Fountain Flow Research Articles

Transition behaviour of weak turbulent fountains

Numerical simulations of fully turbulent weak fountain flow are used to provide direct evidence for the scaling behaviour of fountain flow over the Froude number range Fr = 0.1–2.1 and Reynolds number range Re = 20–3494. For very weak flow at Fr < 0.4, the flow mean penetration height, Zm, scales with Zm/R0 = A1Fr2/3 + A2Fr2/3 where R0 is the source radius. A1 and A2 are constants which quantify the separate effects of the radial acceleration of fountain fluid from the source (A1) and the backpressure from the surrounding intrusion, if present, on the upflow (A2). The evidence presented in this work suggests that the mechanisms for the two parts in the scaling of Zm scale with Fr2/3. The intrusion behaviour varies with the Reynolds number (Re) but there is no Re affect on the fountain penetration height. For Re < 250 the radial intrusion flow is subcritical and has different behaviour. For Fr between 0.4 and 2.1 the effect of source momentum flux increases and the flow structure changes to one where there is a coherent upflow and a cap region where the flow stagnates and then reverses. The two regions have separate scaling behaviour such that the overall height, through this transition range of Froude numbers, can be described by Zm/R=C1Fr2/3 + C2Fr2, where C1 and C2 are constants. Over this transition range the effect of source velocity profile is more significant than the Reynolds number effects and the effect of inlet turbulence is minor.

Numerical simulation of the fountain flow instability in injection molding

For the first time, the viscoelastic flow front instability is studied in the full non-linear regime by numerical simulation. A two-component viscoelastic numerical model is developed which can predict fountain flow behavior in a two-dimensional cavity. The eXtended Pom-Pom (XPP) viscoelastic model is used. The levelset method is used for modeling the two-component flow of polymer and gas. The difficulties arising from the three-phase contact point modeling are addressed, and solved by treating the wall as an interface and the gas as a compressible fluid with a low viscosity. The resulting set of equations is solved in a decoupled way using a finite element formulation. Since the model for the polymer does not contain a solvent viscosity, the time discretized evolution equation for the conformation tensor is substituted into the momentum balance in order to obtain a Stokes like equation for computing the velocity and pressure at the new time level. Weissenberg numbers range from 0.1 to 10. The simulations reveal a symmetric fountain flow for Wi = 0.1–5. For Wi = 10 however, an oscillating motion of the fountain flow is found with a spatial period of three times the channel height, which corresponds to experimental observations.

1709 2噴口不足膨張衝突噴流に関する実験的研究(OS17-2 超音速流と衝撃波,オーガナイズドセッション)

In this paper, twin underexpanded impinging jets are experimentally studied. The flow field is visualized by schlieren and oil-flow method. Local heat transfer coefficient on the plate is calculated using the temperature difference between the adiabatic wall and the constant heat flux wall. The main parameters for the twin jets are the non-dimensional distance between the two nozzle center H/D=2.0, the nozzle to plate separation L/D=2.0 and the pressure ratio defined by p_0/p_b between 3.0 to 4.6, where D is the diameter of each nozzle exit, p_0 is the stagnation pressure and p_b is the back pressure. In this research, it is confirmed that the stagnation bubble is observed for the parameter H/D=2.0, L/D=2.0 and p_0/p_b=4.0 in oil-flow method. It is found that the heat transfer coefficient is increased due to the generation of fountain flow.

