Science.gov

Sample records for acoustic streaming flow

  1. 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].

  2. A simulation of streaming flows associated with acoustic levitators

    NASA Astrophysics Data System (ADS)

    Rednikov, A.; Riley, N.

    2002-04-01

    Steady-state acoustic streaming flow patterns have been observed by Trinh and Robey [Phys. Fluids 6, 3567 (1994)], during the operation of a variety of single axis ultrasonic levitators in a gaseous environment. Microstreaming around levitated samples is superimposed on the streaming flow which is observed in the levitator even in the absence of any particle therein. In this paper, by physical arguments, numerical and analytical simulations we provide entirely satisfactory interpretations of the observed flow patterns in both isothermal and nonisothermal situations.

  3. 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.

  4. 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.

  5. 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. PMID:22280567

  6. 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

  7. 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. PMID:26025507

  8. Acoustically induced streaming flows near a model cod otolith and their potential implications for fish hearing.

    PubMed

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

    2011-08-01

    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. Phase-locked 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. PMID:21877817

  9. 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.

  10. 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

  11. 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

  12. 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

  13. Acoustic streaming jets: A scaling and dimensional analysis

    SciTech Connect

    Botton, V. Henry, D.; Millet, S.; Ben-Hadid, H.; Garandet, J. P.

    2015-10-28

    We present our work on acoustic streaming free jets driven by ultrasonic beams in liquids. These jets are steady flows generated far from walls by progressive acoustic waves. As can be seen on figure 1, our set-up, denominated AStrID for Acoustic Streaming Investigation Device, is made of a water tank in which a 29 mm plane source emits continuous ultrasonic waves at typically 2 MHz. Our approach combines an experimental characterization of both the acoustic pressure field (hydrophone) and the obtained acoustic streaming velocity field (PIV visualization) on one hand, with CFD using an incompressible Navier-Stokes solver on the other hand.

  14. Active micromixer using surface acoustic wave streaming

    DOEpatents

    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.

  15. 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.

  16. Acoustic Investigation of Jet Mixing Noise in Dual Stream Nozzles

    NASA Technical Reports Server (NTRS)

    Khavaran, Abbas; Dahl, Milo D.

    2012-01-01

    In an earlier study, a prediction model for jet noise in dual stream jets was proposed that is founded on velocity scaling laws in single stream jets and similarity features of the mean velocity and turbulent kinetic energy in dual stream flows. The model forms a composite spectrum from four component single-stream jets each believed to represent noise-generation from a distinct region in the actual flow. While the methodology worked effectively at conditions considered earlier, recent examination of acoustic data at some unconventional conditions indicate that further improvements are necessary in order to expand the range of applicability of the model. The present work demonstrates how these predictions compare with experimental data gathered by NASA and industry for the purpose of examining the aerodynamic and acoustic performance of such nozzles for a wide range of core and fan stream conditions. Of particular interest are jets with inverted velocity and temperature profiles and the appearance of a second spectral peak at small aft angles to the jet under such conditions. It is shown that a four-component spectrum succeeds in modeling the second peak when the aft angle refraction effects are properly incorporated into the model. A tradeoff of noise emission takes place between two turbulent regions identified as transition and fully mixed regions as the fan stream velocity exceeds that of the core stream. The effect of nozzle discharge coefficients will also be discussed.

  17. Magnetic resonance imaging of acoustic streaming: absorption coefficient and acoustic field shape estimation.

    PubMed

    Madelin, Guillaume; Grucker, Daniel; Franconi, Jean-Michel; Thiaudiere, Eric

    2006-07-01

    In this study, magnetic resonance imaging (MRI) is used to visualize acoustic streaming in liquids. A single-shot spin echo sequence (HASTE) with a saturation band perpendicular to the acoustic beam permits the acquisition of an instantaneous image of the flow due to the application of ultrasound. An average acoustic streaming velocity can be estimated from the MR images, from which the ultrasonic absorption coefficient and the bulk viscosity of different glycerol-water mixtures can be deduced. In the same way, this MRI method could be used to assess the acoustic field and time-average power of ultrasonic transducers in water (or other liquids with known physical properties), after calibration of a geometrical parameter that is dependent on the experimental setup. PMID:16650447

  18. Acoustic streaming and Sun's meridional circulation

    NASA Astrophysics Data System (ADS)

    Valverde, Jose Manuel

    2016-09-01

    A vast number of physical processes involving oscillations of a bounded viscous fluid are relevantly influenced by acoustic streaming. When this happens a steady circulation of fluid develops in a thin boundary adjacent to the interface. Some examples are refracted sound waves, a fluid inside a spherical cavity undergoing torsional oscillations or a pulsating liquid droplet. Steady streaming around circular interfaces consists of a hemispherically symmetric recirculation of fluid from the equatorial plane to the polar axes closely resembling the meridional circulation pattern observed in the Sun's convection zone that determines the solar cycle. In this paper, it is argued that the acoustic pulsations exhibited by the Sun would lead to acoustic streaming in the boundary of the convection zone. A simple estimation using a typical dominant frequency of 3 mHz and the observed surface oscillation amplitude yields a steady streaming velocity us ∼ 10 m s‑1, which is on the order of the meridional circulation velocity observed in the Sun's convection zone.

  19. Three-Dimensional Phenomena in Microbubble Acoustic Streaming

    NASA Astrophysics Data System (ADS)

    Marin, Alvaro; Rossi, Massimiliano; Rallabandi, Bhargav; Wang, Cheng; Hilgenfeldt, Sascha; Kähler, Christian J.

    2015-04-01

    Ultrasound-driven oscillating microbubbles are used as active actuators in microfluidic devices to perform manifold tasks such as mixing, sorting, and manipulation of microparticles. A common configuration consists of side bubbles created by trapping air pockets in blind channels perpendicular to the main channel direction. This configuration consists of acoustically excited bubbles with a semicylindrical shape that generate significant streaming flow. Because of the geometry of the channels, such flows are generally considered as quasi-two-dimensional. Similar assumptions are often made in many other microfluidic systems based on flat microchannels. However, in this Letter we show that microparticle trajectories actually present a much richer behavior, with particularly strong out-of-plane dynamics in regions close to the microbubble interface. Using astigmatism particle-tracking velocimetry, we reveal that the apparent planar streamlines are actually projections of a stream surface with a pseudotoroidal shape. We, therefore, show that acoustic streaming cannot generally be assumed as a two-dimensional phenomenon in confined systems. The results have crucial consequences for most of the applications involving acoustic streaming such as particle trapping, sorting, and mixing.

  20. Acoustic streaming induced by an ultrasonically oscillating endodontic file.

    PubMed

    Verhaagen, B; Boutsioukis, C; van der Sluis, L W M; Versluis, M

    2014-04-01

    Ultrasonically activated irrigation is an advanced dental technique for irrigation of the root canal system during a root canal treatment. The basic cleaning mechanism is a result of acoustic streaming induced by an oscillating file, leading to mixing of the irrigant and pressure and shear stresses on the walls of the root canal. Here the induced acoustic streaming, pressure, and shear stress are investigated in a two-dimensional cross-section of the root canal, using a combination of theory, numerical predictions, and experimental validation through high-speed particle tracking velocimetry. Acoustic streaming theory describes very well the flow induced by an ultrasonically oscillating endodontic file. It consists of an oscillatory component, which is dominant near the file, and a steady component, or jet, along the axis of oscillation. The importance of the oscillatory component for both the pressure and the shear stress is apparent, as it is two to three orders of magnitude higher than the steady component. A confinement affects the formation of the steady jets; meanwhile the oscillatory velocities and associated pressure and shear stress are increased. Previous work considering only the steady component of the flow therefore, underestimated the hydrodynamic effects induced by ultrasonic files. PMID:25234972

  1. In-Flow Acoustic Sensor

    NASA Technical Reports Server (NTRS)

    Allen, Christopher S. (Inventor)

    1995-01-01

    An acoustic sensor for measuring acoustic waves contained in fluid flow flowing over the sensor is introduced. The acoustic sensor reduces any unwanted self-noise associated with the flowing fluid by providing a nose cone having proper aerodynamic properties and by positioning the diaphragm of a microphone of the sensor at a location where any unwanted noise is at a relatively low level. The nose cone has a rounded, blunt or even sharp tip neither of which creates any major disturbances in the flowing fluid which it intercepts.

  2. Three-dimensional microbubble streaming flows

    NASA Astrophysics Data System (ADS)

    Rallabandi, Bhargav; Marin, Alvaro; Rossi, Massimiliano; Kaehler, Christian; Hilgenfeldt, Sascha

    2014-11-01

    Streaming due to acoustically excited bubbles has been used successfully for applications such as size-sorting, trapping and focusing of particles, as well as fluid mixing. Many of these applications involve the precise control of particle trajectories, typically achieved using cylindrical bubbles, which establish planar flows. Using astigmatic particle tracking velocimetry (APTV), we show that, while this two-dimensional picture is a useful description of the flow over short times, a systematic three-dimensional flow structure is evident over long time scales. We demonstrate that this long-time three-dimensional fluid motion can be understood through asymptotic theory, superimposing secondary axial flows (induced by boundary conditions at the device walls) onto the two-dimensional description. This leads to a general framework that describes three-dimensional flows in confined microstreaming systems, guiding the design of applications that profit from minimizing or maximizing these effects.

  3. Experimental study of streaming flows associated with ultrasonic levitators

    NASA Astrophysics Data System (ADS)

    Trinh, E. H.; Robey, J. L.

    1994-11-01

    Steady-state acoustic streaming flow patterns have been observed during the operation of a variety of resonant single-axis ultrasonic levitators in a gaseous environment and in the 20-37 kHz frequency range. Light sheet illumination and scattering from smoke particles have revealed primary streaming flows which display different characteristics at low and high sound pressure levels. Secondary macroscopic streaming cells around levitated samples are superimposed on the primary streaming flow pattern generated by the standing wave. These recorded flows are quite reproducible, and are qualitatively the same for a variety of levitator physical geometries. An onset of flow instability can also be recorded in nonisothermal systems, such as levitated spot-heated samples when the resonance conditions are not exactly satisfied. A preliminary qualitative interpretation of these experimental results is presented in terms of the superposition of three discrete sets of circulation cells operating on different spatial scales. These relevant length scales are the acoustic wavelength, the levitated sample size, and finally the acoustic boundary layer thickness. This approach fails, however, to explain the streaming flow-field morphology around liquid drops levitated on Earth. Observation of the interaction between the flows cells and the levitated samples also suggests the existence of a steady-state torque induced by the streaming flows.

  4. Evaluation of the successive approximations method for acoustic streaming numerical simulations.

    PubMed

    Catarino, S O; Minas, G; Miranda, J M

    2016-05-01

    This work evaluates the successive approximations method commonly used to predict acoustic streaming by comparing it with a direct method. The successive approximations method solves both the acoustic wave propagation and acoustic streaming by solving the first and second order Navier-Stokes equations, ignoring the first order convective effects. This method was applied to acoustic streaming in a 2D domain and the results were compared with results from the direct simulation of the Navier-Stokes equations. The velocity results showed qualitative agreement between both methods, which indicates that the successive approximations method can describe the formation of flows with recirculation. However, a large quantitative deviation was observed between the two methods. Further analysis showed that the successive approximation method solution is sensitive to the initial flow field. The direct method showed that the instantaneous flow field changes significantly due to reflections and wave interference. It was also found that convective effects contribute significantly to the wave propagation pattern. These effects must be taken into account when solving the acoustic streaming problems, since it affects the global flow. By adequately calculating the initial condition for first order step, the acoustic streaming prediction by the successive approximations method can be improved significantly. PMID:27250122

  5. Acoustic Streaming and Heat and Mass Transfer Enhancement

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Gopinath, A.

    1996-01-01

    A second order effect associated with high intensity sound field, acoustic streaming has been historically investigated to gain a fundamental understanding of its controlling mechanisms and to apply it to practical aspects of heat and mass transfer enhancement. The objectives of this new research project are to utilize a unique experimental technique implementing ultrasonic standing waves in closed cavities to study the details of the generation of the steady-state convective streaming flows and of their interaction with the boundary of ultrasonically levitated near-spherical solid objects. The goals are to further extend the existing theoretical studies of streaming flows and sample interactions to higher streaming Reynolds number values, for larger sample size relative to the wavelength, and for a Prandtl and Nusselt numbers parameter range characteristic of both gaseous and liquid host media. Experimental studies will be conducted in support to the theoretical developments, and the crucial impact of microgravity will be to allow the neglect of natural thermal buoyancy. The direct application to heat and mass transfer in the absence of gravity will be emphasized in order to investigate a space-based experiment, but both existing and novel ground-based scientific and technological relevance will also be pursued.

  6. Droplet Manipulation Using Acoustic Streaming Induced by a Vibrating Membrane.

    PubMed

    Phan, Hoang Van; Alan, Tuncay; Neild, Adrian

    2016-06-01

    We present a simple method for on-demand manipulation of aqueous droplets in oil. With numerical simulations and experiments, we show that a vibrating membrane can produce acoustic streaming. By making use of this vortical flow, we manage to repulse the droplets away from the membrane edges. Then, by simply aligning the membrane at 45° to the flow, the droplets can be forced to follow the membrane's boundaries, thus steering them across streamlines and even between different oil types. We also characterize the repulsion and steering effect with various excitation voltages at different water and oil flow rates. The maximum steering frequency we have achieved is 165 Hz. The system is extremely robust and reliable: the same membrane can be reused after many days and with different oils and/or surfactants at the same operating frequency. PMID:27119623

  7. Numerics of surface acoustic wave (SAW) driven acoustic streaming and radiation force

    NASA Astrophysics Data System (ADS)

    Nama, Nitesh; Barnkob, Rune; Kahler, Christian; Costanzo, Francesco; Jun Huang, Tony

    2015-11-01

    Recently, surface acoustic wave (SAW) based systems have shown great potential for various lab-on-a-chip applications. However, the physical understanding of the precise acoustic fields and associated acoustophoresis is rather limited. In this work, we present a numerical study of the acoustophoretic particle motion inside a SAW-actuated, liquid-filled polydimethylsiloxane (PDMS) microchannel. We utilize a perturbation approach to divide the flow variables into first- and second-order components. The first-order fields result in a time-averaged acoustic radiation force on suspended particles, as well as the time-averaged body force terms that drive the second-order fields. We model the SAW actuation by a displacement function while we utilize impedance boundary conditions to model the PDMS walls. We identify the precise acoustic fields generated inside the microchannel and investigate a range of particle sizes to characterize the transition from streaming-dominated acoustophoresis to radiation-force-dominated acoustophoresis. Lastly, we demonstrate the ability of SAW devices to tune the position of vertical pressure node inside the microchannel by tuning the phase difference between the two incoming surface acoustic waves.

  8. Experimental and analytical investigation of acoustic streaming generated by standing ultrasonic waves in an open boundaries

    NASA Astrophysics Data System (ADS)

    Kwon, K.; Loh, B.-G.; Lee, D.-R.

    2007-12-01

    Acoustic streaming patterns, velocity fields, which is induced by a cylindrical ultrasonic exciter vibrating at 28.4kHz in an open physical boundaries, is analytically and experimentally investigated using Particle Imaging Velocimetry (PIV). Induced acoustic streaming patterns and velocity fields for the gaps of 18mm at which the irrotational tangential velocity becomes a maximum, resulting in a substantial increase in the acoustic streaming velocity and pronounced visualization of streaming patterns between the vibrator and quiescent glass plate are presented. The overall air flow patterns at the gaps of 24, 30, 36mm are similar to the gap of 18 mm but as the gap increases the frequency of occurrence and irregularity of vortices in the gap appear to increase. The symmetric definite steady circular flow with local vortices is observed. The maximum streaming velocity measured stands at 0.16 cm/s with a vibration amplitude of 50 micrometers. Theoretical analysis indicates that the pattern of air flow in the gap is determined by the top and bottom limiting velocities induced by acoustic streaming within the Stokes boundary layer and that the streaming pattern is symmetrical with respect to the center axis of the vibrator by reason of symmetry. The comparison between the experimental data and the theoretical estimation based on Nyborg and Jackson is performed.

  9. Diversity of acoustic streaming in a rectangular acoustofluidic field.

    PubMed

    Tang, Qiang; Hu, Junhui

    2015-04-01

    Diversity of acoustic streaming field in a 2D rectangular chamber with a traveling wave and using water as the acoustic medium is numerically investigated by the finite element method. It is found that the working frequency, the vibration excitation source length, and the distance and phase difference between two separated symmetric vibration excitation sources can cause the diversity in the acoustic streaming pattern. It is also found that a small object in the acoustic field results in an additional eddy, and affects the eddy size in the acoustic streaming field. In addition, the computation results show that with an increase of the acoustic medium's temperature, the speed of the main acoustic streaming decreases first and then increases, and the angular velocity of the corner eddies increases monotonously, which can be clearly explained by the change of the acoustic dissipation factor and shearing viscosity of the acoustic medium with temperature. Commercialized FEM software COMSOL Multiphysics is used to implement the computation tasks, which makes our method very easy to use. And the computation method is partially verified by an established analytical solution. PMID:25541360

  10. Numerical and theoretical analysis of beam vibration induced acoustic streaming and the associated heat transfer

    NASA Astrophysics Data System (ADS)

    Wan, Qun

    The purpose of this research is to numerically and analytically investigate the acoustic streaming and the associated heat transfer, which are induced by a beam vibrating in either standing or traveling waveforms. Analytical results show that the beam vibrating in standing waveforms scatters the acoustic waves into the free space, which have a larger attenuation coefficient and longer propagating traveling wavelength than those of the plane wave. In contrast to a constant Reynolds stress in the plane wave, the Reynolds stress generated by such acoustic wave is expected to drive the free space streaming away from the anti-nodes and towards nodes of the standing wave vibration. The sonic and ultrasonic streamings within the channel between the vibrating beam and a parallel stationary beam are also investigated. The acoustic streaming is utilized to cool the stationary beam, which has either a heat source attached to it or subjected to a uniform heat flux. The sonic streaming is found to be mainly the boundary layer streaming dominating the whole channel while the ultrasonic streaming is clearly composed of two boundary layer streamings near both beams and a core region streaming, which is driven by the streaming velocity at the edge of the boundary layer near the vibrating beam. The standing wave vibration of the beam induces acoustic streaming in a series of counterclockwise eddies, which is directed away from the anti-nodes and towards the nodes. The magnitude of the sonic streaming is proportional to o2A 2 while that of the ultrasonic streaming is proportional to o 3/2A2. Numerical results show that the acoustic streaming induced by the beam vibrating in either standing or traveling waveforms has almost the same cooling efficiency for the heat source and the heat flux cases although the flow and temperature fields within the channel are different. The hysteresis of the ultrasonic streaming flow patterns associated with the change of the aspect ratio of the channel

  11. Backcoupling of acoustic streaming on the temperature field inside high-intensity discharge lamps

    NASA Astrophysics Data System (ADS)

    Schwieger, J.; Baumann, B.; Wolff, M.; Manders, F.; Suijker, J.

    2015-11-01

    Operating high-intensity discharge lamps in the high frequency range (20-300 kHz) provides energy-saving and cost reduction potentials. However, commercially available lamp drivers do not make use of this operating strategy because light intensity fluctuations and even lamp destruction are possible. The reason for the fluctuating discharge arc are acoustic resonances in this frequency range that are excited in the arc tube. The acoustic resonances in turn generate a fluid flow that is caused by the acoustic streaming effect. Here, we present a 3D multiphysics model to determine the influence of acoustic streaming on the temperature field in the vicinity of an acoustic eigenfrequency. In that case a transition from stable to instable behavior occurs. The model is able to predict when light flicker can be expected. The results are in very good accordance with accompanying experiments.

  12. A finite element model for simulating acoustic streaming in cystic breast lesions with experimental validation.

    PubMed

    Nightingale, K R; Trahey, G E

    2000-01-01

    Streaming detection is an ultrasonic technique that can be used to distinguish fluid-filled lesions, or cysts, from solid lesions. With this technique, high intensity ultrasound pulses are used to induce acoustic streaming in cyst fluid, and this motion is detected using Doppler flow estimation methods. Results from a pilot clinical study were recently published in which acoustic streaming was successfully induced and detected in 14 of 15 simple breast cysts and four of 14 sonographically indeterminate breast lesions in vivo. In the study, the detected velocities were found to vary considerably among cysts and for different pulsing regimes. A finite element model of streaming detection is presented. This model is utilized to investigate methods of increasing induced acoustic streaming velocity while minimizing patient exposure to high intensity ultrasound during streaming detection. Parameters studied include intensity, frequency, acoustic beam shape, cyst-diameter, cyst fluid protein concentration, and cyst fluid viscosity. The model, which provides both transient and steady-state solutions, is shown to predict trends in streaming velocity accurately. Experimental results from studies investigating the potential for nonlinear streaming enhancement in cysts are also provided. PMID:18238532

  13. 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.

  14. Theoretical study of time-dependent, ultrasound-induced acoustic streaming in microchannels.

    PubMed

    Muller, Peter Barkholt; Bruus, Henrik

    2015-12-01

    Based on first- and second-order perturbation theory, we present a numerical study of the temporal buildup and decay of unsteady acoustic fields and acoustic streaming flows actuated by vibrating walls in the transverse cross-sectional plane of a long straight microchannel under adiabatic conditions and assuming temperature-independent material parameters. The unsteady streaming flow is obtained by averaging the time-dependent velocity field over one oscillation period, and as time increases, it is shown to converge towards the well-known steady time-averaged solution calculated in the frequency domain. Scaling analysis reveals that the acoustic resonance builds up much faster than the acoustic streaming, implying that the radiation force may dominate over the drag force from streaming even for small particles. However, our numerical time-dependent analysis indicates that pulsed actuation does not reduce streaming significantly due to its slow decay. Our analysis also shows that for an acoustic resonance with a quality factor Q, the amplitude of the oscillating second-order velocity component is Q times larger than the usual second-order steady time-averaged velocity component. Consequently, the well-known criterion v(1)≪c(s) for the validity of the perturbation expansion is replaced by the more restrictive criterion v(1)≪c(s)/Q. Our numerical model is available as supplemental material in the form of comsol model files and matlab scripts. PMID:26764815

  15. Theoretical study of time-dependent, ultrasound-induced acoustic streaming in microchannels

    NASA Astrophysics Data System (ADS)

    Muller, Peter Barkholt; Bruus, Henrik

    2015-12-01

    Based on first- and second-order perturbation theory, we present a numerical study of the temporal buildup and decay of unsteady acoustic fields and acoustic streaming flows actuated by vibrating walls in the transverse cross-sectional plane of a long straight microchannel under adiabatic conditions and assuming temperature-independent material parameters. The unsteady streaming flow is obtained by averaging the time-dependent velocity field over one oscillation period, and as time increases, it is shown to converge towards the well-known steady time-averaged solution calculated in the frequency domain. Scaling analysis reveals that the acoustic resonance builds up much faster than the acoustic streaming, implying that the radiation force may dominate over the drag force from streaming even for small particles. However, our numerical time-dependent analysis indicates that pulsed actuation does not reduce streaming significantly due to its slow decay. Our analysis also shows that for an acoustic resonance with a quality factor Q , the amplitude of the oscillating second-order velocity component is Q times larger than the usual second-order steady time-averaged velocity component. Consequently, the well-known criterion v1≪cs for the validity of the perturbation expansion is replaced by the more restrictive criterion v1≪cs/Q . Our numerical model is available as supplemental material in the form of comsol model files and matlab scripts.

  16. An acoustic streaming instability in thermoacoustic devices utilizing jet pumps.

    PubMed

    Backhaus, S; Swift, G W

    2003-03-01

    Thermoacoustic-Stirling hybrid engines and feedback pulse tube refrigerators can utilize jet pumps to suppress streaming that would otherwise cause large heat leaks and reduced efficiency. It is desirable to use jet pumps to suppress streaming because they do not introduce moving parts such as bellows or membranes. In most cases, this form of streaming suppression works reliably. However, in some cases, the streaming suppression has been found to be unstable. Using a simple model of the acoustics in the regenerators and jet pumps of these devices, a stability criterion is derived that predicts when jet pumps can reliably suppress streaming. PMID:12656366

  17. Theoretical and experimental investigation of acoustic streaming in a porous material

    NASA Astrophysics Data System (ADS)

    Poesio, Pietro; Ooms, Gijs; Schraven, Arthur; van der Bas, Fred

    2002-07-01

    An experimental and theoretical investigation of the influence of high-frequency acoustic waves on the flow of a liquid through a porous material has been made. Particular attention was paid to the phenomenon of acoustic streaming of the liquid in the porous material due to the damping of the acoustic waves. The experiments were 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. A high external pressure was applied in order to avoid cavitation. A microphone was used to measure the damping of the waves in the porous material and also temperature and pressure measurements in the flowing liquid inside the cores were carried out. To model the acoustic streaming effect Darcy's law was extended with a source term representing the momentum transfer from the acoustic waves to the liquid. The model predictions for the pressure distribution inside the core under acoustic streaming conditions are in reasonable agreement with the experimental data.

  18. Theoretical and experimental investigation of acoustic streaming in a porous material.

    PubMed

    Poesio, Pietro; Ooms, Gijs; Schraven, Arthur; van der Bas, Fred

    2002-07-01

    An experimental and theoretical investigation of the influence of high-frequency acoustic waves on the flow of a liquid through a porous material has been made. Particular attention was paid to the phenomenon of acoustic streaming of the liquid in the porous material due to the damping of the acoustic waves. The experiments were 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. A high external pressure was applied in order to avoid cavitation. A microphone was used to measure the damping of the waves in the porous material and also temperature and pressure measurements in the flowing liquid inside the cores were carried out. To model the acoustic streaming effect Darcy's law was extended with a source term representing the momentum transfer from the acoustic waves to the liquid. The model predictions for the pressure distribution inside the core under acoustic streaming conditions are in reasonable agreement with the experimental data. PMID:12241483

  19. Direct calculation of acoustic streaming including the boundary layer phenomena in an ultrasonic air pump

    NASA Astrophysics Data System (ADS)

    Wada, Yuji; Koyama, Daisuke; Nakamura, Kentaro

    2012-05-01

    Direct finite difference fluid simulation of acoustic streaming on the fine-meshed three-dimensiona model by graphics processing unit (GPU)-oriented calculation array is discussed. Airflows due to the acoustic traveling wave are induced when an intense sound field is generated in a gap between a bending transducer and a reflector. Calculation results showed good agreement with the measurements in the pressure distribution. In addition to that, several flow-vortices were observed near the boundary of the reflector and the transducer, which have been often discussed in acoustic tube near the boundary, and have never been observed in the calculation in the ultrasonic air pump of this type.

  20. Two-dimensional streaming flows in high-intensity discharge lamps

    NASA Astrophysics Data System (ADS)

    Dreeben, Thomas D.; Chini, Gregory P.

    2011-05-01

    High-intensity discharge (HID) lamps embody a practical application in which acoustically generated streaming flows are used to significantly improve energy efficiency. Streaming in these lamps is examined using finite-element simulations in conjunction with available experimental results on the basis of the assumption that the streaming motion is excited by two-dimensional acoustic standing waves. Neither the magnitude nor the direction of the time-averaged flows is adequately explained by existing theory. Consequently, a modified streaming analysis is proposed in which the fluctuating flow is driven by an oscillating pressure field rather by a moving boundary and convective terms in both the instantaneous and streaming flows are included. Density variations are also shown to be important to the generation of the observed and simulated streaming. This analysis highlights the differences between streaming flows in HID lamps and those described in canonical problems appearing elsewhere in the literature.

  1. Simulation of nonlinear Westervelt equation for the investigation of acoustic streaming and nonlinear propagation effects.

    PubMed

    Solovchuk, Maxim; Sheu, Tony W H; Thiriet, Marc

    2013-11-01

    This study investigates the influence of blood flow on temperature distribution during high-intensity focused ultrasound (HIFU) ablation of liver tumors. A three-dimensional acoustic-thermal-hydrodynamic coupling model is developed to compute the temperature field in the hepatic cancerous region. The model is based on the nonlinear Westervelt equation, bioheat equations for the perfused tissue and blood flow domains. The nonlinear Navier-Stokes equations are employed to describe the flow in large blood vessels. The effect of acoustic streaming is also taken into account in the present HIFU simulation study. A simulation of the Westervelt equation requires a prohibitively large amount of computer resources. Therefore a sixth-order accurate acoustic scheme in three-point stencil was developed for effectively solving the nonlinear wave equation. Results show that focused ultrasound beam with the peak intensity 2470 W/cm(2) can induce acoustic streaming velocities up to 75 cm/s in the vessel with a diameter of 3 mm. The predicted temperature difference for the cases considered with and without acoustic streaming effect is 13.5 °C or 81% on the blood vessel wall for the vein. Tumor necrosis was studied in a region close to major vessels. The theoretical feasibility to safely necrotize the tumors close to major hepatic arteries and veins was shown. PMID:24180802

  2. Fast acoustic streaming in standing waves: generation of an additional outer streaming cell.

    PubMed

    Reyt, Ida; Daru, Virginie; Bailliet, Hélène; Moreau, Solène; Valière, Jean-Christophe; Baltean-Carlès, Diana; Weisman, Catherine

    2013-09-01

    Rayleigh streaming in a cylindrical acoustic standing waveguide is studied both experimentally and numerically for nonlinear Reynolds numbers from 1 to 30 [Re(NL)=(U0/c0)(2)(R/δν)(2), with U0 the acoustic velocity amplitude at the velocity antinode, c0 the speed of sound, R the tube radius, and δν the acoustic boundary layer thickness]. Streaming velocity is measured by means of laser Doppler velocimetry in a cylindrical resonator filled with air at atmospheric pressure at high intensity sound levels. The compressible Navier-Stokes equations are solved numerically with high resolution finite difference schemes. The resonator is excited by shaking it along the axis at imposed frequency. Results of measurements and of numerical calculation are compared with results given in the literature and with each other. As expected, the axial streaming velocity measured and calculated agrees reasonably well with the slow streaming theory for small ReNL but deviates significantly from such predictions for fast streaming (ReNL>1). Both experimental and numerical results show that when ReNL is increased, the center of the outer streaming cells are pushed toward the acoustic velocity nodes until counter-rotating additional vortices are generated near the acoustic velocity antinodes. PMID:23967913

  3. Experimental investigation of acoustic streaming in a cylindrical wave guide up to high streaming Reynolds numbers.

    PubMed

    Reyt, Ida; Bailliet, Hélène; Valière, Jean-Christophe

    2014-01-01

    Measurements of streaming velocity are performed by means of Laser Doppler Velocimetry and Particle Image Velociimetry in an experimental apparatus consisting of a cylindrical waveguide having one loudspeaker at each end for high intensity sound levels. The case of high nonlinear Reynolds number ReNL is particularly investigated. The variation of axial streaming velocity with respect to the axial and to the transverse coordinates are compared to available Rayleigh streaming theory. As expected, the measured streaming velocity agrees well with the Rayleigh streaming theory for small ReNL but deviates significantly from such predictions for high ReNL. When the nonlinear Reynolds number is increased, the outer centerline axial streaming velocity gets distorted towards the acoustic velocity nodes until counter-rotating additional vortices are generated near the acoustic velocity antinodes. This kind of behavior is followed by outer streaming cells only and measurements in the near wall region show that inner streaming vortices are less affected by this substantial evolution of fast streaming pattern. Measurements of the transient evolution of streaming velocity provide an additional insight into the evolution of fast streaming. PMID:24437742

  4. Acoustic streaming, fluid mixing, and particle transport by a Gaussian ultrasound beam in a cylindrical container

    SciTech Connect

    Marshall, Jeffrey S.; Wu, Junru

    2015-10-15

    A computational study is reported of the acoustic streaming flow field generated by a Gaussian ultrasound beam propagating normally toward the end wall of a cylindrical container. Particular focus is given to examining the effectiveness of the acoustic streaming flow for fluid mixing within the container, for deposition of particles in suspension onto the bottom surface, and for particle suspension from the bottom surface back into the flow field. The flow field is assumed to be axisymmetric with the ultrasound transducer oriented parallel to the cylinder axis and normal to the bottom surface of the container, which we refer to as the impingement surface. Reflection of the sound from the impingement surface and sound absorption within the material at the container bottom are both accounted for in the computation. The computation also accounts for thermal buoyancy force due to ultrasonic heating of the impingement surface, but over the time period considered in the current simulations, the flow is found to be dominated by the acoustic streaming force, with only moderate effect of buoyancy force.

  5. Acoustic streaming, fluid mixing, and particle transport by a Gaussian ultrasound beam in a cylindrical container

    NASA Astrophysics Data System (ADS)

    Marshall, Jeffrey S.; Wu, Junru

    2015-10-01

    A computational study is reported of the acoustic streaming flow field generated by a Gaussian ultrasound beam propagating normally toward the end wall of a cylindrical container. Particular focus is given to examining the effectiveness of the acoustic streaming flow for fluid mixing within the container, for deposition of particles in suspension onto the bottom surface, and for particle suspension from the bottom surface back into the flow field. The flow field is assumed to be axisymmetric with the ultrasound transducer oriented parallel to the cylinder axis and normal to the bottom surface of the container, which we refer to as the impingement surface. Reflection of the sound from the impingement surface and sound absorption within the material at the container bottom are both accounted for in the computation. The computation also accounts for thermal buoyancy force due to ultrasonic heating of the impingement surface, but over the time period considered in the current simulations, the flow is found to be dominated by the acoustic streaming force, with only moderate effect of buoyancy force.

  6. Low-flow characteristics of Alabama streams

    USGS Publications Warehouse

    Bingham, Roy H.

    1982-01-01

    A new procedure for estimating the 7-day, 2-year and the 7-day, 10-year low flow of ungaged Alabama streams is based on geology, drainage area, and mean annual precipitation. One equation for each of the two low-flow frequencies applies statewide to all natural flow streams; the equations do not apply to streams where flow is significantly altered by activities of man. The standard error of estimate of each equation based on map values is 40 percent for 7-day, 2-year low flow and 44 percent for 7-day, 10-year low flow. The rate of streamflow recession is used to account for the effects of geology on low flow. Streamflow recession rate depends primarily on transmissivity and storage characteristics of the aquifers, and average distance from stream channels to divides. Relations of low-flow discharge to geology, drainage area, and mean annual precipitation were analyzed by multiple regression techniques.

  7. Acoustically Generated Flow and Temperature Fields in a Rectangular Cavity

    NASA Astrophysics Data System (ADS)

    Farouk, Bakhtier; Oran, Elaine

    1998-11-01

    Flows induced by a vibrating transducer in a gas-filled two-dimensional cavity are investigated by solving the two-dimensional compressible Navier-Stokes equations. The transducer (driver) is located along the left vertical wall of the cavity whereas the right rigid wall acts as an acoustic reflector. Both the left and right vertical walls of the cavity are considered to be conducting (isothermal) walls. The top and the bottom walls are insulated. The frequency of the driver was varied between 10 and 500 kHz. The length of the cavity was adjusted such that standing waves are formed within the cavity, which in turn create well defined vortical flows (acoustic streaming. The characteristics of the two-dimensional acoustically generated flows are studied systematically by varying the frequency and amplitude of the motion of the transducer and the aspect ratio of the cavity. The result exhibit organized flow structures within the cavity and the existence of lateral temperature gradients. Such acoustically induced temperature gradients are essential in the operation of thermoacoustic engines and refrigerators. The effect of cooling or heating the reflector wall on the acoustically generated flows are also investigated. Long time solutions of the governing equations exhibit the existence of pseudo-steady oscillatory flow conditions.

  8. Gulf stream velocity structure through combined inversion of hydrographic and acoustic Doppler data

    NASA Technical Reports Server (NTRS)

    Pierce, S. D.

    1986-01-01

    Near-surface velocities from an acoustic Doppler instrument are used in conjunction with CTD/O2 data to produce estimates of the absolute flow field off Cape Hatteras. The data set consists of two transects across the Gulf Stream made by the R/V Endeavor cruise EN88 in August 1982. An inverse procedure is applied which makes use of both the acoustic Doppler data and property conservation constraints. Velocity sections at approximately 73 deg. W and 71 deg. W are presented with formal errors of 1-2 cm/s. The net Gulf Stream transports are estimated to be 116 + or - 2 Sv across the south leg and 161 + or - 4 Sv across the north. A Deep Western Boundary Current transport of 4 + or - 1 Sv is also estimated. While these values do not necessarily represent the mean, they are accurate estimates of the synoptic flow field in the region.

  9. Effect of facility variation on the acoustic characteristics of three single stream nozzles

    NASA Technical Reports Server (NTRS)

    Gutierrez, O. A.

    1980-01-01

    The characteristics of the jet noise produced by three single stream nozzles have been investigated statically at the NASA-Lewis Research Center outdoor jet acoustic facility. The nozzles consisted of a 7.6 cm diameter convergent conical, a 10.2 cm diameter convergent conical and an 8-lobe daisy nozzle with 7.6 cm equivalent diameter flow area. The acoustic experiments at NASA covered pressure ratios from 1.4 to 2.5 at total temperatures of 811 K and ambient. The data obtained with four different microphone arrays are compared.

  10. Effect of facility variation on the acoustic characteristics of three single stream nozzles

    NASA Technical Reports Server (NTRS)

    Gutierrez, O. A.

    1980-01-01

    The characteristics of the jet noise produced by three single stream nozzles were investigated statistically at the NASA-Lewis Research Center outdoor jet acoustic facility. The nozzles consisted of a 7.6 cm diameter convergent conical, a 10.2 cm diameter convergent conical and an 8-lobe daisy nozzle with 7.6 cm equivalent diameter flow area. The same nozzles were tested previously at cold flow conditions in other facilities such as the Royal Aircraft Establishment (RAE) 7.3 m acoustic wind tunnel. The acoustic experiments at NASA covered pressure ratios from 1.4 to 2.5 at total temperatures of 811 K and ambient. The data obtained with four different microphone arrays are compared. The results are also compared with data taken at the RAE facility and with a NASA prediction procedure.

  11. Characterization of HIFU transducers designed for sonochemistry application: Acoustic streaming.

    PubMed

    Hallez, L; Touyeras, F; Hihn, J-Y; Bailly, Y

    2016-03-01

    Cavitation distribution in a High Intensity Focused Ultrasound sonoreactors (HIFU) has been extensively described in the recent literature, including quantification by an optical method (Sonochemiluminescence SCL). The present paper provides complementary measurements through the study of acoustic streaming generated by the same kind of HIFU transducers. To this end, results of mass transfer measurements (electrodiffusional method) were compared to optical method ones (Particle Image Velocimetry). This last one was used in various configurations: with or without an electrode in the acoustic field in order to have the same perturbation of the wave propagation. Results show that the maximum velocity is not located at the focal but shifted near the transducer, and that this shift is greater for high powers. The two cavitation modes (stationary and moving bubbles) are greatly affect the hydrodynamic behavior of our sonoreactors: acoustic streaming and the fluid generated by bubble motion. The results obtained by electrochemical measurements show the same low hydrodynamic activity in the transducer vicinity, the same shift of the active focal toward the transducer, and the same absence of activity in the post-focal axial zone. The comparison with theoretical Eckart's velocities (acoustic streaming in non-cavitating media) confirms a very high activity at the "sonochemical focal", accounted for by wave distortion, which induced greater absorption coefficients. Moreover, the equivalent liquid velocities are one order of magnitude larger than the ones measured by PIV, confirming the enhancement of mass transfer by bubbles oscillation and collapse close to the surface, rather than from a pure streaming effect. PMID:26585023

  12. Free jet feasibility study of a thermal acoustic shield concept for AST/VCE application: Single stream nozzles

    NASA Technical Reports Server (NTRS)

    Majjigi, R. K.; Brausch, J. F.; Janardan, B. A.; Balsa, T. F.; Knott, P. R.; Pickup, N.

    1984-01-01

    A technology base for the thermal acoustic shield concept as a noise suppression device for single stream exhaust nozzles was developed. Acoustic data for 314 test points for 9 scale model nozzle configurations were obtained. Five of these configurations employed an unsuppressed annular plug core jet and the remaining four nozzles employed a 32 chute suppressor core nozzle. Influence of simulated flight and selected geometric and aerodynamic flow variables on the acoustic behavior of the thermal acoustic shield was determined. Laser velocimeter and aerodynamic measurements were employed to yield valuable diagnostic information regarding the flow field characteristics of these nozzles. An existing theoretical aeroacoustic prediction method was modified to predict the acoustic characteristics of partial thermal acoustic shields.

  13. Synoptic Gulf Stream velocity profiles through simultaneous inversion of hydrographic and acoustic Doppler data

    NASA Technical Reports Server (NTRS)

    Joyce, T. M.; Wunsch, C.; Pierce, S. D.

    1986-01-01

    Data from a shipborne acoustic profiling device have been combined with conductivity, temperature, depth/O2 sections across the Gulf Stream to form estimates of the absolute flow fields. The procedure for the combination was a form of inverse method. The results suggest that at the time of the observations (June 1982) the net Gulf Stream transport off Hatteras was 107 + or - 11 Sv and that across a section near 72.5 W it had increased to 125 + or - 6 Sv. The transport of the deep western boundary current was 9 + or - 3 Sv. For comparison purposes an inversion was done using the hydrographic/O2 data alone as in previously published results and obtained qualitative agreement with the combined inversion. Inversion of the acoustic measurements alone, when corrected for instrument biases, leaves unacceptably large mass transport residuals in the deep water.

  14. Influence of surface acoustic waves induced acoustic streaming on the kinetics of electrochemical reactions

    NASA Astrophysics Data System (ADS)

    Tietze, Sabrina; Schlemmer, Josefine; Lindner, Gerhard

    2013-12-01

    The kinetics of electrochemical reactions is controlled by diffusion processes of charge carriers across a boundary layer between the electrode and the electrolyte, which result in a shielding of the electric field inside the electrolyte and a concentration gradient across this boundary layer. In accumulators the diffusion rate determines the rather long time needed for charging, which is a major drawback for electric mobility. This diffusion boundary can be removed by acoustic streaming in the electrolyte induced by surface acoustic waves propagating of the electrode, which results in an increase of the charging current and thus in a reduction of the time needed for charging. For a quantitative study of the influence of acoustic streaming on the charge transport an electropolishing cell with vertically oriented copper electrodes and diluted H3PO4-Propanol electrolytes were used. Lamb waves with various excitation frequencies were exited on the anode with different piezoelectric transducers, which induced acoustic streaming in the overlaying electrolytic liquid. An increase of the polishing current of up to approximately 100 % has been obtained with such a set-up.

  15. Peak-flow characteristics of Virginia streams

    USGS Publications Warehouse

    Austin, Samuel H.; Krstolic, Jennifer L.; Wiegand, Ute

    2011-01-01

    Peak-flow annual exceedance probabilities, also called probability-percent chance flow estimates, and regional regression equations are provided describing the peak-flow characteristics of Virginia streams. Statistical methods are used to evaluate peak-flow data. Analysis of Virginia peak-flow data collected from 1895 through 2007 is summarized. Methods are provided for estimating unregulated peak flow of gaged and ungaged streams. Station peak-flow characteristics identified by fitting the logarithms of annual peak flows to a Log Pearson Type III frequency distribution yield annual exceedance probabilities of 0.5, 0.4292, 0.2, 0.1, 0.04, 0.02, 0.01, 0.005, and 0.002 for 476 streamgaging stations. Stream basin characteristics computed using spatial data and a geographic information system are used as explanatory variables in regional regression model equations for six physiographic regions to estimate regional annual exceedance probabilities at gaged and ungaged sites. Weighted peak-flow values that combine annual exceedance probabilities computed from gaging station data and from regional regression equations provide improved peak-flow estimates. Text, figures, and lists are provided summarizing selected peak-flow sites, delineated physiographic regions, peak-flow estimates, basin characteristics, regional regression model equations, error estimates, definitions, data sources, and candidate regression model equations. This study supersedes previous studies of peak flows in Virginia.

  16. Nonlinear acoustic streaming in straight and tapered tubes

    NASA Astrophysics Data System (ADS)

    Tuttle, Brian C.

    In thermoacoustic and Stirling devices such as the pulse-tube refrigerator, efficiency is diminished by the formation of a second-order mean velocity known as Rayleigh streaming. This flow emerges from the interaction of the working gas with the wall of the tube in a thin boundary layer. Recent studies have suggested that streaming velocity can be decreased in a tube by tapering it slightly. This research investigates that claim through the development of a numerical model of Rayleigh streaming in variously tapered tubes. It is found that the numerical simulation of streaming in a straight tube compares well with theory, and the application of different thermal boundary conditions at the tube wall shows that for pressurized helium, inner streaming vortices which appear near an adiabatic tube wall do not develop near an isothermal wall. An order analysis indicates that the temperature dependence of viscosity and thermal conductivity contributes appreciably to an accurate numerical model of streaming. Comparison of Rayleigh streaming in tapered tubes shows the effects of taper angle on the circulation and velocity of the mean flow.

  17. Streaming Velocities and the Baryon Acoustic Oscillation Scale

    NASA Astrophysics Data System (ADS)

    Blazek, Jonathan A.; McEwen, Joseph E.; Hirata, Christopher M.

    2016-03-01

    At the epoch of decoupling, cosmic baryons had supersonic velocities relative to the dark matter that were coherent on large scales. These velocities subsequently slow the growth of small-scale structure and, via feedback processes, can influence the formation of larger galaxies. We examine the effect of streaming velocities on the galaxy correlation function, including all leading-order contributions for the first time. We find that the impact on the baryon acoustic oscillation (BAO) peak is dramatically enhanced (by a factor of ˜5 ) over the results of previous investigations, with the primary new effect due to advection: if a galaxy retains memory of the primordial streaming velocity, it does so at its Lagrangian, rather than Eulerian, position. Since correlations in the streaming velocity change rapidly at the BAO scale, this advection term can cause a significant shift in the observed BAO position. If streaming velocities impact tracer density at the 1% level, compared to the linear bias, the recovered BAO scale is shifted by approximately 0.5%. This new effect, which is required to preserve Galilean invariance, greatly increases the importance of including streaming velocities in the analysis of upcoming BAO measurements and opens a new window to the astrophysics of galaxy formation.

  18. Streaming Velocities and the Baryon Acoustic Oscillation Scale.

    PubMed

    Blazek, Jonathan A; McEwen, Joseph E; Hirata, Christopher M

    2016-03-25

    At the epoch of decoupling, cosmic baryons had supersonic velocities relative to the dark matter that were coherent on large scales. These velocities subsequently slow the growth of small-scale structure and, via feedback processes, can influence the formation of larger galaxies. We examine the effect of streaming velocities on the galaxy correlation function, including all leading-order contributions for the first time. We find that the impact on the baryon acoustic oscillation (BAO) peak is dramatically enhanced (by a factor of ∼5) over the results of previous investigations, with the primary new effect due to advection: if a galaxy retains memory of the primordial streaming velocity, it does so at its Lagrangian, rather than Eulerian, position. Since correlations in the streaming velocity change rapidly at the BAO scale, this advection term can cause a significant shift in the observed BAO position. If streaming velocities impact tracer density at the 1% level, compared to the linear bias, the recovered BAO scale is shifted by approximately 0.5%. This new effect, which is required to preserve Galilean invariance, greatly increases the importance of including streaming velocities in the analysis of upcoming BAO measurements and opens a new window to the astrophysics of galaxy formation. PMID:27058069

  19. Characterization of Three-Stream Jet Flow Fields

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda S.; Wernet, Mark P.

    2016-01-01

    Flow-field measurements were conducted on single-, dual- and three-stream jets using two-component and stereo Particle Image Velocimetry (PIV). The flow-field measurements complimented previous acoustic measurements. The exhaust system consisted of externally-plugged, externally-mixed, convergent nozzles. The study used bypass-to-core area ratios equal to 1.0 and 2.5 and tertiary-to-core area ratios equal to 0.6 and 1.0. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated high-subsonic conditions. Centerline velocity decay rates for the single-, dual- and three-stream axisymmetric jets compared well when axial distance was normalized by an equivalent diameter based on the nozzle system total exit area. The tertiary stream had a greater impact on the mean axial velocity for the small bypass-to-core area ratio nozzles than for large bypass-to-core area ratio nozzles. Normalized turbulence intensities were similar for the single-, dual-, and three-stream unheated jets due to the small difference (10 percent) in the core and bypass velocities for the dual-stream jets and the low tertiary velocity (50 percent of the core stream) for the three-stream jets. For heated jet conditions where the bypass velocity was 65 percent of the core velocity, additional regions of high turbulence intensity occurred near the plug tip which were not present for the unheated jets. Offsetting the tertiary stream moved the peak turbulence intensity levels upstream relative to those for all axisymmetric jets investigated.

  20. Characterization of Three-Stream Jet Flow Fields

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda S.; Wernet, Mark P.

    2016-01-01

    Flow-field measurements were conducted on single-, dual- and three-stream jets using two-component and stereo Particle Image Velocimetry (PIV). The flow-field measurements complimented previous acoustic measurements. The exhaust system consisted of externally-plugged, externally-mixed, convergent nozzles. The study used bypass-to-core area ratios equal to 1.0 and 2.5 and tertiary-to-core area ratios equal to 0.6 and 1.0. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated high-subsonic conditions. Centerline velocity decay rates for the single-, dual- and three-stream axisymmetric jets compared well when axial distance was normalized by an equivalent diameter based on the nozzle system total exit area. The tertiary stream had a greater impact on the mean axial velocity for the small bypass-to-core area ratio nozzles than for large bypass-to-core area ratio nozzles. Normalized turbulence intensities were similar for the single-, dual-, and three-stream unheated jets due to the small difference (10%) in the core and bypass velocities for the dual-stream jets and the low tertiary velocity (50% of the core stream) for the three-stream jets. For heated jet conditions where the bypass velocity was 65% of the core velocity, additional regions of high turbulence intensity occurred near the plug tip which were not present for the unheated jets. Offsetting the tertiary stream moved the peak turbulence intensity levels upstream relative to those for all axisymmetric jets investigated.

  1. Viscous flow drag reduction by acoustic excitation

    NASA Astrophysics Data System (ADS)

    Nagel, Robert T.

    1986-12-01

    An experimental program in which the effectiveness of a single large eddy break up (LEBU) blade is enhanced by proper acoustic excitation is described. Acoustic waves are generated in response to the incident large scale eddies and directed at the blade trailing edge through the test surface floor below the manipulator blade. The acoustic input is phase locked to the incident flow. Control of the acoustic input apparently allows enhancement of the large eddy cancellation process leading to a decrease of skin friction coefficient. Control of this process with acoustic excitation indicates that vortex unwinding is the mechanism for large eddy destruction in the boundary layer. A deeper understanding of this phenomena could lead to better drag reduction technology and further understanding of the physics of the turbulent boundary layer.

  2. New Sensors For Flow Velocity And Acoustics

    NASA Technical Reports Server (NTRS)

    Cho, Y. C.

    1991-01-01

    Paper describes two sensor-development programs at Fluid Mechanics Laboratory at NASA Ames Research Center. One program for digital image velocimetry (DIV) sensors, and other program, for advanced acoustic sensors for wind tunnels. DIV measures, in real time, instantaneous velocity fields of time-varying flow or of collection of objects moving with varying velocities. Advanced acoustic sensors for wind tunnels being developed to reduce effects of interference from wind noise, noise from interactions between flows and sensors, flow-induced vibrations of sensors, deflections of accoustic waves by boundary layers induced by sensors, and reflections from walls and sensor supports.

  3. Scour and deposition patterns in complex flow around stream restoration structures in a meandering stream channel

    NASA Astrophysics Data System (ADS)

    Kozarek, J. L.; Plott, J. R.; Diplas, P.; Sotiropoulos, F.; Lightbody, A.

    2010-12-01

    Instream structures are often employed in stream restoration projects to minimize erosion on the outside of a meander bend where shear stresses are highest, but guidelines for installation are often based on subjective criteria or professional experience. As part of a multiphase study to develop comprehensive quantitative design guidelines for instream structures, a series of experiments were conducted in the sand-bed meandering stream channel in the Outdoor StreamLab (OSL) at the St. Anthony Falls Laboratory (SAFL). Following an experiment with a single rock vane, three arrays of three evenly spaced structures (rock vanes, J-hooks, and bendway weirs) were installed in a single meander bend. To improve fundamental understanding of the interaction of the complex flow field around these structures with the sediment bed in a field-scale meandering stream, high resolution channel topography data were obtained for the entire meander bend at bankfull flow conditions (280 LPS) with and without structure arrays. Three-dimensional flow velocity and turbulence was measured using acoustic Doppler velocimetry for each scenario in nine cross sections located before, after, between, and over the structure installation locations. Velocity point spacing was decreased close to boundaries (bed, bank, or structure). The velocity data confirmed that the velocity core moved away from the outside of the meander bend in the presence of structures; however, increased local shear stresses around the structures increased scour which threatened structure stability. For each structure array, individual structures introduced different velocity patterns including visible recirculation zones and turbulent structures depending on the structure type and where in the meander bend the structure was placed. The results from these experiments will inform stream restoration structure design in a meandering stream.

