Sample records for dacs-sc dendreon buoyant

  1. Buoyant supernova remnants

    Microsoft Academic Search

    Eric M. Jones

    1973-01-01

    It is proposed that the time scale for buoyant rise may be about ore ; they lose their identify. Six SNRs from the lists of Shaver and Goss appear to ; be in the process of forming into toroids. The dominant gravitational term ; causing the rise appears to be fairly local inhomogeneities in the galactic ; gravitational field. A

  2. Hydrostatic Modeling of Buoyant Plumes

    NASA Astrophysics Data System (ADS)

    Stroman, A.; Dewar, W. K.; Wienders, N.; Deremble, B.

    2014-12-01

    The Deepwater Horizon oil spill in the Gulf of Mexico has led to increased interest in understanding point source convection dynamics. Most of the existing oil plume models use a Lagrangian based approach, which computes integral measures such as plume centerline trajectory and plume radius. However, this approach doesn't account for feedbacks of the buoyant plume on the ambient environment. Instead, we employ an Eulerian based approach to acquire a better understanding of the dynamics of buoyant plumes. We have performed a series of hydrostatic modeling simulations using the MITgcm. Our results show that there is a dynamical response caused by the presence of the buoyant plume, in that there is a modification of the background flow. We find that the buoyant plume becomes baroclinically unstable and sheds eddies at the neutral buoyancy layer. We also explore different scenarios to determine the effect of the buoyancy source and the temperature stratification on the evolution of buoyant plumes.

  3. Confined radial buoyant jet

    SciTech Connect

    Fry, D.J.; Adams, E.

    1983-09-01

    A submerged, negatively buoyant radial jet, discharging horizontally beneath a free surface into water of initially uniform density, was studied experimentally and theoretically. The situation relates to the operation of an ocean thermal energy conversion plant and is an example of buoyancy and confinement offering opposing influences on jet trajectory. For shallow submergence, the jet is attached to the free surface while for large submergence or greater (negative) buoyancy, the jet is detached. An experimental program yielded data on jet trajectory, temperature, velocity and discharge conditions associated with transition between attached and detached regimes. A hysteresis effect was noted as the conditions for attachment and detachment were different. Dimensional analysis yielded a single parameter of primary importance and two parameters of secondary importance in describing jet behavior. An integral jet analysis based on a spreading assumption was successfully adapted to include induced velocity and pressure effects on jet behavior.

  4. Buoyant formation number of a starting buoyant jet

    NASA Astrophysics Data System (ADS)

    Wang, Ruo-Qian; Law, Adrian Wing-Keung; Adams, E. Eric; Fringer, Oliver B.

    2009-12-01

    Understanding the influence of buoyancy on the formation number is important for analyzing the development of a starting buoyant jet and the interactions between its vortex ring and trailing stem. Numerical simulations with a large-eddy simulation model are performed to reproduce the starting buoyant jet in conditions ranging from pure jet to lazy plume. From the results, an improved method to determine the formation number is proposed based on the occurrence of a step jump in the vortex ring circulation. A comparison of the numerical results with the experimental data for a starting pure jet is first performed. The widely accepted formation number (?4.0) is obtained, which implies that the method is satisfactory. The effect of buoyancy on the formation number is then investigated for two turbulent discharge conditions of Re=2000 and 2500 and with a wide range of buoyancy flux. Best-fit results are obtained that correlate the formation number with the Richardson number. Finally, a slug model that incorporates buoyancy is developed to allow prediction of the "buoyant formation number" for the starting buoyant jet using a limiting value of 0.33 for the dimensionless energy, which is the same value for a pure jet.

  5. Buoyant formation number of a starting buoyant jet Ruo-Qian Wang,1

    E-print Network

    Fringer, Oliver B.

    Buoyant formation number of a starting buoyant jet Ruo-Qian Wang,1 Adrian Wing-Keung Law,2 E. Eric, Singapore 2 School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798, Singapore 3 Department of Civil and Environmental Engineering, Massachusetts Institute

  6. Buoyant plume simulation programs with interactive graphics

    SciTech Connect

    Davis, L.R. [Oregon State Univ., Corvallis, OR (United States); Hoevekamp, T. [Lehrstuhl fuer Waermeuebertragung und Klimatechnik, Aachen (Germany)

    1995-12-31

    This paper presents the development of integrate interactive graphics for the UDKHDEN and PDS mixing zone models. Iterative graphics were integrated in such a manner as to provide the user with a high degree of freedom in displaying the results graphically on the screen. The graphics created show plume shape, trajectory and concentration contours in multicolored bands. The UDKHDEN program calculates the characteristics of a line of equally spaced buoyant discharges into flowing stratified ambient water. The PDS program considers a buoyant discharge at the surface into ambient waters that has a uniform velocity and temperature distribution. Both programs are used extensively to predict dilution in environmental discharges.

  7. EXPERIMENTS ON BUOYANT PLUME DISPERSION IN A LABORATORY CONVENTION TANK

    EPA Science Inventory

    Buoyant plume dispersion in the convective boundary layer (CBL) is investigated experimentally in a laboratory convection tank. The focus is on highly-buoyant plumes that loft near the CBL capping inversion and resist downward mixing. Highly- buoyant plumes are those with dimen...

  8. Analytical model for a vertical buoyant jet

    SciTech Connect

    Lee, D.W.

    1980-10-01

    An analytical model for a round and two-dimensional turbulent buoyant jet which is discharged vertically into a stagnant ambient is developed. The buoyant jet is considered to have three separate zone models which are matched to form a complete solution. The velocity field is determined for the entire jet and plume regions by the use of an eddy viscosity which varies along the axis of the jet. The centerline decay of buoyancy is determined throughout and the results are compared to existing numerical codes. The model is applied to the disposal of carbon dioxide enriched seawater. The results can be used to provide design information for minimizing or maximizing the dilution of a discharge by the receiving environment.

  9. Vortex-Induced Vibration of a Neutrally Buoyant Tethered Sphere

    Microsoft Academic Search

    Hyeok Lee; Mark C. Thompson; Kerry Hourigan

    Recent preliminary experiments have indicated that a neutrally buoyant tethered sphere develops a large diameter quasi-circular trajectory, unlike the oscillations observed for non-neutrally buoyant tethered spheres. This shows similarities to the path of buoyant bubbles, which may follow zig-zag and\\/or helical paths depending on the Reynolds number. The current study explores the behaviour using well resolved numerical simula- tions. The

  10. The Structure of Round Buoyant Turbulent Plumes.

    NASA Astrophysics Data System (ADS)

    Dai, Zhongtao

    1995-01-01

    An experimental and theoretical study of round buoyant turbulent plumes in still and unstratified environment was conducted, emphasizing self-preserving conditions. The experiments involved downward flowing round negatively -buoyant turbulent plumes created by injecting carbon dioxide and sulfur hexafluoride into still and unstratified air. The mixture fraction and velocity properties were measured using laser-induced iodine fluorescence (LIF) and laser -Doppler velocimetry (LDV), respectively, while the combined mixture fraction/velocity properties were measured using combined LIF/LDV. The present measurements were exploited to evaluate k-varepsilon-g and Reynolds stress models of buoyant turbulent flows, by direct comparisons between model approximations and measurements. In addition, predictions of the models for the self-preserving region of round buoyant turbulent plumes were compared with measurements in order to assess overall model performance. The self-preserving conditions of round buoyant turbulent plumes were observed relatively far from the source under the present test conditions: rm (x - x_0)/d = 87~151 and rm (x - x_0)/{it l}_ {M} =12~43. Present measurements yielded distributions of mean mixture fractions and streamwise velocities in the self-preserving region that were up to 40% narrower, with appropriately scaled values near the axis up to 30% larger than earlier measurements in the literature, indicating that the earlier measurements actually involved transitional plumes. Large mixture fraction fluctuations and turbulence mass fluxes were observed in the self-preserving region due to the strong correlation between mixture fraction and velocity fluctuations. However, present measurements of velocity fluctuations and the Reynolds stress were similar to round nonbuoyant turbulent jets. Other properties reported include: probability density functions and temporal power spectral densities of mixture fraction and velocity fluctuations, integral time and length scales, two-point correlations of mixture fractions, and high-order moments of velocities and combined mixture fraction/velocity statistics. In addition, turbulence kinetic energy dissipation, mixture fraction variance dissipation, pressure/strain and pressure/mixture -fraction-fluctuation-gradient correlations were obtained from budget analysis. Evaluations of the widely used k-varepsilon -g turbulence model revealed that while mean properties were predicted reasonably well, there were deficiencies of corresponding turbulence properties. For example, streamwise turbulence and momentum fluxes exhibited countergradient diffusion. In addition, the turbulent Prandtl/Schmidt number, the ratio of the characteristic velocity and mixture fraction time scales and the coefficient of the radial gradient diffusion approximation for the Reynolds stress, all exhibited variations across the flow rather than remaining constant as prescribed by k-varepsilon -g model. Evaluations of the Reynolds stress model also revealed some deficiencies, especially somewhat poorer predictions of mean properties and a need to improve the model for the pressure/mixture-fraction-fluctuation-gradient correlation.

  11. 46 CFR 160.010-5 - Buoyant apparatus with plastic foam buoyancy.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Buoyant apparatus with plastic foam buoyancy. 160.010-5 Section...160.010-5 Buoyant apparatus with plastic foam buoyancy. (a) Buoyant apparatus with plastic foam buoyancy must have a plastic...

  12. 46 CFR 160.010-5 - Buoyant apparatus with plastic foam buoyancy.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 false Buoyant apparatus with plastic foam buoyancy. 160.010-5 Section...160.010-5 Buoyant apparatus with plastic foam buoyancy. (a) Buoyant apparatus with plastic foam buoyancy must have a plastic...

  13. 46 CFR 160.010-5 - Buoyant apparatus with plastic foam buoyancy.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Buoyant apparatus with plastic foam buoyancy. 160.010-5 Section...160.010-5 Buoyant apparatus with plastic foam buoyancy. (a) Buoyant apparatus with plastic foam buoyancy must have a plastic...

  14. Using buoyant mass to measure the growth of single cells

    E-print Network

    Godin, Michel

    We used a suspended microchannel resonator (SMR) combined with picoliter-scale microfluidic control to measure buoyant mass and determine the 'instantaneous' growth rates of individual cells. The SMR measures mass with ...

  15. Behavior of buoyant moist plumes in turbulent atmospheres

    E-print Network

    Hamza, Redouane

    1981-01-01

    A widely applicable computational model of buoyant moist plumes in turbulent atmospheres has been constructed. To achieve this a one dimensional Planetary Boundary Layer (P.B.L.) model has been developed to account for ...

  16. Formation number of positively and negatively buoyant vortex rings

    NASA Astrophysics Data System (ADS)

    Rodríguez-Rodríguez, Javier; Marugán-Cruz, Carolina; Martínez-Bazán, Carlos

    2010-11-01

    The formation process of both negatively and positively buoyant vortex rings in a piston/cylinder arrangement is investigated numerically with the aim of understanding the effect of buoyancy, characterized by a Richardson number, on the formation number. More specifically, the study focuses on how vorticity is distributed inside the vortex ring and how this vorticity distribution compares with the neutrally buoyant case. It is well known that the kinetic energy of a neutrally buoyant vortex ring, when made dimensionless with its impulse and circulation, has a universal value of End1/3. The limits of validity of this value for moderate Richardson numbers, both in the positively and negatively buoyant cases, are examined.

  17. A new framework for simulating forced homogeneous buoyant turbulent flows

    NASA Astrophysics Data System (ADS)

    Carroll, Phares L.; Blanquart, Guillaume

    2015-06-01

    This work proposes a new simulation methodology to study variable density turbulent buoyant flows. The mathematical framework, referred to as homogeneous buoyant turbulence, relies on a triply periodic domain and incorporates numerical forcing methods commonly used in simulation studies of homogeneous, isotropic flows. In order to separate the effects due to buoyancy from those due to large-scale gradients, the linear scalar forcing technique is used to maintain the scalar variance at a constant value. Two sources of kinetic energy production are considered in the momentum equation, namely shear via an isotropic forcing term and buoyancy via the gravity term. The simulation framework is designed such that the four dimensionless parameters of importance in buoyant mixing, namely the Reynolds, Richardson, Atwood, and Schmidt numbers, can be independently varied and controlled. The framework is used to interrogate fully non-buoyant, fully buoyant, and partially buoyant turbulent flows. The results show that the statistics of the scalar fields (mixture fraction and density) are not influenced by the energy production mechanism (shear vs. buoyancy). On the other hand, the velocity field exhibits anisotropy, namely a larger variance in the direction of gravity which is associated with a statistical dependence of the velocity component on the local fluid density.

  18. Buoyant Magnetic Loops Generated by Global Convective Dynamo Action

    E-print Network

    Nelson, Nicholas J; Brun, A Sacha; Miesch, Mark S; Toomre, Juri

    2012-01-01

    Our global 3D simulations of convection and dynamo action in a Sun-like star reveal that persistent wreaths of strong magnetism can be built within the bulk of the convention zone. Here we examine the characteristics of buoyant magnetic structures that are self-consistently created by dynamo action and turbulent convective motions in a simulation with solar stratification but rotating at three times the current solar rate. These buoyant loops originate within sections of the magnetic wreaths in which turbulent flows amplify the fields to much larger values than is possible through laminar processes. These amplified portions can rise through the convective layer by a combination of magnetic buoyancy and advection by convective giant cells, forming buoyant loops. We measure statistical trends in the polarity, twist, and tilt of these loops. Loops are shown to preferentially arise in longitudinal patches somewhat reminiscent of active longitudes in the Sun, although broader in extent. We show that the strength o...

  19. Arc Evolution in Response to the Subduction of Buoyant Features

    NASA Astrophysics Data System (ADS)

    Jenkins, Luke; Fourel, Loic; Goes, Saskia; Morra, Gabriele

    2015-04-01

    The subduction of buoyant features such as aseismic ridges or oceanic plateaux has been invoked to explain arc deformation, flat subduction and increase in seismic coupling. Other studies have challenged these ideas, attributing a larger role to the overriding plate. However, many open questions remain about the dynamics of the relative simple case of a single freely subducting plate. How big does a plateau need to be to change the arc shape? What is the control of plate's strength on the impact of buoyant features? How do the velocities adapt to the subduction of less dense material? In the present study, we propose a systematic approach in order to tackle these questions. We use a new 3-D coupled fluid-solid subduction model where the interaction between the slab and the isoviscous mantle is only calculated on the slab surface, significantly increasing computational efficiency. The oceanic plate rheology is visco-elasto-plastic and its top surface is free. We find that arc shape is significantly altered by the subduction of buoyant plateaux. Along the subduction plane through the plateau and depending on its size, the dip angle and the retreat velocity significantly decrease. Flat subduction is obtained in the case of large and strongly buoyant plateau/ridge. An interesting feature is that retreat velocity increases right after the plateau or ridge has finished subducting in order to catch up with the rest of the plate. The gradient in retreat velocity obtained along the trench may cause the slab to have a heterogeneous response to ridge push, eventually leading to slab advance where buoyant material is present. We apply our models to the Izu-Bonin-Marianas (IBM) trench and propose that subduction of the buoyant Caroline Island Ridge at the southern edge of the Mariana trench can explain both trench motion history and the current morphology of the IBM slab as imaged by seismic tomography.

  20. Mixing by turbulent buoyant jets in slender containers

    NASA Astrophysics Data System (ADS)

    Voropayev, S. I.; Nath, C.; Fernando, H. J. S.

    2012-10-01

    A turbulent buoyant jet injected vertically into a slender cylinder containing a stratified fluid is investigated experimentally. The working fluid is water, and salt is used to change its density to obtain either a positively or negatively buoyant jet. The interest is the vertical density distribution in container and its dependence on time and other parameters. For each case (lighter or heavier jet) the experimental data could be collapsed into a ‘universal’ time dependent behavior, when properly non-dimensionalized. A theoretical model is advanced to explain the results. Possible applications include refilling of crude oil into U.S. strategic petroleum reserves caverns.

  1. 46 CFR 160.010-6 - Capacity of buoyant apparatus.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...is approved must be the lowest number determined by the following methods: (1) Final buoyancy of the buoyant apparatus in Newtons after the watertight integrity test as described in § 160.010-7 (e) and (f), divided by 145 (divided by 32...

  2. APPLICATION OF BUOYANT MASS TRANSFER MEDIA TO HAZARDOUS MATERIAL SPILLS

    EPA Science Inventory

    A prototype system was designed and developed to slurry buoyant activated carbon into a static body of water. The process was developed to remove spilled soluable hazardous compounds from a watercourse. In a simulated spill, up to 98% removal of Diazinon, an organophosphorus pest...

  3. Hands-On Experiences with Buoyant-Less Water

    ERIC Educational Resources Information Center

    Slisko, Josip; Planinsic, Gorazd

    2010-01-01

    The phenomenon of weightlessness is known to students thanks to videos of amazing things astronauts do in spaceships orbiting the Earth. In this article we propose two hands-on activities which give students opportunities to infer by themselves the absence of buoyant force in a gravity accelerated system. The system is a free-falling or vertically…

  4. The Determination of Formation Number for Starting Buoyant Jets

    NASA Astrophysics Data System (ADS)

    Wang, Ruo-Qian; Law, Adrian Wing-Keung; Eric Adams, E.; Fringer, Oliver B.

    2010-05-01

    Starting buoyant jets are widely observed in nature as well as in engineering applications. The interactions between the leading vortex ring and the trailing stem play a significant role on the development of the staring processes, and the Formation Number is established to be the criterion that demarcates the presence of the trailing stem and thus, the occurrence of pinch-off. In this study, the buoyant formation number for a starting buoyant jet which includes the momentum inducement due to presence of buoyancy is examined numerically. The investigation is based on the results of a series of numerical simulations with the Large-Eddy Simulation (LES) approach to reproduce the starting buoyant jet in a wide range of conditions from pure jets to lazy plumes. Based on the results, the buoyant formation number can be obtained following the occurrence of a step-jump in the vortex ring circulation in the following manner. First, the vorticity is integrated through the half central plane of the computational domain, which a trough can be observed to follow the head vortex ring in the vertical distribution. The trailing stem and the head vortex ring are differentiated based on this trough location. Subsequently, if and just before a pitch off occurs, a step-jump in the circulation of the head vortex ring is typically observed. The jump value is then traced back to the total circulation, and the non-dimensional time that it occurs. This non-dimensional time is found to the same as the formation number for the runs conducted. Using this method, a comparison of the numerical results with the experimental data for a starting pure jet is performed, and the widely accepted formation number (?4.0) is obtained which verifies that the method is satisfactory. The effect of buoyancy on the formation number is then investigated for two turbulent discharge conditions of Re = 2000 and 2500 and with a wide range of buoyancy fluxes.

  5. A Generalized treatment for the computation of turbulent buoyant flows.

    NASA Astrophysics Data System (ADS)

    Demuren, Ayodeji; Grotjans, Holger

    1998-11-01

    This paper presents a generalized treatment for the computation of turbulent buoyant flows. The treatment is valid for all ranges of density differences and it does not invoke the Boussinesq approximation. Furthermore, the proper form for the buoyancy source terms in the turbulent dissipation rate (?) equation is derived, which enables the correct response of the turbulent field to the gravitational field, irrespective of the flow inclination. There is no longer any need to adjust coefficients in horizontal as opposed to vertical buoyant flows. Flows inclined at any angle to gravity as well as recirculating flows can now be computed correctly with the same coefficient. The new formulation for the computation of turbulent buoyant flows is validated by comparison to experimental data for strongly heated cavities, in natural and mixed convection, and at different angles of inclination to gravity. Computations are also performed of the "lock-exchange" flow problem using air at 2930K/293K as the medium. This could serve as a model for temperature propagation in buildings, resulting from a fire outbreak.

  6. Density Driven Removal of Sediment from a Buoyant Muddy Plume

    NASA Astrophysics Data System (ADS)

    Rouhnia, M.; Strom, K.

    2014-12-01

    Experiments were conducted to study the effect of settling driven instabilities on sediment removal from hypopycnal plumes. Traditional approaches scale removal rates with particle settling velocity however, it has been suggested that the removal from buoyant suspensions happens at higher rates. The enhancement of removal is likely due to gravitational instabilities, such as fingering, at two-fluid interface. Previous studies have all sought to suppress flocculation, and no simple model exists to predict the removal rates under the effect of such instabilities. This study examines whether or not flocculation hampers instability formation and presents a simple removal rate model accounting for gravitational instabilities. A buoyant suspension of flocculated Kaolinite overlying a base of clear saltwater was investigated in a laboratory tank. Concentration was continuously measured in both layers with a pair of OBS sensors, and interface was monitored with digital cameras. Snapshots from the video were used to measure finger velocity. Samples of flocculated particles at the interface were extracted to retrieve floc size data using a floc camera. Flocculation did not stop creation of settling-driven fingers. A simple cylinder-based force balance model was capable of predicting finger velocity. Analogy of fingering process of fine grained suspensions to thermal plume formation and the concept of Grashof number enabled us to model finger spacing as a function of initial concentration. Finally, from geometry, the effective cross-sectional area was correlated to finger spacing. Reformulating the outward flux expression was done by substitution of finger velocity, rather than particle settling velocity, and finger area instead of total area. A box model along with the proposed outward flux was used to predict the SSC in buoyant layer. The model quantifies removal flux based on the initial SSC and is in good agreement with the experimental data.

  7. Magnetic Cycles and Buoyant Loops in Convective Dynamos

    NASA Astrophysics Data System (ADS)

    Nelson, Nicholas J.

    2013-01-01

    Solar-type stars display a rich spectrum of magnetic activity. Seeking to explore convective dynamo action in solar-like stars with the anelastic spherical harmonic (ASH) code, we have carried out a series of global 3-D MHD simulations. Here we report on the dynamo mechanisms realized in a series of numerical models of a sun-like star which explore the effects of decreasing diffusion. While these models nominally rotate at three times the current solar rate (3?), the results may be more widely applicable as both these simulations and the solar convection zone achieve similar levels of rotationally constrained convection. Previous simulations at 3? have shown that convective dynamos can build persistent wreath-like structures of strong toroidal magnetic field in the convection zone (Brown et al. 2010). Here we find that magnetic reversals and cycles can be realized at 3? by decreasing the explicit diffusion and thereby making the resolved flows more turbulent. In these more turbulent models, diffusive processes no longer play a primary role in the key dynamical balances which maintain differential rotation and generate the global-scale wreaths. With reduced resistive diffusion of magnetic fields, the axisymmetric poloidal fields can no longer achieve a steady state and this triggers reversals in global magnetic polarity. Additionally, the enhanced levels of turbulence lead to greater intermittency in the toroidal magnetic wreaths, which can create buoyant magnetic loops that rise from the deep interior to the upper regions of our simulated domain. Turbulence-enabled magnetic buoyancy in our most turbulent simulation yields large numbers of buoyant loops, enabling us to examine the distribution of the characteristics of buoyant magnetic loops, such as twist, tilt angle, and relation to axisymmetric fields. These models provide a pathway towards linking convective dynamo models and the emergence of magnetic flux in the Sun and sun-like stars.

  8. On the cooling of a buoyant boundary current

    NASA Astrophysics Data System (ADS)

    Ou, Hsien-Wang

    2005-06-01

    Through a steady-state reduced-gravity model, we examine the downstream evolution of a buoyant boundary current as it is subjected to surface cooling. It is found that the adverse pressure gradient associated with the diminishing buoyancy is countered by falling pressure head, so the overall strength of the current—as measured by the (transport-weighted) mean square velocity—remains unchanged. This constancy also applies to the cross-stream difference of the square velocity because of the vorticity constraint, which leads to the general deduction that the net current shear is enhanced regardless of its upstream sign. As a consequence, if the upstream flow contains near-shore and offshore branches that are comparable in strength, this parity would persist downstream; but if the near-shore branch is weaker to begin with, it may be stagnated by cooling, with the ensuing generation of anti-cyclonic eddies. On account of the geostrophic balance, the buoyant layer narrows as the square root of the buoyancy—the same rate as the falling pressure head, but more rapid than that of the local deformation radius. Some of the model predictions are compared with observations from the Tsushima Current in the Japan/East Sea.

  9. Acoustic scattering from a thermally driven buoyant plume revisited John Oeschger

    E-print Network

    Goodman, Louis

    Acoustic scattering from a thermally driven buoyant plume revisited John Oeschger Coastal Systems and L. Goodman, JASA, Acoustic scattering 1 #12;Far-field weak scattering theory is applied to the case of high frequency broadbandwidth acoustic scattering from a thermally generated buoyant plume

  10. Buoyant Surface Discharges into Water Bodies. I: Flow Classification and Prediction Methodology

    Microsoft Academic Search

    Gilbert R. Jones; Jonathan D. Nash; Robert L. Doneker

    2007-01-01

    Buoyant surface discharges into ambient water bodies can exhibit multiple complex flow processes, which cover the spatial range from the near field with initial jet mixing to the far field with passive ambient diffusion. Multiple flow phenomena can occur, such as buoyant collapse motions, bottom attachment, deflection by the ambient current, and dynamic shoreline interaction, in the near field, and

  11. 46 CFR 160.010-4 - General requirements for buoyant apparatus.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...color of the buoyant apparatus must be primarily vivid reddish orange as defined by sections 13 and 14 of the “Color Names Dictionary.” (o) When fibrous-glass-reinforced plastic is used in the construction of a buoyant apparatus, each cut...

  12. Flow behaviour of negatively buoyant jets in immiscible ambient fluid

    NASA Astrophysics Data System (ADS)

    Geyer, A.; Phillips, J. C.; Mier-Torrecilla, M.; Idelsohn, S. R.; Oñate, E.

    2012-01-01

    In this paper we investigate experimentally the injection of a negatively buoyant jet into a homogenous immiscible ambient fluid. Experiments are carried out by injecting a jet of dyed fresh water through a nozzle in the base of a cylindrical tank containing rapeseed oil. The fountain inlet flow rate and nozzle diameter were varied to cover a wide range of Richardson Ri (8 × 10-4 < Ri < 1.98), Reynolds Re (467 < Re < 5,928) and Weber We (2.40 < We < 308.56) numbers. Based on the Re, Ri and We values for the experiments, we have determined a regime map to define how these values may control the occurrence of the observed flow types. Whereas Ri plays a stronger role when determining the maximum penetration height, the effect of the Reynolds number is stronger predicting the flow behaviour for a specific nozzle diameter and injection velocity.

  13. Incipient buoyant thermal convection in a vertical cylindrical annulus

    SciTech Connect

    Littlefield, D.L. (US Army Ballistic Research Lab., Aberdeen Proving Ground, MD (USA)); Desai, P.V. (Georgia Inst. of Tech., Atlanta (USA))

    1990-11-01

    The incipient buoyant thermal convection in a vertical cylindrical annulus when heated from below is examined. The ends are assumed to be free, and the sidewalls perfectly conducting. The temperature needed to initiate fluid motion is expressed nondimensionally in terms of the Rayleigh number. The analytical conflict that arises for annuli of infinite aspects ratios due to insufficient independent boundary conditions is resolved. Calculations for the critical Rayleigh numbers are presented for a variety of geometries, and the corresponding velocity and temperature perturbations are also shown. The number of cells increases as the aspect and radius ratio decrease with a strong bias towards the development of azimuthally varying cells. These changes in cellular behavior are expected based on physical justifications and comparisons with previous studies.

  14. (Revised May 22, 2012) (1) To experimentally determine the relationship between the buoyant forces on an object that

    E-print Network

    Collins, Gary S.

    sinking and for keeping hot air balloons in flight. In the absence of other forces, the net force, FNet cylinder hanging from it in the air. By doing this any upward buoyant force will be measured directly the buoyant forces on an object that displaces known weights of water. (2) To compare the buoyant behavior

  15. (Revised May 22, 2012) (1) To experimentally determine the relationship between the buoyant forces on objects that

    E-print Network

    Collins, Gary S.

    and for keeping hot air balloons in flight. In the absence of other forces, the net force, FNet, acting with the aluminum cylinder hanging from it in the air. By doing this any upward buoyant force will be measured the buoyant forces on objects that displace known weights of water. (2) To compare the buoyant behavior

  16. Predicting Buoyant Shear Flows Using Anisotropic Dissipation Rate Models

    NASA Technical Reports Server (NTRS)

    So, R. M. C.; Zhao, C. Y.; Gatski, T. B.

    1999-01-01

    This paper examines the modeling of two-dimensional homogeneous stratified turbulent shear flows using the Reynolds-stress and Reynolds-heat-flux equations. Several closure models have been investigated-, the emphasis is placed on assessing the effect of modeling the dissipation rate tensor in the Reynolds-stress equation. Three different approaches are considered: one is an isotropic approach while the other two are anisotropic approaches. The isotropic approach is based on Kolmogorov's hypothesis and a dissipation rate equation modified to account for vortex stretching. One of the anisotropic approaches is based on an algebraic representation of the dissipation rate tensor, while another relies on solving a modeled transport equation for this tensor. In addition, within the former anisotropic approach, two different algebraic representations are examined one is a function of the Reynolds-stress anisotropy tensor, and the other is a function of' the mean velocity gradients. The performance of these closure models is evaluated against experimental and direct numerical simulation data of pure shear flows. pure buoyant flows and buoyant shear flows. Calculations have been carried out over a range of Richardson numbers (Ri) and two different Prandtl numbers (Pr); thus the effect of Pr on the development of counter-gradient heat flux in a stratified shear flow can be assessed. At low Ri, the isotropic model performs well in the predictions of stratified shear flows; however, its performance deteriorates as Ri increases. At high Ri, the transport equation model for the dissipation rate tensor gives the best result. Furthermore, the results also lend credence to the algebraic dissipation rate model based on the Reynolds stress anisotropy tensor. Finally, it is found that Pr has an effect on the development of counter-gradient heat flux. The calculations show that, under the action of shear, counter-gradient heat flux does not occur even at Ri = 1 in an air flow.

  17. Wind-tunnel tests and computer simulations of buoyant wing-tip vortices

    NASA Technical Reports Server (NTRS)

    Costen, R. C.; Davidson, R. E.; Rogers, G. T.

    1974-01-01

    It is demonstrated that wing-tip vortices with buoyant cores can be made in a wind tunnel. Wing-tip vortices generated by an aircraft often become buoyant, because of heating effects due to the jet exhaust or in connection with a descending motion in a stable atmosphere. A description of wind-tunnel studies is given, taking into account the experimental conditions, the transition to turbulence, and the drift of the buoyant vortex. A computer simulation of wing-tip vortices is also discussed.

  18. Shapes of Buoyant and Nonbuoyant Methane Laminar Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Sunderland, Peter B.; Yuan, Zeng-Guang; Urban, David L.

    1997-01-01

    Laminar gas jet diffusion flames represent a fundamental combustion configuration. Their study has contributed to numerous advances in combustion, including the development of analytical and computational combustion tools. Laminar jet flames are pertinent also to turbulent flames by use of the laminar flamelet concept. Investigations into the shapes of noncoflowing microgravity laminar jet diffusion flames have primarily been pursued in the NASA Lewis 2.2-second drop tower, by Cochran and coworkers and by Bahadori and coworkers. These studies were generally conducted at atmospheric pressure; they involved soot-containing flames and reported luminosity lengths and widths instead of the flame-sheet dimensions which are of Greater value to theory evaluation and development. The seminal model of laminar diffusion flames is that of Burke and Schumann, who solved the conservation of momentum equation for a jet flame in a coflowing ambient by assuming the velocity of fuel, oxidizer and products to be constant throughout. Roper and coworkers improved upon this model by allowing for axial variations of velocity and found flame shape to be independent of coflow velocity. Roper's suggestion that flame height should be independent of gravity level is not supported by past or present observations. Other models have been presented by Klajn and Oppenheim, Markstein and De Ris, Villermaux and Durox, and Li et al. The common result of all these models (except in the buoyant regime) is that flame height is proportional to fuel mass flowrate, with flame width proving much more difficult to predict. Most existing flame models have been compared with shapes of flames containing soot, which is known to obscure the weak blue emission of flame sheets. The present work involves measurements of laminar gas jet diffusion flame shapes. Flame images have been obtained for buoyant and nonbuoyant methane flames burning in quiescent air at various fuel flow-rates, burner diameters and ambient pressures. Soot concentrations were minimized by selecting conditions at low flowrates and low ambient pressures; this allows identification of actual flame sheets associated with blue emissions of CH and CO2. The present modeling effort follows that of Roper and is useful in explaining many of the trends observed.

  19. 46 CFR 117.137 - Stowage of life floats and buoyant apparatus.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...of a dark color or of a type certified to be resistant to deterioration from ultraviolent light; and (3) If metal, be corrosion resistant. (d) If the life float or buoyant apparatus does not have a painter attachment fitting, a...

  20. 46 CFR 117.137 - Stowage of life floats and buoyant apparatus.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...of a dark color or of a type certified to be resistant to deterioration from ultraviolent light; and (3) If metal, be corrosion resistant. (d) If the life float or buoyant apparatus does not have a painter attachment fitting, a...

  1. 46 CFR 117.137 - Stowage of life floats and buoyant apparatus.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...of a dark color or of a type certified to be resistant to deterioration from ultraviolent light; and (3) If metal, be corrosion resistant. (d) If the life float or buoyant apparatus does not have a painter attachment fitting, a...

  2. 46 CFR 117.137 - Stowage of life floats and buoyant apparatus.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...of a dark color or of a type certified to be resistant to deterioration from ultraviolent light; and (3) If metal, be corrosion resistant. (d) If the life float or buoyant apparatus does not have a painter attachment fitting, a...

  3. 46 CFR 117.137 - Stowage of life floats and buoyant apparatus.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...of a dark color or of a type certified to be resistant to deterioration from ultraviolent light; and (3) If metal, be corrosion resistant. (d) If the life float or buoyant apparatus does not have a painter attachment fitting, a...

  4. Mixing depth of a submerged, horizontally injected buoyant jet

    SciTech Connect

    Johnstone, H.W.; Zangrando, F.

    1988-05-01

    Tests in the laboratory were conducted to determine the effective mixing depth of turbulent buoyant fluid injected horizontally into an initially unstratified environment through a radial, deeply submerged diffuser. The diffuser was moved slowly during the experiments, at a rate much smaller than the entrainment and mixing process. The effective mixing depth is defined as the relative position between the initial injector level and the lowest position of the resulting mixed layer over which the injected fluid is deposited. Results have applications to discharge of contaminants and heat into large reservoirs (sewage disposal, power plants, OTEC systems) and establishment of a stratified region as is required for operation of salt gradient solar ponds. A functional dependence between mixing depth, scaled by the injector slot-size, and injector Froude number was found. Dependence on submergence was not found for the large submergence values tested; dependence on diffuser radius was not investigated. The laboratory data compare well with results obtained in a reservoir of 3355 m/sup 2/ surface area and indicate a strong dependence of effective mixing depth on the Froude number.

  5. Microstructure and rheology of finite inertia neutrally buoyant suspensions

    E-print Network

    Hamed Haddadi; Jeffrey F. Morris

    2014-03-30

    The microstructure and rheological properties of suspensions of neutrally buoyant hard spherical particles in Newtonian fluid under conditions of finite inertia are studied using the lattice-Boltzmann method (LBM), which is based on a discrete Boltzmann model for the fluid and Newtonian dynamics for the particles. The suspensions are subjected to simple-shear flow and the properties are studied as a function of Reynolds number and volume fraction, $\\phi$. The inertia is characterized by the particle-scale shear flow Reynolds number $Re = \\frac{\\rho \\dot{\\gamma}a^{2}}{\\mu}$, where $a$ is the particle radius, $\\dot{\\gamma}$ is the shear rate and $\\rho$ and $\\mu$ are the density and viscosity of the fluid, respectively. The influences of inertia and of the volume fraction are studied for $0.005\\leqslant Re \\leqslant 5$ and $0.1\\leqslant \\phi \\leqslant 0.35$. The flow-induced microstructure is studied using the pair distribution function $g(\\boldsymbol{r})$. Different stress mechanisms, including those due to surface tractions (stresslet), acceleration, and the Reynolds stress due to velocity fluctuations are computed and their influence on the first and second normal stress differences, the particle pressure and the viscosity of the suspensions are detailed. The probability density functions of particle force and torque are also presented.

  6. Wave induced transport and mixing of buoyant particles

    NASA Astrophysics Data System (ADS)

    Drivdal, Magnus; Broström, Göran; Christensen, Kai H.

    2014-05-01

    The modeling of wave-current and wave-turbulence interactions have received much attention during recent years. Both the breaking of surface waves and the inclusion of the Stokes shear production have been shown to increase the upper ocean turbulence. Furthermore the Coriolis force acting on the Stokes drift redistributes the momentum in the upper ocean, leading to a deflection of the currents. An important application affected by these processes that still needs to be studied is the mixing and drift of particles. Using an ocean column model, modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production as well as the stronger veering by the Coriolis-Stokes force effects the drift of suspended particles. Here the suspended particles are buoyant tracers that can represent oil droplets or plankton, for example fish eggs and larvae. The energy and momentum fluxes as well as the Stokes drift depend on the directional wave spectrum that can be obtained from a wave model or from observations. Comparing with classical Ekman theory some physical effects on the system are studied, and as a realistic test case we use the model to study the oil drift after an offshore oil spill that took place outside the western coast of Norway in 2007. During this accident the average net drift of oil was observed to be approximately 0.1% of the wind speed at an angle of about 90-120 degrees to the right, far slower and more deflected away from the wind direction than predicted by both numerical and empirical models. With wind and wave forcing from ECMWF reanalysis data, it is shown that the wave effects are important for the resultant drift in this case, and has the potential to improve drift forecasting.

  7. Preliminary study of ground handling characteristics of Buoyant Quad Rotor (BQR) vehicles

    NASA Technical Reports Server (NTRS)

    Browning, R. G. E.

    1980-01-01

    A preliminary investigation of mooring concepts appropriate for heavy lift buoyant quad rotor (BQR) vehicles was performed. A review of the evolution of ground handling systems and procedures for all airship types is presented to ensure that appropriate consideration is given to past experiences. Two buoyant quad rotor designs are identified and described. An analysis of wind loads on a moored airship and the effects of these loads on vehicle design is provided. Four mooring concepts are assessed with respect to the airship design, wind loads and mooring site considerations. Basing requirements and applicability of expeditionary mooring at various operational scenarios are addressed.

  8. Note: Buoyant-force assisted liquid membrane electrochemical etching for nano-tip preparation.

    PubMed

    Zeng, Yongbin; Wang, Yufeng; Wu, Xiujuan; Xu, Kun; Qu, Ningsong

    2014-12-01

    A liquid membrane electrochemical etching process for preparing nano-tips is proposed by the introduction of buoyant force to the lower tip, in which the lower portion of the anodic wire is immersed into a floating layer. A mathematical model of this method is derived. Both calculation and experimental results demonstrate that the introduction of buoyant force can significantly decrease the tip radius. The lubricating oil and deionized water floating layers were tested for the processing of nano-tips. Further, high-aspect-ratio nano-electrodes were prepared by applying a relative vertical movement to the anodic wire. PMID:25554341

  9. Application of FDS and FireFOAM in Large Eddy Simulations of a Turbulent Buoyant Helium Plume

    Microsoft Academic Search

    G. Maragkos; P. Rauwoens; B. Merci

    2012-01-01

    Large eddy simulations are conducted in the near-field region of a large turbulent buoyant helium plume. Such plumes are of relevance for fire safety research due to the similar flow features as in the buoyant (smoke) plumes above the fire source. The transient and mean flow dynamics are discussed with and without the use of a Smagorinsky-type subgrid scale (SGS)

  10. 3D Numerical Simulation of Turbulent Buoyant Flow and Heat Transport in a Curved Open Channel

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A three-dimensional buoyancy-extended version of kappa-epsilon turbulence model was developed for simulating the turbulent flow and heat transport in a curved open channel. The density- induced buoyant force was included in the model, and the influence of temperature stratification on flow field was...

  11. BUOYANT PLUME DISPERSAL IN THE CONVECTIVE BOUNDARY LAYER: ANALYSIS OF EXPERIMENTAL DATA AND LAGRANGIAN MODELING

    EPA Science Inventory

    The aim of this research program is to improve our knowledge and predictive capability of buoyant plume dispersion in the convective boundary layer (CBL) with emphasis on the mean (C) and root-mean-square (?c) concentration fields. The CBL turbulence leads to large random fluc...

  12. What is a flux tube? On the magnetic field topology of buoyant flux structures

    E-print Network

    What is a flux tube? On the magnetic field topology of buoyant flux structures Fausto Cattaneo, visually resembling idealised magnetic flux tubes, are generated self-consistently by numerical simulation of the magnetically-active region. We discuss how these results impact our simple ideas of a magnetic flux tube

  13. Applying a Predict-Observe-Explain Sequence in Teaching of Buoyant Force

    ERIC Educational Resources Information Center

    Radovanovic, Jelena; Slisko, Josip

    2013-01-01

    An active learning sequence based on the predict-observe-explain teaching strategy is applied to a lesson on buoyant force. The results obtained clearly justify the use of this teaching method and suggest devising a series of activities to enable more effective removal of students' commonly held alternative conceptions regarding floating and…

  14. Neutrally buoyant anisotropic particles for flow visualization P. Matisse and M. Gorman

    E-print Network

    Neutrally buoyant anisotropic particles for flow visualization P. Matisse and M. Gorman Citation.1063/1.864702 View Table of Contents: http://scitation.aip.org/content/aip/journal/pof1/27/4?ver=pdfcov Published in fluid flows: Comparison of experiments with Lagrangian stochastic models Phys. Fluids 23, 093304 (2011

  15. 46 CFR 160.010-4 - General requirements for buoyant apparatus.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...absorbs little or no water. The life line must...workmanship. (m) Each metal part of a buoyant apparatus...stainless steel or have salt water and salt air corrosion characteristics equal...compatible with each other metal part in contact...

