Vortex Research Papers - Academia.edu (original) (raw)

- by Ralph Milliff
- •
- Geology, Oceanography, Physical Oceanography, Numerical Simulation

The Cargo-X UAV aircraft is a UAV aircraft designed to carry medicines, packages and blood bags in areas that require fast and efficient handling. One of the important components of the Cargo-X UAV aircraft is the wing, so the strength of the wing structure must be seriously considered to ensure safety during flight under unexpected conditions. The purpose of this study was to analyze the wing structure of the UAV Cargo-X aircraft made of sandwich composite material to determine the level of safety of the wing structure. The loading of the wing structure uses the load due to the lift. The wing structure modeling uses CATIA software, while the analysis uses PATRAN/NASTRAN software. From the analysis results, the skin and spar wing structures are safe against loading, while the core section is not safe against loading.

- by Buyung Junaidin
- •
- Vortex

Temporal variations of the Kuroshio volume transport in the Tokara Strait and at the ASUKA line are decomposed by phase-propagating Complex EOF modes of highresolution sea surface dynamic topography (SSDT) field during the first tandem period of TOPEX/POSEIDON and ERS-1 (from October 1992 to December 1993). Both variations are dominated by a mode with nearly semi-annual cycle, which indicates a series of interactions between the Kuroshio and meso-scale eddies. Namely, northern part of a westward-propagating meso-scale eddy at 23°N is captured into the southern side of the Kuroshio at the south of Okinawa, then it moves downstream along the Kuroshio path passing the Tokara Strait, and reaches to the ASUKA line where it merges with another eddy propagating from the east at 30°N. The variation at the ASUKA line is, however, less dominated by this mode; instead, it includes the SSDT variations in the south of Shikoku and the east of Kyushu which would be directly affected by eddies from the east without passing the Tokara Strait. On the other hand, the same analysis for movements of the Kuroshio axis in the Strait indicates that they are governed by short-term variations locally confined to the Kuroshio in the East China Sea without being induced by meso-scale eddies. This results, however, seem to depend strongly on a time scale of interest. It is suggested that the long-term movements of the Kuroshio axis in the Strait would demonstrate coincidence with SSDT variation in the south of Japan. Comparing with numbers of studies on the possible effects of the Tokara Strait to the Kuroshio in the south of Japan, causes of the variations are less well understood. Variations of the Kuroshio in the Tokara Strait are considered to be originated from variations of the Kuroshio in the East China Sea where downstream propagation of signals is often observed (e.g. Qiu et al., 1990; Ichikawa and Beardsley, 1993). Interannual variations of the Kuroshio volume transport in the East China Sea seem to be originated from the upstream region of the Kuroshio (17°-21°N), and to be induced by wind stress changes to the far east (Akitomo et al., 1996). Recently, higher-frequency variations of the Kuroshio volume transport in the east of Taiwan are suggested to be coincident with westward-propagating meso-scale eddies (Zhang et al., 2000). However, detailed understanding of the response of the Kuroshio in the Tokara Strait to meso-scale eddies has not been achieved at this stage. In addition, Feng et al. (2000) found no significant coincidence in the upstream sea surface dynamic topography (SSDT) with longterm meridional shift of the Kuroshio axis in the Tokara

- by Kaoru Ichikawa
- •
- Oceanography, Vortex, High Resolution, Annual Cycle

The Regional Ocean Modeling System (ROMS) is used to systematically investigate equilibrium conditions and seasonal variations of the Benguela system at a resolution of 9 km, including both the large-scale offshore flow regime and the economically and ecologically important coastal upwelling regime. A shelf-edge poleward flow exists in the northern Benguela region (i.e., north of ∼28°S) and is driven primarily by the wind stress curl via the Sverdrup relation. As such, it is strongly seasonal and is most intense during spring and summer, when the wind stress curl is most negative. The poleward flow deepens as it moves southward; between ∼25° and 27°S, much of it veers offshore because of the nature of the wind stress curl and its interaction with the northwestward path of the Benguela Current, which is influenced by alongshore topographical variations. The Benguela Current is driven by nonlinear interactions of passing Agulhas rings and eddies and does not have a striking seasonal s...

- by Frank Shillington
- •
- Oceanography, Modeling, Physical Oceanography, Dynamics

The frequency response of pinned vortex lattice in type-II superconductors is investigated. If frequency is not too low than the AC-absorption is caused by oscillations of the vortex lattice near equilibrium state (Campbell regime). We calculate the field and temperature dependencies ofboth Campbell penetration depth and surface resistance, taking into account the effect of the thermal depinning. In the region of low frequencies jumps of lattice regions between different metastable states (two-level systems) come into play and give main contribution to the AC-response. The field and temperature dependencies of the penetration depth and surface resistance in the last region are also found.

