bluuebunny/crossref_metadata_2025 huggingface dataset:
Caenorhabditis elegans metallothionein isoform specificity – metal binding abilities and the role of histidine in CeMT1 and CeMT2
Authors: Bofill Roger , Orihuela Rubén , Romagosa Míriam , Domènech Jordi , Atrian Sílvia , Capdevila Mercè
Published: October 2009

Two metallothionein (MT) isoforms have been identified in the model nematode Caenorhabditis elegans: CeMT1 and CeMT2, comprising two polypeptides that are 75 and 63 residues in length, respectively. Both isoforms encompass a conserved cysteine pattern (19 in CeMT1 and 18 in CeMT2) and, most significantly, as a result of their coordinative potential, CeMT1 includes four histidines, whereas CeMT2 has only one. In the present study, we present a comprehensive and comparative analysis of the metal [Zn(II), Cd(II) and Cu(I)] binding abilities of CeMT1 and CeMT2, performed through spectroscopic and spectrometric characterization of the recombinant metal–MT complexes synthesized for wild‐type isoforms (CeMT1 and CeMT2), their separate N‐ and C‐terminal moieties (NtCeMT1, CtCeMT1, NtCeMT2 and CtCeMT2) and a ΔHisCeMT2 mutant. The corresponding in vitro Zn/Cd‐ and Zn/Cu‐replacement and acidification/renaturalization processes have also been studied, as well as protein modification strategies that make it possible to identify and quantify the contribution of the histidine residues to metal coordination. Overall, the data obtained in the present study are consistent with a scenario where both isoforms exhibit a clear preference for divalent metal ion binding, rather than for Cu coordination, although this preference is more pronounced towards cadmium for CeMT2, whereas it is markedly clearer towards Zn for CeMT1. The presence of histidines in these MTs is revealed to be decisive for their coordination performance. In CeMT1, they contribute to the binding of a seventh Zn(II) ion in relation to the M(II)6–CeMT2 complexes, both when synthesized in the presence of supplemented Zn(II) or Cd(II). In CeMT2, the unique C‐terminal histidine abolishes the Cu‐thionein character that this isoform would otherwise exhibit.
Contested Identities: Nationalism, Regionalism, and Patriotism in Early American Textbooks
Authors: Nash Margaret A.
Published: October 2009

Immediately after the American Revolution, the founders set about the task of ensuring the continued existence of the fledgling republic. Facing a host of problems—economic, social, and governmental—some founders promoted a concept of schooling that would inculcate patriotism and forge a uniquely American identity. Noah Webster wanted to create an American language, and Benjamin Rush wanted schools to “convert men into republican machines.” Webster, Rush, Thomas Jefferson, and others all wanted to use some version of common schooling to instill in children a sense of nationalism. Textbooks used in these common schools would be a likely way to further promote a sense of American identity. What that identity should be, though, and what the “good citizen” of the new republic should look like, was sharply contested, and textbooks of this period reflect many of the fissures in the work of nation building.
Prothrombotic and Inflammatory Effects of Intravenous Administration of Human Immunoglobulin G in Dogs
Authors: Tsuchiya R. , Akutsu Y. , Ikegami A. , Scott M.A. , Neo S. , Ishikawa T. , Hisasue M. , Yamada T.
Published: October 2009

Background:Intravenous administration of human immunoglobulin G (hIVIgG) has been suggested to potentiate thromboembolism in dogs, but supportive scientific reports are lacking.

Objectives:To determine if hIVIgG therapy promotes hypercoagulability and inflammation in dogs.

Animals:Twelve healthy Beagle dogs.

Methods:Prospective, experimental trial. An hIVIgG/saline solution was infused IV at 1 g/kg BW over 8 hours to 6 dogs, and physiological saline was infused to the other 6 dogs. Blood samples were drawn before, during, and after infusion for serial measurement of indicators of coagulation and inflammation. Data were analyzed by 2‐way repeated measures analysis of variance.

Results:Dogs administered hIVIgG developed mildly decreased blood platelet concentrations without thrombocytopenia (median, 200 × 103/μL; range, 150–302 × 103/μL;P< .01), leukopenia (median, 3.5 × 103/μL; range, 20–62 × 103/μL;P< .001), and mildly increased plasma total protein concentrations (median, 6.3 g/dL; range, 5.6–6.7 g/dL;P< .001). Administration of hIVIgG was also associated with increases in fibrin/fibrinogen degradation products in all dogs (either 5 μg/mL or 10 μg/dL), thrombin‐antithrombin III complexes (median, 7.2 ng/mL; range, 4.9–14.2 ng/mL;P< .001), and C‐reactive protein concentrations (median, 2.5 mg/dL; range, 0.5–4.3 mg/dL;P< .01).