  16. SOOTING BEHAVIOR DYNAMICS OF A NON-BUOYANT LAMINAR DIFFUSION FLAME

    Microsoft Academic Search

    A. FUENTES; S. ROUVREAU; P. JOULAIN; J.-P. Vantelon; G. LEGROS; J. L. TORERO; A. C. FERNANDEZ-PELLO

    2007-01-01

    Local soot concentrations in non-buoyant laminar diffusion flames have been demonstrated to be the outcome of two competitive processes, soot formation and soot oxidation. It was first believed that soot formation was the controlling mechanism and thus soot volume fractions could be scaled with a global residence time. Later studies showed that this is not necessarily the case and the

  17. The Magnetostrophic Rise of A Buoyant Parcel In the Earth's Core

    Microsoft Academic Search

    H. K. Moffatt; D. E. Loper

    1994-01-01

    SUMMARY The dynamics of a buoyant parcel (or blob) of fluid released from the mushy zone on the inner core boundary (ICB) is considered. Estimates of the density defect and of the rise velocity are obtained from consideration of mass conservation and magnetostrophic force balance. When Lorentz and Coriolis forces are of comparable orders of magnitude, the disturbance remains localized

  18. DNA BUOYANT DENSITY SHIFTS DURING 15N DNA STABLE ISOTOPE PROBING.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Successful use of 13C stable isotope probing (SIP) to investigate microbial function in natural environments has stimulated interest in SIP technology using other isotopes. 15N-SIP is effective in buoyant density (BD) gradient separation of isotopically-enriched DNA, however, the resulting change in...

  19. Interaction of a water mist with a buoyant methane diffusion flame

    Microsoft Academic Search

    George Gogos

    1995-01-01

    This work describes observations and measurements from the interaction of a fine water spray from a hollow cone nozzle, with purely buoyant diffusion flames from a natural gas ceramic-plate burner located directly underneath the nozzle. The burner plate was instrumented with thermocouples cemented on its upper and lower surfaces to assess the influence of the spray on the burner temperature.

  20. 46 CFR 180.137 - Stowage of life floats and buoyant apparatus.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...be of a dark color or of a type certified to be resistant to deterioration from ultraviolet light; and (3) If metal, be corrosion resistant. (d) If the life float or buoyant apparatus does not have a painter attachment fitting, a...

  1. 46 CFR 180.137 - Stowage of life floats and buoyant apparatus.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...be of a dark color or of a type certified to be resistant to deterioration from ultraviolet light; and (3) If metal, be corrosion resistant. (d) If the life float or buoyant apparatus does not have a painter attachment fitting, a...

  2. 46 CFR 180.137 - Stowage of life floats and buoyant apparatus.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...be of a dark color or of a type certified to be resistant to deterioration from ultraviolet light; and (3) If metal, be corrosion resistant. (d) If the life float or buoyant apparatus does not have a painter attachment fitting, a...

  3. 46 CFR 180.137 - Stowage of life floats and buoyant apparatus.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...be of a dark color or of a type certified to be resistant to deterioration from ultraviolet light; and (3) If metal, be corrosion resistant. (d) If the life float or buoyant apparatus does not have a painter attachment fitting, a...

  4. 46 CFR 180.137 - Stowage of life floats and buoyant apparatus.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...be of a dark color or of a type certified to be resistant to deterioration from ultraviolet light; and (3) If metal, be corrosion resistant. (d) If the life float or buoyant apparatus does not have a painter attachment fitting, a...

  5. Influence of viscosity contrast on buoyantly unstable miscible fluids in porous media

    E-print Network

    Pramanik, Satyajit; Mishra, Manoranjan

    2015-01-01

    The influence of viscosity contrast on buoyantly unstable miscible fluids in a porous medium is investigated through a linear stability analysis (LSA) as well as direct numerical simulations (DNS). The linear stability method implemented in this paper is based on an initial value approach, which helps to capture the onset of instability more accurately than the quasi-steady state analysis. In the absence of displacement, we show that viscosity contrast delays the onset of instability in buoyantly unstable miscible fluids. Further, it is observed that suitably choosing the viscosity contrast and injection velocity a gravitationally unstable miscible interface can be stabilized completely. Through LSA we draw a phase diagram, which shows three distinct stability regions in a parameter space spanned by the displacement velocity and the viscosity contrast. DNS are performed corresponding to parameters from each regime and the results obtained are in accordance with the linear stability results. Moreover, the conv...

  6. Laboratory Experiments on the Interaction of a Buoyant Coastal Current with a Canyon: Application to the East Greenland Current

    E-print Network

    Sutherland, David A.

    This paper presents a set of laboratory experiments focused on how a buoyant coastal current flowing over a sloping bottom interacts with a canyon and what controls the separation, if any, of the current from the upstream ...

  7. Numerical simulation of buoyant plume dispersion in a stratifice atmosphere using a lagrangian stochastic model

    Microsoft Academic Search

    Hyun-Goo Kim; Yoo-Jeong Noh; Choung-Mook Lee; Don-Bum Choi

    2003-01-01

    In the present paper, numerical simulations of buoyant plume dispersion in a neutral and stable atmospheric boundary layer\\u000a have been carried out. A Lagrangian Stochastic Model (LSM) with a Non-Linear Eddy Viscosity Model (NLEVM) for turbulence is\\u000a used to generate a Reynolds stress field as an input condition of dispersion simulation. A modified plume-rise equation is\\u000a included in dispersion simulation

  8. BUOYANT MAGNETIC LOOPS IN A GLOBAL DYNAMO SIMULATION OF A YOUNG SUN

    SciTech Connect

    Nelson, Nicholas J.; Toomre, Juri [JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309-0440 (United States); Brown, Benjamin P. [Department of Astronomy and Center for Magnetic Self-Organization (CSMO) in Laboratory and Astrophysical Plasmas, University of Wisconsin, Madison, WI 53706-1582 (United States); Brun, Allan Sacha [Laboratoire AIM Paris-Saclay, CEA/Irfu Universite Paris-Diderot CNRS/INSU, 91191 Gif-sur-Yvette (France); Miesch, Mark S. [High Altitude Observatory, NCAR, Boulder, CO 80307-3000 (United States)

    2011-10-01

    The current dynamo paradigm for the Sun and Sun-like stars places the generation site for strong toroidal magnetic structures deep in the solar interior. Sunspots and starspots on Sun-like stars are believed to arise when sections of these magnetic structures become buoyantly unstable and rise from the deep interior to the photosphere. Here, we present the first three-dimensional global magnetohydrodynamic (MHD) simulation in which turbulent convection, stratification, and rotation combine to yield a dynamo that self-consistently generates buoyant magnetic loops. We simulate stellar convection and dynamo action in a spherical shell with solar stratification, but rotating three times faster than the current solar rate. Strong wreaths of toroidal magnetic field are realized by dynamo action in the convection zone. By turning to a dynamic Smagorinsky model for subgrid-scale turbulence, we here attain considerably reduced diffusion in our simulation. This permits the regions of strongest magnetic field in these wreaths to rise toward the top of the convection zone via a combination of magnetic buoyancy instabilities and advection by convective giant cells. Such a global simulation yielding buoyant loops represents a significant step forward in combining numerical models of dynamo action and flux emergence.

  9. The response of buoyant laminar diffusion flames to low-frequency forcing

    SciTech Connect

    Williams, Timothy C.; Shaddix, Christopher R.; Schefer, Robert W. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550 (United States); Desgroux, Pascale [Physicochimie des Processus de Combustion et de l'Atmosphere, Universite des Sciences et Technologies de Lille, Villeneuve d'Ascq Cedex (France)

    2007-12-15

    Buoyant jet diffusion flames are frequently used to investigate phenomena associated with flares or fires, such as the formation and emission of soot, polycyclic aromatic hydrocarbons (PAH), and carbon monoxide (CO). To systematically investigate the influence of transient vortex-flame interactions on these processes, laminar jet flames may be periodically forced. Previous work has demonstrated that forcing the fuel stream at a (low) frequency close to the natural buoyant instability frequency will trigger the production of vortices on the air side of the high-temperature reaction zone, coupling the overall flame response to the forcing frequency. In the work reported here, measurements in methane/air and ethylene/air slot flames show that over a substantial range of forcing frequencies and amplitudes, the dominant, air-side vortex production is locked at precisely one-half the excitation frequency of the fuel stream. This phenomenon is examined in detail through the utilization of several laser diagnostic techniques, yielding measurements of both the frequency response of the flames and phase-locked images of the internal flame structure. Under some conditions the subharmonic response of the flame leads to transient separation of the PAH and soot layers from the surrounding high-temperature flame zone, potentially affecting the soot formation and radiation processes. This data should provide useful information for comparison with detailed modeling aimed to improve the understanding of the complex nature of the buoyant instability in jet flames. (author)

  10. Observations of currents and density structure across a buoyant plume front

    USGS Publications Warehouse

    Gelfenbaum, G.; Stumpf, R.P.

    1993-01-01

    Observations of the Mobile Bay, Alabama, plume during a flood event in April 1991 reveal significant differences in the current field on either side of a front associated with the buoyant plume. During a strong southeasterly wind, turbid, low salinity water from Mobile Bay was pushed through an opening in the west side of the ebb-tidal delta and moved parallel to the coast. A stable front developed between the low salinity water of the buoyant plume (11???) and the high salinity coastal water (>23???) that was being forced landward by the prevailing winds. Despite the shallow water depth of 6 m, measurements of currents, temperature, and salinity show large shears and density gradients in both the vertical and the horizontal directions. At a station outside of the buoyant plume, currents at 0.5 m and 1.5 m below the surface were in the same direction as the wind. Inside the plume, however, currents at 0.5 m below the surface were parallel to the coast, 45??, off the direction of the wind and the magnitude was 45% larger than the magnitude of the surface currents outside the plume. Beneath the level of the plume, the currents were identical to the wind-driven currents in the ambient water south of the front. Our observations suggest that the wind-driven surface currents of the ambient water converged with the buoyant plume at the front and were subducted beneath the plume. The motion of the ambient coastal surface water was in the direction of the local wind stress, however, the motion of the plume had no northerly component of motion. The plume also did not show any flow toward the front, suggesting a balance between the northerly component of wind stress and the southerly component of buoyant spreading. In addition, the motion of the plume did not appear to affect the motion of the underlying ambient water, suggesting a lack of mixing between the two waters. ?? 1993 Estuarine Research Federation.

  11. Large Eddy Simulation of a Forced Round Turbulent Buoyant Plume in Neutral Surroundings

    NASA Technical Reports Server (NTRS)

    Basu, A. J.; Mansour, N. N.; Koga, Dennis (Technical Monitor)

    1999-01-01

    Buoyant flows play an important role in various technological and environmental issues. For example, dispersal of pollutants, smoke, or volcano exhaust in the atmosphere, vertical motion of air, formation of clouds and other weather systems, and flows in cooling towers and fires are all determined primarily by buoyancy effects. The buoyancy force in such flows can originate from either a heat source or due to different densities between a fluid and its surroundings. Whatever the cause, the flow can be understood by studying the effects of the tight coupling between the thermal and the velocity fields since density differences can be characterized as temperature differences.

  12. Dynamic stability of a buoyant quad-rotor aircraft. [for airlifting payloads externally on a sling

    NASA Technical Reports Server (NTRS)

    Nagabhushan, B. L.; Tomlinson, N. P.

    1982-01-01

    Stability characteristics of a buoyant quad-rotor aircraft (BQRA) in hover and forward flight are examined by considering linear, state-variable, and nonlinear flight simulation models of such a configuration. The effects of carrying a sling load on the vehicle dynamics is predicted by considering a coupled model of the two bodies. Inherent stability characteristics of the vehicle are analyzed and compared with those of a helicopter and an airship in free flight. Typical operational conditions that could lead to vehicle instability are described in the flight envelope of interest.

  13. Buoyant Boats

    NSDL National Science Digital Library

    Engineering K-PhD Program,

    Students conduct a simple experiment to see how the water level changes in a beaker when a lump of clay sinks in the water and when the same lump of clay is shaped into a bowl that floats in the water. They notice that the floating clay displaces more water than the sinking clay does, perhaps a surprising result. Then they determine the mass of water that is displaced when the clay floats in the water. A comparison of this mass to the mass of the clay itself reveals that they are approximately the same.

  14. Buoyant Bubbles

    NSDL National Science Digital Library

    Lawrence Hall of Science

    2009-01-01

    What keeps bubbles and other things, like airplanes, floating or flying in the air? In this activity, learners blow bubbles and wave 3x5 cards above, below and on different sides of the bubbles to keep them afloat as long as possible. The Did You Know section explains the Bernoulli principle: how waving cards above the bubbles helps keep them afloat because faster moving air exerts less pressure to push the bubbles down. The activity can be extended by having learners wave their bubbles through an obstacle course they design themselves.

  15. Laboratory experiments on the interaction between inclined negatively buoyant jets and regular waves

    NASA Astrophysics Data System (ADS)

    Ferrari, Simone; Querzoli, Giorgio

    2015-05-01

    In this paper we present the results from a series of laboratory experiments on inclined negatively buoyant jets released in a receiving environment with waves. This simulates the case, typical of many practical applications, of the sea discharge of fluids denser than the receiving environment, as in the case of the brine from a desalination plant. The experiments were performed employing a Light Induced Fluorescence (LIF) technique, in order to measure the concentration fields. Both the jet and the wave motion features were varied, in order to simulate a typical discharge into the Mediterranean Sea. Reference discharges in a stagnant environment were performed as well. The jet behaviour was analyzed from a statistical point of view, both considering the global phenomenon and its single phases. The influence of the wave motion on the inclined negatively buoyant jet geometry and dilution turns out to be a combined action of a split into two branches of the jet and a rotation. Their combined action decreases the jet maximum height and the impact distance, and is the main cause for the higher dilution reached in a wavy environment.

  16. A simple technique for measuring buoyant weight increment of entire, transplanted coral colonies in the field

    PubMed Central

    Herler, Jürgen; Dirnwöber, Markus

    2011-01-01

    Estimating the impacts of global and local threats on coral reefs requires monitoring reef health and measuring coral growth and calcification rates at different time scales. This has traditionally been mostly performed in short-term experimental studies in which coral fragments were grown in the laboratory or in the field but measured ex situ. Practical techniques in which growth and measurements are performed over the long term in situ are rare. Apart from photographic approaches, weight increment measurements have also been applied. Past buoyant weight measurements under water involved a complicated and little-used apparatus. We introduce a new method that combines previous field and laboratory techniques to measure the buoyant weight of entire, transplanted corals under water. This method uses an electronic balance fitted into an acrylic glass underwater housing and placed atop of an acrylic glass cube. Within this cube, corals transplanted onto artificial bases can be attached to the balance and weighed at predetermined intervals while they continue growth in the field. We also provide a set of simple equations for the volume and weight determinations required to calculate net growth rates. The new technique is highly accurate: low error of weight determinations due to variation of coral density (< 0.08%) and low standard error (< 0.01%) for repeated measurements of the same corals. We outline a transplantation technique for properly preparing corals for such long-term in situ experiments and measurements. PMID:22049248

  17. A simple technique for measuring buoyant weight increment of entire, transplanted coral colonies in the field.

    PubMed

    Herler, Jürgen; Dirnwöber, Markus

    2011-10-31

    Estimating the impacts of global and local threats on coral reefs requires monitoring reef health and measuring coral growth and calcification rates at different time scales. This has traditionally been mostly performed in short-term experimental studies in which coral fragments were grown in the laboratory or in the field but measured ex situ. Practical techniques in which growth and measurements are performed over the long term in situ are rare. Apart from photographic approaches, weight increment measurements have also been applied. Past buoyant weight measurements under water involved a complicated and little-used apparatus. We introduce a new method that combines previous field and laboratory techniques to measure the buoyant weight of entire, transplanted corals under water. This method uses an electronic balance fitted into an acrylic glass underwater housing and placed atop of an acrylic glass cube. Within this cube, corals transplanted onto artificial bases can be attached to the balance and weighed at predetermined intervals while they continue growth in the field. We also provide a set of simple equations for the volume and weight determinations required to calculate net growth rates. The new technique is highly accurate: low error of weight determinations due to variation of coral density (< 0.08%) and low standard error (< 0.01%) for repeated measurements of the same corals. We outline a transplantation technique for properly preparing corals for such long-term in situ experiments and measurements. PMID:22049248

  18. The influence of buoyant convection on the nucleation of n-propanol in thermal diffusion cloud chambers

    Microsoft Academic Search

    Frank T. Ferguson; Richard H. Heist; Joseph A. Nuth

    2010-01-01

    A two-dimensional numerical model has been applied to three thermal diffusion cloud chamber (TDCC) investigations of n-propanol in helium taken by two different research groups to provide a quantitative example of how the results in these chambers can be affected by buoyant convection. In the first set of TDCC data, corrections for buoyancy resolve an apparent discontinuity in critical supersaturation

  19. The Effects of Ambient Pressure Upon Global Shape and Hydrodynamic Behavior of Buoyant Laminar Jet Diffusion Flames

    Microsoft Academic Search

    T. YUAN; D. DUROX; E. VILLERMAUX

    1993-01-01

    The action of ambient pressure variation upon buoyant laminar jet diffusion flames is studied experimentally and theoretically at low Reynolds number. For the first time, the flame height and the surface area are measured as a function of ambient pressure at different flow rates and for different burner diameters. Two distinct regimes have been found: one in which the flame

  20. Evaluation and further development of the ADREA-HF code, with emphasis on hydrogen and other buoyant gas release and

    E-print Network

    and further development of the ADREA-HF code, with emphasis on hydrogen and other buoyant gas release, the results of the simulations will be compared with results from physical experiments with hydrogen) Single car garage facility and sensors' location Vehicle and leak location Experimental description

  1. Eruption versus intrusion? Arrest of propagation of constant volume, buoyant, liquid-filled cracks in an elastic, brittle host

    Microsoft Academic Search

    B. Taisne; S. Tait

    2009-01-01

    When a volume of magma is released from a source at depth, one key question is whether or not this will culminate in an eruption or in the emplacement of a shallow intrusion. We address some of the physics behind this question by describing and interpreting laboratory experiments on the propagation of cracks filled with fixed volumes of buoyant liquid

  2. ERUPTION OF A BUOYANTLY EMERGING MAGNETIC FLUX ROPE W. Manchester IV, T. Gombosi, and D. DeZeeuw

    E-print Network

    De Zeeuw, Darren L.

    Zeeuw Center for Space Environment Modeling, University of Michigan, Ann Arbor, MI 48109 and Y. Fan HAO motions transport axial flux and energy to the expanding portion of the magnetic field, driving, the same shearing process has been demonstrated in buoyantly emerging flux ropes (Fan 2001; Magara

  3. Laminar Smoke Point Based Subgrid Soot Radiation Modeling Applied to LES of Buoyant Turbulent Diffusion Flames

    NASA Astrophysics Data System (ADS)

    Chatterjee, Prateep; de Ris, John L.; Wang, Yi; Krishnamoorthy, Niveditha; Dorofeev, Sergey B.

    2012-06-01

    Large eddy simulations (LES) of gaseous buoyant turbulent flames have been conducted with the application of a flamelet based soot-radiation model. The subgrid model applies a turbulent eddy description of soot formation, oxidation and radiation and is based on the laminar smoke point concept. Two parameters, a local turbulent strain rate and prior enthalpy loss/gain fraction influence the soot formation and radiation. Radiation heat transfer is simulated by solving the finite volume discretized form of the radiative transfer equation (RTE) with the subgrid soot-radiation model implemented. The radiant heating of surfaces in close proximity of the flames is computed and predicted heat fluxes and surface temperatures are compared against experimental data. Fire growth in a rack storage arrangement is simulated with the application of a pyrolysis model. Computed heat release rate (HRR) is compared against experimental data.

  4. Wind and tidal forcing of a buoyant plume, Mobile Bay, Alabama

    USGS Publications Warehouse

    Stumpf, R.P.; Gelfenbaum, G.; Pennock, J.R.

    1993-01-01

    AVHRR satellite imagery and in situ observations were combined to study the motion of a buoyant plume at the mouth of Mobile Bay, Alabama. The plume extended up to 30 km from shore, with a thickness of about 1 m. The inner plume, which was 3-8 m thick, moved between the Bay and inner shelf in response to tidal forcing. The tidal prism could be identified through the movement of plume waters between satellite images. The plume responded rapidly to alongshore wind, with sections of the plume moving at speeds of more than 70 cm s-1, about 11% of the wind speed. The plume moved predominantly in the direction of the wind with a weak Ekman drift. The enhanced speed of the plume relative to normal surface drift is probably due to the strong stratification in the plume, which limits the transfer of momentum into the underlying ambient waters. ?? 1993.

  5. Modification of the PPSP (Power Plant Research Program) dispersion model for highly buoyant plumes

    SciTech Connect

    Weil, J.C.; Corio, L.A.

    1988-06-01

    The report describes a modification of the PPSP dispersion model for tall stack plumes. The modification accounts for the dispersion of highly buoyant plumes that loft or remain near the top of the convective boundary layer and resist downward mixing. The main idea is that plume segments are mixed to the ground only by downdrafts with sufficient kinetic energy to overcome the potential energy difference between the plume and the ambient air. Simple analytical expressions are derived for the crosswind-integrated concentration and the ground-level concentration (GLC). They are based on the conservation of plume buoyancy, the probability distribution of the ambient vertical velocities, and the lateral plume spread. Evaluation of the modified model with GLCs around power plant stacks shows that it performs better than the original model.

  6. Dynamics of single rising bubbles in neutrally buoyant liquid-solid suspensions.

    PubMed

    Hooshyar, Nasim; van Ommen, J Ruud; Hamersma, Peter J; Sundaresan, Sankaran; Mudde, Robert F

    2013-06-14

    We experimentally investigate the effect of particles on the dynamics of a gas bubble rising in a liquid-solid suspension while the particles are equally sized and neutrally buoyant. Using the Stokes number as a universal scale, we show that when a bubble rises through a suspension characterized by a low Stokes number (in our case, small particles), it will hardly collide with the particles and will experience the suspension as a pseudoclear liquid. On the other hand, when the Stokes number is high (large particles), the high particle inertia leads to direct collisions with the bubble. In that case, Newton's collision rule applies, and direct exchange of momentum and energy between the bubble and the particles occurs. We present a simple theory that describes the underlying mechanism determining the terminal bubble velocity. PMID:25165930

  7. Buoyant thermal plumes from planetary landers and rovers: Application to sizing of meteorological masts

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.; Sotzen, Kristin S.

    2014-01-01

    Objective. Landers on Mars and Titan may have warm surfaces as a result of solar heating or the carriage of radioisotope power sources. This warmth can perturb downwind meteorological measurements, but cannot be modeled as a simple aerodynamic wake because buoyant forces can be significant. Methods. We use an analytic model from the industrial aerodynamics literature on smoke dispersion from fires and smokestacks to evaluate the plume trajectories. Computational Fluid Dynamics (CFD) simulations are also performed for a Titan lander. Results. CFD yields results similar to the analytic model. (Albeit with a possibly weaker dependence on windspeed than the classic model.) We apply the models to evaluate the probability of immersion of instrumentation in plumes from the Mars Science Laboratory (MSL) Curiosity and for a Titan lander under various wind scenarios. Conclusions. Lander perturbations can be easily calculated. Practice implications. None.

  8. A connexion between turbulence in Rayleigh Taylor flows and turbulence in other buoyant flows

    NASA Astrophysics Data System (ADS)

    Poujade, Olivier

    2007-03-01

    An increasing number of numerical simulations and experiments describing the turbulent spectrum of Rayleigh-Taylor (RT) mixing layers came to light over the past few years. Results reported in recent studies allow to rule out a turbulence àla Kolmogorov as the main mechanism acting on a self similar RT turbulent mixing layer. In this case, the injected power is due to buoyancy motion on a broad range of length scales. We have generalised Lin's spectral equation to buoyant flows and we have shown that this injected power tends to accumulate at large scales so that big whirls can get bigger as the mixing layer thickness increases. Only a small fraction of this power is transferred to small scales through a Kolmogorov cascade and dissipated. This balance between the accumulation of energy at large scales and the buoyancy production can also be applied to Rayleigh-B'enard instabilities. It explains the Bolgiano-Obukov scaling predicted and experimentally observed for these flows.

  9. Characteristic patterns of buoyant flows in the Block Island Sound: Data analysis and numerical simulation

    NASA Astrophysics Data System (ADS)

    Mau, Jenq-Chi

    The surface coastal circulation in and off the Block Island Sound (BIS) is examined based on one-year HF radar (CODAR) observations, bottom-mounted Acoustic Doppler Current Profiler (ADCP) moorings, and a three-dimensional, primitive-equation model to characterize the buoyant flow patterns and their temporal evolution. The surface flow patterns in BIS are determined from one-year CODAR observations and their temporal evolution is examined. Three analysis methods, visual sorting, Self-Organizing Maps (SOM) and Empirical Orthogonal Functions (EOF), are used and their results are compared. The study shows that the SOM analysis nicely complements the traditional EOF analysis, and both are consistent with the visual sorting. A synoptic description of the surface circulation is presented in terms of three characteristic patterns in spring/summer (April to September) and four characteristic patterns in fall/winter (January to March and October to December). The characteristic flow patterns are mainly determined by the wind and seasonal Long Island Sound (LIS) outflows. In spring and summer, a southwestward coastal mean flow is strong, and the wind is generally insignificant. In fall and winter, on the other hand, the coastal mean flow is weak, and the flow is mostly forced by synoptic storms. The Princeton Ocean Model (POM) is applied to study the three-dimensional barotropic semidiurnal tidal response in the New York Bight (NYB) and Block Island Sound (BIS). The model is driven at the open boundary with specified tidal transports. Model tidal sea levels and current ellipses are verified with the coastal sea levels, historical moored bottom pressure and current meter observations, and moored ADCP observations. The model results generally show very good agreement with the observations. The model results also are used to evaluate the CODAR data quality by comparing the total and radial tidal current ellipses. While the CODAR measurements generally are of high quality, the data at the mouth of Long Island Sound seems less reliable. POM also is used to simulate the coastal buoyant flows for a one-year (2001) period. The external forcing includes the LIS outflows, ambient coastal currents, semidiurnal tides, and local winds. Model results are compared with the CODAR and ADCP observations. The agreement in the low-frequency current fluctuations is very good. Consistent with the data analysis, model results indicate that the wind and seasonal LIS outflows are the dominant factors on coastal buoyant outflows. On the other hand, the model predicts a persistent (mean) headland tidal residual eddy south of Montauk Point, which is not supported by the ADCP and CODAR observations. This suggests that small-scale lateral dissipation which is not explicitly treated in the model may be important. This work represents the first comprehensive model and observation comparisons of the coastal buoyant outflows for an entire seasonal cycle. The success of our study is a major step towards developing a model-observational based coastal observatory system.

  10. Further studies on the relationship between platelet buoyant density and platelet age

    SciTech Connect

    Boneu, B.; Vigoni, F.; Boneu, A.; Caranobe, C.; Sie, P.

    1982-01-01

    The relationship between platelet buoyant density and platelet age was investigated in eight human subjects submitted to an autologous chromium labeled platelet survival study. Platelets were isolated after isopycnic centrifugation using eight discontinuous isoosmotic stractan gradients (five subjects), or various continuous and linear isoosmolar gradients (three subjects). A paradoxical radioactivity enrichment of the dense platelets and a premature loss of radioactivity in the light platelets were observed. These results are explained by a shift of the radioactivity distribution curve toward higher densities during the 3-4 days after platelet injection, while the standard deviation of the distribution was conserved throughout the platelet life span. These results suggest that young platelets are heterogeneous and slightly less dense than the total platelet population.

  11. Laboratory Experiments Simulating the Effects of Variable Discharge on Buoyant Coastal Plumes

    NASA Astrophysics Data System (ADS)

    Avener, M. E.; Horner-Devine, A. R.; Rhines, P. B.

    2008-12-01

    River plumes are of great importance to coastal ecosystems because they carry nutrients and contaminants from upstream, which can become trapped near the coast in a growing anticyclonic eddy, or bulge. The degree to which river water is trapped in this coastal eddy is associated strongly with the river discharge. In meso- to macro-tidal systems, ebb and flood tidal phases may result in increases and decreases, respectively, of the effective river discharge of a similar magnitude to the discharge itself. Thus, accumulation of fluid in the bulge may depend on the relative magnitude of the tidal forcing or other modulations of the river discharge. Field observations suggest that under some conditions, discharge variation can cause the anticyclonic eddy to become detached and swept downstream, rather than continuing to grow near the mouth. We carry out laboratory experiments to simulate the effects of periodically varying discharge on buoyant coastal plumes over a range of oscillation periods by injecting a sinusoidally pulsed freshwater inflow into a 2 meter diameter rotating tank of salt water. The depth of the plume in the vicinity of the river mouth is determined from an overhead camera using an optical thickness technique. Using this technique, the temporal evolution of the plume volume can be determined directly. Preliminary results confirm that approximately 65% of the discharge remains in the bulge region in the absence of tidal forcing. In the presence of tidal forcing plume growth appears to be slowed, thereby increasing the transport of buoyant water downstream in the coastal current. Finally, the plume is almost entirely arrested when the pulsing frequency is half of the rotation frequency.

  12. Updraft and Downdraft Cores in TOGA COARE: Why So Many Buoyant Downdraft Cores?.

    NASA Astrophysics Data System (ADS)

    Igau, Richard C.; Lemone, Margaret A.; Wei, Dingying

    1999-07-01

    An examination of the properties of updraft and downdraft cores using Electra data from TOGA COARE shows that they have diameters and vertical velocities similar to cores observed over other parts of the tropical and subtropical oceans. As in previous studies, a core is defined as having vertical velocity of the same sign and greater than an absolute value of 1 m s1 for at least 500 m. A requirement that the core contain either cloud or precipitation throughout is added, but this should not affect the results significantly.Since the Electra was equipped with the Ophir III radiometric temperature sensor, it was also possible to make estimates of core buoyancies. As in TAMEX and EMEX, where core temperatures were estimated using the modified side-looking Barnes radiometer on the NOAA P3s, a significant fraction of both updraft and downdraft cores had apparent virtual temperatures greater than their environments. In fact, the average virtual temperature deviation from the environment for downdraft cores was +0.4 K.Sixteen of the strongest downdraft cores were examined, all of which had positive virtual-temperature deviations, to find the source of this surprising result. It is concluded that the downdraft cores are artificially warm because 100% relative humidity was assumed in calculating virtual temperature. However, reducing core mixing ratios to more physically realistic values does not eliminate warm virtual potential temperature downdraft cores, nor does water loading make all cores negatively buoyant. Thus positively buoyant convective downdrafts do exist, though probably in smaller numbers than previously suggested.

  13. The spatial distribution and speciation of iron in buoyant hydrothermal plumes of the Mid-Cayman Rise

    NASA Astrophysics Data System (ADS)

    Cron, B. R.; Toner, B. M.; Bennett, S. A.; German, C. R.; Dick, G.; Breier, J. A.

    2012-12-01

    Biogeochemical cycling of elements, such as iron and sulfur, at mid-ocean ridge spreading centers may modulate hydrothermal fluxes to the ocean. To better understand the nature and scale of these processes, the geochemical gradients in buoyant plumes were examined at the Mid-Cayman Rise, a short (~110 km) ultra-slow spreading center in the Caribbean Sea that hosts the deepest known high temperature venting. Changes in particulate iron and sulfur speciation were measured in the first 40-50 m of buoyant plumes at two vent fields, Von Damm (2,300m) and Piccard (5,000m). These data will be used to identify products of precipitation reactions and define particulate energy sources available for microbial metabolism. A series of samples were collected by in situ filtration at 0.5 m and 50 m above the Beebe Vents, Piccard hydrothermal field and at 1 m, 8 m, and 40 m above the central spire of the Von Damm vent field using the ROV Jason and CTD-casts. Samples were packaged under dinitrogen and frozen shipboard to preserve oxidation-reduction sensitive species for microprobe Fe 1s and S 1s X-ray absorption near edge structure (XANES) spectroscopy (Advanced Light Source, Lawrence Berkeley National Laboratory, beamline 10.3.2). The Von Damm vent is characterized by shimmering vent fluids with dilute particulates in the buoyant plume. Within the particulate phase, the Von Damm buoyant plume was comprised of 38 mol % Fe-sulfides, 40 mol % Fe(II), and 21 mol % Fe(III) at 1 m. At 8 m it is comprised of 32 mol % Fe-sulfides, 7 % Fe(II), and 59 mol % Fe(III). When the plume reaches 40 m, it is 6 mol % Fe-sulfides, 8 mol % Fe(II), 72 mol % Fe(III), and 14 mol % Fe(0). The Beebe vents are characterized by very dense particle formation in their buoyant plumes. The Beebe vent plume sampled comprised 65 mol % sulfides, 3 % mol Fe(II) & 32 mol % Fe(III)¬¬¬¬ at 0.5 m. As the plume reached 50 m above the vent, the fluids were 43 mol % sulfide and 56 mol % Fe(III). Both buoyant plume samples were dominated by reduced iron species that rapidly become more oxidized as they reacted with deep-sea water entrained into the plume. The next steps for this study are to quantify iron and sulfur species in the plumes, and identify the microbial communities that are closely associated with particulate iron and sulfur using fluorescent in situ hybridization (FISH).

  14. The effects of possibly buoyant flat slab segments on Nazca and South American plate motions

    NASA Astrophysics Data System (ADS)

    Lithgow-Bertelloni, C. R.; Shea, R.; Crameri, F.

    2014-12-01

    Flat slabs are ubiquitous today and in Earth's past, present in at least 10% of present-day subduction zones. The Nazca slab is a classic example with large dip variations along strike, including two prominent flat segments in Peru and Argentina that coincide with the subduction of aseismic ridges. The origin of flat segments remain enigmatic though much work has examined the consequences for upper plate deformation and continued subduction. In the case of the Argentinian flat segment, detailed seismic imaging has shown significantly increased crustal thickness in the flat part of the slab. Our present understanding of oceanic crust formation suggests that incrased crustal thickness forms in response to larger degrees of partial melt, which in turn decrease the water content of the formed crust. The residuum from this process is depleted. The resulting combined lithospheric column is buoyant with respect to the underlying mantle, and likely cold from its contact with the overlying plate and unlikely to undergo the basalt-eclogite transition due to kinetic hindrances. This has consequences for mantle flow and the shear stresses it exerts at the base of the lithosphere and hence to plate motions. Interestingly, the motion of the Nazca-South America pair is difficult to reproduce even in the most sophisticated models (Stadler et al. 2010) without invoking special coupling, rheology or forces. We examine the effects of the subduction of neutral and buoyant flat segments on mantle flow and plate motions, globally and locally for Nazca and South America. We construct high-resolution models of the morphology and density structure of the Nazca slab and embed them in an existing global slab model. We compute the global viscous flow induced and predict plate motions consistent with the density heterogeneity and plate geometry. As an end member we also examine a Nazca slab that dips uniformly with a 30 degree dip. We find, perhaps unsurprisingly, that the most important factor in matching plate velocities today is not the density structure of the slab but its geometry. A slab that dips at 30 degrees reproduces the Nazca plate motions almost exactly, with minor improvements when the real morphology is added. The lower mantle buoyancy remains important for the South American motions. Changes in plate or plate boundary rheology are not needed.

  15. Flame Shapes of Luminous NonBuoyant Laminar Coflowing Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Lin, K.-C.; Faeth, G. M.

    1999-01-01

    Laminar diffusion flames are of interest as model flame systems that are more tractable for analysis and experiments than practical turbulent diffusion flames. Certainly understanding laminar flames must precede understanding more complex turbulent flames while man'y laminar diffusion flame properties are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Laminar diffusion flame shapes have been of interest since the classical study of Burke and Schumann because they involve a simple nonintrusive measurement that is convenient for evaluating flame structure predictions. Motivated by these observations, the shapes of laminar flames were considered during the present investigation. The present study was limited to nonbuoyant flames because most practical flames are not buoyant. Effects of buoyancy were minimized by observing flames having large flow velocities at small pressures. Present methods were based on the study of the shapes of nonbu,3yant round laminar jet diffusion flames of Lin et al. where it was found that a simple analysis due to Spalding yielded good predictions of the flame shapes reported by Urban et al. and Sunderland et al.

  16. Magnetic Cycles and Buoyant Magnetic Structures in a Rapidly Rotating Sun

    NASA Astrophysics Data System (ADS)

    Nelson, Nicholas J.; Brown, B. P.; Brun, S.; Miesch, M. S.; Toomre, J.

    2011-01-01

    Observations of sun-like stars rotating faster than our current sun show that they exhibit solar-like magnetic cycles and features, such as star spots. Using global 3-D simulations to study the coupling of large-scale convection, rotation, and magnetism in a younger sun, we have probed the effects of more rapid rotation on stellar dynamos and the nature of magnetic cycles. Our anelastic spherical harmonics (ASH) code allows study of the convective envelope, occupying the outer 30% by radius of a sun-like star. Major MHD simulations carried out at three times the current solar rotation rate reveal magnetic dynamo action that can produce wreaths of strong toroidal magnetic field at low latitudes, often with opposite polarity in the two hemispheres. The presence of the wreaths is quite surprising, for they arise as quite persistent global structures amidst the vigorous and turbulent convection. We have recently explored behavior in systems with considerably lower diffusivities, achieved with a dynamic Smagorinsky treatment of unresolved turbulence. The lower levels of diffusion create magnetic wreaths that undergo prominent variations in field strength, even exhibiting global magnetic cycles that involve polarity reversals. Additionally, during the cycle maximum, when magnetic energies and mean magnetic fields peak, the wreaths possess buoyant magnetic structures that rise coherently through much of the convective envelope via a combination of advection by convective upflows and magnetic buoyancy. We explore aspects of these rising magnetic structures and the evolving global dynamo action which produces them.

  17. The lateral migration of neutrally-buoyant spheres transported through square microchannels

    NASA Astrophysics Data System (ADS)

    Kim, Young Won; Yoo, Jung Yul

    2008-06-01

    The lateral migration of neutrally-buoyant particles transported through square microchannels has been experimentally investigated over a Reynolds number range of 0.06 <= Re <= 58.65 at the ratio of channel hydraulic diameter to particle size, ? ? 14. Flow Reynolds numbers are determined by applying a conventional particle-tracking algorithm to small tracer particles, while novel imaging techniques have been proposed for identifying and defining the measurement depth of large test particles. By analyzing the spatial distributions of spherical particles, it is revealed that lateral migration of particles markedly occurs even at very low Re, which is induced by the high shear rate due to the small-scale effect. The particle equilibrium position is obtained as a function of Re, and the critical Re at which the particle equilibrium position starts to increase is found in the range 20 <= Re <= 30. The outermost edge of the particle cluster is also in good agreement with previously available data, which provides a good quantitative basis for designing microfluidic devices that are to be used for plasma separation from whole blood.

  18. Swaying motion in buoyant air plume above a horizontal line heat source

    NASA Astrophysics Data System (ADS)

    Noto, K.; Matsumoto, R.

    1986-06-01

    The swaying motion spectrum and frequency of a buoyant air laminar plume arising from a horizontal line heat source inside a 800 mm x 800 mm cross section 1000 mm high enclosure are determined experimentally. A smoke fullness method was developed for the flow visualization of the plume, which transits from laminar to turbulent flow with increase of distance from the heat source, and it is found that the swaying plume does not meander to the axial direction of the heat source. The transition critical Grashof number is found to be 10 to the 8th, and the swaying plume is seen to be in a laminar state for local Grashof numbers of less than 1-2 x 10 to the 8th. Swaying temperatures measured by thermocouples varied irregularly with time. For the laminar swaying motion power spectrum density distribution, frequency bands exist with -4.5 and -8.0 powers of frequency power spectra. Relations are developed to predict plume swaying frequency inside an enclosure of any dimension.

  19. Turbulence Modeling Effects on the Prediction of Equilibrium States of Buoyant Shear Flows

    NASA Technical Reports Server (NTRS)

    Zhao, C. Y.; So, R. M. C.; Gatski, T. B.

    2001-01-01

    The effects of turbulence modeling on the prediction of equilibrium states of turbulent buoyant shear flows were investigated. The velocity field models used include a two-equation closure, a Reynolds-stress closure assuming two different pressure-strain models and three different dissipation rate tensor models. As for the thermal field closure models, two different pressure-scrambling models and nine different temperature variance dissipation rate, Epsilon(0) equations were considered. The emphasis of this paper is focused on the effects of the Epsilon(0)-equation, of the dissipation rate models, of the pressure-strain models and of the pressure-scrambling models on the prediction of the approach to equilibrium turbulence. Equilibrium turbulence is defined by the time rate (if change of the scaled Reynolds stress anisotropic tensor and heat flux vector becoming zero. These conditions lead to the equilibrium state parameters. Calculations show that the Epsilon(0)-equation has a significant effect on the prediction of the approach to equilibrium turbulence. For a particular Epsilon(0)-equation, all velocity closure models considered give an equilibrium state if anisotropic dissipation is accounted for in one form or another in the dissipation rate tensor or in the Epsilon(0)-equation. It is further found that the models considered for the pressure-strain tensor and the pressure-scrambling vector have little or no effect on the prediction of the approach to equilibrium turbulence.

  20. Wave-induced mixing and transport of buoyant particles: application to the Statfjord A oil spill

    NASA Astrophysics Data System (ADS)

    Drivdal, M.; Broström, G.; Christensen, K. H.