During the International Tapir Symposium 16-21 Oct 2011, the conservation of Baird's tapir (Tapirus bairdii) in Honduras received a boost with the signing of a memorandum of understanding between the Minister Director of the Honduran Institute of Conservation and Forestry (ICF) and the Tapir Specialist Group (TSG). Despite this agreement, accelerating levels of hunting and habitat loss continue to pose a threat to Baird's tapir in Honduras. An ongoing study in Cusuco National Park in northwestern Honduras has been monitoring changes in population dynamics of Baird's tapir since 2006 through the collection of occupancy data. The study has iden-suco National Park using the software PRESENCE, and simulate the effects of different management strategies on the future dynamics of the population using the stochastic simulation software VORTEX. The predictions of the theoretical population models are compared to observed changes in occupancy levels. We found that nonintervention resulted in the local extinction of Baird's tapir within a very short time frame, but that various intervention models enabled the population to recover to near carrying capacity. Occupancy and extinction probability were shown to respond markedly to the increase in hunting pressure;; and occupancy models supported the future population predictions generated by VORTEX. Our study suggests that immediate intervention is required to reduce hunting pressure to near historical levels to prevent the imminent local extinction of the species.

- by Michael W. Bruford
- •
- Zoology, Environmental Education, Science Communication, Conservation Biology

Using a self-assembly double template method, we have prepared highly ordered magnetic dot arrays of Ni on submicron scales. For the template preparation we have used colloidal suspensions of polystyrene latex spheres with different diameters ranging from 200 to 700 nm combined with secondary templates of the conducting polymer polypyrrole. By variation of the template parameters and the deposition charge the material shape can be modified significantly from isolated dots to connected 3D networks. Samples have been characterized by magnetometry. Magnetic properties were found to depend strongly on dot size and connectivity leading to a rich variety of magnetic behaviors. r 2004 Published by Elsevier B.V.

- by Mohamed Ali Ghanem
- •
- Mechanical Engineering, Condensed Matter Physics, Self Assembly, Magnetism

Abstract: In this article, we review some of the theoretical solutions used to describe swirl dominated flows in both unidirectional and bidirectional flow orientations. This short survey starts with the Rankine vortex and culminates in the presentation of a compressible solution of the bidirectional vortex. After classifying representative swirl motions as external or internal depending on physical boundary conditions, their commonalities are identified along with their relevance to either geophysical or industrial applications. We also identify ...

- by Joseph Majdalani
- •
- Physics, Mechanics, Fluid Dynamics, Viscosity

In 2010, we proposed vortex-assisted liquid-liquid microextraction (VALLME) that used vortex agitation to disperse microliters of a water-immiscible solvent into an aqueous sample. After extraction, the two phases were separated by centrifugation and the extracting solvent was collected and used for analysis. The seemingly easy steps of VALLME involve complex and poorly understood processes that require consideration of solvent drop breakup and coalescence plus the problem of interphase analyte mass transfer. The overall aim of this review is to transfer knowledge from other disciplines and improve current understanding of VALLME. Initially, the fundamental hydrodynamic and interfacial science concepts of emulsion formation and phase separation applying to VALLME are presented. Building on this knowledge, the effects of several experimental parameters on VALLME are discussed. Advancing the current (and limited) knowledge on the fundamentals behind VALLME is critical to allow cognitive control and full exploitation of the method.

- by Elefteria Psillakis
- •
- Vortex, Microextraction
- by Hikaru Aono
- •
- Vortex, Low Reynolds Number

An experimental investigation has been performed to realize thorough behavior of a vortex tube system. In this work attention has been focussed on the classification of the parameters affecting vortex tube operation. The effective parameters are divided into two different types, namely geometrical and thermophysical ones. A reliable test rig has been designed and constructed to investigate the effect of geometrical parameters i.e. diameter and length of main tube, diameter of outlet orifice, shape of entrance nozzle. Thermo-physical parameters which have been designated and studied are inlet gas pressure, type of gas, cold gas mass ratio and moisture of inlet gas. The effects of these parameters on the cold temperature difference and efficiency are discussed and presented.