  4. Apparatus for focusing flowing gas streams

    DOEpatents

    Nogar, N.S.; Keller, R.A.

    1985-05-20

    Apparatus for focusing gas streams. The principle of hydrodynamic focusing is applied to flowing gas streams in order to provide sample concentration for improved photon and sample utilization in resonance ionization mass spectrometric analysis. In a concentric nozzle system, gas samples introduced from the inner nozzle into the converging section of the outer nozzle are focused to streams 50-250-..mu..m in diameter. In some cases diameters of approximately 100-..mu..m are maintained over distances of several centimeters downstream from the exit orifice of the outer nozzle. The sheath gas employed has been observed to further provide a protective covering around the flowing gas sample, thereby isolating the flowing gas sample from possible unwanted reactions with nearby surfaces. A single nozzle variation of the apparatus for achieving hydrodynamic focusing of gas samples is also described.

  5. Highly Localized Acoustic Streaming and Size-Selective Submicrometer Particle Concentration Using High Frequency Microscale Focused Acoustic Fields.

    PubMed

    Collins, David J; Ma, Zhichao; Ai, Ye

    2016-05-17

    Concentration and separation of particles and biological specimens are fundamental functions of micro/nanofluidic systems. Acoustic streaming is an effective and biocompatible way to create rapid microscale fluid motion and induce particle capture, though the >100 MHz frequencies required to directly generate acoustic body forces on the microscale have traditionally been difficult to generate and localize in a way that is amenable to efficient generation of streaming. Moreover, acoustic, hydrodynamic, and electrical forces as typically applied have difficulty manipulating specimens in the submicrometer regime. In this work, we introduce highly focused traveling surface acoustic waves (SAW) at high frequencies between 193 and 636 MHz for efficient and highly localized production of acoustic streaming vortices on microfluidic length scales. Concentration occurs via a novel mechanism, whereby the combined acoustic radiation and streaming field results in size-selective aggregation in fluid streamlines in the vicinity of a high-amplitude acoustic beam, as opposed to previous acoustic radiation induced particle concentration where objects typically migrate toward minimum pressure locations. Though the acoustic streaming is induced by a traveling wave, we are able to manipulate particles an order of magnitude smaller than possible using the traveling wave force alone. We experimentally and theoretically examine the range of particle sizes that can be captured in fluid streamlines using this technique, with rapid particle concentration demonstrated down to 300 nm diameters. We also demonstrate that locations of trapping and concentration are size-dependent, which is attributed to the combined effects of the acoustic streaming and acoustic forces. PMID:27102956

  6. Flow effects on benthic stream invertebrates and ecological processes

    NASA Astrophysics Data System (ADS)

    Koprivsek, Maja; Brilly, Mitja

    2010-05-01

    is not enough to make a shelter for stream invertebrates. It serves as a shelter only for microorganisms, but the stream invertebrates have to avoid the swift flow or adapt to flow with adaptations described above. To understand what conditions are subject to aquatic organisms and how to adapt, it is essential. Both, knowledge of fluid dynamics in natural watercourses and ecology are needed to understand to what conditions the stream invertebrates are exposed and how they cope with them. Some investigations of near bed flow will be performed on the Glinšica stream. The acoustic Doppler velocimeter SonTek will be adapted to measure so close to the bed as possible. It is expected we should be able to measure the velocities just 0,5 cm above the bed surface. We intend to measure the velocities on a natural and on a regulated reach and then compare the results.

  7. Acoustic grazing flow impedance using waveguide principles

    NASA Technical Reports Server (NTRS)

    Armstrong, D. L.

    1971-01-01

    A grazing flow apparatus was designed to measure the impedance of acoustic materials when installed in environments that subject the material to grazing airflow. The design of the apparatus and the data analysis technique is based on the solution of the convected wave equation in an infinite length waveguide.

  8. Calculations of rotational flows using stream function

    NASA Technical Reports Server (NTRS)

    Hafez, M.; Yam, C.; Tang, K.; Dwyer, H.

    1989-01-01

    The stream function equation is solved for steady two-dimensional (and axisymmetric) rotational flows. Both finite differences and finite volumes discretization techniques are studied, using generalized body fitted coordinates and unstructured staggered grids, respectively. For inviscid transonic flows, a new artificial viscosity scheme which does not produce any artificial vorticity is introduced, for the stability of the mixed flow calculations and for capturing shocks. The solution of Euler equations, in primitive variables, are also considered. The effects of the artificial viscosity and numerical boundary conditions on the total enthalpy and the vorticity distributions are demonstrated.

  9. Flow probability of New Jersey streams

    USGS Publications Warehouse

    Miler, E.G.

    1966-01-01

    This report is one of a series published by the Division of Water Policy and Supply of the New Jersey Department of Conservation and Economic Development to make basic water data available in a form that can be readily used by all interested persons. The objective of the present report is to present flow-duration information based on past records so that estimates of future flows of New Jersey's streams may be made. It is an extension of the flow-duration portions of Water Resources Circular 6 (Miller and McCall, 1961).

  10. Low-flow characteristics of Virginia streams

    USGS Publications Warehouse

    Austin, Samuel H.; Krstolic, Jennifer L.; Wiegand, Ute

    2011-01-01

    Low-flow annual non-exceedance probabilities (ANEP), called probability-percent chance (P-percent chance) flow estimates, regional regression equations, and transfer methods are provided describing the low-flow characteristics of Virginia streams. Statistical methods are used to evaluate streamflow data. Analysis of Virginia streamflow data collected from 1895 through 2007 is summarized. Methods are provided for estimating low-flow characteristics of gaged and ungaged streams. The 1-, 4-, 7-, and 30-day average streamgaging station low-flow characteristics for 290 long-term, continuous-record, streamgaging stations are determined, adjusted for instances of zero flow using a conditional probability adjustment method, and presented for non-exceedance probabilities of 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, 0.02, 0.01, and 0.005. Stream basin characteristics computed using spatial data and a geographic information system are used as explanatory variables in regional regression equations to estimate annual non-exceedance probabilities at gaged and ungaged sites and are summarized for 290 long-term, continuous-record streamgaging stations, 136 short-term, continuous-record streamgaging stations, and 613 partial-record streamgaging stations. Regional regression equations for six physiographic regions use basin characteristics to estimate 1-, 4-, 7-, and 30-day average low-flow annual non-exceedance probabilities at gaged and ungaged sites. Weighted low-flow values that combine computed streamgaging station low-flow characteristics and annual non-exceedance probabilities from regional regression equations provide improved low-flow estimates. Regression equations developed using the Maintenance of Variance with Extension (MOVE.1) method describe the line of organic correlation (LOC) with an appropriate index site for low-flow characteristics at 136 short-term, continuous-record streamgaging stations and 613 partial-record streamgaging stations. Monthly

  11. Estimating stream discharge using stage and multi-level acoustic Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Poulsen, J. B.; Rasmussen, K.; Ledet Jensen, J.; Bering Ovesen, N.

    2011-12-01

    For temperate region countries with small or moderately sized streams, such as those in Denmark, seasonal weed growth imposes a significant temporal change of the stage-discharge relation. In the past such problems were often avoided by using hydraulic structures, however, firm ecology based restrictions prevent that hydraulic structures are made at the discharge stations presently. As a consequence, the nonlinear drift in weed density and structure adds a significant uncertainty to the hydrograph. Furthermore, the expected increase in extreme discharge situations due to climate changes in the Northern part of Europe may further violate a stable relation between stage and discharge in streams. Extreme high flow situations cause abrupt rise in stage, and consequently weed can be partly uprooted and partly bend down along the bed, thereby changing the conveyance of the stream. In addition, extreme high flow situations can cause the streams to flood the banks. If these hydraulic changes occur in between direct measurements of discharge they are not detected or accounted for in the stage-discharge relation, and the hydrograph can be significantly biased. The objective of this research is to investigate how both seasonal and short duration changes in weed distribution and abrupt changes in stage are recognized in the stream's velocity gradient. It is examined whether the use of multi-level acoustic Doppler velocimetry can provide an improved method for hydrograph estimation with lower uncertainty than traditional stage-discharge methods. In this presentation we shall present results from a study where, at two sites in Denmark, the stream velocity field has been mapped by the use of three Acoustic Doppler Velocity Meter (ADVM) instruments. The ADVM instruments are mounted in three different depths, continuously measuring horizontal average water velocities. Velocity and stage data are selected from one summer and two winter periods, and a method for converting velocity

  12. Acoustic streaming in simplified liquid rocket engines with transverse mode oscillations

    NASA Astrophysics Data System (ADS)

    Fischbach, Sean R.; Flandro, Gary A.; Majdalani, Joseph

    2010-06-01

    This study considers a simplified model of a liquid rocket engine in which uniform injection is imposed at the faceplate. The corresponding cylindrical chamber has a small length-to-diameter ratio with respect to solid and hybrid rockets. Given their low chamber aspect ratios, liquid thrust engines are known to experience severe tangential and radial oscillation modes more often than longitudinal ones. In order to model this behavior, tangential and radial waves are superimposed onto a basic mean-flow model that consists of a steady, uniform axial velocity throughout the chamber. Using perturbation tools, both potential and viscous flow equations are then linearized in the pressure wave amplitude and solved to the second order. The effects of the headwall Mach number are leveraged as well. While the potential flow analysis does not predict any acoustic streaming effects, the viscous solution carried out to the second order gives rise to steady secondary flow patterns near the headwall. These axisymmetric, steady contributions to the tangential and radial traveling waves are induced by the convective flow motion through interactions with inertial and viscous forces. We find that suppressing either the convective terms or viscosity at the headwall leads to spurious solutions that are free from streaming. In our problem, streaming is initiated at the headwall, within the boundary layer, and then extends throughout the chamber. We find that nonlinear streaming effects of tangential and radial waves act to alter the outer solution inside a cylinder with headwall injection. As a result of streaming, the radial wave velocities are intensified in one-half of the domain and reduced in the opposite half at any instant of time. Similarly, the tangential waves are either enhanced or weakened in two opposing sectors that are at 90° angle to the radial velocity counterparts. The second-order viscous solution that we obtain clearly displays both an oscillating and a steady flow

  13. Intelligent front-end sample preparation tool using acoustic streaming.

    SciTech Connect

    Cooley, Erika J.; McClain, Jaime L.; Murton, Jaclyn K.; Edwards, Thayne L.; Achyuthan, Komandoor E.; Branch, Darren W.; Clem, Paul Gilbert; Anderson, John Mueller; James, Conrad D.; Smith, Gennifer; Kotulski, Joseph Daniel

    2009-09-01

    We have successfully developed a nucleic acid extraction system based on a microacoustic lysis array coupled to an integrated nucleic acid extraction system all on a single cartridge. The microacoustic lysing array is based on 36{sup o} Y cut lithium niobate, which couples bulk acoustic waves (BAW) into the microchannels. The microchannels were fabricated using Mylar laminates and fused silica to form acoustic-fluidic interface cartridges. The transducer array consists of four active elements directed for cell lysis and one optional BAW element for mixing on the cartridge. The lysis system was modeled using one dimensional (1D) transmission line and two dimensional (2D) FEM models. For input powers required to lyse cells, the flow rate dictated the temperature change across the lysing region. From the computational models, a flow rate of 10 {micro}L/min produced a temperature rise of 23.2 C and only 6.7 C when flowing at 60 {micro}L/min. The measured temperature changes were 5 C less than the model. The computational models also permitted optimization of the acoustic coupling to the microchannel region and revealed the potential impact of thermal effects if not controlled. Using E. coli, we achieved a lysing efficacy of 49.9 {+-} 29.92 % based on a cell viability assay with a 757.2 % increase in ATP release within 20 seconds of acoustic exposure. A bench-top lysing system required 15-20 minutes operating up to 58 Watts to achieve the same level of cell lysis. We demonstrate that active mixing on the cartridge was critical to maximize binding and release of nucleic acid to the magnetic beads. Using a sol-gel silica bead matrix filled microchannel the extraction efficacy was 40%. The cartridge based magnetic bead system had an extraction efficiency of 19.2%. For an electric field based method that used Nafion films, a nucleic acid extraction efficiency of 66.3 % was achieved at 6 volts DC. For the flow rates we tested (10-50 {micro}L/min), the nucleic acid extraction

  14. Heat Transfer and Hydraulic Flow Resistance for Streams of High Velocity

    NASA Technical Reports Server (NTRS)

    Lelchuk, V. L.

    1943-01-01

    Problems of hydraulic flow resistance and heat transfer for streams with velocities comparable with acoustic have present great importance for various fields of technical science. Especially, they have great importance for the field of heat transfer in designing and constructing boilers.of the "Velox" type. In this article a description of experiments and their results as regards definition of the laws of heat transfer in differential form for high velocity air streams inside smooth tubes are given.

  15. SWEPT-POTENTIAL ELECTROCHEMICAL DETECTOR FOR FLOW STREAMS

    EPA Science Inventory

    An instrument has been designed, constructed, and evaluated for electrochemical measurements in flow streams. The instrument is basically a computer-controlled potentiostat with features that are necessary for measurements in flow streams. These features include real-time graphic...

  16. 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.

  17. 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.

  18. Magnetic Polarity Streams and Subsurface Flows

    NASA Astrophysics Data System (ADS)

    Howe, R.; Baker, D.; Harra, L.; van Driel-Gesztelyi, L.; Komm, R.; Hill, F.; González Hernández, I.

    2013-12-01

    An important feature of the solar cycle is the transport of unbalanced magnetic flux from active regions towards the poles, which eventually results in polarity reversal. This transport takes the form of distinct “polarity streams” that are visible in the magnetic butterfly diagram. We compare the poleward migration rate estimated from such streams to that derived from the subsurface meridional flows measured in helioseismic data from the GONG network since 2001, and find that the results are in reasonable agreement.

  19. Improving H-Q rating curves in temprorary streams by using Acoustic Doppler Current meters

    NASA Astrophysics Data System (ADS)

    Marchand, P.; Salles, C.; Rodier, C.; Hernandez, F.; Gayrard, E.; Tournoud, M.-G.

    2012-04-01

    Intermittent rivers pose different challenges to stream rating due to high spatial and temporal gradients. Long dry periods, cut by short duration flush flood events explain the difficulty to obtain reliable discharge data, for low flows as well as for floods: problems occur with standard gauging, zero flow period, etc. Our study aims to test the use of an acoustic Doppler currentmeter (ADC) for improving stream rating curves in small catchments subject to large variations of discharge, solid transport and high eutrophication levels. The study is conducted at the outlet of the river Vène, a small coastal river (67 km2) located close to the city of Montpellier (France). The low flow period lasts for more than 6 month; during this period the river flow is sustained by effluents from urban sewage systems, which allows development of algae and macrophytes in the riverbed. The ADC device (Sontek ®Argonaut SW) is a pulsed Doppler current profiling system designed for measuring water velocity profiles and levels that are used to compute volumetric flow rates. It is designed for shallow waters (less than 4 meter depth). Its main advantages are its low cost and high accuracy (±1% of the measured velocity or ±0.05 m/sec, as reported by the manufacturer). The study will evaluate the improvement in rating curves in an intermittent flow context and the effect of differences in sensitivity between low and high water level, by comparing mean flow velocity obtained by ADC to direct discharges measurements. The study will also report long-term use of ADC device, by considering effects of biofilms, algae and macrophytes, as well as solid transport on the accuracy of the measurements. In conclusion, we show the possibility to improve stream rating and continuous data collection of an intermittent river by using a ADC with some precautions.

  20. 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

  1. Zonal Flow Velocimetry in Spherical Couette Flow using Acoustic Modes

    NASA Astrophysics Data System (ADS)

    Adams, Matthew M.; Mautino, Anthony R.; Stone, Douglas R.; Triana, Santiago A.; Lekic, Vedran; Lathrop, Daniel P.

    2015-11-01

    We present studies of spherical Couette flows using the technique of acoustic mode Doppler velocimetry. This technique uses rotational splittings of acoustic modes to infer the azimuthal velocity profile of a rotating flow, and is of special interest in experiments where direct flow visualization is impractical. The primary experimental system consists of a 60 cm diameter outer spherical shell concentric with a 20 cm diameter sphere, with air or nitrogen gas serving as the working fluid. The geometry of the system approximates that of the Earth's core, making these studies geophysically relevant. A turbulent shear flow is established in the system by rotating the inner sphere and outer shell at different rates. Acoustic modes of the fluid volume are excited using a speaker and measured via microphones, allowingdetermination of rotational splittings. Preliminary results comparing observed splittings with those predicted by theory are presented. While the majority of these studies were performed in the 60 cm diameter device using nitrogen gas, some work has also been done looking at acoustic modes in the 3 m diameter liquid sodium spherical Couette experiment. Prospects for measuring zonal velocity profiles in a wide variety of experiments are discussed.

  2. 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.

  3. 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.

  4. Asymmetric steady streaming as a mechanism for acoustic propulsion of rigid bodies

    NASA Astrophysics Data System (ADS)

    Nadal, François; Lauga, Eric

    2014-08-01

    Recent experiments showed that standing acoustic waves could be exploited to induce self-propulsion of rigid metallic particles in the direction perpendicular to the acoustic wave. We propose in this paper a physical mechanism for these observations based on the interplay between inertial forces in the fluid and the geometrical asymmetry of the particle shape. We consider an axisymmetric rigid near-sphere oscillating in a quiescent fluid along a direction perpendicular to its symmetry axis. The kinematics of oscillations can be either prescribed or can result dynamically from the presence of an external oscillating velocity field. Steady streaming in the fluid, the inertial rectification of the time-periodic oscillating flow, generates steady stresses on the particle which, in general, do not average to zero, resulting in a finite propulsion speed along the axis of the symmetry of the particle and perpendicular to the oscillation direction. Our derivation of the propulsion speed is obtained at leading order in the Reynolds number and the deviation of the shape from that of a sphere. The results of our model are consistent with the experimental measurements, and more generally explains how time periodic forcing from an acoustic field can be harnessed to generate autonomous motion.

  5. Ice and thermal cameras for stream flow observations

    NASA Astrophysics Data System (ADS)

    Tauro, Flavia; Petroselli, Andrea; Grimaldi, Salvatore

    2016-04-01

    Flow measurements are instrumental to establish discharge rating curves and to enable flood risk forecast. Further, they are crucial to study erosion dynamics and to comprehend the organization of drainage networks in natural catchments. Flow observations are typically executed with intrusive instrumentation, such as current meters or acoustic devices. Alternatively, non-intrusive instruments, such as radars and microwave sensors, are applied to estimate surface velocity. Both approaches enable flow measurements over areas of limited extent, and their implementation can be costly. Optical methods, such as large scale particle image velocimetry, have proved beneficial for non-intrusive and spatially-distributed environmental monitoring. In this work, a novel optical-based approach is utilized for surface flow velocity observations based on the combined use of a thermal camera and ice dices. Different from RGB imagery, thermal images are relatively unaffected by illumination conditions and water reflections. Therefore, such high-quality images allow to readily identify and track tracers against the background. Further, the optimal environmental compatibility of ice dices and their relative ease of preparation and storage suggest that the technique can be easily implemented to rapidly characterize surface flows. To demonstrate the validity of the approach, we present a set of experiments performed on the Brenta stream, Italy. In the experimental setup, the axis of the camera is maintained perpendicular with respect to the water surface to circumvent image orthorectification through ground reference points. Small amounts of ice dices are deployed onto the stream water surface during image acquisition. Particle tracers' trajectories are reconstructed off-line by analyzing thermal images with a particle tracking velocimetry (PTV) algorithm. Given the optimal visibility of the tracers and their low seeding density, PTV allows for efficiently following tracers' paths in

  6. Improving acoustic streaming effects in fluidic systems by matching SU-8 and polydimethylsiloxane layers.

    PubMed

    Catarino, S O; Minas, G; Miranda, J M

    2016-07-01

    This paper reports the use of acoustic waves for promoting and improving streaming in tridimensional polymethylmethacrylate (PMMA) cuvettes of 15mm width×14mm height×2.5mm thickness. The acoustic waves are generated by a 28μm thick poly(vinylidene fluoride) - PVDF - piezoelectric transducer in its β phase, actuated at its resonance frequency: 40MHz. The acoustic transmission properties of two materials - SU-8 and polydimethylsiloxane (PDMS) - were numerically compared. It was concluded that PDMS inhibits, while SU-8 allows, the transmission of the acoustic waves to the propagation medium. Therefore, by simulating the acoustic transmission properties of different materials, it is possible to preview the acoustic behavior in the fluidic system, which allows the optimization of the best layout design, saving costs and time. This work also presents a comparison between numerical and experimental results of acoustic streaming obtained with that β-PVDF transducer in the movement and in the formation of fluid recirculation in tridimensional closed domains. Differences between the numerical and experimental results are credited to the high sensitivity of acoustic streaming to the experimental conditions and to limitations of the numerical method. The reported study contributes for the improvement of simulation models that can be extremely useful for predicting the acoustic effects of new materials in fluidic devices, as well as for optimizing the transducers and matching layers positioning in a fluidic structure. PMID:27044029

  7. Capillary-scale polarimetry for flowing streams.

    PubMed

    Swinney, K; Nodorft, J; Bornhop, D J

    2001-05-01

    A micro-polarimeter with a 40 nL probe volume was configured so that it is compatible with capillary-scale flowing stream analysis. The optical configuration consists of two polarizing optics, a capillary, a laser source and a photodetector which is very simple to configure with low cost components. This unique polarimeter is based upon the interaction of a linearly polarized laser beam and a capillary tube, in this case one with an inner diameter of 250 microns. Side illumination of the tube results in a 360 degrees fan of scattered light, which contains a set of interference fringes that change in response to optically active solutes. Solutes that exhibit optical activity are quantifiable and are detected by analyzing the polarization state of the backscattered light. The ability of the instrument to make extremely sensitive optical activity measurements in flowing streams is shown by the determination of (R)-mandelic acid, with a detection limit of 66 x 10(-6) M (507 x 10(-12) g), and the non-optically active control, glycerol. Additionally, the detector was configured to minimize refractive index perturbations. PMID:11394312

  8. 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.

  9. Estimation of acoustical streaming: theoretical model, Doppler measurements and optical visualisation.

    PubMed

    Nowicki, A; Kowalewski, T; Secomski, W; Wójcik, J

    1998-02-01

    An approximate solution for the streaming velocity generated by flat and weakly focused transducers was derived by directly solving the Dirichlet boundary conditions for the Poisson equation, the solution of the Navier-Stokes equation for the axial components of the streaming velocity. The theoretical model was verified experimentally using a 32 MHz pulsed Doppler unit. The experimental acoustical fields were produced by three different 4 mm diameter flat and focused transducers driven by the transmitter generating the average acoustic power within the range from 1 microW to 6 mW. The streaming velocity was measured along the ultrasonic beam from 0 to 2 cm. Streaming was induced in a solution of water and corn starch. The experimental results showed that for a given acoustic power the streaming velocity was independent of the starch density in water, changed from 0.3 to 40 grams of starch in 1 l of distilled water. For applied acoustic powers, the streaming velocity changed linearly from 0.2 to 40 mm/s. Both, the theoretical solutions for plane and focused waves and the experimental results were in good agreement. The streaming velocity field was also visualised using the particle image velocimetry (PIV) and two different evaluation methods. The first based on the FFT-based cross-correlation analysis between small sections for each pair of images and the second employing the algorithm of searching for local displacements between several images. PMID:9614292

  10. Simulation forecasts complex flow streams from Ekofisk

    SciTech Connect

    Arnes, F.C.; Lillejord, H.

    1996-10-28

    A commercial steady-state process flowsheet simulation program serves as the basis for a rigorous calculation model for predicting produced flow rates from the Ekofisk complex in the Norwegian sector of the North Sea. The complex is the center of an extensive gathering system that collects oil and gas streams from several producing fields. Prior to running a production forecast, the simulation model is initiated by matching several years of production. Once the simulation model matches historical production data within acceptable limits, it then is driven by production forecasts from reservoir simulations to develop long-term forecasts of gas, NGL, and oil production. The paper describes the Ekofisk field, the process simulation, implementation of the model, and problems encountered.

  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. 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.

  13. Free jet feasibility study of a thermal acoustic shield concept for AST/VCE application: Dual stream nozzles

    NASA Technical Reports Server (NTRS)

    Janardan, B. A.; Brausch, J. F.; Majjigi, R. K.

    1985-01-01

    The influence of selected geometric and aerodynamic flow variables of an unsuppressed coannular plug nozzle and a coannular plug nozzle with a 20-chute outer stream suppressor were experimentally determined. A total of 136 static and simulated flight acoustic test points were conducted with 9 scale model nozzles. Also, aerodynamic measurements of four selected plumes were made with a laser velocimeter. The presence of the 180 deg shield produced different mixing characteristics on the shield side compared to the unshield side because of the reduced mixing with ambient air on the shielded side. This resulted in a stretching of the jet, yielding a higher peak mean velocity up to a length of 10 equivalent diameters from the nozzle exit. The 180 deg shield in community orientation around the suppressed coannular plug nozzle yielded acoustic benefit at all observer angles for a simulated takeoff. While the effect of shield-to-outer stream velocity ratio was small at angles up to 120 deg, beyond this angle significant acoustic benefit was realized with a shield-to-outer stream velocity ratio of 0.64.

  14. Acoustic streaming in an ultrasonic air pump with three-dimensional finite-difference time-domain analysis and comparison to the measurement.

    PubMed

    Wada, Yuji; Koyama, Daisuke; Nakamura, Kentaro

    2014-12-01

    The direct finite-difference fluid simulation of acoustic streaming on a fine-meshed three-dimensional model using a graphics processing unit (GPU)-based calculation array is discussed. Airflows are induced by an acoustic traveling wave when an intense sound field is generated in a gap between a bending transducer and a reflector. The calculation results showed good agreement with measurements in a pressure distribution. Several flow vortices were observed near the boundary layer of the reflector and the transducer, which have often been observed near the boundary of acoustic tubes, but have not been observed in previous calculations for this type of ultrasonic air pump. PMID:25001051

  15. Experimental investigation of shock-cell noise reduction for dual-stream nozzles in simulated flight comprehensive data report. Volume 1: Test nozzles and acoustic data

    NASA Technical Reports Server (NTRS)

    Yamamoto, K.; Janardan, B. A.; Brausch, J. F.; Hoerst, D. J.; Price, A. O.

    1984-01-01

    Parameters which contribute to supersonic jet shock noise were investigated for the purpose of determining means to reduce such noise generation to acceptable levels. Six dual-stream test nozzles with varying flow passage and plug closure designs were evaluated under simulated flight conditions in an anechoic chamber. All nozzles had combined convergent-divergent or convergent flow passages. Acoustic behavior as a function of nozzle flow passage geometry was measured. The acoustic data consist primarily of 1/3 octave band sound pressure levels and overall sound pressure levels. Detailed schematics and geometric characteristics of the six scale model nozzle configurations and acoustic test point definitions are presented. Tabulation of aerodynamic test conditions and a computer listing of the measured acoustic data are displayed.

  16. Summer base-flow recession curves for Iowa streams

    USGS Publications Warehouse

    Saboe, C.W.

    1966-01-01

    Base-flow recession. curves for the summer months (June through September) were developed in this study for gaging stations on interior Iowa streams having five or more years of record. The tabulated data enables the user, starting with a known base flow at a gage, to estimate base flows for up to 20 days in the future. Rainfall during the period o£ the forecast will require that a new estimate be made after the stream again reaches base flow.

  17. Self-stabilzing ice-stream flow in Northeast Greenland

    NASA Astrophysics Data System (ADS)

    Christianson, Knut; Alley, Richard; Peters, Leo; Anandakrishnan, Sridhar; Jacobel, Robert; Riverman, Kiya; Muto, Atsuhiro

    2013-04-01

    We present radio-echo sounding (RES), global positioning system (GPS), and active-source seismic data from the central portion of the Northeast Greenland Ice Stream (NEGIS) showing that the dynamic effects of the streaming flow control ice-stream extent. NEGIS is the sole fast-flowing ice-stream to initiate deep in the interior (~700 km) of the Greenland Ice Sheet (GIS), and was previously shown to widen downglacier from a small region of high geothermal flux near the ice-divide. Our data reveal water-saturated till lubricating the ice-stream, with the ice-stream likely widening toward the coast from flow around basal roughness and other processes. Ice accelerates and thus thins as it flows into the efficiently lubricated NEGIS, producing marginal troughs in surface topography. These marginal troughs, which lack strong control in the basal topography, create steep gradients in the subglacial hydropotential that generate parallel well-lubricated and 'sticky' bands beneath the ice-stream margins. The 'sticky' bands limit ice entrainment across the margin and thus restrict further widening, producing the long, narrow, and relatively stable ice-stream. However, it remains possible that a sufficiently strong perturbation from the coast could thin the central ice-stream enough to remove the marginal troughs, allowing more efficient flow of ice into the stream and thus drawdown of the ice-sheet.

  18. Effect of acoustic streaming on the mass transfer from a sublimating sphere

    NASA Astrophysics Data System (ADS)

    Kawahara, N.; Yarin, A. L.; Brenn, G.; Kastner, O.; Durst, F.

    2000-04-01

    The effect of the acoustic streaming on the mass transfer from the surface of a sphere positioned in an ultrasonic acoustic levitator is studied both experimentally and theoretically. Acoustic levitation using standing ultrasonic waves is an experimental tool for studying the heat and mass transfer from small solid or liquid samples, because it allows an almost steady positioning of a sample at a fixed location in space. However, the levitator introduces some difficulties. One of the main problems with acoustic levitation is that an acoustic streaming is induced near the sample surface, which affects the heat and mass transfer rates, as characterized by increased Nusselt and Sherwood numbers. The transfer rates are not uniform along the sample surface, and the aim of the present study is to quantify the spatial Sherwood number distribution over the surface of a sphere. The experiments are based on the measurement of the surface shape of a sphere layered with a solid substance as a function of time using a charge-coupled device (CCD) camera with backlighting. The sphere used in this research is a glass sphere layered with a volatile solid substance (naphthalene or camphor). The local mass transfer from the surface both with and without an ultrasonic acoustic field is investigated in order to evaluate the effect of the acoustic streaming. The experimental results are compared with predictions following from the theory outlined [A. L. Yarin, M. Pfaffenlehner, and C. Tropea, J. Fluid Mech. 356, 65 (1998); A. L. Yarin, G. Brenn, O. Kastner, D. Rensink, and C. Tropea, ibid. 399, 151 (1999)] which describes the acoustic field and the resulting acoustic streaming, and the mass transfer at the surface of particles and droplets located in an acoustic levitator. The results are also compared with the experimental data and with the theoretical predictions of Burdukov and Nakoryakov [J. Appl. Mech. Tech. Phys. 6, 51 (1965)], which are valid only in the case of spherical

  19. Analyses of Acoustic Streaming Generated by Four Ultrasonic Vibrators in a Vessel

    NASA Astrophysics Data System (ADS)

    Nakagawa, Masafumi

    2004-05-01

    When ultrasonic waves are applied, the heat transfer at a heated surface in water increases markedly. The origin of this increase in heat transfer is thought to be due to the agitation effect from the microjets of cavitation and from acoustic streaming. The method in which four vibrators are used has the ability of further enhancing heat transfer. This paper presents the method using four vibrators to eject an acoustic stream jet at a selected position in the vessel. Analyses of this method are performed to establish it theoretically and to compare with an experiment previously conducted. The analyses shown in this research indicate that the aspects of acoustic streaming generated by the four vibrators in the vessel can be correctly predicted and provide a foundation for the development of using this method for the enhancement of heat transfer.

  20. 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.

  1. Study of the onset of the acoustic streaming in parallel plate resonators with pulse ultrasound.

    PubMed

    Castro, Angelica; Hoyos, Mauricio

    2016-03-01

    In a previous study, we introduced pulse mode ultrasound as a new method for reducing and controlling the acoustic streaming in parallel plate resonators (Hoyos and Castro, 2013). Here, by modifying other parameters such as the resonator geometry and the particle size, we have found a threshold for particle manipulation with ultrasonic standing waves in confined resonators without the influence of the acoustic streaming. We demonstrate that pulse mode ultrasound open the possibility of manipulating particles smaller than 1 μm size. PMID:26705604

  2. Ice Flow in the North East Greenland Ice Stream

    NASA Technical Reports Server (NTRS)

    Joughin, Ian; Kwok, Ron; Fahnestock, M.; MacAyeal, Doug

    1999-01-01

    Early observations with ERS-1 SAR image data revealed a large ice stream in North East Greenland (Fahnestock 1993). The ice stream has a number of the characteristics of the more closely studied ice streams in Antarctica, including its large size and gross geometry. The onset of rapid flow close to the ice divide and the evolution of its flow pattern, however, make this ice stream unique. These features can be seen in the balance velocities for the ice stream (Joughin 1997) and its outlets. The ice stream is identifiable for more than 700 km, making it much longer than any other flow feature in Greenland. Our research goals are to gain a greater understanding of the ice flow in the northeast Greenland ice stream and its outlet glaciers in order to assess their impact on the past, present, and future mass balance of the ice sheet. We will accomplish these goals using a combination of remotely sensed data and ice sheet models. We are using satellite radar interferometry data to produce a complete maps of velocity and topography over the entire ice stream. We are in the process of developing methods to use these data in conjunction with existing ice sheet models similar to those that have been used to improve understanding of the mechanics of flow in Antarctic ice streams.

  3. Regionalization of winter low-flow characteristics of Tennessee streams

    USGS Publications Warehouse

    Bingham, R.H.

    1986-01-01

    Procedures were developed for estimating winter (December-April) low flows at ungaged stream sites in Tennessee based on surface geology and drainage area size. One set of equations applies to West Tennessee streams, and another set applies to Middle and East Tennessee streams. The equations do not apply to streams where flow is significantly altered by the activities of man. Standard errors of estimate of equations for West Tennessee are 22% - 35% and for middle and East Tennessee 31% - 36%. Statistical analyses indicate that summer low-flow characteristics are the same as annual low-flow characteristics, and that winter low flows are larger than annual low flows. Streamflow-recession indexes, in days per log cycle of decrease in discharge, were used to account for effects of geology on low flow of streams. The indexes in Tennessee range from 32 days/log cycle for clay and shale to 350 days/log cycle for gravel and sand, indicating different aquifer characteristics of the geologic units that contribute to streamflows during periods of no surface runoff. Streamflow-recession rate depends primarily on transmissivity and storage characteristics of the aquifers, and the average distance from stream channels to basin divides. Geology and drainage basin size are the most significant variables affecting low flow in Tennessee streams according to regression analyses. (Author 's abstract)

  4. Two-dimensional streaming flows induced by resonating, thin beams.

    PubMed

    Açikalin, Tolga; Raman, Arvind; Garimella, Suresh V

    2003-10-01

    Miniaturized resonating slender beams are finding increased applications as fluidic actuators for portable electronics cooling. Piezoelectric and ultrasonic "fans" drive a flexural mode of the beam into resonance thus inducing a streaming flow, which can be used to cool microelectronic components. This paper presents analytical, computational, and experimental investigations of the incompressible two-dimensional streaming flows induced by resonating thin beams. Closed-form analytical streaming solutions are presented first for an infinite beam. These are used to motivate a computational scheme to predict the streaming flows from a baffled piezoelectric fan. Experiments are conducted to visualize the asymmetric streaming flows from a baffled piezoelectric fan and the experimental results are found to be in close agreement with the predicted results. The findings are expected to be of relevance in the optimal design and positioning of these solid-state devices in cooling applications. PMID:14587580

  5. Variability in stream flow and specific discharge along three headwater streams in central Montana, USA

    NASA Astrophysics Data System (ADS)

    Payn, R. A.; Gooseff, M. N.; Jencso, K.; McGlynn, B. L.

    2008-12-01

    Specific discharge is commonly used to quantify the runoff at a watershed outlet with respect to the watershed area. However, little is known about how specific discharge is distributed along stream valleys within watersheds. Analyses of stream flow and specific discharge distributions may provide insight into the interactions of runoff generating processes and stream-subsurface exchange. We compare longitudinal distributions of stream channel flow and specific discharge in 3 mountain headwater streams of the Tenderfoot Creek Experimental Forest in central Montana, comprising 2.6-, 1.4-, and 2.3-km valley lengths with 5.5, 4.0, and 4.5 km2 of total contributing area, respectively. We performed an instantaneous tracer release every 100 m along each valley, and used dilution gauging to estimate stream channel flow from each release. Multiple series of tracer tests were performed during the summer baseflow recession following snowmelt. We used topographic analysis of digital elevation models to quantify sub-basin contributing areas to each location where flow was measured. We then calculated specific discharges by normalizing each estimate of stream channel flow by its corresponding sub-basin contributing area. The study streams demonstrated substantial variability in specific discharge in both space and time. For example, a 1300-m upstream segment showed consistently lower specific discharges than an 800-m downstream segment in the same stream, where the ratio of specific discharges in the upstream segment to specific discharges in the downstream segment generally ranged from 0.7 at higher baseflows to 0.3 at lower baseflows. The differences in specific discharges over the segments were likely driven by both the variability in source water input from contributing areas and the variability in the importance of segment-scale stream-subsurface exchange relative to stream channel flow. We compare the stream flow and specific discharge distributions across space and time

  6. 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

  7. 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.

  8. Controlling acoustic streaming in an ultrasonic heptagonal tweezers with application to cell manipulation.

    PubMed

    Bernassau, A L; Glynne-Jones, P; Gesellchen, F; Riehle, M; Hill, M; Cumming, D R S

    2014-01-01

    Acoustic radiation force has been demonstrated as a method for manipulating micron-scale particles, but is frequently affected by unwanted streaming. In this paper the streaming in a multi-transducer quasi-standing wave acoustic particle manipulation device is assessed, and found to be dominated by a form of Eckart streaming. The experimentally observed streaming takes the form of two main vortices that have their highest velocity in the region where the standing wave is established. A finite element model is developed that agrees well with experimental results, and shows that the Reynolds stresses that give rise to the fluid motion are strongest in the high velocity region. A technical solution to reduce the streaming is explored that entails the introduction of a biocompatible agar gel layer at the bottom of the chamber so as to reduce the fluid depth and volume. By this means, we reduce the region of fluid that experiences the Reynolds stresses; the viscous drag per unit volume of fluid is also increased. Particle Image Velocimetry data is used to observe the streaming as a function of agar-modified cavity depth. It was found that, in an optimised structure, Eckart streaming could be reduced to negligible levels so that we could make a sonotweezers device with a large working area of up to 13 mm × 13 mm. PMID:23725599

  9. Satellite imagery of the onset of streaming flow of ice streams C and D, West Antarctica

    USGS Publications Warehouse

    Hodge, S.M.; Doppelhammer, S.K.

    1996-01-01

    Five overlapping Landsat multispectral scanner satellite images of the interior of the West Antarctic ice sheet were enhanced with principal component analysis, high-pass filtering, and linear contrast stretching and merged into a mosaic by aligning surface features in the overlap areas. The mosaic was registered to geodetic coordinates, to an accuracy of about 1 km, using the five scene centers as control points. The onset of streaming flow of two tributaries of ice stream C and one tributary of ice stream D is visible in the mosaic. The onset appears to occur within a relatively short distance, less than the width of the ice stream, typically at a subglacial topographic feature such as a step or ridge. The ice streams extend farther up into the interior than previously mapped. Ice stream D starts about 150 km from the ice divide, at an altitude of about 1500 m, approximately halfway up the convex-upward dome shape of the interior ice sheet. Ice stream D is relatively much longer than ice stream C, possibly because ice stream D is currently active whereas ice stream C is currently inactive. The grounded portion of the West Antarctic ice sheet is perhaps best conceptualized as an ice sheet in which ice streams are embedded over most of its area, with slow moving ice converging into fast moving ice streams in a widely distributed pattern, much like that of streams and rivers in a hydrologic basin. A relic margin appears to parallel most of the south margin of the tributary of ice stream D, separated from the active shear margin by about 10 km or less for a distance of over 200 km. This means there is now evidence for recent changes having occurred in three of the five major ice streams which drain most of West Antarctica (B, C, and D), two of which (B and D) are currently active.

  10. U.S. Stream Flow Measurement and Data Dissemination Improve

    NASA Astrophysics Data System (ADS)

    Hirsch, Robert M.; Costa, John E.

    2004-05-01

    Stream flow information is essential for many important uses across a broad range of scales, including global water balances, engineering design, flood forecasting, reservoir operations, navigation, water supply, recreation, and environmental management. Growing populations and competing priorities for water, including preservation and restoration of aquatic habitat, are spurring demand for more accurate, timely, and accessible water data. To be most useful, stream flow information must be collected in a standardized manner, with a known accuracy, and for a long and continuous time period. The U.S. Geological Survey (USGS) operates over 7000 stream gauges nationwide, which constitute over 90% of the nation's stream gauges that provide daily stream flow records, and that are accessible to the public. Most stream flow records are not based on direct measurement of river discharge, but are derived from continuous measurements of river elevations or stage. These stage data, recorded to 3-mm accuracy, are then converted into discharge by use of a stage/discharge relation (rating) that is unique for each stream gauging location. Because stream beds and banks are not static, neither is the stage discharge rating. Much of the effort and cost associated with stream gauging lies in establishing and updating this relation. Ten years ago, USGS personnel would visit stream gauging stations 8 to 10 times a year to make direct measurements of river depth, width, and velocity using mechanical instruments: a sounding rod or cable, a tagline, and a current meter. From these data, flow rates were computed. The range of measured flow and concurrent river stages were then used to build the rating curve for each site and to track changes to the rating curve.

  11. Computation of three-dimensional flows using two stream functions

    NASA Technical Reports Server (NTRS)

    Greywall, Mahesh S.

    1991-01-01

    An approach to compute 3-D flows using two stream functions is presented. The method generates a boundary fitted grid as part of its solution. Commonly used two steps for computing the flow fields are combined into a single step in the present approach: (1) boundary fitted grid generation; and (2) solution of Navier-Stokes equations on the generated grid. The presented method can be used to directly compute 3-D viscous flows, or the potential flow approximation of this method can be used to generate grids for other algorithms to compute 3-D viscous flows. The independent variables used are chi, a spatial coordinate, and xi and eta, values of stream functions along two sets of suitably chosen intersecting stream surfaces. The dependent variables used are the streamwise velocity, and two functions that describe the stream surfaces. Since for a 3-D flow there is no unique way to define two sets of intersecting stream surfaces to cover the given flow, different types of two sets of intersecting stream surfaces are considered. First, the metric of the (chi, xi, eta) curvilinear coordinate system associated with each type is presented. Next, equations for the steady state transport of mass, momentum, and energy are presented in terms of the metric of the (chi, xi, eta) coordinate system. Also included are the inviscid and the parabolized approximations to the general transport equations.

  12. Acoustic radiation from lifting airfoils in compressible subsonic flow

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  13. Acoustic radiation from lifting airfoils in compressible subsonic flow

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  14. CURRENT FLOW DATA FOR SELECTED USGS STREAM MONITORING STATIONS

    EPA Science Inventory

    This data set contains recent and historical stream flow data for USGS stations. Flow data (cubic feet per second) are available for the most recent 5-6 day period and are compared with long-term average values. Flow data were collected approximately hourly. Flood stage and the m...

  15. 9. INTAKE STREAM ON GROUND LOOKING WEST AS IT FLOWS ...

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

    9. INTAKE STREAM ON GROUND LOOKING WEST AS IT FLOWS DOWNSTREAM TO LAKE MATHEWS, ALL WATER COMING FROM PUMPS. - Colorado River Aqueduct, From Colorado River to Lake Mathews, Parker Dam, San Bernardino County, CA

  16. Modulated stagnation-point flow and steady streaming

    NASA Technical Reports Server (NTRS)

    Merchant, Gregory J.; Davis, Stephen H.

    1989-01-01

    Plane stagnation-point flow is modulated in the free stream so that the velocity components are proportional to K(H) + K cos omega t. Similarity solutions of the Navier-Stokes equations are examined using high-frequency asymptotics for K and K(H) of unit order. Special attention is focused on the steady streaming generated in this flow with strongly non-parallel streamlines.

  17. 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.

  18. Fabrication, operation and flow visualization in surface-acoustic-wave-driven acoustic-counterflow microfluidics.

    PubMed

    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

  19. 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

  20. Feasibility of using acoustic velocity meters for estimating highly organic suspended-solids concentrations in streams

    USGS Publications Warehouse

    Patino, Eduardo

    1996-01-01

    A field experiment was conducted at the Levee 4 canal site below control structure G-88 in the Everglades agricultural area in northwestern Broward County, Florida, to study the relation of acoustic attenuation to suspended-solids concentrations. Acoustic velocity meter and temperature data were obtained with concurrent water samples analyzed for suspended-solids concentrations. Two separate acoustic velocity meter frequencies were used, 200 and 500 kilohertz, to determine the sensitivity of acoustic attenuation to frequency for the measured suspended-solids concentration range. Suspended-solids concentrations for water samples collected at the Levee 4 canal site from July 1993 to September 1994 ranged from 22 to 1,058 milligrams per liter, and organic content ranged from about 30 to 93 percent. Regression analyses showed that attenuation data from the acoustic velocity meter (automatic gain control) and temperature data alone do not provide enough information to adequately describe the concentrations of suspended solids. However, if velocity is also included as one of the independent variables in the regression model, a satisfactory correlation can be obtained. Thus, it is feasible to use acoustic velocity meter instrumentation to estimate suspended-solids concentrations in streams, even when suspended solids are primarily composed of organic material. Using the most comprehensive data set available for the study (500 kiloherz data), the best fit regression model produces a standard error of 69.7 milligrams per liter, with actual errors ranging from 2 to 128 milligrams per liter. Both acoustic velocity meter transmission frequencies of 200 and 500 hilohertz produced similar results, suggesting that transducers of either frequency could be used to collect attenuation data at the study site. Results indicate that calibration will be required for each acoustic velocity meter system to the unique suspended-solids regime existing at each site. More robust solutions may

  1. Simulation of dust streaming in toroidal traps: Stationary flows

    SciTech Connect

    Reichstein, Torben; Piel, Alexander

    2011-08-15

    Molecular-dynamic simulations were performed to study dust motion in a toroidal trap under the influence of the ion drag force driven by a Hall motion of the ions in E x B direction, gravity, inter-particle forces, and friction with the neutral gas. This article is focused on the inhomogeneous stationary streaming motion. Depending on the strength of friction, the spontaneous formation of a stationary shock or a spatial bifurcation into a fast flow and a slow vortex flow is observed. In the quiescent streaming region, the particle flow features a shell structure which undergoes a structural phase transition along the flow direction.

  2. 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.

  3. Regionalization of low-flow characteristics of Tennessee streams

    USGS Publications Warehouse

    Bingham, R.H.

    1986-01-01

    Procedures for estimating 3-day 2-year, 3-day 10-year, 3-day 20-year, and 7-day 10-year low flows at ungaged stream sites in Tennessee are based on surface geology and drainage area size. One set of equations applies to west Tennessee streams, and another set applies to central and east Tennessee streams. The equations do not apply to streams where flow is significantly altered by activities of man. Standard errors of estimate of equations for west Tennessee are 24 to 32% and for central and east Tennessee 31 to 35%. Streamflow recession indexes, in days/log cycle, are used to account for effects of geology of the drainage basin on low flow of streams. The indexes in Tennessee range from 32 days/log cycle for clay and shale to 350 days/log cycle for gravel and sand, indicating different aquifer characteristics of the geologic units that sustain streamflows during periods of no surface runoff. Streamflow recession rate depends primarily on transmissivity and storage characteristics of the aquifers, and the average distance from stream channels to basin divides. Geology and drainage basin size are the most significant variables affecting low flow in Tennessee streams according to regression analyses. (Author 's abstract)

  4. 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.

  5. 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.

  6. Base flow of streams on Long Island, New York

    USGS Publications Warehouse

    Reynolds, Richard J.

    1982-01-01

    On Long Island, base flow under nonurbanized conditions constitutes 90 to 95% of total stream discharge. Base-flow data from 19 continuously gaged streams are presented as monthly mean and annual mean discharge for water years 1960-75, which includes the 1962-66 drought. The data were derived by hydrograph-separation procedures that isolate mean daily base flow from mean daily discharge. A close empirical relationship between annual mean base flow and stream discharge at the 55-% duration point facilities estimation of average base flow and can be used in place of the more time-consuming hydrograph-separation technique. These data are needed in calibration of computer models that will be used to predict the effects of hydrologic stresses, such as sewering, on the Long Island ground-water system. (USGS)

  7. 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.

  8. 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.

  9. Pressure measurement in supersonic air flow by differential absorptive laser-induced thermal acoustics

    NASA Astrophysics Data System (ADS)

    Hart, Roger C.; Herring, G. C.; Balla, R. Jeffrey

    2007-06-01

    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, the streamwise 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.

  10. Use of Acoustic Doppler Instruments for Measuring Discharge in Streams with Appreciable Sediment Transport

    USGS Publications Warehouse

    Mueller, D.S.

    2002-01-01

    The use of Acoustic Doppler current profilers (ADCP) for measuring discharge in streams with sediment transport was discussed. The studies show that the acoustic frequency of an ADCP in combination with the sediment transport characteristics in a river causes the ADCP bottom-tracking algorithms to detect a moving bottom. A moving bottom causes bottom-tracking-referenced water velocities and discharges to be biased low. The results also show that the use of differential global positioning system (DGPS) data allows accurate measurement of water velocities and discharges in such cases.

  11. Characterization of acoustic streaming and heating using synchronized infrared thermography and particle image velocimetry.

    PubMed

    Layman, Christopher N; Sou, In Mei; Bartak, Rico; Ray, Chittaranjan; Allen, John S

    2011-09-01

    Real-time measurements of acoustic streaming velocities and surface temperature fields using synchronized particle image velocimetry and infrared thermography are reported. Measurements were conducted using a 20 kHz Langevin type acoustic horn mounted vertically in a model sonochemical reactor of either degassed water or a glycerin-water mixture. These dissipative phenomena are found to be sensitive to small variations in the medium viscosity, and a correlation between the heat flux and vorticity was determined for unsteady convective heat transfer. PMID:21514205

  12. Acoustics

    NASA Astrophysics Data System (ADS)

    The acoustics research activities of the DLR fluid-mechanics department (Forschungsbereich Stroemungsmechanik) during 1988 are surveyed and illustrated with extensive diagrams, drawings, graphs, and photographs. Particular attention is given to studies of helicopter rotor noise (high-speed impulsive noise, blade/vortex interaction noise, and main/tail-rotor interaction noise), propeller noise (temperature, angle-of-attack, and nonuniform-flow effects), noise certification, and industrial acoustics (road-vehicle flow noise and airport noise-control installations).

  13. Scaling Stream Flow Response to Forest Disturbance: the SID Project

    NASA Astrophysics Data System (ADS)

    Buttle, J. M.; Beall, F. D.; Creed, I. F.; Gordon, A. M.; Mackereth, R.; McLaughlin, J. W.; Sibley, P. K.

    2004-05-01

    We do not have a good understanding of the hydrologic implications of forest harvesting in Ontario, either for current or alternative management approaches. Attempts to address these implications face a three-fold problem: data on hydrologic response to forest disturbance in Ontario are lacking; most studies of these responses have been in regions with forest cover and hydrologic conditions that differ from the Ontario context; and these studies have generally been conducted at relatively small scales (<1 km2). It is generally assumed that hydrologic changes induced by forest disturbance should diminish with increasing scale due to the buffering capacity of large drainage basins. Recent modeling exercises and reanalysis of paired-basin results call this widespread applicability of this assumption into question, with important implications for assessing the cumulative impacts of forest disturbance on basin stream flow. The SID (Scalable Indicators of Disturbance) project combines stream flow monitoring across basin scales with the RHESSys modeling framework to identify forest disturbance impacts on stream flow characteristics in Ontario's major forest ecozones. As a precursor to identifying stream flow response to forest disturbance, we are examining the relative control of basin geology, topography, typology and topology on stream flow characteristics under undisturbed conditions. This will assist in identifying the dominant hydrologic processes controlling basin stream flow that must be incorporated into the RHESSys model framework in order to emulate forest disturbance and its hydrologic impacts. We present preliminary results on stream flow characteristics in a low-relief boreal forest landscape, and explore how the dominant processes influencing these characteristics change with basin scale in this landscape under both reference and disturbance conditions.

  14. Interactive numerical flow visualization using stream surfaces

    NASA Technical Reports Server (NTRS)

    Hultquist, J. P. M.

    1990-01-01

    Particle traces and ribbons are often used to depict the structure of three-dimensional flowfields, but images produced using these models can be ambiguous. Stream surfaces offer a more visually intuitive method for the depiction of flowfields, but interactive response is needed to allow the user to place surfaces which reveal the essential features of a given flowfield. FLORA, a software package which supports the interactive calculation and display of stream surfaces on silicon graphics workstations, is described. Alternative methods for the integration of particle traces are examined, and calculation through computational space is found to provide rapid results with accuracy adequate for most purposes. Rapid calculation of traces is teamed with progressive refinement of appoximated surfaces. An initial approximation provides immediate user feedback, and subsequent improvement of the surface ensures that the final image is an accurate representation of the flowfield.