    2014-12-01

    This study focuses on how wave-current and wave-turbulence interactions modify the transport of buoyant particles in the ocean. Here the particles can represent oil droplets, plastic particles, or plankton such as fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM), modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production, as well as the stronger veering by the Coriolis-Stokes force, affects the drift of the particles. The energy and momentum fluxes, as well as the Stokes drift, depend on the directional wave spectrum obtained from a wave model. As a first test, the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (i.e., classical Ekman theory). Secondly, the model is applied to a case in which we investigate the oil drift after an oil spill off the west coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by oil-drift models. In this case, using wind and wave forcing from the ERA Interim archive it is shown that the wave effects are important for the resultant drift and have the potential to improve drift forecasting.

  1. Near Surface Vapor Bubble Layers in Buoyant Low Stretch Burning of Polymethylmethacrylate

    NASA Technical Reports Server (NTRS)

    Olson, Sandra L.; Tien, J. S.

    1999-01-01

    Large-scale buoyant low stretch stagnation point diffusion flames over solid fuel (polymethylmethacrylate) were studied for a range of aerodynamic stretch rates of 2-12/ sec which are of the same order as spacecraft ventilation-induced stretch in a microgravity environment. An extensive layer of polymer material above the glass transition temperature is observed. Unique phenomena associated with this extensive glass layer included substantial swelling of the burning surface, in-depth bubble formation, and migration and/or elongation of the bubbles normal to the hot surface. The bubble layer acted to insulate the polymer surface by reducing the effective conductivity of the solid. The reduced in-depth conduction stabilized the flame for longer than expected from theory neglecting the bubble layer. While buoyancy acts to move the bubbles deeper into the molten polymer, thermocapillary forces and surface regression both act to bring the bubbles to the burning surface. Bubble layers may thus be very important in low gravity (low stretch) burning of materials. As bubbles reached the burning surface, monomer fuel vapors jetted from the surface, enhancing burning by entraining ambient air flow. Popping of these bubbles at the surface can expel burning droplets of the molten material, which may increase the fire propagation hazards at low stretch rates.

  2. FPluMe: An integral eruption column model based on the Buoyant Plume Theory

    NASA Astrophysics Data System (ADS)

    Folch, Arnau; Costa, Antonio; Macedonio, Giovanni

    2015-04-01

    Estimates of mass flow rate from volcanic eruption columns are crucial for ash dispersion models, used to assess hazard on population and civil aviation. We present a practical model of eruption column model based on the Buoyant Plume Theory (BPT) that accounts for the effect of the atmospheric wind that results in the bending over of the plume trajectory and increases the entrainment of ambient air. The model solves the equations for the conservation of mass, momentum and energy in terms of averaged variables, accounting for fallout and re-entrainment of tephra from and into the column and particle aggregation. For some given atmospheric conditions and a wind profile, the model can be used to determine the height at which volcanic plumes spread in the atmosphere if mass flow rate at the vent is known, or to estimate mass flow rate when the eruption column height is known. For a given column height, if wind effects are not properly accounted for, the values of the mass flow rate can be significantly underestimated. Our model calculations are compared with proposed semi-empirical relationships between the plume height and the source mass flux that account for the atmospheric wind effect.

  3. Wave induced mixing and transport of buoyant particles: application to the Statfjord A oil spill

    NASA Astrophysics Data System (ADS)

    Drivdal, M.; Broström, G.; Christensen, K. H.

    2014-05-01

    The modelling of wave-current and wave-turbulence interactions have received much attention in recent years. In this study the focus is on how these wave effects modify the transport of particles in the ocean. Here the particles are buoyant tracers that can represent oil droplets, plastic particles or plankton, for example fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM), modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production as well as the stronger veering by the Coriolis-Stokes force affect the drift of the particles. The energy and momentum fluxes as well as the Stokes drift depend on the directional wave spectrum that can be obtained from a wave model or from observations. As a first test the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (e.g. classical Ekman theory). Secondly the model is applied to a case where we investigate the oil drift after an offshore oil spill outside the western coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by empirical models. With wind and wave forcing from the ERA Interim archive, it is shown that the wave effects are important for the resultant drift in this case, and has the potential to improve drift forecasting.

  4. Conduit diameter and buoyant rising speed of mantle plumes: Implications for the motion of hot spots and shape of plume conduits

    Microsoft Academic Search

    B. Steinberger; M. Antretter

    2006-01-01

    Mantle plumes are expected to be affected by large-scale flow in the Earth's mantle related to plate motions, subducted slabs, and possibly large-scale upwellings. Motion of plume conduits will depend on both large-scale flow and buoyant rising speed of the conduit through the mantle. Here we present a model of depth-dependent plume conduit temperature, viscosity, radius, and buoyant rising speed

  5. Numerical and experimental modeling of VGF-type buoyant flow under the influence of traveling and rotating magnetic fields

    NASA Astrophysics Data System (ADS)

    Galindo, V.; Niemietz, K.; Pätzold, O.; Gerbeth, G.

    2012-12-01

    Numerical and experimental modeling of a VGF-type (VGF—vertical gradient freeze) buoyant flow under the influence of both traveling and rotating magnetic fields (TMF and RMF, respectively) is presented. Low-temperature flow experiments were carried out using a GaInSn alloy as model fluid. Radial heating and cooling of the melt leading to a meridional double vortex flow like in typical VGF growth was introduced using a double-walled melt container. The flow was found to be significantly influenced by the mutual interaction of buoyant and electromagnetically driven forces. With increasing axial temperature difference, the buoyant flow becomes more concentrated in the upper and lower part of the melt leaving an extended melt zone with low flow velocity around the mid-height. Furthermore, VGF-type buoyancy is found to stabilize TMF- and RMF-induced melt flows. Besides, the time evolution of the flow just above the stability threshold is studied. In the case of combined VGF-type/RMF flow complex fluctuation patterns are observed, which depends sensitively on the applied thermal field.

  6. Genetic Affinities between Trans-Oceanic Populations of Non-Buoyant Macroalgae in the High Latitudes of the Southern Hemisphere

    PubMed Central

    Fraser, Ceridwen I.; Zuccarello, Giuseppe C.; Spencer, Hamish G.; Salvatore, Laura C.; Garcia, Gabriella R.; Waters, Jonathan M.

    2013-01-01

    Marine biologists and biogeographers have long been puzzled by apparently non-dispersive coastal taxa that nonetheless have extensive transoceanic distributions. We here carried out a broad-scale phylogeographic study to test whether two widespread Southern Hemisphere species of non-buoyant littoral macroalgae are capable of long-distance dispersal. Samples were collected from along the coasts of southern Chile, New Zealand and several subAntarctic islands, with the focus on high latitude populations in the path of the Antarctic Circumpolar Current or West Wind Drift. We targeted two widespread littoral macroalgal species: the brown alga Adenocystisutricularis (Ectocarpales, Heterokontophyta) and the red alga Bostrychiaintricata (Ceramiales, Rhodophyta). Phylogenetic analyses were performed using partial mitochondrial (COI), chloroplast (rbcL) and ribosomal nuclear (LSU / 28S) DNA sequence data. Numerous deeply-divergent clades were resolved across all markers in each of the target species, but close phylogenetic relationships – even shared haplotypes – were observed among some populations separated by large oceanic distances. Despite not being particularly buoyant, both Adenocystisutricularis and Bostrychiaintricata thus show genetic signatures of recent dispersal across vast oceanic distances, presumably by attachment to floating substrata such as wood or buoyant macroalgae. PMID:23894421

  7. Temperature Versus Buoyant Mantle Heterogeneities, Evaluating the Origin of OIB Using the Galapagos Archipelago

    NASA Astrophysics Data System (ADS)

    Saal, A. E.; Bourdon, B.; Kurz, M. D.; Hauri, E. H.; Blusztajn, J.; Blichert-Toft, J.; Hart, S. R.; Sims, K. W.

    2007-12-01

    The existence of hot mantle plumes has recently been questioned; instead tectonics and shallow low-melting heterogeneities, rather than excess temperatures, have been proposed to explain the upwelling of mantle beneath oceanic islands basalts (OIB) [1]. Geophysical, petrological and geochemical arguments have been used to suggest that enriched heterogeneities located shallow within the upper mantle are buoyant due to either melt retention or water lowering its solidus and consequently triggering early melting of the fertile blobs. Thus, the opponents of the hotspot model have suggested that shallow fertile and buoyant blobs could reproduce the effects of temperature, including isotope gradients, as the cause for the generation of OIB [1]. Uranium-series disequilibria measured in oceanic lavas may provide insight into the origin of OIB that is independent of previous arguments. Earlier works have shown that U-series isotopes in basalts are sensitive to variations in the upwelling rates of their mantle source, and those can be used to invoke upward movements that may be associated with mantle plumes [2-4]. Those work also demonstrated that there exist a significant relationship between the extent of U-series disequilibria and the buoyancy flux beneath OIB; where lower buoyancy fluxes are associated with lower rates of melting and hence higher (230Th/238U) values [2]. However, most of those works have assumed that the effects of source heterogeneity can be neglected relative to the effects of other key parameters. If the increase in melting rates is truly due to the presence of fertile blobs, then there should be a correlation between clear indices of enrichment such as radiogenic isotopes and extent of U-series disequilibrium in OIB. Furthermore, the fertility of the mantle heterogeneities may or may not be associated with the enrichment of water, which has an important effect on the melting rate and consequently in the U-series isotope of the basalts. To evaluate what factors (temperature versus mantle heterogeneity) are controlling the upwelling mantle beneath oceanic islands we used our data (including volatile and U-series isotopes) for lavas from across the Galapagos archipelago combined with previously published results from the adjacent Galapagos Spreading Ridge lavas [5]. These results suggest that the most important factor controlling the variation in mantle upwelling velocities beneath the Galapagos archipelago and adjacent ridge is the difference in mantle temperature. References 1. Plates, Plumes, and Paradigms (eds Foulger, G.R., Natland, J.H., Presnall, D.C. & Anderson, D.L.) (GSA Special Paper 388, Geological Society of America, Boulder, 2005). 2. Bourdon, B. et al. Nature 444, 713-717, 10.1038 (2006). 3. Bourdon, B. & Sims, K. W. W. in U-series Geochemistry (eds Bourdon, B., Lundstrom, C., Henderson, G. & Turner, S. P.) 215-253 (Mineralogical Society of America, 2003).

  8. Chemical processes in buoyant hydrothermal plumes on the East Pacific Rise near 21°N

    NASA Astrophysics Data System (ADS)

    Mottl, Michael J.; McConachy, Timothy F.

    1990-07-01

    Hydrothermal plume water containing suspended particles of precipitated black "smoke" has been sampled from three hydrothermal vent fields on the East Pacific Rise near 21°N. The samples were taken within the lower 22 m of the buoyant plumes, directly above 273-350°C black smoker vents, using Go-flo bottles mounted on the submersible Alvin. Based on Li as a conservative tracer of the high-temperature endmember solution, mixing ratios of 10 2 to 10 4 g seawater/g vent water are achieved within the lower 22 m of the plumes. The particle concentrations sampled in the lower 13 m of the plumes are much larger than predicted for these mixing ratios, suggesting that the particles are settling within the lower part of the plume. The major minerals in the smoke are pyrrhotite, Fe-rich sphalerite, pyrite, unidentified Fe - S ± Si and Fe - Si ± S phases, chalcopyrite, amorphous silica, sulfur, Fe-oxyhydroxides (including goethite) and anhydrite. Present in trace quantities are barite, isocubanite, wurtzite, covellite, marcasite(?), and unidentified silicates and Alsilicates. Organic matter is common. The composition of the plume solutions indicates that 35 ± 25% of the hydrothermally injected Fe remains in dissolved form (i.e., < 0.45 ?m) within the lower 22 m of the plume, in spite of a 3- to 9-fold excess of H 2S in the vent solutions. Nearly all of the Mn and Si and most of the Ba also remain in solution. H 2S, by contrast, has been largely (70-100%) removed - by precipitation as Sulfides and sulfur, but mainly by oxidation to dissolved species with intermediate oxidation states. Its early removal implies that 50 ± 30% of the injected Fe will eventually precipitate as primary oxides rather than as Sulfides and that Fe can be fractionated from the other chalcophile metals during sulfide precipitation. Compared with the vent water, the particles are enriched in Cu, Co, Ag, Cd, Al, Zn, Pb, and Ni by factors of 4 to 20 relative to Fe and depleted in Ba, S, Si, and Mn. Scavenging from seawater may play a role in Co and Cu enrichment at the NGS field, and for Ag, Cd, and Ni at all three fields, but is negligible for Pb and Zn. These results indicate that two distinct metalliferous components are delivered to the distal regions of a plume as a result of reactions in the lower part of the buoyant plume: 1) a dissolved component that includes about half the Fe and all of the Mn and will eventually precipitate as oxides, and 2) a particulate component consisting of fine-grained sulfide minerals that are enriched in ore metals by factors of 4 to 20.

  9. Trace Metal and Sulfur Dynamics in the First Meter of Buoyant Hydrothermal Vent Plumes

    NASA Astrophysics Data System (ADS)

    Findlay, A.; Gartman, A.; Shaw, T. J.; Luther, G. W., III

    2014-12-01

    The speciation and reactivity of metals and metal sulfides within the buoyant plume is critical to determining the ultimate fate of metals emitted from hydrothermal vents. The concentration, size fractionation, and partitioning of trace metals (Fe, Mn, Cu, Co, Zn, Cd, Pb) were determined within the first meter of the rising plume at three vent fields (TAG, Snakepit, and Rainbow) along the Mid-Atlantic Ridge. At Rainbow, total Fe concentrations exceed total sulfide concentrations by an order of magnitude, whereas at the other two sites, total Fe and total sulfide concentrations are nearly equal. At all three sites, Mn and Fe are primarily in the filtered (< 0.2 ?m) fraction and Cu, Co, Zn, Cd, and Pb are mainly in the unfiltered fraction. At TAG and Snakepit, unfiltered copper is correlated with unfiltered cobalt, and unfiltered zinc is correlated with unfiltered cadmium and lead. At Rainbow, unfiltered zinc, cadmium and lead are correlated, but unfiltered copper and cobalt are not, indicating precipitation dynamics at Rainbow are different than those at TAG and Snakepit due to bulk geochemical differences, including a higher iron to sulfide ratio. A sequential HCl/HNO3 leaching method was used to distinguish metals present in pyrite and chalcopyrite in both unfiltered and filtered samples. Significant portions of unfiltered Cu and Co were extracted in HNO3, whereas unfiltered Zn, Cd, and Pb were extracted in HCl. Up to 95 % of filtered Cu, Co, and Zn, up to 80% Cd, and up to 60 % Pb are only extractable in HNO3, indicating that a significant portion of metals < 0.2 ?m are incorporated into a recalcitrant fraction such as nanoparticulate pyrite or chalcopyrite.

  10. Trench Advance By the Subduction of Buoyant Features - Application to the Izu-Bonin-Marianas Arc

    NASA Astrophysics Data System (ADS)

    Goes, S. D. B.; Fourel, L.; Morra, G.

    2014-12-01

    Most subduction trenches retreat, not only today but throughout the Cenozoic. However, a few trenches clearly advance during part of the evolution, including Izu-Bonin Marianas (IBM) and Kermadec. Trench retreat is well understood as a basic consequence of slab pull, but it is debated what causes trench advance. The IBM trench underwent a complex evolution: right after its initiation, it rotated clockwise, leading to very fast retreat in the north and slow retreat in the south. But since 10-15 Ma, IBM trench motions have switched to advance at the southern end, and since 5 Ma also the northern end is advancing. Based on 2-D subduction models, it has been proposed proposed that the change in age of the subducting plate at the IBM trench (from 40-70 m.y. at the initiation of the trench 45 m.y. ago to 100-140 m.y. lithosphere subducting at the trench today) and its effect on plate strength could explain the transition from trench retreat to trench advance, and that the age gradient (younger in the north and older in the south) could explain the rotation of the trench. However, with new 3-D coupled fluid-solid subduction model where we can include such lateral age gradients, we find that this does not yield the observed behaviour. Instead, we propose an alternative mechanism, involving the subduction of the buoyant Caroline Island Ridge at the southern edge of the Mariana trench and show that it can explain both trench motion history and the current morphology of the IBM slab as imaged by seismic tomography.

  11. Passive buoyant tracers in the ocean surface boundary layer: 1. Influence of equilibrium wind-waves on vertical distributions

    NASA Astrophysics Data System (ADS)

    Kukulka, T.; Brunner, K.

    2015-05-01

    This paper is the first of a two part series that investigates passive buoyant tracers in the ocean surface boundary layer. The first part examines the influence of equilibrium wind-waves on vertical tracer distributions, based on large eddy simulations (LES) of the wave-averaged Navier-Stokes equation. The second part applies the model to investigate observations of buoyant microplastic marine debris, which has emerged as a major ocean pollutant. The LES model captures both Langmuir turbulence (LT) and enhanced turbulent kinetic energy input due to breaking waves (BW) by imposing equilibrium wind-wave statistics for a range of wind and wave conditions. Concentration profiles of LES agree well with analytic solutions obtained for an eddy diffusivity profile that is constant near the surface and transitions into the K-Profile Parameterization (KPP) profile shape at greater depth. For a range of wind and wave conditions, the eddy diffusivity normalized by the product of water-side friction velocity and mixed layer depth, h, mainly depends on a single nondimensional parameter, the peak wavelength (which is related to Stokes drift decay depth) normalized by h. For smaller wave ages, BW critically enhances near-surface mixing, while LT effects are relatively small. For greater wave ages, both BW and LT contribute to elevated near-surface mixing, and LT significantly increases turbulent transport at greater depth. We identify a range of realistic wind and wave conditions for which only Langmuir (and not BW or shear driven) turbulence is capable of deeply submerging buoyant tracers.

  12. Experimental study of heat and mass transfer in a buoyant countercurrent exchange flow

    NASA Astrophysics Data System (ADS)

    Conover, Timothy Allan

    Buoyant Countercurrent Exchange Flow occurs in a vertical vent through which two miscible fluids communicate, the higher-density fluid, residing above the lower-density fluid, separated by the vented partition. The buoyancy- driven zero net volumetric flow through the vent transports any passive scalars, such as heat and toxic fumes, between the two compartments as the fluids seek thermodynamic and gravitational equilibrium. The plume rising from the vent into the top compartment resembles a pool fire plume. In some circumstances both countercurrent flows and pool fires can ``puff'' periodically, with distinct frequencies. One experimental test section containing fresh water in the top compartment and brine (NaCl solution) in the bottom compartment provided a convenient, idealized flow for study. This brine flow decayed in time as the concentrations approached equilibrium. A second test section contained fresh water that was cooled by heat exchangers above and heated by electrical elements below and operated steadily, allowing more time for data acquisition. Brine transport was reduced to a buoyancy- scaled flow coefficient, Q*, and heat transfer was reduced to an analogous coefficient, H*. Results for vent diameter D = 5.08 cm were consistent between test sections and with the literature. Some results for D = 2.54 cm were inconsistent, suggesting viscosity and/or molecular diffusion of heat become important at smaller scales. Laser Doppler Velocimetry was used to measure velocity fields in both test sections, and in thermal flow a small thermocouple measured temperature simultaneously with velocity. Measurement fields were restricted to the plume base region, above the vent proper. In baseline periodic flow, instantaneous velocity and temperature were ensemble averaged, producing a movie of the average variation of each measure during a puffing flow cycle. The temperature movie revealed the previously unknown cold core of the puff during its early development. The renewal-length model for puffing frequency of pool fire plumes was extended to puffing countercurrent flows by estimating inflow dilution. Puffing frequencies at several conditions were reduced to Strouhal number based on dilute plume density. Results for D = 5.08 cm compared favorably to published measurements of puffing pool fires, suggesting that the two different flows obey the same periodic dynamic process.

  13. Two-phase convective mixing under a buoyant plume of CO2 in deep saline aquifers

    NASA Astrophysics Data System (ADS)

    Emami-Meybodi, Hamid; Hassanzadeh, Hassan

    2015-02-01

    The storage of carbon dioxide (CO2) in deep saline aquifers has been suggested as a promising method for stabilizing the atmospheric concentration of CO2. An accurate evaluation of the CO2 trapping mechanisms, such as convective mixing, is crucial for estimates of storage capacity and security. We recently investigated the gravitational stability of the diffusive boundary layer underneath a capillary transition zone by performing a linear stability analysis, which provides a quantitative description of the onset of convection for the two-phase, buoyancy-driven flow in the presence of the capillary transition zone (Emami-Meybodi and Hassanzadeh, 2013). In this paper, we further examine the effect of the capillary transition zone on the onset of convection and subsequent convective mixing using direct numerical simulations. We describe key features of the two-phase convective mixing for systems with low Rayleigh numbers (Ra ? 1000) and the measurement of several global quantities, such as the total CO2 dissolution, Sherwood number, swelling factor, and interface velocity. We show that the commonly used assumption of a sharp CO2-brine interface with constant CO2 concentration at the top of an aquifer (i.e. single-phase system) may lead to erroneous estimates of not only the onset of convection, but also of the rate and magnitude of CO2 dissolution. The significant effect of the capillary transition zone on the dissolution of CO2 under a buoyant plume in saline aquifers is explained; and, the link between the capillary transition zone and the volume change, due to CO2 dissolution and the interface velocity over the mixing process, is demonstrated. Compared to the single-phase system, a crossflow through the interface of the diffusive boundary layer with the capillary transition zone, as well as the upward advance of the interface motion, may enhance the convective mixing early in the period of natural convection. The decrease in the onset time and stronger mass flux may be more profound in the two-phase system than in the previously reported single-phase models. Furthermore, we report several scaling relationships that characterize the mixing process in the presence of the capillary transition zone. Our findings provide further insight into the understanding of the two-phase mixing features and the long-term fate of the injected CO2 in deep saline aquifers.

  14. Synthesis of buoyant metal-coated fly ash cenosphere and its excellent catalytic performance in dye degradation.

    PubMed

    Wang, Wei; Zhai, Jianping; Li, Qin

    2015-04-15

    In this work, Ag(+) and Ag(0) were absorbed onto the surface of 3-mercaptopropyltriethoxysilane modified fly ash cenospheres (FACs) in two Ag activation processes. The activation methods, avoiding traditional surface sensitization by SnCl2, successfully initiated electroless copper particles deposition for the preparation of buoyant Cu-FAC and CuAg-FAC composites. The CuAg-FAC had a much more uniform morphology than the Cu-FAC. The catalytic performance of the Cu-FAC and CuAg-FAC was examined by the reduction of Orange IV azo dye with the presence of NaBH4. 98.4% of Orange IV was rapidly reduced within 25 min by the CuAg-FAC, whereas 76.4% of Orange IV was removed by the Cu-FAC. The results reveal that the degradation processes matched well with the pseudo-first-order kinetics model, and rate constants of 0.057 and 0.186 min(-1) were obtained for the Cu-FAC and CuAg-FAC, respectively. Moreover, two other dyes of Orange II and Reactive Black 5 were also efficiently reduced by the CuAg-FAC which could be easily recycled and stably reused at least four times. These buoyant metal-coated FAC composites would be very useful in various catalytic reductions. PMID:25585281

  15. The effect of shearing on the buoyant migration of melt in compacting-dissolution channels

    NASA Astrophysics Data System (ADS)

    Baltzell, C.; Parmentier, E.; Liang, Y.; Tirupathi, S.

    2013-12-01

    Melt migration in the mantle by porous flow through compacting, high porosity dissolution channels may occur in a variety of settings including both the upwelling mantle beneath spreading centers and the flowing mantle wedge at convergent plate boundaries. Such channels may form by a positive feedback between dissolution and melt percolation. Previous studies [1, 2] have considered the compacting-dissolution channels in the presence of a uniform upwelling mantle flow. In this study the analysis of mantle flow beneath the plate boundaries was extended by introducing a horizontal shearing component. A numerical experiment was formulated using the finite element software deal.II [3] applying a high order Discontinuous Galerkin (DG) method to examine melt flow in a deforming, porous matrix. The conditions are similar to those in [2] except the addition of a prescribed horizontal shear component in the solid matrix. Melt migration occurs within a rectangular domain subject to horizontal periodic boundary conditions. Initially a Gaussian perturbation in the porosity at the base extends vertically through the domain defining a melt channel. By varying the shear and upwelling rates, the porosity and matrix dissolution were examined to determine the behavior of the channel and melt flow. Models of buoyant melt transport through dissolution channels in upwelling mantle sheared on horizontal planes show that shearing deformation introduces several effects that could have important consequences for melt migration. Shearing tends to rotate dissolution channels away from the vertical thus reducing the component of buoyancy acting along the channels and decreasing the stability of the channel. The channels remain more vertical than would be expected if they followed the matrix flow, as determined by the dissolution. Channels thus migrate horizontally relative to the mantle matrix and melt flows horizontally through dissolution channels. Evolution of the channels depends on the ratio of upwelling to shearing rates. A compacting region of reduced porosity develops on the downstream side of a channel. This region advects with the velocity of the matrix. Melt collecting beneath the compacting region generates new tilted melt channels. In the absence of horizontal shear melt rising vertically in the melt channel remains within mantle matrix in the channel. However, horizontal shearing destroys this isolation by causing melt to flow horizontally relative to the matrix. As upwelling rate decreases, and hence the compaction, there is less relative motion between the melt and matrix and the channel behavior agrees more with the theoretical relationship. This behavior may have important geochemical implications for the transport of chemically heterogeneous melts in the deforming mantle. Melt rising in sheared mantle columns may not retain the high pressure signature frequently invoked to explain mid-ocean ridge basalt chemistry if local chemical equilibrium is maintained. [1]. Spiegelman et al. (2001) JGR, 106, 2061-2077. [2]. Schiemenz et al. (2011) Geophys. J. Int. 186, 641-664. [3]. Bangerth et al. (2007) ACM Trans. Math. Software 33, doi: 10.1145/1268776.1268779.

  16. A Field Evaluation of an External and Neutrally Buoyant Acoustic Transmitter for Juvenile Salmon: Implications for Estimating Hydroturbine Passage Survival

    PubMed Central

    Brown, Richard S.; Deng, Z. Daniel; Cook, Katrina V.; Pflugrath, Brett D.; Li, Xinya; Fu, Tao; Martinez, Jayson J.; Li, Huidong; Trumbo, Bradly A.; Ahmann, Martin L.; Seaburg, Adam G.

    2013-01-01

    Turbine-passed fish are exposed to rapid decreases in pressure which can cause barotrauma. The presence of an implanted telemetry tag increases the likelihood of injury or death from exposure to pressure changes, thus potentially biasing studies evaluating survival of turbine-passed fish. Therefore, a neutrally buoyant externally attached tag was developed to eliminate this bias in turbine passage studies. This new tag was designed not to add excess mass in water or take up space in the coelom, having an effective tag burden of zero with the goal of reducing pressure related biases to turbine survival studies. To determine if this new tag affects fish performance or susceptibility to predation, it was evaluated in the field relative to internally implanted acoustic transmitters (JSATS; Juvenile Salmon Acoustic Telemetry System) used widely for survival studies of juvenile salmonids. Survival and travel time through the study reach was compared between fish with either tag type in an area of high predation in the Snake and Columbia rivers, Washington. An additional group of fish affixed with neutrally-buoyant dummy external tags were implanted with passive integrated transponder (PIT) tags and recovered further downstream to assess external tag retention and injury. There were no significant differences in survival to the first detection site, 12 river kilometers (rkm) downstream of release. Travel times were also similar between groups. Conversely, externally-tagged fish had reduced survival (or elevated tag loss) to the second detection site, 65 rkm downstream. In addition, the retention study revealed that tag loss was first observed in fish recaptured approximately 9 days after release. Results suggest that this new tag may be viable for short term (<8 days) single-dam turbine-passage studies and under these situations, may alleviate the turbine passage-related bias encountered when using internal tags, however further research is needed to confirm this. PMID:24204947

  17. Physiological considerations in applying laboratory-determined buoyant densities to predictions of bacterial and protozoan transport in groundwater: Results of in-situ and laboratory tests

    USGS Publications Warehouse

    Harvey, R.W.; Metge, D.W.; Kinner, N.; Mayberry, N.

    1997-01-01

    Buoyant densities were determined for groundwater bacteria and microflagellates (protozoa) from a sandy aquifer (Cape Cod, MA) using two methods: (1) density-gradient centrifugation (DGC) and (2) Stoke's law approximations using sedimentation rates observed during natural-gradient injection and recovery tests. The dwarf (average cell size, 0.3 ??m), unattached bacteria inhabiting a pristine zone just beneath the water table and a majority (~80%) of the morphologically diverse community of free- living bacteria inhabiting a 5-km-long plume of organically-contaminated groundwater had DGC-determined buoyant densities <1.019 g/cm3 before culturing. In the aquifer, sinking rates for the uncultured 2-??m size class of contaminant plume bacteria were comparable to that of the bromide tracer (1.9 x 10-3 M), also suggesting a low buoyant density. Culturing groundwater bacteria resulted in larger (0.8-1.3 ??m), less neutrally- buoyant (1.043-1.081 g/cm3) cells with potential sedimentation rates up to 64-fold higher than those predicted for the uncultured populations. Although sedimentation generally could be neglected in predicting subsurface transport for the community of free-living groundwater bacteria, it appeared to be important for the cultured isolates, at least until they readapt to aquifer conditions. Culturing-induced alterations in size of the contaminant-plume microflagellates (2-3 ??m) were ameliorated by using a lower nutrient, acidic (pH 5) porous growth medium. Buoyant densities of the cultured microflagellates were low, i.e., 1.024-1.034 g/cm3 (using the DGC assay) and 1.017-1.039 g/cm3 (estimated from in-situ sedimentation rates), suggesting good potential for subsurface transport under favorable conditions.

  18. Non-hydrostatic modeling of cohesive sediment transport associated with a subglacial buoyant jet in glacial fjords: A process-oriented approach

    NASA Astrophysics Data System (ADS)

    Salcedo-Castro, Julio; Bourgault, Daniel; Bentley, Samuel J.; deYoung, Brad

    2013-03-01

    Fine sediment transport produced by a subglacial freshwater discharge is simulated with a 2D non-hydrostatic model. The circulation pattern revealed a buoyant jet issuing from the aperture representing the subglacial tunnel, a vertically buoyant plume and a surface gravity current forming part of an estuarine circulation. Momentum-dominated experiments are more sensitive to the presence of suspended sediment in the discharge. At low concentrations, the sediment stays in the vertical plume and surface gravity current, and its concentration is progressively decreased by mixing but no settling is observed through the water column. At high concentrations, the sediment settles in the far field and is transported back to the near field by the landward estuarine current. Sediment settled from the surface layer through convective sedimentation, a process that was more effective than flocculation to transport sediment vertically, and showed vertical velocities faster than 1.0×10-2 m s-1. Implications of these results are discussed.

  19. Hamiltonian structure for a neutrally buoyant rigid body interacting with N vortex rings of arbitrary shape: the case of arbitrary smooth body shape

    Microsoft Academic Search

    Banavara N. Shashikanth; Artan Sheshmani; Scott David Kelly; Jerrold E. Marsden

    2008-01-01

    We present a (noncanonical) Hamiltonian model for the interaction of a neutrally buoyant, arbitrarily shaped smooth rigid\\u000a body with N thin closed vortex filaments of arbitrary shape in an infinite ideal fluid in Euclidean three-space. The rings are modeled\\u000a without cores and, as geometrical objects, viewed as N smooth closed curves in space. The velocity field associated with each ring

  20. Microgravity Experiments and Numerical Modeling of Rotating Buoyant Convection in a Spherical Shell with Latitudinal Thermal Gradients

    NASA Technical Reports Server (NTRS)

    Leslie, Fred W.; Miller, Timothy L.

    1998-01-01

    The results of numerical model calculations are compared with space laboratory experiments for rotating, thermally driven flow in a hemispherical shell, and various flow regimes are described. A spherically symmetric body force, analogous to gravity, is imposed in the radial direction through the use of a dielectric fluid and an electrostatic potential difference across the gap. The spherical boundaries are maintained at constant temperature profiles (with the pole and the inner sphere being the warmer surfaces), and the equatorial wall is an insulator. Typical parameter combinations result in highly nonlinear, but laminar, flow. For weak enough buoyant forcing, the flow is axisymmetric. It consists of a single meridional cell, rising in warm latitudes (in this case, near the pole) and sinking in cool latitudes, with prograde flow in the equatorial region and near the inner hemisphere for other latitudes, and retrograde motion elsewhere. For fast rotation, the first transition due to the instability of this simple flow is also axisymmetric, consisting of rings of convection in the polar region, which propagate poleward. The first nonaxisymmetric convection occurs at Rayleigh numbers which increase with rotation rate. The form of the convection near the transition also depends upon the rate of rotation. Selected flow patterns near the transition as well as those beyond it are studied numerically. For those cases where there exist laboratory experiments with which to compare, the numerical and experimental results agree very well.

  1. In-Situ Optical and Acoustical Measurements of the Buoyant Cyanobacterium P. Rubescens: Spatial and Temporal Distribution Patterns

    PubMed Central

    Hofmann, Hilmar; Peeters, Frank

    2013-01-01

    Optical (fluorescence) and acoustic in-situ techniques were tested in their ability to measure the spatial and temporal distribution of plankton in freshwater ecosystems with special emphasis on the harmful and buoyant cyanobacterium P. rubescens. Fluorescence was measured with the multi-spectral FluoroProbe (Moldaenke FluoroProbe, MFP) and a Seapoint Chlorophyll Fluorometer (SCF). In-situ measurements of the acoustic backscatter strength (ABS) were conducted with three different acoustic devices covering multiple acoustic frequencies (614 kHz ADCP, 2 MHz ADP, and 6 MHz ADV). The MFP provides a fast and reliable technique to measure fluorescence at different wavelengths in situ, which allows discriminating between P. rubescens and other phytoplankton species. All three acoustic devices are sensitive to P. rubescens even if other scatterers, e.g., zooplankton or suspended sediment, are present in the water column, because P. rubescens containing gas vesicles has a strong density difference and hence acoustic contrast to the ambient water and other scatterers. After calibration, the combination of optical and acoustical measurements not only allows qualitative and quantitative observation of P. rubescens, but also distinction between P. rubescens, other phytoplankton, and zooplankton. As the measuring devices can sample in situ at high rates they enable assessment of plankton distributions at high temporal (minutes) and spatial (decimeters) resolution or covering large temporal (seasonal) and spatial (basin scale) scales. PMID:24303028

  2. Multi-Parametric Study of Rising 3D Buoyant Flux Tubes in an Adiabatic Stratification Using AMR

    E-print Network

    Martinez-Sykora, Juan; Cheung, Mark C M

    2015-01-01

    We study the buoyant rise of magnetic flux tubes embedded in an adiabatic stratification using two-and three-dimensional, MHD simulations. We analyze the dependence of the tube evolution on the field line twist and on the curvature of the tube axis in different diffusion regimes. To be able to achieve a comparatively high spatial resolution we use the FLASH code, which has a built-in Adaptive Mesh Refinement (AMR) capability. Our 3D experiments reach Reynolds numbers that permit a reasonable comparison of the results with those of previous 2D simulations. When the experiments are run without AMR, hence with a comparatively large diffusivity, the amount of longitudinal magnetic flux retained inside the tube increases with the curvature of the tube axis. However, when a low-diffusion regime is reached by using the AMR algorithms, the magnetic twist is able to prevent the splitting of the magnetic loop into vortex tubes and the loop curvature does not play any significant role. We detect the generation of vortic...

  3. Some factors affecting the use of lighter than air systems. [economic and performance estimates for dirigibles and semi-buoyant hybrid vehicles

    NASA Technical Reports Server (NTRS)

    Havill, C. D.

    1974-01-01

    The uses of lighter-than-air vehicles are examined in the present day transportation environment. Conventional dirigibles were found to indicate an undesirable economic risk due to their low speeds and to uncertainties concerning their operational use. Semi-buoyant hybrid vehicles are suggested as an alternative which does not have many of the inferior characteristics of conventional dirigibles. Economic and performance estimates for hybrid vehicles indicate that they are competitive with other transportation systems in many applications, and unique in their ability to perform some highly desirable emergency missions.

  4. Turbulent dispersion of slightly buoyant oil droplets and turbulent breakup of crude oil droplets mixed with dispersants

    NASA Astrophysics Data System (ADS)

    Gopalan, Balaji

    In part I, high speed in-line digital holographic cinematography is used for studying turbulent diffusion of slightly buoyant 0.5-1.2 mm diameter diesel droplets (specific gravity of 0.85) and 50 mum diameter neutral density particles. Experiments are performed in a 50x50x70 mm3 sample volume in a controlled, nearly isotropic turbulence facility, which is characterized by 2-D PIV. An automated tracking program has been used for measuring velocity time history of more than 17000 droplets and 15000 particles. The PDF's of droplet velocity fluctuations are close to Gaussian for all turbulent intensities ( u'i ). The mean rise velocity of droplets is enhanced or suppressed, compared to quiescent rise velocity (Uq), depending on Stokes number at lower turbulence levels, but becomes unconditionally enhanced at higher turbulence levels. The horizontal droplet velocity rms exceeds the fluid velocity rms for most of the data, while the vertical ones are higher than the fluid only at the highest turbulence level. The scaled droplet horizontal diffusion coefficient is higher than the vertical one, for 1 < u'i /Uq < 5, consistent with trends of the droplet velocity fluctuations. Conversely, the scaled droplet horizontal diffusion timescale is smaller than the vertical one due to crossing trajectories effect. The droplet diffusion coefficients scaled by the product of turbulence intensity and an integral length scale is a monotonically increasing function of u'i /Uq. Part II of this work explains the formation of micron sized droplets in turbulent flows from crude oil droplets pre-mixed with dispersants. Experimental visualization shows that this breakup starts with the formation of very long and quite stable, single or multiple micro threads that trail behind millimeter sized droplets. These threads form in regions with localized increase in concentration of surfactant, which in turn depends on the flow around the droplet. The resulting reduction of local surface tension, aided by high oil viscosity and stretching by the flow, suppresses capillary breakup and explains the stability of these threads. Due to increasing surface area and diffusion of dispersants into the continuous phase, the threads eventually breakup into ˜3 mum droplets.

  5. JBFA - buoyant flight

    NASA Technical Reports Server (NTRS)

    Ohari, T.

    1982-01-01

    A method was developed whereby a balloon was used to carry lumber out of a forest in order to continue lumber production without destroying the natural environment and view of the forest. Emphasis was on the best shape for a logging balloon, development of a balloon logging system suitable for cutting lumber and safety plans, tests on balloon construction and development of netting, and weather of mountainous areas, especially solutions to problems caused by winds.

  6. Centrifugal forces alter streamline topology and greatly enhance the rate of heat and mass transfer from neutrally buoyant particles to a shear flow.

    PubMed

    Subramanian, G; Koch, D L

    2006-04-01

    Centrifugal forces break the degenerate closed-streamline configuration that occurs in simple shear flow past a neutrally buoyant torque-free particle in the inertialess limit. The broken symmetry allows heat or mass to be convected away in an efficient manner in sharp contrast to the inertialess diffusion-limited scenario. The dimensionless transfer rate, characterized by the Nusselt number, is found to be Nu = 0.33(RePe)(1/3) + O(1) for small but finite Re when RePe > 1. Here, the particle Reynolds number (Re) is a dimensionless measure of the inertial forces, while the Peclet number (Pe) measures the relative importance of the convective and the diffusive transfer mechanisms. The symmetry-breaking bifurcation is expected to occur in generic shearing flows, and represents a possible means for heat or mass transfer enhancement from the dispersed phase in multiphase systems. PMID:16711993

  7. The potential for buoyant displacement gas release events in Tank 241-SY-102 after waste transfer from Tank 241-SY-101

    SciTech Connect

    BE Wells; PE Meyer; G Chen

    2000-05-10

    Tank 241-SY-101 (SY-101) is a double-shell, radioactive waste storage tank with waste that, before the recent transfer and water back-dilution operations, was capable of retaining gas and producing buoyant displacement (BD) gas release events (GREs). Some BD GREs caused gas concentrations in the tank headspace to exceed the lower flammability limit (LFL). A BD GRE occurs when a portion of the nonconvective layer retains enough gas to become buoyant, rises to the waste surface, breaks up, and releases some of its stored gas. The installation of a mixer pump in 1993 successfully mitigated gas retention in the settled solids layer in SY-101 and has since prevented BD GREs. However, operation of the mixer pump over the years caused gas retention in the floating crust layer and a corresponding accelerated waste level growth. The accelerating crust growth trend observed in 1997--98 led to initiation of sequences of waste removal and water back-dilutions in December 1999. Waste is removed from the mixed slurry layer in Tank SY-101 and transferred into Tank 241-Sy-102 (SY-102). Water is then added back to dissolve soluble solids that retain gas. The initial transfer of 89,500 gallons of SY-101 waste, diluted in-line at 0.94:1 by volume with water, to SY-102 was conducted in December 1999. The second transfer of 230,000 gallons of original SY-101 waste, diluted approximately 0.9:1, was completed in January 2000, and the third transfer of 205,500 gallons of original SY-101 waste diluted at 0.9:1 was completed in March 2000.