Conclusion and Clinical Importance:Administration of hIVIgG to dogs promotes hypercoagulability and an inflammatory state. This should be further evaluated and considered when using hIVIgG in dogs with IMHA or other prothrombotic conditions.
Differential induction of bidirectional long‐term changes in neurotransmitter release by frequency‐coded patterns at the cerebellar input
Authors: D’Errico Anna , Prestori Francesca , D'Angelo Egidio
Published: October 2009

Sensory stimulation conveys spike discharges of variable frequency and duration along the mossy fibres of cerebellum raising the question of whether and how these patterns determine plastic changes at the mossy fibre–granule cell synapse. Although various combinations of high‐frequency bursts and membrane depolarization can induce NMDA receptor‐dependent long‐term depression (LTD) and long‐term potentiation (LTP), the effect of different discharge frequencies remained unknown. Here we show that low‐frequency mossy fibre stimulation (100 impulses−1 Hz) induces mGlu receptor‐dependent LTD. For various burst frequencies, the plasticity–[Ca2+]i relationship was U‐shaped resembling the Bienenstok–Cooper–Munro (BCM) learning rule. Moreover, LTD expression was associated with increased paired‐pulse ratio, coefficient of variation and failure rate, and with a decrease in release probability, therefore showing changes opposite to those characterizing LTP. The plasticity–[Ca2+]i relationship and the changes in neurotransmitter release measured by varying induction frequencies were indistinguishable from those obtained by varying high‐frequency burst duration. These results suggest that different glutamate receptors converge onto a final common mechanism translating the frequency and duration of mossy fibre discharges into a regulation of the LTP/LTD balance, which may play an important role in adapting spatio‐temporal signal transformations at the cerebellar input stage.
Relationship between plasma free fatty acid, intramyocellular triglycerides and long‐chain acylcarnitines in resting humans
Authors: Kanaley Jill A. , Shadid Samyah , Sheehan Michael T. , Guo ZengKui , Jensen Michael D.
Published: October 2009

We hypothesized that plasma non‐esterified fatty acids (NEFA) are trafficked directly to intramyocellular long‐chain acylcarnitines (imLCAC) rather than transiting intramyocellular triglycerides (imTG) on the way to resting muscle fatty acid oxidation. Overnight fasted adults (n= 61) received intravenous infusions of [U‐13C]palmitate (0400–0830 h) and [U‐13C]oleate (0800–1400 h) labelling plasma NEFA, imTG, imLCAC and im‐non‐esterified FA (imNEFA). Two muscle biopsies (0830 and 1400 h) were performed following 6 h, overlapping, sequential palmitate/oleate tracer infusions. Enrichment of plasma palmitate was ∼15 times greater than enrichment of imTG, imNEFA‐palmitate and im‐palmitoyl‐carnitine. Fatty acid enrichment in LCAC was correlated with imTG and imNEFA; there was a significant correlation between imTG concentrations and imLCAC concentrations in women (r= 0.51, P= 0.005), but not men (r= 0.30, P= 0.11). We estimated that ∼11% of NEFA were stored in imTG. imTG NEFA storage was correlated only with NEFA concentrations (r= 0.52, P= 0.004) in women and with (r= 0.45, P= 0.02) in men. At rest, plasma NEFA are trafficked largely to imTG before they enter LCAC oxidative pools; thus, imTG are an important, central pool that regulates the delivery of fatty acids to the intracellular environment. Factors relating to plasma NEFA storage into imTG differ in men and women.
Synaptically induced sodium signals in hippocampal astrocytes in situ
Authors: Langer Julia , Rose Christine R.
Published: October 2009

Astrocytes are in close contact to excitatory synapses and express transporters which mediate the sodium‐dependent uptake of glutamate. In cultured astrocytes, selective activation of glutamate transport results in sodium elevations which stimulate Na+/K+‐ATPase and glucose uptake, indicating that synaptic release of glutamate might couple excitatory neuronal activity to glial sodium homeostasis and metabolism. Here, we analysed intracellular sodium transients evoked by synaptic stimulation in acute mouse hippocampal slices using quantitative sodium imaging with the sodium‐sensitive fluorescent indicator dye SBFI (sodium‐binding benzofuran isophthalate). We found that short bursts of Schaffer collateral stimulation evoke sodium transients in the millimolar range in both CA1 pyramidal neurons and in SR101‐positive astrocytes of the stratum radiatum. At low stimulation intensities, glial sodium transients were confined to one to two primary branches and adjacent fine processes and only weakly invaded the soma. Increasing the number of activated afferent fibres by increasing the stimulation intensity elicited global sodium transients detectable in the processes as well as the somata of astrocytes. Pharmacological analysis revealed that neuronal sodium signals were mainly attributable to sodium influx through ionotropic glutamate receptors. Activation of ionotropic receptors also contributed to glial sodium transients, while TBOA‐sensitive glutamate transport was the major pathway responsible for sodium influx into astrocytes. Our results thus establish that glutamatergic synaptic transmission in the hippocampus results in sodium transients in astrocytes that are mainly mediated by activation of glutamate transport. They support the proposed link between excitatory synaptic activity, glutamate uptake and sodium signals in astrocytes of the hippocampus.
An Analysis of Uniform Shear Flow Past a Porous Plate Attached to a Plane Surface
Authors: Kiya M. , Arie M. , Koshikawa K.
Published: October 2009

The wake-source model of Koo and James was extended to the case of a two-dimensional porous plate attached to a plane surface along which a turbulent boundary layer developed. The approaching stream is replaced by a uniform shear flow of linearly-varying velocity profile such that the height of the plate is much smaller than the boundary-layer thickness. The theory requires as input the pressure-drop coefficient of the porous plate and the boundary-layer velocity profile at an appropriate location upstream of the plate.
Multidimensional Fluid Transients by Latticework
Authors: Wylie E. B. , Streeter V. L.
Published: October 2009