- by M.H. saidi
- •
- Mechanical Engineering, Refrigeration, Vortex, Vortex Tube
- by stefanus tobing
- •
- Vortex dynamics, Vortex
- by Gianni Pedrizzetti and +1
- •
- Magnetic Resonance Imaging, Rheology, Hemorheology, Flow

Cyclone separatorsan overview. A cyclone separator is used to separate larger, heavy particles from smaller, lighter particles. It does that by using a spinning column of gas to force the larger, heavier particles out to the walls of the... more

- by ahmed said
- •
- Mechanical Engineering, Chemical Engineering, Vortex, Hydrocyclone

Empedocles-the-scientist got a minoritarian attention, and this paper was meant to do something in order to redress the situation.
Two preliminary questions are addressed here at the beginning: (1) how folklore, speculation and 'science' do coexist in his verses? (2) what to thing of the seemingly secundary doxai, esp. when they show no clear connection with the leading ideas of an ancient student of nature? My remarks on these topics include a note on virtual disciplines and polumathia.
Then some minor topics are examined: thermal waters; eyes as lanterns; why earth remains immobile despite the cosmic vortex.
My final (and larger) section is devoted to B31.100 (the klepsudra simile) and the possibility that Emp. has in mind the secondary branches of the bronchial tubes

- by Livio Rossetti
- •
- Philosophy, History of Science, Ancient Greek Philosophy, History of Life Sciences

An experimental investigation has been carried out in order to evaluate the detection of cavitation in actual hydraulic turbines. The methodology is based on the analysis of structural vibrations, acoustic emissions and hydrodynamic pressures measured in the machine. The proposed techniques have been checked in real prototypes suffering from different types of cavitation. In particular, one Kaplan, two Francis and one Pump-Turbine have been investigated in the field. Additionally, one Francis located in a laboratory has also been tested.

- by Deepak sharma
- •
- Mechanical Engineering, Civil Engineering, Signal Processing, Vibrations

Since the Stone Age, human beings manipulated their consciousness. There is little doubt that psychotropic plants were used in the Neolithic period, and it is most probable that this and other methods of consciousness alteration, such as sensory deprivation, auditory driving and extensive motor behavior were employed even earlier, during the Palaeolithic. With the invention of writing and subsequent development of literature, descriptions of individual experiences of divine revelations, out-of-body states and related practices made their appearance. Ancient Greeks went further and began to expound altered states of consciousness as a complex world view, basing their approach on the belief that human ability to attain the ultimate truth is limited by nature, and only liberation from the restraint of the mortal flesh can allow a glimpse into the realm of the absolute. These ideas persisted till late antiquity, and were further developed by the adherents of syncretistic cults and philosophical schools drawing on the heritage of the entire Mediterranean world – as well as on the inherent human drive to attain extreme experiences by means of consciousness alteration.

- by Yulia Ustinova
- •
- Mystery Cults, Dionysus, Apollo, Drugs

RESUMO (see Abstract bellow) Os Estados Não Ordinários de Consciência, ENOC, induzidos especialmente por alguns tipos específicos de agentes psicoativos, como a ayahuasca, propiciam visões, tratadas neste trabalho também como mirações.... more

- by JOSÉ E MIKOSZ
- •
- Psychedelics, Visionary Art, Ayahuasca, Vortex
- by Theory Of Everything
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- Physical Chemistry, Gravitation, Theory, Vortex

Di Indonesia, terutama pada mahasiswa biologi/bioteknologi kajian microbiology merupakan kajian wajib dalam bentuk mata kuliah bagi mahasiswa prodi biologi, kimia, biotechnology, farmasi, kedokteran, lingkungan, dan teknologi pangan. Kajian mikrobiologi di perguruan tinggi selalu disertai dengan pelaksanaan praktikum untuk membekali mahasiswa untuk menguasai softskill keterampilan kerja ilmiah. Mahasiswa dibekali dengan keterampilan menentukan masalah, mengembangkan hipotesis atau pertanyaan-pertanyaan, merancang percobaan, melakukan pengamatan untuk menjawab pertanyaan dan menarik kesimpulan. Selain softskill, keterampilan hands-on yang meliputi cara menggunakan alat, mengoperasikan peralatan atau instrument seperti di laboratorium genetika dan biologi molekuler wajib dibutuhkan untuk mahasiswa dalam melakukan sebuah praktikum maupun penelitian. Kemampuan atau keterampilan hands-on ini disebut juga dengan teknik laboratorium. Teknik labarotorium merupakan kiat-kiat mengenai seluk beluk laboratorium. Sebelum melakukan praktikum di dalam laboratorium diperlukan pengenalan mengenai beberapa pengetahuan pokok dan teknik-teknik laboratorium ini untuk mencegah timbulnya bahaya yang ditimbulkan oleh alat dan bahan dalam laboratorium maupun kesalahan dalam penggunaan peralatan (Tim Kimia Dasar, 2012: 1).

