selected so that in each region the Mach number can be assumed constant and the area variation can be approximated by an exponential area variation. Consequently, the state variable equation in each region has constant coefficients. The transmission matrix for each region is obtained by solving the constant coefficient acoustic state variable differential equation. The transmission matrix for the duct or nozzle is the product of the individual transmission matrices of each region. Solutions are presented for several geometries with and without mean flow.

  20. Flow patterns and transport in Rayleigh surface acoustic wave streaming: combined finite element method and raytracing numerics versus experiments.

    PubMed

    Frommelt, Thomas; Gogel, Daniel; Kostur, Marcin; Talkner, Peter; Hänggi, Peter; Wixforth, Achim

    2008-10-01

    This work presents an approach for determining the streaming patterns that are generated by Rayleigh surface acoustic waves in arbitrary 3-D geometries by finite element method (FEM) simulations. An efficient raytracing algorithm is applied on the acoustic subproblem to avoid the unbearable memory demands and computational time of a conventional FEM acoustics simulation in 3-D. The acoustic streaming interaction is modeled by a body force term in the Stokes equation. In comparisons between experiments and simulated flow patterns, we demonstrate the quality of the proposed technique. PMID:18986877

  1. Low-frequency acoustic atomization with oscillatory flow around micropillars in a microfluidic device

    SciTech Connect

    Cheung, Yin Nee E-mail: mtnwong@ntu.edu.sg; Wong, Teck Neng E-mail: mtnwong@ntu.edu.sg; Nguyen, Nam Trung

    2014-10-06

    This letter reports a low frequency acoustic atomization technique with oscillatory extensional flow around micropillars. Large droplets passing through two micropillars are elongated. Small droplets are then produced through the pinch-off process at the spindle-shape ends. As the actuation frequency increases, the droplet size decreases with increasing monodispersity. This method is suitable for in-situ mass production of fine droplets in a multi-phase environment without external pumping. Small particles encapsulation was demonstrated with the current technique.

  2. Visualizing flow fields using acoustic Doppler current profilers and the Velocity Mapping Toolbox

    USGS Publications Warehouse

    Jackson, P. Ryan

    2013-01-01

    The purpose of this fact sheet is to provide examples of how the U.S. Geological Survey is using acoustic Doppler current profilers for much more than routine discharge measurements. These instruments are capable of mapping complex three-dimensional flow fields within rivers, lakes, and estuaries. Using the Velocity Mapping Toolbox to process the ADCP data allows detailed visualization of the data, providing valuable information for a range of studies and applications.

  3. Experimental investigation of flow induced dust acoustic shock waves in a complex plasma

    NASA Astrophysics Data System (ADS)

    Jaiswal, S.; Bandyopadhyay, P.; Sen, A.

    2016-08-01

    We report on experimental observations of flow induced large amplitude dust-acoustic shock waves in a complex plasma. The experiments have been carried out in a Π shaped direct current glow discharge experimental device using kaolin particles as the dust component in a background of Argon plasma. A strong supersonic flow of the dust fluid is induced by adjusting the pumping speed and neutral gas flow into the device. An isolated copper wire mounted on the cathode acts as a potential barrier to the flow of dust particles. A sudden change in the gas flow rate is used to trigger the onset of high velocity dust acoustic shocks whose dynamics are captured by fast video pictures of the evolving structures. The physical characteristics of these shocks are delineated through a parametric scan of their dynamical properties over a range of flow speeds and potential hill heights. The observed evolution of the shock waves and their propagation characteristics are found to compare well with model numerical results based on a modified Korteweg-de-Vries-Burgers type equation.

  4. Topics in structural dynamics: Nonlinear unsteady transonic flows and Monte Carlo methods in acoustics

    NASA Technical Reports Server (NTRS)

    Haviland, J. K.

    1974-01-01

    The results are reported of two unrelated studies. The first was an investigation of the formulation of the equations for non-uniform unsteady flows, by perturbation of an irrotational flow to obtain the linear Green's equation. The resulting integral equation was found to contain a kernel which could be expressed as the solution of the adjoint flow equation, a linear equation for small perturbations, but with non-constant coefficients determined by the steady flow conditions. It is believed that the non-uniform flow effects may prove important in transonic flutter, and that in such cases, the use of doublet type solutions of the wave equation would then prove to be erroneous. The second task covered an initial investigation into the use of the Monte Carlo method for solution of acoustical field problems. Computed results are given for a rectangular room problem, and for a problem involving a circular duct with a source located at the closed end.

  5. Investigation of coherent structures generated by acoustic tube in turbulent flow separation control

    NASA Astrophysics Data System (ADS)

    Ma, Xingyu; Geisler, Reinhard; Agocs, Janos; Schröder, Andreas

    2015-02-01

    An acoustic tube was designed in order to control the turbulent flow separation downstream of a backward-facing step. The Reynolds number based on the free-stream velocity and the step height was Re h = 2.0 × 104. As an active flow control device, the acoustic tube generated periodic pressure perturbations at a frequency of f a = 100 Hz, which was close to the most amplified frequency of the shedding instability of the turbulent shear layer. Spanwise vortices rolled up due to the perturbations. 2D-2C particle image velocimetry was used to measure separated shear layer and the reattachment area downstream of the BFS. The flow control results show that the acoustic tube can suppress recirculation regions behind the step and reduce the reattachment length by 43.7 %. The roll-up and pairing processes of the vortices lead to an increase in the total Reynolds shear stress. The coherent structures are extracted by proper orthogonal decomposition and represented by two pairs of modes, of which the coherence is analyzed by the corresponding coefficients. Both the primary and secondary series of vortices are reconstructed as traveling waves with the fundamental frequency f a and the overtone frequency 2 f a, respectively.

  6. Sound propagation in and radiation from acoustically lined flow ducts: A comparison of experiment and theory

    NASA Technical Reports Server (NTRS)

    Plumblee, H. E., Jr.; Dean, P. D.; Wynne, G. A.; Burrin, R. H.

    1973-01-01

    The results of an experimental and theoretical study of many of the fundamental details of sound propagation in hard wall and soft wall annular flow ducts are reported. The theory of sound propagation along such ducts and the theory for determining the complex radiation impedance of higher order modes of an annulus are outlined, and methods for generating acoustic duct modes are developed. The results of a detailed measurement program on propagation in rigid wall annular ducts with and without airflow through the duct are presented. Techniques are described for measuring cut-on frequencies, modal phase speed, and radial and annular mode shapes. The effects of flow velocity on cut-on frequencies and phase speed are measured. Comparisons are made with theoretical predictions for all of the effects studies. The two microphone method of impedance is used to measure the effects of flow on acoustic liners. A numerical study of sound propagation in annular ducts with one or both walls acoustically lined is presented.

  7. Research on power-law acoustic transient signal detection based on wavelet transform

    NASA Astrophysics Data System (ADS)

    Han, Jian-hui; Yang, Ri-jie; Wang, Wei

    2007-11-01

    Aiming at the characteristics of acoustic transient signal emitted from antisubmarine weapon which is being dropped into water (torpedo, aerial sonobuoy and rocket assisted depth charge etc.), such as short duration, low SNR, abruptness and instability, based on traditional power-law detector, a new method to detect acoustic transient signal is proposed. Firstly wavelet transform is used to de-noise signal, removes random spectrum components and improves SNR. Then Power- Law detector is adopted to detect transient signal. The simulation results show the method can effectively extract envelop characteristic of transient signal on the condition of low SNR. The performance of WT-Power-Law markedly outgoes that of traditional Power-Law detection method.

  8. 77 FR 3761 - Free Flow Power Corporation, Northland Power Mississippi River LLC; Notice Announcing Filing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-25

    ... Energy Regulatory Commission Free Flow Power Corporation, Northland Power Mississippi River LLC; Notice..., the order of priority is as follows: 1. Free Flow Power Corporation; Project No. 12817-002. 2..., Sr., Deputy Secretary. BILLING CODE 6717-01-P...

  9. Influence of ultrasound power on acoustic streaming and micro-bubbles formations in a low frequency sono-reactor: mathematical and 3D computational simulation.

    PubMed

    Sajjadi, Baharak; Raman, Abdul Aziz Abdul; Ibrahim, Shaliza

    2015-05-01

    This paper aims at investigating the influence of ultrasound power amplitude on liquid behaviour in a low-frequency (24 kHz) sono-reactor. Three types of analysis were employed: (i) mechanical analysis of micro-bubbles formation and their activities/characteristics using mathematical modelling. (ii) Numerical analysis of acoustic streaming, fluid flow pattern, volume fraction of micro-bubbles and turbulence using 3D CFD simulation. (iii) Practical analysis of fluid flow pattern and acoustic streaming under ultrasound irradiation using Particle Image Velocimetry (PIV). In mathematical modelling, a lone micro bubble generated under power ultrasound irradiation was mechanistically analysed. Its characteristics were illustrated as a function of bubble radius, internal temperature and pressure (hot spot conditions) and oscillation (pulsation) velocity. The results showed that ultrasound power significantly affected the conditions of hotspots and bubbles oscillation velocity. From the CFD results, it was observed that the total volume of the micro-bubbles increased by about 4.95% with each 100 W-increase in power amplitude. Furthermore, velocity of acoustic streaming increased from 29 to 119 cm/s as power increased, which was in good agreement with the PIV analysis.

  10. Surface acoustic wave induced particle manipulation in a PDMS channel--principle concepts for continuous flow applications.

    PubMed

    Johansson, Linda; Enlund, Johannes; Johansson, Stefan; Katardjiev, Ilia; Yantchev, Ventsislav

    2012-04-01

    A device for acoustic particle manipulation in the 40 MHz range for continuous-flow operation in a 50 μm wide PDMS channel has been evaluated. Unidirectional interdigital transducers on a Y-cut Z-propagation lithium nixobate wafer were used to excite a surface acoustic wave that generated an acoustic standing wave inside the microfluidic channel. It was shown that particle alignment nodes with different inter-node spacing could be obtained, depending on device design and driving frequency. The observed inter-node spacing differed from the standard half-wavelength inter-node spacing generally employed in bulk acoustic transducer excited resonant systems. This effect and the related issue of acoustic node positions relative the channel walls, which is fundamental for most continuous flow particle manipulation operations in channels, was evaluated in measurements and simulations. Specific applications of particle separation and alignment where these systems can offer benefits relative state-of the art designs were identified.

  11. Pressure Measurement in Supersonic Air Flow by Differential Absorptive Laser-Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Hart, Roger C.; Herring, Gregory C.; Balla, Robert J.

    2007-01-01

    Nonintrusive, off-body flow barometry in Mach-2 airflow has been demonstrated in a large-scale supersonic wind tunnel using seedless laser-induced thermal acoustics (LITA). The static pressure of the gas flow is determined with a novel differential absorption measurement of the ultrasonic sound produced by the LITA pump process. Simultaneously, stream-wise velocity and static gas temperature of the same spatially-resolved sample volume were measured with this nonresonant time-averaged LITA technique. Mach number, temperature and pressure have 0.2%, 0.4%, and 4% rms agreement, respectively, in comparison with known free-stream conditions.

  12. Measurement of the flow velocity in unmagnetized plasmas by counter propagating ion-acoustic waves

    SciTech Connect

    Ma, J.X.; Li Yangfang; Xiao Delong; Li Jingju; Li Yiren

    2005-06-15

    The diffusion velocity of an inhomogeneous unmagnetized plasma is measured by means of the phase velocities of ion-acoustic waves propagating along and against the direction of the plasma flow. Combined with the measurement of the plasma density distributions by usual Langmuir probes, the method is applied to measure the ambipolar diffusion coefficient and effective ion collision frequency in inhomogeneous plasmas formed in an asymmetrically discharged double-plasma device. Experimental results show that the measured flow velocities, diffusion coefficients, and effective collision frequencies are in agreement with ion-neutral collision dominated diffusion theory.

  13. Acoustic noise from volcanoes - Theory and experiment

    NASA Technical Reports Server (NTRS)

    Woulff, G.; Mcgetchin, T. R.

    1976-01-01

    The paper discusses some theoretical aspects of acoustic investigation of volcanoes and describes a field experiment involving the recording, analysis, and interpretation of acoustic radiation from energetic fumaroles at Volcan Acatenango, Guatemala, during mid-January 1973. Particular attention is given to deriving information about the flow velocity of the erupting medium from acoustics as a means to study eruption dynamics. Theoretical considerations suggest that acoustic power radiated during gaseous volcanic eruptions may be related to gas exit velocity according to appropriate power laws. Eruption acoustics proves useful as a means of quantitative monitoring of volcanic activity.

  14. Acoustic radiation damping of flat rectangular plates subjected to subsonic flows

    NASA Technical Reports Server (NTRS)

    Lyle, Karen Heitman

    1993-01-01

    The acoustic radiation damping for various isotropic and laminated composite plates and semi-infinite strips subjected to a uniform, subsonic and steady flow has been predicted. The predictions are based on the linear vibration of a flat plate. The fluid loading is characterized as the perturbation pressure derived from the linearized Bernoulli and continuity equations. Parameters varied in the analysis include Mach number, mode number and plate size, aspect ratio and mass. The predictions are compared with existing theoretical results and experimental data. The analytical results show that the fluid loading can significantly affect realistic plate responses. Generally, graphite/epoxy and carbon/carbon plates have higher acoustic radiation damping values than similar aluminum plates, except near plate divergence conditions resulting from aeroelastic instability. Universal curves are presented where the acoustic radiation damping normalized by the mass ratio is a linear function of the reduced frequency. A separate curve is required for each Mach number and plate aspect ratio. In addition, acoustic radiation damping values can be greater than or equal to the structural component of the modal critical damping ratio (assumed as 0.01) for the higher subsonic Mach numbers. New experimental data were acquired for comparison with the analytical results.

  15. Free jet feasibility study of a thermal acoustic shield concept for AST/VCE application-dual flow. Comprehensive data report. Volume 1: Test nozzles and acoustic data

    NASA Technical Reports Server (NTRS)

    Janardan, B. A.; Brausch, J. F.; Price, A. O.

    1984-01-01

    Acoustic and diagnostic data that were obtained to determine the influence of selected geometric and aerodynamic flow variables of coannular nozzles with thermal acoustic shields are summarized in this comprehensive data report. A total of 136 static and simulated flight acoustic test points were conducted with 9 scale-model nozzles The tested nozzles included baseline (unshielded), 180 deg shielded, and 360 deg shielded dual flow coannular plug configurations. The baseline configurations include a high radius ratio unsuppressed coannular plug nozzle and a coanuular plug nozzle and a coannular plug nozzle with a 20-chute outer stream suppressor. The tests were conducted at nozzle temperatures and pressure typical of operating conditions of variable cycle engine.

  16. Distributed Power Flow Control: Distributed Power Flow Control using Smart Wires for Energy Routing

    SciTech Connect

    2012-04-24

    GENI Project: Smart Wire Grid is developing a solution for controlling power flow within the electric grid to better manage unused and overall transmission capacity. The 300,000 miles of high-voltage transmission line in the U.S. today are congested and inefficient, with only around 50% of all transmission capacity utilized at any given time. Increased consumer demand should be met in part with more efficient and an economical power flow. Smart Wire Grid’s devices clamp onto existing transmission lines and control the flow of power within—much like how internet routers help allocate bandwidth throughout the web. Smart wires could support greater use of renewable energy by providing more consistent control over how that energy is routed within the grid on a real-time basis. This would lessen the concerns surrounding the grid’s inability to effectively store intermittent energy from renewables for later use.

  17. Flow and acoustic field due to an inclined plate with a downstream splitter

    NASA Technical Reports Server (NTRS)

    Kim, C. M.; Conlisk, A. T.

    1993-01-01

    In the present work, the high Reynolds number flow past an inclined plate with a splitter plate placed in its wake is considered numerically. A numerical conformal mapping technique is employed to transform the two-plate system into the same number of cylinders: the flow field is assumed to be two-dimensional. The vortex shedding from the inclined plate is modelled using the discrete vortex method. It is shown that the splitter plate has a profound effect on the development of the flow over a range of values of a suitably defined offset parameter and for a range of positions of the leading edge of the splitter plate. The acoustic field is also calculated and the spectrum reflects the flow results.

  18. Effect of acoustic coupling on power-law flame acceleration in spherical confinement

    NASA Astrophysics Data System (ADS)

    Akkerman, V'yacheslav; Law, Chung K.

    2013-01-01

    A model describing acoustically-generated parametric instability in a spherical chamber is developed for quasi-one-dimensional, low-Mach number flames. We demonstrate how sound waves generated by a centrally-ignited, outwardly-propagating accelerating flamefront can be incorporated into an existing theory of self-similar flame acceleration in free space [V. Akkerman, C. K. Law, and V. Bychkov, "Self-similar accelerative propagation of expanding wrinkled flames and explosion triggering," Phys. Rev. E 83, 026305 (2011)], 10.1103/PhysRevE.83.026305. Being reflected from the chamber wall, flame-generated acoustics interact with the flamefront and the attendant hydrodynamic flamefront cellular instability. This in turn affects the subsequent flame morphology and propagation speed. It is shown that the acoustics modify the power-law flame acceleration, concomitantly facilitating or inhibiting the transition to detonation in confinement, which allows reconciliation of a discrepancy in experimental measurements of different groups.

  19. Power Flow Controller for Renewables: Transformer-less Unified Power Flow Controller for Wind and Solar Power Transmission

    SciTech Connect

    2012-02-08

    GENI Project: MSU is developing a power flow controller to improve the routing of electricity from renewable sources through existing power lines. The fast, innovative, and lightweight circuitry that MSU is incorporating into its controller will eliminate the need for a separate heavy and expensive transformer, as well as the construction of new transmission lines. MSU’s controller is better suited to control power flows from distributed and intermittent wind and solar power systems than traditional transformer-based controllers are, so it will help to integrate more renewable energy into the grid. MSU‘s power flow controller can be installed anywhere in the existing grid to optimize energy transmission and help reduce transmission congestion.

  20. Acoustic divergence with gene flow in a lekking hummingbird with complex songs.

    PubMed

    González, Clementina; Ornelas, Juan Francisco

    2014-01-01

    Hummingbirds have developed a remarkable diversity of learned vocalizations, from single-note songs to phonologically and syntactically complex songs. In this study we evaluated if geographic song variation of wedge-tailed sabrewings (Campylopterus curvipennis) is correlated with genetic divergence, and examined processes that explain best the origin of intraspecific song variation. We contrasted estimates of genetic differentiation, genetic structure, and gene flow across leks from microsatellite loci of wedge-tailed sabrewings with measures for acoustic signals involved in mating derived from recordings of males singing at leks throughout eastern Mexico. We found a strong acoustic structure across leks and geography, where lek members had an exclusive assemblage of syllable types, differed in spectral and temporal measurements of song, and song sharing decreased with geographic distance. However, neutral genetic and song divergence were not correlated, and measures of genetic differentiation and migration estimates indicated gene flow across leks. The persistence of acoustic structuring in wedge-tailed sabrewings may thus best be explained by stochastic processes across leks, in which intraspecific vocal variation is maintained in the absence of genetic differentiation by postdispersal learning and social conditions, and by geographical isolation due to the accumulation of small differences, producing most dramatic changes between populations further apart. PMID:25271429

  1. Acoustic Divergence with Gene Flow in a Lekking Hummingbird with Complex Songs

    PubMed Central

    González, Clementina; Ornelas, Juan Francisco

    2014-01-01

    Hummingbirds have developed a remarkable diversity of learned vocalizations, from single-note songs to phonologically and syntactically complex songs. In this study we evaluated if geographic song variation of wedge-tailed sabrewings (Campylopterus curvipennis) is correlated with genetic divergence, and examined processes that explain best the origin of intraspecific song variation. We contrasted estimates of genetic differentiation, genetic structure, and gene flow across leks from microsatellite loci of wedge-tailed sabrewings with measures for acoustic signals involved in mating derived from recordings of males singing at leks throughout eastern Mexico. We found a strong acoustic structure across leks and geography, where lek members had an exclusive assemblage of syllable types, differed in spectral and temporal measurements of song, and song sharing decreased with geographic distance. However, neutral genetic and song divergence were not correlated, and measures of genetic differentiation and migration estimates indicated gene flow across leks. The persistence of acoustic structuring in wedge-tailed sabrewings may thus best be explained by stochastic processes across leks, in which intraspecific vocal variation is maintained in the absence of genetic differentiation by postdispersal learning and social conditions, and by geographical isolation due to the accumulation of small differences, producing most dramatic changes between populations further apart. PMID:25271429

  2. Self-heating study of bulk acoustic wave resonators under high RF power.

    PubMed

    Ivira, Brice; Fillit, René-Yves; Ndagijimana, Fabien; Benech, Philippe; Parat, Guy; Ancey, Pascal

    2008-01-01

    The present work first provides an experimental technique to study self-heating of bulk acoustic wave (BAW) resonators under high RF power in the gigahertz range. This study is specially focused on film bulk acoustic wave resonators and solidly mounted resonators processed onto silicon wafers and designed for wireless systems. Precisely, the reflection coefficient of a one-port device is measured while up to several watts are applied and power leads to electrical drifts of impedances. In the following, we describe how absorbed power can be determined from the incident one in real time. Therefore, an infrared camera held over the radio frequency micro electromechanical system (RF-MEMS) surface with an exceptional spatial resolution reaching up to 2 microm/pixels gives accurate temperature mapping of resonators after emissivity correction. From theoretical point of view, accurate three-dimensional (3-D) structures for finite-element modeling analyses are carried out to know the best materials and architectures to use for enhancing power handling. In both experimental and theoretical investigations, comparison is made between film bulk acoustic wave resonators and solidly mounted resonators. Thus, the trend in term of material, architecture, and size of device for power application such as in transmission path of a transceiver is clearly identified. PMID:18334320

  3. Self-heating study of bulk acoustic wave resonators under high RF power.

    PubMed

    Ivira, Brice; Fillit, René-Yves; Ndagijimana, Fabien; Benech, Philippe; Parat, Guy; Ancey, Pascal

    2008-01-01

    The present work first provides an experimental technique to study self-heating of bulk acoustic wave (BAW) resonators under high RF power in the gigahertz range. This study is specially focused on film bulk acoustic wave resonators and solidly mounted resonators processed onto silicon wafers and designed for wireless systems. Precisely, the reflection coefficient of a one-port device is measured while up to several watts are applied and power leads to electrical drifts of impedances. In the following, we describe how absorbed power can be determined from the incident one in real time. Therefore, an infrared camera held over the radio frequency micro electromechanical system (RF-MEMS) surface with an exceptional spatial resolution reaching up to 2 microm/pixels gives accurate temperature mapping of resonators after emissivity correction. From theoretical point of view, accurate three-dimensional (3-D) structures for finite-element modeling analyses are carried out to know the best materials and architectures to use for enhancing power handling. In both experimental and theoretical investigations, comparison is made between film bulk acoustic wave resonators and solidly mounted resonators. Thus, the trend in term of material, architecture, and size of device for power application such as in transmission path of a transceiver is clearly identified.

  4. Optimal power flow using sequential quadratic programming

    NASA Astrophysics Data System (ADS)

    Nejdawi, Imad M.

    1999-11-01

    Optimal power flow (OPF) is an operational as well as a planning tool used by electric utilities to help them operate their network in the most economic and secure mode of operation. Various algorithms to solve the OPF problem evolved over the past three decades; linear programming (LP) techniques were among the major mathematical programming methods utilized. The linear models of the objective function and the linearization of the constraints are the main features of these techniques. The main advantages of the LP approach are simplicity and speed. Nonlinear programming techniques have been applied to OPF solution. The major drawback is the expensive solution of large sparse systems of equations. This research is concerned with the development of a new OPF solution algorithm using sequential quadratic programming (SQP). In this formulation, a small dense system the size of which is equal to the number of control variables is solved in an inner loop. The Jacobian and Hessian terms are calculated in an outer loop. The total number of outer loop iterations is comparable to those in an ordinary load flow in contrast to 20--30 iterations in other nonlinear methods. In addition, the total number of floating point operations is less than that encountered in direct methods by two orders of magnitude. We also model dispatch over a twenty four-hour time horizon in a transmission constrained power network that includes price-responsive loads where large energy customers can operate their loads in time intervals with lowest spot prices.

  5. Stick-slip instabilities in sheared granular flow: The role of friction and acoustic vibrations.

    PubMed

    Lieou, Charles K C; Elbanna, Ahmed E; Langer, J S; Carlson, J M

    2015-08-01

    We propose a theory of shear flow in dense granular materials. A key ingredient of the theory is an effective temperature that determines how the material responds to external driving forces such as shear stresses and vibrations. We show that, within our model, friction between grains produces stick-slip behavior at intermediate shear rates, even if the material is rate strengthening at larger rates. In addition, externally generated acoustic vibrations alter the stick-slip amplitude, or suppress stick-slip altogether, depending on the pressure and shear rate. We construct a phase diagram that indicates the parameter regimes for which stick-slip occurs in the presence and absence of acoustic vibrations of a fixed amplitude and frequency. These results connect the microscopic physics to macroscopic dynamics and thus produce useful information about a variety of granular phenomena, including rupture and slip along earthquake faults, the remote triggering of instabilities, and the control of friction in material processing.

  6. Acoustic well cleaner

    DOEpatents

    Maki, Jr., Voldi E.; Sharma, Mukul M.

    1997-01-21

    A method and apparatus are disclosed for cleaning the wellbore and the near wellbore region. A sonde is provided which is adapted to be lowered into a borehole and which includes a plurality of acoustic transducers arranged around the sonde. Electrical power provided by a cable is converted to acoustic energy. The high intensity acoustic energy directed to the borehole wall and into the near wellbore region, redissolves or resuspends the material which is reducing the permeability of the formation and/or restricting flow in the wellbore.

  7. Averaged indicators of secondary flow in repeated acoustic Doppler current profiler crossings of bends

    USGS Publications Warehouse

    Dinehart, R.L.; Burau, J.R.

    2005-01-01

    [1] Cross-stream velocity was measured in a large river bend at high spatial resolution over three separate survey episodes. A suite of methods for resolving cross-stream velocity distributions was tested on data collected using acoustic Doppler current profilers (ADCP) in the sand-bedded Sacramento River, California. The bend was surveyed with repeated ADCP crossings at eight cross sections during a rising limb of high discharge in February 2004 and twice on recession in March 2004. By translating and interpolating repeated ADCP crossings to planar grids, velocity ensembles at similar positions along irregular boat paths could be averaged. The averaging minimized turbulent fluctuations in streamwise velocities over 1 m/s, enabling the resolution of weaker cross-stream velocities (???15-30 cm/s). Secondary-flow influence on suspended sediment was inferred from a lateral region of acoustic backscatter intensity aligned with outward flow over the point bar. A near-bed decrease in backscatter intensity across the pool corresponded with inward cross-stream flow. These suspension indicators were used to orient averaged velocity grids for unambiguously defining the cross-stream velocity magnitudes. Additional field investigations could test whether the correlation between cross-stream velocity and backscatter intensity patterns results from helical recirculation of suspended sediment to the inside of the bend. These river measurements, consistent with classic and recent laboratory studies, show that ADCP surveys can provide refined views of secondary flow and sediment movement in large rivers.

  8. Equivalent Relaxations of Optimal Power Flow

    SciTech Connect

    Bose, S; Low, SH; Teeraratkul, T; Hassibi, B

    2015-03-01

    Several convex relaxations of the optimal power flow (OPF) problem have recently been developed using both bus injection models and branch flow models. In this paper, we prove relations among three convex relaxations: a semidefinite relaxation that computes a full matrix, a chordal relaxation based on a chordal extension of the network graph, and a second-order cone relaxation that computes the smallest partial matrix. We prove a bijection between the feasible sets of the OPF in the bus injection model and the branch flow model, establishing the equivalence of these two models and their second-order cone relaxations. Our results imply that, for radial networks, all these relaxations are equivalent and one should always solve the second-order cone relaxation. For mesh networks, the semidefinite relaxation and the chordal relaxation are equally tight and both are strictly tighter than the second-order cone relaxation. Therefore, for mesh networks, one should either solve the chordal relaxation or the SOCP relaxation, trading off tightness and the required computational effort. Simulations are used to illustrate these results.

  9. Evaluation of Acoustic Doppler Current Profiler to Measure Discharge at New York Power Authority's Niagara Power Project, Niagara Falls, New York

    USGS Publications Warehouse

    Zajd, Henry J.

    2007-01-01

    The need for accurate real-time discharge in the International Niagara River hydro power system requires reliable, accurate and reproducible data. The U.S. Geological Survey has been widely using Acoustic Doppler Current Profilers (ADCP) to accurately measure discharge in riverine channels since the mid-1990s. The use of the ADCP to measure discharge has remained largely untested at hydroelectric-generation facilities such as the New York Power Authority's (NYPA) Niagara Power Project in Niagara Falls, N.Y. This facility has a large, engineered diversion channel with the capacity of high volume discharges in excess of 100,000 cubic feet per second (ft3/s). Facilities such as this could benefit from the use of an ADCP, if the ADCP discharge measurements prove to be more time effective and accurate than those obtained from the flow-calculation techniques that are currently used. Measurements of diversion flow by an ADCP in the 'Pant Leg' diversion channel at the Niagara Power Project were made on November 6, 7, and 8, 2006, and compared favorably (within 1 percent) with those obtained concurrently by a conventional Price-AA current-meter measurement during one of the ADCP measurement sessions. The mean discharge recorded during each 2-hour individual ADCP measurement session compared favorably with (3.5 to 6.8 percent greater than) the discharge values computed by the flow-calculation method presently in use by NYPA. The use of ADCP technology to measure discharge could ultimately permit increased power-generation efficiency at the NYPA Niagara Falls Power Project by providing improved predictions of the amount of water (and thus the power output) available.

  10. Estimating oil concentration and flow rate with calibrated vessel-mounted acoustic echo sounders

    PubMed Central

    Weber, Thomas C.; De Robertis, Alex; Greenaway, Samuel F.; Smith, Shep; Mayer, Larry; Rice, Glen

    2012-01-01

    As part of a larger program aimed at evaluating acoustic techniques for mapping the distribution of subsurface oil and gas associated with the Deepwater Horizon-Macondo oil spill, observations were made on June 24 and 25, 2010 using vessel-mounted calibrated single-beam echo sounders on the National Oceanic and Atmospheric Administration ship Thomas Jefferson. Coincident with visual observations of oil at the sea surface, the 200-kHz echo sounder showed anomalously high-volume scattering strength in the upper 200 m on the western side of the wellhead, more than 100 times higher than the surrounding waters at 1,800-m distance from the wellhead, and weakening with increasing distance out to 5,000 m. Similar high-volume scattering anomalies were not observed at 12 or 38 kHz, although observations of anomalously low-volume scattering strength were made in the deep scattering layer at these frequencies at approximately the same locations. Together with observations of ocean currents, the acoustic observations are consistent with a rising plume of small (< 1-mm radius) oil droplets. Using simplistic but reasonable assumptions about the properties of the oil droplets, an estimate of the flow rate was made that is remarkably consistent with those made at the wellhead by other means. The uncertainty in this acoustically derived estimate is high due to lack of knowledge of the size distribution and rise speed of the oil droplets. If properly constrained, these types of acoustic measurements can be used to rapidly estimate the flow rate of oil reaching the surface over large temporal and spatial scales. PMID:22167799

  11. Estimating oil concentration and flow rate with calibrated vessel-mounted acoustic echo sounders.

    PubMed

    Weber, Thomas C; De Robertis, Alex; Greenaway, Samuel F; Smith, Shep; Mayer, Larry; Rice, Glen

    2012-12-11

    As part of a larger program aimed at evaluating acoustic techniques for mapping the distribution of subsurface oil and gas associated with the Deepwater Horizon-Macondo oil spill, observations were made on June 24 and 25, 2010 using vessel-mounted calibrated single-beam echo sounders on the National Oceanic and Atmospheric Administration ship Thomas Jefferson. Coincident with visual observations of oil at the sea surface, the 200-kHz echo sounder showed anomalously high-volume scattering strength in the upper 200 m on the western side of the wellhead, more than 100 times higher than the surrounding waters at 1,800-m distance from the wellhead, and weakening with increasing distance out to 5,000 m. Similar high-volume scattering anomalies were not observed at 12 or 38 kHz, although observations of anomalously low-volume scattering strength were made in the deep scattering layer at these frequencies at approximately the same locations. Together with observations of ocean currents, the acoustic observations are consistent with a rising plume of small (< 1-mm radius) oil droplets. Using simplistic but reasonable assumptions about the properties of the oil droplets, an estimate of the flow rate was made that is remarkably consistent with those made at the wellhead by other means. The uncertainty in this acoustically derived estimate is high due to lack of knowledge of the size distribution and rise speed of the oil droplets. If properly constrained, these types of acoustic measurements can be used to rapidly estimate the flow rate of oil reaching the surface over large temporal and spatial scales. PMID:22167799

  12. Acoustic Absorption Characteristics of an Orifice With a Mean Bias Flow

    NASA Technical Reports Server (NTRS)

    Ahuja, K. K.; Gaeta, R. J., Jr.; DAgostino, M.; Jones, Mike (Technical Monitor)

    2000-01-01

    The objective of the study reported here was to acquire acoustic and flow data for numerical validation of impedance models that simulate bias flow through perforates. The impedance model is being developed by researchers at High Technology Corporation. This report documents normal incidence impedance measurements a singular circular orifice with mean flow passing through it. All measurements are made within a 1.12 inch (28.5 mm) diameter impedance tube. The mean flow is introduced upstream of the orifice (with the flow and incident sound wave travelling in the same direction) with an anechoic termination downstream of the orifice. Velocity profiles are obtained upstream of the orifice to characterize the inflow boundary conditions. Velocity in the center of the orifice is also obtained. All velocity measurements are made with a hot wire anemometer and subsequent checked with mass flow measurements made concurrently. All impedance measurements are made using the Two-Microphone Method. Although we have left the analysis of the data to the developers of the impedance models that simulate bias flow through perforate, our initial examination indicates that our results follow the trends consistent with published theory on impedance of perforates with a steady bias flow.

  13. Acoustic resolution photoacoustic Doppler flowmetry: practical considerations for obtaining accurate measurements of blood flow

    NASA Astrophysics Data System (ADS)

    Brunker, J.; Beard, P.

    2014-03-01

    An assessment has been made of various experimental factors affecting the accuracy of flow velocities measured using a pulsed time correlation photoacoustic Doppler technique. In this method, Doppler time shifts are quantified via crosscorrelation of pairs of photoacoustic waveforms generated in moving absorbers using pairs of laser light pulses, and the photoacoustic waves are detected using an ultrasound transducer. The acoustic resolution mode is employed by using the transducer focal width, rather than the large illuminated volume, to define the lateral spatial resolution. This enables penetration depths of several millimetres or centimetres, unlike methods using the optical resolution mode, which limits the maximum penetration depth to approximately 1 mm. In the acoustic resolution mode, it is difficult to detect time shifts in highly concentrated suspensions of flowing absorbers, such as red blood cell suspensions and whole blood, and this challenge supposedly arises because of the lack of spatial heterogeneity. However, by assessing the effect of different absorption coefficients and tube diameters, we offer an alternative explanation relating to light attenuation and parabolic flow. We also demonstrate a new signal processing method that surmounts the previous problem of measurement under-reading. This method is a form of signal range gating and enables mapping of the flow velocity profile across the tube as well as measurement of the average flow velocity. We show that, using our signal processing scheme, it is possible to measure the flow of whole blood using a relatively low frequency detector. This important finding paves the way for application of the technique to measurements of blood flow several centimetres deep in living tissue.

  14. Using numerical models and volume rendering to interpret acoustic imaging of hydrothermal flow

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Bennett, K.; Takle, J.; Rona, P. A.; Silver, D.

    2009-12-01

    Our acoustic imaging system will be installed onto the Neptune Canada observatory at the Main Endeavour Field, Juan de Fuca Ridge, which is a Ridge 2000 Integrated Study Site. Thereafter, 16-30 Gb of acoustic imaging data will be collected daily. We are developing a numerical model of merging plumes that will be used to guide expectations and volume rendering software that transforms volumetric acoustic data into photo-like images. Hydrothermal flow is modeled as a combination of merged point sources which can be configured in any geometry. The model stipulates the dissipation or dilution of the flow and uses potential fields and complex analysis to combine the entrainment fields produced by each source. The strengths of this model are (a) the ability to handle a variety of scales especially the small scale as the potential fields can be specified with an effectively infinite boundary condition, (b) the ability to handle line, circle and areal source configurations, and (c) the ability to handle both high temperature focused flow and low temperature diffuse flow. This model predicts the vertical and horizontal velocities and the spatial distribution of effluent from combined sources of variable strength in a steady ambient velocity field. To verify the accuracy of the model’s results, we compare the model predictions of plume centerlines for the merging of two relatively strong point sources with the acoustic imaging data collected at Clam Acres, Southwest Vent Field, EPR 21°N in 1990. The two chimneys are 3.5 m apart and the plumes emanating from their tops merge approximately 18 mab. The model is able to predict the height of merging and the bending of the centerlines. Merging is implicitly observed at Grotto Vent, Main Endeavour Field, in our VIP 2000 data from July 2000: although there are at least 5 vigorous black smokers only a single plume is discernable in the acoustic imaging data. Furthermore, the observed Doppler velocity data increases with height

  15. Passive Acoustic Detection of Wind Turbine In-Flow Conditions for Active Control and Optimization

    SciTech Connect

    Murray, Nathan E.

    2012-03-12

    Wind is a significant source of energy; however, the human capability to produce electrical energy still has many hurdles to overcome. One of these is the unpredictability of the winds in the atmospheric boundary layer (ABL). The ABL is highly turbulent in both stable and unstable conditions (based on the vertical temperature profile) and the resulting fluctuations can have a dramatic impact on wind turbine operation. Any method by which these fluctuations could be observed, estimated, or predicted could provide a benefit to the wind energy industry as a whole. Based on the fundamental coupling of velocity fluctuations to pressure fluctuations in the nearly incompressible flow in the ABL, This work hypothesizes that a ground-based array of infrasonic pressure transducers could be employed to estimate the vertical wind profile over a height relevant for wind turbines. To analyze this hypothesis, experiments and field deployments were conducted. Wind tunnel experiments were performed for a thick turbulent boundary layer over a neutral or heated surface. Surface pressure and velocity probe measurements were acquired simultaneously. Two field deployments yielded surface pressure data from a 49 element array. The second deployment at the Reese Technology Center in Lubbock, TX, also included data from a smaller aperture, 96-element array and a 200-meter tall meteorological tower. Analysis of the data successfully demonstrated the ability to estimate the vertical velocity profile using coherence data from the pressure array. Also, dynamical systems analysis methods were successful in identifying and tracking a gust type event. In addition to the passive acoustic profiling method, this program also investigated a rapid response Doppler SODAR system, the optimization of wind turbine blades for enhanced power with reduced aeroacoustic noise production, and the implementation of a wireless health monitoring system for the wind turbine blades. Each of these other objectives

  16. Acoustic characterization of a new trisacryl contrast agent. Part II: Flow phantom study and in vivo quantification.

    PubMed

    Lavisse, Sonia; Peronneau, Pierre; Rouffiac, Valerie; Paci, Angelo; Vigouroux, Julie; Opolon, Paule; Roche, Alain; Lassau, Nathalie

    2008-03-01

    The biocompatible trisacryl particles (TMP) are made of a cross-linked acrylic copolymer. Their inherent acoustic properties, studied for a contrast agent application, have been previously demonstrated in a in vitro Couette device. To measure their acoustic behaviour under circulating blood conditions, the TMP backscatter enhancement was further evaluated on a home-made flow phantom at different TMP doses (0.12-15.6 mg/ml) suspended in aqueous and blood media, and in nude mice (aorta and B16 grafted melanoma). Integrated backscatter (IB) was measured by spectral analysis of the Doppler signals recorded from an ultrasound system (Aplio) combined with a 12-MHz probe. Doppler phantom experiments revealed a maximal IB of 17+/-0.88 dB and 7.5+/-0.7 dB in aqueous and blood media, respectively. IB measured on mice aorta, in pulsed Doppler mode, confirmed a constant maximal value of 7.29+/-1.72 dB over the first minutes after injection of a 7.8 mg/ml TMP suspension. Following the injection, a 60% enhancement of intratumoral vascularization detection was observed in power Doppler mode. A preliminary histological study revealed inert presence of some TMP in lungs 8 and 16 days after injection. Doppler phantom experiments on whole blood allowed to anticipate the in vivo acoustic behaviour. Both protocols demonstrated TMP effectiveness in significantly increasing Doppler signal intensity and intratumoral vascularization detection. However, it was also shown that blood conditions seemed to shadow the TMP contrast effect, as compared to in vitro observations. These results encourage further investigations on the specific TMP targeting and on their bio-distribution in the different tissues.

  17. Design of Low-power Wake-up Circuits in Underwater Acoustic Communication

    NASA Astrophysics Data System (ADS)

    Cuixia, Zhang; Jiaxin, Wu; Yuanxuan, Li

    In underwater acoustic communication, the power consumption of the underwater communication equipments at harsh conditions of marine environment is an important problem. Under that scenario, we propose a design of low-power wake-up circuits based on SCM C8051F020 system. Compare to traditional wake-up circuits which directly judge the energy of received signals, our approach can greatly reduce the misjudgment caused by the environmental disturbance, and the performance of energy conservation is effective. The low-power wake-up circuits possess a promising application prospect in the long-distance wireless underwater communication.

  18. Characteristics of geodesic acoustic mode zonal flow and ambient turbulence at the edge of the HL-2A tokamak plasmas

    SciTech Connect

    Zhao, K. J.; Dong, J. Q.; Yan, L. W.; Hong, W. Y.; Lan, T.; Liu, A. D.; Qian, J.; Cheng, J.; Yu, D. L.; Huang, Y.; He, H. D.; Liu, Yi.; Yang, Q. W.; Duan, X. R.; Song, X. M.; Ding, X. T.; Liu, Y.

    2007-12-15

    The three-dimensional characteristics of the geodesic acoustic mode zonal flows (GAMZFs) and the ambient turbulence (AT) at the edge of the HuanLiuqi-2A tokamak [Y. Liu et al., Nucl. Fusion 45, S203 (2005)] are investigated with Langmuir probe arrays and the results are presented in detail. The toroidal and poloidal symmetries, and the radial scale of the GAMZFs are simultaneously identified. The envelopes of the high frequency components of the AT in the presence of the GAMZFs are analyzed. The GAM frequency components (GAMFCs) of the coherent envelopes are also shown to have poloidal and toroidal symmetries, and similar radial scales as the GAMZF does. The correlation between the GAMFCs of the envelopes and the GAMs is high, with phase shifts between {pi}/2 to {pi}, indicating that the GAMZFs may regulate the AT and the regulation is embodied in the envelopes. Three-wave coupling between GAM and AT is found to be a plausible formation mechanism for the former, which acts on the whole spectra of the latter within its scale length. The temporal evolutions of the total fluctuation power, the GAM and the AT powers show that the AT power decreases when GAM power increases and vice versa, indicating possible regulating effects of the latter on the former.