  8. An Experimental Field Dataset with Buoyant, Neutral, and Dense Gas Atmospheric Releases and Model Comparisons in Low-Wind Speed (Diffusion) Conditions

    SciTech Connect

    Veronica E. Wannberg, Gustavious Williams, Patrick Sawyer, and Richard Venedam

    2010-09-01

    Aunique field dataset from a series of low–wind speed experiments, modeling efforts using three commonly used models to replicate these releases, and statistical analysis of how well these models were able to predict the plume concentrations is presented. The experiment was designed to generate a dataset to describe the behavior of gaseous plumes under low-wind conditions and the ability of current, commonly used models to predict these movements. The dataset documents the release and transport of three gases: ammonia (buoyant), ethylene (neutral), and propylene (dense) in low–wind speed (diffusion) conditions. Release rates ranged from 1 to 20 kg h21. Ammonia and ethylene had five 5-min releases each to represent puff releases and five 20-min releases each to represent plume releases. Propylene had five 5-min puffs, six 20-min plumes, and a single 30-min plume. Thirty-two separate releases ranging from 6 to 47 min were conducted, of which only 30 releases generated useful data. The data collected included release rates, atmospheric concentrations to 100 m from the release point, and local meteorological conditions. The diagnostics included nine meteorological stations on 100-m centers and 36 photoionization detectors in a radial pattern. Three current stateof- the-practice models, Aerial locations of Hazardous Atmospheres (ALOHA), Emergency Prediction Information code (EPIcode), and Second-Order Closure Integrated Puff (SCIPUFF), were used to try to duplicate the measured field results. Low wind speeds are difficult to model, and all of the models had difficulty replicating the field measurements. However, the work does show that these models, if used correctly, are conservative (overpredict concentrations) and can be used for safety and emergency planning.

  9. Hypertriglyceridemia during late pregnancy is associated with the formation of small dense low-density lipoproteins and the presence of large buoyant high-density lipoproteins.

    PubMed

    Silliman, K; Shore, V; Forte, T M

    1994-08-01

    Late pregnancy is a unique metabolic state where there are transient increases in the concentrations of plasma triglyceride (TG), cholesterol, and apolipoprotein (apo) B. Despite the hypertriglyceridemic environment, we recently reported that there is an unusual shift in high-density lipoprotein (HDL) subclass distribution from smaller HDL subclasses to the largest, most buoyant HDL2b subclass. In the present investigation, we determined whether the subclasses of low-density lipoprotein (LDL) also change during this transient hyperlipidemic state and whether such changes were associated with plasma TG and apolipoprotein concentrations. Thirty-six Hispanic subjects at 35 to 36 weeks' gestation and at 6 weeks' postpartum were studied. At 35 to 36 weeks of gestation, plasma concentrations of TG, cholesterol, and apo B were increased (218 +/- 62, 234 +/- 48, and 130 +/- 35 mg/dL, respectively) over levels at 6 weeks' postpartum (112 +/- 69, 197 +/- 36, and 97 +/- 25 mg/dL respectively). However, lipoprotein(a) [Lp(a)] concentrations were not changed during pregnancy compared with postpartum. LDL subclass patterns (A, B, or I) were determined by nondenaturing polyacrylamide gradient gel electrophoresis in our group of 36 pregnant women. During late pregnancy, 97% of subjects were categorized as LDL subclass patterns B or I, indicating that small, dense LDL particles predominated. This predominance of small, dense LDL was associated with plasma TG concentration, where there was a significant inverse relationship (r = -.45, P < .01) between the LDL peak particle diameter and plasma TG concentration. In an apparent anomaly, there were significant increases in the concentrations of HDL cholesterol (HDL-C) and HDL2 mass, even though small, dense LDL particles predominated.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8052144

  10. ANALYSIS OF BUOYANT SURFACE JETS

    EPA Science Inventory

    To obtain improved prediction of heated plume characteristics from a surface jet, an integral analysis computer model was modified and a comprehensive set of field and laboratory data available from the literature was gathered, analyzed, and correlated for estimating the magnitud...

  11. Candle Flames in Non-Buoyant Atmospheres

    NASA Technical Reports Server (NTRS)

    Dietrich, D. L.; Ross, H. D.; Shu, Y.; Tien, J. S.

    1999-01-01

    This paper addresses the behavior of a candle flame in a long-duration, quiescent microgravity environment both on the space Shuttle and the Mir Orbiting Station (OS). On the Shuttle, the flames became dim blue after an initial transient where there was significant yellow (presumably soot) in the flame. The flame lifetimes were typically less than 60 seconds. The safety-mandated candlebox that contained the candle flame inhibited oxygen transport to the flame and thus limited the flame lifetime. 'Me flames on the Mir OS were similar, except that the yellow luminosity persisted longer into the flame lifetime because of a higher initial oxygen concentration. The Mir flames burned for as long as 45 minutes. The difference in the flame lifetime between the Shuttle and Mir flames was primarily the redesigned candlebox that did not inhibit oxygen transport to the flame. In both environments, the flame intensity and the height-to-width ratio gradually decreased as the ambient oxygen content in the sealed chamber slowly decreased. Both sets of experiments showed spontaneous, axisymmetric flame oscillations just prior to extinction. The paper also presents a numerical model of candle flame. The model is detailed in the gas-phase, but uses a simplified liquid/wick phase. 'Me model predicts a steady flame with a shape and size quantitatively similar to the Shuttle and Mir flames. ne model also predicts pre-extinction flame oscillations if the decrease in ambient oxygen is small enough.

  12. Experimental investigation of a stratified buoyant wake 

    E-print Network

    Kraft, Wayne Neal

    2004-11-15

    , v?rms, in the wake of a cylinder with stable buoyancy (triangles), unstable buoyancy (squares), no buoyancy (circles), and a typical Rayleigh Taylor mixing layer for the same.... Decay of vertical velocity fluctuations, v?rms, in the very near wake of a cylinder with stable buoyancy, unstable buoyancy, and no buoyancy. .................36 12. Variation of the location of peak v?rms with mixing...

  13. A New Tanarctid Arthrotardigrade with Buoyant Bodies

    Microsoft Academic Search

    Aslak Jörgensen; Reinhardt Møbjerg Kristensen

    2001-01-01

    Four cruises have revealed a very rich tardigrade fauna inhabiting the shell gravel at the Faroe Bank and Bill Bailey Bank in the North Atlantic. This study presents the description of Tanarctus bubulubus sp. n., which is one of the many new tanarctids from the Faroe Bank. The new species is found from 104 m to 200 m and is

  14. Two-link swimming using buoyant orientation

    E-print Network

    Burton, Lisa Janelle

    The scallop theorem posits that a two-link system immersed in a fluid at low Reynolds number cannot achieve any net translation via cyclic changes in its hinge angle. Here, we propose an approach to “breaking” this theorem, ...

  15. Size distribution and buoyant density of Burkholderia pseudomallei

    Microsoft Academic Search

    Jose-Luis Sagripanti; Monica Carrera; Jeannie Robertson; Avram Levy; Timothy J. J. Inglis

    2011-01-01

    The size and density of microbial cells determine the time that pathogens can remain airborne and thus, their potential to\\u000a infect by the respiratory route. We determined the density and size distribution of Burkholderia pseudomallei cells in comparison with other Burkholderia species, including B. mallei and B. thailandensis, all prepared and analyzed under similar conditions. The observed size distribution and

  16. PIV Measurements in Weakly Buoyant Gas Jet Flames

    NASA Technical Reports Server (NTRS)

    Sunderland, Peter B.; Greenbberg, Paul S.; Urban, David L.; Wernet, Mark P.; Yanis, William

    2001-01-01

    Despite numerous experimental investigations, the characterization of microgravity laminar jet diffusion flames remains incomplete. Measurements to date have included shapes, temperatures, soot properties, radiative emissions and compositions, but full-field quantitative measurements of velocity are lacking. Since the differences between normal-gravity and microgravity diffusion flames are fundamentally influenced by changes in velocities, it is imperative that the associated velocity fields be measured in microgravity flames. Velocity measurements in nonbuoyant flames will be helpful both in validating numerical models and in interpreting past microgravity combustion experiments. Pointwise velocity techniques are inadequate for full-field velocity measurements in microgravity facilities. In contrast, Particle Image Velocimetry (PIV) can capture the entire flow field in less than 1% of the time required with Laser Doppler Velocimetry (LDV). Although PIV is a mature diagnostic for normal-gravity flames , restrictions on size, power and data storage complicate these measurements in microgravity. Results from the application of PIV to gas jet flames in normal gravity are presented here. Ethane flames burning at 13, 25 and 50 kPa are considered. These results are presented in more detail in Wernet et al. (2000). The PIV system developed for these measurements recently has been adapted for on-rig use in the NASA Glenn 2.2-second drop tower.

  17. 46 CFR 108.697 - Buoyant work vests.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...Subpart 160.077 of this chapter. (b) Commercial hybrid PFD's carried as work vests must be— (1) Used, stowed...and have the same method of operation as each other hybrid PFD carried on board. [CGD 78-174A, 51 FR 4351,...

  18. Second order closure modeling of turbulent buoyant wall plumes

    NASA Technical Reports Server (NTRS)

    Zhu, Gang; Lai, Ming-Chia; Shih, Tsan-Hsing

    1992-01-01

    Non-intrusive measurements of scalar and momentum transport in turbulent wall plumes, using a combined technique of laser Doppler anemometry and laser-induced fluorescence, has shown some interesting features not present in the free jet or plumes. First, buoyancy-generation of turbulence is shown to be important throughout the flow field. Combined with low-Reynolds-number turbulence and near-wall effect, this may raise the anisotropic turbulence structure beyond the prediction of eddy-viscosity models. Second, the transverse scalar fluxes do not correspond only to the mean scalar gradients, as would be expected from gradient-diffusion modeling. Third, higher-order velocity-scalar correlations which describe turbulent transport phenomena could not be predicted using simple turbulence models. A second-order closure simulation of turbulent adiabatic wall plumes, taking into account the recent progress in scalar transport, near-wall effect and buoyancy, is reported in the current study to compare with the non-intrusive measurements. In spite of the small velocity scale of the wall plumes, the results showed that low-Reynolds-number correction is not critically important to predict the adiabatic cases tested and cannot be applied beyond the maximum velocity location. The mean and turbulent velocity profiles are very closely predicted by the second-order closure models. but the scalar field is less satisfactory, with the scalar fluctuation level underpredicted. Strong intermittency of the low-Reynolds-number flow field is suspected of these discrepancies. The trends in second- and third-order velocity-scalar correlations, which describe turbulent transport phenomena, are also predicted in general, with the cross-streamwise correlations better than the streamwise one. Buoyancy terms modeling the pressure-correlation are shown to improve the prediction slightly. The effects of equilibrium time-scale ratio and boundary condition are also discussed.

  19. Heat transfer from a negatively buoyant wall jet

    NASA Astrophysics Data System (ADS)

    Kapoor, K.; Jaluria, Y.

    1988-02-01

    An experimental investigation is conducted on the heat transfer characteristics of a turbulent, negatively bouyant, 2-D wall jet. A jet of hot air is discharged adjacent to a water-cooled, isothermal surface in an extensive environment. The heat transfer to the surface from the elevated temperature jet is measured along the isothermal surface for several values of wall, jet and ambient temperatures. Wide ranges of Grashof (Gr) and Reynolds number (Re) are investigated. It is found that the total heat transfer rate to the isothermal vertical surface decreases with an increase in Gr/Re squared. The effect of the surface temperature T sub s on the downward penetration of the jet and on the heat transfer rate is also investigated. Correlating equations are derived from the experimental data to characterize the dependence of the surface heat transfer rate on the various physical parameters governing the transport process. An interesting flow circumstance arises when the surface temperature is higher than the ambient temperature but lower than the jet discharge temperature, since the downward wall jet flow interacts with an upward buoyancy induced flow adjacent to the wall. The heat transfer mechanisms are investigated in detail for this flow.

  20. A numerical study of interacting buoyant cooling-tower plumes

    Microsoft Academic Search

    R. B. Bornoff; M. R. Mokhtarzadeh-Dehghan

    2001-01-01

    The compact design of mechanical cooling towers necessitates that the plumes are issued into the cross-wind in close proximity. An improved understanding of the interaction of adjacent plumes is therefore required for better design of such cooling towers, which may lead to a reduction in their environmental impact. This paper presents the results of a numerical investigation into the interaction

  1. Label-free buoyant mass assays with suspended microchannel resonators

    E-print Network

    Von Muhlen, Marcio Goldani

    2010-01-01

    Improved methods are needed for routine, inexpensive monitoring of biomarkers that could facilitate earlier detection and characterization of complex diseases like cancer. Development of new assay formats based on microfluidic, ...

  2. Bottom tension fence-type water buoyant containment boom

    SciTech Connect

    Brown, L. S.; March, F. A.

    1981-06-02

    A flexible, fence-type, water-borne pollutant containment boom is disclosed having a flexible, permanently attached tension reinforcing belt of continuous, substantially parallel, high modulus, aramid fibers adhesively secured to the boom proximate its bottom edge and having a plurality of handles spaced along the top edge of the boom, the handles being molded on both sides of the boom and overlapping the top edge and surrounding openings cut in the boom proximate the top edge leaving flaps of boom material to selectively close the openings.

  3. Flow-induced reconfiguration of buoyant and flexible aquatic vegetation

    E-print Network

    Nepf, Heidi

    Plant posture can play a key role in the health of aquatic vegetation, by setting drag, controlling light availability, and mediating the exchange of nutrients and oxygen. We study the flow-induced reconfiguration of ...

  4. Buoyant plane plumes from heated horizontal confined wires and cylinders

    Microsoft Academic Search

    Guy Lauriat; Gilles Desrayaud

    1994-01-01

    Two-dimensional computations are reported for time-dependent laminar buoyancy-induced flows above a horizontal heated source\\u000a immersed in an air-filled vessel. Two kinds of heated source were considered: a line heat source, modelled as a heat source\\u000a term in the energy equation, and a heat-flux cylinder of small diameter. First, comparisons are presented for the results\\u000a obtained for these two heated sources.

  5. The Multiphase Buoyant Plume Solution of the Dusty Gas Model

    E-print Network

    Cerminara, Matteo

    2015-01-01

    Starting from the balance equations of mass, momentum and energy we formulate an integral 1D model for a poly-disperse mixture injected in the atmosphere. We write all the equations, either in their most general formulation or in the more simplified, taking particular care in considering all the underlying hypothesis in order to make clear when it is possible and appropriate to use them. Moreover, we put all the equations in a non-dimensional form, making explicit all the dimensionless parameters that drive the dynamics of these phenomena. In particular, we find parameters to measure: the goodness of the Boussinesq approximation, the injected mass flow, the column stability and his eventual collapse, and the importance of the atmospheric stratification, the initial kinetic energy and the gravitational potential energy. We show that setting to zero some of these parameters, it is possible to recover some of the existing jet and plume models for single-phase flows. Moreover, we write a simplified set of equatio...

  6. Negatively Buoyant Flow Along Vertical Cylinders at High Rayleigh Numbers

    Microsoft Academic Search

    R. A. AHMAD; E. C. MATHIAS; S. BORAAS

    1992-01-01

    Conditions that must be satisfied before the launch of a Space Transportation System (STS) include combinations of ambient temperature and wind speed that are intended to prevent ice formation on the External Tank (ET) and a local air temperature around the STS of 33°F (0.56°C) or less. Nineteen effluent gases are purged or vented from the STS into the launch

  7. Negatively buoyant flow along vertical cylinders at high Rayleigh numbers

    Microsoft Academic Search

    R. A. Ahmad; E. C. Mathias; S. Boraas

    1990-01-01

    A combined three-dimensional and two-dimensional computational fluid dynamics analysis was carried out to determine a maximum theoretical effect of the Space Transportation System (STS) effluents, particularly gaseous oxygen, on the STS environment. The results of the analysis indicate surface temperatures on the east Redesigned Solid Rocket Motors (RSRMs) as much as 7 F colder than ambient, mostly due to the

  8. Negatively buoyant flow along vertical cylinders at high Rayleigh numbers

    NASA Astrophysics Data System (ADS)

    Ahmad, R. A.; Mathias, E. C.; Boraas, S.

    1990-07-01

    A combined three-dimensional and two-dimensional computational fluid dynamics analysis was carried out to determine a maximum theoretical effect of the Space Transportation System (STS) effluents, particularly gaseous oxygen, on the STS environment. The results of the analysis indicate surface temperatures on the east Redesigned Solid Rocket Motors (RSRMs) as much as 7 F colder than ambient, mostly due to the effect of the vented oxygen vapor. Due to the Rayleigh number's dependence on the cube of the length and the large length associated with the RSRMs and the External Tank, the Rayleigh numbers obtained in this study are one to three orders of magnitude higher than those found in the literature despite the relatively nominal value of 0.72 for the Prandtl number.

  9. MEASUREMENT OF BUOYANT JET ENTRAINMENT FROM SINGLE AND MULTIPLE SOURCES

    EPA Science Inventory

    An experimental investigation was conducted to determine the dilution characteristics of single and multiple discharges typical of modern natural and mechanical draft cooling towers. Simultaneous measurements of velocity and tracer concentration profiles were taken at various dow...

  10. Buoyant Low Stretch Diffusion Flames Beneath Cylindrical PMMA Samples

    NASA Technical Reports Server (NTRS)

    Olson, S. L.; Tien, J. S.

    1999-01-01

    A unique new way to study low gravity flames in normal gravity has been developed. To study flame structure and extinction characteristics in low stretch environments, a normal gravity low-stretch diffusion flame is generated using a cylindrical PMMA sample of varying large radii. Burning rates, visible flame thickness, visible flame standoff distance, temperature profiles in the solid and gas, and radiative loss from the system were measured. A transition from the blowoff side of the flammability map to the quenching side of the flammability map is observed at approximately 6-7/ sec, as determined by curvefits to the non-monotonic trends in peak temperatures, solid and gas-phase temperature gradients, and non-dimensional standoff distances. A surface energy balance reveals that the fraction of heat transfer from the flame that is lost to in-depth conduction and surface radiation increases with decreasing stretch until quenching extinction is observed. This is primarily due to decreased heat transfer from the flame, while the magnitude of the losses remains the same. A unique local extinction flamelet phenomena and associated pre-extinction oscillations are observed at very low stretch. An ultimate quenching extinction limit is found at low stretch with sufficiently high induced heat losses.

  11. Neutrally buoyant diapirs: A model for Venus coronae

    Microsoft Academic Search

    Dorothy M. Koch; Michael Manga

    1996-01-01

    Coronae are typically circular features, 100-600 km in diameter, characterized by a deformed annular ring that is often topographically high. The central region may be raised or depressed relative to the ambient elevation. Previous studies have proposed an evolutionary progression beginning with dome-shaped features which have radiating extensional rifts, followed by plateau-shaped features which have both concentric deformation and radial

  12. Dispersion in two-dimensional turbulent buoyant plumes

    E-print Network

    Rocco, Stefano; Woods, Andrew W.

    2015-06-02

    1979 and Carazzo et al. 2008 ), with applications for modelling volcanic plumes in the atmosphere, hydrothermal plumes in the ocean ( Woods 2010 ), effluent spreading in shallow estuaries and river outflows into shallow lakes ( Daoyi & Jirka 1998...

  13. Solutions for turbulent buoyant plumes rising from circular sources

    NASA Astrophysics Data System (ADS)

    Michaux, G.; Vauquelin, O.

    2008-06-01

    Analytical solutions are developed for turbulent plumes rising from circular sources of positive buoyancy in a quiescent environment of uniform density. From governing equations written in a form which encompasses both the Boussinesq and non-Boussinesq cases, we derive analytical expressions for all plume variables (radius, velocity, and density deficit) in terms of a single quantity ?, called the plume function. For given source conditions, we then show that ? (and, subsequently, all plume variables) can be evaluated at any height from two integral functions which are defined for lazy and forced plumes. For a practical use, these integral functions are given in tables. Moreover, exact values and locations of the maximum velocity and the plume neck are determined.

  14. 46 CFR 160.010-3 - Inflatable buoyant apparatus.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... It does not need a canopy. (2) Capacity (Regulation III/38.2.1). The carrying capacity must be not less than four persons. ...arrangements for righting. (6) One with a capacity of 13 or more persons must be...

  15. Three-Dimensional Recomposition of the Absorption Field Inside a Non-Buoyant Sooting Diffusion Flame 

    E-print Network

    Legros, Guillaume; Fuentes, Andres; Ben-Abdallah, Philippe; Baillargeat, Jacques; Joulain, Pierre; Vantelon, Jean-Pierre; Torero, Jose L

    A remote scanning retrieval method was developed to investigate the soot layer produced by a laminar diffusion flame established over a flat plate burner in microgravity. Experiments were conducted during parabolic flights. ...

  16. Preventing Buoyant Displacement Gas Release Events in Hanford Double-Shell Waste Tanks

    SciTech Connect

    Meyer, Perry A.; Stewart, Charles W.

    2001-01-01

    This report summarizes the predictive methods used to ensure that waste transfer operations in Hanford waste tanks do not create waste configurations that lead to unsafe gas release events. The gas release behavior of the waste in existing double-shell tanks has been well characterized, and the flammable gas safety issues associated with safe storage of waste in the current configuration are being formally resolved. However, waste is also being transferred between double-shell tanks and from single-shell tanks into double-shell tanks by saltwell pumping and sluicing that create new wastes and waste configurations that have not been studied as well. Additionally, planning is underway for various waste transfer scenarios to support waste feed delivery to the proposed vitrification plant. It is critical that such waste transfers do not create waste conditions with the potential for dangerous gas release events.

  17. Mountain Building Driven by Subduction Accretion and Thinning of Buoyant Asthensophere

    NASA Astrophysics Data System (ADS)

    Buck, W. R.

    2011-12-01

    The force required to thicken crust and produce mountain ranges is not supplied by the plate tectonic driving forces of ridge push and slab pull. I show that the compressive force needed to create mountains can be produce by local thinning of low-density asthenosphere. A long period of subduction can cause such thinning because asthenosphere will accrete onto the cold surface of subducting slabs and be carried to great depths with that slab. Four requirements must be met for mountains to be built in this way: (1) "Normal" asthenosphere must be lighter than underlying mantle by 100-200 kg/m3 and it must be 100-300 km thick; (2) Subduction at typical rates has to operate for 10's of Ma to thin asthenosphere significantly; (3) Flow of asthenosphere into the region of thinning asthenosphere must be restricted due to surrounding thick lithosphere (or tectosphere), (4) The continental lithosphere overlying the thinned asthenosphere must be thin and weak. The possibility that the asthenosphere is hotter and less dense than the underlying mantle was suggested in the earliest papers on mantle plumes. Numerical models of asthenospheric flow and lithospheric deformation based on the thin sheet approximation illustrate how mountain chains like the Andes can be produced. A corollary of this model is that if ridge capture occurs after a period of asthenospheric thinning then a flood of asthenosphere would pass through the resulting slab window. Numerical models show how such rapid thickening of asthenosphere could lead to the kind of uplift and continental extension that began in the Western United States during the Miocene.

  18. On the flow around a buoyant cylinder within a rapidly rotating horizontal cylindrical container

    Microsoft Academic Search

    R. F. Gans

    1979-01-01

    Steady flow in a cylinder of finite length rotating rapidly at right angles to the earth's gravity and containing a rigid cylindrical float is found under the assumption of small viscosity. The float is modelled by a 'rigid free surface'. The major new result is a prediction of the rotation rate of the interface, which differs by a factor of

  19. Modelling fluctuations in the concentration of neutrally buoyant substances in the atmosphere

    NASA Astrophysics Data System (ADS)

    Ride, David John

    1987-12-01

    The probability density function (PDF) of the perceived concentration of a contaminant in the atmosphere is modeled using simple, physical representations of the dispersing contaminant. Sensors are characterized by the time taken to achieve a reading and by a threshold level of concentration below which the sensor does not respond and thus records a concentration of zero. A literature search of theoretical and experimental work concerning concentration fluctuations is conducted, and the merits - or otherwise - of of some common PDF's in common use are discussed.

  20. 46 CFR 185.730 - Servicing of inflatable liferafts, inflatable buoyant apparatus, inflatable life jackets, and...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... (b) Each inflatable lifejacket and hybrid inflatable lifejacket or work vest must...specified by the Commandant. (d) Each hybrid inflatable life jacket or work vest must...Commandant, except for emergency repairs carried out on board the vessel. [CGD...

  1. 46 CFR 185.730 - Servicing of inflatable liferafts, inflatable buoyant apparatus, inflatable life jackets, and...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... (b) Each inflatable lifejacket and hybrid inflatable lifejacket or work vest must...specified by the Commandant. (d) Each hybrid inflatable life jacket or work vest must...Commandant, except for emergency repairs carried out on board the vessel. [CGD...

  2. ESTIMATING SURFACE CONCENTRATIONS FROM AN ELEVATED, BUOYANT PLUME IN A LIMITED-MIXED CONVECTIVE BOUNDARY LAYER

    EPA Science Inventory

    In the past decade, recent advances have suggested that convective scaling can be used to parameterize diffusion from a plume in the convective boundary layer (CBL). New methods such as convective scaling need to be explored because the traditionally used Gaussian plume model doe...

  3. Influence of a buoyant river plume on phytoplankton nutrient dynamics: What controls standing stocks and productivity?

    E-print Network

    Hickey, Barbara

    . Geophys. Res., 114, C00B11, doi:10.1029/2008JC004913. 1. Introduction [2] The Columbia River is the single March 2009; accepted 14 May 2009; published 24 July 2009. [1] The influence of the Columbia River plume and/or silicic acid (in waters not influenced by the Columbia River plume) would quickly become

  4. Near-Limit Flamelet Phenomena in Buoyant Low Stretch Diffusion Flames Beneath a Solid Fuel

    NASA Technical Reports Server (NTRS)

    Olson, S. L.; Tien, J. S.

    2000-01-01

    A unique near-limit low stretch multidimensional stable flamelet phenomena has been observed for the first time which extends the material flammability limit beyond the one-dimensional low stretch flammability limit to lower burning rates and higher relative heat losses than is possible with uniform flame coverage. During low stretch experiments burning the underside of very large radii (greater than or = 75 cm stretch rate less than or = 3/s) cylindrical cast PMMA samples, multidimensional flamelets were observed, in contrast with a one-dimensional flame that was found to blanket the surface for smaller radii samples ( higher stretch rate). Flamelets were observed by decreasing the stretch rate or by increasing the conductive heat loss from the flame. Flamelets are defined as flames that cover only part of the burning sample at any given time, but persist for many minutes. Flamelet phenomena is viewed as the flame's method of enhancing oxygen flow to the flame, through oxygen transport into the edges of the flamelet. Flamelets form as heat losses (surface radiation and solid-phase conduction) become large relative to the weakened heat release of the low stretch flame. While heat loss rates remain fairly constant, the limiting factor in the heat release of the flame is hypothesized to be the oxygen transport to the flame in this low stretch (low convective) environment. Flamelet extinction is frequently caused by encroachment of an adjacent flamelet. Large-scale whole-body flamelet oscillations at 1.2 - 1.95 Hz are noted prior to extinction of a flamelet. This oscillation is believed to be due a repeated process of excess fuel leakage through the dark channels between the flamelets, fuel premixing with slow incoming oxidizer, and subsequent rapid flame spread and retreat of the flamelet through the premixed layer. The oscillation frequency is driven by gas-phase diffusive time scales.

  5. Buoyant replenishment in silicic magma reservoirs: Experimental approach and implications for magma

    E-print Network

    Long, Bernard

    on replenishment of rhyolite magma chambers by rhyolite magma using corn syrup-water solutions. We emphasize small ascent through the mush. Our results have implications for rhyolites bearing crystals with disequilibrium decades to investigate these processes. This study focuses on rhyolite magma replenishing rhyolite

  6. Initial dilution of a vertical round non-buoyant jet in wavy cross-flow environment

    NASA Astrophysics Data System (ADS)

    Wang, Ya-na; Chen, Yong-ping; Xu, Zhen-shan; Pan, Yi; Zhang, Chang-kuan; Li, Chi-wai

    2015-05-01

    The phenomenon of wastewater discharged into coastal waters can be simplified as a turbulent jet under the effect of waves and currents. Previous studies have been carried out to investigate the jet behaviors under the current only or the wave only environment. To obtain better understanding of the jet behaviors in a realistic situation, a series of physical experiments on the initial dilution of a vertical round jet in the wavy cross-flow environment are conducted. The diluted processes of the jet are recorded by a high-resolution camcorder and the concentration fields of the jet are measured with a peristaltic suction pumping system. When the jet is discharged into the wavy cross-flow environment, a distinctive phenomenon, namely "effluent clouds", is observed. According to the quantitative measurements, the jet width in the wavy cross-flow environment increases more significantly than that does in the cross-flow only environment, indicating that the waves impose a positive effect on the enhancement of jet initial dilution. In order to generalize the experimental findings, a comprehensive velocity scale u a and a characteristic length scale l are introduced. Through dimensional analysis, it is found that the dimensionless centerline concentration trajectories y c/l is in proportion to 1/3 power of the dimensionless downstream distance x/l, and the dimensionless centerline dilution S c Q/(u a l 2) is proportional to the square of the dimensionless centerline trajectory y c /l. Several empirical equations are then derived by using the Froude number of cross-flow Fr c as a reference coefficient. This paper provides a better understanding and new estimations of the jet initial dilution under the combined effect of waves and cross-flow current.

  7. Upscaling of Capillary Trapping in a Buoyant Plume: Application to CO2 Sequestration in Aquifers

    NASA Astrophysics Data System (ADS)

    Szulczewski, M.; Juanes, R.

    2007-12-01

    CO2 sequestration refers to the capture and long-term storage of anthropogenic CO2 in order to limit its emission to the atmosphere. Injection into geological formations is one option to store CO2. Deep saline aquifers are prime candidates for CO2 storage because they have a huge storage capacity and they are widely distributed. One of the major concerns in any sequestration project is the potential leakage of the CO2 into the atmosphere. CO2 tends to migrate to the top of the geologic structure. This upward migration is sometimes delayed or suppressed by low permeability layers that impede the vertical flow of gas - hydrodynamic or structural trapping. However, the success of a sequestration project relies to a great extent on the magnitude of capillary trapping (Juanes et al., Water Resour. Res. 2006), in which the CO2 phase is disconnected into an immobile (trapped) fraction. Here, we investigate, by means of laboratory experiments and numerical simulation, the scale dependence of capillary trapping. The basic flow unit is a transparent glass-bead pack - a Hele-Shaw cell filled with glass beads. This design enables simple visualization techniques to be used to monitor the flow. The present paper confirms that current field-scale simulation models of CO2 storage overestimate the amount that is actually trapped, because they do not capture the small-scale variability due to viscous and gravity instabilities, and permeability channeling.

  8. Approximate Value of Buoyant Force: A Water-Filled Balloon Demonstration

    ERIC Educational Resources Information Center

    Radovanovic, Jelena; Slisko, Josip

    2012-01-01

    Floating and sinking might be common phenomena, encountered on a daily basis, but still represent conceptually complex scientific topics. Research has shown that most students have certain experiences and their own "theories" that explain why objects sink or float. Unfortunately, many of these "theories" are either misconceptions or are valid only…

  9. Meeting the Skills Needs of a Buoyant Economy: Apprenticeship--The Irish Experience

    ERIC Educational Resources Information Center

    O'Connor, Len

    2006-01-01

    The Irish economy has grown at an unprecedented rate over the last decade and the demand for skilled workers has increased dramatically. The Irish Standards-Based Apprenticeship (SBA) system has been one of the cornerstones of intermediate skills development with the capacity to produce high-quality craft workers and in sufficient numbers to meet…

  10. Displacement forces on a neutral current detector from a buoyant and flexible cable under tension

    SciTech Connect

    Walston, S.

    1994-05-01

    As a means for maintaining order in the 112 NCD readout cables, it is proposed to put the cables under tension in such a way that they lie as straight as possible and rest along the top surface of the acrylic D{sub 2}O vessel. However, one aim is to avoid using top anchor points to secure the NCDs in the D{sub 2}O vessel, but rather to just let the counter`s inherent buoyancy maintain the necessary vertical orientation. As a result, applying a tension to the readout cable may pull the counters too far off of vertical. Whether or not the counter is pulled too far off of vertical depends in large part on the characteristics of the cable, i.e. modulus of elasticity and initial radius of curvature. Given that the applied tension in equilibrium is just equal to the restoring force on the counter when pulled off of vertical by some arbitrarily small amount, and given that the final radius of curvature of the readout cable is 6 meters (the radius of the D{sub 2}O vessel), what then must the modulus of elasticity be for a given initial radius of curvature of the cable? This assumes that the cable will be wrapped around a spool or somehow coiled for shipment. This also assumes that upon delivery of the cables, some effort can be made to straighten them out somewhat. For this approximation, the buoyancy of the cables is assumed to be negligible. The small length of cable that does not rest against the inner surface of the D{sub 2}O vessel is also neglected.

  11. LMP2A Does Not Require Palmitoylation To Localize to Buoyant Complexes or for Function

    Microsoft Academic Search

    Rebecca B. Katzman; Richard Longnecker

    2004-01-01

    Epstein-Barr virus (EBV) latent membrane protein 2A (LMP2A) is expressed constitutively in lipid rafts in latently infected B lymphocytes. Lipid rafts are membrane microdomains enriched in cholesterol and sphin- golipids selective for specific protein association. Lipid rafts have been shown to be necessary for B-cell receptor (BCR) signal transduction. LMP2A prevents BCR recruitment to lipid rafts, thereby abrogating BCR function.

  12. Numerical Study on the Turbulent Flow Structures of a Buoyant Pool Fire

    NASA Astrophysics Data System (ADS)

    Cheung, Sherman C. P.; Se, Camby M. K.; Yeoh, G. H.; Tu, Jiyuan

    2010-05-01

    In attempting to capture the non-linearity of the fire turbulent flow structures, a fully-coupled Large Eddy Simulation (LES) model which incorporates all essential subgrid scale (SGS) turbulence, combustion, radiation and soot chemistry considerations has been developed. This paper presents a thorough validation study comparing predictions of the present model with a one-meter diameter methane pool fire experimental data [1] as well as numerical results from other well-known LES models [2-3]. The predicted time-averaged velocities and turbulent quantities have been found to be in good agreement with the experimental data and other model predictions. In term of transient flow structures, for the very first time, the predicted instantaneous velocity field show satisfactory agreement with the Particle Image Velocimetry (PIV) measurements demonstrating the success of capturing the temporal vortical structure by the present model. Quantitative comparisons of velocity time history and pulsation frequency also show close agreement against experimentally evaluated quantities. Nonetheless, turbulent kinetic energy was slightly over-predicted by the present model. Possible sources of errors are discussed leading to the potential direction for future model.

  13. Buoyant production and consumption of turbulence kinetic energy in cloud-topped mixed layers

    NASA Technical Reports Server (NTRS)

    Randall, D. A.

    1984-01-01

    It is pointed out that studies of the entraining planetary boundary layer (PBL) have generally emphasized the role of buoyancy fluxes in driving entrainment. The buoyancy flux is proportional to the rate of conversion of the potential energy of the mean flow into the kinetic energy of the turbulence. It is not unusual for conversion to proceed in both directions simultaneously. This occurs, for instance, in both clear and cloudy convective mixed layers which are capped by inversions. A partitioning of the net conversion into positive parts, generating turbulence kinetic energy (TKE), and negative parts (TKE-consuming), would make it possible to include the positive part in the gross production rate, and closure would be achieved. Three different approaches to partitioning have been proposed. The present investigation is concerned with a comparison of the three partitioning theories. Particular attention is given to the cloud-topped mixed layer because in this case the differences between two partitioning approaches are most apparent.

  14. Similarity solutions in buoyancy-controlled turbulent diffusion flame modeling; Turbulent buoyant diffusion flame modeling

    Microsoft Academic Search

    M. A. Pivovarov; H. Zhang; D. E. Ramakev; P. A. Tatem; F. W. Williams

    1993-01-01

    This paper considers the applicability of different versions of the k-[epsilon] hypothesis of turbulence for flame modeling. Utilizing similarity solutions, the authors find that the k-[epsilon] hypothesis gives a finite radius for a weak axisymmetric plume above the heat source. The radius of this plume is defined as an eigenvalue of the boundary value problem with unknown boundary. Solving this

  15. A buoyant tornado-probe concept incorporating an inverted lifting device. [and balloon combination

    NASA Technical Reports Server (NTRS)

    Grant, F. C.

    1973-01-01

    Addition of an inverted lifting device to a simple balloon probe is shown to make possible low-altitude entry to tornado cores with easier launch conditions than for the simple balloon probe. Balloon-lifter combinations are particularly suitable for penetration of tornadoes with average to strong circulation, but tornadoes of less than average circulation which are inaccessible to simple balloon probes become accessible. The increased launch radius which is needed for access to tornadoes over a wide range of circulation results in entry times of about 3 minutes. For a simple balloon probe the uninflated balloon must be first dropped on, or near, the track of the tornado from a safe distance. The increase in typical launch radius from about 0.75 kilometer to slightly over 1.0 kilometer with a balloon-lifter combination suggests that a direct air launch may be feasible.

  16. Numerical analysis of buoyant-convective liquid metal flow in channels exposed to strong magnetic fields

    Microsoft Academic Search

    Chiara Mistrangelo; Leo Buhler

    2011-01-01

    In the currently proposed helium cooled lead lithium blanket design the liquid metal serves mainly to breed tritium and the heat flux is removed by helium flowing at high pressure in channels grooved in the walls. The use of a separate coolant has the advantage that the liquid metal can flow in the blanket with smaller velocities compared to those

  17. Observations of the frontal region of a buoyant river plume using an autonomous underwater vehicle

    NASA Astrophysics Data System (ADS)

    Rogowski, Peter; Terrill, Eric; Chen, Jialin

    2014-11-01

    To characterize the transitional region from the near-field to far-field of a river plume entering coastal waters, we conducted four surveys using an autonomous underwater vehicle (AUV) to target the outflow of the New River Inlet, North Carolina, during maximum ebb tide. The utilization of a mobile sensor to synoptically observe current velocity data in tandem with natural river plume tracers (e.g., colored dissolved organic matter, salinity) was essential in understanding the mechanisms driving the observed circulation and mixing patterns within these waters. We find that this region is regularly impacted by two primary processes: (1) the interaction of an old dredged channel plume with the main discharge and (2) the recirculation of the discharge plume by an eddy that persistently forms between the old channel and main discharge location. Wind-driven processes in the nearshore can enhance the interaction of these two plumes resulting in unstable regions where mixing of the merged plume with the receiving waters is accelerated. We also conduct comparisons between AUV velocity observations from two surveys and their corresponding velocity outputs from a parallelized quasi-3-D model. We conclude that the ability to observe the estuarine outflow transitional region at near-synoptic temporal scales and resolutions discussed in this paper is key in providing the mechanisms driving local circulation which is essential for proper parameterization of high-resolution numerical coastal models.

  18. A Buoyant Pop Net for Accurately Sampling Fish at Artificial Habitat Structures

    Microsoft Academic Search

    Eric W. Larson; David L. Johnson; William E. Lynch Jr

    1986-01-01

    We developed and evaluated the efficiency of a remotely operated pop net for sampling the entire fish assemblage associated with fish-attracting structures. The pop net collected an average of 99% of subadult and adult bluegills Lepomis macrochirus and largemouth bass Micropterus salmoides available to capture in pool tests conducted at 3–13°C and various light intensities. There was no evidence of

  19. Long-Lived, Maneuverable, Semi-Buoyant Platform for Venus Upper Atmosphere Exploration

    NASA Astrophysics Data System (ADS)

    Lee, G.; Sokol, D.; Polidan, R.; Bolisay, L.; Barnes, N.

    2014-06-01

    This presentation discusses the continued development of the Northrop Grumman/L’GARDE team’s long-lived, maneuverable platform to explore the Venus upper atmosphere. It focuses on the overall mission architecture and concept of operations.

  20. Lessons from randomized phase III studies with active cancer immunotherapies – Outcomes from the 2006 Meeting of the Cancer Vaccine Consortium (CVC)

    Microsoft Academic Search

    Lothar H. Finke; Kerry Wentworth; Brent Blumenstein; Natalie S. Rudolph; Hyam Levitsky; Axel Hoos

    2007-01-01

    After years of effort to develop active cancer immunotherapies, seven candidate products achieved promising results in phase I\\/II studies that triggered phase III randomized studies. One candidate to date has received an approvable letter from the United States Food and Drug Administration (FDA), defining a clear path to licensure for sipuleucel-T (Provenge®, Dendreon) within the next couple of years. The

  1. Alginate gel-coated oil-entrapped alginate-tamarind gum-magnesium stearate buoyant beads of risperidone.

    PubMed

    Bera, Hriday; Boddupalli, Shashank; Nandikonda, Sridhar; Kumar, Sanoj; Nayak, Amit Kumar

    2015-07-01

    A novel alginate gel-coated oil-entrapped calcium-alginate-tamarind gum (TG)-magnesium stearate (MS) composite floating beads was developed for intragastric risperidone delivery with a view to improving its oral bioavailability. The TG-blended alginate core beads containing olive oil and MS as low-density materials were accomplished by ionotropic gelation technique. Effects of polymer-blend ratio (sodium alginate:TG) and crosslinker (CaCl2) concentration on drug entrapment efficiency (DEE, %) and cumulative drug release after 8h (Q8h, %) were studied to optimize the core beads by a 3(2) factorial design. The optimized beads (F-O) exhibited DEE of 75.19±0.75% and Q8h of 78.04±0.38% with minimum errors in prediction. The alginate gel-coated optimized beads displayed superior buoyancy and sustained drug release property. The drug release profiles of the drug-loaded uncoated and coated beads were best fitted in Higuchi kinetic model with Fickian and anomalous diffusion driven mechanisms, respectively. The optimized beads yielded a notable sustained drug release profile as compared to marketed immediate release preparation. The uncoated and coated Ca-alginate-TG-MS beads were also characterized by SEM, FTIR and P-XRD analyses. Thus, the newly developed alginate-gel coated oil-entrapped alginate-TG-MS composite beads are suitable for intragastric delivery of risperidone over a prolonged period of time. PMID:25861741

  2. Photooxidation of aqueous trichloroethylene using a buoyant photocatalyst with reaction progress monitored via micro-headspace GC\\/MS

    Microsoft Academic Search

    Sam Lohse; Jeffrey J. Rosentreter

    2006-01-01

    Although photooxidation has previously been shown to be successful in removing organic contaminants from water, methods combining the rapid photooxidation of the desired contaminant with easy catalyst manipulation and removal are few and far between. In the absence of an easy means of catalyst removal, the photooxidation process becomes more costly and time consuming, and photocatalysis cannot be employed as

  3. Ranitidine Hydrochloride-loaded Ethyl Cellulose and Eudragit RS 100 Buoyant Microspheres: Effect of pH Modifiers

    PubMed Central

    Kotagale, N. R.; Parkhe, A. P.; Jumde, A. B.; Khandelwal, H. M.; Umekar, M. J.