- by Kevin Febrianus Moda
- •
- Vortex, Biologi, Bioteknologi, Instrumentasi

El aislamiento de la vía aérea es un área esencial en la anestesia. Los anestesiólogos se consideran los profesionales más expertos para resolver cualquier problema relacionado con una vía aérea difícil. Sin embargo, las complicaciones derivadas del manejo incorrecto de la vía aérea siguen siendo una de las causas más frecuentes de morbimortalidad asociada a la anestesia.
La estrategia mediante algoritmos de tratamiento para resolver estas dificultades ha demostrado su fracaso debido a varios factores relacionados con su estructura y su aplicación clínica.
El enfoque Vortex surge como una respuesta a las limitaciones encontradas en los algoritmos de manejo de una vía aérea difícil, utilizando una estrategia de ayudas para reducir la carga cognitiva y el error de fijación. Esta nueva estrategia puede representar una solución al problema de la dificultad de la vía aérea y, poder así, reducir la incidencia de complicaciones.

- by Ricardo M Urtubia, MD, MSc
- •
- Algorithms, Airway Management, Vortex, Difficult Airway
- by Valerio Cappozzo
- •
- Dante Studies, Manuscript Studies, Medieval Islam, History of Astronomy

This article presents a geometric kinematic approach to demonstrate the existence of the proton charge as a consequence of the rotation of a 4 dimensional framework of the universe and the existence of the electron and its charge as a consequence of proton creation. In this article, the author presents the existence of the proton and electron charges as the endpoints of a vortex charge tunnel that passes through the interior dimension of the 4-Ball universe connecting two points in our 3 dimensional surface volume.

- by Warren R Giordano
- •
- Quantum Physics, Cosmology (Physics), General Relativity, Topology

Vortex filament statement of Helmholtz's vortex theorems, Biot-Savart Law, starting, bound & trailing vortices of wings, Lanchester's experiment, Prandtl's Lifting line theory-downwash and induced drag, Elliptic loading & wings of elliptic platforms, expression for induced drag, minimum induced drag for Elliptic platform. Source and vortex panel methods for airfoils. Replacement of an airfoil by a concentrated vortex at quarter-chord point, importance of three-quarter chord point for discretization, use of quarter chord and three-quarter chord points in vortex panel method for wings.

Easterly waves (EWs) are prominent features of the intertropical convergence zone (ITCZ), found in both the Atlantic and Pacific during the Northern Hemisphere summer and fall, where they commonly serve as precursors to hurricanes over both basins. A large proportion of Atlantic EWs are known to form over Africa, but the origin of EWs over the Caribbean and east Pacific in particular has not been established in detail. In this study reanalyses are used to examine the coherence of the large-scale wave signatures and to obtain track statistics and energy conversion terms for EWs across this region. Regression analysis demonstrates that some EW kinematic structures readily propagate between the Atlantic and east Pacific, with the highest correlations observed across Costa Rica and Panama. Track statistics are consistent with this analysis and suggest that some individual waves are maintained as they pass from the Atlantic into the east Pacific, whereas others are generated locally in the Caribbean and east Pacific. Vortex anomalies associated with the waves are observed on the leeward side of the Sierra Madre, propagating northwestward along the coast, consistent with previous modeling studies of the interactions between zonal flow and EWs with model topography similar to the Sierra Madre. An energetics analysis additionally indicates that the Caribbean low-level jet and its extension into the east Pacific-known as the Papagayo jet-are a source of energy for EWs in the region. Two case studies support these statistics, as well as demonstrate the modulation of EW track and storm development location by the MJO.

- by Kevin Hodges
- •
- Oceanography, Modeling, Case Studies, Climate

We consider charge transport properties of 2+1 dimensional conformal field theories at non-zero temperature. For theories with only Abelian U(1) charges, we describe the action of particle-vortex duality on the hydrodynamic-to-collisionless crossover function: this leads to powerful functional constraints for self-dual theories. For N =8 supersymmetric, SU(N ) Yang-Mills theory at the conformal fixed point, exact hydrodynamic-to-collisionless crossover functions of the SO(8) Rcurrents can be obtained in the large N limit by applying the AdS/CFT correspondence to Mtheory. In the gravity theory, fluctuating currents are mapped to fluctuating gauge fields in the background of a black hole in 3+1 dimensional anti-de Sitter space. The electromagnetic self-duality of the 3+1 dimensional theory implies that the correlators of the R-currents obey a functional constraint similar to that found from particle-vortex duality in 2+1 dimensional Abelian theories.

- by Subir Sachdev
- •
- Field Theory, Quantum Physics, Quantum Field Theory, Supersymmetry

Vortex interactions with flames play a key role in many practical combustion applications. Such interactions drive a large class of combustion instabilities, they control to a great extent the structure of turbulent flames and the corresponding rates of reaction, they occur under transient operations or when flames travel in ducts containing obstacles. Vortices of various types are often used to enhance mixing, organize the flame region, and improve the flame stabilization process. The analysis of flame/ vortex interactions has value in the development of our understanding of basic mechanisms in turbulent combustion and combustion instability. The problem has been extensively investigated in recent years. Progress accomplished in theoretical, numerical and experimental investigations on flame/vortex interactions is reviewed in this article.