An evaluation of a discretized method of analysis for low-velocity two and three-dimensional transient fluid-flow problems is presented. The method assumes the continuum can be represented by a latticework of flow elements and that the physical response in the continuum can be determined by solving the one-dimensional transient flow equations in the line elements. The approach is explained, and validated by presenting comparisons between numerical and analytical hydrodynamic solutions.
Shear Layer Transition and the Sharp-Edged Orifice
Authors: Clark J. A. , Kit Lam
Published: October 2009

The present experiments provide information about free shear layer transition to turbulence and the associated three-dimensional behavior patterns of vortex growth and breakdown. The free shear layers of a submerged jet were generated from two-dimensional sharp-edged orifices. Two distinct types of growth patterns, namely, the twisting growth pattern and the interlocking growth pattern were observed. The interaction phenomena of these vortex tubes are hypothesized to be associated with mutual induction. Quantitative data of exit central velocity, pre-coalescent wavelength between consecutive vortices, and vortex shedding frequency were measured and the interrelationships of Strouhal number, Reynolds number and the dimensionless convection velocity of vortices are discussed.
Review—Bluff Body Flows Applicable to Vehicle Aerodynamics
Authors: Bearman P. W.
Published: October 2009

This paper attempts to review those aspects of bluff body aerodynamics that are relevant to the understanding of vehicle flows. Vehicles often have complex body shapes and are influenced by the proximity of the ground. The effect of the ground is discussed in some detail and results for bluff bodies mounted in wind tunnels above fixed and moving ground planes are presented. It is concluded that drag is little affected by ground proximity and ground representation whereas lift is often sensitive to both. The effect of slanting the base of a bluff body is discussed and the two main flow regimes that result are described. The influence of the wind on vehicle flows is investigated and it is found that vehicle mean flows are sensitive to the turbulence level in the relative wind. Finally numerical prediction methods are considered.
Straight-Walled, Two-Dimensional Diffusers—Transitory Stall and Peak Pressure Recovery
Authors: Ashjaee J. , Johnston J. P.
Published: October 2009

Straight-walled, two-dimensional diffusers of large aspect ratio were investigated experimentally for the purpose of studying the regime of incipient transitory stall, the location of the geometry of peak diffuser pressure recovery. Twelve symmetric diffusers of constant nondimensional length (L/W1 = 15) with total included angles ranging from 4 to 24 degrees, covering attached, intermittently detaching, and unsteady detached flows were examined. Tests were run at one inlet blockage, 2δ1 / W1 = 0.027, and at an inlet Reynolds number of U1 W1/ν = 2.2 × 105 with air flow at low inlet Mach number. Pressure recovery and flow direction intermittency were obtained along the diffuser walls. An objective comparison of the UIM method of Ghose and Kline and an improved prediction method [Appendix] was performed with respect to these new experimental data. Some new conclusions are drawn concerning the nature of the flow in the vicinity of peak pressure recovery.
Effect of Wake-Type Nonuniform Inlet Velocity Profiles on First Appreciable Stall in Plane-Wall Diffusers
Authors: Kaiser K. F. , McDonald A. T.
Published: October 2009

The combustor diffuser in a gas turbine engine must accept a high-speed, unsteady, distorted flow from the engine compressor. It must deliver flow to the combustor with minimum loss in total pressure and minimum velocity profile distortion. Both pressure recovery and outlet flow distortion characteristics of diffusers must be considered in design tradeoffs. The purpose of this investigation was to study the effects of nonuniform inlet velocity profiles on the inception of stall in two-dimensional plane-wall diffusers. Centrally-located “wake-type” inlet velocity profiles were chosen to simulate the flow conditions at the inlet of a combustor diffuser. The inlet distortion was characterized by dimensionless wake strength and wake width parameters. The experiments were performed on an open surface water table to make flow visualization possible. A centerline or pocket-type stall, such as previously reported in swirling flows, was observed for sufficiently severe inlet profile distortion. A new definition of first appreciable stall, based on a fraction of the exit area stalled, was introduced to characterize stalls which did not occur on a solid surface.
Analysis of the Three-Dimensional Flow in a Turbine Scroll
Authors: Hamed A. , Baskharone E.
Published: October 2009

The present analysis describes the three dimensional compressible inviscid flow in the scroll and the vaneless nozzle of a radial inflow turbine. The solution to this flow field, which is further complicated by the geometrical shape of the boundaries, is obtained using the finite element method. Symmetric and nonsymmetric scroll cross sectional geometries are investigated to determine their effect on the general flow field and on the exit flow condiitons.
Investigation of a Reattaching Turbulent Shear Layer: Flow Over a Backward-Facing Step
Authors: Kim J. , Kline S. J. , Johnston J. P.
Published: October 2009