  19. Transition and acoustic response of recirculation structures in an unconfined co-axial isothermal swirling flow

    NASA Astrophysics Data System (ADS)

    Santhosh, R.; Miglani, Ankur; Basu, Saptarshi

    2013-08-01

    This paper reports the first observations of transition from a pre-vortex breakdown (Pre-VB) flow reversal to a fully developed central toroidal recirculation zone in a non-reacting, double-concentric swirling jet configuration and its response to longitudinal acoustic excitation. This transition proceeds with the formation of two intermediate, critical flow regimes. First, a partially penetrated vortex breakdown bubble (VBB) is formed that indicates the first occurrence of an enclosed structure as the centre jet penetration is suppressed by the growing outer roll-up eddy; resulting in an opposed flow stagnation region. Second, a metastable transition structure is formed that marks the collapse of inner mixing vortices. In this study, the time-averaged topological changes in the coherent recirculation structures are discussed based on the non-dimensional modified Rossby number (Rom) which appears to describe the spreading of the zone of swirl influence in different flow regimes. Further, the time-mean global acoustic response of pre-VB and VBB is measured as a function of pulsing frequency using the relative aerodynamic blockage factor (i.e., maximum radial width of the inner recirculation zone). It is observed that all flow modes except VBB are structurally unstable as they exhibit severe transverse radial shrinkage (˜20%) at the burner Helmholtz resonant modes (100-110 Hz). In contrast, all flow regimes show positional instability as seen by the large-scale, asymmetric spatial shifting of the vortex core centres. Finally, the mixing transfer function M (f) and magnitude squared coherence λ2(f) analysis is presented to determine the natural coupling modes of the system dynamic parameters (u', p'), i.e., local acoustic response. It is seen that the pre-VB flow mode exhibits a narrow-band, low pass filter behavior with a linear response window of 100-105 Hz. However, in the VBB structure, presence of critical regions such as the opposed flow stagnation region

  20. Acoustic Seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  1. Acoustic seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  2. A GIS-based Computational Tool for Multidimensional Flow Velocity by Acoustic Doppler Current Profilers

    NASA Astrophysics Data System (ADS)

    Kim, D.; Winkler, M.; Muste, M.

    2015-06-01

    Acoustic Doppler Current Profilers (ADCPs) provide efficient and reliable flow measurements compared to other tools for characteristics of the riverine environments. In addition to originally targeted discharge measurements, ADCPs are increasingly utilized to assess river flow characteristics. The newly developed VMS (Velocity Mapping Software) aims at providing an efficient process for quality assurance, mapping velocity vectors for visualization and facilitating comparison with physical and numerical model results. VMS was designed to provide efficient and smooth work flows for processing groups of transects. The software allows the user to select group of files and subsequently to conduct statistical and graphical quality assurance on the files as a group or individually as appropriate. VMS also enables spatial averaging in horizontal and vertical plane for ADCP data in a single or multiple transects over the same or consecutive cross sections. The analysis results are displayed in numerical and graphical formats.

  3. Errors in acoustic doppler profiler velocity measurements caused by flow disturbance

    USGS Publications Warehouse

    Mueller, D.S.; Abad, J.D.; Garcia, C.M.; Gartner, J.W.; Garcia, M.H.; Oberg, K.A.

    2007-01-01

    Acoustic Doppler current profilers (ADCPs) are commonly used to measure streamflow and water velocities in rivers and streams. This paper presents laboratory, field, and numerical model evidence of errors in ADCP measurements caused by flow disturbance. A state-of-the-art three-dimensional computational fluid dynamic model is validated with and used to complement field and laboratory observations of flow disturbance and its effect on measured velocities. Results show that near the instrument, flow velocities measured by the ADCP are neither the undisturbed stream velocity nor the velocity of the flow field around the ADCP. The velocities measured by the ADCP are biased low due to the downward flow near the upstream face of the ADCP and upward recovering flow in the path of downstream transducer, which violate the flow homogeneity assumption used to transform beam velocities into Cartesian velocity components. The magnitude of the bias is dependent on the deployment configuration, the diameter of the instrument, and the approach velocity, and was observed to range from more than 25% at 5cm from the transducers to less than 1% at about 50cm from the transducers for the scenarios simulated. ?? 2007 ASCE.

  4. Turbofan Acoustic Propagation and Radiation

    NASA Technical Reports Server (NTRS)

    Eversman, Walter

    2000-01-01

    This document describes progress in the development of finite element codes for the prediction of near and far field acoustic radiation from the inlet and aft fan ducts of turbofan engines. The report consists of nine papers which have appeared in archival journals and conference proceedings, or are presently in review for publication. Topics included are: 1. Aft Fan Duct Acoustic Radiation; 2. Mapped Infinite Wave Envelope Elements for Acoustic Radiation in a Uniformly Moving Medium; 3. A Reflection Free Boundary Condition for Propagation in Uniform Flow Using Mapped Infinite Wave Envelope Elements; 4. A Numerical Comparison Between Multiple-Scales and FEM Solution for Sound Propagation in Lined Flow Ducts; 5. Acoustic Propagation at High Frequencies in Ducts; 6. The Boundary Condition at an Impedance Wall in a Nonuniform Duct with Potential Flow; 7. A Reverse Flow Theorem and Acoustic Reciprocity in Compressible Potential Flows; 8. Reciprocity and Acoustics Power in One Dimensional Compressible Potential Flows; and 9. Numerical Experiments on Acoustic Reciprocity in Compressible Potential Flows.

  5. Application of acoustical methods for estimating water flow and constituent loads in Perdido Bay, Florida

    USGS Publications Warehouse

    Grubbs, J.W.; Pittman, J.R.

    1997-01-01

    Water flow and quality data were collected from December 1994 to September 1995 to evaluate variations in discharge, water quality, and chemical fluxes (loads) through Perdido Bay, Florida. Data were collected at a cross section parallel to the U.S. Highway 98 bridge. Discharges measured with an acoustic Doppler current profiler (ADCP) and computed from stage-area and velocity ratings varied roughly between + or - 10,000 cubic feet per second during a typical tidal cycle. Large reversals in flow direction occurred rapidly (less than 1 hour), and complete reversals (resulting in near peak net-upstream or downstream discharges) occurred within a few hours of slack water. Observations of simultaneous upstream and downstream flow (bidirectional flow) were quite common in the ADCP measurements, with opposing directions of flow occurring predominantly in vertical layers. Continuous (every 15 minutes) discharge data were computed for the period from August 18, 1995, to September 28, 1995, and filtered daily mean discharge values were computed for the period from August 19 to September 26, 1995. Data were not computed prior to August 18, 1995, either because of missing data or because the velocity rating was poorly defined (because of insufficient data) for the period prior to landfall of hurricane Erin (August 3, 1995). The results of the study indicate that acoustical techniques can yield useful estimates of continuous (instantaneous) discharge in Perdido Bay. Useful estimates of average daily net flow rates can also be obtained, but the accuracy of these estimates will be limited by small rating shifts that introduce bias into the instantaneous values that are used to compute the net flows. Instantaneous loads of total nitrogen ranged from -180 to 220 grams per second for the samples collected during the study, and instantaneous loads of total phosphorous ranged from -10 to 11 grams per second (negative loads indicate net upstream transport). The chloride concentrations

  6. Streaming flow from ultrasound contrast agents by acoustic waves in a blood vessel model.

    PubMed

    Cho, Eunjin; Chung, Sang Kug; Rhee, Kyehan

    2015-09-01

    To elucidate the effects of streaming flow on ultrasound contrast agent (UCA)-assisted drug delivery, streaming velocity fields from sonicated UCA microbubbles were measured using particle image velocimetry (PIV) in a blood vessel model. At the beginning of ultrasound sonication, the UCA bubbles formed clusters and translated in the direction of the ultrasound field. Bubble cluster formation and translation were faster with 2.25MHz sonication, a frequency close to the resonance frequency of the UCA. Translation of bubble clusters induced streaming jet flow that impinged on the vessel wall, forming symmetric vortices. The maximum streaming velocity was about 60mm/s at 2.25MHz and decreased to 15mm/s at 1.0MHz for the same acoustic pressure amplitude. The effect of the ultrasound frequency on wall shear stress was more noticeable. Maximum wall shear stress decreased from 0.84 to 0.1Pa as the ultrasound frequency decreased from 2.25 to 1.0MHz. The maximum spatial gradient of the wall shear stress also decreased from 1.0 to 0.1Pa/mm. This study showed that streaming flow was induced by bubble cluster formation and translation and was stronger upon sonication by an acoustic wave with a frequency near the UCA resonance frequency. Therefore, the secondary radiant force, which is much stronger at the resonance frequency, should play an important role in UCA-assisted drug delivery.

  7. Parametric and experimental analysis using a power flow approach

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1990-01-01

    A structural power flow approach for the analysis of structure-borne transmission of vibrations is used to analyze the influence of structural parameters on transmitted power. The parametric analysis is also performed using the Statistical Energy Analysis approach and the results are compared with those obtained using the power flow approach. The advantages of structural power flow analysis are demonstrated by comparing the type of results that are obtained by the two analytical methods. Also, to demonstrate that the power flow results represent a direct physical parameter that can be measured on a typical structure, an experimental study of structural power flow is presented. This experimental study presents results for an L shaped beam for which an available solution was already obtained. Various methods to measure vibrational power flow are compared to study their advantages and disadvantages.

  8. Transitioning of power flow in beam models with bends

    NASA Technical Reports Server (NTRS)

    Hambric, Stephen A.

    1990-01-01

    The propagation of power flow through a dynamically loaded beam model with 90 degree bends is investigated using NASTRAN and McPOW. The transitioning of power flow types (axial, torsional, and flexural) is observed throughout the structure. To get accurate calculations of the torsional response of beams using NASTRAN, torsional inertia effects had to be added to the mass matrix calculation section of the program. Also, mass effects were included in the calculation of BAR forces to improve the continuity of power flow between elements. The importance of including all types of power flow in an analysis, rather than only flexural power, is indicated by the example. Trying to interpret power flow results that only consider flexural components in even a moderately complex problem will result in incorrect conclusions concerning the total power flow field.

  9. Use of acoustic velocity methodology and remote sensing techniques to measure unsteady flow on the lower Yazoo River in Mississippi

    USGS Publications Warehouse

    Turnipseed, D. Phil; Cooper, Lance M.; Davis, Angela A.

    1998-01-01

    Methodologies have been developed for computing continuous discharge during varied, non-uniform low and medium flows on the Yazoo River at the U.S. Geological Survey streamgage below Steele Bayou near Long Lake, Mississippi, using acoustic signal processing and conventional streamgaging techniques. Procedures were also developed to compute locations of discharges during future high flow events when the stream reach is subject to hi-directional and reverse flow caused by rising stages on the Mississippi River using a combination of acoustic equipment and remote sensing technology. A description of the study area is presented. Selected results of these methods are presented for the period from March through September 1997.

  10. Thermometric- and Acoustic-Based Beam Power Monitor for Ultra-Bright X-Rays

    SciTech Connect

    Bentsen, Gregory; /Rochester U. /SLAC

    2010-08-25

    A design for an average beam power monitor for ultra-bright X-ray sources is proposed that makes simultaneous use of calorimetry and radiation acoustics. Radiation incident on a solid target will induce heating and ultrasonic vibrations, both of which may be measured to give a fairly precise value of the beam power. The monitor is intended for measuring ultra-bright Free-Electron Laser (FEL) X-ray beams, for which traditional monitoring technologies such as photo-diodes or scintillators are unsuitable. The monitor consists of a Boron Carbide (B{sub 4}C) target designed to absorb most of the incident beam's energy. Resistance temperature detectors (RTD) and piezoelectric actuators are mounted on the outward faces of the target to measure the temperature changes and ultrasonic vibrations induced by the incident beam. The design was tested using an optical pulsed beam (780 nm, 120 and 360 Hz) from a Ti:sapphire oscillator at several energies between 0.8 and 2.6 mJ. The RTDs measured an increase in temperature of about 10 K over a period of several minutes. The piezoelectric sensors recorded ringing acoustic oscillations at 580 {+-} 40 kHz. Most importantly, the amplitude of the acoustic signals was observed to scale linearly with beam power up to 2 mJ of pulse energy. Above this pulse energy, the vibrational signals became nonlinear. Several causes for this nonlinearity are discussed, including amplifier saturation and piezoelectric saturation. Despite this nonlinearity, these measurements demonstrate the feasibility of such a beam power measurement device. The advantage of two distinct measurements (acoustic and thermometric) provides a useful method of calibration that is unavailable to current LCLS diagnostics tools.

  11. Application of the mobility power flow approach to structural response from distributed loading

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1988-01-01

    The problem of the vibration power flow through coupled substructures when one of the substructures is subjected to a distributed load is addressed. In all the work performed thus far, point force excitation was considered. However, in the case of the excitation of an aircraft fuselage, distributed loading on the whole surface of a panel can be as important as the excitation from directly applied forces at defined locations on the structures. Thus using a mobility power flow approach, expressions are developed for the transmission of vibrational power between two coupled plate substructures in an L configuration, with one of the surfaces of one of the plate substructures being subjected to a distributed load. The types of distributed loads that are considered are a force load with an arbitrary function in space and a distributed load similar to that from acoustic excitation.

  12. MIDDLE GORGE POWER PLANT, OWENS RIVER STREAM FLOWING OVER TAIL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    MIDDLE GORGE POWER PLANT, OWENS RIVER STREAM FLOWING OVER TAIL RACE OF POWER PLANT AND PENSTOCK HEADGATE TO LOWER GORGE CONTROL PLANT. A MINIMAL FLOW OF RIVER WATER IS REQUIRED TO MAINTAIN FISH LIFE - Los Angeles Aqueduct, Middle Gorge Power Plant, Los Angeles, Los Angeles County, CA

  13. Application of acoustic tomography to reconstruct the horizontal flow velocity field in a shallow river

    NASA Astrophysics Data System (ADS)

    Razaz, Mahdi; Kawanisi, Kiyosi; Kaneko, Arata; Nistor, Ioan

    2015-12-01

    A novel acoustic tomographic measurement system capable of resolving sound travel time in extremely shallow rivers is introduced and the results of an extensive field measurements campaign are presented and further discussed. Acoustic pulses were transmitted over a wide frequency band of 20-35 kHz between eight transducers for about a week in a meandering reach of theBāsen River, Hiroshima, Japan. The purpose of the field experiment was validating the concept of acoustic tomography in rivers for visualizing current fields. The particular novelty of the experiment resides in its unusual tomographic features: subbasin scale (100 m × 270 m) and shallowness (0.5-3.0 m) of the physical domain, frequency of the transmitted acoustic signals (central frequency of 30 kHz), and the use of small sampling intervals (105 s). Inverse techniques with no a priori statistical information were used to estimate the depth-average current velocity components from differential travel times. Zeroth-order Tikhonov regularization, in conjunction with L-curve method deployed to stabilize the solution and to determine the weighting factor appearing in the inverse analysis. Concurrent direct environmental measurements were provided in the form of ADCP readings close to the right and left bank. Very good agreement found between along-channel velocities larger than 0.2 m/s obtained from the two techniques. Inverted quantities were, however, underestimated, perhaps due to vicinity of the ADCPs to the banks and strong effect of river geometry on the readings. In general, comparing the visualized currents with direct nodal measurements illustrate the plausibility of the tomographically reconstructed flow structures.

  14. High Efficiency Mixing Chip with Liquid Flow Actuators Operated by Surface Acoustic Waves

    NASA Astrophysics Data System (ADS)

    Saiki, Tsunemasa; Utsumi, Yuichi

    Surface acoustic wave (SAW) devices can be used as component parts for micro total analysis systems (μTASs), because the structures of these are very simple. We thus fabricated a mixing chip with liquid flow actuators operated only by the SAWs. The chip is mainly consisted of one Y-type flow channel, two pumps and one mixer. The pump is located at each upstream area of merging point of the flow channel, and the mixer is located at its downstream area. Incidentally, the flow actuators have interdigital transducers (IDTs) to generate the SAWs. The IDTs were fabricated by patterning Al/Cr on a LiNbO3 substrate, and the flow channel wall was made of epoxy-based negative resist SU-8. Using the mixing chip, we carried out a mixing experiment of two water solutions with different concentrations by using glycerin, and a chemical reaction experiment of luminol luminescence. Through the experimentations, it was found that the local and rapid mixing of continuous liquid flow was possible by using the SAW actuators, and the availability of our fabricated mixing chip as a reactor was demonstrated.

  15. Nonlinear effects of flow unsteadiness on the acoustic radiation of a heaving airfoil

    NASA Astrophysics Data System (ADS)

    Manela, Avshalom

    2013-12-01

    The study considers the combined effects of boundary animation (small-amplitude heaving) and incoming flow unsteadiness (incident vorticity) on the vibroacoustic signature of a thin rigid airfoil in low-Mach number flow. The potential-flow problem is analysed using the Brown and Michael equation, yielding the incident vortex trajectory and time evolution of trailing edge wake. The dynamical description serves as an effective source term to evaluate the far-field sound using Powell-Howe analogy. The results identify the fluid-airfoil system as a dipole-type source, and demonstrate the significance of nonlinear eddy-airfoil interactions on the acoustic radiation. Based on the value of scaled heaving frequency ωa/U (with ω the dimensional heaving frequency, a the airfoil half-chord, and U the mean flow speed), the system behaviour can be divided into two characteristic regimes: (i) for ωa/U≪1, the effect of heaving is minor, and the acoustic response is well approximated by considering the interaction of a line vortex with a stationary airfoil; (ii) for ωa/U≫1, the impact of heaving is dominant, radiating sound through an “airfoil motion” dipole oriented along the direction of heaving. In between (for ωa/U~O(1)), an intermediate regime takes place. The results indicate that trailing edge vorticity has a two-fold impact on the acoustic far field: while reducing pressure fluctuations generated by incident vortex interaction with the airfoil, trailing edge vortices transmit sound along the mean-flow direction, characterized by airfoil heaving frequency. The “silencing” effect of trailing edge vorticity is particularly efficient when the incident vortex passes close to the airfoil trailing edge: at that time, application of the Kutta condition implies the release of a trailing edge vortex in the opposite direction to the incident vortex; the released vortex then detaches from the airfoil and follows the incident vortex, forming a “silent” vortex pair

  16. A standing-wave flow measurement system for small diameter pipes using long acoustic waves

    NASA Astrophysics Data System (ADS)

    Ikpe, E. S.; Scarrott, G.; Weight, J. P.; Grattan, K. T. V.

    1993-09-01

    An exploratory investigation, using laboratory fabricated acoustic components, of standing-wave flow measurement techniques for liquids and gases in pipes of diameter up to about 25 mm was undertaken, using long acoustic waves. The results show a linear sensitivity based on the ``sing-around'' technique, often associated with contrapropagating time-of-flight flowmeters. A repeatability test at a volume flow rate of 1.5 l per minute indicates that, within the 95% confidence limit, only 5% of the readings will lie outside the range of 1.1-1.9 l per minute. The transducer used in the above investigation comprises a section of the pipe wall which acts as part of a resonating transmitter or detector of long waves in a fluid. The measurement cell is closed and generates a known standing-wave pattern. The results obtained suggest that, in the future, the initial accuracy obtained in this study can be significantly enhanced with further improvements to the transducers, the measurement cell, the electronics, and test procedures, on which work is continuing, to produce a device competitive with those using other technologies.

  17. Coupling of head and body movements to acoustic flow in sighted adults

    NASA Astrophysics Data System (ADS)

    Stoffregen, Thomas A.; Kim, Chunggon; Ito, Kiyohide; Bardy, Benoit G.

    2005-09-01

    Blindfolded sighted persons were found to detect acoustic flow patterns and use this information to control action. A moving room (a large box on wheels, with no floor, that moved in the subject's fore-aft axis) was used. Blindfolded sighted persons (1) stood comfortably or (2) moved their head backward and forward to track audible room motion. Pink noise was presented through four speakers attached to the room, or mounted on stationary stands. Room motion was a sinusoid at 0.2 Hz, 22 cm, along subject's fore-aft axis. When standing comfortably, participants exhibited weak but consistent coupling of body sway with room motion. Tracking of room motion with head movements was robust, matching both the frequency and amplitude of room motion. This was true even when the only information about room motion came from reflected sound (i.e., when the speakers were stationary). The results suggest a strong ability of sighted persons to use acoustic flow in the perception and control of their own action. [Work supported by NSF (BCS-0236627).

  18. Reflection of an acoustic line source by an impedance surface with uniform flow

    NASA Astrophysics Data System (ADS)

    Brambley, E. J.; Gabard, G.

    2014-10-01

    An exact analytic solution is derived for the 2D acoustic pressure field generated by a time-harmonic line mass source located above an impedance surface with uniform grazing flow. Closed-form asymptotic solutions in the far field are also provided. The analysis is valid for both locally-reacting and nonlocally-reacting impedances, as is demonstrated by analyzing a nonlocally reacting effective impedance representing the presence of a thin boundary layer over the surface. The analytic solution may be written in a form suggesting a generalization of the method of images to account for the impedance surface. The line source is found to excite surface waves on the impedance surface, some of which may be leaky waves which contradict the assumption of decay away from the surface predicted in previous analyses of surface waves with flow. The surface waves may be treated either (correctly) as unstable waves or (artificially) as stable waves, enabling comparison with previous numerical or mathematical studies which make either of these assumptions. The computer code for evaluating the analytic solution and far-field asymptotics is provided in the supplementary material. It is hoped this work will provide a useful benchmark solution for validating 2D numerical acoustic codes.

  19. A computational modeling approach of the jet-like acoustic streaming and heat generation induced by low frequency high power ultrasonic horn reactors.

    PubMed

    Trujillo, Francisco Javier; Knoerzer, Kai

    2011-11-01

    High power ultrasound reactors have gained a lot of interest in the food industry given the effects that can arise from ultrasonic-induced cavitation in liquid foods. However, most of the new food processing developments have been based on empirical approaches. Thus, there is a need for mathematical models which help to understand, optimize, and scale up ultrasonic reactors. In this work, a computational fluid dynamics (CFD) model was developed to predict the acoustic streaming and induced heat generated by an ultrasonic horn reactor. In the model it is assumed that the horn tip is a fluid inlet, where a turbulent jet flow is injected into the vessel. The hydrodynamic momentum rate of the incoming jet is assumed to be equal to the total acoustic momentum rate emitted by the acoustic power source. CFD velocity predictions show excellent agreement with the experimental data for power densities higher than W(0)/V ≥ 25kWm(-3). This model successfully describes hydrodynamic fields (streaming) generated by low-frequency-high-power ultrasound.

  20. Moisture estimation in power transformer oil using acoustic signals and spectral kurtosis

    NASA Astrophysics Data System (ADS)

    Leite, Valéria C. M. N.; Veloso, Giscard F. C.; Borges da Silva, Luiz Eduardo; Lambert-Torres, Germano; Borges da Silva, Jonas G.; Onofre Pereira Pinto, João

    2016-03-01

    The aim of this paper is to present a new technique for estimating the contamination by moisture in power transformer insulating oil based on the spectral kurtosis analysis of the acoustic signals of partial discharges (PDs). Basically, in this approach, the spectral kurtosis of the PD acoustic signal is calculated and the correlation between its maximum value and the moisture percentage is explored to find a function that calculates the moisture percentage. The function can be easily implemented in DSP, FPGA, or any other type of embedded system for online moisture monitoring. To evaluate the proposed approach, an experiment is assembled with a piezoelectric sensor attached to a tank, which is filled with insulating oil samples contaminated by different levels of moisture. A device generating electrical discharges is submerged into the oil to simulate the occurrence of PDs. Detected acoustic signals are processed using fast kurtogram algorithm to extract spectral kurtosis values. The obtained data are used to find the fitting function that relates the water contamination to the maximum value of the spectral kurtosis. Experimental results show that the proposed method is suitable for online monitoring system of power transformers.

  1. Incident signal power comparison for localization of concurrent multiple acoustic sources.

    PubMed

    Salvati, Daniele; Canazza, Sergio

    2014-01-01

    In this paper, a method to solve the localization of concurrent multiple acoustic sources in large open spaces is presented. The problem of the multisource localization in far-field conditions is to correctly associate the direction of arrival (DOA) estimated by a network array system to the same source. The use of systems implementing a Bayesian filter is a traditional approach to address the problem of localization in multisource acoustic scenario. However, in a real noisy open space the acoustic sources are often discontinuous with numerous short-duration events and thus the filtering methods may have difficulty to track the multiple sources. Incident signal power comparison (ISPC) is proposed to compute DOAs association. ISPC is based on identifying the incident signal power (ISP) of the sources on a microphone array using beamforming methods and comparing the ISP between different arrays using spectral distance (SD) measurement techniques. This method solves the ambiguities, due to the presence of simultaneous sources, by identifying sounds through a minimization of an error criterion on SD measures of DOA combinations. The experimental results were conducted in an outdoor real noisy environment and the ISPC performance is reported using different beamforming techniques and SD functions. PMID:24701179

  2. Incident Signal Power Comparison for Localization of Concurrent Multiple Acoustic Sources

    PubMed Central

    2014-01-01

    In this paper, a method to solve the localization of concurrent multiple acoustic sources in large open spaces is presented. The problem of the multisource localization in far-field conditions is to correctly associate the direction of arrival (DOA) estimated by a network array system to the same source. The use of systems implementing a Bayesian filter is a traditional approach to address the problem of localization in multisource acoustic scenario. However, in a real noisy open space the acoustic sources are often discontinuous with numerous short-duration events and thus the filtering methods may have difficulty to track the multiple sources. Incident signal power comparison (ISPC) is proposed to compute DOAs association. ISPC is based on identifying the incident signal power (ISP) of the sources on a microphone array using beamforming methods and comparing the ISP between different arrays using spectral distance (SD) measurement techniques. This method solves the ambiguities, due to the presence of simultaneous sources, by identifying sounds through a minimization of an error criterion on SD measures of DOA combinations. The experimental results were conducted in an outdoor real noisy environment and the ISPC performance is reported using different beamforming techniques and SD functions. PMID:24701179

  3. 1KW Power Transmission Using Wireless Acoustic-Electric Feed-Through (WAEF)

    NASA Technical Reports Server (NTRS)

    Sherrit, S.; Bao, X.; Badescu, M.; Aldrich, J.; Bar-Cohen, Y.; Biederman, W.

    2008-01-01

    A variety of space applications require the delivery of power into sealed structures. Since the structural integrity can be degraded by holes for cabling we present an alternative method of delivering power and information using stress waves to the internal space of a sealed structure. One particular application of this technology is in sample return missions where it is critical to preserve the sample integrity and to prevent earth contamination. Therefore, the container has to be hermetically sealed and the integrity of the seal must be monitored in order to insure to a high degree of reliability the integrity of the sample return vessel. In this study we investigated the use of piezoelectric acoustic-electric power feed-through devices to transfer electric power wirelessly through a solid wall by using elastic or acoustic waves. The technology is applicable to a range of space and terrestrial applications where power is required by electronic equipment inside sealed containers, vacuum or pressure vessels, etc., where holes in the wall are prohibitive or may result in significant structural performance degradation or unnecessarily complex designs. To meet requirements of higher power applications, the feasibility to transfer kilowatts level power was investigated. Pre-stressed longitudinal piezoelectric feed-through devices were analyzed by finite element models and an equivalent circuit model was developed to predict the power transfer characteristics to different electric loads. Based on the results of the analysis a prototype device was designed, fabricated and a demonstration of the transmission of electric power up to 1.068-kW was successfully conducted. Efficiencies in the 80-90% range were also demonstrated and methods to increase the efficiency further are currently being considered.

  4. Effects of energetic coherent motions on the power and wake of an axial-flow turbine

    NASA Astrophysics Data System (ADS)

    Chamorro, L. P.; Hill, C.; Neary, V. S.; Gunawan, B.; Arndt, R. E. A.; Sotiropoulos, F.

    2015-05-01

    A laboratory experiment examined the effects of energetic coherent motions on the structure of the wake and power fluctuations generated by a model axial-flow hydrokinetic turbine. The model turbine was placed in an open-channel flow and operated under subcritical conditions. The incoming flow was locally perturbed with vertically oriented cylinders of various diameters. An array of three acoustic Doppler velocimeters aligned in the cross-stream direction and a torque transducer were used to collect high-resolution and synchronous measurements of the three-velocity components of the incoming and wake flow as well as the turbine power. A strong scale-to-scale interaction between the large-scale and broadband turbulence shed by the cylinders and the turbine power revealed how the turbulence structure modulates the turbine behavior. In particular, the response of the turbine to the distinctive von Kármán-type vortices shed from the cylinders highlighted this phenomenon. The mean and fluctuating characteristics of the turbine wake are shown to be very sensitive to the energetic motions present in the flow. Tip vortices were substantially dampened and the near-field mean wake recovery accelerated in the presence of energetic motions in the flow. Strong coherent motions are shown to be more effective than turbulence levels for triggering the break-up of the spiral structure of the tip-vortices.

  5. Numerical study of acoustic instability in a partly lined flow duct using the full linearized Navier-Stokes equations

    NASA Astrophysics Data System (ADS)

    Xin, Bo; Sun, Dakun; Jing, Xiaodong; Sun, Xiaofeng

    2016-07-01

    Lined ducts are extensively applied to suppress noise emission from aero-engines and other turbomachines. The complex noise/flow interaction in a lined duct possibly leads to acoustic instability in certain conditions. To investigate the instability, the full linearized Navier-Stokes equations with eddy viscosity considered are solved in frequency domain using a Galerkin finite element method to compute the sound transmission in shear flow in the lined duct as well as the flow perturbation over the impedance wall. A good agreement between the numerical predictions and the published experimental results is obtained for the sound transmission, showing that a transmission peak occurs around the resonant frequency of the acoustic liner in the presence of shear flow. The eddy viscosity is an important influential factor that plays the roles of both providing destabilizing and making coupling between the acoustic and flow motions over the acoustic liner. Moreover, it is shown from the numerical investigation that the occurrence of the sound amplification and the magnitude of transmission coefficient are closely related to the realistic velocity profile, and we find it essential that the actual variation of the velocity profile in the axial direction over the liner surface be included in the computation. The simulation results of the periodic flow patterns possess the proper features of the convective instability over the liner, as observed in Marx et al.'s experiment. A quantitative comparison between numerical and experimental results of amplitude and phase of the instability is performed. The corresponding eigenvalues achieve great agreement.

  6. Simulation of a hot coaxial jet: Direct noise prediction and flow-acoustics correlations

    NASA Astrophysics Data System (ADS)

    Bogey, Christophe; Barré, Sébastien; Juvé, Daniel; Bailly, Christophe

    2009-03-01

    A coaxial jet originating from parallel coplanar pipe nozzles is computed by a compressible large eddy simulation (LES) using low-dissipation and low-dispersion schemes in order to determine its acoustic field and to study noise generation mechanisms. The jet streams are at high velocities, the primary stream is heated, and the Reynolds number based on the primary velocity and the secondary diameter is around 106. High levels of turbulence intensity are also specified at the nozzle exit. The jet aerodynamic field and the near-pressure field are both obtained directly from the LES. The far-field noise is calculated by solving the linear acoustic equations, from the unsteady LES data on a cylindrical surface surrounding the jet. A good agreement is observed in terms of directivity, levels, and narrow-band spectra with noise measurements carried out during the EU project CoJeN for a coaxial jet displaying same stream velocities and temperatures, coplanar nozzle outlets with identical area ratio, and a high Reynolds number. However, certainly due to differences in the properties of the nozzle-exit boundary layers with respect to the experiment, some unexpected peaks are noticed in the simulation spectra. They are attributed to the development of a Von Kármán street in the inner mixing layer and to vortex pairings in the outer shear layer. High correlation levels are also calculated between the pressure waves radiated in the downstream direction and flow quantities such as axial velocity, vorticity norm, density, and temperature, taken around the end of the primary and secondary potential cores. Noise generation in the coaxial jet therefore appears significant around the end of the two potential cores. These flow regions are characterized by intermittency, a dominant Strouhal number, and variations in the convection velocity as similarly found in single jets. The use of density or temperature to compute flow-noise correlations finally seems appropriate for a heated

  7. Aircraft IR/acoustic detection evaluation. Volume 2: Development of a ground-based acoustic sensor system for the detection of subsonic jet-powered aircraft

    NASA Technical Reports Server (NTRS)

    Kraft, Robert E.

    1992-01-01

    The design and performance of a ground-based acoustic sensor system for the detection of subsonic jet-powered aircraft is described and specified. The acoustic detection system performance criteria will subsequently be used to determine target detection ranges for the subject contract. Although the defined system has never been built and demonstrated in the field, the design parameters were chosen on the basis of achievable technology and overall system practicality. Areas where additional information is needed to substantiate the design are identified.

  8. Repeated surveys by acoustic Doppler current profiler for flow and sediment dynamics in a tidal river

    USGS Publications Warehouse

    Dinehart, R.L.; Burau, J.R.

    2005-01-01

    A strategy of repeated surveys by acoustic Doppler current profiler (ADCP) was applied in a tidal river to map velocity vectors and suspended-sediment indicators. The Sacramento River at the junction with the Delta Cross Channel at Walnut Grove, California, was surveyed over several tidal cycles in the Fall of 2000 and 2001 with a vessel-mounted ADCP. Velocity profiles were recorded along flow-defining survey paths, with surveys repeated every 27 min through a diurnal tidal cycle. Velocity vectors along each survey path were interpolated to a three-dimensional Cartesian grid that conformed to local bathymetry. A separate array of vectors was interpolated onto a grid from each survey. By displaying interpolated vector grids sequentially with computer animation, flow dynamics of the reach could be studied in three-dimensions as flow responded to the tidal cycle. Velocity streamtraces in the grid showed the upwelling of flow from the bottom of the Sacramento River channel into the Delta Cross Channel. The sequential display of vector grids showed that water in the canal briefly returned into the Sacramento River after peak flood tides, which had not been known previously. In addition to velocity vectors, ADCP data were processed to derive channel bathymetry and a spatial indicator for suspended-sediment concentration. Individual beam distances to bed, recorded by the ADCP, were transformed to yield bathymetry accurate enough to resolve small bedforms within the study reach. While recording velocity, ADCPs also record the intensity of acoustic backscatter from particles suspended in the flow. Sequential surveys of backscatter intensity were interpolated to grids and animated to indicate the spatial movement of suspended sediment through the study reach. Calculation of backscatter flux through cross-sectional grids provided a first step for computation of suspended-sediment discharge, the second step being a calibrated relation between backscatter intensity and sediment

  9. Biosonar resolving power: echo-acoustic perception of surface structures in the submillimeter range.

    PubMed

    Simon, Ralph; Knörnschild, Mirjam; Tschapka, Marco; Schneider, Annkathrin; Passauer, Nadine; Kalko, Elisabeth K V; von Helversen, Otto

    2014-01-01

    The minimum distance for which two points still can be separated from each other defines the resolving power of a visual system. In an echo-acoustic context, the resolving power is usually measured as the smallest perceivable distance of two reflecting surfaces on the range axis and is found to be around half a millimeter for bats employing frequency modulated (FM) echolocation calls. Only few studies measured such thresholds with physical objects, most often bats were trained on virtual echoes i.e., echoes generated and played back by a computer; moreover, bats were sitting while they received the stimuli. In these studies differences in structure depth between 200 and 340 μm were found. However, these low thresholds were never verified for free-flying bats and real physical objects. Here, we show behavioral evidence that the echo-acoustic resolving power for surface structures in fact can be as low as measured for computer generated echoes and even lower, sometimes below 100 μm. We found this exceptional fine discrimination ability only when one of the targets showed spectral interferences in the frequency range of the bats' echolocation call while the other target did not. This result indicates that surface structure is likely to be perceived as a spectral quality rather than being perceived strictly in the time domain. Further, it points out that sonar resolving power directly depends on the highest frequency/shortest wavelength of the signal employed.

  10. Acoustic Power Absorption and its Relation to Vector Magnetic Field of a Sunspot

    NASA Astrophysics Data System (ADS)

    Gosain, S.; Mathew, S. K.; Venkatakrishnan, P.

    2011-02-01

    The distribution of acoustic power over sunspots shows an enhanced absorption near the umbra - penumbra boundary. Previous studies revealed that the region of enhanced absorption coincides with the region of strongest transverse potential field. The aim of this paper is to i) utilize the high-resolution vector magnetograms derived using Hinode SOT/SP observations and study the relationship between the vector magnetic field and power absorption and ii) study the variation of power absorption in sunspot penumbrae due to the presence of spine-like radial structures. It is found that i) both potential and observed transverse fields peak at a similar radial distance from the center of the sunspot, and ii) the magnitude of the transverse field, derived from Hinode observations, is much larger than the potential transverse field derived from SOHO/MDI longitudinal-field observations. In the penumbra, the radial structures called spines (intra-spines) have stronger (weaker) field strength and are more vertical (horizontal). The absorption of acoustic power in the spine and intra-spine shows different behavior, with the absorption being larger in the spine as compared to the intra-spine.

  11. Power flows and Mechanical Intensities in structural finite element analysis

    NASA Technical Reports Server (NTRS)

    Hambric, Stephen A.

    1989-01-01

    The identification of power flow paths in dynamically loaded structures is an important, but currently unavailable, capability for the finite element analyst. For this reason, methods for calculating power flows and mechanical intensities in finite element models are developed here. Formulations for calculating input and output powers, power flows, mechanical intensities, and power dissipations for beam, plate, and solid element types are derived. NASTRAN is used to calculate the required velocity, force, and stress results of an analysis, which a post-processor then uses to calculate power flow quantities. The SDRC I-deas Supertab module is used to view the final results. Test models include a simple truss and a beam-stiffened cantilever plate. Both test cases showed reasonable power flow fields over low to medium frequencies, with accurate power balances. Future work will include testing with more complex models, developing an interactive graphics program to view easily and efficiently the analysis results, applying shape optimization methods to the problem with power flow variables as design constraints, and adding the power flow capability to NASTRAN.

  12. Acoustic resonance excitation of turbulent heat transfer and flow reattachment downstream of a fence

    NASA Astrophysics Data System (ADS)

    Selcan, Claudio; Cukurel, Beni; Shashank, Judah

    2015-12-01

    The current work investigates the aero-thermal impact of standing sound waves, excited in a straight channel geometry, on turbulent, separating and reattaching flow over a fence. Effects of distinct frequency resonant forcing (ReH = 10,050 and f = 122 Hz) are quantified by wall static pressure measurements and detailed convective heat transfer distributions via liquid crystal thermometry. Acoustic boundary conditions are numerically predicted and the computed longitudinal resonance mode shapes are experimentally verified by surface microphone measurements. Findings indicate the presence of a resonant sound field to exert strong influence on local heat transfer downstream of the fence, whereas the boundary layer upstream of the obstacle remains notable unaffected. Upstream shift of the maximum heat transfer location and an earlier pressure recovery indicate a reduction in time averaged flow reattachment length of up to 37 %. Although the streamwise peak Nusselt increased by only 5 %, the heat transfer level in the vicinity of the unexcited reattachment zone was locally enhanced up to 25 %. Despite prominent impact of resonant forcing on the fence wake flow, the total pressure drop penalty remained invariant. Observations demonstrate the significant aero-thermal implications of shear layer excitation by standing sound waves superimposed on the channel flow field.

  13. Normal incidence acoustic insertion loss of perforated plates with bias flow.

    PubMed

    Phong, Vincent; Papamoschou, Dimitri

    2015-12-01

    The transmission of sound at normal incidence through perforated plates with bias flow is investigated experimentally and theoretically over a large parameter space. A specially designed experimental apparatus enabled the measurement of insertion loss with bias flow Mach number up to 0.25. A theoretical model for insertion loss was constructed based on inviscid, one-dimensional wave propagation with mean flow through a single contraction/expansion chamber. The mass end correction of the contraction is modified for hole interaction effects and mean flow. Hydrodynamic losses are modeled using a vena contracta coefficient dependent on both perforation geometry and Reynolds number. Losses in acoustic energy that occur in the mixing region downstream of the perforations are modeled as fluctuations in entropy. The proposed model was validated experimentally over a range of plate thickness, porosity, and hole size. The experimental results indicate an increase in insertion loss with increasing frequency, followed by saturation and decline as resonant conditions are established in the perforations. The insertion loss at low frequency increases with increasing Mach number through the perforation. The proposed model captures these trends and its predictions are shown to be more accurate than those of past models. PMID:26723345

  14. Shear flow of angular grains: Acoustic effects and nonmonotonic rate dependence of volume

    NASA Astrophysics Data System (ADS)

    Lieou, Charles K. C.; Elbanna, Ahmed E.; Langer, J. S.; Carlson, J. M.

    2014-09-01

    Naturally occurring granular materials often consist of angular particles whose shape and frictional characteristics may have important implications on macroscopic flow rheology. In this paper, we provide a theoretical account for the peculiar phenomenon of autoacoustic compaction—nonmonotonic variation of shear band volume with shear rate in angular particles—recently observed in experiments. Our approach is based on the notion that the volume of a granular material is determined by an effective-disorder temperature known as the compactivity. Noise sources in a driven granular material couple its various degrees of freedom and the environment, causing the flow of entropy between them. The grain-scale dynamics is described by the shear-transformation-zone theory of granular flow, which accounts for irreversible plastic deformation in terms of localized flow defects whose density is governed by the state of configurational disorder. To model the effects of grain shape and frictional characteristics, we propose an Ising-like internal variable to account for nearest-neighbor grain interlocking and geometric frustration and interpret the effect of friction as an acoustic noise strength. We show quantitative agreement between experimental measurements and theoretical predictions and propose additional experiments that provide stringent tests on the new theoretical elements.

  15. Experimental feasibility of investigating acoustic waves in Couette flow with entropy and pressure gradients

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Zorumski, William E.; Rawls, John W., Jr.

    1990-01-01

    The feasibility is discussed for an experimental program for studying the behavior of acoustic wave propagation in the presence of strong gradients of pressure, temperature, and flow. Theory suggests that gradients effects can be experimentally observed as resonant frequency shifts and mode shape changes in a waveguide. A convenient experimental geometry for such experiments is the annular region between two co-rotating cylinders. Radial temperature gradients in a spinning annulus can be generated by differentially heating the two cylinders via electromagnetic induction. Radial pressure gradients can be controlled by varying the cylinder spin rates. Present technology appears adequate to construct an apparatus to allow independent control of temperature and pressure gradients. A complicating feature of a more advanced experiment, involving flow gradients, is the requirement for independently controlled cylinder spin rates. Also, the boundary condition at annulus terminations must be such that flow gradients are minimally disturbed. The design and construction of an advanced apparatus to include flow gradients will require additional technology development.

  16. Acoustic resonance excitation of turbulent heat transfer and flow reattachment downstream of a fence

    NASA Astrophysics Data System (ADS)

    Selcan, Claudio; Cukurel, Beni; Shashank, Judah

    2016-10-01

    The current work investigates the aero-thermal impact of standing sound waves, excited in a straight channel geometry, on turbulent, separating and reattaching flow over a fence. Effects of distinct frequency resonant forcing (ReH = 10,050 and f = 122 Hz) are quantified by wall static pressure measurements and detailed convective heat transfer distributions via liquid crystal thermometry. Acoustic boundary conditions are numerically predicted and the computed longitudinal resonance mode shapes are experimentally verified by surface microphone measurements. Findings indicate the presence of a resonant sound field to exert strong influence on local heat transfer downstream of the fence, whereas the boundary layer upstream of the obstacle remains notable unaffected. Upstream shift of the maximum heat transfer location and an earlier pressure recovery indicate a reduction in time averaged flow reattachment length of up to 37 %. Although the streamwise peak Nusselt increased by only 5 %, the heat transfer level in the vicinity of the unexcited reattachment zone was locally enhanced up to 25 %. Despite prominent impact of resonant forcing on the fence wake flow, the total pressure drop penalty remained invariant. Observations demonstrate the significant aero-thermal implications of shear layer excitation by standing sound waves superimposed on the channel flow field.