  15. 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

  16. Valve effectively controls amount of contaminant in flow stream

    NASA Technical Reports Server (NTRS)

    Schnitzer, T. E.

    1966-01-01

    Contaminant valve with a coaxial groove rotor uniformly deposits contaminant into a flow stream under full pressure and flow conditions. The valve tests filters and filter elements of hydraulic oil, fuel, or lubricant systems without any detrimental effect on the performance.

  17. Scale Model Acoustic Test Validation of IOP-SS Water Prediction using Loci-STREAM-VoF

    NASA Technical Reports Server (NTRS)

    Nielsen, Tanner; West, Jeff

    2015-01-01

    The Scale Model Acoustic Test (SMAT) is a 5% scale test of the Space Launch System (SLS), which is currently being designed at Marshall Space Flight Center (MSFC). SMAT consists of a 5% scale representation of the ignition overpressure sound-suppression system (IOP-SS) that is being tested to quantify the water flow and induced air entrainment in and around the mobile launcher exhaust hole. This data will be compared with computational fluid dynamics (CFD) simulations using the newly developed Loci-STREAM Volume of Fluid (VoF) methods. Compressible and incompressible VoF methods have been formulated, and are currently being used to simulate the water flow of SMAT IOP-SS. The test data will be used to qualitatively and quantitatively assess and validate the VoF methods.

  18. 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.

  19. Analysis of some acoustics-jet flow interaction problems

    NASA Technical Reports Server (NTRS)

    Chow, P. L.

    1984-01-01

    Analytical problems in the interactions between the mean-shear flows and the acoustic field in the planar and circular jets are examined. These problems are basic in understanding the effects of coherent large structure on the generation and complications of sound in a sub-sonic jet. Three problems were investigated: (1) spatial (vs. temporal) normal mode analysis in a planar jets; (2) a slightly divergent, planar jet; and (3) acoustic waves in an axisymmetrical jet.

  20. Numerical simulation of acoustofluidic manipulation by radiation forces and acoustic streaming for complex particles.

    PubMed

    Hahn, Philipp; Leibacher, Ivo; Baasch, Thierry; Dual, Jurg

    2015-11-21

    The numerical prediction of acoustofluidic particle motion is of great help for the design, the analysis, and the physical understanding of acoustofluidic devices as it allows for a simple and direct comparison with experimental observations. However, such a numerical setup requires detailed modeling of the acoustofluidic device with all its components and thorough understanding of the acoustofluidic forces inducing the particle motion. In this work, we present a 3D trajectory simulation setup that covers the full spectrum, comprising a time-harmonic device model, an acoustic streaming model of the fluid cavity, a radiation force simulation, and the calculation of the hydrodynamic drag. In order to make quantitatively accurate predictions of the device vibration and the acoustic field, we include the viscous boundary layer damping. Using a semi-analytical method based on Nyborg's calculations, the boundary-driven acoustic streaming is derived directly from the device simulation and takes into account cavity wall vibrations which have often been neglected in the literature. The acoustic radiation forces and the hydrodynamic drag are calculated numerically to handle particles of arbitrary shape, structure, and size. In this way, complex 3D particle translation and rotation inside experimental microdevices can be predicted. We simulate the rotation of a microfiber in an amplitude-modulated 2D field and analyze the results with respect to experimental observations. For a quantitative verification, the motion of an alumina microdisk is compared to a simple experiment. Demonstrating the potential of the simulation setup, we compute the trajectory of a red blood cell inside a realistic microdevice under the simultaneous effects of acoustic streaming and radiation forces. PMID:26448531

  1. Stream Flow Estimation via Belief Propagation for Sparsely Instrumented Watersheds

    NASA Astrophysics Data System (ADS)

    Krekeler, C. R.; Nagarajan, K.; Graham, W. D.; Slatton, K. C.

    2009-12-01

    Knowledge of stream flow rates is critical for management of in-stream flows and mitigation of flooding and drought events. Unfortunately, spatially dense networks of in situ stream flow measurements are not generally available and would be prohibitively expensive to deploy and maintain. Since measurements are only available at relatively sparse spatial frequencies, a data assimilation technique that best utilizes available measurements in a computationally efficient manner is required. Complexities in underlying geology, groundwater-surface water interactions, and rainfall patterns also need to be captured for optimal performance. In this study, a probabilistic technique based on Bayesian Networks and belief propagation is used to estimate and forecast stream flow based on flow at surrounding locations, rainfall, and groundwater levels, and to quantify the uncertainty of the estimates. The causal nature and inherent tree-like structure of stream flow suggests that belief propagation based on message passing is a computationally efficient method to propagate partial observations to improve flow estimates at other stations across the watershed. Stations are considered as part of an array of nodes that communicate evidence of flow measurements to their neighbors via conditional probability densities defining the links between the nodes. The probability density functions are generated based on the relationship between estimates of flow from the Watershed Assessment Model (WAM), calibrated for our study site at the Santa Fe River Watershed in North Central Florida, USA from 1990 through 2008. Rainfall values were obtained from NEXRAD datasets, while Suwannee River Water Management District provided groundwater levels at a network of wells in the watershed. Performance of the proposed method is evaluated by comparing the results to flow measured at several USGS gage stations along the river not used to develop the algorithm, using various metrics such as Nash

  2. 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

  3. 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.

  4. Free-Stream Boundaries of Turbulent Flows

    NASA Technical Reports Server (NTRS)

    Corrsin, Stanley; Kistler, Alan L

    1955-01-01

    Report presents the results of an experimental and theoretical study made of the instantaneously sharp and irregular front which is always found to separate turbulent fluid from contiguous "nonturbulent" fluid at a free-stream boundary. This distinct demarcation is known to give an intermittent character to hot-wire signals in the boundary zone. The overall behavior of the front is described statistically in terms of its wrinkle-amplitude growth and its lateral propagation relative to the fluid as functions of downstream coordinate.

  5. Assessing stream aquifer interactions through inverse modeling of flow routing

    NASA Astrophysics Data System (ADS)

    Szilagyi, Jozsef; Parlange, Marc B.; Balint, Gabor

    2006-07-01

    SummaryFlux-exchange between stream and aquifer is assessed on a 85.9 km stretch of the Danube River in Hungary. Streamflow is modeled with a spatially and temporally discretized version of the linear kinematic wave equation written in a state-space form which allows for an easy inversion of flow routing. By knowing in- and outflow of the reach, lateral flux exchange between stream and groundwater can be assessed. Continuous baseflow separation, in terms of groundwater gained by the river between the two gaging stations, is made possible at the downstream station by routing groundwater discharged to the stream reach, separately from streamflow measured at the upstream gaging station.

  6. 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).

  7. 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).

  8. Development of acoustic observation method for seafloor hydrothermal flows

    NASA Astrophysics Data System (ADS)

    Mochizuki, M.; Tamura, H.; Asada, A.; Kinoshita, M.; Tamaki, K.

    2012-12-01

    In October 2009, we conducted seafloor reconnaissance using a manned deep-sea submersible Shinkai6500 in Central Indian Ridge 18-20deg.S, where hydrothermal plume signatures were previously perceived. Acoustic video camera "DIDSON" was equipped on the top of Shinkai6500 in order to get acoustic video images of hydrothermal plumes. The acoustic video images of the hydrothermal plumes had been captured in three of seven dives. We could identify shadings inside the acoustic video images of the hydrothermal plumes. Silhouettes of the hydrothermal plumes varied from second to second, and the shadings inside them also varied. These variations corresponded to internal structures and flows of the plumes. 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. Ins. of Industrial Science, University of Tokyo has understood DIDSON's superior performance and tried to develop a new 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. The proposed method to observe and measure hydrothermal flow is the one to utilize a sheet-like acoustic beam. Scanning with concentrated acoustic beam gives distances to the edges of the hydrothermal flows. And then, the shapes of the flows can be identified even in low and zero visibility conditions. Tank experiment was conducted. The purposes of this experiment were to make an attempt at proposed method to delineate underwater hydrothermal flows and to understand relationships among acoustic video image, flow rate and water temperature. Water was heated in the hot tub and pumped to the water tank through the silicon tube. We observed water flows discharging from the tip of the tube with DIDSON. Flow rate had been controlled and temperatures of the

  9. Testing the instream flow method in trout streams

    SciTech Connect

    Studley, T.K.; Railsback, S.F.; Asce, M.

    1995-12-31

    Pacific Gas and Electric Company`s (PG&E) Department of Research and Development and co-sponsors are fieldtesting the Instream Flow Incremental Methodology (IFIM) at a number of trout stream study sites. Fish populations, flows, and other variables were measured for an eight-year baseline period. Three levels of increasingly sophisticated predictions of population response to increased flows were made. The flow increases have been implemented and additional data are being collected to test the predictions. The baseline data and prediction analyses indicate that (1) using different habitat suitability criteria produces substantially different predictions of how populations respond to flow changes, (2) overlaps in habitat used by trout species can lead to misleading predictions of a population`s response to flow changes, and (3) factors other than habitat during summer low flows can limit trout populations (these include spawning habitat, high flows, stream channel characteristics, and stream temperature). Comprehensive field studies are expensive, but are more likely to result in instream flows that provide a cost-effective tradeoff between power and fisheries values.

  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. Optimized open-flow mixing: insights from microbubble streaming

    NASA Astrophysics Data System (ADS)

    Rallabandi, Bhargav; Wang, Cheng; Guo, Lin; Hilgenfeldt, Sascha

    2015-11-01

    Microbubble streaming has been developed into a robust and powerful flow actuation technique in microfluidics. Here, we study it as a paradigmatic system for microfluidic mixing under a continuous throughput of fluid (open-flow mixing), providing a systematic optimization of the device parameters in this practically important situation. Focusing on two-dimensional advective stirring (neglecting diffusion), we show through numerical simulation and analytical theory that mixing in steady streaming vortices becomes ineffective beyond a characteristic time scale, necessitating the introduction of unsteadiness. By duty cycling the streaming, such unsteadiness is introduced in a controlled fashion, leading to exponential refinement of the advection structures. The rate of refinement is then optimized for particular parameters of the time modulation, i.e. a particular combination of times for which the streaming is turned ``on'' and ``off''. The optimized protocol can be understood theoretically using the properties of the streaming vortices and the throughput Poiseuille flow. We can thus infer simple design principles for practical open flow micromixing applications, consistent with experiments. Current Address: Mechanical and Aerospace Engineering, Princeton University.

  12. Acoustic waves superimposed on incompressible flows

    NASA Technical Reports Server (NTRS)

    Hodge, Steve

    1990-01-01

    The use of incompressible approximations in deriving solutions to the Lighthill wave equation was investigated for problems where an analytical solution could be found. A particular model problem involves the determination of the sound field of a spherical oscillating bubble in an ideal fluid. It is found that use of incompressible boundary conditions leads to good approximations in the important region of high acoustic wave number.

  13. Mass flow rate measurement in abrasive jets using acoustic emission

    NASA Astrophysics Data System (ADS)

    Ivantsiv, V.; Spelt, J. K.; Papini, M.

    2009-09-01

    The repeatability of abrasive jet machining operations is presently limited by fluctuations in the mass flow rate due to powder compaction, stratification and humidity effects. It was found that the abrasive mass flow rate for a typical abrasive jet micromachining setup could be determined by using data from the acoustic emission of the abrasive jet impacting a flat plate. Two methods for extracting the mass flow rate from the acoustic emission were developed and compared. In the first method, the number of particle impacts per unit time was determined by a direct count of peaks in the acoustic emission signal. The second method utilizes the power spectrum density of the acoustic emission in a specific frequency range. Both measures were found to correlate strongly with the mass flow rate measured by weighing samples of blasted powder for controlled time periods. It was found that the peak count method permits measurement of the average frequency of the impacts and the mass flow rate, but can only be applied to flow rates in which the impact frequency is approximately one order of magnitude less than the frequency of the target plate ringing. The power spectrum density method of signal processing is applicable to relatively fine powders and to flow rates at which the average impact frequency is of the same order of magnitude as that of the ringing due to the impact. The acoustic emission technique can be used to monitor particle flow variations over a wide range of time periods and provides a straightforward and accurate means of process control.

  14. Acoustically excited heated jets. 3: Mean flow data

    NASA Technical Reports Server (NTRS)

    Lepicovsky, J.; Ahuja, K. K.; Brown, W. H.; Salikuddin, M.; Morris, P. J.

    1988-01-01

    This is Part 3 of a report on the excitability of heated jets under the influence of acoustic excitation. The effects of upstream internal acoustic excitation on jet mixing were described in Part 1. Part 2 described the effects of external excitation on flow mixing. Part 3 contains quantitative results from the measurements of mean Mach number and temperature and consists of radial profiles and centerline distributions measured at selected jet operating conditions for internally excited and unexcited jets. The mean flow data are presented in both graphical and tabulated forms. For the sake of completeness, this part contains temperature probe calibration curves also.

  15. 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.

  16. 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.

  17. Acoustic signal propagation and measurement in natural stream channels for application to surrogate bed load measurements: Halfmoon Creek, Colorado.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Monitoring sediment-generated noise using submerged hydrophones is a surrogate method for measuring bed load transport in streams with the potential for improving estimates of bed load transport through widespread, inexpensive monitoring. Understanding acoustic signal propagation in natural stream e...

  18. Sources of acidic storm flow in an Appalachian Headwater Stream

    NASA Astrophysics Data System (ADS)

    Swistock, Bryan R.; Dewalle, David R.; Sharpe, William E.

    1989-10-01

    A study was conducted to quantify the source of increased dissolved aluminum concentrations during acidic storm flows on a small Pennsylvania stream. Data for six episodes during fall 1986 and spring 1987 showed depressions in stream pH and increases in sulfates, conductivity, dissolved organic carbon, and dissolved aluminum. Flow separation analyses were conducted using 18O as a tracer in a three-component mass balance tracer model. Results showed that soil water and groundwater are the dominant flow sources, accounting for approximately 20 and 75% of total flow during storms, respectively. Channel precipitation generally provided less than 5% of total flows. Hydrograph separation using aluminum agreed with 18O results, while other chemical parameters produced unsatisfactory results. The data support Hewlett's (1982) variable source area concept of storm flow generation with inputs of older, deep circulating groundwater from low-elevation source areas early in an event and later inputs of younger soil water and possibly shallow groundwater from expanding source areas at higher elevations. The results suggest that the most toxic runoff events for aquatic life occur during large storms when the greatest inputs of soil water cause elevated stream dissolved aluminum concentrations. Reductions in storm flow acidity and dissolved aluminum concentrations on this catchment will be most dependent upon changes in soil water and/or groundwater chemistry.

  19. Superadiabatic evolution of acoustic and vorticity perturbations in Couette flow

    NASA Astrophysics Data System (ADS)

    Favraud, Gael; Pagneux, Vincent

    2014-03-01

    Nonadiabatic transitions between the acoustic and the vorticity modes perturbing a plane Couette flow are examined in the context of higher-order WKB asymptotics. In the case of the Schrödinger equation, it is known that looking at the solution expressed in the superadiabatic base, composed of higher-order asymptotic solutions, smoothes quantum state transitions. Then, increasing the order of the superadiabatic base causes these transitions to tend to the Gauss error function, and, once an optimal order is reached, the asymptotic process starts to diverge. We show that for perturbations in Couette flow, similar results can be applied on the amplitudes of the vorticity and acoustic modes. This allows us to more closely track the emergence of the acoustic modes in the presence of the vorticity mode.

  20. Annual and seasonal low-flow characteristics of Iowa streams

    USGS Publications Warehouse

    Lara, Oscar G.

    1979-01-01

    The low-flow characteristics of Iowa streams are described by annual and seasonal low-flow frequency and duration data. Tabulated in this report are low-flow data collected at 135 gaging stations on Iowa streams, three on the Mississippi River, four on the Missour River, and 426 partial-record sites. The information contained in this report is based on all of the daily discharge records collected by the U.S. Geological Survey through the 1976 water year. Consideration is given to the regional aspects of low-flow characteristics by including regression equations to estimate the average discharge and generalized maps to estimate the 7-day, 2-year and 7-day, 10-year discharges at ungaged sites. (Kosco-USGS)

  1. Troughs under threshold modeling of minimum flows in perennial streams

    NASA Astrophysics Data System (ADS)

    Önöz, B.; Bayazit, M.

    2002-02-01

    Troughs under threshold analysis has so far found little application in the modeling of minimum streamflows. In this study, all the troughs under a certain threshold level are considered in deriving the probability distribution of annual minima through the total probability theorem. For the occurrence of minima under the threshold, Poissonian, binomial or negative binomial processes are assumed. The magnitude of minima follows the generalized Pareto, exponential or power distribution. It is shown that asymptotic extreme value distributions for minima or the two-parameter Weibull distribution is obtained for the annual minima, depending on which models are assumed for the occurrence and magnitude of troughs under the threshold. Derived distributions can be used for modeling the minimum flows in streams which do not have zero flows. Expressions for the T-year annual minimum flow are obtained. An example illustrates the application of the troughs under threshold model to the minimum flows observed in a stream.

  2. High-flow frequencies for selected streams in Oklahoma

    USGS Publications Warehouse

    Huntzinger, Thomas L.

    1978-01-01

    Streamflow records are analyzed statistically to determine high-flow characteristics of selected streams in Oklahoma. Tables are included which show the 2-, 5-, 10-, 25-, 50-, and 100-year high-flow frequencies for durations of 1, 3, 7, 30, 90, and 365 days. The log-Pearson Type III frequency distribution was used in the computations. Streamflow records used include data extending from 1903 to 1974.

  3. IN SITU TREATMENT OF HAZARDOUS MATERIAL SPILLS IN FLOWING STREAMS

    EPA Science Inventory

    Two methods of applying activated carbon adsorption treatment to flowing streams were evaluated under comparable conditions. The first involved subsurface introduction of buoyant carbon into the water column followed by the floating of the carbon to the surface and subsequent rem...

  4. 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.

  5. Stream flow in Minnesota: Indicator of climate change

    NASA Astrophysics Data System (ADS)

    Novotny, Eric V.; Stefan, Heinz G.

    2007-02-01

    SummaryStream flow records (up to the year 2002) from 36 USGS gauging stations in five major river basins of Minnesota were studied. Seven annual stream flow statistics were extracted and analyzed: mean annual flow, 7-day low flow in winter, 7-day low flow in summer, peak flow due to snow melt runoff, peak flow due to rainfall as well as high and extreme flow days (number of days with flow rates greater than the mean plus one or two standard deviations, respectively). The Mann-Kendal non-parametric test was used to detect significant trends over time windows from 90 to 10 years in combination with the Trend Free Pre-Whitening (TFPW) method for correcting time series data for serial correlation. Streamflows in the state of Minnesota have varied over the period of record. Trends differed significantly from one river basin to another, and became more accentuated for shorter time windows. Periodicity was detected in the trends for the Red River of the North, the Mississippi River, and the Minnesota River basins for six of the statistics studied. Periods were on the order of 13-15 and 25 years, and the amplitudes were particularly strong after 1980. Peak flow due to snowmelt, typically the highest flow in each year, appears to be the only streamflow statistic that has not changed at a significant rate. Peak flows due to rainfall events in the summer are increasing, as well as the number of days with higher flows (high flow days). Increases in low flow (base flow) in summer and in winter have been significant. Wetter summers and more frequent snow melt events due to warmer winters are the likely cause. Stream flows in Minnesota reflect observed changes in precipitation with increases in mean annual precipitation, a larger number of intense rainfall events, more days with precipitation and earlier and more frequent snowmelt events. For water resources management the results suggest that the threat of snowmelt flooding has not increased, but floods due to rainfall events

  6. Leading-edge receptivity to free-stream disturbance waves for hypersonic flow over a parabola

    NASA Astrophysics Data System (ADS)

    Zhong, Xiaolin

    2001-08-01

    The receptivity of hypersonic boundary layers to free-stream disturbances, which is the process of environmental disturbances initially entering the boundary layers and generating disturbance waves, is altered considerably by the presence of bow shocks in hypersonic flow fields. This paper presents a numerical simulation study of the generation of boundary layer disturbance waves due to free-stream waves, for a two-dimensional Mach 15 viscous flow over a parabola. Both steady and unsteady flow solutions of the receptivity problem are obtained by computing the full Navier Stokes equations using a high-order-accurate shock-fitting finite difference scheme. The effects of bow-shock/free-stream-sound interactions on the receptivity process are accurately taken into account by treating the shock as a discontinuity surface, governed by the Rankine-Hugoniot relations. The results show that the disturbance waves generated and developed in the hypersonic boundary layer contain both first-, second-, and third-mode waves. A parametric study is carried out on the receptivity characteristics for different free-stream waves, frequencies, nose bluntness characterized by Strouhal numbers, Reynolds numbers, Mach numbers, and wall cooling. In this paper, the hypersonic boundary-layer receptivity is characterized by a receptivity parameter defined as the ratio of the maximum induced wave amplitude in the first-mode-dominated region to the amplitude of the free-stream forcing wave. It is found that the receptivity parameter decreases when the forcing frequency or nose bluntness increase. The results also show that the generation of boundary layer waves is mainly due to the interaction of the boundary layer with the acoustic wave field behind the bow shock, rather than interactions with the entropy and vorticity wave fields.

  7. IMPACTS OF LAND USE ON HYDROLOGIC FLOW PERMANENCE IN HEADWATER STREAMS

    EPA Science Inventory

    Extensive urbanization in the watershed can alter the stream hydrology by increasing peak runoff frequency and reducing base flows, causing subsequent impairment of stream community structure. In addition, development effectively eliminates some headwater streams, being piped an...

  8. Analysis of transient storage subject to unsteady flow: Diel flow variation in an Antarctic stream

    USGS Publications Warehouse

    Runkel, R.L.; McKnight, Diane M.; Andrews, E.D.

    1998-01-01

    Transport of dissolved material in streams and small rivers may be characterized using tracer-dilution methods and solute transport models. Recent studies have quantified stream/substream interactions using models of transient storage. These studies are based on tracer-dilution data obtained during periods of steady flow. We present a modeling framework for the analysis of transient storage in stream systems with unsteady flows. The framework couples a kinematic wave routing model with a solute transport model that includes transient storage. The routing model provides time-varying flows and cross-sectional areas that are used as input to the solute transport model. The modeling framework was used to quantify stream/substream interaction in Huey Creek, an Antarctic stream fed exclusively by glacial meltwater. Analysis of tracer-dilution data indicates that there was substantial interaction between the flowing surface water and the hyporheic (substream) zone. The ratio of storage zone area to stream cross-sectional area (A(s)/A) was >1 in all stream reaches, indicating that the substream area contributing to hyporheic exchange was large relative to stream cross-sectional area. The rate of exchange, as governed by the transient storage exchange coefficient (??), was rapid because of a high stream gradient and porous alluvial materials. Estimates of ?? generally exceed those determined for other small streams. The high degree of hyporheic exchange supports the hypothesis that weathering reactions within the hyporheos account for observed increases in solute concentration with stream length, as noted in other studies of Antarctic streams.

  9. Acoustic diffraction in a trifurcated waveguide with mean flow

    NASA Astrophysics Data System (ADS)

    Ayub, M.; Tiwana, M. H.; Mann, A. B.

    2010-12-01

    Diffraction of acoustic plane wave through a semi-infinite hard duct which is placed symmetrically inside an infinite soft/hard duct has been analyzed rigorously. Convective flow has been taken into consideration for the analysis. In this paper the applied method of solution is integral transform and Wiener-Hopf technique. The imposition of boundary conditions result in a 2×2 matrix Wiener-Hopf equation associated with a new canonical scattering problem which has been solved explicitly by expansion coefficient method. The graphs are plotted for sundry parameters of interest. Kernel functions are factorized. The results have applications to duct acoustics.

  10. 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.

  11. 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.

  12. 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.

  13. Low-flow characteristics of streams West Virginia

    USGS Publications Warehouse

    Friel, E.A.; Embree, W.N.; Jack, A.R.; Atkins, J.T., Jr.

    1989-01-01

    Low-flow characteristics of selected streams in West Virginia were determined at continuous-record and partial-record sites. Daily discharges at 100 continuous-record gaging stations on unregulated streams were used to compute selected low-flow frequency values. Estimates of low-flow frequency values at 296 partial-record sites (ones having only discharge measurements) were made using the relation defined by concurrent flows with a continuous-record station. Low-flow characteristics at continuous-record stations were related to drainage area and a variability index to produce equations which can be used to estimate low-flow characteristics at ungaged sites in West Virginia. The State was divided into two hydrologic regions. Drainage area and a streamflow-variability index were determined to be the most significant. The streamflow variability index was computed from duration curves and was used to account for the integrated effects of geology and other hydrologic characteristics. The standard error of estimate for the 7-day low flow with a 2-year recurrence interval is 43% for Region 1 and 57% for Region 2. The standard error of estimate for the 7-day low flow with a 10-year recurrence interval is 82% for Region 1 and 83% for Region 2. (USGS)

  14. Low flows and flow duration of Tennessee streams through 1981

    USGS Publications Warehouse

    Bingham, R.H.

    1985-01-01

    Estimates of low-flow characteristics and flow duration for the period of record at continuous-record streamflow gages are essential in hydrologic studies and water-resources management. This report provides estimates of low flow for 1, 3, 7, 14, 30, 60, and 90 consecutive days for recurrence intervals of 2, 5, 10 , and 20 years for continuous-record streamflow gages in Tennessee. These estimates were used in correlation methods to estimate low flow at partial-record streamflow sites for 1, 3, and 7 consecutive days for a recurrence interval of 10 years; and 3 consecutive days for a recurrence interval of 20 years. (USGS)

  15. a Reverse Flow Theorem and Acoustic Reciprocity in Compressible Potential Flows in Ducts

    NASA Astrophysics Data System (ADS)

    EVERSMAN, W.

    2001-09-01

    A reverse flow theorem for acoustic propagation in compressible potential flow has been obtained directly from the field equations without recourse to energy conservation arguments. A reciprocity theorem for the scattering matrix for the propagation of acoustic modes in a duct with either acoustically rigid walls or acoustically absorbing walls follows. It is found that for a source at a specific end of the duct, suitably scaled reflection matrices in direct and reverse flow have a reciprocal relationship. Scaled transmission matrices obtained for direct flow and reversed flow with simultaneous switching of source location from one end to the other also have a reciprocal relationship. A related reverse flow theorem specialized to one-dimensional acoustic propagation has also been obtained. Reciprocity relationships for the scattering coefficients for propagation are derived, and are found to be similar though much simpler than in the case of multi-mode propagation. In one-dimensional flow, reciprocal relations and power conservation arguments are used to show that scaled power reflection and transmission coefficients are invariant to flow reversal and switching of source location from one end of the duct to the other. Numerical verification of the reciprocal relationships is given in a companion paper.

  16. Streams of Content, Limited Attention: The Flow of Information through Social Media

    ERIC Educational Resources Information Center

    Boyd, Danah

    2010-01-01

    The future of Web 2.0 is about content streams or streams of information. The metaphor implied by "streams" is powerful. The idea is that individuals are living inside the stream: adding to it, consuming it, redirecting it. The goal today is to be attentively aligned--"in flow"--with these information streams, to be aware of information as it…

  17. The role of hillslopes in stream flow response: connectivity, flow path, and transit time

    NASA Astrophysics Data System (ADS)

    McGuire, K. J.; McDonnell, J. J.

    2006-12-01

    Subsurface flow from hillslopes is widely recognized as an important contributor to stream flow generation; however, processes that control how and when hillslopes connect to streams remain unclear. Much of the difficulty in deciphering hillslope response in the stream is due to riparian zone modulation of these inputs. We investigated stream and hillslope runoff dynamics in a 10 ha catchment in the western Cascades of Oregon where the riparian zone has been removed by debris flows, providing an unambiguous hillslope hydrologic signal to the stream channel. Water transit time was used as a framework to develop a conceptual stream flow generation model for the small basin. We based our conceptualization on observations of hydrometric, stable isotope, and applied tracer responses and computed transit times for multiple runoff components using a simple linear systems model. Event water mean transit times (8 to 34 h) and rapid breakthrough from applied hillslope tracer additions, demonstrated that contributing areas extend far upslope during events. Despite rapid hillslope transport processes during events, vadose zone water and runoff mean transit times during non-storm conditions were greater than the timescale of storm events. Vadose zone water mean transit times ranged between 10 and 25 days. Hillslope seepage and catchment baseflow mean transit times were between 1 and 2 years. We describe a conceptual model that captures variable physical flow pathways and transit times through changing antecedent wetness conditions that illustrate the different stages of hillslope and stream connectivity.

  18. Tidal controls on the flow of ice streams

    NASA Astrophysics Data System (ADS)

    Rosier, Sebastian H. R.; Gudmundsson, G. Hilmar

    2016-05-01

    The flow of many Antarctic ice streams is known to be significantly influenced by tides. In the past, modeling studies have implemented the tidal forces acting on a coupled ice stream/ice shelf system in a number of different ways, but the consequences that this has on the modeled response of ice streams to tides have, until now, not been considered. Here we investigate for the first time differences in model response that are only due to differences in the way tidal forcings are implemented. We find that attempts to simplify the problem by neglecting flexural stresses are generally not valid and forcing models with only changes in ocean back pressure will not capture either the correct amplitudes or length scale.

  19. Dust acoustic soliton and double layers with streaming dust and superthermal particles

    NASA Astrophysics Data System (ADS)

    Shan, S. Ali; Mushtaq, A.

    2013-07-01

    Dust acoustic waves are investigated in plasma system containing dynamic and streaming dust, supertherrmal electrons and ions. Linear and nonlinear studies are carried out and elaborated with the help of parameters taken for Saturn's F-ring. An energy integral equation is obtained by using the Sagdeev potential approach, and results are displayed by solving it analytically and numerically. The dependence of nonlinear structures on κ values, the ratio of electron to dust equilibrium densities μ ed , Mach number M, and dust streaming speed v d0 have been presented. The streaming speed appears as a destructive partner for the Mach number M in the pseudoenergy equation and hence plays a dominant modifying role in the formation of nonlinear structures. It plays a destructive role for some of the solitons and works as a source, for the emergence of new solitons (region). Formation of double layers are also investigated and shown that the amplitude, width and existence of double layers structures are predominantly affected by the presence of superthermal electrons, ions, and streaming dust beam.

  20. Acoustic wave flow sensor using quartz thickness shear mode resonator.

    PubMed

    Qin, Lifeng; Zeng, Zijing; Cheng, Hongbin; Wang, Qing-Ming

    2009-09-01

    A quartz thickness shear mode (TSM) bulk acoustic wave resonator was used for in situ and real-time detection of liquid flow rate in this study. A special flow chamber made of 2 parallel acrylic plates was designed for flow measurement. The flow chamber has a rectangular flow channel, 2 flow reservoirs for stabilizing the fluid flow, a sensor mounting port for resonator holding, one inlet port, and one outlet port for pipe connection. A 5-MHz TSM quartz resonator was edge-bonded to the sensor mounting port with one side exposed to the flowing liquid and other side exposed to air. The electrical impedance spectra of the quartz resonator at different volumetric flow rate conditions were measured by an impedance analyzer for the extraction of the resonant frequency through a data-fitting method. The fundamental, 3rd, 5th, 7th, and 9th resonant frequency shifts were found to be around 920, 3572, 5947, 8228, and 10,300 Hz for flow rate variation from 0 to 3000 mL/min, which had a corresponding Reynolds number change from 0 to 822. The resonant frequency shifts of different modes are found to be quadratic with flow rate, which is attributed to the nonlinear effect of quartz resonator due to the effective normal pressure imposing on the resonator sensor by the flowing fluid. The results indicate that quartz TSM resonators can be used for flow sensors with characteristics of simplicity, fast response, and good repeatability. PMID:19811997

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

    PubMed

    Daily, David Jesse; Thomson, Scott L

    2013-01-15

    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

  2. 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.

  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 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.

  5. Characterization and classification of invertebrates as indicators of flow permanence in headwater streams

    EPA Science Inventory

    Headwater streams represent a large proportion of river networks and many have temporary flow. Litigation has questioned whether these streams are jurisdictional under the Clean Water Act. Our goal was to identify indicators of flow permanence by comparing invertebrate assemblage...

  6. Free-jet feasibility study of a thermal acoustic shield concept for AST/VCE application-dual stream nozzles. Comprehensive data report. Volume 2: Laser velocimeter and suppressor. Base pressure 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. Aerodynamic laser velocimeter measurements were made for four selected plumes. In addition, static pressure data in the chute base region of the suppressor configurations were obtained to assess the influence of the shield stream on the suppressor base drag.

  7. 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.

  8. 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

  9. Fire, flow and dynamic equilibrium in stream macroinvertebrate communities

    USGS Publications Warehouse

    Arkle, R.S.; Pilliod, D.S.; Strickler, K.

    2010-01-01

    The complex effects of disturbances on ecological communities can be further complicated by subsequent perturbations within an ecosystem. We investigated how wildfire interacts with annual variations in peak streamflow to affect the stability of stream macroinvertebrate communities in a central Idaho wilderness, USA. We conducted a 4-year retrospective analysis of unburned (n = 7) and burned (n = 6) catchments, using changes in reflectance values (??NBR) from satellite imagery to quantify the percentage of each catchment's riparian and upland vegetation that burned at high and low severity. For this wildland fire complex, increasing riparian burn severity and extent were associated with greater year-to-year variation, rather than a perennial increase, in sediment loads, organic debris, large woody debris (LWD) and undercut bank structure. Temporal changes in these variables were correlated with yearly peak flow in burned catchments but not in unburned reference catchments, indicating that an interaction between fire and flow can result in decreased habitat stability in burned catchments. Streams in more severely burned catchments exhibited increasingly dynamic macroinvertebrate communities and did not show increased similarity to reference streams over time. Annual variability in macroinvertebrates was attributed, predominantly, to the changing influence of sediment, LWD, riparian cover and organic debris, as quantities of these habitat components fluctuated annually depending on burn severity and annual peak streamflows. These analyses suggest that interactions among fire, flow and stream habitat may increase inter-annual habitat variability and macroinvertebrate community dynamics for a duration approaching the length of the historic fire return interval of the study area. ?? 2009 Blackwell Publishing Ltd.

  10. Propagation of acoustic perturbations in a gas flow with dissipation

    NASA Astrophysics Data System (ADS)

    Zavershinskii, I. P.; Molevich, N. E.

    1992-10-01

    In an earlier study (Ingard and Singhal, 1973), it has been found that, in a nondissipating moving medium, an acoustic wave propagating from a source in the flow direction has a smaller amplitude than a wave moving against the flow. Here, it is demonstrated that consideration of dissipation phenomena, which are related to the shear and bulk viscosities and heat conductivity of a medium, leads to an additional anisotropy of the sound amplitude, whose sign is opposite to that obtained in the above mentioned study.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Rogava, Andria; Gogoberidze, Grigol

    2005-05-01

    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.

  13. 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

  14. Determination of trunk streams via using flow accumulation values

    NASA Astrophysics Data System (ADS)

    Farek, Vladimir

    2013-04-01

    There is often a problem, with schematisation of catchments and a channel networks in a broken relief like sandstone landscape (with high vertical segmentation, narrow valley lines, crags, sheer rocks, endorheic hollows etc.). Usual hydrological parameters (subcatchment areas, altitude of highest point of subcatchment, water discharge), which are mostly used for determination of trunk stream upstream the junction, are frequently not utilizable very well in this kind of relief. We found, that for small, relatively homogeneous catchments (within the meaning of land-use, geological subsurface, anthropogenic influence etc.), which are extremely shaped, the value called "flow accumulation" (FA) could be very useful. This value gives the number of cells of the Digital Elevation Model (DEM) grid, which are drained to each cell of the catchment. We can predict that the stream channel with higher values of flow accumulation represents the main stream. There are three crucial issues with this theory. At first it is necessary to find the most suitable algorithm for calculation flow accumulation in a broken relief. Various algorithms could have complications with correct flow routing (representation of divergent or convergent character of the flow), or with keeping the flow paths uninterrupted. Relief with high curvature changes (alternating concave/convex shapes, high steepness changes) causes interrupting of flow lines in many algorithms used for hydrological computing. Second - set down limits of this theory (e.g. the size and character of a surveyed catchment). Third - verify this theory in reality. We tested this theory on sandstone landscape of National park Czech Switzerland. The main data source were high-resolution LIDAR (Light Detection and Ranging) DEM snapshots of surveyed area. This data comes from TU Dresden project called Genesis (Geoinformation Networks For The Cross- Border National Park Region Saxon- Bohemian Switzerland). In order to solve these issues GIS

  15. Irreversibility and complex network behavior of stream flow fluctuations

    NASA Astrophysics Data System (ADS)

    Serinaldi, Francesco; Kilsby, Chris G.

    2016-05-01

    Exploiting the duality between time series and networks, directed horizontal visibility graphs (DHVGs) are used to perform an unprecedented analysis of the dynamics of stream flow fluctuations with focus on time irreversibility and long range dependence. The analysis relies on a large quality-controlled data set consisting of 699 daily time series recorded in the continental United States (CONUS) that are not affected by human activity and primarily reflects meteorological conditions. DHVGs allow a clear visualization and quantification of time irreversibility of flow dynamics, which can be interpreted as a signature of nonlinearity, and long range dependence resulting from the interaction of atmospheric, surface and underground processes acting at multiple spatio-temporal scales. Irreversibility is explored by mapping the time series into ingoing, outgoing, and undirected graphs and comparing the corresponding degree distributions. Using surrogate data preserving up to the second order linear temporal dependence properties of the observed series, DHVGs highlight the additional complexity introduced by nonlinearity into flow fluctuation dynamics. We show that the degree distributions do not decay exponentially as expected, but tend to follow a subexponential behavior, even though sampling uncertainty does not allow a clear distinction between apparent or true power law decay. These results confirm that the complexity of stream flow dynamics goes beyond a linear representation involving for instance the combination of linear processes with short and long range dependence, and requires modeling strategies accounting for temporal asymmetry and nonlinearity.

  16. Global Stream Temperatures and Flows under Climate Change

    NASA Astrophysics Data System (ADS)

    van Vliet, M. T.; Yearsley, J. R.; Franssen, W. H.; Ludwig, F.; Haddeland, I.; Lettenmaier, D. P.; Kabat, P.

    2012-12-01

    Climate change will affect thermal and hydrologic regimes of rivers, having a direct impact on human water use and freshwater ecosystems. Here we assess the impact of climate change on stream temperature and streamflow globally. We used a physically-based stream temperature river basin model (RBM) linked to the Variable Infiltration Capacity (VIC) model. The modelling framework was adapted for global application including impacts of reservoirs and thermal heat discharges, and was validated using observed water temperature and river discharge records in large river basins globally. VIC-RBM was forced with an ensemble of bias-corrected Global Climate Model (GCM) output resulting in global projections of daily streamflow and water temperature for the 21st century. Global mean and high (95th percentile) stream temperatures are projected to increase on average by 0.8-1.6 (1.0-2.2)°C for the SRES B1-A2 scenario for 2071-2100 relative to 1971-2000. The largest water temperature increases are projected for Europe, North America, Southeast Asia, South Africa and parts of Australia. In these regions, the sensitivities for warming are exacerbated by projected decreases in summer low flows. Large increases in water temperature combined with decreases in low flows are found for the southeastern U.S., Europe and eastern China. These regions could potentially be affected by increased deterioration of water quality and freshwater habitats, and reduced water available for beneficial uses such as thermoelectric power production.

  17. 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

  18. 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.

  19. 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

  20. Observations and Modelling of Stream Flow and Stream Phosphorus In Four Nested Grassland Catchments

    NASA Astrophysics Data System (ADS)

    Moynihan, D.; Horgan, F.; Kiely, G.; Scanlon, T.

    The ability to monitor and model the physical and chemical dynamics of stream catchments has become of major importance over the past few years. There is now a greater awareness of the adverse affects of excess phosphorus concentrations on stream water quality and consequently more attention is being focused on the implementation of models to trace and predict the paths of surface and subsurface flow which aid in agri-chemical transport. One such model is Topmodel (a topography based hydrological model) Beven et al. (2000). For a grassland catchment in Ireland a modified version of topmodel is used to simulate the observed catchment dynamics by deriving relationships from the integration of modelled hydrological processes with observed hydrochemical data. Water quality and continuous flow data collected from four nested catchments (15ha, 25ha, 2km2, 15km2) is modelled. The effect of scale was also examined. A linear relationship holds between the flow at catchment 1 (15ha) and catchment 2 (25ha), but the scale effect between the larger areas is non ­ linear and dependent on the hydrological, vegetation and soil parameters. Topmodel is shown to simulate the hydrology well, but less accurate for the phosphorous.

  1. Apparatus for irradiating a continuously flowing stream of fluid

    DOEpatents

    Speir, Leslie G.; Adams, Edwin L.

    1984-01-01

    An apparatus for irradiating a continuously flowing stream of fluid is diosed. The apparatus consists of a housing having a spherical cavity and a spherical moderator containing a radiation source positioned within the spherical cavity. The spherical moderator is of lesser diameter than the spherical cavity so as to define a spherical annular volume around the moderator. The housing includes fluid intake and output conduits which open onto the spherical cavity at diametrically opposite positions. Fluid flows through the cavity around the spherical moderator and is uniformly irradiated due to the 4.pi. radiation geometry. The irradiation source, for example a .sup.252 CF neutron source, is removable from the spherical moderator through a radial bore which extends outwardly to an opening on the outside of the housing. The radiation source may be routinely removed without interrupting the flow of fluid or breaching the containment of the fluid.

  2. Stream flow changes across North Carolina (USA) 1955-2012 with implications for environmental flow management

    NASA Astrophysics Data System (ADS)

    Meitzen, Kimberly M.

    2016-01-01

    This study examines changes in stream flow conditions across North Carolina, relates these changes to geomorphological conditions of rivers, and makes recommendations for environmental flow guidelines to conserve and protect riverine ecosystems. Monthly stream flow percentile metrics (90th, 75th, 50th, 25th, and 10th percentiles) are compared over two time periods (1955-1980 and 1984-2012) for 63 gages distributed statewide. The results showed that stream flow changes vary spatially by flow magnitude, ecoregion, basin, and temporally by months. The greatest changes involve decreases to the 10th, 25th, 50th, and 75th percentiles and the least amount of change is associated with 90th percentile flows. The spring and summer months of February through August have the greatest flow reductions, while September, November, and December exhibit magnitude increases for the 75th and 90th percentile flows. The Blue Ridge has the least amount of change, whereas the Piedmont and Coastal Plain have the greatest change. The few gages that do not show significant magnitude decreases to the 10th percentile flow are below major dams on the Neuse, Cape Fear, and Roanoke rivers. These same dammed rivers exhibit increases to the 90th percentile flows. The Tar River Basin, which is free of dams, shows opposite effects, with significant decreases to the 10th percentile flows and minimal changes to the 75th and 90th percentile flows. This study elucidates the importance of establishing environmental flow criteria that apply statewide across North Carolina. Sustainable environmental flow criteria need to be established that conserve seasonal patterns of flows, sustain low flows (from increases and decreases), and protect headwater and tributary accumulation areas from over-abstraction.

  3. Estimates of Flow Duration, Mean Flow, and Peak-Discharge Frequency Values for Kansas Stream Locations

    USGS Publications Warehouse

    Perry, Charles A.; Wolock, David M.; Artman, Joshua C.

    2004-01-01

    Streamflow statistics of flow duration and peak-discharge frequency were estimated for 4,771 individual locations on streams listed on the 1999 Kansas Surface Water Register. These statistics included the flow-duration values of 90, 75, 50, 25, and 10 percent, as well as the mean flow value. Peak-discharge frequency values were estimated for the 2-, 5-, 10-, 25-, 50-, and 100-year floods. Least-squares multiple regression techniques were used, along with Tobit analyses, to develop equations for estimating flow-duration values of 90, 75, 50, 25, and 10 percent and the mean flow for uncontrolled flow stream locations. The contributing-drainage areas of 149 U.S. Geological Survey streamflow-gaging stations in Kansas and parts of surrounding States that had flow uncontrolled by Federal reservoirs and used in the regression analyses ranged from 2.06 to 12,004 square miles. Logarithmic transformations of climatic and basin data were performed to yield the best linear relation for developing equations to compute flow durations and mean flow. In the regression analyses, the significant climatic and basin characteristics, in order of importance, were contributing-drainage area, mean annual precipitation, mean basin permeability, and mean basin slope. The analyses yielded a model standard error of prediction range of 0.43 logarithmic units for the 90-percent duration analysis to 0.15 logarithmic units for the 10-percent duration analysis. The model standard error of prediction was 0.14 logarithmic units for the mean flow. Regression equations used to estimate peak-discharge frequency values were obtained from a previous report, and estimates for the 2-, 5-, 10-, 25-, 50-, and 100-year floods were determined for this report. The regression equations and an interpolation procedure were used to compute flow durations, mean flow, and estimates of peak-discharge frequency for locations along uncontrolled flow streams on the 1999 Kansas Surface Water Register. Flow durations, mean

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

    PubMed Central

    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

    2012-01-01

    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 m3 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). PMID:21903931

  5. Energetic Geodesic Acoustic Modes Associated with Two-Stream-like Instabilities in Tokamak Plasmas.

    PubMed

    Qu, Z S; Hole, M J; Fitzgerald, M

    2016-03-01

    An unstable branch of the energetic geodesic acoustic mode (EGAM) is found using fluid theory with fast ions characterized by their narrow width in energy distribution and collective transit along field lines. This mode, with a frequency much lower than the thermal GAM frequency ω_{GAM}, is now confirmed as a new type of unstable EGAM: a reactive instability similar to the two-stream instability. The mode can have a very small fast ion density threshold when the fast ion transit frequency is smaller than ω_{GAM}, consistent with the onset of the mode right after the turn-on of the beam in DIII-D experiments. The transition of this reactive EGAM to the velocity gradient driven EGAM is also discussed. PMID:26991183

  6. Seasonal Stream Flow Forecasting and Decision Support in Central Texas

    NASA Astrophysics Data System (ADS)

    Watkins, D. W.; Nykanen, D. K.; Mahmoud, M.; Wei, W.

    2003-12-01

    A decision support model based on stream flow ensemble forecasts has been developed for the Lower Colorado River Authority in Central Texas, and predictive skill is added to climatology-based forecasts by conditioning the ensembles on observable climate indicators. These indicators include stream flow (persistence), soil moisture, and large-scale recurrent patterns such as the El Nino-Southern Oscillation, Pacific Decadal Oscillation, and the North Atlantic Oscillation. In the absence of historical soil moisture measurements, the Variable Infiltration Capacity (VIC) Retrospective Land Surface Data Set is applied. Strong correlation between observed runoff volumes and runoff volumes simulated by the (uncalibrated) VIC model indicates the viability of this approach. Following correlation analysis to screen potential predictors, a Bayesian procedure for updating ensemble probabilities is outlined, and various skill scores are reviewed for evaluating forecast performance. Verification of the ensemble forecasts using a resampling procedure indicates a small but potentially significant improvement in forecast skill over climatology that could be exploited in seasonal water management decisions. Future work involves evaluation of seasonal soil moisture forecasts, further evaluation of annual flow forecasts, incorporation of climate forecasts in reservoir operating rules, and estimation of the value of the forecasts.

  7. 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

  8. The Secondary Stream of Interstellar Neutral Hydrogen Flow

    NASA Astrophysics Data System (ADS)

    Nakagawa, H.; Fukunishi, H.; Watanabe, S.; Takahashi, Y.; Taguchi, M.; Yamazaki, A.

    2005-12-01

    The solar system is located in a low-density interstellar cloud. Neutral hydrogen and helium atoms of the interstellar medium can penetrate deep into the heliosphere without being completely interrupted by the solar wind plasma. Consequently, there is a uniform flow of interplanetary hydrogen and helium in the solar system. This neutral hydrogen and helium flow is called `interstellar wind'. Spacecraft data demonstrated that the upstream direction of the interplanetary neutral helium flow is (254.7°+-0.4°, 5.2°+-0.2°) in the ecliptic coordinate system [Witte, 2004; Vallerga et al., 2004; Gloeckler et al., 2004], while it is (252.5°+-0.5°, 8.8°+-0.5°) for the interplanetary neutral hydrogen [Lallement, et al., 2005; Quemerais et al., 1999]. The presence of this well-established primary stream leads the hydrogen and helium glows to symmetry with respect to the 74° / 254° ecliptic longitude axis. Meanwhile, the existence of a secondary stream of the neutral wind inside the heliosphere arriving from a direction between about 260° and 290° ecliptic longitude, about 10° - 40° different from the upstream primary interstellar neutral flow direction, has been proposed recently by a synthetic analysis of a wide variety of spacecraft observations [M. R. Collier, private communication]. In this study, we have performed a detailed analysis of the interstellar hydrogen resonance glow data obtained from ultraviolet imaging spectrometer (UVS) measurements onboard Nozomi spacecraft. Although the UVS instrument instantaneously points a certain direction with the field-of-view which is perpendicular to the spin axis controlled toward the Earth, spatial distributions of emissions are measured by using the spin and orbital motion of the Nozomi spacecraft. One year observations enable us to derive the full sky image of Lyman alpha emission. We plotted the data obtained in the ecliptic plane from 2000 to 2001 and compared them with the model calculations in cases of the

  9. Response of turbine flow meters to acoustic perturbations

    NASA Astrophysics Data System (ADS)

    Stoltenkamp, P. W.; Bergervoet, J. T. M.; Willems, J. F. H.; van Uittert, F. M. R.; Hirschberg, A.

    2008-08-01

    Acoustic pulsations can have a significant effect on gas turbine flow meters during volume flow measurements. These systematic errors are investigated experimentally for high-frequency pulsations and are compared to the results of a quasi-steady theory. Although significant deviations were found from the quasi-steady theory, the quadratic dependence of the velocity amplitude appears to remain valid for all measurements. The exact quadratic dependence is a function of Strouhal number of the pulsations. In the range of Strouhal numbers below 2.5, based on the chord length at the tip of the rotor blade and the flow velocity at the rotor inlet plane, we find a slow decrease in the error with increasing Strouhal number, Sr. The shape of the leading edge of the rotor blades does not affect this behaviour.

  10. Does stream flow structure woody riparian vegetation in subtropical catchments?

    PubMed

    James, Cassandra S; Mackay, Stephen J; Arthington, Angela H; Capon, Samantha J; Barnes, Anna; Pearson, Ben

    2016-08-01

    The primary objective of this study was to test the relevance of hydrological classification and class differences to the characteristics of woody riparian vegetation in a subtropical landscape in Queensland, Australia. We followed classification procedures of the environmental flow framework ELOHA - Ecological Limits of Hydrologic Alteration. Riparian surveys at 44 sites distributed across five flow classes recorded 191 woody riparian species and 15, 500 individuals. There were differences among flow classes for riparian species richness, total abundance, and abundance of regenerating native trees and shrubs. There were also significant class differences in the occurrence of three common tree species, and 21 indicator species (mostly native taxa) further distinguished the vegetation characteristics of each flow class. We investigated the influence of key drivers of riparian vegetation structure (climate, depth to water table, stream-specific power, substrate type, degree of hydrologic alteration, and land use) on riparian vegetation. Patterns were explained largely by climate, particularly annual rainfall and temperature. Strong covarying drivers (hydrology and climate) prevented us from isolating the independent influences of these drivers on riparian assemblage structure. The prevalence of species considered typically rheophytic in some flow classes implies a more substantial role for flow in these classes but needs further testing. No relationships were found between land use and riparian vegetation composition and structure. This study demonstrates the relevance of flow classification to the structure of riparian vegetation in a subtropical landscape, and the influence of covarying drivers on riparian patterns. Management of environmental flows to influence riparian vegetation assemblages would likely have most potential in sites dominated by rheophytic species where hydrological influences override other controls. In contrast, where vegetation assemblages are

  11. Flow-excited acoustic resonance of two tandem cylinders in cross-flow

    NASA Astrophysics Data System (ADS)

    Mohany, A.; Ziada, S.

    2005-11-01

    The aeroacoustic response of two tandem cylinders in cross-flow is investigated experimentally. Eleven spacing ratios between the cylinders, in the range of L/D=1.2 4.5, have been tested to investigate the effect of the gap between the cylinders on the excitation mechanism of acoustic resonance. During the tests, the acoustic cross-modes of the duct housing the cylinders are self-excited. Similar tests are performed on isolated cylinders. The aeroacoustic response of the tandem cylinders is found to be considerably different from that of isolated cylinders. For isolated cylinders, acoustic resonance of a given mode occurs over a single range of flow velocity and is excited by the natural vortex shedding process observed in the absence of acoustic resonance. In the case of tandem cylinders with a spacing ratio inside the proximity region, L/D is less than 3.5, the resonance occurs over two different ranges of flow velocity. One of these ranges is similar to that observed for isolated cylinders and the other occurs at much lower flow velocities. The latter resonance range seems to be triggered by the instability of the separated flow in the gap between the cylinders. Outside the proximity region, the aeroacoustic response of the two tandem cylinders is similar to that of isolated cylinder.

