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Sample records for acoustic streaming flow

  1. 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.

  2. 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.

  3. 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.

  4. Selective particle and cell capture in a continuous flow using micro-vortex acoustic streaming.

    PubMed

    Collins, David J; Khoo, Bee Luan; Ma, Zhichao; Winkler, Andreas; Weser, Robert; Schmidt, Hagen; Han, Jongyoon; Ai, Ye

    2017-04-10

    Acoustic streaming has emerged as a promising technique for refined microscale manipulation, where strong rotational flow can give rise to particle and cell capture. In contrast to hydrodynamically generated vortices, acoustic streaming is rapidly tunable, highly scalable and requires no external pressure source. Though streaming is typically ignored or minimized in most acoustofluidic systems that utilize other acoustofluidic effects, we maximize the effect of acoustic streaming in a continuous flow using a high-frequency (381 MHz), narrow-beam focused surface acoustic wave. This results in rapid fluid streaming, with velocities orders of magnitude greater than that of the lateral flow, to generate fluid vortices that extend the entire width of a 400 μm wide microfluidic channel. We characterize the forces relevant for vortex formation in a combined streaming/lateral flow system, and use these acoustic streaming vortices to selectively capture 2 μm from a mixed suspension with 1 μm particles and human breast adenocarcinoma cells (MDA-231) from red blood cells.

  5. Acoustic streaming and thermal instability of flow generated by ultrasound in a cylindrical container

    NASA Astrophysics Data System (ADS)

    Green, Adam; Marshall, Jeffrey S.; Ma, Dong; Wu, Junru

    2016-10-01

    A vertically orientated ultrasonic transducer contained within a closed cylindrical Pyrex tube was used to study the acoustic streaming flow within a cylindrical container. A particle-image velocimetry (PIV) system incorporating fluorescent 1.5 μm seeding particles suspended in a mixture of diethyl-phthalate and ethanol, whose optical index was matched to that of Pyrex, was used to allow for undistorted PIV imaging within the Pyrex tube. Temperature on the end-wall surface and acoustic pressure within the cylinder were measured for different end-wall materials. Variables considered included acoustic absorption and reflection coefficients, ultrasound intensity, container height, and thermal properties of the end-wall material. It was observed that a quasi-steady flow field driven by acoustic streaming is rapidly established within the container, which is typically dominated by a stationary vortex ring with downward flow along the ring axis. After sufficient time this quasi-stationary flow exhibits a thermal instability causing it to transform into a secondary flow state. Different types of secondary flow states were observed, including cases where the flow along the cylinder axis is oriented upward toward the ultrasound transducer and cases where the axial flow changes directions along the cylinder axis.

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

    PubMed

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

    2015-09-01

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

  7. 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.

  8. 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.

  9. 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

  10. Experimental and numerical investigation of Acoustic streaming (Eckart streaming)

    NASA Astrophysics Data System (ADS)

    Dridi, Walid; Botton, Valery; Henry, Daniel; Ben Hadid, Hamda

    The application of sound waves in the bulk of a fluid can generate steady or quasi-steady flows reffered to as Acoustic streaming flows. We can distinguish two kind of acoustic streaming: The Rayleigh Streaming is generated when a standing acoustic waves interfere with solid walls to give birth to an acoustic boundary layer. Steady recirculations are then driven out of the boundary layer and can be used in micro-gravity, where the free convection is too weak or absent, to enhance the convective heat or mass transfer and cooling the electronic devises [1]. The second kind is the Eckart streaming, which is a flow generated far from the solid boundaries, it can be used to mix a chemical solutions [2], and to drive a viscous liquids in channels [3-4], in micro-gravity area. Our study focuses on the Eckart streaming configuration, which is investigated both numerical and experimental means. The experimental configuration is restricted to the case of a cylindrical non-heated cavity full of water or of a water+glycerol mixture. At the middle of one side of the cavity, a plane ultrasonic transducer generates a 2MHz wave; an absorber is set at the opposite side of the cavity to avoid any reflections. The velocity field is measured with a standard PIV system. [1] P. Vainshtein, M. Fichman and C. Gutfinger, "Acoustic enhancement of heat transfer between two parallel plates", International Journal of Heat and Mass Transfert, 1995, 38(10), 1893. [2] C. Suri, K. Tekenaka, H. Yanagida, Y. Kojima and K. Koyama, "Chaotic mixing generated by acoustic streaming", Ultrasonics, 2002, 40, 393 [3] O.V. Rudenko and A.A. Sukhorukov, "Nonstationnary Eckart streaming and pumping of liquid in ultrasonic field", Acoustical Physics, 1998, 44, 653. [4] Kenneth D. Frampton, Shawn E. Martin and Keith Minor, "The scaling of acoustic streaming for application in micro-fluidic devices", Applied Acoustics, 2003, 64,681

  11. Acoustic streaming of a sharp edge.

    PubMed

    Ovchinnikov, Mikhail; Zhou, Jianbo; Yalamanchili, Satish

    2014-07-01

    Anomalous acoustic streaming is observed emanating from sharp edges of solid bodies that are vibrating in fluids. The streaming velocities can be orders of magnitude higher than expected from the Rayleigh streaming at similar amplitudes of vibration. Acoustic velocity of fluid relative to a solid body diverges at a sharp edge, giving rise to a localized time-independent body force acting on the fluid. This force results in a formation of a localized jet. Two-dimensional numerical simulations are performed to predict acoustic streaming for low amplitude vibration using two methods: (1) Steady-state solution utilizing perturbation theory and (2) direct transient solution of the Navier-Stokes equations. Both analyses agree with each other and correctly predict the streaming of a sharp-edged vibrating blade measured experimentally. The origin of the streaming can be attributed to the centrifugal force of the acoustic fluid flow around a sharp edge. The dependence of this acoustic streaming on frequency and velocity is examined using dimensional analysis. The dependence law is devised and confirmed by numerical simulations.

  12. Acoustic Doppler velocimeter-induced acoustic streaming and its implications for measurement

    NASA Astrophysics Data System (ADS)

    Poindexter, C. M.; Rusello, P. J.; Variano, E. A.

    2011-05-01

    The acoustic Doppler velocimeter (ADV) is widely used for the characterization of fluid flow. Secondary flows ("acoustic streaming") generated by the ADV's acoustic pulses may affect the accuracy of measurements in experiments with small velocities. We assessed the impact of acoustic streaming on flow measurement using particle image velocimetry. The probes of two different ADVs were successively mounted in a tank of quiescent water. The probes' ultrasound emitters were aligned with a laser light sheet. Observed flow was primarily in the axial direction, accelerating from the ultrasound emitter and peaking within centimeters of the velocimeter sampling volume before dropping off. We measured the dependence of acoustic streaming velocity on ADV configuration, finding that different settings induce streaming ranging from negligible to more than 2.0 cm s-1. From these results, we describe cases where acoustic streaming affects velocity measurements and also cases where ADVs accurately measure their own acoustic streaming.

  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. Acoustic streaming jets: A scaling and dimensional analysis

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    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.

  15. Near-field acoustic streaming jet

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    A numerical and experimental investigation of the acoustic streaming flow in the near field of a circular plane ultrasonic transducer in water is performed. The experimental domain is a parallelepipedic cavity delimited by absorbing walls to avoid acoustic reflection, with a top free surface. The flow velocities are measured by particle image velocimetry, leading to well-resolved velocity profiles. The theoretical model is based on a linear acoustic propagation model, which correctly reproduces the acoustic field mapped experimentally using a hydrophone, and an acoustic force term introduced in the Navier-Stokes equations under the plane-wave assumption. Despite the complexity of the acoustic field in the near field, in particular in the vicinity of the acoustic source, a good agreement between the experimental measurements and the numerical results for the velocity field is obtained, validating our numerical approach and justifying the planar wave assumption in conditions where it is a priori far from obvious. The flow structure is found to be correlated with the acoustic field shape. Indeed, the longitudinal profiles of the velocity present a wavering linked to the variations in acoustic intensity along the beam axis and transverse profiles exhibit a complex shape strongly influenced by the transverse variations of the acoustic intensity in the beam. Finally, the velocity in the jet is found to increase as the square root of the acoustic force times the distance from the origin of the jet over a major part of the cavity, after a strong short initial increase, where the velocity scales with the square of the distance from the upstream wall.

  16. Active micromixer using surface acoustic wave streaming

    SciTech Connect

    Branch; Darren W. , Meyer; Grant D. , Craighead; Harold G.

    2011-05-17

    An active micromixer uses a surface acoustic wave, preferably a Rayleigh wave, propagating on a piezoelectric substrate to induce acoustic streaming in a fluid in a microfluidic channel. The surface acoustic wave can be generated by applying an RF excitation signal to at least one interdigital transducer on the piezoelectric substrate. The active micromixer can rapidly mix quiescent fluids or laminar streams in low Reynolds number flows. The active micromixer has no moving parts (other than the SAW transducer) and is, therefore, more reliable, less damaging to sensitive fluids, and less susceptible to fouling and channel clogging than other types of active and passive micromixers. The active micromixer is adaptable to a wide range of geometries, can be easily fabricated, and can be integrated in a microfluidic system, reducing dead volume. Finally, the active micromixer has on-demand on/off mixing capability and can be operated at low power.

  17. Acoustic and streaming velocity components in a resonant waveguide at high acoustic levels.

    PubMed

    Daru, Virginie; Reyt, Ida; Bailliet, Hélène; Weisman, Catherine; Baltean-Carlès, Diana

    2017-01-01

    Rayleigh streaming is a steady flow generated by the interaction between an acoustic wave and a solid wall, generally assumed to be second order in a Mach number expansion. Acoustic streaming is well known in the case of a stationary plane wave at low amplitude: it has a half-wavelength spatial periodicity and the maximum axial streaming velocity is a quadratic function of the acoustic velocity amplitude at antinode. For higher acoustic levels, additional streaming cells have been observed. Results of laser Doppler velocimetry measurements are here compared to direct numerical simulations. The evolution of axial and radial velocity components for both acoustic and streaming velocities is studied from low to high acoustic amplitudes. Two streaming flow regimes are pointed out, the axial streaming dependency on acoustics going from quadratic to linear. The evolution of streaming flow is different for outer cells and for inner cells. Also, the hypothesis of radial streaming velocity being of second order in a Mach number expansion, is not valid at high amplitudes. The change of regime occurs when the radial streaming velocity amplitude becomes larger than the radial acoustic velocity amplitude, high levels being therefore characterized by nonlinear interaction of the different velocity components.

  18. Cyclones and attractive streaming generated by acoustical vortices.

    PubMed

    Riaud, Antoine; Baudoin, Michael; Thomas, Jean-Louis; Bou Matar, Olivier

    2014-07-01

    Acoustical and optical vortices have attracted great interest due to their ability to capture and manipulate particles with the use of radiation pressure. Here we show that acoustical vortices can also induce axial vortical flow reminiscent of cyclones, whose topology can be controlled by adjusting the properties of the acoustical beam. In confined geometry, the phase singularity enables generating "attractive streaming" with the flow directed toward the transducer. This opens perspectives for contactless vortical flow control.

  19. Investigation of acoustic streaming patterns around oscillating sharp edges

    PubMed Central

    Nama, Nitesh; Huang, Po-Hsun; Huang, Tony Jun; Costanzo, Francesco

    2014-01-01

    Oscillating sharp edges have been employed to achieve rapid and homogeneous mixing in microchannels using acoustic streaming. Here we use a perturbation approach to study the flow around oscillating sharp edges in a microchannel. This work extends prior experimental studies to numerically characterize the effect of various parameters on the acoustically induced flow. Our numerical results match well with the experimental results. We investigated multiple device parameters such as the tip angle, oscillation amplitude, and channel dimensions. Our results indicate that, due to the inherent nonlinearity of acoustic streaming, the channel dimensions could significantly impact the flow patterns and device performance. PMID:24903475

  20. Frequency effects on the scale and behavior of acoustic streaming.

    PubMed

    Dentry, Michael B; Yeo, Leslie Y; Friend, James R

    2014-01-01

    Acoustic streaming underpins an exciting range of fluid manipulation phenomena of rapidly growing significance in microfluidics, where the streaming often assumes the form of a steady, laminar jet emanating from the device surface, driven by the attenuation of acoustic energy within the beam of sound propagating through the liquid. The frequencies used to drive such phenomena are often chosen ad hoc to accommodate fabrication and material issues. In this work, we seek a better understanding of the effects of sound frequency and power on acoustic streaming. We present and, using surface acoustic waves, experimentally verify a laminar jet model that is based on the turbulent jet model of Lighthill, which is appropriate for acoustic streaming seen at micro- to nanoscales, between 20 and 936 MHz and over a broad range of input power. Our model eliminates the critically problematic acoustic source singularity present in Lighthill's model, replacing it with a finite emission area and enabling determination of the streaming velocity close to the source. At high acoustic power P (and hence high jet Reynolds numbers ReJ associated with fast streaming), the laminar jet model predicts a one-half power dependence (U∼P1/2∼ ReJ) similar to the turbulent jet model. However, the laminar model may also be applied to jets produced at low powers-and hence low jet Reynolds numbers ReJ-where a linear relationship between the beam power and streaming velocity exists: U∼P∼ReJ2. The ability of the laminar jet model to predict the acoustic streaming behavior across a broad range of frequencies and power provides a useful tool in the analysis of microfluidics devices, explaining peculiar observations made by several researchers in the literature. In particular, by elucidating the effects of frequency on the scale of acoustically driven flows, we show that the choice of frequency is a vitally important consideration in the design of small-scale devices employing acoustic streaming

  1. Frequency effects on the scale and behavior of acoustic streaming

    NASA Astrophysics Data System (ADS)

    Dentry, Michael B.; Yeo, Leslie Y.; Friend, James R.

    2014-01-01

    Acoustic streaming underpins an exciting range of fluid manipulation phenomena of rapidly growing significance in microfluidics, where the streaming often assumes the form of a steady, laminar jet emanating from the device surface, driven by the attenuation of acoustic energy within the beam of sound propagating through the liquid. The frequencies used to drive such phenomena are often chosen ad hoc to accommodate fabrication and material issues. In this work, we seek a better understanding of the effects of sound frequency and power on acoustic streaming. We present and, using surface acoustic waves, experimentally verify a laminar jet model that is based on the turbulent jet model of Lighthill, which is appropriate for acoustic streaming seen at micro- to nanoscales, between 20 and 936 MHz and over a broad range of input power. Our model eliminates the critically problematic acoustic source singularity present in Lighthill's model, replacing it with a finite emission area and enabling determination of the streaming velocity close to the source. At high acoustic power P (and hence high jet Reynolds numbers ReJ associated with fast streaming), the laminar jet model predicts a one-half power dependence (U ˜P1/2˜ ReJ) similar to the turbulent jet model. However, the laminar model may also be applied to jets produced at low powers—and hence low jet Reynolds numbers ReJ—where a linear relationship between the beam power and streaming velocity exists: U ˜P˜ReJ2. The ability of the laminar jet model to predict the acoustic streaming behavior across a broad range of frequencies and power provides a useful tool in the analysis of microfluidics devices, explaining peculiar observations made by several researchers in the literature. In particular, by elucidating the effects of frequency on the scale of acoustically driven flows, we show that the choice of frequency is a vitally important consideration in the design of small-scale devices employing acoustic streaming

  2. Acoustofluidics 13: Analysis of acoustic streaming by perturbation methods.

    PubMed

    Sadhal, S S

    2012-07-07

    In this Part 13 of the tutorial series "Acoustofluidics--exploiting ultrasonic standing waves forces and acoustic streaming in microfluidic systems for cell and particle manipulation," the streaming phenomenon is presented from an analytical standpoint, and perturbation methods are developed for analyzing such flows. Acoustic streaming is the phenomenon that takes place when a steady flow field is generated by the absorption of an oscillatory field. This can happen either by attenuation (quartz wind) or by interaction with a boundary. The latter type of streaming can also be generated by an oscillating solid in an otherwise still fluid medium or vibrating enclosure of a fluid body. While we address the first kind of streaming, our focus is largely on the second kind from a practical standpoint for application to microfluidic systems. In this Focus article, we limit the analysis to one- and two-dimensional problems in order to understand the analytical techniques with examples that most-easily illustrate the streaming phenomenon.

  3. Long-term measurement of stream flow and salinity in a tidal river by the use of the fluvial acoustic tomography system

    NASA Astrophysics Data System (ADS)

    Kawanisi, Kiyosi; Razaz, Mahdi; Kaneko, Arata; Watanabe, Satoshi

    2010-01-01

    SummaryLong-term variation of stream flow of a tidal river was measured by an innovative technology, called the fluvial acoustic tomography (FAT). The reciprocal sound transmission was performed between two acoustic stations, located on both sides of the river. Even in the tidal river with the periodic intrusion of salt wedges, the cross-sectional average velocities along the river stream axis, estimated from the travel time difference data, were consistent with the average velocities, observed by an array of moored downward-looking ADCPs. The cross-sectional average salinity was also estimated by using the mean travel time data collected from the reciprocal sound transmission, the mean values of temperature measured by the conductivity-temperature ( C- T) sensors, and the ray simulation result. The derived salinity data from the FAT are comparable with that obtained by the C- T sensors. It is concluded that the fluvial acoustic tomography (FAT) is a prospective method for the continuous monitoring of tidal river discharge and temperature/salinity variations.

  4. Scaling and dimensional analysis of acoustic streaming jets

    NASA Astrophysics Data System (ADS)

    Moudjed, B.; Botton, V.; Henry, D.; Ben Hadid, H.; Garandet, J.-P.

    2014-09-01

    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.

  5. 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.

  6. Controlling the acoustic streaming by pulsed ultrasounds.

    PubMed

    Hoyos, Mauricio; Castro, Angélica

    2013-01-01

    We propose a technique based on pulsed ultrasounds for controlling, reducing to a minimum observable value the acoustic streaming in closed ultrasonic standing wave fluidic resonators. By modifying the number of pulses and the repetition time it is possible to reduce the velocity of the acoustic streaming with respect to the velocity generated by the continuous ultrasound mode of operation. The acoustic streaming is observed at the nodal plane where a suspension of 800nm latex particles was focused by primary radiation force. A mixture of 800nm and 15μm latex particles has been also used for showing that the acoustic streaming is hardly reduced while primary and secondary forces continue to operate. The parameter we call "pulse mode factor" i.e. the time of applied ultrasound divided by the duty cycle, is found to be the adequate parameter that controls the acoustic streaming. We demonstrate that pulsed ultrasound is more efficient for controlling the acoustic streaming than the variation of the amplitude of the standing waves.

  7. Experimental Acoustic Velocity Measurements in a Tidally Affected Stream

    USGS Publications Warehouse

    Storm, J.B.; ,

    2002-01-01

    The U.S. Geological Survey (USGS) constructed a continuous steamgaging station on the tidally affected Escatawpa River at Interstate 10 near Orange Grove, Mississippi, in August 2001. The gage collects water quantity parameters of stage and stream velocity, and water quality parameters of water temperature, specific conductance, and salinity. Data are transmitted to the local USGS office via the GOES satellite and are presented on a near real-time web page. Due to tidal effects, the stream has multiple flow regimes which include downstream, bi-directional, and reverse flows. Advances in acoustic technology have made it possible to gage streams of this nature where conventional methods have been unsuccessful. An experimental mount was designed in an attempt to recognize, describe, and quantify these flow regimes by using acoustic Doppler equipment.

  8. Valveless micropump driven by acoustic streaming

    NASA Astrophysics Data System (ADS)

    Choe, Youngki; Sok Kim, Eun

    2013-04-01

    This paper describes two valveless micropumps built on a 260 µm thick PZT with 20 µm thick parylene acoustic Fresnel lenses with air cavities. The micropumps produce in-plane body force through acoustic streaming effect of high-intensity acoustic beam that is generated by acoustic wave interference. The fabricated micropumps were shown to move microspheres, which have a diameter of 70-90 µm and a density of 0.99 g cm-3, on the water surface to form U-shape streams of microspheres with a drift velocity of 7.3 cm s-1 when the micropumps were located 4 mm below the water surface and driven by 160 Vpeak-to-peak pulsed sinusoidal waves. The driven microspheres formed U-shape streaming even without any fluidic channel according to the serial connection of the pie-shaped lenses and top electrodes. A micropump with a straight-lined fluidic channel was also fabricated and tested to show a 9.2 cm s-1 microspheres' drift velocity and a 9.5 mL min-1 volume pumping rate when combined with the acrylic acoustic wave reflector. Both the Fresnel lens and top electrode were patterned in a pie-shape with its apex angle of 90° to form asymmetric acoustic pressure distribution at the focal plane of the acoustic Fresnel lenses in order to push water in one direction.

  9. Acoustofluidics 14: Applications of acoustic streaming in microfluidic devices.

    PubMed

    Wiklund, Martin; Green, Roy; Ohlin, Mathias

    2012-07-21

    In part 14 of the tutorial series "Acoustofluidics--exploiting ultrasonic standing wave forces and acoustic streaming in microfluidic systems for cell and particle manipulation", we provide a qualitative description of acoustic streaming and review its applications in lab-on-a-chip devices. The paper covers boundary layer driven streaming, including Schlichting and Rayleigh streaming, Eckart streaming in the bulk fluid, cavitation microstreaming and surface-acoustic-wave-driven streaming.

  10. 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.

  11. 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.

  12. Experimental Study of Streaming Flows Associated with Ultrasonic Levitators

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    Steady-state acoustic streaming flow patterns have been observed during the operation of a variety of resonant single-axis ultrasonic levitators n a gaseous environment and in the 18 to 37 KHz frequency range.

  13. 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.

  14. On boundary layer transition in high-subsonic and transonic flow under the influence of acoustic disturbances and free-stream turbulence

    NASA Technical Reports Server (NTRS)

    Murthy, S. V.; Steinle, F. W.

    1985-01-01

    The existing data base which quantifies the roles played by the Mach number, turbulence level, and acoustic noise in the flow quality of wind tunnels is reviewed. Attention is given to the effects on end (ET) and beginning (BT) transitions in flows over a 10 deg cone in transonic channels. The Re of both ET and BT flows were significantly affected by the Mach number, acoustic noise level and the noise frequency content. A unit increment in the Mach number increased the Re beyond 3,000,000, while noise below the 1 percent level in the rms pressure coefficient did not alter the transition phenomenon. More data are required on the effects of turbulence, which was a significant factor, and in the settling chamber, test section, plenum and diffuser to trace the locations and magnitudes of the acoustic sources.

  15. Acoustic streaming induced by ultrasonic flexural vibrations and associated enhancement of convective heat transfer.

    PubMed

    Loh, Byoung-Gook; Hyun, Sinjae; Ro, Paul I; Kleinstreuer, Clement

    2002-02-01

    Acoustic streaming induced by ultrasonic flexural vibrations and the associated convection enhancement are investigated. Acoustic streaming pattern, streaming velocity, and associated heat transfer characteristics are experimentally observed. Moreover, analytical analysis based on Nyborg's formulation is performed along with computational fluid dynamics (CFD) simulation using a numerical solver CFX 4.3. Two distinctive acoustic streaming patterns in half-wavelength of the flexural vibrations are observed, which agree well with the theory. However, acoustic streaming velocities obtained from CFD simulation, based on the incompressible flow assumption, exceed the theoretically estimated velocity by a factor ranging from 10 to 100, depending upon the location along the beam. Both CFD simulation and analytical analysis reveal that the acoustic streaming velocity is proportional to the square of the vibration amplitude and the wavelength of the vibrating beam that decreases with the excitation frequency. It is observed that the streaming velocity decreases with the excitation frequency. Also, with an open-ended channel, a substantial increase in streaming velocity is observed from CFD simulations. Using acoustic streaming, a temperature drop of 40 degrees C with a vibration amplitude of 25 microm at 28.4 kHz is experimentally achieved.

  16. A viable method to predict acoustic streaming in presence of cavitation.

    PubMed

    Louisnard, O

    2017-03-01

    The steady liquid flow observed under ultrasonic emitters generating acoustic cavitation can be successfully predicted by a standard turbulent flow calculation. The flow is driven by the classical averaged volumetric force density calculated from the acoustic field, but the inertial term in Navier-Stokes equations must be kept, and a turbulent solution must be sought. The acoustic field must be computed with a realistic model, properly accounting for dissipation by the cavitation bubbles [Louisnard, Ultrason. Sonochem., 19, (2012) 56-65]. Comparison with 20kHz experiments, involving the combination of acoustic streaming and a perpendicular forced flow in a duct, shows reasonably good agreement. Moreover, the persistence of the cavitation effects on the wall facing the emitter, in spite of the deflection of the streaming jet, is correctly reproduced by the model. It is also shown that predictions based either on linear acoustics with the correct turbulent solution, or with Louisnard's model with Eckart-Nyborg's theory yields unrealistic results.

  17. Sound radiation from single and annular stream nozzles, with modal decomposition of in-duct acoustic power

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.

    1987-01-01

    An experimental program was carried out to study the acoustic characteristics of single and annular stream duct-nozzle systems at various flow conditions by using a refined acoustic impulse technique. In this technique, signal synthesis and signal averaging processes are incorporated to generate a desired impulsive signal from acoustic driver(s) and to eliminate background noise (flow noise) from in-duct and far field signals, respectively. The contribution of higher order modes to incident reflected and transmitted acoustic powers is accounted for by using a modal decomposition process. The annular stream terminations were tested statically at various annular stream flow velocities with no inner stream flow. The results derived from the experiments include in-duct acoustic powers, termination reflection coefficients, transmission coefficients, far field power, and acoustic dissipation.

  18. 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.

  19. 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.

  20. Characterization of high intensity focused ultrasound transducers using acoustic streaming.

    PubMed

    Hariharan, Prasanna; Myers, Matthew R; Robinson, Ronald A; Maruvada, Subha H; Sliwa, Jack; Banerjee, Rupak K

    2008-03-01

    A new approach for characterizing high intensity focused ultrasound (HIFU) transducers is presented. The technique is based upon the acoustic streaming field generated by absorption of the HIFU beam in a liquid medium. The streaming field is quantified using digital particle image velocimetry, and a numerical algorithm is employed to compute the acoustic intensity field giving rise to the observed streaming field. The method as presented here is applicable to moderate intensity regimes, above the intensities which may be damaging to conventional hydrophones, but below the levels where nonlinear propagation effects are appreciable. Intensity fields and acoustic powers predicted using the streaming method were found to agree within 10% with measurements obtained using hydrophones and radiation force balances. Besides acoustic intensity fields, the streaming technique may be used to determine other important HIFU parameters, such as beam tilt angle or absorption of the propagation medium.

  1. Nanoliter-droplet acoustic streaming via ultra high frequency surface acoustic waves.

    PubMed

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

    2014-08-06

    The relevant length scales in sub-nanometer amplitude surface acoustic wave-driven acoustic streaming are demonstrated. We demonstrate the absence of any physical limitations preventing the downscaling of SAW-driven internal streaming to nanoliter microreactors and beyond by extending SAW microfluidics up to operating frequencies in the GHz range. This method is applied to nanoliter scale fluid mixing.

  2. 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.