- by Dominique Thévenin
- •
- Mechanical Engineering, Chemical Engineering, Chemistry, Theory

We simulate numerically the unsteady flow past a reverse delta wing to characterize the structure of the vortical flow and associated unsteady phenomena, and quantify the impact of such structures on the aerodynamic performance. We select the most cost-effective gridsize/time-step combination by performing a coupled sensitivity analysis. We successfully validate our numerical approach against well established results for a delta wing. We establish that the flow past a reverse delta wing is always unsteady even at small angles of attack. The shear layer separating at the leading edge of the reverse delta wing rolls-up into spanwise vortical structures that, as they are convected downstream, pair, realign and reorganize generating suction that contributes substantially to the lift produced by a reverse delta wing. The tip vortices confine the vortical structures to the leeward side and contribute to a less extent to lift. Power spectral density analysis shows that the unsteadiness of the lift coefficient is related

- by Ahmed Mahgoub
- •
- Mechanical Engineering, Aerospace Engineering, Geology, Aerodynamics
- by Stefan Louis Arriaga-Weiss
- •
- Machine Learning, Migration, Ecology, Environmental Change
- by Doç. Dr. Bahar Aşcı
- •
- Scenario planning, Vortex dynamics, Vortex
- by Pavel Berloff
- •
- Oceanography, Atmospheric Modeling, Physical Oceanography, Physical

- by Warren R Giordano
- •
- Quantum Physics, Cosmology (Physics), General Relativity, Topology

Through investigating history, evolution of the concept, and development in the theories of electrons, I am convinced that what was missing in our understanding of the electron is a structure, into which all attributes of the electron could be incorporated in a self-consistent way. It is hereby postulated that the topological structure of the electron is a closed two-turn Helix (a so-called Hubius Helix) that is generated by circulatory motion of a mass-less particle at the speed of light. A formulation is presented to describe an isolated electron at rest and at high speed. It is shown that the formulation is capable of incorporating most (if not all) attributes of the electron, including spin, magnetic moment, fine structure constant, anomalous magnetic moment, and charge quantization into one concrete description of the Hubius Helix. The equations for the description emerge accordingly. Implications elicited by the postulate are elaborated. Inadequacy of the formulation is discussed.

- by Qiu Hong Hu
- •
- Geometry And Topology, Knot Theory, Zitterbewegung, Solitons

From February 29th to March 3rd 2016, a range wide, multistakeholder
species conservation planning workshop took place for the Chacoan peccary (Catagonus wagneri) in Asuncion, Paraguay. Details on the status of the Chacoan peccary, the workshop and its outcomes can be found in Altrichter et al. elsewhere in this Volume of Suiform Soundings. This paper focusses on the use of the population viability analysis software “Vortex” (Lacy and Pollak, 2015) as an integral component of the workshop.

- by Anthony J Giordano
- •
- Paraguay, Argentina, Bolivia, Endangered Species

A new method for designing propeller blade sections is presented. A vortex lattice method is used to evaluate the performance and the time-dependent pressure distribution on the blade surface in a non-uniform flow, while efficient optimization algorithms are used to modify the blade sections. Two different designs were carried out in this study. The first was a design to realize a target pressure distribution in a rotating three-dimensional flow. A two-dimensional wing theory was used to obtain the target pressure distribution. The predicted increase in efficiency and the reduction in the cavity volume were confirmed by model experiments. The second was a design to maximize the propeller efficiency. By this method, the propeller efficiency was improved by 1.2% under the constrains of constant thrust and a prescribed margin for face cavitation.

- by koyu kimura
- •
- Design, Agricultural Biotechnology, Optimization, Conception