  12. Dilatant till facilitates ice-stream flow in northeast Greenland

    NASA Astrophysics Data System (ADS)

    Christianson, Knut; Peters, Leo E.; Alley, Richard B.; Anandakrishnan, Sridhar; Jacobel, Robert W.; Riverman, Kiya L.; Muto, Atsuhiro; Keisling, Benjamin A.

    2014-09-01

    We present radio-echo sounding (RES), global positioning system (GPS), and active-source seismic data across the central portion of the Northeast Greenland Ice Stream (NEGIS). NEGIS widens downglacier from a small region of high geothermal flux near the ice divide. Our data reveal high-porosity (40+%) water-saturated till lubricating the ice stream. Ice accelerates and thins as it flows into NEGIS, producing marginal troughs in surface topography. These troughs create steep gradients in the subglacial hydropotential that generate parallel “sticky” and “slippery” bands beneath the shear margins. The low-porosity “sticky” sediment bands limit ice entrainment across the margins and thus restrict further widening, producing the long, narrow, and relatively stable ice stream. However, the observed relations among surface elevation, basal water routing, broad sedimentary drape, and till dilatancy suggest that rapid shifts in ice dynamics are possible, including rapid transmission of ocean forcing inland. The source and routing of the subglacial till are unclear, but our data help constrain hypotheses.

  13. Simulation of stream-groundwater exchange and near-stream flow paths of two first-order mountain streams using MODFLOW

    SciTech Connect

    Wroblicky, G.J.; Campana, M.E.; Dahm, C.N.; Valett, H.M.; Morrice, J.A.; Baker, M.A.; Henry, K.S.

    1994-12-31

    Hydrologic exchange between surface water and groundwater has been shown to exert strong controls on stream biota and biogeochemical processes. To quantify such exchange, the authors constructed two-dimensional unconfined groundwater flow models for two first-order stream sites in New Mexico, Aspen Creek and Rio Calaveras, using the U.S.G.S. modular three-dimensional finite-difference groundwater flow model (MODFLOW). They calibrated the model to hydraulic head, stream stage, and seepage meter measurements. Model-calibrated flow rates between the stream and local aquifer system range between 10{sup {minus}4} and 10{sup {minus}6} cm/s at Aspen Creek, and 10 {sup {minus}4} and 10 {sup {minus}7} cm/s at Rio Calaveras. Modeled flow rates at both sites tended to under predict seepage meter estimates by one-half to one order of magnitude. A particle tracking code (MODPATH) delineated near-stream flow paths. Near-stream flow paths were found to be associated with stream meander bends and areas where the streambed slope increased significantly.

  14. Acoustic communication in two freshwater gobies: ambient noise and short-range propagation in shallow streams.

    PubMed

    Lugli, M; Fine, M L

    2003-07-01

    Noise is an important theoretical constraint on the evolution of signal form and sensory performance. In order to determine environmental constraints on the communication of two freshwater gobies Padogobius martensii and Gobius nigricans, numerous noise spectra were measured from quiet areas and ones adjacent to waterfalls and rapids in two shallow stony streams. Propagation of goby sounds and waterfall noise was also measured. A quiet window around 100 Hz is present in many noise spectra from noisy locations. The window lies between two noise sources, a low-frequency one attributed to turbulence, and a high-frequency one (200-500 Hz) attributed to bubble noise from water breaking the surface. Ambient noise from a waterfall (frequencies below 1 kHz) attenuates as much as 30 dB between 1 and 2 m, after which values are variable without further attenuation (i.e., buried in the noise floor). Similarly, courtship sounds of P. martensii attenuate as much as 30 dB between 5 and 50 cm. Since gobies are known to court in noisy as well as quiet locations in these streams, their acoustic communication system (sounds and auditory system) must be able to cope with short-range propagation dictated by shallow depths and ambient noise in noisy locations. PMID:12880062

  15. Selected flows with free surfaces: Streams and drops

    NASA Astrophysics Data System (ADS)

    Kowalewski, Tomasz A.

    1995-03-01

    The basic purpose of the research described in this article was to develop a non contact method for diagnosing the physical parameters of the free surface of a liquid using drop oscillation analysis. In particular, the purpose is to measure the temperature of an evaporating surface. The realization of this goal has led to the development of new experimental techniques which make it possible to record fast processes using video and digital imaging equipment. Experimental studies of the process of the formation of drops as a result of the controlled breakup of a stream revealed the existence of an additional phase in the process based on the formation of microstreams and microsatellites with micrometer-like dimensions. A comparison of measurement results with Eggers' asymptotic model (23) confirmed the model's basic assumption of the local nature of the final phase in the disintegration of the stream, which at the same time points to the existence of a number of discrepancies which provide evidence of the limitations of this approximation. The next part of the article presents the results of observations of the instability of streams of liquid caused by its evaporation. In an attempt to analyze the mechanisms which initiate the turbulence of the evaporating surface, the author focused on surface tension gradients as an essential factor in the destabilization of small-diameter streams. The author also described the occurrence of a number of new phenomena in the destabilization of a stream, including the separation of surface fragments, their stabilization by the flow of vapor, and a quasistable change in the trajectory of the stream. The author also developed an experimental method which makes it possible to detect and produce a precise description of the deformation of drops. Measurements of the oscillations of small drops in the air led to the development of a complete non-linear model of the oscillations of a viscous drop and made it possible to verify simplified

  16. Strategies for single particle manipulation using acoustic and flow fields.

    PubMed

    Oberti, S; Möller, D; Neild, A; Dual, J; Beyeler, F; Nelson, B J; Gutmann, S

    2010-02-01

    Acoustic radiation forces have often been used for the manipulation of large amounts of micrometer sized suspended particles. The nature of acoustic standing wave fields is such that they are present throughout the whole fluidic volume; this means they are well suited to such operations, with all suspended particles reacting at the same time upon exposure. Here, this simultaneous positioning capability is exploited to pre-align particles along the centerline of channels, so that they can successively be removed by means of an external tool for further analysis. This permits a certain degree of automation in single particle manipulation processes to be achieved as initial identification of particles' location is no longer necessary, rather predetermined. Two research fields in which applications are found have been identified. First, the manipulation of copolymer beads and cells using a microgripper is presented. Then, sample preparation for crystallographic analysis by positioning crystals into a loop using acoustic manipulation and a laminar flow will be presented. PMID:19837446

  17. Trapping of Embolic Particles in a Vessel Phantom by Cavitation-Enhanced Acoustic Streaming

    PubMed Central

    Maxwell, Adam D.; Park, Simone; Vaughan, Benjamin L.; Cain, Charles A.; Grotberg, James B.; Xu, Zhen

    2014-01-01

    Cavitation clouds generated by short, high-amplitude, focused ultrasound pulses were previously observed to attract, trap, and erode thrombus fragments in a vessel phantom. This phenomenon may offer a noninvasive method to capture and eliminate embolic fragments flowing through the bloodstream during a cardiovascular intervention. In this article, the mechanism of embolus trapping was explored by particle image velocimetry (PIV). PIV was used to examine the fluid streaming patterns generated by ultrasound in a vessel phantom with and without crossflow of blood-mimicking fluid. Cavitation enhanced streaming, which generated fluid vortices adjacent to the focus. The focal streaming velocity, uf, was as high as 120 cm/s, while mean crossflow velocities, uc, were imposed up to 14 cm/s. When a solid particle 3-4 mm diameter was introduced into crossflow, it was trapped near the focus. Increasing uf promoted particle trapping while increasing uc promoted particle escape. The maximum crossflow Reynolds number at which particles could be trapped, Rec, was approximately linear with focal streaming number, Ref, i.e. Rec = 0.25Ref + 67.44 (R2=0.76) corresponding to dimensional velocities uc=0.084uf + 3.122 for 20 < uf < 120 cm/s. The fluidic pressure map was estimated from PIV and indicated a negative pressure gradient towards the focus, trapping the embolus near this location. PMID:25109407

  18. Trapping of embolic particles in a vessel phantom by cavitation-enhanced acoustic streaming

    NASA Astrophysics Data System (ADS)

    Maxwell, Adam D.; Park, Simone; Vaughan, Benjamin L.; Cain, Charles A.; Grotberg, James B.; Xu, Zhen

    2014-09-01

    Cavitation clouds generated by short, high-amplitude, focused ultrasound pulses were previously observed to attract, trap, and erode thrombus fragments in a vessel phantom. This phenomenon may offer a noninvasive method to capture and eliminate embolic fragments flowing through the bloodstream during a cardiovascular intervention. In this article, the mechanism of embolus trapping was explored by particle image velocimetry (PIV). PIV was used to examine the fluid streaming patterns generated by ultrasound in a vessel phantom with and without crossflow of blood-mimicking fluid. Cavitation enhanced streaming, which generated fluid vortices adjacent to the focus. The focal streaming velocity, uf, was as high as 120 cm/s, while mean crossflow velocities, uc, were imposed up to 14 cm/s. When a solid particle 3-4 mm diameter was introduced into crossflow, it was trapped near the focus. Increasing uf promoted particle trapping while increasing uc promoted particle escape. The maximum crossflow Reynolds number at which particles could be trapped, Rec, was approximately linear with focal streaming number, Ref, i.e. Rec = 0.25Ref + 67.44 (R2 = 0.76) corresponding to dimensional velocities uc = 0.084uf + 3.122 for 20 < uf < 120 cm/s. The fluidic pressure map was estimated from PIV and indicated a negative pressure gradient towards the focus, trapping the embolus near this location.

  19. Bubble size prediction in co-flowing streams

    NASA Astrophysics Data System (ADS)

    van Hoeve, W.; Dollet, B.; Gordillo, J. M.; Versluis, M.; van Wijngaarden, L.; Lohse, D.

    2011-06-01

    In this paper, the size of bubbles formed through the breakup of a gaseous jet in a co-axial microfluidic device is derived. The gaseous jet surrounded by a co-flowing liquid stream breaks up into monodisperse microbubbles and the size of the bubbles is determined by the radius of the inner gas jet and the bubble formation frequency. We obtain the radius of the gas jet by solving the Navier-Stokes equations for low-Reynolds-number flows and by conservation of momentum. The prediction of the bubble size is based on the system's control parameters only, i.e. the inner gas flow rate Qi, the outer liquid flow rate Qo, and the tube radius R. For a very low gas-to-liquid flow rate ratio (Qi/Qo→0) the bubble radius scales as r_{b}/R \\propto \\sqrt{Q_{i}/Q_{o}} , independently of the inner-to-outer viscosity ratio ηi/ηo and of the type of the velocity profile in the gas, which can be either flat or parabolic, depending on whether high-molecular-weight surfactants cover the gas-liquid interface or not. However, in the case in which the gas velocity profiles are parabolic and the viscosity ratio is sufficiently low, i.e. ηi/ηoLt1, the bubble diameter scales as rb~(Qi/Qo)β, with β smaller than 1/2.

  20. A coupled stream flow and depth-integrated subsurface flow model for catchment hydrology

    NASA Astrophysics Data System (ADS)

    Pan, Yi; Weill, Sylvain; Ackerer, Philippe; Delay, Frederick

    2015-11-01

    Few hydrological models that couple stream flow and subsurface flow in shallow aquifers are based on a compromise between simple and complex depiction of the system, although this compromise could result in tractable tools for various applications. We present a depth-integrated approach in which flows in the vadose and saturated zones are assumed to be parallel to the bottom of the aquifer and thus are integrated in the direction normal to the bottom of the aquifer. The hydrodynamic parameters are also integrated in this direction, and gravity effects are preserved. Stream flow is handled by a diffusive-wave equation that is calculated over a network of one-dimensional bonds. The first-order coupling between the stream and subsurface flows exchanges water fluxes between the stream network and the subsurface compartment according to the hydraulic head differences between the systems. Three synthetic test cases, one including a comparison with a three-dimensional code, are used to evaluate the general behavior of the coupled model. It is shown that the approach reproduces the main hydrological features at the catchment scale, including the generation of runoff, infiltration-exfiltration into (from) the vadose zone, and smooth transient head variations in the aquifer.

  1. Three-dimensional features on oscillating microbubbles streaming flows

    NASA Astrophysics Data System (ADS)

    Rossi, Massimiliano; Marin, Alvaro G.; Wang, Cheng; Hilgenfeldt, Sascha; Kähler, Christian J.

    2013-11-01

    Ultrasound-driven oscillating micro-bubbles have been used as active actuators in microfluidic devices to perform manifold tasks such as mixing, sorting and manipulation of microparticles. A common configuration consists in side-bubbles, created by trapping air pockets in blind channels perpendicular to the main channel direction. This configuration results in bubbles with a semi-cylindrical shape that creates a streaming flow generally considered quasi two-dimensional. However, recent experiments performed with three-dimensional velocimetry methods have shown how microparticles can present significant three-dimensional trajectories, especially in regions close to the bubble interface. Several reasons will be discussed such as boundary effects of the bottom/top wall, deformation of the bubble interface leading to more complex vibrational modes, or bubble-particle interactions. In the present investigation, precise measurements of particle trajectories close to the bubble interface will be performed by means of 3D Astigmatic Particle Tracking Velocimetry. The results will allow us to characterize quantitatively the three-dimensional features of the streaming flow and to estimate its implications in practical applications as particle trapping, sorting or mixing.

  2. A mixing layer theory for flow resistance in shallow streams

    NASA Astrophysics Data System (ADS)

    Katul, Gabriel; Wiberg, Patricia; Albertson, John; Hornberger, George

    2002-11-01

    A variety of surface roughness characterizations have emerged from nineteenth and twentieth century studies of channel hydraulics. When the water depth h is much larger than the characteristic roughness height ks, roughness formulations such as Manning's n and the friction factor f can be explicitly related to the momentum roughness height zo in the log-law formulation for turbulent boundary layers, thereby unifying roughness definitions for a given surface. However, when h is comparable to (or even smaller than) ks, the log-law need not be valid. Using a newly proposed mixing layer analogy for the inflectional velocity profile within and just above the roughness layer, a model for the flow resistance in shallow flows is developed. The key model parameter is the characteristic length scale describing the depth of the Kelvin-Helmholtz wave instability. It is shown that the new theory, originally developed for canopy turbulence, recovers much of the earlier roughness results for flume experiments and shallow gravel streams. This study is the first to provide such a unifying framework between canopy atmospheric turbulence and shallow gravel stream roughness characterization. The broader implication of this study is to support the merger of a wealth of surface roughness characterizations independently developed in nineteenth and twentieth century hydraulics and atmospheric sciences and to establish a connection between roughness formulations across traditionally distinct boundary layer types.

  3. Acoustic streaming induced elimination of nonspecifically bound proteins from a surface acoustic wave biosensor: Mechanism prediction using fluid-structure interaction models

    NASA Astrophysics Data System (ADS)

    Sankaranarayanan, Subramanian K. R. S.; Singh, Reetu; Bhethanabotla, Venkat R.

    2010-11-01

    Biosensors typically operate in liquid media for detection of biomarkers and suffer from fouling resulting from nonspecific binding of protein molecules to the device surface. In the current work, using a coupled field finite element fluid-structure interaction simulation, we have identified that fluid motion induced by high intensity sound waves, such as those propagating in these sensors, can lead to the efficient removal of the nonspecifically bound proteins thereby eliminating sensor fouling. We present a computational analysis of the acoustic-streaming phenomenon induced biofouling elimination by surface acoustic-waves (SAWs) propagating on a lithium niobate piezoelectric crystal. The transient solutions generated from the developed coupled field fluid solid interaction model are utilized to predict trends in acoustic-streaming induced forces for varying design parameters such as voltage intensity, device frequency, fluid viscosity, and density. We utilize these model predictions to compute the various interaction forces involved and thereby identify the possible mechanisms for removal of nonspecifically-bound proteins. For the range of sensor operating conditions simulated, our study indicates that the SAW motion acts as a body force to overcome the adhesive forces of the fouling proteins to the device surface whereas the acoustic-streaming induced hydrodynamic forces prevent their reattachment. The streaming velocity fields computed using the finite element models in conjunction with the proposed particle removal mechanism were used to identify the optimum conditions that lead to improved removal efficiency. We show that it is possible to tune operational parameters such as device frequency and input voltage to achieve effective elimination of biofouling proteins in typical biosensing media. Our simulation results agree well with previously reported experimental observations. The findings of this work have significant implications in designing reusable

  4. Downscaling stream flow time series from monthly to daily scales using an auto-regressive stochastic algorithm: StreamFARM

    NASA Astrophysics Data System (ADS)

    Rebora, N.; Silvestro, F.; Rudari, R.; Herold, C.; Ferraris, L.

    2016-06-01

    Downscaling methods are used to derive stream flow at a high temporal resolution from a data series that has a coarser time resolution. These algorithms are useful for many applications, such as water management and statistical analysis, because in many cases stream flow time series are available with coarse temporal steps (monthly), especially when considering historical data; however, in many cases, data that have a finer temporal resolution are needed (daily). In this study, we considered a simple but efficient stochastic auto-regressive model that is able to downscale the available stream flow data from monthly to daily time resolution and applied it to a large dataset that covered the entire North and Central American continent. Basins with different drainage areas and different hydro-climatic characteristics were considered, and the results show the general good ability of the analysed model to downscale monthly stream flows to daily stream flows, especially regarding the reproduction of the annual maxima. If the performance in terms of the reproduction of hydrographs and duration curves is considered, better results are obtained for those cases in which the hydrologic regime is such that the annual maxima stream flow show low or medium variability, which means that they have a low or medium coefficient of variation; however, when the variability increases, the performance of the model decreases.

  5. A model of unsteady subsonic flow with acoustics excluded

    NASA Astrophysics Data System (ADS)

    Fedorchenko, A. T.

    1997-03-01

    Diverse subsonic initial-boundary-value problems (flows in a closed volume initiated by blowing or suction through permeable walls, flows with continuously distributed sources, viscous flows with substantial heat fluxes, etc.) are considered, to show that they cannot be solved by using the classical theory of incompressible fluid motion which involves the equation div u = 0. Application of the most general theory of compressible fluid flow may not be best in such cases, because then we encounter difficulties in accurately resolving the complex acoustic phenomena as well as in assigning the proper boundary conditions. With this in mind a new non-local mathematical model, where div u [not equal] 0 in the general case, is proposed for the simulation of unsteady subsonic flows in a bounded domain with continuously distributed sources of mass, momentum and entropy, also taking into account the effects of viscosity and heat conductivity when necessary. The exclusion of sound waves is one of the most important features of this model which represents a fundamental extension of the conventional model of incompressible fluid flow. The model has been built up by modifying both the general system of equations for the motion of compressible fluid (viscous or inviscid as required) and the appropriate set of boundary conditions. Some particular cases of this model are discussed. A series of exact time-dependent solutions, one- and two-dimensional, is presented to illustrate the model.

  6. Numerical investigation of symmetry breaking and critical behavior of the acoustic streaming field in high-intensity discharge lamps

    NASA Astrophysics Data System (ADS)

    Baumann, Bernd; Schwieger, Joerg; Wolff, Marcus; Manders, Freddy; Suijker, Jos

    2015-06-01

    For energy efficiency and material cost reduction it is preferred to drive high-intensity discharge lamps at frequencies of approximately 300 kHz. However, operating lamps at these high frequencies bears the risk of stimulating acoustic resonances inside the arc tube, which can result in low frequency light flicker and even lamp destruction. The acoustic streaming effect has been identified as the link between high frequency resonances and low frequency flicker. A highly coupled three-dimensional multiphysics model has been set up to calculate the acoustic streaming velocity field inside the arc tube of high-intensity discharge lamps. It has been found that the velocity field suffers a phase transition to an asymmetrical state at a critical acoustic streaming force. In certain respects the system behaves similar to a ferromagnet near the Curie point. It is discussed how the model allows to investigate the light flicker phenomenon. Concerning computer resources the procedure is considerably less demanding than a direct approach with a transient model.

  7. The Effects of the Impedance of the Flow Source on the Design of Tidal Stream Generators

    NASA Astrophysics Data System (ADS)

    Salter, S.

    2011-12-01

    The maximum performance of a wind turbine is set by the well-known Betz limit. If the designer of a wind turbine uses too fast a rotation, too large a blade chord or too high an angle of blade pitch, the air flow can take an easier path over or around the rotor. Most estimates of the tidal stream resource use equations borrowed from wind and would be reasonably accurate for a single unit. But water cannot flow through the seabed or over rotors which reach to the surface. If contra-rotating, vertical-axis turbines with a rectangular flow-window are placed close to one another and reach from the surface close to the seabed, the leakage path is blocked and they become more like turbines in a closed duct. Instead of an equation with area times velocity-cubed we should use the first power of volume flow rate though the rotor times the pressure difference across it. A long channel with a rough bed will already be losing lots of energy and will behave more like a high impedance flow. Attempts to block it with closely-packed turbines will increase the head across the turbines with only a small effect on flow rate. The same thing will occur if a close-packed line of turbines is built out to sea from a headland. It is necessary to understand the impedance of the flow source all the way out to mid-ocean. In deep seas where the current velocities at the seabed are too slow to disturb the ooze the friction coefficients will be similar to those of gloss paint, perhaps 0.0025. But the higher velocities in shallow water will remove ooze and quite large sediments leaving rough, bare rock and leading to higher friction-coefficients. Energy dissipation will be set by the higher friction coefficients and the cube of the higher velocities. The presence of turbines will reduce seabed losses and about one third of the present loss can be converted to electricity. The velocity reduction would be about 10%. In many sites the energy output will be far higher than the wind turbine equations

  8. Non-ideal Effects in Streaming Bi-Dust Acoustic Instability

    SciTech Connect

    Puerta, J.; Castro, E.; Martin, P.; Arias, H.

    2006-12-04

    Streaming dust acoustic instabilities in the presence of a dust beam in a weakly non-ideal dusty plasma have been studied considering a new form for the state equation with two kind of grains. Fluctuating charging effects are not considered in this work. Homogeneous dust-acoustic waves (DAWS) are studied for a perturbed plasma in a very low frequency regime, where dusty plasmas support new kind of waves and instabilities due to the dust collective dynamics. In this analysis a fluid model is used and electrons and ions are determined by their Boltzmann factors in order to find an adequate dispersion relation, which has several parameters depending of the state equation constants. In this paper we use the state equation structured by Ree and Hoover using Pade approximant for a hard-sphere gas in the form P = nT 1 + nb{sub 0} (1 + a{sub 1}b{sub 0}n + a{sub 2}b{sub 0}{sup 2}n{sup 2}/1 - b{sub 1}b{sub 0}n + b{sub 2}b{sub 0}{sup 2}n{sup 2}) is applied, where b0 is calculated by the second virial term for the hard-core model. This type of equation is more accurate than other expressions and easier to manipulate. Comparisons between the ideal and non ideal cases is performed. Constants a1, a2, b1, b2, are calculated with the Pade method. The onset of the instability and also the growth rates are studied in function of relevant parameters of the system as the radius of the grains and their densities. In our analysis the instability region for non ideal plasma is compared with that of the ideal ones.

  9. Cause and solution for false upstream boat velocities measured with a StreamPro acoustic doppler current profiler

    USGS Publications Warehouse

    Mueller, David S.; Rehmel, Mike S.; Wagner, Chad R.

    2007-01-01

    In 2003, Teledyne RD Instruments introduced the StreamPro acoustic Doppler current profiler which does not include an internal compass. During stationary moving-bed tests the StreamPro often tends to swim or kite from the end of the tether (the instrument rotates then moves laterally in the direction of the rotation). Because the StreamPro does not have an internal compass, it cannot account for the rotation. This rotation and lateral movement of the StreamPro on the end of the tether generates a false upstream velocity, which cannot be easily distinguished from a moving-bed bias velocity. A field test was completed to demonstrate that this rotation and lateral movement causes a false upstream boat velocity. The vector dot product of the boat velocity and the unit vector of the depth-averaged water velocity is shown to be an effective method to account for the effect of the rotation and lateral movement.

  10. Ensemble stream flow predictions using the ECMWF forecasts

    NASA Astrophysics Data System (ADS)

    Kiczko, Adam; Romanowicz, Renata; Osuch, Marzena; Pappenberger, Florian; Karamuz, Emilia

    2015-04-01

    Floods and low flows in rivers are seasonal phenomena that can cause several problems to society. To anticipate high and low flow events, flow forecasts are crucial. They are of particular importance in mountainous catchments, where the lead time of forecasts is usually short. In order to prolong the forecast lead-time, numerical weather predictions (NWPs) are used as a hydrological model driving force. The forecasted flow is commonly given as one value, even though it is uncertain. There is an increasing interest in accounting for the uncertainty in flood early warning and decision support systems. When NWP are given in the form of ensembles, such as the ECMWF forecasts, the uncertainty of these forecasts can be accounted for. Apart from the forecast uncertainty the uncertainty related to the hydrological model used also plays an important role in the uncertainty of the final flow prediction. The aim of this study is the development of a stream flow prediction system for the Biała Tarnowska, a mountainous catchment in the south of Poland. We apply two different hydrological models. One is a conceptual HBV model for rainfall-flow predictions, applied within a Generalised Likelihood Uncertainty Estimation (GLUE) framework, the second is a data-based DBM model, adjusted for Polish conditions by adding the Soil Moisture Accounting (SMA) and snow-melt modules. Both models provide the uncertainty of the predictions, but the DBM approach is much more numerically efficient, therefore more suitable for the real-time forecasting.. The ECMWF forecasts require bias reduction in order to correspond to observations. Therefore we applied Quantile Mapping with and without seasonal adjustment for bias correction. Up to seven-days ahead forecast skills are compared using the Relative Operation Characteristic (ROC) graphs, for the flood warning and flood alarm flow value thresholds. The ECMWF forecasts are obtained from the project TIGGE (http

  11. Stream responses as the sum of flow component responses

    NASA Astrophysics Data System (ADS)

    Stewart, Michael

    2014-05-01

    Catchment flows are often treated as continuums of hydrological processes from low flow to peak flow and back to low flow again, when analysing streamflow by methods like recession analysis or flow duration curve analysis. Such a conception of catchment response could not be further from the truth, catchment drainage instead is the sum of various flow components deriving from different parts of the catchment, as is well-understood by modellers. Why then have we traditionally applied the analysis methods to streamflow rather than to the separated components? (Apart, that is, for practical reasons.) Applying recession analyses to separated components turns out to give surprising results, and removes confusion arising from the mixture of components in streamflow (Stewart, 2014). The simplest separation of components is into quickflow and baseflow, which have very different sources and behaviours as shown in particular by tracer measurements. Quickflow is direct runoff from runoff events and often drops to zero between events, while baseflow is sourced from groundwater aquifers and continues as long as the stream flows. As an example, recession analysis using recession plots (i.e. plots of Q (flow) versus -dQ/dt) for quickflow and baseflow was applied to data from Glendhu GH1, New Zealand, a schist catchment of 2.2 km2. Whereas the streamflow points were fitted by power law slopes of up to 4 (i.e. dQ/dt = -0.09Q4) which proved to be artifacts due to the mixing of components noted above, the quickflow and baseflow points fitted power law slopes of 1.5 revealing the actual quadratic nature of storage reservoirs in the catchment. Other catchments have given similar results although a wider selection may show differences, nevertheless the message remains: In order to understand catchment and hillslope responses we need to be analysing separated components, not just streamflow. Stewart, M.K. 2014: New base flow separation and recession analysis methods for streamflow

  12. Characterizing the Drivers of Intermittent Flow in Arctic Alaska Streams

    NASA Astrophysics Data System (ADS)

    Betts, E.; Kane, D. L.; Stephan, N.

    2012-12-01

    Fish and wildlife species in the Arctic have developed life history strategies to deal with the extreme climate of the North. In the case of Arctic grayling, these strategies include long life, yearly spawning and migration.. In order to understand how such a species will be affected by a changing climate, we must first determine how these adaptive strategies may be at odds with the changing Arctic landscape. Arctic grayling migrate to spawning grounds just after spring break-up; then they migrate to feeding sites in early summer and finally in the fall migrate back to their overwintering sites. Low precipitation and high evapotranspiration rates during the summer can lead to low water levels and a fragmentation of the hydrologic landscape. This fragmentation creates a barrier to fish migration. The Kuparuk River is a perennial stream originating in the foothills of the Brooks Range on the North Slope of Alaska. The basin is underlain by continuous permafrost which essentially blocks the surface system from interacting with the subpermafrost groundwater system. Shallow subsurface flow occurs in the active layer, that area above permafrost which undergoes seasonal thawing in the summer. Sections of the Kuparuk are intermittent in that during low flows in the system these reaches appear dry (no flow in channel). Water reappears in the channel, downstream of these dry reaches, and it is believed that water continues to flow below the surface through the unfrozen thaw bulb beneath these reaches. These dry reaches act as summer barriers to fish migration within the Kuparuk River system. Previous research of this phenomenon sought to understand the location and timing of these dry events. The current research to be presented here attempts to determine the drivers of these dry channel events. Dye tracers and discharge measurements are used to determine the amount of hyporheic flow along these dry reaches and a statistical model incorporating soil moisture, precipitation

  13. Adequacy of satellite derived rainfall data for stream flow modeling

    USGS Publications Warehouse

    Artan, G.; Gadain, Hussein; Smith, Jody L.; Asante, Kwasi; Bandaragoda, C.J.; Verdin, J.P.

    2007-01-01

    Floods are the most common and widespread climate-related hazard on Earth. Flood forecasting can reduce the death toll associated with floods. Satellites offer effective and economical means for calculating areal rainfall estimates in sparsely gauged regions. However, satellite-based rainfall estimates have had limited use in flood forecasting and hydrologic stream flow modeling because the rainfall estimates were considered to be unreliable. In this study we present the calibration and validation results from a spatially distributed hydrologic model driven by daily satellite-based estimates of rainfall for sub-basins of the Nile and Mekong Rivers. The results demonstrate the usefulness of remotely sensed precipitation data for hydrologic modeling when the hydrologic model is calibrated with such data. However, the remotely sensed rainfall estimates cannot be used confidently with hydrologic models that are calibrated with rain gauge measured rainfall, unless the model is recalibrated. ?? Springer Science+Business Media, Inc. 2007.

  14. Ensemble stream flow predictions, a way towards better hydrological forecasting

    NASA Astrophysics Data System (ADS)

    Edlund, C.

    2009-04-01

    The hydrological forecasting division at SMHI has been using hydrological EPS and hydrological probabilities forecasts operationally since some years ago. The inputs to the hydrological model HBV are the EPS forecasts from ECMWF. From the ensemble, non-exceedance probabilities are estimated and final correction of the ensemble spread, based on evaluation is done. Ensemble stream flow predictions are done for about 80 indicator basins in Sweden, where there is a real-time discharge gauge. The EPS runs are updated daily against the latest observed discharge. Flood probability maps for exceeding a certain threshold, i.e. a certain warning level, are produced automatically once a day. The flood probabilistic forecasts are based on a HBV- model application, (called HBV-Sv, HBV Sweden) that covers the whole country and consist of 1001 subbasins with an average size between 200 and 700 km2. Probabilities computations for exceeding a certain warning level are made for each one of these 1001 subbasins. Statistical flood levels have been calculated for each river sub-basin. Hydrological probability forecasts should be seen as an early warning product that can give better support in decision making to end-users communities, for instance Civil Protections Offices and County Administrative Boards, within flood risk management. The main limitations with probability forecasts are: on one hand, difficulties to catch small-scale rain (mainly due to resolution of meteorological models); on the other hand, the hydrological model can't be updated against observations in all subbasins. The benefits of working with probabilities consist, first of all, of a new approach when working with flood risk management and scenarios. A probability forecast can give an early indication for Civil Protection that "something is going to happen" and to gain time in preparing aid operations. The ensemble stream flow prediction at SMHI is integrated with the national forecasting system and the products

  15. Imaging the position-dependent 3D force on microbeads subjected to acoustic radiation forces and streaming.

    PubMed

    Lamprecht, Andreas; Lakämper, Stefan; Baasch, Thierry; Schaap, Iwan A T; Dual, Jurg

    2016-07-01

    Acoustic particle manipulation in microfluidic channels is becoming a powerful tool in microfluidics to control micrometer sized objects in medical, chemical and biological applications. By creating a standing acoustic wave in the channel, the resulting pressure field can be employed to trap or sort particles. To design efficient and reproducible devices, it is important to characterize the pressure field throughout the volume of the microfluidic device. Here, we used an optically trapped particle as probe to measure the forces in all three dimensions. By moving the probe through the volume of the channel, we imaged spatial variations in the pressure field. In the direction of the standing wave this revealed a periodic energy landscape for 2 μm beads, resulting in an effective stiffness of 2.6 nN m(-1) for the acoustic trap. We found that multiple fabricated devices showed consistent pressure fields. Surprisingly, forces perpendicular to the direction of the standing wave reached values of up to 20% of the main-axis-values. To separate the direct acoustic force from secondary effects, we performed experiments with different bead sizes, which attributed some of the perpendicular forces to acoustic streaming. This method to image acoustically generated forces in 3D can be used to either minimize perpendicular forces or to employ them for specific applications in novel acoustofluidic designs. PMID:27302661

  16. Influence of acoustic streaming on ultrasonic particle manipulation in a 100-well ring-transducer microplate

    NASA Astrophysics Data System (ADS)

    Ohlin, Mathias; Christakou, Athanasia E.; Frisk, Thomas; Önfelt, Björn; Wiklund, Martin

    2013-03-01

    We characterize and quantify the performance of ultrasonic particle aggregation and positioning in a 100-well microplate. We analyze the result when operating a planar ultrasonic ring transducer at different single actuation frequencies in the range 2.20-2.40 MHz, and compare with the result obtained from different schemes of frequency-modulated actuation. Compared to our previously used wedge transducer design, the ring transducer has a larger contact area facing the microplate, resulting in lower temperature increase for a given actuation voltage. Furthermore, we analyze the dynamics of acoustic streaming occurring simultaneously with the particle trapping in the wells of the microplate, and we define an adaptive ultrasonic actuation scheme for optimizing both efficiency and robustness of the method. The device is designed as a tool for ultrasound-mediated cell aggregation and positioning. This is a method for high-resolution optical characterization of time-dependent cellular processes at the level of single cells. In this paper, we demonstrate how to operate our device in order to optimize the scanning time of 3D confocal microscopy with the aim to perform high-resolution time-lapse imaging of cells or cell-cell interactions in a highly parallel manner.

  17. 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.

  18. 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.

  19. Acoustic forcing on swirling flow: experiments and simulation

    NASA Astrophysics Data System (ADS)

    Hubschmid, W.; Denisov, A.; Biagioli, F.

    2014-09-01

    We investigated the effect of sound irradiated from loudspeakers on the flow of preheated air in the combustion chamber of a swirl burner. The temporally periodic pattern of the flow generated by the sound was detected by fast particle image velocimetry (PIV), with a repetition rate that was adapted to the observation of 12 phase angles of the irradiated monochromatic sound. The strong observed movement of the air is related to the movement by the sound itself, as determined by the pressure measurements with microphones. The PIV measurements reveal also a nonlinear interaction between the irradiated sound and the precession of the vortex core. The accuracy of the sound measurements was tested by determining in quiescent air the acoustic velocity by microphones and as well by PIV; good agreement was obtained thereby. Numerical calculations, using large eddy simulation and accounting for the sound forcing by variation in the mass flow at the inlet of the computational domain, approximately reproduce some of the experimental results.

  20. Factors influencing the stream-aquifer flow exchange coefficient.

    PubMed

    Morel-Seytoux, Hubert J; Mehl, Steffen; Morgado, Kyle

    2014-01-01

    Knowledge of river gain from or loss to a hydraulically connected water table aquifer is crucial in issues of water rights and also when attempting to optimize conjunctive use of surface and ground waters. Typically in groundwater models this exchange flow is related to a difference in head between the river and some point in the aquifer, through a "coefficient." This coefficient has been defined differently as well as the location for the head in the aquifer. This paper proposes a new coefficient, analytically derived, and a specific location for the point where the aquifer head is used in the difference. The dimensionless part of the coefficient is referred to as the SAFE (stream-aquifer flow exchange) dimensionless conductance. The paper investigates the factors that influence the value of this new conductance. Among these factors are (1) the wetted perimeter of the cross-section, (2) the degree of penetration of the cross-section, and (3) the shape of the cross-section. The study shows that these factors just listed are indeed ordered in their respective level of importance. In addition the study verifies that the analytical correct value of the coefficient is matched by finite difference simulation only if the grid system is sufficiently fine. Thus the use of the analytical value of the coefficient is an accurate and efficient alternative to ad hoc estimates for the coefficient typically used in finite difference and finite element methods. PMID:24010703

  1. 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.

  2. Prediction of Stream Flow in Ungauged Basins - a Comprehensive Framework

    NASA Astrophysics Data System (ADS)

    Ganti, R.; Agarwal, V.; Shetty, A.

    2012-12-01

    It is well established that critical information on stream-flow is essential in reducing uncertainties in planning and design of various water resource projects. Lack of data, at the desired spatial and temporal resolution, poses an enormous challenge in developing meaningful prediction models. Powerful techniques like Artificial Neural Network (ANN) modeling provide reasonably accurate prediction models, however development of such models require substantial amount of past data. Currently, empirical equations developed across the span of several hundred years are used on a regionalized basis. These equations are usually very simple, allowing for easy application, however not very accurate. This limited accuracy can be attributed to the use of noisy data and inclusion of only limited stream-flow variables. This study is an attempt to process noisy data and incorporate catchment variables to improve the accuracy of existing relationships whilst maintaining their simplicity. This study presents a comprehensive framework starting from data-processing to data-analysis that enables the development of regionalized empirical equations. A case-study has been presented for the sub-basins in "Dakshina Kannada" (Coastal Karnataka, India). Firstly, the data has first been processed to remove any outliers and estimate missing values, by replacing missing values with the average values of the neighboring entries for discrete data-sets or by using Least Square principles (LS) for continuously distributed date. Secondly, the existing models have been improved based on the processed dataset obtained through Exploratory Data Analysis (EDA). Further, utilizing Principal Component Analysis (PCA) other important parameters have been identified. All these parameters have then been included to arrive at an "improved regionalized relationship". Finally, the improved regionalized relationships have been evaluated for their performance based on the Correlation Coefficient and Standard Error

  3. Estimating Flow-Duration and Low-Flow Frequency Statistics for Unregulated Streams in Oregon

    USGS Publications Warehouse

    Risley, John; Stonewall, Adam J.; Haluska, Tana

    2008-01-01

    Flow statistical datasets, basin-characteristic datasets, and regression equations were developed to provide decision makers with surface-water information needed for activities such as water-quality regulation, water-rights adjudication, biological habitat assessment, infrastructure design, and water-supply planning and management. The flow statistics, which included annual and monthly period of record flow durations (5th, 10th, 25th, 50th, and 95th percent exceedances) and annual and monthly 7-day, 10-year (7Q10) and 7-day, 2-year (7Q2) low flows, were computed at 466 streamflow-gaging stations at sites with unregulated flow conditions throughout Oregon and adjacent areas of neighboring States. Regression equations, created from the flow statistics and basin characteristics of the stations, can be used to estimate flow statistics at ungaged stream sites in Oregon. The study area was divided into 10 regression modeling regions based on ecological, topographic, geologic, hydrologic, and climatic criteria. In total, 910 annual and monthly regression equations were created to predict the 7 flow statistics in the 10 regions. Equations to predict the five flow-duration exceedance percentages and the two low-flow frequency statistics were created with Ordinary Least Squares and Generalized Least Squares regression, respectively. The standard errors of estimate of the equations created to predict the 5th and 95th percent exceedances had medians of 42.4 and 64.4 percent, respectively. The standard errors of prediction of the equations created to predict the 7Q2 and 7Q10 low-flow statistics had medians of 51.7 and 61.2 percent, respectively. Standard errors for regression equations for sites in western Oregon were smaller than those in eastern Oregon partly because of a greater density of available streamflow-gaging stations in western Oregon than eastern Oregon. High-flow regression equations (such as the 5th and 10th percent exceedances) also generally were more accurate

  4. Effects of Debris Flows on Stream Ecosystems of the Klamath Mountains, Northern California

    NASA Astrophysics Data System (ADS)

    Cover, M. R.; Delafuente, J. A.; Resh, V. H.

    2006-12-01

    We examined the long-term effects of debris flows on channel characteristics and aquatic food webs in steep (0.04-0.06 slope), small (4-6 m wide) streams. A large rain-on-snow storm event in January 1997 resulted in numerous landslides and debris flows throughout many basins in the Klamath Mountains of northern California. Debris floods resulted in extensive impacts throughout entire drainage networks, including mobilization of valley floor deposits and removal of vegetation. Comparing 5 streams scoured by debris flows in 1997 and 5 streams that had not been scoured as recently, we determined that debris-flows decreased channel complexity by reducing alluvial step frequency and large woody debris volumes. Unscoured streams had more diverse riparian vegetation, whereas scoured streams were dominated by dense, even-aged stands of white alder (Alnus rhombiflia). Benthic invertebrate shredders, especially nemourid and peltoperlid stoneflies, were more abundant and diverse in unscoured streams, reflecting the more diverse allochthonous resources. Debris flows resulted in increased variability in canopy cover, depending on degree of alder recolonization. Periphyton biomass was higher in unscoured streams, but primary production was greater in the recently scoured streams, suggesting that invertebrate grazers kept algal assemblages in an early successional state. Glossosomatid caddisflies were predominant scrapers in scoured streams; heptageniid mayflies were abundant in unscoured streams. Rainbow trout (Oncorhynchus mykiss) were of similar abundance in scoured and unscoured streams, but scoured streams were dominated by young-of-the-year fish while older juveniles were more abundant in unscoured streams. Differences in the presence of cold-water (Doroneuria) versus warm-water (Calineuria) perlid stoneflies suggest that debris flows have altered stream temperatures. Debris flows have long-lasting impacts on stream communities, primarily through the cascading effects of

  5. Flow Dynamics and Stability of the NE Greenland Ice Stream from Active Seismics and Radar

    NASA Astrophysics Data System (ADS)

    Riverman, K. L.; Alley, R. B.; Anandakrishnan, S.; Christianson, K. A.; Peters, L. E.; Muto, A.

    2015-12-01

    We find that dilatant till facilitates rapid ice flow in central Greenland, and regions of dryer till limit the expansion of ice flow. The Northeast Greenland Ice Stream (NEGIS) is the largest ice stream in Greenland, draining 8.4% of the ice sheet's area. Fast ice flow initiates near the ice sheet summit in a region of high geothermal heat flow and extends some 700km downstream to three outlet glaciers along the NE Coast. The flow pattern and stability mechanism of this ice stream are unique to others in Greenland and Antarctica, and merit further study to ascertain the sensitivity of this ice stream to future climate change. In this study, we present the results of the first-ever ground-based geophysical survey of the initiation zone of NEGIS. Based on radar and preliminary seismic data, Christianson et al. (2014, EPSL) propose a flow mechanism for the ice stream based on topographically driven hydropotential lows which generate 'sticky' regions of the bed under the ice stream margins. We further test this hypothesis using a 40km reflection seismic survey across both ice stream margins. We find that regions of 'sticky' bed as observed by the radar survey are coincident with regions of the bed with seismic returns indicating drier subglacial sediments. These findings are further supported by five amplitude-verses-offset seismic surveys indicating dilatant till within the ice stream and consolidated sediments within its margins.

  6. 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

  7. 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.

  8. 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.

  9. Scientists discover massive jet streams flowing inside the sun

    NASA Astrophysics Data System (ADS)

    1997-07-01

    These new findings will help them understand the famous sunspot cycle and associated increases in solar activity that can affect the Earth with power and communications disruptions. The observations are the latest made by the Solar Oscillations Investigation (SOI) group at Stanford University, CA, and they build on discoveries by the SOHO science team over the past year. "We have detected motion similar to the weather patterns in the Earth's atmosphere", said Dr. Jesper Schou of Stanford. "Moreover, in what is a completely new discovery, we have found a jet-like flow near the poles. This flow is totally inside the Sun. It is completely unexpected, and cannot be seen at the surface." "These polar streams are on a small scale, compared to the whole Sun, but they are still immense compared to atmospheric jet streams on the Earth", added Dr. Philip Scherrer, the SOI principal investigator at Stanford. "Ringing the Sun at about 75 degrees latitude, they consist of flattened oval regions about 30,000 kilometres across where material moves about ten percent (about 130 km/h) faster than its surroundings. Although these are the smallest structures yet observed inside the Sun, each is still large enough to engulf two Earths." Additionally, there are features similar to the Earth's trade winds on the surface of the Sun. The Sun rotates much faster at the equator than at the poles. However, Stanford researchers Schou and Dr. Alexander G. Kosovichev have found that there are belts in the northern and southern hemispheres where currents flow at different speeds relative to each other. Six of these gaseous bands move slightly faster than the material surrounding them. The solar belts are more than 65 thousand km across and they contain "winds" that move about 15 kilometres per hour relative to their surroundings. The first evidence of these belts was found more than a decade ago by Dr. Robert Howard of the Mount Wilson Observatory. The Stanford researchers have now shown that

  10. Scientists discover massive jet streams flowing inside the sun

    NASA Astrophysics Data System (ADS)

    1997-08-01

    These new findings will help them understand the famous sunspot cycle and associated increases in solar activity that can affect the Earth with power and communications disruptions. The observations are the latest made by the Solar Oscillations Investigation (SOI) group at Stanford University, CA, and they build on discoveries by the SOHO science team over the past year. "We have detected motion similar to the weather patterns in the Earth's atmosphere", said Dr. Jesper Schou of Stanford. "Moreover, in what is a completely new discovery, we have found a jet-like flow near the poles. This flow is totally inside the Sun. It is completely unexpected, and cannot be seen at the surface." "These polar streams are on a small scale, compared to the whole Sun, but they are still immense compared to atmospheric jet streams on the Earth", added Dr. Philip Scherrer, the SOI principal investigator at Stanford. "Ringing the Sun at about 75 degrees latitude, they consist of flattened oval regions about 30,000 kilometres across where material moves about ten percent (about 130 km/h) faster than its surroundings. Although these are the smallest structures yet observed inside the Sun, each is still large enough to engulf two Earths." Additionally, there are features similar to the Earth's trade winds on the surface of the Sun. The Sun rotates much faster at the equator than at the poles. However, Stanford researchers Schou and Dr. Alexander G. Kosovichev have found that there are belts in the northern and southern hemispheres where currents flow at different speeds relative to each other. Six of these gaseous bands move slightly faster than the material surrounding them. The solar belts are more than 65 thousand km across and they contain "winds" that move about 15 kilometres per hour relative to their surroundings. The first evidence of these belts was found more than a decade ago by Dr. Robert Howard of the Mount Wilson Observatory. The Stanford researchers have now shown that

  11. Stream flow, salmon and beaver dams: roles in the structuring of stream fish communities within an anadromous salmon dominated stream.

    PubMed

    Mitchell, Sean C; Cunjak, Richard A

    2007-11-01

    The current paradigm of fish community distribution is one of a downstream increase in species richness by addition, but this concept is based on a small number of streams from the mid-west and southern United States, which are dominated by cyprinids. Further, the measure of species richness traditionally used, without including evenness, may not be providing an accurate reflection of the fish community. We hypothesize that in streams dominated by anadromous salmonids, fish community diversity will be affected by the presence of the anadromous species, and therefore be influenced by those factors affecting the salmonid population. Catamaran Brook, New Brunswick, Canada, provides a long-term data set to evaluate fish community diversity upstream and downstream of an obstruction (North American beaver Castor canadensis dam complex), which affects distribution of Atlantic salmon Salmo salar. The Shannon Weiner diversity index and community evenness were calculated for sample sites distributed throughout the brook and over 15 years. Fish community diversity was greatest upstream of the beaver dams and in the absence of Atlantic salmon. The salmon appear to depress the evenness of the community but do not affect species richness. The community upstream of the beaver dams changes due to replacement of slimy sculpin Cottus cognatus by salmon, rather than addition, when access is provided. Within Catamaran Brook, location of beaver dams and autumn streamflow interact to govern adult Atlantic salmon spawner distribution, which then dictates juvenile production and effects on fish community. These communities in an anadromous Atlantic salmon dominated stream do not follow the species richness gradient pattern shown in cyprinid-dominated streams and an alternative model for stream fish community distribution in streams dominated by anadromous salmonids is presented. This alternative model suggests that community distribution may be a function of semipermeable obstructions

  12. Selected flow characteristics of streams in the Willamette River Basin, Oregon

    USGS Publications Warehouse

    Swift, C. H., III

    1966-01-01

    Flow-duration, annual low-flow, and annual high-flow tables through September 30, 1963, are given in this report for 110 stream-gaging stations in the Willamette and Sandy River basins. These tables summarize the basic data needed to define the streamflow characteristics at the gaging stations. The content of each of the three summary tables is described, and techniques for preparing flow-duration curves, low-flow frequency curves, and high-flow frequency curves are explained.

  13. Application of acoustic velocity meters for gaging discharge of three low-velocity tidal streams in the St. Johns River basin, northeast Florida

    USGS Publications Warehouse

    Sloat, J.V.; Gain, W.S.

    1995-01-01

    Index-velocity data collected with acoustic velocity meters, stage data, and cross-sectional area data were used to calculate discharge at three low-velocity, tidal streamflow stations in north-east Florida. Discharge at three streamflow stations was computed as the product of the channel cross-sectional area and the mean velocity as determined from an index velocity measured in the stream using an acoustic velocity meter. The tidal streamlflow stations used in the study were: Six Mile Creek near Picolata, Fla.; Dunns Creek near Satsuma, Fla.; and the St. Johns River at Buffalo Bluff. Cross-sectional areas at the measurement sections ranged from about 3,000 square feet at Six Mile Creek to about 18,500 square feet at St. Johns River at Buffalo Bluff. Physical characteristics for all three streams were similar except for drainage area. The topography primarily is low-relief, swampy terrain; stream velocities ranged from about -2 to 2 feet per second; and the average change in stage was about 1 foot. Instantaneous discharge was measured using a portable acoustic current meter at each of the three streams to develop a relation between the mean velocity in the stream and the index velocity measured by the acoustic velocity meter. Using least-squares linear regression, a simple linear relation between mean velocity and index velocity was determined. Index velocity was the only significant linear predictor of mean velocity for Six Mile Creek and St. Johns River at Buffalo Bluff. For Dunns Creek, both index velocity and stage were used to develop a multiple-linear predictor of mean velocity. Stage-area curves for each stream were developed from bathymetric data. Instantaneous discharge was computed by multiplying results of relations developed for cross-sectional area and mean velocity. Principal sources of error in the estimated discharge are identified as: (1) instrument errors associated with measurement of stage and index velocity, (2) errors in the representation of

  14. 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.

  15. A stream-gaging network analysis for the 7-Day, 10-year annual low flow in New Hampshire streams

    USGS Publications Warehouse

    Flynn, Robert H.

    2003-01-01

    The 7-day, 10-year (7Q10) low-flow-frequency statistic is a widely used measure of surface-water availability in New Hampshire. Regression equations and basin-characteristic digital data sets were developed to help water-resource managers determine surface-water resources during periods of low flow in New Hampshire streams. These regression equations and data sets were developed to estimate streamflow statistics for the annual and seasonal low-flow-frequency, and period-of-record and seasonal period-of-record flow durations. generalized-least-squares (GLS) regression methods were used to develop the annual 7Q10 low-flow-frequency regression equation from 60 continuous-record stream-gaging stations in New Hampshire and in neighboring States. In the regression equation, the dependent variables were the annual 7Q10 flows at the 60 stream-gaging stations. The independent (or predictor) variables were objectively selected characteristics of the drainage basins that contribute flow to those stations. In contrast to ordinary-least-squares (OLS) regression analysis, GLS-developed estimating equations account for differences in length of record and spatial correlations among the flow-frequency statistics at the various stations. A total of 93 measurable drainage-basin characteristics were candidate independent variables. On the basis of several statistical parameters that were used to evaluate which combination of basin characteristics contribute the most to the predictive power of the equations, three drainage-basin characteristics were determined to be statistically significant predictors of the annual 7Q10: (1) total drainage area, (2) mean summer stream-gaging station precipitation from 1961 to 90, and (3) average mean annual basinwide temperature from 1961 to 1990. To evaluate the effectiveness of the stream-gaging network in providing regional streamflow data for the annual 7Q10, the computer program GLSNET (generalized-least-squares NETwork) was used to analyze the

  16. 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.

  17. 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

  18. 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

  19. Flow-flame interactions causing acoustically coupled heat release fluctuations in a thermo-acoustically unstable gas turbine model combustor

    SciTech Connect

    Steinberg, A.M.; Boxx, I.; Stoehr, M.; Meier, W.; Carter, C.D.