Fountain flow revisited: The effect of various fluid mechanics parameters

AbstractNumerical simulations have been undertaken for the benchmark problem of fountain flow present in injection‐mold filling. The finite element method (FEM) is used to provide numerical results for both cases of planar and axisymmetric domains under laminar, isothermal, steady‐state conditions for Newtonian fluids. The effects of inertia, gravity, surface tension, compressibility, slip at the wall, and pressure dependence of the viscosity are all considered individually in parametric studies covering a wide range of the relevant parameters. These results extend previous ones regarding the shape of the front, and in particular the centerline front position, as a function of the dimensionless parameters. The pressures from the simulations have been used to compute the excess pressure losses in the system (front pressure correction or exit correction). Inertia leads to highly extended front positions relative to the inertialess Newtonian values, which are 0.895 for the planar case and 0.835 for the axisymmetric one. Gravity acting in the direction of flow shows the same effect, while gravity opposing the flow gives a reduced bulge of the fountain. Surface tension, slip at the wall, and compressibility, all decrease the shape of the front. Pressure‐dependence of the viscosity leads to increased front position as a corresponding dimensionless parameter goes from zero (no effect) to higher values of the pressure‐shift factor. The exit correction increases monotonically with inertia, compressibility, and gravity, while it decreases monotonically with slip and pressure‐dependence of the viscosity. Contour plots of the primary variables (velocity‐pressure) show interesting trends compared with the base case (zero values of the dimensionless parameters and of surface tension). © 2009 American Institute of Chemical Engineers AIChE J, 2010

Effect of Viscoelasticity in Fountain Flow of Polyethylene Melts

Abstract Fountain flow is the phenomenon of deceleration and outward motion of fluid particles as they approach a slower moving interface. Numerical simulations have been undertaken for the flow of viscoelastic fluids, obeying an integral constitutive equation of the K-BKZ type, capable of describing the behavior of polymer melts. Two polyethylene melts are considered, a branched LDPE and a linear HDPE. Their rheology is well captured by the integral model. The flow simulations are performed for planar and axisymmetric geometries and show the shape and extent of the free surface, as well as the stresses and pressures in the system. The semicircle is a good rough approximation for the free surface of fountain flow, but detailed computations show the effect of elasticity on the free surface, which is non-monotonic for the LDPE as the elasticity level (or apparent shear rate) increases. The less elastic HDPE shows a monotonic decrease in the extent of the flow front as elasticity increases. In all cases, the excess pressure losses (front pressure correction) increase with increasing flow rate. The effect of a nonzero second normal stress difference is to extend the flow front and increase the pressure losses.

Fountain flow of pseudoplastic and viscoplastic fluids

Numerical simulations have been undertaken for the benchmark problem of fountain flow present in injection-mold filling. The Finite Element Method (FEM) is used to provide numerical results for both cases of planar and axisymmetric domains under steady-state conditions. The Herschel–Bulkley model of viscoplasticity is used, which reduces with appropriate modifications to the Bingham, power-law and Newtonian models. The present results extend previous ones regarding the shape of the front, which is essential in correctly capturing the flow field. In particular the centreline front position is found as a function of the dimensionless power-law index (in the case of pseudoplasticity) and the dimensionless yield stress (in the case of viscoplasticity). The pressures from the simulations have been used to compute the excess pressure losses in the system (front pressure correction or exit correction). Both shear-thinning and shear-thickening lead to more extended front positions relative to the Newtonian values, which are 0.895 for the planar case and 0.835 for the axisymmetric one. Viscoplasticity leads also to more extended front positions as the dimensionless yield stress goes from zero (Newtonian behaviour) to higher values of the yield stress. In both cases of non-Newtonian behaviour, the front tends to follow the development of the fully developed Poiseuille velocity profile, which tends towards a plug-like profile at the extreme cases of non-Newtonianness. The front pressure (exit) correction increases monotonically with the decrease in the power-law index and the increase in the dimensionless yield stress.

An Innovative Continuous Flow System for Monitoring Heavy Metal Pollution in Water Using TransgenicXenopus laevisTadpoles

While numerous detection methods exist for environmental heavy metal monitoring, easy-to-use technologies combining rapidity with in vivo measurements are lacking. Multiwell systems exploiting transgenic tadpoles are ideal but require time-consuming placement of individuals in wells. We developed a real-time flow-through system, based on Fountain Flow cytometry, which measures in situ contaminant-induced fluorescence in transgenic amphibian larvae immersed in water samples. The system maintains the advantages of transgenic amphibians, but requires minimal human intervention. Portable and self-contained, it allows on-site measurements. Optimization exploited a transgenic Xenopus laevis bearing a chimeric gene with metal responsive elements fused to eGFP. The transgene was selectively induced by 1 microM Zn(2+). Using this tadpole we show the continuous flow method to be as rapid and sensitive as image analysis. Flow-through readings thus accelerate the overall process of data acquisition and render fluorescent monitoring of tadpoles suitable for on-site tracking of heavy metal pollution.