    2011-01-01

    A floating type of dosage form of ranitidine hydrochloride in the form of microspheres capable of floating on simulated gastric fluid was prepared by solvent evaporation technique. Microspheres prepared with ethyl cellulose, Eudragit® RS100 alone or in combination were evaluated for percent yield, drug entrapment, percent buoyancy and drug release and the results demonstrated satisfactory performance. Microspheres exhibited ranitidine hydrochloride release influenced by changing ranitidine hydrochloride-polymer and ranitidine hydrochloride-polymer-polymer ratio. Incorporation of a pH modifier has been the usual strategy employed to enhance the dissolution rate of weakly basic drug from floating microspheres. Further citric acid, fumaric acid, tartaric acid were employed as pH modifiers. Microspheres prepared with ethyl cellulose, Eudragit® RS100 and their combination that showed highest release were utilized to study the effect of pH modifiers on ranitidine hydrochloride release from microspheres which is mainly affected due to modulation of microenvironmental pH. In vitro release of ranitidine hydrochloride from microspheres into simulated gastric fluid at 37° showed no significant burst effect. However the amount of release increased with time and significantly enhanced by pH modifiers. 15% w/w concentration of fumaric acid provide significant drug release from ranitidine hydrochloride microspheres prepared with ranitidine hydrochloride:ethyl cellulose (1:3), ranitidine hydrochloride:Eudragit® RS100 (1:2) and ranitidine hydrochloride:ethyl cellulose:Eudragit® RS100 (1:2:1) whereas citric acid, tartaric acid showed significant cumulative release at 20% w/w. In all this study suggest that ethyl celluose, Eudragit® RS100 alone or in combination with added pH modifiers can be useful in floating microspheres which can be proved beneficial to enhance the bioavailability of ranitidine hydrochloride. PMID:23112396

  4. Numerical study of wall effects on buoyant gas-bubble rise in a liquid-filled finite cylinder

    PubMed Central

    Mukundakrishnan, Karthik; Quan, Shaoping; Eckmann, David M.; Ayyaswamy, Portonovo S.

    2009-01-01

    The wall effects on the axisymmetric rise and deformation of an initially spherical gas bubble released from rest in a liquid-filled, finite circular cylinder are numerically investigated. The bulk and gas phases are considered incompressible and immiscible. The bubble motion and deformation are characterized by the Morton number (Mo), Eötvös number (Eo), Reynolds number (Re), Weber number (We), density ratio, viscosity ratio, the ratios of the cylinder height and the cylinder radius to the diameter of the initially spherical bubble (H* = H/d0, R* = R/d0). Bubble rise in liquids described by Eo and Mo combinations ranging from (1,0.01) to (277.5,0.092), as appropriate to various terminal state Reynolds numbers (ReT) and shapes have been studied. The range of terminal state Reynolds numbers includes 0.02 < ReT < 70. Bubble shapes at terminal states vary from spherical to intermediate spherical-cap–skirted. The numerical procedure employs a front tracking finite difference method coupled with a level contour reconstruction of the front. This procedure ensures a smooth distribution of the front points and conserves the bubble volume. For the wide range of Eo and Mo examined, bubble motion in cylinders of height H* = 8 and R* ? 3, is noted to correspond to the rise in an infinite medium, both in terms of Reynolds number and shape at terminal state. In a thin cylindrical vessel (small R*), the motion of the bubble is retarded due to increased total drag and the bubble achieves terminal conditions within a short distance from release. The wake effects on bubble rise are reduced, and elongated bubbles may occur at appropriate conditions. For a fixed volume of the bubble, increasing the cylinder radius may result in the formation of well-defined rear recirculatory wakes that are associated with lateral bulging and skirt formation. The paper includes figures of bubble shape regimes for various values of R*, Eo, Mo, and ReT. Our predictions agree with existing results reported in the literature. PMID:17930342

  5. A robust k-?-v 2 \\/k elliptic blending turbulence model applied to near-wall, separated and buoyant flows

    Microsoft Academic Search

    F. Billard; D. Laurence

    This paper first reconsiders evolution over 20 years of the k-epsilon-v2-f strand of eddy-viscosity models, developed since P. Durbin’s 1991 original proposal for a near-wall eddy viscosity model based on the physics of the full Reynolds stress transport models, but retaining only the wall-normal fluctuating velocity variance, v2, and its source, f, the redistribution by pressure fluctuations. Added to the

  6. Carbon and Water Program Protocols for Neutrally Buoyant Sediment Traps Twilight Zone Explorer at BATS, June 2007-December 2009

    E-print Network

    Buesseler, Ken

    Carboys for filtered seawater o Mounting board, filter cassette and holder for filtering seawater o Flojet, fill tubes to baffle with new filtered seawater · Save ~1-2 L of filtered 150 m seawater for rinsing purposes ­ store in fridge · Pour 500 mL of buffered brine/formalin solution down fill tube into bottom

  7. Buoyant thermocapillary flow with nonuniform supra-heating. I - Liquid-phase behavior. II - Two-phase behavior

    NASA Astrophysics Data System (ADS)

    Schiller, David N.; Sirignano, William A.

    1992-03-01

    The present computational study of transient heat transfer and fluid flow in a circular pool of n-decane which is undergoing central radiative heating from above gives attention to the volumetric absorption of the radiation incident on the pool surface. The first part of this study notes that buoyancy influences the number and recirculation rates of the subsurface vortices by stabilizing hot subsurface fluid above the colder core fluid; this affects the liquid surface temperature profile and in turn governs the velocity profile that is due to thermocapillarity. In the second part, the effects of gas-liquid phase coupling, variable density and thermophysical properties, and vaporization are considered.

  8. Buoyant thermocapillary flow with nonuniform supra-heating. I - Liquid-phase behavior. II - Two-phase behavior

    NASA Technical Reports Server (NTRS)

    Schiller, David N.; Sirignano, William A.

    1992-01-01

    The present computational study of transient heat transfer and fluid flow in a circular pool of n-decane which is undergoing central radiative heating from above gives attention to the volumetric absorption of the radiation incident on the pool surface. The first part of this study notes that buoyancy influences the number and recirculation rates of the subsurface vortices by stabilizing hot subsurface fluid above the colder core fluid; this affects the liquid surface temperature profile and in turn governs the velocity profile that is due to thermocapillarity. In the second part, the effects of gas-liquid phase coupling, variable density and thermophysical properties, and vaporization are considered.

  9. Thermal field in a water body for solar energy storage and extraction due to a buoyant two-dimensional surface water jet

    SciTech Connect

    Jaluria, Y.; O'Mara, B.T. (Rutgers Univ., New Brunswick, NJ (USA))

    1989-01-01

    An experimental study on the thermal field arising in an enclosed water body being employed for energy storage, as sensible heat, due to a horizontally discharged, heated, water jet is carried out. Two-dimensional surface discharges are considered, with an outflow located at the far end of a water body, which is simulated in the laboratory by a tank of rectangular cross section. Energy loss occurs ant the sides and at the top of the water body largely by convective transport and at the bottom by conduction to the ground. The study initially considers the transient behavior of the water body due to the input of thermal energy. A rapid transient, followed by a very gradual variation to an essentially steady-state temperature distribution, is observed. Experimental results are obtained in this steady regime for a water body of large extent, simulated by allowing a gradual outflow far from the inflow. The effects of the inflow conditions, aspect ratio, and the position of the outflow on the resulting thermal stratification are then studied in detail. Several interesting trends are observed and related to the basic mechanisms that arise in such energy storage systems. These flows are of interest in the storage and the extraction of energy, as sensible heat, in systems such as salt-gradient solar ponds. The thermal field is important in the design of such storage systems, particularly with respect to the selection of inlet conditions and the location of the outflow.

  10. Thermal field in a water body for solar energy storage and extraction due to a buoyant two-dimensional surface water jet

    Microsoft Academic Search

    Y. Jaluria; B. T. OMara

    1989-01-01

    An experimental study on the thermal field arising in an enclosed water body being employed for energy storage, as sensible heat, due to a horizontally discharged, heated, water jet is carried out. Two-dimensional surface discharges are considered, with an outflow located at the far end of a water body, which is simulated in the laboratory by a tank of rectangular

  11. Hands-on experiences with buoyant-less water This article has been downloaded from IOPscience. Please scroll down to see the full text article.

    E-print Network

    Planin?iè, Gorazd

    the transparent globe. Einstein lifted the device, left it to fall freely and the ball ended up in the cup. 292 PH, the spring is not strong enough to pull the ball up into the cup. The puzzle was to imagine a Figure 1. The birthday present given to Einstein. sure method to bring the ball into the cup, without opening

  12. Common Variants in the Promoter of the Hepatic Lipase Gene Are Associated With Lower Levels of Hepatic Lipase Activity, Buoyant LDL, and Higher HDL2 Cholesterol

    Microsoft Academic Search

    Alberto Zambon; Samir S. Deeb; John E. Hokanson; B. Greg Brown; John D. Brunzell

    Increased hepatic lipase (HL) activity is associated with small, dense, low density lipoprotein (LDL) and low high density lipoprotein2 (HDL2) cholesterol (-C) levels. A polymorphism in the promoter region of the HL gene (LIPC) is associated with HDL-C levels. To test whether this association is mediated by differences in HL activity between different LIPC promoter genotypes, the LIPC promoter polymorphism

  13. Non-hydrostatic modeling of cohesive sediment transport associated with a subglacial buoyant jet in glacial fjords: A process-oriented approach

    E-print Network

    deYoung, Brad

    decreased by mixing but no settling is observed through the water column. At high concentrations December 2012 Available online 5 January 2013 Keywords: Glacier Convective sedimentation Plume Flocculation, the sediment settles in the far field and is transported back to the near field by the landward estuarine

  14. Numerical simulation of buoyant, turbulent flow. I - Free convection along a heated, vertical, flat plate. II - Free and mixed convection in a heated cavity

    Microsoft Academic Search

    W. M. To; J. A. C. Humphrey

    1986-01-01

    Numerical models are presented to predict free and mixed convection low Reynolds number turbulent flows. A k-epsilon model and an algebraic stress model are used for the case of free convection along a heated vertical flat plate. Both models are found to yield accurate results for the mean flow and heat transfer, and measurements compare well with previous predictions. In

  15. 46 CFR 180.175 - Survival craft equipment.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...painter, and a light. (f) Equipment specifications for life floats and buoyant apparatus...buoyant apparatus must meet the following specifications: (1) Lifeline and pendants. ...than 3 times the distance between the deck where the life float or buoyant...

  16. 46 CFR 160.049-1 - Incorporation by reference.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...EQUIPMENT Specification for a Buoyant Cushion Plastic Foam § 160.049-1 Incorporation by... 160.055—Life Preservers, Unicellular Plastic Foam, Adult and Child. 164.015—Plastic Foam, Unicellular, Buoyant, Sheet and...

  17. 46 CFR 160.049-1 - Incorporation by reference.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...EQUIPMENT Specification for a Buoyant Cushion Plastic Foam § 160.049-1 Incorporation by... 160.055—Life Preservers, Unicellular Plastic Foam, Adult and Child. 164.015—Plastic Foam, Unicellular, Buoyant, Sheet and...

  18. 46 CFR 160.048-2 - Types and sizes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant Cushion, Fibrous Glass § 160.048-2 Types and sizes. (a) Types. Buoyant cushions shall be of the box type, i.e., have top,...

  19. 30 CFR 250.910 - Which of my facilities are subject to the Platform Verification Program?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (1) Your new floating platform is a buoyant offshore facility that does not have...ship-shaped hull The entire platform is subject to the Platform... (2) Your new floating platform is a buoyant offshore facility with a...

  20. 30 CFR 250.910 - Which of my facilities are subject to the Platform Verification Program?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... (1) Your new floating platform is a buoyant offshore facility that does not have...ship-shaped hull The entire platform is subject to the Platform... (2) Your new floating platform is a buoyant offshore facility with a...

  1. 30 CFR 250.910 - Which of my facilities are subject to the Platform Verification Program?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... (1) Your new floating platform is a buoyant offshore facility that does not have...ship-shaped hull, The entire platform is subject to the Platform... (2) Your new floating platform is a buoyant offshore facility with a...

  2. 30 CFR 250.910 - Which of my facilities are subject to the Platform Verification Program?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... (1) Your new floating platform is a buoyant offshore facility that does not have...ship-shaped hull, The entire platform is subject to the Platform... (2) Your new floating platform is a buoyant offshore facility with a...

  3. 30 CFR 250.910 - Which of my facilities are subject to the Platform Verification Program?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... (1) Your new floating platform is a buoyant offshore facility that does not have...ship-shaped hull, The entire platform is subject to the Platform... (2) Your new floating platform is a buoyant offshore facility with a...

  4. CONSEQUENCES OF NON-LINEAR DENSITY EFFECTS ON BUOYANCY AND PLUME BEHAVIOR

    EPA Science Inventory

    Aquatic plumes, as turbulent streams, grow by entraining ambient water. Buoyant plumes rise and dense ones sink, but, non-linear kinetic effects can reverse the buoyant force in mid-phenomenon. The class of nascent-density plumes begin as buoyant, upwardly accelerating plumes tha...

  5. 46 CFR 160.060-6 - Construction-nonstandard vests.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant...and Child § 160.060-6 Construction—nonstandard vests....

  6. 46 CFR 160.049-4 - Construction and workmanship.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant...Plastic Foam § 160.049-4 Construction and workmanship. (a)...

  7. 46 CFR 160.060-6 - Construction-nonstandard vests.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant...and Child § 160.060-6 Construction—nonstandard vests....

  8. 46 CFR 160.052-6 - Construction-nonstandard vests.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant...and Child § 160.052-6 Construction—nonstandard vests....

  9. 46 CFR 160.052-6 - Construction-nonstandard vests.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant...and Child § 160.052-6 Construction—nonstandard vests....

  10. Familial hypobetalipoproteinemia caused by a mutation in the apolipoprotein B gene that results in a truncated species of apolipoprotein B (B-31). A unique mutation that helps to define the portion of the apolipoprotein B molecule required for the formation of buoyant, triglyceride-rich lipoproteins.

    PubMed Central

    Young, S G; Hubl, S T; Smith, R S; Snyder, S M; Terdiman, J F

    1990-01-01

    Apolipoprotein B-100 has a crucial structural role in the formation of VLDL and LDL. Familial hypobetalipoproteinemia, a syndrome in which the concentration of LDL cholesterol in plasma is abnormally low, can be caused by mutations in the apo B gene that prevent the translation of a full-length apo B-100 molecule. Prior studies have revealed that truncated species of apo B [e.g., apo B-37 (1728 amino acids), apo B-46 (2057 amino acids)] can occasionally be identified in the plasma of subjects with familial hypobetalipoproteinemia; in each of these cases, the truncated apo B species has been a prominent protein component of VLDL. In this report, we describe a kindred with hypobetalipoproteinemia in which the plasma of four affected heterozygotes contained a unique truncated apo B species, apo B-31. Apolipoprotein B-31 is caused by the deletion of a single nucleotide in the apo B gene, and it is predicted to contain 1425 amino acids. Apolipoprotein B-31 is the shortest of the mutant apo B species to be identified in the plasma of a subject with hypobetalipoproteinemia. In contrast to longer truncated apo B species, apo B-31 was undetectable in the VLDL and the LDL; however, it was present in the HDL fraction and the lipoprotein-deficient fraction of plasma. The density distribution of apo B-31 in the plasma suggests the possibility that the amino-terminal 1425 amino acids of apo B-100 are sufficient to permit the formation and secretion of small, dense lipoproteins but are inadequate to support the formation of the more lipid-rich VLDL and LDL particles. Images PMID:2312735

  11. Buoyancy of Convective Vertical Motions in the Inner Core of Intense Hurricanes. Part II: Case Studies

    Microsoft Academic Search

    Matthew D. Eastin; William M. Gray; Peter G. Black

    2005-01-01

    This is the second of two papers on the buoyancy of convective vertical motions in the inner core of intense hurricanes. This paper uses extensive airborne radar, dropwindsonde, and flight-level observations in Hurricanes Guillermo (1997) and Georges (1998) to illustrate typical azimuthal distribution of buoyant convection and demonstrate that the low-level eye can be an important source region for buoyant

  12. Water-supported wind actuated power generating assembly

    Microsoft Academic Search

    Hoar

    1982-01-01

    A counterweighted elongate buoyant body that floats on the surface of the sea or a lake has at least one sail supporting mast extending upwardly therefrom as well as vanes that tend to maintain the sails substantially normal to the direction of movement of the wind. The buoyant body is by frame means maintained within the confines of a circular

  13. Slow chemical reactions in power plant plumes: application to sulfates

    SciTech Connect

    Forney, L.J.; Giz, Z.G.

    1980-01-01

    Slow chemical reactions in which plume travel time is short compared with characteristic chemical reaction times are incorporated into the MIT buoyant plume theory. Conservation equations are written for a buoyant plume in a crosswind. Approximate solutions to the conservation equations are derived and compared with numerical results. Approximate solutions compared favorably with representative field data. (1 diagram, 4 graphs, 29 references, 1 table)

  14. 46 CFR 160.052-2 - Size and model.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...160.052-2 Size and model. (a) A standard buoyant vest is manufactured...b) and is a: (1) Model AP, adult (for persons...in performance to the standard buoyant vest; and (3) Assigned a model designation by the...

  15. 46 CFR 160.052-2 - Size and model.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...160.052-2 Size and model. (a) A standard buoyant vest is manufactured...b) and is a: (1) Model AP, adult (for persons...in performance to the standard buoyant vest; and (3) Assigned a model designation by the...

  16. 46 CFR 160.052-2 - Size and model.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...160.052-2 Size and model. (a) A standard buoyant vest is manufactured...b) and is a: (1) Model AP, adult (for persons...in performance to the standard buoyant vest; and (3) Assigned a model designation by the...

  17. 46 CFR 160.052-2 - Size and model.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...160.052-2 Size and model. (a) A standard buoyant vest is manufactured...b) and is a: (1) Model AP, adult (for persons...in performance to the standard buoyant vest; and (3) Assigned a model designation by the...

  18. 46 CFR 160.052-2 - Size and model.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...160.052-2 Size and model. (a) A standard buoyant vest is manufactured...b) and is a: (1) Model AP, adult (for persons...in performance to the standard buoyant vest; and (3) Assigned a model designation by the...

  19. Measurements of single spherical particle trajectories with lateral migration in a slit with one porous wall under laminar flow conditions

    Microsoft Academic Search

    J. R. Otis; F. W. Altena; J. T. Mahar; G. Belfort

    1986-01-01

    Lateral migration of spherical, neutrally buoyant particles moving in Poiseuille flow was measured in a slit with a porous membrane at one wall. Neutrally buoyant particles with diameters of 226 µm were injected into 22% glycerol-water solution flowing vertically in a slit channel (1.6 × 50 × 152 mm). The particles were illuminated with a strobe at 25 flashes\\/sec and

  20. 46 CFR 160.052-7 - Inspections and tests-standard and nonstandard vests. 1

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...The buoyant inserts from adult size buoyant vests shall provide not...the inserts from child medium size vests shall provide not less...the inserts from child small size vests shall provide not less than 7 pounds buoyancy. (f) Body strap test. The...

  1. 46 CFR 160.052-7 - Inspections and tests-standard and nonstandard vests. 1

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...The buoyant inserts from adult size buoyant vests shall provide not...the inserts from child medium size vests shall provide not less...the inserts from child small size vests shall provide not less than 7 pounds buoyancy. (f) Body strap test. The...

  2. 46 CFR 160.048-1 - Incorporation by reference.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...for a Buoyant Cushion, Fibrous Glass § 160.048-1 Incorporation...MIL-B-2766—Batt, Fibrous Glass, Lifesaving Equipment. ...Drill. L-P-375C—Plastic Film, Flexible, Vinyl Chloride...on the date kapok or fibrous glass buoyant cushions are...

  3. Chemical dieferentiation of a convecting planetary interior: Consequences for a one plate planet such as Venus

    Microsoft Academic Search

    E. M. Parmerltier; P. C. Hess

    1992-01-01

    Partial melting to generate the crust of a planet creates compostionally buoyant residual mantle. In the absence of mantle flow associated with plate tectonics, this buoyant, refractory layer may collect at the top of the mantle with important implications for the evolution of the interior and surface. In this study models of the thermal and chemical evolution of a planetary

  4. Entropy bounds and black hole remnants

    Microsoft Academic Search

    Jacob D. Bekenstein

    1994-01-01

    We rederive the universal bound on entropy with the help of black holes while allowing for Unruh-Wald buoyancy. We consider a box full of entropy lowered toward and then dropped into a Reissner-Nordström black hole in equilibrium with thermal radiation. We avoid the approximation that the buoyant pressure varies slowly across the box, and compute the buoyant force exactly. We

  5. The gas content and buoyancy of strombolian ash plumes

    Microsoft Academic Search

    Matthew Patrick

    2007-01-01

    Plinian plumes erupt with a bulk density greater than that of air, and depend upon air entrainment during their gas-thrust phase to become buoyant; if entrainment is insufficient, the column collapses into a potentially deadly pyroclastic flow. This study shows that strombolian ash plumes can be erupted in an initially buoyant state due to their extremely high initial gas content,

  6. 46 CFR 160.048-1 - Incorporation by reference.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...Specification for a Buoyant Cushion, Fibrous Glass § 160.048-1 Incorporation by reference...specification: MIL-B-2766—Batt, Fibrous Glass, Lifesaving Equipment. (2) Federal...issue in effect on the date kapok or fibrous glass buoyant cushions are manufactured,...

  7. Underwater Unmanned Vehicle Boeing gave us the opportunity to compete against the Electrical Engineering Dept. The competition was

    E-print Network

    Demirel, Melik C.

    . Controlled wirelessly in the X direction, forward/backward motion Must use LiPo batteries and an Arduino for the arduino to achieve the wireless goal. For propulsion we used a water pump. We also put a servo on the back buoyant and as it takes on water it will become negatively buoyant. Outcomes Overall the project

  8. Parametric study of modern airship productivity

    NASA Technical Reports Server (NTRS)

    Ardema, M. D.; Flaig, K.

    1980-01-01

    A method for estimating the specific productivity of both hybrid and fully buoyant airships is developed. Various methods of estimating structural weight of deltoid hybrids are discussed and a derived weight estimating relationship is presented. Specific productivity is used as a figure of merit in a parametric study of fully buoyant ellipsoidal and deltoid hybrid semi-buoyant vehicles. The sensitivity of results as a function of assumptions is also determined. No airship configurations were found to have superior specific productivity to transport airplanes.

  9. Experimental study of gravitation effects in the flow of a particle-laden thin film on an inclined plane

    E-print Network

    Ward, Thomas

    The flow of viscous, particle-laden wetting thin films on an inclined plane is studied experimentally as the particle concentration is increased to the maximum packing limit. The slurry is a non-neutrally buoyant mixture ...

  10. 46 CFR 160.060-8 - Marking.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...No.). (b) Waterproof marking. Marking of buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water it will withstand vigorous rubbing by hand while wet without printed matter becoming illegible. [CGD...

  11. 46 CFR 160.060-8 - Marking.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...No.). (b) Waterproof marking. Marking of buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water it will withstand vigorous rubbing by hand while wet without printed matter becoming illegible. [CGD...

  12. 46 CFR 160.052-8 - Marking.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...Lot No.) (b) Waterproof marking. Marking for buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water it will withstand vigorous rubbing by hand while wet without the printed matter becoming illegible. [CGD...

  13. 46 CFR 160.047-6 - Marking.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... (b) Waterproof marking tags. Marking for buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water, it will withstand vigorous rubbing by hand while wet without the printed matter becoming illegible....

  14. 46 CFR 160.047-6 - Marking.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... (b) Waterproof marking tags. Marking for buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water, it will withstand vigorous rubbing by hand while wet without the printed matter becoming illegible....

  15. 46 CFR 160.052-8 - Marking.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...Lot No.) (b) Waterproof marking. Marking for buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water it will withstand vigorous rubbing by hand while wet without the printed matter becoming illegible. [CGD...

  16. 46 CFR 160.052-8 - Marking.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...Lot No.) (b) Waterproof marking. Marking for buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water it will withstand vigorous rubbing by hand while wet without the printed matter becoming illegible. [CGD...

  17. 46 CFR 160.047-6 - Marking.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... (b) Waterproof marking tags. Marking for buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water, it will withstand vigorous rubbing by hand while wet without the printed matter becoming illegible....

  18. 46 CFR 160.060-8 - Marking.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...No.). (b) Waterproof marking. Marking of buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water it will withstand vigorous rubbing by hand while wet without printed matter becoming illegible. [CGD...

  19. 46 CFR 160.060-8 - Marking.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...No.). (b) Waterproof marking. Marking of buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water it will withstand vigorous rubbing by hand while wet without printed matter becoming illegible. [CGD...

  20. 46 CFR 160.052-8 - Marking.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...Lot No.) (b) Waterproof marking. Marking for buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water it will withstand vigorous rubbing by hand while wet without the printed matter becoming illegible. [CGD...

  1. 46 CFR 160.052-8 - Marking.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...Lot No.) (b) Waterproof marking. Marking for buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water it will withstand vigorous rubbing by hand while wet without the printed matter becoming illegible. [CGD...

  2. 46 CFR 160.047-6 - Marking.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... (b) Waterproof marking tags. Marking for buoyant vests shall be sufficiently waterproof so that after 72 hours submergence in water, it will withstand vigorous rubbing by hand while wet without the printed matter becoming illegible....

  3. MECH 222 Syllabus Page 1 Department of Mechanical Engineering

    E-print Network

    on a submerged surface. Describe buoyant force and apply it for submerged and floating bodies. Explain why curve and pump performance data to predict performance and select an appropriate pump. #12;MECH 222

  4. 46 CFR 164.015-3 - Material and workmanship.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...workmanship. (a) The unicellular plastic foam shall be all new material complying...015-4(a). (b) The unicellular plastic foam shall be produced in sheet stock...

  5. 46 CFR 164.015-3 - Material and workmanship.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...workmanship. (a) The unicellular plastic foam shall be all new material complying...015-4(a). (b) The unicellular plastic foam shall be produced in sheet stock...

  6. 46 CFR 160.049-3 - Materials.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...EQUIPMENT Specification for a Buoyant Cushion Plastic Foam § 160.049-3 Materials. (a) General...requirements of subpart 164.019. (b) Unicellular plastic foam. The unicellular plastic foam shall be all new material complying...

  7. 46 CFR 164.015-5 - Procedure for acceptance.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...Procedure for acceptance. (a) Unicellular plastic foam is not subject to formal approval...manufacturer. (c) Acceptance of unicellular plastic foam prior to being incorporated...

  8. 46 CFR 164.015-5 - Procedure for acceptance.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...Procedure for acceptance. (a) Unicellular plastic foam is not subject to formal approval...manufacturer. (c) Acceptance of unicellular plastic foam prior to being incorporated...

  9. 46 CFR 164.015-5 - Procedure for acceptance.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...Procedure for acceptance. (a) Unicellular plastic foam is not subject to formal approval...manufacturer. (c) Acceptance of unicellular plastic foam prior to being incorporated...

  10. 33 CFR 146.20 - Work vests.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...Each buoyant work vest carried under the permissive...077 as a commercial hybrid PFD. (b) Use...safety apparel and may be carried aboard OCS facilities...operation as each other hybrid PFD carried on board. [CGD...

  11. 33 CFR 146.20 - Work vests.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...Each buoyant work vest carried under the permissive...077 as a commercial hybrid PFD. (b) Use...safety apparel and may be carried aboard OCS facilities...operation as each other hybrid PFD carried on board. [CGD...

  12. 33 CFR 146.20 - Work vests.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...Each buoyant work vest carried under the permissive...077 as a commercial hybrid PFD. (b) Use...safety apparel and may be carried aboard OCS facilities...operation as each other hybrid PFD carried on board. [CGD...

  13. 33 CFR 146.20 - Work vests.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...Each buoyant work vest carried under the permissive...077 as a commercial hybrid PFD. (b) Use...safety apparel and may be carried aboard OCS facilities...operation as each other hybrid PFD carried on board. [CGD...

  14. 33 CFR 146.20 - Work vests.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...Each buoyant work vest carried under the permissive...077 as a commercial hybrid PFD. (b) Use...safety apparel and may be carried aboard OCS facilities...operation as each other hybrid PFD carried on board. [CGD...

  15. Carbon dioxide hydrate particles for ocean carbon sequestration

    E-print Network

    Chow, A.C.

    This paper presents strategies for producing negatively buoyant CO[subscript 2] hydrate composite particles for ocean carbon sequestration. Our study is based on recent field observations showing that a continuous-jet ...

  16. 46 CFR 25.30-20 - Fire extinguishing equipment required.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...30-20( a 1) Fire extinguishers are...a1)): 1. Closed compartment under thwarts and seats... 4. Closed stowage compartments in which combustible...themselves, require that fire extinguishers be carried...wells. 2. Glove compartments. 3. Buoyant...

  17. 46 CFR 25.30-20 - Fire extinguishing equipment required.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...30-20( a 1) Fire extinguishers are...a1)): 1. Closed compartment under thwarts and seats... 4. Closed stowage compartments in which combustible...themselves, require that fire extinguishers be carried...wells. 2. Glove compartments. 3. Buoyant...

  18. 46 CFR 25.30-20 - Fire extinguishing equipment required.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...30-20( a 1) Fire extinguishers are...a1)): 1. Closed compartment under thwarts and seats... 4. Closed stowage compartments in which combustible...themselves, require that fire extinguishers be carried...wells. 2. Glove compartments. 3. Buoyant...

  19. Design and Field-test of Solar-passive Thermal Refugia for Overwintering Mozambique Tilapia (Oreochromis mossambicus) in Central Texas 

    E-print Network

    Putegnat, John William

    2013-12-05

    . An experimental, solar-passive thermal refuge was designed, produced, and tested in triplicate trials for each of two insulation treatments. The refuge design envisaged a floorless, floating greenhouse with translucent roof and walls. Each unit was made buoyant...

  20. 33 CFR 181.4 - Incorporation by reference.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...in this part, and the sections affected are: Underwriters Laboratories, Inc. (UL) 12 Laboratory Drive, Research Triangle Park, NC 27709-3995 UL 1123, Marine Buoyant Devices, 181.703. February 17, 1995. [CGD 81-023, 55 FR...

  1. 33 CFR 181.4 - Incorporation by reference.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...in this part, and the sections affected are: Underwriters Laboratories, Inc. (UL) 12 Laboratory Drive, Research Triangle Park, NC 27709-3995 UL 1123, Marine Buoyant Devices, 181.703. February 17, 1995. [CGD 81-023, 55 FR...

  2. EXPERIMENTAL SIMULATION OF SINGLE AND MULTIPLE CELL COOLING TOWER PLUMES

    EPA Science Inventory

    An experimental investigation was conducted to determine the dilution characteristics of single and multiple port buoyant discharges typical of modern natural and mechanical draft cooling towers. Simultaneous measurements of velocity and tracer concentration profiles were taken a...

  3. Interactions between Soot and CH* in a Laminar Boundary Layer Type Diffusion Flame in Microgravity 

    E-print Network

    Fuentes, Andres; Legros, Guillaume; Claverie, Alain; Joulain, Pierre; Vantelon, Jean-Pierre; Torero, Jose L

    A three-dimensional laminar non-buoyant diffusion flame was studied with the objective of improving the understanding of the soot production. The flame originated from a porous ethylene burner discharging into a laminar ...

  4. FLOCCULATION-FLOTATION AIDS FOR TREATMENT OF COMBINED SEWER OVERFLOWS

    EPA Science Inventory

    The objectives of this study were to investigate the flocculation/flotation characteristics of combined sewer overflow through laboratory and field testing. The concept involves the introduction of chemicals and buoyant flotation aids into the overflow and the subsequent cofloccu...

  5. Sedimentation Of Oil-MIneral Aggregates For Remediation Of Vegetable Oil Spills

    EPA Science Inventory

    A response alternative for floating vegetable oil spills based on sedimentation of negatively buoyant oil-mineral aggregrates followed by anaerobic biodegradation in the sediments is under investigation. Sedimentation of floating canola oil by interaction with montmorillonite wa...

  6. Carbon flow and ecosystem dynamics in the Mississippi River plume described by inverse analysis 

    E-print Network

    Breed, Greg Allen

    2002-01-01

    Planktonic ecosystem dynamics in the buoyant Mississippi River plume were investigated using inverse analysis, a technique that incorporates data describing ecosystem processes and calculates rates of unknown trophic flows and sedimentation...

  7. Experimentally Determining the Molar Mass of Carbon Dioxide Using a Mylar Balloon.

    ERIC Educational Resources Information Center

    Jackson, Barbara Albers; Crouse, David J.

    1998-01-01

    Describes how to determine the mass of a gas in a flexible, lightweight container and argues that the buoyant force of air needs to be taken into account. Recommends the use of mylar and describes equipment preparation. (DDR)

  8. Numerical simulation of tropical cumulus congestus during TOGA COARE

    E-print Network

    Mechem, David B.

    2013-09-17

    suppressed to active phases, a number which corresponds well with previous estimates of the congestus contribution to precipitation. Domain-mean profiles and statistics from conditionally sampled buoyant cloud cores are compared with similar quantities from a...

  9. Geochemistry: Rise of the continents

    NASA Astrophysics Data System (ADS)

    Lee, Cin-Ty A.; McKenzie, N. Ryan

    2015-07-01

    The continents are archives of Earth's evolution. Analysis of the isotopic signature of continental crust globally suggests that buoyant, silicic continents began to form 3 billion years ago, possibly linked to the onset of plate tectonics.

  10. A Tale of Two Spills: Novel Science and Policy Implications of an Emerging New Oil Spill Model

    E-print Network

    Adams, E. Eric

    The 2010 Deepwater Horizon oil release posed the challenges of two types of spill: a familiar spill characterized by buoyant oil, fouling and killing organisms at the sea surface and eventually grounding on and damaging ...

  11. Intracellular Water Exchange for Measuring the Dry Mass, Water Mass and Changes in Chemical Composition of Living Cells

    E-print Network

    Cermak, Nathan

    We present a method for direct non-optical quantification of dry mass, dry density and water mass of single living cells in suspension. Dry mass and dry density are obtained simultaneously by measuring a cell’s buoyant ...

  12. Sooting Behaviour Dynamics of a Non-Bouyant Laminar Diffusion Flame 

    E-print Network

    Fuentes, Andres; Legros, Guillaume; Rouvreau, Sebastien; Joulain, Pierre; Vantelon, Jean-Pierre; Torero, Jose L; Fernandez-Pello, Carlos

    2007-01-01

    Local soot concentrations in non-buoyant laminar diffusion flames have been demonstrated to be the outcome of two competitive processes, soot formation and soot oxidation. It was first believed that soot formation was the ...

  13. Predicting flow reversals in chaotic natural convection using data assimilation

    E-print Network

    Danforth, Chris

    ) and other industrial applications. In these heat pumps, buoyant forces move fluid through a closed loop. The thermosyphon, a type of natural convection loop or non-mechanical heat pump, can be likened to a toy model

  14. Finite element analysis of floatation of rectangular tunnels following earthquake induced liquefaction

    E-print Network

    Madabhushi, S. S. C.; Madabhushi, S. P. G.

    2014-10-29

    Underground structures such as tunnels, pipelines, car parks etc. can suffer severe damage during strong earthquake events. As many of these structures are buoyant, soil liquefaction due to earthquake loading can result in their floatation...

  15. 46 CFR 160.048-3 - Materials.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...for a Buoyant Cushion, Fibrous Glass § 160.048-3 Materials...properly processed. (c) Fibrous glass. The fibrous glass shall comply with the requirements...inserts shall be flexible vinyl film not less than 0.008 inch...

  16. 46 CFR 160.050-3 - Materials.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...this subchapter for Type C material. The buoy's body shall...suitable buoyant type synthetic material having a minimum breaking...or other suitable synthetic material having a minimum breaking...oxidation, and ultraviolet light degradation. (e) Thread....

  17. 46 CFR 160.050-3 - Materials.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...this subchapter for Type C material. The buoy's body shall...suitable buoyant type synthetic material having a minimum breaking...or other suitable synthetic material having a minimum breaking...oxidation, and ultraviolet light degradation. (e) Thread....

  18. 46 CFR 160.050-3 - Materials.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...this subchapter for Type C material. The buoy's body shall...suitable buoyant type synthetic material having a minimum breaking...or other suitable synthetic material having a minimum breaking...oxidation, and ultraviolet light degradation. (e) Thread....

  19. 46 CFR 160.050-3 - Materials.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...this subchapter for Type C material. The buoy's body shall...suitable buoyant type synthetic material having a minimum breaking...or other suitable synthetic material having a minimum breaking...oxidation, and ultraviolet light degradation. (e) Thread....

  20. 46 CFR 160.050-3 - Materials.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...this subchapter for Type C material. The buoy's body shall...suitable buoyant type synthetic material having a minimum breaking...or other suitable synthetic material having a minimum breaking...oxidation, and ultraviolet light degradation. (e) Thread....

  1. NOAA Technical Memorandum GLERL-151 Dynamics and Numerical Modeling of River Plumes in Lakes

    E-print Network

    NOAA Technical Memorandum GLERL-151 Dynamics and Numerical Modeling of River Plumes in Lakes Navid OCEANIC AND ATMOSPHERIC ADMINISTRATION Jane Lubchenco Under Secretary for Oceans & Atmosphere NOAA ...........................................................................................................12 2.2 Surface Buoyant Plumes

  2. 46 CFR 160.062-2 - Types.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING...062-1(a)(1) are of the diaphram-spring plunger type, which releases a buoyant...be designed and tested to operate with spring-tensioned gripes. Such gripes...

  3. 46 CFR 160.062-2 - Types.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING...062-1(a)(1) are of the diaphram-spring plunger type, which releases a buoyant...be designed and tested to operate with spring-tensioned gripes. Such gripes...

  4. 46 CFR 160.062-2 - Types.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING...062-1(a)(1) are of the diaphram-spring plunger type, which releases a buoyant...be designed and tested to operate with spring-tensioned gripes. Such gripes...

  5. 46 CFR 160.062-2 - Types.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING...062-1(a)(1) are of the diaphram-spring plunger type, which releases a buoyant...be designed and tested to operate with spring-tensioned gripes. Such gripes...

  6. 46 CFR 131.710 - Approved work vests.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Approved work vests. 131.710 Section 131...COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Work Vests § 131.710 Approved work vests. Each buoyant work...

  7. 46 CFR 164.015-5 - Procedure for acceptance.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...Procedure for acceptance. (a) Unicellular plastic foam is not subject to formal approval...manufacturer. (c) Acceptance of unicellular plastic foam prior to being incorporated...

  8. 46 CFR 164.015-3 - Material and workmanship.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...workmanship. (a) The unicellular plastic foam shall be all new material complying...015-4(a). (b) The unicellular plastic foam shall be produced in sheet stock...

  9. 46 CFR 160.049-3 - Materials.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...EQUIPMENT Specification for a Buoyant Cushion Plastic Foam § 160.049-3 Materials. (a) General...requirements of subpart 164.019. (b) Unicellular plastic foam. The unicellular plastic foam shall be all new material complying...

  10. 46 CFR 160.048-5 - Inspections and tests. 1

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant Cushion, Fibrous Glass § 160.048-5 Inspections and tests. 1 1 The manufacturer of a personal flotation device must meet 33 CFR...

  11. 46 CFR 160.048-3 - Materials.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...EQUIPMENT Specification for a Buoyant Cushion, Fibrous Glass § 160.048-3 Materials. (a) General...subchapter and shall be properly processed. (c) Fibrous glass. The fibrous glass shall comply with the requirements of...

  12. 46 CFR 160.048-3 - Materials.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...EQUIPMENT Specification for a Buoyant Cushion, Fibrous Glass § 160.048-3 Materials. (a) General...subchapter and shall be properly processed. (c) Fibrous glass. The fibrous glass shall comply with the requirements of...

  13. 46 CFR 160.047-7 - Recognized laboratory.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant Vest, Kapok or Fibrous Glass, Adult and Child § 160.047-7 Recognized laboratory. (a) A manufacturer seeking Coast Guard approval of...

  14. 46 CFR 160.047-7 - Recognized laboratory.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant Vest, Kapok or Fibrous Glass, Adult and Child § 160.047-7 Recognized laboratory. (a) A manufacturer seeking Coast Guard approval of...

  15. Capillary Pinning of Immiscible Gravity Currents in Porous Media

    NASA Astrophysics Data System (ADS)

    Zhao, B.; MacMinn, C. W.; Szulczewski, M.; Huppert, H. E.; Juanes, R.