  3. Acoustic streaming in the transducer plane in ultrasonic particle manipulation devices.

    PubMed

    Lei, Junjun; Glynne-Jones, Peter; Hill, Martyn

    2013-06-07

    In acoustofluidic manipulation and sorting devices, Rayleigh streaming flows are typically found in addition to the acoustic radiation forces. However, experimental work from various groups has described acoustic streaming that occurs in planar devices in a plane parallel to the transducer face. This is typically a four-quadrant streaming pattern with the circulation parallel to the transducer. Understanding its origins is essential for creating designs that limit or control this phenomenon. The cause of this kind of streaming pattern has not been previously explained as it is different from the well-known classical streaming patterns such as Rayleigh streaming and Eckart streaming, whose circulation planes are generally perpendicular to the face of the acoustic transducer. In order to gain insight into these patterns we present a numerical method based on Nyborg's limiting velocity boundary condition that includes terms ignored in the Rayleigh analysis, and verify its predictions against experimental PIV results in a simple device. The results show that the modelled particle trajectories match those found experimentally. Analysis of the dominant terms in the driving equations shows that the origin of this kind of streaming pattern is related to the circulation of the acoustic intensity.

  4. 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.

  5. Acoustic concentration of particles in fluid flow

    DOEpatents

    Ward, Michael D.; Kaduchak, Gregory

    2010-11-23

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

  6. Acoustic streaming produced by a cylindrical bubble undergoing volume and translational oscillations in a microfluidic channel.

    PubMed

    Doinikov, Alexander A; Combriat, Thomas; Thibault, Pierre; Marmottant, Philippe

    2016-09-01

    A theoretical model is developed for acoustic streaming generated by a cylindrical bubble confined in a fluid channel between two planar elastic walls. The bubble is assumed to undergo volume and translational oscillations. The volume oscillation is caused by an imposed acoustic pressure field and generates the bulk scattered wave in the fluid gap and Lamb-type surface waves propagating along the fluid-wall interfaces. The translational oscillation is induced by the velocity field of an external sound source such as another bubble or an oscillatory fluid flow. The acoustic streaming is assumed to result from the interaction of the volume and the translational modes of the bubble oscillations. The general solutions for the linear equations of fluid motion and the equations of acoustic streaming are calculated with no restrictions on the ratio between the viscous penetration depth and the bubble size. Approximate solutions for the limit of low viscosity are provided as well. Simulations of streamline patterns show that the geometry of the streaming resembles flows generated by a source dipole, while the vortex orientation is governed by the driving frequency, bubble size, and the distance of the bubble from the source of translational excitation. Experimental verification of the developed theory is performed using data for streaming generated by bubble pairs.

  7. Acoustic streaming produced by a cylindrical bubble undergoing volume and translational oscillations in a microfluidic channel

    NASA Astrophysics Data System (ADS)

    Doinikov, Alexander A.; Combriat, Thomas; Thibault, Pierre; Marmottant, Philippe

    2016-09-01

    A theoretical model is developed for acoustic streaming generated by a cylindrical bubble confined in a fluid channel between two planar elastic walls. The bubble is assumed to undergo volume and translational oscillations. The volume oscillation is caused by an imposed acoustic pressure field and generates the bulk scattered wave in the fluid gap and Lamb-type surface waves propagating along the fluid-wall interfaces. The translational oscillation is induced by the velocity field of an external sound source such as another bubble or an oscillatory fluid flow. The acoustic streaming is assumed to result from the interaction of the volume and the translational modes of the bubble oscillations. The general solutions for the linear equations of fluid motion and the equations of acoustic streaming are calculated with no restrictions on the ratio between the viscous penetration depth and the bubble size. Approximate solutions for the limit of low viscosity are provided as well. Simulations of streamline patterns show that the geometry of the streaming resembles flows generated by a source dipole, while the vortex orientation is governed by the driving frequency, bubble size, and the distance of the bubble from the source of translational excitation. Experimental verification of the developed theory is performed using data for streaming generated by bubble pairs.

  8. 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.

  9. 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.

  10. 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.

  11. Acoustic streaming related to minor loss phenomenon in differentially heated elements of thermoacoustic devices

    NASA Astrophysics Data System (ADS)

    Mironov, Mikhail; Gusev, Vitalyi; Auregan, Yves; Lotton, Pierrick; Bruneau, Michel; Piatakov, Pavel

    2002-08-01

    It is demonstrated that the differentially heated stack, the heart of all thermoacoustic devices, provides a source of streaming additional to those associated with Reynolds stresses in quasi-unidirectional gas flow. This source of streaming is related to temperature-induced asymmetry in the generation of vortices and turbulence near the stack ends. The asymmetry of the hydrodynamic effects in an otherwise geometrically symmetric stack is due to the temperature difference between stack ends. The proposed mechanism of streaming excitation in annular thermoacoustic devices operates even in the absence of thermo-viscous interaction of sound waves with resonator walls. copyright 2002 Acoustical Society of America.

  12. 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.

  13. 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.

  14. 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.

  15. Investigation of refracting flows for acoustic suppression

    NASA Technical Reports Server (NTRS)

    Sloan, D.; Purves, R. B.; Farquhar, B. W.

    1977-01-01

    An experimental program to determine the possibility of using refracting flows for the suppression of aircraft inlet noise has been completed. Observations of wave behavior in accelerating duct flows have suggested that acoustic wave refraction could be used to direct inlet noise away from the ground upward to where it causes less annoyance. Measurements have also shown that acoustic wave refraction can cause large improvements in the effectiveness of acoustic lining material.

  16. Drops subjected to surface acoustic waves: flow dynamics

    NASA Astrophysics Data System (ADS)

    Brunet, Philippe; Baudoin, Michael; Bou Matar, Olivier; Dynamique Des Systèmes Hors Equilibre Team; Aiman-Films Team

    2012-11-01

    Ultrasonic acoustic waves of frequency beyond the MHz are known to induce streaming flow in fluids that can be suitable to perform elementary operations in microfluidics systems. One of the currently appealing geometry is that of a sessile drop subjected to surface acoustic waves (SAW). Such Rayleigh waves produce non-trival actuation in the drop leading to internal flow, drop displacement, free-surface oscillations and atomization. We recently carried out experiments and numerical simulations that allowed to better understand the underlying physical mechanisms that couple acoustic propagation and fluid actuation. We varied the frequency and amplitude of actuation, as well as the properties of the fluid, and we measured the effects of these parameters on the dynamics of the flow. We compared these results to finite-elements numerical simulations.

  17. Droplet actuation by surface acoustic waves: an interplay between acoustic streaming and radiation pressure

    NASA Astrophysics Data System (ADS)

    Brunet, Philippe; Baudoin, Michael; Matar, Olivier Bou; Zoueshtiagh, Farzam

    2010-11-01

    Surface acoustic waves (SAW) are known to be a versatile technique for the actuation of sessile drops. Droplet displacement, internal mixing or drop splitting, are amongst the elementary operations that SAW can achieve, which are useful on lab-on-chip microfluidics benches. On the purpose to understand the underlying physical mechanisms involved during these operations, we study experimentally the droplet dynamics varying different physical parameters. Here in particular, the influence of liquid viscosity and acoustic frequency is investigated: it is indeed predicted that both quantities should play a role in the acoustic-hydrodynamic coupling involved in the dynamics. The key point is to compare the relative magnitude of the attenuation length, i.e. the scale within which the acoustic wave decays in the fluid, and the size of the drop. This relative magnitude governs the relative importance of acoustic streaming and acoustic radiation pressure, which are both involved in the droplet dynamics.

  18. Frequency effect on streaming phenomenon induced by Rayleigh surface acoustic wave in microdroplets

    NASA Astrophysics Data System (ADS)

    Alghane, M.; Fu, Y. Q.; Chen, B. X.; Li, Y.; Desmulliez, M. P. Y.; Walton, A. J.

    2012-10-01

    Acoustic streaming of ink particles inside a water microdroplet generated by a surface acoustic wave (SAW) has been studied numerically using a finite volume numerical method and these results have been verified using experimental measurements. Effects of SAW excitation frequency, droplet volume, and radio-frequency (RF) power are investigated, and it has been shown that SAW excitation frequency influences the SAW attenuation length, lSAW, and hence the acoustic energy absorbed by liquid. It has also been observed that an increase of excitation frequency generally enhances the SAW streaming behavior. However, when the frequency exceeds a critical value that depends on the RF power applied to the SAW device, weaker acoustic streaming is observed resulting in less effective acoustic mixing inside the droplet. This critical value is characterised by a dimensionless ratio of droplet radius to SAW attenuation length, i.e., Rd/lSAW. With a mean value of Rd/lSAW ≈ 1, a fast and efficient mixing can be induced, even at the lowest RF power of 0.05 mW studied in this paper. On the other hand, for the Rd/lSAW ratios much larger than ˜1, significant decreases in streaming velocities were observed, resulting in a transition from regular (strong) to irregular (weak) mixing/flow. This is attributed to an increased absorption rate of acoustic wave energy that leaks into the liquid, resulting in a reduction of the acoustic energy radiated away from the SAW interaction region towards the droplet free surface. It has been demonstrated in this study that a fast and efficient mixing process with a smaller RF power could be achieved if the ratio of Rd/lSAW ≤ 1 in the SAW-droplet based microfluidics.

  19. Acoustic streaming in two-dimensional freely suspended smectic liquid crystal films

    NASA Astrophysics Data System (ADS)

    Yablonskii, S. V.; Kurbatov, N. M.; Parfenyev, V. M.

    2017-01-01

    We study horizontal streaming excited by means of a low-frequency and low-intensity acoustic wave in 2D freely suspended films of thermotropic smectic liquid crystals. Acoustic pressure induces fast periodic transverse oscillations of the film, which produce in-plane stationary couples of vortices slowly rotating in opposite directions owing to hydrodynamic nonlinearity. The parameters of the vortices are measured using a new method, based on tracking solidlike disk-shaped islands. The horizontal motion occurs only when the amplitude of the acoustic pressure exceeds the threshold value, which can be explained by Bingham-like behavior of the smectic film. The measurements above threshold are in good agreement with existing theoretical predictions. We demonstrate experimentally that in-plane flow is well controlled by changing the acoustic pressure, excitation frequency, and geometry of the film. The observations open the way to using the phenomenon in nondisplay applications.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. An acoustic travel time method for continuous velocity monitoring in shallow tidal streams

    NASA Astrophysics Data System (ADS)

    Razaz, Mahdi; Kawanisi, Kiyosi; Nistor, Ioan; Sharifi, Soroosh

    2013-08-01

    Long-term variations of streamflow in a tidal channel were measured using a Fluvial Acoustic Tomography (FAT) system through one transmission path. FAT is an innovative acoustic technology that utilizes the time-of-travel method to determine velocity between two points from multiple ray paths that traverse the entire cross-section of stream. Due to high spatial variability of flow distribution stationary ADCP measurements were not likely to yield true section-averaged flow velocity and moving-boat ADCP method was therefore used to provide reference data. As such, two short-term moving boat ADCP campaigns were carried out by the authors. In the first campaign, a couple of acoustic stations were added to the FAT system in order to resolve flow angularity in addition to the mean velocity. Comparing the FAT results with corresponding ADCP section-averaged flow direction and velocity indicated remarkable consistency. Second campaign was designed to capture the influence of salt wedge intrusion on the sound propagation pattern. It was found that FAT velocity measurements bias high if acoustic stations lay inside the cooler freshwater layer. Ray-tracing hindcasts suggest that installing acoustic stations inside the salt wedge may significantly improve function of output of the system. Comparing salinities evaluated from long-term FAT travel time records with nodal salinity measurements provided by conductivity-temperature sensors reveals the potential ability of FAT in measuring salt flux.

  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.

  6. Acoustic radiation force on a heated sphere including effects of heat transfer and acoustic streaming

    NASA Technical Reports Server (NTRS)

    Lee, Chun P.; Wang, Taylor G.

    1988-01-01

    A previous theoretical result on the subject of the acoustic radiation force on a heated sphere (Lee and Wang, 1984) is reexamined. For a more complete understanding, effects of heat transfer and acoustic streaming are taken into consideration. Essentially, it was found that, at high sound-pressure levels in a steady situation, the force is not affected significantly by the temperature profile, consistent with the result of an experimental work (Leung and Wang, 1985). This resolves the earlier apparent contradiction between the theory and the experiment. If excessive hot air is accumulated around the sphere, which can happen in transient situations, the force can be weakened or reversed in sign. A heat transfer model due to acoustic streaming was also found.

  7. 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.

  8. Flow-frequency characteristics of Vermont streams

    USGS Publications Warehouse

    Olson, Scott A.

    2002-01-01

    The safe and economical design of infrastructure in and near waterways and the effective management of flood-hazard areas require information on streamflow that may not be readily available. This report provides estimates of flow-frequency characteristics for gaged streams in Vermont and describes methods for estimating flow-frequency characteristics for ungaged streams. The flow-frequency characteristics investigated are the magnitude of peak discharges at recurrence intervals of 2, 5, 10, 25, 50, 100, and 500 years, and the magnitude of daily-mean discharges exceeded 25, 50, and 75 percent of the time. Peak-flow frequency characteristics for gaged streams were computed following the guidelines in Bulletin 17B of the U.S. Interagency Advisory Committee on Water Data. To determine the peak-flow exceedance probabilities at stream-gaging stations in Vermont, a new generalized skew coefficient map for the State was developed. This new map has greater resolution and more current data than the existing National map. The standard error of the new map is 0.269. Two methods of extending streamflow record were applied to improve estimates of peak-flow frequency for streams with short flow records (10 to 15 years) in small drainage areas (sites less than 15 square miles). In the first method, a two-station comparison, data from a long-record site was used to adjust the frequency characteristics at the short-record site. This method was applied to 31 crest-stage gages--stations at which only instantaneous peak discharges are determined--in Vermont. The second method used rainfall-runoff modeling. Precipitation and evapotranspiration data from 1948 to 1999 for numerous climate data-collection sites were used as input to a model to simulate flows at 10 stream-gaging stations in Vermont. Also, methods are described to estimate flow-frequency characteristics for ungaged and unregulated rural streams in Vermont. The peak-flow estimating methods were developed by generalized

  9. 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.

  10. 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.

  11. 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.

  12. Low-flow characteristics of Indiana streams

    USGS Publications Warehouse

    Fowler, K.K.; Wilson, J.T.

    1996-01-01

    Knowledge of low-flow characteristics of streams is essential for management of water resources. Low-flow characteristics are presented for 229 continuous-record, streamflow-gaging stations and 285 partial-record stations in Indiana. Low- flow-frequency characteristics were computed for 210 continuous-record stations that had at least 10 years of record, and flow-duration curves were computed for all continuous-record stations. Low-flow-frequency and flow-duration analyses are based on available streamflow records through September 1993. Selected low-flow-frequency curves were computed for annual low flows and seasonal low flows. The four seasons are represented by the 3-month groups of March-May, June-August, September-November, and December- February. The 7-day, 10-year and the 7-day, 2 year low flows were estimated for 285 partial-record stations, which are ungaged sites where streamflow measurements were made at base flow. The same low-flow characteristics were estimated for 19 continuous-record stations where less than 10 years of record were available. Precipitation and geology directly influence the streams in Indiana. Streams in the northern, glaciated part of the State tend to have higher sustained base flows than those in the nonglaciated southern part. Flow at several of the continuous-record gaging stations is affected by some form of regulation or diversion. Low-flow characteristics for continuous-record stations at which flow is affected by regulation are determined using the period of record affected by regulation; natural flows prior to regulation are not used.

  13. Viscous flow drag reduction by acoustic excitation

    NASA Technical Reports Server (NTRS)

    Nagel, Robert T.

    1986-01-01

    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.

  14. Numerical study of thermoviscous effects in ultrasound-induced acoustic streaming in microchannels.

    PubMed

    Muller, Peter Barkholt; Bruus, Henrik

    2014-10-01

    We present a numerical study of thermoviscous effects on the acoustic streaming flow generated by an ultrasound standing-wave resonance in a long straight microfluidic channel containing a Newtonian fluid. These effects enter primarily through the temperature and density dependence of the fluid viscosity. The resulting magnitude of the streaming flow is calculated and characterized numerically, and we find that even for thin acoustic boundary layers, the channel height affects the magnitude of the streaming flow. For the special case of a sufficiently large channel height, we have successfully validated our numerics with analytical results from 2011 by Rednikov and Sadhal for a single planar wall. We analyzed the time-averaged energy transport in the system and the time-averaged second-order temperature perturbation of the fluid. Finally, we have made three main changes in our previously published numerical scheme to improve the numerical performance: (i) The time-averaged products of first-order variables in the time-averaged second-order equations have been recast as flux densities instead of as body forces. (ii) The order of the finite-element basis functions has been increased in an optimal manner. (iii) Based on the International Association for the Properties of Water and Steam (IAPWS 1995, 2008, and 2011), we provide accurate polynomial fits in temperature for all relevant thermodynamic and transport parameters of water in the temperature range from 10 to 50 °C.

  15. 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.

  16. Low-flow characteristics of Indiana streams

    USGS Publications Warehouse

    Stewart, J.A.

    1983-01-01

    Knowledge of low-flow data for Indiana streams is essential to the planners and developers of water resources for municipal, industrial, and recreational uses in the State. Low-flow data for 219 continuous-record gaging stations through the 1978 water year and for some stations since then are presented in tables and curves. Flow-duration and low-flow-frequency data were estimated or determined for continuous-record stations having more than 10 years of record. In addition, low-flow-frequency data were estimated for 248 partial-record stations. Methods for estimating these data are included in the report. (USGS)

  17. Stream flow and analysis study

    SciTech Connect

    Jackson, D.G.

    1983-11-04

    Lockwood Greene Engineers, Inc. (LGE) was retained by E.I. duPont de Nemours and Co., Inc., Savannah River Plant, Aiken, South Carolina, to conduct on-site flow measurements and sampling of tributaries and outfalls flowing into a portion of Tim`s Branch Creek. Water samples were analyzed for chemical characteristics. This report presents the results of the flow and analytical data collected during the 24 hour monitoring period, October 5 and 6, 1983. Tim`s Branch Creek is a tributary of the Upper Three Runs Creek which in turn is a tributary of the Savannah River. A map outlining the drainage area within the Savannah River Plant is included in this report.

  18. PIV for the characterization of focused field induced acoustic streaming: seeding particle choice evaluation.

    PubMed

    Ben Haj Slama, Rafika; Gilles, Bruno; Ben Chiekh, Maher; Béra, Jean-Christophe

    2017-04-01

    This research evaluates the use of Particle Image Velocimetry (PIV) technique for characterizing acoustic streaming flow generated by High Intensity Focused Ultrasound (HIFU). PIV qualification tests, focusing on the seeding particle size (diameter of 5, 20 and 50μm) were carried out in degassed water subjected to a focused field of 550kHz-frequency with an acoustic pressure amplitude of 5.2, 10.5 and 15.7bar at the focus. This study shows that the ultrasonic field, especially the radiation force, can strongly affect seeding particle behavior. Large particles (50μm-diameter) are repelled from the focal zone and gathered at radiation pressure convergence lines on either side of the focus. The calculation of the acoustic radiation pressure applied on these particles explains the observed phenomenon. PIV measurements do not, therefore, properly characterize the streaming flow in this case. On the contrary, small particles (5μm-diameter) velocity measurements were in good agreement with the Computational Fluid Dynamics (CFD) simulations of the water velocity field. A simple criterion approximating the diameter threshold below which seeding particles are qualified for PIV in presence of focused ultrasound is then proposed.

  19. Online sensing of palladium in flowing streams.

    PubMed

    Bu, Xiaodong; Williams, Michael; Jo, Junyong; Koide, Kazunori; Welch, Christopher J

    2017-01-05

    Rapid palladium (Pd) catalyzed deallylation of an uncoloured reagent within a flowing stream affords a dose dependent colour formation that can be used for convenient online analysis of trace levels of Pd contamination using a modified HPLC instrument. An application to the online sensing of Pd breakthrough from a flow through Pd adsorption cartridge is described. An alternative configuration of the instrumentation allows the rapid (<1 min) and accurate measurement of Pd levels within samples injected via a conventional HPLC autosampler.

  20. 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.

  1. Acoustically induced current flow in graphene

    NASA Astrophysics Data System (ADS)

    Miseikis, V.; Cunningham, J. E.; Saeed, K.; O'Rorke, R.; Davies, A. G.

    2012-03-01

    We demonstrate the directed control of charge carriers in graphene using the electric field that accompanies the propagation of surface acoustic waves (SAWs) on a piezoelectric surface. Graphene grown by chemical vapor deposition was transferred to the surface of lithium niobate, allowing its direct integration with interdigital transducers used for SAW generation and detection. Radio frequency (RF) signal applied to the transducers at their resonant frequency was found to generate a direct current flow by the transport of p-type charge carriers. The acoustically induced current scales linearly with the applied RF power and can be observed even in presence of a counter-flow current induced by an applied bias.

  2. Nonlinear Acoustics Used To Reduce Leakage Flow

    NASA Technical Reports Server (NTRS)

    Daniels, Christopher C.; Steinetz, Bruce M.

    2004-01-01

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

  3. 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.

  4. 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

  5. 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.

  6. Investigation of refracting flows for acoustic suppression

    NASA Technical Reports Server (NTRS)

    Sloan, D.; Purves, R. B.; Farquhar, B. W.

    1977-01-01

    An experimental investigation to determine the possibility of using refracting flows for the suppression of aircraft inlet noise is described. Observations of wave refraction in duct flows and measurements of the increase in effectiveness of acoustic linings due to refraction have suggested methods for the design of engine inlet ducts which can either suppress noise internally or direct it to where it causes less annoyance.

  7. Acoustic instability driven by cosmic-ray streaming

    NASA Astrophysics Data System (ADS)

    Begelman, Mitchell C.; Zweibel, Ellen G.

    1994-08-01

    We study the linear stability of compressional waves in a medium through which cosmic rays stream at the Alfven speed due to strong coupling with Alfven waves. Acoustic waves can be driven unstable by the cosmic-ray drift, provided that the streaming speed is sufficiently large compared to the thermal sound speed. Two effects can cause instability: (1) the heating of the thermal gas due to the damping of Alfven waves driven unstable by cosmic-ray streaming; and (2) phase shifts in the cosmic-ray pressure perturbation caused by the combination of cosmic-ray streaming and diffusion. The instability does not depend on the magnitude of the background cosmic-ray pressure gradient, and occurs whether or not cosmic-ray diffusion is important relative to streaming. When the cosmic-ray pressure is small compared to the gas pressure, or cosmic-ray diffusion is strong, the instability manifests itself as a weak overstability of slow magnetosonic waves. Larger cosmic-ray pressure gives rise to new hybrid modes, which can be strongly unstable in the limits of both weak and strong cosmic-ray diffusion and in the presence of thermal conduction. Parts of our analysis parallel earlier work by McKenzie & Webb (which were brought to our attention after this paper was accepted for publication), but our treatment of diffusive effects, thermal conduction, and nonlinearities represent significant extensions. Although the linear growth rate of instability is independent of the background cosmic-ray pressure gradient, the onset of nonlinear eff ects does depend on absolute value of DEL (vector differential operator) Pc. At the onset of nonlinearity the fractional amplitude of cosmic-ray pressure perturbations is delta PC/PC approximately (kL) -1 much less than 1, where k is the wavenumber and L is the pressure scale height of the unperturbed cosmic rays. We speculate that the instability may lead to a mode of cosmic-ray transport in which plateaus of uniform cosmic-ray pressure are

  8. Acoustic instability driven by cosmic-ray streaming

    NASA Technical Reports Server (NTRS)

    Begelman, Mitchell C.; Zweibel, Ellen G.

    1994-01-01

    We study the linear stability of compressional waves in a medium through which cosmic rays stream at the Alfven speed due to strong coupling with Alfven waves. Acoustic waves can be driven unstable by the cosmic-ray drift, provided that the streaming speed is sufficiently large compared to the thermal sound speed. Two effects can cause instability: (1) the heating of the thermal gas due to the damping of Alfven waves driven unstable by cosmic-ray streaming; and (2) phase shifts in the cosmic-ray pressure perturbation caused by the combination of cosmic-ray streaming and diffusion. The instability does not depend on the magnitude of the background cosmic-ray pressure gradient, and occurs whether or not cosmic-ray diffusion is important relative to streaming. When the cosmic-ray pressure is small compared to the gas pressure, or cosmic-ray diffusion is strong, the instability manifests itself as a weak overstability of slow magnetosonic waves. Larger cosmic-ray pressure gives rise to new hybrid modes, which can be strongly unstable in the limits of both weak and strong cosmic-ray diffusion and in the presence of thermal conduction. Parts of our analysis parallel earlier work by McKenzie & Webb (which were brought to our attention after this paper was accepted for publication), but our treatment of diffusive effects, thermal conduction, and nonlinearities represent significant extensions. Although the linear growth rate of instability is independent of the background cosmic-ray pressure gradient, the onset of nonlinear eff ects does depend on absolute value of DEL (vector differential operator) P(sub c). At the onset of nonlinearity the fractional amplitude of cosmic-ray pressure perturbations is delta P(sub C)/P(sub C) approximately (kL) (exp -1) much less than 1, where k is the wavenumber and L is the pressure scale height of the unperturbed cosmic rays. We speculate that the instability may lead to a mode of cosmic-ray transport in which plateaus of uniform cosmic

  9. 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

  10. Acoustic propagation under tidally driven, stratified flow.

    PubMed

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

    2007-05-01

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

  11. 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.

  12. 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.

  13. 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

  14. Low-flow characteristics of Florida streams

    USGS Publications Warehouse

    Rumenik, R.P.

    1996-01-01

    Knowledge of the low-flow characteristics of Florida streams and rivers is essential in planning for the availability of adequate quantities of water for commercial- and public-water supply, agricultural irrigation, artificial recharge, and the dilution of waste discharge. This report provides low-flow characteristics for 216 continuous-record gaging stations using frequency analysis techniques. Included are low-flow frequency characteristics for 143 unregulated, gaging stations; and sample percentiles for 32 stations that were subject to regulation or diversion, and sample percentiles for 41 stations, regulated and unregulated, that exhibited significant trends in the annual low-flow time series. Estimates of low-flow frequency characteristics are provided for 242 partial-record stations and miscellaneous sites based on correlations with daily mean discharges at continuous-record stations. Low-flow measurement data are available at approximately 1,300 continuous-record gaging stations, partial- record stations and miscellaneous sites. Historic low-flow measurement data are accessible through the U.S. Geological Survey Automatic Data Processing System.

  15. 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.

  16. Calibration of AN Acoustic Sensor (geophone) for Continuous Bedload Monitoring in Mountainous Streams

    NASA Astrophysics Data System (ADS)

    Tsakiris, A. G.; Papanicolaou, T.

    2010-12-01

    Measurement of bedload rates is a crucial component in the study of alluvial processes in mountainous streams. Stream restoration efforts, the validation of morphodynamic models and the calibration empirical transport formulae rely on accurate bedload transport measurements. Bedload measurements using traditional methods (e.g. samplers, traps) are time consuming, resource intensive and not always feasible, especially at higher flow conditions. These limitations could potentially be addressed by acoustic instruments, which may provide unattended, continuous bedload measurements even at higher flow conditions, provided that these instruments are properly calibrated. The objective of this study is to calibrate an acoustic instrument (geophone) for performing bedload measurements in a well-monitored laboratory environment at conditions corresponding to low flow regime in mountainous streams. The geophone was manufactured by ClampOn® and was attached to the bottom of a steel plate with dimensions 0.15x0.15 m. The geophone registers the energy of the acoustic signal produced by the movement of the bedload particles over the steel plate with time resolution of one second. The plate-sensor system was installed in an acrylic housing such that the steel plate top surface was at the same level with the surface of a flat porous bed consisting of unisize spheres with diameter 19.1 mm. Unisize spherical glass particles, 15.9 mm in diameter, were preplaced along a 2 m long section upstream of the sensor, and were entrained over the steel plate. In these experiments, the geophone records spanned the complete experiment duratio. Plan view video of the particle movement over the steel plate was recorded via an overhead camera, and was used to calculate the actual bedload rate over the steel plate. Synchronized analysis of this plan view video and the geophone time series revealed that the geophone detected 62% of the bedload particles passing over the steel plate, which triggered

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. Surface-acoustic-wave (SAW) flow sensor

    NASA Astrophysics Data System (ADS)

    Joshi, Shrinivas G.