Hydrodynamical simulations of Galactic fountains - II. Evolution of multiple fountains

Using 3D hydrodynamical simulations, we studied in detail the fountain flow and its dependence with several factors, such as the Galactic rotation, the distance to the Galactic center, and the presence of a hot gaseous halo. We have considered the observed size-frequency distribution of young stellar clusters within the Galaxy in order to appropriately fuel the multiple fountains in our simulations. The present work confirms the localized nature of the fountain flows: the freshly ejected metals tend to fall back close to the same Galactocentric region where they are delivered. Therefore, the fountains do not change significantly the radial profile of the disk chemical abundance. The multiple fountains simulations also allowed to consistently calculate the feedback of the star formation on the halo gas. Finally, we have also considered the possibility of mass infall from the intergalactic medium and its interaction with the clouds that are formed by the fountains. Though our simulations are not suitable to reproduce the slow rotational pattern that is typically observed in the halos around the disk galaxies, they indicate that the presence of an external gas infall may help to slow down the rotation of the gas in the clouds and thus the amount of angular momentum that they transfer to the coronal gas, as previously suggested in the literature.

On the transient coating of a straight tube with a viscoelastic material

We examine the pressure-driven coating of a straight, long tube with a finite amount of viscoelastic liquid. This combines the formation and elongation of an open bubble pushing the liquid downstream with the motion of the advancing liquid front and the deposition of a film along the tube wall. The mixed finite element method is combined with the discontinuous Galerkin method for computing the polymeric contribution to the stress tensor, while a quasi-elliptic grid generation scheme is used for tessellating the highly deforming domain. Global remeshing is adopted to overcome local distortion and coarsening of the mesh which arises from the attachment of advancing front nodes on the wall. The accuracy of the solution is achieved by selectively refining the mesh along areas where sharp boundary layers in stress arise and in particular at the bubble front. An extensive parametric analysis is performed using the affine, single-mode Phan-Tien and Tanner constitutive model. The thickness of the remaining film increases as the solvent contribution to viscosity decreases, because of the sharply increased normal viscoelastic stresses along the bubble front. The effect of decreasing the extensional parameter ɛ PTT is similar because this decreases the shear and extensional thinning in the liquid. The transient nature of the process delays the development of the viscoelastic stresses as the Deborah number increases. The streamlines relative to the liquid tip follow the usual ‘fountain flow’ pattern as long as the bubble and the liquid front do not interact. The non-affine, multi-mode PTT model with constants obtained from the literature for a PIB solution in C14 predicts a slightly thinner deposited film and a flatter bubble front because of its stronger shear thinning. Moreover, it predicts a higher dimensionless bubble velocity because of the very small viscosity ratio of the solvent and a V-shape in the radial distribution of the first normal stress difference and the birefringence just behind the contact line in qualitative agreement with experiments and theory for planar fountain flow.

Direct numerical simulation of turbulent intermediate Froude number fountain flow