This article deals with the interaction of co-rotating vortices, in configurations similar to those found in the extended nearwake of typical transport aircraft. The fundamental process of vortex merging is analyzed and modeled in detail in a twodimensional context, giving insight into the conditions for merging and its physical origin, and yielding predictions for the resulting flow. Three-dimensional effects, in the form an elliptic short-wave instability arising in the initial co-rotating vortex flow, are described and analyzed theoretically. They are found to cause significant changes in the merging process, such as earlier merging and larger final vortex cores. Illustrations from recent experimental, numerical and theoretical studies are given, and the relevance of the results for applications to real aircraft wakes is discussed. To cite this article: P. Meunier et al., C. R. Physique 6 (2005).  2005 Académie des sciences. Published by Elsevier SAS. All rights reserved. Résumé Aspects physiques de la fusion de tourbillons. Cet article traite de l'interaction entre tourbillons co-rotatifs, dans des configurations semblables à celles présentes dans le sillage proche et moyen des avions de transport. Le processus fondamental de fusion des tourbillons est analysé et modélisé en détail dans une description bidimensionnelle, donnant accès à des conditions pour la fusion et son origine physique, ainsi qu'aux propriétés de l'écoulement résultant. Les effets tridimensionnels, sous forme d'une instabilité elliptique à courte longueur d'onde des vortex co-rotatifs initiaux, sont décrits et analysés théoriquement. Ils sont à l'origine de modifications importantes de la fusion, comme un démarrage plus rapide du processus et un vortex final plus gros. Des illustrations d'études expérimentales, numériques et théoriques récentes sont données, et la pertinence des résultats pour des applications aux sillages réalistes des avions est discutée. Pour citer cet article : P. Meunier et al., C. R. Physique 6 (2005).

- by Patrice Meunier
- •
- Interaction, Mathematical Sciences, Physical sciences, Vortex

Two hurricane eye features that have yet to be adequately explained are the clear-air moat that forms at the outer edge of the eye and the hub cloud that forms near the circulation centre. To investigate whether these features can be explained by the spatial distribution of the subsidence field, we have derived an analytical solution of the Sawyer-Eliassen transverse circulation equation for a three-region approximation with an unforced central eye region of intermediate or high inertial stability, a diabatically-forced eyewall region of high inertial stability, and an unforced far-field of low inertial stability. This analytical solution isolates the conditions under which the subsidence is concentrated near the edge of the eye. The crucial parameter is the dimensionless dynamical radius of the eye, defined as the physical radius of the eye divided by the characteristic Rossby length in the eye. When this dimensionless dynamical radius is less than 0.6, there is less than 10% horizontal variation in the subsidence rate across the eye; when it is greater than 1.8, the subsidence rate at the edge of the eye is more than twice as strong as at the centre of the eye. When subsidence is concentrated at the edge of the eye, the largest temperature anomalies occur near there rather than at the vortex centre. This warm-ring structure, as opposed to a warm-core structure, is often observed in the lower troposphere of intense hurricanes.

- by Brian McNoldy and +1
- •
- Oceanography, Atmospheric sciences, Vortex, Spatial Distribution

The dynamics of the North Atlantic subpolar gyre (SPG) are assessed under present and glacial boundary conditions by investigating the SPG sensitivity to surface wind-stress changes in a coupled climate model. To this end, the gyre transport is decomposed in Ekman, thermohaline, and bottom transports. Surface wind-stress variations are found to play an important indirect role in SPG dynamics through their effect on water-mass densities. Our results suggest the existence of two dynamically distinct regimes of the SPG, depending on the absence or presence of deep water formation (DWF) in the Nordic Seas and a vigorous Greenland–Scotland ridge (GSR) overflow. In the first regime, the GSR overflow is weak and the SPG strength increases with wind-stress as a result of enhanced outcropping of isopycnals in the centre of the SPG. As soon as a vigorous GSR overflow is established, its associated positive density anomalies on the southern GSR slope reduce the SPG strength. This has implications for past glacial abrupt climate changes, insofar as these can be explained through latitudinal shifts in North Atlantic DWF sites and strengthening of the North Atlantic current. Regardless of the ultimate trigger, an abrupt shift of DWF into the Nordic Seas could result both in a drastic reduction of the SPG strength and a sudden reversal in its sensitivity to wind-stress variations. Our results could provide insight into changes in the horizontal ocean circulation during abrupt glacial climate changes, which have been largely neglected up to now in model studies.

- by Andreas Born
- •
- Oceanography, Climate Change, Abrupt Climate Change, Climate Dynamics
- by Pierre Bonnechere
- •
- Ancient Greek Religion, Synesthesia, Vortex, Katábasis

Functional imaging computational fluid dynamics simulations of right ventricular (RV) inflow fields were obtained by comprehensive software using individual animal-specific dynamic imaging data input from three-dimensional (3-D) real-time echocardiography (RT3D) on a CRAY T-90 supercomputer. Chronically instrumented, lightly sedated awake dogs (n = 7) with normal wall motion (NWM) at control and normal or diastolic paradoxical septal motion (PSM) during RV volume overload were investigated. Up to the E-wave peak, instantaneous inflow streamlines extended from the tricuspid orifice to the RV endocardial surface in an expanding fanlike pattern. During the descending limb of the E-wave, large-scale (macroscopic or global) vortical motions ensued within the filling RV chamber. Both at control and during RV volume overload (with or without PSM), blood streams rolled up from regions near the walls toward the base. The extent and strength of the ring vortex surrounding the main stream were...