    1991-03-01

    The use of a surface-acoustic-wave (SAW) device to measure the rate of gas flow is described. A SAW oscillator heated to a suitable temperature above ambient is placed in the path of a flowing gas. Convective cooling caused by the gas flow results in a change in the oscillator frequency. A 73-MHz oscillator fabricated on 128 deg rotated Y-cut lithium niobate substrate and heated to 55 C above ambient shows a frequency variation greater than 142 kHz for flow-rate variation from 0 to 1000 cu cm/min. The output of the sensor can be calibrated to provide a measurement of volume flow rate, pressure differential across channel ports, or mass flow rate. High sensitivity, wide dynamic range, and direct digital output are among the attractive features of this sensor. Theoretical expressions for the sensitivity and response time of the sensor are derived. It is shown that by using ultrasonic Lamb waves propagating in thin membranes, a flow sensor with faster response than a SAW sensor can be realized.

  2. 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.

  3. 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.

  4. Streaming Induced by High-Amplitude Acoustic Pulses and its Implications.

    NASA Astrophysics Data System (ADS)

    Starritt, Hazel Catherine

    Available from UMI in association with The British Library. This thesis investigates some aspects of the nonlinear propagation of high amplitude ultrasound in the context of medical diagnostic applications. Nonlinear propagation occurring in focused diagnostic fields is shown to enhance acoustic streaming in water due to the increased absorption of the high frequency components in the distorted wave. The results of an extensive experimental investigation of streaming in water are presented. The streaming velocities were measured using the technique of hot film anemometry and were found to vary with total acoustic power, pulse repetition frequency, pulse duration and pulse pressure amplitude. The velocity in a high amplitude beam was shown to be enhanced typically by a factor of 5 compared with that in a low amplitude beam of the same acoustic power. Measurements of acoustic parameters were made for comparison. The results showed that in a nonlinear field absorption is enhanced in the region immediately on the transducer side of the focus and this region is shown to act as the "source pump" for the stream. The maximum streaming velocities generated by commercial ultrasonic equipment were measured in the fields of pulsed Doppler units, with maximum velocities generated in the fields of scanned imaging beams being an order of magnitude lower. Streams in stationary beams were observed to become established in time periods which are short compared with the "dwell time" of the transducer at a single location in clinical use. The implications of acoustic streaming and the forces associated with it are discussed in the context of the current diagnostic usage of ultrasound. In particular, obstetric applications are considered where the fetus is scanned through a low loss fluid path in which nonlinear propagation and acoustic streaming may occur.

  5. 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.

  6. Chemical composition of streams during low flow; Fairfax County, Virginia

    USGS Publications Warehouse

    Larson, J.D.

    1978-01-01

    Water samples were collected and stream discharges were measured at 49 sites in Fairfax County, Virginia during a period of low flow in August 1977. In addition, pesticide and metal content of residue on stream-bottom sediments from several major streams in the county were analysed. Waters from the streams in Fairfax County have generally good chemical quality during low flow. One stream in Vienna, Virginia has a high sodium chloride content, suggesting an upstream discharge of salty water. Higher concentrations of dissolved, solids reflect both the effects of geology and urbanization. Streams draining Triassic rocks in the western section of the county are characterized by the greatest natural concentration of dissolved minerals in the water. The concentrations of pesticide and metal residue associated with bottom sediments suggest a low level of pollution in the streams. One site in western Fairfax County contained above-normal levels of polychlorinated biphenyls (PCB's) in the stream sediments.

  7. 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.

  8. 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.

  9. Finite difference calculation of acoustic streaming including the boundary layer phenomena in an ultrasonic air pump on graphics processing unit array

    NASA Astrophysics Data System (ADS)

    Wada, Yuji; Koyama, Daisuke; Nakamura, Kentaro

    2012-09-01

    Direct finite difference fluid simulation of acoustic streaming on the fine-meshed threedimension 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 not yet been observed in the calculation in the ultrasonic air pump of this type.

  10. 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.

  11. 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.

  12. 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

  13. Global characteristics of stream flow seasonality and variability

    USGS Publications Warehouse

    Dettinger, M.D.; Diaz, Henry F.

    2000-01-01

    Monthly stream flow series from 1345 sites around the world are used to characterize geographic differences in the seasonality and year-to-year variability of stream flow. Stream flow seasonality varies regionally, depending on the timing of maximum precipitation, evapotranspiration, and contributions from snow and ice. Lags between peaks of precipitation and stream flow vary smoothly from long delays in high-latitude and mountainous regions to short delays in the warmest sectors. Stream flow is most variable from year to year in dry regions of the southwest United States and Mexico, the Sahel, and southern continents, and it varies more (relatively) than precipitation in the same regions. Tropical rivers have the steadiest flows. El Nin??o variations are correlated with stream flow in many parts of the Americas, Europe, and Australia. Many stream flow series from North America, Europe, and the Tropics reflect North Pacific climate, whereas series from the eastern United States, Europe, and tropical South America and Africa reflect North Atlantic climate variations.

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

    NASA Astrophysics Data System (ADS)

    Açıkalın, 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.

  15. 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.

  16. 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.

  17. Numerical simulation of 3D boundary-driven acoustic streaming in microfluidic devices.

    PubMed

    Lei, Junjun; Hill, Martyn; Glynne-Jones, Peter

    2014-02-07

    This article discusses three-dimensional (3D) boundary-driven streaming in acoustofluidic devices. Firstly, the 3D Rayleigh streaming pattern in a microchannel is simulated and its effect on the movement of microparticles of various sizes is demonstrated. The results obtained from this model show good comparisons with 3D experimental visualisations and demonstrate the fully 3D nature of the acoustic streaming field and the associated acoustophoretic motion of microparticles in acoustofluidic devices. This method is then applied to another acoustofluidic device in order to gain insights into an unusual in-plane streaming pattern. The origin of this streaming has not been fully described and its characteristics cannot be explained from the classical theory of Rayleigh streaming. The simulated in-plane streaming pattern was in good agreement with the experimental visualisation. The mechanism behind it is shown to be related to the active sound intensity field, which supports our previous findings on the mechanism of the in-plane acoustic streaming pattern visualised and modelled in a thin-layered capillary device.

  18. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. Cell agglomeration in the wells of a 24-well plate using acoustic streaming.

    PubMed

    Kurashina, Yuta; Takemura, Kenjiro; Friend, James

    2017-02-28

    Cell agglomeration is essential both to the success of drug testing and to the development of tissue engineering. Here, a MHz-order acoustic wave is used to generate acoustic streaming in the wells of a 24-well plate to drive particle and cell agglomeration. Acoustic streaming is known to manipulate particles in microfluidic devices, and even provide concentration in sessile droplets, but concentration of particles or cells in individual wells has never been shown, principally due to the drag present along the periphery of the fluid in such a well. The agglomeration time for a range of particle sizes suggests that shear-induced migration plays an important role in the agglomeration process. Particles with a diameter of 45 μm agglomerated into a suspended pellet under exposure to 2.134 MHz acoustic waves at 1.5 W in 30 s. Additionally, BT-474 cells also agglomerated as adherent masses at the center bottom of the wells of tissue-culture treated 24-well plates. By switching to low cell binding 24-well plates, the BT-474 cells formed suspended agglomerations that appeared to be spheroids, fully fifteen times larger than any cell agglomerates without the acoustic streaming. In either case, the viability and proliferation of the cells were maintained despite acoustic irradiation and streaming. Intermittent excitation was effective in avoiding temperature excursions, consuming only 75 mW per well on average, presenting a convenient means to form fully three-dimensional cellular masses potentially useful for tissue, cancer, and drug research.

  5. Acoustic streaming effects in megasonic cleaning of EUV photomasks: a continuum model

    NASA Astrophysics Data System (ADS)

    Kapila, Vivek; Deymier, Pierre A.; Shende, Hrishikesh; Pandit, Viraj; Raghavan, Srini; Eschbach, Florence O.

    2005-11-01

    Removal of nano-scale contaminant particles from the photomasks is of critical importance to the implementation of EUV lithography for 32nm node. Megasonic cleaning has traditionally been used for photomask cleaning and extensions to sub 50nm particulates removal is being considered as a pattern damage free cleaning approach. Several mechanisms for removal are believed to be active in megasonic cleaning systems, e.g., cavitation, and acoustic streaming (Eckart, Schlichting, and microstreaming). It is often difficult to separate the effects of these individual mechanisms on contamination removal in a conventional experimental setup. Therefore, a theoretical approach is undertaken in this work with a focus on determining the contribution of acoustic streaming in cleaning process. A continuum model is used to describe the interaction between megasonic waves and a substrate (fused silica) immersed in a fluid (water). The model accounts for the viscous nature of the fluid. We calculate the acoustic vibrational modes of the system. These in turn are used to determine the acoustic streaming forces that lead to Schlichting streaming in a narrow acoustic boundary layer at the substrate/fluid interface. These forces are subsequently used to estimate the streaming velocities that may in turn apply a pressure and drag force on the contaminant particles adhering to the substrate. These effects are calculated as a function of angle of incidence, frequency and intensity of the megasonic wave. The relevance of this study is then discussed in the context of the cleaning efficiency and pattern damage in competing megasonic cleaning technologies, such as immersion, and nozzle-based systems.

  6. Forced motion and acoustic radiation of an elastic cylinder in axial flow

    NASA Astrophysics Data System (ADS)

    Manela, A.; Miloh, T.

    2012-07-01

    We study the forced motion and far-field acoustic radiation of an elastic cylinder subject to uniform axial flow and actuated at its upstream end by small-amplitude periodic displacement and rotation. The linearized problem is analysed under subcritical conditions of low nondimensional stream-flow velocity, uflow. It is found that the forced motion at subcritical conditions is affected by the properties of the in vacuo system. A resonance is excited when the cylinder is actuated at one of its in vacuo eigenfrequencies, ωres, manifested by relatively large deflections. Fluid flow acts to regularize this behavior by transferring energy from the upstream driver to the fluid. The dynamical description is used as a source term in the formulation of the vibroacoustic problem. Assuming the cylinder is well-streamlined and neglecting the effect of vortex shedding, the far field sound is attributed directly to cylinder vibration. Acoustic radiation of a dipole type is found in the limit where the cylinder is acoustically compact. Following the dynamical description, it is shown that fluid flow reduces the sound level compared to that in the absence of mean flow, when actuation is applied close to ω=ωres. In addition, we demonstrate that far-field sound can be controlled by varying the actuation parameters. Analytical description of the dynamical and acoustic fields is obtained in the limit u≪1, and found in close agreement with the exact numerical solution up to u˜O(1). Discrepancies between the approximate and exact solutions are observed close to the resonance frequencies, and rationalized in terms of the strong fluid-structure coupling occurring when ω→ωres. At ω=ωres, a qualitative description of the effect of fluid stream flow on the system behavior is supplied.

  7. Using Streamlines to Visualize Acoustic Energy Flow Across Boundaries

    DTIC Science & Technology

    2008-07-01

    radiate from a point source in a homogeneous fluid and propagate across a plane boundary into a dissimilar homogeneous fluid, the acoustic field may...associated with diffraction i.e., those components that vanish with increasing frequency. The energy flow from a continuous-wave monopole point source...vector, averaged over a wave cycle. It is seen that the acoustic energy flow is not always in line with the “Snell’s law” or stationary phase path. Also

  8. 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.

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

    USGS Publications Warehouse

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

    1998-01-01

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

  10. 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

  11. Particle analysis in an acoustic cytometer

    DOEpatents

    Kaduchak, Gregory; Ward, Michael D

    2012-09-18

    The present invention is a method and apparatus for acoustically manipulating one or more particles. Acoustically manipulated particles may be separated by size. The particles may be flowed in a flow stream and acoustic radiation pressure, which may be radial, may be applied to the flow stream. This application of acoustic radiation pressure may separate the particles. In one embodiment, the particles may be separated by size, and as a further example, the larger particles may be transported to a central axis.

  12. 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

  13. Design of optimum acoustic treatment for rectangular ducts with flow

    NASA Technical Reports Server (NTRS)

    Motsinger, R. E.; Kraft, R. E.; Zwick, J. W.

    1976-01-01

    A design optimization technique for acoustic treatment in rectangular ducts with uniform mean flow is presented. The technique is based on the acoustic wave solution in terms of series of characteristic duct modes. The analysis allows multiple axial treatment sections along the length of the duct and requires a known modal characterization of the sound source. Conditions of acoustic pressure and acoustic velocity continuity are used to match modal solutions at planes of impedance discontinuity in the duct. Experimental techniques for obtaining this modal characterization are presented. Using duct modes measured at the source plane, the optimization technique is exercised to design an optimized single element liner in a case without mean flow, and optimized single and dual element liners in cases with mean flow. The validity of the program for predicting noise suppression is demonstrated by comparing analytical predictions with measured data for several (non-optimum) cases. Application to treatment design in turbomachinery exhaust ducts is considered.

  14. 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.

  15. 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.

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

    PubMed

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

    2007-06-15

    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.

  17. 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

  18. 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.

  19. 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.

  20. Numerical study of acoustic modes in ducted shear flow

    NASA Astrophysics Data System (ADS)

    Vilenski, Gregory G.; Rienstra, Sjoerd W.

    2007-11-01

    The propagation of small-amplitude modes in an inviscid but sheared mean flow inside a duct is studied numerically. For isentropic flow in a circular duct with zero swirl and constant mean flow density the pressure modes are described in terms of the eigenvalue problem for the Pridmore-Brown equation. Since for sufficiently high Helmholtz and wavenumbers, which are of great interest for applications, the field equation is inherently stiff, special care is taken to insure the stability of the numerical algorithm designed to tackle this problem. The accuracy of the method is checked against the well-known analytical solution for uniform flow. The numerical method is shown to be consistent with the analytical predictions at least for Helmholtz numbers up to 100 and circumferential wavenumbers as large as 50, typical Mach numbers being up to 0.65. In order to gain further insight into the possible structure of the modal solutions and to obtain an independent verification of the robustness of the numerical scheme, comparison to the asymptotic solution of the problem based on the WKB method is performed. The asymptotic solution is also used as a benchmark for computations with high Helmholtz numbers, where numerical solutions of other authors are not available. The bulk of the analysis concentrates on the influence of the wall lining. The proposed numerical procedure is adapted in order to include Ingard-Myers boundary conditions. In parallel with this, the WKB solution is used to check the numerical predictions of the typical behaviour of the axial wavenumber in the complex plane, when the wall impedance varies in the complex plane. Numerical analysis of the problem with zero mean flow at the wall and acoustic lining shows that the use of Ingard-Myers condition in combination with an appropriate slip-stream approximation instead of the actual no-slip mean flow profile gives valid results in the limit of vanishing boundary-layer thickness, although the boundary layer

  1. An assessment of low flows in streams in northeastern Wyoming

    USGS Publications Warehouse

    Armentrout, G.W.; Wilson, J.F.

    1987-01-01

    Low flows were assessed and summarized in the following basins in northeastern Wyoming: Little Bighorn, Tongue, Powder, Little Missouri, Belle Fourche, Cheyenne, and Niobrara River, and about 200 river miles of the North Platte River and its tributaries. Only existing data from streamflow stations and miscellaneous observation sites during the period, 1930-80, were used. Data for a few stations in Montana and South Dakota were used in the analysis. Data were available for 56 perennial streams, 38 intermittent streams, and 34 ephemeral streams. The distribution of minimum observed flows of record at all stations and sites and the 7-day, 10-year low flows at mountain stations and main-stem plains stations are shown on a map. Seven day low flows were determined by fitting the log Pearsons Type III distribution to the data; results are tabulated only for the stations with at least 10 years of record that included at least one major drought. Most streams that originate in the foothills and plains have no flow during part of every year, and are typical of much of the study area. For stations on these streams , the frequency of the annual maximum number of consecutive days of no flow was determined, as an indicator of the likelihood of extended periods of no flow or drought. For estimates at ungaged sites on streams in the Bighorn Mountains only, a simple regression of 7-day, 10-year low flow on drainage area has a standard error of 64%, based on 19 stations with drainage areas of 2 to 200 sq mi. The 7-day, 10-year low flow in main-stem streams can be interpolated from graphs of 7-day, 10-year low flow versus distance along the main channel. Additional studies of low flow are needed. The data base, particularly synoptic baseflow information, needs considerable expansion. Also, the use of storage-analysis procedures should be considered as a means of assessing the availability of water in streams that otherwise are fully appropriated or that are ephemeral. (Author 's

  2. Analysis Pipeline: Streaming Flow Analysis with Alerting

    DTIC Science & Technology

    2011-01-01

    NOT MAKE ANY WARRANTY OF ANY KIND WITH RESPECT TO FREEDOM FROM PATENT , TRADEMARK, OR COPYRIGHT INFRINGEMENT. This presentation may be reproduced in...Implementors of products exporting or collecting network flow data with IPFIX will meet at the event to test the interoperability of their products against...Capabilities Finite State Beacon Detection Sensor Outage Detection IPv6 Tunnel Detection Passive FTP Detection Watchlists Flow counts Flow field based

  3. Hot-wire amperometric monitoring of flowing streams.

    PubMed

    Wang, J; Jasinski, M; Flechsig, G U; Grundler, P; Tian, B

    2000-01-10

    This paper describes the design of a hot-wire electrochemical flow detector, and the advantages accrued from the effects of locally increased temperature, mainly thermally induced convection, upon the amperometric monitoring of flowing streams. A new hydrodynamic modulation voltammetric approach is presented, in which the solution flow rate remains constant while the temperature of the working electrode is modulated. Factors influencing the response, including the flow rate, temperature pulse, or applied potential, have been investigated. The hot-wire operation results also in a significant enhancement of the flow injection amperometric response. The minimal flow rate dependence observed with the heated electrode should benefit the on-line monitoring of streams with fluctuated natural convection, as well as various in-situ remote sensing applications.

  4. Particle migration and sorting in microbubble streaming flows

    PubMed Central

    Thameem, Raqeeb; Hilgenfeldt, Sascha

    2016-01-01

    Ultrasonic driving of semicylindrical microbubbles generates strong streaming flows that are robust over a wide range of driving frequencies. We show that in microchannels, these streaming flow patterns can be combined with Poiseuille flows to achieve two distinctive, highly tunable methods for size-sensitive sorting and trapping of particles much smaller than the bubble itself. This method allows higher throughput than typical passive sorting techniques, since it does not require the inclusion of device features on the order of the particle size. We propose a simple mechanism, based on channel and flow geometry, which reliably describes and predicts the sorting behavior observed in experiment. It is also shown that an asymptotic theory that incorporates the device geometry and superimposed channel flow accurately models key flow features such as peak speeds and particle trajectories, provided it is appropriately modified to account for 3D effects caused by the axial confinement of the bubble. PMID:26958103

  5. 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.

  6. Effects of heat exchange and nonlinearity on acoustic streaming in a vibrating cylindrical cavity.

    PubMed

    Gubaidullin, Amir A; Yakovenko, Anna V

    2015-06-01

    Acoustic streaming in a gas filled cylindrical cavity subjected to the vibration effect is investigated numerically. Both thermally insulated walls and constant temperature walls are considered. The range of vibration frequencies from low frequencies, at which the process can be described by an approximate analytical solution, to high frequencies giving rise to strong nonlinear effects is studied. Frequencies lower than the resonant one are chosen, and nonlinearity is achieved due to the large amplitude. The problem is solved in an axisymmetric statement. The dependence of acoustic streaming in narrow channels at vibration frequencies lower than the resonant one on the type of thermal boundary conditions is shown. The streaming vortices' directions of rotation in the case of constant temperature walls are found to be opposite to those in the case of thermally insulated walls. Different nonlinear effects, which increase with the frequency of vibration, are obtained. Nonlinear effects manifesting as the nonuniformity of average temperature, pressure, and density are in turn found to be influencing the streaming velocity and streaming structure.

  7. 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.

  8. 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.

  9. On acoustic intensity measurements in the presence of mean flow

    NASA Technical Reports Server (NTRS)

    Munro, D. H.; Ingard, K. U.

    1979-01-01

    A theoretical analysis demonstrates that the technique of measuring acoustic intensity by means of cross correlation between nearby microphones cannot, in general, be extended to situations in which there is mean flow. However, it may be possible to use this technique to measure intensities in ducts with mean flow at frequencies below their cutoff frequencies.

  10. Experimental Studies of Acoustics in a Spherical Couette Flow

    NASA Astrophysics Data System (ADS)

    Gowen, Savannah; Adams, Matthew; Stone, Douglas; Lathrop, Daniel

    2016-11-01

    The Earth, like many other astrophysical bodies, contains turbulent flows of conducting fluid which are able to sustain magnetic field. To investigate the hydromagnetic flow in the Earth's outer core, we have created an experiment which generates flows in liquid sodium. However, measuring these flows remains a challenge because liquid sodium is opaque. One possible solution is the use of acoustic waves. Our group has previously used acoustic wave measurements in air to infer azimuthal velocity profiles, but measurements attempted in liquid sodium remain challenging. In the current experiments we measure acoustic modes and their mode splittings in both air and water in a spherical Couette device. The device is comprised of a hollow 30-cm outer sphere which contains a smaller 10-cm rotating inner sphere to drive flow in the fluid in between. We use water because it has material properties that are similar to those of sodium, but is more convenient and less hazardous. Modes are excited and measured using a speaker and microphones. Measured acoustic modes and their mode splittings correspond well with the predicted frequencies in air. However, water modes are more challenging. Further investigation is needed to understand acoustic measurements in the higher density media.

  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. 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.

  13. U.S. stream flow measurement and data dissemination improve

    USGS Publications Warehouse

    Hirsch, Robert M.; Costa, John E.

    2004-01-01

    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.

  14. Echo-acoustic flow shapes object representation in spatially complex acoustic scenes.

    PubMed

    Greiter, Wolfgang; Firzlaff, Uwe

    2017-03-08

    Echolocating bats use echoes of their sonar emissions to determine the position and distance of objects or prey. Target distance is represented as a map of echo delay in the auditory cortex (AC) of bats. During a bat's flight through a natural complex environment, echo streams are reflected from multiple objects along its flight path. Separating such complex streams of echoes or other sounds is a challenge for the auditory system of bats as well as other animals. We investigated the representation of multiple echo streams in the AC of anaesthetized bats (Phyllostomus discolor) and tested the hypothesis, if neurons can lock on echoes from specific objects in a complex echo-acoustic pattern while the representation of surrounding objects is suppressed. We combined naturalistic pulse/echo sequences simulating a bat's flight through a virtual acoustic space with extracellular recordings. Neurons could selectively lock on echoes from one object in complex echo streams originating from two different objects along a virtual flight path. The objects were processed sequentially in the order in which they were approached. Object selection depended on sequential changes of echo delay and amplitude but not on absolute values. Furthermore, the detailed representation of the object echo delays in the cortical target range map was not fixed but could be dynamically adapted depending on the temporal pattern of sonar emission during target approach within a simulated flight sequence.

  15. 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.

  16. Low-flow, base-flow, and mean-flow regression equations for Pennsylvania streams

    USGS Publications Warehouse

    Stuckey, Marla H.

    2006-01-01

    Low-flow, base-flow, and mean-flow characteristics are an important part of assessing water resources in a watershed. These streamflow characteristics can be used by watershed planners and regulators to determine water availability, water-use allocations, assimilative capacities of streams, and aquatic-habitat needs. Streamflow characteristics are commonly predicted by use of regression equations when a nearby streamflow-gaging station is not available. Regression equations for predicting low-flow, base-flow, and mean-flow characteristics for Pennsylvania streams were developed from data collected at 293 continuous- and partial-record streamflow-gaging stations with flow unaffected by upstream regulation, diversion, or mining. Continuous-record stations used in the regression analysis had 9 years or more of data, and partial-record stations used had seven or more measurements collected during base-flow conditions. The state was divided into five low-flow regions and regional regression equations were developed for the 7-day, 10-year; 7-day, 2-year; 30-day, 10-year; 30-day, 2-year; and 90-day, 10-year low flows using generalized least-squares regression. Statewide regression equations were developed for the 10-year, 25-year, and 50-year base flows using generalized least-squares regression. Statewide regression equations were developed for harmonic mean and mean annual flow using weighted least-squares regression. Basin characteristics found to be significant explanatory variables at the 95-percent confidence level for one or more regression equations were drainage area, basin slope, thickness of soil, stream density, mean annual precipitation, mean elevation, and the percentage of glaciation, carbonate bedrock, forested area, and urban area within a basin. Standard errors of prediction ranged from 33 to 66 percent for the n-day, T-year low flows; 21 to 23 percent for the base flows; and 12 to 38 percent for the mean annual flow and harmonic mean, respectively. The

  17. Acoustics of dual-stream high-speed jets

    NASA Astrophysics Data System (ADS)

    Debiasi, Marco Tullio

    2000-10-01

    This work presents the results of noise measurements in high-speed, round jets whose Mach number and velocity simulate the conditions of jet engines at take-off. The Mach number of the jet potential core ranged from 1.27 to 1.77 and the velocity ranged from 550 m/s to 1010 m/s. Most of the jets were silenced with a coflow that prevented the formation of Mach waves, a dominant contribution to supersonic jet noise. This method, called Mach Wave Elimination, relies on the shielding effect of the coflow which makes the motion of the eddies subsonic with respect to the surrounding streams, thus impeding the creation of Mach waves. Schlieren photography and pitot probe surveys were used to detect the principal features and the growth rate of the jets. Microphone measurements were performed inside an anechoic chamber at many positions around the jet exit. The results were corrected for the microphone response and for the effect of human sensitivity to sound. Equal-thrust comparison of different experimental results shows that elimination of Mach waves is very effective in reducing noise in the direction of strongest emission. Except for localized shock-associated components, noise emission was found to be insensitive to nozzle exit pressure and to depend principally on the values of fully-expanded Mach number and velocity in the jet potential core. Jets with a shorter Mach wave emitting region exhibited better noise suppression. Best results were obtained with an eccentric coflow that allows the shear layer of the upper part of the jet to grow naturally while silencing the jet in the downward direction. Coflows are capable of reducing the near-field screech peaks by up to 10 dB in imperfectly-expanded jets. Scaling the experimental results to a fall-size engine shows that eccentric coflows reduce the noise perceived in the direction of peak emission by up to 11 dB. Preliminary analysis of the application of this silencing technique to engine design indicates that Mach

  18. 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.

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

    PubMed

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

    2015-05-01

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

  20. 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...

  1. 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...

  2. Estimating River Basin Evapotranspiration From Stream-Flow Time Series

    NASA Astrophysics Data System (ADS)

    Palmroth, S.; Katul, G. G.; Hui, D.; Oren, R.; McCarthy, H. R.; Jackson, R. B.