Fountains are an important flow in many industrial and geophysical problems but the understanding of this flow at low Froude numbers is limited. In this study we use direct numerical simulation to examine two regimes of turbulent fountain flow, weak flow at Fr=2.2 and very weak flow at Fr=0.45. At Fr=0.45 buoyancy stabilises the flow and there is little entrainment of ambient fluid. Kelvin--Helmholtz instabilities are generated at the interface between the upwelling flow and the ambient fluid. At Fr= 2.2 the shear interaction between the rising and falling flow streams becomes important as it drives both large and small scale vortex structures. Large scale structures draw ambient fluid into the fountain while small scale structures exchange mass between the upflow and downflow. Periodic ejection of mass from the top of the fountain is shown to be an important dynamic in the flow. The results provided here can assist in analytical model development. References J. S. Turner. Jets and plumes with negative or reversing buoyancy. J. Fluid Mech., 26:779--792, 1966. doi:10.1017/S0022112066001526. T. Mizushina, F. Ogino, H. Takeuchi, and H. Ikawa. An experimental study of vertical turbulent jet with negative buoyancy. Warme-und Stoffubertragung, 16:15--21, 1982. doi:10.1007/BF01322802. R. W. Cresswell and R. T. Szczepura. Experimental investigation into a turbulent jet with negative buoyancy. Phys. Fluids A, 5:2865--2878, 1993. doi:10.1063/1.858749. N. B. Kaye and G. R. Hunt. Weak fountains. J. Fluid Mech., 558:319--328, 2006. doi:10.1017/S0022112006000383. N. Williamson, N. Srinarayana, S. W. Armfield, G. D. McBain, and W. Lin. Low-reynolds-number fountain behaviour. J. Fluid Mech., 608:297--317, 2008. doi:10.1017/S0022112008002310. W. Lin and S. W. Armfield. Very weak axisymmetric fountains in a homogeneous fluid. Numer. Heat Transfer A, 38:377--396, 2000. doi:10.1080/104077800750022520. P. D. Friedman, V. D. Vadokoot, W. J. Meyer, and S. Carey. Instability threshold of a negatively buoyant fountain. Exp. Fluids, 42:751--759, 2007. doi:10.1007/s00348-007-0283-5. H. Zhang and R. E. Baddour. Maximum penetration of vertical round dense jets at small and large {F}roude numbers. J. Hydraulic Eng., 124:550--553, 1998. doi:10.1061/(ASCE)0733-9429(1998)124:5(550). B. R. Morton, G. I. Taylor, and J. S. Turner. Turbulent gravitational convection from maintained and instantaneous sources. Proc. R. Soc. Lond., 234:1--23, 1956. http://www.jstor.org/stable/99936. B. P. Leonard and S. Mokhtari. Beyond first-order upwinding: the ultra-sharp alternative for non-oscillatory steady state simulation of convection. Int. J. Numer. Meth. Engng, 30:729--766, 1990. doi:10.1002/nme.1620300412. I. H. Campbell and J. S. Turner. Fountains in magma chambers. J. Petrol., 30:885--923, 1989. http://petrology.oxfordjournals.org/cgi/content/abstract/30/4/885 W. D. Baines, J. S. Turner, and I. H. Campbell. Turbulent fountains in an open chamber. J. Fluid Mech., 212:557--592, 1990. doi:10.1017/S0022112090002099. W. Lin and S. W. Armfield. Direct simulation of weak axisymmetric fountains in a homogeneous fluid. J. Fluid Mech., 403:67--88, 2000. doi:10.1017/S0022112099006953. E. Kaminski, S. Tait, and G. Carazzo. Turbulent entrainment in jets with arbitrary buoyancy. J. Fluid Mech., 526:361--376, 2005. doi:10.1017/S0022112004003209.

Prediction of fiber orientation in a rotating compressing and expanding mold

AbstractIn the rotating/compressing/expanding mold (RCEM), one mold wall can expand, compress, and rotate during injection molding, thus offering opportunities to control the thermomechanical history of a polymer and its microstructure. A computer simulation of flow and fiber orientation in RCEM was developed. The predictive model extends the generalized Hele‐Shaw formulation to account for compression/expansion and rotation of the mold wall, and uses the Folgar–Tucker model for fiber orientation predictions. A 20% GF polypropylene was molded under various molding conditions. The predicted fiber orientation distributions were compared with experiments. The model compares favorably with experiments, provided that the fiber orientation equation is modified by a strain‐reduction factor that slows the transient development of fiber alignment. The effect of fountain flow on orientation must also be included to correctly predict fiber orientation near the mold walls, mainly for the case of stationary and linear motions of the mold surface. Compression or expansion of the mold has only a small effect on fiber orientation, but rotation of the mold dramatically changes the orientation, causing fibers to align in the tangential direction across the entire thickness of the molding. This rotation action perturbs the fountain flow and becomes the dominant factor affecting fiber alignment across the entire cavity thickness. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.