  17. Pressure probe and hot-film probe rsponses to acoustic excitation in mean flow

    NASA Technical Reports Server (NTRS)

    Parrott, T. L.; Jones, M. G.

    1986-01-01

    An experiment was conducted to compare the relative responses of a hot-film probe and a pressure probe positioned in a flow duct carrying mean flow and progressive acoustic waves. The response of each probe was compared with that of a condenser-type microphone flush mounted in the duct wall for flow Mach numbers up to about 0.5. The response of the pressure probe was less than that of the flush-mounted microphone by not more than about 2.1 dB at the highest centerline Mach number. This decreased response of the probe can likely be attributed to flow-induced impedance changes at the probe sensor orifices. The response of the hot-film probe, expressed in terms of fluctuating pressure, was greater than that of the flush-mounted microphone by as much as 6.0 dB at the two higher centerline Mach numbers. Removal of the contribution from fluctuating temperature in the hot-film analytical model greatly improved the agreement between the two transducer responses.

  18. Flow and mixing characteristics of swirling double-concentric jets subject to acoustic excitation

    NASA Astrophysics Data System (ADS)

    Huang, R. F.; Jufar, S. R.; Hsu, C. M.

    2013-01-01

    Characteristic flow modes, flow evolution processes, jet spread width, turbulence properties, and dispersion characteristics of swirling double-concentric jets were studied experimentally. Jet pulsations were induced by means of acoustic excitation. Streak pictures of smoke flow patterns, illuminated by a laser-light sheet, were recorded by a high-speed digital camera. A hot-wire anemometer was used to digitize instantaneous velocity instabilities in the flow. Jet spread width was obtained through a binary edge identification technique. Tracer-gas concentrations were measured for information on jet dispersions. Two characteristic flow patterns were observed: (1) synchronized vortex rings appeared in the low excitation intensity regime (the excitation intensity less than one) and (2) synchronized puffing turbulent jets appeared in the high excitation intensity regime (the excitation intensity greater than one). In the high excitation intensity regime, the "suction back" phenomenon occurred and therefore induced in-tube mixing. The jet spread width and turbulent fluctuation intensity exhibited particularly large values in the high excitation intensity regime at the excitation Strouhal numbers smaller than 0.85. At the excitation Strouhal numbers >0.85, the high-frequency effect caused significant decay of jet breakup and dispersion—the jet spread width and fluctuation intensity decreased sharply and may, at very high Strouhal numbers, asymptotically approach values almost the same as the values associated with unexcited jets. Exciting the jets at the high excitation intensity regime, the effects of puffing motion and in-tube mixing caused breakup of the jet in the near field and therefore resulted in a small Lagrangian integral time and small length scales of fluctuating eddies. This effect, in turn, caused drastic dispersion of the central jet fluids. It is possible that the excited jets can attain 90 % more improvements than the unexcited jets. We provide a

  19. Flow and mixing characteristics of swirling double-concentric jets subject to acoustic excitation

    NASA Astrophysics Data System (ADS)

    Huang, R. F.; Jufar, S. R.; Hsu, C. M.

    2012-12-01

    Characteristic flow modes, flow evolution processes, jet spread width, turbulence properties, and dispersion characteristics of swirling double-concentric jets were studied experimentally. Jet pulsations were induced by means of acoustic excitation. Streak pictures of smoke flow patterns, illuminated by a laser-light sheet, were recorded by a high-speed digital camera. A hot-wire anemometer was used to digitize instantaneous velocity instabilities in the flow. Jet spread width was obtained through a binary edge identification technique. Tracer-gas concentrations were measured for information on jet dispersions. Two characteristic flow patterns were observed: (1) synchronized vortex rings appeared in the low excitation intensity regime (the excitation intensity less than one) and (2) synchronized puffing turbulent jets appeared in the high excitation intensity regime (the excitation intensity greater than one). In the high excitation intensity regime, the "suction back" phenomenon occurred and therefore induced in-tube mixing. The jet spread width and turbulent fluctuation intensity exhibited particularly large values in the high excitation intensity regime at the excitation Strouhal numbers smaller than 0.85. At the excitation Strouhal numbers >0.85, the high-frequency effect caused significant decay of jet breakup and dispersion—the jet spread width and fluctuation intensity decreased sharply and may, at very high Strouhal numbers, asymptotically approach values almost the same as the values associated with unexcited jets. Exciting the jets at the high excitation intensity regime, the effects of puffing motion and in-tube mixing caused breakup of the jet in the near field and therefore resulted in a small Lagrangian integral time and small length scales of fluctuating eddies. This effect, in turn, caused drastic dispersion of the central jet fluids. It is possible that the excited jets can attain 90 % more improvements than the unexcited jets. We provide a

  20. Power formula for open-channel flow resistance

    USGS Publications Warehouse

    Chen, Cheng-lung

    1988-01-01

    This paper evaluates various power formulas for flow resistance in open channels. Unlike the logarithmic resistance equation that can be theoretically derived either from Prandtl's mixing-length hypothesis or von Karman's similarity hypothesis, the power formula has long had an appearance of empiricism. Nevertheless, the simplicity in the form of the power formula has made it popular among the many possible forms of flow resistance formulas. This paper reexamines the concept and rationale of the power formulation, thereby addressing some critical issues in the modeling of flow resistance.

  1. Comparisons of power transfer functions and flow transfer functions

    SciTech Connect

    Grimm, K.N.; Meneghetti, D.

    1987-11-15

    Transfer functions may be used to calculate component feedbacks or temperature increments by convolution of the transfer function with the appropriate fractional change in system-quantity. Power-change transfer functions have been reported. The corresponding flow transfer functions for this case, and comparison with the power transfer functions, are reported here. Results of feedback simulation of ramped flow transients using flow transfer functions are also described.

  2. Dependence of acoustic surface gravity on geometric configuration of matter for axially symmetric background flows in the Schwarzschild metric

    NASA Astrophysics Data System (ADS)

    Tarafdar, Pratik; Das, Tapas K.

    2015-09-01

    In black hole evaporation process, the mass of the hole anti-correlates with the Hawking temperature. This indicates that the smaller holes have higher surface gravity. For analogue Hawking effects, however, the acoustic surface gravity is determined by the local values of the dynamical velocity of the stationary background fluid flow and the speed of propagation of the characteristic perturbation embedded in the background fluid, as well as by their space derivatives evaluated along the direction normal to the acoustic horizon, respectively. The mass of the analogue system — whether classical or quantum — does not directly contribute to extremize the value of the associated acoustic surface gravity. For general relativistic axially symmetric background fluid flow in the Schwarzschild metric, we show that the initial boundary conditions describing such accretion influence the maximization scheme of the acoustic surface gravity and associated analogue temperature. Aforementioned background flow onto black holes can assume three distinct geometric configurations. Identical set of initial boundary conditions can lead to entirely different phase-space behavior of the stationary flow solutions, as well as the salient features of the associated relativistic acoustic geometry. This implies that it is imperative to investigate how the measure of the acoustic surface gravity corresponding to the accreting black holes gets influenced by the geometric configuration of the inflow described by various thermodynamic equations of state. Such investigation is useful to study the effect of Einstenian gravity on the nonconventional classical features as observed in Hawking like effect in a dispersive medium in the limit of a strong dispersion relation.

  3. Combustion Instability Analysis and the Effects of Drop Size on Acoustic Driving Rocket Flow

    NASA Technical Reports Server (NTRS)

    Harper, Brent (Technical Monitor); Ellison, L. Renea; Moser, Marlow D.

    2004-01-01

    High frequency combustion instability, the most destructive kind, is generally solved on a per engine basis. The instability often is the result of compounding acoustic oscillations, usually from the propellant combustion itself. To counteract the instability the chamber geometry can be changed and/or the method of propellant injection can be altered. This experiment will alter the chamber dimensions slightly; using a cylindrical shape of constant diameter and the length will be varied from six to twelve inches in three-inch increments. The main flowfield will be the products of a high OF hydrogen/oxygen flow. The liquid fuel will be injected into this flowfield using a modulated injector. It will allow for varied droplet size, feed rate, spray pattern, and location for the mixture within the chamber. The response will be deduced from the chamber pressure oscillations.

  4. High Accuracy Acoustic Relative Humidity Measurement in Duct Flow with Air

    PubMed Central

    van Schaik, Wilhelm; Grooten, Mart; Wernaart, Twan; van der Geld, Cees

    2010-01-01

    An acoustic relative humidity sensor for air-steam mixtures in duct flow is designed and tested. Theory, construction, calibration, considerations on dynamic response and results are presented. The measurement device is capable of measuring line averaged values of gas velocity, temperature and relative humidity (RH) instantaneously, by applying two ultrasonic transducers and an array of four temperature sensors. Measurement ranges are: gas velocity of 0–12 m/s with an error of ±0.13 m/s, temperature 0–100 °C with an error of ±0.07 °C and relative humidity 0–100% with accuracy better than 2 % RH above 50 °C. Main advantage over conventional humidity sensors is the high sensitivity at high RH at temperatures exceeding 50 °C, with accuracy increasing with increasing temperature. The sensors are non-intrusive and resist highly humid environments. PMID:22163610

  5. High accuracy acoustic relative humidity measurement in duct flow with air.

    PubMed

    van Schaik, Wilhelm; Grooten, Mart; Wernaart, Twan; van der Geld, Cees

    2010-01-01

    An acoustic relative humidity sensor for air-steam mixtures in duct flow is designed and tested. Theory, construction, calibration, considerations on dynamic response and results are presented. The measurement device is capable of measuring line averaged values of gas velocity, temperature and relative humidity (RH) instantaneously, by applying two ultrasonic transducers and an array of four temperature sensors. Measurement ranges are: gas velocity of 0-12 m/s with an error of ± 0.13 m/s, temperature 0-100 °C with an error of ± 0.07 °C and relative humidity 0-100% with accuracy better than 2 % RH above 50 °C. Main advantage over conventional humidity sensors is the high sensitivity at high RH at temperatures exceeding 50 °C, with accuracy increasing with increasing temperature. The sensors are non-intrusive and resist highly humid environments.

  6. Tunnelling effects for acoustic waves in slowly varying axisymmetric flow ducts

    NASA Astrophysics Data System (ADS)

    Nielsen, R. B.; Peake, N.

    2016-10-01

    The multiple-scales Wentzel-Kramers-Brillouin (WKB) approximation is used to model the propagation of acoustic waves in an axisymmetric duct with a constriction in the presence of mean flow. An analysis of the reflection/transmission process of modes tunnelling through the constriction is conducted, and the key mathematical feature is the presence of two turning points, located at either real axial locations or in the complex plane. The resulting asymptotic solution consists of WKB solutions in regions away from the constriction and an inner solution valid in the near vicinity of the constriction. A solution which is uniformly valid throughout the duct is also derived. A range of test cases are considered, and the importance of accounting for the inner region, even in cases in which the turning points lie away from the real axis, is demonstrated.

  7. Power flow analysis of two coupled plates with arbitrary characteristics

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1990-01-01

    In the last progress report (Feb. 1988) some results were presented for a parametric analysis on the vibrational power flow between two coupled plate structures using the mobility power flow approach. The results reported then were for changes in the structural parameters of the two plates, but with the two plates identical in their structural characteristics. Herein, limitation is removed. The vibrational power input and output are evaluated for different values of the structural damping loss factor for the source and receiver plates. In performing this parametric analysis, the source plate characteristics are kept constant. The purpose of this parametric analysis is to determine the most critical parameters that influence the flow of vibrational power from the source plate to the receiver plate. In the case of the structural damping parametric analysis, the influence of changes in the source plate damping is also investigated. The results obtained from the mobility power flow approach are compared to results obtained using a statistical energy analysis (SEA) approach. The significance of the power flow results are discussed together with a discussion and a comparison between the SEA results and the mobility power flow results. Furthermore, the benefits derived from using the mobility power flow approach are examined.

  8. Effect of grazing flow on structural-acoustic response of an elastic plate with sound in a duct

    NASA Astrophysics Data System (ADS)

    Manchakattil Sucheendran, Mahesh

    The design of supersonic and hypersonic vehicles involves the challenging task of designing thin panels that can withstand severe unsteady pressure and thermal loads. A good understanding and accurate prediction of the coupled structural-acoustic response of thin panels subjected to sound waves are key elements of this design process. Due to the cost of in-flight testing, the experimental assessment of the structural-acoustic response of skin panels is usually conducted in ground-based facilities consisting of a duct in which acoustic waves propagate at grazing incidence with skin panels mounted along the duct walls. A key limitation of such facility is the absence of flow, the impact of which on the structural-acoustic response of the skin panel is still poorly understood. To shed some insight on this key contribution, this analytical and numerical study focuses on the structural-acoustic interaction of sound with a thin elastic plate mounted flush on a wall in a rectangular duct in the presence of a uniform mean subsonic and supersonic flow. A linear, time-harmonic theory based on modal descriptions of the plate velocity and duct acoustic fields is first developed. The theory includes the effect of uniform mean flow in the duct and clamped and simply-supported boundary conditions for the plate. The sound radiated by the plate is calculated using Doak's theory [22], extended in this work to account for subsonic and supersonic uniform mean flow in the duct, and verified using the numerical solver. The theoretical model provides important insight on the effect of flow in the duct on the coupled response of the plate. Four metrics characterizing the coupled response are considered: the deviation of the peak response frequency from the in vacuo natural frequency of plate, the amplitude of the peak response, the effective acoustic damping of the plate, and the plate modal coupling through the duct acoustic field. The theory is extended to estimate the onset of

  9. Low-Dispersion Scheme for Nonlinear Acoustic Waves in Nonuniform Flow

    NASA Technical Reports Server (NTRS)

    Baysal, Oktay; Kaushik, Dinesh K.; Idres, Moumen

    1997-01-01

    The linear dispersion-relation-preserving scheme and its boundary conditions have been extended to the nonlinear Euler equations. This allowed computing, a nonuniform flowfield and a nonlinear acoustic wave propagation in such a medium, by the same scheme. By casting all the equations, boundary conditions, and the solution scheme in generalized curvilinear coordinates, the solutions were made possible for non-Cartesian domains and, for the better deployment of the grid points, nonuniform grid step sizes could be used. It has been tested for a number of simple initial-value and periodic-source problems. A simple demonstration of the difference between a linear and nonlinear propagation was conducted. The wall boundary condition, derived from the momentum equations and implemented through a pressure at a ghost point, and the radiation boundary condition, derived from the asymptotic solution to the Euler equations, have proven to be effective for the nonlinear equations and nonuniform flows. The nonreflective characteristic boundary conditions also have shown success but limited to the nonlinear waves in no mean flow, and failed for nonlinear waves in nonuniform flow.

  10. Measuring intake flows in hydroelectric plants with an acoustic scintillation flowmeter

    SciTech Connect

    Lemon, D.D.

    1995-12-31

    The Acoustic Scintillation Flowmeter (ASFM) offers some unique advantages for measuring intake flows in hydroelectric plants. The method is non-intrusive, resulting in a minimum of flow interference and is well-suited to use in low-head dams and other applications where intake tunnels are short or have awkward geometries. Deployment in intake gate slots is straightforward, allowing data to be collected quickly and easily, with a minimum of plant down-time. An example of such flow measurements is shown. Interest in assessing the capability of the ASFM to make the highly-accurate measurements suitable for system efficiency evaluations led to our performing a series of tow-tank tests. Over a range of speeds from 0.5 to 5.0 m/sec, the mean deviation between the towing speed and the ASFM measurements was less than 0.5%. Measurements at an instrumented dam site are planned as the next stage in the accuracy assessment.

  11. A power flow based model for the analysis of vulnerability in power networks

    NASA Astrophysics Data System (ADS)

    Wang, Zhuoyang; Chen, Guo; Hill, David J.; Dong, Zhao Yang

    2016-10-01

    An innovative model which considers power flow, one of the most important characteristics in a power system, is proposed for the analysis of power grid vulnerability. Moreover, based on the complex network theory and the Max-Flow theorem, a new vulnerability index is presented to identify the vulnerable lines in a power grid. In addition, comparative simulations between the power flow based model and existing models are investigated on the IEEE 118-bus system. The simulation results demonstrate that the proposed model and the index are more effective in power grid vulnerability analysis.

  12. Ultrasonic power transfer from a spherical acoustic wave source to a free-free piezoelectric receiver: Modeling and experiment

    SciTech Connect

    Shahab, S.; Gray, M.; Erturk, A.

    2015-03-14

    Contactless powering of small electronic components has lately received growing attention for wireless applications in which battery replacement or tethered charging is undesired or simply impossible, and ambient energy harvesting is not a viable solution. As an alternative to well-studied methods of contactless energy transfer, such as the inductive coupling method, the use of ultrasonic waves transmitted and received by piezoelectric devices enables larger power transmission distances, which is critical especially for deep-implanted electronic devices. Moreover, energy transfer by means of acoustic waves is well suited in situations where no electromagnetic fields are allowed. The limited literature of ultrasonic acoustic energy transfer is mainly centered on proof-of-concept experiments demonstrating the feasibility of this method, lacking experimentally validated modeling efforts for the resulting multiphysics problem that couples the source and receiver dynamics with domain acoustics. In this work, we present fully coupled analytical, numerical, and experimental multiphysics investigations for ultrasonic acoustic energy transfer from a spherical wave source to a piezoelectric receiver bar that operates in the 33-mode of piezoelectricity. The fluid-loaded piezoelectric receiver under free-free mechanical boundary conditions is shunted to an electrical load for quantifying the electrical power output for a given acoustic source strength of the transmitter. The analytical acoustic-piezoelectric structure interaction modeling framework is validated experimentally, and the effects of system parameters are reported along with optimal electrical loading and frequency conditions of the receiver.

  13. Parametric and experimental analysis using a power flow approach

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1988-01-01

    Having defined and developed a structural power flow approach for the analysis of structure-borne transmission of structural vibrations, the technique is used to perform an analysis of the influence of structural parameters on the transmitted energy. As a base for comparison, the parametric analysis is first performed using a Statistical Energy Analysis approach and the results compared with those obtained using the power flow approach. The advantages of using structural power flow are thus demonstrated by comparing the type of results obtained by the two methods. Additionally, to demonstrate the advantages of using the power flow method and to show that the power flow results represent a direct physical parameter that can be measured on a typical structure, an experimental investigation of structural power flow is also presented. Results are presented for an L-shaped beam for which an analytical solution has already been obtained. Furthermore, the various methods available to measure vibrational power flow are compared to investigate the advantages and disadvantages of each method.

  14. Monitoring Thermal Fatigue Damage In Nuclear Power Plant Materials Using Acoustic Emission

    SciTech Connect

    Meyer, Ryan M.; Ramuhalli, Pradeep; Watson, Bruce E.; Pitman, Stan G.; Roosendaal, Timothy J.; Bond, Leonard J.

    2012-04-26

    Proactive aging management of nuclear power plant passive components requires technologies to enable monitoring and accurate quantification of material condition at early stages of degradation (i.e., pre-macrocrack). Acoustic emission (AE) is well-suited to continuous monitoring of component degradation and is proposed as a method to monitor degradation during accelerated thermal fatigue tests. A key consideration is the ability to separate degradation responses from external sources such as water spray induced during thermal fatigue testing. Water spray provides a significant background of acoustic signals, which can overwhelm AE signals caused by degradation. Analysis of AE signal frequency and energy is proposed in this work as a means for separating degradation signals from background sources. Encouraging results were obtained by applying both frequency and energy filters to preliminary data. The analysis of signals filtered using frequency and energy provides signatures exhibiting several characteristics that are consistent with degradation accumulation in materials. Future work is planned to enable verification of the efficacy of AE for thermal fatigue crack initiation detection. While the emphasis has been placed on the use of AE for crack initiation detection during accelerated aging tests, this work also has implications with respect to the use of AE as a primary tool for early degradation monitoring in nuclear power plant materials. The development of NDE tools for characterization of aging in materials can also benefit from the use of a technology such as AE which can continuously monitor and detect crack initiation during accelerated aging tests.

  15. Mobility power flow analysis of an L-shaped plate structure subjected to distributed loading

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.; Cimmerman, B.

    1990-01-01

    An analytical investigation based in the Mobility Power Flow (MPF) method is presented for the determination of the vibrational response and power flow for two coupled flat plate structures in an L-shaped configuration, subjected to distributed excitation. The principle of the MPF method consists of dividing the global structure into a series of subsystems coupled together using mobility functions. Each separate subsystem is analyzed independently to determine the structural mobility functions for the junction and excitation locations. The mobility functions, together with the characteristics of the junction between the subsystems, are then used to determine the response of the global structure and the MPF. In the considered coupled plate structure, MPF expressions are derived for distributed mechanical excitation which is independent of the structure response. However using a similar approach with some modifications excitation by an acoustic plane wave can be considered. Some modifications are required to deal with the latter case are necessary because the forces (acoustic pressure) acting on the structure are dependent on the response of the structure due to the presence of the scattered pressure.

  16. Computing an operating parameter of a unified power flow controller

    DOEpatents

    Wilson, David G; Robinett, III, Rush D

    2015-01-06

    A Unified Power Flow Controller described herein comprises a sensor that outputs at least one sensed condition, a processor that receives the at least one sensed condition, a memory that comprises control logic that is executable by the processor; and power electronics that comprise power storage, wherein the processor causes the power electronics to selectively cause the power storage to act as one of a power generator or a load based at least in part upon the at least one sensed condition output by the sensor and the control logic, and wherein at least one operating parameter of the power electronics is designed to facilitate maximal transmittal of electrical power generated at a variable power generation system to a grid system while meeting power constraints set forth by the electrical power grid.

  17. Measuring Power Flow in Electric Vehicles

    NASA Technical Reports Server (NTRS)

    Griffin, Daniel C., Jr; Wiker, G. A.

    1983-01-01

    Instrument accommodates fast rise and fall times of waveforms characteristic of modern, efficient power controllers. Power meter multiplies analog signals proportional to voltage and current, and converts resulting signal to frequency. Two mechanical counters provided: one for charging, one for discharging.

  18. Shear-horizontal surface acoustic wave phononic device with high density filling material for ultra-low power sensing applications

    SciTech Connect

    Richardson, M.; Bhethanabotla, V. R.; Sankaranarayanan, S. K. R. S.

    2014-06-23

    Finite element simulations of a phononic shear-horizontal surface acoustic wave (SAW) sensor based on ST 90°-X Quartz reveal a dramatic reduction in power consumption. The phononic sensor is realized by artificially structuring the delay path to form an acoustic meta-material comprised of a periodic microcavity array incorporating high-density materials such as tantalum or tungsten. Constructive interference of the scattered and secondary reflected waves at every microcavity interface leads to acoustic energy confinement in the high-density regions translating into reduced power loss. Tantalum filled cavities show the best performance while tungsten inclusions create a phononic bandgap. Based on our simulation results, SAW devices with tantalum filled microcavities were fabricated and shown to significantly decrease insertion loss. Our findings offer encouraging prospects for designing low power, highly sensitive portable biosensors.

  19. LDV measurement of bird ear vibrations to determine inner ear impedance and middle ear power flow

    NASA Astrophysics Data System (ADS)

    Muyshondt, Pieter G. G.; Pires, Felipe; Dirckx, Joris J. J.

    2016-06-01

    The mechanical behavior of the middle ear structures in birds and mammals is affected by the fluids in the inner ear (IE) that are present behind the oval window. In this study, the aim was to gather knowledge of the acoustic impedance of the IE in the ostrich, to be able to determine the effect on vibrations and power flow in the single-ossicle bird middle ear for future studies. To determine the IE impedance, vibrations of the ossicle were measured for both the quasi-static and acoustic stimulus frequencies. In the acoustic regime, vibrations were measured with a laser Doppler vibrometer and electromagnetic stimulation of the ossicle. The impedance of the inner ear could be determined by means of a simple RLC model in series, which resulted in a stiffness reactance of KIE = 0.20.1012 Pa/m3, an inertial impedance of MIE = 0.652.106 Pa s2/m3, and a resistance of RIE = 1.57.109 Pa s/m. The measured impedance is found to be considerably smaller than what is found for the human IE.

  20. Acoustical gas core reactor with MHD power generation for burst power in a bimodal system

    NASA Astrophysics Data System (ADS)

    Dugan, E. T.; Jacobs, A. M.; Oliver, C. C.; Lear, W. E., Jr.

    Research is being conducted on gas core reactors for space nuclear power to establish the scientific feasibility and engineering validation of a reactor and energy conversion system that can significantly improve specific power, dynamic performance and system efficiency. Rapid achievement of burst mode (GWe) operation at core power densities of 1 kW/mL and reactor masses of a kg/MWt are research objectives; coupled with MHD conversion, system efficiencies of 40 percent for open cycle operation and heat rejection temperatures of 1500 K or higher for closed cycle operation are anticipated. The design of the gas core reactor/MHD generator configuration to directly produce pulsed electrical power, thereby alleviating external power conditioning requirements, is also a research objective.

  1. Fuzzy modelling of power system optimal load flow

    SciTech Connect

    Miranda, V.; Saraiva, J.T. )

    1992-05-01

    In this paper, a fuzzy model for power system operation is presented. Uncertainties in loads and generations are modeled as fuzzy numbers. System behavior under known (while uncertain) injections is dealt with by a DC fuzzy power flow model. System optimal (while uncertain) operation is calculated with linear programming procedures where the problem nature and structure allows some efficient techniques such as Dantzig Wolfe decomposition and dual simplex to be used. Among the results, one obtains a fuzzy cost value for system operation and possibility distributions for branch power flows and power generations. Some risk analysis is possible, as system robustness and exposure indices can be derived and hedging policies can be investigated.

  2. Improvement of Power Efficiency for Underwater Acoustic Communication Using Orthogonal Signal Division Multiplexing over Multiple Transducers

    NASA Astrophysics Data System (ADS)

    Ebihara, Tadashi

    2013-07-01

    In underwater acoustic (UWA) communication, power efficiency is one of the important characteristics. This paper is about multistream transmission using orthogonal signal division multiplexing (OSDM) as a technique to increase power efficiency. In this work, the performance of multistream transmission using OSDM is evaluated both experimentally in a test tank and by numerical simulation. Through this study, it is confirmed that the multistream transmission scheme is effective in enhancing the power efficiency compared with the single-stream transmission using higher order modulation. Moreover, the performance of multistream transmission using OSDM is compared with the existing scheme, multistream transmission using orthogonal frequency division multiplexing (OFDM). The obtained results suggest that multistream transmission using OSDM is attractive because it can achieve the same bit-error rate (BER) and the same data rate with less power of the signal, compared with the reference. Although the calculation cost of OSDM in the receiver remains as an issue, multistream transmission using OSDM may contribute to high-speed UWA communication because of its excellent power efficiency.

  3. Power flow control using distributed saturable reactors

    DOEpatents

    Dimitrovski, Aleksandar D.

    2016-02-13

    A magnetic amplifier includes a saturable core having a plurality of legs. Control windings wound around separate legs are spaced apart from each other and connected in series in an anti-symmetric relation. The control windings are configured in such a way that a biasing magnetic flux arising from a control current flowing through one of the plurality of control windings is substantially equal to the biasing magnetic flux flowing into a second of the plurality of control windings. The flow of the control current through each of the plurality of control windings changes the reactance of the saturable core reactor by driving those portions of the saturable core that convey the biasing magnetic flux in the saturable core into saturation. The phasing of the control winding limits a voltage induced in the plurality of control windings caused by a magnetic flux passing around a portion of the saturable core.

  4. Method and apparatus for acoustically monitoring the flow of suspended solid particulate matter. [Patent application; monitoring char flow in coal gasifier

    DOEpatents

    Roach, P.D.; Raptis, A.C.

    1980-11-24

    A method and apparatus for monitoring char flow in a coal gasifier system includes flow monitor circuits which measure acoustic attenuation caused by the presence of char in a char line and provides a char flow/no flow indication and an indication of relative char density. The flow monitor circuits compute the ratio of signals in two frequency bands, a first frequency band representative of background noise, and a second higher frequency band in which background noise is attenuated by the presence of char. Since the second frequency band contains higher frequencies, the ratio can be used to provide a flow/no flow indication. The second band can also be selected so that attenuation is monotonically related to particle concentration, providing a quantitative measure of char concentration.

  5. Extraction of the acoustic component of a turbulent flow exciting a plate by inverting the vibration problem

    NASA Astrophysics Data System (ADS)

    Lecoq, D.; Pézerat, C.; Thomas, J.-H.; Bi, W. P.

    2014-06-01

    An improvement of the Force Analysis Technique (FAT), an inverse method of vibration, is proposed to identify the low wavenumbers including the acoustic component of a turbulent flow that excites a plate. This method is a significant progress since the usual techniques of measurements with flush-mounted sensors are not able to separate the acoustic and the aerodynamic energies of the excitation because the aerodynamic component is too high. Moreover, the main cause of vibration or acoustic radiation of the structure might be due to the acoustic part by a phenomenon of spatial coincidence between the acoustic wavelengths and those of the plate. This underlines the need to extract the acoustic part. In this work, numerical experiments are performed to solve both the direct and inverse problems of vibration. The excitation is a turbulent boundary layer and combines the pressure field of the Corcos model and a diffuse acoustic field. These pressures are obtained by a synthesis method based on the Cholesky decomposition of the cross-spectra matrices and are used to excite a plate. Thus, the application of the inverse problem FAT that requires only the vibration data shows that the method is able to identify and to isolate the acoustic part of the excitation. Indeed, the discretization of the inverse operator (motion equation of the plate) acts as a low-pass wavenumber filter. In addition, this method is simple to implement because it can be applied locally (no need to know the boundary conditions), and measurements can be carried out on the opposite side of the plate without affecting the flow. Finally, an improvement of FAT is proposed. It regularizes optimally and automatically the inverse problem by analyzing the mean quadratic pressure of the reconstructed force distribution. This optimized FAT, in the case of the turbulent flow, has the advantage of measuring the acoustic component up to higher frequencies even in the presence of noise. the aerodynamic component

  6. Electrochemistry in Organisms: Electron Flow and Power Output

    ERIC Educational Resources Information Center

    Chirpich, Thomas P.

    1975-01-01

    Presents a series of calculations, appropriate for the freshman level, to determine the flow of electrons to oxygen along the electron transport chain. States that living organisms resemble fuel cells and develops calculations for determining power output. (GS)

  7. The Acoustic Analogy: A Powerful Tool in Aeroacoustics with Emphasis on Jet Noise Prediction

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Doty, Michael J.; Hunter, Craig A.

    2004-01-01

    The acoustic analogy introduced by Lighthill to study jet noise is now over 50 years old. In the present paper, Lighthill s Acoustic Analogy is revisited together with a brief evaluation of the state-of-the-art of the subject and an exploration of the possibility of further improvements in jet noise prediction from analytical methods, computational fluid dynamics (CFD) predictions, and measurement techniques. Experimental Particle Image Velocimetry (PIV) data is used both to evaluate turbulent statistics from Reynolds-averaged Navier-Stokes (RANS) CFD and to propose correlation models for the Lighthill stress tensor. The NASA Langley Jet3D code is used to study the effect of these models on jet noise prediction. From the analytical investigation, a retarded time correction is shown that improves, by approximately 8 dB, the over-prediction of aft-arc jet noise by Jet3D. In experimental investigation, the PIV data agree well with the CFD mean flow predictions, with room for improvement in Reynolds stress predictions. Initial modifications, suggested by the PIV data, to the form of the Jet3D correlation model showed no noticeable improvements in jet noise prediction.

  8. ACOUSTIC SCALE FROM THE ANGULAR POWER SPECTRA OF SDSS-III DR8 PHOTOMETRIC LUMINOUS GALAXIES

    SciTech Connect

    Seo, Hee-Jong; Ho, Shirley; White, Martin; Reid, Beth; Schlegel, David J.; Cuesta, Antonio J.; Padmanabhan, Nikhil; Ross, Ashley J.; Percival, Will J.; Nichol, Robert C.; Saito, Shun; De Putter, Roland; Eisenstein, Daniel J.; Xu Xiaoying; Skibba, Ramin; Schneider, Donald P.; Verde, Licia; Bizyaev, Dmitry; Brewington, Howard; Brinkmann, J.; and others

    2012-12-10

    We measure the acoustic scale from the angular power spectra of the Sloan Digital Sky Survey III (SDSS-III) Data Release 8 imaging catalog that includes 872, 921 galaxies over {approx}10,000 deg{sup 2} between 0.45 < z < 0.65. The extensive spectroscopic training set of the Baryon Oscillation Spectroscopic Survey luminous galaxies allows precise estimates of the true redshift distributions of galaxies in our imaging catalog. Utilizing the redshift distribution information, we build templates and fit to the power spectra of the data, which are measured in our companion paper, to derive the location of Baryon acoustic oscillations (BAOs) while marginalizing over many free parameters to exclude nearly all of the non-BAO signal. We derive the ratio of the angular diameter distance to the sound horizon scale D{sub A} (z)/r{sub s} = 9.212{sup +0.416}{sub -{sub 0.404}} at z = 0.54, and therefore D{sub A} (z) = 1411 {+-} 65 Mpc at z = 0.54; the result is fairly independent of assumptions on the underlying cosmology. Our measurement of angular diameter distance D{sub A} (z) is 1.4{sigma} higher than what is expected for the concordance {Lambda}CDM, in accordance to the trend of other spectroscopic BAO measurements for z {approx}> 0.35. We report constraints on cosmological parameters from our measurement in combination with the WMAP7 data and the previous spectroscopic BAO measurements of SDSS and WiggleZ. We refer to our companion papers (Ho et al.; de Putter et al.) for investigations on information of the full power spectrum.

  9. Ion-acoustic solitons and vortices in the e-p-i plasma with field-aligned inhomogeneous flow

    NASA Astrophysics Data System (ADS)

    Saleem, H.; Ali, S.; Saeed, U.; Haque, Q.

    2016-09-01

    The linear and nonlinear characteristics of the ion-acoustic waves are studied in a magnetized electron-positron-ion (e-p-i) plasma with shear flow along the ambient magnetic field. The sheared flow reduces or enhances the frequency of the wave strongly depending upon its polarity and nonlinear equations yield stable electrostatic structures in the form of solitons and vortices. Therefore, it is suggested that in the presence of shear flow, the electrostatic fields with real frequency ωr < csk (where cs is the ion sound speed) exist in e-p-i plasmas. Numerical solutions are discussed using the normalized parameters.

  10. Baryon acoustic oscillations in 2D: Modeling redshift-space power spectrum from perturbation theory

    NASA Astrophysics Data System (ADS)

    Taruya, Atsushi; Nishimichi, Takahiro; Saito, Shun

    2010-09-01

    We present an improved prescription for the matter power spectrum in redshift space taking proper account of both nonlinear gravitational clustering and redshift distortion, which are of particular importance for accurately modeling baryon acoustic oscillations (BAOs). Contrary to the models of redshift distortion phenomenologically introduced but frequently used in the literature, the new model includes the corrections arising from the nonlinear coupling between the density and velocity fields associated with two competitive effects of redshift distortion, i.e., Kaiser and Finger-of-God effects. Based on the improved treatment of perturbation theory for gravitational clustering, we compare our model predictions with the monopole and quadrupole power spectra of N-body simulations, and an excellent agreement is achieved over the scales of BAOs. Potential impacts on constraining dark energy and modified gravity from the redshift-space power spectrum are also investigated based on the Fisher-matrix formalism, particularly focusing on the measurements of the Hubble parameter, angular diameter distance, and growth rate for structure formation. We find that the existing phenomenological models of redshift distortion produce a systematic error on measurements of the angular diameter distance and Hubble parameter by 1%-2% , and the growth-rate parameter by ˜5%, which would become non-negligible for future galaxy surveys. Correctly modeling redshift distortion is thus essential, and the new prescription for the redshift-space power spectrum including the nonlinear corrections can be used as an accurate theoretical template for anisotropic BAOs.

  11. Baryon acoustic oscillations in 2D: Modeling redshift-space power spectrum from perturbation theory

    SciTech Connect

    Taruya, Atsushi; Nishimichi, Takahiro; Saito, Shun

    2010-09-15

    We present an improved prescription for the matter power spectrum in redshift space taking proper account of both nonlinear gravitational clustering and redshift distortion, which are of particular importance for accurately modeling baryon acoustic oscillations (BAOs). Contrary to the models of redshift distortion phenomenologically introduced but frequently used in the literature, the new model includes the corrections arising from the nonlinear coupling between the density and velocity fields associated with two competitive effects of redshift distortion, i.e., Kaiser and Finger-of-God effects. Based on the improved treatment of perturbation theory for gravitational clustering, we compare our model predictions with the monopole and quadrupole power spectra of N-body simulations, and an excellent agreement is achieved over the scales of BAOs. Potential impacts on constraining dark energy and modified gravity from the redshift-space power spectrum are also investigated based on the Fisher-matrix formalism, particularly focusing on the measurements of the Hubble parameter, angular diameter distance, and growth rate for structure formation. We find that the existing phenomenological models of redshift distortion produce a systematic error on measurements of the angular diameter distance and Hubble parameter by 1%-2%, and the growth-rate parameter by {approx}5%, which would become non-negligible for future galaxy surveys. Correctly modeling redshift distortion is thus essential, and the new prescription for the redshift-space power spectrum including the nonlinear corrections can be used as an accurate theoretical template for anisotropic BAOs.

  12. Effect of grazing flow on the acoustic impedance of Helmholtz resonators consisting of single and clustered orifices

    NASA Technical Reports Server (NTRS)

    Hersch, A. S.; Walker, B.

    1979-01-01

    A semiempirical fluid mechanical model is derived for the acoustic behavior of thin-walled single orifice Helmholtz resonators in a grazing flow environment. The incident and cavity sound fields are connected in terms of an orifice discharge coefficient whose values are determined experimentally using the two-microphone method. Measurements show that at high grazing flow speeds, acoustical resistance is almost linearly proportional to the grazing flow speed and almost independent of incident sound pressure. The corresponding values of reactance are much smaller and tend towards zero. For thicker-walled orifice plates, resistance and reactance were observed to be less sensitive to grazing flow as the ratio of plate thickness to orifice diameter increased. Loud tones were observed to radiate from a single orifice Helmholtz resonator due to interaction between the grazing flow shear layer and the resonator cavity. Measurements showed that the tones radiated at a Strouhal number equal to 0.26. The effects of grazing flow on the impedance of Helmholtz resonators consisting of clusters of orifices was also studied. In general, both resistance and reaction were found to be virtually independent of orifice relative spacing and number. These findings are valid with and without grazing flow.

  13. Benthic microbial fuel cell as direct power source for an acoustic modem and seawater oxygen/temperature sensor system.

    PubMed

    Gong, Yanming; Radachowsky, Sage E; Wolf, Michael; Nielsen, Mark E; Girguis, Peter R; Reimers, Clare E

    2011-06-01

    Supported by the natural potential difference between anoxic sediment and oxic seawater, benthic microbial fuel cells (BMFCs) promise to be ideal power sources for certain low-power marine sensors and communication devices. In this study a chambered BMFC with a 0.25 m(2) footprint was used to power an acoustic modem interfaced with an oceanographic sensor that measures dissolved oxygen and temperature. The experiment was conducted in Yaquina Bay, Oregon over 50 days. Several improvements were made in the BMFC design and power management system based on lessons learned from earlier prototypes. The energy was harvested by a dynamic gain charge pump circuit that maintains a desired point on the BMFC's power curve and stores the energy in a 200 F supercapacitor. The system also used an ultralow power microcontroller and quartz clock to read the oxygen/temperature sensor hourly, store data with a time stamp, and perform daily polarizations. Data records were transmitted to the surface by the acoustic modem every 1-5 days after receiving an acoustic prompt from a surface hydrophone. After jump-starting energy production with supplemental macroalgae placed in the BMFC's anode chamber, the average power density of the BMFC adjusted to 44 mW/m(2) of seafloor area which is better than past demonstrations at this site. The highest power density was 158 mW/m(2), and the useful energy produced and stored was ≥ 1.7 times the energy required to operate the system. PMID:21545151

  14. a Method of Measuring the Dynamic Flow Resistance and the Acoustic Measurement of the Effective Static Flow Resistance in Stratified Rockwool Samples

    NASA Astrophysics Data System (ADS)

    Picard, M. A.; Solana, P.; Urchueguía, J. F.

    1998-09-01

    In our work we have analyzed different stratified rockwool samples, with considerable differences regarding density, mean pore diameter, and porosity, by means of a new method for the measurement of the dynamic flow resistance based on the electrical analogy. This method enables us to measure this parameter without the need for placing the sample between two microphones. Our experimental results have been compared to those obtained with a different measurement scheme and, from a theoretical point of view, we have examined the extent to which the capillary pore approximation can be utilized in intermediate flow regimes and Poiseuille flow regimes and in real situations. For this purpose, a static flow resistivity, which was also approximated using an acoustic method and a commonly accepted theoretical approximation, was calculated based on a microscopic study of the samples and the fibre's diameter. Regarding the conclusions obtained, the results show that the new experimental procedure for determining the dynamic flow resistance is of interest in the intermediate and Poiseuille flow regimes in which, within the limitation of our experimental set-up, good results were obtained. The acoustic procedure for measuring a static flow resistivity delivered good results only for a regime close to Poiseuille, which was obtained only with higher density samples.

  15. A New Power Flow Tracing Method Based on Directed Circuit

    NASA Astrophysics Data System (ADS)

    Zhang, Weimin; Guo, Xiaojing; Liu, Yaonian; Ni, Defu; Wang, Lina; Jia, Yanbing

    In this paper, a power-sharing principle is proposed, base on the generation of the directed path. The principle is used to calculate the contributions of individual generators and loads to line flows and the real power transfer among individual generators and loads that are significant to transmission open access. From the IEEE 14-bus power systems, the effectiveness and availability of the method are verified.

  16. Generating expansion model incorporating compact DC power flow equations

    SciTech Connect

    Nderitu, D.G.; Sparrow, F.T.; Yu, Z.

    1998-12-31

    This paper presents a compact method of incorporating the spatial dimension into the generation expansion problem. Compact DC power flow equations are used to provide real-power flow coordination equations. Using these equations the marginal contribution of a generator to th total system loss is formulated as a function of that generator`s output. Incorporating these flow equations directly into the MIP formulation of the generator expansion problem results in a model that captures a generator`s true net marginal cost, one that includes both the cost of generation and the cost of transport. This method contrasts with other methods that iterate between a generator expansion model and an optimal power flow model. The proposed model is very compact and has very good convergence performance. A case study with data from Kenya is used to provide a practical application to the model.

  17. A Novel Device for Total Acoustic Output Measurement of High Power Transducers

    NASA Astrophysics Data System (ADS)

    Howard, S.; Twomey, R.; Morris, H.; Zanelli, C. I.