Incompressible flow over a backward-facing step is studied in order to investigate the flow characteristics in the separated shear-layer, the reattachment zone, and the redeveloping boundary layer after reattachment. Two different step-heights are used: h/δs = 2.2 and h/δs = 3.3. The boundary layer at separation is turbulent for both cases. Turbulent intensities and shear stress reach maxima in the reattachment zone, followed by rapid decay near the surface after reattachment. Downstream of reattachnent, the flow returns very slowly to the structure of an ordinary turbulent boundary layer. In the reattached layer the conventional normalization of outerlayer eddy viscosity by U∞ δ* does not collapse the data. However, it was found that normalization by U∞ (δ − δ*) does collapse the data to within ± 10% of a single curve as far downstream as x/xR ≈ 2, the last data station. This result illustrates the strong downstream persistence of the energetic turbulence structure created in the separated shear layer.
Aspects of Outflow From Large Vessels
Authors: Kubie J. , Oates H. S.
Published: October 2009

An investigation has been made of flow phenomena associated with outflow from large horizontal cylindrical vessels with a vortex-free outlet on their bottom surface. This paper concentrates on the flow regimes and the variation of the level in the vessels with the flowrate. It is shown, both theoretically and experimentally, that there are two distinct regimes of outflow from the vessel, which are separated by a critical flowrate which is a strong function of the diameter of the outflow orifice. For the flowrates below the critical the level variation does not depend on the diameter of the outflow orifice, but the level variation depends strongly on it for the flowrates above the critical value. A model of transition between the flow regimes is also developed.
Linearized Solutions for the Supersonic Flow Through Turbomachinery Blade Rows (Using Actuator Disk Theory)
Authors: Horlock J. H. , Grainger C. F.
Published: October 2009

An actuator disk method is developed for calculating the flow through the blade rows of a turbomachine in which the velocity relative to the blading may be supersonic. The method is compared with calculations of the fully supersonic flow through a twisted blade row using a three-dimensional method of characteristics.
Three Dimensional Supersonic Flow Through a Cascade of Twisted Flat Plates
Authors: Grainger C. F.
Published: October 2009

The three-dimensional flow through a cascade of twisted flat-plate blades is calculated using a computer program based on a finite-difference approximation to the method of characteristics. The relative flow is supersonic but the axial flow is subsonic. For two-dimensional flow under similar conditions, the inlet flow field is one of “unique-incidence,” the effect discussed by Starken (5) and others. The main purpose of the present work is to extend the understanding of this effect to three-dimensional flow. Important differences between the two and three-dimensional flow fields are explained in terms of the interaction between neighboring sections of the flow.
Theoretical Prediction of Onset of Horizontal Slug Flow
Authors: Mishima Kaichiro , Ishii Mamoru
Published: October 2009

A criterion for the onset of a slug flow in a horizontal duct is derived theoretically. A potential flow analysis is carried out by considering waves of finite amplitude. The stability criterion is obtained by introducing the wave deformation limit and the “most dangerous wave” concept in the stability analysis. The present theoretical criterion for slug formation shows very good agreement with a large number of experimental data and with some empirical correlations.
Numerical Analysis of Turbulent Wakes of Turbomachinery Rotor Blades
Authors: Hah C. , Lakshminarayana B.
Published: October 2009

The wakes of turbomachinery rotor blades are turbulent, three-dimensional, and are subjected to curvature and rotation effects. The objective of this study is to predict the development of such wakes and compare the predictions with the existing data. A finite difference procedure is employed in the numerical analysis of the wake utilizing the continuity, momentum, and turbulence closure equations in the rotating curvilinear and non-orthogonal coordinate system. The turbulence closure is affected by the modified Reynolds stress model. The effects of curvature and rotation on the turbulence structure are accounted for with this turbulence closure model. The pedictions from the present turbulence model agree well with the mean velocity and the turbulence wake data.
Rotational Inviscid Flow in a Variable Area Annulus, Pipe or Channel
Authors: Munson B. R.
Published: October 2009

Theoretical and experimental results concerning rotational inviscid flow in an annulus, pipe or channel of variable cross-section are given. Vorticity and continuity considerations are used to determine the velocity profile downstream from the variable area portion in terms of the velocity profile upstream. The lengthening or shortening of vortex lines alters the vorticity in the flow. Regimes of possible reverse flow and flow separation are obtained. The agreement between the theory and experiment is good.
The Influence of Swirl on the Flow Characteristics of a Reciprocating Piston-Cylinder Assembly
Authors: Morse A. , Whitelaw J. H. , Yianneskis M.
Published: October 2009

Measurements of three orthogonal components of mean velocity and the rms values of the corresponding velocity fluctuations have been obtained by laser-Doppler anemometry in the axisymmetric swirling flow in a motored piston-cylinder assembly. The crank was rotated at 200 rpm and the inlet arrangement, a simulated open valve inclined at 60 deg to the cylinder head, provided swirl numbers at entry of approximately 0.45 and 1.20. There was no significant compression. The present results and previous results without swirl are compared.
Two Aspects of Cavitation Damage in the Incubation Zone: Scaling by Energy Considerations and Leading Edge Damage
Authors: Stinebring D. R. , Holl J. William , Arndt Roger E. A.
Published: October 2009

This study focused on two aspects of the cavitation damage problem, namely an energy approach to the scaling of cavitation damage in the incubation zone and damage near the leading edge of a test model. The damage to the surface of the models was in the form of small indentations in which no material was removed. For a wide range of velocities namely 14.9 to 59.3 m/s the rate of pit formation per unit area in the maximum damage zone increased by the sixth power of velocity. Furthermore it is shown that the damage rate versus velocity data are in good agreement with three other investigations. The volumes of the pits were found to increase by the fifth power of velocity. A relationship between the volume of a pit and the cavitation bubble collapse energy absorbed was developed. The damage to the leading edge was felt to be due to the reentrant jet striking the leading edge of the cavity creating a short term pressure rise causing the collapse of any cavitation bubbles in this area.
The Linear Instability Due to the Compressible Crossflow on a Swept Wing
Authors: Lekoudis S. G.
Published: October 2009