- by Michael Womack and +1
- •
- Physiology, Biomechanics, Dogs, Hemodynamics

Two commercial CFD codes were used to simulate the strongly swirling single-phase flow with core recirculation within an axial hydrocyclone. Both packages used a Differential Reynolds Stress Model with default constants for the turbulence closure. The effect of omitting wall reflection terms was also investigated and it was generally found that this lead to better agreement with experiment. Interestingly, the predicted velocity profiles from the two CFD codes did not agree with each other. Possible reasons for this are different turbulence modelling approaches with different terms for the turbulent diffusion and rapid pressure-strain terms. ᭧

- by R. Delfos
- •
- Mechanical Engineering, Chemical Engineering, Design, Computational Fluid Dynamics

The present Note deals with the identification and tracking of vortices in a time-resolved unsteady flow. The approach is based on the combination of two existing post-processing tools that are Galilean invariant functions: feature flow field f and vortex identification algorithm γ 2 . An analytical development shows that the joint use of γ 2 and the streamlines of f allows to identify and track the location of the center of a vortex core with a non-zero convection velocity. We discuss the applicability of this procedure to actual flows for which the assumptions of the analytical approach may not be strictly valid. The procedure is validated using PIV measurements performed in an oscillating flow in a model of thermoacoustic refrigerator. This method proves to be efficient for the automated analysis of convection processes when large numbers of vortices are involved. To cite this article: A. Berson et al., C. R. Mecanique 337 (2009).

P. (2009) Reduced-order modelling of vortex-induced vibration of catenary riser. Ocean Engineering, 36 (Abstract A new reduced-order model capable of analyzing the vortex-induced vibration of catenary riser in the ocean current has been developed. This semi analytical-numerical approach is versatile and allows for a significant reduction in computational effort for the analysis of fluid-riser interactions. The incoming current flow is assumed to be steady, uniform, unidirectional and perpendicular to the riser plane of initial equilibrium curvature. The equations of riser 3-D motion are based on a pinned-pinned, tensioned-beam or flexural cable, modelling which accounts for overall effects of riser bending, extensibility, sag, inclination and structural nonlinearities. The unsteady hydrodynamic forces associated with cross-flow and in-line vibrations are modelled as distributed van der Pol wake oscillators. This hydrodynamic model has been modified in order to capture the effect of varying initial curvature of the inclined flexible cylinder and to describe the space-time fluctuation of lift and drag forces. Depending on the vortex-excited in-plane/out-ofplane modes and system fluid-structure parameters, the parametric studies are carried out to determine the maximum response amplitudes of catenary risers, along with the occurrence of unimodal lock-in phenomenon. The obtained results highlight the effect of initial curvatures on the nonlinear dynamics of riser undergoing vortex-induced vibration.

- by Narakorn Srinil
- •
- Civil Engineering, Ocean Engineering, Nonlinear dynamics, Modeling

Small populations with restricted geographic ranges such as rhinoceros (Rhinoceros unicornis) are prone to extinction
due to anthropogenic factors. The identification of factors underpinning the survival of such species is of critical
importance for population persistence. We used VORTEX population viability analysis (PVA) to assess rhino population
viability in Nepal. We simulated deterministic single-population models under different scenarios to assess viability of
two distinct rhino populations in Nepal: a source population in Chitwan National Park and an augmented population in
Bardia National Park. The impacts of poaching on the populations and the potential for rhino translocation from one
population to another were assessed under the PVA framework. Population and demographic data were obtained from
censuses and from published literature. The model output suggested that the Chitwan population is stable and capable of
supplying at least 10 rhinos every 3 years for translocation provided poaching is restricted (≤15 animals per 3 years).
However, the Bardia population is more vulnerable and unable to persist without supplementation even at the lowest
poaching rate (2 animals per year). Supplementation of at least 10 animals every 3 years for 30 years is crucial for establishing
a viable population of rhinos in Bardia. This level of supplementation can withstand the poaching rate of ≤2 animals
per year. Our study demonstrates that poaching is the major factor determining rhino population viability in Nepal.
The supplementation of the Bardia rhino population with animals from the Chitwan population and increased effort to
reduce poaching are expected to enhance the viability of rhino populations in Nepal.