    2006-12-01

    Estimates of annual evapotransporation (ET) were inverted from continuous stream-flow (Q) records using a simplified watershed water balance and nonlinear reservoir model modified from Brutsaert and Nieber (1977). We focused on the uppermost section (1751 km2 ) of the Neuse River Basin in North Carolina U.S., where the climate is warm and humid and land cover is dominated by forests and agricultural land (totaling ~78% in 1999). We selected 11 U. S. Geological Survey stream-flow measurement stations and reconstructed annual ET from each drainage area, ranging from 26 to 1386 km2, over the period of the operation of each station (10 - 79 years). Scaled to the sub-basin, the stream-flow-based estimates of annual ET (for 2001 - 2004) agreed well with the estimates based on scaled eddy-covariance measured nearby at the Duke Forest AmeriFlux sites. Based on the longest stream-flow datasets, no clear overall trend in Q or the parameters of the reservoir model were found suggesting that the hydrologic properties of the watersheds have changed little over time. Inter-annual variation in precipitation typically explained more than half of the variation in ET while ET was mostly uncorrelated with measured pan evaporation. Thus, annual ET was more closely related to the replenishment of the water storage available for ET than its climatic driving force. We demonstrate that stream-flow records can be useful for providing continuous estimates of ET and, thereby, benchmarks for modeling regional fluxes of water and of other elements, e.g. carbon, that are closely coupled with water.

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

    PubMed

    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.

  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. 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.

  6. Low-flow characteristics of streams West Virginia

    USGS Publications Warehouse

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

    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)

  7. 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…

  8. Sample stream distortion modeled in continuous-flow electrophoresis

    NASA Technical Reports Server (NTRS)

    Rhodes, P. H.

    1979-01-01

    Buoyancy-induced disturbances in an electrophoresis-type chamber were investigated. Five tracer streams (latex) were used to visualize the flows while a nine-thermistor array sensed the temperature field. The internal heating to the chamber was provided by a 400 Hz electrical field. Cooling to the chamber was provided on the front and back faces and, in addition, on both chamber side walls. Disturbances to the symmetric base flow in the chamber occurred in the broad plane of the chamber and resulted from the formation of lateral and axial temperature gradients. The effect of these gradients was to retard or increase local flow velocities at different positions in the chamber cross section, which resulted in lateral secondary flows being induced in the broad plane of the chamber. As the adverse temperature gradients increased in magnitude, the critical Rayleigh number was approached and reverse (separated) flow became apparent, which, subsequently, led to the onset of time variant secondary flows.

  9. Low-flow characteristics of streams in Maryland and Delaware

    USGS Publications Warehouse

    Carpenter, David H.; Hayes, Donald C.

    1996-01-01

    Hydrologic information on the variability of streamflow during low-flow periods is presented. At-site data on low-flow characteristics of streamflow under natural conditions are given for 94 continuous-record gaging stations in Maryland, Delaware, and surrounding States, and for 131 low-flow partial-record gaging stations in Maryland and Delaware. Equations and transfer methods are developed to estimate low-flow characteristics at ungaged stream sites in Maryland and Delaware for average 7-, 14-, and 30-consecutive-day low-flow discharges for recurrence intervals of 2, 10, and 20 years. Estimates of the accuracy of the methods are presented. Maryland and Delaware are divided into four regions on the basis of physiography and the results of regression analyses. Equations are developed from a generalized least-squares multiple regression technique to estimate low-flow characteristics for the Eastern Shore region, the eastern-Piedmont region, and the western region. Adjustments are necessary to low-flow discharges estimated from the equation for the western region because of the effects of carbonate rocks on low flows. An equation is developed on the basis of a distance-weighted average of low-flow discharges at gaging stations to estimate low-flow characteristics for the southern region. Two methods are developed for transferring low-flow characteristics to ungaged sites on gaged streams. One method transfers low-flow characteristics to an ungaged site either upstream or downstream from a gaging station and the other method transfers the characteristics to an ungaged site between gaging stations.

  10. 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.

  11. 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.

  12. 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.

  13. 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...

  14. Low-flow characteristics for selected streams in Indiana

    USGS Publications Warehouse

    Fowler, Kathleen K.; Wilson, John T.

    2015-01-01

    The management and availability of Indiana’s water resources increase in importance every year. Specifically, information on low-flow characteristics of streams is essential to State water-management agencies. These agencies need low-flow information when working with issues related to irrigation, municipal and industrial water supplies, fish and wildlife protection, and the dilution of waste. Industrial, municipal, and other facilities must obtain National Pollutant Discharge Elimination System (NPDES) permits if their discharges go directly to surface waters. The Indiana Department of Environmental Management (IDEM) requires low-flow statistics in order to administer the NPDES permit program. Low-flow-frequency characteristics were computed for 272 continuous-record stations. The information includes low-flow-frequency analysis, flow-duration analysis, and harmonic mean for the continuous-record stations. For those stations affected by some form of regulation, low-flow frequency curves are based on the longest period of homogeneous record under current conditions. Low-flow-frequency values and harmonic mean flow (if sufficient data were available) were estimated for the 166 partial-record stations. Partial-record stations are ungaged sites where streamflow measurements were made at base flow.

  15. Coupling airborne laser scanning and acoustic Doppler current profiler data to model stream rating curves

    NASA Astrophysics Data System (ADS)

    Lam, N.; Lyon, S. W.; Kean, J. W.

    2015-12-01

    The rating curve enables the translation of water depth into discharge through a reference cross section. Errors in estimating stream channel geometry can therefore result in increased discharge uncertainty. This study investigates coupling national-scale airborne laser scanning (ALS) and acoustic Doppler current profiler (ADCP) bathymetric survey data for generating stream rating curves. Specifically, stream channel geometries were generated from coupled ALS and ADCP scanning data collected for a well-monitored site located in northern Sweden. These data were used to define the hydraulic geometry required by a physically-based 1-D hydraulic model. The results of our study demonstrate that the effects of potential scanning data errors on the model generated rating curve were less than the uncertainties due to stream gauging measurements and empirical rating curve fitting. Further analysis of the ALS data showed that an overestimation of the streambank elevation (the main scanning data error) was primarily due to vegetation that could be adjusted for through a root-mean-square-error bias correction. We consider these findings encouraging as hydrometric agencies can potentially leverage national-scale ALS and ADCP instrumentation to reduce the cost and effort required for maintaining and establish rating curves at gauging stations.

  16. A surface acoustic wave-driven micropump for particle uptake investigation under physiological flow conditions in very small volumes.

    PubMed

    Strobl, Florian G; Breyer, Dominik; Link, Phillip; Torrano, Adriano A; Bräuchle, Christoph; Schneider, Matthias F; Wixforth, Achim

    2015-01-01

    Static conditions represent an important shortcoming of many in vitro experiments on the cellular uptake of nanoparticles. Here, we present a versatile microfluidic device based on acoustic streaming induced by surface acoustic waves (SAWs). The device offers a convenient method for introducing fluid motion in standard cell culture chambers and for mimicking capillary blood flow. We show that shear rates over the whole physiological range in sample volumes as small as 200 μL can be achieved. A precise characterization method for the induced flow profile is presented and the influence of flow on the uptake of Pt-decorated CeO2 particles by endothelial cells (HMEC-1) is demonstrated. Under physiological flow conditions the particle uptake rates for this system are significantly lower than at low shear conditions. This underlines the vital importance of the fluidic environment for cellular uptake mechanisms.

  17. Magnetic and acoustic investigations of turbulent spherical Couette flow

    NASA Astrophysics Data System (ADS)

    Adams, Matthew Michael

    This dissertation describes experiments in spherical Couette devices, using both gas and liquid sodium. The experimental geometry is motivated by the Earth's outer core, the seat of the geodynamo, and consists of an outer spherical shell and an inner sphere, both of which can be rotated independently to drive a shear flow in the fluid lying between them. In the case of experiments with liquid sodium, we apply DC axial magnetic fields, with a dominant dipole or quadrupole component, to the system. We measure the magnetic field induced by the flow of liquid sodium using an external array of Hall effect magnetic field probes, as well as two probes inserted into the fluid volume. This gives information about possible velocity patterns present, and we extend previous work categorizing flow states, noting further information that can be extracted from the induced field measurements. The limitations due to a lack of direct velocity measurements prompted us to work on developing the technique of using acoustic modes to measure zonal flows. Using gas as the working fluid in our 60 cm diameter spherical Couette experiment, we identified acoustic modes of the container, and obtained excellent agreement with theoretical predictions. For the case of uniform rotation of the system, we compared the acoustic mode frequency splittings with theoretical predictions for solid body flow, and obtained excellent agreement. This gave us confidence in extending this work to the case of differential rotation, with a turbulent flow state. Using the measured splittings for this case, our colleagues performed an inversion to infer the pattern of zonal velocities within the flow, the first such inversion in a rotating laboratory experiment. This technique holds promise for use in liquid sodium experiments, for which zonal flow measurements have historically been challenging.

  18. 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.

  19. 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.

  20. Continuous flow two-dimensional acoustic orientation of nonspherical cells.

    PubMed

    Jakobsson, Ola; Antfolk, Maria; Laurell, Thomas

    2014-06-17

    Flow cytometry is a frequently used method when it comes to cell sorting and analysis. Nonspherical cells, such as red blood cells or sperm cells, however, pose a challenge as they reduce the precision of light scatter measurements which interfere with the analysis of these and other cell populations in the same sample. Here, we present a microfluidic chip for acoustophoresis utilizing ultrasonic standing waves to focus and orient red blood cells in two dimensions in the channel center. The cells can be oriented to show either their flat or up-ended side toward the optical axis and the observer. In an acoustic standing wave field the cells will be rotated until the direction of the smallest dimension is parallel with the direction where the acoustic energy is strongest. While keeping the cells focused in the channel center utilizing acoustic resonances in two dimensions, the orientation can be controlled by increasing the acoustic energy in either the horizontal or vertical resonance mode. It was shown that 87.8 ± 3.8% of the red blood cells could be horizontally oriented while 98.7 ± 0.3% could be vertically oriented. The ability to control the orientation of nonspherical cells with high accuracy is a beneficial feature and potential contribution to the rapidly growing field of flow and image cytometry.

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

    USGS Publications Warehouse

    Winter, T.C.

    1999-01-01

    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 surfacewater 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.

  2. The effects of stream bank vegetation on the flow characteristics and turbulent flow field of the main channel.

    NASA Astrophysics Data System (ADS)

    Valyrakis, M.; Yagci, O.; McGann, N. J.; Turker, U.

    2014-12-01

    Over the last two decades, the role of vegetation in the environmental and ecological restoration of surface water bodies has received much attention. Numerous studies have investigated the effects of vegetation on flow velocity at various locations ranging from the floodplain, river-bank and main channel. There is a general agreement amongst such studies, that the presence of vegetation may cause a decrease in flow velocity locally, followed by increased flows laterally, in non-vegetated regions. This experimental study attempts to present the findings of an elaborate set of flow measurements that aim at quantifying changes to the flow field at the main channel, at the bank inside the vegetated region and at their interface, for increasing vegetation density. To this goal an inclined section is constructed with acrylic panels sloping at, in a 1.8m wide re-circulating flume, to simulate the stream-bank. The main-channel bed comprises of coarse sand of 1.5mm nominal diameter, while 6mm diameter acrylic rods are used to simulate the vegetated river-bank. Ten velocity and turbulent intensity profiles are developed across the test cross-section, for each vegetation density, via acoustic Doppler velocimetry along a fine measurement grid. The experiments are run under uniform flow and stable bed conditions, for a range of six different vegetation densities changed by adding more vegetation elements in a staggered arrangement along the stream-bank. These detailed observations are further analyzed, with emphasis on the effects on the main channel. Measurements near the bed with implications for sediment transport are further discussed.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. The effect of in-stream activities on the Njoro River, Kenya. Part I: Stream flow and chemical water quality

    NASA Astrophysics Data System (ADS)

    Yillia, Paul T.; Kreuzinger, Norbert; Mathooko, Jude M.

    For shallow streams in sub-Saharan Africa, in-stream activities could be described as the actions by people and livestock, which take place within or besides stream channels. This study examined the nature of in-stream activities along a rural stream in Kenya and established the inequality in water allocation for various livelihood needs, as well as the negative impact they have on dry weather stream flow and chemical water quality. Seven locations along the stream were studied in wet and dry weather of 2006. Enumeration consisted of making head counts of people and livestock and tallying visitors at hourly intervals from 6 a.m. to 7 p.m. To estimate water abstraction, filled containers of known volume were counted and the stream was sampled to examine the impact on water quality. Water samples were obtained upstream and downstream of in-stream activities before (6 a.m.) and during (11 a.m., 6 p.m.) activities. Samples were analyzed for suspended solids, turbidity, BOD 5, total nitrogen and total phosphorus. The daily total abstraction at the middle reaches during dry weather was 120-150 m 3 day -1. More than 60% of abstraction was done by water vendors. Vended water from the stream was sold at US 3.5-7.5 per m 3 and vendors earned between US 3-6 a day. Abstracted water contributed approximately 40-60% of the total daily consumptive water use in the riparian area during dry weather but >30% of the morning stream flow was abstracted thereby upsetting stream flow in the lower reaches. The daily total water abstraction correlated positively ( R2, 0.98) and significantly ( p < 0.05) with the daily total human visit, which was diurnally periodic with two peaks, occurring between 9 a.m. and 10 a.m. and from 4 p.m. to 5 p.m. This diurnal pattern of visits and the corresponding in-stream activities affected water quality. In particular, suspended solids, turbidity and BOD 5 levels increased significantly ( p < 0.05) downstream during in-stream activities. It was concluded

  12. 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.

  13. Radiation of cylindrical duct acoustic modes with flow mismatch

    NASA Technical Reports Server (NTRS)

    Savkar, S. D.; Edelfelt, I. H.

    1975-01-01

    Calculations for the radiation of spinning acoustic modes, with or without a centerbody, and with or without flow temperature and velocity discontinuity, are presented. Solutions to the appropriate convected wave equations devised around Fourier transforms and Wiener-Hopf technique are presented. The decomposition of the asymmetric kernel, resulting from a flow and temperature mismatch, is carried out in part exactly and partially using the so-called Carrier-Koiter approximation procedure. The resulting solutions offer a good approximation to the radiation of both symmetric and asymmetric modes through a flow discontinuity represented as a plug flow jet issuing from a cylindrical duct. Besides the Koiter approximation, the major limitation on the calculation program is the difficulty of calculating the high order Bessel functions with sufficient accuracy.

  14. Regional characteristics of extreme drought patterns in stream flow records

    NASA Astrophysics Data System (ADS)

    Nasrollahi, N.; Ahmadi, M.; Alaeipour, A.

    2010-12-01

    Global warming has shown dramatic effects on natural systems in some parts of the world. Middle East is one of the locations that is affected by the severe changes in the climate conditions. In this study, the regional characteristics of severe seasonal droughts have been studied by analyzing the extreme value properties of the annual maximum series of river stream flows in the last 30 years. The study region is Karun River located in south western Iran. Karun River is Iran's most effluent, and the only navigable river which is 720 km long. It rises in the Zard Kuh Mountains and continues toward the Persian Gulf. There are a number of dams on the Karun River, with the purpose of generating hydroelectric power and flood control. The area is divided into 10 catchments with daily stream flow records. To investigate the drought periods, the threshold level is defined by percentiles from the flow duration curve. Two different regionalization tools are compared, L-moment diagrams and empirical orthogonal functions. The L-moment and EOF diagrams provided virtually the same conclusions with regard to clustering of catchments, and large scale trends were found in the data which confirms a regional pattern.

  15. 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.

  16. 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

  17. 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

  18. Trends in peak flows of selected streams in Kansas

    USGS Publications Warehouse

    Rasmussen, T.J.; Perry, C.A.

    2001-01-01

    The possibility of a systematic change in flood potential led to an investigation of trends in the magnitude of annual peak flows in Kansas. Efficient design of highway bridges and other flood-plain structures depends on accurate understanding of flood characteristics. The Kendall's tau test was used to identify trends at 40 stream-gaging stations during the 40-year period 1958-97. Records from 13 (32 percent) of the stations showed significant trends at the 95-percent confidence level. Only three of the records (8 percent) analyzed had increasing trends, whereas 10 records (25 percent) had decreasing trends, all of which were for stations located in the western one-half of the State. An analysis of flow volume using mean annual discharge at 29 stations in Kansas resulted in 6 stations (21 percent) with significant trends in flow volumes. All six trends were decreasing and occurred in the western one-half of the State. The Kendall's tau test also was used to identify peak-flow trends over the entire period of record for 54 stream-gaging stations in Kansas. Of the 23 records (43 percent) showing significant trends, 16 (30 percent) were decreasing, and 7 (13 percent) were increasing. The trend test then was applied to 30-year periods moving in 5-year increments to identify time periods within each station record when trends were occurring. Systematic changes in precipitation patterns and long-term declines in ground-water levels in some stream basins may be contributing to peak-flow trends. To help explain the cause of the streamflow trends, the Kendall's tau test was applied to total annual precipitation and ground-water levels in Kansas. In western Kansas, the lack of precipitation and presence of decreasing trends in ground-water levels indicated that declining water tables are contributing to decreasing trends in peak streamflow. Declining water tables are caused by ground-water withdrawals and other factors such as construction of ponds and terraces. Peak-flow

  19. 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.

  20. Acoustic equations for a gas stream in rigid-body rotation

    NASA Astrophysics Data System (ADS)

    Garcia-Ybarra, Pedro L.; Marin-Antuña, Jose M.

    2017-02-01

    The classical topic of wave propagation in a rotating gas is revisited by deducing scalar wave equations for propagation of acoustic and rotational waves through a plug flow of gas in rigid-body rotation with arbitrary intensities of the radial stratification. In the light of these novel equations, wave propagation is analyzed in two different base gas states: isothermal and homentropic. In both cases, previous findings are recovered that assess the validity of the equations and new results are established. In the non-homentropic but isothermal case, the set of governing equations is reduced to two coupled scalar wave equations with space dependent coefficients for the disturbances of density and pressure. Travelling wave solutions with variable amplitude have been obtained in the limit of weak stratification both for inertial waves as for acoustic waves which, in general, propagate on different frequency bands that overlap in the small wavenumber region. Furthermore, the entropy stratification in the base state is stable and compels the propagation of internal waves, leading to hybrid acoustic-inertial-vortical modes. In the homentropic case, the adiabatic relation between pressure and density disturbances allows to reduce further the governing equations to a single fourth-order scalar wave equation. In this case, the sound propagation velocity depends on the distance to the rotation axis and solutions are found by multiple-scale analyses in the form of waves with slowly varying amplitude and wavenumber. The corresponding eikonal equation shows that acoustic rays are refracted towards the rotation axis, propagating and spinning along and around it. In that way, the swirling gas behaves as an axial waveguide trapping inside any acoustic ray propagating in the vortex with large enough azimuthal and/or vertical wavenumber component.

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

    PubMed

    Trujillo, Francisco Javier; Knoerzer, Kai

    2011-11-01

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

  2. Study of acoustic radiation during air stream filtration through a porous medium

    NASA Astrophysics Data System (ADS)

    Zaslavskii, Yu. M.; Zaslavskii, V. Yu.

    2012-11-01

    The paper presents results of laboratory experiments on studying the characteristics of acoustic emission generated by a flow of compressed air, which is filtered by porous pumice samples with and without partial fluid saturation. The construction features of the laboratory setup and details of the experiments are described. Porous samples with dry and partially fluid-filled pores are used. The visual patterns of the acoustic emission spectrum, which occurs under stationary filtration of the compressed air, are presented, and its amplitude-frequency distribution characteristic for different sample porosities and different degrees of their fluid saturation is shown. It is demonstrated that the relaxation times of the emission noise level differ. This is revealed during the sharp elimination of the drop in pressure from such samples, i.e., in the nonstationary filtration mode.

  3. 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

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

    PubMed

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

    2012-12-11

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

  5. The effect of fluid streams in porous media on acoustic compression wave propagation, transmission, and reflection

    NASA Astrophysics Data System (ADS)

    Madeo, A.; Djeran-Maigre, I.; Rosi, G.; Silvani, C.

    2013-03-01

    In geomechanics, a relevant role is played by coupling phenomena between compressible fluid seepage flow and deformation of the solid matrix. The behavior of complex porous materials can be greatly influenced by such coupling phenomena. A satisfactorily theoretical framework for their description is not yet completely attained. In this paper, we discuss how the model developed in dell'Isola et al. (Int J Solids Struct 46:3150-3164, 2009) can describe how underground flows or, more generally, confined streams of fluid in deformable porous matrices affect compression wave propagation and their reflection and transmission at a solid-material discontinuity surface. Further work will investigate the effect of stream flow in porous media on shear waves, generalizing what done in Djeran Maigre and Kuznetsov (Comptes Rendus Mécanique 336(1-2):102-107, 2008) for shear waves in one-constituent orthotropic two-layered plates. The presented treatment shows that the presence of fluid streams considerably affect reflection and transmission phenomena in porous media.

  6. Electrohydrodynamic distortion of sample streams in continuous flow electrophoresis

    NASA Technical Reports Server (NTRS)

    Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

    1989-01-01

    Continuous flow electrophoresis experiments were carried out, using an electrolyte and a sample both made of aqueous solutions of phosphate buffer (with polystyrene latex added for visibility), to investigate causes of the sample spreading in this procedure. It is shown theoretically that an electric field perpendicular to a circular filament of conducting fluid surrounded by a fluid of different conductivity produces an electrohydrodynamic flow, which distorts the filament into an ellipse. Experimental results were found to be fully consistent with theretical predictions. It was found that the rate of distortion of the sample stream into a ribbon was proportional to the square of the applied voltage gradient. Furthermore, the orientation of the ribbon depends on the ratios of dielectric constant and electrical conductivity between the buffer and the sample.

  7. Comparison of Methods for Estimating Low Flow Characteristics of Streams

    USGS Publications Warehouse

    Tasker, Gary D.

    1987-01-01

    Four methods for estimating the 7-day, 10-year and 7-day, 20-year low flows for streams are compared by the bootstrap method. The bootstrap method is a Monte Carlo technique in which random samples are drawn from an unspecified sampling distribution defined from observed data. The nonparametric nature of the bootstrap makes it suitable for comparing methods based on a flow series for which the true distribution is unknown. Results show that the two methods based on hypothetical distribution (Log-Pearson III and Weibull) had lower mean square errors than did the G. E. P. Box-D. R. Cox transformation method or the Log-W. C. Boughton method which is based on a fit of plotting positions.

  8. Numerical Study of Laminar Flow over Acoustic Cavities

    NASA Astrophysics Data System (ADS)

    Owen, Matthew; Cheng, Gary

    2016-11-01

    Fluid flow over an open cavity often emits acoustic waves with certain natural frequencies dependent on the geometry of the cavity and the properties and flow conditions of the fluid. Numerical studies of this kind, Computational Aeroacoustics (CAA), pose a grave challenge to the accuracy and efficiency of numerical methods. This project examines the Space-Time Conservation Element Solution Element (CESE) method developed by Dr. S.C. Chang at NASA GRC and compares numerical results of two-dimensional flow to previous experimental data found in literature. The conclusion the project reached is that the test data agrees well with one of the modes of the predicted frequencies, and that further testing is needed to be able to match experimental results. Funding from NSF REU site Grant EEC 1358991 is greatly appreciated.

  9. Contrasts between debris flows, hyperconcentrated flows and stream flows at a channel of Mount Semeru, East Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Lavigne, Franck; Suwa, Hiroshi

    2004-07-01

    In order to differentiate between different types of sediment-laden-flows in volcanic channels, we carried out observation of debris flows, hyperconcentrated flows, and stream flows in the Curah Lengkong river on the southeast slope of Mount Semeru in East Java, Indonesia. The aims of this study are: (1) to provide quantitative data for these flows in motion; (2) to compare the data for different types of flow that occur in the same river; (3) to assess the influence of rainfall on debris flows, hyperconcentrated flows, and streamflow generation. The Curah Lengkong river transports large volumes of sediment, in the range of 1×10 5 to 5×10 5 m 3 per debris flow, and 10 3 to 10 5 m 3 per hyperconcentrated flow and stream flow. Large sediment discharges result from the following factors: continuous and voluminous sediment supply of fine juvenile material by daily explosions of the Semeru volcano, pyroclastic source material emplaced on steep slopes, strong erosion of weathered river banks, and strong rainfall intensities. The occurrence of the flows focuses in the period from November through April, and the daily timing of it is the mid to late afternoon. Nearly all debris flows are triggered by stationary rainfall confined to the upper slopes of Mount Semeru, whereas hyperconcentrated flows and stream flows are mainly generated by migratory or regional rains driven upwards on the eastern slope. This slope receives its maximum of annual rainfall (3800 mm) at 800 m asl. The peak surface velocity of debris flows is always greater than the peak frontal velocity. The peak discharge of debris flows occurs several minutes after the passage of the flow front. Volumetric concentrations of sediment are high (48% to 69%) between the debris flow front and the point of peak discharge; after the peak discharge it usually decreases gradually. Contrary to the case of debris flows, high concentration of sediment appears in various portion of hyperconcentrated flows and stream flows

  10. 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.

  11. 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.

  12. 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

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

    PubMed

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

    2014-09-07

    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 (R(2) = 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.

  14. 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

  15. Assessment of climate change and its impact on forest stream flow using wavelet analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Characterization of stream flow is essential to water resource management, water supply planning, environmental protection, and ecological restoration; while climate change can exacerbate stream flow and add instability to the flow. In this study, the wavelet analysis technique was employed to asse...

  16. Low-flow characteristics of streams in the Lahaina District, West Maui, Hawai'i

    USGS Publications Warehouse

    Cheng, Chui Ling

    2014-01-01

    The purpose of this study was to characterize streamflow availability under natural low-flow conditions for streams in the Lahaina District, west Maui, Hawaiʻi. The study-area streams included Honolua Stream and tributary Pāpua Gulch, Honokahua Stream and tributary Mokupeʻa Gulch, Kahana Stream, Honokōwai Stream and tributaries Amalu and Kapāloa Streams, Wahikuli Gulch and tributary Hāhākea Gulch, Kahoma Stream and tributary Kanahā Stream, Kauaʻula Stream, Launiupoko Stream, Olowalu Stream, and Ukumehame Gulch. The results of this study can be used to assist in the determination of technically defensible instream-flow standards for the study-area streams. Low-flow characteristics for natural (unregulated) streamflow conditions were represented by flow-duration discharges that are equaled or exceeded between 50 and 95 percent of the time. Partial-record sites were established on 10 main streams and 5 tributary streams, mainly upstream from existing surface-water diversions. Flow characteristics were determined using historical and current streamflow data from continuous-record streamflow-gaging stations and miscellaneous sites, and additional data collected as part of this study. Based on strategically scheduled observations, six of the study-area streams were ephemeral streams that were observed to remain dry at least 50 percent of the time: Pāpua Gulch, Honokahua Stream and its tributary Mokupeʻa Gulch, Kahana Stream, and Wahikuli Gulch and its tributary Hāhākea Gulch. For the remaining streams with measurable flow, Honolua, Honokōwai, Kahoma, Kanahā, Kauaʻula, Launiupoko, and Olowalu Streams, and Ukumehame Gulch, flow-duration discharges were computed for the 30-year base period (water years 1984–2013), using two record-augmentation techniques. The 95-percent flow-duration discharges ranged from 0 to 4.8 cubic feet per second (ft3/s). The 50-percent flow-duration discharges ranged from 0.47 to 9.5 ft3/s. This study also estimated the streamflow

  17. Linear growth rates of resistive tearing modes with sub-Alfvénic streaming flow

    SciTech Connect

    Wu, L. N.; Ma, Z. W.