    2010-12-15

    A detailed analysis of the flow-flame interactions associated with acoustically coupled heat-release rate fluctuations was performed for a 10 kW, CH{sub 4}/air, swirl stabilized flame in a gas turbine model combustor exhibiting self-excited thermo-acoustic oscillations at 308 Hz. High-speed stereoscopic particle image velocimetry, OH planar laser induced fluorescence, and OH* chemiluminescence measurements were performed at a sustained repetition rate of 5 kHz, which was sufficient to resolve the relevant combustor dynamics. Using spatio-temporal proper orthogonal decomposition, it was found that the flow-field contained several simultaneous periodic motions: the reactant flux into the combustion chamber periodically oscillated at the thermo-acoustic frequency (308 Hz), a helical precessing vortex core (PVC) circumscribed the burner nozzle at 515 Hz, and the PVC underwent axial contraction and extension at the thermo-acoustic frequency. The global heat release rate fluctuated at the thermo-acoustic frequency, while the heat release centroid circumscribed the combustor at the difference between the thermo-acoustic and PVC frequencies. Hence, the three-dimensional location of the heat release fluctuations depended on the interaction of the PVC with the flame surface. This motivated the compilation of doubly phase resolved statistics based on the phase of both the acoustic and PVC cycles, which showed highly repeatable periodic flow-flame configurations. These include flames stabilized between the inflow and inner recirculation zone, large-scale flame wrap-up by the PVC, radial deflection of the inflow by the PVC, and combustion in the outer recirculation zones. Large oscillations in the flame surface area were observed at the thermo-accoustic frequency that significantly affected the total heat-release oscillations. By filtering the instantaneous reaction layers at different scales, the importance of the various flow-flame interactions affecting the flame area was

  20. A preliminary design study on an acoustic muffler for the laminar flow transition research apparatus

    NASA Technical Reports Server (NTRS)

    Abrahamson, A. L.

    1984-01-01

    An acoustic muffler design of a research tool for studying laminar flow and the mechanisms of transition, the Laminar Flow and Transition Research Apparatus (LFTRA) is investigated. Since the presence of acoustic pressure fluctuations is known to affect transition, low background noise levels in the test section of the LFTRA are mandatory. The difficulties and tradeoffs of various muffler design concepts are discussed and the most promising candidates are emphasized.

  1. 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

  2. Hydrogeomorphic controls on hyporheic and riparian transport in two headwater mountain streams during base flow recession

    NASA Astrophysics Data System (ADS)

    Ward, Adam S.; Schmadel, Noah M.; Wondzell, Steven M.; Harman, Ciaran; Gooseff, Michael N.; Singha, Kamini

    2016-02-01

    Solute transport along riparian and hyporheic flow paths is broadly expected to respond to dynamic hydrologic forcing by streams, aquifers, and hillslopes. However, direct observation of these dynamic responses is lacking, as is the relative control of geologic setting as a control on responses to dynamic hydrologic forcing. We conducted a series of four stream solute tracer injections through base flow recession in each of two watersheds with contrasting valley morphology in the H.J. Andrews Experimental Forest, monitoring tracer concentrations in the stream and in a network of shallow riparian wells in each watershed. We found hyporheic mean arrival time, temporal variance, and fraction of stream water in the bedrock-constrained valley bottom and near large roughness elements in the wider valley bottom were not variable with discharge, suggesting minimal control by hydrologic forcing. Conversely, we observed increases in mean arrival time and temporal variance and decreasing fraction stream water with decreasing discharge near the hillslopes in the wider valley bottom. This may indicate changes in stream discharge and valley bottom hydrology control transport in less constrained locations. We detail five hydrogeomorphic responses to base flow recession to explain observed spatial and temporal patterns in the interactions between streams and their valley bottoms. Models able to account for the transition from geologically dominated processes in the near-stream subsurface to hydrologically dominated processes near the hillslope will be required to predict solute transport and fate in valley bottoms of headwater mountain streams.

  3. MODIFICATION OF STREAM FLOW ROUTING FOR BANK STORAGE

    EPA Science Inventory

    Bank storage is a process in which volumes of water are temporally retained by alluvial stream banks during flood events, and gradually released as baseflows. This process has implications on ground-water resource

  4. Techniques for estimating peak-flow frequency relations for North Dakota streams

    USGS Publications Warehouse

    Williams-Sether, Tara

    1992-01-01

    This report presents techniques for estimating peak-flow frequency relations for North Dakota streams. In addition, a generalized skew coefficient analysis was completed for North Dakota to test the validity of using the generalized skew coefficient map in Bulletin 17B of the Hydrology Subcommittee of the Interagency Advisory Committee on Water Data, 1982, 'Guidelines for Determining Flood Flow Frequency.' The analysis indicates that the generalized skew coefficient map in Bulletin 17B provides accurate estimates of generalized skew coefficient values for natural-flow streams in North Dakota. Peak-flow records through 1988 for 192 continuous- and partial-record streamflow gaging stations that had 10 or more years of record were used in a generalized least-squares regression analysis that relates peak flows for selected recurrence intervals to selected basin characteristics. Peak-flow equations were developed for recurrence intervals of 2, 10, 15, 25, 50, 100, and 500 years for three hydrologic regions in North Dakota. The peak-flow equations are applicable to natural-flow streams that have drainage areas of less than or equal to 1,000 square miles. The standard error of estimate for the three hydrologic regions ranges from 60 to 70 percent for the 100-year peak-flow equations. Methods are presented for transferring peak-flow data from gaging stations to ungaged sites on the same stream and for determining peak flows for ungaged sites on ungaged streams. Peak-flow relations, weighted estimates of peak flow, and selected basin characteristics are tabulated for the 192 gaging stations used in the generalized skew coefficient and regression analyses. Peak-flow relations also are provided for 63 additional gaging stations that were not used in the generalized skew coefficient and regression analyses. These 63 gaging stations generally represent streams that are significantly controlled by regulation and those that have drainage areas greater than 1,000 square miles.

  5. Forced flow of a vapor-liquid stream in a horizontal pipe with film boiling

    NASA Astrophysics Data System (ADS)

    Kalinin, É. K.; Panevin, V. I.; Firsov, V. P.

    1986-05-01

    The stream structure and flow regime during film boiling of liquid nitrogen in a horizontal pipe are investigated. Data on heat transfer are obtained and a model is proposed for calculating the parameters of the two-phase stream along the channel length.

  6. Flow variability and ongoing margin shifts on Bindschadler and MacAyeal Ice Streams, West Antarctica

    NASA Astrophysics Data System (ADS)

    Hulbe, C. L.; Scambos, T. A.; Klinger, M.; Fahnestock, M. A.

    2016-02-01

    Ice streams on the Ross Sea side of the West Antarctic Ice Sheet are known to experience flow variability on hourly, annual, and multicentury time scales. We report here on observations of flow variability at the decade scale on the Bindschadler and MacAyeal Ice Streams (BIS and MacIS). Our analysis makes use of archived ice velocity data and new mappings from composited Landsat 7 and Landsat 8 imagery that together span the interval from 1985 to 2014. Both ice streams speedup and slowdown in a range of about ±5 m a-2 over our various comparison intervals. The rates of change are variable in both time and space, and there is no evidence of external forcing at work across the two streams. Widespread changes are most likely linked to instability in the subglacial till and/or subglacial water flow. Sticky spots near the confluence of the two ice streams are loci for speed changes. These relatively young and slow-flowing features appear to be forcing shifts in margin position near the outlets of both streams. The margin jumps reduce the effective outlet widths of the streams by 20% and 30% on BIS and MacIS, respectively. Those magnitudes are similar to the outlet narrowing experienced by Kamb Ice Stream prior to its stagnation.

  7. HOW WELL CAN YOU ESTIMATE LOW FLOW AND BANKFULL DISCHARGE FROM STREAM CHANNEL HABITAT DATA?

    EPA Science Inventory

    Modeled estimates of stream discharge are becoming more important because of reductions in the number of gauging stations and increases in flow alteration from land development and climate change. Field measurements of channel morphology are available at thousands of streams and...

  8. HYDRAULIC ANALYSIS OF BASE-FLOW AND BANK STORAGE IN ALLUVIAL STREAMS

    EPA Science Inventory

    This paper presents analytical solutions, which describe the effect of time-variable net recharge (net accretion to water table) and bank storage in alluvial aquifers on the sustenance of stream flows during storm and inter-storm events. The solutions relate the stream discharge,...

  9. 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.

  10. The influence of stream thermal regimes and preferential flow paths on hyporheic exchange in a glacial meltwater stream

    NASA Astrophysics Data System (ADS)

    Cozzetto, Karen D.; Bencala, Kenneth E.; Gooseff, Michael N.; McKnight, Diane M.

    2013-09-01

    Given projected increases in stream temperatures attributable to global change, improved understanding of relationships between stream temperatures and hyporheic exchange would be useful. We conducted two conservative tracer injection experiments in a glacial meltwater stream, to evaluate the effects of hyporheic thermal gradients on exchange processes, including preferential flow paths (PFPs). The experiments were conducted on the same day, the first (a stream injection) during a cool, morning period and the second (dual stream and hyporheic injections) during a warm, afternoon period. In the morning, the hyporheic zone was thermally uniform at 4°C, whereas by the afternoon the upper 10 cm had warmed to 6-12°C and exhibited greater temperature heterogeneity. Solute transport modeling showed that hyporheic cross-sectional areas (As) at two downstream sites were two and seven times lower during the warm experiment. Exchange metrics indicated that the hyporheic zone had less influence on downstream solute transport during the warm, afternoon experiment. Calculated hyporheic depths were less than 5 cm, contrasting with tracer detection at 10 and 25 cm depths. The hyporheic tracer arrival at one downstream site was rapid, comparable to the in-stream tracer arrival, providing evidence for PFPs. We thus propose a conceptual view of the hyporheic zone in this reach as being dominated by discrete PFPs weaving through hydraulically isolated areas. One explanation for the simultaneous increase in temperature heterogeneity and As decrease in a warmer hyporheic zone may be a flow path preferentiality feedback mechanism resulting from a combination of temperature-related viscosity decreases and streambed heterogeneity.

  11. CURRENT FLOW DATA FOR SELECTED USGS STREAM MONITORING STATIONS IN WASHINGTON STATE

    EPA Science Inventory

    This data set contains recent stream flow data for USGS stations in Washington State. Flow data (cubic feet per second) are available for the most recent 5-6 day period and are compared with long-term average values. Flow data were collected approximately hourly. Flood stage and ...

  12. Best Practices for Continuous Monitoring of Temperature and Flow in Wadeable Streams (Final Report)

    EPA Science Inventory

    This final report is a technical "best practices" document describing sensor deployment for and collection of continuous temperature and flow data at ungaged sites in wadeable streams. This document addresses questions related to equipment needs; configuration, placement, and ins...

  13. Subglacial water flow inferred from stream measurements at South Cascade Glacier, Washington, USA

    USGS Publications Warehouse

    Fountain, A.G.

    1992-01-01

    Comparisons of water discharge and cation load in each of the two main streams indicate that subglacial hydraulic processes differ between drainage basins. One stream drains from a conduit that is isolated in its lower reach from the surrounding subglacial region and receives water routed englacially from the surface. The upper reach of the conduit also receives water rounted englacially from the surface as well as from a distributed subglacial flow system. The other main stream drains from a conduit coupled to a debris layer beneath the glacier. Observations of the layer in natural ice tunnels indicate that the water may flow within a thin layer of debris. A one-dimensional model of flow through the debris layer can explain both the base-flow and diurnal variations of the second main stream. -from Author

  14. Best Practices for Continuous Monitoring of Temperature and Flow in Wadeable Streams (External Review Draft)

    EPA Science Inventory

    This external review draft report is a technical "best practices" document describing sensor deployment for and data collection of continuous temperature and flow at ungaged sites in wadeable streams. This document addresses questions related to equipment needs; configuration, pl...

  15. A quest for macroinvertebrate indicators of flow conditions in small, suburban stream

    EPA Science Inventory

    Alteration of hydrologic variability is considered a key pathway by which urbanization affects stream assemblages; however, understanding the mechanisms of alteration remains a challenge. One approach is to identify biological metrics that show distinct responses to flows, which ...

  16. Organic carbon flow in a swamp-stream ecosystem

    SciTech Connect

    Mulholland, P.J.

    1981-01-01

    An annual organic carbon budget is presented for an 8-km segment of Creeping Swamp, an undisturbed, third-order swamp-stream in the Coastal Plain of North Carolina, USA. Annual input of organic carbon (588 gC/m/sup 2/) was 96% allochthonous and was dominated by leaf litter inputs (36%) and fluvial, dissolved organic carbon (DOC) inputs (31%). Although the swamp-stream was primarily heterotrophic, autochthonous organic carbon input, primarily from filamentous algae, was important during February and March when primary production/ecosystem respiration (P/R) ratios of the flooded portions were near one. Annual output of organic carbon via fluvial processes (214 gC/m/sup 2/), 95% as DOC, was 36% of total annual inputs, indicating that the swamp-stream segment ecosystem was 64% efficient at retaining organic carbon. Organic carbon dynamics in the Creeping Swamp segment were compared to those reported for upland stream segments using indices of organic matter processing suggested by Fisher (1977) and a loading potential index suggested here. Creeping Swamp, while loading at a high rate, retains a much larger portion of its organic carbon inputs than two upland streams. Despite the high degree of retention and oxidation of organic inputs to Creeping Swamp, there is a net annual fluvial export of 21 gC/m/sup 2/, mostly in the dissolved form. Watersheds drained by swamp-streams in the southeastern United States are thought to have large organic carbon exports compared to upland forested drainages, because the stream network covers a much greater proportion of the total watershed area.

  17. Acoustic tests of a 15.2 centimeter-diameter potential flow convergent nozzle

    NASA Technical Reports Server (NTRS)

    Karchmer, A. M.; Dorsch, R. G.; Friedman, R.

    1974-01-01

    An experimental investigation of the jet noise radiated to the far field from a 15.2-cm-diam potential flow convergent nozzle has been conducted. Tests were made with unheated airflow over a range of subsonic nozzle exhaust velocities from 62 to 310m/sec. Mean and turbulent velocity measurements in the flow field of the nozzle exhaust indicated no apparent flow anomalies. Acoustic measurements yielded data uncontaminated by internal and/or background noise to velocities as low as 152m/sec. Finally, no significantly different acoustic characteristics between the potential flow nozzle and simple convergent nozzles were found.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

  19. Numerical Experiments on Acoustic Reciprocity in Compressible Potential Flows in Ducts

    NASA Astrophysics Data System (ADS)

    EVERSMAN, W.

    2001-09-01

    A reciprocity theorem for the scattering matrix for the propagation of acoustic modes in a duct with acoustically hard walls or with acoustically absorbing walls has been given in a companion publication. It was found that for a source at a specified end of the duct, suitably scaled reflection matrices in direct and reverse flow have a reciprocal relationship. Scaled transmission matrices obtained for direct flow and reversed flow with simultaneous switching of source location from one end to the other also have a reciprocal relationship. A reverse flow theorem for the equivalent one-dimensional propagation model, which is a good approximation to the three-dimensional model at low frequencies, was also obtained. In this case, using reciprocity and acoustic power conservation arguments it is additionally found that the acoustic power transmission coefficient is the same for a source at either end of the duct for a given flow direction. This result leads to an invariance theorem which relates acoustic power propagated due to sources of equal pressure amplitude at the two ends of the duct. A numerical verification of these reciprocal relationships is given here for propagation in axially symmetric (circular and annular) ducts with multi-modal propagation and at low frequencies when a one-dimensional model is appropriate.

  20. Characterising temporary streams' regimes using qualitative "aquatic states" instead of quantitative flow measures.

    NASA Astrophysics Data System (ADS)

    Gallart, F.; Prat, N.

    2012-04-01

    The analysis of the biological communities found in stream reaches is currently used for the assessment of the quality of stream waters. Nevertheless, in temporary streams, these communities are largely varying in time, strongly depending on the occurrence of the sets of aquatic mesohabitats determined by the hydrological conditions (hereafter called Aquatic States). Particularly, the interruption of the flow in a stream, or even its total desiccation, plays a determinant role in their ecological communities so much so that temporary streams should be considered a distinct class of ecosystems instead of simply hydrologically challenged permanent streams. Within the EU MIRAGE project (grant FP7 n° 211732), two complementary tools have been developed to analyse and characterise the regime of temporary streams: the Aquatic States Frequency Graph (ASFG) that shows the monthly frequency of occurrence of the diverse Aquatic States throughout the year, and the Temporary Stream Regime Plot (TSRP) that maps the value of two metrics that describe respectively the relative number of months with flow per year (Mf) and the seasonal predictability of the zero-flow periods (Sd6). The ASFG allows a rapid appraisal of the stream regime relevant for the development of the aquatic life and is useful for anticipating the sampling calendars but is somewhat dependent of the subjective criteria of the observer. On the contrary, the TSRP manages much less information but allows the comparison and classification of the regimes and is based on the more objective criterion of the presence-absence of flow. In the case of lack of observations, rainfall-runoff models may be used to develop these analyses, although a threshold value for zero flow must be assessed as models usually do not simulate the absence of flow.

  1. Development of the Hydroecological Integrity Assessment Process for Determining Environmental Flows for New Jersey Streams

    USGS Publications Warehouse

    Kennen, Jonathan G.; Henriksen, James A.; Nieswand, Steven P.

    2007-01-01

    The natural flow regime paradigm and parallel stream ecological concepts and theories have established the benefits of maintaining or restoring the full range of natural hydrologic variation for physiochemical processes, biodiversity, and the evolutionary potential of aquatic and riparian communities. A synthesis of recent advances in hydroecological research coupled with stream classification has resulted in a new process to determine environmental flows and assess hydrologic alteration. This process has national and international applicability. It allows classification of streams into hydrologic stream classes and identification of a set of non-redundant and ecologically relevant hydrologic indices for 10 critical sub-components of flow. Three computer programs have been developed for implementing the Hydroecological Integrity Assessment Process (HIP): (1) the Hydrologic Indices Tool (HIT), which calculates 171 ecologically relevant hydrologic indices on the basis of daily-flow and peak-flow stream-gage data; (2) the New Jersey Hydrologic Assessment Tool (NJHAT), which can be used to establish a hydrologic baseline period, provide options for setting baseline environmental-flow standards, and compare past and proposed streamflow alterations; and (3) the New Jersey Stream Classification Tool (NJSCT), designed for placing unclassified streams into pre-defined stream classes. Biological and multivariate response models including principal-component, cluster, and discriminant-function analyses aided in the development of software and implementation of the HIP for New Jersey. A pilot effort is currently underway by the New Jersey Department of Environmental Protection in which the HIP is being used to evaluate the effects of past and proposed surface-water use, ground-water extraction, and land-use changes on stream ecosystems while determining the most effective way to integrate the process into ongoing regulatory programs. Ultimately, this scientifically defensible

  2. 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.

  3. 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.

  4. 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.

  5. Incompressible flow computations based on the vorticity-stream function and velocity-pressure formulations

    NASA Technical Reports Server (NTRS)

    Tezduyar, T. E.; Liou, J.; Ganjoo, D. K.

    1990-01-01

    Finite element procedures and computations based on the velocity-pressure and vorticity-stream function formulations of incompressible flows are presented. Two new multistep velocity-pressure formulations are proposed and compared with the vorticity-stream function and one-step formulations. The example problems chosen are the standing vortex problem and flow past a circular cylinder. Benchmark quality computations are performed for the cylinder problem. The numerical results indicate that the vorticity-stream function formulation and one of the two new multistep formulations involve much less numerical dissipation than the one-step formulation.

  6. Flow Durations, Low-Flow Frequencies, and Monthly Median Flows for Selected Streams in Connecticut through 2005

    USGS Publications Warehouse

    Ahearn, Elizabeth A.

    2008-01-01

    Flow durations, low-flow frequencies, and monthly median streamflows were computed for 91 continuous-record, streamflow-gaging stations in Connecticut with 10 or more years of record. Flow durations include the 99-, 98-, 97-, 95-, 90-, 85-, 80-, 75-, 70-, 60-, 50-, 40-, 30-, 25-, 20-, 10-, 5-, and 1-percent exceedances. Low-flow frequencies include the 7-day, 10-year (7Q10) low flow; 7-day, 2-year (7Q2) low flow; and 30-day, 2-year (30Q2) low flow. Streamflow estimates were computed for each station using data for the period of record through water year 2005. Estimates of low-flow statistics for 7 short-term (operated between 3 and 10 years) streamflow-gaging stations and 31 partial-record sites were computed. Low-flow estimates were made on the basis of the relation between base flows at a short-term station or partial-record site and concurrent daily mean streamflows at a nearby index station. The relation is defined by the Maintenance of Variance Extension, type 3 (MOVE.3) method. Several short-term stations and partial-record sites had poorly defined relations with nearby index stations; therefore, no low-flow statistics were derived for these sites. The estimated low-flow statistics for the short-term stations and partial-record sites include the 99-, 98-, 97-, 95-, 90-, and 85-percent flow durations; the 7-day, 10-year (7Q10) low flow; 7-day, 2-year (7Q2) low flow; and 30-day, 2-year (30Q2) low-flow frequencies; and the August median flow. Descriptive information on location and record length, measured basin characteristics, index stations correlated to the short-term station and partial-record sites, and estimated flow statistics are provided in this report for each station. Streamflow estimates from this study are stored on USGS's World Wide Web application 'StreamStats' (http://water.usgs.gov/osw/streamstats/connecticut.html).

  7. Relation of streams, lakes, and wetlands to groundwater flow systems

    NASA Astrophysics Data System (ADS)

    Winter, Thomas C.

    Surface-water bodies are integral parts of groundwater flow systems. Groundwater interacts with surface water in nearly all landscapes, ranging from small streams, lakes, and wetlands in headwater areas to major river valleys and seacoasts. Although it generally is assumed that topographically high areas are groundwater recharge areas and topographically low areas are groundwater discharge areas, this is true primarily for regional flow systems. The superposition of local flow systems associated with surface-water bodies on this regional framework results in complex interactions between groundwater and surface water in all landscapes, regardless of regional topographic position. Hydrologic processes associated with the surface-water bodies themselves, such as seasonally high surface-water levels and evaporation and transpiration of groundwater from around the perimeter of surface-water bodies, are a major cause of the complex and seasonally dynamic groundwater flow fields associated with surface water. These processes have been documented at research sites in glacial, dune, coastal, mantled karst, and riverine terrains. Résumé Les eaux de surface sont parties intégrantes des systèmes aquifères. Les eaux souterraines interagissent avec les eaux de surface dans presque tous les types d'environnements, depuis les petits ruisseaux, les lacs et les zones humides jusqu'aux bassins versants des vallées des grands fleuves et aux lignes de côte. Il est en général admis que les zones topographiquement hautes sont des lieux de recharge des aquifères et les zones basses des lieux de décharge, ce qui est le cas des grands systèmes aquifères régionaux. La superposition de systèmes locaux, associés à des eaux de surface, à l'organisation régionale d'écoulements souterrains résulte d'interactions complexes entre les eaux souterraines et les eaux de surface dans tous les environnements, quelle que soit la situation topographique régionale. Les processus

  8. Solute transport processes in flow-event-driven stream-aquifer interaction

    NASA Astrophysics Data System (ADS)

    Xie, Yueqing; Cook, Peter G.; Simmons, Craig T.

    2016-07-01

    The interaction between streams and groundwater controls key features of the stream hydrograph and chemograph. Since surface runoff is usually less saline than groundwater, flow events are usually accompanied by declines in stream salinity. In this paper, we use numerical modelling to show that, at any particular monitoring location: (i) the increase in stream stage associated with a flow event will precede the decrease in solute concentration (arrival time lag for solutes); and (ii) the decrease in stream stage following the flow peak will usually precede the subsequent return (increase) in solute concentration (return time lag). Both arrival time lag and return time lag increase with increasing wave duration. However, arrival time lag decreases with increasing wave amplitude, whereas return time lag increases. Furthermore, while arrival time lag is most sensitive to parameters that control river velocity (channel roughness and stream slope), return time lag is most sensitive to groundwater parameters (aquifer hydraulic conductivity, recharge rate, and dispersitivity). Additionally, the absolute magnitude of the decrease in river concentration is sensitive to both river and groundwater parameters. Our simulations also show that in-stream mixing is dominated by wave propagation and bank storage processes, and in-stream dispersion has a relatively minor effect on solute concentrations. This has important implications for spreading of contaminants released to streams. Our work also demonstrates that a high contribution of pre-event water (or groundwater) within the flow hydrograph can be caused by the combination of in-stream and bank storage exchange processes, and does not require transport of pre-event water through the catchment.

  9. Passive control of flow-excited acoustic resonance in rectangular cavities using upstream mounted blocks

    NASA Astrophysics Data System (ADS)

    Shaaban, Mahmoud; Mohany, Atef

    2015-04-01

    A passive method for controlling the flow-excited acoustic resonance resulting from subsonic flows over rectangular cavities in channels is investigated. A cavity with length to depth ratio of is tested in air flow of Mach number up to 0.45. When the acoustic resonance is excited, the sound pressure level in the cavity reaches 162 dB. Square blocks are attached to the surface of the channel and centred upstream of the cavity leading edge to suppress the flow-excited acoustic resonance in the cavity. Six blocks of different widths are tested at three different upstream distances. The results show that significant attenuation of up to 30 dB of the excited sound pressure level is achieved using a block with a width to height ratio of 3, while blocks that fill the whole width of the channel amplify the pressure of the excited acoustic resonance. Moreover, it is found that placing the block upstream of the cavity causes the onset of the acoustic resonance to occur at higher flow velocities. In order to investigate the nature of the interactions that lead to suppression of the acoustic resonance and to identify the changes in flow patterns due to the placement of the block, 2D measurements of turbulence intensity in the shear layer and the block wake region are performed. The location of the flow reattachment point downstream of the block relative to the shear layer separation point has a major influence on the suppression level of the excited acoustic resonance. Furthermore, higher attenuation of noise is related to lower span-wise correlation of the shear-layer perturbation.

  10. ON THE HYDRAULICS OF STREAM FLOW ROUTING WITH BANK STORAGE

    EPA Science Inventory

    Bank storage is a process in which volumes of water are temporally retained by alluvial stream banks during flood events, and gradually released to partially sustain baseflow. This process has important hydrologic and ecological implications. In this paper, analytical solutions a...

  11. Availability and Distribution of Base Flow in Lower Honokohau Stream, Island of Maui

    USGS Publications Warehouse

    Fontaine, Richard A.

    2003-01-01

    Honokohau Stream is one of the few perennial streams in the Lahaina District of West Maui. Current Honokohau water-use practices often lead to conflicts among water users, which are most evident during periods of base flow. To better manage the resource, data are needed that describe the availability and distribution of base flow in lower Honokohau Stream and how base flow is affected by streamflow diversion and return-flow practices. Flow-duration discharges for percentiles ranging from 50 to 95 percent were estimated at 13 locations on lower Honokohau Stream using data from a variety of sources. These sources included (1) available U.S. Geological Survey discharge data, (2) published summaries of Maui Land & Pineapple Company, Inc. diversion and water development-tunnel data, (3) seepage run and low-flow partial-record discharge measurements made for this study, and (4) current (2003) water diversion and return-flow practices. These flow-duration estimates provide a detailed characterization of the distribution and availability of base flow in lower Honokohau Stream. Estimates of base-flow statistics indicate the significant effect of Honokohau Ditch diversions on flow in the stream. Eighty-six percent of the total flow upstream from the ditch is diverted from the stream. Immediately downstream from the diversion dam there is no flow in the stream 91.2 percent of the time, except for minor leakage through the dam. Flow releases at the Taro Gate, from Honokohau Ditch back into the stream, are inconsistent and were found to be less than the target release of 1.55 cubic feet per second on 9 of the 10 days on which measurements were made. Previous estimates of base-flow availability downstream from the Taro Gate release range from 2.32 to 4.6 cubic feet per second (1.5 to 3.0 million gallons per day). At the two principal sites where water is currently being diverted for agricultural use in the valley (MacDonald's and Chun's Dams), base flows of 2.32 cubic feet per

  12. Pool-Type Fishways: Two Different Morpho-Ecological Cyprinid Species Facing Plunging and Streaming Flows

    PubMed Central

    Branco, Paulo; Santos, José M.; Katopodis, Christos; Pinheiro, António; Ferreira, Maria T.

    2013-01-01

    Fish are particularly sensitive to connectivity loss as their ability to reach spawning grounds is seriously affected. The most common way to circumvent a barrier to longitudinal connectivity, and to mitigate its impacts, is to implement a fish passage device. However, these structures are often non-effective for species with different morphological and ecological characteristics so there is a need to determine optimum dimensioning values and hydraulic parameters. The aim of this work is to study the behaviour and performance of two species with different ecological characteristics (Iberian barbel Luciobarbus bocagei–bottom oriented, and Iberian chub Squalius pyrenaicus–water column) in a full-scale experimental pool-type fishway that offers two different flow regimes–plunging and streaming. Results showed that both species passed through the surface notch more readily during streaming flow than during plunging flow. The surface oriented species used the surface notch more readily in streaming flow, and both species were more successful in moving upstream in streaming flow than in plunging flow. Streaming flow enhances upstream movement of both species, and seems the most suitable for fishways in river systems where a wide range of fish morpho-ecological traits are found. PMID:23741465

  13. Channelised Subglacial Hydrology Modulates West Antarctic Ice Stream Basal Conditions and Flow

    NASA Astrophysics Data System (ADS)

    Siegert, M. J.; Ross, N.; Schroeder, D. M.

    2014-12-01

    Ice-sheet models show a coincidence between ice flux and basal water-flow maxima, as water at the bed of an ice sheets acts generally to lubricate the basal interface. Hydrological flow paths support this view with ice and basal-water drainage basins being well-aligned. At the scale of an individual ice stream, however, we reveal a significant offset of this alignment. Airborne geophysical data across the trunk of the Institute Ice Stream reveal how subglacial hydrology acts to subdue ice flow in two ways: first, by removing basal sediment, which decreases opportunity for the deformation of basal material and increases basal roughness; and, second, by reducing basal water pressures. The macro flow of basal water beneath the ice stream is known well from high-resolution bed elevation data and satellite imagery, which reveal well-organised water flow along the Robin Subglacial Basin, terminating at the grounding line as a channel carving upwards into the adjacent ice shelf. The highest ice flow is offset from this channelized zone, however. Maximum velocities are located where the bed is very smooth and radio-echo returns are strong; consistent with a dilated weak sedimentary material at the ice stream bed. The geophysical evidence is consistent with the removal of basal sediment from the deepest regions of the Robin Subglacial Basin by the action of water and illustrates how accumulation of sedimentary material from ice streams is not necessary a precise locator for maximum ice-flow velocities at the scale of individual ice streams. The figure shows a radar section across the Institute Ice Stream, West Antarctica, revealing two modes of basal environment. One is flat and smooth, indicative of a soft wet bed. The other is rougher, as a consequence of the removal of basal material and water channelisation. This latter region is located in the deepest regions of the Robin Subglacial Basin. The former region is located beneath the highest ice flow speeds.

  14. 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

  15. Altered stream-flow regimes and invasive plant species: The Tamarix case

    USGS Publications Warehouse

    Stromberg, J.C.; Lite, S.J.; Marler, R.; Paradzick, C.; Shafroth, P.B.; Shorrock, D.; White, J.M.; White, M.S.

    2007-01-01

    Aim: To test the hypothesis that anthropogenic alteration of stream-flow regimes is a key driver of compositional shifts from native to introduced riparian plant species. Location: The arid south-western United States; 24 river reaches in the Gila and Lower Colorado drainage basins of Arizona. Methods: We compared the abundance of three dominant woody riparian taxa (native Populus fremontii and Salix gooddingii, and introduced Tamarix) between river reaches that varied in stream-flow permanence (perennial vs. intermittent), presence or absence of an upstream flow-regulating dam, and presence or absence of municipal effluent as a stream water source. Results: Populus and Salix were the dominant pioneer trees along the reaches with perennial flow and a natural flood regime. In contrast, Tamarix had high abundance (patch area and basal area) along reaches with intermittent stream flows (caused by natural and cultural factors), as well as those with dam-regulated flows. Main conclusions: Stream-flow regimes are strong determinants of riparian vegetation structure, and hydrological alterations can drive dominance shifts to introduced species that have an adaptive suite of traits. Deep alluvial groundwater on intermittent rivers favours the deep-rooted, stress-adapted Tamarix over the shallower-rooted and more competitive Populus and Salix. On flow-regulated rivers, shifts in flood timing favour the reproductively opportunistic Tamarix over Populus and Salix, both of which have narrow germination windows. The prevailing hydrological conditions thus favour a new dominant pioneer species in the riparian corridors of the American Southwest. These results reaffirm the importance of reinstating stream-flow regimes (inclusive of groundwater flows) for re-establishing the native pioneer trees as the dominant forest type. ?? 2007 The Authors Journal compilation ?? 2007 Blackwell Publishing Ltd.

  16. Predicting spatial distribution of postfire debris flows and potential consequences for native trout in headwater streams

    USGS Publications Warehouse

    Sedell, Edwin R; Gresswell, Bob; McMahon, Thomas E.

    2015-01-01

    Habitat fragmentation and degradation and invasion of nonnative species have restricted the distribution of native trout. Many trout populations are limited to headwater streams where negative effects of predicted climate change, including reduced stream flow and increased risk of catastrophic fires, may further jeopardize their persistence. Headwater streams in steep terrain are especially susceptible to disturbance associated with postfire debris flows, which have led to local extirpation of trout populations in some systems. We conducted a reach-scale spatial analysis of debris-flow risk among 11 high-elevation watersheds of the Colorado Rocky Mountains occupied by isolated populations of Colorado River Cutthroat Trout (Oncorhynchus clarkii pleuriticus). Stream reaches at high risk of disturbance by postfire debris flow were identified with the aid of a qualitative model based on 4 primary initiating and transport factors (hillslope gradient, flow accumulation pathways, channel gradient, and valley confinement). This model was coupled with a spatially continuous survey of trout distributions in these stream networks to assess the predicted extent of trout population disturbances related to debris flows. In the study systems, debris-flow potential was highest in the lower and middle reaches of most watersheds. Colorado River Cutthroat Trout occurred in areas of high postfire debris-flow risk, but they were never restricted to those areas. Postfire debris flows could extirpate trout from local reaches in these watersheds, but trout populations occupy refugia that should allow recolonization of interconnected, downstream reaches. Specific results of our study may not be universally applicable, but our risk assessment approach can be applied to assess postfire debris-flow risk for stream reaches in other watersheds.

  17. Variability in isotopic composition of base flow in two headwater streams of the southern Appalachians

    NASA Astrophysics Data System (ADS)

    Singh, Nitin K.; Emanuel, Ryan E.; McGlynn, Brian L.

    2016-06-01

    We investigated the influence of hillslope scale topographic characteristics and the relative position of hillslopes along streams (i.e., internal catchment structure) on the isotopic composition of base flow in first-order, forested headwater streams at Coweeta Hydrologic Laboratory. The study focused on two adjacent forested catchments with different topographic characteristics. We used stable isotopes (18O and 2H) of water together with stream gauging and geospatial analysis to evaluate relationships between internal catchment structure and the spatiotemporal variability of base flow δ18O. Base flow δ18O was variable in space and time along streams, and the temporal variability of base flow δ18O declined with increasing drainage area. Base flow became enriched in 18O moving along streams from channel heads to catchment outlets but the frequency of enrichment varied between catchments. The spatiotemporal variability in base flow δ18O was high adjacent to large hillslopes with short flow paths, and it was positively correlated with the relative arrangement of hillslopes within the catchment. These results point to influence of unique arrangement of hillslopes on the patterns of downstream enrichment. Spatial variability in base flow δ18O within the streams was relatively low during dry and wet conditions, but it was higher during the transition period between dry and wet conditions. These results suggest that the strength of topographic control on the isotopic composition of base flow can vary with catchment wetness. This study highlights that topographic control on base flow generation and isotopic composition is important even at fine spatial scales.

  18. Flow and Acoustic Properties of Low Reynolds Number Underexpanded Supersonic Jets. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Hu, Tieh-Feng

    1981-01-01

    Jet noise on underexpanded supersonic jets are studied with emphasis on determining the role played by large scale organized flow fluctuations in the flow and acoustic processes. The experimental conditions of the study were chosen as low Reynolds number (Re=8,000) Mach 1.4 and 2.1, and moderate Reynolds number (Re=68,000) Mach 1.6 underexpanded supersonic jets exhausting from convergent nozzles. At these chosen conditions, detailed experimental measurements were performed to improve the understanding of the flow and acoustic properties of underexpanded supersonic jets.

  19. Acoustic thermometric data on blood flow and thermal output in forearm under physical pressure

    NASA Astrophysics Data System (ADS)

    Anosov, A. A.; Belyaev, R. V.; Vilkov, V. A.; Kazanskii, A. S.; Kuryatnikova, N. A.; Mansfel'd, A. D.

    2013-07-01

    The influence of blood flow and thermal output on temperature changes in the human forearm under physical pressure is studied by acoustic thermometry. Compression of the shoulder with a tourniquet decreases blood flow, which make it possible to evaluate the thermal output characteristics only. In calculating the depth temperature of the forearm, the thermal conductivity equation was used and blood flow and additional thermal output sources were taken into account. According to the calculations in which the experimental data were used, the peak depth temperature of the forearm at rest is 36°C. Due to thermal output alone (without blood flow), physical pressure increases this temperature to 37°C, and when both factors are considered, the temperature rises to 38°C. The experiments in question have allowed us to test acoustic thermographic method on subjects, which is an important step in adopting acoustic thermography in clinical practice.

  20. Steady computational analysis of shrouded plug nozzle flows using unequal stream pressures

    NASA Astrophysics Data System (ADS)

    Ruhs, Kevin Paul

    This study focuses on the effects of unequal core and bypass stream feed pressures in a high pressure ratio, two-stream nozzle notionally designed for supersonic business jet applications. Whereas previous analysis used a measured mass average pressure of the core and bypass streams, equal pressures were not exactly maintained in the experimental work and the effect of the imbalance is the primary motivation for the present study. The plug nozzle geometry used is a sub-scale model of a Gulfstream Aerospace Corporation concept that features an extended shroud. It uses two inlet streams, representing core and bypass streams from a turbofan engine. Nozzle pressure ratios range from unity to 6.23. Experimental measurements included pressure taps on the plug and shroud, schlieren and shadowgraph figures, mass flows for both streams, and thrust values. The computational analysis employed the General Equation and Mesh Solver, or GEMS code. Previous computational analysis was performed by Kapilavai, giving a basis analysis involving grid generation and refinement, error convergence studies, axisymmetric analysis, and unsteady computations. Unequal core and bypass stream pressure or swirl in the core stream is used to replicate experimental data and assess performance. The results of using these conditions were explored, including pressure on the plug and shroud, shock characteristics, separation and recirculation zones, mass flows and discharge coefficients, and thrust efficiencies.

  1. Analysing subglacial geology hidden beneath the ice streams flowing into the Weddell Sea (West Antarctica)

    NASA Astrophysics Data System (ADS)

    Ferraccioli, F.; King, O.; Jordan, T. A.; Ross, N.; Bingham, R. G.; Le Brocq, A. M.; Smith, A.; Hindmarsh, R. C. A.; Siegert, M. J.

    2014-12-01

    Subglacial geology provides important controls on the onset and maintenance of fast glacial flow in the West Antarctic Ice Sheet (WAIS). Widespread subglacial sediments deposited within deep rift basins, thinner drapes of marine sediments within the West Antarctic Rift System (WARS) and high geothermal heat flux associated with Cenozoic magmatism have been previously identified as key geological controls that can modulate ice sheet dynamics. Here, we compile a suite of new and vintage aeromagnetic and airborne gravity observations to examine the large-scale geological setting of several major ice streams flowing into the Weddell Sea Embayment and assess the role of geological controls on subglacial topography and WAIS flow regimes. We focus on the subglacial geology beneath the Institute and Moeller ice streams, the Rutford ice stream and the Evans ice stream. We show that the Moeller ice stream is underlain by a major strike-slip fault system, which is part of the tectonic boundary between East and West Antarctica. A set of en-echelon subglacial basins formed along the strike-slip fault and these basins appear to steer enhanced flow far inland. Deep sedimentary basins are not present along this fault system, however, suggesting that subglacial sediments are not necessarily a geological template for the onset of fast glacial flow. The recently identified Robin Subglacial Basin that underlies the fast flowing coastal region of the Institute ice stream contains 1-3 km of sedimentary infill and smooth bedrock topography. Enhanced flow in the tributaries of the Institute ice stream cuts across the Ellsworth Mountains and is controlled by basement faults displacing metasedimentary and metavolcanic rocks. Prominent magnetic anomalies overlie outcrops of Jurassic granitic intrusions and enable us to trace their subglacial extent beneath the catchments of Institute, Moeller and Rutford ice streams. These large granitoid bodies form topographic highs that appear to divert

  2. Monitoring strategies of stream phosphorus under contrasting climate-driven flow regimes

    NASA Astrophysics Data System (ADS)

    Goyenola, G.; Meerhoff, M.; Teixeira-de Mello, F.; González-Bergonzoni, I.; Graeber, D.; Fosalba, C.; Vidal, N.; Mazzeo, N.; Ovesen, N. B.; Jeppesen, E.; Kronvang, B.

    2015-10-01

    Climate and hydrology are relevant control factors determining the timing and amount of nutrient losses from land to downstream aquatic systems, in particular of phosphorus (P) from agricultural lands. The main objective of the study was to evaluate the differences in P export patterns and the performance of alternative monitoring strategies in streams under contrasting climate-driven flow regimes. We compared a set of paired streams draining lowland micro-catchments under temperate climate and stable discharge conditions (Denmark) and under sub-tropical climate and flashy conditions (Uruguay). We applied two alternative nutrient sampling programs (high-frequency composite sampling and low-frequency instantaneous-grab sampling) and estimated the contribution derived from point and diffuse sources fitting a source apportionment model. We expected to detect a pattern of higher total and particulate phosphorus export from diffuse sources in streams in Uruguay streams, mostly as a consequence of higher variability in flow regime (higher flashiness). Contrarily, we found a higher contribution of dissolved P in flashy streams. We did not find a notably poorer performance of the low-frequency sampling program to estimate P exports in flashy streams compared to the less variable streams. We also found signs of interaction between climate/hydrology and land use intensity, in particular in the presence of point sources of P, leading to a bias towards underestimation of P in hydrologically stable streams and overestimation of P in flashy streams. Based on our findings, we suggest that the evaluation and use of more accurate monitoring methods, such as automatized flow-proportional water samplers and automatized bankside analyzers, should be prioritized whenever logistically possible. However, it seems particularly relevant in currently flashy systems and also in systems where climate change predictions suggest an increase in stream flashiness.

  3. Flow directionality, mountain barriers and functional traits determine diatom metacommunity structuring of high mountain streams

    PubMed Central

    Dong, Xiaoyu; Li, Bin; He, Fengzhi; Gu, Yuan; Sun, Meiqin; Zhang, Haomiao; Tan, Lu; Xiao, Wen; Liu, Shuoran; Cai, Qinghua

    2016-01-01

    Stream metacommunities are structured by a combination of local (environmental filtering) and regional (dispersal) processes. The unique characters of high mountain streams could potentially determine metacommunity structuring, which is currently poorly understood. Aiming at understanding how these characters influenced metacommunity structuring, we explored the relative importance of local environmental conditions and various dispersal processes, including through geographical (overland), topographical (across mountain barriers) and network (along flow direction) pathways in shaping benthic diatom communities. From a trait perspective, diatoms were categorized into high-profile, low-profile and motile guild to examine the roles of functional traits. Our results indicated that both environmental filtering and dispersal processes influenced metacommunity structuring, with dispersal contributing more than environmental processes. Among the three pathways, stream corridors were primary pathway. Deconstructive analysis suggested different responses to environmental and spatial factors for each of three ecological guilds. However, regardless of traits, dispersal among streams was limited by mountain barriers, while dispersal along stream was promoted by rushing flow in high mountain stream. Our results highlighted that directional processes had prevailing effects on metacommunity structuring in high mountain streams. Flow directionality, mountain barriers and ecological guilds contributed to a better understanding of the roles that mountains played in structuring metacommunity. PMID:27090223

  4. Optical and acoustical measuring techniques. [for Doppler measurement of flow velocities

    NASA Technical Reports Server (NTRS)

    Cliff, W. C.

    1977-01-01

    The paper reviews the techniques of laser and acoustic Doppler measurement of fluid velocities in confined and free flows. The main mathematical relations are presented, and some systems are studied. Resolution properties of coaxial, bistatic, and pulsed CO2 laser Doppler velocimeter systems are compared. Schematics for pulsed and continuous wave acoustic Doppler systems are discussed. Both of these types of systems benefit from using a bistatic configuration instead of a coaxial system. The pulsed systems avoid contamination of source noise by not sampling until after the source noise has passed the receiver. Comparison of wind velocity measured with a pulsed acoustic Doppler and with a boundary layer profile is made.

  5. 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.

  6. Effects of flow scarcity on leaf-litter processing under oceanic climate conditions in calcareous streams.

    PubMed

    Martínez, Aingeru; Pérez, Javier; Molinero, Jon; Sagarduy, Mikel; Pozo, Jesús

    2015-01-15

    Although temporary streams represent a high proportion of the total number and length of running waters, historically the study of intermittent streams has received less attention than that of perennial ones. The goal of the present study was to assess the effects of flow cessation on litter decomposition in calcareous streams under oceanic climate conditions. For this, leaf litter of alder was incubated in four streams (S1, S2, S3 and S4) with different flow regimes (S3 and S4 with zero-flow periods) from northern Spain. To distinguish the relative importance and contribution of decomposers and detritivores, fine- and coarse-mesh litter bags were used. We determined processing rates, leaf-C, -N and -P concentrations, invertebrate colonization in coarse bags and benthic invertebrates. Decomposition rates in fine bags were similar among streams. In coarse bags, only one of the intermittent streams, S4, showed a lower rate than that in the other ones as a consequence of lower invertebrate colonization. The material incubated in fine bags presented higher leaf-N and -P concentrations than those in the coarse ones, except in S4, pointing out that the decomposition in this stream was driven mainly by microorganisms. Benthic macroinvertebrate and shredder density and biomass were lower in intermittent streams than those in perennial ones. However, the bags in S3 presented a greater amount of total macroinvertebrates and shredders comparing with the benthos. The most suitable explanation is that the fauna find a food substrate in bags less affected by calcite precipitation, which is common in the streambed at this site. Decomposition rate in coarse bags was positively related to associated shredder biomass. Thus, droughts in streams under oceanic climate conditions affect mainly the macroinvertebrate detritivore activity, although macroinvertebrates may show distinct behavior imposed by the physicochemical properties of water, mainly travertine precipitation, which can

  7. Low-flow characteristics of streams on the Olympic Peninsula, Washington

    USGS Publications Warehouse

    Haushild, W.L.; LaFrance, D.E.

    1977-01-01

    Streams in lowland basins of the Olympic Peninsula, Washington, generally have their low flows in summer and peak flows in winter, whereas streams originating at higher elevations in the mountains have their low flows in late summer-early fall and they have both winter and spring peak flows. Data from long-term stations indicate no important trend in low flows during 1940-73 but they do indicate that low flows generally were lower during the relatively dry 1940 's than during the relatively wet 1950-73 period. The magnitude and frequency of 7-day low flows were estimated for 116 sites either from frequency analyses of a data at long-term stations or from correlation of data at a short-term station with data at an appropriate long-term station. (Woodard-USGS)

  8. Dating base flow in streams using dissolved gases and diurnal temperature changes

    NASA Astrophysics Data System (ADS)

    Sanford, Ward E.; Casile, Gerolamo; Haase, Karl B.

    2015-12-01

    A method is presented for using dissolved CFCs or SF6 to estimate the apparent age of stream base flow by indirectly estimating the mean concentration of the tracer in the inflowing groundwater. The mean value is estimated simultaneously with the mean residence times of the gas and water in the stream by sampling the stream for one or both age tracers, along with dissolved nitrogen and argon at a single location over a period of approximately 12-14 h. The data are fitted to an equation representing the temporal in-stream gas exchange as it responds to the diurnal temperature fluctuation. The efficacy of the method is demonstrated by collecting and analyzing samples at six different stream locations across parts of northern Virginia, USA. The studied streams drain watersheds with areas of between 2 and 122 km2 during periods when the diurnal stream temperature ranged between 2 and 5°C. The method has the advantage of estimating the mean groundwater residence time of discharge from the watershed to the stream without the need for the collection of groundwater infiltrating to streambeds or local groundwater sampled from shallow observation wells near the stream.

  9. Particle manipulation affected by streaming flows in vertically actuated open rectangular chambers

    NASA Astrophysics Data System (ADS)

    Agrawal, Prashant; Gandhi, Prasanna S.; Neild, Adrian

    2016-03-01

    Particle movement in vibration assisted microfluidic systems is significantly affected by time-averaged streaming flows. These flows can demonstrate either particle collection or dispersion characteristics, depending on the parameters used and system specifics. Here we investigate particle collection within streaming flows in vertically actuated open rectangular chambers at frequencies in the range of 100 Hz. Capillary waves, created at the water-air interface under the action of low frequency vibration, generate streaming fields in the liquid bulk. In addition, the spatial variation in the flow field gives rise to particle collection due to inertial effects. In order to understand the interplay between these effects, 2D simulations are employed to understand the first order field induced particle collection, while an experimental study is performed to investigate the effect of the 3D streaming fields on particle motion. By altering the chamber dimensions, two observations are presented: first by taking measures to reduce the strength of the streaming field, particles as small as 50 nm in diameter can be collected. Second, the streaming fields themselves can be used to trap particles, which in conjunction with the collection forces can cause particle separation.

  10. Rethinking hyporheic flow and transient storage to advance understanding of stream-catchment connections

    USGS Publications Warehouse

    Bencala, K.E.; Gooseff, M.N.; Kimball, B.A.

    2011-01-01

    Although surface water and groundwater are increasingly referred to as one resource, there remain environmental and ecosystem needs to study the 10 m to 1 km reach scale as one hydrologic system. Streams gain and lose water over a range of spatial and temporal scales. Large spatial scales (kilometers) have traditionally been recognized and studied as river-aquifer connections. Over the last 25 years hyporheic exchange flows (1-10 m) have been studied extensively. Often a transient storage model has been used to quantify the physical solute transport setting in which biogeochemical processes occur. At the longer 10 m to 1 km scale of stream reaches it is now clear that streams which gain water overall can coincidentally lose water to the subsurface. At this scale, the amounts of water transferred are not necessarily significant but the exchanges can, however, influence solute transport. The interpretation of seemingly straightforward questions about water, contaminant, and nutrient fluxes into and along a stream can be confounded by flow losses which are too small to be apparent in stream gauging and along flow paths too long to be detected in tracer experiments. We suggest basic hydrologic approaches, e.g., measurement of flow along the channel, surface and subsurface solute sampling, and routine measurements of the water table that, in our opinion, can be used to extend simple exchange concepts from the hyporheic exchange scale to a scale of stream-catchment connection. Copyright 2011 by the American Geophysical Union.

  11. Base-flow measurements at partial-record sites on small streams in South Carolina

    USGS Publications Warehouse

    Barker, Carroll

    1986-01-01

    This report contains site descriptions and base-flow data collected at 362 partial-record sites in South Carolina. These data include site name, site description, latitude, longitude, drainage area, instantaneous streamflow, and date of the streamflow measurement. The base-flow data can be used as an aid to estimate low flow characteristics at ungaged locations on streams in South Carolina. Partial record data collection sites were established in all physiographic provinces except the lower Coastal Plain. Data collection sites were not established in the lower Coastal Plain because of the widespread occurrence of zero during drought periods in all but the larger streams. (USGS)

  12. Improvement of trout streams in Wisconsin by augmenting low flows with ground water

    USGS Publications Warehouse

    Novitzki, R.P.