The problem of the propagation of three-dimensional laminar instabilities, due to crossflow, in a three-dimensional compressible boundary layer, is examined using linear theory. The theory is applied to the case of a transonic swept wing. It is shown that compressibility has a mild stabilizing effect in the regions where the crossflow is strong. The problem of defining the direction of propagation of the disturbances is discussed.
Evaporation of Small Water Drops Containing Salt in a High Pressure Steam Environment
Authors: Gardner G. C.
Published: October 2009

It is important ot be able to calculate the lifetime of drops in central power station boilers so as to determine their penetration into the superheater sections of once-through boilers and as necessary input for the design of spray separators in recirculation boilers. The evaporation rate may be reduced by a large number of factors such as the elevation of the boiling point when the salt concentration in a drop becomes substantial or by the fact that the drop is evaporating in a medium with a density which may be more than a quarter of the water density. All the factors are considered and calculations suitable for deskwork are presented.
Prediction and Measurement of Mass, Heat, and Momentum Transport in a Nonreacting Turbulent Flow of a Jet in an Opposing Stream
Authors: Elghobashi S. E. , Samuelsen G. S. , Wuerer J. E. , LaRue J. C.
Published: October 2009

The paper addresses the measurement and prediction of heat, mass, and momentum transport in a confined axisymmetric turbulent nonreacting flow of a jet in an opposing stream. The predictions are obtained by solving numerically the conservation equations of the mean flow and the transport equations of the kinetic energy of turbulence and its dissipation rate and the mean square temperature fluctuations. The predicted velocity field is in agreement with the experiment, but the predicted scalar fields point to the need of examining the employed model of a scalar turbulent diffusion.
Two-Dimensional Turbulent Offset Jet-Boundary Interaction
Authors: Hoch J. , Jiji L. M.
Published: October 2009

This paper presents a theoretical and experimental study of two-dimensional, turbulent jet-boundary interaction. The jet is discharged parallel to and offset from a solid wall in the presence of a secondary freestream. An integral approach which makes use of the entrainment concept is used to predict the jet characteristics. The theoretical model departs from previous studies by relaxing the constant base pressure and radius of curvature restrictions and treating both as variables in the preattachment region. In general, good agreement is observed between experimental and theoretical predictions.
The Third Two-Dimensional Problem of Three-Dimensional Blade Systems of Hydraulic Machines—Part 1: Theoretical Analysis
Authors: Agarwal P. K. , Viktorov G. V.
Published: October 2009

This is the first part of a study of “third” two-dimensional problem of three-dimensional blade systems of hydraulic machines. Proposed herein is a method of obtaining and evaluating the three-dimensional effect on a system of hydraulic machine blades with arbitrary geometry. An analysis method indicating the velocity distributions on surfaces perpendicular to the mean axisymmetric stream surfaces has been formulated to help create a general understanding and awareness of the flow conditions in the runner passage. An application of generalized analytic functions for inviscid, incompressible flow has been made to find out the general solution on an auxiliary plane, transformed conformally from the physical plane. Integral equation systems for the tangential velocity and the velocity potential function have been deduced. Thus, the solution of the three-dimensional flow problem is supplied by two-dimensional computation methods.
Universal Similarity in the Wakes of Stationary and Vibrating Bluff Structures
Authors: Griffin Owen M.
Published: October 2009

A universal wake Strouhal number, St* =fsd′/Ub, has been proposed and is based upon the Strouhal frequency fs of the incident flow, the measured wake width d′ at the end of the vortex formation region, and the mean velocity Ub at the edge of the separated boundary layer. This universal parameter collapses these characteristic parameters for bluff bodies onto a single curve for wake Reynolds numbers between Re* = 100 and 107. The pressure drag, vortex shedding frequency and base pressure are related through an inverse dependence between St* and a wake drag coefficient CD* = CD/(d′/d) K2, where K = (1−Cpb)1/2. The product St* CD* is equal to a constant value of 0.073 ± 0.005 for Re* in this same range of Reynolds numbers.
Computation of the Turbulent Flow in an Internal Combustion Engine During Compression
Authors: Bernard P. S.
Published: October 2009

A set of closed dynamical equations for the mean and variance of the turbulent vorticity field are used to study the piston driven flow in a two-dimensional model of an internal combustion engine cyclinder during the compression stroke. A dominant feature of the flow is observed to be the development of large corner vortices. In their vicinity intense production of turbulence occurs which locally greatly exceeds that resulting from the compression of intake generated turbulence. A comparison of the flow field at two strokes to bore ratios is made.
Experimental and Theoretical Study of Surge in a Small Centrifugal Compressor
Authors: Hansen K. E. , Jo̸rgensen P. , Larsen P. S.
Published: October 2009