    2014-07-15

    The tearing instability with sub-Alfvénic streaming flow along the external magnetic field is investigated using resistive MHD simulation. It is found that the growth rate of the tearing mode instability is larger than that without the streaming flow. With the streaming flow, there exist two Alfvén resonance layers near the central current sheet. The larger perturbation of the magnetic field in two closer Alfvén resonance layers could lead to formation of the observed cone structure and can largely enhance the development of the tearing mode for a narrower streaming flow. For a broader streaming flow, a larger separation of Alfvén resonance layers reduces the magnetic reconnection. The linear growth rate decreases with increase of the streaming flow thickness. The growth rate of the tearing instability also depends on the plasma beta (β). When the streaming flow is embedded in the current sheet, the growth rate increases with β if β < β{sub s}, but decreases if β > β{sub s}. The existence of the specific value β{sub s} can be attributed to competition between the suppressing effect of β and the enhancing effect of the streaming flow on the magnetic reconnection. The critical value β{sub s} increases with increase of the streaming flow strength.

  18. Acoustic Intensity Measurements in the Presence of Low Mach Number Flow

    DTIC Science & Technology

    1993-09-01

    broadband acoustic holography ,3 intensity measurements in the presence of flow,"𔄁𔄀. 7 in-situ evaluation of the acoustic impedance and sound absorption...Cross Spectra" Ph.D. Thesis, Catholic University, (1987). 3. Loyau, T., Pascal, J., Gaillard, P., "Broadband Acoustic Holography Reconstruction From...AD-A269 995 The Pennsylvania State University APPLIED RESEARCH LABORATORY P.O. Box 30 State College, PA 16804 ACOUSTIC INTENSITY MEASUREMENTS IN THE

  19. 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

  20. Methods for estimating low-flow statistics for Massachusetts streams

    USGS Publications Warehouse

    Ries, Kernell G.; Friesz, Paul J.

    2000-01-01

    Methods and computer software are described in this report for determining flow duration, low-flow frequency statistics, and August median flows. These low-flow statistics can be estimated for unregulated streams in Massachusetts using different methods depending on whether the location of interest is at a streamgaging station, a low-flow partial-record station, or an ungaged site where no data are available. Low-flow statistics for streamgaging stations can be estimated using standard U.S. Geological Survey methods described in the report. The MOVE.1 mathematical method and a graphical correlation method can be used to estimate low-flow statistics for low-flow partial-record stations. The MOVE.1 method is recommended when the relation between measured flows at a partial-record station and daily mean flows at a nearby, hydrologically similar streamgaging station is linear, and the graphical method is recommended when the relation is curved. Equations are presented for computing the variance and equivalent years of record for estimates of low-flow statistics for low-flow partial-record stations when either a single or multiple index stations are used to determine the estimates. The drainage-area ratio method or regression equations can be used to estimate low-flow statistics for ungaged sites where no data are available. The drainage-area ratio method is generally as accurate as or more accurate than regression estimates when the drainage-area ratio for an ungaged site is between 0.3 and 1.5 times the drainage area of the index data-collection site. Regression equations were developed to estimate the natural, long-term 99-, 98-, 95-, 90-, 85-, 80-, 75-, 70-, 60-, and 50-percent duration flows; the 7-day, 2-year and the 7-day, 10-year low flows; and the August median flow for ungaged sites in Massachusetts. Streamflow statistics and basin characteristics for 87 to 133 streamgaging stations and low-flow partial-record stations were used to develop the equations. The

  1. Steady Flow of Acoustically Fluidized Long Runout Landslides

    NASA Astrophysics Data System (ADS)

    Melosh, H. J.

    2001-12-01

    The high mobility exhibited by long runout landslides remains a geologic puzzle. In 1979 I proposed that the presence of strong internal vibrations could fluidize the rock debris composing such a landslide, and permit very large volumes of rock debris (more than 106 m3) to flow with a low coefficient of friction. Numerical simulations by Campbell in 1995 verified that a low friction mode of motion is theoretically possible but their time resolution was insufficient to validate my proposed mechanism. Since my initial proposal I performed laboratory studies of vibrated granular materials that support the rheology predicted by acoustic fluidization theory. I now report theoretical studies that apply this rheologic law to the steady flow of granular material down an incline of uniform slope. Although numerical solutions of the resulting highly nonlinear equations are generally necessary, a simple analytic solution is possible when the sound waves in the landslide propagate only short distances compared to the thickness of the slide mass. This solution shows that sustained flow is possible if a "regeneration parameter" equal to 1/2 Q e sin2 θ is equal to about 1. In this equation Q denotes the rate of energy absorption by inelastic processes, e is the vibrational energy generation efficiency, and θ is the (constant) slope. For plausible values of these parameters the critical slope on which steady sliding is possible is between 7 and 11 degrees, far lower than permitted by the static coefficient of friction. These slopes are similar to those observed for long runout landslides on the Earth, Venus, Mars and Io. The solution also shows that the velocity-depth profile is close to parabolic. Although a basal shear concentration has been reported for the Blackhawk landslide (which also possesses a basal layer of fine sand), more uniform shear is inferred in homogeneous slide masses. Campbell's numerical simulations also exhibit a parabolic velocity profile through the

  2. 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.

  3. Viscous interaction of flow redevelopment after flow reattachment with supersonic external streams

    NASA Technical Reports Server (NTRS)

    Chow, W. L.; Spring, D. J.

    1975-01-01

    A flow model has been developed to study the flow development after reattachment with supersonic external streams. Special attention is given to the pressure difference across the viscous layer, and it is suggested that such a flow redevelopment can be treated as a relaxation of this pressure difference. Upon correlating the pressure difference with a slope parameter of the velocity profile, the system of equations governing the flow would produce a saddle point singularity corresponding to the fully rehabilitated asymptotic flow condition. A method of calculation for this flowfield, in conjunction with the matching of the upstream flow, has been derived and is discussed. Samples of calculations are also presented. Reasonably good agreement with experimental data has also been observed.

  4. 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.

  5. Patterns and age distribution of ground-water flow to streams

    USGS Publications Warehouse

    Modica, E.; Reilly, T.E.; Pollock, D.W.

    1997-01-01

    Simulations of ground-water flow in a generic aquifer system were made to characterize the topology of ground-water flow in the stream subsystem and to evaluate its relation to deeper ground-water flow. The flow models are patterned after hydraulic characteristics of aquifers of the Atlantic Coastal Plain and are based on numerical solutions to three-dimensional, steady-state, unconfined flow. The models were used to evaluate the effects of aquifer horizontal-to-vertical hydraulic conductivity ratios, aquifer thickness, and areal recharge rates on flow in the stream subsystem. A particle tracker was used to determine flow paths in a stream subsystem, to establish the relation between ground-water seepage to points along a simulated stream and its source area of flow, and to determine ground-water residence time in stream subsystems. In a geometrically simple aquifer system with accretion, the source area of flow to streams resembles an elongated ellipse that tapers in the downgradient direction. Increased recharge causes an expansion of the stream subsystem. The source area of flow to the stream expands predominantly toward the stream headwaters. Baseflow gain is also increased along the reach of the stream. A thin aquifer restricts ground-water flow and causes the source area of flow to expand near stream headwaters and also shifts the start-of-flow to the drainage basin divide. Increased aquifer anisotropy causes a lateral expansion of the source area of flow to streams. Ground-water seepage to the stream channel originates both from near- and far-recharge locations. The range in the lengths of flow paths that terminate at a point on a stream increase in the downstream direction. Consequently, the age distribution of ground water that seeps into the stream is skewed progressively older with distance downstream. Base flow ia an integration of ground water with varying age and potentially different water quality, depending on the source within the drainage basin

  6. 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.

  7. 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.

  8. Low-Flow Characteristics and Regionalization of Low-Flow Characteristics for Selected Streams in Arkansas

    USGS Publications Warehouse

    Funkhouser, Jaysson E.; Eng, Ken; Moix, Matthew W.

    2008-01-01

    Water use in Arkansas has increased dramatically in recent years. Since 1990, the use of water for all purposes except power generation has increased 53 percent (4,004 cubic feet per second in 1990 to 6,113 cubic feet per second in 2005). The biggest users are agriculture (90 percent), municipal water supply (4 percent) and industrial supply (2 percent). As the population of the State continues to grow, so does the demand for the State's water resources. The low-flow characteristics of a stream ultimately affect its utilization by humans. Specific information on the low-flow characteristics of streams is essential to State water-management agencies such as the Arkansas Department of Environmental Quality, the Arkansas Natural Resources Commission, and the Arkansas Game and Fish Commission when dealing with problems related to irrigation, municipal and industrial water supplies, fish and wildlife conservation, and dilution of waste. Low-flow frequency data are of particular value to management agencies responsible for the development and management of the State's water resources. This report contains the low-flow characteristics for 70 active continuous-streamflow record gaging stations, 59 inactive continuous-streamflow record stations, and 101 partial-record gaging stations. These characteristics are the annual 7-day, 10-year low flow and the annual 7-day, 2-year low flow, and the seasonal, bimonthly, and monthly 7-day, 10-year low flow for the 129 active and inactive continuous-streamflow record and 101 partial-record gaging stations. Low-flow characteristics were computed on the basis of streamflow data for the period of record through September 2005 for the continuous-streamflow record and partial-record streamflow gaging stations. The low-flow characteristics of these continuous- and partial-record streamflow gaging stations were utilized in a regional regression analysis to produce equations for estimating the annual, seasonal, bimonthly, and monthly

  9. 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

  10. 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.

  11. 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

  12. 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

  13. Streaming a single job in a flow shop

    SciTech Connect

    Benli, O.

    1994-12-31

    Very simply stated, lot streaming is moving some portion of a process batch ahead to begin a downstream operation. The problem to be considered in this paper is the following: a single job consisting of U units is to be processed on m machines. Given the maximum number of possible transfer batches in between the machines, the problem is to find the timing and the size of the transfer batches ({open_quotes}sublots{close_quotes}) so as to minimize the makespan. A general formulation of this problem is presented as a mixed integer linear program. This formulation allows for different number of sublots among the stages, variable length sublots, and intermittent idling on a machine. By restricting some of the parameter values (such as m = 2) or the constraints (such as no idling of machines), the well known results from literature can be obtained. The formulation basically is a periodic review model with variable period lengths. Furthermore, the approach is general enough to permit the use of other objective functions such as minimizing the mean flow time (in this case the objective function is quadratic). The possible significance of this generalized approach in the integration of production planning and machine scheduling will be discussed in conclusion.

  14. 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

  15. Low-flow statistics of selected streams in Chester County, Pennsylvania

    USGS Publications Warehouse

    Schreffler, Curtis L.

    1998-01-01

    Low-flow statistics for many streams in Chester County, Pa., were determined on the basis of data from 14 continuous-record streamflow stations in Chester County and data from 1 station in Maryland and 1 station in Delaware. The stations in Maryland and Delaware are on streams that drain large areas within Chester County. Streamflow data through the 1994 water year were used in the analyses. The low-flow statistics summarized are the 1Q10, 7Q10, 30Q10, and harmonic mean. Low-flow statistics were estimated at 34 partial-record stream sites throughout Chester County.

  16. 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

  17. 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.

  18. StreamStats in Oklahoma - Drainage-Basin Characteristics and Peak-Flow Frequency Statistics for Ungaged Streams

    USGS Publications Warehouse

    Smith, S. Jerrod; Esralew, Rachel A.

    2010-01-01

    drainage-basin outlet for the period 1961-1990, 10-85 channel slope (slope between points located at 10 percent and 85 percent of the longest flow-path length upstream from the outlet), and percent impervious area. The Oklahoma StreamStats application interacts with the National Streamflow Statistics database, which contains the peak-flow regression equations in a previously published report. Fourteen peak-flow (flood) frequency statistics are available for computation in the Oklahoma StreamStats application. These statistics include the peak flow at 2-, 5-, 10-, 25-, 50-, 100-, and 500-year recurrence intervals for rural, unregulated streams; and the peak flow at 2-, 5-, 10-, 25-, 50-, 100-, and 500-year recurrence intervals for rural streams that are regulated by Natural Resources Conservation Service floodwater retarding structures. Basin characteristics and streamflow statistics cannot be computed for locations in playa basins (mostly in the Oklahoma Panhandle) and along main stems of the largest river systems in the state, namely the Arkansas, Canadian, Cimarron, Neosho, Red, and Verdigris Rivers, because parts of the drainage areas extend outside of the processed hydrologic units.

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

    NASA Technical Reports Server (NTRS)

    Succi, G.

    1982-01-01

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

  20. 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

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

    SciTech Connect

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

    2015-09-01

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

  2. 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,...

  3. 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...

  4. 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

  5. Low-flow characteristics of streams in the Puget Sound region, Washington

    USGS Publications Warehouse

    Hidaka, F.T.

    1973-01-01

    Periods of low streamflow are usually the most critical factor in relation to most water uses. The purpose of this report is to present data on low-flow characteristics of streams in the Puget Sound region, Washington, and to briefly explain some of the factors that influence low flow in the various basins. Presented are data on low-flow frequencies of streams in the Puget Sound region, as gathered at 150 gaging stations. Four indexes were computed from the flow-flow-frequency curves and were used as a basis to compare the low-flow characteristics of the streams. The indexes are the (1) low-flow-yield index, expressed in unit runoff per square mile; (2) base-flow index, or the ratio of the median 7-day low flow to the average discharge; (3) slope index, or slope of annual 7-day low-flow-frequency curve; and (4) spacing index, or spread between the 7-day and 183-day low-flow-frequency curves. The indexes showed a wide variation between streams due to the complex interrelation between climate, topography, and geology. The largest low-flow-yield indexes determined--greater than 1.5 cfs (cubic feet per second) per square mile--were for streams that head at high altitudes in the Cascade and Olympic Mountains and have their sources at glaciers. The smallest low-flow-yield indexes--less than 0.5 cfs per square mile--were for the small streams that drain the lowlands adjacent to Puget Sound. Indexes between the two extremes were for nonglacial streams that head at fairly high altitudes in areas of abundant precipitation. The base-flow index has variations that can be attributed to a basin's hydrogeology, with very little influence from climate. The largest base-flow indexes were obtained for streams draining permeable unconsolidated glacial and alluvial sediments in parts of the lowlands adjacent to Puget Sound. Large volume of ground water in these materials sustain flows during late summer. The smallest indexes were computed for streams draining areas underlain by

  6. 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.

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

    USGS Publications Warehouse

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

    2013-01-01

    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.

  8. 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...

  9. 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...

  10. 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 ...

  11. Flow Data for Solute Transport Modeling from Tracer Experiments in a Stream Not Continuously Gaining Water

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    In-stream tracer experiments are a well-established method for determining flow data to be incorporated in solute transport modeling. For a gaining stream, this method is implemented to provide spatial flow data at scales of minutes and tens of meters without physical disturbance to the flow of water, the streambed, or biota. Of importance for solute transport modeling, solute inflow loading along the stream can be estimated with this spatial data. The tracer information can also be interpreted to characterize hyporheic exchange time-scales for a stream with hyporheic exchange flowpaths (HEFs) that are short relative to the distance over which the stream gains water. The interpretation of tracer data becomes uncertain for a stream that is not gaining water continuously over intended study reach. We demonstrate, with straight-forward mass-balances, uncertainties for solute loading which arise in the analysis of streams locally losing water while predominantly gaining water (and solutes) over a larger scale. With field data from Mineral Creek (Silverton, Colorado) we illustrate the further uncertainty distinguishing HEFs from (locally) losing segments of the stream. Comparison of bromide tracer with ambient sulfate concentrations suggests that subsurface inflows and outflows, concurrent with likely HEFs, occur in a hydrogeochemical setting of multiple, dispersed and mixed, sources of water along a 64 m sub-reach of the predominately gaining, but locally losing, stream. To compute stream-reach mass-balances (the simplest of water quality models) there is a need to quantitatively define the character and source of contaminants entering streams from ground-water pathways, as well as the potential for changes in water chemistry and contaminant concentrations along flow paths crossing the sediment-water interface. Identification of inflow solute mass requires quantifying water gain, loss, and hyporheic exchange in addition to concentration.

  12. 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.

  13. Topological Creation of Acoustic Pseudospin Multipoles in a Flow-Free Symmetry-Broken Metamaterial Lattice.

    PubMed

    Zhang, Zhiwang; Wei, Qi; Cheng, Ying; Zhang, Ting; Wu, Dajian; Liu, Xiaojun

    2017-02-24

    The discovery of topological acoustics has revolutionized fundamental concepts of sound propagation, giving rise to strikingly unconventional acoustic edge modes immune to scattering. Because of the spinless nature of sound, the "spinlike" degree of freedom crucial to topological states in acoustic systems is commonly realized with circulating background flow or preset coupled resonator ring waveguides, which drastically increases the engineering complexity. Here we realize the acoustic pseudospin multipolar states in a simple flow-free symmetry-broken metamaterial lattice, where the clockwise (anticlockwise) sound propagation within each metamolecule emulates pseudospin down (pseudospin up). We demonstrate that tuning the strength of intermolecular coupling by simply contracting or expanding the metamolecule can induce the band inversion effect between the pseudospin dipole and quadrupole, which leads to a topological phase transition. Topologically protected edge states and reconfigurable topological one-way transmission for sound are further demonstrated. These results provide diverse routes to construct novel acoustic topological insulators with versatile applications.

  14. Topological Creation of Acoustic Pseudospin Multipoles in a Flow-Free Symmetry-Broken Metamaterial Lattice

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiwang; Wei, Qi; Cheng, Ying; Zhang, Ting; Wu, Dajian; Liu, Xiaojun

    2017-02-01

    The discovery of topological acoustics has revolutionized fundamental concepts of sound propagation, giving rise to strikingly unconventional acoustic edge modes immune to scattering. Because of the spinless nature of sound, the "spinlike" degree of freedom crucial to topological states in acoustic systems is commonly realized with circulating background flow or preset coupled resonator ring waveguides, which drastically increases the engineering complexity. Here we realize the acoustic pseudospin multipolar states in a simple flow-free symmetry-broken metamaterial lattice, where the clockwise (anticlockwise) sound propagation within each metamolecule emulates pseudospin down (pseudospin up). We demonstrate that tuning the strength of intermolecular coupling by simply contracting or expanding the metamolecule can induce the band inversion effect between the pseudospin dipole and quadrupole, which leads to a topological phase transition. Topologically protected edge states and reconfigurable topological one-way transmission for sound are further demonstrated. These results provide diverse routes to construct novel acoustic topological insulators with versatile applications.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. Trends in base flow, total flow, and base-flow index of selected streams in and near Oklahoma through 2008

    USGS Publications Warehouse

    Esralew, Rachel A.; Lewis, Jason M.

    2010-01-01

    The U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, investigated trends in base flow, total flow, and base-flow index of selected streams in Oklahoma and evaluated possible causes for trends. Thirty-seven streamflow-gaging stations that had unregulated or moderately regulated streamflow were selected for trend analysis. Statistical evaluation of trends in annual and seasonal (winter-spring and summer-autumn) base flow, total flow, and base-flow index at 37 selected streamflow-gaging stations in Oklahoma was performed by using a Kendall's tau trend test. This trend analysis also was performed for annual and seasonal precipitation for nine climate divisions in the study area, annual peak flows, the number of days where flow was zero or less than 1 cubic foot per second (both annually and seasonally), and annual winter groundwater levels for 35 shallow wells near the analyzed stations. Precipitation-adjusted trends using LOESS regressions and Kendall's tau were computed for annual and seasonal base-flow and total-flow volumes in order to identify the presence of underlying trends in streamflow that are not associated with annual or seasonal variations in precipitation. In general, upward trends in precipitation were detected for climate divisions in north-central Oklahoma and south-central and southeastern Kansas. More climate divisions had statistically significant upward trends in total precipitation for annual water years than in winter-spring or summer-autumn water years. Significant trends in annual or seasonal base-flow volume were detected for 22 stations, 19 of which had trends that were upward in direction. Significant trends in annual or seasonal total-flow volume were detected for 14 stations, 9 of which had trends that were upward in direction. Most stations that had significant upward trends in annual or seasonal total-flow volume also had significant upward trends in base-flow volume for the same period. Precipitation

  20. Testing and comparison of four ionic tracers to measure stream flow loss by multiple tracer injection

    USGS Publications Warehouse

    Zellweger, G.W.

    1994-01-01

    An injectate containing lithium, sodium, chloride and bromide was added continuously at five sites along a 507 m study reach of St Kevin Gulch, Lake County, Colorado to determine which sections of the stream were losing water to the stream bed and to ascertain how well the four tracers performed. The acidity of the stream (pH 3.6) made it possible for lithium and sodium, which are normally absorbed by ion exchange with stream bed sediment, to be used as conservative tracers. Net flow losses as low as 0.81 s-1, or 8% of flow, were calculated between measuring sites. By comparing the results of simultaneous injection it was determined whether subsections of the study reach were influent or effluent. Evaluation of tracer concentrations along 116 m of stream indicated that all four tracers behaved conservatively. Discharges measured by Parshall flumes were 4-18% greater than discharges measured by tracer dilution. -from Author

  1. Passive microfluidic control of two merging streams by capillarity and relative flow resistance.

    PubMed

    Kim, Sung-Jin; Lim, Yong Taik; Yang, Haesik; Shin, Yong Beom; Kim, Kyuwon; Lee, Dae-Sik; Park, Se Ho; Kim, Youn Tae

    2005-10-01

    In the progress of microfluidic devices, a simple and precise control of multiple streams has been essential for complex microfluidic networks. Consequently, microfluidic devices, which have a simple structure, typically use external energy sources to control the multiple streams. Here, we propose a pure passive scheme that uses capillarity without using external force or external regulation to control the merging of two streams and even to regulate their volumetric flow rate (VFR). We accomplish this process by controlling the geometry of two inlets and a junction, and by regulating the hydrophilicity of a substrate. Additionally, we use the relative flow resistance to control the VFR ratio of the merged two streams. Our results will significantly simplify the control of multiple streams without sacrificing precision.

  2. Tree leaf control on low flow water quality in a small Virginia stream

    USGS Publications Warehouse

    Slack, K.V.; Feltz, H.R.

    1968-01-01

    Impaired water quality in a small stream was related to autumn leaf fall from riparian vegetation. Dissolved oxygen and pH decreased, and water color, specific conductance, iron, manganese, and bicarbonate values increased as the rate of leaf fall increased. Similar quality changes occurred in laboratory cultures of tree leaves in filtered stream water, but the five leaf species studied produced widely differing results. Stream quality improved rapidly following channel flushing by storm flow. Organic loading by tree litter can exert significant control on water composition, especially during low flow.

  3. 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).

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. Pool-type fishways: two different morpho-ecological cyprinid species facing plunging and streaming flows.

    PubMed

    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.

  9. 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.

  10. 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

  11. Estimating the magnitude of peak flows for streams in Kentucky for selected recurrence intervals

    USGS Publications Warehouse

    Hodgkins, Glenn A.; Martin, Gary R.

    2003-01-01

    This report gives estimates of, and presents techniques for estimating, the magnitude of peak flows for streams in Kentucky for recurrence intervals of 2, 5, 10, 25, 50, 100, 200, and 500 years. A flowchart in this report guides the user to the appropriate estimates and (or) estimating techniques for a site on a specific stream. Estimates of peak flows are given for 222 U.S. Geological Survey streamflow-gaging stations in Kentucky. In the development of the peak-flow estimates at gaging stations, a new generalized skew coefficient was calculated for the State. This single statewide value of 0.011 (with a standard error of prediction of 0.520) is more appropriate for Kentucky than the national skew isoline map in Bulletin 17B of the Interagency Advisory Committee on Water Data. Regression equations are presented for estimating the peak flows on ungaged, unregulated streams in rural drainage basins. The equations were developed by use of generalized-least-squares regression procedures at 187 U.S. Geological Survey gaging stations in Kentucky and 51 stations in surrounding States. Kentucky was divided into seven flood regions. Total drainage area is used in the final regression equations as the sole explanatory variable, except in Regions 1 and 4 where main-channel slope also was used. The smallest average standard errors of prediction were in Region 3 (from -13.1 to +15.0 percent) and the largest average standard errors of prediction were in Region 5 (from -37.6 to +60.3 percent). One section of this report describes techniques for estimating peak flows for ungaged sites on gaged, unregulated streams in rural drainage basins. Another section references two previous U.S. Geological Survey reports for peak-flow estimates on ungaged, unregulated, urban streams. Estimating peak flows at ungaged sites on regulated streams is beyond the scope of this report, because peak flows on regulated streams are dependent upon variable human activities.

  12. 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.

  13. 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...

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Methods for estimating flow-duration and annual mean-flow statistics for ungaged streams in Oklahoma

    USGS Publications Warehouse

    Esralew, Rachel A.; Smith, S. Jerrod

    2010-01-01

    Flow statistics can be used to provide decision makers with surface-water information needed for activities such as water-supply permitting, flow regulation, and other water rights issues. Flow statistics could be needed at any location along a stream. Most often, streamflow statistics are needed at ungaged sites, where no flow data are available to compute the statistics. Methods are presented in this report for estimating flow-duration and annual mean-flow statistics for ungaged streams in Oklahoma. Flow statistics included the (1) annual (period of record), (2) seasonal (summer-autumn and winter-spring), and (3) 12 monthly duration statistics, including the 20th, 50th, 80th, 90th, and 95th percentile flow exceedances, and the annual mean-flow (mean of daily flows for the period of record). Flow statistics were calculated from daily streamflow information collected from 235 streamflow-gaging stations throughout Oklahoma and areas in adjacent states. A drainage-area ratio method is the preferred method for estimating flow statistics at an ungaged location that is on a stream near a gage. The method generally is reliable only if the drainage-area ratio of the two sites is between 0.5 and 1.5. Regression equations that relate flow statistics to drainage-basin characteristics were developed for the purpose of estimating selected flow-duration and annual mean-flow statistics for ungaged streams that are not near gaging stations on the same stream. Regression equations were developed from flow statistics and drainage-basin characteristics for 113 unregulated gaging stations. Separate regression equations were developed by using U.S. Geological Survey streamflow-gaging stations in regions with similar drainage-basin characteristics. These equations can increase the accuracy of regression equations used for estimating flow-duration and annual mean-flow statistics at ungaged stream locations in Oklahoma. Streamflow-gaging stations were grouped by selected drainage

  19. 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.

  20. 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

  1. 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.

  2. 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

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

    PubMed

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

    2016-04-19

    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.

  4. Low-speed wind-tunnel investigation of the aerodynamic and acoustic performance of a translating grid choked flow inlet

    NASA Technical Reports Server (NTRS)

    Abbott, J. M.; Miller, B. A.; Golladay, R. L.

    1974-01-01

    The aerodynamic and acoustic performance of a translating grid choked-flow inlet was determined in a low-speed wind tunnel at free-stream velocities of 24, 32, and 45 m/sec and incidence angles of 0, 10, 20, 30, 35, 40, 45, and 50 deg. The inlet was sized to fit a 13.97- centimeter-diameter fan with a design weight flow of 2.49 kg/sec. Measurements were made to determine inlet total pressure recovery, flow distortion, and sound pressure level for both choked and unchoked geometries over a range of inlet weight flows. For the unchoked geometry, inlet total pressure recovery ranged from 0.983 to 0.989 at incidence angles less than 40 deg. At 40 deg incidence angle, inlet cowl separation was encountered which resulted in lower values of pressure recovery and higher levels of fan broadband noise. For the choked geometry, increasing total pressure losses occurred with increasing inlet weight flow that prevented the inlet from reaching full choked conditions with the particular fan used. These losses were attributed to the high Mach number drag rise characteristics of airfoil grid. At maximum attainable inlet weight flow, the total pressure recovery at static conditions was 0.935. The fan blade passing frequency and other fan generated pure tones were eliminated from the noise spectrum, but the broadband level was increased.