    1973-01-01

    Approximately 2 cubic feet per second of ground water were introduced into the Little Plover River in 1968 when natural streamflow ranged from 3 to 4 cubic feet per second. These augmentation flows were retained undiminished through the 2-mile reach of stream monitored. Maximum stream temperatures were reduced as much as 5?F (3?C) at the augmentation site during the test period, although changes became insignificant more than 1 mile downstream. Maximum temperatures might be reduced as much as 10?F (6?C) during critical periods, based on estimates using a stream temperature model developed as part of the study. During critical periods significant temperature improvement may extend 2 miles or more downstream. Changes in minimum DO (dissolved oxygen) levels were slight, primarily because of the high natural DO levels occurring during the test period. Criteria for considering other streams for flow augmentation are developed on the basis of the observed hydrologic responses in the Little Plover River. Augmentation flows of nearly 2? cubic feet per second of ground water were introduced into the headwater reach of Black Earth Creek from the end of June through mid-October 1969. Streamflow ranged from 1 to 2 cubic feet per second at the augmentation site, and the average flow at the gaging station at Black Earth, approximately 8 miles downstream, ranged from 25 to 50 cubic feet per second. Augmentation flows were retained through the 8-mile reach of stream. Temperature of the augmentation flow as it entered the stream ranged from 60? to 70?F (about 16? to 21?C) during the test period, and minimum stream temperatures were raised 5?F (3?C) or more at the augmentation site, with changes extending from 2 to 3 miles downstream. Augmentation during critical periods could maintain stream temperatures between 40? and 70?F (4? and 21?C) through most of the study reach. DO levels were increased by as much as 2 milligrams per liter or more below the augmentation site, although the

  13. Extraction of conjugate main-stream structures from a complex network flow.

    PubMed

    Tamura, Koutarou; Takayasu, Hideki; Takayasu, Misako

    2015-04-01

    We introduce a method to extract main-stream structures for a given complex network flow by trimming less effective links. As the resulting main streams generally have an almost loopless treelike structure, we can define the stream basin size for each node, which characterizes the importance of the node with regard to the flow. As a real-world example, we apply this method to an interfirm trading network, both for the money flow and its conjugate-the material or service flow-confirming that both basin size distributions follow a similar power law that differs significantly from the basin size distributions of rivers in nature. We theoretically analyze the process of trimming and derive a consistent statistical formulation between the original link number and the basin size. PMID:25974555

  14. 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

  15. The Effects of a Fully Submerged Boulder Array on the Surrounding Mean and Turbulent Flow Fields in Mountain Streams

    NASA Astrophysics Data System (ADS)

    Papanicolaou, T.; Tsakiris, A. G.; Hajimirzaie, S. M.; Buchholz, J.

    2014-12-01

    Arrays of large immobile boulders in mountainous stream reaches modify the patterns of bedload movement through the controls that they exert on their surrounding flow field. Boulders within an array generate complex mean and turbulent patterns in their vicinity, resulting to a variable bed shear stress field. At the same time, boulder arrays generate form drag, which reduces the bed shear stress applied by the flow on the incoming bedload sediment. This study aims to assess the collective effects of a boulder array on its surrounding time-averaged and turbulent flow fields, as well as the collective array form drag effects accounting for the variable bed shear stress distribution around a boulder of the array. Controlled laboratory experiments are conducted with a single boulder and an array of identical, isolated boulders mounted atop a flat, rough bed and subjected to identical flow conditions. The mean and turbulent flow fields around the boulder with and without the presence of a boulder array are resolved via a Laser Doppler Velocimeter and an Acoustic Doppler Velocimeter, respectively. The results show that an individual boulder modifies the time-averaged streamwise velocity and turbulence intensity in its immediate vicinity along the streamwise (x/dc < 2-3) and vertical (z/dc < 1) directions. At locations further from the boulder, the time-averaged streamwise velocity was found to be globally decelerated, likely due to the form drag generated collectively by the boulder array. Our results suggested that the collective array form drag absorbs a portion of the total applied shear by the flow, hence reducing the bed shear stress exerted by the flow on the individual boulders of the array. Furthermore, the array was found to significantly reduce the turbulence intensity near the bed. Overall, our findings suggest that the collective boulder array has sizeable effects on the surrounding flow field and bed shear stress distribution, which should not be ignored in

  16. Resonance and streaming of armored microbubbles

    NASA Astrophysics Data System (ADS)

    Spelman, Tamsin; Bertin, Nicolas; Stephen, Olivier; Marmottant, Philippe; Lauga, Eric

    2015-11-01

    A new experimental technique involves building a hollow capsule which partially encompasses a microbubble, creating an ``armored microbubble'' with long lifespan. Under acoustic actuation, such bubble produces net streaming flows. In order to theoretically model the induced flow, we first extend classical models of free bubbles to describe the streaming flow around a spherical body for any known axisymmetric shape oscillation. A potential flow model is then employed to determine the resonance modes of the armored microbubble. We finally use a more detailed viscous model to calculate the surface shape oscillations at the experimental driving frequency, and from this we predict the generated streaming flows.

  17. 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.

  18. Integrating Acoustic Imaging of Flow Regimes With Bathymetry: A Case Study, Main Endeavor Field

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Rona, P. A.; Jackson, D. R.; Jones, C. D.

    2003-12-01

    A unified view of the seafloor and the hydrothermal flow regimes (plumes and diffuse flow) is constructed for three major vent clusters in the Main Endeavour Field (e.g., Grotto, S&M, and Salut) of the Endeavour Segment, Juan de Fuca Ridge. The Main Endeavour Field is one of RIDGE 2000's Integrated Study Sites. A variety of visualization techniques are used to reconstruct the plumes (3D) and the diffuse flow field (2D) based on our acoustic imaging data set (July 2000 cruise). Plumes are identified as volumes of high backscatter intensity (indicating high particulate content or sharp density contrasts due to temperature variations) that remained high intensity when successive acoustic pings were subtracted (indicating that the acoustic targets producing the backscatter were in motion). Areas of diffuse flow are detected using our acoustic scintillation technique (AST). For the Grotto vent region (where a new Doppler technique was used to estimate vertical velocities in the plume), we estimate the areal partitioning between black smoker and diffuse flow in terms of volume fluxes. The volumetric and areal regions, where plume and diffuse flow were imaged, are registered over the bathymetry and compared to geologic maps of each region. The resulting images provide a unified view of the seafloor by integrating hydrothermal flow with geology.

  19. 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.

  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. Determining long time-scale hyporheic zone flow paths in Antarctic streams

    USGS Publications Warehouse

    Gooseff, M.N.; McKnight, Diane M.; Runkel, R.L.; Vaughn, B.H.

    2003-01-01

    In the McMurdo Dry Valleys of Antarctica, glaciers are the source of meltwater during the austral summer, and the streams and adjacent hyporheic zones constitute the entire physical watershed; there are no hillslope processes in these systems. Hyporheic zones can extend several metres from each side of the stream, and are up to 70 cm deep, corresponding to a lateral cross-section as large as 12 m2, and water resides in the subsurface year around. In this study, we differentiate between the near-stream hyporheic zone, which can be characterized with stream tracer experiments, and the extended hyporheic zone, which has a longer time-scale of exchange. We sampled stream water from Green Creek and from the adjacent saturated alluvium for stable isotopes of D and 18O to assess the significance and extent of stream-water exchange between the streams and extended hyporheic zones over long time-scales (days to weeks). Our results show that water residing in the extended hyporheic zone is much more isotopically enriched (up to 11??? D and 2.2??? 18O) than stream water. This result suggests a long residence time within the extended hyporheic zone, during which fractionation has occured owing to summer evaporation and winter sublimation of hyporheic water. We found less enriched water in the extended hyporheic zone later in the flow season, suggesting that stream water may be exchanged into and out of this zone, on the time-scale of weeks to months. The transient storage model OTIS was used to characterize the exchange of stream water with the extended hyporheic zone. Model results yield exchange rates (??) generally an order magnitude lower (10-5 s-1) than those determined using stream-tracer techniques on the same stream. In light of previous studies in these streams, these results suggest that the hyporheic zones in Antarctic streams have near-stream zones of rapid stream-water exchange, where 'fast' biogeochemical reactions may influence water chemistry, and extended

  2. Determining long time-scale hyporheic zone flow paths in Antarctic streams

    NASA Astrophysics Data System (ADS)

    Gooseff, Michael N.; McKnight, Diane M.; Runkel, Robert L.; Vaughn, Bruce H.

    2003-06-01

    In the McMurdo Dry Valleys of Antarctica, glaciers are the source of meltwater during the austral summer, and the streams and adjacent hyporheic zones constitute the entire physical watershed; there are no hillslope processes in these systems. Hyporheic zones can extend several metres from each side of the stream, and are up to 70 cm deep, corresponding to a lateral cross-section as large as 12 m2, and water resides in the subsurface year around. In this study, we differentiate between the near-stream hyporheic zone, which can be characterized with stream tracer experiments, and the extended hyporheic zone, which has a longer time-scale of exchange. We sampled stream water from Green Creek and from the adjacent saturated alluvium for stable isotopes of D and 18O to assess the significance and extent of stream-water exchange between the streams and extended hyporheic zones over long time-scales (days to weeks). Our results show that water residing in the extended hyporheic zone is much more isotopically enriched (up to 11 D and 2·2 18O) than stream water. This result suggests a long residence time within the extended hyporheic zone, during which fractionation has occurred owing to summer evaporation and winter sublimation of hyporheic water. We found less enriched water in the extended hyporheic zone later in the flow season, suggesting that stream water may be exchanged into and out of this zone, on the time-scale of weeks to months. The transient storage model OTIS was used to characterize the exchange of stream water with the extended hyporheic zone. Model results yield exchange rates () generally an order magnitude lower (10-5 s-1) than those determined using stream-tracer techniques on the same stream. In light of previous studies in these streams, these results suggest that the hyporheic zones in Antarctic streams have near-stream zones of rapid stream-water exchange, where fast biogeochemical reactions may influence water chemistry, and extended hyporheic

  3. Is there a geomorphic expression of interbasin groundwater flow in watersheds? Interactions between interbasin groundwater flow, springs, streams, and geomorphology

    NASA Astrophysics Data System (ADS)

    Frisbee, Marty D.; Tysor, Elizabeth H.; Stewart-Maddox, Noah S.; Tsinnajinnie, Lani M.; Wilson, John L.; Granger, Darryl E.; Newman, Brent D.

    2016-02-01

    Interbasin groundwater flow (IGF) can play a significant role in the generation and geochemical evolution of streamflow. However, it is exceedingly difficult to identify IGF and to determine the location and quantity of water that is exchanged between watersheds. How does IGF affect landscape/watershed geomorphic evolution? Can geomorphic metrics be used to identify the presence of IGF? We examine these questions in two adjacent sedimentary watersheds in northern New Mexico using a combination of geomorphic/landscape metrics, springflow residence times, and spatial geochemical patterns. IGF is expressed geomorphically in the landscape placement of springs and flow direction and shape of stream channels. Springs emerge preferentially on one side of stream valleys where landscape incision has intercepted IGF flow paths. Stream channels grow toward the IGF source and show little bifurcation. In addition, radiocarbon residence times of springs decrease and the geochemical composition of springs changes as the connection to IGF is lost.

  4. 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.

  5. Size-selective sorting in bubble streaming flows: Particle migration on fast time scales

    NASA Astrophysics Data System (ADS)

    Thameem, Raqeeb; Rallabandi, Bhargav; Hilgenfeldt, Sascha

    2015-11-01

    Steady streaming from ultrasonically driven microbubbles is an increasingly popular technique in microfluidics because such devices are easily manufactured and generate powerful and highly controllable flows. Combining streaming and Poiseuille transport flows allows for passive size-sensitive sorting at particle sizes and selectivities much smaller than the bubble radius. The crucial particle deflection and separation takes place over very small times (milliseconds) and length scales (20-30 microns) and can be rationalized using a simplified geometric mechanism. A quantitative theoretical description is achieved through the application of recent results on three-dimensional streaming flow field contributions. To develop a more fundamental understanding of the particle dynamics, we use high-speed photography of trajectories in polydisperse particle suspensions, recording the particle motion on the time scale of the bubble oscillation. Our data reveal the dependence of particle displacement on driving phase, particle size, oscillatory flow speed, and streaming speed. With this information, the effective repulsive force exerted by the bubble on the particle can be quantified, showing for the first time how fast, selective particle migration is effected in a streaming flow. We acknowledge support by the National Science Foundation under grant number CBET-1236141.

  6. A model for the pressure excitation spectrum and acoustic impedance of sound absorbers in the presence of grazing flow

    NASA Technical Reports Server (NTRS)

    Rice, E. J.

    1973-01-01

    The acoustic impedance of sound absorbers in the presence of grazing flow is essential information when analyzing sound propagation within ducts. A unification of the theory of the nonlinear acoustic resistance of Helmholtz resonators including grazing flow is presented. The nonlinear resistance due to grazing flow is considered to be caused by an exciting pressure spectrum produced by the interaction of the grazing flow and the jets flowing from the resonator orifices. With this exciting pressure spectrum the resonator can be treated in the same manner as a resonator without grazing flow but with an exciting acoustic spectrum.

  7. Method For Enhanced Gas Monitoring In High Density Flow Streams

    DOEpatents

    Von Drasek, William A.; Mulderink, Kenneth A.; Marin, Ovidiu

    2005-09-13

    A method for conducting laser absorption measurements in high temperature process streams having high levels of particulate matter is disclosed. An impinger is positioned substantially parallel to a laser beam propagation path and at upstream position relative to the laser beam. Beam shielding pipes shield the beam from the surrounding environment. Measurement is conducted only in the gap between the two shielding pipes where the beam propagates through the process gas. The impinger facilitates reduced particle presence in the measurement beam, resulting in improved SNR (signal-to-noise) and improved sensitivity and dynamic range of the measurement.

  8. Estimates of Median Flows for Streams on the 1999 Kansas Surface Water Register

    USGS Publications Warehouse

    Perry, Charles A.; Wolock, David M.; Artman, Joshua C.

    2004-01-01

    The Kansas State Legislature, by enacting Kansas Statute KSA 82a?2001 et. seq., mandated the criteria for determining which Kansas stream segments would be subject to classification by the State. One criterion for the selection as a classified stream segment is based on the statistic of median flow being equal to or greater than 1 cubic foot per second. As specified by KSA 82a?2001 et. seq., median flows were determined from U.S. Geological Survey streamflow-gaging-station data by using the most-recent 10 years of gaged data (KSA) for each streamflow-gaging station. Median flows also were determined by using gaged data from the entire period of record (all-available hydrology, AAH). Least-squares multiple regression techniques were used, along with Tobit analyses, to develop equations for estimating median flows for uncontrolled stream segments. The drainage area of the gaging stations on uncontrolled stream segments used in the regression analyses ranged from 2.06 to 12,004 square miles. A logarithmic transformation of the data was needed to develop the best linear relation for computing median flows. In the regression analyses, the significant climatic and basin characteristics, in order of importance, were drainage area, mean annual precipitation, mean basin permeability, and mean basin slope. Tobit analyses of KSA data yielded a model standard error of prediction of 0.285 logarithmic units, and the best equations using Tobit analyses of AAH data had a model standard error of prediction of 0.250 logarithmic units. These regression equations and an interpolation procedure were used to compute median flows for the uncontrolled stream segments on the 1999 Kansas Surface Water Register. Measured median flows from gaging stations were incorporated into the regression-estimated median flows along the stream segments where available. The segments that were uncontrolled were interpolated using gaged data weighted according to the drainage area and the bias between the

  9. The role of heating, cavitation and acoustic streaming in mediating ultrasound-induced changes of TGF-beta gene expression in bone cells

    NASA Astrophysics Data System (ADS)

    Harle, J.; Mayia, F.

    2004-01-01

    This paper relates ultrasound-induced changes in bone cell function to quantitative data assessing the level of several interaction mechanisms within the exposure environment. Characterisation of ultrasound fields in terms of resultant levels of heating, cavitation and acoustic streaming may provide a novel means of accurately assessing the likelihood of biological effects in vitro.

  10. A logistic regression equation for estimating the probability of a stream in Vermont having intermittent flow

    USGS Publications Warehouse

    Olson, Scott A.; Brouillette, Michael C.

    2006-01-01

    A logistic regression equation was developed for estimating the probability of a stream flowing intermittently at unregulated, rural stream sites in Vermont. These determinations can be used for a wide variety of regulatory and planning efforts at the Federal, State, regional, county and town levels, including such applications as assessing fish and wildlife habitats, wetlands classifications, recreational opportunities, water-supply potential, waste-assimilation capacities, and sediment transport. The equation will be used to create a derived product for the Vermont Hydrography Dataset having the streamflow characteristic of 'intermittent' or 'perennial.' The Vermont Hydrography Dataset is Vermont's implementation of the National Hydrography Dataset and was created at a scale of 1:5,000 based on statewide digital orthophotos. The equation was developed by relating field-verified perennial or intermittent status of a stream site during normal summer low-streamflow conditions in the summer of 2005 to selected basin characteristics of naturally flowing streams in Vermont. The database used to develop the equation included 682 stream sites with drainage areas ranging from 0.05 to 5.0 square miles. When the 682 sites were observed, 126 were intermittent (had no flow at the time of the observation) and 556 were perennial (had flowing water at the time of the observation). The results of the logistic regression analysis indicate that the probability of a stream having intermittent flow in Vermont is a function of drainage area, elevation of the site, the ratio of basin relief to basin perimeter, and the areal percentage of well- and moderately well-drained soils in the basin. Using a probability cutpoint (a lower probability indicates the site has perennial flow and a higher probability indicates the site has intermittent flow) of 0.5, the logistic regression equation correctly predicted the perennial or intermittent status of 116 test sites 85 percent of the time.

  11. Response of macrophyte communities to flow regulation in mountain streams.

    PubMed

    Abati, Silverio; Minciardi, Maria Rita; Ciadamidaro, Simone; Fattorini, Simone; Ceschin, Simona

    2016-07-01

    River macrophytes are widely used in freshwater ecosystem assessment because of their sensitivity to anthropogenic pressures, even if there are only a few studies that investigated how macrophytes respond to water regime alterations. In this study, we analyzed the effects of dams on river macrophyte communities through a comparison between upstream and downstream sides from 18 dams located in Alps and Apennines. A co-inertia analysis and a Mantel test were applied to assess if the analysis of environmental parameters could be effective in predicting macrophyte community structure. We analyzed morphological and physicochemical inter-site differences and tested the influence of dams on various aspects of community structure (composition, richness, diversity, dominance, coverage) using multivariate randomized block permutation procedure. Plant similarity between sites was evaluated at the level of phylum, and indicator species analysis was performed to identify the taxa most sensitive or tolerant to water regulation. We found that the overall environmental setting overwhelms the dam impact and that the influence of hydrological alteration became apparent when comparing upstream and downstream assemblages at the same dam. In particular, we found that most of taxa had a higher affinity with the downstream side and that in general, stream regulation increases plant richness and coverage, but reduces community evenness. Analyses based on higher taxonomic groups (phyla) demonstrated that this community can be effectively used in bioassessment even at phylum level analysis. In particular, we found that bryophytes, strictly linked with changes in substrate stability, show particular sensitivity to water regulation in mountain streams. PMID:27315127

  12. Mean annual runoff and peak flow estimates based on channel geometry of streams in southeastern Montana

    USGS Publications Warehouse

    Omang, R.J.; Parrett, Charles; Hull, J.A.

    1983-01-01

    Equations using channel-geometry measurements were developed for estimating mean runoff and peak flows of ungaged streams in southeastern Montana. Two separate sets of esitmating equations were developed for determining mean annual runoff: one for perennial streams and one for ephemeral and intermittent streams. Data from 29 gaged sites on perennial streams and 21 gaged sites on ephemeral and intermittent streams were used in these analyses. Data from 78 gaged sites were used in the peak-flow analyses. Southeastern Montana was divided into three regions and separate multiple-regression equations for each region were developed that relate channel dimensions to peak discharge having recurrence intervals of 2, 5, 10, 25, 50, and 100 years. Channel-geometery relations were developed using measurements of the active-channel width and bankfull width. Active-channel width and bankfull width were the most significant channel features for estimating mean annual runoff for al types of streams. Use of this method requires that onsite measurements be made of channel width. The standard error of estimate for predicting mean annual runoff ranged from about 38 to 79 percent. The standard error of estimate relating active-channel width or bankfull width to peak flow ranged from about 37 to 115 percent. (USGS)

  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. Stability Dust-Ion-Acoustic Wave In Dusty Plasmas With Stream -Influence Of Charge Fluctuation Of Dust Grains

    SciTech Connect

    Atamaniuk, Barbara; Zuchowski, Krzysztof

    2006-01-15

    There is a quickly increasing wealth of experimental data on so-called dusty plasmas i. e. ionized gases or usual plasmas that contain micron sized charged particles. Interest in these structures is driven both by their importance in many astrophysical as well as commercial situations. Among them are linear and nonlinear wave phenomena. We consider the influence of dust charge fluctuations on stability of the ion-acoustic waves when the stream of particles is present. It is assumed that all grains of dust have equal masses but charges are not constant in time-they may fluctuate in time. The dust charges are not really independent of the variations of the plasma potentials. All modes will influence the charging mechanism, and feedback will lead to several new interesting and unexpected phenomena. The charging of the grains depends on local plasma characteristics. If the waves disturb these characteristic, then charging of the grains is affected and the grain charge is modified, with a resulting feedback on the wave mode. In case considering here, when temperature of electrons is much greater then the temperature of the ions and temperature of electrons is not great enough for further ionization of the ions, we show that stability of the acoustic wave depends only one phenomenological coefficient.

  15. 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.

  16. Technical Note: Variability of flow discharge in lateral inflow-dominated stream channels

    NASA Astrophysics Data System (ADS)

    Chang, C.-M.; Yeh, H.-D.

    2015-02-01

    The influence of the temporal changes in lateral inflow rate on the discharge variability in stream channels is explored through the analysis of diffusion wave equation (the linearized St. Venant equations). To account for variability and uncertainty, the lateral inflow rate is regarded as a temporal random function. Based on the spectral representation theory, analytical expressions for the covariance function and evolutionary power spectral density of the random discharge perturbation process are derived to quantify variability in stream flow discharge induced by the temporal changes in lateral inflow rate. Upon evaluating the closed-form expressions, it is found that the variability in stream flow discharge increases with distance from the upstream boundary of the channel and time as well. The temporal correlation scale of inflow rate fluctuations plays a positive role in enhancing the variability of the flow discharge in channels. The treatment of the discharge variance gives us a quantitative estimate of uncertainty from the use of the deterministic model.

  17. Extraction of conjugate main-stream structures from a complex network flow

    NASA Astrophysics Data System (ADS)

    Tamura, Koutarou; Takayasu, Hideki; Takayasu, Misako

    2015-04-01

    We introduce a method to extract main-stream structures for a given complex network flow by trimming less effective links. As the resulting main streams generally have an almost loopless treelike structure, we can define the stream basin size for each node, which characterizes the importance of the node with regard to the flow. As a real-world example, we apply this method to an interfirm trading network, both for the money flow and its conjugate—the material or service flow—confirming that both basin size distributions follow a similar power law that differs significantly from the basin size distributions of rivers in nature. We theoretically analyze the process of trimming and derive a consistent statistical formulation between the original link number and the basin size.

  18. Streaming driven by sessile microbubbles: Explaining flow patterns and frequency response

    NASA Astrophysics Data System (ADS)

    Rallabandi, Bhargav; Wang, Cheng; Guo, Lin; Hilgenfeldt, Sascha

    2013-11-01

    Ultrasound excitation of bubbles drives powerful steady streaming flows which have found widespread applications in microfluidics, where bubbles are typically of semicircular cross section and attached to walls of the device (sessile). While bubble-driven streaming in bulk fluid is well understood, this practically relevant case presents additional complexity introduced by the wall and contact lines. We develop an asymptotic theory that takes into account the presence of the wall as well as the oscillation dynamics of the bubble, providing a complete description of the streaming flow as a function only of the driving frequency, the bubble size, and the physical properties of the fluid. We show that the coupling between different bubble oscillation modes sustains the experimentally observed streaming flow vortex pattern over a broad range of frequencies, greatly exceeding the widths of individual mode resonances. Above a threshold frequency, we predict, and observe in experiment, reversal of the flow direction. Our analytical theory can be used to guide the design of microfluidic devices, both in situations where robust flow patterns insensitive to parameter changes are desired (e.g. lab-on-a-chip sorters), and in cases where intentional modulation of the flow field appearance is key (e.g. efficient mixers). Current address: Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology.

  19. A logistic regression equation for estimating the probability of a stream flowing perennially in Massachusetts

    USGS Publications Warehouse

    Bent, Gardner C.; Archfield, Stacey A.

    2002-01-01

    A logistic regression equation was developed for estimating the probability of a stream flowing perennially at a specific site in Massachusetts. The equation provides city and town conservation commissions and the Massachusetts Department of Environmental Protection with an additional method for assessing whether streams are perennial or intermittent at a specific site in Massachusetts. This information is needed to assist these environmental agencies, who administer the Commonwealth of Massachusetts Rivers Protection Act of 1996, which establishes a 200-foot-wide protected riverfront area extending along the length of each side of the stream from the mean annual high-water line along each side of perennial streams, with exceptions in some urban areas. The equation was developed by relating the verified perennial or intermittent status of a stream site to selected basin characteristics of naturally flowing streams (no regulation by dams, surface-water withdrawals, ground-water withdrawals, diversion, waste-water discharge, and so forth) in Massachusetts. Stream sites used in the analysis were identified as perennial or intermittent on the basis of review of measured streamflow at sites throughout Massachusetts and on visual observation at sites in the South Coastal Basin, southeastern Massachusetts. Measured or observed zero flow(s) during months of extended drought as defined by the 310 Code of Massachusetts Regulations (CMR) 10.58(2)(a) were not considered when designating the perennial or intermittent status of a stream site. The database used to develop the equation included a total of 305 stream sites (84 intermittent- and 89 perennial-stream sites in the State, and 50 intermittent- and 82 perennial-stream sites in the South Coastal Basin). Stream sites included in the database had drainage areas that ranged from 0.14 to 8.94 square miles in the State and from 0.02 to 7.00 square miles in the South Coastal Basin.Results of the logistic regression analysis

  20. The influence of subglacial hydrology on the flow of Kamb Ice Stream, West Antarctica

    NASA Astrophysics Data System (ADS)

    Wel, Narelle; Christoffersen, Poul; Bougamont, Marion

    2013-03-01

    Ice streams on the Siple Coast, West Antarctica, have a complex history of flow because their basal motion is governed by time-varying basal conditions. Although the mechanical interaction between ice and till is well established, very little is known about the potential effect of regionally scaled water transport in a basal water system, which has only recently become apparent. To investigate the combined effect of hydrological and mechanical processes, we developed the Hydrology, Ice and Till model, in which ice flow is coupled to a Coulomb-plastic till layer and a basal water system consisting of discrete conduits. When the model is applied to Kamb Ice Stream (KIS), results confirm that it is capable of oscillating between fast and stagnant modes of flow. We show that when subglacial conduits are disregarded or do not extend to the grounding line, the oscillatory behavior of the ice stream is governed by the basal thermal regime. When conduits extend to the grounding line, the modelled ice stream oscillation period is increased, peak speeds are reduced, and oscillations may ultimately cease if the volume of water supplied is sufficiently high. Three different hydrological states characterize the behavioral patterns of ice flow and these states are distinguished by conditions at the grounding line. Modelled ice stream velocities were found to oscillate with fast and slow periods typically lasting a few hundred years, although varying according to hydrological activity. Our results indicate that KIS could reactivate this century, given its hydrological setting and ~170 years of stagnation.

  1. Estimating selected low-flow frequency statistics and harmonic-mean flows for ungaged, unregulated streams in Indiana

    USGS Publications Warehouse

    Martin, Gary R.; Fowler, Kathleen K.; Arihood, Leslie D.

    2016-01-01

    Information on low-flow characteristics of streams is essential for the management of water resources. This report provides equations for estimating the 1-, 7-, and 30-day mean low flows for a recurrence interval of 10 years and the harmonic-mean flow at ungaged, unregulated stream sites in Indiana. These equations were developed using the low-flow statistics and basin characteristics for 108 continuous-record streamgages in Indiana with at least 10 years of daily mean streamflow data through the 2011 climate year (April 1 through March 31). The equations were developed in cooperation with the Indiana Department of Environmental Management.Regression techniques were used to develop the equations for estimating low-flow frequency statistics and the harmonic-mean flows on the basis of drainage-basin characteristics. A geographic information system was used to measure basin characteristics for selected streamgages. A final set of 25 basin characteristics measured at all the streamgages were evaluated to choose the best predictors of the low-flow statistics.Logistic-regression equations applicable statewide are presented for estimating the probability that selected low-flow frequency statistics equal zero. These equations use the explanatory variables total drainage area, average transmissivity of the full thickness of the unconsolidated deposits within 1,000 feet of the stream network, and latitude of the basin outlet. The percentage of the streamgage low-flow statistics correctly classified as zero or nonzero using the logistic-regression equations ranged from 86.1 to 88.9 percent.Generalized-least-squares regression equations applicable statewide for estimating nonzero low-flow frequency statistics use total drainage area, the average hydraulic conductivity of the top 70 feet of unconsolidated deposits, the slope of the basin, and the index of permeability and thickness of the Quaternary surficial sediments as explanatory variables. The average standard error of

  2. Transport of nitrate and ammonium during stream flow events from a southeastern USA Coastal Plain in-stream wetland - 1997 to 1999

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In-stream wetlands (ISW) intercept stream water and act as nitrogen (N) sinks influencing nitrate and ammonium export to downstream aquatic ecosystems. Nitrogen assimilation and storage by ISW, however, can be affected by storm flows, seasonal changes in water quality or shifts in N pools, resulting...

  3. Incorporating seepage losses into the unsteady streamflow equations for simulating intermittent flow along mountain front streams

    USGS Publications Warehouse

    Niswonger, R.G.; Prudic, D.E.; Pohll, G.; Constantz, J.

    2005-01-01

    Seepage losses along numerous mountain front streams that discharge intermittently onto alluvial fans and piedmont alluvial plains are an important source of groundwater in the Basin and Range Province of the Western United States. Determining the distribution of seepage loss along mountain front streams is important when assessing groundwater resources of the region. Seepage loss along a mountain front stream in northern Nevada was evaluated using a one-dimensional unsteady streamflow model. Seepage loss was incorporated into the spatial derivatives of the streamflow equations. Because seepage loss from streams is dependent on stream depth, wetted perimeter, and streambed properties, a two-dimensional variably saturated flow model was used to develop a series of relations between seepage loss and stream depth for each reach. This method works when streams are separated from groundwater by variably saturated sediment. Two periods of intermittent flow were simulated to evaluate the modeling approach. The model reproduced measured flow and seepage losses along the channel. Seepage loss in the spring of 2000 was limited to the upper reaches on the alluvial plain and totaled 196,000 m3, whereas 64% of the seepage loss in the spring of 2004 occurred at the base of the alluvial plain and totaled 273,000 m3. A greater seepage loss at the base of the piedmont alluvial plain is attributed to increased streambed hydraulic conductivity caused by less armoring of the channel. The modeling approach provides a method for quantifying and distributing seepage loss along mountain front streams that cross alluvial fans or piedmont alluvial plains. Copyright 2005 by the American Geophysical Union.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. 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. PMID:12051421

  6. 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.

  7. Solar forcing of the stream flow of a continental scale South American river.

    PubMed

    Mauas, Pablo J D; Flamenco, Eduardo; Buccino, Andrea P

    2008-10-17

    Solar forcing on climate has been reported in several studies although the evidence so far remains inconclusive. Here, we analyze the stream flow of one of the largest rivers in the world, the Paraná in southeastern South America. For the last century, we find a strong correlation with the sunspot number, in multidecadal time scales, and with larger solar activity corresponding to larger stream flow. The correlation coefficient is r=0.78, significant to a 99% level. In shorter time scales we find a strong correlation with El Niño. These results are a step toward flood prediction, which might have great social and economic impacts. PMID:18999720

  8. Method of measuring the mass flow rate of a substance entering a cocurrent fluid stream

    DOEpatents

    Cochran, Jr., Henry D.

    1978-04-11

    This invention relates to an improved method of monitoring the mass flow rate of a substance entering a cocurrent fluid stream. The method very basically consists of heating equal sections of the fluid stream above and below the point of entry of the substance to be monitored, and measuring and comparing the resulting change in temperature of the sections. Advantage is taken of the difference in thermal characteristics of the fluid and the substance to be measured to correlate temperature differences in the sections above and below the substance feed point for providing an indication of the mass flow rate of the substance.

  9. 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.

  10. Estimates of median flows for streams on the Kansas surface water register

    USGS Publications Warehouse

    Perry, Charles A.; Wolock, David M.; Artman, Joshua C.

    2002-01-01

    The Kansas State Legislature, by enacting Kansas Statute KSA 82a-2001 et. seq., mandated the criteria for determining which Kansas stream segments would be subject to classification by the State. One criterion for the selection as a classified stream segment is based on the statistic of median flow being equal to or greater than 1 cubic foot per second. As specified by KSA 82a-2001 et. seq., median flows were determined from U.S. Geological Survey streamflow-gaging-station data by using the most-recent 10-years of gaged data (KSA) for each streamflow-gaging station. Median flows also were determined by using gaged data from the entire period of record (all-available hydrology, AAH). Least-squares multiple regression techniques were used, along with Tobit analyses, to develop equations for estimating median flows for uncontrolled stream segments. The drainage area of the uncontrolled gaging stations used in the regression analyses ranged from 2.06 to 12,004 square miles. A logarithmic transformation of the data was needed to develop the best linear relation for computing median flows. In the regression analyses, the significant climatic and basin characteristics, in order of importance, were drainage area, mean annual precipitation, mean basin permeability, and mean basin slope. Tobit analyses of KSA data yielded a root mean square error of 0.285 logarithmic units, and the best equations using Tobit analyses of AAH data had a root mean square error of 0.247 logarithmic units. These equations and an interpolation procedure were used to compute median flows for the uncontrolled stream segments on the Kansas Surface Water Register. Measured median flows from gaging stations were incorporated into the regression-estimated median flows along the stream segments where available. The segments that were uncontrolled were interpolated using gaged data weighted according to the drainage area and the bias between the regression-estimated and gaged flow information. On

  11. 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.

  12. Median and Low-Flow Characteristics for Streams under Natural and Diverted Conditions, Northeast Maui, Hawaii

    USGS Publications Warehouse

    Gingerich, Stephen B.

    2005-01-01

    Flow-duration statistics under natural (undiverted) and diverted flow conditions were estimated for gaged and ungaged sites on 21 streams in northeast Maui, Hawaii. The estimates were made using the optimal combination of continuous-record gaging-station data, low-flow measurements, and values determined from regression equations developed as part of this study. Estimated 50- and 95-percent flow duration statistics for streams are presented and the analyses done to develop and evaluate the methods used in estimating the statistics are described. Estimated streamflow statistics are presented for sites where various amounts of streamflow data are available as well as for locations where no data are available. Daily mean flows were used to determine flow-duration statistics for continuous-record stream-gaging stations in the study area following U.S. Geological Survey established standard methods. Duration discharges of 50- and 95-percent were determined from total flow and base flow for each continuous-record station. The index-station method was used to adjust all of the streamflow records to a common, long-term period. The gaging station on West Wailuaiki Stream (16518000) was chosen as the index station because of its record length (1914-2003) and favorable geographic location. Adjustments based on the index-station method resulted in decreases to the 50-percent duration total flow, 50-percent duration base flow, 95-percent duration total flow, and 95-percent duration base flow computed on the basis of short-term records that averaged 7, 3, 4, and 1 percent, respectively. For the drainage basin of each continuous-record gaged site and selected ungaged sites, morphometric, geologic, soil, and rainfall characteristics were quantified using Geographic Information System techniques. Regression equations relating the non-diverted streamflow statistics to basin characteristics of the gaged basins were developed using ordinary-least-squares regression analyses. Rainfall

  13. Flow-Through Stream Modeling with MODFLOW and MT3D: Certainties and Limitations.

    PubMed

    Ben Simon, Rose; Bernard, Stéphane; Meurville, Charles; Rebour, Vincent

    2015-01-01

    This paper aims to assess MODFLOW and MT3D capabilities for simulating the spread of contaminants from a river exhibiting an unusual relationship with an alluvial aquifer, with the groundwater head higher than the river head on one side and lower on the other (flow-through stream). A series of simulation tests is conducted using a simple hypothetical model so as to characterize and quantify these limitations. Simulation results show that the expected contaminant spread could be achieved with a specific configuration composed of two sets of parameters: (1) modeled object parameters (hydraulic groundwater gradient, hydraulic conductivity values of aquifer and streambed), and (2) modeling parameters (vertical discretization of aquifer, horizontal refinement of stream modeled with River [RIV] package). The influence of these various parameters on simulation results is investigated, and potential complications and errors are identified. Contaminant spread from stream to aquifer is not always reproduced by MT3D due to the RIV package's inability to simulate lateral exchange fluxes between stream and aquifer. This paper identifies the need for a MODFLOW streamflow package allowing lateral stream-aquifer interactions and streamflow routine calculations. Such developments could be of particular interest for modeling contaminated flow-through streams. PMID:25557038

  14. No Snow No Flow: How Montane Stream Networks Respond to Drought

    NASA Astrophysics Data System (ADS)

    Grant, G.; Nolin, A. W.; Selker, J. S.; Lewis, S.; Hempel, L. A.; Jefferson, A.; Walter, C.; Roques, C.

    2015-12-01

    Hydrologic extremes, such as drought, offer an exceptional opportunity to explore how runoff generation mechanisms and stream networks respond to changing precipitation regimes. The winter of 2014-2015 was the warmest on record in western Oregon, US, with record low snowpacks, and was followed by an anomalously warm, dry spring, resulting in historically low streamflows. But a year like 2015 is more than an outlier meteorological year. It provides a unique opportunity to test fundamental hypotheses for how montane hydrologic systems will respond to anticipated changes in amount and timing of recharge. In particular, the volcanic Cascade Mountains represent a "landscape laboratory" comprised of two distinct runoff regimes: the surface-flow dominated Western Cascade watersheds, with flashy streamflow regimes, rapid baseflow recession, and very low summer flows; and (b) the spring-fed High Cascade watersheds, with a slow-responding streamflow regime, and a long and sustained baseflow recession that maintains late summer streamflow through deep-groundwater contributions to high volume, coldwater springs. We hypothesize that stream network response to the extremely low snowpack and recharge varies sharply in these two regions. In surface flow dominated streams, the location of channel heads can migrate downstream, contracting the network longitudinally; wetted channel width and depth contract laterally as summer recession proceeds and flows diminish. In contrast, in spring-fed streams, channel heads "jump" to the next downstream spring when upper basin spring flow diminishes to zero. Downstream of flowing springs, wetted channel width and depth contract laterally as flows recede. To test these hypotheses, we conducted a field campaign to measure changing discharge, hydraulic geometry, and channel head location in both types of watersheds throughout the summer and early fall. Multiple cross-section sites were established on 6 streams representing both flow regime types

  15. Hyporheic Zone Denitrification: Flow Path Controls and Scaling Consequences for N budgets for the Whole Stream

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.; Bohlke, J. K.; Voytek, M. A.; Scott, D.; Tobias, C. R.

    2013-12-01

    Denitrification is thought to be enhanced by hyporheic transport but there is little direct evidence from the field that relates controlling processes to whole-stream consequences for N budgets. To demonstrate at a field site we injected 15 NO3-, Br (conservative tracer) and SF6 (gas exchange tracer) and compared measures of whole-stream denitrification with in situ hyporheic denitrification measurements in both shallow and deeper flow paths of contrasting geomorphic units such as channel thalwegs and side cavities. Hyporheic denitrification accounted for between a few percent and 200% of whole-stream denitrification. The reaction rate constant was positively related to hyporheic exchange rate (which increases substrate delivery), concentrations of substrates DOC and nitrate, microbial denitrifier abundance as indicated by nirS, and measures related to granular surface area and presence of anoxic microzones in otherwise suboxic porewater. Reaction efficiency in individual hyporheic flow paths was quantified as the dimensionless product of reaction rate constant and hyporheic residence time, λhzτhz (also defined as a Damköhler number, Daden-hz). At the stream reach scale the reaction significance was quantified by a dimensionless index Rs that combines the product of Da hz and the proportion of stream discharge passing through the hyporheic zone. Reaction progress was optimal in the subset of hyporheic flow paths where Da den-hz ~ 1, which avoids inefficient transport through very long flow paths after substrates have been used up but also avoids inefficient pathways that require repeated entries and exits through very short hyporheic flow paths to complete the reaction. We conclude that the zone of significant denitrification in the streambed can be substantially less than the full depth of the hyporheic zone, which is one reason previous researchers were not able to explain whole-stream denitrification rates based on total hyporheic-zone metrics such as

  16. 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.

  17. Surface acoustic streaming in microfluidic system for rapid multicellular tumor spheroids generation

    NASA Astrophysics Data System (ADS)

    AlHasan, Layla; Qi, Aisha; Al-Aboodi, Aswan; Rezk, Amged; Shilton, Richie R.; Chan, Peggy P. Y.; Friend, James; Yeo, Leslie

    2013-12-01

    In this study, we developed a novel and rapid method to generate in vitro three-dimensional (3D) multicellular tumor spheroids using a surface acoustic wave (SAW) device. A SAW device with single-phase unidirectional transducer electrodes (SPUTD) on lithium niobate substrate was fabricated using standing UV photolithography and wet-etching techniques. To generate spheroids, the SAW device was loaded with medium containing human breast carcinoma (BT474) cells, an oscillating electrical signal at resonant frequency was supplied to the SPUDT to generate acoustic radiation in the medium. Spheroids with uniform size and shape can be obtained using this method in less than 1 minute, and the size of the spheroids can be controlled through adjusting the seeding density. The resulting spheroids were used for further cultivation and were monitored using an optical microscope in real time. The viability and actin organization of the spheroids were assessed using live/dead viability staining and actin cytoskeleton staining, respectively. Compared to spheroids generated using the liquid overlay method, the SAW generated spheroids exhibited higher circularity and higher viability. The F-actin filaments of spheroids appear to aggregate compared to that of untreated cells, indicating that mature spheroids can be obtained using this method. This spheroid generating method can be useful for a variety of biological studies and clinical applications.

  18. Relating low-flow characteristics to the base flow recession time constant at partial record stream gauges

    USGS Publications Warehouse

    Eng, K.; Milly, P.C.D.

    2007-01-01

    Base flow recession information is helpful for regional estimation of low-flow characteristics. However, analyses that exploit such information generally require a continuous record of streamflow at the estimation site to characterize base flow recession. Here we propose a simple method for characterizing base flow recession at low-flow partial record stream gauges (i.e., sites with very few streamflow measurements under low-streamflow conditions), and we use that characterization as the basis for a practical new approach to low-flow regression. In a case study the introduction of a base flow recession time constant, estimated from a single pair of strategically timed streamflow measurements, approximately halves the root-mean-square estimation error relative to that of a conventional drainage area regression. Additional streamflow measurements can be used to reduce the error further.

  19. Spatial statistics, variation and trends in SPI and their relation to stream flow in Portugal

    NASA Astrophysics Data System (ADS)

    de Lima, M. Isabel P.; Silva, Álvaro P.; Espírito Santo, Fátima; de Lima, João L. M. P.

    2015-04-01

    Stream flow regimes and variability are highly dependent on the precipitation input across the drainage basin, although it also depends on other factors (e.g. physiography and land use). Changes in precipitation, of natural or anthropogenic origin, are likely to affect surface runoff regimes and other hydrological processes. However, from surface runoff data alone it is difficult to disentangle between the nature of changes in the runoff regime. Thus, the main focus of this study is using spatial statistics derived from the Standardized Precipitation Index (SPI) calculated at several times scales for Portuguese river basins to get a better insight into climate change impacts on stream flow variability and trends across the basins. SPI constitutes a practical tool to assess, monitor and evaluate spatio-temporal variability of dry/wet conditions, over different periods, and here we are applying it at the basin scale using monthly precipitation data. The spatial interpolation and analysis functions in GIS are used to obtain SPI statistical values for each basin. A special focus is given on the synthesis of the severe or extreme wet/dry events. The statistics are used to better understand the flow variability in Iberian water courses flowing to the Atlantic Ocean, which drainage basins have different geometric, geological and climatic characteristics, as well as land use. Long stream flow time series are examined for trends in flow rates and fluctuations, and peak flows, which is expected to have implications for ecological processes and human usage throughout basins.

  20. PIV measurements of the streaming fluid flow due to the adsorption of particles

    NASA Astrophysics Data System (ADS)

    Patel, Harsh; Musunuri, Naga; Amah, Edison; Fischer, Ian; Singh, Pushpendra

    2015-11-01

    The particle image velocimetry (PIV) technique is used to study the streaming flow that is induced when a spherical particle is adsorbed at a liquid surface. The flow causes powders sprinkled on a liquid surface to disperse on the surface. The dispersion can occur so quickly that it appears explosive, especially for small particles on the surface of mobile liquids like water. The measurements show that the adsorption of a spherical particle causes an axisymmetric streaming flow about the vertical line passing through the center of the particle. The fluid directly below the particle rises upward, and near the surface, it moves away from the particle. The flow, which develops within a fraction of second after the adsorption of the particle, persists for several seconds. The flow strength, and the volume over which it extends, decreases with decreasing particle size. The streaming flow induced by the adsorption of two or more particles is a combination of the flows which they induce individually. The work was supported by National Science Foundation.

  1. Calculating discharge of phosphorus and nitrogen with groundwater base flow to a small urban stream reach

    NASA Astrophysics Data System (ADS)

    Fitzgerald, Alex; Roy, James W.; Smith, James E.

    2015-09-01

    Elevated levels of nutrients, especially phosphorus, in urban streams can lead to eutrophication and general degradation of stream water quality. Contributions of phosphorus from groundwater have typically been assumed minor, though elevated concentrations have been associated with riparian areas and urban settings. The objective of this study was to investigate the importance of groundwater as a pathway for phosphorus and nitrogen input to a gaining urban stream. The stream at the 28-m study reach was 3-5 m wide and straight, flowing generally eastward, with a relatively smooth bottom of predominantly sand, with some areas of finer sediments and a few boulders. Temperature-based methods were used to estimate the groundwater flux distribution. Detailed concentration distributions in discharging groundwater were mapped using in-stream piezometers and diffusion-based peepers, and showed elevated levels of soluble reactive phosphorus (SRP) and ammonium compared to the stream (while nitrate levels were lower), especially along the south bank, where groundwater fluxes were lower and geochemically reducing conditions dominated. Field evidence suggests the ammonium may originate from nearby landfills, but that local sediments likely contribute the SRP. Ammonium and SRP mass discharges with groundwater were then estimated as the product of the respective concentration distributions and the groundwater flux distribution. These were determined as approximately 9 and 200 g d-1 for SRP and ammonium, respectively, which compares to stream mass discharges over the observed range of base flows of 20-1100 and 270-7600 g d-1, respectively. This suggests that groundwater from this small reach, and any similar areas along Dyment's Creek, has the potential to contribute substantially to the stream nutrient concentrations.

  2. Validating alternative methodologies to estimate the hydrological regime of temporary streams when flow data are unavailable

    NASA Astrophysics Data System (ADS)

    Llorens, Pilar; Gallart, Francesc; Latron, Jérôme; Cid, Núria; Rieradevall, Maria; Prat, Narcís

    2016-04-01

    Aquatic life in temporary streams is strongly conditioned by the temporal variability of the hydrological conditions that control the occurrence and connectivity of diverse mesohabitats. In this context, the software TREHS (Temporary Rivers' Ecological and Hydrological Status) has been developed, in the framework of the LIFE Trivers project, to help managers for adequately implement the Water Framework Directive in this type of water bodies. TREHS, using the methodology described in Gallart et al (2012), defines six temporal 'aquatic states', based on the hydrological conditions representing different mesohabitats, for a given reach at a particular moment. Nevertheless, hydrological data for assessing the regime of temporary streams are often non-existent or scarce. The scarcity of flow data makes frequently impossible the characterization of temporary streams hydrological regimes and, as a consequence, the selection of the correct periods and methods to determine their ecological status. Because of its qualitative nature, the TREHS approach allows the use of alternative methodologies to assess the regime of temporary streams in the lack of observed flow data. However, to adapt the TREHS to this qualitative data both the temporal scheme (from monthly to seasonal) as well as the number of aquatic states (from 6 to 3) have been modified. Two alternatives complementary methodologies were tested within the TREHS framework to assess the regime of temporary streams: interviews and aerial photographs. All the gauging stations (13) belonging to the Catalan Internal Catchments (NE, Spain) with recurrent zero flows periods were selected to validate both methodologies. On one hand, non-structured interviews were carried out to inhabitants of villages and small towns near the gauging stations. Flow permanence metrics for input into TREHS were drawn from the notes taken during the interviews. On the other hand, the historical series of available aerial photographs (typically 10

  3. 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

  4. A difference theory for noise propagation in an acoustically lined duct with mean flow

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Rice, E. J.

    1973-01-01

    A finite difference formulation is presented for sound propagation in a two-dimensional straight soft-walled duct with uniform flow. The difference analysis is developed in terms of complex notation. The governing acoustic difference equations and the appropriate displacement boundary conditions associated with uniform flow are presented for the sound attenuation in straight hard and soft-walled ducts. At present the finite Mach number case is solved only for the one-dimensional hard walled duct.

  5. A difference theory for noise propagation in an acoustically lined duct with mean flow.

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Rice, E. J.

    1973-01-01

    A finite difference formulation is presented for sound propagation in a two-dimensional straight soft-walled duct with uniform flow. The difference analysis is developed in terms of complex notation. The governing acoustic difference equations and the appropriate displacement boundary conditions associated with uniform flow are presented. Example calculations are presented for the sound attenuation in straight hard and soft-walled ducts. At present the finite Mach number case is solved only for the one-dimensional hard walled duct.

  6. 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.

  7. 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

  8. Three-axis acoustic device for levitation of droplets in an open gas stream and its application to examine sulfur dioxide absorption by water droplets.

    PubMed

    Stephens, Terrance L; Budwig, Ralph S

    2007-01-01

    Two acoustic devices to stabilize a droplet in an open gas stream (single-axis and three-axis levitators) have been designed and tested. The gas stream was provided by a jet apparatus with a 64 mm exit diameter and a uniform velocity profile. The acoustic source used was a Langevin vibrator with a concave reflector. The single-axis levitator relied primarily on the radial force from the acoustic field and was shown to be limited because of significant droplet wandering. The three-axis levitator relied on a combination of the axial and radial forces. The three-axis levitator was applied to examine droplet deformation and circulation and to investigate the uptake of SO(2) from the gas stream to the droplet. Droplets ranging in diameters from 2 to 5 mm were levitated in gas streams with velocities up to 9 ms. Droplet wandering was on the order of a half droplet diameter for a 3 mm diameter droplet. Droplet circulation ranged from the predicted Hadamard-Rybczynski pattern to a rotating droplet pattern. Droplet pH over a central volume of the droplet was measured by planar laser induced fluorescence. The results for the decay of droplet pH versus time are in general agreement with published theory and experiments. PMID:17503939

  9. Unsteady Boundary-Layer Flow over Jerked Plate Moving in a Free Stream of Viscoelastic Fluid

    PubMed Central

    Mehmood, Ahmer; Ali, Asif; Saleem, Najma

    2014-01-01

    This study aims to investigate the unsteady boundary-layer flow of a viscoelastic non-Newtonian fluid over a flat surface. The plate is suddenly jerked to move with uniform velocity in a uniform stream of non-Newtonian fluid. Purely analytic solution to governing nonlinear equation is obtained. The solution is highly accurate and valid for all values of the dimensionless time 0 ≤ τ < ∞. Flow properties of the viscoelastic fluid are discussed through graphs. PMID:24892060

  10. Effects of dust correlations on the marginal stability of ion stream driven dust acoustic waves

    NASA Astrophysics Data System (ADS)

    Shukla, Manish K.; Avinash, K.

    2016-06-01

    The effect of dust–dust correlations on the marginal stability of dust acoustic waves excited by ion drift is studied. The ion drift is driven by the electric field {E}0 which is generally present in the discharge. Correlation effects on marginal stability are studied using augmented Debye–Hückel approximation. The marginal stability boundary is calculated in {E}0-{P}0 (P 0 is the pressure of the neutral gas) space with correlated dust grains. We show that due to dust-dust correlation the stability boundary moves into the unstable region thereby stabilizing the DAW. The effects are significant for smaller values of κ (=a/{λ }d) below unity (a is the mean particle distance and {λ }d is Debye length).

  11. Climate and Land-Cover Change Impacts on Stream Flow in the Southwest U.S.

    EPA Science Inventory

    Vegetation change in arid and semi-arid climatic regions of the American West are a primary concern in sustaining key ecosystem services such as clean, reliable water sources for multiple uses. Land cover and climate change impacts on stream flow were investigated in a southeast ...

  12. Ecosystem Consequences of Contrasting Flow Regimes in an Urban Effects Stream Mesocosm Study

    EPA Science Inventory

    A stream mesocosm experiment was conducted to study the ecosystem-wide effects of two replicated flow hydrograph treatments programmed in an attempt to compare a simulated predevelopment condition to the theoretical changes that new development brings, while accounting for engine...

  13. FLOW REGIME, JUVENILE ABUNDANCE, AND THE ASSEMBLAGE STRUCTURE OF STREAM FISHES

    EPA Science Inventory

    The assemblage of fishes in a second-order stream in east-central Illinois was compared through seine sampling for two years with distinctly different flow regimes. In both years adult (age 0) fish were most abundant in late spring and early summer while juvenile (age 0) abundanc...

  14. Quasi-steady acoustic response of wall perforations subject to a grazing-bias flow combination

    NASA Astrophysics Data System (ADS)

    Tonon, D.; Moers, E. M. T.; Hirschberg, A.