    2010-03-01

    The objective of this work was to develop a device for ultrasound power measurement applicable over a broad range of medical transducer types, orientations and powers, and which supports automatic measurements to simplify use and minimize errors. Considering all the recommendations from standards such as IEC 61161, an accurate electromagnetic null-balance has been designed for ultrasound power measurements. The sensing element is placed in the water to eliminate errors due to surface tension and water evaporation, and the motion and detection of force is constrained to one axis, to increase immunity to vibration from the floor, water sloshing and water surface waves. A transparent tank was designed so it could easily be submerged in a larger tank to accommodate large transducers or side-firing geometries, and can also be turned upside-down for upward-firing transducers. A vacuum lid allows degassing the water and target in situ. An external control module was designed to operate the sensing/driving loop and to communicate to a local computer for data logging. The sensing algorithm, which incorporates temperature compensation, compares the feedback force needed to cancel the motion for sources in the "on" and "off" states. These two states can be controlled by the control unit or manually by the user, under guidance by a graphical user interface (the system presents measured power live during collection). Software allows calibration to standard weights, or to independently calibrated acoustic sources. The design accommodates a variety of targets, including cone, rubber, brush targets and an oil-filled target for power measurement via buoyancy changes. Measurement examples are presented, including HIFU sources operating at powers from 1 to 100.

  18. Power flow analysis of two coupled plates with arbitrary characteristics

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1988-01-01

    The limitation of keeping two plates identical is removed and the vibrational power input and output are evaluated for different area ratios, plate thickness ratios, and for different values of the structural damping loss factor for the source plate (plate with excitation) and the receiver plate. In performing this parametric analysis, the source plate characteristics are kept constant. The purpose of this parametric analysis is to be able to determine the most critical parameters that influence the flow of vibrational power from the source plate to the receiver plate. In the case of the structural damping parametric analysis, the influence of changes in the source plate damping is also investigated. As was done previously, results obtained from the mobility power flow approach will be compared to results obtained using a statistical energy analysis (SEA) approach. The significance of the power flow results are discussed together with a discussion and a comparison between SEA results and the mobility power flow results. Furthermore, the benefits that can be derived from using the mobility power flow approach, are also examined.

  19. Structural Dynamic Assessment of the GN2 Piping System for NASA's New and Powerful Reverberant Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    McNelis, Mark E.; Staab, Lucas D.; Akers, James C.; Hughes, William O.; Chang, Li C.; Hozman, Aron D.; Henry, Michael W.

    2012-01-01

    The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) has led the design and build of the new world-class vibroacoustic test capabilities at the NASA GRC's Plum Brook Station in Sandusky, Ohio, USA from 2007 to 2011. SAIC-Benham has completed construction of a new reverberant acoustic test facility to support the future testing needs of NASA's space exploration program and commercial customers. The large Reverberant Acoustic Test Facility (RATF) is approximately 101,000 cubic feet in volume and was designed to operate at a maximum empty chamber acoustic overall sound pressure level (OASPL) of 163 dB. This combination of size and acoustic power is unprecedented amongst the world s known active reverberant acoustic test facilities. Initial checkout acoustic testing was performed on March 2011 by SAIC-Benham at test levels up to 161 dB OASPL. During testing, several branches of the gaseous nitrogen (GN2) piping system, which supply the fluid to the noise generating acoustic modulators, failed at their T-junctions connecting the 12 in. supply line to their respective 4 in. branch lines. The problem was initially detected when the oxygen sensors in the horn room indicated a lower than expected oxygen level from which was inferred GN2 leaks in the piping system. In subsequent follow up inspections, cracks were identified in the failed T-junction connections through non-destructive evaluation testing. Through structural dynamic modeling of the piping system, the root cause of the T-junction connection failures was determined. The structural dynamic assessment identified several possible corrective design improvements to the horn room piping system. The effectiveness of the chosen design repairs were subsequently evaluated in September 2011 during acoustic verification testing to 161 dB OASPL.

  20. Structural Dynamic Assessment of the GN2 Piping System for NASA's New and Powerful Reverberant Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    McNelis, Mark E.; Staab, Lucas D.; Akers, James C.; Hughes, WIlliam O.; Chang, Li, C.; Hozman, Aron D.; Henry, Michael W.

    2012-01-01

    The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) has led the design and build of the new world-class vibroacoustic test capabilities at the NASA GRC's Plum Brook Station in Sandusky, Ohio, USA from 2007-2011. SAIC-Benham has completed construction of a new reverberant acoustic test facility to support the future testing needs of NASA's space exploration program and commercial customers. The large Reverberant Acoustic Test Facility (RATF) is approximately 101,000 cu ft in volume and was designed to operate at a maximum empty chamber acoustic overall sound pressure level (OASPL) of 163 dB. This combination of size and acoustic power is unprecedented amongst the world's known active reverberant acoustic test facilities. Initial checkout acoustic testing was performed on March 2011 by SAIC-Benham at test levels up to 161 dB OASPL. During testing, several branches of the gaseous nitrogen (GN2) piping system, which supply the fluid to the noise generating acoustic modulators, failed at their "t-junctions" connecting the 12 inch supply line to their respective 4 inch branch lines. The problem was initially detected when the oxygen sensors in the horn room indicated a lower than expected oxygen level from which was inferred GN2 leaks in the piping system. In subsequent follow up inspections, cracks were identified in the failed "t-junction" connections through non-destructive evaluation testing . Through structural dynamic modeling of the piping system, the root cause of the "t-junction" connection failures was determined. The structural dynamic assessment identified several possible corrective design improvements to the horn room piping system. The effectiveness of the chosen design repairs were subsequently evaluated in September 2011 during acoustic verification testing to 161 dB OASPL.

  1. ac power control in the Core Flow Test Loop

    SciTech Connect

    McDonald, D.W.

    1980-01-01

    This work represents a status report on a development effort to design an ac power controller for the Core Flow Test Loop. The Core Flow Test Loop will be an engineering test facility which will simulate the thermal environment of a gas-cooled fast-breeder reactor. The problems and limitations of using sinusoidal ac power to simulate the power generated within a nuclear reactor are addressed. The transformer-thyristor configuration chosen for the Core Flow Test Loop power supply is presented. The initial considerations, design, and analysis of a closed-loop controller prototype are detailed. The design is then analyzed for improved performance possibilities and failure modes are investigated at length. A summary of the work completed to date and a proposed outline for continued development completes the report.

  2. Fully Nonlinear Edge Gyrokinetic Simulations of Kinetic Geodesic-Acoustic Modes and Boundary Flows

    SciTech Connect

    Xu, X Q; Belli, E; Bodi, K; Candy, J; Chang, C S; Cohen, B I; Cohen, R H; Colella, P; Dimits, A M; Dorr, M R; Gao, Z; Hittinger, J A; Ko, S; Krasheninnikov, S; McKee, G R; Nevins, W M; Rognlien, T D; Snyder, P B; Suh, J; Umansky, M V

    2008-09-18

    We present edge gyrokinetic neoclassical simulations of tokamak plasmas using the fully nonlinear (full-f) continuum code TEMPEST. A nonlinear Boltzmann model is used for the electrons. The electric field is obtained by solving the 2D gyrokinetic Poisson Equation. We demonstrate the following: (1) High harmonic resonances (n > 2) significantly enhance geodesic-acoustic mode (GAM) damping at high-q (tokamak safety factor), and are necessary to explain both the damping observed in our TEMPEST q-scans and experimental measurements of the scaling of the GAM amplitude with edge q{sub 95} in the absence of obvious evidence that there is a strong q dependence of the turbulent drive and damping of the GAM. (2) The kinetic GAM exists in the edge for steep density and temperature gradients in the form of outgoing waves, its radial scale is set by the ion temperature profile, and ion temperature inhomogeneity is necessary for GAM radial propagation. (3) The development of the neoclassical electric field evolves through different phases of relaxation, including GAMs, their radial propagation, and their long-time collisional decay. (4) Natural consequences of orbits in the pedestal and scrape-off layer region in divertor geometry are substantial non-Maxwellian ion distributions and flow characteristics qualitatively like those observed in experiments.

  3. A comparative fluid flow characterisation in a low frequency/high power sonoreactor and mechanical stirred vessel.

    PubMed

    Sajjadi, Baharak; Raman, Abdul Aziz Abdul; Ibrahim, Shaliza

    2015-11-01

    This study aims at analysing the jet-like acoustic streaming generated under low-frequency and high-power ultrasound irradiation and comparing it with fluid streaming generated by traditional mechanical mixing. The main characteristics of fluid flow, which include radial, axial and tangential terms of velocity and their effects on fluid flow pattern, pressure distribution, axial mixing time and turbulence intensity were considered at different power inputs. Both 3D CFD simulation and Particle Image Velocimetry (PIV) were used in this study. The CFD results indicated that the jet-like acoustic streaming reached the velocity magnitude of 145 cm/s at 400 W, which reduced the mixing time to 1.38 s. However, the minimum mixing time of 3.18 s corresponding to the impeller rotational speed of 800 RPM was observed for mechanical stirring. A uniform axial flow pattern was generated under ultrasound irradiation whereas the tangential flow pattern was more prominent in the stirred vessel. Besides, the highest turbulence was observed in the vicinity of the ultrasound transducer and impeller with the values of 138% and 82% for the ultrasonicator and stirred vessel, respectively. The predicted fluid flow pattern under ultrasound irradiation was in a reasonable agreement with that obtained from PIV, with a reasonable accuracy.

  4. Continuous Surveillance Technique for Flow Accelerated Corrosion of Pipe Wall Using Electromagnetic Acoustic Transducer

    NASA Astrophysics Data System (ADS)

    Kojima, F.; Kosaka, D.; Umetani, K.

    2011-06-01

    In this paper, we propose a on-line monitoring technique using electromagnetic acoustic transducer (EMAT). In the series of laboratory experiments, carbon steel pipes were used and each sample was fabricated to simulate FAC. Electromagnetic acoustic resonance method (EMAR) is successfully tested for pipe wall thickness measurements. The validity and the feasibility of our method are also demonstrated through the laboratory experiments.

  5. Solar cycle variations in the powers and damping rates of low-degree solar acoustic oscillations

    NASA Astrophysics Data System (ADS)

    Broomhall, A.-M.; Pugh, C. E.; Nakariakov, V. M.

    2015-12-01

    Helioseismology uses the Sun's natural resonant oscillations to study the solar interior. The properties of the solar oscillations are sensitive to the Sun'2019;s magnetic activity cycle. Here we examine variations in the powers, damping rates, and energy supply rates of the most prominent acoustic oscillations in unresolved, Sun-as-a-star data, obtained by the Birmingham Solar Oscillations Network (BiSON) during solar cycles 22, 23, and the first half of 24. The variations in the helioseismic parameters are compared to the 10.7 cm flux, a well-known global proxy of solar activity. As expected the oscillations are most heavily damped and the mode powers are at a minimum at solar activity maximum. The 10.7 cm flux was linearly regressed using the fractional variations of damping rates and powers observed during cycle 23. In general, good agreement is found between the damping rates and the 10.7 cm flux. However, the linearly regressed 10.7 cm flux and fractional variation in powers diverge in cycles 22 and 24, indicating that the relationship between the mode powers and the 10.7 cm flux is not consistent from one cycle to the next. The energy supply rate of the oscillations, which is usually approximately constant, also decreases at this time. We have determined that this discrepancy is not because of the first-order bias introduced by an increase in the level of background noise or gaps in the data. Although we cannot categorically rule out an instrumental origin, the divergence observed in cycle 24, when the data were of high quality and the data coverage was over 80%, raises the possibility that the effect may be solar in origin.

  6. Research on stochastic power-flow study methods. Final report

    SciTech Connect

    Heydt, G. T.

    1981-01-01

    A general algorithm to determine the effects of uncertainty in bus load and generation on the output of conventional power flow analysis is presented. The use of statistical moments is presented and developed as a means for representing the stochastic process. Statistical moments are used to describe the uncertainties, and facilitate the calculations of single and multivarlate probability density functions of input and output variables. The transformation of the uncertainty through the power flow equations is made by the expansion of the node equations in a multivariate Taylor series about an expected operating point. The series is truncated after the second order terms. Since the power flow equations are nonlinear, the expected values of output quantities is in general not the solution to the conventional load flow problem using expected values of input quantities. The second order transformation offers a correction vector and allows the consideration of larger uncertainties which have caused significant error in the current linear transformation algorithms. Voltage controlled busses are included with consideration of upper and lower limits. The finite reactive power available at generation sites, and fixed ranges of transformer tap movement may have a significant effect on voltage and line power flow statistics. A method is given which considers limitation constraints in the evaluation of all output quantities. The bus voltages, line power flows, transformer taps, and generator reactive power requirements are described by their statistical moments. Their values are expressed in terms of the probability that they are above or below specified limits, and their expected values given that they do fall outside the limits. Thus the algorithm supplies information about severity of overload as well as probability of occurrence. An example is given for an eleven bus system, evaluating each quantity separately. The results are compared with Monte Carlo simulation.

  7. [Comparision of forced expiratory time, recorded by two spirometers with flow sensors of various types, and acoustic duration of tracheal forced expiratory noises].

    PubMed

    Malaeva, V V; Pochekutova, I A; Korenbaum, V I

    2015-01-01

    In the sample of 44 volunteers forced expiratory time values obtained in spirometers, equipped with flow sensor of Lilly type and turbine flow sensor, and acoustic duration of tracheal forced expiratory noises are compared. It is shown that spirometric forced expiratory time is dependent on flow sensor type. Therefore it can't be used in diagnostic aims.

  8. Uncertainty of canal seepage losses estimated using flowing water balance with acoustic Doppler devices

    NASA Astrophysics Data System (ADS)

    Martin, Chad A.; Gates, Timothy K.

    2014-09-01

    Seepage losses from unlined irrigation canals amount to a large fraction of the total volume of water diverted for agricultural use, posing problems to both water conservation and water quality. Quantifying these losses and identifying areas where they are most prominent are crucial for determining the severity of seepage-related complications and for assessing the potential benefits of seepage reduction technologies and materials. A relatively easy and inexpensive way to estimate losses over an extensive segment of a canal is the flowing water balance, or inflow-outflow, method. Such estimates, however, have long been considered fraught with ambiguity due both to measurement error and to spatial and temporal variability. This paper presents a water balance analysis that evaluates uncertainty in 60 tests on two typical earthen irrigation canals. Monte Carlo simulation is used to account for a number of different sources of uncertainty. Issues of errors in acoustic Doppler flow measurement, in water level readings, and in evaporation estimates are considered. Storage change and canal wetted perimeter area, affected by variability in the canal prism, as well as lagged vs. simultaneous measurements of discharge at the inflow and outflow ends also are addressed. Mean estimated seepage loss rates for the tested canal reaches ranged from about -0.005 (gain) to 0.110 m3 s-1 per hectare of canal wetted perimeter (or -0.043 to 0.95 m d-1) with estimated probability distributions revealing substantial uncertainty. Across the tests, the average coefficient of variation was about 240% and the average 90th inter-percentile range was 0.143 m3 s-1 per hectare (1.24 m d-1). Sensitivity analysis indicates that while the predominant influence on seepage uncertainty is error in measured discharge at the upstream and downstream ends of the canal test reach, the magnitude and uncertainty of storage change due to unsteady flow also is a significant influence. Recommendations are

  9. Dynamic Power Flow Controller: Compact Dynamic Phase Angle Regulators for Transmission Power Routing

    SciTech Connect

    2012-01-03

    GENI Project: Varentec is developing compact, low-cost transmission power controllers with fractional power rating for controlling power flow on transmission networks. The technology will enhance grid operations through improved use of current assets and by dramatically reducing the number of transmission lines that have to be built to meet increasing contributions of renewable energy sources like wind and solar. The proposed transmission controllers would allow for the dynamic control of voltage and power flow, improving the grid’s ability to dispatch power in real time to the places where it is most needed. The controllers would work as fail-safe devices whereby the grid would be restored to its present operating state in the event of a controller malfunction instead of failing outright. The ability to affordably and dynamically control power flow with adequate fail-safe switchgear could open up new competitive energy markets which are not possible under the current regulatory structure and technology base.

  10. Studies of acoustic-electric feed-throughs for power transmission through structures

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Doty, Benjamin; Badescu, Mircea; Bao, Xiaoqi; Bar-Cohen, Yoseph; Aldrich, Jack; Chang, Zensheu

    2006-01-01

    There are numerous engineering design problems where the use of wires to transfer power and communicate data thru the walls of a structure is prohibitive or significantly difficult that it may require a complex design. Using physical feedthroughs in such systems may make them susceptible to leakage of chemicals or gasses, loss of pressure or vacuum, as well as difficulties in providing adequate thermal or electrical insulation. Moreover, feeding wires thru a wall of a structure reduces the strength of the structure and makes the structure prone to cracking due to fatigue that can result from cyclic loading and stress concentrations. One area that has already been identified to require a wireless alternative to electrical feedthroughs is the container of the Mars Sample Return Mission, which will need wireless sensors to sense a pressure leak and to avoid potential contamination. The idea of using elastic or acoustic waves to transfer power was suggested recently by [Y. Hu, et al., July 2003]. This system allows for the avoidance of cabling or wiring. The technology is applicable to the transfer of power for actuation, sensing and other tasks inside any sealed container or vacuum/pressure vessel. An alternative approach to the modeling presented previously [Sherrit et a., 2005] used network analysis to solve the same problem in a clear and expandable manner. Experimental tests on three different designs of these devices were performed. The three designs used different methods of coupling the piezoelectric element to the wall. In the first test the piezoelectric material was bolted using a backing structure. In the second test the piezoelectric was clamped after the application of grease and finally the piezoelectric element was attached using a conductive epoxy. The mechanical clamp with grease produced the highest measured efficiency of 53% however this design was the least practical from a fabrication viewpoint. The power transfer efficiency of conductive epoxy

  11. Self-powered water splitting using flowing kinetic energy.

    PubMed

    Tang, Wei; Han, Yu; Han, Chang Bao; Gao, Cai Zhen; Cao, Xia; Wang, Zhong Lin

    2015-01-14

    By utilizing a water-flow-driven triboelectric nanogenerator, a fully self-powered water-splitting process is demonstrated using the electricity converted from a water flow without additional energy costs. Considering the extremely low costs, the demonstrated approach is universally applicable and practically usable for future water electrolysis, which may initiate a research direction in the field of triboelectrolysis and possibly impacts energy science in general.

  12. Continuous measurements of flow rate in a shallow gravel-bed river by a new acoustic system

    NASA Astrophysics Data System (ADS)

    Kawanisi, K.; Razaz, M.; Ishikawa, K.; Yano, J.; Soltaniasl, M.

    2012-05-01

    The continuous measurement of river discharge for long periods of time is crucial in water resource studies. However, the accurate estimation of river discharge is a difficult and labor-intensive procedure; thus, a robust and efficient method of measurement is required. Continuous measurements of flowrate have been carried out in a wide, shallow gravel bed river (water depth ≈ 0.6 m under low-flow conditions, width ≈ 115 m) using Fluvial Acoustic Tomography System (FATS) that has 25 kHz broadband transducers with horizontally omnidirectional and vertically hemispherical beam patterns. Reciprocal sound transmissions were performed between the two acoustic stations located diagonally on both sides of the river. The horizontal distance between the transducers was 301.96 m. FATS enabled the measurement of the depth- and range-averaged sound speed and flow velocity along the ray path. In contrast to traditional point/transect measurements of discharge, in a fraction of a second, FATS covers the entire cross section of river in a single measurement. The flow rates measured by FATS were compared to those estimated by moving boat Acoustic Doppler Current Profiler (ADCP) and rating curve (RC) methods. FATS estimates were in good agreement with ADCP estimates over a range of 20 to 65 m3 s-1. The RMS of residual between the two measurements was 2.41 m3 s-1. On the other hand the flowrate by RC method fairly agreed with FATS estimates for greater discharges than around 40 m3 s-1. This inconsistency arises from biased RC estimates in low flows. Thus, the flow rates derived from FATS could be considered reliable.

  13. An ultra-low power and flexible acoustic modem design to develop energy-efficient underwater sensor networks.

    PubMed

    Sánchez, Antonio; Blanc, Sara; Yuste, Pedro; Perles, Angel; Serrano, Juan José

    2012-01-01

    This paper is focused on the description of the physical layer of a new acoustic modem called ITACA. The modem architecture includes as a major novelty an ultra-low power asynchronous wake-up system implementation for underwater acoustic transmission that is based on a low-cost off-the-shelf RFID peripheral integrated circuit. This feature enables a reduced power dissipation of 10 μW in stand-by mode and registers very low power values during reception and transmission. The modem also incorporates clear channel assessment (CCA) to support CSMA-based medium access control (MAC) layer protocols. The design is part of a compact platform for a long-life short/medium range underwater wireless sensor network.

  14. An Ultra-Low Power and Flexible Acoustic Modem Design to Develop Energy-Efficient Underwater Sensor Networks

    PubMed Central

    Sánchez, Antonio; Blanc, Sara; Yuste, Pedro; Perles, Angel; Serrano, Juan José

    2012-01-01

    This paper is focused on the description of the physical layer of a new acoustic modem called ITACA. The modem architecture includes as a major novelty an ultra-low power asynchronous wake-up system implementation for underwater acoustic transmission that is based on a low-cost off-the-shelf RFID peripheral integrated circuit. This feature enables a reduced power dissipation of 10 μW in stand-by mode and registers very low power values during reception and transmission. The modem also incorporates clear channel assessment (CCA) to support CSMA-based medium access control (MAC) layer protocols. The design is part of a compact platform for a long-life short/medium range underwater wireless sensor network. PMID:22969324

  15. Low power, constant-flow air pump systems

    SciTech Connect

    Polito, M.D.; Albert, B.

    1994-01-01

    A rugged, yet small and lightweight constant-flow air pump system has been designed. Flow control is achieved using a novel approach which is three times more power efficient than previous designs. The resultant savings in battery size and weight makes these pumps ideal for sampling air on balloon platforms. The pump package includes meteorological sensors and an onboard computer that stores time and sensor data and turns the constant-flow pump circuit on/off. Some applications of these systems are also presented in this report.

  16. Flow lasers. [fluid mechanics of high power continuous output operations

    NASA Technical Reports Server (NTRS)

    Christiansen, W. H.; Russell, D. A.; Hertzberg, A.

    1975-01-01

    The present work reviews the fluid-mechanical aspects of high-power continuous-wave (CW) lasers. The flow characteristics of these devices appear as classical fluid-mechanical phenomena recast in a complicated interactive environment. The fundamentals of high-power lasers are reviewed, followed by a discussion of the N2-CO2 gas dynamic laser. Next, the HF/DF supersonic diffusion laser is described, and finally the CO electrical-discharge laser is discussed.

  17. Uncertainty analysis of power monitoring transit time ultrasonic flow meters

    SciTech Connect

    Orosz, A.; Miller, D. W.; Christensen, R. N.; Arndt, S.

    2006-07-01

    A general uncertainty analysis is applied to chordal, transit time ultrasonic flow meters that are used in nuclear power plant feedwater loops. This investigation focuses on relationships between the major parameters of the flow measurement. For this study, mass flow rate is divided into three components, profile factor, density, and a form of volumetric flow rate. All system parameters are used to calculate values for these three components. Uncertainty is analyzed using a perturbation method. Sensitivity coefficients for major system parameters are shown, and these coefficients are applicable to a range of ultrasonic flow meters used in similar applications. Also shown is the uncertainty to be expected for density along with its relationship to other system uncertainties. One other conclusion is that pipe diameter sensitivity coefficients may be a function of the calibration technique used. (authors)

  18. Application of Newton's optimal power flow in voltage/reactive power control

    SciTech Connect

    Bjelogrlic, M.; Babic, B.S. ); Calovic, M.S. ); Ristanovic, P. )

    1990-11-01

    This paper considers an application of Newton's optimal power flow to the solution of the secondary voltage/reactive power control in transmission networks. An efficient computer program based on the latest achievements in the sparse matrix/vector techniques has been developed for this purpose. It is characterized by good robustness, accuracy and speed. A combined objective function appropriate for various system load levels with suitable constraints, for treatment of the power system security and economy is also proposed. For the real-time voltage/reactive power control, a suboptimal power flow procedure has been derived by using the reduced set of control variables. This procedure is based on the sensitivity theory applied to the determination of zones for the secondary voltage/reactive power control and corresponding reduced set of regulating sources, whose reactive outputs represent control variables in the optimal power flow program. As a result, the optimal power flow program output becomes a schedule to be used by operators in the process of the real-time voltage/reactive power control in both normal and emergency operating states.

  19. A neural network-based power system stabilizer using power flow characteristics

    SciTech Connect

    Park, Y.M.; Choi, M.S.; Lee, K.Y.

    1996-06-01

    A neural network-based Power System Stabilizer (Neuro-PSS) is designed for a generator connected to a multi-machine power system utilizing the nonlinear power flow dynamics. The uses of power flow dynamics provide a PSS for a wide range operation with reduced size neutral networks. The Neuro-PSS consists of two neutral networks: Neuro-Identifier and Neuro-Controller. The low-frequency oscillation is modeled by the Neuro-Identifier using the power flow dynamics, then a Generalized Backpropagation-Thorough-Time (GBTT) algorithm is developed to train the Neuro-Controller. The simulation results show that the Neuro-PSS designed in this paper performs well with good damping in a wide operation range compared with the conventional PSS.

  20. An energy signature scheme for steam trap assessment and flow rate estimation using pipe-induced acoustic measurements

    NASA Astrophysics Data System (ADS)

    Olama, Mohammed M.; Allgood, Glenn O.; Kuruganti, Teja P.; Lake, Joe E.

    2012-06-01

    The US Congress has passed legislation dictating that all government agencies establish a plan and process for improving energy efficiencies at their sites. In response to this legislation, Oak Ridge National Laboratory (ORNL) has recently conducted a pilot study to explore the deployment of a wireless sensor system for a real-time measurement-based energy efficiency optimization framework within the steam distribution system within the ORNL campus. We make assessments on the real-time status of the distribution system by observing the state measurements of acoustic sensors mounted on the steam pipes/traps/valves. In this paper, we describe a spectral-based energy signature scheme that interprets acoustic vibration sensor data to estimate steam flow rates and assess steam traps health status. Experimental results show that the energy signature scheme has the potential to identify different steam trap health status and it has sufficient sensitivity to estimate steam flow rate. Moreover, results indicate a nearly quadratic relationship over the test region between the overall energy signature factor and flow rate in the pipe. The analysis based on estimated steam flow and steam trap status helps generate alerts that enable operators and maintenance personnel to take remedial action. The goal is to achieve significant energy-saving in steam lines by monitoring and acting on leaking steam pipes/traps/valves.

  1. Numerical performance analysis of acoustic Doppler velocity profilers in the wake of an axial-flow marine hydrokinetic turbine

    SciTech Connect

    Richmond, Marshall C.; Harding, Samuel F.; Romero Gomez, Pedro DJ

    2015-09-01

    The use of acoustic Doppler current profilers (ADCPs) for the characterization of flow conditions in the vicinity of both experimental and full scale marine hydrokinetic (MHK) turbines is becoming increasingly prevalent. The computation of a three dimensional velocity measurement from divergent acoustic beams requires the assumption that the flow conditions are homogeneous between all beams at a particular axial distance from the instrument. In the near wake of MHK devices, the mean fluid motion is observed to be highly spatially dependent as a result of torque generation and energy extraction. This paper examines the performance of ADCP measurements in such scenarios through the modelling of a virtual ADCP (VADCP) instrument in the velocity field in the wake of an MHK turbine resolved using unsteady computational fluid dynamics (CFD). This is achieved by sampling the CFD velocity field at equivalent locations to the sample bins of an ADCP and performing the coordinate transformation from beam coordinates to instrument coordinates and finally to global coordinates. The error in the mean velocity calculated by the VADCP relative to the reference velocity along the instrument axis is calculated for a range of instrument locations and orientations. The stream-wise velocity deficit and tangential swirl velocity caused by the rotor rotation lead to significant misrepresentation of the true flow velocity profiles by the VADCP, with the most significant errors in the transverse (cross-flow) velocity direction.

  2. An Energy Signature Scheme for Steam Trap Assessment and Flow Rate Estimation Using Pipe-Induced Acoustic Measurements

    SciTech Connect

    Olama, Mohammed M; Allgood, Glenn O; Kuruganti, Phani Teja; Lake, Joe E

    2012-01-01

    The US Congress has passed legislation dictating that all government agencies establish a plan and process for improving energy efficiencies at their sites. In response to this legislation, Oak Ridge National Laboratory (ORNL) has recently conducted a pilot study to explore the deployment of a wireless sensor system for a real-time measurement-based energy efficiency optimization framework within the steam distribution system within the ORNL campus. We make assessments on the real-time status of the distribution system by observing the state measurements of acoustic sensors mounted on the steam pipes/traps/valves. In this paper, we describe a spectral-based energy signature scheme that interprets acoustic vibration sensor data to estimate steam flow rates and assess steam traps health status. Experimental results show that the energy signature scheme has the potential to identify different steam trap health status and it has sufficient sensitivity to estimate steam flow rate. Moreover, results indicate a nearly quadratic relationship over the test region between the overall energy signature factor and flow rate in the pipe. The analysis based on estimated steam flow and steam trap status helps generate alerts that enable operators and maintenance personnel to take remedial action. The goal is to achieve significant energy-saving in steam lines by monitoring and acting on leaking steam pipes/traps/valves.

  3. Exact Convex Relaxation of Optimal Power Flow in Radial Networks

    SciTech Connect

    Gan, LW; Li, N; Topcu, U; Low, SH

    2015-01-01

    The optimal power flow (OPF) problem determines a network operating point that minimizes a certain objective such as generation cost or power loss. It is nonconvex. We prove that a global optimum of OPF can be obtained by solving a second-order cone program, under a mild condition after shrinking the OPF feasible set slightly, for radial power networks. The condition can be checked a priori, and holds for the IEEE 13, 34, 37, 123-bus networks and two real-world networks.

  4. Radiant power flow and absorptance in thin films.

    PubMed

    Baumeister, P W

    1969-02-01

    Equations are developed for the flow of radiant power, transmittance, and absorptance of an absorbing multilayer, in terms of its characteristic matrix and the admittance of the surrounding media. This is applied to the design of bandpass filters and absorbing coatings. Some uv bandpass filters which contain several aluminum films are designed.

  5. Mechanical Power Flow Changes during Multijoint Movement Acquisition

    ERIC Educational Resources Information Center

    Kadota, Koji; Matsuo, Tomoyuki; Hashizume, Ken; Tezuka, Kazushi

    2006-01-01

    We investigated the differences in mechanical power flow in early and late practice stages during a cyclic movement consisting of upper arm circumduction to clarify the change in mechanical energy use with skill acquisition. Seven participants practiced the task every other day until their joint angular movements conformed to those of an expert.…

  6. Vibrational power flow models for transversely vibrating finite Mindlin plate

    NASA Astrophysics Data System (ADS)

    Park, Young-Ho; Hong, Suk-Yoon

    2008-11-01

    In this paper, power flow models were developed to analyze transversely vibrating finite Mindlin plate considering the effects of shear distortion and rotatory inertia, which are very important at high frequencies. The energy governing equations for far-field propagating out-of-plane waves in the Mindlin plate were newly derived by using the classical displacement solutions for out-of-plane motions in the Mindlin plate. The derived energy governing equations are composed of the energetics of three kinds of far-field propagating waves. Below the critical frequency, the energy governing equation for only one kind of far-field propagating wave, which is analogous to that for flexural wave in the Kirchhoff plate, is obtained. On the other hand, above the critical frequency, the energy governing equations for all three kinds of far-field propagating waves are derived. The developed power flow models are in the general forms incorporating not only the Mindlin plate theory but also the Kirchhoff plate theory. To verify the validity and accuracy of the derived models, numerical analyses are performed for the case where the finite Mindlin plates are excited by a harmonic point force, and the spatial distributions and levels of energy density and intensity obtained by the developed power flow solutions for the Mindlin plate are compared with those obtained by the classical displacement solutions for the Mindlin plate, the traditional power flow solutions, and the classical displacement solutions for the Kirchhoff plate for various excitation frequencies and hysteretic damping factors.

  7. Automotive Power Flow System; Auto Mechanics I: 9043.04.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    This automotive power flow system course sets the foundation in the theory of operation of the standard and automatic transmission, clutch assemblies, drive-line and rear axle assemblies. This is a one or two quinmester credit course covering 45 clock hours. In the fourth quinmester course in the tenth year, instruction consists of lectures,…

  8. Application of Interline Power Flow Controller (IPFC) to Power Oscillation Damping

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Yokoyama, Akihiko; Ide, Toshiro

    This paper presents a study of the effect of the Interline Power Flow Controller (IPFC) on power oscillation damping and the design process of its damping controller. The power injection model of IPFC suitable for this study is developed in this paper. The damping effect of the PI controller, which is originally for constant power flow control, is evaluated first, and modal analysis of the power system is carried out. Then the pole shifting technique is adopted to stabilize the oscillatory mode having insufficient damping ratio by use of a PSS-type supplementary damping controller. The design process of the supplementary damping controller and the selection of input signal according to the mode observability are presented. Simulation results demonstrate that the IPFC with the above control system is an effective tool to damp power oscillations.

  9. Primary-Side Power Flow Control of Wireless Power Transfer for Electric Vehicle Charging

    SciTech Connect

    Miller, John M.; Onar, Omer C.; Chinthavali, Madhu

    2014-12-22

    Various noncontacting methods of plug-in electric vehicle charging are either under development or now deployed as aftermarket options in the light-duty automotive market. Wireless power transfer (WPT) is now the accepted term for wireless charging and is used synonymously for inductive power transfer and magnetic resonance coupling. WPT technology is in its infancy; standardization is lacking, especially on interoperability, center frequency selection, magnetic fringe field suppression, and the methods employed for power flow regulation. This paper proposes a new analysis concept for power flow in WPT in which the primary provides frequency selection and the tuned secondary, with its resemblance to a power transmission network having a reactive power voltage control, is analyzed as a transmission network. Analysis is supported with experimental data taken from Oak Ridge National Laboratory s WPT apparatus. Lastly, this paper also provides an experimental evidence for frequency selection, fringe field assessment, and the need for low-latency communications in the feedback path.

  10. A power flow method for evaluating vibration from underground railways

    NASA Astrophysics Data System (ADS)

    Hussein, M. F. M.; Hunt, H. E. M.

    2006-06-01

    One of the major sources of ground-borne vibration is the running of trains in underground railway tunnels. Vibration is generated at the wheel-rail interface, from where it propagates through the tunnel and surrounding soil into nearby buildings. An understanding of the dynamic interfaces between track, tunnel and soil is essential before engineering solutions to the vibration problem can be found. A new method has been developed to evaluate the effectiveness of vibration countermeasures. The method is based on calculating the mean power flow from the tunnel, paying attention to that part of the power which radiates upwards to places where buildings' foundations are expected to be found. The mean power is calculated for an infinite train moving through the tunnel with a constant velocity. An elegant mathematical expression for the mean power flow is derived, which can be used with any underground-tunnel model. To evaluate the effect of vibration countermeasures and track properties on power flow, a comprehensive three-dimensional analytical model is used. It consists of Euler-Bernoulli beams to account for the rails and the track slab. These are coupled in the wavenumber-frequency domain to a thin shell representing the tunnel embedded within an infinite continuum, with a cylindrical cavity representing the surrounding soil.

  11. Invulnerability of power grids based on maximum flow theory

    NASA Astrophysics Data System (ADS)

    Fan, Wenli; Huang, Shaowei; Mei, Shengwei

    2016-11-01

    The invulnerability analysis against cascades is of great significance in evaluating the reliability of power systems. In this paper, we propose a novel cascading failure model based on the maximum flow theory to analyze the invulnerability of power grids. In the model, node initial loads are built on the feasible flows of nodes with a tunable parameter γ used to control the initial node load distribution. The simulation results show that both the invulnerability against cascades and the tolerance parameter threshold αT are affected by node load distribution greatly. As γ grows, the invulnerability shows the distinct change rules under different attack strategies and different tolerance parameters α respectively. These results are useful in power grid planning and cascading failure prevention.

  12. Problems in Assessment of Wind Energy Potential and Acoustic Noise Distribution when Designing Wind Power Plants

    NASA Astrophysics Data System (ADS)

    Bezrukovs, Valerijs; Bezrukovs, Vladislavs; Levins, Nikolajs

    2011-01-01

    Interest in the use of renewable energy in Latvia is increasing every year. Government support and availability of large unpopulated areas on the coast makes the use of these lands for the placement of large wind power plants (WPP) attractive. The key factors that determine the choice of the location of WPP are reliable information about distribution of the resource of wind energy in this area and the influence of wind turbines on the environment. The paper presents the results of years-long observations on the density fluctuations of wind energy at heights of 10 to 60 m in the area in the Baltic Sea coast in Ventspils and Ainaži. The velocity observations since 2007 have been gathered by measurements complex of the LOGGER 9200 Symphonie type. The results are presented in the form of tables, bar charts and graphs. Extrapolation results of wind velocity and density mean values on heights up to 150 m for the two areas with different terrain types were shown. The distribution of acoustic noise in the vicinity of the WPP was studied and an assessment of its impact on the environment in accordance with the Latvian government requirements was conducted.

  13. MONITORING POWER PLANT EFFICIENCY USING THE MICROWAVE-EXCITED THERMAL-ACOUSTIC EFFECT TO MEASURE UNBURNED CARBON

    SciTech Connect

    Robert C. Brown; Robert J. Weber; Jeffrey J. Swetelitsch

    2005-01-01

    The objective of this project is to explore microwave-excited thermal-acoustic (META) phenomena for quantitative analysis of granular and powdered materials, with the culmination of the research to be an on-line carbon-in-ash monitor for coal-fired power plants. This technique of analyzing unburned carbon in fly ash could be a less tedious and time consuming method as compared to the traditional LOI manual procedure. Phase 1 of the research focused on off-line single-frequency thermal-acoustic measurements where an off-line fly ash monitor was constructed that could operate as analytical tool to explore instrument and methodology parameters for quantifying the microwave-excited thermal-acoustic effect of carbon in fly ash, and it was determined that the off-line thermal-acoustic technique could predict the carbon content of a random collection of fly ashes with a linear correlation constant of R{sup 2} = 0.778. Much higher correlations are expected for fly ashes generated from a single boiler. Phase 2 of the research developing a methodology to generate microwave spectra of various powders, including fly ash, coal, and inorganic minerals, and to determine if these microwave spectra could be used for chemical analyses. Although different minerals produced different responses, higher resolution microwave spectra would be required to be able to distinguish among minerals. Phase 3 of the research focused on the development of an on-line fly ash monitor that could be adapted to measure either a thermal-acoustic or thermal-elastic response to due microwave excitation of fly ash. The thermal-acoustic response was successfully employed for this purpose but the thermal-elastic response was too weak to yield a useful on-line device.

  14. The effects of liquid height/volume, initial concentration of reactant and acoustic power on sonochemical oxidation.

    PubMed

    Lim, Myunghee; Ashokkumar, Muthupandian; Son, Younggyu

    2014-11-01

    Even though much knowledge on acoustic cavitation and its application has been accumulated over the past decades, further research is still required to develop industrial uses of acoustic cavitation. It is because the available information is mainly based on small-scale sonoreactors and the design and optimization of sonoreactors for large-scale applications have not been widely studied. In this study, the effects of liquid height/volume, initial concentration of the reactant and input acoustic power on sonochemical oxidation reactions including iodide ion oxidation, As(III) oxidation, and hydrogen peroxide generation were investigated using a 291kHz sonoreactor with various liquid height/volumes (50, 100, 200, 300, 500, and 1000mL) and input powers (23, 40, and 82W). As the liquid height/volume and the input power changed, the power density varied from 23 to 1640W/L and the maximum cavitation yields of triiodide ion for 23, 40, and 82W were observed at 0.05, 0.1, and 0.2/0.3L, respectively. It was found that low power was more effective for the small volume and the large volume required high power level and the moderate power density, approximately 400W/L, was suggested for the sonochemical oxidation of iodide ion in the 291kHz sonoreactor in this study. Similar results were observed in the generation of hydrogen peroxide and the sonochemical oxidation of As(III) to As(V). It was also revealed that KI dosimetry could be applicable for the estimation of the sonochemical reactions of non-volatile compounds such as As(III).

  15. Measured and calculated acoustic attenuation rates of tuned resonator arrays for two surface impedance distribution models with flow

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Abrahamson, A. Louis; Jones, Michael G.

    1988-01-01

    An experiment was performed to validate two analytical models for predicting low frequency attenuation of duct liner configurations built from an array of seven resonators that could be individually tuned via adjustable cavity depths. These analytical models had previously been developed for high frequency aero-engine inlet duct liner design. In the low frequency application, the liner surface impedance distribution is unavoidably spatially varying by virtue of available fabrication techniques. The characteristic length of this spatial variation may be a significant fraction of the acoustic wavelength. Comparison of measured and predicted attenuation rates and transmission losses for both modal decomposition and finite element propagation models were in good to excellent agreement for a test frequency range that included the first and second cavity resonance frequencies. This was true for either of two surface impedance distribution modeling procedures used to simplify the impedance boundary conditions. In the presence of mean flow, measurements revealed a fine scale structure of acoustic hot spots in the attenuation and phase profiles. These details were accurately predicted by the finite element model. Since no impedance changes due to mean flow were assumed, it is concluded that this fine scale structure was due to convective effects of the mean flow interacting with the surface impedance nonuniformities.

  16. Flight and Static Exhaust Flow Properties of an F110-GE-129 Engine in an F-16XL Airplane During Acoustic Tests

    NASA Technical Reports Server (NTRS)

    Holzman, Jon K.; Webb, Lannie D.; Burcham, Frank W., Jr.

    1996-01-01

    The exhaust flow properties (mass flow, pressure, temperature, velocity, and Mach number) of the F110-GE-129 engine in an F-16XL airplane were determined from a series of flight tests flown at NASA Dryden Flight Research Center, Edwards, California. These tests were performed in conjunction with NASA Langley Research Center, Hampton, Virginia (LARC) as part of a study to investigate the acoustic characteristics of jet engines operating at high nozzle pressure conditions. The range of interest for both objectives was from Mach 0.3 to Mach 0.9. NASA Dryden flew the airplane and acquired and analyzed the engine data to determine the exhaust characteristics. NASA Langley collected the flyover acoustic measurements and correlated these results with their current predictive codes. This paper describes the airplane, tests, and methods used to determine the exhaust flow properties and presents the exhaust flow properties. No acoustics results are presented.

  17. Simultaneous backward data transmission and power harvesting in an ultrasonic transcutaneous energy transfer link employing acoustically dependent electric impedance modulation.

    PubMed

    Ozeri, Shaul; Shmilovitz, Doron

    2014-09-01

    The advancement and miniaturization of body implanted medical devices pose several challenges to Ultrasonic Transcutaneous Energy Transfer (UTET), such as the need to reduce the size of the piezoelectric resonator, and the need to maximize the UTET link power-transfer efficiency. Accordingly, the same piezoelectric resonator that is used for energy harvesting at the body implant, may also be used for ultrasonic backward data transfer, for instance, through impedance modulation. This paper presents physical considerations and design guidelines of the body implanted transducer of a UTET link with impedance modulation for a backward data transfer. The acoustic matching design procedure was based on the 2×2 transfer matrix chain analysis, in addition to the Krimholtz Leedom and Matthaei KLM transmission line model. The UTET power transfer was carried out at a frequency of 765 kHz, continuous wave (CW) mode. The backward data transfer was attained by inserting a 9% load resistance variation around its matched value (550 Ohm), resulting in a 12% increase in the acoustic reflection coefficient. A backward data transmission rate of 1200 bits/s was experimentally demonstrated using amplitude shift keying, simultaneously with an acoustic power transfer of 20 mW to the implant. PMID:24861424

  18. Simultaneous backward data transmission and power harvesting in an ultrasonic transcutaneous energy transfer link employing acoustically dependent electric impedance modulation.