Experimental results for deep surge in a small single-stage centrifugal compressor are compared to predictions based on the lumped parameter Greitzer model developed for axial compressors. Both negative and positive flow branches of the steady characteristic, being essential for the model, were measured. Predictions are in fair agreement with data when using a relaxation time smaller than the one proposed for axial compressors. The stability limit of the model equations have been studied for finite amplitude disturbances.
The Effect of Froude Number on Entrainment in Two-Dimensional Line Plumes
Authors: Phillips W. F.
Published: October 2009

Theoretical results are presented which predict the entrainment coefficient in a forced plume as a function of the local Froude number. The model does not require any external specification of the velocity and temperature profiles. The Froude number for any plume, in a motionless isothermal ambient, approaches a universal constant, at a large distance above the source. However, it is shown here that the development length for the Froude number, in plumes with high discharge Froude number, is of the order of a few hundred times the discharge width.
Complete Velocity Profile and “Optimum” Skin Friction Formulas for the Plane Wall-Jet
Authors: Hammond G. P.
Published: October 2009

An analytic expression for the complete velocity profile of a plane, turbulent wall-jet in “stagnant” surroundings is obtained by coupling Spalding’s single formula for the inner layer with a sine function for the “wake component.” This expression is transformed at the velocity maxima to yield an “optimum log-law” for skin friction. An approximate skin friction formula based on the “initial conditions” of the wall-jet is also presented. The formulas are generally in good agreement with experimental data. The complete velocity profile does not exhibit the conventional “law of the wall” behavior and modifications are consequently recommended to the usual treatment of the near-wall region in numerical calculation procedures for wall-jet flows. The use of the “Clauser plot” method of skin friction measurement is similarly shown to be in error when applied to wall-jets.
Reynolds Number Effects on the Nearfield Mean Characteristics of a Laboratory Model Thermal Plume
Authors: Kuhlman J. M. , Chu L.-C.
Published: October 2009

Laboratory model data are presented for the three dimensional time averaged thermal characteristics of a buoyant rectangular surface thermal plume in a crossflow. Plume trajectories and widths, as determined from dye studies and thermocouple measurements, and isotherm contours have been obtained for internal Froude numbers ranging from 0.79–1.3, for crossflow-to-jet velocity ratios of 0.56 and 1.13, at a nominal Reynolds number of 20,000 and a Froude number of 0.058. These data are compared with earlier model studies at lower Reynolds number, where a surprisingly large effect of Reynolds number upon buoyant jet development has been found.
A Multigrid Scheme for Three-Dimensional Body-Fitted Coordinates in Turbomachine Applications
Authors: Camarero R. , Reggio M.
Published: October 2009

An efficient numerical scheme for the generation of curvilinear body-fitted coordinate systems in three dimensions is presented. The grid is obtained by the solution of a system of three elliptic partial differential equations. The method is based on the classical SOR scheme with an acceleration of convergence using the multigrid technique. The full approximation scheme has been used and is described with the overall algorithm. A number of numerical experiments are given with comparisons to illustrate the efficiency of the method. Practical applications to typical three-dimensional turbomachinery geometries are then shown.
Transient Droplet Heating at High Peclet Number
Authors: Dwyer H. A. , Kee R. J. , Barr P. K. , Sanders B. R.
Published: October 2009

The transient heating of a spherical liquid particle at high Peclet number has been calculated with the use of adaptive grids for low Reynolds numbers. The use of adaptive grids greatly enhances the efficiency of the calculations and allows for the large Peclet numbers to be studied. The results of the calculations show that the transient period of internal isotherm redistribution represents a significant part of the droplet total heating. Even for the Pe = 1600 case, the initial heating period caused more than 50 percent of particle heating, and the asymptotic heating results cannot be used with good accuracy. The methods employed in the study have great potential, and will be applied to unsteady droplet evaporization and burning in future studies.
Simple and Explicit Formulas for the Friction Factor in Turbulent Pipe Flow
Authors: Haaland S. E.
Published: October 2009

Explicit, but accurate formulas for the friction factor are given as a substitute for the more inconvenient implicit formulas which are at present considered to be the most accurate.
Prediction of the Trajectory of Triple Jets in a Uniform Crossflow
Authors: Makihata T. , Miyai Y.
Published: October 2009

This paper describes the results of numerical prediction of the trajectories of turbulent triple jets issuing into a uniform crossflow. The prediction technique is based on the momentum integral equation and the law of conservation of momentum, together with the interference of the triple jets under the assumption of an axially symmetrical flow pattern for each of the jets. Results are presented for both triple buoyant and nonbuoyant jets, with the velocity ratio of jet flow to crossflow ranging from 3.0 to 10.6. The numerical predictions agree well with authors’ and other experimental data.
Interaction of an Acoustic Disturbance and a Two-Dimensional Turbulent Jet: Experimental Data
Authors: Thomas F. O. , Goldschmidt V. W.
Published: October 2009

An experimental study was performed to determine the effects a periodic acoustic disturbance had upon a two-dimensional turbulent jet in both the initial and similarity regions. Correlation and energy spectra measurements in the initial region indicate that acoustic forcing within a certain frequency range is capable of restructuring the flow in this region. In particular, these measurements suggest the presence of vortical flow structures arranged symmetrically with respect to the jet centerline. Measurements of the mean and turbulent flow structure in the similarity region of the jet indicate strong acoustically induced effects. Evidence suggests that the interaction effects observed in the similarity region are intimately related to those in the initial region.
Effect of Tumbling and Burning on the Drag of Bluff Objects
Authors: Ragland K. W. , Mason M. A. , Simmons W. W.
Published: October 2009