    2013-04-01

    Well known examples of acoustical dampers are the aero-engine liners, the IC-engine exhaust mufflers, and the liners in combustion chambers. These devices comprise wall perforations, responsible for their sound absorbing features. Understanding the effect of the flow on the acoustic properties of a perforation is essential for the design of acoustic dampers. In the present work the effect of a grazing-bias flow combination on the impedance of slit shaped wall perforations is experimentally investigated by means of a multi-microphone impedance tube. Measurements are carried out for perforation geometries relevant for in technical applications. The focus of the experiments is on the low Strouhal number (quasi-steady) behavior. Analytical models of the steady flow and of the low frequency aeroacoustic behavior of a two-dimensional wall perforation are proposed for the case of a bias flow directed from the grazing flow towards the opposite side of the perforated wall. These theoretical results compare favorably with the experiments, when a semi-empirical correction is used to obtain the correct limit for pure bias flow.

  15. Acoustic effects on profile drag of a laminar flow airfoil

    NASA Astrophysics Data System (ADS)

    Shearin, John G.; Jones, Michael G.; Baals, Robert A.

    1987-09-01

    A two-dimensional laminar flow airfoil (NLF-0414) was subjected to high-intensity sound (pure tones and white noise) over a frequency range of 2 to 5 kHz, while immersed in a flow of 240 ft/sec (Rn of 3 million) in a quiet flow facility. Using a wake-rake, wake dynamic pressures were determined and the deficit in momentum was used to calculate a two dimensional drag coefficient. Significant increases in drag were observed when the airfoil was subjected to the high intensity sound at critical sound frequencies. However, the increased drag was not accompanied by movement of the transition location.

  16. Urban contribution of pharmaceuticals and other organic wastewater contaminants to streams during differing flow conditions

    USGS Publications Warehouse

    Kolpin, D.W.; Skopec, M.; Meyer, M.T.; Furlong, E.T.; Zaugg, S.D.

    2004-01-01

    During 2001, 76 water samples were collected upstream and downstream of select towns and cities in Iowa during high-, normal- and low-flow conditions to determine the contribution of urban centers to concentrations of pharmaceuticals and other organic wastewater contaminants (OWCs) in streams under varying flow conditions. The towns ranged in population from approximately 2000 to 200 000. Overall, one or more OWCs were detected in 98.7% of the samples collected, with 62 of the 105 compounds being found. The most frequently detected compounds were metolachlor (pesticide), cholesterol (plant and animal sterol), caffeine (stimulant), β-sitosterol (plant sterol) and 1,7-dimethylxanthine (caffeine degradate). The number of OWCs detected decreased as streamflow increased from low- (51 compounds detected) to normal- (28) to high-flow (24) conditions. Antibiotics and other prescription drugs were only frequently detected during low-flow conditions. During low-flow conditions, 15 compounds (out of the 23) and ten compound groups (out of 11) detected in more than 10% of the streams sampled had significantly greater concentrations in samples collected downstream than in those collected upstream of the urban centers. Conversely, no significant differences in the concentrations were found during high-flow conditions. Thus, the urban contribution of OWCs to streams became progressively muted as streamflow increased.

  17. Regionalization of Low Flows in Hawaii Streams for Past and Future Rainfall Conditions

    NASA Astrophysics Data System (ADS)

    Bassiouni, M.

    2014-12-01

    The Hawaiian Islands experience large inter-annual rainfall variations and statistically significant long-term downward trends in streamflow, especially low flows, have been detected. Low flows in Hawaii streams provide a variety of beneficial uses that include maintaining fish habitat, supplying freshwater for irrigation and domestic uses, and protecting traditional and customary Hawaiian rights. However, the variability of low flows in ungaged streams in Hawaii has not been quantified and potential effects of climate change on low flows need to be better understood to properly manage surface-water resources. Regionalization of streamflow for ungaged areas in Hawaii provides a useful case study because streamflow, climate, and basin characteristics are extremely spatially and temporally variable. Here we present the development of statistical models to estimate low flows of ungaged streams in Hawaii for past and future rainfall conditions. We discuss the benefits and limitations of applying simple statistical approaches to improve understanding of changes in low flows in heterogeneous and data poor regions and to explicitly evaluate uncertainty and data needs in the context of climate change predictions for regional water-resources management.

  18. Evaluating Key Watershed Components of Low Flow Regimes in New England Streams.

    PubMed

    Morrison, Alisa C; Gold, Arthur J; Pelletier, Marguerite C

    2016-05-01

    Water resource managers seeking to optimize stream ecosystem services and abstractions of water from watersheds need an understanding of the importance of land use, physical and climatic characteristics, and hydrography on different low flow components of stream hydrographs. Within 33 USGS gaged watersheds of southern New England, we assessed relationships between watershed variables and a set of low flow parameters by using an information-theoretical approach. The key variables identified by the Akaike Information Criteria (AIC) weighting factors as generating positive relationships with low flow events included percent stratified drift, mean elevation, drainage area, and mean August precipitation. The extent of wetlands in the watershed was negatively related to low flow magnitudes. Of the various land use variables, the percentage of developed land was found to have the highest importance and a negative relationship on low flow magnitudes, but was less important than wetlands and physical and climatic features. Our results suggest that management practices aimed to sustain low flows in fluvial systems can benefit from attention to specific watershed features. We draw attention to the finding that streams located in watersheds with high proportions of wetlands may require more stringent approaches to withdrawals to sustain fluvial ecosystems during drought periods, particularly in watersheds with extensive development and limited deposits of stratified drift. PMID:27136170

  19. 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

  20. 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.

  1. 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.

  2. Constraints upon the Response of Fish and Crayfish to Environmental Flow Releases in a Regulated Headwater Stream Network

    PubMed Central

    Chester, Edwin T.; Matthews, Ty G.; Howson, Travis J.; Johnston, Kerrylyn; Mackie, Jonathon K.; Strachan, Scott R.; Robson, Belinda J.

    2014-01-01

    In dry climate zones, headwater streams are often regulated for water extraction causing intermittency in perennial streams and prolonged drying in intermittent streams. Regulation thereby reduces aquatic habitat downstream of weirs that also form barriers to migration by stream fauna. Environmental flow releases may restore streamflow in rivers, but are rarely applied to headwaters. We sampled fish and crayfish in four regulated headwater streams before and after the release of summer-autumn environmental flows, and in four nearby unregulated streams, to determine whether their abundances increased in response to flow releases. Historical data of fish and crayfish occurrence spanning a 30 year period was compared with contemporary data (electrofishing surveys, Victoria Range, Australia; summer 2008 to summer 2010) to assess the longer–term effects of regulation and drought. Although fish were recorded in regulated streams before 1996, they were not recorded in the present study upstream or downstream of weirs despite recent flow releases. Crayfish (Geocharax sp. nov. 1) remained in the regulated streams throughout the study, but did not become more abundant in response to flow releases. In contrast, native fish (Gadopsis marmoratus, Galaxias oliros, Galaxias maculatus) and crayfish remained present in unregulated streams, despite prolonged drought conditions during 2006–2010, and the assemblages of each of these streams remained essentially unchanged over the 30 year period. Flow release volumes may have been too small or have operated for an insufficient time to allow fish to recolonise regulated streams. Barriers to dispersal may also be preventing recolonisation. Indefinite continuation of annual flow releases, that prevent the unnatural cessation of flow caused by weirs, may eventually facilitate upstream movement of fish and crayfish in regulated channels; but other human–made dispersal barriers downstream need to be identified and ameliorated, to allow

  3. Constraints upon the response of fish and crayfish to environmental flow releases in a regulated headwater stream network.

    PubMed

    Chester, Edwin T; Matthews, Ty G; Howson, Travis J; Johnston, Kerrylyn; Mackie, Jonathon K; Strachan, Scott R; Robson, Belinda J

    2014-01-01

    In dry climate zones, headwater streams are often regulated for water extraction causing intermittency in perennial streams and prolonged drying in intermittent streams. Regulation thereby reduces aquatic habitat downstream of weirs that also form barriers to migration by stream fauna. Environmental flow releases may restore streamflow in rivers, but are rarely applied to headwaters. We sampled fish and crayfish in four regulated headwater streams before and after the release of summer-autumn environmental flows, and in four nearby unregulated streams, to determine whether their abundances increased in response to flow releases. Historical data of fish and crayfish occurrence spanning a 30 year period was compared with contemporary data (electrofishing surveys, Victoria Range, Australia; summer 2008 to summer 2010) to assess the longer-term effects of regulation and drought. Although fish were recorded in regulated streams before 1996, they were not recorded in the present study upstream or downstream of weirs despite recent flow releases. Crayfish (Geocharax sp. nov. 1) remained in the regulated streams throughout the study, but did not become more abundant in response to flow releases. In contrast, native fish (Gadopsis marmoratus, Galaxias oliros, Galaxias maculatus) and crayfish remained present in unregulated streams, despite prolonged drought conditions during 2006-2010, and the assemblages of each of these streams remained essentially unchanged over the 30 year period. Flow release volumes may have been too small or have operated for an insufficient time to allow fish to recolonise regulated streams. Barriers to dispersal may also be preventing recolonisation. Indefinite continuation of annual flow releases, that prevent the unnatural cessation of flow caused by weirs, may eventually facilitate upstream movement of fish and crayfish in regulated channels; but other human-made dispersal barriers downstream need to be identified and ameliorated, to allow

  4. Methods for estimating flow-duration curve and low-flow frequency statistics for ungaged locations on small streams in Minnesota

    USGS Publications Warehouse

    Ziegeweid, Jeffrey R.; Lorenz, David L.; Sanocki, Chris A.; Czuba, Christiana R.

    2015-01-01

    Equations developed in this study apply only to stream locations where flows are not substantially affected by regulation, diversion, or urbanization. All equations presented in this study will be incorporated into StreamStats, a web-based geographic information system tool developed by the U.S. Geological Survey. StreamStats allows users to obtain streamflow statistics, basin characteristics, and other information for user-selected locations on streams through an interactive map.

  5. Distribution of Amphipods (Gammarus nipponensis Ueno) Among Mountain Headwater Streams with Different Legacies of Debris Flow Occurrence

    EPA Science Inventory

    To understand the impacts of debris flows on the distribution of an amphipod with limited dispersal ability in the context of stream networks, we surveyed the presence of Gammarus nipponensis in 87 headwater streams with different legacies of debris flow occurrence within an 8.5-...

  6. A biological tool to assess flow connectivity in reference temporary streams from the Mediterranean Basin.

    PubMed

    Cid, N; Verkaik, I; García-Roger, E M; Rieradevall, M; Bonada, N; Sánchez-Montoya, M M; Gómez, R; Suárez, M L; Vidal-Abarca, M R; Demartini, D; Buffagni, A; Erba, S; Karaouzas, I; Skoulikidis, N; Prat, N

    2016-01-01

    Many streams in the Mediterranean Basin have temporary flow regimes. While timing for seasonal drought is predictable, they undergo strong inter-annual variability in flow intensity. This high hydrological variability and associated ecological responses challenge the ecological status assessment of temporary streams, particularly when setting reference conditions. This study examined the effects of flow connectivity in aquatic macroinvertebrates from seven reference temporary streams across the Mediterranean Basin where hydrological variability and flow conditions are well studied. We tested for the effect of flow cessation on two streamflow indices and on community composition, and, by performing random forest and classification tree analyses we identified important biological predictors for classifying the aquatic state either as flowing or disconnected pools. Flow cessation was critical for one of the streamflow indices studied and for community composition. Macroinvertebrate families found to be important for classifying the aquatic state were Hydrophilidae, Simuliidae, Hydropsychidae, Planorbiidae, Heptageniidae and Gerridae. For biological traits, trait categories associated to feeding habits, food, locomotion and substrate relation were the most important and provided more accurate predictions compared to taxonomy. A combination of selected metrics and associated thresholds based on the most important biological predictors (i.e. Bio-AS Tool) were proposed in order to assess the aquatic state in reference temporary streams, especially in the absence of hydrological data. Although further development is needed, the tool can be of particular interest for monitoring, restoration, and conservation purposes, representing an important step towards an adequate management of temporary rivers not only in the Mediterranean Basin but also in other regions vulnerable to the effects of climate change. PMID:26209067

  7. Investigation of technology for the monitoring of UF/sub 6/ mass flow in UF/sub 6/ streams diluted with H/sub 2/

    SciTech Connect

    Baker, O.J.; Cooley, J.N.; Hewgley, W.A.; Moran, B.W.; Swindle, D.W. Jr.

    1986-12-01

    The applicability, availability, and effectiveness of gas flow meters are assessed as a means for verifying the mass flows of pure UF/sub 6/ streams diluted with a carrier gas. The initial survey identified the orifice, pitot tube, thermal, vortex shedding, and vortex precession (swirl) meters as promising for the intended use. Subsequent assessments of these flow meters revealed that two - the orifice meter and the pitot tube meter - are the best choices for the proposed applications: the first is recommended for low velocity gas, small diameter piping; the latter, for high velocity gas, large diameter piping. Final selection of the gas flow meters should be based on test loop evaluations in which the proposed meters are subjected to gas flows, temperatures, and pressures representative of those expected in service. Known instruments are evaluated that may be applicable to the measurement of uranium or UF/sub 6/ concentration in a UF/sub 6/ - H/sub 2/ process stream at an aerodynamic enrichment plant. Of the six procedures evaluated, four have been used for process monitoring in a UF/sub 6/ environment: gas mass spectrometry, infrared-ultraviolet-visible spectrophotometry, gas chromatography, and acoustic gas analysis. The remaining two procedures, laser fluorimetry and atomic absorption spectroscopy, would require significant development work before they could be used for process monitoring. Infrared-ultravioloet-visible spectrophotometry is judged to be the best procedure currently available to perform the required measurement.

  8. 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.

  9. Microbial responses to changes in flow status in temporary headwater streams: a cross-system comparison

    PubMed Central

    Febria, Catherine M.; Hosen, Jacob D.; Crump, Byron C.; Palmer, Margaret A.; Williams, D. Dudley

    2015-01-01

    Microbial communities are responsible for the bulk of biogeochemical processing in temporary headwater streams, yet there is still relatively little known about how community structure and function respond to periodic drying. Moreover, the ability to sample temporary habitats can be a logistical challenge due to the limited capability to measure and predict the timing, intensity and frequency of wet-dry events. Unsurprisingly, published datasets on microbial community structure and function are limited in scope and temporal resolution and vary widely in the molecular methods applied. We compared environmental and microbial community datasets for permanent and temporary tributaries of two different North American headwater stream systems: Speed River (Ontario, Canada) and Parkers Creek (Maryland, USA). We explored whether taxonomic diversity and community composition were altered as a result of flow permanence and compared community composition amongst streams using different 16S microbial community methods (i.e., T-RFLP and Illumina MiSeq). Contrary to our hypotheses, and irrespective of method, community composition did not respond strongly to drying. In both systems, community composition was related to site rather than drying condition. Additional network analysis on the Parkers Creek dataset indicated a shift in the central microbial relationships between temporary and permanent streams. In the permanent stream at Parkers Creek, associations of methanotrophic taxa were most dominant, whereas associations with taxa from the order Nitrospirales were more dominant in the temporary stream, particularly during dry conditions. We compared these results with existing published studies from around the world and found a wide range in community responses to drying. We conclude by proposing three hypotheses that may address contradictory results and, when tested across systems, may expand understanding of the responses of microbial communities in temporary streams to

  10. E. coli transport to stream water column from bottom sediments to the stream water column in base flow conditions

    NASA Astrophysics Data System (ADS)

    Pachepsky, Yakov; Shelton, Daniel; Stocker, Matthew

    2016-04-01

    E. coli as an indicator bacterium is commonly used to characterize microbiological water quality, to evaluate surface water sources for microbiological impairment, and to assess management practices that lead to the decrease of pathogens and indicator influx in surface water sources for recreation and irrigation. Bottom sediments present a large reservoir of fecal indicator bacteria that are known to be released to water column during high flow events caused by rainstorms and snowmelt. The objective of this work was to see if the influx of E. coli from sediments to water occurs also during base flow periods when groundwater rather than runoff provides the major water input to the stream. The experiment was carried out at the first-order creek in Maryland flowing in the riparian zone in base flow conditions. An inert tracer was released to creek water from the manifold for 5 hours. Streamflow and concentrations of E. coli and tracer were monitored in water 10 m below tracer release location, and at the downstream location at 450 m from the release location. The tracer mass recovered at the downstream location was close to the released tracer mass. We then could directly compare the total numbers of E. coli in volumes of water containing tracer at the upstream (release) location and the downstream location. There was a substantial (3 to 6 times) increase in flow between the upstream and downstream locations as well as the substantial increase in the E. coli total numbers in water (14 to 26 times). The average E. coli influx from the bottom sediment was about 400 cells m-2s-1. Although this value is about 2 to 5 times less than published E. coli release rates during high flow events, it still can substantially change the microbial water quality assessment without any input from animal agriculture or manure application. Interesting research objectives include finding out whether the transport of E. coli from bottom sediment to water column during the base flow periods

  11. The efficacy of stream power and flow duration on geomorphic responses to catastrophic flooding

    NASA Astrophysics Data System (ADS)

    Magilligan, F. J.; Buraas, E. M.; Renshaw, C. E.

    2015-01-01

    Geomorphologists have long studied the impacts of extreme floods, yet the association between the magnitude of flow parameters (discharge, velocity, shear stress, or stream power) and resulting geomorphic effectiveness remains vague and non-deterministic. Attempts have been made to include flow duration and total expenditure of stream power, in combination with peak unit stream power, as important variables, but there has been minimal exploration of this hydraulic combination. Taking advantage of Tropical Storm Irene's rapid track through eastern Vermont (USA) in late summer 2011, this paper presents the array of geomorphic responses to a short duration (time to peak of < 8 h) but high magnitude flood that was the twentieth century flood of record for numerous watersheds. We present herein the geomorphic imprint of Tropical Storm Irene flooding within a larger context of fluvial theory concerning the role of, and trade-off between, the magnitude of energy expenditure during a flood and its duration. Focusing on a detailed field effort within the 187-km2 Saxtons River basin in southeastern VT, augmented by select sites along the adjacent lower gradient Williams River (291-km2), we elucidate (1) the geomorphic effects of a short duration flood in a humid, well-vegetated landscape; (2) the relationship between geomorphic response and (a) peak stream power, (b) total stream power, and (c) flow duration of stream power above a critical threshold; and (3) the spatial variation of geomorphic effects relative to reach-scale geologic and geomorphic controls. Flooding associated with Tropical Storm Irene ranged from the 1000 year recurrence interval (RI) flood (based on Weibull flood frequency analysis) to the 300 year RI flood (log Pearson Type III). Discharges spawned a peak unit stream power of 712 W/m2 (Saxtons River) and 361 W/m2 (Williams River), with total energy expenditure throughout the event of ~ 16,000 × 103 and 15,000 × 103 J, respectively. For the Saxtons

  12. Using ion flows parallel and perpendicular to gravity to modify dust acoustic waves

    NASA Astrophysics Data System (ADS)

    Thomas, E.; Fisher, R.

    2008-11-01

    Recent studies of dust acoustic waves have shown that the dust kinetic temperature can play an important role in determining the resulting dispersion relation [M. Rosenberg, et al., Phys. Plasmas, 15, 073701 (2008)]. In these studies, it is believed that ion flows play a dominant role in determining both the kinetic temperature of the charged microparticles as well as providing the source of energy for triggering the waves. In this presentation, results will be presented on the effects of ion flow on spatial structure and velocity distribution of dust acoustic waves. Here, the waves will be formed in dusty plasmas consisting of 3 ± 1 micron diameter silica microspheres. Two separate electrodes will be used to modify the ion flow in the plasma -- one parallel to the direction of gravity and one perpendicular to the direction of gravity. Particle image velocimetry (PIV) techniques will be used to observe the particles and to measure their velocity distributions.

  13. Riparian indicators of flow frequency in a tropical montane stream network

    NASA Astrophysics Data System (ADS)

    Pike, Andrew S.; Scatena, Frederick N.

    2010-03-01

    SummaryMany field indicators have been used to approximate the magnitude and frequency of flows in a variety of streams and rivers, yet due to a scarcity of long-term flow records in tropical mountain streams, little to no work has been done to establish such relationships between field features and the flow regime in these environments. Furthermore, the transition between the active channel of a river and the adjacent flood zone (i.e. bankfull) is an important geomorphologic and ecological boundary, but is rarely identifiable in steep mountain channels that lack alluvial flood plains. This study (a) quantifies relationships between field indicators and flow frequency in alluvial and steepland channels in a tropical mountain stream network and (b) identifies a reference active channel boundary in these channels, based on statistically defined combinations of riparian features, that corresponds to the same flow frequency of the bankfull stage and the effective discharge in adjacent alluvial channels. The relative elevation of transitions in riparian vegetation, soil, and substrate characteristics were first surveyed at nine stream gages in and around the Luquillo Experimental Forest in Northeastern Puerto Rico. The corresponding discharge, flow frequency, and recurrence intervals associated with these features was then determined from long-term 15-min discharge records and a partial duration series analysis. Survey data indicate that mosses and short grasses dominate at a stage often inundated by sub-effective flows. Herbaceous vegetation is associated with intermediate discharges that correspond to the threshold for sediment mobilization. Near-channel woody shrubs and trees establish at elevations along the channel margin inundated by a less frequent discharge that is coincident with the effective discharge of bed load sediment transport. Our data demonstrate that in alluvial channels in the study, both the bankfull stage (as marked by a flood plain) and the

  14. Aeroacoustics of Three-Stream Jets

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda S.

    2012-01-01

    Results from acoustic measurements of noise radiated from a heated, three-stream, co-annular exhaust system operated at subsonic conditions are presented. The experiments were conducted for a range of core, bypass, and tertiary stream temperatures and pressures. The nozzle system had a fan-to-core area ratio of 2.92 and a tertiary-to-core area ratio of 0.96. The impact of introducing a third stream on the radiated noise for third-stream velocities below that of the bypass stream was to reduce high frequency noise levels at broadside and peak jet-noise angles. Mid-frequency noise radiation at aft observation angles was impacted by the conditions of the third stream. The core velocity had the greatest impact on peak noise levels and the bypass-to-core mass flow ratio had a slight impact on levels in the peak jet-noise direction. The third-stream jet conditions had no impact on peak noise levels. Introduction of a third jet stream in the presence of a simulated forward-flight stream limits the impact of the third stream on radiated noise. For equivalent ideal thrust conditions, two-stream and three-stream jets can produce similar acoustic spectra although high-frequency noise levels tend to be lower for the three-stream jet.

  15. Interactions between hyporheic flow produced by stream meanders, bars, and dunes

    USGS Publications Warehouse

    Stonedahl, Susa H.; Harvey, Judson W.; Packman, Aaron I.

    2013-01-01

    Stream channel morphology from grain-scale roughness to large meanders drives hyporheic exchange flow. In practice, it is difficult to model hyporheic flow over the wide spectrum of topographic features typically found in rivers. As a result, many studies only characterize isolated exchange processes at a single spatial scale. In this work, we simulated hyporheic flows induced by a range of geomorphic features including meanders, bars and dunes in sand bed streams. Twenty cases were examined with 5 degrees of river meandering. Each meandering river model was run initially without any small topographic features. Models were run again after superimposing only bars and then only dunes, and then run a final time after including all scales of topographic features. This allowed us to investigate the relative importance and interactions between flows induced by different scales of topography. We found that dunes typically contributed more to hyporheic exchange than bars and meanders. Furthermore, our simulations show that the volume of water exchanged and the distributions of hyporheic residence times resulting from various scales of topographic features are close to, but not linearly additive. These findings can potentially be used to develop scaling laws for hyporheic flow that can be widely applied in streams and rivers.

  16. Polymer-template-assisted growth of gold nanowires using a novel flow-stream technique.

    PubMed

    Metwalli, E; Moulin, J-F; Perlich, J; Wang, W; Diethert, A; Roth, S V; Müller-Buschbaum, P

    2009-10-01

    By utilizing a fluidic device, a gold nanoparticle dispersion is cast onto a nanostructured polymer template using solution subjected to hydrodynamic flow. With in situ grazing incidence small-angle X-ray scattering (GISAXS), the progressive gold deposition from a stream of gold solution onto the polymer template of a diblock copolymer with parallel cylinder morphology arranged into powder-like domains is investigated. The continuously flowing solution causes a systematic increase in the X-ray contrast between both of the microphase-separated blocks of the block copolymer film, indicating flow-induced selective gold immobilization on one block. Both in situ GISAXS data and atomic force microscopy of the metal-deposited polymer film prove the 1D coalescence of nanoparticles into continuous nanowires. With additional gold nanoparticle upload by the continuous flow-stream method, the selectivity of the nanoparticle deposition diminishes as a result of the formation of a pseudo uniform gold layer. Consequently, this flow-stream deposition technique introduces an easy alternative method to the vapor deposition technique for surface gold nanopatterning. PMID:19572494

  17. Assessing the ecological base and peak flow of the alpine streams in Central Taiwan

    NASA Astrophysics Data System (ADS)

    Wei, C.; Yang, P. S.; Tian, P. L.

    2009-04-01

    The ecological base and peak flow are crucial for the assessment and design for habitat rehabilitation and recovery. The amount of discharge affects the aquatic creatures and may severely damage the existence and balance of the community under extreme conditions. Aquatic insects are selected as the target species in this study to evaluate the influence of the discharge and to estimate the ecological base and peak flow. The distribution of the number of species and abundance (density) versus discharge is assessed to define the critical discharge. Two streams located at the alpine area in central Taiwan are selected as the study area to evaluate the base and peak flow. From the preliminary data (Aug 2008 to Dec 2008) collected from one stream Creek C originating from Sitou Area in Central Taiwan shows that the abundance of several species varies with the discharge. The dominate family and genus of aquatic insects is Baetidae (Order Ephemeroptera) and Baetis spp. that accounts for 32.47% and 31.11%, respectively. The Hilsenhoff family biotic index (FBI) shows that the water quality is classified to "Good" and "Very Good" level while the river pollution index (RPI) indicates that the stream is non-polluted. The discharge of base flow interpreted from the 95% curve of duration for the daily discharge is 0.0234 cms. Consistent observations are yet to be collected to yield more accurate result and ecological peak flow in rainy and typhoon seasons.

  18. 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.

  19. 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.

  20. Spectral measurement of nonequilibrium arc-jet free-stream flow

    NASA Technical Reports Server (NTRS)

    Gopaul, Nigel K. J. M.

    1993-01-01

    Spectra of radiation emitted by the free-stream flow of air in an arcjet wind tunnel at NASA-Ames Research Center were studied experimentally. The arcjet produces a high energy gaseous flow that is expanded to low density and low temperature to produce high velocities in the free-stream for simulating atmospheric entry conditions. The gamma and the delta band systems of nitric oxide emitted by the free stream were measured in the second order. The NO-beta band system, which is in the same spectral region as the NO-gamma and NO-delta band systems, was not present in the data. Only transitions from the lowest vibrational level of the upper state of both the NO-gamma and NO-delta band systems were observed. The rotational temperature determined from these band systems was 660 +/- 50 deg K. The maximum possible vibrational temperature was determined to be less than 850 +/- 50 deg K. The electronic temperature determined from the ratio of the intensities of the NO-gamma and NO-delta band systems was 7560 +/- 340 K. The results indicate that the arcjet free-stream flow is in thermal nonequilibrium.

  1. Production of Local Acoustic Radiation Force to Constrain Direction of Microcapsules in Flow

    NASA Astrophysics Data System (ADS)

    Kohji Masuda,; Nobuyuki Watarai,; Ryusuke Nakamoto,; Yusuke Muramatsu,

    2010-07-01

    We have ever reported our attempt to control the direction of microcapsules in flow by acoustic radiation force. However, the diameter of capsules was too large to be applied in vivo. Furthermore, the acoustic radiation force affected only the focal area because focused ultrasound was used. Thus, we have improved our experiment by using microcapsules as small as blood cells and introducing a plane wave of ultrasound. We prepared an artificial blood vessel including a Y-form bifurcation established in two observation areas. Then, we newly defined the induction index to evaluate the difference in capsule density in two downstream paths. As a result, the optimum angle of ultrasound emission to induct to the desired path was derived. The induction index increased in proportion to the central frequency of ultrasound, which is affected by the aggregation of capsules to receive more acoustic radiation force.

  2. Numerical investigation of the spatial scale and time dependency of tile drainage contribution to stream flow

    NASA Astrophysics Data System (ADS)

    Thomas, Nicholas W.; Arenas, Antonio A.; Schilling, Keith E.; Weber, Larry J.

    2016-07-01

    Tile drainage systems are pervasive in the Central U.S., significantly altering the hydrologic system. The purpose of this study was to assess the effects of tile drainage systems on streamflow. A physically based coupled hydrologic model was applied to a 45 km2 agricultural Iowa watershed. Tile drainage was incorporated though an equivalent porous medium approach, calibrated though numerical experimentation. Experimental results indicated that a significant increase in hydraulic conductivity of the equivalent medium layer was needed to achieve agreement in total outflow with an explicit numerical representation of a tiled system. Watershed scale analysis derived the tile drainage contribution to stream flow (QT/Q) from a numerical tracer driven analysis of instream surface water. During precipitation events tile drainage represented 30% of stream flow, whereas during intervals between precipitations events, 61% of stream flow originated from the tile system. A division of event and non-event periods produced strong correlations between QT/Q and drainage area, positive for events, and negative for non-events. The addition of precipitation into the system acted to saturate near surface soils, increase lateral soil water movement, and dilute the relatively stable instream tile flow. Increased intensity precipitation translated the QT/Q relationship downward in a consistent manner. In non-event durations, flat upland areas contributed large contributions of tile flow, diluted by larger groundwater (non-tile) contribution to stream flow in the downstream steeper portion of the watershed. Study results provide new insights on the spatiotemporal response of tile drainage to precipitation and contributions of tile drainage to streamflow at a watershed scale, with results having important implications for nitrate transport.

  3. Field study and simulation of diurnal temperature effects on infiltration and variably saturated flow beneath an ephemeral stream

    USGS Publications Warehouse

    Ronan, A.D.; Prudic, D.E.; Thodal, C.E.; Constantz, J.

    1998-01-01

    Two experiments were performed to investigate flow beneath an ephemeral stream and to estimate streambed infiltration rates. Discharge and stream-area measurements were used to determine infiltration rates. Stream and subsurface temperatures were used to interpret subsurface flow through variably saturated sediments beneath the stream. Spatial variations in subsurface temperatures suggest that flow beneath the streambed is dependent on the orientation of the stream in the canyon and the layering of the sediments. Streamflow and infiltration rates vary diurnally: Stream flow is lowest in late afternoon when stream temperature is greatest and highest in early morning when stream temperature is least. The lower afternoon streamflow is attributed to increased infiltration rates; evapotranspiration is insufficient to account for the decreased streamflow. The increased infiltration rates are attributed to viscosity effects on hydraulic conductivity from increased stream temperatures. The first set of field data was used to calibrate a two-dimensional variably saturated flow model that includes heat transport. The model was calibrated to (1) temperature fluctuations in the subsurface and (2) infiltration rates determined from measured stream flow losses. The second set of field data was to evaluate the ability to predict infiltration rates on the basis of temperature measurements alone. Results indicate that the variably saturated subsurface flow depends on downcanyon layering of the sediments. They also support the field observations in indicating that diurnal changes in infiltration can be explained by temperature dependence of hydraulic conductivity. Over the range of temperatures and flows monitored, diurnal stream temperature changes can be used to estimate streambed infiltration rates. It is often impractical to maintain equipment for determining infiltration rates by traditional means; however, once a model is calibrated using both infiltration and temperature data

  4. Application of two- and three-dimensional computational fluid dynamics models to complex ecological stream flows

    NASA Astrophysics Data System (ADS)

    Shen, Yi; Diplas, Panayiotis

    2008-01-01

    SummaryComplex flow patterns generated by irregular channel topography, such as boulders, submerged large woody debris, riprap and spur dikes, provide unique habitat for many aquatic organisms. Numerical modeling of the flow structures surrounding these obstructions is challenging, yet it represents an important tool for aquatic habitat assessment. In this study, the ability of two- (2-D) and three-dimensional (3-D) computational fluid dynamics models to reproduce these localized complex flow features is examined. The 3-D model is validated with laboratory data obtained from the literature for the case of a flow around a hemisphere under emergent and submerged conditions. The performance of the 2-D and 3-D models is then evaluated by comparing the numerical results with field measurements of flow around several boulders located at a reach of the Smith River, a regulated mountainous stream, obtained at base and peak flows. Close agreement between measured values and the velocity profiles predicted by the two models is obtained outside the wakes behind the hemisphere and boulders. However, the results suggest that in the vicinity of these obstructions the 3-D model is better suited for reproducing the circulation flow behavior at both low and high discharges. Application of the 2-D and 3-D models to meso-scale stream flows of ecological significance is furthermore demonstrated by using a recently developed spatial hydraulic metric to quantify flow complexity surrounding a number of brown trout spawning sites. It is concluded that the 3-D model can provide a much more accurate description of the heterogeneous velocity patterns favored by many aquatic species over a broad range of flows, especially under deep flow conditions when the various obstructions are submerged. Issues pertaining to selection of appropriate models for a variety of flow regimes and potential implication of the 3-D model on the development of better habitat suitability criteria are discussed. The

  5. Estimation of geomorphically significant flows in alpine streams of the Rocky Mountains, Colorado (USA)

    USGS Publications Warehouse

    Surian, N.; Andrews, E.D.

    1999-01-01

    Streamflows recorded at 24 gauging stations in the Rocky Mountains of Colorado were analyzed to derive regional regression equations for estimating the natural flow duration and flood frequency in reaches where the natural flows are unknown or have been altered by diversion or regulation. The principal objective of this analysis is to determine whether the relatively high, infrequent, but geomorphically and ecologically important flows in the Rocky Mountains can be accurately estimated by regional flow duration equations. The region considered in this study is an area of relatively abundant runoff, and, consequently, intense water resources development. The specific streams analyzed here, however, are unaltered and remain nearly pristine. Regional flow duration equations are derived for two situations. When the mean annual discharge is known, flows ??? 10% of the time can be estimated with an uncertainty of ??9% for the 10% exceedance flow, to ??11%forthe 1.0% exceedance flow. When the mean annual discharge is unknown, the relatively high, infrequent flow can be estimated using the mean basin precipitation rate (in m3/s), and basin relief with an uncertainty of ??23% for the 10% exceedance flow to ??21% for the 1.0% exeedance flow. The uncertainty in estimated discharges using the equations derived in this analysis is substantially smaller than has been previously reported, especially for the geomorphically significant flows which are relatively large and infrequent. The improvement is due primarily to the quality of streamflow records analyzed and a well-defined hydrologic region.

  6. Geological control of flow in the Institute and Möller Ice Streams, West Antarctica

    NASA Astrophysics Data System (ADS)

    Jordan, T. A.; Ferraccioli, F.; Ross, N.; Corr, H.; Bingham, R. G.; Rippin, D. M.; Le Brocq, A.; Siegert, M. J.

    2012-12-01

    The conditions at the base of an ice sheet influence its flow, and reflect the ongoing interaction between moving ice and the underlying geology. Critical influences on ice flow include subglacial topography, bed lithology, and geothermal heat flux. These factors are influenced either directly by local geology, or by the regional tectonic setting. Geophysical methods have been used in many parts of Antarctica, such as the Siple Coast, to reveal the role subglacial geology plays in influencing ice flow. Until recently, however, the Institute and Möller Ice Streams, which drain ~20% of the West Antarctic Ice Sheet into the Weddell Sea, were only covered by sparse airborne radar (~50 km line spacing), and reconnaissance aeromagnetic data, limiting our understanding of the geological template for this sector of the West Antarctic Ice Sheet. Here we present our geological interpretation of the first integrated aerogeophysical survey over the catchments of the Institute and Möller Ice Streams, which collected ~25,000 km of new aerogeophysical data during the 2010/11 field season. These new airborne radar, magnetic and gravity data reveals both the subglacial topography, and the subglacial geology. Our maps show the fastest flowing coastal part of the Institute Ice Stream crosses a sedimentary basin underlain by thinned continental crust. Further inland two distinct ice flow provinces are recognised: the Pagano Ice Flow Province, which follows the newly identified, ~75 km wide, sinistral strike-slip Pagano Fault Zone at the boundary between East and West Antarctica; and the Ellsworth Ice Flow Province, which is controlled by the Permo-Triassic structural grain of folded Middle Cambrian-Permian meta-sediments, and Jurassic granitic rocks which form significant subglacial highlands. Our new data highlight the importance of understanding subglacial geology when explaining the complex pattern of ice flow observed in the ice sheet interior.

  7. 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.

  8. Magnitude and frequency of high flows of unregulated streams in Kansas

    USGS Publications Warehouse

    Jordan, P.R.

    1984-01-01

    Information on high flow magnitude and frequency is needed for hydrologic evaluation of such factors as flood control storage and dam safety. High flow information given in this report is for streamflows unaffected by major regulation, such as by large reservoirs. High flow magnitude and frequency data are given for 91 streamflow gaging stations throughout Kansas. Results of frequency calculations are given for durations of high flow of 1 , 3, 7, 15, 30, 60, 90, 120, and 183 consecutive days. Accuracy of the magnitude-frequency values is influenced by the variability of flow, the number of years of flow record, and the recurrence interval calculated. High flow magnitude and frequency for ungaged sites can be estimated from regression equations using significant drainage basin characteristics of contributing-drainage area; 50-yr, 24-hr rainfall; and free-water-surface evaporation. Standard errors of estimate for ungaged sites on ungaged streams range from 31% to 49%, generally increasing with recurrence interval. If an ungaged site is near a gaging station having 10 or more yr of record on the same stream, the data for the gaging station may be used to improve the regression estimates. (Author 's abstract)

  9. Magnitude and frequency of high flows of unregulated streams in Kansas

    USGS Publications Warehouse

    Jordan, Paul Robert

    1986-01-01

    Information on high-flow magnitude and frequency is needed for hydrologic evaluation of such factors as flood-control storage and dam safety. High-flow information given in this report is for streamflows unaffected by major regulation, such as by large reservoirs. High-flow magnitude and frequency data are given for 91 streamflow-gaging stations throughout Kansas. Results of frequency calculations are given for durations of high flow of 1, 3, 7, 15, 30, 60, 90, 120, and 183 consecutive days. Accuracy of the magnitude-frequency values is influenced by the variability of flow, the number of years of flow record, and the recurrence interval calculated. High-flow magnitude and frequency for ungaged sites can be estimated from regression equations using significant drainage-basin characteristics of contributing-drainage area; 50-year, 24-hour rainfall; and free-water-surface evaporation. Standard errors of estimate for ungaged sites on ungaged streams range from 31 to 49 percent, generally increasing with recurrence interval. If an ungaged site is near a gaging station having 10 or more years of record on the same stream, the data for the gaging station may be used to improve the regression estimates.

  10. An evaluation of the relations between flow regime components, stream characteristics, species traits and meta-demographic rates of warmwater stream fishes: Implications for aquatic resource management

    USGS Publications Warehouse

    Peterson, James T.; Shea, C.P.

    2015-01-01

    Fishery biologists are increasingly recognizing the importance of considering the dynamic nature of streams when developing streamflow policies. Such approaches require information on how flow regimes influence the physical environment and how those factors, in turn, affect species-specific demographic rates. A more cost-effective alternative could be the use of dynamic occupancy models to predict how species are likely to respond to changes in flow. To appraise the efficacy of this approach, we evaluated relative support for hypothesized effects of seasonal streamflow components, stream channel characteristics, and fish species traits on local extinction, colonization, and recruitment (meta-demographic rates) of stream fishes. We used 4 years of seasonal fish collection data from 23 streams to fit multistate, multiseason occupancy models for 42 fish species in the lower Flint River Basin, Georgia. Modelling results suggested that meta-demographic rates were influenced by streamflows, particularly short-term (10-day) flows. Flow effects on meta-demographic rates also varied with stream size, channel morphology, and fish species traits. Small-bodied species with generalized life-history characteristics were more resilient to flow variability than large-bodied species with specialized life-history characteristics. Using this approach, we simplified the modelling framework, thereby facilitating the development of dynamic, spatially explicit evaluations of the ecological consequences of water resource development activities over broad geographic areas. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

  11. 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. PMID:24433748

  12. 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.

  13. 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.

  14. Methods for Estimating Magnitude and Frequency of Peak Flows for Natural Streams in Utah

    USGS Publications Warehouse

    Kenney, Terry A.; Wilkowske, Chris D.; Wright, Shane J.

    2007-01-01

    Estimates of the magnitude and frequency of peak streamflows is critical for the safe and cost-effective design of hydraulic structures and stream crossings, and accurate delineation of flood plains. Engineers, planners, resource managers, and scientists need accurate estimates of peak-flow return frequencies for locations on streams with and without streamflow-gaging stations. The 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence-interval flows were estimated for 344 unregulated U.S. Geological Survey streamflow-gaging stations in Utah and nearby in bordering states. These data along with 23 basin and climatic characteristics computed for each station were used to develop regional peak-flow frequency and magnitude regression equations for 7 geohydrologic regions of Utah. These regression equations can be used to estimate the magnitude and frequency of peak flows for natural streams in Utah within the presented range of predictor variables. Uncertainty, presented as the average standard error of prediction, was computed for each developed equation. Equations developed using data from more than 35 gaging stations had standard errors of prediction that ranged from 35 to 108 percent, and errors for equations developed using data from less than 35 gaging stations ranged from 50 to 357 percent.

  15. Lagrangian mass-flow investigations of inorganic contaminants in wastewater-impacted streams

    USGS Publications Warehouse

    Barber, L.B.; Antweiler, R.C.; Flynn, J.L.; Keefe, S.H.; Kolpin, D.W.; Roth, D.A.; Schnoebelen, D.J.; Taylor, H.E.; Verplanck, P.L.

    2011-01-01

    Understanding the potential effects of increased reliance on wastewater treatment plant (WWTP) effluents to meet municipal, agricultural, and environmental flow requires an understanding of the complex chemical loading characteristics of the WWTPs and the assimilative capacity of receiving waters. Stream ecosystem effects are linked to proportions of WWTP effluent under low-flow conditions as well as the nature of the effluent chemical mixtures. This study quantifies the loading of 58 inorganic constituents (nutrients to rare earth elements) from WWTP discharges relative to upstream landscape-based sources. Stream assimilation capacity was evaluated by Lagrangian sampling, using flow velocities determined from tracer experiments to track the same parcel of water as it moved downstream. Boulder Creek, Colorado and Fourmile Creek, Iowa, representing two different geologic and hydrologic landscapes, were sampled under low-flow conditions in the summer and spring. One-half of the constituents had greater loads from the WWTP effluents than the upstream drainages, and once introduced into the streams, dilution was the predominant assimilation mechanism. Only ammonium and bismuth had significant decreases in mass load downstream from the WWTPs during all samplings. The link between hydrology and water chemistry inherent in Lagrangian sampling allows quantitative assessment of chemical fate across different landscapes. ?? 2011 American Chemical Society.

  16. Flowing catalyst particles in annular stream around a plug in lift pot

    SciTech Connect

    Skraba, F.W.

    1987-06-23

    A catalytic cracking process is described comprising (a) flowing a stream of hot cracking catalyst particles longitudinally through at least a portion of a lift pot in an annular stream around a plug which is positioned in the lift pot and which has an upstream end; a downstream end and a longitudinal axis; the hot cracking catalyst particles flow generally radially inwardly toward the plug axis past the downstream end of the plug, and then longitudinally into a riser-reactor; (b) introducing an oil feedstock into the stream of hot cracking catalyst particles as it is moving radially inwardly from around the periphery of the downstream end of the plug for the formation of a reaction mixture with the hot cracking catalyst. The hot catalyst particles and the oil feedstock moves at approximately right angles to each other at the point at which the oil feedstock is introduced; and (c) flowing the reaction mixture through the riser-reactor and into a disengagement chamber. The mixture flows into the disengagement chamber comprising cracked oil product and catalyst particles.

  17. Impact of transient stream flow on water exchange and reactions in the hyporheic zone of an in-stream gravel bar

    NASA Astrophysics Data System (ADS)

    Trauth, Nico; Schmidt, Christian; Fleckenstein, Jan H.

    2015-04-01

    Groundwater-surface water exchange is an important process that can facilitate the degradation of critical substances like nitrogen-species and contaminants, supporting a healthy status of the aquatic ecosystem. In our study, we simulate water exchange, solute transport and reactions within a natural in-stream gravel bar using a coupled surface and subsurface numerical model. Stream water flow is simulated by computational fluid dynamics software that provides hydraulic head distributions at the streambed, which are used as an upper boundary condition for a groundwater model. In the groundwater model water exchange, solute transport, aerobic respiration and denitrification in the subsurface are simulated. Ambient groundwater flow is introduced by lateral upstream and downstream hydraulic head boundaries that generate neutral, losing or gaining stream conditions. Stream water transports dissolved oxygen, organic carbon (as the dominant electron donor) and nitrate into the subsurface, whereas an additional nitrate source exists in the ambient groundwater. Scenarios of stream flow events varying in duration and stream stage are simulated and compared with steady state scenarios with respect to water fluxes, residence times and the solute turn-over rates. Results show, that water exchange and solute turn-over rates highly depend on the interplay between event characteristics and ambient groundwater levels. For scenarios, where the stream flow event shifts the hydraulic system to a net-neutral hydraulic gradient between the average stream stage and the ambient groundwater level (minimal exchange between ground- and surface water), solute consumption is higher, compared to the steady losing or gaining case. In contrast, events that induce strong losing conditions lead to a lower potential of solute consumption.

  18. A millennium-length reconstruction of Bear River stream flow, Utah

    NASA Astrophysics Data System (ADS)

    DeRose, R. J.; Bekker, M. F.; Wang, S.-Y.; Buckley, B. M.; Kjelgren, R. K.; Bardsley, T.; Rittenour, T. M.; Allen, E. B.

    2015-10-01

    The Bear River contributes more water to the eastern Great Basin than any other river system. It is also the most significant source of water for the burgeoning Wasatch Front metropolitan area in northern Utah. Despite its importance for water resources for the region's agricultural, urban, and wildlife needs, our understanding of the variability of Bear River's stream flow derives entirely from the short instrumental record (1943-2010). Here we present a 1200-year calibrated and verified tree-ring reconstruction of stream flow for the Bear River that explains 67% of the variance of the instrumental record over the period from 1943 to 2010. Furthermore, we developed this reconstruction from a species that is not typically used for dendroclimatology, Utah juniper (Juniperus osteosperma). We identify highly significant periodicity in our reconstruction at quasi-decadal (7-8 year), multi-decadal (30 year), and centennial (>50 years) scales. The latter half of the 20th century was found to be the 2nd wettest (∼40-year) period of the past 1200 years, while the first half of the 20th century marked the 4th driest period. The most severe period of reduced stream flow occurred during the Medieval Warm Period (ca. mid-1200s CE) and persisted for ∼70 years. Upper-level circulation anomalies suggest that atmospheric teleconnections originating in the western tropical Pacific are responsible for the delivery of precipitation to the Bear River watershed during the October-December (OND) season of the previous year. The Bear River flow was compared to recent reconstructions of the other tributaries to the Great Salt Lake (GSL) and the GSL level. Implications for water management could be drawn from the observation that the latter half of the 20th century was the 2nd wettest in 1200 years, and that management for future water supply should take into account the stream flow variability over the past millennium.

  19. A Mechanism for Cytoplasmic Streaming: Kinesin-Driven Alignment of Microtubules and Fast Fluid Flows.

    PubMed

    Monteith, Corey E; Brunner, Matthew E; Djagaeva, Inna; Bielecki, Anthony M; Deutsch, Joshua M; Saxton, William M

    2016-05-10

    The transport of cytoplasmic components can be profoundly affected by hydrodynamics. Cytoplasmic streaming in Drosophila oocytes offers a striking example. Forces on fluid from kinesin-1 are initially directed by a disordered meshwork of microtubules, generating minor slow cytoplasmic flows. Subsequently, to mix incoming nurse cell cytoplasm with ooplasm, a subcortical layer of microtubules forms parallel arrays that support long-range, fast flows. To analyze the streaming mechanism, we combined observations of microtubule and organelle motions with detailed mathematical modeling. In the fast state, microtubules tethered to the cortex form a thin subcortical layer and undergo correlated sinusoidal bending. Organelles moving in flows along the arrays show velocities that are slow near the cortex and fast on the inward side of the subcortical microtubule layer. Starting with fundamental physical principles suggested by qualitative hypotheses, and with published values for microtubule stiffness, kinesin velocity, and cytoplasmic viscosity, we developed a quantitative coupled hydrodynamic model for streaming. The fully detailed mathematical model and its simulations identify key variables that can shift the system between disordered (slow) and ordered (fast) states. Measurements of array curvature, wave period, and the effects of diminished kinesin velocity on flow rates, as well as prior observations on f-actin perturbation, support the model. This establishes a concrete mechanistic framework for the ooplasmic streaming process. The self-organizing fast phase is a result of viscous drag on kinesin-driven cargoes that mediates equal and opposite forces on cytoplasmic fluid and on microtubules whose minus ends are tethered to the cortex. Fluid moves toward plus ends and microtubules are forced backward toward their minus ends, resulting in buckling. Under certain conditions, the buckling microtubules self-organize into parallel bending arrays, guiding varying directions

  20. Combustion Oscillations in a Twin-Stream Afterburner

    NASA Astrophysics Data System (ADS)

    Macquisten, M. A.

    1995-12-01

    In a modern turbo-fan engine, the afterburner flame-holders are positioned in the mixing flow between the core and bypass streams. These two streams have different velocities and temperatures. They also have different duct lengths and, therefore, different acoustic properties. The influence of such a twin-stream supply on acoustically coupled combustion oscillations is investigated in this paper. Measurements on an experimental rig show how differences in the acoustic impedances, the mean velocities and the mean temperatures in the two supply streams lead to appreciably different unsteady heat release rates in the two streams. These affect the frequency of the combustion oscillations. A theory explains these results and correctly describes the variation in frequency as the properties of the two supply streams are varied.

  1. Evaluation of a method of estimating low-flow frequencies from base-flow measurements at Indiana streams

    USGS Publications Warehouse

    Wilson, John Thomas

    2000-01-01

    A mathematical technique of estimating low-flow frequencies from base-flow measurements was evaluated by using data for streams in Indiana. Low-flow frequencies at low- flow partial-record stations were estimated by relating base-flow measurements to concurrent daily flows at nearby streamflow-gaging stations (index stations) for which low-flowfrequency curves had been developed. A network of long-term streamflow-gaging stations in Indiana provided a sample of sites with observed low-flow frequencies. Observed values of 7-day, 10-year low flow and 7-day, 2-year low flow were compared to predicted values to evaluate the accuracy of the method. Five test cases were used to evaluate the method under a variety of conditions in which the location of the index station and its drainage area varied relative to the partial-record station. A total of 141 pairs of streamflow-gaging stations were used in the five test cases. Four of the test cases used one index station, the fifth test case used two index stations. The number of base-flow measurements was varied for each test case to see if the accuracy of the method was affected by the number of measurements used. The most accurate and least variable results were produced when two index stations on the same stream or tributaries of the partial-record station were used. All but one value of the predicted 7-day, 10-year low flow were within 15 percent of the values observed for the long-term continuous record, and all of the predicted values of the 7-day, 2-year lowflow were within 15 percent of the observed values. This apparent accuracy, to some extent, may be a result of the small sample set of 15. Of the four test cases that used one index station, the most accurate and least variable results were produced in the test case where the index station and partial-record station were on the same stream or on streams tributary to each other and where the index station had a larger drainage area than the partial-record station. In

  2. 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.

  3. EFFECTS OF LOW FLOW ON INVASION PROCESS OF EXOTIC STREAM INVERTEBRATES

    NASA Astrophysics Data System (ADS)

    Yamane, Naoya; Sakai, Toru; Miyake, Yo

    This study aimed to demonstrate recent invasion status and low-flow resistance of two exotic invertebrates, Pyasa acuta and Crangonyx floridanus, in Shigenobu River, Ehime, Japan. Six years of longitudinal survey revealed that density of these two invasive species were high in the middle and lower segments of the mainstem, in which stream habitats were degraded. Furthermore, the distribution of Crangonyx floridanus appeared to expand toward upstream along the river. A short-term survey during a descending flow showed that Crangonyx floridanus decreased along with other major invertebrate taxa. In contrast, relative abundance of Pyasa acuta increased as flow decreased, indicating that this invasive species has relatively high resistance to low flow. Thus, low flow was suggested to facilitate the invasion of Pyasa acuta.