    PubMed

    Ozeri, Shaul; Shmilovitz, Doron

    2014-09-01

    The advancement and miniaturization of body implanted medical devices pose several challenges to Ultrasonic Transcutaneous Energy Transfer (UTET), such as the need to reduce the size of the piezoelectric resonator, and the need to maximize the UTET link power-transfer efficiency. Accordingly, the same piezoelectric resonator that is used for energy harvesting at the body implant, may also be used for ultrasonic backward data transfer, for instance, through impedance modulation. This paper presents physical considerations and design guidelines of the body implanted transducer of a UTET link with impedance modulation for a backward data transfer. The acoustic matching design procedure was based on the 2×2 transfer matrix chain analysis, in addition to the Krimholtz Leedom and Matthaei KLM transmission line model. The UTET power transfer was carried out at a frequency of 765 kHz, continuous wave (CW) mode. The backward data transfer was attained by inserting a 9% load resistance variation around its matched value (550 Ohm), resulting in a 12% increase in the acoustic reflection coefficient. A backward data transmission rate of 1200 bits/s was experimentally demonstrated using amplitude shift keying, simultaneously with an acoustic power transfer of 20 mW to the implant.

  19. Exploiting flow to control the in vitro spatiotemporal distribution of microbubble-seeded acoustic cavitation activity in ultrasound therapy

    NASA Astrophysics Data System (ADS)

    Pouliopoulos, Antonios N.; Bonaccorsi, Simone; Choi, James J.

    2014-11-01

    Focused ultrasound and microbubbles have been extensively used to generate therapeutic bioeffects. Despite encouraging in vivo results, there remains poor control of the magnitude and spatial distribution of these bioeffects due to the limited ability of conventional pulse shapes and sequences to control cavitation dynamics. Thus current techniques are restricted by an efficacy-safety trade-off. The primary aim of the present study was to incorporate the presence of flow in the design of new short pulse sequences, which can more uniformly distribute the cavitation activity. Microbubbles flowing (fluid velocity: 10 mm s-1) through a 300 μm tube were sonicated with a focused 0.5 MHz transducer while acoustic emissions were captured with an inserted focused 7.5 MHz passive cavitation detector. The two foci were co-axially aligned and their focal points were overlapped. Whereas conventional sequences are composed of a long burst (>10 000 cycles) emitted at a low burst repetition frequency (<10 Hz), we decomposed this burst into short pulses by adding intervals to facilitate inter-pulse microbubble movement. To evaluate how this sequence influenced cavitation distribution, we emitted short pulses (peak-rarefactional pressure (PRP): 40-366 kPa, pulse length (PL): 5-25 cycles) at high pulse repetition frequencies (PRF: 0.625-10 kHz) for a burst length of 100 ms. Increased cavitation persistence, implied by the duration of the microbubble acoustic emissions, was a measure of improved distribution due to the presence of flow. Sonication at lower acoustic pressures, longer pulse intervals and lower PLs improved the spatial distribution of cavitation. Furthermore, spectral analysis of the microbubble emissions revealed that the improvement at low pressures is due to persisting stable cavitation. In conclusion, new short-pulse sequences were shown to improve spatiotemporal control of acoustic cavitation dynamics during physiologically relevant flow. This

  20. Acoustic conditions in the vicinity of an orifice that depends on grazing flow boundary layers. An experimental investigation. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Kompenhans, J.

    1977-01-01

    The reflection factor at a tube which ends at a plate over which a flow is forming was determined as a function of the Strouhal number, formed from the flow velocity, the aperture radius, and the acoustic frequency. Several adjacent openings were investigated to determine the interactions between several openings.

  1. Magnetic Amplifier-Based Power-Flow Controller

    DOE PAGES

    Dimitrovski, Aleksandar; Li, Zhi; Ozpineci, Burak

    2015-02-05

    The concept of the magnetic amplifier, a common electromagnetic device in electronic applications in the past, has seldom been used in power systems. In this paper, we introduce the magnetic amplifier-based power-flow controller (MAPFC), an innovative low-cost device that adopts the idea of the magnetic amplifier for power-flow control applications. The uniqueness of MAPFC is in the use of the magnetization of the ferromagnetic core, shared by an ac and a dc winding, as the medium to control the ac winding reactance inserted in series with the transmission line to be controlled. Large power flow in the line can bemore » regulated by the small dc input to the dc winding. Moreover, a project on the R&D of an MAPFC has been funded by the U.S. Department of Energy (DOE) and conducted by the Oak Ridge National Laboratory (ORNL), the University of Tennessee-Knoxville, and Waukesha Electric Systems, Inc. since early 2012. Findings from the project are presented along with some results obtained in a laboratory environment.« less

  2. Magnetic Amplifier-Based Power-Flow Controller

    SciTech Connect

    Dimitrovski, Aleksandar; Li, Zhi; Ozpineci, Burak

    2015-02-05

    The concept of the magnetic amplifier, a common electromagnetic device in electronic applications in the past, has seldom been used in power systems. In this paper, we introduce the magnetic amplifier-based power-flow controller (MAPFC), an innovative low-cost device that adopts the idea of the magnetic amplifier for power-flow control applications. The uniqueness of MAPFC is in the use of the magnetization of the ferromagnetic core, shared by an ac and a dc winding, as the medium to control the ac winding reactance inserted in series with the transmission line to be controlled. Large power flow in the line can be regulated by the small dc input to the dc winding. Moreover, a project on the R&D of an MAPFC has been funded by the U.S. Department of Energy (DOE) and conducted by the Oak Ridge National Laboratory (ORNL), the University of Tennessee-Knoxville, and Waukesha Electric Systems, Inc. since early 2012. Findings from the project are presented along with some results obtained in a laboratory environment.

  3. A synchronized particle image velocimetry and infrared thermography technique applied to an acoustic streaming flow

    PubMed Central

    Sou, In Mei; Layman, Christopher N.; Ray, Chittaranjan

    2013-01-01

    Subsurface coherent structures and surface temperatures are investigated using simultaneous measurements of particle image velocimetry (PIV) and infrared (IR) thermography. Results for coherent structures from acoustic streaming and associated heating transfer in a rectangular tank with an acoustic horn mounted horizontally at the sidewall are presented. An observed vortex pair develops and propagates in the direction along the centerline of the horn. From the PIV velocity field data, distinct kinematic regions are found with the Lagrangian coherent structure (LCS) method. The implications of this analysis with respect to heat transfer and related sonochemical applications are discussed. PMID:24347810

  4. A synchronized particle image velocimetry and infrared thermography technique applied to an acoustic streaming flow.

    PubMed

    Sou, In Mei; Allen, John S; Layman, Christopher N; Ray, Chittaranjan

    2011-11-01

    Subsurface coherent structures and surface temperatures are investigated using simultaneous measurements of particle image velocimetry (PIV) and infrared (IR) thermography. Results for coherent structures from acoustic streaming and associated heating transfer in a rectangular tank with an acoustic horn mounted horizontally at the sidewall are presented. An observed vortex pair develops and propagates in the direction along the centerline of the horn. From the PIV velocity field data, distinct kinematic regions are found with the Lagrangian coherent structure (LCS) method. The implications of this analysis with respect to heat transfer and related sonochemical applications are discussed. PMID:24347810

  5. An experimental investigation of the generation and consequences of acoustic waves in an axial flow compressor Large axial spacings between blade rows

    NASA Astrophysics Data System (ADS)

    Parker, R.; Stoneman, S. A. T.

    1985-03-01

    The excitation of acoustic waves by vortex shedding from the inlet guide vanes in the annulus of a single-stage, low-speed axial-flow compressor test rig is investigated experimentally, in an effort to examine the assumptions made in the study of Parker (1984) and to provide data for mathematical models of these phenomena. The experimental setup and the transducers used to measure the operating and acoustic parameters are described in detail and illustrated with photographs and drawings, and the results are presented graphically. It is found that each mode excited can be associated with several excitation frequencies of the rotor blades, indicating forced blade vibration due to acoustic resonances.

  6. Resistive Network Optimal Power Flow: Uniqueness and Algorithms

    SciTech Connect

    Tan, CW; Cai, DWH; Lou, X

    2015-01-01

    The optimal power flow (OPF) problem minimizes the power loss in an electrical network by optimizing the voltage and power delivered at the network buses, and is a nonconvex problem that is generally hard to solve. By leveraging a recent development on the zero duality gap of OPF, we propose a second-order cone programming convex relaxation of the resistive network OPF, and study the uniqueness of the optimal solution using differential topology, especially the Poincare-Hopf Index Theorem. We characterize the global uniqueness for different network topologies, e.g., line, radial, and mesh networks. This serves as a starting point to design distributed local algorithms with global behaviors that have low complexity, are computationally fast, and can run under synchronous and asynchronous settings in practical power grids.

  7. EFFECT OF COMBUSTOR INLET GEOMETRY ON ACOUSTIC SIGNATURE AND FLOW FIELD BEHAVIOUR OF THE LOW SWIRL INJECTOR

    SciTech Connect

    Therkelsen, Peter L.; Littlejohn, David; Cheng, Robert K.; Portillo, J. Enrique; Martin, Scott M.

    2009-11-30

    Low Swirl Injector (LSI) technology is a lean premixed combustion method that is being developed for fuel-flexible gas turbines. The objective of this study is to characterize the fuel effects and influences of combustor geometry on the LSI's overall acoustic signatures and flowfields. The experiments consist of 24 flames at atmospheric condition with bulk flows ranging between 10 and 18 m/s. The flames burn CH{sub 4} (at {phi} = 0.6 & 0.7) and a blend of 90% H{sub 2} - 10% CH{sub 4} by volume (at {phi} = 0.35 & 0.4). Two combustor configurations are used, consisting of a cylindrical chamber with and without a divergent quarl at the dump plane. The data consist of pressure spectral distributions at five positions within the system and 2D flowfield information measured by Particle Imaging Velocimetry (PIV). The results show that acoustic oscillations increase with U{sub 0} and {phi}. However, the levels in the 90% H{sub 2} flames are significantly higher than in the CH{sub 4} flames. For both fuels, the use of the quarl reduces the fluctuating pressures in the combustion chamber by up to a factor of 7. The PIV results suggest this to be a consequence of the quarl restricting the formation of large vortices in the outer shear layer. A Generalized Instability Model (GIM) was applied to analyze the acoustic response of baseline flames for each of the two fuels. The measured frequencies and the stability trends for these two cases are predicted and the triggered acoustic mode shapes identified.

  8. Low-speed wind-tunnel investigation of the aerodynamic and acoustic performance of a translating grid choked flow inlet

    NASA Technical Reports Server (NTRS)

    Abbott, J. M.; Miller, B. A.; Golladay, R. L.

    1974-01-01

    The aerodynamic and acoustic performance of a translating grid choked-flow inlet was determined in a low-speed wind tunnel at free-stream velocities of 24, 32, and 45 m/sec and incidence angles of 0, 10, 20, 30, 35, 40, 45, and 50 deg. The inlet was sized to fit a 13.97- centimeter-diameter fan with a design weight flow of 2.49 kg/sec. Measurements were made to determine inlet total pressure recovery, flow distortion, and sound pressure level for both choked and unchoked geometries over a range of inlet weight flows. For the unchoked geometry, inlet total pressure recovery ranged from 0.983 to 0.989 at incidence angles less than 40 deg. At 40 deg incidence angle, inlet cowl separation was encountered which resulted in lower values of pressure recovery and higher levels of fan broadband noise. For the choked geometry, increasing total pressure losses occurred with increasing inlet weight flow that prevented the inlet from reaching full choked conditions with the particular fan used. These losses were attributed to the high Mach number drag rise characteristics of airfoil grid. At maximum attainable inlet weight flow, the total pressure recovery at static conditions was 0.935. The fan blade passing frequency and other fan generated pure tones were eliminated from the noise spectrum, but the broadband level was increased.

  9. MHD Flow Control and Power Generation in Low-Temperature Supersonic Flows

    NASA Astrophysics Data System (ADS)

    Adamovich, Igor; Nishihara, Munetake

    2006-10-01

    The paper presents results of cold MHD flow deceleration and MHD power generation experiments using repetitively pulsed, short pulse duration, high voltage discharge to produce ionization in M=3 nitrogen and air flows. MHD effect on the flow is detected from the flow static pressure measurements. Retarding Lorentz force applied to the flow produces a static pressure increase of up to 17-20%, while accelerating force of the same magnitude results in static pressure increase of up to 5-7%. No discharge polarity effect on the static pressure was detected in the absence of the magnetic field. The fraction of the discharge input power going into Joule heat in nitrogen and dry air, inferred from the present experiments, is low, α=0.1, primarily because energy remains frozen in the vibrational energy mode of nitrogen. Comparison of the experimental results with the modeling calculations shows that the retarding Lorentz force increases the static pressure rise produced by Joule heating of the flow, while the accelerating Lorentz force reduces the pressure rise. This result provides first direct evidence of cold supersonic flow deceleration by Lorentz force.

  10. Peak power prediction of a vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Yu, V. K.; Chen, D.

    2014-12-01

    The vanadium redox flow battery (VRFB) is a promising grid-scale energy storage technology, but future widespread commercialization requires a considerable reduction in capital costs. Determining the appropriate battery size for the intended power range can help minimize the amount of materials needed, thereby reducing capital costs. A physics-based model is an essential tool for predicting the power range of large scale VRFB systems to aid in the design optimization process. This paper presents a modeling framework that accounts for the effects of flow rate on the pumping losses, local mass transfer rate, and nonuniform vanadium concentration in the cell. The resulting low-order model captures battery performance accurately even at high power densities and remains computationally practical for stack-level optimization and control purposes. We first use the model to devise an optimal control strategy that maximizes battery life during discharge. Assuming optimal control is implemented, we then determine the upper efficiency limits of a given VRFB system and compare the net power and associated overpotential and pumping losses at different operating points. We also investigate the effects of varying the electrode porosity, stack temperature, and total vanadium concentration on the peak power.

  11. 76 FR 48845 - Free Flow Power Corporation; Notice of Preliminary Permit Application Accepted for Filing and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-09

    ... Energy Regulatory Commission Free Flow Power Corporation; Notice of Preliminary Permit Application..., 2011, Free Flow Power Corporation filed an application, pursuant to section 4(f) of the Federal Power...: Ramya Swaminathan, Free Flow Power Corporation, 239 Causeway Street, Boston, MA 02114; phone (978)...

  12. 76 FR 48846 - Free Flow Power Corporation; Notice of Preliminary Permit Application Accepted for Filing and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-09

    ... Energy Regulatory Commission Free Flow Power Corporation; Notice of Preliminary Permit Application..., 2011, Free Flow Power Corporation filed an application, pursuant to section 4(f) of the Federal Power...: Ramya Swaminathan, Free Flow Power Corporation, 239 Causeway Street, Boston, MA 02114; phone (978)...

  13. Reversible swarming and separation of self-propelled chemically powered nanomotors under acoustic fields.

    PubMed

    Xu, Tailin; Soto, Fernando; Gao, Wei; Dong, Renfeng; Garcia-Gradilla, Victor; Magaña, Ernesto; Zhang, Xueji; Wang, Joseph

    2015-02-18

    The collective behavior of biological systems has inspired efforts toward the controlled assembly of synthetic nanomotors. Here we demonstrate the use of acoustic fields to induce reversible assembly of catalytic nanomotors, controlled swarm movement, and separation of different nanomotors. The swarming mechanism relies on the interaction between individual nanomotors and the acoustic field, which triggers rapid migration and assembly around the nearest pressure node. Such on-demand assembly of catalytic nanomotors is extremely fast and reversible. Controlled movement of the resulting swarm is illustrated by changing the frequency of the acoustic field. Efficient separation of different types of nanomotors, which assemble in distinct swarming regions, is illustrated. The ability of acoustic fields to regulate the collective behavior of catalytic nanomotors holds considerable promise for a wide range of practical applications. PMID:25634724

  14. Vector computer implementation of power flow outage studies

    SciTech Connect

    Granelli, G.P.; Montagna, M.; Pasini, G.L. ); Marannino, P. )

    1992-05-01

    This paper presents an application of vector and parallel processing to power flow outage studies on large-scale networks. Standard sparsity programming is not well suited to the capabilities of vector and parallel computers because of the extremely short vectors processed in load flow studies. In order to improve computation efficiency, the operations required to perform both forward/backward solution and power residual calculation are gathered in the form of long FORTRAN DO loops. Two algorithms are proposed and compared with the results of a program written for scalar processing. Simulations for the outage studies on IEEE standard networks and some different configurations of the Italian and European (UCPTE) EHV systems are run on a CRAY Y-MP8/432 vector computer (and partially on a IBM 3090/200S VF). The multitasking facility of the CRAY computer is also exploited in order to shorten the wall clock time required by a complete outage simulation.

  15. Artificial bee colony algorithm for solving optimal power flow problem.

    PubMed

    Le Dinh, Luong; Vo Ngoc, Dieu; Vasant, Pandian

    2013-01-01

    This paper proposes an artificial bee colony (ABC) algorithm for solving optimal power flow (OPF) problem. The objective of the OPF problem is to minimize total cost of thermal units while satisfying the unit and system constraints such as generator capacity limits, power balance, line flow limits, bus voltages limits, and transformer tap settings limits. The ABC algorithm is an optimization method inspired from the foraging behavior of honey bees. The proposed algorithm has been tested on the IEEE 30-bus, 57-bus, and 118-bus systems. The numerical results have indicated that the proposed algorithm can find high quality solution for the problem in a fast manner via the result comparisons with other methods in the literature. Therefore, the proposed ABC algorithm can be a favorable method for solving the OPF problem.

  16. Artificial Bee Colony Algorithm for Solving Optimal Power Flow Problem

    PubMed Central

    Le Dinh, Luong; Vo Ngoc, Dieu

    2013-01-01

    This paper proposes an artificial bee colony (ABC) algorithm for solving optimal power flow (OPF) problem. The objective of the OPF problem is to minimize total cost of thermal units while satisfying the unit and system constraints such as generator capacity limits, power balance, line flow limits, bus voltages limits, and transformer tap settings limits. The ABC algorithm is an optimization method inspired from the foraging behavior of honey bees. The proposed algorithm has been tested on the IEEE 30-bus, 57-bus, and 118-bus systems. The numerical results have indicated that the proposed algorithm can find high quality solution for the problem in a fast manner via the result comparisons with other methods in the literature. Therefore, the proposed ABC algorithm can be a favorable method for solving the OPF problem. PMID:24470790

  17. Wireless acoustic-electric feed-through for power and signal transmission

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart (Inventor); Bar-Cohen, Yoseph (Inventor); Bao, Xiaoqi (Inventor); Doty, Benjamin (Inventor); Badescu, Mircea (Inventor); Chang, Zensheu (Inventor)

    2011-01-01

    An embodiment provides electrical energy from a source on one side of a medium to a load on the other side of the medium, the embodiment including a first piezoelectric to generate acoustic energy in response to electrical energy from the source, and a second piezoelectric to convert the received acoustic energy to electrical energy used by the load. Other embodiments are described and claimed.

  18. Convective flow reversal in self-powered enzyme micropumps

    PubMed Central

    Ortiz-Rivera, Isamar; Shum, Henry; Agrawal, Arjun; Sen, Ayusman; Balazs, Anna C.

    2016-01-01

    Surface-bound enzymes can act as pumps that drive large-scale fluid flows in the presence of their substrates or promoters. Thus, enzymatic catalysis can be harnessed for “on demand” pumping in nano- and microfluidic devices powered by an intrinsic energy source. The mechanisms controlling the pumping have not, however, been completely elucidated. Herein, we combine theory and experiments to demonstrate a previously unreported spatiotemporal variation in pumping behavior in urease-based pumps and uncover the mechanisms behind these dynamics. We developed a theoretical model for the transduction of chemical energy into mechanical fluid flow in these systems, capturing buoyancy effects due to the solution containing nonuniform concentrations of substrate and product. We find that the qualitative features of the flow depend on the ratios of diffusivities δ=DP/DS and expansion coefficients β=βP/βS of the reaction substrate (S) and product (P). If δ>1 and δ>β (or if δ<1 and δ<β), an unexpected phenomenon arises: the flow direction reverses with time and distance from the pump. Our experimental results are in qualitative agreement with the model and show that both the speed and direction of fluid pumping (i) depend on the enzyme activity and coverage, (ii) vary with the distance from the pump, and (iii) evolve with time. These findings permit the rational design of enzymatic pumps that accurately control the direction and speed of fluid flow without external power sources, enabling effective, self-powered fluidic devices. PMID:26903618

  19. Convective flow reversal in self-powered enzyme micropumps.

    PubMed

    Ortiz-Rivera, Isamar; Shum, Henry; Agrawal, Arjun; Sen, Ayusman; Balazs, Anna C

    2016-03-01

    Surface-bound enzymes can act as pumps that drive large-scale fluid flows in the presence of their substrates or promoters. Thus, enzymatic catalysis can be harnessed for “on demand” pumping in nano- and microfluidic devices powered by an intrinsic energy source. The mechanisms controlling the pumping have not, however, been completely elucidated. Herein, we combine theory and experiments to demonstrate a previously unreported spatiotemporal variation in pumping behavior in urease-based pumps and uncover the mechanisms behind these dynamics. We developed a theoretical model for the transduction of chemical energy into mechanical fluid flow in these systems, capturing buoyancy effects due to the solution containing nonuniform concentrations of substrate and product. We find that the qualitative features of the flow depend on the ratios of diffusivities δ=D(P)/D(S) and expansion coefficients β=β(P)/β(S) of the reaction substrate (S) and product (P). If δ>1 and δ>β (or if δ<1 and δ<β ), an unexpected phenomenon arises: the flow direction reverses with time and distance from the pump. Our experimental results are in qualitative agreement with the model and show that both the speed and direction of fluid pumping (i) depend on the enzyme activity and coverage, (ii) vary with the distance from the pump, and (iii) evolve with time. These findings permit the rational design of enzymatic pumps that accurately control the direction and speed of fluid flow without external power sources, enabling effective, self-powered fluidic devices. PMID:26903618

  20. Single-phase power distribution system power flow and fault analysis

    NASA Technical Reports Server (NTRS)

    Halpin, S. M.; Grigsby, L. L.

    1992-01-01

    Alternative methods for power flow and fault analysis of single-phase distribution systems are presented. The algorithms for both power flow and fault analysis utilize a generalized approach to network modeling. The generalized admittance matrix, formed using elements of linear graph theory, is an accurate network model for all possible single-phase network configurations. Unlike the standard nodal admittance matrix formulation algorithms, the generalized approach uses generalized component models for the transmission line and transformer. The standard assumption of a common node voltage reference point is not required to construct the generalized admittance matrix. Therefore, truly accurate simulation results can be obtained for networks that cannot be modeled using traditional techniques.

  1. Assessment of the application of acoustic emission technology for monitoring the presence of sand under multiphase flow condition

    SciTech Connect

    El-Alej, M. Mba, D. Yeung, H.

    2014-04-11

    The monitoring of multiphase flow is an established process that has spanned several decades. This paper demonstrates the use of acoustic emission (AE) technology to investigate sand transport characteristic in three-phase (air-water-sand) flow in a horizontal pipe where the superficial gas velocity (VSG) had a range of between 0.2 ms{sup −1} to 2.0 ms{sup −1} and superficial liquid velocity (VSL) had a range of between 0.2 ms{sup −1} to 1.0 ms{sup −1}. The experimental findings clearly show a correlation exists between AE energy levels, sand concentration, superficial gas velocity (VSG) and superficial liquid velocity (VSL)

  2. [Thermoelastic excitation of acoustic waves in biological models under the effect of the high peak-power pulsed electromagnetic radiation of extremely high frequency].

    PubMed

    Gapeev, A B; Rubanik, A V; Pashovkin, T N; Chemeris, N K

    2007-01-01

    The capability of high peak-power pulsed electromagnetic radiation of extremely high frequency (35,27 GHz, pulse widths of 100 and 600 ns, peak power of 20 kW) to excite acoustic waves in model water-containing objects and muscular tissue of animals has been experimentally shown for the first time. The amplitude and duration of excited acoustic pulses are within the limits of accuracy of theoretical assessments and have a complex nonlinear dependence on the energy input of electromagnetic radiation supplied. The velocity of propagation of acoustic pulses in water-containing models and isolated muscular tissue of animals was close to the reference data. The excitation of acoustic waves in biological systems under the action of high peak-power pulsed electromagnetic radiation of extremely high frequency is the important phenomenon, which essentially contributes to the understanding of the mechanisms of biological effects of these electromagnetic fields.

  3. Power spectral signatures of interplanetary corotating and transient flows

    NASA Technical Reports Server (NTRS)

    Goldstein, M. L.; Burlaga, L. F.; Matthaeus, W. H.

    1984-01-01

    Studies of the time behavior of the galactic cosmic ray intensity have concluded that long term decreases in the intensity are generally associated with systems of interplanetary flows that contain flare generated shock waves, magnetic clouds and other transient phenomena. The magnetic field power spectral signatures of such flow systems are compared to power spectra obtained during times when the solar wind is dominated by stable corotating streams that do not usually produce long-lived reduction in the cosmic ray intensity. The spectral signatures of these two types of regimes (transient and corotating) are distinct. However, the distinguishing features are not the same throughout the heliosphere. In data collected beyond 1 AU the primary differences are in the power spectra of the magnitude of the magnetic field rather than in the power in the field components. Consequently, decreases in cosmic ray intensity are very likely due to magnetic mirror forces and gradient drifts rather than to small angle scattering due to cyclotron wave-particle interactions.

  4. Further developments in LP-based optimal power flow

    SciTech Connect

    Alsac, O.; Bright, J.; Prais, M.; Stott, B.P )

    1990-08-01

    Over the past twenty five years, the optimal power flow (OPF) approach that has received the most widespread practical application is the one based on linear programming (LP). Special customized LP methods have been utilized primarily for fast reliable security-constrained dispatch using decoupled separable OPF problem formulations. They have been used in power system planning, operations and control. Nevertheless, while the LP approach has a number of important attributes, its range of application in the OPF field has remained somewhat restricted. This paper describes further developments that have transformed the LP approach into a truly general-purpose OPF solver, with computational and other advantages over even recent nonlinear programming (NLP) methods. The nonseparable loss-minimization problem can now be solved, giving the same results as NLP on power systems of any size and type.

  5. NASA powered lift facility internally generated noise and its transmission to the acoustic far field

    NASA Technical Reports Server (NTRS)

    Huff, Ronald G.

    1988-01-01

    Noise tests of NASA Lewis Research Center's Powered Lift Facility (PLF) were performed to determine the frequency content of the internally generated noise that reaches the far field. The sources of the internally generated noise are the burner, elbows, valves, and flow turbulence. Tests over a range of nozzle pressure ratios from 1.2 to 3.5 using coherence analysis revealed that low frequency noise below 1200 Hz is transmitted through the nozzle. Broad banded peaks at 240 and 640 Hz were found in the transmitted noise. Aeroacoustic excitation effects are possible in this frequency range. The internal noise creates a noise floor that limits the amount of jet noise suppression that can be measured on the PLF and similar facilities.

  6. Biogeochemical processes controlling methane in gassy coastal sediments—Part 2: groundwater flow control of acoustic turbidity in Eckernförde Bay Sediments

    NASA Astrophysics Data System (ADS)

    Albert, Daniel B.; Martens, Christopher S.; Alperin, Marc J.

    1998-12-01

    To understand the origin of the methane distributions in sediments of Eckernförde Bay, three sites were sampled in May 1994 for determination of methane, sulfate and chloride concentrations in the sediment porewaters. In much of the Bay, bubbles of biogenic methane gas within the sediments lead to widespread 'acoustic turbidity' seen in acoustic surveys, masking the sedimentary structure below the gassy horizon. Acoustic windows, where the gas does not appear to be present, occur in several locations in the Bay, often surrounded by acoustically turbid sediments. Pockmarks, shallow depressions in the sediment, are also found in Bay sediments and may show acoustic turbidity at even shallower depths below the interface than surrounding sediments. One site of each type was sampled in this study. The site probably representative of much of the bay below 20 m water depth, revealed methane saturated conditions by about 75 cm depth below the interface, confirming inferences from acoustic scattering data that free gas was present in the sediment. Above this, the methane concentration profile was concave-upward, indicative of methane oxidation in the overlying, sulfate-reducing sediments. These porewaters showed a slightly decreasing chlorinity with depth. At an acoustic window site, methane concentrations rose to a maximum at about 125 cm depth, but did not reach saturation. Below this depth they decreased in a concave-down pattern. Chloride concentrations decreased markedly with depth, indicative of vertical freshwater flow from below. The third site was a pockmark exhibiting very shallow acoustic turbidity at about 25 cm depth. Here methane concentrations rose to exceed saturation within 25 cm depth below the interface and the porewaters became almost fresh by 1.5 m depth, indicative of a stronger flow of freshwater from below. These groundwater flows have competing effects on the methane inventory. They help exclude sulfate from the sediment, allowing the earlier

  7. Solving the power flow equations: a monotone operator approach

    SciTech Connect

    Dvijotham, Krishnamurthy; Low, Steven; Chertkov, Michael

    2015-07-21

    The AC power flow equations underlie all operational aspects of power systems. They are solved routinely in operational practice using the Newton-Raphson method and its variants. These methods work well given a good initial “guess” for the solution, which is always available in normal system operations. However, with the increase in levels of intermittent generation, the assumption of a good initial guess always being available is no longer valid. In this paper, we solve this problem using the theory of monotone operators. We show that it is possible to compute (using an offline optimization) a “monotonicity domain” in the space of voltage phasors. Given this domain, there is a simple efficient algorithm that will either find a solution in the domain, or provably certify that no solutions exist in it. We validate the approach on several IEEE test cases and demonstrate that the offline optimization can be performed tractably and the computed “monotonicity domain” includes all practically relevant power flow solutions.

  8. Magnetogasdynamic Power Extraction and Flow Conditioning for a Gas Turbine

    NASA Technical Reports Server (NTRS)

    Adamovich, Igor V.; Rich, J. William; Schneider, Steven; Blankson, Isaiah

    2003-01-01

    An extension of the Russian AJAX concept to a turbojet is being explored. This magnetohydrodynamic (MHD) energy bypass engine cycle incorporating conventional gas turbine technology has MHD flow conditioning at the inlet to electromagnetically extract part of the inlet air kinetic energy. The electrical power generated can be used for various on-board vehicle requirements including plasma flow control around the vehicle or it may be used for augmenting the expanding flow in the high speed nozzle by MHD forces to generate more thrust. In order to achieve this interaction, the air needs to be ionized by an external means even up to fairly high flight speeds, and the leading candidates may be classified as electrical discharge devices. The present kinetic modeling calculations suggest that the use of electron beams with characteristics close to the commercially available e-beam systems (electron energy approx. 60 keV, beam current approx. 0.2 mA/sq cm) to sustain ionization in intermediate pressure, low-temperature (P = 0.1 atm, T = 300 K) supersonic air flows allows considerable reduction of the flow kinetic energy (up to 10 to 20 percent in M = 3 flows). The calculations also suggest that this can be achieved at a reasonable electron beam efficiency (eta approx. 5), even if the e-beam window losses are taken into account. At these conditions, the exit NO and O atom concentrations due to e-beam initiated chemical reactions do not exceed 30 ppm. Increasing the beam current up to approx. 2 mA/sq cm, which corresponds to a maximum electrical conductivity of sigma(sub max) approx. 0.8 mho/m at the loading parameter of K = 0.5, would result in a much greater reduction of the flow kinetic energy (up to 30 to 40 percent). The MHD channel efficiency at these conditions would be greatly reduced (to eta approx. 1) due to increased electron recombination losses in the channel. At these conditions, partial energy conversion from kinetic energy to heat would result in a

  9. Perception of power modulation of light in conjunction with acoustic stimulation

    NASA Astrophysics Data System (ADS)

    Hahlweg, Cornelius F.; Weyer, Cornelia; Gercke-Hahn, Harald; Gutzmann, Holger L.; Brahmann, Andre; Rothe, Hendrik

    2013-09-01

    The present paper is derived from an ongoing study on the human perception of combined optical and acoustical periodical stimuli. Originating from problems of occupational medicine concerning artificial illumination and certain machinery with coherent optical and acoustical emissions there are effects which are interesting in the context of Optics and Music. Because of the difficulties in evaluation of physical and psychological effects of such coherent stimuli in a first step we questioned if such coherence is perceivable at all. Concept, experimental set-up and first results are discussed in short.

  10. A high-powered siren for stable acoustic levitation of dense materials in the earth's gravity

    NASA Technical Reports Server (NTRS)

    Gammel, Paul M.; Croonquist, Arvid P.; Wang, Taylor G.

    1988-01-01

    Levitation of large dense samples (e.g., 1-cm diameter steel balls) has been performed in a 1-g environment. A siren was used to study the effects of reflector geometry and variable-frequency operation in order to attain stable acoustic positioning. The harmonic content and spatial distribution of the acoustic field have been investigated. The best stability was obtained with an open reflector system, using a flat lower reflector and a slightly concave upper reflector while operating at a frequency slightly below resonance.

  11. Design and Modeling of High Power Density Acoustic Transducer Materials for Autonomous Undersea Vehicles

    NASA Astrophysics Data System (ADS)

    Heitmann, Adam Arthur

    Advances in piezocrystal transducer materials technology has opened new avenues to impact the size, weight, and power consumption of sonar systems for deployment in autonomous undersea vehicles (AUVs). Although piezocrystals exhibit exceptional electromechanical properties, they have low ferroelectric Curie temperatures, small electrical coercivities, and exhibit temperature, electrical field, and/or stress induced phase transitions between ferroelectric phases with differing electromechanical properties. New piezocrystal materials are required that can provide the compositional tailoring capability needed to increase the Curie temperature and coercive field, ameliorate the deleterious effects of ferroelectric-ferroelectric phase transitions, and enable property optimization for specific transducer applications. Currently, new piezocrystal systems and compositions are selected almost exclusively by empirical 'make and measure' approaches guided by past experiences. These empirical processes can be time and labor intensive and as a result there exists only limited predictive capability for finding new piezocrystal compositions even in known piezocrystal systems. In this study we seek to develop a comprehensive phenomenological theory and a unified parameterization scheme applicable to binary and ternary ferroelectric solid solution systems in order to enable the accelerated development and characterization of new piezocrystal systems for optimized transducer performance. A modified form of the classical Ginzburg-Landau-Devonshire theory of weak first-order transitions is applied to perovskite-structured ferroelectric systems based on the ternary oxide compounds, barium titanate and lead titanate, which places special emphasis on the role played by the crystallographic anisotropy of polarization. It is shown that the theory produces excellent qualitative agreement with the experimentally measured phase diagram topologies, crystal lattice parameters, and

  12. Estimation of broadband acoustic power due to rib forces on a reinforced panel under turbulent boundary layer-like pressure excitation. II. Applicability and validation.

    PubMed

    Rumerman, M L

    2001-02-01

    The previous paper showed that, when the attachment forces on a rib-reinforced panel subjected to turbulent boundary layer excitation can be considered to radiate independently, the rib-related acoustic power in a broad (e.g., one-third octave) frequency band can be estimated as the product of the average mean squared force, the real part of the radiation admittance of an attachment force, and the number of ribs. This paper shows that the radiation condition is always approximated when the acoustic wavelength is less than twice the rib spacing of a periodically reinforced panel, and generally applies at lower frequencies where the acoustic wavelength is less than four times the rib spacing. The procedure is used to estimate the broadband acoustic power radiated per rib of an infinite periodically reinforced membrane and plate in water, and the results are shown to agree with those of "exact" calculations.

  13. Acoustic, Visual and Spatial Indicators for the Description of the Soundscape of Waterfront Areas with and without Road Traffic Flow

    PubMed Central

    Puyana Romero, Virginia; Maffei, Luigi; Brambilla, Giovanni; Ciaburro, Giuseppe

    2016-01-01

    High flows of road traffic noise in urban agglomerations can negatively affect the livability of squares and parks located at the neighborhood, district and city levels, therefore pushing anyone who wants to enjoy calmer, quieter areas to move to non-urban parks. Due to the distances between these areas, it is not possible to go as regularly as would be necessary to satisfy any needs. Even if cities are densely populated, the presence of a sea or riverfront offers the possibility of large restorative places, or at least with potential features for being the natural core of an urban nucleus after a renewal intervention. This study evaluates the soundscape of the Naples waterfront, presenting an overview of the most significant visual, acoustic and spatial factors related to the pedestrian areas, as well as areas open to road traffic and others where the road traffic is limited. The factors were chosen with feature selection methods and artificial neural networks. The results show how certain factors, such as the perimeter between the water and promenade, the visibility of the sea or the density of green areas, can affect the perception of the soundscape quality in the areas with road traffic. In the pedestrian areas, acoustic factors, such as loudness or the A-weighted sound level exceeded for 10% of the measurement duration (LA10), influence the perceived quality of the soundscape. PMID:27657105

  14. A supervisor for the successive 3D computations of magnetic, mechanical and acoustic quantities in power oil inductors and transformers

    SciTech Connect

    Reyne, G.; Magnin, H.; Berliat, G.; Clerc, C.

    1994-09-01

    A supervisor has been developed so as to allow successive 3D computations of different quantities by different softwares on the same physical problem. Noise of a given power oil transformer can be deduced from the surface vibrations of the tank. These vibrations are obtained through a mechanic computation whose Inputs are the electromagnetic forces provided . by an electromagnetic computation. Magnetic, mechanic and acoustic experimental data are compared with the results of the 3D computations. Stress Is put on the main characteristics of the supervisor such as the transfer of a given quantity from one mesh to the other.

  15. Primary-Side Power Flow Control of Wireless Power Transfer for Electric Vehicle Charging

    DOE PAGES

    Miller, John M.; Onar, Omer C.; Chinthavali, Madhu

    2014-12-22

    Various noncontacting methods of plug-in electric vehicle charging are either under development or now deployed as aftermarket options in the light-duty automotive market. Wireless power transfer (WPT) is now the accepted term for wireless charging and is used synonymously for inductive power transfer and magnetic resonance coupling. WPT technology is in its infancy; standardization is lacking, especially on interoperability, center frequency selection, magnetic fringe field suppression, and the methods employed for power flow regulation. This paper proposes a new analysis concept for power flow in WPT in which the primary provides frequency selection and the tuned secondary, with its resemblancemore » to a power transmission network having a reactive power voltage control, is analyzed as a transmission network. Analysis is supported with experimental data taken from Oak Ridge National Laboratory s WPT apparatus. Lastly, this paper also provides an experimental evidence for frequency selection, fringe field assessment, and the need for low-latency communications in the feedback path.« less

  16. Performance and flow analysis of vortex wind power turbines

    SciTech Connect

    Rangwalla, A.A.; Hsu, C.T.

    1982-10-01

    The theoretical study presented investigates some possible vortex flow solutions in the tornado-type wind energy system and evaluates the power coefficient that can be obtained theoretically. The actuator disc concept is applied to the vortex wind turbine configuration. The Burgers vortex model is then introduced and the performance of a turbine using it is derived. A generalized analytical solution of the model is given, followed by a numerical solution of the complete equations. The stability of a Burgers vortex is discussed. (LEW)

  17. Development of acoustic agglomerator. Test plan for high temperature high pressure acoustic agglomerator

    NASA Astrophysics Data System (ADS)

    1985-08-01

    The design specifications for the HTHP AA Facility are listed. The facility is an open-loop, air flow system with subsystems and components to provide the high temperature, high pressure, residence time, dust loading and acoustic irradiation to simulate the aerosol and Hot Gas Cleanup (HGCU) AA system of a Pressurized Fluid Bed Combustor (PFBC), Combined Cycle Power Plant. Data sampling, instrumentation, and automatic controls and data analysis systems are also provided. This test plan describes the testing to be done on the high temperature, high pressure acoustic agglomerator (HTHP AA) at Pen State University's High Intensity Acoustic Laboratory.

  18. Pulsatile flow of power-law fluid model for blood flow under periodic body acceleration.

    PubMed

    Chaturani, P; Palanisamy, V

    1990-01-01

    A mathematical model has been proposed to study the pulsatile flow of a power-law fluid through rigid circular tubes under the influence of a periodic body acceleration. Numerical solutions have been obtained by using finite difference method. The accuracy of the numerical procedure has been checked by comparing the obtained numerical results with other numerical and analytical solutions. It is found that the agreement between them is quite good. Interaction of non-Newtonian nature of fluid with the body acceleration has been investigated by using the physiological data for two particular cases (coronary and femoral arteries). The axial velocity, fluid acceleration, wall shear stress and instantaneous volume flow rate have been computed and their variations with different parameters have been analyzed. The following important observations have been made: (i) The velocity and acceleration profiles can have more than one maxima, this is in contrast with usual parabolic profiles where they have only one maximum at the axis. As n increases, the maxima shift towards the axis; (ii) For the flow with no body acceleration, the amplitude of both, wall shear and flow rate, increases with n, whereas for the flow with body acceleration, the amplitude of wall shear (flow rate) increases (decreases) as n increases; (iii) In the absence of body acceleration, pseudoplastic (dilatant) fluids, with low frequency pulsations, have higher (lower) value of maximum flow rate Qmax than Newtonian fluids, whereas for high frequencies, opposite behavior has been observed; for flow with body acceleration pulsations gives higher (lower) value of Qmax for pseudoplastic (dilatant) fluids than Newtonian fluids.

  19. Studies of acoustic effects on a flow boundary layer in air

    NASA Technical Reports Server (NTRS)

    Mechel, F.; Schilz, W.

    1986-01-01

    Effects of sound fields on the flow boundary layer on a flat plate subjected to a parallel flow are studied. The boundary layer is influenced by controlling the stagnation point flow at the front edge of the plate. Depending on the Reynolds number and sound frequency, excitation or suppression of turbulent is observed. Measurements were taken at wind velocities between 10 and 30 m/sec and sound frequencies between 0.2 and 3.0 kHz.

  20. Acoustics and Thrust of Separate Flow Exhaust Nozzles With Mixing Devices Investigated for High Bypass Ratio Engines

    NASA Technical Reports Server (NTRS)

    Saiyed, Naseem H.

    2000-01-01

    Typical installed separate-flow exhaust nozzle system. The jet noise from modern turbofan engines is a major contributor to the overall noise from commercial aircraft. Many of these engines use separate nozzles for exhausting core and fan streams. As a part of NASA s Advanced Subsonic Technology (AST) program, the NASA Glenn Research Center at Lewis Field led an experimental investigation using model-scale nozzles in Glenn s Aero-Acoustic Propulsion Laboratory. The goal of the investigation was to develop technology for reducing the jet noise by 3 EPNdB. Teams of engineers from Glenn, the NASA Langley Research Center, Pratt & Whitney, United Technologies Research Corporation, the Boeing Company, GE Aircraft Engines, Allison Engine Company, and Aero Systems Engineering contributed to the planning and implementation of the test.

  1. Cold-flow acoustic evaluation of a small scale, divergent, lobed nozzle for supersonic jet noise suppression

    NASA Technical Reports Server (NTRS)

    Huff, R. G.; Groesbeck, D. E.