The drag on various tumbling, nonburning wooden plates, cubes, rods, and wood chips was determined by measuring the free-fall velocity. The drag coefficient was reduced by a factor of 0.46 to 0.72 compared to the drag coefficient with the largest flat surface oriented perpendicular to the flow. The drag coefficient of burning wooden cubes and disks which are not tumbling was half that of identical nonburning, nontumbling cubes and disks. The drag coefficient of burning wooden cylinders with axes normal to the flow was slightly larger than nonburning cylinders with the same orientation. The information was obtained in order to better model the trajectory of solid fuel particles in furnaces.
Near-Wall Similarity in a Shear-Driven Three-Dimensional Turbulent Boundary Layer
Authors: Pierce F. J. , McAllister J. E.
Published: October 2009

Ten of eleven proposed three-dimensional similarity models identified in the literature are evaluated with direct wall shear, velocity field, and pressure gradient data from a three-dimensional shear-driven boundary layer flow. Results define an upper limit on velocity vector skewing for each model’s predictive ability. When combined with earlier results for pressure-driven flows, each model’s predictive ability with and without pressure gradients is summarized.
Behavior of Air Bubbles in an Axial-Flow Pump Impeller
Authors: Murakami M. , Minemura K.
Published: October 2009

Motion of air bubbles in a high-specific-speed axial-flow pump impeller was analyzed on the basis of measured streak lines of air bubbles in the impeller. The results were compared with those obtained by a numerical solution of the bubble motion equations for three dimensional flow. Governing factors of the bubble motion are the drag force due to the surrounding water and the force due to the pressure gradient. Trajectories of the bubbles deviate somewhat from the streamlines of water, and the amount of the deviation is dependent on the bubble diameter and also on specific-speeds of the pumps and flow rate of water.
Laminar Flow in the Entrance Region of Elliptical Ducts
Authors: Bhatti M. S.
Published: October 2009

A closed-form analytical solution is developed to hitherto unsolved problem of steady laminar flow of a Newtonian fluid in the entrance region of elliptical ducts. The analysis is based on the Karman-Pohlhausen integral method and entails solution of the integrated forms of the mass and the momentum balance equations. According to this analysis, the hydrodynamic entrance length based on 99 percent approach to the fully developed flow is equal to 0.5132λ/(1+λ2) where λ is the aspect ratio. Also, the fully developed incremental pressure defect is found to be 7/6 which is independent of the aspect ratio. In the limit when the flow becomes fully developed, the solution converges to the known exact asymptotic solution. Available, wide-ranging velocity measurements for a circular tube agree with the analytical predictions within 7 percent. Also, available pressure drop measurements near the inlet of a circular tube agree with the analytical predictions within 2 percent.
On the Skin Friction Coefficient for a Fully Rough Flat Plate
Authors: Mills A. F. , Hang Xu
Published: October 2009

A comparison of the Prandtl-Schlichting formula for skin friction of a fully rough plate with recently obtained experimental data shows an average error of 17.5 percent. It is suggested that the reason for this discrepancy is a failure to account for the wake component of the velocity profile. The integral momentum equation is used to derive a new skin friction theory which when compared to the same data gives an average error of 2.7 percent. A new skin friction formula is proposed which is valid over a wide parameter range.
Fixed Wake Theory for Vertical Axis Wind Turbines
Authors: Wilson R. E. , Walker S. N.
Published: October 2009

A theory for vertical axis wind turbines has been developed using a fixed wake approach. The theory combines some of the best features of vortex and streamtube approaches. This approach accounts for flow differences between fore-and-aft-blade positions that are predicted by vortex methods while retaining the low computation costs associated with streamtube theories. The theory is applied to high tip speed ratio operation of a Darrieus Rotor where the use of linear aerodynamics results in explicit calculation of the induced velocities. Comparison to test results shows good agreement.
A Theory of the Wilson Line for Steam at Low Pressures
Authors: Dobbins R. A.
Published: October 2009

An algebraic method for determining the onset of condensation—the position of the Wilson line on a Mollier diagram—in steam at low pressures is presented. The method is based on the assumptions that the exponent of the nucleation rate expression is large and that the nucleation pulse duration is small. Under these conditions the growth integrals can be evaluated for specific rate expressions for the formation of stable droplets and their subsequent growth. The onset of condensation for a specified expansion rate is then determined by the solution to a system of algebraic equations. The method is illustrated using the classical nucleation rate and the droplet growth rate expression of Gyarmathy. The analytical solution agrees well with a published exact numerical solution by Gyarmathy. An extensive comparison of the predictions of the present method with the experimental results of Yellot (1933), Gyarmathy and Meyer (1965), Barschdorff (1965), and Moses and Stein (1978) is presented. The favorable comparison suggests that the method provides an efficient means for predicting the onset of condensation for various initial states and various expansion rates. The predictions of the theory on the role of the expansion rate, the initial stagnation conditions, and the history of the expansion are discussed.
Decreasing the Side Wall Contamination in Wind Tunnels
Authors: Motohashi T. , Blackwelder R. F.
Published: October 2009