  4. Regulation of ice stream flow through subglacial formation of gas hydrates

    NASA Astrophysics Data System (ADS)

    Winsborrow, Monica; Andreassen, Karin; Hubbard, Alun; Plaza-Faverola, Andreia; Gudlaugsson, Eythor; Patton, Henry

    2016-05-01

    Variations in the flow of ice streams and outlet glaciers are a primary control on ice sheet stability, yet comprehensive understanding of the key processes operating at the ice-bed interface remains elusive. Basal resistance is critical, especially sticky spots--localized zones of high basal traction--for maintaining force balance in an otherwise well-lubricated/high-slip subglacial environment. Here we consider the influence of subglacial gas-hydrate formation on ice stream dynamics, and its potential to initiate and maintain sticky spots. Geophysical data document the geologic footprint of a major palaeo-ice-stream that drained the Barents Sea-Fennoscandian ice sheet approximately 20,000 years ago. Our results reveal a ~250 km2 sticky spot that coincided with subsurface shallow gas accumulations, seafloor fluid expulsion and a fault complex associated with deep hydrocarbon reservoirs. We propose that gas migrating from these reservoirs formed hydrates under high-pressure, low-temperature subglacial conditions. The gas hydrate desiccated, stiffened and thereby strengthened the subglacial sediments, promoting high traction--a sticky spot--that regulated ice stream flow. Deep hydrocarbon reservoirs are common beneath past and contemporary glaciated areas, implying that gas-hydrate regulation of subglacial dynamics could be a widespread phenomenon.

  5. Mitigation of biocide and fungicide concentrations in flow-through vegetated stream mesocosms.

    PubMed

    Stang, Christoph; Elsaesser, David; Bundschuh, Mirco; Ternes, Thomas A; Schulz, Ralf

    2013-11-01

    Organic chemicals entering surface waters may interact with aquatic macrophytes, which in turn may reduce potential negative effects on aquatic organisms. The overall objective of the present study was to determine the significance of aquatic macrophytes to the retention of organic chemicals in slow-flowing streams and thus their contribution to the mitigation of the risks that these compounds may pose to aquatic ecosystems. Hence, we conducted a study on the mitigation of the biocides triclosan and triclocarban and the fungicides imazalil, propiconazole and thiabendazole, which were experimentally spiked to five flow-through stream mesocosms (45 m length, 0.4 m width, 0.26 m water depth, discharge 1 L/s), four of which were planted with the submerged macrophyte (Planch.). Chemical analyses were performed using liquid chromatography-tandem mass spectrometry following solid-phase extraction for water samples and accelerated solvent extraction for macrophyte and sediment samples. The peak reductions of biocide and fungicide concentrations from the inlet to the outlet sampling sites were ≥48% in all stream mesocosms, and the peak reductions in the vegetated stream mesocosms were 20 to 25% greater than in the unvegetated mesocosm. On average, 7 ± 3 to 10 ± 3% and 28 ± 8 to 34 ± 14% of the initially applied amount of fungicides and biocides, respectively, were retained by macrophytes. There was a significant correlation between retention by macrophytes and the lipophility of the compounds. PMID:25602429

  6. 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.

  7. 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.

  8. 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

  9. Effect of snow accumulation and melt on the stream flow in the Jordan River, East Mediterranean

    NASA Astrophysics Data System (ADS)

    Rimmer, Alon; Hartmann, Andreas

    2010-05-01

    Snow melt on high mountains, at low latitudes (<40 degrees N), can be an important component of the surface water flow during the winter and spring seasons. As opposed to snow cover at high latitudes which are persistent due to below zero temperatures, snow cover in warmer climates is rapidly changing, potentially resulting in several complete melting cycles during one winter season. In the Mt. Hermon region (Israel-Lebanon-Syria border, East Mediterranean, ~33.5 degrees N) previous studies have concluded that snow storage accounts for ~10% of the Jordan River annual yields. Here we apply a modified version of HYdrological Model for Karst Environment (HYMKE) to estimate the effect of snow accumulation and snow melt on the timing of stream flow in the Jordan River. It is a system approach, physically based karst hydrology model, which receives daily precipitation and potential evaporation time series as input. The modeled fast flow stream component is correlated with the physical area of the catchment, while the area of the groundwater aquifer is a parameter which is calibrated against the separated measured baseflow. We have added a snowmelt routine before the main equations in HYMKE creating the following model structure: the snow routine (1), surface layer water balance (2), surface ("fast") flow (3), vadose zone flow (4), and groundwater ("base flow", 5). The new snowmelt routine uses the measured precipitation and temperature data, and analyzes it separately to produce snow and snowmelt at 56 discrete stripes of 50 m' height each, ranging in elevation from 75 m' to 2825 m'. It uses a standard HBV (Hydrological Bureau Waterbalance-section) approach based on a degree-day temperature-index. With current available temperature data the actual temperature gradient was calibrated, and the daily temperature at each elevation stripe was evaluated. However, due to the lack of measured snowmelt, several parameters of the model could not be calibrated, and were adopted

  10. Channel water balance and exchange with subsurface flow along a mountain headwater stream in Montana, United States

    USGS Publications Warehouse

    Payn, R.A.; Gooseff, M.N.; McGlynn, B.L.; Bencala, K.E.; Wondzell, S.M.

    2009-01-01

    Channel water balances of contiguous reaches along streams represent a poorly understood scale of stream-subsurface interaction. We measured reach water balances along a headwater stream in Montana, United States, during summer base flow recessions. Reach water balances were estimated from series of tracer tests in 13 consecutive reaches delineated evenly along a 2.6 km valley segment. For each reach, we estimated net change in discharge, gross hydrologic loss, and gross hydrologic gain from tracer dilution and mass recovery. Four series of tracer tests were performed during relatively high, intermediate, and low base flow conditions. The relative distribution of channel water along the stream was strongly related to a transition in valley structure, with a general increase in gross losses through the recession. During tracer tests at intermediate and low flows, there were frequent substantial losses of tracer mass (>10%) that could not be explained by net loss in flow over the reach, indicating that many of the study reaches were concurrently losing and gaining water. For example, one reach with little net change in discharge exchanged nearly 20% of upstream flow with gains and losses along the reach. These substantial bidirectional exchanges suggest that some channel interactions with subsurface flow paths were not measurable by net change in flow or transient storage of recovered tracer. Understanding bidirectional channel water balances in stream reaches along valleys is critical to an accurate assessment of stream solute fate and transport and to a full assessment of exchanges between the stream channel and surrounding subsurface.

  11. Prediction of effects of daily flow fluctuations on stream biota. Technical completion report

    SciTech Connect

    Hooper, F.F.; Ottey, D.R.

    1982-12-01

    The short-term effects of regulated daily discharges on benthos communities were examined in a small Michigan trout stream. Flow regulation designs simulated fluctuations produced by storage and release for hydroelectric generation, as well as different constant daily stream diversions. Impacts on the dynamics of micro-distribution, species diversity, and behavior were evaluated on stable artificial substrates. Invertebrate drift rates were measured at different discharges during light and dark periods. The caddisfly G. nigrior became less active and oriented downstream when exposed to high discharge, and underwent movements to protected substrate faces. The mayfly Baetis vagans also changed micro-positioning in response to flow fluctuations, but total density changes generally were more pronounced. There was evidence for increased species diversity during low discharges.

  12. Quantifying the contribution of land use and climate change to stream flow alteration in tropical catchments

    NASA Astrophysics Data System (ADS)

    Marhaento, Hero; Booij, Martijn J.; Hoekstra, Arjen Y.

    2015-04-01

    A new approach is introduced to measure the quantitative contribution of land use and climate change to stream flow alteration based on the changes in the proportion of excess water relative to changes in the proportion of excess energy. The quantitative contribution is estimated based on three measures: (1) the resultant length (R) which indicates the magnitude of the changes in the proportion of excess water and energy with a higher resultant indicating a higher magnitude; (2) the slope of change (θ in arc degree) which indicates the magnitude of the contribution of land use and climate changes with a higher slope reflecting a higher contribution of climate change; and (3) the relative contribution of land use and climate changes to stream flow alteration (C in %). In this study, we applied our approach to five catchments (Pidekso, Keduang, Samin, Madiun and Kening) ranging in size from 234 to 3759 km2 on Java, Indonesia. The hydro-climatic data cover the period 1975 - 2012 and the land use maps acquired from multi-temporal satellite imageries (i.e. for the years 1972, 1994, 2002 and 2013) were used and analyzed. The approach consists of four steps: (1) performing abrupt change detection on annual stream flow using Pettitt's test; (2) calculating the proportion of excess water and the proportion of excess energy for the period before and after the abrupt change of the stream flow; (3) calculating the quantitative contribution of land use and climate change to stream flow changes; (4) comparing the results with the Mann-Kendall trend analysis of variability in precipitation and potential evapotranspiration, and the land use change analysis. The results show that all catchments have a simultaneous increase of the proportion of excess water and energy for the period after the abrupt change compared to the period before the abrupt change. The Samin catchment gives the highest R value with a value of 0.9 followed by Pidekso catchment (0.7), Keduang catchment (0

  13. 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.

  14. 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.

  15. 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.

  16. Flow on Magnetizable Particles in Turbulent Air Streams. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Davey, K. R.

    1979-01-01

    The flow of magnetizable particles in a turbulent air stream in the presence of an imposed magnetic field and the phenomenon of drag reduction produced by the introduction of particles in turbulent boundary layer are investigated. The nature of the particle magnetic force is discussed and the inherent difference between electric and magnetic precipitation is considered. The incorporation of turbulent diffusion theory with an imposed magnetic migration process both with and without inertia effects is examined.

  17. 78 FR 65306 - Best Practices for Continuous Monitoring of Temperature and Flow in Wadeable Streams

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-31

    ...EPA is announcing a 30-day public comment period for the draft document titled, ``Best Practices for Continuous Monitoring of Temperature and Flow in Wadeable Streams'' (EPA/600/R-13/170). The EPA also is announcing that either ERG or Versar, EPA contractors for external scientific peer review, will select an independent group of experts to conduct a letter peer review of the draft document.......

  18. Relation Between Fog & Summer Stream Flow on the North Coast of California in Redwood National Park

    NASA Astrophysics Data System (ADS)

    Lavery, K.

    2012-12-01

    There are three common definitions of fog; visibility less than 800 meters (Dawson 1998), ceiling height less than 400 meters (Liepper 1995, Johnstone & Dawson 2010) or low level stratus that touches the ground. Regardless of the definition used the ecological importance of fog is evidenced by the commonly used term occult precipitation i.e. water that is not accounted for. Fog is most common on the coast of Northern California during summer, the time of least precipitation. The diurnal flux in stream flows is also most evident in the summer. Diurnal flux and seasonal trends in stream flow are thought to be controlled by precipitation and evapotranspiration. Fog impacts both precipitation and evapotranspiration. While changes in fog regimes are expected to occur as a result of climate change, the ability to measure fog and anticipate the implications are in nascent stages. Although, methods for detecting fog using satellite imagery have been developed they have not been perfected and they generally only give height info for the cloud deck (top of clouds). Although deck height is important for aviation and enables some inference of what is occurring on the ground the thickness and base height are important variables for developing a greater understanding of the impacts of fog. Fog harps will be used to detect fog on the ground. Fog harp data will be compared with the results of satellite imagery analysis for presence or absence of fog. After detrending, stream flow data will be divided into categories of fog and no fog. The two categories will be tested for a statistically significant difference. The results have the potential to help solve a piece of the climate change puzzle. The data will help with the anticipation of change in stream flows in areas with high levels of summer fog and Mediterranean climates as well as refine techniques for analyzing satellite imagery for presence or absence of fog.

  19. 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.

  20. Fine Magnetic Structure and Origin of Counter-streaming Mass Flows in a Quiescent Solar Prominence

    NASA Astrophysics Data System (ADS)

    Shen, Yuandeng; Liu, Yu; Liu, Ying D.; Chen, P. F.; Su, Jiangtao; Xu, Zhi; Liu, Zhong

    2015-11-01

    We present high-resolution observations of a quiescent solar prominence that consists of a vertical and a horizontal foot encircled by an overlying spine and has ubiquitous counter-streaming mass flows. While the horizontal foot and the spine were connected to the solar surface, the vertical foot was suspended above the solar surface and was supported by a semicircular bubble structure. The bubble first collapsed, then reformed at a similar height, and finally started to oscillate for a long time. We find that the collapse and oscillation of the bubble boundary were tightly associated with a flare-like feature located at the bottom of the bubble. Based on the observational results, we propose that the prominence should be composed of an overlying horizontal spine encircling a low-lying horizontal and vertical foot, in which the horizontal foot consists of shorter field lines running partially along the spine and has ends connected to the solar surface, while the vertical foot consists of piling-up dips due to the sagging of the spine fields and is supported by a bipolar magnetic system formed by parasitic polarities (i.e., the bubble). The upflows in the vertical foot were possibly caused by the magnetic reconnection at the separator between the bubble and the overlying dips, which intruded into the persistent downflow field and formed the picture of counter-streaming mass flows. In addition, the counter-streaming flows in the horizontal foot were possibly caused by the imbalanced pressure at the both ends.

  1. Artificial intelligence based models for stream-flow forecasting: 2000-2015

    NASA Astrophysics Data System (ADS)

    Yaseen, Zaher Mundher; El-shafie, Ahmed; Jaafar, Othman; Afan, Haitham Abdulmohsin; Sayl, Khamis Naba

    2015-11-01

    The use of Artificial Intelligence (AI) has increased since the middle of the 20th century as seen in its application in a wide range of engineering and science problems. The last two decades, for example, has seen a dramatic increase in the development and application of various types of AI approaches for stream-flow forecasting. Generally speaking, AI has exhibited significant progress in forecasting and modeling non-linear hydrological applications and in capturing the noise complexity in the dataset. This paper explores the state-of-the-art application of AI in stream-flow forecasting, focusing on defining the data-driven of AI, the advantages of complementary models, as well as the literature and their possible future application in modeling and forecasting stream-flow. The review also identifies the major challenges and opportunities for prospective research, including, a new scheme for modeling the inflow, a novel method for preprocessing time series frequency based on Fast Orthogonal Search (FOS) techniques, and Swarm Intelligence (SI) as an optimization approach.

  2. Iso-acoustic focusing of cells for size-insensitive acousto-mechanical phenotyping

    PubMed Central

    Augustsson, Per; Karlsen, Jonas T.; Su, Hao-Wei; Bruus, Henrik; Voldman, Joel

    2016-01-01

    Mechanical phenotyping of single cells is an emerging tool for cell classification, enabling assessment of effective parameters relating to cells' interior molecular content and structure. Here, we present iso-acoustic focusing, an equilibrium method to analyze the effective acoustic impedance of single cells in continuous flow. While flowing through a microchannel, cells migrate sideways, influenced by an acoustic field, into streams of increasing acoustic impedance, until reaching their cell-type specific point of zero acoustic contrast. We establish an experimental procedure and provide theoretical justifications and models for iso-acoustic focusing. We describe a method for providing a suitable acoustic contrast gradient in a cell-friendly medium, and use acoustic forces to maintain that gradient in the presence of destabilizing forces. Applying this method we demonstrate iso-acoustic focusing of cell lines and leukocytes, showing that acoustic properties provide phenotypic information independent of size. PMID:27180912

  3. Iso-acoustic focusing of cells for size-insensitive acousto-mechanical phenotyping.

    PubMed

    Augustsson, Per; Karlsen, Jonas T; Su, Hao-Wei; Bruus, Henrik; Voldman, Joel

    2016-01-01

    Mechanical phenotyping of single cells is an emerging tool for cell classification, enabling assessment of effective parameters relating to cells' interior molecular content and structure. Here, we present iso-acoustic focusing, an equilibrium method to analyze the effective acoustic impedance of single cells in continuous flow. While flowing through a microchannel, cells migrate sideways, influenced by an acoustic field, into streams of increasing acoustic impedance, until reaching their cell-type specific point of zero acoustic contrast. We establish an experimental procedure and provide theoretical justifications and models for iso-acoustic focusing. We describe a method for providing a suitable acoustic contrast gradient in a cell-friendly medium, and use acoustic forces to maintain that gradient in the presence of destabilizing forces. Applying this method we demonstrate iso-acoustic focusing of cell lines and leukocytes, showing that acoustic properties provide phenotypic information independent of size. PMID:27180912

  4. Iso-acoustic focusing of cells for size-insensitive acousto-mechanical phenotyping

    NASA Astrophysics Data System (ADS)

    Augustsson, Per; Karlsen, Jonas T.; Su, Hao-Wei; Bruus, Henrik; Voldman, Joel

    2016-05-01

    Mechanical phenotyping of single cells is an emerging tool for cell classification, enabling assessment of effective parameters relating to cells' interior molecular content and structure. Here, we present iso-acoustic focusing, an equilibrium method to analyze the effective acoustic impedance of single cells in continuous flow. While flowing through a microchannel, cells migrate sideways, influenced by an acoustic field, into streams of increasing acoustic impedance, until reaching their cell-type specific point of zero acoustic contrast. We establish an experimental procedure and provide theoretical justifications and models for iso-acoustic focusing. We describe a method for providing a suitable acoustic contrast gradient in a cell-friendly medium, and use acoustic forces to maintain that gradient in the presence of destabilizing forces. Applying this method we demonstrate iso-acoustic focusing of cell lines and leukocytes, showing that acoustic properties provide phenotypic information independent of size.

  5. Ecological Response to Extreme Flow Events in Streams and Rivers: Implications of Climate Change for Aquatic Biodiversity

    NASA Astrophysics Data System (ADS)

    Hawkins, C. P.; Vander Laan, J. J.; Dhungel, S.; Tarboton, D. G.

    2014-12-01

    We used the USEPA's 2008-2009 National Rivers and Streams Assessment (NRSA) data to assess the potential sensitivity of stream biodiversity to both spatial variation in measures of extreme flow and likely changes in extreme flows associated with projected climate change. The NRSA data consisted of macroinvertebrate samples collected at 1313 reference-quality sites. We characterized the hydrologic regimes at each of these sites by developing Random Forest empirical models from long-term (≥ 20 years) daily flow records obtained from 601 gaged USGS stations. These models described spatial variation in 16 flow variables as a function of climate and watershed attributes. Three of the models characterized aspects of extreme flow: the mean number of zero-flow events per year (ZeroDays), the mean number of high-flow events per year (HighDays = number of events per year that exceed the 95th percentile of mean annual flow), and the coefficient of variation of daily flows (CV). We used these models to predict the flow attributes expected at each of the 1313 sites with ecological data. We then built additional Random Forest models that related among-site differences in stream macroinvertebrate taxonomic composition, assemblage richness, and the likelihood of observing individual taxa to the 16 measures of flow regime and other environmental predictors. At the national level, ZeroDays was an important predictor of macroinvertebrate biodiversity: richness declined as ZeroDays increased. A similar pattern was observed when analyses were restricted to lowland and plains streams. For eastern highland streams, HighDays was a better predictor of stream biodiversity than aspects of low flow: richness declined as HighDays increased. For western streams, CV was a better predictor of biodiversity than either ZeroDays or HighDays: biodiversity decreased as CV increased. Empirical models that linked flow attributes to climate change projections imply that flow regime response to climate

  6. Acoustic response of Helmholtz dampers in the presence of hot grazing flow

    NASA Astrophysics Data System (ADS)

    Ćosić, B.; Wassmer, D.; Terhaar, S.; Paschereit, C. O.

    2015-01-01

    Thermoacoustic instabilities are high amplitude instabilities of premixed gas turbine combustors. Cooled passive dampers are used to attenuate or suppress these instabilities in the combustion chamber. For the first time, the influence of temperature differences between the grazing flow in the combustor and the cross-flow emanating from the Helmholtz damper is comprehensively investigated in the linear and nonlinear amplitude regime. The flow field inside the resonator and in the vicinity of the neck is measured with high-speed particle image velocimetry for various amplitudes and at different momentum-flux ratios of grazing and purging flow. Seeding is used as a tracer to qualitatively assess the mixing of the grazing and purging flow as well as the ingestion into the neck of the resonator. Experimentally, the acoustic response for various temperature differences between grazing and purging flow is investigated. The multi-microphone method, in combination with two microphones flush-mounted in the resonator volume and two microphones in the plane of the resonator entrance, is used to determine the impedance of the Helmholtz resonator in the linear and nonlinear amplitude regime for various temperatures and different momentum-flux ratios. Additionally, a thermocouple was used to measure the temperature in the neck. The acoustic response and the temperature measurements are used to obtain the virtual neck length and the effective area jump from a detailed impedance model. This model is extended to include the observed acoustic energy dissipation caused by the density gradients at the neck vicinity. A clear correlation between temperature differences and changes of the mass end-correction is confirmed. The capabilities of the impedance model are demonstrated.

  7. 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.

  8. Steady streaming: A key mixing mechanism in low-Reynolds-number acinar flows

    PubMed Central

    Kumar, Haribalan; Tawhai, Merryn H.; Hoffman, Eric A.; Lin, Ching-Long

    2011-01-01

    Study of mixing is important in understanding transport of submicron sized particles in the acinar region of the lung. In this article, we investigate transport in view of advective mixing utilizing Lagrangian particle tracking techniques: tracer advection, stretch rate and dispersion analysis. The phenomenon of steady streaming in an oscillatory flow is found to hold the key to the origin of kinematic mixing in the alveolus, the alveolar mouth and the alveolated duct. This mechanism provides the common route to folding of material lines and surfaces in any region of the acinar flow, and has no bearing on whether the geometry is expanding or if flow separates within the cavity or not. All analyses consistently indicate a significant decrease in mixing with decreasing Reynolds number (Re). For a given Re, dispersion is found to increase with degree of alveolation, indicating that geometry effects are important. These effects of Re and geometry can also be explained by the streaming mechanism. Based on flow conditions and resultant convective mixing measures, we conclude that significant convective mixing in the duct and within an alveolus could originate only in the first few generations of the acinar tree as a result of nonzero inertia, flow asymmetry, and large Keulegan–Carpenter (KC) number. PMID:21580803

  9. Large-eddy simulation of flow past a real-life stream restoration structure

    NASA Astrophysics Data System (ADS)

    Kang, Seokkoo; Sotiropoulos, Fotis

    2011-11-01

    We carry out high-resolution large-eddy simulation (LES) of flow around a rock vane, which is a widely used stream restoration structure. Mean velocities and turbulence statistics collected downstream of the rock vane installed in a laboratory flume are compared with the LES results. The comparisons demonstrate that the LES is able to accurately predict the measured mean velocities and turbulence statistics. The simulation shows that the rock vane effectively directs the oncoming flow away from the structure and creates a reduced velocity region in the downstream region. The computed results also reveal that the rock vane creates strong secondary helical flow that directs the near-bed flow toward the sidewall to which the rock vane is attached. This finding points to the conclusion that the downstream secondary flow can create deposition of sediments near the sidewall in a mobile bed condition, which can serve as an important mechanism for protecting near-bank scour in natural streams. This work was supported by National Center for Earth-surface Dynamics (NCED), ECORIVER21 project in South Korea, National Cooperative Highway Research Program (NCHRP) and Minnesota Supercomputing Institue (MSI).

  10. Steady streaming: A key mixing mechanism in low-Reynolds-number acinar flows.

    PubMed

    Kumar, Haribalan; Tawhai, Merryn H; Hoffman, Eric A; Lin, Ching-Long

    2011-04-01

    Study of mixing is important in understanding transport of submicron sized particles in the acinar region of the lung. In this article, we investigate transport in view of advective mixing utilizing Lagrangian particle tracking techniques: tracer advection, stretch rate and dispersion analysis. The phenomenon of steady streaming in an oscillatory flow is found to hold the key to the origin of kinematic mixing in the alveolus, the alveolar mouth and the alveolated duct. This mechanism provides the common route to folding of material lines and surfaces in any region of the acinar flow, and has no bearing on whether the geometry is expanding or if flow separates within the cavity or not. All analyses consistently indicate a significant decrease in mixing with decreasing Reynolds number (Re). For a given Re, dispersion is found to increase with degree of alveolation, indicating that geometry effects are important. These effects of Re and geometry can also be explained by the streaming mechanism. Based on flow conditions and resultant convective mixing measures, we conclude that significant convective mixing in the duct and within an alveolus could originate only in the first few generations of the acinar tree as a result of nonzero inertia, flow asymmetry, and large Keulegan-Carpenter (K(C)) number. PMID:21580803

  11. Iron-rich colloids as carriers of phosphorus in streams: A field-flow fractionation study.

    PubMed

    Baken, Stijn; Regelink, Inge C; Comans, Rob N J; Smolders, Erik; Koopmans, Gerwin F

    2016-08-01

    Colloidal phosphorus (P) may represent an important fraction of the P in natural waters, but these colloids remain poorly characterized. In this work, we demonstrate the applicability of asymmetric flow field-flow fractionation (AF4) coupled to high resolution ICP-MS for the characterization of low concentrations of P-bearing colloids. Colloids from five streams draining catchments with contrasting properties were characterized by AF4-ICP-MS and by membrane filtration. All streams contain free humic substances (2-3 nm) and Fe-bearing colloids (3-1200 nm). Two soft water streams contain primary Fe oxyhydroxide-humic nanoparticles (3-6 nm) and aggregates thereof (up to 150 nm). In contrast, three harder water streams contain larger aggregates (40-1200 nm) which consist of diverse associations between Fe oxyhydroxides, humic substances, clay minerals, and possibly ferric phosphate minerals. Despite the diversity of colloids encountered in these contrasting streams, P is in most of the samples predominantly associated with Fe-bearing colloids (mostly Fe oxyhydroxides) at molar P:Fe ratios between 0.02 and 1.5. The molar P:Fe ratio of the waters explains the partitioning of P between colloids and truly dissolved species. Waters with a high P:Fe ratio predominantly contain truly dissolved species because the Fe-rich colloids are saturated with P, whereas waters with a low P:Fe ratio mostly contain colloidal P species. Overall, AF4-ICP-MS is a suitable technique to characterize the diverse P-binding colloids in natural waters. Such colloids may increase the mobility or decrease the bioavailability of P, and they therefore need to be considered when addressing the transport and environmental effects of P in catchments. PMID:27140905

  12. Physical controls and predictability of stream hyporheic flow evaluated with a multiscale model

    USGS Publications Warehouse

    Stonedahl, Susa H.; Harvey, Judson W.; Detty, Joel; Aubeneau, Antoine; Packman, Aaron I.

    2012-01-01

    Improved predictions of hyporheic exchange based on easily measured physical variables are needed to improve assessment of solute transport and reaction processes in watersheds. Here we compare physically based model predictions for an Indiana stream with stream tracer results interpreted using the Transient Storage Model (TSM). We parameterized the physically based, Multiscale Model (MSM) of stream-groundwater interactions with measured stream planform and discharge, stream velocity, streambed hydraulic conductivity and porosity, and topography of the streambed at distinct spatial scales (i.e., ripple, bar, and reach scales). We predicted hyporheic exchange fluxes and hyporheic residence times using the MSM. A Continuous Time Random Walk (CTRW) model was used to convert the MSM output into predictions of in stream solute transport, which we compared with field observations and TSM parameters obtained by fitting solute transport data. MSM simulations indicated that surface-subsurface exchange through smaller topographic features such as ripples was much faster than exchange through larger topographic features such as bars. However, hyporheic exchange varies nonlinearly with groundwater discharge owing to interactions between flows induced at different topographic scales. MSM simulations showed that groundwater discharge significantly decreased both the volume of water entering the subsurface and the time it spent in the subsurface. The MSM also characterized longer timescales of exchange than were observed by the tracer-injection approach. The tracer data, and corresponding TSM fits, were limited by tracer measurement sensitivity and uncertainty in estimates of background tracer concentrations. Our results indicate that rates and patterns of hyporheic exchange are strongly influenced by a continuum of surface-subsurface hydrologic interactions over a wide range of spatial and temporal scales rather than discrete processes.

  13. Macroinvertebrate assemblage recovery following a catastrophic flood and debris flows in an Appalachian mountain stream

    USGS Publications Warehouse

    Snyder, C.D.; Johnson, Z.B.

    2006-01-01

    In June 1995, heavy rains caused severe flooding and massive debris flows on the Staunton River, a 3rd-order stream in the Blue Ridge Mountains (Virginia, USA). Scouring caused the loss of the riparian zone and repositioned the stream channel of the lower 2.1 km of the stream. Between 1998 and 2001, we conducted seasonal macroinvertebrate surveys at sites on the Staunton River and on White Oak Canyon Run, a reference stream of similar size and geology that was relatively unaffected by the flood. Our study was designed to determine the extent to which flood-induced changes to the stream channel and riparian habitats caused long-term changes to macroinvertebrate community structure and composition. Sites within the impacted zone of the Staunton River supported diverse stable benthic macroinvertebrate assemblages 3 y after the flood despite dramatic and persistent changes in environmental factors known to be important controls on stream ecosystem function. However, significant differences in total macroinvertebrate density and trophic structure could be attributed to the flood. In autumn, densities of most feeding guilds, including shredders, were higher at impacted-zone sites than at all other sites, suggesting higher overall productivity in the impacted zone. Higher shredder density in the impacted zone was surprising in light of expected decreases in leaf-litter inputs because of removal of riparian forests. In contrast, in spring, we observed density differences in only one feeding guild, scrapers, which showed higher densities at impacted-zone sites than at all other sites. This result conformed to a priori expectations that reduced shading in the impacted zone would lead to increased light and higher instream primary production. We attribute the seasonal differences in trophic structure to the effects of increased temperatures on food quality and to the relationship between the timing of our sampling and the emergence patterns of important taxa. ?? 2006 by The

  14. Investigation of Mixing a Supersonic Stream with the Flow Downstream of a Wedge

    NASA Technical Reports Server (NTRS)

    Sheeley, Joseph

    1997-01-01

    The flow characteristics in the base region of a two-dimensional supersonic compression ramp are investigated. A stream-wise oriented air jet, M = 1.75, is injected through a thin horizontal slot into a supersonic air main flow, M = 2.3, at the end of a two-dimensional compression ramp. The velocity profile and basic characteristics of the flow in the base region immediately following the ramp are determined. Visualization of the flowfield for qualitative observations is accomplished via Dark Central Ground Interferometry (DCGI). Two-dimensional velocity profiles are obtained using Laser Doppler Velocimetry (LDV). The study is the initial phase of a four-year investigation of base flow mixing. The current study is to provide more details of the flowfield.

  15. 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.

  16. Precipitation induced stream flow: An event based chemical and isotopic study of a small stream in the Great Plains region of the USA

    USGS Publications Warehouse

    Machavaram, M.V.; Whittemore, D.O.; Conrad, M.E.; Miller, N.L.

    2006-01-01

    A small stream in the Great Plains of USA was sampled to understand the streamflow components following intense precipitation and the influence of water storage structures in the drainage basin. Precipitation, stream, ponds, ground-water and soil moisture were sampled for determination of isotopic (D, 18O) and chemical (Cl, SO4) composition before and after two intense rain events. Following the first storm event, flow at the downstream locations was generated primarily through shallow subsurface flow and runoff whereas in the headwaters region - where a pond is located in the stream channel - shallow ground-water and pond outflow contributed to the flow. The distinct isotopic signatures of precipitation and the evaporated pond water allowed separation of the event water from the other sources that contributed to the flow. Similarly, variations in the Cl and SO4 concentrations helped identify the relative contributions of ground-water and soil moisture to the streamflow. The relationship between deuterium excess and Cl or SO4 content reveals that the early contributions from a rain event to streamflow depend upon the antecedent climatic conditions and the position along the stream channel within the watershed. The design of this study, in which data from several locations within a watershed were collected, shows that in small streams changes in relative contributions from ground water and soil moisture complicate hydrograph separation, with surface-water bodies providing additional complexity. It also demonstrates the usefulness of combined chemical and isotopic methods in hydrologic investigations, especially the utility of the deuterium excess parameter in quantifying the relative contributions of various source components to the stream flow. ?? 2006 Elsevier B.V. All rights reserved.

  17. Parametrisation of initial conditions for seasonal stream flow forecasting in the Swiss Rhine basin

    NASA Astrophysics Data System (ADS)

    Schick, Simon; Rössler, Ole; Weingartner, Rolf

    2016-04-01

    Current climate forecast models show - to the best of our knowledge - low skill in forecasting climate variability in Central Europe at seasonal lead times. When it comes to seasonal stream flow forecasting, initial conditions thus play an important role. Here, initial conditions refer to the catchments moisture at the date of forecast, i.e. snow depth, stream flow and lake level, soil moisture content, and groundwater level. The parametrisation of these initial conditions can take place at various spatial and temporal scales. Examples are the grid size of a distributed model or the time aggregation of predictors in statistical models. Therefore, the present study aims to investigate the extent to which the parametrisation of initial conditions at different spatial scales leads to differences in forecast errors. To do so, we conduct a forecast experiment for the Swiss Rhine at Basel, which covers parts of Germany, Austria, and Switzerland and is southerly bounded by the Alps. Seasonal mean stream flow is defined for the time aggregation of 30, 60, and 90 days and forecasted at 24 dates within the calendar year, i.e. at the 1st and 16th day of each month. A regression model is employed due to the various anthropogenic effects on the basins hydrology, which often are not quantifiable but might be grasped by a simple black box model. Furthermore, the pool of candidate predictors consists of antecedent temperature, precipitation, and stream flow only. This pragmatic approach follows the fact that observations of variables relevant for hydrological storages are either scarce in space or time (soil moisture, groundwater level), restricted to certain seasons (snow depth), or regions (lake levels, snow depth). For a systematic evaluation, we therefore focus on the comprehensive archives of meteorological observations and reanalyses to estimate the initial conditions via climate variability prior to the date of forecast. The experiment itself is based on four different

  18. The Evolution of Flow Stripes and Internal Layers on Kamb Ice Stream, Antarctica

    NASA Astrophysics Data System (ADS)

    Campbell, I.; Welch, B.; Jacobel, R.; Pettersson, R.

    2006-12-01

    Flowstripes are ubiquitous features indicating fast ice flow on glaciers, ice streams and floating ice shelves. Model studies show that they are an expected consequence where flow is strongly convergent, or whenever velocity at the bed is large compared to shearing through the ice thickness (Gudmundsson et al., 1998). Under these conditions, basal undulations are effectively transmitted to the surface where they are advected for long distances downstream. Folding of internal layers depicted in radar profiles is also a common occurrence in ice streams. In the case of Kamb Ice Stream (KIS), "stacks" of internal layers folds on the scale of 1-3 kilometers in wavelength in the cross-flow direction have been traced for over 100 kilometers (Ng and Conway, 2004). The question is: What relationship, if any, do these folds have with respect to surface flowstripes? We have traced surface flowstripes in Radarsat and MODIS imagery for several hundred kilometers on KIS from the onset of streaming flow into the stagnant trunk. We compare the morphology and evolution of these features at the surface to the internal layer folds in cross-ice stream profiles at five transects along the length of KIS, including those analyzed by Ng and Conway (2004). We find little correspondence between the internal layer folds in the cross-flow radar profiles and the flowstripes seen on the surface directly above. The initial wavelengths of internal layer folds are generally in the range of 1-3 km and tend to converge downstream, ending with wavelengths typically less than a kilometer. Surface flowstripes, though having similar wavelengths (on the order of 1.5 to 3 km at onset), remain roughly subparallel for tens to hundreds of kilometers, eventually becoming less distinct as the ice stagnates but retaining their wavelength and spacing. We are thus able to identify examples where flowstripes cross above internal layers. The amplitude of internal layer folds we have measured decreases towards the

  19. Effects of a flood pulse on exchange flows along a sinuous stream

    NASA Astrophysics Data System (ADS)

    Käser, D.; Brunner, P.; Renard, P.; Perrochet, P.; Schirmer, M.; Hunkeler, D.

    2012-04-01

    Flood pulses are important events for river ecosystems: they create hydrological interactions at the terrestrial/aquatic interface that fuel biological productivity and shape the hyporheic-riparian habitats. For example, floods promote faunal activity and decomposition by increasing the supply of oxygenated water in downwelling areas, while the following recession periods tend to provide stable thermal conditions favoured by fish or insects in areas of groundwater upwelling. This 3-D modelling study investigates the effect of stream stage transience (with events characterised by their intensity and duration) on hydrological exchanges between the surface and the near-stream subsurface. It evaluates, in particular, its effect on streams of varying sinuosity by quantifying the dynamic response of: (1) subsurface flow paths, (2) the exchange pattern at the sediment-water interface, and (3) integrative measures such as total exchange flux and total storage. Understanding geomorphological controls on groundwater/surface water interactions is attractive because topography is generally better constrained than subsurface parameters, and can be used in data-poor situations. The numerical model represents a hypothetical alluvial plain limited by impervious bedrock on all four sides, and in which the channel meanders according to the sine-generated curve of Langbein and Leopold (1966). As the model (HydroGeoSphere) couples surface and subsurface flow, the stream stage transience is imposed by a fluctuating head at the channel inlet. Preliminary results show that a simple rectangular flood pulse in an idealised sinuous stream without additional complexity can generate multiple flow direction reversals at a single point in the channel. The initial conditions of the groundwater table, the channel sinuosity and the time characteristics of the flood pulse all control exchange flow features in different ways. Results are also compared with 'bank storage' analytical solutions that

  20. Effects of flow intermittency and pharmaceutical exposure on the structure and metabolism of stream biofilms.

    PubMed

    Corcoll, Natàlia; Casellas, Maria; Huerta, Belinda; Guasch, Helena; Acuña, Vicenç; Rodríguez-Mozaz, Sara; Serra-Compte, Albert; Barceló, Damià; Sabater, Sergi

    2015-01-15

    Increasing concentrations of pharmaceutical compounds occur in many rivers, but their environmental risk remains poorly studied in stream biofilms. Flow intermittency shapes the structure and functions of ecosystems, and may enhance their sensitivity to toxicants. This study evaluates the effects of a long-term exposure of biofilm communities to a mixture of pharmaceutical compounds at environmental concentrations on biofilm bioaccumulation capacity, the structure and metabolic processes of algae and bacteria communities, and how their potential effects were enhanced or not by the occurrence of flow intermittency. To assess the interaction between those two stressors, an experiment with artificial streams was performed. Stream biofilms were exposed to a mixture of pharmaceuticals, as well as to a short period of flow intermittency. Results indicate that biofilms were negatively affected by pharmaceuticals. The algal biomass and taxa richness decreased and unicellular green algae relatively increased. The structure of the bacterial (based on denaturing gradient gel electrophoresis of amplified 16S rRNA genes) changed and showed a reduction of the operational taxonomic units (OTUs) richness. Exposed biofilms showed higher rates of metabolic processes, such as primary production and community respiration, attributed to pharmaceuticals stimulated an increase of green algae and heterotrophs, respectively. Flow intermittency modulated the effects of chemicals on natural communities. The algal community became more sensitive to short-term exposure of pharmaceuticals (lower EC50 value) when exposed to water intermittency, indicating cumulative effects between the two assessed stressors. In contrast to algae, the bacterial community became less sensitive to short-term exposure of pharmaceuticals (higher EC50) when exposed to water intermittency, indicating co-tolerance phenomena. According to the observed effects, the environmental risk of pharmaceuticals in nature is high

  1. The Estimated Likelihood of Nutrients and Pesticides in Nontidal Headwater Streams of the Maryland Coastal Plain During Base Flow

    EPA Science Inventory

    Water quality in nontidal headwater (first-order) streams of the Coastal Plain during base flow in the late winter and spring is related to land use, hydrogeology, and other natural or human influences in contributing watersheds. A random survey of 174 headwater streams of the Mi...

  2. Flow duration of Kentucky streams through 1990; historical and monthly flow characteristics, including the effects of reservoirs

    USGS Publications Warehouse

    Ruhl, K.J.; Burns, R.J.; Martin, G.R.; Allgeier, D.P.

    1995-01-01

    This report presents flow-duration tables and plots for selected streamflow sites in Kentucky with three or more years of continuous record through 1990. Flow duration describes the frequency with which given streamflows are equalled or exceeded. The flow-duration tables were computed using daily mean discharge values for the entire period specified and for each month of the period specified. Only complete years of record were used for the computation. For sites where the streamflow is affected by regulation, separate tables are presented for the period before regulation (unregulated), the period of record after regulation (regulated) and the entire period of record (historical). Flow-duration plots are also presented for each station using the data for the entire period specified. Where practicable, several flow-duration plots are shown together. This includes stations on the same stream, such as main-stem stations, and stations within the same watershed. For stations affected by regulation, which have up to three sets of data available for one station (unregulated, regulated, and historical), the three plots are shown together to clearly illustrate the influence of regulation in augmenting low flows and reducing high flows.

  3. 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.

  4. Experimental validation of a two-dimensional shear-flow model for determining acoustic impedance

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    Tests were conducted to validate a two-dimensional shear-flow analytical model for determining the acoustic impedance of a liner test specimen in a grazing-incidence, grazing-flow environment. The tests were limited to a test specimen chosen to exhibit minimal effects of grazing flow so that the results obtained by using the shear-flow analytical model would be expected to match those obtained from normal-incidence impedance measurements. Impedances for both downstream and upstream sound propagation were generally consistent with those from normal-incidence measurements. However, sensitivity of the grazing-incidence impedance to small measurement or systematic errors in propagation constant varied dramatically over the range of test frequencies.

  5. Morphological divergence and flow-induced phenotypic plasticity in a native fish from anthropogenically altered stream habitats.

    PubMed

    Franssen, Nathan R; Stewart, Laura K; Schaefer, Jacob F

    2013-11-01

    Understanding population-level responses to human-induced changes to habitats can elucidate the evolutionary consequences of rapid habitat alteration. Reservoirs constructed on streams expose stream fishes to novel selective pressures in these habitats. Assessing the drivers of trait divergence facilitated by these habitats will help identify evolutionary and ecological consequences of reservoir habitats. We tested for morphological divergence in a stream fish that occupies both stream and reservoir habitats. To assess contributions of genetic-level differences and phenotypic plasticity induced by flow variation, we spawned and reared individuals from both habitats types in flow and no flow conditions. Body shape significantly and consistently diverged in reservoir habitats compared with streams; individuals from reservoirs were shallower bodied with smaller heads compared with individuals from streams. Significant population-level differences in morphology persisted in offspring but morphological variation compared with field-collected individuals was limited to the head region. Populations demonstrated dissimilar flow-induced phenotypic plasticity when reared under flow, but phenotypic plasticity in response to flow variation was an unlikely explanation for observed phenotypic divergence in the field. Our results, together with previous investigations, suggest the environmental conditions currently thought to drive morphological change in reservoirs (i.e., predation and flow regimes) may not be the sole drivers of phenotypic change. PMID:24363894

  6. Herbicides and herbicide degradation products in upper midwest agricultural streams during august base-flow conditions

    USGS Publications Warehouse

    Kalkhoff, S.J.; Lee, K.E.; Porter, S.D.; Terrio, P.J.; Thurman, E.M.

    2003-01-01

    Herbicide concentrations in streams of the U.S. Midwest have been shown to decrease through the growing season due to a variety of chemical and physical factors. The occurrence of herbicide degradation products at the end of the growing season is not well known. This study was conducted to document the occurrence of commonly used herbicides and their degradation products in Illinois, Iowa, and Minnesota streams during base-flow conditions in August 1997. Atrazine, the most frequently detected herbicide (94%), was present at relatively low concentrations (median 0.17 μg L−1). Metolachlor was detected in 59% and cyanazine in 37% of the samples. Seven of nine compounds detected in more than 50% of the samples were degradation products. The total concentration of the degradation products (median of 4.4 μg L−1) was significantly greater than the total concentration of parent compounds (median of 0.26 μg L−1). Atrazine compounds were present less frequently and in significantly smaller concentrations in streams draining watersheds with soils developed on less permeable tills than in watersheds with soils developed on more permeable loess. The detection and concentration of triazine compounds was negatively correlated with antecedent rainfall (April–July). In contrast, acetanalide compounds were positively correlated with antecedant rainfall in late spring and early summer that may transport the acetanalide degradates into ground water and subsequently into nearby streams. The distribution of atrazine degradation products suggests regional differences in atrazine degradation processes.

  7. Low-flow characteristics of streams in the Kishwaukee River basin, Illinois

    USGS Publications Warehouse

    Allen, Howard E., Jr.; Cowan, Ellen A.

    1985-01-01

    Seven-day, 2-year, and 7-day, 10-year natural low flows are estimated at five continuous-record gaging stations based on streamflow records and records of wastewater effluent furnished by treatment plants. Low flows are also estimated at 22 partial-record stations by relating natural low-flow estimates for long-term stations to discharge measurements at partial-record stations. Standard error of estimates for the 27 gaged sites averaged 33 percent for 2-year estimates and 51 percent for 10-year estimates. A technique for estimating flows at ungaged stream sites is based on drainage area and indexes of streamflow recession. Streamflow-recession indexes were used to account for effects of geology on low flows. Multiple-regression analyses relates the low flows to drainage area and streamflow recession rates. Average standard errors of estimates of 61 and 97 percent were indicated for the 2-year and 10-year estimating equations, respectively. Wastewater treatment plant location and effluent discharged during 7-day low-flow periods in 1981 are presented for use in adjusting natural low-flow estimates at gaged and ungaged sites to represent 1981 streamflow conditions. (USGS)

  8. Comparative Analysis of Continuous Acoustic Emission (AE) Data, Acquired from 12 and 16 Bit Streaming Systems during Rock Deformation Experiments

    NASA Astrophysics Data System (ADS)

    Flynn, J.; Goodfellow, S. D.; Nasseri, M. H.; Reyes-Montes, J. M.; Young, R.

    2013-12-01

    A comparative analysis of continuous acoustic emission (AE) data acquired during a triaxial compression test, using a 12-bit and a 16-bit acquisition system, is presented. A cylindrical sample (diameter 50.1 mm and length 125 mm) of Berea sandstone was triaxally deformed at a confining pressure of 15 MPa and a strain rate of 1.6E-06 s-1. The sample was loaded differentially until failure occurred at approximately σ1 = 160 MPa. AE activity was monitored for the duration of the experiment by an array of 8 broadband piezoelectric transducers coupled to the rock sample. Raw signals were amplified by 40 dB using pre-amplifiers equipped with filter modules with a frequency passband of 100 kHz to 1 MHz. The amplifiers had a split output enabling the measured signal to be fed into a 12-bit and a 16-bit acquisition system. AE waveforms were continuously recorded at 10 MS/s on 8 data acquisition channels per system. Approximately 4,500 events were harvested and source located from the continuous data for each system. P-wave arrivals were automatically picked and event locations calculated using the downhill Simplex method and a time-varying transverse isotropic velocity model based on periodical surveys across the sample. Events detected on the 12-bit and 16-bit systems were compared both in terms of their P-wave picks and their source locations. In the early stages of AE activity, there appeared to be little difference between P-wave picks and hypocenter locations from both data sets. As the experiment progressed into the post-peak stress regime, which was accompanied by an increase in AE rate and amplitude, fewer events could be harvested from the 12-bit data compared to the 16-bit data. This is linked to the observation of a higher signal-to-noise ratio on AE waveforms harvested from the 16-bit stream compared to those from the 12-bit stream, which results in an easier identification of P-wave onsets. Similarly a higher confidence in source location is expected. Analysis

  9. Hydro-acoustic instabilities in compressible turbulent channel flow with porous walls

    NASA Astrophysics Data System (ADS)

    Scalo, Carlo; Rahbari, Iman

    2015-11-01

    C. Scalo, J. Bodart, and S. K. Lele, Phys. Fluids (2015) manipulated wall-bounded compressible turbulence by applying impedance boundary conditions (IBC) acoustically tuned to the characteristic time scale of the large-scale eddies. Near-wall turbulence was overhauled by hydro-acoustic instabilities - comprised of coherent spanwise Kelvin-Helmholtz rollers driven by Helmholtz-like acoustic resonance - while outer-layer turbulence was left structurally unaltered. We discuss linear modeling results of the observed flow response, supported by new high-fidelity simulations up to transonic bulk Mach numbers. For IBCs with zero reactance, corresponding to a Darcy-like formulation for porous walls, two dominant modes are identified whose Reynolds stress distributions overlap with the impermeable-wall turbulent buffer layer, directly affecting the near-wall turbulence cycle. For the range of wavenumbers investigated, the transition from subcritical to supercritical permeability does not significantly alter the structure of the unstable modes, showing that wall-permeability accentuates pre-existing, otherwise stable, modes. Implications on flow control strategies for compressible boundary layers over porous walls are discussed. School of Mechanical Engineering.

  10. 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

  11. 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

  12. Assessing the Vulnerability of Streams to Increased Frequency and Severity of Low Flows in the Southeastern United States

    NASA Astrophysics Data System (ADS)

    Konrad, C. P.

    2014-12-01

    A changing climate poses risks to the availability and quality of water resources. Among the risks, increased frequency and severity of low flow periods in streams would be significant for many in-stream and out-of-stream uses of water. While down-scaled climate projections serve as the basis for understanding impacts of climate change on hydrologic systems, a robust framework for risk assessment incorporates multiple dimensions of risks including the vulnerability of hydrologic systems to climate change impacts. Streamflow records from the southeastern US were examined to assess the vulnerability of streams to increased frequency and severity of low flows. Long-term (>50 years) records provide evidence of more frequent and severe low flows in more streams than would be expected from random chance. Trends in low flows appear to be a result of changes in the temporal distribution rather than the annual amount of preciptation and/or in evaporation. Base flow recession provides an indicator of a stream's vulnerability to such changes. Linkages between streamflow patterns across temporal scales can be used for understanding and asessing stream responses to the various possible expressions of a changing climate.

  13. Experimental determination of the structure coefficient of a twisted stream flowing in the intertube space of a heat exchanger

    NASA Astrophysics Data System (ADS)

    Dzyubenko, B. V.

    1981-05-01

    The dependence of the structure coefficient of a stream flowing in a bundle of helically curved tubes of oval profile on the determining parameters is established, along with the features of this system.

  14. Perched groundwater-surface interactions and their consequences in stream flow generation in a semi-arid headwater catchment

    NASA Astrophysics Data System (ADS)

    Molenat, Jerome; Bouteffeha, Maroua; Raclot, Damien; Bouhlila, Rachida

    2013-04-01

    In semi-arid headwater catchment, it is usually admitted that stream flow comes predominantly from Hortonian overland flow (infiltration excess overland flow). Consequently, subsurface flow processes, and especially perched or shallow groundwater flow, have not been studied extensively. Here we made the assumption that perched groundwater flow could play a significant role in stream flow generation in semi-arid catchment. To test this assumption, we analyzed stream flow time series of a headwater catchment in the Tunisian Cap Bon region and quantified the flow fraction coming from groundwater discharge and that from overland flow. Furthermore, the dynamics of the perched groundwater was analyzed, by focusing on the different perched groundwater-surface interaction processes : diffuse and local infiltration, diffuse exfiltration, and direct groundwater discharge to the stream channel. This work is based on the 2.6 km² Kamech catchment (Tunisia), which belongs to the long term Mediterranean hydrological observatory OMERE (Voltz and Albergel, 2002). Results show that even though Hortonian overland flow was the main hydrological process governing the stream flow generation, groundwater discharge contribution to the stream channel annually accounted for from 10% to 20 % depending on the year. Furthermore, at some periods, rising of groundwater table to the soil surface in bottom land areas provided evidences of the occurrence of saturation excess overland flow processes during some storm events. Reference Voltz , M. and Albergel , J., 2002. OMERE : Observatoire Méditerranéen de l'Environnement Rural et de l'Eau - Impact des actions anthropiques sur les transferts de masse dans les hydrosystèmes méditerranéens ruraux. Proposition d'Observatoire de Recherche en Environnement, Ministère de la Recherche.

  15. Effective number of breeders provides a link between interannual variation in stream flow and individual reproductive contribution in a stream salmonid.

    PubMed

    Whiteley, Andrew R; Coombs, Jason A; Cembrola, Matthew; O'Donnell, Matthew J; Hudy, Mark; Nislow, Keith H; Letcher, Benjamin H

    2015-07-01

    The effective number of breeders that give rise to a cohort (N(b)) is a promising metric for genetic monitoring of species with overlapping generations; however, more work is needed to understand factors that contribute to variation in this measure in natural populations. We tested hypotheses related to interannual variation in N(b) in two long-term studies of brook trout populations. We found no supporting evidence for our initial hypothesis that N^(b) reflects N^(c) (defined as the number of adults in a population at the time of reproduction). N^(b) was stable relative to N^(C) and did not follow trends in abundance (one stream negative, the other positive). We used stream flow estimates to test the alternative hypothesis that environmental factors constrain N(b). We observed an intermediate optimum autumn stream flow for both N^(b) (R(2) = 0.73, P = 0.02) and full-sibling family evenness (R(2) = 0.77, P = 0.01) in one population and a negative correlation between autumn stream flow and full-sib family evenness in the other population (r = -0.95, P = 0.02). Evidence for greater reproductive skew at the lowest and highest autumn flow was consistent with suboptimal conditions at flow extremes. A series of additional tests provided no supporting evidence for a related hypothesis that density-dependent reproductive success was responsible for the lack of relationship between N(b) and N(C) (so-called genetic compensation). This work provides evi