  5. 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

  6. Observation of acoustic streaming in water/sensor plate/thin water layer/128YX-LiNbO3 for realizing disposable digital microfluidic system

    NASA Astrophysics Data System (ADS)

    Kondoh, Jun; Toyoizumi, Hitoshi

    2012-09-01

    One application of a surface acoustic wave (SAW) device is a droplet manipulator. If a sensor is fabricated on the manipulation surface, digital microfluidic system (DMFS) is realized. For disposable application, structure of sensor plate/liquid layer/ 128YX-LiNbO3 is proposed. In this paper, acoustic streaming on a DMFS is experimentally observed. As the streaming in a droplet depends on a contact angle, it in the tank was observed. The radiation patterns on the 128YX-LiNbO3 and sensor plate are differences. The results indicate that the radiation on the sensor plate depends on plate material and thickness.

  7. 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.

  8. A computational approach for flow-acoustic coupling in closed side branches.

    PubMed

    Radavich, P M; Selamet, A; Novak, J M

    2001-04-01

    The quarter-wave resonator, which produces a narrow band of high acoustic attenuation at regularly spaced frequency intervals, is a common type of silencer used in ducts. The presence of mean flow in the main duct, however, is likely to promote an interaction between these acoustic resonances and the flow. The coupling for some discrete flow conditions leads to the production of both large wave amplitudes in the side branch and high noise levels in the main duct, thereby transforming the quarter-wave silencer into a noise generator. The present approach employs computational fluid dynamics (CFD) to model this complex interaction between the flow and acoustic resonances at low Mach number by solving the unsteady, turbulent, and compressible Navier-Stokes equations. Comparisons between the present computations and the experiments of Ziada [PVP-Vol. 258, ASME, 35-59 (1993)] for a system with two coaxial side branches show that the method is capable of reproducing the physics of the flow-acoustic coupling and predicting the flow conditions when the coupling occurs. The theory of Howe [IMA J. Appl. Math. 32, 187-209 (1984)] is then employed to determine the location and timing of the acoustic power production during a cycle.

  9. 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.

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

    USGS Publications Warehouse

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

    2015-01-01

    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.

  11. 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.

  12. Field and laboratory experiments on high dissolution rates of limestone in stream flow

    NASA Astrophysics Data System (ADS)

    Hattanji, Tsuyoshi; Ueda, Mariko; Song, Wonsuh; Ishii, Nobuyuki; Hayakawa, Yuichi S.; Takaya, Yasuhiko; Matsukura, Yukinori

    2014-01-01

    Field and laboratory experiments were performed to examine dissolution rates of limestone in stream flow. Field experiments were conducted in three stream sites (A-C) with different lithological or hydrological settings around a limestone plateau in the Abukuma Mts., Japan. Sites A and B are allogenic streams, which flow from non-limestone sources into dolines, and site C has a karst spring source. Tablets made of limestone from the same plateau with a diameter of 3.5 cm and a thickness of 1 cm were placed in the streams for 3 years (2008-2011) where alkalinity, pH and major cation concentrations were measured periodically. The saturation indices of calcite (SIc) of stream water were - 2.8 ± 0.4 at site A, - 2.5 ± 0.4 at site B and - 0.5 ± 0.4 at site C. Annual weight loss ratios for tablets were extremely high at site A (0.11-0.14 mg cm- 2 d- 1), high at site B (0.05 mg cm- 2 d- 1), and low at site C (0.005 mg cm- 2 d- 1). The contrasting rates of weight loss are mainly explained by chemical conditions of stream water. In addition, laboratory experiments for dissolution of limestone tablets using a flow-through apparatus revealed that flow conditions around the limestone tablet is another important factor for dissolution in the stream environment. These results revealed that limestone dissolves at a rapid rate where water unsaturated to calcite continuously flows, such as in an allogenic stream.

  13. 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.

  14. 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)

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. Restoring native fish assemblages to a regulated California stream using the natural flow regime concept.

    PubMed

    Kiernan, Joseph D; Moyle, Peter B; Crain, Patrick K

    2012-07-01

    We examined the response of fishes to establishment of a new flow regime in lower Putah Creek, a regulated stream in California, U.S.A. The new flow regime was designed to mimic the seasonal timing of natural increases and decreases in stream flow. We monitored fish assemblages annually at six sample sites distributed over approximately 30 km of stream for eight years before and nine years after the new flow regime was implemented. Our purpose was to determine whether more natural stream flow patterns would reestablish native fishes and reduce the abundances of alien (nonnative) fishes. At the onset of our study, native fishes were constrained to habitat immediately (<1 km) below the diversion dam, and alien species were numerically dominant at all downstream sample sites. Following implementation of the new flow regime, native fishes regained dominance across more than 20 km of lower Putah Creek. We propose that the expansion of native fishes was facilitated by creation of favorable spawning and rearing conditions (e.g., elevated springtime flows), cooler water temperatures, maintenance of lotic (flowing) conditions over the length of the creek, and displacement of alien species by naturally occurring high-discharge events. Importantly, restoration of native fishes was achieved by manipulating stream flows at biologically important times of the year and only required a small increase in the total volume of water delivered downstream (i.e., water that was not diverted for other uses) during most water years. Our results validate that natural flow regimes can be used to effectively manipulate and manage fish assemblages in regulated rivers.

  20. 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.

  1. Proper Orthogonal Decomposition Analysis of Shear-Coaxial Injector Flows with and without Transverse Acoustic Forcing

    DTIC Science & Technology

    2011-10-26

    ORGANIZATION REPORT NUMBER Air Force Research Laboratory (AFMC) AFRL/RZSA 10 E. Saturn Blvd. Edwards AFB CA 93524-7680 AFRL-RZ-ED-VG-2011-435 9...nitrogen jets to pressure perturbations due to transverse acoustic forcing at a pressure antinode ( PAN ). The role of injector exit geometry on the flow...Set-Up: Pressure Antinode • Pressure antinode ( PAN ) – condition of maximum pressure perturbation in the acoustic field • Piezo-sirens forced in

  2. Proper Orthogonal Decomposition Analysis of Shear-Coaxial Injector Flows With and Without Transverse Acoustic Forcing

    DTIC Science & Technology

    2011-10-13

    ORGANIZATION REPORT NUMBER Air Force Research Laboratory (AFMC) AFRL/RZSA 10 E. Saturn Blvd. Edwards AFB CA 93524-7680 AFRL-RZ-ED-TP-2011-402 9...nitrogen jets to pressure perturbations due to transverse acoustic forcing at a pressure antinode ( PAN ). The role of injector exit geometry on the flow...cryogenic coaxial nitrogen jets to pressure perturbations due to transverse acoustic forcing at a pressure antinode ( PAN ). The role of injector exit

  3. Numerical Investigation of the Spatiotemporal Contribution of Tile Drainage to Stream Flow

    NASA Astrophysics Data System (ADS)

    Thomas, N. W.; Schilling, K. E.; Weber, L. J.

    2015-12-01

    Tile drainage systems are pervasive in the Central U.S., significantly altering the hydrologic system. A physically based coupled hydrologic model was applied to a 45 km2 agricultural Iowa watershed. The tile drainage contribution to stream flow (QT/Q) was derived from a tracer driven analysis of instream surface water. QT/Q varied instantaneously from 6% to 71 % at the basin outlet, with tile flow correlating linearly with total stream flow. In low precipitation periods 62 % of stream flow traveled through the tile system. In heavy precipitation periods a dilution effect shifted QT/Q to 27 %. Precipitation driven events produced a strong positive logarithmic correlation between QT/Q and drainage area. The addition of precipitation into the system saturated near surface soils, increased lateral soil water movement, and diluted the relatively stable instream tile flow. A negative logarithmic trend in QT/Q to drainage area persisted non-event durations. Larger groundwater (non-tile) contribution to stream flow at the outlet diluted instream tile flow at increased drainage areas. Logarithmic regression slopes were consistent for event and non-event periods, respectively. While, the intercept responded in a predicable manner to precipitation intensity. This study, indicates a strong systematic response of QT/Q to meteorological forcing, drainage area over a single year.

  4. Probability density functions of the stream flow discharge in linearized diffusion wave models

    NASA Astrophysics Data System (ADS)

    Chang, Ching-Min; Yeh, Hund-Der

    2016-12-01

    This article considers stream flow discharge moving through channels subject to the lateral inflow and described by a linearized diffusion wave equation. The variability of lateral inflow is manifested by random fluctuations in time, which is the only source of uncertainty as to flow discharge quantification. The stochastic nature of stream flow discharge is described by the probability density function (PDF) obtained using the theory of distributions. The PDF of the stream flow discharge depends on the hydraulic properties of the stream flow, such as the wave celerity and hydraulic diffusivity as well as the temporal correlation scale of the lateral inflow rate fluctuations. The focus in this analysis is placed on the influence of the temporal correlation scale and the wave celerity coefficient on the PDF of the flow discharge. The analysis demonstrates that a larger temporal correlation scale causes an increase of PDF of the lateral inflow rate and, in turn, the PDF of the flow discharge which is also affected positively by the wave celerity coefficient.

  5. Experimental studies of the streaming flow due to the adsorption of particles at a liquid surface

    NASA Astrophysics Data System (ADS)

    Singh, Pushpendra; Musunuri, Naga; Fischer, Ian

    2016-11-01

    The particle image velocimetry (PIV) technique is used to study the streaming flow that is induced when particles are adsorbed at a liquid surface. The flow develops within a fraction of second after the adsorption of the particle and persists for several seconds. The fluid directly below the particle rises upward, and near the surface, it moves away from the particle. The flow causes powders sprinkled on a liquid surface to disperse on the surface. 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.

  6. 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

  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. 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.

  9. 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.

  10. 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.

  11. Low-flow characteristics and profiles for selected streams in the Roanoke River basin, North Carolina

    USGS Publications Warehouse

    Weaver, J.C.

    1996-01-01

    An understanding of the magnitude and frequency of low-flow discharges is an important part of protecting surface-water resources and planning for municipal and industrial economic expansion. Low-flow characteristics are summarized for 22 continuous-record gaging stations in North Carolina (19 sites) and Virginia (3 sites) and 60 partial-record gaging stations in the North Carolina Roanoke River Basin. Records of discharge collected through the 1994 water year are used. Flow characteristics included in the summary are (1) average annual unit flow, (2) 7Q10 low-flow discharge, the minimum average discharge for a 7-consecutive-day period occurring, on average, once in 10 years; (3) 30Q2 low-flow discharge; (4) W7Q10 low-flow discharge, similar to 7Q10 discharge except that flow during November through March only is considered; and (5) 7Q2 low-flow discharge. The potential for sustaining base flows is moderate to high in the western part of the basin as well as in the eastern and western fringes of the Piedmont and Coastal Plain physiographic provinces, respectively. Areas of low potential for sustaining base flow exist in the central part of the basin (between eastern Caswell County and western Warren County), where soils have low infiltration rates, and in lower regions of the Coastal Plain, where small streams tend to have zero flow during prolonged drought. Drainage area and low-flow discharge profiles are presented for 10 streams in the Roanoke River Basin in North Carolina and reflect a wide range in basin size, characteristics, and streamflow conditions. The selected streams are Town Fork Creek, Hogans Creek, Mayo River, Buffalo Creek, Smith River, Country Line Creek, Dan River, Marlow Creek, Hyco River, and Roanoke River. The drainage-area profiles show the increases in drainage areas as streams travel their course in the basin. At the mouths of streams profiles, the drainage areas range from 22 miles to about 9,700 miles. Low-flow discharges for each stream

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. IOD and ENSO impacts on the extreme stream-flows of Citarum river in Indonesia

    NASA Astrophysics Data System (ADS)

    Sahu, Netrananda; Behera, Swadhin K.; Yamashiki, Yosuke; Takara, Kaoru; Yamagata, Toshio

    2012-10-01

    Extreme stream-flow events of Citarum River are derived from the daily stream-flows at the Nanjung gauge station. Those events are identified based on their persistently extreme flows for 6 or more days during boreal fall when the seasonal mean stream-flow starts peaking-up from the lowest seasonal flows of June-August. Most of the extreme events of high-streamflows were related to La Niña conditions of tropical Pacific. A few of them were also associated with the negative phases of IOD and the newly identified El Niño Modoki. Unlike the cases of extreme high streamflows, extreme low streamflow events are seen to be associated with the positive IODs. Nevertheless, it was also found that the low-stream-flow events related to positive IOD events were also associated with El Niño events except for one independent event of 1977. Because the occurrence season coincides the peak season of IOD, not only the picked extreme events are seen to fall under the IOD seasons but also there exists a statistically significant correlation of 0.51 between the seasonal IOD index and the seasonal streamflows. There also exists a significant lag correlation when IOD of June-August season leads the streamflows of September-November. A significant but lower correlation coefficient (0.39) is also found between the seasonal streamflow and El Niño for September-November season only.

  19. Can gene flow have negative demographic consequences? Mixed evidence from stream threespine stickleback

    PubMed Central

    Moore, Jean-Sébastien; Hendry, Andrew P.

    2009-01-01

    Dispersal and gene flow can have both positive and negative effects on population size, but little empirical support from nature exists for the negative effects. We test for such effects in a stream population of threespine stickleback (Gasterosteus aculeatus L.) that is subject to high gene flow from a lake and is thus maladapted to stream conditions. In this system, maladaptation increases with distance along the stream, and this increase is associated with decreasing population densities until stickleback are no longer present (2.5 km from the lake). We conducted field experiments to inform whether this association might reflect a negative role for gene flow in constraining population size and therefore causing a local range limit. We specifically tested predictions deriving from theory: peripheral populations should show partial local adaptation, be under strong selection and not simply be maintained by dispersal. First, a transplant experiment suggested a weak home-site advantage in the peripheral population. Second, a mark–recapture study showed directional selection for a stream-adapted phenotype in 1 of 2 years. Third, another mark–recapture experiment showed that dispersal is limited to the point that positive demographic effects of dispersal are probably minimal. We conclude that, although gene flow does constrain morphological maladaptation in the outlet stream population, the evidence for its contribution to population size and range limits is mixed. We discuss the implications of our work for the study of factors influencing the evolution of species' ranges. PMID:19414468

  20. 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.

    2016-09-06

    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

  1. 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.

  2. (A new time of flight) Acoustic flow meter using wide band signals and adaptive beamforming techniques

    NASA Astrophysics Data System (ADS)

    Murgan, I.; Ioana, C.; Candel, I.; Anghel, A.; Ballester, J. L.; Reeb, B.; Combes, G.

    2016-11-01

    In this paper we present the result of our research concerning the improvement of acoustic time of flight flow metering for water pipes. Current flow meters are based on the estimation of direct time of flight by matched filtering of the received and emitted signals by acoustic transducers. Currently, narrow band signals are used, as well as a single emitter/receptor transducer configuration. Although simple, this configuration presents a series of limitations such as energy losses due to pipe wall/water interface, pressure/flow transients, sensitivity to flow induced vibrations, acoustic beam deformations and shift due to changes in flow velocity and embedded turbulence in the flow. The errors associated with these limitations reduce the overall robustness of existing flow meters, as well as the measured flow rate range and lower accuracy. In order to overcome these limitations, two major innovations were implemented at the signal processing level. The first one concerns the use of wide band signals that optimise the power transfer throughout the acoustic path and also increase the number of velocity/flow readings per second. Using wide band signals having a high duration-bandwidth product increases the precision in terms of time of flight measurements and, in the same time, improves the system robustness. The second contribution consists in the use of a multiple emitter - multiple receivers configuration (for one path) in order to compensate the emitted acoustic beam shift, compensate the time of flight estimation errors and thus increase the flow meter's robustness in case of undesired effects such as the “flow blow” and transient/rapid flow rate/velocity changes. Using a new signal processing algorithm that take advantage of the controlled wide band content coming from multiple receivers, the new flow meters achieves a higher accuracy in terms of flow velocity over a wider velocity range than existing systems. Tests carried out on real scale experimental

  3. 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.

  4. 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

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

    SciTech Connect

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

    2016-02-13

    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 flowpaths. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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

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

    DOEpatents

    Sinha, Dipen N.; Pantea, Cristian

    2016-09-13

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

  11. Monthly low-flow characteristics of Georgia streams

    USGS Publications Warehouse

    Carter, R.F.; Fanning, J.D.

    1982-01-01

    Statistics of monthly minimum flows are presented for 129 streamflow stations for each month of the year. Flow statistics provided are the log-Pearson Type III distribution. The probable magnitude of average standard errors due to time-sampling bias is tabulated. The average standard errors were found to be similar over a wide area comprising approximately the northern two-thirds of the State. In this area, the average standard error of estimate for a low-flow statistic with a recurrence interval of 20 years and estimated on the basis of 10 years of record is about 17%. In the southern third of the State, the average standard errors were found to lie in a narrow range, but were significantly greater than in the north. In the southern area, the average standard error of estimate for a low flow statistic with a recurrence interval of 20 years and estimated on the basis of 10 years of record is about 40%. (USGS)

  12. Estimating the magnitude and frequency of low flows of streams in Massachusetts

    USGS Publications Warehouse

    Risley, J.C.

    1994-01-01

    The report presents techniques used for estimating 7-day 2-year (7Q2) and 7-day 10-year (7Q10) flows at continuous-record streamflow-gaging stations, partial-record stations, and ungaged sites on streams in Massachusetts. A two-parameter log-normal probability distribution was used to compute low flows at 31 continuous-record stream-flow-gaging stations. Graphical and mathematical techniques were used to estimate low flows at partial-record stations. Regional regression techniques commonly are used to estimate 7Q2 and 7Q10 flows at ungaged stream sites. The development and application of a low-flow regression model is described. The model contains two parameters, mean and standard deviation, computed from separate regression equations that use total drainage area and basin relief as independent variables. The coefficients of determination of the mean and standard deviation regression equations are 0.964 and 0.960, respec- tively; the percentage of standard error of the regression of each equation are 35 and 34, respec- tively. The model is applicable for basins in Massachusetts having a drainage area of 5 to 150 square miles, a slope of less than 4 percent, and an area of stratified drift greater than 4 percent of the total drainage area. A computer program is presented that can be used to compute 7Q2 and 7Q10 flows and the 95-percent intervals of confidence and prediction for a given basin.

  13. 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.

  14. Methods for estimating low-flow characteristics of ungaged streams in selected areas, northern Florida

    USGS Publications Warehouse

    Rumenik, R.P.; Grubbs, J.W.

    1996-01-01

    Methods for estimating low-flow frequency characteristics at ungaged sites were developed for two areas in northern Florida. In the Yellow, Blackwater, Escambia, and Perdido River Basins study area (northwestern Florida), regional regression equations were developed for estimating the 7- and 30-day, 2- and 10-year low-flow characteristic (Q7,2, Q7,10, Q30,2, and Q30,10) by determining values of basin characteristics from digital Geographical Information System (GIS) coverages or hardcopy maps. A GIS, ARC-INFO, was used to quantify basin characteristics that were used in regression equations. Sources of digital data used in this analysis are elevation data, from a digital elevation model, stream length and location data from a digital hydrography coverage, and watershed boundaries digitized from topographic maps. The most accurate regression equations employed a basin characteristic that was based on a simple conceptual model of one- dimensional ground-water flow using Darcy's law. Slightly less accurate equations were obtained using drainage area as the only explanatory variable. The standard error of prediction for the Darcy and drainage area equations of Q7,2 was 65 and 74 percent, respectively; Q7,10, 58 and 62 percent, respectively; Q30,2, 51 and, 54 percent, respectively; and Q30,10, 44 and 51 percent, respectively. In the Santa Fe River Basin study area (northeastern Florida), a flow-routing method was used to estimate low-flow characteristics at ungaged sites from low stream- flow analyses based on records at gaged sites. The use of the flow-routing method is suggested for areas where regression analysis proves unsuccessful, where low-flow characteristics have been defined at a significant number of sites, and where information about the basin characteristics has been thoroughly researched. Low-flow frequency characteristics determined at 40 sites and measurements made during five synoptic runs in 1989-91 were used to develop a flow-routing method. Low-flow

  15. 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.

  16. 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

  17. Integration of manual channel initiation and flow path tracing in extracting stream features from lidar-derived DTM

    NASA Astrophysics Data System (ADS)

    Gaspa, M. C.; De La Cruz, R. M.; Olfindo, N. T.; Borlongan, N. J. B.; Perez, A. M. C.

    2016-10-01

    Stream network delineation based on LiDAR-derived digital terrain model (DTM) may produce stream segments that are inexistent or incomplete because of limitations imposed by extraction procedure, terrain and data. The applicability of a common threshold value in defining streams such as those implemented through the D8 algorithm also remains in question because the threshold varies depending on the geomorphology of the area. Flat areas and improper hydrologic conditioning produce erratic stream network. To counteract these limitations, this study proposes a workflow that improves the stream network produced by the D8 algorithm. It incorporates user-defined channel initiation points as inputs to a tool developed to automatically trace the flow of water into the next actual stream segment. Spurious streams along digital dams and flat areas are also manually reshaped. The proposed workflow is implemented in Iligan River Basin, Philippines using LiDARderived DTM of 1-meter resolution. The Flow Path Tracing (FPT) method counteracts the limits imposed by extraction procedure, terrain and data. It is applicable to different typologies of watersheds by eliminating the need to use site-specific threshold in determining streams. FPT is implemented as a Phyton script to automate the tracing of the streams using the flow direction raster. The FPT method is compared to the blue line digitization and the D8 method using morphometric parameters, such as stream number, stream order and stream length, to assess its performance. Results show that streams derived from the FPT method has higher stream order, number and length. An accuracy of 93.5% produced from field validation of the FPT method's streams strengthens the findings that integrating manual channel head initiation and flow path tracing can be used for nationwide extraction of streams using LiDAR-derived-DTM in the Philippines.

  18. 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

  19. 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 ...

  20. 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...

  1. Ptaquiloside from bracken in stream water at base flow and during storm events.

    PubMed

    Clauson-Kaas, Frederik; Ramwell, Carmel; Hansen, Hans Chr B; Strobel, Bjarne W

    2016-12-01

    The bracken fern (Pteridium spp.) densely populates both open and woodland vegetation types around the globe. Bracken is toxic to livestock when consumed, and a group of potent illudane-type carcinogens have been identified, of which the compound ptaquiloside (PTA) is the most abundant. The highly water soluble PTA has been shown to be leachable from bracken fronds, and present in the soil and water below bracken stands. This has raised concerns over whether the compound might pose a risk to drinking water sources. We investigated PTA concentrations in a small stream draining a bracken-infested catchment at base flow and in response to storm events during a growth season, and included sampling of the bracken canopy throughfall. Streams in other bracken-dominated areas were also sampled at base flow for comparison, and a controlled pulse experiment was conducted in the field to study the in-stream dynamics of PTA. Ptaquiloside concentrations in the stream never exceeded 61 ng L(-1) in the base flow samples, but peaked at 2.2 μg L(-1) during the studied storm events. The mass of PTA in the stream, per storm event, was 7.5-93 mg from this catchment. A clear temporal connection was observed between rainfall and PTA concentration in the stream, with a reproducible time lag of approx. 1 h from onset of rain to elevated concentrations, and returning rather quickly (about 2 h) to base flow concentration levels. The concentration of PTA behaved similar to an inert tracer (Cl(-)) in the pulse experiment over a relative short time scale (minutes-hours) reflecting no PTA sorption, and dispersion and dilution considerably lowered the observed PTA concentrations downstream. Bracken throughfall revealed a potent and lasting source of PTA during rainfall, with concentrations up to 169 μg L(-1), that did not decrease over the course of the event. In the stream, the throughfall contribution to PTA cannot be separated from a possible below-ground input from litter, rhizomes

  2. 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.

  3. 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.

  4. Regression Equations for Estimating Flood Flows at Selected Recurrence Intervals for Ungaged Streams in Pennsylvania

    USGS Publications Warehouse

    Roland, Mark A.; Stuckey, Marla H.

    2008-01-01

    Regression equations were developed for estimating flood flows at selected recurrence intervals for ungaged streams in Pennsylvania with drainage areas less than 2,000 square miles. These equations were developed utilizing peak-flow data from 322 streamflow-gaging stations within Pennsylvania and surrounding states. All stations used in the development of the equations had 10 or more years of record and included active and discontinued continuous-record as well as crest-stage partial-record stations. The state was divided into four regions, and regional regression equations were developed to estimate the 2-, 5-, 10-, 50-, 100-, and 500-year recurrence-interval flood flows. The equations were developed by means of a regression analysis that utilized basin characteristics and flow data associated with the stations. Significant explanatory variables at the 95-percent confidence level for one or more regression equations included the following basin characteristics: drainage area; mean basin elevation; and the percentages of carbonate bedrock, urban area, and storage within a basin. The regression equations can be used to predict the magnitude of flood flows for specified recurrence intervals for most streams in the state; however, they are not valid for streams with drainage areas generally greater than 2,000 square miles or with substantial regulation, diversion, or mining activity within the basin. Estimates of flood-flow magnitude and frequency for streamflow-gaging stations substantially affected by upstream regulation are also presented.

  5. 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.

    2015-12-24

    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.

  6. 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

  7. 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

  8. 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-...

  9. Morphodynamic Response of Laboratory Stream Beds to Unsteady Flow Events of Varying Magnitude and Duration

    NASA Astrophysics Data System (ADS)

    Binns, A. D.; Gunsolus, E. H.

    2014-12-01

    Natural processes and anthropogenic activities can cause short-term flow increases in rivers. These changes in flow, such as those caused by extreme rainfall events or seasonal variation in precipitation patterns, can result in substantial, and sometimes quite rapid, adjustments in sediment regime and alluvial stream morphology. Such morphological adjustments can pose short-term erosion hazards, increased risk of flooding, degradation to aquatic habitat, damage to in-stream engineering infrastructure, and re-mobilization of pollutants. Alterations in river hydraulics, sediment transport and stream morphology from specific unsteady events prove challenging to accurately predict and assess. This research quantifies the morphodynamic response of stream beds to unsteady flow events of varying magnitude and duration. For this purpose, a series of experimental runs is conducted in a 0.31 m-wide, 5.0 m-long laboratory sediment transport flume comprised of a well-sorted medium sand. All runs start from flat-bed initial conditions with a given longitudinal slope. The bed is allowed to develop under constant base-flow (antecedent) conditions until equilibrium conditions are reached. For each run a prescribed increase in flow rate for a pre-determined duration is applied to simulate the unsteady flow event. The magnitude of the increase in flow rate and the duration of the event are systematically varied from run to run. In each run measurements of bed morphology are conducted prior to the event (during antecedent flow conditions), at the conclusion of the event, and following a return base-flow (antecedent) conditions. Sediment transport rates are monitored throughout each run. The morphological response and the time-scale of the bed adjustments to unsteady events is quantified. The effect of the magnitude and duration of the flow increase on this increase is evaluated. This study contributes to the development of predictive tools for engineers and hydrologists to better

  10. 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.

  11. The use of a continuous flow-reactor employing a mixed hydrogen-liquid flow stream for the efficient reduction of imines to amines.

    PubMed

    Saaby, Steen; Knudsen, Kristian Rahbek; Ladlow, Mark; Ley, Steven V

    2005-06-21

    Imines have been reduced to amines in high yield, and with excellent chemoselectivity, by catalytic hydrogenation in a continuous flow-reactor, utilising an electrochemically-generated hydrogen source to produce a mixed hydrogen-liquid flow stream.

  12. 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.