Numerical simulation of the filling phase in the polymer injection moulding process with a conservative level set method

Numerical simulations are widely used in polymer processing in order to understand the interaction between the material properties and the process. In the injection moulding process, one of the numerical simulation problems encountered is the tracking of the polymer-air front or interface during the filling stage [1]. In this study, this is achieved by using the classical level set method, which reveals to be conservative. On the contrary, in the case of confined volume of two phases flow, such as an air bubble moving in a constant volume of liquid, the method needs a correction in order to be conservative [2-3]. For a non-Newtonian non-isothermal flow, the simulation involves a coupling between heat transfer, continuity and momentum equations and the rheological material parameters. A finite element method is used to solve this equations set. The results show clearly the expected fountain flow effect. Temperature, velocity, pressure and viscosity fields are calculated and the influence of the thermal contact resistance between the polymer and the mould is presented.

Accretion of gas on to nearby spiral galaxies

We present evidence for cosmological gas accretion onto spiral galaxies in the local universe. The accretion is seen through its effects on the dynamics of the extra-planar neutral gas. The accretion rates that we estimate for two nearby spiral galaxies are of the order of their star formation rates. Our model shows that most of the extra-planar gas is produced by supernova feedback (galactic fountain) and only 10 20% comes from accretion. The accreting material must have low specific angular momentum about the disc’s spin axis, although the magnitude of the specific angular-momentum vector can be higher. We also explore the effects of a hot corona on the dynamics of the extra-planar gas and find that it is unlikely to be responsible for the observed kinematical pattern and the source of accreted gas. However, the interaction with the fountain flow should profoundly affect the hydrodynamics of the corona.

Study on Weld Characteristics of Thin-wall Injection Molded Polypropylene Plates

This paper deals with a fundamental study on the weld structure of thin-wall injection molded polypropylene plates. Effects of the mold temperature and plate thickness on the weld characteristics were investigated. In the experiment, several measurements were performed; distribution of the optical retardation, specific latent heat for fusion, V notch depth and width, and tensile strength of the specimen. The results indicated that the fountain flow of the melt occurred in the filling stage even with a plate thickness of 0.3 mm. It was also shown that molecular orientation in the weld region was relatively low. Thermal property measurement showed that crystallinity of the molded specimen was affected not only by the mold wall temperature but also by the plate thickness. Mechanical strength reduction by the existence of the weld was experimentally confirmed through the tensile test, and it was shown that the thin-wall polypropylene plate molded at high mold temperature broke from the weld region under small strain.

Numerical simulation of a fountain flow on nonstaggered Cartesian grid system

A liquid–air fountain flow due to the downward motion of a rectangular sleeve over a stationary piston is studied in the paper. Two-dimensional incompressible laminar flows are assumed to prevail in both air and liquid regions. A single set of governing equations over the entire physical domain including the liquid, the air, and the liquid–air interface (free surface) is solved with the extended weighting function scheme and the NAPPLE (nonstaggered APPLE) algorithm on a fixed nonstaggered Cartesian grid system. To ensure the required dynamic contact angle, the liquid meniscus near the sleeve wall is corrected by solving the force balance equation with the geometry method. This is equivalent to introducing a slip condition at the contact line, and thus successfully removes the stress singularity. Steady state solution of the velocity and the pressure as well as the shape of the free surface is obtained. The numerical result evidences the existence of a toroidal-like motion on the free surface postulated by Dussan [E.B. Dussan V., Immiscible liquid displacement in a capillary tube: the moving contact line, AIChE J. 23 (1977) 131–133], although it is quite weak and thin. The resulting free surface profile agrees with the existing experimental observation excellently. Influence of the piston on the flow is discussed.