    2012-12-01

    Gravity currents in porous media have attracted much interest recently in the context of geological carbon dioxide (CO2) storage, where supercritical CO2 is injected underground into deep saline aquifers. Capillary effects can be very important in the spreading and migration of the buoyant CO2 after injection because the typical pore size is very small (~10-100 um), but the impact of capillarity on these flows is not well understood. Here, we study the impact of capillarity on a finite-release gravity current of a buoyant non-wetting fluid. Via simple, table-top experiments, we show that capillary pressure hysteresis causes pinning of a portion of the initial interface, which ultimately stops the spreading of the buoyant current at a finite distance. In addition, capillarity causes blunting at the leading edge of the draining buoyant current. We demonstrate through micromodel experiments that the height of the nose of the current is controlled by the pore geometry as well as the balance between capillarity and gravity. Our analysis suggests that capillary pinning and capillary blunting exert a fundamental control on the interface evolution of immiscible finite-release gravity currents in the context of CO2 sequestration in deep saline aquifers.apillary pressure hysteresis leads to pinning of a portion of the initial interface as the buoyant fluid (air; left) spreads over the denser fluid (glycerol-water; right), here in a flow cell packed with glass beads (1.25 mm diameter). Capillary entry pressure causes blunting at the leading edge of the draining buoyant current. Capillary pinning is responsible for ultimately arresting the migration of the buoyant current, while the combined effects of pinning and blunting creates a rectangular shaped buoyant current in this experiment.

  16. Full CD3\\/TCR activation through cholesterol-depleted lipid rafts

    Microsoft Academic Search

    Alexandre K. Rouquette-Jazdanian; Claudette Pelassy; Jean-Philippe Breittmayer; Claude Aussel

    2007-01-01

    Exogenous bacterial sphingomyelinase (SMase) and C6-Ceramides (C6-Cer) considerably lower buoyant cholesterol on sucrose density-gradient (at least 55% less cholesterol). In opposition, short C2-Cer fails to displace buoyant cholesterol. Note that neither SMase nor C6-Cer delocalize raft markers (Lck, LAT, CD55, and GM1). They are still anchored in ceramides-rich\\/cholesterol-poor domains, demonstrating that cholesterol is not necessary for their buoyancy. SMase-treated cells,

  17. Simulation environment and guidance system for AUV tracing chemical plume in 3-dimensions

    Microsoft Academic Search

    Yu Tian; Aiqun Zhang

    2010-01-01

    Due to its significant potential applications, underwater chemical plume exploration and source localization via an autonomous underwater vehicle (AUV) is currently a hot subject both in AUV and oceanic engineering research communities. Chemical plume including buoyant stem and non-buoyant part such as deep-sea hydrothermal plume is a typical dynamic 3D feature in the ocean environment; therefore, finding and tracing chemical

  18. Manufacturing processes of composite materials for a human-powered submarine

    Microsoft Academic Search

    A. J. Maisano

    2003-01-01

    Human-powered submarines are controllable underwater vehicles, which are designed and built to achieve maximum speed over a 100-meter course. Manufacturing the submarine as close to neutrally buoyant as possible has become a priority for competing teams. As human-powered submarines have decreased in volume to minimize mass, the insertion of buoyant materials during the manufacturing process has taken on a new

  19. Operational considerations for the airship in short-haul transportation

    NASA Technical Reports Server (NTRS)

    Walker, C. D.

    1975-01-01

    The airship's problems and the possibilities for their solution in a short-haul transportation environment are surveyed. The problems are derived from both past experience and envisioned operation. Problems relative to both fully buoyant and semi-buoyant configurations are considered and their origins in principle discussed. Also addressed in this paper are the state-of-the-art technologies with the potential of providing answers to the airship's operational difficulties.

  20. Investigation of the free flow electrophoretic process. Volume 1: Executive summary

    NASA Technical Reports Server (NTRS)

    Weiss, R. A.; Lanham, J. W.; Richman, D. W.; Walker, C. D.

    1979-01-01

    The effect of gravity on the free flow electrophoretic process was investigated. The demonstrated effects were then compared with predictions made by mathematical models. Results show that the carrier buffer flow was affected by gravity induced thermal convection and that the movement of the separating particle streams was affected by gravity induced buoyant forces. It was determined that if gravity induced buoyant forces were included in the mathematical models, then effective predictions of electrophoresis chamber separation performance were possible.

  1. The stability of buoyancy-driven coastal currents

    Microsoft Academic Search

    R. W. GRIFFITHS; P. F. LINDEN

    1981-01-01

    Griffiths, R.W. and Linden, P.F., 1981. The stability of buoyancy-driven coastal currents. Dyn. Atmos. Oceans, 5: 281--306. Buoyancy-driven boundary currents were generated in the laboratory by releasing buoyant fluid from a source adjacent to a vertical boundary in a rotating container. The boundary removed the Coriolis force parallel to it, allowing the buoyant fluid to spread in a current along

  2. Water-supported wind actuated power generating assembly

    SciTech Connect

    Hoar, R.A.

    1982-02-23

    A counterweighted elongate buoyant body that floats on the surface of the sea or a lake has at least one sail supporting mast extending upwardly therefrom as well as vanes that tend to maintain the sails substantially normal to the direction of movement of the wind. The buoyant body is by frame means maintained within the confines of a circular series of piles. The counterweight and means for pivoting each sail from a position normal to the direction of the wind to substantially parallel thereto cooperate to impart a transverse rocking motion to the buoyant body that has an eccentric transverse arcuate member depending therefrom that is engaged by a pair of rollers, as the transverse member moves relative to the pair of rollers a bellows is receprocated upwardly and downwardly to draw water into and discharge it from a check valve controlled confined space to a reservoir situated at a substantial distance above the surface of the body of water. Water discharges by gravity from the reservoir to a turbine or the like to power a generator to produce electricity for power purposes. Power means pivot the sails substantially parallel to the direction of the wind after the latter has rolled the buoyant body to a first position. The counterweight then rolls the buoyant body to a second position where upon the power means pivot the sails to positions substantially normal to the direction of the wind to start another power generating cycle.

  3. Feasibility study of modern airships. Phase 2: Executive summary

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A feasibility study of modern airships has been completed. Three promising modern airship systems' concepts and their associated missions were studied; (1) a heavy-lift airship, employing a non-rigid hull and a significant amount of rotor lift, used for short-range transport and positioning of heavy military and civil payloads, (2) a VTOL (vertical take-off and landing), metalclad, partially buoyant airship used as a short-haul commercial transport; and (3) a class of fully-buoyant airships used for long-endurance Navy missions. The heavy-lift airship concept offers a substantial increase in vertical lift capability over existing systems and is projected to have lower total operating costs per ton-mile. The VTOL airship transport concept appears to be economically competitive with other VTOL aircraft concepts but can attain significantly lower noise levels. The fully-buoyant airship concept can provide an airborne platform with long endurance that satisfies many Navy mission requirements.

  4. Feasibility of modern airships - Design definition and performance of selected concepts

    NASA Technical Reports Server (NTRS)

    Huston, R. R.; Ardema, M. D.

    1977-01-01

    Three promising modern airship system concepts and their associated missions were studied: (1) a heavy-lift airship, employing a nonrigid hull and a significant amount of rotor lift, used for short-range transporting and positioning of heavy military and civil payloads; (2) a VTOL (vertical take-off and landing), metal-clad, partially buoyant airship used as a short-haul commercial transport; (3) a fully-buoyant airship used for long-endurance Navy missions. The heavy-lift airship concept offers a dramatic increase in vertical lift capability over existing systems at significantly lower costs per ton-mile. The VTOL airship transport concept appears to be economically competititve with other VTOL aircraft concepts but can attain significantly lower noise levels. The fully-buoyant airship concept can provide an airborne platform with long endurance that satisfies many Navy mission requirements.

  5. Computer aided airship design

    NASA Technical Reports Server (NTRS)

    Davis, S. J.; Rosenstein, H.

    1975-01-01

    The Comprehensive Airship Sizing and Performance Computer Program (CASCOMP) is described which was developed and used in the design and evaluation of advanced lighter-than-air (LTA) craft. The program defines design details such as engine size and number, component weight buildups, required power, and the physical dimensions of airships which are designed to meet specified mission requirements. The program is used in a comparative parametric evaluation of six advanced lighter-than-air concepts. The results indicate that fully buoyant conventional airships have the lightest gross lift required when designed for speeds less than 100 knots and the partially buoyant concepts are superior above 100 knots. When compared on the basis of specific productivity, which is a measure of the direct operating cost, the partially buoyant lifting body/tilting prop-rotor concept is optimum.

  6. Deep recycling of oceanic asthenosphere material during subduction

    NASA Astrophysics Data System (ADS)

    Liu, Lijun; Zhou, Quan

    2015-04-01

    Uncertainties in the origin and composition of oceanic asthenosphere lead to different views on its temporal evolution upon subduction. We investigate the evolution of asthenosphere material during subduction using high-resolution geodynamic models. In contrast to some earlier models suggesting that limited amount of asthenosphere material can be entrained during subduction, we find that much of the subslab mantle (>100 km thick) could recycle into the deep mantle following the slab, even if this mantle layer remains buoyant and less viscous during entrainment. Our results support the hypothesis that observed trench-parallel subslab seismic anisotropy is a downward continuation of the anisotropic asthenosphere. The entrainment of sometimes buoyant asthenosphere material provides a new mechanism for reducing slab dip angle which is consistent the shallower Pacific slab underneath Japan than that farther south. Episodic release of entrained buoyant materials during subduction can also explain enigmatic intraplate volcanism, such as the Changbaishan volcano in Northeast China.

  7. Attraction of minute particles to invariant regions of volume preserving flows by transients.

    PubMed

    Shinbrot, T; Alvarez, M M; Zalc, J M; Muzzio, F J

    2001-02-12

    We find that tracer material can be concentrated into invariant regions of flows due exclusively to transient effects, as are produced when tracers temporarily become more buoyant than the surrounding fluid. This can occur either as a single event, e.g., if the tracer is initially weakly buoyant, or under periodic forcing, e.g., when external effects (such as solar heating) change the tracer density periodically. We study both cases in experiments, in a model, and in direct numerical simulations of laminar flow in a stirred tank. Focusing occurs for very small tracer size and inertia in flows that are instantaneously strictly volume conserving. PMID:11178045

  8. LTA structures and materials technology. [airships

    NASA Technical Reports Server (NTRS)

    Mayer, N. J.

    1975-01-01

    The state-of-the-art concerning structures and materials technology is reviewed. It is shown that many present materials developments resulting from balloon and aircraft research programs can be applied to new concepts in LTA vehicles. Both buoyant and semi-buoyant vehicles will utilize similar approaches to solving structural problems and could involve pressurized non-rigid and unpressurized rigid structures. System designs common to both and vital to structural integrity will include much of the past technology as well. Further research is needed in determination of structural loads, especially in future design concepts.

  9. Target-strength studies on Atlantic cod (Gadus morhua) in Newfoundland waters

    Microsoft Academic Search

    G. A. Rose; D. R. Porter

    1996-01-01

    (standardized to cod) was 1.5 dB higher at night when cod were up to 140 m oV bottom. Night-time TS did not diVer from theex situTS-daytime TS was significantly lower by 1.5 dB. Our findings are consistent with cod being neutrally buoyant oV bottom (night) and negatively buoyant nearer bottom in the day-time. Pooled neutrally buoyantin situandex situTS (38 kHz)

  10. Chemically Driven Hydrodynamic Instabilities

    NASA Astrophysics Data System (ADS)

    Almarcha, C.; Trevelyan, P. M. J.; Grosfils, P.; de Wit, A.

    2010-01-01

    In the gravity field, density changes triggered by a kinetic scheme as simple as A+B?C can induce or affect buoyancy-driven instabilities at a horizontal interface between two solutions containing initially the scalars A and B. On the basis of a general reaction-diffusion-convection model, we analyze to what extent the reaction can destabilize otherwise buoyantly stable density stratifications. We furthermore show that, even if the underlying nonreactive system is buoyantly unstable, the reaction breaks the symmetry of the developing patterns. This is demonstrated both numerically and experimentally on the specific example of a simple acid-base neutralization reaction.

  11. Capillary pinning of immiscible gravity currents in porous media

    NASA Astrophysics Data System (ADS)

    Zhao, Benzhong; MacMinn, Christopher; Huppert, Herbert; Juanes, Ruben

    2013-11-01

    Gravity currents in porous media have attracted interest recently in the context of geological carbon dioxide (CO2) storage. Capillarity can be important in the spreading and migration of the buoyant CO2 after injection because the typical pore size is very small, but the impact of capillarity on these flows is not well understood. Here, we study the impact of capillarity on the buoyant spreading of a finite gravity current of non-wetting fluid into a dense, wetting fluid in a vertically confined, horizontal aquifer. We show via simple, table-top experiments using glass bead packs that capillary pressure hysteresis pins a portion of the fluid-fluid interface. The horizontal extent of the pinned portion of the interface grows over time and this is responsible for ultimately stopping the spreading of the buoyant current after a finite distance. In addition, capillarity blunts the leading edge of the buoyant current. We demonstrate through micromodel experiments that the characteristic height of the nose of the current is controlled by the pore throat size distribution and the balance between capillarity and gravity. We develop a theoretical model that captures the evolution of immiscible gravity currents and predicts the maximum migration distance.

  12. Dynamics of convective dissolution from a migrating current of carbon dioxide

    NASA Astrophysics Data System (ADS)

    Hidalgo, Juan J.; MacMinn, Christopher W.; Juanes, Ruben

    2013-12-01

    During geologic storage of carbon dioxide (CO2), trapping of the buoyant CO2 after injection is essential in order to minimize the risk of leakage into shallower formations through a fracture or abandoned well. Models for the subsurface behavior of the CO2 are useful for the design, implementation, and long-term monitoring of injection sites, but traditional reservoir-simulation tools are currently unable to resolve the impact of small-scale trapping processes on fluid flow at the scale of a geologic basin. Here, we study the impact of solubility trapping from convective dissolution on the up-dip migration of a buoyant gravity current in a sloping aquifer. To do so, we conduct high-resolution numerical simulations of the gravity current that forms from a pair of miscible analogue fluids. Our simulations fully resolve the dense, sinking fingers that drive the convective dissolution process. We analyze the dynamics of the dissolution flux along the moving CO2-brine interface, including its decay as dissolved buoyant fluid accumulates beneath the buoyant current. We show that the dynamics of the dissolution flux and the macroscopic features of the migrating current can be captured with an upscaled sharp-interface model.

  13. (This is a sample cover image for this issue. The actual cover is not yet available at this time.) This article appeared in a journal published by Elsevier. The attached

    E-print Network

    Bush, John W.M.

    are released, and fertilization occurs in the fluid. Unlike animals that copulate ­ for whom the motility model Encounter rate Random walk External fertilization a b s t r a c t Many organisms reproduce or negatively buoyant, and, as a result, fertilization occurs on a two- dimensional surface rather than

  14. The fine art of surfacing: Its efficacy in broadcast spawning Jan Molacek a,1

    E-print Network

    Denny, Mark

    are released, and fertilization occurs in the fluid. Unlike animals that copulate ­ for whom the motility Mathematical model Encounter rate Random walk External fertilization a b s t r a c t Many organisms reproduce or negatively buoyant, and, as a result, fertilization occurs on a two- dimensional surface rather than

  15. Economic projections for Belgium – Spring 2007

    Microsoft Academic Search

    2007-01-01

    Since the projections published in December 2006, the international environment has remained buoyant. GDP growth in the euro area, which proved stronger than previously expected over the last months, should keep going at a solid pace in 2007. In Belgium, economic activity has been particularly strong in 2006. It should slow down slightly in 2007 and 2008, to return to

  16. 46 CFR 109.334 - Working over water.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Working over water. 109.334 Section 109.334...Equipment § 109.334 Working over water. The master or person in charge...that each person working over the water is wearing a life preserver or a buoyant work...

  17. Film flow of a suspension of liquid drops Department of Applied Mathematics, Illinois Institute of Technology, 10 West 32nd Street, Chicago,

    E-print Network

    Heller, Barbara

    buoyant liquid drops down an inclined plane wall is investigated by numerical simulation in the limit near the inclined plane but not near the free surface. © 2002 American Institute of Physics. #DOI: 10 of a suspension of liquid drops down an inclined plane, distin­ guishe

  18. Film flow of a suspension of liquid drops Department of Applied Mathematics, Illinois Institute of Technology, 10 West 32nd Street, Chicago,

    E-print Network

    Heller, Barbara

    buoyant liquid drops down an inclined plane wall is investigated by numerical simulation in the limit near the inclined plane but not near the free surface. © 2002 American Institute of Physics. DOI: 10 of a suspension of liquid drops down an inclined plane, distin- guished from the channel flow

  19. 49 CFR 214.107 - Working over or adjacent to water.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    (a) Bridge workers working over or adjacent to water with a depth of four feet or more, or where the danger of drowning exists, shall be provided and shall use life vests or buoyant work vests in compliance with U.S. Coast Guard requirements in 46 CFR 160.047, 160.052, and...

  20. 49 CFR 214.107 - Working over or adjacent to water.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    (a) Bridge workers working over or adjacent to water with a depth of four feet or more, or where the danger of drowning exists, shall be provided and shall use life vests or buoyant work vests in compliance with U.S. Coast Guard requirements in 46 CFR 160.047, 160.052, and...

  1. 46 CFR 26.30-1 - Approved unicellular plastic foam work vests.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 false Approved unicellular plastic foam work vests. 26.30-1 Section 26.30-1 Shipping...OPERATIONS Work Vest § 26.30-1 Approved unicellular plastic foam work vests. (a) Buoyant work vests carried under...

  2. 46 CFR 164.015-1 - Applicable specifications and standards.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...of the issue in effect on the date the plastic foam material is manufactured, form a...this section shall be kept on file by the plastic foam manufacturer with this...

  3. 46 CFR 26.30-1 - Approved unicellular plastic foam work vests.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Approved unicellular plastic foam work vests. 26.30-1 Section 26.30-1 Shipping...OPERATIONS Work Vest § 26.30-1 Approved unicellular plastic foam work vests. (a) Buoyant work vests carried under...

  4. 46 CFR 164.015-1 - Applicable specifications and standards.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...of the issue in effect on the date the plastic foam material is manufactured, form a...this section shall be kept on file by the plastic foam manufacturer with this...

  5. 46 CFR 26.30-1 - Approved unicellular plastic foam work vests.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Approved unicellular plastic foam work vests. 26.30-1 Section 26.30-1 Shipping...OPERATIONS Work Vest § 26.30-1 Approved unicellular plastic foam work vests. (a) Buoyant work vests carried under...

  6. 46 CFR 164.015-1 - Applicable specifications and standards.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...of the issue in effect on the date the plastic foam material is manufactured, form a...this section shall be kept on file by the plastic foam manufacturer with this...

  7. Lattice Boltzmann algorithm for surface tension with greatly reduced microcurrents

    Microsoft Academic Search

    S. V. Lishchuk; C. M. Care; I. Halliday

    2003-01-01

    We present an algorithm for inserting an interface between the immiscible phases of a multicomponent lattice Boltzmann fluid which is based solely upon the appropriate continuum physics: stress boundary conditions and continuity of velocity. Results are presented for the algorithm when applied to static, neutrally buoyant drops. It is shown that the present algorithm gives a significant reduction in the

  8. Autocrine\\/Paracrine Activation of the GABAA Receptor Inhibits the Proliferation of Neurogenic Polysialylated Neural Cell Adhesion Molecule-Positive (PSA-NCAM) Precursor Cells from Postnatal Striatum

    Microsoft Academic Search

    Laurent Nguyen; Brigitte Malgrange; Ingrid Breuskin; Lucien Bettendorff; Gustave Moonen; Shibeshih Belachew; Jean-Michel Rigo

    GABA and its type A receptor (GABAAR) are present in the immature CNS and may function as growth-regulatory signals during the development of embryonic neural precursor cells. In the present study, on the basis of their isopycnic properties in a buoyant density gradient, we developed an isolation procedure that allowed us to purify proliferative neural precursor cells from early postnatal

  9. Resolving the Confidence Crisis

    ERIC Educational Resources Information Center

    Apter, Terri

    2006-01-01

    As children approach adolescence, they often experience confusion and uncertainty as they attempt to appear more grown up than they really feel. Research on both girls and boys has documented that the buoyant self-confidence of younger children often gives way to self-consciousness as young adolescents become aware of the complexity and difficulty…

  10. Flicker noise of ion-selective membranes and turbulent convection in the depleted layer

    Microsoft Academic Search

    Shneior Lifson; Benjamin Gavish; Shimon Reich

    1978-01-01

    Flicker noise of electric currents through ion-selective membranes is explained. It is attributed to the depletion of salt on one side of the membrane, which creates a thin layer of high resistance. Joule heating in this depletion layer and the ensuing temperature gradient, as well as the concentration gradient, give rise to buoyant forces which may create a turbulent convection

  11. Particle laden flows through an inverted chimney with applications to ocean carbon sequestration

    E-print Network

    Chow, Aaron C.

    Plumes of negatively buoyant hydrate particles, formed by reacting liquid CO[subscript 2] with seawater at ocean depths of 1000–1500 m, have been suggested as a way to help sequester CO[subscript 2]. The vertical flux of ...

  12. Atmospheric Pollutants and Trace Gases Odor and Gas Release from Anaerobic Treatment Lagoons for Swine Manure

    Microsoft Academic Search

    Teng-Teeh Lim; Albert J. Heber; Ji-Qin Ni; Alan L. Sutton; Ping Shao

    releases are also needed to evaluate odor effects through science-based setback models (Lim et al., 2000). Odor Odor and gas release from anaerobic lagoons for treating swine is evaluated by determining odor concentration (OC), waste affect air quality in neighboring communities but rates of release are not well documented. A buoyant convective flux chamber (BCFC) intensity, and hedonic tone (HT)

  13. NEW DEVELOPMENT IN DISPERSION EXPERIMENTS AND MODELS FOR THE CONVECTIVE BOUNDARY LAYER

    EPA Science Inventory

    We present recent experiments and modeling studies of dispersion in the convective boundary layer (CBL) with focus on highly-buoyant plumes that "loft" near the CBL top and resist downward mixing. Such plumes have been a significant problem in earlier dispersion models; they a...

  14. RESEARCH ARTICLE Caldera resurgence during magma replenishment

    E-print Network

    /or erupted into each system; this magma is chemically distinct from rhyolite magma which was resident in each the system, it is able to heat, remobilize, and mingle with residual crystal-rich rhyolite remaining in the shallow mag- ma chamber. Dacite and remobilized rhyolite rise buoyantly to form laccoliths by lifting

  15. The Birth of TCJ: Father's Curiosity Launched Paul Boyer on His Journey into Indian Country

    ERIC Educational Resources Information Center

    Hernandez, Juan Avila

    2009-01-01

    From its inception in 1988, the "Tribal College Journal" (TCJ) has been a family affair. Paul Boyer, the buoyant founder of the TCJ who published, produced, and edited the magazine until 1995, says the magazine sprouted not from an idealistic plan but from a combination of his own youthful enthusiasm; the support and guidance of his late father,…

  16. Three-dimensional miscible, porous media displacements for the quarter five-spot configuration

    Microsoft Academic Search

    Amir Riaz

    2003-01-01

    Three-dimensional miscible displacements with gravity override are investigated in homogeneous and heterogeneous porous media using high accuracy numerical simulations. Special emphasis is placed on the interpretation of the dynamics in terms of the vorticity production related to viscosity, permeability and gravity. Comparison with experimental results show that three-dimensional neutrally buoyant displacements give a better estimate of the displacement efficiency than

  17. Capillary pinning of immiscible gravity currents in porous media

    NASA Astrophysics Data System (ADS)

    Zhao, Benzhong; MacMinn, Christopher; Szulczewski, Michael; Huppert, Herbert; Juanes, Ruben

    2012-11-01

    Gravity currents in porous media have attracted much interest recently in the context of geological carbon dioxide (CO2) storage, where supercritical CO2 is injected underground into deep saline aquifers. Capillary effects can be very important in the spreading and migration of the buoyant CO2 after injection because the typical pore size is very small (~10-100 ?m), but the impact of capillarity on these flows is not well understood. Here, we study the impact of capillarity on a finite-release gravity current of a buoyant non-wetting fluid. Via simple, table-top experiments, we show that capillary pressure hysteresis causes pinning of a portion of the initial interface, which ultimately stops the spreading of the buoyant current at a finite distance. In addition, capillarity causes blunting at the leading edge of the draining buoyant current. We demonstrate through micromodel experiments that the height of the nose of the current is controlled by the pore geometry as well as the balance between capillarity and gravity. Our analysis suggests that capillary pinning and capillary blunting exert a fundamental control on the interface evolution of immiscible finite-release gravity currents in the context of CO2 sequestration in deep saline aquifers.

  18. Formation of tabular plutons - results and implications of centrifuge modelling

    Microsoft Academic Search

    Carlo DIETL; Hemin KOYI

    2008-01-01

    * ?Correspondingauthor Geophysical investigations reveal that many granitoid plutons possess a tabular shape: either laccolithic, lopolithic or phacolithic. In this study, the results of a centrifuge experiment are used to understand the formation mechanisms of these features. The model was build of a sequence of 14 differently coloured plasticine layers. Two buoyant layers - with a volume of c. 40

  19. Volcanic plumes: What is the Realistic Neutral Buoyancy Height?

    Microsoft Academic Search

    M. Herzog; H. Graf

    2007-01-01

    Atmospheric residence time, interaction with radiation and chemical processes as well as the sedimentation of volcanic ash and sulphate particles depend on the injection height and it is important to calculate this parameter as exactly as possible. Explosive volcanic eruptions form buoyant plumes after sufficient entrainment has taken place. If explosive energy is high, overshooting may take place and the

  20. The neutral Buoyancy heights of Plinian and co-ignimbrite eruptions

    Microsoft Academic Search

    M. Herzog; H.-F. Graf

    2009-01-01

    Atmospheric residence time, interaction with radiation and chemical processes as well as the sedimentation of volcanic ash and sulphate particles depend on the injection height and it is important to calculate this parameter as exactly as possible. Explosive volcanic eruptions form buoyant plumes after sufficient entrainment has taken place. If explosive energy is high, overshooting may take place and the

  1. Transient plume influence in measurement of convective heat release rates of fast-growing fires using a large-scale fire products collector

    Microsoft Academic Search

    Hong-Zeng Yu; Hongzeng

    1990-01-01

    A theory for strongly buoyant transient plumes was used to determine whether the convective heat flow measured by a large-scale Fire Products Collector (FPC) could approximate the instantaneous convective heat release rate generated by fast-growing fires. The theory was confirmed by the plume data of rack storage fires. The theory provides a scheme for deriving the convective heat release rate

  2. J. Fluid Mech. (2007), vol. 578, pp. 3565. c 2007 Cambridge University Press doi:10.1017/S0022112007004739 Printed in the United Kingdom

    E-print Network

    Thomas, Peter J.

    2007-01-01

    are generated inside a rotating tank filled with salt water by the continuous release of buoyant fresh water of the earth. As a result the discharged fresh water is confined to the coastal zone, where it forms a current 2005 and in revised form 31 October 2006) Laboratory experiments simulating gravity-driven coastal

  3. THE DYNAMIC EVOLUTION OF TWISTED MAGNETIC FLUX TUBES IN A THREE-DIMENSIONAL CONVECTING FLOW. II. TURBULENT PUMPING AND THE COHESION OF -LOOPS

    E-print Network

    Abbett, Bill

    to originate via a dynamo mechanism at or near the base of the solar convection zone. If so, magnetic flux must and characteristics of active regions observed at the solar surface and described by such empirical relations as Hale to characterize the observations is to assume that magnetic flux rises buoyantly through the interior in the form

  4. A pseudo three-dimensional convection model 

    E-print Network

    Jenkins, Edwin Wayne

    1976-01-01

    equations in physics. J. Comout. ~Ph s. , 9, 440-465. Lilly, D. K. , 1962: On the numerical simulation of buoyant convection. Tellus, 14, 148-172. Lilly, D. K. , 1965: On the computational stability of numerical solutions of time dependent nonlinear...

  5. 40 CFR Appendix W to Part 51 - Guideline on Air Quality Models

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...S. Department of Energy, Washington, D...Characterize Diffusion from Point Sources—A Workshop...S. Department of Energy, Oak Ridge, TN...buoyant line and point sources. AMS/APCA...of the impingement point, or those associated...sufficient kinetic energy to pass over...

  6. 40 CFR Appendix W to Part 51 - Guideline on Air Quality Models

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...S. Department of Energy, Washington, D...Characterize Diffusion from Point Sources—A Workshop...S. Department of Energy, Oak Ridge, TN...buoyant line and point sources. AMS/APCA...of the impingement point, or those associated...sufficient kinetic energy to pass over...

  7. 40 CFR Appendix W to Part 51 - Guideline on Air Quality Models

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...S. Department of Energy, Washington, D...Characterize Diffusion from Point Sources—A Workshop...S. Department of Energy, Oak Ridge, TN...buoyant line and point sources. AMS/APCA...of the impingement point, or those associated...sufficient kinetic energy to pass over...

  8. 40 CFR Appendix W to Part 51 - Guideline on Air Quality Models

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...S. Department of Energy, Washington, D...Characterize Diffusion from Point Sources—A Workshop...S. Department of Energy, Oak Ridge, TN...buoyant line and point sources. AMS/APCA...of the impingement point, or those associated...sufficient kinetic energy to pass over...

  9. 40 CFR Appendix W to Part 51 - Guideline on Air Quality Models

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...S. Department of Energy, Washington, D...Characterize Diffusion from Point Sources—A Workshop...S. Department of Energy, Oak Ridge, TN...buoyant line and point sources. AMS/APCA...of the impingement point, or those associated...sufficient kinetic energy to pass over...

  10. Initial rise of bubbles in cohesive sediments by a process of viscoelastic fracture

    Microsoft Academic Search

    C. K. Algar; B. P. Boudreau; M. A. Barry

    2011-01-01

    An understanding of the mechanics of bubble rise in sediments is essential because of the role of bubbles in releasing methane to the atmosphere and the formation and melting of gas hydrates. Past models to describe and predict the rise of other buoyant geological bodies through a surrounding solid (e.g., magmas and hydrofractures) appear not to be applicable to bubbles

  11. Field observations and modeling of dispersion processes around ocean outfalls

    Microsoft Academic Search

    L. Washburn; Burton H. Jones

    1996-01-01

    Buoyant plumes discharged from ocean outfalls are important for dispersing municipal and industrial wastewater into the coastal marine environment. Ocean outfalls are designed to produce high levels of initial dilution to minimize environmental impacts. However, very few field studies of operating ocean outfalls have been reported in the literature. In recent years comprehensive field studies have been conducted around large

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

    EPA Science Inventory

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

  13. Application of microbead biological filters

    Microsoft Academic Search

    Michael B. Timmons; John L. Holder; James M. Ebeling

    2006-01-01

    The application of floating microbead filters to aquaculture is reviewed and discussed. The microbead filter is distinctly different from the more commonly used floating bead filters that are used today. Conventional bead filters work in pressured vessels and use a media that is only slightly buoyant. The required mass of beads for the volume required make the media a relatively

  14. 2008 Nature Publishing Group Coupled caldera subsidence and stirring

    E-print Network

    Jellinek, Mark

    © 2008 Nature Publishing Group LETTERS Coupled caldera subsidence and stirring inferred from ground subsidence related to catastrophic sinking of a magma chamber roof, accompanied by buoyant flow subsidence and eruption: eruption initiates subsidence of the chamber roof, which in turn drives the ongoing

  15. 14 CFR 91.509 - Survival equipment for overwater operations.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...RULES Large and Turbine-Powered Multiengine Airplanes and Fractional...an airplane for a flight over water more than 50 nautical miles...an airplane for flight over water more than 30 minutes flying... (4) One self-buoyant, water-resistant, portable...

  16. Bifurcation of volcanic plumes in a crosswind

    Microsoft Academic Search

    Gerald G. J. Ernstl; John P. Davis; R. Stephen J. Sparks

    1994-01-01

    Bent-over buoyant jets distorted by a crosscurrent develop a vortex pair structure and can bifurcate to produce two distinct lobes which diverge from one another downwind. The region downwind of the source between the lobes has relatively low proportions of discharged fluid. Factors invoked by previous workers to cause or enhance bifurcation include buoyancy, release of latent heat at the

  17. SCOOP--An Improved Submarine Cable Recovery System

    Microsoft Academic Search

    G. Rich; J. Ewald; C. Jeffcoat; R. Weller

    1984-01-01

    For more than twenty years, acoustically controlled, buoyant subsurface arrays have been utilized by research institutions and industry for mooring, location, and retrieval of oceanographic instruments. Submarine telecommunications cable laying and repair operations typically involve location and retrieval of free cable ends left on the seafloor. In deep water areas, conventional methods for cable-end location and recovery included the use

  18. Design Considerations for Tsunamis and Storm Surges

    E-print Network

    Petta, Jason

    , Bangladesh, India, Sri Lanka, Maldives and East Africa #12;Indian Ocean Tsunami Map #12;Banda Aceh, Indonesia Pass, MS · 1,836 people killed and estimated total economic impact in Louisiana and Mississippi may and storm surges · Forces considered in design: Buoyant Forces Surge Forces Drag Forces Impact Forces

  19. Apparatus for Teaching Physics.

    ERIC Educational Resources Information Center

    Gottlieb, Herbert H., Ed.

    1979-01-01

    Describes the following: a device which converts the displacement of a pendulum into an electric signal and is used as a voltage generator of low frequencies; a turn-by-turn transformer demonstration; how to remove the buoyant force on a piece of cork immersed in water; and how to demonstrate Coulomb's Law on the overhead projector. (GA)

  20. Pollutant dispersion in a large indoor space: Part 2 Computational Fluid Dynamics (CFD) predictions and comparison with ascale model experiment for isothermal flow

    Microsoft Academic Search

    Elizabeth U. Finlayson; Ashok J. Gadgil; Tracy L. Thatcher; Richard G. Sextro

    2002-01-01

    This paper reports on an investigation of the adequacy of Computational fluid dynamics (CFD), using a standard Reynolds Averaged Navier Stokes (RANS) model, for predicting dispersion of neutrally buoyant gas in a large indoor space. We used CFD to predict pollutant (dye) concentration profiles in a water filled scale model of an atrium with a continuous pollutant source. Predictions from

  1. Applicability of an integrated plume rise model for the dispersion from wild-land fires

    NASA Astrophysics Data System (ADS)

    Kukkonen, J.; Nikmo, J.; Sofiev, M.; Riikonen, K.; Petäjä, T.; Virkkula, A.; Levula, J.; Schobesberger, S.; Webber, D. M.

    2014-11-01

    We have presented an overview of a mathematical model, BUOYANT, that was originally designed for the evaluation of the dispersion of buoyant plumes originated from major warehouse fires. The model addresses the variations of the cross-plume integrated properties of a buoyant plume in the presence of a vertically varying atmosphere. The model also includes a treatment for a rising buoyant plume interacting with an inversion layer. We have compared the model predictions with the data of two prescribed wild-land fire experiments. For the SCAR-C experiment in Quinault (US) in 1994, the predicted vertical extents of the plume at maximum plume rise were between 500 and 800 m and between 200 and 700 m, using two alternative meteorological data sets. The corresponding observed injection heights of the aerosol particles measured using an airborne lidar (light detection and ranging) ranged from 250 to 600 m. For the prescribed burning experiment in Hyytiälä (Finland) in 2009, the model predictions were compared with plume elevations and diameters, determined based on particulate matter number concentration measurements onboard an aeroplane. However, the agreement between modelled and measured results substantially depends on how the properties of the source term are evaluated, especially regarding the convective heat fluxes from the fire. The results demonstrate that in field experiments on wild-land fires, there are substantial uncertainties in estimating both (i) the source terms for the atmospheric dispersion computations and (ii) the relevant vertical meteorological profiles.

  2. An analogue study for flame flickering

    Microsoft Academic Search

    T. Yuan; D. Durox; E. Villermaux

    1994-01-01

    An analogue experiment is proposed to simulate flame flickering comprising a free ascending column fed on its side with a light gas (helium) emerging from a vertical slot in ambient air. The convective motion of the helium jet is considered to represent the motion of burnt gases of buoyant jet flames. The helium jet is accelerated by buoyancy effects and

  3. Numerical Modeling of Magnetohydrodynamic Convection in a Rapidly Rotating Spherical Shell: Weak and Strong Field Dynamo Action

    Microsoft Academic Search

    Weijia Kuang; Jeremy Bloxham

    1999-01-01

    In this paper we describe a numerical model for investigating magnetohydrodynamic (MHD) convective flow of a Boussinesq fluid in a rapidly rotating spherical shell, driven by the buoyancy forces arising from incoming buoyant flux at the inner core boundary. The model is designed to investigate the generation of magnetic field in the Earth's fluid outer core. Our model differs from

  4. Migration pathways of corn earworm (Lepidoptera: Noctuidae) indicated by tetroon trajectories

    Microsoft Academic Search

    J. K. Westbrook; R. S. Eyster; W. W. Wolf; P. D. Lingren; J. R. Raulston

    1995-01-01

    The corn earworm moth, Helicoverpa zea (Lepidoptera: Noctuidae), is a nocturnal pest insect that is capable of long-distance flights. Buoyant superpressure balloons (tetroons) with attached transponders were tracked as surrogate markers of moths migrating from three corn-growing regions in Texas. Launches were synchronized with peak emergence of corn earworm moths in June and July 1992. The tetroons were launched at

  5. Non-Archimedean character of quantum buoyancy and the generalized second law of thermodynamics

    Microsoft Academic Search

    Jacob D. Bekenstein

    1999-01-01

    Quantum buoyancy has been proposed as the mechanism protecting the generalized second law when an entropy-bearing object is slowly lowered towards a black hole and then dropped in. We point out that the original derivation of the buoyant force from a fluid picture of the acceleration radiation is invalid unless the object is almost at the horizon, because otherwise typical

  6. Joint Discussion 3 Solar active regions and 3D magnetic structure

    Microsoft Academic Search

    Debi Prasad Choudhary; Michal Sobotka

    2007-01-01

    Keeping in view of the modern powerful observing tools, among others Hinode (formerly SOLAR-B), STEREO and Frequency-Agile Solar Radiotelescope, and sophisticated modelling techniques, Joint Discussion 3 during the IAU General Assembly 2006 focused on the properties of magnetic field of solar active regions starting in deep interior of the Sun, from where they buoyantly rise to the coronal heights where

  7. Photoinhibition and the availability of inorganic carbon restrict photosynthesis by surface blooms of cyanobacteria

    Microsoft Academic Search

    Bas W. Ibelings; Stephen C. Maberly

    1998-01-01

    When buoyant cyanobacteria form a surface bloom, they may obtain inorganic carbon from the water and the atmosphere. In this study, artificial blooms of cyanobacteria were exposed to different concentrations of CO? in the atmosphere and HCO, in the water. The conditions and photosynthetic activity within the bloom were measured with microelectrodes sensing O?, pH, and light. Net rates of

  8. PHYSICAL, CHEMICAL, AND CHRONOLOGICAL CHARACTERISTICS OF CONTINENTAL MANTLE

    E-print Network

    Jellinek, Mark

    PHYSICAL, CHEMICAL, AND CHRONOLOGICAL CHARACTERISTICS OF CONTINENTAL MANTLE Received 30 June 2004 basins where the shallow mantle eventually contributes to the destruction of the overlying crust, the shallow mantle beneath continents serves as a stiff, buoyant ``root'' whose presence may be essential

  9. Location and extent of Tertiary structures in Cook Inlet Basin, Alaska, and mantle dynamics that focus deformation and subsidence

    USGS Publications Warehouse

    Haeussler, Peter J.; Saltus, Richard W.

    2011-01-01

    Subduction of the buoyant Yakutat microplate likely caused deformation to be focused preferentially in upper Cook Inlet. The upper Cook Inlet region has both the highest degree of shortening and the deepest part of the Neogene basin. This forearc region has a long-wavelength magnetic high, a large isostatic gravity low, high conductivity in the lower mantle, low p-wave velocity (Vp), and a high p-wave to shear-wave velocity ratio (Vp/Vs). These data suggest that fluids in the mantle wedge caused serpentinization of mafic rocks, which may, at least in part, contribute to the long-wavelength magnetic anomaly. This area lies adjacent to the subducting and buoyant Yakutat microplate slab. We suggest the buoyant Yakutat slab acts much like a squeegee to focus mantle-wedge fluid flow at the margins of the buoyant slab. Such lateral flow is consistent with observed shear-wave splitting directions. The additional fluid in the adjacent mantle wedge reduces the wedge viscosity and allows greater corner flow. This results in focused subsidence, deformation, and gravity anomalies in the forearc region.

  10. Disengaged and Disaffected Young People: Surviving the System

    ERIC Educational Resources Information Center

    Lumby, Jacky

    2012-01-01

    There are counter-narratives of youth as at risk and as buoyant and agentive. The article maps the conceptual terrain concerning resilience, well-being, buoyancy, enjoyment and happiness and selects factors related to the successful navigation of schooling. It analyses data from a subset of a national data set, from 65 young people considered to…

  11. The Astrophysical Journal, 762:4 (23pp), 2013 January 1 doi:10.1088/0004-637X/762/1/4 C 2013. The American Astronomical Society. All rights reserved. Printed in the U.S.A.