  13. High amplitude nonlinear acoustic wave driven flow fields in cylindrical and conical resonators.

    PubMed

    Antao, Dion Savio; Farouk, Bakhtier

    2013-08-01

    A high fidelity computational fluid dynamic model is used to simulate the flow, pressure, and density fields generated in a cylindrical and a conical resonator by a vibrating end wall/piston producing high-amplitude standing waves. The waves in the conical resonator are found to be shock-less and can generate peak acoustic overpressures that exceed the initial undisturbed pressure by two to three times. A cylindrical (consonant) acoustic resonator has limitations to the output response observed at one end when the opposite end is acoustically excited. In the conical geometry (dissonant acoustic resonator) the linear acoustic input is converted to high energy un-shocked nonlinear acoustic output. The model is validated using past numerical results of standing waves in cylindrical resonators. The nonlinear nature of the harmonic response in the conical resonator system is further investigated for two different working fluids (carbon dioxide and argon) operating at various values of piston amplitude. The high amplitude nonlinear oscillations observed in the conical resonator can potentially enhance the performance of pulse tube thermoacoustic refrigerators and these conical resonators can be used as efficient mixers.

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  17. Acoustic programming in step-split-flow lateral-transport thin fractionation.

    PubMed

    Ratier, Claire; Hoyos, Mauricio

    2010-02-15

    We propose a new separation scheme for micrometer-sized particles combining acoustic forces and gravitational field in split-flow lateral-transport thin (SPLITT)-like fractionation channels. Acoustic forces are generated by ultrasonic standing waves set up in the channel thickness. We report on the separation of latex particles of two different sizes in a preliminary experiment using this proposed hydrodynamic acoustic sorter, HAS. Total binary separation of 5 and 10 microm diameter particles has been achieved. Numerical simulations of trajectories of particles flowing through a step-SPLITT under the conditions which combine acoustic standing waves and gravity show a very good agreement with the experiment. Calculations in order to compare separations obtained by the acoustic programming s-SPLITT fractionation and the conventional SPLITT fractionation show that the improvement in separation time is around 1 order of magnitude and could still be improved; this is the major finding of this work. This separation technique can be extended to biomimetic particles and blood cells.

  18. 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.

  19. 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

  20. 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

  1. Ground water stratification and delivery of nitrate to an incised stream under varying flow conditions

    USGS Publications Warehouse

    Böhlke, J.K.; O'Connell, M. E.; Prestegaard, K.L.

    2007-01-01

    Ground water processes affecting seasonal variations of surface water nitrate concentrations were investigated in an incised first-order stream in an agricultural watershed with a riparian forest in the coastal plain of Maryland. Aquifer characteristics including sediment stratigraphy, geochemistry, and hydraulic properties were examined in combination with chemical and isotopic analyses of ground water, macropore discharge, and stream water. The ground water flow system exhibits vertical stratification of hydraulic properties and redox conditions, with sub-horizontal boundaries that extend beneath the field and adjacent riparian forest. Below the minimum water table position, ground water age gradients indicate low recharge rates (2-5 cm yr-1) and long residence times (years to decades), whereas the transient ground water wedge between the maximum and minimum water table positions has a relatively short residence time (months to years), partly because of an upward increase in hydraulic conductivity. Oxygen reduction and denitrification in recharging ground waters are coupled with pyrite oxidation near the minimum water table elevation in a mottled weathering zone in Tertiary marine glauconitic sediments. The incised stream had high nitrate concentrations during high flow conditions when much of the ground water was transmitted rapidly across the riparian zone in a shallow oxic aquifer wedge with abundant outflow macropores, and low nitrate concentrations during low flow conditions when the oxic wedge was smaller and stream discharge was dominated by upwelling from the deeper denitrified parts of the aquifer. Results from this and similar studies illustrate the importance of near-stream geomorphology and subsurface geology as controls of riparian zone function and delivery of nitrate to streams in agricultural watersheds. ?? ASA, CSSA, SSSA.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Size Differentiation Of A Continuous Stream Of Particles Using Acoustic Emissions

    NASA Astrophysics Data System (ADS)

    Nsugbe, E.; Starr, A.; Foote, P.; Ruiz-Carcel, C.; Jennions, I.

    2016-11-01

    Procter and Gamble (P&G) require an online system that can monitor the particle size distribution of their washing powder mixing process. This would enable the process to take a closed loop form which would enable process optimisation to take place in real time. Acoustic Emission (AE) was selected as the sensing method due to its non-invasive nature and primary sensitivity to frequencies which particle events emanate. This work details the results of the first experiment carried out in this research project. This experiment involved the use of AE to distinguish between the sizes of sieved polyethylene particle (53-250microns) and glass beads (150-600microns) which were dispensed on a target plate using a funnel. By conducting a threshold analysis of the impact peaks in the signal, the sizes of the particles could be distinguished and a signal feature was found which could be directly linked to the sizes of the particles.

  8. 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

  9. Stream habitat analysis using the instream flow incremental methodology

    USGS Publications Warehouse

    Bovee, Ken D.; Lamb, Berton L.; Bartholow, John M.; Stalnaker, Clair B.; Taylor, Jonathan; Henriksen, Jim

    1998-01-01

    This document describes the Instream Flow Methodology in its entirety. This also is to serve as a comprehensive introductory textbook on IFIM for training courses as it contains the most complete and comprehensive description of IFIM in existence today. This should also serve as an official guide to IFIM in publication to counteract the misconceptions about the methodology that have pervaded the professional literature since the mid-1980's as this describes IFIM as it is envisioned by its developers. The document is aimed at the decisionmakers of management and allocation of natural resources in providing them an overview; and to those who design and implement studies to inform the decisionmakers. There should be enough background on model concepts, data requirements, calibration techniques, and quality assurance to help the technical user design and implement a cost-effective application of IFIM that will provide policy-relevant information. Some of the chapters deal with basic organization of IFIM, procedural sequence of applying IFIM starting with problem identification, study planning and implementation, and problem resolution.

  10. Flow of springs and small streams in the Tecolote Tunnel area of Santa Barbara County, California

    USGS Publications Warehouse

    Rantz, S.E.

    1961-01-01

    This report presents the results of an investigation to determine the effect of the construction of Tecolote Tunnel in southern Santa Barbara County, California, on the flow of springs and spring-fed streams in the tunnel area. A program of monthly measurement of discharge for this purpose began in late 1948 at 125 springs and streams; tunnel construction started in March 1950 and was completed in January 1956. By late 1951 appreciable seepage was entering the tunnel. Incidental to the primary objective of this study, but a necessary part of the investigation, were a study of the discharge pattern of the springs and streams of the region, and an evaluation of the effect on flow of both the Arvin-Tehachapi earthquake of July 21, 1952 and the Refugio brush fire of early September 1955. The most striking characteristic of the regimen of flow in the area is the rapid response of discharge to precipitation. An interesting effect was observed in July 1952 when the Arvin-Tehachapi earthquake abruptly increased the flow at 18 measuring sites. At 15 of these sites this effect was felt for only several months, but at three of the sites the effect remained for several years. As for the Refugio fire, there is some reason to believe that the summer flow of many springs and streams may have increased in the years that followed as a result of decreased evapotranspiration losses, but the evidence is inconclusive. The many complex and interrelated factors that influence the discharge of springs and spring-fed streams make it exceedingly difficult to isolate the effect of Tecolote Tunnel on the flow Another major difficulty in evaluating the effect of the tunnel stems from the fact that the calibration period for this study was only three years long, lasting from late 1948 to late 1951, and was uniformly deficient in precipitation, Furthermore, these inadequacies of the calibration period in regard to short length of record and limited range in precipitation, cannot be overcome by

  11. 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.

  12. Effects of Urbanization on the Flow Regimes of Semi-Arid Southern California Streams

    NASA Astrophysics Data System (ADS)

    Hawley, R. J.; Bledsoe, B. P.; Stein, E. D.

    2010-12-01

    Stream channel erosion and associated habitat degradation are pervasive in streams draining urban areas in the southwestern US. The prevalence of these impacts results from the inherent sensitivity of streams in semi-arid climates to changes in flow and sediment regimes, and past inattention to management of geomorphically effective flows. Addressing this issue is difficult due to the lack of data linking ranges of flow (from small to large runoff events) to geomorphic channel response. Forty-three U. S. Geological Survey gages with record lengths greater than ~15 yrs and watershed areas less than ~250 square kilometers were used to empirically model the effects of urbanization on streams in southern California. The watersheds spanned a gradient of urban development and ranged from 0 to 23% total impervious area in 2001. With little flow control at the subdivision scale to date, most impervious area in the region is relatively well-connected to surface-drainage networks. Consequently, total impervious area was an effective surrogate for urbanization, and emerged as a significant (p < 0.05) predictor of instantaneous peak-flow rates at the 1.5- and 2-yr recurrence intervals, with decreasing significance and influence at higher return periods. For example, peak factors for a watershed with 20% imperviousness were ~10, 6, and 2 for the 1.5-, 2-, and 5-yr flows, respectively, with no discernable influence at flows greater than the 10-yr event. Most importantly with respect to geomorphic response, urbanization extent was a significant predictor of duration density functions, which integrate the magnitude and duration of mean daily discharges. This approach expands on previous scaling procedures to produce histogram-style cumulative flow duration graphs for ungaged sites based on urbanization extent and other watershed descriptors. Urbanization resulted in proportionally-longer durations of all geomorphically-effective flows, with a more pronounced effect on the

  13. Broadening of analyte streams due to a transverse pressure gradient in free-flow isoelectric focusing.

    PubMed

    Dutta, Debashis

    2017-02-10

    Pressure-driven cross-flows can arise in free-flow isoelectric focusing systems (FFIEF) due to a non-uniform electroosmotic flow velocity along the channel width induced by the pH gradient in this direction. In addition, variations in the channel cross-section as well as unwanted differences in hydrostatic heads at the buffer/sample inlet ports can also lead to such pressure-gradients which besides altering the equilibrium position of the sample zones have a tendency to substantially broaden their widths deteriorating the separations. In this situation, a thorough assessment of stream broadening due to transverse pressure-gradients in FFIEF devices is necessary in order to establish accurate design rules for the assay. The present article describes a mathematical framework to estimate the noted zone dispersion in FFIEF separations based on the method-of-moments approach under laminar flow conditions. A closed-form expression has been derived for the spatial variance of the analyte streams at their equilibrium positions as a function of the various operating parameters governing the assay performance. This expression predicts the normalized stream variance under the chosen conditions to be determined by two dimensionless Péclet numbers evaluated based on the transverse pressure-driven and electrophoretic solute velocities in the separation chamber, respectively. Moreover, the analysis shows that while the stream width can be expected to increase with an increase in the value of the first Péclet number, the opposite trend will be followed with respect to the latter. The noted results have been validated using Monte Carlo simulations that also establish a time/length scale over which the predicted equilibrium stream width is attained in the system.

  14. Methods for estimating selected low-flow frequency statistics and harmonic mean flows for streams in Iowa

    USGS Publications Warehouse

    Eash, David A.; Barnes, Kimberlee K.

    2012-01-01

    A statewide study was conducted to develop regression equations for estimating six selected low-flow frequency statistics and harmonic mean flows for ungaged stream sites in Iowa. The estimation equations developed for the six low-flow frequency statistics include: the annual 1-, 7-, and 30-day mean low flows for a recurrence interval of 10 years, the annual 30-day mean low flow for a recurrence interval of 5 years, and the seasonal (October 1 through December 31) 1- and 7-day mean low flows for a recurrence interval of 10 years. Estimation equations also were developed for the harmonic-mean-flow statistic. Estimates of these seven selected statistics are provided for 208 U.S. Geological Survey continuous-record streamgages using data through September 30, 2006. The study area comprises streamgages located within Iowa and 50 miles beyond the State's borders. Because trend analyses indicated statistically significant positive trends when considering the entire period of record for the majority of the streamgages, the longest, most recent period of record without a significant trend was determined for each streamgage for use in the study. The median number of years of record used to compute each of these seven selected statistics was 35. Geographic information system software was used to measure 54 selected basin characteristics for each streamgage. Following the removal of two streamgages from the initial data set, data collected for 206 streamgages were compiled to investigate three approaches for regionalization of the seven selected statistics. Regionalization, a process using statistical regression analysis, provides a relation for efficiently transferring information from a group of streamgages in a region to ungaged sites in the region. The three regionalization approaches tested included statewide, regional, and region-of-influence regressions. For the regional regression, the study area was divided into three low-flow regions on the basis of hydrologic

  15. Acoustic wave propagation in bubbly flow with gas, vapor or their mixtures.

    PubMed

    Zhang, Yuning; Guo, Zhongyu; Gao, Yuhang; Du, Xiaoze

    2017-03-29

    Presence of bubbles in liquids could significantly alter the acoustic waves in terms of wave speed and attenuation. In the present paper, acoustic wave propagation in bubbly flows with gas, vapor and gas/vapor mixtures is theoretically investigated in a wide range of parameters (including frequency, bubble radius, void fraction, and vapor mass fraction). Our finding reveals two types of wave propagation behavior depending on the vapor mass fraction. Furthermore, the minimum wave speed (required for the closure of cavitation modelling in the sonochemical reactor design) is analyzed and the influences of paramount parameters on it are quantitatively discussed.

  16. Time-domain characterization of the acoustic damping of a perforated liner with bias flow.

    PubMed

    Zhong, Zhiyuan; Zhao, Dan

    2012-07-01

    Combustion instabilities are caused by the interaction of unsteady heat releases and acoustic waves. To mitigate combustion instabilities, perforated liners, typically subjected to a low Mach number bias flow (a cooling flow through perforated holes), are fitted along the bounding walls of a combustor. They dissipate the acoustic waves by generating vorticity at the rims of perforated apertures. To investigate the absorption of plane waves by a perforated liner with bias flow, a time-domain numerical model of a cylindrical lined duct is developed. The liners' damping mechanism is characterized by using a time-domain "compliance." The development of such time-domain compliance is based on simplified or unsimplified Rayleigh conductivity. Numerical simulations of two different configurations of lined duct systems are performed by combining a 1D acoustic wave model with the compliance model. Comparison is then made between the results from the present models, and those from the experiment and the frequency-domain model of previous investigation [Eldredge and Dowling, J. Fluid Mech. 485, 307-335(2003)]. Good agreement is observed. This confirms that the present model can be used to simulate the propagation and dissipation of acoustic plane waves in a lined duct in real-time.

  17. Numerical acoustic analysis of a turbulent flow around a bluff body

    NASA Astrophysics Data System (ADS)

    Cianferra, Marta; Ianniello, Sandro; Armenio, Vincenzo

    2016-11-01

    A body invested by a fluid flow gives rise to vortical and turbulent three-dimensional fields, whose structure depends on the shape of the body itself and the Reynolds number. Then, pressure fluctuations occur in the field and propagate far away as noise. The acoustic analogy based on the Ffowcs Williams-Hawkings (FWH) equation represents a rigorous way to deal with the problem, enabling the evaluation of noise through a post-processing of fluid dynamic data. Moreover, the presence of separate source terms theoretically allows to identify the dominant generating noise mechanisms taking place in the flow, which, of course, repre- sents a key information in view of any possible reduction or alteration of the acoustic field. This paper deals with a numerical, FWH-based acoustic analysis of a turbulent flow around a bluff body and, in particular, a 3D square cylinder in a uniform velocity field. The fluid dynamic solution is obtained through Large eddy simulations carried out using a standard Smagorinsky model at different Reynolds numbers. The acoustic solution is pursued by different integral solution forms of the FWH equation, in the attempt of recognizing the main noise sources and pointing out the potentiality and possible weak-points of the alternative numerical approaches.

  18. Flow characteristics of Wisconsin streams: Flow-duration, Hhgh-flow, and low-flow tables for selected streams through water-year 1960

    USGS Publications Warehouse

    Young, K.B.

    1964-01-01

    The collection of data on the flow of rivers in Wisconsin started on a continuing basis in 1913. A few streamflow records were started in the late 1800's, one as early as 1888 (Chippewa River at Chippewa Falls). Much of the work has been done under cooperative arrangements between the U.S. Geological Survey and various State and Federal agencies. These data have been published in the form of daily discharge tables, and monthly and yearly summaries.

  19. 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.

  20. 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.

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

    DOE PAGES

    Frisbee, Marty D.; Tysor, Elizabeth H.; Stewart-Maddox, Noah; ...

    2016-02-13

    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 streammore » channels. Springs emerge preferentially on one side of stream valleys where landscape incision has intercepted IGF flowpaths. 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.« less

  2. Interaction between acoustics and subsonic ducted flow in a ramjet configuration

    NASA Astrophysics Data System (ADS)

    Gutmark, E.; Schadow, K. C.

    A subsonic ducted air flow was studied experimentally using a hot-wire anemometer and a high frequency response pressure transducer. The experiments were performed in three stages. A free jet, a jet discharged into an open and closed duct and a forced jet in a closed duct. The shear layer instability frequencies associated with the initial vortex shedding, first vortex merging, and jet-column instability were identified in the unforced cases. Subsequently, the interaction of the jet flow with the first longitudinal pressure mode excited in the acoustic cavity was studied. The highest response of the jet flow to the acoustic wave was obtained when the forcing frequency matched the local most amplified frequency, for example, the first vortex merging frequency in the initial shear layer or the preferred jet frequency at the end of the potential core.

  3. STABLE HEATING OF CLUSTER COOLING FLOWS BY COSMIC-RAY STREAMING

    SciTech Connect

    Fujita, Yutaka; Ohira, Yutaka

    2011-09-10

    We study heating of cool cores in galaxy clusters by cosmic-ray (CR) streaming using numerical simulations. In this model, CRs are injected by the central active galactic nucleus (AGN) and move outward with Alfven waves. The waves are excited by the streaming itself and become nonlinear. If magnetic fields are large enough, CRs can prevail in and heat the entire core because of a large Alfven velocity. We find that the CR streaming can stably heat both high- and low-temperature clusters for a long time without the assistance of thermal conduction, and it can prevent the development of massive cooling flows. If there is even a minor contribution from thermal conduction, the heating can be stabilized further. We discuss the reason for the stability and indicate that the CR pressure is insensitive to changes in the intracluster medium (ICM) and that the density dependence of the heating term is similar to that of radiative cooling.

  4. 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.

  5. Groundwater, springs, and stream flow generation in an alpine meadow of a tropical glacierized catchment

    NASA Astrophysics Data System (ADS)

    Gordon, R.; Lautz, L. K.; McKenzie, J. M.; Mark, B. G.; Chavez, D.

    2013-12-01

    Melting tropical glaciers supply approximately half of dry season stream discharge in glacierized valleys of the Cordillera Blanca, Peru. The remainder of streamflow originates as groundwater stored in alpine meadows, moraines and talus slopes. A better understanding of the dynamics of alpine groundwater, including sources and contributions to streamflow, is important for making accurate estimates of glacial inputs to the hydrologic budget, and for our ability to make predictions about future water resources as glaciers retreat. Our field study, conducted during the dry season in the Llanganuco valley, focused on a 0.5-km2 alpine meadow complex at 4400 m elevation, which includes talus slopes, terminal moraines, and a debris fan. Two glacial lakes and springs throughout the complex feed a network of stream channels that flow across the meadow (~2 km total length). We combined tracer measurements of stream and spring discharge and groundwater-surface water exchange with synoptic sampling of water isotopic and geochemical composition, in order to characterize and quantify contributions to streamflow from different geomorphic features. Surface water inputs to the stream channels totaled 58 l/s, while the stream gained an additional 57 l/s from groundwater inputs. Water chemistry is primarily controlled by flowpath type (surface/subsurface) and length, as well as bedrock lithology, while stable water isotopic composition appears to be controlled by water source (glacial lake, meadow or deep groundwater). Stream water chemistry is most similar to meadow groundwater springs, but isotopic composition suggests that the majority of stream water, which issues from springs at the meadow/fan interface, is from the same glacial source as the up-gradient lake. Groundwater sampled from piezometers in confined meadow aquifers is unique in both chemistry and isotopic composition, but does not contribute a large percentage of stream water exiting this small meadow, as quantified by

  6. 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.

  7. An acoustic-convective splitting-based approach for the Kapila two-phase flow model

    NASA Astrophysics Data System (ADS)

    ten Eikelder, M. F. P.; Daude, F.; Koren, B.; Tijsseling, A. S.

    2017-02-01

    In this paper we propose a new acoustic-convective splitting-based numerical scheme for the Kapila five-equation two-phase flow model. The splitting operator decouples the acoustic waves and convective waves. The resulting two submodels are alternately numerically solved to approximate the solution of the entire model. The Lagrangian form of the acoustic submodel is numerically solved using an HLLC-type Riemann solver whereas the convective part is approximated with an upwind scheme. The result is a simple method which allows for a general equation of state. Numerical computations are performed for standard two-phase shock tube problems. A comparison is made with a non-splitting approach. The results are in good agreement with reference results and exact solutions.

  8. 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.

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

    PubMed

    Barber, Larry B; Antweiler, Ronald C; Flynn, Jennifer L; Keefe, Steffanie H; Kolpin, Dana W; Roth, David A; Schnoebelen, Douglas J; Taylor, Howard E; Verplanck, Philip L

    2011-04-01

    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.

  10. 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

  11. Contribution of return flows to streamflow in selected stream reaches in Illinois, 1988-89

    USGS Publications Warehouse

    LaTour, J.K.

    1993-01-01

    Water returns by sewage-treatment plants and various water users can be a significant part of streamflow. Knowledge of the effect of return flows on stream- flow is needed for purposes of assessing streamwater quality and water supply. The results of a study by the U.S. Geological Survey, in cooperation with the Illinois Environmental Protection Agency, are presented to describe the contribution of return flows to streamflow for five stream reaches in Illinois during 1988-89. The reaches studied were South Branch Kishwaukee River upstream from De Kaib, Mackinaw River upstream from Congerville, Addison Creek upstream from Bellwood, Flag Creek upstream from Willow Springs, and Thorn Creek upstream from Glenwood. The annual average contributions of return flows to streamflow in each reach ranged from 1 to 99 percent of the annual average streamflow. Return flows significantly affected streamflows in the Flag Creek and Thorn Creek reaches. Significant return flows probably sustained streamflows in the Addison Creek, Flag Creek, and Thorn Creek reaches. Return flows exceeded streamflow during at least 1 month during the 1988 drought at all of the study reaches, except the Thorn Creek reach. Of the amount of return flows that exceeded streamflow, all reaches lost an estimated 0.01 to 0.34 Mgal/d (million gallons per day) to evaporation and 0.36 to 1.33 Mgal/d to infiltration. An analysis-of-variance test indicated that return flows did not differ among seasons. A second analysis indicated that the proportion of return flows to streamflow did differ seasonally. Return flows during July through September 1988-89 constituted a large proportion (67 percent) of the annual streamflows.

  12. Macroinvertebrate response to flow changes in a subalpine stream: predictions from two-dimensional hydrodynamic models

    USGS Publications Warehouse

    Waddle, T.J.; Holmquist, J.G.

    2013-01-01

    Two-dimensional hydrodynamic models are being used increasingly as alternatives to traditional one-dimensional instream flow methodologies for assessing adequacy of flow and associated faunal habitat. Two-dimensional modelling of habitat has focused primarily on fishes, but fish-based assessments may not model benthic macroinvertebrate habitat effectively. We extend two-dimensional techniques to a macroinvertebrate assemblage in a high-elevation stream in the Sierra Nevada (Dana Fork of the Tuolumne River, Yosemite National Park, CA, USA). This stream frequently flows at less than 0.03?m3?s?1 in late summer and is representative of a common water abstraction scenario: maximum water abstraction coinciding with seasonally low flows. We used two-dimensional modelling to predict invertebrate responses to reduced flows that might result from increased abstraction. We collected site-specific field data on the macroinvertebrate assemblage, bed topography and flow conditions and then coupled a two-dimensional hydrodynamic model with macroinvertebrate indices to evaluate habitat across a range of low flows. Macroinvertebrate indices were calculated for the wetted area at each flow. A surrogate flow record based on an adjacent watershed was used to evaluate frequency and duration of low flow events. Using surrogate historical records, we estimated that flow should fall below 0.071?m3?s?1 at least 1?day in 82 of 95?years and below 0.028?m3?s?1 in 48 of 95?years. Invertebrate metric means indicated minor losses in response to modelled discharge reductions, but wetted area decreased substantially. Responses of invertebrates to water abstraction will likely be a function of changing habitat quantity rather than quality.

  13. 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

  14. 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.

  15. 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.

  16. Acoustic oscillation phenomena in low-velocity steady flow with heating

    NASA Technical Reports Server (NTRS)

    Liburdy, J. A.; Wofford, J. L.

    1980-01-01

    Thermally driven acoustic oscillations in low-velocity mean flows are investigated. A criterion is developed for marginal stability with respect to a fluid temperature increase; a cylindrical geometry is chosen for flow in a constant-area tube where any circumferential variation is neglected. The range of parameters of concern is limited to conditions resembling cryogenic storage designs proposed for long-term space missions; helium was chosen as the fluid in order to allow comparison with zero flow rate results in half-open tubes.

  17. StreamFlow 1.0: an extension to the spatially distributed snow model Alpine3D for hydrological modelling and deterministic stream temperature prediction

    NASA Astrophysics Data System (ADS)

    Gallice, Aurélien; Bavay, Mathias; Brauchli, Tristan; Comola, Francesco; Lehning, Michael; Huwald, Hendrik

    2016-12-01

    Climate change is expected to strongly impact the hydrological and thermal regimes of Alpine rivers within the coming decades. In this context, the development of hydrological models accounting for the specific dynamics of Alpine catchments appears as one of the promising approaches to reduce our uncertainty of future mountain hydrology. This paper describes the improvements brought to StreamFlow, an existing model for hydrological and stream temperature prediction built as an external extension to the physically based snow model Alpine3D. StreamFlow's source code has been entirely written anew, taking advantage of object-oriented programming to significantly improve its structure and ease the implementation of future developments. The source code is now publicly available online, along with a complete documentation. A special emphasis has been put on modularity during the re-implementation of StreamFlow, so that many model aspects can be represented using different alternatives. For example, several options are now available to model the advection of water within the stream. This allows for an easy and fast comparison between different approaches and helps in defining more reliable uncertainty estimates of the model forecasts. In particular, a case study in a Swiss Alpine catchment reveals that the stream temperature predictions are particularly sensitive to the approach used to model the temperature of subsurface flow, a fact which has been poorly reported in the literature to date. Based on the case study, StreamFlow is shown to reproduce hourly mean discharge with a Nash-Sutcliffe efficiency (NSE) of 0.82 and hourly mean temperature with a NSE of 0.78.

  18. Flow and heat transfer of plane surfaces moving in parallel and reversely to the free stream

    NASA Astrophysics Data System (ADS)

    Lin, Hsiao-Tsung; Huang, Shih-Feng

    1994-01-01

    Two types of classical forced convection problems have been extensively studied for the past years. They are the Blasius problem of a steady flow over a stationary flat plate; and the Sakiadis problem of a plate moving continuously in a quiescent ambient fluid. In this paper, we study the general forced convection problem of surface moving continuously in a flowing stream by using a quite different transformation to obtain similarity solutions. The present solutions are very accurate for any relative speed of the surface and the free stream over a wide range of Prandtl number between 0.01 and 10 000. We study not only the case of a plane surface moving in parallel to the free stream but also the case of a surface moving reversely. The latter case has not been studied previously. For application convenience, very accurate correlation equations are proposed for predicting the wall friction and heat transfer for any velocity ratio of the surface and the free stream.

  19. 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.