Mechanical and Electrical Properties of Vapor Grown Carbon Fiber/Polypropylene Composites Made by Injection Molding

We made pellets by adding 0-20 wt% vapor grown carbon fiber (VGCF) to polypropylene and made an injection molding test piece with the pellets so as to test the rheological, as well as the mechanical, electrical, and injection molding properties. In the test piece made by injection molding, the quantity of VGCF in the surface layer is extremely small as compared to the quantity of addition. The value of resistance at the end of flow of the injection-molded product is smaller than that measured at other locations, which is considered to be the influence of the fountain flow at the end of flow. In addition, it is known that the above phenomenon is attributable to the fact that the orientation is in the direction of thickness in the same way as the orientation of glass fiber and carbon fiber. Even if the additive rate of VGCF is the same, the value of resistance changes substantially depending on the thickness of injection-molded products. One of the causes is considered to be the orientation of VGCF, and the orientation of VGCF in the test piece is considered to be strong in the direction of flow. There exists a proportionality relation between the shear rate and the value of resistance calculated on the basis of the rate of flow, which is one of the molding conditions.

Radial Slot Jet Impingement Flow and Heat Transfer on a Cylindrical Target

To better understand and facilitate design of an impinging jet device, the heat transfer on a cylindrical target exposed to radial impinging slot jets was investigated using numerical methods. Numerical models were created to test the performance of the shear stress transport, standard and realizable k-e, v 2 f, and Reynolds stress model turbulence models vs published test data. Based on the validation study, the v 2 f model was ultimately selected for further work. Models were then constructed to simulate a cylinder exposed to a radial array of slot jets. Parametric variations were conducted to produce information about the influence of jet speed, number of nozzles, and other independent design variables, upon heat transfer. The number of nozzles was varied from 2 to 8, jet Reynolds number Re from 5,000 to 80,000, and target diameter from 5 to 10 times the nozzle hydraulic diameter. The physics of the flows are discussed, finding, for example, that interaction of adjacent opposed wall jets caused a static pressure rise and resulted in flow separation on the surface of the cylindrical target. This separation and the fountain flow between the two wall jets greatly influenced the local heat transfer, causing a rise in Nusselt number Nu of an order of magnitude. The resulting average Nu values varied from 19 to 217 and were condensed into a correlation equation incorporating the ratio of nozzle width to target diameter, number of nozzles, Reynolds number, and Prandtl number.

Computational flow and heat transfer of a row of circular jets impinging on a concave surface

A computational investigation is carried out to study the flow and heat transfer from a row of circular jets impinging on a concave surface. The computational domain simulates the impingement cooling zone of a gas turbine nozzle guide vane. The parameters, which are varied in the study include jet Reynolds number (Red = 5000–67800), inter-jet distance to jet diameter ratio (c/d = 3.33 and 4.67) and target plate distance to jet diameter ratio (H/d = 1, 3 and 4). The flow field, predicted with K-ω turbulence model and using Fluent 6.2.16, is characterized with the presence of a pair of counter rotating vortices, an upwash fountain flow and entrainment. The local pressure coefficient and Nusselt number variations along the concave plate are presented and these values are found to under predict the available experimental data by about 12%.