    E-print Network

    Demoulin, Pascal

    in either a convectively stable or unstable rotating shell. The magnetic loop is introduced into the shell December 7 ABSTRACT We present three-dimensional numerical simulations of a magnetic loop evolving in such a way that it is buoyant only in a certain portion in longitude, thus creating an -loop. Due

  12. Models of Rising Active Region Flux Tubes George H. Fisher

    E-print Network

    Fisher, George H.

    of the convection zone is studied by means of numerical simula­ tions. We have considered flux loop evolution, 2680 Woodlawn Drive, Honolulu HI 96822, USA Abstract. The buoyant rise of a magnetic flux loop­ lioseismology. Our major conclusions are the following: 1) The latitudes of loop emergence are consistent

  13. Helicity of the Photospheric Magnetic Field Alexei A. Pevtsov, Richard C. Canfield

    E-print Network

    Canfield, Richard

    there is buoyant and rises to the surface as \\Omega\\Gamma/187 ed loops whose ends are anchored in the convectively been used in several studies of\\Omega loops rising through the convective zone [Fisher et al., 1995], chromospheric filaments [Martin et al., 1994; Rust, 1999] and sheared coronal loops [Rust and Kumar, 1996

  14. THE SIZES OF ACTIVE REGIONS AND CONVECTIVE TRIGGERING OF

    E-print Network

    Petrovay, Kristóf

    THE SIZES OF ACTIVE REGIONS AND CONVECTIVE TRIGGERING OF THE BUOYANT LOOP INSTABILITY K. PETROVAY layer to be linearly stable and they are only destabilized by finite­amplitude convective disturbances. INTRODUCTION According to the presently most widely accepted view, active regions (AR's) are formed by a loop

  15. On the Origin of Activity in Solar-Type Stars Richard C. Canfield

    E-print Network

    Canfield, Richard

    flux tubes, which may be formed into -shaped loops by their interaction with convective cells are writhed by the Coriolis effect and helical convective turbulence. These -shaped loops emerge through of the convection zone. Once generated, this magnetic flux rises through the convection zone as discrete buoyant

  16. Explosive Volcanic Eruptions from Linear Vents on Earth, Venus and Mars: Comparisons with Circular Vent Eruptions

    NASA Technical Reports Server (NTRS)

    Glaze, Lori S.; Baloga, Stephen M.; Wimert, Jesse

    2010-01-01

    Conditions required to support buoyant convective plumes are investigated for explosive volcanic eruptions from circular and linear vents on Earth, Venus, and Mars. Vent geometry (linear versus circular) plays a significant role in the ability of an explosive eruption to sustain a buoyant plume. On Earth, linear and circular vent eruptions are both capable of driving buoyant plumes to equivalent maximum rise heights, however, linear vent plumes are more sensitive to vent size. For analogous mass eruption rates, linear vent plumes surpass circular vent plumes in entrainment efficiency approximately when L(sub o) > 3r(sub o) owing to the larger entrainment area relative to the control volume. Relative to circular vents, linear vents on Venus favor column collapse and the formation of pyroclastic flows because the range of conditions required to establish and sustain buoyancy is narrow. When buoyancy can be sustained, however, maximum plume heights exceed those from circular vents. For current atmospheric conditions on Mars, linear vent eruptions are capable of injecting volcanic material slightly higher than analogous circular vent eruptions. However, both geometries are more likely to produce pyroclastic fountains, as opposed to convective plumes, owing to the low density atmosphere. Due to the atmospheric density profile and water content on Earth, explosive eruptions enjoy favorable conditions for producing sustained buoyant columns, while pyroclastic flows would be relatively more prevalent on Venus and Mars. These results have implications for the injection and dispersal of particulates into the planetary atmosphere and the ability to interpret the geologic record of planetary volcanism.

  17. THE JOURNAL OF BIOLOGICAL CHEMISTRY Vol. 242, No. 21, Issue of November 10, pp. 4994-5001, 1967

    E-print Network

    Olins, Ada L.

    , endotoxin has been dissociated by SDS1 (6) and sodium deoxycholate (7). In the latter investigation, size calculated from short column equilibrium centrifugation by the method of La Bar and Baldwin (II). Viscosities were meas- ured in a Ubbelohde viscometer. The buoyant density in

  18. O the Sampling of Suspensions in Laminar Flow

    Microsoft Academic Search

    Francis Joseph Jones

    1991-01-01

    Dilute suspensions (o = 0.002) of neutrally buoyant, uniform diameter spheres in viscous liquids (eta = 60 mPacdots) are sampled through pores in the wall of a stirred tank. These studies are performed with the intention of investigating screening effects near the sampling orifice which cause samples to be deficient in the dispersed phase. o sbs\\/o _t, the ratio of

  19. Trajectories of Inertial Particles and Fluid Elements Peter O'Malley

    E-print Network

    Fygenson, Deborah Kuchnir

    1 Trajectories of Inertial Particles and Fluid Elements Peter O'Malley Physics Department Haverford examines the trajectories and velocities of neutrally buoyant 1 and 2 mm particles in two-dimensional fluid College, Haverford PA 19041 May 8th , 2008 The behavior of large or heavy particles in a fluid flow has

  20. Watching the world sweat: Development and utilization of an in-situ conductivity sensor for monitoring chloride dynamics in high temperature hydrothermal fluids at divergent plate boundaries

    Microsoft Academic Search

    Benjamin Isaac Larson

    2008-01-01

    The magmatic upwelling that drives plate tectonic motion at divergent plate boundaries also heats seawater circulating within the Earth's crust. The seawater undergoes physical and chemical changes beneath the surface and the resulting buoyant hydrothermal fluid ascends to the seafloor where it is comes out of structures called hydrothermal vents. One subsurface process of particular interest is phase separation, which

  1. Multi-gradient drilling method and system

    DOEpatents

    Maurer, William C. (Houston, TX); Medley, Jr., George H. (Spring, TX); McDonald, William J. (Houston, TX)

    2003-01-01

    A multi-gradient system for drilling a well bore from a surface location into a seabed includes an injector for injecting buoyant substantially incompressible articles into a column of drilling fluid associated with the well bore. Preferably, the substantially incompressible articles comprises hollow substantially spherical bodies.

  2. Condensation in Jets, Industrial Plumes and Cooling Tower Plumes

    Microsoft Academic Search

    T. M. L. Wigley

    1975-01-01

    The one-dimensional theory for the condensation of buoyant plumes is extended to include supersaturation as an extra variable. An additional equation describing the dynamics of droplet growth is used to make the system tractable. Some simple mathematical results are obtained which allow one to relate the theory to, and so extend, a commonly used graphical representation of the condensation process.

  3. Smelting of foundry iron on magnesia-alumina slags with a charge containing slags from ferroalloys production

    Microsoft Academic Search

    Zh. E. Sleptsov; V. Ao Shatlov

    1998-01-01

    Smelting foundry iron in blast furnaces is more difficult than smelting conversion pig iron. Foundry-iron smelting has several distinctive features: significant heating of the hearth; an increase in the buoyant effect of the hearth gases; upward movement of the slag region; a reduction in smelting rate and furnace productivity and an increase in unit coke consumption. The widespread practice of

  4. Marine riser system with dual purpose lift and heave compensator mechanism

    Microsoft Academic Search

    S. B. Wetmore; J. F. McNary; A. Person

    1979-01-01

    Apparatus for drilling a well at a location submerged below a body of water includes a buoyant foundation structure. The foundation structure is floatable on the surface of the body of water and is subject to vertical motion in response to waves and the like. A riser handling and tensioning mechanism is mounted to the foundation structure and is operable

  5. Liquid backmixing in bubble columns via computer-automated radioactive particle tracking (CARPT)

    Microsoft Academic Search

    Y. B. Yang; N. Devanathan; M. P. Dudukovi?

    1993-01-01

    A single, fully wettable, neutrally buoyant, small radioactive particle and 16 scintillation detectors are utilized to monitor particle motion in gas-liquid bubble columns of different heights and diameters and at different gas superficial velocities. Instantaneous velocities, time-averaged velocities, Reynolds stresses and eddy diffusivities are computed from the particle position versus time data. Anisotropy, indicated by the data, was confirmed by

  6. 46 CFR 160.073-15 - Tests.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...Float-Free Link or Life Floats and Buoyant Apparatus § 160.073-15 Tests. (a) The manufacturer shall perform a tensile test on the first three links made from a particular spool of wire. The test must be done by slowly loading the...

  7. 46 CFR 160.073-15 - Tests.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...Float-Free Link or Life Floats and Buoyant Apparatus § 160.073-15 Tests. (a) The manufacturer shall perform a tensile test on the first three links made from a particular spool of wire. The test must be done by slowly loading the...

  8. 46 CFR 160.073-15 - Tests.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...Float-Free Link or Life Floats and Buoyant Apparatus § 160.073-15 Tests. (a) The manufacturer shall perform a tensile test on the first three links made from a particular spool of wire. The test must be done by slowly loading the...

  9. 46 CFR 160.073-15 - Tests.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...Float-Free Link or Life Floats and Buoyant Apparatus § 160.073-15 Tests. (a) The manufacturer shall perform a tensile test on the first three links made from a particular spool of wire. The test must be done by slowly loading the...

  10. 46 CFR 160.073-15 - Tests.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...Float-Free Link or Life Floats and Buoyant Apparatus § 160.073-15 Tests. (a) The manufacturer shall perform a tensile test on the first three links made from a particular spool of wire. The test must be done by slowly loading the...

  11. The Great Plankton Race

    NSDL National Science Digital Library

    COSEE Ocean Learning Communities

    2012-07-12

    In this activity, learners are challenged to design a planktonic organism that will neither float like a cork nor sink like a stone. They are given pictures of planktonic organisms and simple materials. The best model of a planktonic organism will sink slowly or be neutrally buoyant. After designing with their teammates, learners test and race their plankton in a simulated ocean.

  12. The development and implementation of an ionic-polymer-metal-composite propelled vessel guided by a goal-seeking algorithm 

    E-print Network

    Vickers, Jason Aaron

    2007-09-17

    . The gravitational force is given in (2.1), mgF g = , (2.1) where FB g B is the gravitational force, m is the vessel, and g is the acceleration due to gravity. The buoyant force, FB b B can be represented as , (2.2) gVF wwb ??= ? where VB w B...

  13. Respiratory and plumage gas volumes in unrestrained diving ducks ( Aythya affinis)

    Microsoft Academic Search

    Richard Stephenson

    1995-01-01

    Closed-circuit plethysmography and inert gas equilibration analysis were used to measure the volumes of gas in the respiratory system and plumage at the end of voluntary dives in unrestrained lesser scaup (Aythya affinis). Total (respiratory plus plumage) gas volumes were measured by helium dilution and estimated from body mass, body tissue density and buoyant force. These two techniques yielded results

  14. Moving mass control for underwater vehicles

    Microsoft Academic Search

    C. A. Woolsey; N. E. Leonard

    2002-01-01

    We present two reduced-dimensional, noncanonical Hamiltonian models for a neutrally buoyant underwater vehicle coupled to an internal moving mass. It is expected that these models will be useful in designing nonlinear control laws for underwater gliders as well as for spacecraft, atmospheric re-entry vehicles, and other vehicles which use internal moving mass actuators. To illustrate, we investigate stability of a

  15. Blimplane a Conceptual Hybrid UAV for Venus Exploration

    NASA Astrophysics Data System (ADS)

    Ashish, Mr.; Alam, Mr.; Limaye, Mr.

    2015-04-01

    A Semi-Buoyant Aerial Platform is proposed. High fidelity CFD simulation are done to get the vehicle aerodynamic performance.The vehicle can perform surveillance and station keeping missions for altitude range 60–80km. It can take a payload of 100 kg.

  16. Chemical differentiation of a convecting planetary interior - Consequences for a one plate planet such as Venus

    Microsoft Academic Search

    E. M. Parmentier; P. C. Hess

    1992-01-01

    Simple models of the thermal and chemical evolution of a planetary interior are developed to explore the possible consequences of a chemically buoyant depleted mantle layer for planetary evolution. As the depleted layer thickens the melting temperature at the top of the underlying convecting mantle also increases and the degree of partial melting of the mantle added to the depleted

  17. nature physics | VOL 6 | FEBRUARY 2010 | www.nature.com/naturephysics 77 Bubble trouble

    E-print Network

    Loss, Daniel

    A fine nozzle immersed in a tank injects air slowly into water. As a bubble grows, it is pulled upwards and stretched by buoyant forces. Surface tension acts to thin down the thread of air linking the bubble' and breaks loose. A flat solid disc hits a liquid surface from above at high speed. The impact drives water

  18. Buoyancy characteristics of the bloater (Coregonus hoyi) in relation to patterns of vertical migration and acoustic backscattering

    USGS Publications Warehouse

    Fleischer, Guy W.; TeWinkel, Leslie M.

    1998-01-01

    Acoustic studies in Lake Michigan found that bloaters (Coregonus hoyi) were less reflective per size than the other major pelagic species. This difference in in situ acoustic backscattering could indicate that the deep-water bloaters have compressed swimbladders for much of their vertical range with related implications on buoyancy. To test this hypothesis, the buoyancy characteristics of bloaters were determined with fish placed in a cage that was lowered to bottom and monitored with an underwater camera. We found bloaters were positively buoyant near surface, neutrally buoyant at intermediate strata, and negatively buoyant near bottom. This pattern was consistent for the range of depths bloaters occur. The depth of neutral buoyancy (near the 50-n strata) corresponds with the maximum extent of vertical migration for bloaters observed in acoustic surveys. Fish below this depth would be negatively buoyant which supports our contention that bloaters deeper in the water column have compressed swimbladders. Understanding the buoyancy characteristics of pelagic fishes will help to predict the effects of vertical migration on target strength measurement and confirms the use of acoustics as a tool to identify and quantify the ecological phenomenon of vertical migration.

  19. Deep cross-equatorial flow in the Atlantic measured with SOFAR floats

    Microsoft Academic Search

    Philip L. Richardson; William J. Schmitz

    1993-01-01

    Neutrally buoyant SOFAR floats at nominal depths of 800, 1800, and 3300 m were tracked for 21 months in the vicinity of tropical boundary currents in the Atlantic near 6°N and at several sites near 11°N as well as along the equator. Trajectories at 1800 m show a swift (>50 cm\\/s), narrow (100 km wide), southward flowing deep western boundary

  20. River Influences on Shelf Ecosystems: Introduction and Synthesis1 , B.M. and R.M. Kudela2

    E-print Network

    Hickey, Barbara

    different numerical model applications including an ecosystem model, on35 the buoyant plume originating from and Atmospheric Sciences, Oregon State University, Corvallis,13 Oregon, USA14 4 Northwest Fisheries Science Center as the effects of the32 resultant plume on phytoplankton standing stocks, growth and grazing rates, and33

  1. RELATING ERROR BOUNDS FOR MAXIMUM CONCENTRATION ESTIMATES TO DIFFUSION METEOROLOGY UNCERTAINTY (JOURNAL VERSION)

    EPA Science Inventory

    The paper relates the magnitude of the error bounds of data, used as inputs to a Gaussian dispersion model, to the magnitude of the error bounds of the model output. The research addresses the uncertainty in estimating the maximum concentrations from elevated buoyant sources duri...

  2. # 1 2 3 4 5 6 7 Date 7/10 7/15 8/7 8/9 8/18 8/18 8/18

    E-print Network

    Collins, Gary S.

    efficiency profile to calculate plume rise. FEPS: A model which is based on Briggs equation for buoyant. Export: For further processing such as in AIRPACT, to model the effects of atmospheric chemistrySky Modeling Pathway Modeling Of Large Wildfire Emissions In The Pacific Northwest Levi M. Golston, Joseph K

  3. River Influences on Shelf Ecosystems: Introduction and synthesis B. M. Hickey,1

    E-print Network

    Kurapov, Alexander

    an ecosystem model, on the buoyant plume originating from the Columbia River. This introductory paper provides and coastal waters in an eastern boundary current system, as well as the effects of the resultant plume presents results deduced from four field studies and two different numerical model applications, including

  4. Overview, results, and conclusions for the EPRI Plume-Model Validation and Development Project: plains site. Final report

    Microsoft Academic Search

    N. E. Bowne; R. J. Londergan

    1983-01-01

    The project is designed to provide data bases and analyses for rigorous operational and diagnostic validation of plume models. The behavior and fate of buoyant plumes emitted from tall stacks are the foci of attention. The project is field measurement oriented and is configured to generate data about plume behavior in three levels of topographic complexity. A staff of nine

  5. Atmos. Chem. Phys., 12, 19952006, 2012 www.atmos-chem-phys.net/12/1995/2012/

    E-print Network

    Meskhidze, Nicholas

    , with the 1-D plume-rise model BUOYANT, and with the prescribed plume-top position (the approach widely used al., 2000; Luderer et al., 2006). Most of atmospheric composition models distribute the fire-1995-2012 © Author(s) 2012. CC Attribution 3.0 License. Atmospheric Chemistry and Physics Evaluation of the smoke

  6. Localized precipitation and runoff on Mars Edwin S. Kite,1,2

    E-print Network

    Kite, Edwin

    April 2011; published 13 July 2011. [1] We use the Mars Regional Atmospheric Modeling System (MRAMS . Mars has a lowdensity atmosphere, so deep convection can be triggered by small amounts of latent heat release. In our reference simulation, the buoyant plume lifts vapor above condensation level, forming a 20

  7. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. ???, XXXX, DOI:10.1029/, Localized precipitation and runoff on Mars

    E-print Network

    Kite, Edwin

    Abstract. We use the Mars Regional Atmospheric Modeling System (MRAMS) to sim- ulate lake storms on Mars-density atmosphere, so deep convection can be triggered by small amounts of latent heat release. In our reference simulation, the buoyant plume lifts vapor above condensation level, forming a 20km-high optically-thick cloud

  8. Expression of Sporophytic Storage Proteins in the Corm of the Quillwort (Isoetes echinospora Dur.)

    Microsoft Academic Search

    James D. Decamp; David A. Stetler; Augustus E. DeMaggio

    1994-01-01

    Parenchyma cells from the corm tissue of the aquatic lycopod lsoefes echinospora Dur. were shown by electron microscopy to be packed with amyloplasts, lipid bodies, and protein bodies. The protein bodies are morphologically similar to those identified in seeds and certain vegetative tissues of higher plants. Globoid- containing protein bodies (1-10 pm) isolated in a sucrose gradient possessed a buoyant

  9. Constraining mantle density structure using geological evidence of surface uplift rates: The case of the African Superplume

    Microsoft Academic Search

    Michael Gurnis; Jerry X. Mitrovica; Jeroen Ritsema; Hendrik-Jan van Heijst

    2000-01-01

    We explore the hypothesis that southern Africa is actively being uplifted by a large-scale, positively buoyant structure within the mid-lower mantle. Using a new formulation in which dynamic topography and uplift rate are jointly used, we place constraints on mantle density and viscosity. The solution of the momentum equation is coupled with the advection of the density field to solve

  10. The Astrophysical Journal, 722:825846, 2010 October 10 doi:10.1088/0004-637X/722/1/825 C 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A.

    E-print Network

    Sarazin, Craig

    we show is consistent with a sloshing cold front. The plume is consistent with having formed due with buoyantly lifted plumes seen in other systems (e.g., M87). Alternatively, the plume may be a gas sloshing sloshing in the core. The torus of sloshed gas is seen close to edge-on, leading to the somewhat ragged

  11. Experimenting with sodar in support of emergency preparedness at Three Mile Island1

    Microsoft Academic Search

    Heck

    1989-01-01

    In November 1988 at Three Mile Island Unit 1 (TMI-1), GPU Nuclear successfully completed the annual drill-for-grade that, from a modeling point of view, broke new ground for this plant. The meteorological and modeling aspects of the drill scenario were unprecedented for two reasons. First, the plume was buoyant and rose far above the height of the meteorological tower located

  12. Vesiculation rates of obsidian domes inferred from H2O concentration Jonathan M. Castro,1

    E-print Network

    Fourier transform infrared (FTIR) spectromicroscopy on interlayered obsidian-pumice samples. The H2O (Figure 1). These interlayered obsidian- pumice assemblages were collected near the margins of coarse pumice outcrops, which have been interpreted to be the remains of pumiceous diapirs that rose buoyantly

  13. The initial giant umbrella cloud of the May 18th, 1980, explosive eruption of Mount St. Helens

    USGS Publications Warehouse

    Sparks, R.S.J.; Moore, J.G.; Rice, C.J.

    1986-01-01

    The initial eruption column of May 18th, 1980 reached nearly 30 km altitude and released 1017 joules of thermal energy into the atmosphere in only a few minutes. Ascent of the cloud resulted in forced intrusion of a giant umbrella-shaped cloud between altitudes of 10 and 20 km at radial horizontal velocities initially in excess of 50 m/s. The mushroom cloud expanded 15 km upwind, forming a stagnation point where the radial expansion velocity and wind velocity were equal. The cloud was initiated when the pyroclastic blast flow became buoyant. The flow reduced its density as it moved away from the volcano by decompression, by sedimentation, and by mixing with and heating the surrounding air. Observations indicate that much of the flow, covering an area of 600 km2, became buoyant within 1.5 minutes and abruptly ascended to form the giant cloud. Calculations are presented for the amount of air that must have been entrained into the flow to make it buoyant. Assuming an initial temperature of 450??C and a magmatic origin for the explosion, these calculations indicate that the flow became buoyant when its temperature was approximately 150??C and the flow consisted of a mixture of 3.25 ?? 1011 kg of pyroclasts and 5.0 ?? 1011 kg of air. If sedimentation is considered, these figures reduce to 1.1 ?? 1011 kg of pyroclasts and 1.0 ?? 1011 kg of air. ?? 1986.

  14. The Effect of Point Mutations on the Free Energy of Transmembrane aaa-Helix Dimerization

    E-print Network

    of dimeri- zation in a non-denaturing detergent solution and have observed the changes in energy arising from two of the mutants previously studied. Use of the detergent pentaoxyethylene octyl ether (C8E5) is a great advan- tage, since its micelles are neutrally buoyant and the detergent allows a reversible

  15. PILOT DEMONSTRATION OF THE AIR CURTAIN SYSTEM FOR FUGITIVE PARTICLE CONTROL

    EPA Science Inventory

    The report gives results of the demonstration of the technical and economic feasibility of using an air curtain transport system to control buoyant fugitive particle emissions. (Fugitive emissions are the major source of uncontrolled emissions for many industrial plants. There ar...

  16. Buoyancy Can-Can

    ERIC Educational Resources Information Center

    Nelson, Jim; Nelson, Jane Bray

    2015-01-01

    In this paper, a discrepant event is used to initiate a learning cycle lesson to help students develop an understanding of the concept and equation for buoyant force. The data are gathered using readily available equipment and then graphically analyzed using a four-step analysis consistent with the modeling instructional approach. This laboratory…

  17. Transient wind-driven upwelling in a submarine canyon: A process-oriented modeling study

    Microsoft Academic Search

    Jochen Kämpf

    2006-01-01

    A hydrodynamic model is employed to study flow near a submarine canyon during conditions of upwelling-favorable coastal winds. Findings reveal that up-canyon flow is the rapid geostrophic adjustment to barotropic pressure gradients establishing across the canyon. Stratification leads to the formation of a cyclonic eddy within the canyon, trapping neutrally buoyant matter, and limits the upwelling depth only when a

  18. A simple model of dry convective helical vortices (with applications to the atmospheric dust devil)

    Microsoft Academic Search

    Michael V. Kurgansky

    2005-01-01

    An asymptotic solution of inviscid Boussinesq equations for a ‘dry convective Rankine vortex’ with prescribed buoyant forcing is given. The obtained vortex solution demonstrates monotonic growth with height of the vortex core radius, which becomes infinite at a certain critical altitude, and the corresponding attenuation of the vertical vorticity. This idealized vortex is then embedded in a convectively unstable boundary

  19. Density variation amongst mid-ocean ridge basalts: Implications for magma mixing and the scarcity of primitive lavas

    Microsoft Academic Search

    R. S. J. Sparks; P. Meyer; H. Sigurdsson

    1980-01-01

    Densities calculated from glass compositions of observed mid-ocean ridge basalts show that the more primitive melts are likely to be buoyant in more evolved melts. Consideration of this and other physical properties indicates that convective mixing between most basaltic magmas occurs under intermittently turbulent to turbulent conditions (transitional Reynolds Numbers) accounting for the widespread occurrence of hybrid lavas. Hypothetical picritic

  20. ensl-00167302,version1-18Aug2007 Measurement of particle and bubble accelerations in turbulence

    E-print Network

    Paris-Sud XI, Université de

    ensl-00167302,version1-18Aug2007 Measurement of particle and bubble accelerations in turbulence R motion are resolved and the particle acceleration is measured. For neutrally buoyant par- ticles, our 1.4) and to air bubbles. We observe that the acceleration variance strongly depends on the particle

  1. Thompson/Ocean 420/Winter 2005 Internal Gravity Waves 1 I. Two-layer internal waves

    E-print Network

    Thompson, LuAnne

    Thompson/Ocean 420/Winter 2005 Internal Gravity Waves 1 u1 I. Two-layer internal waves The simplest. The ocean analogy is a wave much like the surface gravity waves we have studied, but which acts-sea interface. For gravity waves, the wave speed, as well as the frequency, is proportional to the buoyant

  2. 70 VOLUME 58J O U R N A L O F T H E A T M O S P H E R I C S C I E N C E S 2001 American Meteorological Society

    E-print Network

    Fedorovich, Evgeni

    the neutrally buoyant boundary layer in the initial portion of the wind tunnel flow and a quasi Meteorological Society Numerical and Laboratory Study of a Horizontally Evolving Convective Boundary Layer. Part are presented from a large eddy simulation (LES) and wind tunnel study of the turbulence regime

  3. Penetration of mantle plumes through depleted lithosphere

    E-print Network

    Brandeis, Geneviève

    Penetration of mantle plumes through depleted lithosphere D. Jurine, C. Jaupart, and G. Brandeis are used to study how a laminar thermal plume deforms and penetrates a buoyant and viscous layer, which deforms the interface. For B penetration into the upper layer occurs with a significant

  4. 46 CFR 160.060-2 - Type and model.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Type and model. 160.060-2 Section 160.060-2...and Child § 160.060-2 Type and model. Each buoyant vest specified in this subpart is a: (a) Standard: (1) Model AY, adult (for persons weighing...

  5. 46 CFR 160.060-2 - Type and model.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Type and model. 160.060-2 Section 160.060-2...and Child § 160.060-2 Type and model. Each buoyant vest specified in this subpart is a: (a) Standard: (1) Model AY, adult (for persons weighing...

  6. Modeling dispersion at distances of meters from urban sources

    Microsoft Academic Search

    Akula Venkatram; Vlad Isakov; Jing Yuan; David Pankratz

    2004-01-01

    This paper describes the evaluation and improvement of dispersion models for estimating ground-level concentrations in the vicinity of small sources located in urban areas. The models were evaluated with observations from a tracer study conducted at the University of California, Riverside. This experiment simulated a non-buoyant release from the top of a small source in an urban area. The tracer,

  7. Plasmid heterogeneity in various strains of Bacillus megaterium

    Microsoft Academic Search

    Ulf Stahl; Karl Esser

    1983-01-01

    Seven different strains of Bacillusmegaterium, obtained from strain collections, were investigated for the presence of plasmids. 6 of these contained up to four plasmids which although having identical buoyant density, could be attributed to at least 8 different size classes with contour lengths ranging from 0.63 to 8 µm. With one exception, an identity of these do not appear to

  8. Convective instability of a boundary layer with temperature-and strain-rate-dependent viscosity in terms of `available buoyancy'

    Microsoft Academic Search

    C. P. Conrad; P. Molnar

    1999-01-01

    Cold mantle lithosphere is gravitationally unstable with respect to the hotter buoyant asthenosphere beneath it, leading to the possibility that the lower part of the mantle lithosphere could sink into the mantle in convective downwelling. Such instabilities are driven by the negative thermal buoyancy of the cold lithosphere and retarded largely by viscous stress in the lithosphere. Because of the

  9. 46 CFR 26.30-1 - Approved unicellular plastic foam work vests.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Approved unicellular plastic foam work vests. 26.30-1 Section 26.30-1 Shipping...OPERATIONS Work Vest § 26.30-1 Approved unicellular plastic foam work vests. (a) Buoyant work vests carried under...

  10. 46 CFR 164.015-1 - Applicable specifications and standards.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...of the issue in effect on the date the plastic foam material is manufactured, form a...this section shall be kept on file by the plastic foam manufacturer with this...

  11. Lightning Strikes on Airborne Grounded Systems 

    E-print Network

    Malinga, Gilbert Aporu

    2014-10-13

    , NOAA, 2014. ........................................................................................ 4 Fig. 1-2 Schematic illustrating airborne wind turbines based on the concept of a tethered buoyant blimp (Altaeros, 2014... of airborne structures of varied diameter. ............................... 73 Table 4-3 Surface electrical charge, tQ induced on cylindrical structures of varied geometry, representing an airborne wind turbine, as a function of elevation...

  12. Gel Electrophoresis and Photography

    E-print Network

    Simpson, Larry

    is the molecular biology of trypanosomes, which are flagellated protozoa that cause several important human on the basis of sedimentation coefficients Or buoyant densities, and scintillation counters were required of restriction enzymes and cloning in bacterial plasmids or phages to obtain large quantities of pure fragments

  13. Sediment supply to the ocean: The temporal and spatial variability of rivers and plumes

    Microsoft Academic Search

    Mark D. Morehead

    1999-01-01

    Our research group (Delta Force) has undertaken a source to sink modeling effort, in which each of the major processes controlling sediment supply, deposition, reworking and ultimate burial are simulated. This dissertation focuses on the sediment and water supplied by rivers and the initial deposition of sediment from buoyant surficial plumes. The knowledge of riverine and plume processes gleaned from

  14. J. Astrophys. Astr. (0000) 00, 000--000 Vector Magnetic Fields, Subsurface Stresses and

    E-print Network

    Pevtsov, Alexei A.

    emergence processes (e.g., Spruit 1981, Chou and Fisher 1989, D'Silva and Choudhuri 1993, Fan, Fisher and Mc tubes ris­ ing buoyantly to the solar surface (D'Silva and Choudhuri 1993, Fan, Fisher and Mc(r; `; z) defined by its axial component B a = (0; 0; B z (r)) and meridional component Bm = (0; B ` (r); 0

  15. RESEARCH ARTICLE Near-wall velocity measurements by particle-shadow tracking

    E-print Network

    Lajeunesse, Eric

    on Fig. 1. The x and y axes are oriented, respec- tively, along and transverse to the flow direction of fine tracer particles of diameter D. Ideally the best is to use neutrally buoyant particles for the method. A punctual light source enlightens the wall under a small incidence angle a. A camera oriented

  16. Active salinity choice and enhanced swimming endurance in 0 to 8-d-old larvae of diadromous gobies, including Sicydium punctatum (Pisces), in Dominica, West Indies

    Microsoft Academic Search

    K. N. I. Bell; J. A. Brown

    1995-01-01

    We studied the early life history of diadromous gobies in Dominica, West Indies, from May 1989 to May 1991, emphasising Sicydium punctatum Perugia. The transition of newly hatched larvae from upriver nest sites to the sea was studied in laboratory experiments. Newly hatched larvae are negatively buoyant but avoid settling to the bottom by active swimming during drift to the

  17. Organization of G Proteins and Adenylyl Cyclase at the Plasma Membrane

    Microsoft Academic Search

    Chunfa Huang; John R. Hepler; Linda T. Chen; Alfred G. Gilman; Richard G. W. Anderson; Susanne M. Mumby

    There is mounting evidence for the organization and compartmentation of signaling molecules at the plasma membrane. We find that hormone-sensitive adenylyl cyclase activity is enriched in a subset of regulatory G protein-containing fractions of the plasma membrane. These subfractions resemble, in low buoyant density, structures of the plasma membrane termed caveolae. Immunofluorescence experiments revealed a punctate pat- tern of G

  18. Published: October 14, 2011 r 2011 American Chemical Society 19178 dx.doi.org/10.1021/ja207515j |J. Am. Chem. Soc. 2011, 133, 1917819188

    E-print Network

    Kay, Mark A.

    ÀShell Nanoparticles: Discovery of Previously Invisible Biomarkers Davide Tamburro,,,§ Claudia Fredolini,,,|| Virginia and albumin. The MS input sample is strictly limited in the maximum total protein (g) content, a value, and are very labile. To overcome these barriers, we created porous, buoyant, coreÀshell hydrogel nanoparticles

  19. The impact of cultural diversity on the effectiveness of construction project teams

    Microsoft Academic Search

    Mohammed Dulaimi; Amjad Hariz

    2011-01-01

    Before the global financial crisis hit the region in 2008, the buoyant construction activities in the United Arab Emirates, especially in Dubai, were successful in attracting many multinational companies and professionals from across the globe. One of the main drawbacks of this business environment is the increasingly high competition between such companies to recruit and retain the needed human resources.

  20. Continental tectonics in the aftermath of plate tectonics

    Microsoft Academic Search

    Peter Molnar

    1988-01-01

    It is shown that the basic tenet of plate tectonics, rigid-body movements of large plates of lithosphere, fails to apply to continental interiors. There, buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity. The role of crustal blocks and of the detachment of crustal fragments in this process is

  1. Thermal properties of magnetic flux tubes. II. Storage of flux in the solar overshoot region

    Microsoft Academic Search

    M. Rempel

    2003-01-01

    We consider the consequences of radiative heating for the storage of magnetic flux in the overshoot region at the bottom of the solar convection zone. In the first part of the paper, we study the evolution of axisymmetric flux tubes (flux rings), which are initially in neutrally buoyant mechanical equilibrium. Radiative heating leads to a slow upward drift of the

  2. Applicability of an integrated plume rise model for the dispersion from wild-land fires

    NASA Astrophysics Data System (ADS)

    Kukkonen, J.; Nikmo, J.; Sofiev, M.; Riikonen, K.; Petäjä, T.; Virkkula, A.; Levula, J.; Schobesberger, S.; Webber, D. M.

    2014-01-01

    We have presented an overview of a mathematical model, BUOYANT, that was originally designed for the evaluation of the dispersion of buoyant plumes originated from major warehouse fires. The model addresses the variations of the cross-plume integrated properties of a buoyant plume in the presence of a vertically varying atmosphere. The model also includes a treatment for a rising buoyant plume interacting with an inversion layer. We have compared the model predictions with the data of two prescribed wild-land fire experiments. For the SCAR-C experiment in Quinault (US) in 1994, the predicted vertical extents of the plume at maximum plume rise were between 500-800 m and 200-700 m, using two alternative meteorological datasets. The corresponding observed injection heights of the aerosol particles measured using an airborne LIDAR (LIght Detection And Ranging) ranged from 250 and 600 m. For the prescribed burning experiment in Hyytiälä (Finland) in 2009, the model predictions were compared with plume elevations and diameters, determined based on particulate matter number concentration measurements on board an aeroplane. The agreement of modelled and measured results was good, provided that one assumes the measured maximum convective heat fluxes as input data for the model. The results demonstrate that in field experiments on wild-land fires, there are substantial uncertainties in estimating both (i) the source terms for the atmospheric dispersion computations, and (ii) the relevant vertical meteorological profiles. The results provide more confidence that cross-plume integrated mathematical models, such as the BUOYANT model, can be used to fairly good accuracy for evaluating the dispersion from major wild-land fires.

  3. Flat subduction dynamics and deformation of the South American plate: Insights from analog modeling

    NASA Astrophysics Data System (ADS)

    Espurt, Nicolas; Funiciello, Francesca; Martinod, Joseph; Guillaume, Benjamin; Regard, Vincent; Faccenna, Claudio; Brusset, Stéphane

    2008-06-01

    We present lithospheric-scale analog models, investigating how the absolute plates' motion and subduction of buoyant oceanic plateaus can affect both the kinematics and the geometry of subduction, possibly resulting in the appearance of flat slab segments, and how it changes the overriding plate tectonic regime. Experiments suggest that flat subductions only occur if a large amount of a buoyant slab segment is forced into subduction by kinematic boundary conditions, part of the buoyant plateau being incorporated in the steep part of the slab to balance the negative buoyancy of the dense oceanic slab. Slab flattening is a long-term process (~10 Ma), which requires the subduction of hundreds of kilometers of buoyant plateau. The overriding plate shortening rate increases if the oceanic plateau is large enough to decrease the slab pull effect. Slab flattening increases the interplate friction force and results in migration of the shortening zone within the interior of the overriding plate. The increase of the overriding plate topography close to the trench results from (1) the buoyancy of the plate subducting at trench and (2) the overriding plate shortening. Experiments are compared to the South American active margin, where two major horizontal slab segments had formed since the Pliocene. Along the South American subduction zone, flat slab segments below Peru and central Chile/NW Argentina appeared at ~7 Ma following the beginning of buoyant slab segments' subduction. In northern Ecuador and northern Chile, the process of slab flattening resulting from the Carnegie and Iquique ridges' subductions, respectively, seems to be active but not completed. The formation of flat slab segments below South America from the Pliocene may explain the deceleration of the Nazca plate trenchward velocity.

  4. Mechanism for generating power from wave motion on a body of water

    SciTech Connect

    Sachs, G.A.; Sachs, H.K.

    1982-09-28

    A mechanism for generating power from wave motion on a body of water is described. The mechanism includes a buoyant body which is adapted to float on a body of water and to roll and pitch in response to the wave motion of the water. A gyro-wave energy transducer is mounted on the buoyant body for translating the pendulum-like motions of the buoyant body into rotational motion. The gyro-wave energy transducer includes a gimbal comprised of first and second frames, with the first frame being pivotally mounted to the second frame and the second frame being pivotally mounted to the buoyant body. A gyroscope is mounted to the first frame for rotation about an axis perpendicular to the axes of rotation of the first and second frames. A motor/generator is coupled to the gyroscope for maintaining a controlled rotational velocity for the gyroscope. Transferring members are associated with one of the first and second frames for transferring torque of one of the first and second frames to the gyroscope about an axis that is perpendicular to that of the gyroscope which results in rotation of the other of the first and second frames. An electrical generator is responsive to the relative rotational movement of the first and second frames for generating electrical energy. A storage battery is mounted on the buoyant body for storing and releasing electrical energy and is operatively coupled to the motor/generator and the electrical generator. A control circuit is associated with the generator and the motor/generator unit of the gyroscope and is responsive to the time rate of change of current produced by the generator for controlling the rotational velocity of the gyroscope in order to maintain maximum power output from the electrical generator.

  5. Rethinking Recycling in Arcs

    NASA Astrophysics Data System (ADS)

    Kelemen, P.; Behn, M. D.; Jagoutz, O.

    2012-12-01

    Hacker et al EPSL 2011 and Behn et al Nature Geosci 2011 investigated pathways for return of buoyant, subducted material to arc crust. These include (1) diapirs rising into the hot mantle wedge, with extensive melts adding a component to arc magmas, (2) flow of material back up a relatively cold "subduction channel", adding solids to the lower crust and small-degree partial melts to the upper crust, (3) flow from the forearc along the base of arc crust, and (4) imbrication of forearc material into arc crust. These processes add felsic, incompatible-element-rich components to arc crust. The flux of incompatible elements such as Th in arc lavas, thought to be mainly recycled from subducted sediments, is > sediment subduction flux. There are large uncertainties: arc crustal growth rates are imprecise; young, primitive arc lavas may not be representative of magmatic flux into arc crust; sediment subduction flux may have varied. Nevertheless, this result is found for all arcs examined, using recently published growth rates. Perhaps arc growth rates that include subduction erosion are systematically overestimated. Instead or in addition, maybe significant Th comes from material other than sediments. Here, we consider the implications of pathways 1-4 for arc growth rates and incompatible element enrichment, in the context of subduction erosion and arc-arc collision. Subducting arc lithologies can become separated, with only felsic components returned to arc crust. Buoyant lithologies are mobile in viscous instabilities at > 700-800°C. Whereas thin layers such as sediments may become mobile all at once, instabilities may periodically strip the hottest parts from the top of thick buoyant layers, replacing them with hot mantle. In arc-arc collision, the top of a subducting plate starts at about 0°C on the seafloor, so heating is slow. In subduction erosion, forearc material in the subducting package can be > 200°C before erosion so buoyant lithologies reach 700-800°C faster, and in larger volumes at a given time. Subduction erosion rarely, if ever, transports significant amounts of buoyant material deep into the convecting mantle. Because buoyant material can remain part of the crust, it may often be a mistake to add all of the eroded material to the observed arc volume to derive crustal growth rates. Buoyancy instabilities during subduction erosion or arc-arc collision will accumulate felsic arc crust. For example, > 50% of Aleutian arc lavas and exposed plutons are more buoyant than mantle peridotite at 700-800°C, 3-4 GPa. The buoyant material has an average of 60-62 wt% SiO2, molar Mg/(Mg+Fe) 0.4-0.5, and trace elements identical to bulk continental crust, though western Aleutian lavas have the most depleted Sr, Nd and Pb isotope ratios of all arc lavas worldwide. In general, density sorting of arc lithologies, and subsequent partial melting as buoyant rocks rise through the mantle wedge or along a subduction channel, could lead to a kind of double and triple distillation. Incompatible elements such as Th would be enriched in arc crust, retaining correlations with isotopic indicators of a recycled sediment component, while Th-poor, dense, mafic lavas and lower crustal cumulates return to the convecting mantle.