    1975-01-01

    A supersonic jet noise suppressor was tested with cold flow for acoustic and thrust characteristics at nozzle- to atmospheric-pressure ratios of 1.5 to 4.0. Jet noise suppression and spectral characteristics of the divergent, lobed, suppressor (DLS) nozzle with and without an ejector are presented. Suppression was obtained at nozzle pressure ratios of 2.5 to 4.0. The largest, maximum-lobe, sound pressure level suppression with a hard-wall ejector was 14.6 decibels at a nozzle pressure ratio of 3.5. The thrust loss was 2 percent. In general, low-frequency jet noise was suppressed, leaving higher frequencies essentially unchanged. Without the ejector the nozzle showed a thrust loss of 11 percent together with slightly poorer noise suppression.

  2. Design and implementation of an omni-directional underwater acoustic micro-modem based on a low-power micro-controller unit.

    PubMed

    Won, Tae-Hee; Park, Sung-Joon

    2012-01-01

    For decades, underwater acoustic communication has been restricted to the point-to-point long distance applications such as deep sea probes and offshore oil fields. For this reason, previous acoustic modems were typically characterized by high data rates and long working ranges at the expense of large size and high power consumption. Recently, as the need for underwater wireless sensor networks (UWSNs) has increased, the research and development of compact and low-power consuming communication devices has become the focus. From the consideration that the requisites of acoustic modems for UWSNs are low power consumption, omni-directional beam pattern, low cost and so on, in this paper, we design and implement an omni-directional underwater acoustic micro-modem satisfying these requirements. In order to execute fast digital domain signal processing and support flexible interfaces with other peripherals, an ARM Cortex-M3 is embedded in the micro-modem. Also, for the realization of small and omni-directional properties, a spherical transducer having a resonant frequency of 70 kHz and a diameter of 34 mm is utilized for the implementation. Physical layer frame format and symbol structure for efficient packet-based underwater communication systems are also investigated. The developed acoustic micro-modem is verified analytically and experimentally in indoor and outdoor environments in terms of functionality and performance. Since the modem satisfies the requirements for use in UWSNs, it could be deployed in a wide range of applications requiring underwater acoustic communication. PMID:22438765

  3. Design and implementation of an omni-directional underwater acoustic micro-modem based on a low-power micro-controller unit.

    PubMed

    Won, Tae-Hee; Park, Sung-Joon

    2012-01-01

    For decades, underwater acoustic communication has been restricted to the point-to-point long distance applications such as deep sea probes and offshore oil fields. For this reason, previous acoustic modems were typically characterized by high data rates and long working ranges at the expense of large size and high power consumption. Recently, as the need for underwater wireless sensor networks (UWSNs) has increased, the research and development of compact and low-power consuming communication devices has become the focus. From the consideration that the requisites of acoustic modems for UWSNs are low power consumption, omni-directional beam pattern, low cost and so on, in this paper, we design and implement an omni-directional underwater acoustic micro-modem satisfying these requirements. In order to execute fast digital domain signal processing and support flexible interfaces with other peripherals, an ARM Cortex-M3 is embedded in the micro-modem. Also, for the realization of small and omni-directional properties, a spherical transducer having a resonant frequency of 70 kHz and a diameter of 34 mm is utilized for the implementation. Physical layer frame format and symbol structure for efficient packet-based underwater communication systems are also investigated. The developed acoustic micro-modem is verified analytically and experimentally in indoor and outdoor environments in terms of functionality and performance. Since the modem satisfies the requirements for use in UWSNs, it could be deployed in a wide range of applications requiring underwater acoustic communication.

  4. Unveiling acoustic physics of the CMB using nonparametric estimation of the temperature angular power spectrum for Planck

    SciTech Connect

    Aghamousa, Amir; Shafieloo, Arman; Arjunwadkar, Mihir; Souradeep, Tarun E-mail: shafieloo@kasi.re.kr E-mail: tarun@iucaa.ernet.in

    2015-02-01

    Estimation of the angular power spectrum is one of the important steps in Cosmic Microwave Background (CMB) data analysis. Here, we present a nonparametric estimate of the temperature angular power spectrum for the Planck 2013 CMB data. The method implemented in this work is model-independent, and allows the data, rather than the model, to dictate the fit. Since one of the main targets of our analysis is to test the consistency of the ΛCDM model with Planck 2013 data, we use the nuisance parameters associated with the best-fit ΛCDM angular power spectrum to remove foreground contributions from the data at multipoles ℓ ≥50. We thus obtain a combined angular power spectrum data set together with the full covariance matrix, appropriately weighted over frequency channels. Our subsequent nonparametric analysis resolves six peaks (and five dips) up to ℓ ∼1850 in the temperature angular power spectrum. We present uncertainties in the peak/dip locations and heights at the 95% confidence level. We further show how these reflect the harmonicity of acoustic peaks, and can be used for acoustic scale estimation. Based on this nonparametric formalism, we found the best-fit ΛCDM model to be at 36% confidence distance from the center of the nonparametric confidence set—this is considerably larger than the confidence distance (9%) derived earlier from a similar analysis of the WMAP 7-year data. Another interesting result of our analysis is that at low multipoles, the Planck data do not suggest any upturn, contrary to the expectation based on the integrated Sachs-Wolfe contribution in the best-fit ΛCDM cosmology.

  5. The effect of the size of the opening on the acoustic power radiated by a reed woodwind instrument

    NASA Astrophysics Data System (ADS)

    Guilloteau, Alexis; Guillemain, Philippe; Kergomard, Jean; Jousserand, Michael

    2015-05-01

    For a given note, the maker of woodwind instruments can choose between different sizes for the toneholes under the condition that the location is appropriate. The present paper aims at analyzing the consequences of this choice on the power radiated by a hole, which depends on the coupling between the acoustic resonator and the excitation mechanism of the self-sustained oscillation, thus on the blowing pressure. For that purpose a simplified reed instrument is investigated, with a cylindrical pipe and a unique orifice at the pipe termination. The orifice diameter was varied between the pipe diameter and a size such that the instrument did not play. The pipe length was in each case adjusted to keep the resonance frequency constant. A simple analytical model predicts that, for a given mouth pressure of the instrumentalist, the radiated power does not depend on the size of the hole if it is wide enough and if resonator losses are ignored. Numerical solution of a model including losses confirms this result: the difference in radiated power between two diaphragm sizes remains smaller than the difference obtained if the radiated power would be proportional to the orifice cross section area. This is confirmed by experiments using an artificial mouth, but the results show that the linear losses are underestimated, and that significant nonlinear losses occur. The measurements are limited to the acoustic pressure at a given distance of the orifice. Experiments also show that rounding edges of the orifice reduces nonlinear losses resulting in an increase of the power radiated and of the extinction threshold, and resulting in a larger dynamical range.

  6. Laminar and turbulent nozzle-jet flows and their acoustic near-field

    SciTech Connect

    Bühler, Stefan; Obrist, Dominik; Kleiser, Leonhard

    2014-08-15

    We investigate numerically the effects of nozzle-exit flow conditions on the jet-flow development and the near-field sound at a diameter-based Reynolds number of Re{sub D} = 18 100 and Mach number Ma = 0.9. Our computational setup features the inclusion of a cylindrical nozzle which allows to establish a physical nozzle-exit flow and therefore well-defined initial jet-flow conditions. Within the nozzle, the flow is modeled by a potential flow core and a laminar, transitional, or developing turbulent boundary layer. The goal is to document and to compare the effects of the different jet inflows on the jet flow development and the sound radiation. For laminar and transitional boundary layers, transition to turbulence in the jet shear layer is governed by the development of Kelvin-Helmholtz instabilities. With the turbulent nozzle boundary layer, the jet flow development is characterized by a rapid changeover to a turbulent free shear layer within about one nozzle diameter. Sound pressure levels are strongly enhanced for laminar and transitional exit conditions compared to the turbulent case. However, a frequency and frequency-wavenumber analysis of the near-field pressure indicates that the dominant sound radiation characteristics remain largely unaffected. By applying a recently developed scaling procedure, we obtain a close match of the scaled near-field sound spectra for all nozzle-exit turbulence levels and also a reasonable agreement with experimental far-field data.

  7. Shape of gas flow paths causes power law tailing

    NASA Astrophysics Data System (ADS)

    Kawanishi, T.; Sakami, A.; Hayashi, Y.

    2004-12-01

    In soil and/or groundwater remediation, we often see prolonged tailings: continuous outflow of low concentration pollutants for very long time, and in many cases power low behavior of late-time time-concentration curves. We considered that this kind of tailing can be caused by the shape of the gaseous flow introduced in saturated/unsaturated porous media. When gas is introduced to porous media, like air-sparging or soil vapor extraction, the shape of the gas flow path would be tree-like, or to some extent "fractal." So, there would be a distribution of the distance that a solute would have to travel by diffusion before getting to a gas/water interface, and we might expect that the distribution of this "diffusion distance" would be power-law-like. In order to see if tailing can be caused by this mechanism, simple column experiments were carried out. A column, 64 mm in inner diameter and 240 mm in height, was prepared and was packed with 1mm diameter glass beads. Nitrogen gas containing 5 % CO2 and 5% He was supplied from the bottom of the column, and after the water in the column is approximately saturated with CO2, the sparging gas was changed to pure nitrogen. The CO2 and He concentrations in the effluent gas was monitored and recorded. As the result, we saw tailing: the double-log plots of the concentration vs. time relationship was practically linear, and the absolute value of the slope in the double-log charts were 1.28, 0.95 and 0.83 according to the gas flow rates of 40, 80 and 120 ml/min, respectively. Slope less than 1.00 showed that these tailings cannot be explained by Freundlich-type adsorption behavior. Model analysis showed that this power low time-concentration behavior with the slope of approximately -1.0 can be explained by the power law distribution of diffusion distance \\textit{a} with PDF p(\\textit{a}) proportional to \\textit{a}^{-1}.

  8. Convective flow reversal in self-powered enzyme micropumps

    NASA Astrophysics Data System (ADS)

    Shum, Henry; Ortiz-Rivera, Isamar; Agrawal, Arjun; Sen, Ayusman; Balazs, Anna

    2015-11-01

    It was recently shown that a surface-bound patch of enzymes in a fluid filled chamber can drive large scale flow in the presence of the enzyme's substrate. Evidence suggested that the flow was buoyancy driven but the pumping speed, or even direction, was not always consistent with estimates based on heat released by the reaction. Hence, we develop and analyze a model for density variations due to changes in solution composition as the reaction proceeds. If the reaction causes an increase in solution density, then we intuitively expect the fluid to sink down and spread outward, away from the pump. If the reaction substrate and product have different diffusion coefficients, however, the pump can exhibit much more complex behavior, such as pushing fluid outwards at early times and pulling fluid inwards later on. Two parameters, the ratio of solutal expansion coefficients and the ratio of diffusion coefficients, determine the pump dynamics. The predicted reversal of pumping direction is experimentally verified with a urease pump. We further show that not only the speed but also the direction of pumping varies with the amount of enzyme present on the patch. A better understanding of these pumps will aid in the design of responsive, chemically powered microfluidic flow control.

  9. Ecosystem Services Flows: Why Stakeholders' Power Relationships Matter.

    PubMed

    Felipe-Lucia, María R; Martín-López, Berta; Lavorel, Sandra; Berraquero-Díaz, Luis; Escalera-Reyes, Javier; Comín, Francisco A

    2015-01-01

    The ecosystem services framework has enabled the broader public to acknowledge the benefits nature provides to different stakeholders. However, not all stakeholders benefit equally from these services. Rather, power relationships are a key factor influencing the access of individuals or groups to ecosystem services. In this paper, we propose an adaptation of the "cascade" framework for ecosystem services to integrate the analysis of ecological interactions among ecosystem services and stakeholders' interactions, reflecting power relationships that mediate ecosystem services flows. We illustrate its application using the floodplain of the River Piedra (Spain) as a case study. First, we used structural equation modelling (SEM) to model the dependence relationships among ecosystem services. Second, we performed semi-structured interviews to identify formal power relationships among stakeholders. Third, we depicted ecosystem services according to stakeholders' ability to use, manage or impair ecosystem services in order to expose how power relationships mediate access to ecosystem services. Our results revealed that the strongest power was held by those stakeholders who managed (although did not use) those keystone ecosystem properties and services that determine the provision of other services (i.e., intermediate regulating and final services). In contrast, non-empowered stakeholders were only able to access the remaining non-excludable and non-rival ecosystem services (i.e., some of the cultural services, freshwater supply, water quality, and biological control). In addition, land stewardship, access rights, and governance appeared as critical factors determining the status of ecosystem services. Finally, we stress the need to analyse the role of stakeholders and their relationships to foster equal access to ecosystem services.

  10. Ecosystem Services Flows: Why Stakeholders’ Power Relationships Matter

    PubMed Central

    Felipe-Lucia, María R.; Martín-López, Berta; Lavorel, Sandra; Berraquero-Díaz, Luis; Escalera-Reyes, Javier; Comín, Francisco A.

    2015-01-01

    The ecosystem services framework has enabled the broader public to acknowledge the benefits nature provides to different stakeholders. However, not all stakeholders benefit equally from these services. Rather, power relationships are a key factor influencing the access of individuals or groups to ecosystem services. In this paper, we propose an adaptation of the “cascade” framework for ecosystem services to integrate the analysis of ecological interactions among ecosystem services and stakeholders’ interactions, reflecting power relationships that mediate ecosystem services flows. We illustrate its application using the floodplain of the River Piedra (Spain) as a case study. First, we used structural equation modelling (SEM) to model the dependence relationships among ecosystem services. Second, we performed semi-structured interviews to identify formal power relationships among stakeholders. Third, we depicted ecosystem services according to stakeholders’ ability to use, manage or impair ecosystem services in order to expose how power relationships mediate access to ecosystem services. Our results revealed that the strongest power was held by those stakeholders who managed (although did not use) those keystone ecosystem properties and services that determine the provision of other services (i.e., intermediate regulating and final services). In contrast, non-empowered stakeholders were only able to access the remaining non-excludable and non-rival ecosystem services (i.e., some of the cultural services, freshwater supply, water quality, and biological control). In addition, land stewardship, access rights, and governance appeared as critical factors determining the status of ecosystem services. Finally, we stress the need to analyse the role of stakeholders and their relationships to foster equal access to ecosystem services. PMID:26201000

  11. Splitting a droplet with oil encapsulation using surface acoustic wave excited by electric signal with low power

    NASA Astrophysics Data System (ADS)

    Zhang, Anliang; Zha, Yan; Fu, Xingting

    2013-07-01

    A new method for splitting a droplet with oil encapsulation is presented. An interdigital transducer and a reflector are fabricated on a 128° yx-LiNbO3 piezoelectric substrate using microelectric technology. An electric signal with the power of 12.3 dBm is applied to the interdigital transducer to generate surface acoustic wave, which is radiated into a droplet with oil encapsulation, leading to surface acoustic wave streaming force. When the electric signal is suddenly moved off, the breakup of the droplet occurs due to inertial force. Color dye solution droplets encapsulated by oil droplets are demonstrated. The effects of electric power, the volume ratio of color dye solution to oil, and the volume of mother droplet on the breakup of droplets are studied. As applications, the presented method is successfully applied to mixture operation and color development reaction of two droplets. The method provides a new sample preparation technique, which is helpful for microfluidic biochemical analysis in a piezoelectric microfluidic system.

  12. Computation of unsteady transonic flows through rotating and stationary cascades. 3: Acoustic far-field analysis

    NASA Technical Reports Server (NTRS)

    Slutsky, S.; Fischer, D.; Erdos, J. I.

    1977-01-01

    A small perturbation type analysis has been developed for the acoustic far field in an infinite duct extending upstream and downstream of an axial turbomachinery stage. The analysis is designed to interface with a numerical solution of the near field of the blade rows and, thereby, to provide the necessary closure condition to complete the statement of infinite duct boundary conditions for the subject problem. The present analysis differs from conventional inlet duct analyses in that a simple harmonic time dependence was not assumed, since a transient signal is generated by the numerical near-field solution and periodicity is attained only asymptotically. A description of the computer code developed to carry out the necessary convolutions numerically is included, as well as the results of a sample application using an impulsively initiated harmonic signal.

  13. Accuracy of a pulse-coherent acoustic Doppler profiler in a wave-dominated flow

    USGS Publications Warehouse

    Lacy, J.R.; Sherwood, C.R.

    2004-01-01

    The accuracy of velocities measured by a pulse-coherent acoustic Doppler profiler (PCADP) in the bottom boundary layer of a wave-dominated inner-shelf environment is evaluated. The downward-looking PCADP measured velocities in eight 10-cm cells at 1 Hz. Velocities measured by the PCADP are compared to those measured by an acoustic Doppler velocimeter for wave orbital velocities up to 95 cm s-1 and currents up to 40 cm s-1. An algorithm for correcting ambiguity errors using the resolution velocities was developed. Instrument bias, measured as the average error in burst mean speed, is -0.4 cm s-1 (standard deviation = 0.8). The accuracy (root-mean-square error) of instantaneous velocities has a mean of 8.6 cm s-1 (standard deviation = 6.5) for eastward velocities (the predominant direction of waves), 6.5 cm s-1 (standard deviation = 4.4) for northward velocities, and 2.4 cm s-1 (standard deviation = 1.6) for vertical velocities. Both burst mean and root-mean-square errors are greater for bursts with ub ??? 50 cm s-1. Profiles of burst mean speeds from the bottom five cells were fit to logarithmic curves: 92% of bursts with mean speed ??? 5 cm s-1 have a correlation coefficient R2 > 0.96. In cells close to the transducer, instantaneous velocities are noisy, burst mean velocities are biased low, and bottom orbital velocities are biased high. With adequate blanking distances for both the profile and resolution velocities, the PCADP provides sufficient accuracy to measure velocities in the bottom boundary layer under moderately energetic inner-shelf conditions.

  14. Evaluation of acoustic doppler velocity meters to quantify flow from Comal Springs and San Marcos Springs, Texas

    USGS Publications Warehouse

    Gary, Marcus O.; Gary, Robin H.; Asquith, William H.

    2008-01-01

    Comal Springs and San Marcos Springs are the two largest springs in Texas, are major discharge points for the San Antonio segment of the Edwards aquifer, and provide habitat for several Federally listed endangered species that depend on adequate springflows for survival. It is therefore imperative that the Edwards Aquifer Authority have accurate and timely springflow data to guide resource management. Discharge points for Comal Springs and San Marcos Springs are submerged in Landa Lake and in Spring Lake, respectively. Flows from the springs currently (2008) are estimated by the U.S Geological Survey in real time as surface-water discharge from conventional stage-discharge ratings at sites downstream from each spring. Recent technological advances and availability of acoustic Doppler velocity meters (ADVMs) now provide tools to collect data (stream velocity) related to springflow that could increase accuracy of real-time estimates of the springflows. The U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, did a study during May 2006 through September 2007 to evaluate ADVMs to quantify flow from Comal and San Marcos Springs. The evaluation was based on two monitoring approaches: (1) placement of ADVMs in important spring orifices - spring run 3 and spring 7 at Comal Springs, and diversion spring at San Marcos Springs; and (2) placement of ADVMs at the nearest flowing streams - Comal River new and old channels for Comal Springs, Spring Lake west and east outflow channels and current (2008) San Marcos River streamflow-gaging site for San Marcos Springs. For Comal Springs, ADVM application at spring run 3 and spring 7 was intended to indicate whether the flows of spring run 3 and spring 7 can be related to total springflow. The findings indicate that velocity data from both discharge features, while reflecting changes in flow, do not reliably show a direct relation to measured streamflow and thus to total Comal Springs flow. ADVMs at the Comal

  15. On the one-dimensional acoustic propagation in conical ducts with stationary mean flow.

    PubMed

    Barjau, Ana

    2007-12-01

    This paper proposes a direct time-domain calculation of the time-domain responses of anechoic conical tubes with steady weak mean flow. The starting point is the approximated linear one-dimensional wave equation governing the velocity potential for the case of steady flow with low Mach number. A traveling solution with general space-dependent propagation velocity is then proposed from which the inward and outward pressure and velocity impulse responses can be obtained. The results include the well-known responses of conical and cylindrical ducts with zero mean flow.

  16. Frequency effects on the scale and behavior of acoustic streaming.

    PubMed

    Dentry, Michael B; Yeo, Leslie Y; Friend, James R

    2014-01-01

    Acoustic streaming underpins an exciting range of fluid manipulation phenomena of rapidly growing significance in microfluidics, where the streaming often assumes the form of a steady, laminar jet emanating from the device surface, driven by the attenuation of acoustic energy within the beam of sound propagating through the liquid. The frequencies used to drive such phenomena are often chosen ad hoc to accommodate fabrication and material issues. In this work, we seek a better understanding of the effects of sound frequency and power on acoustic streaming. We present and, using surface acoustic waves, experimentally verify a laminar jet model that is based on the turbulent jet model of Lighthill, which is appropriate for acoustic streaming seen at micro- to nanoscales, between 20 and 936 MHz and over a broad range of input power. Our model eliminates the critically problematic acoustic source singularity present in Lighthill's model, replacing it with a finite emission area and enabling determination of the streaming velocity close to the source. At high acoustic power P (and hence high jet Reynolds numbers ReJ associated with fast streaming), the laminar jet model predicts a one-half power dependence (U∼P1/2∼ ReJ) similar to the turbulent jet model. However, the laminar model may also be applied to jets produced at low powers-and hence low jet Reynolds numbers ReJ-where a linear relationship between the beam power and streaming velocity exists: U∼P∼ReJ2. The ability of the laminar jet model to predict the acoustic streaming behavior across a broad range of frequencies and power provides a useful tool in the analysis of microfluidics devices, explaining peculiar observations made by several researchers in the literature. In particular, by elucidating the effects of frequency on the scale of acoustically driven flows, we show that the choice of frequency is a vitally important consideration in the design of small-scale devices employing acoustic streaming

  17. Generation of Acoustic Gravity Waves by Periodic Radio Transmissions from a High-Power Ionospheric Heater

    NASA Astrophysics Data System (ADS)

    Frolov, Vladimir; Chernogor, Leonid; Rozumenko, Victor

    The Radiophysical Research Institute (Nizhny Novgorod, Russia) and Kharkiv V. N. Karazin National University (Kharkiv, Ukraine) have studied opportunities for the effective generation of acoustic gravity waves (AGWs) in 3 - 180-min period range. The excitation of such waves was conducted for the last several years using the SURA heating facility (Nizhny Novgorod). The detection of the HF-induced AGWs was carried out in the Radiophysical Observatory located near Kharkiv City at a distance of about 960 km from the SURA. A coherent radar for vertical sounding, an ionosonde, and magnetometer chains were used in our measurements. The main results are the following (see [1-5]): 1. Infrasound oscillation trains with a period of 6 min are detected during periodic SURA heater turn-on and -off. Similar oscillation trains are detected after long time pumping, during periodic transmissions with a period of 20 s, as well as after pumping turn-off. The train recordings begin 28 - 54 min after the heater turn-on or -off, and the train propagation speeds are about 300 - 570 m/s, the value of which is close to the sound speed at upper atmospheric altitudes. The amplitude of the Doppler shift frequency is of 10 - 40 mHz, which fits to the 0.1 - 0.3% electron density disturbances at ionospheric altitudes. The amplitude of the infrasound oscillations depends on the SURA mode of operation and the state of the upper atmosphere and ionosphere. 2. High-power radio transmissions stimulate the generation (or enhancement) of waves at ionospheric altitudes in the range of internal gravity wave periods. The HF-induced waves propagate with speeds of 360 - 460 m/s and produce changes in electron density with amplitudes of 2 - 3%. The generation of such periodic perturbations is more preferable with periods of 10 - 60 minutes. Their features depend significantly on the heater mode of operation. It should be stressed that perturbation intensity increases when a pumping wave frequency approaches

  18. Temperature and velocity determination of shock-heated flows with non-resonant heterodyne laser-induced thermal acoustics

    NASA Astrophysics Data System (ADS)

    Förster, F. J.; Baab, S.; Lamanna, G.; Weigand, B.

    2015-12-01

    Non-resonant laser-induced thermal acoustics (LITA), a four-wave mixing technique, was applied to post-shock flows within a shock tube. Simultaneous single-shot determination of temperature, speed of sound and flow velocity behind incident and reflected shock waves at different pressure and temperature levels are presented. Measurements were performed non-intrusively and without any seeding. The paper describes the technique and outlines its advantages compared to more established laser-based methods with respect to the challenges of shock tube experiments. The experiments include argon and nitrogen as test gas at temperatures of up to 1000 K and pressures of up to 43 bar. The experimental data are compared to calculated values based on inviscid one-dimensional shock wave theory. The single-shot uncertainty of the technique is investigated for worst-case test conditions resulting in relative standard deviations of 1, 1.7 and 3.4 % for Mach number, speed of sound and temperature, respectively. For all further experimental conditions, calculated values stay well within the 95 % confidence intervals of the LITA measurement.

  19. Multi-Objective Differential Evolution for Voltage Security Constrained Optimal Power Flow in Deregulated Power Systems

    NASA Astrophysics Data System (ADS)

    Roselyn, J. Preetha; Devaraj, D.; Dash, Subhransu Sekhar

    2013-11-01

    Voltage stability is an important issue in the planning and operation of deregulated power systems. The voltage stability problems is a most challenging one for the system operators in deregulated power systems because of the intense use of transmission line capabilities and poor regulation in market environment. This article addresses the congestion management problem avoiding offline transmission capacity limits related to voltage stability by considering Voltage Security Constrained Optimal Power Flow (VSCOPF) problem in deregulated environment. This article presents the application of Multi Objective Differential Evolution (MODE) algorithm to solve the VSCOPF problem in new competitive power systems. The maximum of L-index of the load buses is taken as the indicator of voltage stability and is incorporated in the Optimal Power Flow (OPF) problem. The proposed method in hybrid power market which also gives solutions to voltage stability problems by considering the generation rescheduling cost and load shedding cost which relieves the congestion problem in deregulated environment. The buses for load shedding are selected based on the minimum eigen value of Jacobian with respect to the load shed. In the proposed approach, real power settings of generators in base case and contingency cases, generator bus voltage magnitudes, real and reactive power demands of selected load buses using sensitivity analysis are taken as the control variables and are represented as the combination of floating point numbers and integers. DE/randSF/1/bin strategy scheme of differential evolution with self-tuned parameter which employs binomial crossover and difference vector based mutation is used for the VSCOPF problem. A fuzzy based mechanism is employed to get the best compromise solution from the pareto front to aid the decision maker. The proposed VSCOPF planning model is implemented on IEEE 30-bus system, IEEE 57 bus practical system and IEEE 118 bus system. The pareto optimal

  20. Measurement and Analysis of Coherent Flow Structures over Sand Dunes in the Missouri River near St. Louis, MO, by means of an Acoustic Doppler Current Profiler and a Multibeam Echo Sounder

    NASA Astrophysics Data System (ADS)

    Boldt, J.; Oberg, K. A.; Best, J. L.; Parsons, D. R.

    2011-12-01

    The topology, magnitude, and sediment transport capabilities of large-scale turbulence generated over alluvial sand dunes is influential in creating and maintaining dune morphology and in dominating both the flow field and the transport of suspended sediment above dune-covered beds. Combined measurements by means of an acoustic Doppler current profiler (ADCP) and a multibeam echo sounder (MBES) were made in order to examine flow over a series of sand dunes in the Missouri River, near St. Louis, MO, USA in October 2007. The bed topography of the Missouri River was mapped using a RESON 7125 MBES immediately before the ADCP data collection. Time series of velocity and acoustic backscatter were measured using a down-looking 1200 kHz ADCP while anchored at two locations in the dune field. The ADCP used in this study has a sampling rate of 2-3 Hz with 20-25 cm bin sizes. Two time series were collected having durations of 712 and 589 seconds at one location, while the third time series, collected about 4 meters upstream, was 2,270 seconds in duration. Measured streamwise velocities ranged from 0.1 to 2.7 ms-1 for all three stationary time series. Sediment concentration profiles were obtained at the same two locations as the stationary ADCP data using a P-61 sediment sampler and were compared to ADCP acoustic backscatter. Characteristics of turbulent flow structures in a sand bed river are presented. This paper presents data that can be used to investigate the issue of obtaining reliable estimates of turbulence parameters with an ADCP. The analyses will include mean velocity profiles, turbulence intensities, Reynolds shear stresses, quadrant analysis, power spectra, cross-correlation, and frequency analysis. Semi-periodic patterns were observed in each time series, characterized by periods of elevated acoustic backscatter with positive vertical velocities, followed by reduced acoustic backscatter with negative vertical velocities. The utility and limitations of combined

  1. Resource Evaluation and Energy Production Estimate for a Tidal Energy Conversion Installation using Acoustic Flow Measurements

    NASA Astrophysics Data System (ADS)

    Gagnon, Ian; Baldwin, Ken; Wosnik, Martin

    2015-11-01

    The ``Living Bridge'' project plans to install a tidal turbine at Memorial Bridge in the Piscataqua River at Portsmouth, NH. A spatio-temporal tidal energy resource assessment was performed using long term bottom-deployed Acoustic Doppler Current Profilers ADCP. Two locations were evaluated: at the planned deployment location and mid-channel. The goal was to determine the amount of available kinetic energy that can be converted into usable electrical energy on the bridge. Changes in available kinetic energy with ebb/flood and spring/neap tidal cycles and electrical energy demand were analyzed. A system model is used to calculate the net energy savings using various tidal generator and battery bank configurations. Differences in the tidal characteristics between the two measurement locations are highlighted. Different resource evaluation methodologies were also analyzed, e.g., using a representative ADCP ``bin'' vs. a more refined, turbine-geometry-specific methodology, and using static bin height vs. bin height that move w.r.t. the free surface throughout a tidal cycle (representative of a bottom-fixed or floating turbine deployment, respectively). ADCP operating frequencies and bin sizes affect the standard deviation of measurements, and measurement uncertainties are evaluated. Supported by NSF-IIP grant 1430260.

  2. Electromagnetic Launch Vehicle Fairing and Acoustic Blanket Model of Received Power Using FEKO

    NASA Technical Reports Server (NTRS)

    Trout, Dawn H.; Stanley, James E.; Wahid, Parveen F.

    2011-01-01

    Evaluating the impact of radio frequency transmission in vehicle fairings is important to sensitive spacecraft. This paper employees the Multilevel Fast Multipole Method (MLFMM) feature of a commercial electromagnetic tool to model the fairing electromagnetic environment in the presence of an internal transmitter. This work is an extension of the perfect electric conductor model that was used to represent the bare aluminum internal fairing cavity. This fairing model includes typical acoustic blanketing commonly used in vehicle fairings. Representative material models within FEKO were successfully used to simulate the test case.

  3. Flowfield characteristics of an aerodynamic acoustic levitator

    NASA Astrophysics Data System (ADS)

    Yarin, A. L.; Brenn, G.; Keller, J.; Pfaffenlehner, M.; Ryssel, E.; Tropea, C.

    1997-11-01

    A droplet held in a single-axis ultrasonic levitator will principally sustain a certain external blowing along the levitation axis, which introduces the possibility of investigating heat and/or mass transfer from the droplet under conditions which are not too remote from those in spray systems. The focus of the present work is on the influence of the acoustic field on the external flow. More specifically, an axisymmetric submerged gas jet in an axial standing acoustic wave is examined, both in the absence and presence of a liquid droplet. Flow visualization is first presented to illustrate the global flow effects and the operating windows of jet velocities and acoustic powers which are suitable for further study. An analytic and numeric solution, based on the parabolic boundary layer equations are then given for the case of no levitated droplet, providing quantitative estimates of the acoustic field/flow interaction. Detailed velocity measurements using a laser Doppler anemometer verify the analytic results and extend these to the case of a levitated droplet. Some unresolved discrepancy remains in predicting the maximum velocity attainable before the droplet is blown out of the levitator. Two methods are developed to estimate the sound pressure level in the levitator by comparing flowfield patterns with analytic results. These results and observations are used to estimate to what extent acoustic aerodynamic levitators can be used in the future for investigating transport properties of individual droplets.

  4. Near-Field Acoustic Power Level Analysis of F31/A31 Open Rotor Model at Simulated Cruise Conditions, Technical Report II

    NASA Technical Reports Server (NTRS)

    Sree, Dave

    2015-01-01

    Near-field acoustic power level analysis of F31A31 open rotor model has been performed to determine its noise characteristics at simulated cruise flight conditions. The non-proprietary parts of the test data obtained from experiments in the 8x6 supersonic wind tunnel were provided by NASA-Glenn Research Center. The tone and broadband components of total noise have been separated from raw test data by using a new data analysis tool. Results in terms of sound pressure levels, acoustic power levels, and their variations with rotor speed, freestream Mach number, and input shaft power, with different blade-pitch setting angles at simulated cruise flight conditions, are presented and discussed. Empirical equations relating models acoustic power level and input shaft power have been developed. The near-field acoustic efficiency of the model at simulated cruise conditions is also determined. It is hoped that the results presented in this work will serve as a database for comparison and improvement of other open rotor blade designs and also for validating open rotor noise prediction codes.

  5. A transient method for measuring the gas volume fraction in a mixed gas-liquid flow using acoustic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Dehua; Wang, Xiuming; Che, Chengxuan; Cong, Jiansheng; Xu, Delong; Wang, Xiaomin

    2010-08-01

    In this paper, the feasibility of measuring the gas volume fraction in a mixed gas-liquid flow by using an acoustic resonant spectroscopy (ARS) method in a transient way is studied theoretically and experimentally. Firstly, the effects of sizes and locations of a single air bubble in a cylindrical cavity with two open ends on resonant frequencies are investigated numerically. Then, a transient measurement system for ARS is established, and the trends of the resonant frequencies (RFs) and resonant amplitudes (RAs) in the cylindrical cavity with gas flux inside are investigated experimentally. The measurement results by the proposed transient method are compared with those by steady-state ones and numerical ones. The numerical results show that the RFs of the cavity are highly sensitive to the volume of the single air bubble. A tiny bubble volume perturbation may cause a prominent RF shift even though the volume of the air bubble is smaller than 0.1% of that of the cavity. When the small air bubble moves, the RF shift will change and reach its maximum value as it is located at the middle of the cavity. As the gas volume fraction of the two-phase flow is low, both the RFs and RAs from the measurement results decrease dramatically with the increasing gas volume, and this decreasing trend gradually becomes even as the gas volume fraction increases further. These experimental results agree with the theoretical ones qualitatively. In addition, the transient method for ARS is more suitable for measuring the gas volume fraction with randomness and instantaneity than the steady-state one, because the latter could not reflect the random and instant characteristics of the mixed fluid due to the time consumption for frequency sweeping. This study will play a very important role in the quantitative measurement of the gas volume fraction of multiphase flows.

  6. Precision control of high temperature furnaces using an auxiliary power supply and charged particle current flow

    DOEpatents

    Pollock, G.G.

    1997-01-28

    Two power supplies are combined to control a furnace. A main power supply heats the furnace in the traditional manner, while the power from the auxiliary supply is introduced as a current flow through charged particles existing due to ionized gas or thermionic emission. The main power supply provides the bulk heating power and the auxiliary supply provides a precise and fast power source such that the precision of the total power delivered to the furnace is improved. 5 figs.

  7. Precision control of high temperature furnaces using an auxiliary power supply and charged practice current flow

    DOEpatents

    Pollock, George G.

    1997-01-01

    Two power supplies are combined to control a furnace. A main power supply heats the furnace in the traditional manner, while the power from the auxiliary supply is introduced as a current flow through charged particles existing due to ionized gas or thermionic emission. The main power supply provides the bulk heating power and the auxiliary supply provides a precise and fast power source such that the precision of the total power delivered to the furnace is improved.

  8. Vocal power and pressure-flow relationships in excised tiger larynges.

    PubMed

    Titze, Ingo R; Fitch, W Tecumseh; Hunter, Eric J; Alipour, Fariborz; Montequin, Douglas; Armstrong, Douglas L; McGee, Joann; Walsh, Edward J

    2010-11-15

    Despite the functional importance of loud, low-pitched vocalizations in big cats of the genus Panthera, little is known about the physics and physiology of the mechanisms producing such calls. We investigated laryngeal sound production in the laboratory using an excised-larynx setup combined with sound-level measurements and pressure-flow instrumentation. The larynges of five tigers (three Siberian or Amur, one generic non-pedigreed tiger with Bengal ancestry and one Sumatran), which had died of natural causes, were provided by Omaha's Henry Doorly Zoo over a five-year period. Anatomical investigation indicated the presence of both a rigid cartilaginous plate in the arytenoid portion of the glottis, and a vocal fold fused with a ventricular fold. Both of these features have been confusingly termed 'vocal pads' in the previous literature. We successfully induced phonation in all of these larynges. Our results showed that aerodynamic power in the glottis was of the order of 1.0 W for all specimens, acoustic power radiated (without a vocal tract) was of the order of 0.1 mW, and fundamental frequency ranged between 20 and 100 Hz when a lung pressure in the range of 0-2.0 kPa was applied. The mean glottal airflow increased to the order of 1.0 l s(-1) per 1.0 kPa of pressure, which is predictable from scaling human and canine larynges by glottal length and vibrational amplitude. Phonation threshold pressure was remarkably low, on the order of 0.3 kPa, which is lower than for human and canine larynges phonated without a vocal tract. Our results indicate that a vocal fold length approximately three times greater than that of humans is predictive of the low fundamental frequency, and the extraordinarily flat and broad medial surface of the vocal folds is predictive of the low phonation threshold pressure.

  9. Vocal power and pressure–flow relationships in excised tiger larynges

    PubMed Central

    Titze, Ingo R.; Fitch, W. Tecumseh; Hunter, Eric J.; Alipour, Fariborz; Montequin, Douglas; Armstrong, Douglas L.; McGee, JoAnn; Walsh, Edward J.

    2010-01-01

    Despite the functional importance of loud, low-pitched vocalizations in big cats of the genus Panthera, little is known about the physics and physiology of the mechanisms producing such calls. We investigated laryngeal sound production in the laboratory using an excised-larynx setup combined with sound-level measurements and pressure–flow instrumentation. The larynges of five tigers (three Siberian or Amur, one generic non-pedigreed tiger with Bengal ancestry and one Sumatran), which had died of natural causes, were provided by Omaha's Henry Doorly Zoo over a five-year period. Anatomical investigation indicated the presence of both a rigid cartilaginous plate in the arytenoid portion of the glottis, and a vocal fold fused with a ventricular fold. Both of these features have been confusingly termed ‘vocal pads’ in the previous literature. We successfully induced phonation in all of these larynges. Our results showed that aerodynamic power in the glottis was of the order of 1.0 W for all specimens, acoustic power radiated (without a vocal tract) was of the order of 0.1 mW, and fundamental frequency ranged between 20 and 100 Hz when a lung pressure in the range of 0–2.0 kPa was applied. The mean glottal airflow increased to the order of 1.0 l s–1 per 1.0 kPa of pressure, which is predictable from scaling human and canine larynges by glottal length and vibrational amplitude. Phonation threshold pressure was remarkably low, on the order of 0.3 kPa, which is lower than for human and canine larynges phonated without a vocal tract. Our results indicate that a vocal fold length approximately three times greater than that of humans is predictive of the low fundamental frequency, and the extraordinarily flat and broad medial surface of the vocal folds is predictive of the low phonation threshold pressure. PMID:21037066

  10. Vocal power and pressure-flow relationships in excised tiger larynges.

    PubMed

    Titze, Ingo R; Fitch, W Tecumseh; Hunter, Eric J; Alipour, Fariborz; Montequin, Douglas; Armstrong, Douglas L; McGee, Joann; Walsh, Edward J

    2010-11-15

    Despite the functional importance of loud, low-pitched vocalizations in big cats of the genus Panthera, little is known about the physics and physiology of the mechanisms producing such calls. We investigated laryngeal sound production in the laboratory using an excised-larynx setup combined with sound-level measurements and pressure-flow instrumentation. The larynges of five tigers (three Siberian or Amur, one generic non-pedigreed tiger with Bengal ancestry and one Sumatran), which had died of natural causes, were provided by Omaha's Henry Doorly Zoo over a five-year period. Anatomical investigation indicated the presence of both a rigid cartilaginous plate in the arytenoid portion of the glottis, and a vocal fold fused with a ventricular fold. Both of these features have been confusingly termed 'vocal pads' in the previous literature. We successfully induced phonation in all of these larynges. Our results showed that aerodynamic power in the glottis was of the order of 1.0 W for all specimens, acoustic power radiated (without a vocal tract) was of the order of 0.1 mW, and fundamental frequency ranged between 20 and 100 Hz when a lung pressure in the range of 0-2.0 kPa was applied. The mean glottal airflow increased to the order of 1.0 l s(-1) per 1.0 kPa of pressure, which is predictable from scaling human and canine larynges by glottal length and vibrational amplitude. Phonation threshold pressure was remarkably low, on the order of 0.3 kPa, which is lower than for human and canine larynges phonated without a vocal tract. Our results indicate that a vocal fold length approximately three times greater than that of humans is predictive of the low fundamental frequency, and the extraordinarily flat and broad medial surface of the vocal folds is predictive of the low phonation threshold pressure. PMID:21037066

  11. Evaluation of the Lattice-Boltzmann Equation Solver PowerFLOW for Aerodynamic Applications

    NASA Technical Reports Server (NTRS)

    Lockard, David P.; Luo, Li-Shi; Singer, Bart A.; Bushnell, Dennis M. (Technical Monitor)

    2000-01-01

    A careful comparison of the performance of a commercially available Lattice-Boltzmann Equation solver (Power-FLOW) was made with a conventional, block-structured computational fluid-dynamics code (CFL3D) for the flow over a two-dimensional NACA-0012 airfoil. The results suggest that the version of PowerFLOW used in the investigation produced solutions with large errors in the computed flow field; these errors are attributed to inadequate resolution of the boundary layer for reasons related to grid resolution and primitive turbulence modeling. The requirement of square grid cells in the PowerFLOW calculations limited the number of points that could be used to span the boundary layer on the wing and still keep the computation size small enough to fit on the available computers. Although not discussed in detail, disappointing results were also obtained with PowerFLOW for a cavity flow and for the flow around a generic helicopter configuration.

  12. Computational Analysis of the Flow and Acoustic Effects of Jet-Pylon Interaction

    NASA Technical Reports Server (NTRS)

    Hunter, Craig A.; Thomas, Russell H.; Abdol-Hamid, K. S.; Pao, S. Paul; Elmiligui, Alaa A.; Massey, Steven J.

    2005-01-01

    Computational simulation and prediction tools were used to understand the jet-pylon interaction effect in a set of bypass-ratio five core/fan nozzles. Results suggest that the pylon acts as a large scale mixing vane that perturbs the jet flow and jump starts the jet mixing process. The enhanced mixing and associated secondary flows from the pylon result in a net increase of noise in the first 10 diameters of the jet s development, but there is a sustained reduction in noise from that point downstream. This is likely the reason the pylon nozzle is quieter overall than the baseline round nozzle in this case. The present work suggests that focused pylon design could lead to advanced pylon shapes and nozzle configurations that take advantage of propulsion-airframe integration to provide additional noise reduction capabilities.

  13. Effect of flow on the acoustic performance of extended reaction lined ducts

    NASA Technical Reports Server (NTRS)

    Hersh, A. S.; Walker, B.