The Dynamism of the Trinity in Bonaventure and Eckhart

The Dynamism of the Trinity in Bonaventure and Eckhart Thee, God, I come from, to thee go, All day long I like fountain flow, From thy hand out, swayed about Mote-like in thy mighty glow. These verses of Gerard Manley Hopkins are a succinct expression of the dynamic procession of all things from God. Hopkins did not write matching lines to express the return, or consummation, of the universe in its divine source, at least in this poem, but a passage from “The Wreck of the Deutschland” captures his sense of God as the goal of all life and action: Stanching, quenching ocean of a motionable mind; Ground of being, and granite of it: past all Grasp God, throned behind Death with a sovereignty that heeds but hides, bodes but abides. The master paradigm of exitus and reditus, the procession out and return to God, is perhaps natural to the religious mind as it reflects upon the nature of the universe. In Western thought the evolution of this dynamic This essay was presented March 11, 2006, at Saint Louis University during a symposium in honor of Zachary Hayes, OFM. I am happy to be able to dedicate this paper to my old friend and colleague. As its content will make clear, I owe him an immense debt of gratitude for his scholarship over the years, especially on Bonaventure . Gerard Manley Hopkins. A Selection of His Poems and Prose, by W.H. Gardner (Baltimore: Penguin Books, 1953), No. 63 (untitled); and “The Wreck of the Deutschland,” No. 1, Stanza 32. 137 Franciscan Studies 65 (2007) 08.McGinn.indd 137 12/5/07 17:51:26 Bernard McGinn 138 paradigm was shaped by the way in which Neoplatonic thinkers, both pagan and Christian, sought to express how the First Principle overflows into the universe while at the same time drawing all things back to Itself. What was unique to Christian theologians was how they brought this dynamic process into God’s very self as a way for expressing the Church’s faith in God as Trinity. From this perspective, the extra-divine dynamism of creation is rooted in the intra-divine flow of life found in Father, Son, and Holy Spirit. I. A Brief Sketch of Some Aspects of the Evolution of Trinitarian Theology This dynamic view of God as Trinity is rooted in New Testament texts, especially in the Gospel of John. During the pre-Nicene period, the time characterized by what Bernard Lonergan called a mixture of naïve and dogmatic realism concerning the doctrine of the Trinity, Christian theologians expressed the inner divine life by appealing to concrete images, such as vegetative growth, flowing water, and the radiation of light. When they attempted a more systematic view of their belief that the one God was nevertheless three they turned to the philosophical vocabulary available to them. Thus Athenagoras, writing about 176 C.E., says that “the Son of God is the Word of the Father in Ideal Form and Energizing Power (en idea kai energeia),” making use of both Platonic and Aristotelian terms. He goes on to describe the Holy Spirit more concretely as “an effluence of God (aporraian … tou theou) which flows forth from him and returns like a ray of the sun.” During the fourth century, the clarification of the Church’s faith at Nicaea and its defense and elaboration during the half-century between Nicaea and the First Council of Constantinople produced a basic trinitarian grammar that placed the mystery in its proper dogmatic language. This led to the beginnings of the critical realism (again, Lonergan’s term) that On Lonergan’s categories of three kinds of realism (naïve, dogmatic, and critical ) and their application to the development of the doctrine of the Trinity, see Bernard Lonergan, The Way to Nicea. The Dialectical Development of Trinitarian Theology (Philadelphia: Westminster, 1976), especially 106-37. Tertullian in chapter 7 of his Adversus Praxean used the analogies of “roottree -fruit,” “fountain-river-stream,” and “sun-ray-apex” to present the Trinity. Athenagoras. Legatio and De Resurrectione, edited and translated by William R. Schoedel (Oxford: At the Clarendon Press, 1972), Legatio 10 (20-22). On early Christian trinitarianism...

First Results from the Arecibo Galactic HiSurvey: The Disk/Halo Interface Region in the Outer Galaxy

The consortium for Galactic studies with the Arecibo L-band Feed Array (ALFA) is conducting a neutral hydrogen (H I) survey of the whole Arecibo sky (declination range from -1° to 38°), with high angular (35) and velocity resolution (0.2 km s-1). The precursor observations with ALFA of a region in the Galactic anticenter reveal numerous isolated, small (a few parsecs in size), and cold (Tk < 400 K) H I clouds at low negative velocities, distinctly separated from the H I disk emission (low-velocity clouds [LVCs]). These clouds are most likely located in the transition region between the Galactic disk and halo (at scale heights of 60-900 pc), yet they have properties of typical cold neutral clouds. LVCs are colder and, most likely, smaller and less massive than Lockman's clouds in the disk/halo interface region of the inner Galaxy. Our observations demonstrate that the cloudy structure of the interface region is most likely a general phenomenon, not restricted to the inner Galaxy. LVCs have sizes and radial velocities in agreement with the expectations for clouds formed in low-temperature fountain flows, although we measure a factor of 10 higher H I column densities. Alternatively, LVCs could represent the final stages of the infalling intergalactic material in the ongoing construction of the Galaxy. In the same data set at higher negative velocities, we have discovered a companion H I cloud located 50' southwest of HVC 186+19-114. HVC 186+19-114 is a typical compact high-velocity cloud (HVC) with a well-defined core/envelope structure. The companion cloud has a diameter of only 7' × 9' and is one of the smallest HVCs known, most likely stripped from the main cloud through the interactions with the halo medium.