  6. Survival of LLSVPs for Billions of Years in a Vigorously Convecting Mantle: Replenishment and Destruction of Chemical Anomaly

    NASA Astrophysics Data System (ADS)

    Mulyukova, Elvira; Steinberger, Bernhard; Dabrowski, Marcin; Sobolev, Stephan

    2015-04-01

    We study segregation of the subducted oceanic crust (OC) at the core mantle boundary, its ability to accumulate and form large-scale compositional anomaly (such as the LLSVPs), and its susceptibility to get entrained by the hot rising plumes. Based on the results from our high-resolution numerical simulations of 2D thermochemical mantle convection, we propose that the longevity of LLSVPs for up to three billion years, and possibly longer, can be ensured by a balance in the rate of segregation of high-density OC-material to the CMB, and the rate of its entrainment away from the CMB by mantle upwellings. For a range of parameters tested in this study, a large-scale compositional anomaly forms at the CMB, which is similar in shape and size to the seismically observed LLSVPs - high topography of over 1000 km, steep edges, and occupying a few % (~ 2%) of the total mantle volume. In our simulations, neutrally buoyant thermochemical piles - those in which the thermally induced negative density anomaly is balanced by the presence of a fraction of compositionally anomalous high density material - best resemble the geometry of LLSVPs. Such neutrally buoyant piles tend to emerge and survive for a long time (over 3Gyr) in simulations with quite different parameters. For moderate compositional density anomaly of oceanic crust, the neutrally buoyant piles form at the CMB and contain ~ 80% of dense OC material. For high compositional density anomaly, a dense layer forms at the base of the mantle, and a neutrally buoyant pile develops on top of it. In the latter case, the dense basal layer and the neutrally buoyant pile on top of it are clearly separated by a jump in the concentration of the compositionally anomalous material. We conclude from our numerical study that for a plausible range of values of density anomaly of OC material in the lower mantle - it is likely that it segregates to the CMB, gets mechanically mixed with the ambient material, and forms neutrally buoyant large scale compositional anomalies similar in shape to the LLSVPs. To perform this numerical study, we developed an efficient FEM code with dynamically adaptive time and space resolution, and marker-in-cell methodology. This enabled us to model thermochemical mantle convection at realistically high convective vigor, strong thermally induced viscosity variations, and long term evolution of compositional fields. Confidence in our numerical results was gained through thorough benchmarking of the code, together with the resolution studies, all in the light of the characteristic length and time scales of governing processes in our modeled system.

  7. Trench migration and overriding plate stress in dynamic subduction models

    NASA Astrophysics Data System (ADS)

    Holt, A. F.; Becker, T. W.; Buffett, B. A.

    2015-04-01

    On Earth, oceanic plates subduct beneath a variety of overriding plate (OP) styles, from relatively thin and negatively buoyant oceanic OPs to thick and neutrally/positively buoyant continental OPs. The inclusion of an OP in numerical models of self-consistent subduction has been shown to reduce the rate that subducting slabs roll back relative to the equivalent single plate models. We use dynamic, 2-D subduction models to investigate how the mechanical properties, namely viscosity, thickness, and density, of the OP modify the slab rollback rate and the state of stress of the OP. In addition, we examine the role of the subducting plate (SP) viscosity. Because OP deformation accommodates the difference between the slab rollback rate and the far-field OP velocity, we find that the temporal variations in the rollback rate results in temporal variations in OP stress. The slabs in our models roll back rapidly until they reach the lower mantle viscosity increase, at which point the rollback velocity decreases. Concurrent with this reduction in rollback rate is a switch from an OP dominated by extensional stresses to a compressional OP. As in single plate models, the viscosity of the SP exerts a strong control on subducting slab kinematics; weaker slabs exhibit elevated sinking velocities and rollback rates. The SP viscosity also exerts a strong control on the OP stress regime. Weak slabs, either due to reduced bulk viscosity or stress-dependent weakening, have compressional OPs, while strong slabs have dominantly extensional OPs. While varying the viscosity of the OP alone does not substantially affect the OP stress state, we find that the OP thickness and buoyancy plays a substantial role in dictating the rate of slab rollback and OP stress state. Models with thick and/or negatively buoyant OPs have reduced rollback rates, and increased slab dip angles, relative to slabs with thin and/or positively buoyant OPs. Such elevated trench rollback for models with positively buoyant OPs induces extensional stresses in the OP, while OPs that are strongly negatively buoyant are under compression. While rollback is driven by the negative buoyancy of the subducting slab in such models of free subduction, we conclude that the physical properties of the OP potentially play a significant role in modulating both rollback rates and OP deformation style on Earth.

  8. Falling bodies through sharply stratified fluids: theory and experiments

    NASA Astrophysics Data System (ADS)

    McLaughlin, Richard; Camassa, Roberto; Falcon, Claudia; Harenberg, Steve; Mertens, Keith; Reis, Johnny; Schlieper, William; Watson, Bailey; White, Brian; UNC RTG Fluids Group Team

    2011-11-01

    The motion of bodies and fluids moving through a stratified background fluid arises naturally in the context of carbon (marine snow) settling in the ocean, as well as less naturally in the context of the DWH Gulf oil spill. The details of the settling rates may affect the ocean contribution to the earth's carbon cycle. We look at phenomena associated with many falling spheres in stratified fluids, as well as behavior of multiphase buoyant plumes penetrating strong stratification. We present careful measurements critical heights for fully miscible jets and companion analytical prediction. In turn, we examine cases involving clouds of sinking particulate and rising buoyant oil emulsions and associated plume trapping behaviors. NSF DMS RTG 0943851, NSF DMS 1009750, NSF CMG ARC-1025523, NSF RAPID CBET-1045653.

  9. A Lagrangian Particle Transport and Diffusion Model for Non-passive Scalars

    NASA Astrophysics Data System (ADS)

    Kaplan, H.

    2015-07-01

    We present a model of the transport and diffusion of materials whose density differs from the ambient air density or where there is excess momentum above the ambient flow. The model describes the evolution of the material concentration and can be applied to both positively and negatively buoyant pollutants. In order to calculate the transport and diffusion, we use a Monte-Carlo technique to follow the Lagrangian trajectories of many particles. This makes the model suitable for the calculation of transport and diffusion in non-homogeneous areas such as complex terrain or within an urban canopy. Results are compared with wind-tunnel observations of neutral jet releases under different conditions. Comparisons with wind-tunnel observations are made also for releases of negatively and positively buoyant materials. The agreement with observations is good.

  10. Numerical simulations of the magnetorotational instability in protoneutron stars: I. Influence of buoyancy

    E-print Network

    Guilet, Jerome

    2015-01-01

    The magneto-rotational instability (MRI) is considered to be a promising mechanism to amplify the magnetic field in fast rotating protoneutron stars. In contrast to accretion disks, radial buoyancy driven by entropy and lepton fraction gradients is expected to have a dynamical role as important as rotation and shear. We investigate the poorly known impact of buoyancy on the non-linear phase of the MRI, by means of three dimensional numerical simulations of a local model in the equatorial plane of a protoneutron star. The use of the Boussinesq approximation allows us to utilise a shearing box model with clean shearing periodic boundary conditions, while taking into account the buoyancy driven by radial entropy and composition gradients. We find significantly stronger turbulence and magnetic fields in buoyantly unstable flows. On the other hand, buoyancy has only a limited impact on the strength of turbulence and magnetic field amplification for buoyantly stable flows in the presence of a realistic thermal diff...

  11. Pore-throat sizes in sandstones, siltstones, and shales: Reply

    USGS Publications Warehouse

    Nelson, Philip H.

    2011-01-01

    In his discussion of my article (Nelson, 2009), W. K. Camp takes issue with the concept that buoyancy is not the dominant force in forming and maintaining the distribution of gas in tight-gas accumulations (Camp, 2011). I will restrict my response to the issues he raised regarding buoyant versus nonbuoyant drive and to a few comments regarding water saturation and production. I claim that the pressure generated in petroleum source rocks (Pg), instead of the buoyancy pressure (Pb), provides the energy to charge most tight sandstones with gas. The arguments are fourfold: (1) buoyant columns of sufficient height seldom exist in low-permeability sand-shale sequences, (2) tight-gas systems display a pressure profile that declines instead of increases upward, (3) gas is pervasive in overpressured systems, and (4) source rocks can generate pore pressures sufficiently high to charge tight sandstones.

  12. Evaluation of advanced airship concepts

    NASA Technical Reports Server (NTRS)

    Joner, B. A.; Schneider, J. J.

    1975-01-01

    A historical overview of the airship, technical and operational characteristics of conventional and hybrid concepts, and the results of a parametric design analysis and evaluation are presented. The lift capabilities of certain buoyant fluids for a hypothetical 16 million cu.ft. volume airship are compared. The potential advanced airship concepts are surveyed, followed by a discussion of the six configurations: conventional nonrigid, conventional rigid, Deltoid (Dynairship), Guppoid (Megalifter), Helipsoid, and Heli-Stat. It is suggested that a partially buoyant Helipsoid concept of the optimum buoyancy ratio has the potential to solve the problems facing future airship development, such as Ballast and Ballast Recovery System, Full Low-Speed Controllability, Susceptibility to Wind/Gusting, Weather/Icing Constraints, Ground Handling/Hangaring, and Direct/Indirect Operating Costs.

  13. Feasibility study of modern airships, phase 1. Volume 2: Parametric analysis (task 3). [lift, weight (mass)

    NASA Technical Reports Server (NTRS)

    Lancaster, J. W.

    1975-01-01

    Various types of lighter-than-air vehicles from fully buoyant to semibuoyant hybrids were examined. Geometries were optimized for gross lifting capabilities for ellipsoidal airships, modified delta planform lifting bodies, and a short-haul, heavy-lift vehicle concept. It is indicated that: (1) neutrally buoyant airships employing a conservative update of materials and propulsion technology provide significant improvements in productivity; (2) propulsive lift for VTOL and aerodynamic lift for cruise significantly improve the productivity of low to medium gross weight ellipsoidal airships; and (3) the short-haul, heavy-lift vehicle, consisting of a simple combination of an ellipsoidal airship hull and existing helicopter componentry, provides significant potential for low-cost, near-term applications for ultra-heavy lift missions.

  14. Aeromechanical stability analysis of a multirotor vehicle model representing a hybrid heavy lift airship (HHLA)

    NASA Technical Reports Server (NTRS)

    Venkatesan, C.; Friedmann, P. P.

    1984-01-01

    Hybrid Heavy Lift Airship (HHLA) is a proposed candidate vehicle aimed at providing heavy lift capability at low cost. This vehicle consists of a buoyant envelope attached to a supporting structure to which four rotor systems, taken from existing helicopters are attached. Nonlinear equations of motion capable of modelling the dynamics of this coupled multi-rotor/support frame/vehicle system have been developed. Using these equations of motion the aeroelastic and aeromechanical stability analysis is performed aimed at identifying potential instabilities which could occur for this type of vehicle. The coupling between various blade, supporting structure and rigid body modes is identified. Furthermore, the effects of changes in buoyancy ratio (Buoyant lift/total weight) on the dynamic characteristics of the vehicle are studied. The dynamic effects found are of considerable importance for the design of such vehicles. The analytical model developed is also useful for studying the aeromechanical stability of single rotor and tandem rotor coupled rotor/fuselage systems.

  15. A hybrid airship concept for Naval missions

    NASA Technical Reports Server (NTRS)

    Harper, M.

    1976-01-01

    A preliminary analysis of a hybrid semibuoyant delta-planform airship was performed using a computer synthesis program. The delta-planform hull shape was studied parametrically to determine the effects on vehicle performance for two Navy antisubmarine missions. The effects of buoyancy ratio, design speed, and altitude were also studied. The results suggest that long-range mission vehicles require a near buoyant or fully buoyant design and that there is no special advantage to the use of a lifting-body hull shape. For shorter-range missions, hybrid vehicles may have merit, and optimum vehicle buoyancy varies depending on whether a minimum-weight or minimum-fuel-consumption design is desired. As compared with conventionally shaped airships, the benefits, if any, from a lifting-body configuration will be limited to missions requiring relatively higher flight speeds.

  16. Dissipative inertial transport patterns near coherent Lagrangian eddies in the ocean

    E-print Network

    F. J. Beron-Vera; M. J. Olascoaga; G. Haller; M. Farazmand; J. Trinanes; Y. Wang

    2015-02-23

    Recent developments in dynamical systems theory have revealed long-lived and coherent Lagrangian (i.e., material) eddies in incompressible, satellite-derived surface ocean velocity fields. Paradoxically, observed drifting buoys and floating matter tend to create dissipative-looking patterns near oceanic eddies, which appear to be inconsistent with the conservative fluid particle patterns created by coherent Lagrangian eddies. Here we show that inclusion of inertial effects (i.e., those produced by the buoyancy and size finiteness of an object) in a rotating two-dimensional incompressible flow context resolves this paradox. Specifically, we obtain that anticyclonic coherent Lagrangian eddies attract (repel) negatively (positively) buoyant finite-size particles, while cyclonic coherent Lagrangian eddies attract (repel) positively (negatively) buoyant finite-size particles. We show how these results explain dissipative-looking satellite-tracked surface drifter and subsurface float trajectories, as well as satellite-derived \\emph{Sargassum} distributions.

  17. Aeromechanical stability analysis of a multirotor vehicle with application to hybrid heavy lift helicopter dynamics

    NASA Technical Reports Server (NTRS)

    Venkatesan, C.; Friedmann, P. P.

    1984-01-01

    The Hybrid Heavy Lift Helicopter (HHLH) is a potential candidate vehicle aimed at providing heavy lift capability at low cost. This vehicle consists of a buoyant envelope attached to a supporting structure. Four rotor systems are also attached to the supporting structure. Nonlinear equations of motion capable of modeling the dynamics of this multi-rotor/support frame/vehicle system have been developed and used to study the fundamental aeromechanical stability characteristics of this class of vehicles. The mechanism of coupling between the blades, supporting structure and rigid body modes is identified and the effect of buoyancy ratio (buoyant lift/total weight) on the vehicle dynamics is studied. It is shown that dynamics effects have a major role in the design of such vehicles. The analytical model developed is also useful for studying the aeromechanical stability of single rotor and tandem rotor coupled rotor/fuselage systems.

  18. Biomimetic mechanics behaviors of the strider leg vertically pressing water

    NASA Astrophysics Data System (ADS)

    Liu, Jianlin; Sun, Jing; Mei, Yue

    2014-06-01

    Water striders capture the amazing feature to walk on water surface, and this phenomenon triggered extensive investigations in the past decades. We model the strider leg as a fiber vertically pressing into water surface and explore some striking mechanics behaviors in this process. First, the meniscus morphology is exactly solved by a numerical scheme. Based upon this solution, a non-dimensional parameter is defined in order to properly characterize the "capillary effect" of the objects with different volumes. The discussion of the buoyant force shows that the apparent contact angle has little impact on the variation of the water-supporting force. Besides this, there is no need for the strider leg to pierce into water, for the pinning of the triple contact line ensures a bigger buoyant force. In addition, the radius of the leg should be in an appropriate range to support the body weight. These analyses may cast light on how to design new-typed miniature aquatic devices.

  19. Measurements of single spherical particle trajectories with lateral migration in a slit with one porous wall under laminar flow conditions

    NASA Astrophysics Data System (ADS)

    Otis, J. R.; Altena, F. W.; Mahar, J. T.; Belfort, G.

    1986-01-01

    Lateral migration of spherical, neutrally buoyant particles moving in Poiseuille flow was measured in a slit with a porous membrane at one wall. Neutrally buoyant particles with diameters of 226 ?m were injected into 22% glycerol-water solution flowing vertically in a slit channel (1.6 × 50 × 152 mm). The particles were illuminated with a strobe at 25 flashes/sec and photographed with a 4 × 5 camera under dark field conditions. Measured particle trajectories are compared with theoretically predicted trajectories based on Altena and Belfort's (1984) model. The theoretical trajectories are within the limits of error in the measured trajectories. By confirming the Altena and Belfort (1984) model within the range of experimental conditions tested here, inertial interactions should be included when modeling membrane fouling of dilute suspensions (Belfort et al. 1982).

  20. Precise measurements of droplet-droplet contact forces in quasi-2D emulsions

    NASA Astrophysics Data System (ADS)

    Lowensohn, Janna; Orellana, Carlos; Weeks, Eric

    2015-03-01

    We use microscopy to visualize a quasi-2D oil-in-water emulsion confined between two parallel slides. We then use the droplet shapes to infer the forces they exert on each other. To calibrate our force law, we set up an emulsion in a tilted sample chamber so that the droplets feel a known buoyant force. By correlating radius of the droplet and length of contacts with the buoyant forces, we validate our empirical force law. We improve upon prior work in our lab by using a high-resolution camera to image each droplet multiple times, thus providing sub-pixel resolution and reducing the noise. Our new technique identifies contact forces with only a 1% uncertainty, five times better than prior work. We demonstrate the utility of our technique by examining the normal modes of the droplet contact network in our samples.

  1. HYDROGEL TRACER BEADS: THE DEVELOPMENT, MODIFICATION, AND TESTING OF AN INNOVATIVE TRACER FOR BETTER UNDERSTANDING LNAPL TRANSPORT IN KARST AQUIFERS

    SciTech Connect

    Amanda Laskoskie, Harry M. Edenborn, and Dorothy J. Vesper

    2012-01-01

    The goal of this specific research task is to develop proxy tracers that mimic contaminant movement to better understand and predict contaminant fate and transport in karst aquifers. Hydrogel tracer beads are transported as a separate phase than water and can used as a proxy tracer to mimic the transport of non-aqueous phase liquids (NAPL). They can be constructed with different densities, sizes & chemical attributes. This poster describes the creation and optimization of the beads and the field testing of buoyant beads, including sampling, tracer analysis, and quantitative analysis. The buoyant beads are transported ahead of the dissolved solutes, suggesting that light NAPL (LNAPL) transport in karst may occur faster than predicted from traditional tracing techniques. The hydrogel beads were successful in illustrating this enhanced transport.

  2. Mechanism of slugging in gas-solid fluidized beds with large particles

    SciTech Connect

    Puncochar, M.; Drahos, J.; Cermak, J.

    1988-01-01

    Slugging is an effect encountered frequently in fluidization. Bubbles in fluidized bed grow larger as they rise through the bed and slugging occurs if the bubble size approaches bed diameter. Prediction of the onset of slugging is of great importance as the mass and heat transfer in slugging bed differ considerably from those in bubbling or turbulent regimes of fluidization. A new dynamic model describing the mechanism of slugging in gas-solid fluidized bed of large particles is proposed in this paper. The model is based on a simplified form of Newton's law of motion which is applied to the process of compression of a plug or solid particles. Three kinds of forces are considered: buoyant, gravity, and shear force between particles and wall. The onset of slugging is defined as a point at which upward (buoyant) and downward (gravity and shear) forces are in equilibrium and no additional compression of the plug is possible.

  3. Investigation of the free flow electrophoretic process. Volume 2: Technical analysis

    NASA Technical Reports Server (NTRS)

    Weiss, R. A.; Lanham, J. W.; Richman, D. W.; Walker, C. D.

    1979-01-01

    The effect of gravity on the free flow electrophoretic process was investigated. The demonstrated effects were then compared with predictions made by mathematical models. Results show that the carrier buffer flow was affected by gravity induced thermal convection and that the movement of the separating particle streams was affected by gravity induced buoyant forces. It was determined that if gravity induced buoyant forces were included in the mathematical models, then effective predictions of electrophoresis chamber separation performance were possible. The results of tests performed using various methods of electrophoresis using supportive media show that the mobility and the ability to separate were essentially independent of concentration, providing promise of being able to perform electrophoresis with higher inlet concentrations in space.

  4. A comparison between laboratory and numerical simulations of gravity-driven coastal currents with a geostrophic theory

    NASA Astrophysics Data System (ADS)

    Gregorio, Sandy; Thomas, Peter; Haidvogel, Dale; Taskinoglu, Ezgi; Skeen, Andrew

    2011-11-01

    Laboratory and numerical simulations of buoyant, gravity-driven coastal currents are summarized and compared to the inviscid geostrophic theory of Thomas & Linden 2007. The lengths, widths and velocities of the buoyant currents are studied. Agreement between the laboratory and numerical experiments and the geostrophic theory is found to depend on two non-dimensional parameters which characterize, respectively, the steepness of the plumes isopycnal interface and the strength of horizontal viscous forces (quantified by the horizontal Ekman number). The best agreement between experiments (both laboratory and numerical) and the geostrophic theory are found for the least viscous flows. At elevated values of the horizontal Ekman number, laboratory and numerical experiments depart more significantly from theory. MEOM/LEGI from the 1st of October 2011.

  5. The influence of variable physical properties and buoyancy on heat exchanger design for near- and supercritical conditions

    Microsoft Academic Search

    M. van der Kraan; M. M. W. Peeters; M. V. Fernandez Cid; G. F. Woerlee; W. J. T. Veugelers; G. J. Witkamp

    2005-01-01

    Computational fluid dynamics simulations were done on heated supercritical carbon dioxide flowing up or down in a vertical pipe. The impairment or enhancement of heat transfer caused by the temperature-induced variation of physical properties was investigated, as well as the effect of buoyancy. The simulations show, for non-buoyant flow, that for pressures above 120bar, the effect of variation in physical

  6. Holographic analysis of three-dimensional inertial migration of spherical particles in micro-scale pipe flow

    Microsoft Academic Search

    Yong-Seok Choi; Sang-Joon Lee

    2010-01-01

    The inertial migration of neutrally buoyant spherical particles suspended in a micro-scale pipe flow was investigated in a\\u000a Reynolds number range of 1.6 ? Re ? 77.4. A microtube, 350 ?m in diameter, was used for the micro-scale pipe flow, and the ratios of the tube diameter (D) to the particle diameter (d) were D\\/d = 50, 23, and 12. The three-dimensional positions of the particles were

  7. Thermal Effects on the "Ice-Cube Puzzle"

    ERIC Educational Resources Information Center

    Lima, F. M. S.; Monteiro, F. F.

    2012-01-01

    When an ice cube floating on water in a container melts, it is said in some textbooks that the water level does not change. However, as pointed out by Lan in a recent work, when the buoyant force from a less dense fluid resting above the waterline is taken into account, one should expect a detectable "increase" in the volume of water. Here in this…

  8. Thunderstorm influence on boundary layer winds 

    E-print Network

    Schmidt, Jill Marie

    1986-01-01

    layer and raindrops rapidly evaporate. The latent heat of evaporation cools the mixed air maKing it colder than its environment and thus, negatively buoyant, enhancing the downward movement of a now drier downdraft. Hjelmfelt ( 1984), examining two... the weaker outflows and the other described the stronger outflows. Six significant ambient conditions contributed to the thunderstorm building process, i. e. , I) horizontal moisture convergence below cloud base, B) vertical flux divergence of latent heat...

  9. Three-dimensional structure in a tidal convergence front

    Microsoft Academic Search

    David M. Farmer; Eric A. D'Asaro; Mark V. Trevorrow; Geoffry T. Dairiki

    1995-01-01

    Lagrangian measurements of the structure of a tidal convergence zone were made in Haro Strait, on the western boundary of the U.S. and Canada. Acoustic imaging of the ocean surface from below was used in combination with a sub-surface, acoustically tracked, neutrally buoyant float and several CTDs. Generally, regions of high acoustic back-scatter were correlated with surface convergence and downwelling,

  10. A New Test Method for Material Flammability Assessment in Microgravity and Extraterrestrial Environments

    NASA Technical Reports Server (NTRS)

    Olson, S. L.; Beeson, H. D.; Haas, J. P.; Baas, J. S.

    2004-01-01

    The objective of this research is to modify the well-instrumented standard cone configuration to provide a reproducible bench-scale test environment that simulates the buoyant or ventilation flow that would be generated by or around a burning surface in a spacecraft or extraterrestrial gravity level. We will then develop a standard test method with pass-fail criteria for future use in spacecraft materials flammability screening. (For example, dripping of molten material will be an automatic fail.)

  11. Lattice Boltzmann algorithm for surface tension with greatly reduced microcurrents.

    PubMed

    Lishchuk, S V; Care, C M; Halliday, I

    2003-03-01

    We present an algorithm for inserting an interface between the immiscible phases of a multicomponent lattice Boltzmann fluid which is based solely upon the appropriate continuum physics: stress boundary conditions and continuity of velocity. Results are presented for the algorithm when applied to static, neutrally buoyant drops. It is shown that the present algorithm gives a significant reduction in the spurious velocities which are reported for previous schemes and a concomitant improvement in the isotropy of the interface. PMID:12689196

  12. An aerobot for global in situ exploration of Titan

    Microsoft Academic Search

    J. L. Hall; V. V. Kerzhanovich; A. H. Yavrouian; J. A. Jones; C. V. White; B. A. Dudik; G. A. Plett; J. Mennella; A. Elfes

    2006-01-01

    This paper describes the design and component testing of an aerobot that would be capable of global in situ exploration of Saturn’s moon, Titan, over a 6–12 month mission lifetime. The proposed aerobot is a propeller-driven, buoyant vehicle that resembles terrestrial airships. However, the extremely cold Titan environment requires the use of cryogenic materials of construction and careful thermal design

  13. Ceiling Jet-Driven Wall Flows in Compartment Fires

    Microsoft Academic Search

    LEONARD Y. COOPER

    1988-01-01

    Analytic estimates are developed for depth of penetration and lateral entrainment of negatively buoyant, ceiling jet-driven wall flows during early times of compartment fire scenarios. When walls are not too far from the fire source of the order of the fire-to-ceiling distance, it is found that the penetration of these downward wall flows is a large fraction of the fire-to-ceiling

  14. On modelling combustion, radiation and soot processes in compartment fires

    Microsoft Academic Search

    G. H. Yeoh; R. K. K. Yuen; S. C. P. Chueng; W. K. Kwok

    2003-01-01

    A Reynolds-Averaging-Navier–Stokes Computational-Fluid-Dynamics-based fire model is developed to solve a turbulent buoyant fire in a single-, two- and multi-compartment structure. The model is evaluated as part of a complete prediction procedure involving the modelling of the simultaneously occurring flow, convection, combustion, soot generation and burnout and radiation phenomena. Computational results are compared against available experimental data. Proper handling of the

  15. Ceiling jet-driven wall flows in compartment fires

    Microsoft Academic Search

    L. Y. Cooper

    1987-01-01

    Analytic estimates are developed for the early depth of penetration of and the lateral entrainment into negatively buoyant, ceiling jet-driven wall flows which are generic to compartment fire scenarios. When walls are not too far from the fire source, of the order of the fire-to-ceiling distance, it is found that the penetration of the downward flow near such walls is

  16. The Columbia River Plume Study: Subtidal variability in the velocity and salinity fields

    Microsoft Academic Search

    B. M. Hickey; L. J. Pietrafesa; D. A. Jay; W. C. Boicourt

    1998-01-01

    A comprehensive study of the strongly wind driven midlatitude buoyant plume from the Columbia River, located on the U.S. west coast, demonstrates that the plume has two basic structures during the fall\\/winter season, namely, a thin (---5-15 m), strongly stratified plume tending west to northwestward during periods of southward or light northward wind stress and a thicker (---10-40 m), weakly

  17. Revaluation of the role of cholesterol in stabilizing rafts implicated in T cell receptor signaling

    Microsoft Academic Search

    Alexandre K. Rouquette-Jazdanian; Claudette Pelassy; Jean-Philippe Breittmayer; Claude Aussel

    2006-01-01

    T lymphocytes contain two kinetic pools of cholesterol extractable with methyl-?-cyclodextrin (m-?-CD): a fast pool (31.5%, t1\\/2=17 s) and a slow pool (68.5%, t1\\/2=15 min). Purification of detergent-resistant membranes (DRMs) shows that the fast pool corresponds to buoyant cholesterol. Cholesterol extraction of the fast pool (i.e. cholesterol from rafts) still allows the buoyancy of signaling proteins and their phosphorylation under

  18. Zn-Pb-Cu massive sulfide deposits: Brine-pool types occur in collisional orogens, black smoker types occur in backarc and\\/or arc basins

    Microsoft Academic Search

    Michael Solomon; Cecilio Quesada

    2003-01-01

    Volcanic-hosted, massive sulfide deposits of Zn-Pb-Cu type were derived either from seawater-dominated, buoyant fluids that built mounds on the seafloor, e.g., the ores of the Hokuroku Basin, Japan, or from saline fluids that reversed buoyancy on mixing with seawater and filled basins on the seafloor, e.g., several ores of the Iberian pyrite belt and the Mount Read province in Tasmania.

  19. Bobble-Heated Cooling Flows

    Microsoft Academic Search

    Eugene Churazov; Hans Böhringer; Marcus Brüggen; William Forman; Christine Jones; Christian Kaiser; Rashid Sunyaev

    2002-01-01

    We speculate on the possibility that radiative energy losses of the gas in cooling flows are balanced by the (mechanical)\\u000a energy input from a central supermassive black hole. We argue that the efficiency of the mechanical energy dissipation can\\u000a be high even in the absence of strong shocks. A qualitative picture of a cooling flow heated by buoyant bubbles is

  20. Photoassisted oxidation of oil films on water. Final performance report, January 1, 1990--March 31, 1993

    SciTech Connect

    Heller, A.

    1994-04-19

    The objective of the project has been the development of a technology for cleaning up oil spills on water through their photocatalytic oxidation. The photocatalyst used was titanium dioxide. Nanocrytalline TiO{sub 2}, of anatase or anatase/rutile phase, was bound to hollow ceramic microspheres of sufficiently low density to be buoyant on water. In the presence of these, under sunlight, oil films were photocatalytically oxidized by dissolved oxygen.

  1. Orbital Processing of High-Quality Zn-Alloyed CdTe Compound Semiconductors

    NASA Technical Reports Server (NTRS)

    Larson, David J., Jr.; Dudley, M.; Raghothamachar, B.; Alexander, J. I. D.; Carlson, F. M.; Gillies, D.; Volz, M.; Ritter, T. M.; DiMarzio, D.

    1999-01-01

    The objective of this research is to investigate the influences of gravitationally-dependent phenomena (hydrostatic and buoyant) on the growth and quality of doped and alloyed Cadmium-Zinc-Telluride (CdZnTe) crystals grown by the modified seeded Bridgman-Stockbarger technique. It is hypothesized that the damping of the gravitationally-dependent buoyancy convection will substantially enhance chemical homogeneity and the near-elimination of hydrostatic pressure will enable significant reduction in defect (dislocations and twins) density.

  2. Buoyancy is the primary source of generating bodyroll in front-crawl swimming.

    PubMed

    Yanai, Toshimasa

    2004-05-01

    The present study was conducted to determine the contribution of the turning effect of buoyant force for generating bodyroll and its relationship with the subjects' variability in swimming speed at distance pace and sub-maximal sprinting pace. The performances of front crawl swimming performed by 11 skilled swimmers were recorded with two panning periscopes for three-dimensional analysis. The bodyroll (BR) exhibited by each of the 11 male competitive swimmers was determined for every given instant as the time-integral of the conceptual angular velocity of the entire body about the long-axis, which was computed from the angular momentum and the moment of inertia of entire body. The part of BR generated by the buoyancy torque (BR(BT)) was determined from the moment of inertia of the entire body and the double time-integral of the buoyancy torque. The mean value for the peak-to-peak amplitude of the buoyancy torque was 15 Nm at distance pace and 19 Nm at sub-maximum sprinting speed. The contribution of buoyancy to BR was significantly greater ( P < 0.01) than that of the hydrodynamic forces. The individual swimming speed at sub-maximal sprinting pace was positively correlated ( P < 0.04) with the contribution of buoyancy to BR. These results showed that the skilled swimmers used buoyant force as the primary source of generating BR, and that faster swimmers used buoyant force more effectively to generate BR than slower swimmers. Based on the results and subsequent theoretical analysis, possible patterns of arm-BR coordination that may increase the effectiveness of using buoyant force for BR are discussed. PMID:15046989

  3. Non-Archimedean character of quantum buoyancy and the generalized second law of thermodynamics

    Microsoft Academic Search

    Jacob D. Bekenstein

    1999-01-01

    Quantum buoyancy has been proposed as the mechanism protecting the\\u000ageneralized second law when an entropy--bearing object is slowly lowered\\u000atowards a black hole and then dropped in. We point out that the original\\u000aderivation of the buoyant force from a fluid picture of the acceleration\\u000aradiation is invalid unless the object is almost at the horizon, because\\u000aotherwise typical

  4. Convective CO2 dissolution: Analog experiments and direct numerical simulations

    Microsoft Academic Search

    J. A. Neufeld; M. A. Hesse; A. Riaz; H. A. Tchelepi; H. E. Huppert

    2009-01-01

    Geological carbon capture and storage, in which CO2 is injected into deep saline aquifers for permanent storage, forms an integral part of the CO2 mitigation strategies. At representative conditions CO2 is buoyant and therefore may leak into surface waters or the atmosphere. A possible route to stable CO2 storage is through convective dissolution of CO2 into the ambient brine; the

  5. Distribution of Covalent DNA Adducts in Mouse Epidermal Subpopulations after Topical Application of Benzo(a)pyrene and 7,12-Dimethylbenz(a)anthracene

    Microsoft Academic Search

    Wanda Baer-Dubowska; Rebecca J. Morris; Rosalynn D. Gill; John DiGiovanni

    1990-01-01

    The distribution of benzo(a)pyrene |B(a)P| and 7,12-dimethyl- benz(a)anthracene (DMBA):DNA adducts was examined in five different subpopulations of SENCAR mouse epidermal cells separated based on buoyant density in continuous gradients of 61.5% Percoli. Three fractions consisted of primarily basal cells (Fractions 3 to 5), while two less dense fractions (Fractions 1 and 2) consisted of primarily differentiating kera- tinocytes. The levels

  6. Rayleigh-Taylor Turbulence is Nothing Like Kolmogorov Turbulence in the Self-Similar Regime

    SciTech Connect

    Poujade, Olivier [Commissariat a l'Energie Atomique, BP12, Bruyeres-le-Cha circumflex tel, 91168 (France)

    2006-11-03

    An increasing number of numerical simulations and experiments describing the turbulent spectrum of Rayleigh-Taylor (RT) mixing layers came to light over the past few years. Results reported in recent studies allow to rule out a Kolmogorov-like turbulence as a mechanism acting on a self-similar RT turbulent mixing layer. A different mechanism is presented, which complies with both numerical and experimental results and relates RT flow to other buoyant flows.

  7. The plastome of a brown alga, Dictyota dichotoma

    Microsoft Academic Search

    M. Kuhsel; K. V. Kowallik

    1985-01-01

    Summary  Plastids of the brown algaDictyota dichotoma contain a single homogeneous DNA species which bands at a buoyant density of 1.693 g\\/cm3 in neutral CsCl equilibrium density gradients. The corresponding nuclear DNA has a density of 1.715 g\\/cm3. The molecular size of the plastid DNA is 123 kbp as calculated by both electron microscopy of spread intact circular molecules\\u000a and gel

  8. Visualization of convection loops due to Rayleigh–Benard convection during solidification

    Microsoft Academic Search

    Pramod Kumar; Kandadai Srinivasan; Pradip Dutta

    2006-01-01

    This paper describes the techniques adopted for visualization of Rayleigh–Benard convection during solidification of eutectic, hypo- and hyper-eutectic salt solutions. Neutrally buoyant hollow glass spheres were inducted in the body of the solidifying salt solution. The convection currents were captured by scattering of a laser beam by these beads. The apparatus has two components, namely: (i) measurement of interface\\/mushy region

  9. Isolation and characterization of bacteriophage BCJA1, a novel temperate bacteriophage active against the alkaliphilic bacterium, Bacillus clarkii

    Microsoft Academic Search

    Ken F. Jarrell; Tatiana Vydykhan; Peter Lee; M. Dorothy Agnew; Nikhil A. Thomas

    1997-01-01

    The isolation and characterization of a novel bacteriophage active against the obligately alkaliphilic bacterium Bacillus clarkii is described. The bacteriophage, designated BCJA1, is a member of the Siphoviridae family with a B1 morphology. It possesses\\u000a an isometric head, which measures 65 nm between opposite apices, and a noncontractile tail of 195 nm length. It had a buoyant\\u000a density of 1.518

  10. Particle trajectory simulation of dispersion around a building

    Microsoft Academic Search

    Giovanni Leuzzi; Paolo Monti

    1998-01-01

    Lagrangian stochastic (LS) models have shown to be a powerful technique to calculate pollutant dispersion in complex flows. In this work, a three-dimensional LS model of dispersion has been tested by means of a comparison with EPA wind-tunnel observations of a buoyant plume in the vicinity of a building (Snyder, 1992, FMF Internal Report, U.S. Environmental Protection Agency, Research Triangle

  11. A model for the origin of large silicic magma chambers: precursors of caldera-forming eruptions

    Microsoft Academic Search

    A. Mark Jellinek; Donald J. DePaolo

    2003-01-01

    The relatively low rates of magma production in island arcs and continental extensional settings require that the volume of silicic magma involved in large catastrophic caldera-forming (CCF) eruptions must accumulate over periods of 10 5 to 10 6 years. We address the question of why buoyant and otherwise eruptible high-silica magma should accumulate for long times in shallow chambers rather than

  12. Rayleigh-Taylor Turbulence is Nothing Like Kolmogorov Turbulence in the Self-Similar Regime

    NASA Astrophysics Data System (ADS)

    Poujade, Olivier

    2006-11-01

    An increasing number of numerical simulations and experiments describing the turbulent spectrum of Rayleigh-Taylor (RT) mixing layers came to light over the past few years. Results reported in recent studies allow to rule out a Kolmogorov-like turbulence as a mechanism acting on a self-similar RT turbulent mixing layer. A different mechanism is presented, which complies with both numerical and experimental results and relates RT flow to other buoyant flows.

  13. Rayleigh-Taylor turbulence is nothing like Kolmogorov turbulence in the self-similar regime.

    PubMed

    Poujade, Olivier

    2006-11-01

    An increasing number of numerical simulations and experiments describing the turbulent spectrum of Rayleigh-Taylor (RT) mixing layers came to light over the past few years. Results reported in recent studies allow to rule out a Kolmogorov-like turbulence as a mechanism acting on a self-similar RT turbulent mixing layer. A different mechanism is presented, which complies with both numerical and experimental results and relates RT flow to other buoyant flows. PMID:17155550

  14. Preparation of gravimetric standards for measurements of atmospheric oxygen and reevaluation of atmospheric oxygen concentration

    Microsoft Academic Search

    Yasunori Tohjima; Toshinobu Machida; Tomonori Watai; Isao Akama; Taketo Amari; Yasushi Moriwaki

    2005-01-01

    Fourteen standard mixtures composed of ambient levels of CO2, Ar, O2, and N2 have been prepared in 10-L high-pressure aluminum cylinders by a gravimetric technique for atmospheric O2 measurements. A highly precise balance with a precision of 2.5 mg is used to determine the masses of individual components in the cylinders. To balance the buoyant forces on both sides of

  15. Volatile Transport by Volcanic Plumes on Earth, Venus and Mars

    NASA Technical Reports Server (NTRS)

    Glaze, Lori S.; Self, Stephen; Baloga, Steve; Stofan, Ellen R.

    2012-01-01

    Explosive volcanic eruptions can produce sustained, buoyant columns of ash and gas in the atmosphere (Fig. 1). Large flood basalt eruptions may also include significant explosive phases that generate eruption columns. Such eruptions can transport volcanic volatiles to great heights in the atmosphere. Volcanic eruption columns can also redistribute chemical species within the atmosphere by entraining ambient atmosphere at low altitudes and releasing those species at much higher altitudes.

  16. Captive Water Current Power System

    SciTech Connect

    Wuenscher, H. F.; Wuenscher, H. A.

    1984-01-31

    Current energy is converted into shaft power in two stages; First, buoyant power units with stationary hydrofoil wings reach faster than the current speed by sweeping out a captive path. Second, turbines at said power units convert the fast relative local current into shaft power. Power units sweeping along the water surface, using cycloidal turbine methods, as well as power units sweeping on a submerged path, using axial flow turbine methods, are described.

  17. Acoustic imaging of hydrothermal plumes. East Pacific rise, 21°N, 109°W

    Microsoft Academic Search

    P. A. Rona; D. R. Palmer; C. Jones; D. A. Chayes; M. Czarnecki; E. W. Carey; J. C. Guerrero

    1991-01-01

    We report the first observations based on acoustic imaging of large-scale structure and time variability of buoyant plumes emanating from black smoker-type seafloor hot springs. Three-dimensional plume reconstructions were made from a digital data set of acoustic backscattering information recorded on a prototype submersible-mounted sonar system. The acoustic images of two adjacent black smokers depict volume and show zones of

  18. Acoustic imaging of hydrothermal plumes, East Pacific Rise, 21°N, 109°W

    Microsoft Academic Search

    P. A. Rona; D. R. Palmer; C. Jones; D. A. Chayes; M. Czarnecki; E. W. Carey; J. C. Guerrero

    1991-01-01

    We report the first observations based on acoustic imaging of large-scale structure and time variability of buoyant plumes emanating from black smoker-type seafloor hot springs. Three-dimensional plume reconstructions were made from a digital data set of acoustic backscattering information recorded on a prototype submersible-mounted sonar system. The acoustic images of two adjacent black smokers depict volume and show zones of

  19. Sphingomyelin-enriched Microdomains at the Golgi Complex

    Microsoft Academic Search

    Ioannis Gkantiragas; Britta Brugger; Ernstpeter Stuven; Dora Kaloyanova; Xue-Yi Li; Kristina Lohr; Friedrich Lottspeich; Felix T. Wieland; J. Bernd Helms

    2001-01-01

    Sphingomyelin- and cholesterol-enriched microdomains can be isolated as detergent-resistant membranes from total cell extracts (total-DRM). It is generally believed that this total-DRM represents microdomains of the plasma membrane. Here we describe the purification and detailed characterization of microdomains from Golgi membranes. These Golgi-derived detergent-insolu- ble complexes (GICs) have a low buoyant density and are highly enriched in lipids, containing 25%

  20. Stability Analysis of Large-Scale Incompressible Flow Calculations on Massively Parallel Computers

    SciTech Connect

    LEHOUCQ,RICHARD B.; ROMERO,LOUIS; SALINGER,ANDREW G.

    1999-10-25

    A set of linear and nonlinear stability analysis tools have been developed to analyze steady state incompressible flows in 3D geometries. The algorithms have been implemented to be scalable to hundreds of parallel processors. The linear stability of steady state flows are determined by calculating the rightmost eigenvalues of the associated generalize eigenvalue problem. Nonlinear stability is studied by bifurcation analysis techniques. The boundaries between desirable and undesirable operating conditions are determined for buoyant flow in the rotating disk CVD reactor.