    1983-01-01

    A model is developed for the effects of uniform and boundary-layer mean flow on the attenuation and propagation of harmonically excited sound waves in an extended reaction lined cylindrical duct. A duct geometry consisting of an annular outer region of bulk material surrounding an inner cylinder of air is utilized. A numerical solution is obtained for the coupled wave equations governing the motion of the sound in both the inner and annular regions. It is found that the numerically predicted attenuation and propagations constants are in excellent agreement with measured values using Kevlar as the liner material for plane-wave mode (O,O) excitation over a wide range of mean flows and sound frequency. The boundary-layer effects are determined to be unimportant, at least for plane-wave sound. In addition, numerical studies indicate small differences between the use of either the radial velocity or the radial displacement boundary conditions.

  14. Mechanical signature analysis: Machinery vibration, flow-induced vibration, and acoustic noise analysis

    SciTech Connect

    Braun, S.; Lu, K.H.; Au Yang, M.K.; Ungar, E.E.; Simonis, J.C.

    1987-01-01

    This book contains over 30 selections. Some of the titles are: A New Method in the Fault Diagnosis of Turbomachine and Its Application; Vibration Control of a Cylindrical Off-Shore Structure; Design Evaluation of Flow-Induced Vibrations for a Large Shell and Tube Type Nuclear Heat Exchanger; Simulation of Fluid-Structure Interaction Between a Drywell Penetration and a High Energy Line Break in a BWR.

  15. Two-wavelength quadrature multipoint detection of partial discharge in power transformers using fiber Fabry-Perot acoustic sensors

    NASA Astrophysics Data System (ADS)

    Dong, Bo; Han, Ming; Wang, Anbo

    2012-06-01

    A reliable and low-cost two-wavelength quadrature interrogating method has been developed to demodulate optical signals from diaphragm-based Fabry-Perot interferometric fiber optic sensors for multipoint partial discharge detection in power transformers. Commercial available fused-silica parts (a wafer, a fiber ferrule, and a mating sleeve) and a cleaved optical single mode fiber were bonded together to form an extrinsic Fabry-Perot acoustic sensor. Two lasers with center wavelengths separated by a quarter of the period of sensor interference fringes were used to probe acousticwave- induced diaphragm vibration. A coarse wavelength-division multiplexing (CWDM) add/drop multiplexer was used to separate the reflected two wavelengths before two photo detectors. Optical couplers were used to distribute mixed laser light to each sensor-detector module for multiplexing purpose. Sensor structure, detection system design and experiment results are presented.

  16. Power flow controller with a fractionally rated back-to-back converter

    DOEpatents

    Divan, Deepakraj M.; Kandula, Rajendra Prasad; Prasai, Anish

    2016-03-08

    A power flow controller with a fractionally rated back-to-back (BTB) converter is provided. The power flow controller provide dynamic control of both active and reactive power of a power system. The power flow controller inserts a voltage with controllable magnitude and phase between two AC sources at the same frequency; thereby effecting control of active and reactive power flows between the two AC sources. A transformer may be augmented with a fractionally rated bi-directional Back to Back (BTB) converter. The fractionally rated BTB converter comprises a transformer side converter (TSC), a direct-current (DC) link, and a line side converter (LSC). By controlling the switches of the BTB converter, the effective phase angle between the two AC source voltages may be regulated, and the amplitude of the voltage inserted by the power flow controller may be adjusted with respect to the AC source voltages.

  17. Communications and control for electric power systems: Power flow classification for static security assessment

    NASA Technical Reports Server (NTRS)

    Niebur, D.; Germond, A.

    1993-01-01

    This report investigates the classification of power system states using an artificial neural network model, Kohonen's self-organizing feature map. The ultimate goal of this classification is to assess power system static security in real-time. Kohonen's self-organizing feature map is an unsupervised neural network which maps N-dimensional input vectors to an array of M neurons. After learning, the synaptic weight vectors exhibit a topological organization which represents the relationship between the vectors of the training set. This learning is unsupervised, which means that the number and size of the classes are not specified beforehand. In the application developed in this report, the input vectors used as the training set are generated by off-line load-flow simulations. The learning algorithm and the results of the organization are discussed.

  18. Electromagnetic Launch Vehicle Fairing and Acoustic Blanket Model of Received Power Using FEKO

    NASA Technical Reports Server (NTRS)

    Trout, Dawn H.; Stanley, James E.; Wahid, Parveen F.

    2011-01-01

    Evaluating the impact of radio frequency transmission in vehicle fairings is important to electromagnetically sensitive spacecraft. This study employs the multilevel fast multipole method (MLFMM) from a commercial electromagnetic tool, FEKO, to model the fairing electromagnetic environment in the presence of an internal transmitter with improved accuracy over industry applied techniques. This fairing model includes material properties representative of acoustic blanketing commonly used in vehicles. Equivalent surface material models within FEKO were successfully applied to simulate the test case. Finally, a simplified model is presented using Nicholson Ross Weir derived blanket material properties. These properties are implemented with the coated metal option to reduce the model to one layer within the accuracy of the original three layer simulation.

  19. Acoustic agglomeration of power-plant fly ash. A comprehensive semi-annual progress report

    SciTech Connect

    Reethof, G.

    1980-02-01

    Results obtained during the reporting period are presented. The agglomeration of submicron fly ash particles has been studied as a function of sound pressure level, sound frequency, loading, and exposure time. A second generation model of the agglomeration process is being developed. A high-frequency, high-intensity variable speed siren delivering at least 600 W at frequencies up to 4000 Hz has been developed and tested. Details on the design and operation are presented. The agglomeration chamber has been completely cleaned and the aerosol generating system has been rebuilt. A mathematical model of the acoustics of agglomeration is being developed. Preliminary results of computerized electron microscopic scanning of fly ash particles during agglomeration are presented. (DMC)

  20. Service Oriented Architectural Model for Load Flow Analysis in Power Systems

    NASA Astrophysics Data System (ADS)

    Muthu, Balasingh Moses; Veilumuthu, Ramachandran; Ponnusamy, Lakshmi

    2011-07-01

    The main objective of this paper is to develop the Service Oriented Architectural (SOA) Model for representation of power systems, especially of computing load flow analysis of large interconnected power systems. The proposed SOA model has three elements namely load flow service provider, power systems registry and client. The exchange of data using XML makes the power system services standardized and adaptable. The load flow service is provided by the service provider, which is published in power systems registry for enabling universal visibility and access to the service. The message oriented style of SOA using Simple Object Access Protocol (SOAP) makes the service provider and the power systems client to exist in a loosely coupled environment. This proposed model, portraits the load flow services as Web services in service oriented environment. To suit the power system industry needs, it easily integrates with the Web applications which enables faster power system operations.

  1. Time series power flow analysis for distribution connected PV generation.

    SciTech Connect

    Broderick, Robert Joseph; Quiroz, Jimmy Edward; Ellis, Abraham; Reno, Matthew J.; Smith, Jeff; Dugan, Roger

    2013-01-01

    Distributed photovoltaic (PV) projects must go through an interconnection study process before connecting to the distribution grid. These studies are intended to identify the likely impacts and mitigation alternatives. In the majority of the cases, system impacts can be ruled out or mitigation can be identified without an involved study, through a screening process or a simple supplemental review study. For some proposed projects, expensive and time-consuming interconnection studies are required. The challenges to performing the studies are twofold. First, every study scenario is potentially unique, as the studies are often highly specific to the amount of PV generation capacity that varies greatly from feeder to feeder and is often unevenly distributed along the same feeder. This can cause location-specific impacts and mitigations. The second challenge is the inherent variability in PV power output which can interact with feeder operation in complex ways, by affecting the operation of voltage regulation and protection devices. The typical simulation tools and methods in use today for distribution system planning are often not adequate to accurately assess these potential impacts. This report demonstrates how quasi-static time series (QSTS) simulation and high time-resolution data can be used to assess the potential impacts in a more comprehensive manner. The QSTS simulations are applied to a set of sample feeders with high PV deployment to illustrate the usefulness of the approach. The report describes methods that can help determine how PV affects distribution system operations. The simulation results are focused on enhancing the understanding of the underlying technical issues. The examples also highlight the steps needed to perform QSTS simulation and describe the data needed to drive the simulations. The goal of this report is to make the methodology of time series power flow analysis readily accessible to utilities and others responsible for evaluating

  2. Time-domain simulation of constitutive relations for nonlinear acoustics including relaxation for frequency power law attenuation media modeling

    NASA Astrophysics Data System (ADS)

    Jiménez, Noé; Camarena, Francisco; Redondo, Javier; Sánchez-Morcillo, Víctor; Konofagou, Elisa E.

    2015-10-01

    We report a numerical method for solving the constitutive relations of nonlinear acoustics, where multiple relaxation processes are included in a generalized formulation that allows the time-domain numerical solution by an explicit finite differences scheme. Thus, the proposed physical model overcomes the limitations of the one-way Khokhlov-Zabolotskaya-Kuznetsov (KZK) type models and, due to the Lagrangian density is implicitly included in the calculation, the proposed method also overcomes the limitations of Westervelt equation in complex configurations for medical ultrasound. In order to model frequency power law attenuation and dispersion, such as observed in biological media, the relaxation parameters are fitted to both exact frequency power law attenuation/dispersion media and also empirically measured attenuation of a variety of tissues that does not fit an exact power law. Finally, a computational technique based on artificial relaxation is included to correct the non-negligible numerical dispersion of the finite difference scheme, and, on the other hand, improve stability trough artificial attenuation when shock waves are present. This technique avoids the use of high-order finite-differences schemes leading to fast calculations. The present algorithm is especially suited for practical configuration where spatial discontinuities are present in the domain (e.g. axisymmetric domains or zero normal velocity boundary conditions in general). The accuracy of the method is discussed by comparing the proposed simulation solutions to one dimensional analytical and k-space numerical solutions.

  3. An acoustic doppler current profiler survey of flow velocities in Detroit River, a connecting channel of the Great Lakes

    USGS Publications Warehouse

    Holtschlag, David J.; Koschik, John A.

    2003-01-01

    Acoustic Doppler current profilers (ADCP) were used to survey flow velocities in Detroit River from July 8-19, 2002, as part of a study to assess the susceptibility of public water intakes to contaminants on the St. Clair-Detroit River Waterway. More than 3.5 million point velocities were measured at 130 cross sections. Cross sections were generally spaced about 1,800 ft apart along the river from the head of Detroit River at the outlet of Lake St. Clair to the mouth of Detroit River on Lake Erie. Two transects were surveyed at each cross section, one in each direction across the river. Along each transect, velocity profiles were generally obtained 0.8-2.2 ft apart. At each velocity profile, average water velocity data were obtained at 1.64 ft intervals of depth. The raw position and velocity data from the ADCP field survey were adjusted for local magnetic anomalies using global positioning system (GPS) measurements at the end points of the transects. The adjusted velocity and ancillary data can be retrieved though the internet and extracted to column-oriented data files.

  4. An acoustic doppler current profiler survey of flow velocities in St. Clair River, a connecting channel of the Great Lakes

    USGS Publications Warehouse

    Holtschlag, David J.; Koschik, John A.

    2003-01-01

    Acoustic Doppler current profilers (ADCP) were used to measure flow velocities in St. Clair River during a survey in May and June of 2002, as part of a study to assess the susceptibility of public water intakes to contaminants on the St. Clair-Detroit River Waterway. The survey provides 2.7 million point velocity measurements at 104 cross sections. Sections are spaced about 1,630 ft apart along the river from Port Huron to Algonac, Michigan, a distance of 28.6 miles. Two transects were obtained at each cross section, one in each direction across the river. Along each transect, velocity profiles were obtained 2-4 ft apart. At each velocity profile, average water velocity data were obtained at 1.64 ft intervals of depth. The raw position and velocity data from the ADCP field survey were adjusted for local magnetic anomalies using global positioning system (GPS) measurements at the end points of the transects. The adjusted velocity and ancillary data can be retrieved through the internet and extracted to column-oriented data files.

  5. Analytical and experimental study of the acoustics and the flow field characteristics of cavitating self-resonating water jets

    SciTech Connect

    Chahine, G.L.; Genoux, P.F.; Johnson, V.E. Jr.; Frederick, G.S.

    1984-09-01

    Waterjet nozzles (STRATOJETS) have been developed which achieve passive structuring of cavitating submerged jets into discrete ring vortices, and which possess cavitation incipient numbers six times higher than obtained with conventional cavitating jet nozzles. In this study we developed analytical and numerical techniques and conducted experimental work to gain an understanding of the basic phenomena involved. The achievements are: (1) a thorough analysis of the acoustic dynamics of the feed pipe to the nozzle; (2) a theory for bubble ring growth and collapse; (3) a numerical model for jet simulation; (4) an experimental observation and analysis of candidate second-generation low-sigma STRATOJETS. From this study we can conclude that intensification of bubble ring collapse and design of highly resonant feed tubes can lead to improved drilling rates. The models here described are excellent tools to analyze the various parameters needed for STRATOJET optimizations. Further analysis is needed to introduce such important factors as viscosity, nozzle-jet interaction, and ring-target interaction, and to develop the jet simulation model to describe the important fine details of the flow field at the nozzle exit.

  6. Relationship of blood flow and metabolism to acoustic processing centers of the dolphin brain.

    PubMed

    Houser, Dorian S; Moore, Patrick W; Johnson, Shawn; Lutmerding, Betsy; Branstetter, Brian; Ridgway, Sam H; Trickey, Jennifer; Finneran, James J; Jensen, Eric; Hoh, Carl

    2010-09-01

    Odontocete brain tissues associated with auditory processing are hypertrophied and modified relative to their terrestrial counterparts. The relationship between the functional demand on these tissues and metabolic substrate requirements is unknown. Using positron emission tomography (PET), relative cerebral blood flow was measured in a bottlenose dolphin. Approximately 60 mCi (13)NH(3) was administered to the dolphin via a catheter inserted into the hepatic vein and threaded proximate to the vena cava. Radiolabel initially appeared as distributed focal points in the cerebellum. Increasing scan time resulted in an increase in the number of focal regions and in the diffusivity of label activity throughout the brain. The time course and spatial distribution of radiolabel was consistent with a cerebral blood supply dominated by the spinal meningeal arteries. Blood flow was predominantly observed in the cerebellum and neocortex, particularly the auditory and visual cortex. Differential brain glucose uptake, previously measured in a separate dolphin, showed good agreement with the differential supply of blood to brain tissues. Rates of blood supply and glucose uptake in the auditory cortex, inferior colliculus, and cerebellum are consistent with a high metabolic demand of tissues which are important to the integration of auditory and other sensory inputs. PMID:20815480

  7. Features Of Cavity Flow And Acoustics Of Stratospheric Observatory For Infrared Astronomy

    NASA Technical Reports Server (NTRS)

    Srinivasan, G. R.; Klotz, S. P.; Tu, Eugene (Technical Monitor)

    1996-01-01

    The stratospheric observatory for infrared astronomy (SOFIA) is a 2.5 meter aperture Cassegrain telescope with a Nasmyth focus that will be housed in an open cavity in the Boeing 747-SP aircraft and operated at altitudes around 41,000 feet for infrared (IR) viewing of celestial events of astronomical nature. At these altitudes the IR viewing capability of SOFIA far exceeds that of any ground based system. To minimize IR transmission losses, SOFIA will operate with an open cavity. Such an open cavity during flight creates several challenging aerodynamic and aeroacoustic design problems. Foremost of these are: the shear layer over the cavity may cause unwanted resonance if the cavity is untreated; this might give rise to excessive sound pressure levels (SPL) in the cavity and thus affect the unsteady loads on the telescope; the unsteady flow within the cavity produces large dynamic loads and moments that will impact the pointing accuracy of the telescope; the open cavity and the shear layer control devices produce additional drag that will affect directly the time of flight of the mission; the aft location of the cavity down stream of port wing will affect the the flow on the aircraft control surfaces and thus the stability of the aircraft. Also, the highly turbulent shear layer over the cavity and the temperature gradients and 'hot spots' within the cavity can produce a wave front error of the image when it reaches the focal plane of the recorder.

  8. Acoustic Telemetry Evaluation of Juvenile Salmonid Passage and Survival at John Day Dam with Emphasis on the Prototype Surface Flow Outlet, 2008

    SciTech Connect

    Weiland, Mark A.; Ploskey, Gene R.; Hughes, James S.; Deng, Zhiqun; Fu, Tao; Monter, Tyrell J.; Johnson, Gary E.; Khan, Fenton; Wilberding, Matthew C.; Cushing, Aaron W.; Zimmerman, Shon A.; Faber, Derrek M.; Durham, Robin E.; Townsend, Richard L.; Skalski, John R.; Kim, Jina; Fischer, Eric S.; Meyer, Matthew M.

    2009-12-01

    The main purpose of the study was to evaluate the performance of Top Spill Weirs installed at two spillbays at John Day Dam and evaluate the effectiveness of these surface flow outlets at attracting juvenile salmon away from the powerhouse and reducing turbine passage. The Juvenile Salmonid Acoustic Telemetry System (JSATS) was used to estimate survival of juvenile salmonids passing the dam and also for calculating performance metrics used to evaluate the efficiency and effectiveness of the dam at passing juvenile salmonids.

  9. Experimental measurement of structural power flow on an aircraft fuselage

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1989-01-01

    An experimental technique is used to measure the structural power flow through an aircraft fuselage with the excitation near the wing attachment location. Because of the large number of measurements required to analyze the whole of an aircraft fuselage, it is necessary that a balance be achieved between the number of measurement transducers, the mounting of these transducers, and the accuracy of the measurements. Using four transducers mounted on a bakelite platform, the structural intensity vectors at locations distributed throughout the fuselage are measured. To minimize the errors associated with using a four transducers technique the measurement positions are selected away from bulkheads and stiffeners. Because four separate transducers are used, with each transducer having its own drive and conditioning amplifiers, phase errors are introduced in the measurements that can be much greater than the phase differences associated with the measurements. To minimize these phase errors two sets of measurements are taken for each position with the orientation of the transducers rotated by 180 deg and an average taken between the two sets of measurements. Results are presented and discussed.

  10. Pseudopotential approach for dust acoustic solitary waves in dusty plasmas with kappa-distributed ions and electrons and dust grains having power law size distribution

    SciTech Connect

    Banerjee, Gadadhar; Maitra, Sarit

    2015-04-15

    Sagdeev's pseudopotential method is used to study small as well as arbitrary amplitude dust acoustic solitons in a dusty plasma with kappa distributed electrons and ions with dust grains having power law size distribution. The existence of potential well solitons has been shown for suitable parametric region. The criterion for existence of soliton is derived in terms of upper and lower limit for Mach numbers. The numerical results show that the size distribution can affect the existence as well as the propagation characteristics of the dust acoustic solitons. The effect of kappa distribution is also highlighted.

  11. Organised Coherent Motion in Atmospheric Boundary Layer Flow in the Proximity to Tall Plant Canopies as Detected in Acoustic Doppler Profiler and Tower-based Observations

    NASA Astrophysics Data System (ADS)

    Foken, T.; Thomas, C. K.

    2007-12-01

    We investigated coherent structures above and in a tall plant canopy during a field campaign at a mountainous site in Germany (WALDATEM-2003). Data from a remote sensing acoustic Doppler system in concert with in-situ point measurements of turbulence in flow velocity and scalars deployed on towers yielded continuous observations from the forest ground to 200 m above the ground with a vertical resolution of 10 m at a sampling frequency of 0.4 and 20 Hz respectively. Coherent structures were extracted from time series utilizing wavelet transform techniques allowing for single structure analysis and averaged statistics of detected events. In addition to their spatiotemporal scales, we focused on the identification of generating mechanisms and surface parameters affecting coherent structures. Time scales were on the order of 20 to 36 s depending on the upstream topography and canopy morphology. Lateral transport dominated scalar coherent exchange. Vertical profiles of time scales in longitudinal and vertical velocities were mirror images showing an increase/ decrease, respectively, with height. Time scales in scalars were nearly height-constant. The ratio of the contribution of coherent structures to total vertical exchange was 0.2 for momentum and 0.25 to 0.4 for sensible heat. Analysis of power spectra confirmed an interaction between inactive eddies of atmospheric boundary layer scale and the horizontal flow in 4 % of all studied cases only, mainly under near-neutral stratification. Evaluation of the Mixing-Layer Analogy suggested that vertical shear caused by the immense canopy drag was the dominant generating mechanism. However, daytime coherent structures were found to be a superposition of shear generated events and convectional eddies. The latter led to an increase of vertical coherency in the flow around noon. At night, terrain induced linear gravity waves showed similar time scales as coherent structures emphasizing the need to differentiate between these two

  12. Low power underwater acoustic DPSK detection: Theoretical prediction and experimental results

    NASA Astrophysics Data System (ADS)

    Dunne, Andrew

    This thesis presents two methods of analyzing the effectiveness of a prototype differential phase-shift keying (DPSK) detection circuit. The first method is to make modifications to the existing hardware to reliably output and record the cross-correlation values of the DPSK detection process. The second method is to write a MATLAB detection algorithm which accurately simulates the detection results of the hardware system without the need of any electronics. These two systems were tested and verified with a bench test using computer generated DPSK signals. The hardware system was tested using real acoustic data from shallow and deep water at-sea tests to determine the effectiveness of the DPSK detection circuit in different ocean environments. The hydrophone signals from the tests were recorded so that the cross-correlation values could be verified using the MATLAB detector. As a result of this study, these two systems provided more insight into how well the DPSK detection prototype works and helped to identify ways of improving the detection reliability and overall performance of the prototype DPSK detection circuit.

  13. Impact of chevron spacing and asymmetric distribution on supersonic jet acoustics and flow

    NASA Astrophysics Data System (ADS)

    Heeb, N.; Gutmark, E.; Kailasanath, K.

    2016-05-01

    An experimental investigation into the effect of chevron spacing and distribution on supersonic jets was performed. Cross-stream and streamwise particle imaging velocimetry measurements were used to relate flow field modification to sound field changes measured by far-field microphones in the overexpanded, ideally expanded, and underexpanded regimes. Drastic modification of the jet cross-section was achieved by the investigated configurations, with both elliptic and triangular shapes attained downstream. Consequently, screech was nearly eliminated with reductions in the range of 10-25 dB depending on the operating condition. Analysis of the streamwise velocity indicated that both the mean shock spacing and strength were reduced resulting in an increase in the broadband shock associated noise spectral peak frequency and a reduction in the amplitude, respectively. Maximum broadband shock associated noise amplitude reductions were in the 5-7 dB range. Chevron proximity was found to be the primary driver of peak vorticity production, though persistence followed the opposite trend. The integrated streamwise vorticity modulus was found to be correlated with peak large scale turbulent mixing noise reduction, though optimal overall sound pressure level reductions did not necessarily follow due to the shock/fine scale mixing noise sources. Optimal large scale mixing noise reductions were in the 5-6 dB range.

  14. Results of Tests Performed on the Acoustic Quiet Flow Facility Three-Dimensional Model Tunnel

    NASA Technical Reports Server (NTRS)

    Barna, P. S.

    1995-01-01

    The test results briefly described in this report were obtained on the three-dimensional 1:48 scale tunnel modeled on the design proposed by Messrs. D.S.M.A. Corporation. More particularly, while the test chamber dimensions were indeed scaled down in the ration of 1:48, including the contraction and the collector as well, the duct system itself leading to and from the chamber was adapted to suit laboratory conditions and space limitations. Earlier tests with the two-dimensional model showed that blowing mode was preferred as against the suction mode, hence all tests were performed with blowing only. At the exit of the contraction the maximum airspeed attained with the 1 HP blower unit was about 200 ft/sec. This airspeed may be increased in future if desired. The test results show that pressure recovery in the diffuser was about 34 percent due to the large blockage at its entrance. Velocity traverses taken across the diffuser entrance explain the reason for this blockage. Recirculation, studied with both, hot-wire anemometry and flow-visualization techniques, was largely affected by the design of the test chamber itself and the amount of vent-air admitted to the chamber. Vent-air helped to decrease the level of turbulence.

  15. Analyzing panel acoustic contributions toward the sound field inside the passenger compartment of a full-size automobile.

    PubMed

    Wu, Sean F; Moondra, Manmohan; Beniwal, Ravi

    2015-04-01

    The Helmholtz equation least squares (HELS)-based nearfield acoustical holography (NAH) is utilized to analyze panel acoustic contributions toward the acoustic field inside the interior region of an automobile. Specifically, the acoustic power flows from individual panels are reconstructed, and relative contributions to sound pressure level and spectrum at any point of interest are calculated. Results demonstrate that by correlating the acoustic power flows from individual panels to the field acoustic pressure, one can correctly locate the panel allowing the most acoustic energy transmission into the vehicle interior. The panel on which the surface acoustic pressure amplitude is the highest should not be used as indicative of the panel responsible for the sound field in the vehicle passenger compartment. Another significant advantage of this HELS-based NAH is that measurements of the input data only need to be taken once by using a conformal array of microphones in the near field, and ranking of panel acoustic contributions to any field point can be readily performed. The transfer functions between individual panels of any vibrating structure to the acoustic pressure anywhere in space are calculated not measured, thus significantly reducing the time and effort involved in panel acoustic contributions analyses.

  16. Non-Newtonian Power-Law Fluid Flow over a Shrinking Sheet

    NASA Astrophysics Data System (ADS)

    Fang, Tie-Gang; Tao, Hua; Zhong, Yong-Fang

    2012-11-01

    The boundary layer flow of power-law fluids over a shrinking sheet with mass transfer is revisited. Closed-form analytical solutions are found and presented for special cases. One of the presented solutions has an algebraic decay behavior. These analytical solutions might offer valuable insight into the nonlinear boundary layer flow for power-law fluids.

  17. Low-power, cylindrical, air-coupled acoustic levitation/concentration devices: Symmetry breaking of the levitation volume

    NASA Astrophysics Data System (ADS)

    Kaduchak, Gregory; Kogan, Aleksandr S.; Kwiatkowski, Christopher S.; Sinha, Dipen N.

    2002-11-01

    A cylindrical acoustic device for levitation and/or concentration of aerosols and small liquid/solid samples (up to several millimeters in diameter) in air has been developed [Kaduchak et al., Rev. Sci. Instrum. 73, 1332-1336]. It is inexpensive, low-power, and, in its simplest embodiment, does not require accurate alignment of a resonant cavity. It is constructed from a cylindrical PZT tube with thickness-to-radius ratio h/aapprox0.03. The novelty of the device is that the lowest-order breathing mode of the tube is tuned to match a resonant mode of the interior air-filled cylindrical cavity. A high-Q cavity results that is driven very efficiently; drops of water in excess of 1-mm diameter are levitated for approximately 100 mW of input electrical power. The present research addresses modifying the different spatial configurations of the standing wave field within the cavity. By breaking the cylindrical symmetry, it is shown that pressure nodes can be localized for collection or separation of aerosolds or other particulate matter. Several different symmetry-breaking configurations are demonstrated. It is shown that experimental observations of the nodal arrangements agree with theoretical predictions.

  18. Ultrathin, rollable, paper-based triboelectric nanogenerator for acoustic energy harvesting and self-powered sound recording.

    PubMed

    Fan, Xing; Chen, Jun; Yang, Jin; Bai, Peng; Li, Zhaoling; Wang, Zhong Lin

    2015-04-28

    A 125 μm thickness, rollable, paper-based triboelectric nanogenerator (TENG) has been developed for harvesting sound wave energy, which is capable of delivering a maximum power density of 121 mW/m(2) and 968 W/m(3) under a sound pressure of 117 dBSPL. The TENG is designed in the contact-separation mode using membranes that have rationally designed holes at one side. The TENG can be implemented onto a commercial cell phone for acoustic energy harvesting from human talking; the electricity generated can be used to charge a capacitor at a rate of 0.144 V/s. Additionally, owing to the superior advantages of a broad working bandwidth, thin structure, and flexibility, a self-powered microphone for sound recording with rolled structure is demonstrated for all-sound recording without an angular dependence. The concept and design presented in this work can be extensively applied to a variety of other circumstances for either energy-harvesting or sensing purposes, for example, wearable and flexible electronics, military surveillance, jet engine noise reduction, low-cost implantable human ear, and wireless technology applications. PMID:25790372

  19. Ultrathin, rollable, paper-based triboelectric nanogenerator for acoustic energy harvesting and self-powered sound recording.

    PubMed

    Fan, Xing; Chen, Jun; Yang, Jin; Bai, Peng; Li, Zhaoling; Wang, Zhong Lin

    2015-04-28

    A 125 μm thickness, rollable, paper-based triboelectric nanogenerator (TENG) has been developed for harvesting sound wave energy, which is capable of delivering a maximum power density of 121 mW/m(2) and 968 W/m(3) under a sound pressure of 117 dBSPL. The TENG is designed in the contact-separation mode using membranes that have rationally designed holes at one side. The TENG can be implemented onto a commercial cell phone for acoustic energy harvesting from human talking; the electricity generated can be used to charge a capacitor at a rate of 0.144 V/s. Additionally, owing to the superior advantages of a broad working bandwidth, thin structure, and flexibility, a self-powered microphone for sound recording with rolled structure is demonstrated for all-sound recording without an angular dependence. The concept and design presented in this work can be extensively applied to a variety of other circumstances for either energy-harvesting or sensing purposes, for example, wearable and flexible electronics, military surveillance, jet engine noise reduction, low-cost implantable human ear, and wireless technology applications.

  20. Application of acoustic doppler current profilers for measuring three-dimensional flow fields and as a surrogate measurement of bedload transport

    USGS Publications Warehouse

    Conaway, J.S.

    2005-01-01

    Acoustic Doppler current profilers (ADCPs) have been in use in the riverine environment for nearly 20 years. Their application primarily has been focused on the measurement of streamflow discharge. ADCPs emit high-frequency sound pulses and receive reflected sound echoes from sediment particles in the water column. The Doppler shift between transmitted and return signals is resolved into a velocity component that is measured in three dimensions by simultaneously transmitting four independent acoustical pulses. To measure the absolute velocity magnitude and direction in the water column, the velocity magnitude and direction of the instrument must also be computed. Typically this is accomplished by ensonifying the streambed with an acoustical pulse that also provides a depth measurement for each of the four acoustic beams. Sediment transport on or near the streambed will bias these measurements and requires external positioning such as a differentially corrected Global Positioning Systems (GPS). Although the influence of hydraulic structures such as spur dikes and bridge piers is typically only measured and described in one or two dimensions, the use of differentially corrected GPS with ADCPs provides a fully three-dimensional measurement of the magnitude and direction of the water column at such structures. The measurement of these flow disturbances in a field setting also captures the natural pulsations of river flow that cannot be easily quantified or modeled by numerical simulations or flumes. Several examples of measured three-dimensional flow conditions at bridge sites throughout Alaska are presented. The bias introduced to the bottom-track measurement is being investigated as a surrogate measurement of bedload transport. By fixing the position of the ADCP for a known period of time the apparent velocity of the streambed at that position can be determined. Initial results and comparison to traditionally measured bedload values are presented. These initial

  1. Phase Inversion: Inferring Solar Subphotospheric Flow and Other Asphericity from the Distortion of Acoustic Waves

    NASA Technical Reports Server (NTRS)

    Gough, Douglas; Merryfield, William J.; Toomre, Juri

    1998-01-01

    A method is proposed for analyzing an almost monochromatic train of waves propagating in a single direction in an inhomogeneous medium that is not otherwise changing in time. An effective phase is defined in terms of the Hilbert transform of the wave function, which is related, via the JWKB approximation, to the spatial variation of the background state against which the wave is propagating. The contaminating effect of interference between the truly monochromatic components of the train is eliminated using its propagation properties. Measurement errors, provided they are uncorrelated, are manifest as rapidly varying noise; although that noise can dominate the raw phase-processed signal, it can largely be removed by low-pass filtering. The intended purpose of the analysis is to determine the distortion of solar oscillations induced by horizontal structural variation and material flow. It should be possible to apply the method directly to sectoral modes. The horizontal phase distortion provides a measure of longitudinally averaged properties of the Sun in the vicinity of the equator, averaged also in radius down to the depth to which the modes penetrate. By combining such averages from different modes, the two-dimensional variation can be inferred by standard inversion techniques. After taking due account of horizontal refraction, it should be possible to apply the technique also to locally sectoral modes that propagate obliquely to the equator and thereby build a network of lateral averages at each radius, from which the full three-dimensional structure of the Sun can, in principle, be determined as an inverse Radon transform.

  2. EVALUATION OF ACOUSTIC FORCES ON A PARTICLE IN AEROSOL MEDIUM

    SciTech Connect

    Lee, S; Richard Dimenna, R

    2007-09-27

    The acoustic force exerted on a solid particle was evaluated to develop a fundamental understanding of the critical physical parameters or constraints affecting particle motion and capture in a collecting device. The application of an acoustic force to the collection of a range of submicron-to-micron particles in a highly turbulent airflow stream laden with solid particles was evaluated in the presence of other assisting and competing forces. This scoping estimate was based on the primary acoustic force acting directly on particles in a dilute aerosol system, neglecting secondary interparticle effects such as agglomeration of the sub-micron particles. A simplified analysis assuming a stable acoustic equilibrium with an infinite sound speed in the solid shows that for a solid-laden air flow in the presence of a standing wave, particles will move toward the nearest node. The results also show that the turbulent drag force on a 1-{micro}m particle resulting from eddy motion is dominant when compared with the electrostatic force or the ultrasonic acoustic force. At least 180 dB acoustic pressure level at 1 MHz is required for the acoustic force to be comparable to the electrostatic or turbulent drag forces in a high-speed air stream. It is noted that particle size and pressure amplitude are dominant parameters for the acoustic force. When acoustic pressure level becomes very large, the acoustic energy will heat up the surrounding air medium, which may cause air to expand. With an acoustic power of about 600 watts applied to a 2000-lpm air flow, the air temperature can increase by as much as 15 C at the exit of the collector.

  3. Acoustic behaviors of unsaturated soils

    NASA Astrophysics Data System (ADS)

    Lu, Z.

    2011-12-01

    Soils are unconsolidated granular materials, consisting of solid particles, water and air. Their mechanical and dynamic behaviors are determined by the discrete nature of the media as well as external and inter-particle forces. For unsaturated soils, two factors significantly affect soils acoustic/seismic responses: external pressure and internal water potential/matric suction. In triaxial cell tests, unsaturated soils were subjected to predefined stress paths to undergo stages of normal consolidation, unload-reload cycles, and failure. The stress deformation curve and stress-P-wave velocity were measured and compared. The study revealed that soil's dynamic response to external pressure are similar to those of the load-deformation behaviors and demonstrated that acoustic velocity can be used to monitor the state of stress of soils. In a long term field soil survey, the P-wave velocities were found to be correlated with water potential as expressed as a power-law relationship. The above phenomena can be understood by using the Terzaghi' s the principle of effective stress. The measured results were in good agreement with Brutsaert theory. The effective stress concept can also be applied to explain the observations in a soil pipe flow study in which soil internal erosion processes were monitored and interpreted by the temporal evolution of the P-wave velocity. In addition to above linear acoustic behaviors, soils, like other earth materials, exhibit astonishing non-classical nonlinear behaviors such as end-point memory, hysteresis, strain -dependent shear modulus, resonant frequency shift, and phase shift, harmonics generation, etc. A nonlinear acoustic study of a soil as a function of water content showed that the nonlinear acoustic parameter are much sensitive to the variations of soil water content than that of the acoustic velocity.

  4. 76 FR 24014 - Free Flow Power Corporation; Notice of Intent To File License Application, Filing of Pre...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-29

    ... Project, P-13338- 001 and Mississippi Lock & Dam No. 9--Auxiliary Lock Water Power Project, P-14148-000. f... Energy Regulatory Commission [Project Nos. P-13338-001; P-14148-000 Free Flow Power Corporation; Notice... 25, 2011. d. Submitted by: Free Flow Power Corporation (Free Flow Power), on behalf of its...

  5. Feedwater flow measurement and experience using clamp-on transit-time ultrasonic flow meter in nuclear power plants

    SciTech Connect

    Ha, J. H.; Jang, W. H.; Lee, J. Y.; Jang, H. C.; Kim, H. B.

    2006-07-01

    This paper addresses the feedwater flow measurement technology for the nuclear power plant using a clamp-on transit-time ultrasonic flow meter (UFM) equipped with special mounting fixture, Wave Injector, for high temperature application. The velocity profile correction factor was determined for OPR1000 (Optimized Power Reactor 1000) feedwater flow based on the experimental data from the test facilities, the numerical simulation and the empirical data. Various activities were done to verify the performance of UFM such as the calibration tests, the reproducibility tests and pipe configuration effect tests. Uncertainty analyses were done to evaluate all the uncertainty- contributing sources and hardware characteristics and to find out the applicable uncertainty factors. Site tests were performed to verify the applicability and the reliability at the normal operating conditions of nuclear power plants. The results demonstrated that the UFM technology with Wavelnjector can be used for measuring the feedwater flow of nuclear power plants with approximately {+-}0.63% measurement uncertainty, and it is expected to recover the lost plant power due to the anomaly in venturi flow meter. (authors)

  6. Millimeter-Gap Magnetically Insulated Transmission Line Power Flow Experiments

    SciTech Connect

    Hutsel, Brian Thomas; Stoltzfus, Brian S.; Fowler, William E.; LeChien, Keith R.; Mazarakis, Michael G.; Moore, James K.; Mulville, Thomas D.; Savage, Mark E.; Stygar, William A.; McKenney, John L.; Jones, Peter A.; MacRunnels, Diego J.; Long, Finis W.; Porter, John L.

    2014-09-01

    An experiment platform has been designed to study vacuum power flow in magnetically insulated transmission lines (MITLs). The platform was driven by the 400-GW Mykonos-V accelerator. The experiments conducted quantify the current loss in a millimeter-gap MITL with respect to vacuum conditions in the MITL for two different gap distances, 1.0 and 1.3 mm. The current loss for each gap was measured for three different vacuum pump down times. As a ride along experiment, multiple shots were conducted with each set of hardware to determine if there was a conditioning effect to increase current delivery on subsequent shots. The experiment results revealed large differences in performance for the 1.0 and 1.3 mm gaps. The 1.0 mm gap resulted in current loss of 40%-60% of peak current. The 1.3 mm gap resulted in current losses of less than 5% of peak current. Classical MITL models that neglect plasma expansion predict that there should be zero current loss, after magnetic insulation is established, for both of these gaps. The experiments result s indicate that the vacuum pressure or pump down time did not have a significant effect on the measured current loss at vacuum pressures between 1e-4 and 1e-5 Torr. Additionally, there was not repeatable evidence of a conditioning effect that reduced current loss for subsequent full-energy shots on a given set of hardware. It should be noted that the experiments conducted likely did not have large loss contributions due to ion emission from the anode due to the relatively small current densi-ties (25-40 kA/cm) in the MITL that limited the anode temperature rise due to ohmic heating. The results and conclusions from these experiments may have limited applicability to MITLs of high current density (>400 kA/cm) used in the convolute and load region of the Z which experience temperature increases of >400° C and generate ion emission from anode surfaces.

  7. Flow cytometry: A powerful technology for measuring biomarkers

    SciTech Connect

    Jett, J.H.

    1994-09-01

    A broad definition of a biomarker is that it is a measurable characteristic of a biological system that changes upon exposure to a physical or chemical insult. While the definition can be further refined, it is sufficient for the purposes of demonstrating the advantages of flow cytometry for making quantitative measurements of biomarkers. Flow cytometry and cell sorting technologies have emerged during the past 25 years to take their place alongside other essential tools used in biology such as optical and electron microscopy. This paper describes the basics of flow cytometry technology, provides illustrative examples of applications of the technology in the field of biomarkers, describes recent developments in flow cytometry that have not yet been applied to biomarker measurements, and projects future developments of the technology. The examples of uses of flow cytometry for biomarker quantification cited in this paper are meant to be illustrative and not exhaustive in the sense of providing a review of the field.

  8. 78 FR 41389 - Free Flow Power Corporation; Notice of Application Ready for Environmental Analysis and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-10

    ... PayneBridge, LLC. e. Name of Project: Williams Dam Water Power Project. f. Location: At the existing... (NAVD 88). In addition to the dam, the Williams Dam Water Power Project would consist of the following... Energy Regulatory Commission Free Flow Power Corporation; Notice of Application Ready for...

  9. Measurement of the Doppler power of flowing blood using ultrasound Doppler devices.

    PubMed

    Huang, Chih-Chung; Chou, Hung-Lung; Chen, Pay-Yu

    2015-02-01

    Measurement of the Doppler power of signals backscattered from flowing blood (henceforth referred to as the Doppler power of flowing blood) and the echogenicity of flowing blood have been used widely to assess the degree of red blood cell (RBC) aggregation for more than 20 y. Many studies have used Doppler flowmeters based on an analogue circuit design to obtain the Doppler shifts in the signals backscattered from flowing blood; however, some recent studies have mentioned that the analogue Doppler flowmeter exhibits a frequency-response problem whereby the backscattered energy is lost at higher Doppler shift frequencies. Therefore, the measured Doppler power of flowing blood and evaluations of RBC aggregation obtained using an analogue Doppler device may be inaccurate. To overcome this problem, the present study implemented a field-programmable gate array-based digital pulsed-wave Doppler flowmeter to measure the Doppler power of flowing blood, in the aim of providing more accurate assessments of RBC aggregation. A clinical duplex ultrasound imaging system that can acquire pulsed-wave Doppler spectrograms is now available, but its usefulness for estimating the ultrasound scattering properties of blood is still in doubt. Therefore, the echogenicity and Doppler power of flowing blood under the same flow conditions were measured using a laboratory pulser-receiver system and a clinical ultrasound system, respectively, for comparisons. The experiments were carried out using porcine blood under steady laminar flow with both RBC suspensions and whole blood. The experimental results indicated that a clinical ultrasound system used to measure the Doppler spectrograms is not suitable for quantifying Doppler power. However, the Doppler power measured using a digital Doppler flowmeter can reveal the relationship between backscattering signals and the properties of blood cells because the effects of frequency response are eliminated. The measurements of the Doppler power and

  10. Unified power flow controller: Modeling, stability analysis, control strategy and control system design

    NASA Astrophysics Data System (ADS)

    Sreenivasachar, Kannan

    2001-07-01

    Unified power flow controller (UPFC) has been the most versatile Flexible AC Transmission System (FACTS) device due to its ability to control real and reactive power flow on transmission lines while controlling the voltage of the bus to which it is connected. UPFC being a multi-variable power system controller it is necessary to analyze its effect on power system operation. To study the performance of the UPFC in damping power oscillations using PSCAD-EMTDC software, a de-coupled control system has been designed for the shunt inverter to control the UPFC bus voltage and the DC link capacitor voltage. The series inverter of a UPFC controls the real power flow in the transmission line. One problem associated with using a high gain PI controller (used to achieve fast control of transmission line real power flow) for the series inverter of a UPFC to control the real power flow in a transmission line is the presence of low damping. This problem is solved in this research by using a fuzzy controller. A method to model a fuzzy controller in PSCAD-EMTDC software has also been described. Further, in order to facilitate proper operation between the series and the shunt inverter control system, a new real power coordination controller has been developed and its performance was evaluated. The other problem concerning the operation of a UPFC is with respect to transmission line reactive power flow control. Step changes to transmission line reactive power references have significant impact on the UPFC bus voltage. To reduce the adverse effect of step changes in transmission line reactive power references on the UPFC bus voltage, a new reactive power coordination controller has been designed. Transient response studies have been conducted using PSCAD-EMTDC software to show the improvement in power oscillation damping with UPFC. These simulations include the real and reactive power coordination controllers. Finally, a new control strategy has been proposed for UPFC. In this

  11. Particle analysis in an acoustic cytometer

    DOEpatents

    Kaduchak, Gregory; Ward, Michael D

    2012-09-18

    The present invention is a method and apparatus for acoustically manipulating one or more particles. Acoustically manipulated particles may be separated by size. The particles may be flowed in a flow stream and acoustic radiation pressure, which may be radial, may be applied to the flow stream. This application of acoustic radiation pressure may separate the particles. In one embodiment, the particles may be separated by size, and as a further example, the larger particles may be transported to a central axis.