To study boundary layers in the transitional Reynolds number regime, the useful spanwise and streamwise extent of wind tunnels is often limited by turbulent fluid emanating from the side walls. Some or all of the turbulent fluid can be removed by sucking fluid out at the corners, as suggested by Amini [1]. It is shown that by optimizing the suction slot width, the side wall contamination can be dramatically decreased without a concomitant three-dimensional distortion of the laminar boundary layer.
Measurement of a Recirculating, Two-Dimensional, Turbulent Flow and Comparison to Turbulence Model Predictions. II: Transient Case
Authors: Boyle D. R. , Golay M. W.
Published: October 2009

Measurements of transient water flows are performed in a 1/15-scale Fast Flux Test Facility nuclear reactor outlet plenum. During a repeated inlet-flow coastdown transient, measurements are made of the time-dependent, ensemble-averaged values of the velocity, turbulence kinetic energy, and Reynolds stress fields. These data are compared to predictions from a fluid dynamic simulation which uses a two-equation turbulence model. In general the comparison is good, and most observed transient disagreements can be attributed to errors in the calculation of the initial conditions rather than transient effects.
The Flow Past a Surface-Mounted Obstacle
Authors: Bergeles G. , Athanassiadis N.
Published: October 2009

The length of the recirculating region past a two dimensional obstacle was investigated experimentally with a single hot wire. The width (W) of the obstacle could be changed in multiple values of obstacle height (H). The results show that upstream of the obstacle the length of the main recirculating region remains unchanged with obstacle width and equal to 0.85H; however the downstream length of the recirculating region is a strong function of the width and changes almost linearly from 11 obstacle heights for W/H=1.0 to 3 for W/H greater than four.
The Buckling of a Vertical Liquid Column
Authors: Kimura Shigeo , Bejan Adrian
Published: October 2009

This paper documents the sinuous flow of a vertical water column which impinges on a horizontal surface. It is shown experimentally that the solid obstacle buckles the column into a plane sinuous (static) shape whose wavelength scales with the local column diameter. The measured ratio (buckling wavelength)/(column diameter) is of order π/2, in agreement with the buckling theory of inviscid flow.
Cavitation Inception Tests on Axisymmetric Headforms
Authors: Pan Sen-sen , Yang Zhan-ming , Hsu Pei-shuen
Published: October 2009

Six axisymmetric headforms were tested in the 350-mm dia water tunnel at China Ship Scientific Research Center (CSSRC) for observation and measurement of cavitation inception. Among them, three of the flow patterns were displayed and analyzed by holography. Results of the tests show that cavitation inception on the headforms was closely related to the structure of the near-wall flow past the body with different flow regimes corresponding to different features of cavitation inception. By carefully fitting a trip wire of suitable height on a hemispherical headform, it was observed that under conditions of low air content, this artificial means of boundary transition may bring about a significant reduction in cavitation inception number.
Viscous Effects in the Inception of Cavitation
Authors: Arakeri V. H. , Acosta Allan
Published: October 2009

The inception of cavitation in the steady flow of liquids around bodies is seen to depend upon the real fluid flow around the bodies as well as the supply of nucleating cavitation sources—or nuclei—within the fluid. A primary distinction is made between bodies having a laminar separation or not having a laminar separation. The former group is relatively insensitive to the nuclei concentration whereas the latter is much more sensitive. Except for the case of fully separated wake flows and for gaseous cavitation by diffusion the cavitation inception index tends always to be less than the magnitude of the minimum pressure coefficient and only approaches that value for high Reynolds numbers in flows well supplied with nuclei.
Two-Dimensional Performance Analysis and Design of MHD Channels
Authors: Doss E. , Geyer H. , Ahluwalia R. K. , Im K.
Published: October 2009

A two-dimensional model for MHD channel design and analysis has been developed for three different modes of operation: velocity, Mach number, and pressure. Given the distribution of any of these three parameters along the channel, the channel aspect ratio, and the channel operating conditions, the MHD channel geometry can be predicted. The developed two-dimensional design model avoids unnecessary assumptions for surface losses and boundary layer voltage drops that are required in one-dimensional calculations and, thus, can yield a better prediction of MHD channel geometry and performance. The subject model includes a simplified treatment for possible arcing near the electrode walls. A one-dimensional model for slag flow along the channel walls is also incorporated. The effects of wall temperature and slag carry-over on channel performance are discussed.
Transient Fluid Flow in Porous Media: Inertia-Dominated to Viscous-Dominated Transition
Authors: Nilson R. H.
Published: October 2009

A one-dimensional isothermal flow is induced by a step change in the pressure at the boundary of a semi-infinite medium. The early flow is inertia-dominated, in accordance with Ergun’s equation, and is self-similar in the variable x/t3. The late flow is viscous-dominated, in accordance with Darcy’s law, and is self-similar in the variable x/t. Comprehensive numerical results are presented for both of these asymptotic regimes and also for the intermediate transition period which is governed by Forchheimer’s equation. The only explicit parameter is the pressure ratio, N, which is varied from N → ∞ (strong gas-compression), through N → 1 (constant compressibility liquid), to N → 0 (strong gas-rarefaction). The solution procedure is based on a generalized separation-of-variables approach which should also be useful in other problems which possess self-similar asymptotic solutions both at early times and at late times.