- by Hemanta Kafley and +1
- •
- Nepal, Population viability analysis, Rhinoceros, Vortex

The unsteady flow past a reverse delta wing is simulated numerically to characterize the structure of the vortical flow and associated unsteady phenomena and quantify the impact of such structures on the aerodynamic performance. The most cost-effective grid-size/time-step combination is selected by performing a coupled sensitivity analysis. This numerical approach is successfully validated against well-established results for a delta wing. It is established that the flow past a reverse delta wing is always unsteady even at small angles of attack. The shear layer separating at the leading edge of the reverse delta wing rolls up into spanwise vortical structures that, as they are convected downstream, pair, realign, and reorganize, generating suction that contributes substantially to the lift produced by a reverse delta wing. The tip vortices confine the vortical structures to the leeward side and contribute to a less extent to lift. Power spectral density analysis shows that the unsteadiness of the lift coefficient is related to vortex shedding and reorganization of the vortical structures. Finally, it is confirmed that the lift-to-drag ratio of a delta wing and a reverse delta wing is, surprisingly, about the same.

- by Ahmed Osama Mahgoub
- •
- Aerodynamics, Low Speed Aerodynamics, ANSYS FLUENT, Vortex

The presence of some high voltage towers in flood stream is one of the most important problems that may lead to the collapse of these towers. The main reason for collapse is the soil erosion around the tower foundation during flood. The shape of the foundation is a vital factor in scouring process. This research is focused on studying different shapes of a tower foundation and its effect on the maximum scour depth. A sediment scour model has been investigated by using Flow 3D V 11.2 Program. The numerical simulation results of the maximum scour depth surrounding a single square pile model have been assured using prior experimental findings and showed good agreement. After that, different four shapes of footing and five values of the inclination angle for pyramid and cone footing have been investigated. The results of cuboid footing have been used as a reference to compare with different shapes. Seventy-two numerical runs have been carried out considering the wide range of Froude number ranging from 0.26 to 0.50 under clear water condition. It is found that, for pyramid and cone footing, the lager the inclination angle, the smaller the scour depth will be and vice versa. The cone footing is better than the other footing shapes. An empirical equation has been developed by using the nonlinear regression to predict the relative maximum scour depth around the footing.

- by IAEME Publication
- •
- Civil Engineering, Flood, Vortex, Footing

1] The offshore propagation of mesoscale eddies contributes significantly to expanding the area of high chlorophyll concentration beyond the coastal upwelling center as shown by satellite data of chlorophyll, wind stress, sea level anomalies between (1997 -2003) off central Chile. Mesoscale eddies ($6.45 Â 10 3 km 2 ) formed near the coastal zone in spring-summer have mean seaward speeds of 1.68kmdAˋ1andreach1.68 km d À1 and reach 1.68kmdAˋ1andreach500 km offshore in winter. Chlorophyll concentrations along eddy paths are elevated by nutrient pumping and by nutrients and/or chlorophyll transported from the coastal zone. Eddies make up >50% of the winter (weak upwelling) chlorophyll peak in the coastal transition zone. Coupling between eddies and upwelling extends central Chile's high productivity area offshore and prolongs it towards winter.

- by Gabriel Yuras
- •
- Productivity, Sea Level, Multidisciplinary, Chemical and Biological Engineering

This paper presents numerical simulation results for vortex-induced vibration of a circular cylinder in laminar flow. A vortex method is implemented to solve the two-dimensional Navier-Stokes equations in terms of vorticity. In order to validate the numerical code, the flow past a fixed cylinder is first investigated for which enough experimental and numerical results are available. Basic characteristics of the dynamic response and vortex shedding for an elastically mounted circular cylinder are then investigated for 70 < Re < 170. The lock-in phenomenon is captured at certain reduced velocities where the lift coefficient takes a considerable value associated with a high amplitude response. The wake structure exhibits the 2S or C (2S) modes of vortex shedding in this range of Reynolds numbers, as opposed to the 2P mode which is observed in the turbulent flow regime. The numerical results are in acceptable agreement with available experimental and numerical data.

- by Taneda Singh
- •
- Mechanical Engineering, Applied Mathematics, Modeling, Fluid Dynamics

Various methods and techniques are being used currently in order to improve the cleaning efficiency of electrostatic precipitators (EP). These techniques have been developed on the basis of past experience, measurements and performance data of industrial and laboratory scale units. The aim of this paper is to present a simulation method that can be used to give insight to the collection mechanisms and phenomena that take place inside electrostatic precipitators. The effects of the electrostatic forces on the particle and gas phases are taken into account. Emphasis is given to the impact of the ionic wind on the gas flow and its influence on the particle transverse transport velocities. The numerical results show the development of cross stream vortices due to ionic wind, with their magnitude depending on the applied wire-to-plate voltage. The vortices affect the collection efficiency of the EP, particularly, in the case of small size particles. Flow uniformity from plate to plate leads to increased collection efficiency of the EP. r

- by A. Varonos
- •
- Engineering, Electrostatics, Fluids, Simulation