  12. PRSA hydrogen tank thermal acoustic oscillation study

    NASA Technical Reports Server (NTRS)

    Riemer, D. H.

    1979-01-01

    The power reactant storage assembly (PRSA) hydrogen tank test data were reviewed. Two hundred and nineteen data points illustrating the effect of flow rate, temperature ratio and configuration were identified. The test data were reduced to produce the thermal acoustic oscillation parameters. Frequency and amplitude were determined for model correlation. A comparison of PRSA hydrogen tank test data with the analytical models indicated satisfactory agreement for the supply and poor agreement for the full line.

  13. Ocean acoustic hurricane classification.

    PubMed

    Wilson, Joshua D; Makris, Nicholas C

    2006-01-01

    Theoretical and empirical evidence are combined to show that underwater acoustic sensing techniques may be valuable for measuring the wind speed and determining the destructive power of a hurricane. This is done by first developing a model for the acoustic intensity and mutual intensity in an ocean waveguide due to a hurricane and then determining the relationship between local wind speed and underwater acoustic intensity. From this it is shown that it should be feasible to accurately measure the local wind speed and classify the destructive power of a hurricane if its eye wall passes directly over a single underwater acoustic sensor. The potential advantages and disadvantages of the proposed acoustic method are weighed against those of currently employed techniques. PMID:16454274

  14. Ocean acoustic hurricane classification.

    PubMed

    Wilson, Joshua D; Makris, Nicholas C

    2006-01-01

    Theoretical and empirical evidence are combined to show that underwater acoustic sensing techniques may be valuable for measuring the wind speed and determining the destructive power of a hurricane. This is done by first developing a model for the acoustic intensity and mutual intensity in an ocean waveguide due to a hurricane and then determining the relationship between local wind speed and underwater acoustic intensity. From this it is shown that it should be feasible to accurately measure the local wind speed and classify the destructive power of a hurricane if its eye wall passes directly over a single underwater acoustic sensor. The potential advantages and disadvantages of the proposed acoustic method are weighed against those of currently employed techniques.

  15. Active micromixer using surface acoustic wave streaming

    SciTech Connect

    Branch; Darren W. , Meyer; Grant D. , Craighead; Harold G.

    2011-05-17

    An active micromixer uses a surface acoustic wave, preferably a Rayleigh wave, propagating on a piezoelectric substrate to induce acoustic streaming in a fluid in a microfluidic channel. The surface acoustic wave can be generated by applying an RF excitation signal to at least one interdigital transducer on the piezoelectric substrate. The active micromixer can rapidly mix quiescent fluids or laminar streams in low Reynolds number flows. The active micromixer has no moving parts (other than the SAW transducer) and is, therefore, more reliable, less damaging to sensitive fluids, and less susceptible to fouling and channel clogging than other types of active and passive micromixers. The active micromixer is adaptable to a wide range of geometries, can be easily fabricated, and can be integrated in a microfluidic system, reducing dead volume. Finally, the active micromixer has on-demand on/off mixing capability and can be operated at low power.

  16. Development of Millimeter-Wave Velocimetry and Acoustic Time-of-Flight Tomography for Measurements in Densely Loaded Gas-Solid Riser Flow

    SciTech Connect

    Fort, James A.; Pfund, David M.; Sheen, David M.; Pappas, Richard A.; Morgen, Gerald P.

    2007-04-01

    The MFDRC was formed in 1998 to advance the state-of-the-art in simulating multiphase turbulent flows by developing advanced computational models for gas-solid flows that are experimentally validated over a wide range of industrially relevant conditions. The goal was to transfer the resulting validated models to interested US commercial CFD software vendors, who would then propagate the models as part of new code versions to their customers in the US chemical industry. Since the lack of detailed data sets at industrially relevant conditions is the major roadblock to developing and validating multiphase turbulence models, a significant component of the work involved flow measurements on an industrial-scale riser contributed by Westinghouse, which was subsequently installed at SNL. Model comparisons were performed against these datasets by LANL. A parallel Office of Industrial Technology (OIT) project within the consortium made similar comparisons between riser measurements and models at NETL. Measured flow quantities of interest included volume fraction, velocity, and velocity-fluctuation profiles for both gas and solid phases at various locations in the riser. Some additional techniques were required for these measurements beyond what was currently available. PNNL’s role on the project was to work with the SNL experimental team to develop and test two new measurement techniques, acoustic tomography and millimeter-wave velocimetry. Acoustic tomography is a promising technique for gas-solid flow measurements in risers and PNNL has substantial related experience in this area. PNNL is also active in developing millimeter wave imaging techniques, and this technology presents an additional approach to make desired measurements. PNNL supported the advanced diagnostics development part of this project by evaluating these techniques and then by adapting and developing the selected technology to bulk gas-solids flows and by implementing them for testing in the SNL riser

  17. Scaling and dimensional analysis of acoustic streaming jets

    SciTech Connect

    Moudjed, B.; Botton, V.; Henry, D.; Ben Hadid, H.

    2014-09-15

    This paper focuses on acoustic streaming free jets. This is to say that progressive acoustic waves are used to generate a steady flow far from any wall. The derivation of the governing equations under the form of a nonlinear hydrodynamics problem coupled with an acoustic propagation problem is made on the basis of a time scale discrimination approach. This approach is preferred to the usually invoked amplitude perturbations expansion since it is consistent with experimental observations of acoustic streaming flows featuring hydrodynamic nonlinearities and turbulence. Experimental results obtained with a plane transducer in water are also presented together with a review of the former experimental investigations using similar configurations. A comparison of the shape of the acoustic field with the shape of the velocity field shows that diffraction is a key ingredient in the problem though it is rarely accounted for in the literature. A scaling analysis is made and leads to two scaling laws for the typical velocity level in acoustic streaming free jets; these are both observed in our setup and in former studies by other teams. We also perform a dimensional analysis of this problem: a set of seven dimensionless groups is required to describe a typical acoustic experiment. We find that a full similarity is usually not possible between two acoustic streaming experiments featuring different fluids. We then choose to relax the similarity with respect to sound attenuation and to focus on the case of a scaled water experiment representing an acoustic streaming application in liquid metals, in particular, in liquid silicon and in liquid sodium. We show that small acoustic powers can yield relatively high Reynolds numbers and velocity levels; this could be a virtue for heat and mass transfer applications, but a drawback for ultrasonic velocimetry.

  18. A High-Order Immersed Boundary Method for Acoustic Wave Scattering and Low-Mach Number Flow-Induced Sound in Complex Geometries

    PubMed Central

    Seo, Jung Hee; Mittal, Rajat

    2010-01-01

    A new sharp-interface immersed boundary method based approach for the computation of low-Mach number flow-induced sound around complex geometries is described. The underlying approach is based on a hydrodynamic/acoustic splitting technique where the incompressible flow is first computed using a second-order accurate immersed boundary solver. This is followed by the computation of sound using the linearized perturbed compressible equations (LPCE). The primary contribution of the current work is the development of a versatile, high-order accurate immersed boundary method for solving the LPCE in complex domains. This new method applies the boundary condition on the immersed boundary to a high-order by combining the ghost-cell approach with a weighted least-squares error method based on a high-order approximating polynomial. The method is validated for canonical acoustic wave scattering and flow-induced noise problems. Applications of this technique to relatively complex cases of practical interest are also presented. PMID:21318129

  19. Fractionating power and outlet stream polydispersity in asymmetrical flow field-flow fractionation. Part I: isocratic operation.

    PubMed

    Williams, P Stephen

    2016-05-01

    Asymmetrical flow field-flow fractionation (As-FlFFF) has become the most commonly used of the field-flow fractionation techniques. However, because of the interdependence of the channel flow and the cross flow through the accumulation wall, it is the most difficult of the techniques to optimize, particularly for programmed cross flow operation. For the analysis of polydisperse samples, the optimization should ideally be guided by the predicted fractionating power. Many experimentalists, however, neglect fractionating power and rely on light scattering detection simply to confirm apparent selectivity across the breadth of the eluted peak. The size information returned by the light scattering software is assumed to dispense with any reliance on theory to predict retention, and any departure of theoretical predictions from experimental observations is therefore considered of no importance. Separation depends on efficiency as well as selectivity, however, and efficiency can be a strong function of retention. The fractionation of a polydisperse sample by field-flow fractionation never provides a perfectly separated series of monodisperse fractions at the channel outlet. The outlet stream has some residual polydispersity, and it will be shown in this manuscript that the residual polydispersity is inversely related to the fractionating power. Due to the strong dependence of light scattering intensity and its angular distribution on the size of the scattering species, the outlet polydispersity must be minimized if reliable size data are to be obtained from the light scattering detector signal. It is shown that light scattering detection should be used with careful control of fractionating power to obtain optimized analysis of polydisperse samples. Part I is concerned with isocratic operation of As-FlFFF, and part II with programmed operation.

  20. Estimating the vibration level of an L-shaped beam using power flow techniques

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.; Mccollum, M.; Rassineux, J. L.; Gilbert, T.

    1986-01-01

    The response of one component of an L-shaped beam, with point force excitation on the other component, is estimated using the power flow method. The transmitted power from the source component to the receiver component is expressed in terms of the transfer and input mobilities at the excitation point and the joint. The response is estimated both in narrow frequency bands, using the exact geometry of the beams, and as a frequency averaged response using infinite beam models. The results using this power flow technique are compared to the results obtained using finite element analysis (FEA) of the L-shaped beam for the low frequency response and to results obtained using statistical energy analysis (SEA) for the high frequencies. The agreement between the FEA results and the power flow method results at low frequencies is very good. SEA results are in terms of frequency averaged levels and these are in perfect agreement with the results obtained using the infinite beam models in the power flow method. The narrow frequency band results from the power flow method also converge to the SEA results at high frequencies. The advantage of the power flow method is that detail of the response can be retained while reducing computation time, which will allow the narrow frequency band analysis of the response to be extended to higher frequencies.

  1. Novel wave power analysis linking pressure-flow waves, wave potential, and the forward and backward components of hydraulic power.

    PubMed

    Mynard, Jonathan P; Smolich, Joseph J

    2016-04-15

    Wave intensity analysis provides detailed insights into factors influencing hemodynamics. However, wave intensity is not a conserved quantity, so it is sensitive to diameter variations and is not distributed among branches of a junction. Moreover, the fundamental relation between waves and hydraulic power is unclear. We, therefore, propose an alternative to wave intensity called "wave power," calculated via incremental changes in pressure and flow (dPdQ) and a novel time-domain separation of hydraulic pressure power and kinetic power into forward and backward wave-related components (ΠP±and ΠQ±). Wave power has several useful properties:1) it is obtained directly from flow measurements, without requiring further calculation of velocity;2) it is a quasi-conserved quantity that may be used to study the relative distribution of waves at junctions; and3) it has the units of power (Watts). We also uncover a simple relationship between wave power and changes in ΠP±and show that wave reflection reduces transmitted power. Absolute values of ΠP±represent wave potential, a recently introduced concept that unifies steady and pulsatile aspects of hemodynamics. We show that wave potential represents the hydraulic energy potential stored in a compliant pressurized vessel, with spatial gradients producing waves that transfer this energy. These techniques and principles are verified numerically and also experimentally with pressure/flow measurements in all branches of a central bifurcation in sheep, under a wide range of hemodynamic conditions. The proposed "wave power analysis," encompassing wave power, wave potential, and wave separation of hydraulic power provides a potent time-domain approach for analyzing hemodynamics. PMID:26873972

  2. Novel wave power analysis linking pressure-flow waves, wave potential, and the forward and backward components of hydraulic power.

    PubMed

    Mynard, Jonathan P; Smolich, Joseph J

    2016-04-15

    Wave intensity analysis provides detailed insights into factors influencing hemodynamics. However, wave intensity is not a conserved quantity, so it is sensitive to diameter variations and is not distributed among branches of a junction. Moreover, the fundamental relation between waves and hydraulic power is unclear. We, therefore, propose an alternative to wave intensity called "wave power," calculated via incremental changes in pressure and flow (dPdQ) and a novel time-domain separation of hydraulic pressure power and kinetic power into forward and backward wave-related components (ΠP±and ΠQ±). Wave power has several useful properties:1) it is obtained directly from flow measurements, without requiring further calculation of velocity;2) it is a quasi-conserved quantity that may be used to study the relative distribution of waves at junctions; and3) it has the units of power (Watts). We also uncover a simple relationship between wave power and changes in ΠP±and show that wave reflection reduces transmitted power. Absolute values of ΠP±represent wave potential, a recently introduced concept that unifies steady and pulsatile aspects of hemodynamics. We show that wave potential represents the hydraulic energy potential stored in a compliant pressurized vessel, with spatial gradients producing waves that transfer this energy. These techniques and principles are verified numerically and also experimentally with pressure/flow measurements in all branches of a central bifurcation in sheep, under a wide range of hemodynamic conditions. The proposed "wave power analysis," encompassing wave power, wave potential, and wave separation of hydraulic power provides a potent time-domain approach for analyzing hemodynamics.

  3. Mapping thunder sources by inverting acoustic and electromagnetic observations

    NASA Astrophysics Data System (ADS)

    Anderson, J. F.; Johnson, J. B.; Arechiga, R. O.; Thomas, R. J.

    2014-12-01

    We present a new method of locating current flow in lightning strikes by inversion of thunder recordings constrained by Lightning Mapping Array observations. First, radio frequency (RF) pulses are connected to reconstruct conductive channels created by leaders. Then, acoustic signals that would be produced by current flow through each channel are forward modeled. The recorded thunder is considered to consist of a weighted superposition of these acoustic signals. We calculate the posterior distribution of acoustic source energy for each channel with a Markov Chain Monte Carlo inversion that fits power envelopes of modeled and recorded thunder; these results show which parts of the flash carry current and produce thunder. We examine the effects of RF pulse location imprecision and atmospheric winds on quality of results and apply this method to several lightning flashes over the Magdalena Mountains in New Mexico, USA. This method will enable more detailed study of lightning phenomena by allowing researchers to map current flow in addition to leader propagation.

  4. High intensity focused ultrasound sonothrombolysis: the use of perfluorocarbon droplets to achieve clot lysis at reduced acoustic powers

    PubMed Central

    Pajek, Daniel; Burgess, Alison; Huang, Yuexi; Hynynen, Kullervo

    2014-01-01

    The purpose of this study was to evaluate use of intravascular perfluorocarbon (PFC) droplets to reduce the sonication powers required to achieve clot lysis using high intensity focused ultrasound (HIFU). HIFU with droplets was initially applied to blood clots in an in vitro flow apparatus and inertial cavitation thresholds were determined. An embolic model for ischemic stroke was used to demonstrate the feasibility of this technique in vivo. Recanalization with intravascular droplets was achieved in vivo at 24±5% of the sonication power without droplets. Rabbits receiving 1 ms pulsed sonication during continuous intravascular droplet infusion recanalized in 71% of cases (p=0.041 vs controls). Preliminary experiments showed that damage was contained to the ultrasonic focus, suggesting that safe treatments would be possible with a more tightly focused hemispherical array that allows the whole focus to be placed inside of the main arteries in the human brain. PMID:25023095

  5. Exercise performance while wearing a tight-fitting powered air purifying respirator with limited flow.

    PubMed

    Johnson, Arthur T; Mackey, Kathryn R; Scott, William H; Koh, Frank C; Chiou, Ken Y H; Phelps, Stephanie J

    2005-07-01

    Sixteen subjects exercised at 80-85% of maximal aerobic capacity on a treadmill while wearing a tight-fitting, FRM40-Turbo Powered Air Purifying Respirator (PAPR). The PAPR was powered by a DC power supply to give flow rates of 0%, 30%, 66%, 94%, and 100% of rated maximum blower capacity of 110 L/min. As flow rate was reduced, so was performance time. There was a 20% reduction in performance time as blower flow changed from 100% to 0% of maximum. Significant differences in breathing apparatus comfort and facial thermal comfort were found as flow rate varied. It was concluded that inadequate blower flow rate decreases performance time, facial cooling, and respirator comfort. PMID:16020100

  6. The effect of the coupling between the top plate and the fingerboard on the acoustic power radiated by a classical guitar (L).

    PubMed

    García-Mayén, Héctor; Santillán, Arturo

    2011-03-01

    An experimental investigation on the coupling between the fingerboard and the top plate of a classical guitar at low frequencies is presented. The study was carried out using a finished top plate under fixed boundary conditions and a commercial guitar. Radiated sound power was determined in one-third octave bands up to the band of 1 kHz based on measurements of sound intensity. The results provide evidence that the way in which the fingerboard and top plate are coupled is not a relevant factor in the radiated acoustic power of the classical guitar in the studied frequency range.

  7. The effect of the coupling between the top plate and the fingerboard on the acoustic power radiated by a classical guitar (L).

    PubMed

    García-Mayén, Héctor; Santillán, Arturo

    2011-03-01

    An experimental investigation on the coupling between the fingerboard and the top plate of a classical guitar at low frequencies is presented. The study was carried out using a finished top plate under fixed boundary conditions and a commercial guitar. Radiated sound power was determined in one-third octave bands up to the band of 1 kHz based on measurements of sound intensity. The results provide evidence that the way in which the fingerboard and top plate are coupled is not a relevant factor in the radiated acoustic power of the classical guitar in the studied frequency range. PMID:21428477

  8. Extension of vibrational power flow techniques to two-dimensional structures

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1987-01-01

    In the analysis of the vibration response and structure-borne vibration transmission between elements of a complex structure, statistical energy analysis (SEA) or Finite Element Analysis (FEA) are generally used. However, an alternative method is using vibrational power flow techniques which can be especially useful in the mid- frequencies between the optimum frequency regimes for FEA and SEA. Power flow analysis has in general been used on one-dimensional beam-like structures or between structures with point joints. In this paper, the power flow technique is extended to two-dimensional plate like structures joined along a common edge without frequency or spatial averaging the results, such that the resonant response of the structure is determined. The power flow results are compared to results obtained using FEA at low frequencies and SEA at high frequencies. The agreement with FEA results is good but the power flow technique has an improved computational efficiency. Compared to the SEA results the power flow results show a closer representation of the actual response of the structure.

  9. Extension of vibrational power flow techniques to two-dimensional structures

    NASA Technical Reports Server (NTRS)

    Cuschieri, Joseph M.

    1988-01-01

    In the analysis of the vibration response and structure-borne vibration transmission between elements of a complex structure, statistical energy analysis (SEA) or finite element analysis (FEA) are generally used. However, an alternative method is using vibrational power flow techniques which can be especially useful in the mid frequencies between the optimum frequency regimes for SEA and FEA. Power flow analysis has in general been used on 1-D beam-like structures or between structures with point joints. In this paper, the power flow technique is extended to 2-D plate-like structures joined along a common edge without frequency or spatial averaging the results, such that the resonant response of the structure is determined. The power flow results are compared to results obtained using FEA results at low frequencies and SEA at high frequencies. The agreement with FEA results is good but the power flow technique has an improved computational efficiency. Compared to the SEA results the power flow results show a closer representation of the actual response of the structure.

  10. EOIL power scaling in a 1-5 kW supersonic discharge-flow reactor

    NASA Astrophysics Data System (ADS)

    Davis, Steven J.; Lee, Seonkyung; Oakes, David B.; Haney, Julie; Magill, John C.; Paulsen, Dwane A.; Cataldi, Paul; Galbally-Kinney, Kristin L.; Vu, Danthu; Polex, Jan; Kessler, William J.; Rawlins, Wilson T.

    2008-02-01

    Scaling of EOIL systems to higher powers requires extension of electric discharge powers into the kW range and beyond with high efficiency and singlet oxygen yield. We have previously demonstrated a high-power microwave discharge approach capable of generating singlet oxygen yields of ~25% at ~50 torr pressure and 1 kW power. This paper describes the implementation of this method in a supersonic flow reactor designed for systematic investigations of the scaling of gain and lasing with power and flow conditions. The 2450 MHz microwave discharge, 1 to 5 kW, is confined near the flow axis by a swirl flow. The discharge effluent, containing active species including O II(a1Δ g, b1Σ g +), O( 3P), and O 3, passes through a 2-D flow duct equipped with a supersonic nozzle and cavity. I2 is injected upstream of the supersonic nozzle. The apparatus is water-cooled, and is modular to permit a variety of inlet, nozzle, and optical configurations. A comprehensive suite of optical emission and absorption diagnostics is used to monitor the absolute concentrations of O II(a), O II(b), O( 3P), O 3, I II, I(2P 3/2), I(2P 1/2), small-signal gain, and temperature in both the subsonic and supersonic flow streams. We discuss initial measurements of singlet oxygen and I* excitation kinetics at 1 kW power.

  11. Analysis of electrode system for generation of high-power electrodynamic flow

    NASA Astrophysics Data System (ADS)

    Rebrov, I. E.; Khomich, V. Yu.; Yamshchikov, V. A.

    2016-08-01

    A high-power electrodynamic flow in atmospheric air is numerically simulated and experimentally studied. An electrode system consisting of a cylindrical plasma emitter and a plane metal grid collector of ions is used to generate a flow with a speed of 2 m/s and a volume rate of 15 L/s.

  12. Pressure drop and pumping power for fluid flow through round tubes

    NASA Technical Reports Server (NTRS)

    Jelinek, D.

    1973-01-01

    Program, written for Hewlett-Packard 9100A electronic desk computer provides convenient and immediate solution to problem of calculating pressure drop and fluid pumping power for flow through round tubes. Program was designed specifically for steady-state analysis and assumes laminar flow.

  13. Indirect measurement of the thermal-acoustic efficiency spectrum of a long turbulent burner

    NASA Technical Reports Server (NTRS)

    Mahan, J. R.; Jones, J. D.; Blevins, L. R.; Cline, J. G.

    1983-01-01

    A new method is described for deducing the thermal-acoustic efficiency spectrum (defined as the fraction of combustion heat release converted to acoustic energy at a given frequency) of a long turbulent burner from the sound spectrum measured in the far field. The method, which is based on a one-dimensional model of the unsteady flow in the burner, is applied to a tubular diffusion-flame hydrogen burner whose length is large compared to its diameter. The results for thermal powers ranging from 4.5 to 22.3 kW show that the thermal-acoustic efficiency is relatively insensitive to the burner power level, decreasing from a value of around 0.0001 at 150 Hz with a slope of about 20 dB per decade. Evidence is presented indicating that acoustic agitation of the flame below 500 Hz, especially in the neighborhood of the resonant frequencies of the burner, is a significant acoustic source.

  14. Capabilities, Design, Construction and Commissioning of New Vibration, Acoustic, and Electromagnetic Capabilities Added to the World's Largest Thermal Vacuum Chamber at NASA's Space Power Facility

    NASA Technical Reports Server (NTRS)

    Motil, Susan M.; Ludwiczak, Damian R.; Carek, Gerald A.; Sorge, Richard N.; Free, James M.; Cikanek, Harry A., III

    2011-01-01

    NASA s human space exploration plans developed under the Exploration System Architecture Studies in 2005 included a Crew Exploration Vehicle launched on an Ares I launch vehicle. The mass of the Crew Exploration Vehicle and trajectory of the Ares I coupled with the need to be able to abort across a large percentage of the trajectory generated unprecedented testing requirements. A future lunar lander added to projected test requirements. In 2006, the basic test plan for Orion was developed. It included several types of environment tests typical of spacecraft development programs. These included thermal-vacuum, electromagnetic interference, mechanical vibration, and acoustic tests. Because of the size of the vehicle and unprecedented acoustics, NASA conducted an extensive assessment of options for testing, and as result, chose to augment the Space Power Facility at NASA Plum Brook Station, of the John H. Glenn Research Center to provide the needed test capabilities. The augmentation included designing and building the World s highest mass capable vibration table, the highest power large acoustic chamber, and adaptation of the existing World s largest thermal vacuum chamber as a reverberant electromagnetic interference test chamber. These augmentations were accomplished from 2007 through early 2011. Acceptance testing began in Spring 2011 and will be completed in the Fall of 2011. This paper provides an overview of the capabilities, design, construction and acceptance of this extraordinary facility.

  15. Morphology and flow fields of three-dimensional dunes, Rio Paraná, Argentina: Results from simultaneous multibeam echo sounding and acoustic Doppler current profiling

    NASA Astrophysics Data System (ADS)

    Parsons, D. R.; Best, J. L.; Orfeo, O.; Hardy, R. J.; Kostaschuk, R.; Lane, S. N.

    2005-12-01

    Most past studies of river dune dynamics have concentrated on two-dimensional (2-D) bed forms, with constant heights and straight crest lines transverse to the flow, and their associated turbulent flow structure. This morphological simplification imposes inherent limitations on the interpretation and understanding of dune form and flow dynamics in natural channels, where dune form is predominantly three-dimensional. For example, studies over 2-D forms neglect the significant influence that lateral flows and secondary circulation may have on the flow structure and thus dune morphology. This paper details a field study of a swath of 3-D dunes in the Rio Paraná, Argentina. A large (0.35 km wide, 1.2 km long) area of dunes was surveyed using a multibeam echo sounder (MBES) that provided high-resolution 3-D detail of the river bed. Simultaneous with the MBES survey, 3-D flow information was obtained with an acoustic Doppler current profiler (ADCP), revealing a complicated pattern of dune morphology and associated flow structure within the swath. Dune three-dimensionality appears intimately connected to the morphology of the upstream dune, with changes in crest line curvature and crest line bifurcations/junctions significantly influencing the downstream dune form. Dunes with lobe or saddle-shaped crest lines were found to have larger, more structured regions of vertical velocity with smaller separation zones than more 2-D straight-crested dunes. These results represent the first integrated study of 3-D dune form and mean flow structure from the field and show several similarities to recent laboratory models of flow over 3-D dunes.

  16. Economic Concerns in Optimal Power Dispatch in the Presence of a Generalized Unified Power Flow Controller under Practical Constraints

    NASA Astrophysics Data System (ADS)

    Suresh, Chintalapudi V.; Sivanagaraju, Sirigiri; Reddy, P. Umapathi

    2016-09-01

    In power system restructuring, pricing the electrical power plays a vital role in cost allocation between suppliers and consumers. In optimal power dispatch problem, not only the cost of active power generation but also the costs of reactive power generated by the generators, shunt capacitors, transmission losses and device investment costs should be considered. In this paper, a more realistic multi-fuel total cost objective is formulated by considering all the above mentioned costs. As the characteristics of reactive power cost curve are similar to that of active power cost curve, a non-convex reactive power cost function is formulated. The formulated cost function is optimized by satisfying equality, in-equality and practical constraints and also device limits using the proposed uniform distributed two-stage particle swarm optimization. In this paper, power injection model of generalized unified power flow controller (GUPFC) including converter switching losses is presented. The proposed objective functions are optimized in the presence of UPFC and GUPFC and finally suitable device is identified for the standard IEEE-30 bus test system.

  17. Power and Flow Experience in Time-Intensive Business Simulation Game

    ERIC Educational Resources Information Center

    Kiili, Kristian; Lainema, Timo

    2010-01-01

    Power is an influential component of social interaction and there are reasons for thinking that it may have important effects both on decision-making and psychological and interpersonal processes. The aim of this paper was to study the relations between the feeling of power, decision-making and flow experience in a collaborative business…

  18. Gelled propellant flow: Boundary layer theory for power-law fluids in a converging planar channel

    NASA Astrophysics Data System (ADS)

    Kraynik, Andrew M.; Geller, A. S.; Glick, J. H.

    1989-10-01

    A boundary layer theory for the flow of power-law fluids in a converging planar channel has been developed. This theory suggests a Reynolds number for such flows, and following numerical integration, a boundary layer thickness. This boundary layer thickness has been used in the generation of a finite element mesh for the finite element code FIDAP. FIDAP was then used to simulate the flow of power-law fluids through a converging channel. Comparison of the analytic and finite element results shows the two to be in very good agreement in regions where entrance and exit effects (not considered in the boundary layer theory) can be neglected.

  19. Integrating fluorescent dye flow-curve testing and acoustic Doppler velocimetry profiling for in situ hydraulic evaluation and improvement of clarifier performance.

    PubMed

    Tarud, F; Aybar, M; Pizarro, G; Cienfuegos, R; Pastén, P

    2010-08-01

    Enhancing the performance of clarifiers requires a thorough understanding of their hydraulics. Fluorescence spectroscopy and acoustic doppler velocimeter (ADV) profiling generally have been used separately to evaluate secondary settlers. We propose that simultaneous use of these techniques is needed to obtain a more reliable and useful evaluation. Experiments were performed on laboratory- and full-scale clarifiers. Factors affecting Fluorescein and Rhodamine 6G properties were identified. Underestimations up to 500% in fluorescence intensities may be derived from differential fluorescence quenching by oxygen. A careful control and interpretation of fluorescent dye experiments is needed to minimize artifacts in real settings. While flow-curve tests constructed under controlled conditions provided a more accurate overall quantitative estimation of the hydraulic performance, ADV velocity and turbulence profiling provided a detailed spatial understanding of flow patterns that was used to troubleshoot and fix the causes of hydraulic short-circuits.

  20. Integrating fluorescent dye flow-curve testing and acoustic Doppler velocimetry profiling for in situ hydraulic evaluation and improvement of clarifier performance.

    PubMed

    Tarud, F; Aybar, M; Pizarro, G; Cienfuegos, R; Pastén, P

    2010-08-01

    Enhancing the performance of clarifiers requires a thorough understanding of their hydraulics. Fluorescence spectroscopy and acoustic doppler velocimeter (ADV) profiling generally have been used separately to evaluate secondary settlers. We propose that simultaneous use of these techniques is needed to obtain a more reliable and useful evaluation. Experiments were performed on laboratory- and full-scale clarifiers. Factors affecting Fluorescein and Rhodamine 6G properties were identified. Underestimations up to 500% in fluorescence intensities may be derived from differential fluorescence quenching by oxygen. A careful control and interpretation of fluorescent dye experiments is needed to minimize artifacts in real settings. While flow-curve tests constructed under controlled conditions provided a more accurate overall quantitative estimation of the hydraulic performance, ADV velocity and turbulence profiling provided a detailed spatial understanding of flow patterns that was used to troubleshoot and fix the causes of hydraulic short-circuits. PMID:20853746

  1. Interaction of acoustic waves generated by coupled plate

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1990-01-01

    When two substructures are coupled, the acoustic field generated by the motion of each of the substructures will interact with the motion of the other substructure. This would be the case of a structure enclosing an acoustic cavity. A technique to model the interaction of the generated sound fields from the two components of a coupled structure, and the influence of this interaction on the vibration of the structural components is presented. Using a mobility power flow approach, each element of the substructure is treated independently both when developing the structural response and when determining the acoustic field generated by this component. The presence of the other substructural components is introduced by assuming these components to be rigid baffles. The excitation of one of the substructures is assumed to be by an incident acoustic wave which is dependent of the motion of the substructure. The sound field generated by the motion of the substructure is included in the solution of the response.

  2. A MILP-Based Distribution Optimal Power Flow Model for Microgrid Operation

    SciTech Connect

    Liu, Guodong; Starke, Michael R; Zhang, Xiaohu; Tomsovic, Kevin

    2016-01-01

    This paper proposes a distribution optimal power flow (D-OPF) model for the operation of microgrids. The proposed model minimizes not only the operating cost, including fuel cost, purchasing cost and demand charge, but also several performance indices, including voltage deviation, network power loss and power factor. It co-optimizes the real and reactive power form distributed generators (DGs) and batteries considering their capacity and power factor limits. The D-OPF is formulated as a mixed-integer linear programming (MILP). Numerical simulation results show the effectiveness of the proposed model.

  3. Bidirectional control system for energy flow in solar powered flywheel

    NASA Technical Reports Server (NTRS)

    Nola, Frank J. (Inventor)

    1987-01-01

    An energy storage system for a spacecraft is provided which employs a solar powered flywheel arrangement including a motor/generator which, in different operating modes, drives the flywheel and is driven thereby. A control circuit, including a threshold comparator, senses the output of a solar energy converter, and when a threshold voltage is exceeded thereby indicating the availability of solar power for the spacecraft loads, activates a speed control loop including the motor/generator so as to accelerate the flywheel to a constant speed and thereby store mechanical energy, while also supplying energy from the solar converter to the loads. Under circumstances where solar energy is not available and thus the threshold voltage is not exceeded, the control circuit deactivates the speed control loop and activates a voltage control loop that provides for operation of the motor as a generator so that mechanical energy from the flywheel is converted into electrical energy for supply to the spacecraft loads.

  4. Acoustic cooling engine

    DOEpatents

    Hofler, Thomas J.; Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1988-01-01

    An acoustic cooling engine with improved thermal performance and reduced internal losses comprises a compressible fluid contained in a resonant pressure vessel. The fluid has a substantial thermal expansion coefficient and is capable of supporting an acoustic standing wave. A thermodynamic element has first and second ends and is located in the resonant pressure vessel in thermal communication with the fluid. The thermal response of the thermodynamic element to the acoustic standing wave pumps heat from the second end to the first end. The thermodynamic element permits substantial flow of the fluid through the thermodynamic element. An acoustic driver cyclically drives the fluid with an acoustic standing wave. The driver is at a location of maximum acoustic impedance in the resonant pressure vessel and proximate the first end of the thermodynamic element. A hot heat exchanger is adjacent to and in thermal communication with the first end of the thermodynamic element. The hot heat exchanger conducts heat from the first end to portions of the resonant pressure vessel proximate the hot heat exchanger. The hot heat exchanger permits substantial flow of the fluid through the hot heat exchanger. The resonant pressure vessel can include a housing less than one quarter wavelength in length coupled to a reservoir. The housing can include a reduced diameter portion communicating with the reservoir. The frequency of the acoustic driver can be continuously controlled so as to maintain resonance.

  5. Low-speed wind tunnel investigation of the aerodynamic and acoustic performance of a translating-centerbody choked-flow inlet

    NASA Technical Reports Server (NTRS)

    Miller, B. A.; Abbott, J. M.

    1973-01-01

    Low-speed wind-tunnel tests were conducted to determine the effects of free-stream velocity and incidence angle on the aerodynamic and acoustic performance of a translating centerbody choked-flow inlet. The inlet was sized to fit a 13.97 cm diameter fan with a design weight flow of 2.49 kg/sec. Performance was determined at free-stream velocities to 45 meters per second and incidence angles of 0 deg to 50 deg. The inlet was operated in both the choked and unchoked modes over a range of weight flows. Measurements were made of inlet total pressure recovery, flow distortion, surface static pressure distribution, and fan noise suppression. In the choked mode, increasing incidence angle tended to reduce the amount of inlet noise suppression for a given amount of inlet suction. This tendency was overcome by applying sufficient inlet suction to increase the flow Mach number. At 45 meters per second free-stream velocity, at least 22 decibels of suppression were measured at 35 deg incidence angle with a total pressure recovery of 0.985.

  6. Power flow tracing in a simplified highly renewable European electricity network

    NASA Astrophysics Data System (ADS)

    Tranberg, Bo; Thomsen, Anders B.; Rodriguez, Rolando A.; Andresen, Gorm B.; Schäfer, Mirko; Greiner, Martin

    2015-10-01

    The increasing transmission capacity needs in a future energy system raise the question of how associated costs should be allocated to the users of a strengthened power grid. In contrast to straightforward oversimplified methods, a flow tracing based approach provides a fair and consistent nodal usage and thus cost assignment of transmission investments. This technique follows the power flow through the network and assigns the link capacity usage to the respective sources or sinks using a diffusion-like process, thus taking into account the underlying network structure and injection pattern. As a showcase, we apply power flow tracing to a simplified model of the European electricity grid with a high share of renewable wind and solar power generation, based on long-term weather and load data with an hourly temporal resolution.

  7. Fluctuation in e-mail sizes weakens power-law correlations in e-mail flow

    NASA Astrophysics Data System (ADS)

    Matsubara, Yoshitsugu; Hieida, Yasuhiro; Tadaki, Shin-ichi

    2013-09-01

    Power-law correlations have been observed in packet flow over the Internet. The possible origin of these correlations includes demand for Internet services. We observe the demand for e-mail services in an organization, and analyze correlations in the flow and the sequence of send requests using a Detrended Fluctuation Analysis (DFA). The correlation in the flow is found to be weaker than that in the send requests. Four types of artificial flow are constructed to investigate the effects of fluctuations in e-mail sizes. As a result, we find that the correlation in the flow originates from that in the sequence of send requests. The strength of the power-law correlation decreases as a function of the ratio of the standard deviation of e-mail sizes to their average.

  8. High Average Power Laser Gain Medium With Low Optical Distortion Using A Transverse Flowing Liquid Host

    DOEpatents

    Comaskey, Brian J.; Ault, Earl R.; Kuklo, Thomas C.

    2005-07-05

    A high average power, low optical distortion laser gain media is based on a flowing liquid media. A diode laser pumping device with tailored irradiance excites the laser active atom, ion or molecule within the liquid media. A laser active component of the liquid media exhibits energy storage times longer than or comparable to the thermal optical response time of the liquid. A circulation system that provides a closed loop for mixing and circulating the lasing liquid into and out of the optical cavity includes a pump, a diffuser, and a heat exchanger. A liquid flow gain cell includes flow straighteners and flow channel compression.

  9. Experimental results using active control of traveling wave power flow

    NASA Technical Reports Server (NTRS)

    Miller, David W.; Hall, Steven R.

    1991-01-01

    Active structural control experiments conducted on a 24-ft pinned-free beam derived feedback compensators on the basis of a traveling-wave approach. A compensator is thus obtained which eliminates resonant behavior by absorbing all impinging power. A causal solution is derived for this noncausal compensator which mimics its behavior in a given frequency range, using the Wiener-Hopf. This optimal Wiener-Hopf compensator's structure-damping performance is found to exceed any obtainable by means of rate feedback. Performance limitations encompassed the discovery of frequencies above which the sensor and actuator were no longer dual and an inadvertent coupling of the control hardware to unmodeled structure torsion modes.

  10. Acoustic levitator for containerless measurements on low temperature liquids

    SciTech Connect

    Benmore, Chris J; Weber, Richard; Neuefeind, Joerg C; Rey, Charles A A

    2009-01-01

    A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops at temperatures from -40 to +40 C. The levitator consisted of: (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) a acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of ~ 22 kHz and could produce sound pressure levels up to 160 dB. The force applied by the acoustic field could be modulated using a frequency generator to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids.

  11. Acoustic levitator for structure measurements on low temperature liquid droplets.

    PubMed

    Weber, J K R; Rey, C A; Neuefeind, J; Benmore, C J

    2009-08-01

    A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops of 1-3 mm in diameter at temperatures in the range -40 to +40 degrees C. The levitator comprised (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) an acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1 kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of approximately 22 kHz and could produce sound pressure levels of up to 160 dB. The force applied by the acoustic field could be modulated to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids.

  12. Manipulating Liquids With Acoustic Radiation Pressure Phased Arrays

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C.

    1999-01-01

    High-intensity ultrasound waves can produce the effects of "Acoustic Radiation Pressure" (ARP) and "acoustic streaming." These effects can be used to propel liquid flows and to apply forces that can be used to move or manipulate floating objects or liquid surfaces. NASA's interest in ARP includes the remote-control agitation of liquids and the manipulation of bubbles and drops in liquid experiments and propellant systems. A high level of flexibility is attained by using a high-power acoustic phased array to generate, steer, and focus a beam of acoustic waves. This is called an Acoustic Radiation Pressure Phased Array, or ARPPA. In this approach, many acoustic transducer elements emit wavelets that converge into a single beam of sound waves. Electronically coordinating the timing, or "phase shift," of the acoustic waves makes it possible to form a beam with a predefined direction and focus. Therefore, a user can direct the ARP force at almost any desired point within a liquid volume. ARPPA lets experimenters manipulate objects anywhere in a test volume. This flexibility allow it to be used for multiple purposes, such as to agitate liquids, deploy and manipulate drops or bubbles, and even suppress sloshing in spacecraft propellant tanks.

  13. Acoustic levitator for structure measurements on low temperature liquid droplets.

    PubMed

    Weber, J K R; Rey, C A; Neuefeind, J; Benmore, C J

    2009-08-01

    A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops of 1-3 mm in diameter at temperatures in the range -40 to +40 degrees C. The levitator comprised (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) an acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1 kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of approximately 22 kHz and could produce sound pressure levels of up to 160 dB. The force applied by the acoustic field could be modulated to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids. PMID:19725664

  14. Accelerated ions from pulsed-power-driven fast plasma flow in perpendicular magnetic field

    NASA Astrophysics Data System (ADS)

    Takezaki, Taichi; Takahashi, Kazumasa; Sasaki, Toru; Kikuchi, Takashi; Harada, Nob.

    2016-06-01

    To understand the interaction between fast plasma flow and perpendicular magnetic field, we have investigated the behavior of a one-dimensional fast plasma flow in a perpendicular magnetic field by a laboratory-scale experiment using a pulsed-power discharge. The velocity of the plasma flow generated by a tapered cone plasma focus device is about 30 km/s, and the magnetic Reynolds number is estimated to be 8.8. After flow through the perpendicular magnetic field, the accelerated ions are measured by an ion collector. To clarify the behavior of the accelerated ions and the electromagnetic fields, numerical simulations based on an electromagnetic hybrid particle-in-cell method have been carried out. The results show that the behavior of the accelerated ions corresponds qualitatively to the experimental results. Faster ions in the plasma flow are accelerated by the induced electromagnetic fields modulated with the plasma flow.

  15. Acoustic transducer

    DOEpatents

    Drumheller, D.S.

    1997-12-30

    An acoustic transducer is described comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2,000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers. 4 figs.

  16. Acoustic transducer

    DOEpatents

    Drumheller, Douglas S.

    1997-01-01

    An acoustic transducer comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers.

  17. 76 FR 53434 - Free Flow Power Corporation; Northland Power Mississippi River LLC; Notice of Competing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-26

    ...' express permission. The proposed projects are described as follows: Free Flow's hydrokinetic Project... hydrokinetic Project, Project No. 14093-000 would consist of: (1) Up to 160 TREK generating units installed...

  18. 76 FR 53434 - Free Flow Power Corporation, Northland Power Mississippi River LLC; Notice of Competing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-26

    ... described as follows: Free Flow's hydrokinetic Project, Project No. 12861-003 would consist of: (1) Up to 1... sold to a local utility. Northland's hydrokinetic Project, Project No. 14098-000 would consist of:...

  19. 76 FR 53433 - Free Flow Power Corporation; Northland Power Mississippi River LLC; Notice of Competing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-26

    .... The proposed projects are described as follows: Free Flow's hydrokinetic Project, Project No. 12842... kilowatt-hours (kWh), which would be sold to a local utility. Northland's hydrokinetic Project, Project...

  20. 76 FR 53431 - Free Flow Power Corporation; Northland Power Mississippi River LLC; Notice of Competing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-26

    ... described as follows: Free Flow's hydrokinetic Project, Project No. 12857-002 would consist of: (1) Up to 2... be sold to a local utility. Northland's hydrokinetic Project, Project No. 14073-000 would consist...