  20. Changes in hyporheic exchange flow following experimental wood removal in a small, low-gradient stream

    NASA Astrophysics Data System (ADS)

    Wondzell, Steven M.; Lanier, Justin; Haggerty, Roy; Woodsmith, Richard D.; Edwards, Richard T.

    2009-05-01

    We investigated the response of hyporheic exchange flow (HEF) to wood removal in a small, low-gradient, gravel bed stream in southeast Alaska using a series of groundwater models built to simulate HEF for the initial conditions immediately after wood removal and 1 month, 2 years, 4 years, and 16 years following wood removal. The models were based on topographic surveys of the stream channel and surrounding floodplain, and surveyed water surface elevations (WSEs) were used to assign stream boundary conditions. Using the groundwater flow model, MODFLOW, and the particle tracking model, MODPATH, we calculated hyporheic exchange fluxes, their residence time distributions, and both longitudinal and plan view spatial patterns of downwelling and upwelling zones. In the first few years, streambed scour and sediment deposition smoothed the streambed and WSE profile, reducing HEF. Also, large contiguous patches of downwelling or upwelling were fragmented, nearly doubling the total number of patches present on the streambed. As the stream continued to adjust to the loss of wood, those trends began to reverse. Accretion of sediment onto alternating bars resulted in better developed pool-riffle morphology, enhanced HEF, and increased residence times and also resulted in downwelling and upwelling zones coalescing into elongated patches along bar margins. This study showed that the hyporheic zone is sensitive to changes in wood loading and that initial changes in HEF resulting from the direct effects of wood removal were contrary to longer-term channel adjustments to changes in wood loading.

  1. 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.

  2. 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

  3. The method design of coordinates mapping in PIV measurement system for flow field of impinging streams

    NASA Astrophysics Data System (ADS)

    Li, Fubao; Wang, Dexi; Li, Qin

    2009-12-01

    In the Particle Image Velocimetry (PIV) measurement system for flow field of impinging streams, in order to realize the calculation of real flow field data from sequence image, the method of coordinates mapping applying neural network is designed. This method is to put a plat with normal pitch grid in the area of transparent Liquid-continuous impinging streams reactor, with the grid plan going through the cylinder axis of the reactor filled with water. Digital camera is fixed outside the container, with the light axis vertical to the grid plan. Software tool is utilized to obtain Educate vector collect for educating neural network. The network which finished training can counterchange the pixel coordinate of the measured plan in the liquid into real coordinate.

  4. The method design of coordinates mapping in PIV measurement system for flow field of impinging streams

    NASA Astrophysics Data System (ADS)

    Li, Fubao; Wang, Dexi; Li, Qin

    2010-01-01

    In the Particle Image Velocimetry (PIV) measurement system for flow field of impinging streams, in order to realize the calculation of real flow field data from sequence image, the method of coordinates mapping applying neural network is designed. This method is to put a plat with normal pitch grid in the area of transparent Liquid-continuous impinging streams reactor, with the grid plan going through the cylinder axis of the reactor filled with water. Digital camera is fixed outside the container, with the light axis vertical to the grid plan. Software tool is utilized to obtain Educate vector collect for educating neural network. The network which finished training can counterchange the pixel coordinate of the measured plan in the liquid into real coordinate.

  5. 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.

  6. 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.

  7. The contribution of glacier melt to stream flow in the Wind River Range, WY

    NASA Astrophysics Data System (ADS)

    Cable, J. M.; Williams, D. G.; Bachman, S. A.

    2008-12-01

    The Wind River Range (Wyoming) boasts the largest concentration of glaciers in the American Rockies, and together with adjacent mountain ranges is the source of several major river systems in the western US. Declines in the volume of these glaciers associated with recent climate warming are well documented. Such declines of alpine glaciers will reduce the amount of water available for agricultural and domestic use, especially in late summer and fall. The contribution of glacial melt to stream flow remains largely unquantified in many parts of the U.S., particularly in Wyoming. In this study, we estimated the fractional contribution of glacier melt water from Dinwoody Glacier to flow in Dinwoody Creek in the Wind River Range on diurnal, seasonal, and interannual time scales. The stable isotope composition of water from the Dinwoody Creek watershed was determined on spatially and temporally intensive scales in 2007 and 2008. Spatially intensive sampling took place in the summers of both years; water samples were collected from (1) above and below major confluences along Dinwoody Creek, from (2) Dinwoody Glacier, (3) rain water, and (4) snow. Stream samples were collected over the entire melt season using an automated stream sampler placed beside an unimpaired USGS gauging station low in the watershed. Glacial melt contributed significantly to stream flow during periods of peak daily discharge (afternoon) and during late summer peak flow (late-August). In 2008, snow persisted late into the summer, so snowmelt was the main source of streamflow in mid-summer (July). Disappearance of glaciers in this watershed will affect both ecosystem and human water supplies during the late summer period, particularly in years when snowfields do not persist late into the summer.

  8. 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.

  9. 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.

  10. 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

  11. FINE MAGNETIC STRUCTURE AND ORIGIN OF COUNTER-STREAMING MASS FLOWS IN A QUIESCENT SOLAR PROMINENCE

    SciTech Connect

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

    2015-11-20

    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.

  12. 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.

  13. Associations of stream health to altered flow and water temperature in the Sierra Nevada, California

    USGS Publications Warehouse

    Carlisle, Daren M.; S. Mark Nelson,; May, Jason

    2016-01-01

    Alteration of streamflow and thermal conditions may adversely affect lotic invertebrate communities, but few studies have assessed these phenomena using indicators that control for the potentially confounding influence of natural variability. We designed a study to assess how flow and thermal alteration influence stream health – as indicated by the condition of invertebrate communities. We studied thirty streams in the Sierra Nevada, California, that span a wide range of hydrologic modification due to storage reservoirs and hydroelectric diversions. Daily water temperature and streamflows were monitored, and basic chemistry and habitat conditions were characterized when invertebrate communities were sampled. Streamflow alteration, thermal alteration, and invertebrate condition were quantified by predicting site-specific natural expectations using statistical models developed using data from regional reference sites. Monthly flows were typically depleted (relative to natural expectations) during fall, winter, and spring. Most hydrologically altered sites experienced cooled thermal conditions in summer, with mean daily temperatures as much 12 °C below natural expectations. The most influential predictor of invertebrate community condition was the degree of alteration of March flows, which suggests that there are key interactions between hydrological and biological processes during this month in Sierra Nevada streams. Thermal alteration was also an important predictor – particularly at sites with the most severe hydrological alteration.

  14. 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.

  15. Turbulent Mixing of Primary and Secondary Flow Streams in a Rocket-Based Combined Cycle Engine

    NASA Technical Reports Server (NTRS)

    Cramer, J. M.; Greene, M. U.; Pal, S.; Santoro, R. J.; Turner, Jim (Technical Monitor)

    2002-01-01

    This viewgraph presentation gives an overview of the turbulent mixing of primary and secondary flow streams in a rocket-based combined cycle (RBCC) engine. A significant RBCC ejector mode database has been generated, detailing single and twin thruster configurations and global and local measurements. On-going analysis and correlation efforts include Marshall Space Flight Center computational fluid dynamics modeling and turbulent shear layer analysis. Potential follow-on activities include detailed measurements of air flow static pressure and velocity profiles, investigations into other thruster spacing configurations, performing a fundamental shear layer mixing study, and demonstrating single-shot Raman measurements.

  16. 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

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

    NASA Astrophysics Data System (ADS)

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

    1999-09-01

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

  18. Suppression of flow-acoustic coupling in sidebranch ducts by interface modification

    NASA Astrophysics Data System (ADS)

    Knotts, B. D.; Selamet, A.

    2003-08-01

    The flow-acoustic coupling of shear layer instabilities with the acoustic resonances at the interface of a closed sidebranch and main duct can produce high-amplitude pure-tone noise, known as "whistle". This study investigates experimentally the effect of various interface geometry modifications on whistles. The objective of the modifications is to suppress the noise by redirecting the shear layer at the main duct-sidebranch interface. Interchangeable suppressor blocks of varying shapes and sizes mounted upstream and downstream of the sidebranch opening are used to change the geometry. The block shapes include those with square edges, ramps, bevelled edges, and curved (radiused) edges. The experiments are conducted in a flow facility at conditions that include certain ranges of Strouhal numbers known to coincide with significant noise generation. The effectiveness of various suppressors in reducing the noise is assessed by analyzing the measured sound pressure levels.

  19. MEMS based hair flow-sensors as model systems for acoustic perception studies

    NASA Astrophysics Data System (ADS)

    Krijnen, Gijs J. M.; Dijkstra, Marcel; van Baar, John J.; Shankar, Siripurapu S.; Kuipers, Winfred J.; de Boer, Rik J. H.; Altpeter, Dominique; Lammerink, Theo S. J.; Wiegerink, Remco

    2006-02-01

    Arrays of MEMS fabricated flow sensors inspired by the acoustic flow-sensitive hairs found on the cerci of crickets have been designed, fabricated and characterized. The hairs consist of up to 1 mm long SU-8 structures mounted on suspended membranes with normal translational and rotational degrees of freedom. Electrodes on the membrane and on the substrate form variable capacitors, allowing for capacitive read-out. Capacitance versus voltage, frequency dependence and directional sensitivity measurements have been successfully carried out on fabricated sensor arrays, showing the viability of the concept. The sensors form a model system allowing for investigations on sensory acoustics by their arrayed nature, their adaptivity via electrostatic interaction (frequency tuning and parametric amplification) and their susceptibility to noise (stochastic resonance).

  20. MEMS based hair flow-sensors as model systems for acoustic perception studies.

    PubMed

    Krijnen, Gijs J M; Dijkstra, Marcel; van Baar, John J; Shankar, Siripurapu S; Kuipers, Winfred J; de Boer, Rik J H; Altpeter, Dominique; Lammerink, Theo S J; Wiegerink, Remco

    2006-02-28

    Arrays of MEMS fabricated flow sensors inspired by the acoustic flow-sensitive hairs found on the cerci of crickets have been designed, fabricated and characterized. The hairs consist of up to 1 mm long SU-8 structures mounted on suspended membranes with normal translational and rotational degrees of freedom. Electrodes on the membrane and on the substrate form variable capacitors, allowing for capacitive read-out. Capacitance versus voltage, frequency dependence and directional sensitivity measurements have been successfully carried out on fabricated sensor arrays, showing the viability of the concept. The sensors form a model system allowing for investigations on sensory acoustics by their arrayed nature, their adaptivity via electrostatic interaction (frequency tuning and parametric amplification) and their susceptibility to noise (stochastic resonance).

  1. 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

  2. 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.

  3. Evaluating ecological effects of small-scale agricultural diversions on stream flow in Coastal California

    NASA Astrophysics Data System (ADS)

    Deitch, M. J.; Kondolf, G. M.; Merenlender, A. M.

    2005-05-01

    In the absence of summer precipitation, grape growers in the California wine country often pump water directly from the stream for frost protection, irrigation, and heat protection. Managers may not be able to evaluate the impacts of the many small diversions on flow or anadromous salmonid habitat because of the uncertainty of human water needs. Building on previous research to predict diversion impacts on streamflow, we monitored flow in Franz Creek (a third-order stream draining 40 km2 in Sonoma County) to evaluate our model, and then measured water coverage in riffles and pools to quantify the change in salmonid habitat that these diversions would cause. Our model reasonably predicted flow decreases from diversion for frost protection: flow decreased by up to 80% on each cold morning, causing 50% riffle loss. Though it was not indicated in our model, the loss of habitat on hot summer days (suggesting diversion for heat protection) was also dramatic: levels dropped suddenly, reducing volume in intermittent pools by over 50%. Both changes in flow led to sudden reductions in habitat, suggesting that diversions are a major impediment to salmonid restoration in the region.

  4. 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).

  5. 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.

  6. 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

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

    USGS Publications Warehouse

    Jackson, P. Ryan

    2013-01-01

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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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...

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. Determination of ammonium in Kjeldahl digests by gas-diffusion flow-injection analysis with a bulk acoustic wave-impedance sensor.

    PubMed

    Su, X L; Nie, L H; Yao, S Z

    1997-11-01

    A novel flow-injection analysis (FIA) system has been developed for the rapid and direct determination of ammonium in Kjeldahl digests. The method is based on diffusion of ammonia across a PTFE gas-permeable membrane from an alkaline (NaOH/EDTA) stream into a stream of diluted boric acid. The trapped ammonium in the acceptor is determined on line by a bulk acoustic wave (BAW)-impedance sensor and the signal is proportional to the ammonium concentration present in the digests. The proposed system exhibits a favorable frequency response to 5.0 x 10(-6)-4.0 x 10(-3) mol l(-1) ammonium with a detection limit of 1.0 x 10(-6) mol l(-1), and the precision was better than 1% (RSD) for 0.025-1.0 mM ammonium at a through-put of 45-50 samples h(-1). Results obtained for nitrogen determination in amino acids and for proteins determination in blood products are in good agreement with those obtained by the conventional distillation/titration method, respectively. The effects of composition of acceptor stream, cell constant of conductivity electrode, sample volume, flow rates and potential interferents on the FIA signals were discussed in detail.

  18. 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.

  19. Estimating peak-flow frequency statistics for selected gaged and ungaged sites in naturally flowing streams and rivers in Idaho

    USGS Publications Warehouse

    Wood, Molly S.; Fosness, Ryan L.; Skinner, Kenneth D.; Veilleux, Andrea G.

    2016-06-27

    The U.S. Geological Survey, in cooperation with the Idaho Transportation Department, updated regional regression equations to estimate peak-flow statistics at ungaged sites on Idaho streams using recent streamflow (flow) data and new statistical techniques. Peak-flow statistics with 80-, 67-, 50-, 43-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities (1.25-, 1.50-, 2.00-, 2.33-, 5.00-, 10.0-, 25.0-, 50.0-, 100-, 200-, and 500-year recurrence intervals, respectively) were estimated for 192 streamgages in Idaho and bordering States with at least 10 years of annual peak-flow record through water year 2013. The streamgages were selected from drainage basins with little or no flow diversion or regulation. The peak-flow statistics were estimated by fitting a log-Pearson type III distribution to records of annual peak flows and applying two additional statistical methods: (1) the Expected Moments Algorithm to help describe uncertainty in annual peak flows and to better represent missing and historical record; and (2) the generalized Multiple Grubbs Beck Test to screen out potentially influential low outliers and to better fit the upper end of the peak-flow distribution. Additionally, a new regional skew was estimated for the Pacific Northwest and used to weight at-station skew at most streamgages. The streamgages were grouped into six regions (numbered 1_2, 3, 4, 5, 6_8, and 7, to maintain consistency in region numbering with a previous study), and the estimated peak-flow statistics were related to basin and climatic characteristics to develop regional regression equations using a generalized least squares procedure. Four out of 24 evaluated basin and climatic characteristics were selected for use in the final regional peak-flow regression equations.Overall, the standard error of prediction for the regional peak-flow regression equations ranged from 22 to 132 percent. Among all regions, regression model fit was best for region 4 in west

  20. 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.

  1. Relationships between hydraulic parameters in a small stream under varying flow and seasonal conditions

    USGS Publications Warehouse

    Hart, D.R.; Mulholland, P.J.; Marzolf, E.R.; DeAngelis, D.L.; Hendricks, S.P.

    1999-01-01

    Twenty conservative tracer injections were carried out in the same reach of a small woodland stream in order to determine how variation in discharge and leaf accumulation affect stream hydraulic parameters. The injections were made at various discharge rates ranging from 2-6 to 40 1/s. Five of the injections were made during late autumn, when there were large accumulations of leaves in the stream. Estimates of hydraulic parameters were made by fitting a transient storage solute transport model to conservative tracer concentration profiles. Velocity increased almost linearly with increasing discharge, indicating a decline in the Darcy friction factor. Dispersion also increased with increasing discharge, especially for the lower flow injections. The relative size of the storage zone was small (???0??1). There was no definable relationship between discharge and the relative storage zone size, but the rates of exchange between the storage zone and the main channel increased markedly with increasing discharge. The presence of large accumulations of leaves had a clear effect on the hydraulic characteristics of the stream, producing much higher friction factors, larger storage zone sizes and lower velocity than would have been predicted by discharge alone. Copyright ?? 1999 John Wiley & Sons, Ltd.

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

    PubMed

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

    2012-04-01

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

  3. Effects of compressibility and free-stream turbulence on boundary layer transition in high-subsonic and transonic flows

    NASA Technical Reports Server (NTRS)

    Murthy, S. V.; Steinle, F. W.

    1986-01-01

    Based on the existing boundary layer transition data, the effects of compressibility, pressure fluctuations, and free-stream turbulence have been reexamined for subsonic and transonic flow speeds. It is confirmed that the compressibility effects may be adequately expressed in terms of a simple correlation with free-stream Mach number. Pressure fluctuations, especially at low levels, do not seem to significantly affect the transition phenomenon. Effects of free-stream turbulence in high-subsonic and transonic flows are similar to the trends observed for low-speed flows and the transition process is hastened. The trends, as seen from slender cone flow data, seem to suggest power law correlations between transition Reynolds number and free-stream turbulence.

  4. 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 evidence that N(b) is a useful metric of population-specific individual reproductive contribution for genetic monitoring across populations and the link we provide between stream flow and N(b) could be used to help predict population resilience to environmental change.

  5. Analysis of pulsatile blood flow in constricted bifurcated arteries with vorticity-stream function approach.

    PubMed

    Chakravarty, S; Sen, S

    2008-01-01

    This theoretical investigation deals with an analysis of pulsatile blood flow in a model bifurcated artery having a stenosis in the parent arterial lumen. The geometry of the bifurcated arterial segment with an implanted stenosis in the parent duct is given an appropriate mathematical shape with the introduction of suitable curvature at the lateral junction and the flow divider. The vascular wall deformability is duly accounted for although the development of atherosclerosis in the arteries reduces its elastic property to some extent. The streaming blood contained in the bifurcated artery is treated to be Newtonian. The flow dynamic analysis applies two-dimensional unsteady incompressible nonlinear Navier-Stokes equations rewritten in the vorticity-stream function formulation. Following a radial coordinate transformation, these equations are solved numerically by a finite difference scheme with the approximate choice of the inlet and boundary conditions in concert with the biophysical point of view. The final numerical results are highlighted at the end of the paper through the exhibition of the wall shear stress and several time-variant patterns of streamlines and vorticity contours of the flow phenomena, which are highly influenced by the severity of the stenosis and the angle of bifurcation. The applicability of the present model is thus established.

  6. Use of an integrated flow model to estimate ecologically relevant hydrologic characteristics at stream biomonitoring sites

    USGS Publications Warehouse

    Kennen, J.G.; Kauffman, L.J.; Ayers, M.A.; Wolock, D.M.; Colarullo, S.J.

    2008-01-01

    We developed an integrated hydroecological model to provide a comprehensive set of hydrologic variables representing five major components of the flow regime at 856 aquatic-invertebrate monitoring sites in New Jersey. The hydroecological model simulates streamflow by routing water that moves overland and through the subsurface from atmospheric delivery to the watershed outlet. Snow accumulation and melt, evapotranspiration, precipitation, withdrawals, discharges, pervious- and impervious-area runoff, and lake storage were accounted for in the water balance. We generated more than 78 flow variables, which describe the frequency, magnitude, duration, rate of change, and timing of flow events. Highly correlated variables were filtered by principal component analysis to obtain a non-redundant subset of variables that explain the majority of the variation in the complete set. This subset of variables was used to evaluate the effect of changes in the flow regime on aquatic-invertebrate assemblage structure at 856 biomonitoring sites. We used non-metric multidimensional scaling (NMS) to evaluate variation in aquatic-invertebrate assemblage structure across a disturbance gradient. We employed multiple linear regression (MLR) analysis to build a series of MLR models that identify the most important environmental and hydrologic variables driving the differences in the aquatic-invertebrate assemblages across the disturbance gradient. The first axis of NMS ordination was significantly related to many hydrologic, habitat, and land-use/land-cover variables, including the average number of annual storms producing runoff, ratio of 25-75% exceedance flow (flashiness), diversity of natural stream substrate, and the percentage of forested land near the stream channel (forest buffer). Modifications in the hydrologic regime as the result of changes in watershed land use appear to promote the retention of highly tolerant aquatic species; in contrast, species that are sensitive to

  7. 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.

  8. Propagation and scattering of acoustic-vorticity waves in annular swirling flows

    NASA Astrophysics Data System (ADS)

    Golubev, Vladimir Viktorovich

    1997-08-01

    The dissertation presents a fundamental extension of unsteady aerodynamic theory developed to predict fluctuating forces on aircraft structural components. These excitations may result from a variety of upstream flow non-uniformities such as atmospheric turbulence, airframe tip vortices and wakes, engine inlet distortions and secondary flows. In the frame of reference of a downstream aircraft component, an upstream flow non- uniformity appears as a propagating vorticity wave (a gust). Classical treatment of gust interaction problems developed for uniform, potential upstream mean flows is based on the fact that it is possible to consider separately incident or scattered acoustic, entropic and vortical modes of unsteady flow motion. A purely vortical gust remains 'frozen' as it convects with the flow. The coupling between different unsteady components may occur only at the surface of a solid structure, or in the close vicinity of a lifting body. The classical approach, however, is not justified for an aircraft engine system where the internal turbomachinery flow is non-uniform and non-potential as it exhibits a strong swirling motion. In such a flow, acting centrifugal and Coriolis forces couple the various unsteady modes which thus can no longer be determined independently of each other. The new developed theory follows the decomposition of unsteady velocity field into vortical and potential components. In spite of the modal coupling, this decomposition elucidates the physical phenomena associated with unsteady swirling motion by indicating the degree of interaction between the various modes. It paves the way for generalizing the classical definition of a gust for vortical swirling flows. The concept of a generalized gust is developed based on the eigenmode pseudospectral analysis of the coupled equations of unsteady swirling motion. This analysis reveals two distinct regions of eigenvalues corresponding to pressure-dominated nearly-sonic and vorticity- dominated

  9. Linking stream flow and groundwater to avian habitat in a desert riparian system.

    PubMed

    Merritt, David M; Bateman, Heather L

    2012-10-01

    Increasing human populations have resulted in aggressive water development in arid regions. This development typically results in altered stream flow regimes, reduced annual flow volumes, changes in fluvial disturbance regimes, changes in groundwater levels, and subsequent shifts in ecological patterns and processes. Balancing human demands for water with environmental requirements to maintain functioning ecosystems requires quantitative linkages between water in streams and ecosystem attributes. Streams in the Sonoran Desert provide important habitat for vertebrate species, including resident and migratory birds. Habitat structure, food, and nest-building materials, which are concentrated in riparian areas, are provided directly or indirectly by vegetation. We measured riparian vegetation, groundwater and surface water, habitat structure, and bird occurrence along Cherry Creek, a perennial tributary of the Salt River in central Arizona, USA. The purpose of this work was to develop an integrated model of groundwater-vegetation-habitat structure and bird occurrence by: (1) characterizing structural and provisioning attributes of riparian vegetation through developing a bird habitat index (BHI), (2) validating the utility of our BHI through relating it to measured bird community composition, (3) determining the riparian plant species that best explain the variability in BHI, (4) developing predictive models that link important riparian species to fluvial disturbance and groundwater availability along an arid-land stream, and (5) simulating the effects of changes in flow regime and groundwater levels and determining their consequences for riparian bird communities. Riparian forest and shrubland vegetation cover types were correctly classified in 83% of observations as a function of fluvial disturbance and depth to water table. Groundwater decline and decreased magnitude of fluvial disturbance caused significant shifts in riparian cover types from riparian forest to

  10. Using acoustics to estimate inspiratory flow rate and drug removed from a dry powder inhaler.

    PubMed

    Holmes, Martin S; Seheult, Jansen; Geraghty, Colm; D'Arcy, Shona; Costello, Richard W; Reilly, Richard B

    2013-01-01

    Morbidity and mortality rates of chronic respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD) are rising. There is a strong requirement for more effective management of these chronic diseases. Dry powder inhalers (DPIs) are one kind of devices currently employed to deliver medication aimed at controlling asthma and COPD symptoms. Despite their proven effectiveness when used correctly, some patients are unable to reach the inspiratory flow rate required to remove medication from the breath actuated devices and as a result, the medication does not reach the airways. This study employs an acoustic recording device, attached to a common DPI to record the audio signals of simulated inhalations. A rotameter was used to measure the flow rate through the inhaler while a milligram weighing scale was used to measure the amount of drug removed from each simulated inhalation. It was found that a strong correlation existed (R(2)>0.96) when average power, median amplitude, root mean square and mean absolute deviation were used to predict peak inspiratory flow rate. At a flow of 30 L/Min (mean absolute deviation=0.0049), it was found that 77% of the total emitted dose was removed from the inhaler. Results indicate that acoustic measurements may be used in the prediction of inspiratory flow rate and quantity of medication removed from an inhaler.

  11. Analysis of a micro-scale pump which uses controlled acoustic streaming for fluid locomotion

    SciTech Connect

    Dohner, J.L.

    1998-01-01

    In this report the analysis of a micro-scale pump is described. This micro-pump uses active control to produce a distributed body force in a fluid micro-channel. The desired effect of this body force is to drive fluid through the channel. Limitations, assumptions, and design parameters are discussed. The mathematical analysis of pump dynamics is explained in detail. A perturbation analysis is used on the equations of mass, momentum and state to produce equations of motion for first and second order effects. The first order effects are described by linear wave motion in the fluid and are found by using integral equation methods. The second order effects are driven by body forces resulting from first order effects. Thus, by controlling the production of wave motion in the channel, second order excitation can also be controlled. This report is all theory and therefore needs experimental validation. Although many of the assumptions used in this report have been used elsewhere in the literature and have been found to be sufficient, there are many aspects of the problem which have been left unresolved. In particular, flow separation in the fluid channel is a critical problem. If the fluid does not separate, pumping will occur through the channel, however, if internal or external forces are not sufficient to stop separation, this type of pump will not function.

  12. Superamphiphobic Silicon-Nanowire-Embedded Microsystem and In-Contact Flow Performance of Gas and Liquid Streams.

    PubMed

    Ko, Dong-Hyeon; Ren, Wurong; Kim, Jin-Oh; Wang, Jun; Wang, Hao; Sharma, Siddharth; Faustini, Marco; Kim, Dong-Pyo

    2016-01-26

    Gas and liquid streams are invariably separated either by a solid wall or by a membrane for heat or mass transfer between the gas and liquid streams. Without the separating wall, the gas phase is present as bubbles in liquid or, in a microsystem, as gas plugs between slugs of liquid. Continuous and direct contact between the two moving streams of gas and liquid is quite an efficient way of achieving heat or mass transfer between the two phases. Here, we report a silicon nanowire built-in microsystem in which a liquid stream flows in contact with an underlying gas stream. The upper liquid stream does not penetrate into the lower gas stream due to the superamphiphobic nature of the silicon nanowires built into the bottom wall, thereby preserving the integrity of continuous gas and liquid streams, although they are flowing in contact. Due to the superamphiphobic nature of silicon nanowires, the microsystem provides the best possible interfacial mass transfer known to date between flowing gas and liquid phases, which can achieve excellent chemical performance in two-phase organic syntheses.

  13. 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.

  14. Upper washita river experimental watersheds: reservoir, groundwater, and stream flow data.

    PubMed

    Moriasi, Daniel N; Starks, Patrick J; Guzman, Jorge A; Garbrecht, Jurgen D; Steiner, Jean L; Stoner, J Chris; Allen, Paul B; Naney, James W

    2014-07-01

    Surface and