Pressure Driven Poiseuille Flow
DEFF Research Database (Denmark)
Stotz, Ingo Leonardo; Iaffaldano, Giampiero; Davies, D. Rhodri
2018-01-01
and lithosphere mutually exchange, by virtue of Newton's third law of motion. In light of these constraints, the notion that subduction is the main driver of present–day Pacific plate motion becomes somewhat unviable, as the pulling force that would be required by slabs exceeds the maximum available from......The Pacific plate is thought to be driven mainly by slab pull, associated with subduction along the Aleutians–Japan, Marianas–Izu–Bonin and Tonga–Kermadec trenches. This implies that viscous flow within the sub–Pacific asthenosphere is mainly generated by overlying plate motion (i.e. Couette flow......), and that the associated shear–stresses at the lithosphere's base are resisting such motion. Recent studies on glacial isostatic adjustment and lithosphere dynamics provide tighter constraints on the viscosity and thickness of Earth's asthenosphere and, therefore, on the amount of shear–stress that asthenosphere...
Poiseuille Flow of Fluid Whose Viscosity is Temperature Dependent ...
African Journals Online (AJOL)
We discuss a fluid flowing between two parallel plates. We assume a Poiseuille flow. Furthermore, we assume that the viscosity μ, depends on temperature T. We show that the velocity equation has two solutions. Graph features prominently in the presentation.
Transient solute transport with sorption in Poiseuille flow
Hesse, M. A.; Zhang, L.; Wang, M.
2016-12-01
Sorption onto the wall has been observed to both increase [Lungu and Moffatt, 1982] and decrease the average solute transport velocity [Golay, 1958], relative to the mean flow velocity. Similarly, opposite conclusion have been reached for the effect of sorption on dispersion. In this work, we study transient solute transport in Poiseuille flow with sorptive boundary and initial transversely uniform distribution (linear release) to reconcile the two different views on solute transport (figure 1) with sorption. Two-dimensional simulations in figure 2 show that there is a transition from fast transport dominated by a fast-moving pulse in the middle of the channel at early times, to slow transport at late times once desorption from the walls becomes important. A set of series solutions for zeroth, first and second longitudinal moment have been derived and we show that the zeroth-order term in the solution corresponds to the slow transport in the late regime, while the first-order term corresponds to the fast transport in the early regime (figure 3). Based on the analytical solution, the time scales for early regime and late regimes of both the velocity and the dispersion coefficient have been determined for an equilibrium sorption model and a kinetic linear sorption model. Furthermore, we give approximated analytical solution when both adsorption and desorption are slow. References M.J.E. Golay. Theory of chromatography in open and coated tubular columns iwth round and rectangular cross-sections. In D.H.Desty, editor, Gas Chromatography, pages 36-53, New York, 1958. Academic Press Inc. E.M. Lungu and H.K. Moffatt. the effect of wall conductance on heat diffusion in duct flow. Journal of Engineering Mathematics, 1692 ;121-136, 1982.
Crisis bifurcations in plane Poiseuille flow
Zammert, S.; Eckhardt, B.E.
2015-01-01
Many shear flows follow a route to turbulence that has striking similarities to bifurcation scenarios in low-dimensional dynamical systems. Among the bifurcations that appear, crisis bifurcations are important because they cause global transitions between open and closed attractors, or indicate
Non-Equilibrium Molecular Dynamics Simulation of Poiseuille Flow in a Carbon Nanochannel
Ni, Guo Liang; He, Ming Li; Hua, Yao Zu; Abareshi, Bagher
2017-01-01
International audience; The numerical simulation of a Poiseuille flow in a narrow channel using the molecular dynamics simulation (MDS) is performed. Poiseuille flow of liquid Argon in a carbon nanochannel is simulated by embedding the fluid particles in a uniform force field. Density, velocity and Temperature profiles across the channel are investigated. When particles will be inserted into the flow, it is expected that the dynamics of flow will depend on the thermostat chosen. To obtain a m...
Fedosov, Dmitry A; Karniadakis, George Em; Caswell, Bruce
2010-04-14
Polymer fluids are modeled with dissipative particle dynamics (DPD) as undiluted bead-spring chains and their solutions. The models are assessed by investigating their steady shear-rate properties. Non-Newtonian viscosity and normal stress coefficients, for shear rates from the lower to the upper Newtonian regimes, are calculated from both plane Couette and plane Poiseuille flows. The latter is realized as reverse Poiseuille flow (RPF) generated from two Poiseuille flows driven by uniform body forces in opposite directions along two-halves of a computational domain. Periodic boundary conditions ensure the RPF wall velocity to be zero without density fluctuations. In overlapping shear-rate regimes the RPF properties are confirmed to be in good agreement with those calculated from plane Couette flow with Lees-Edwards periodic boundary conditions (LECs), the standard virtual rheometer for steady shear-rate properties. The concentration and the temperature dependence of the properties of the model fluids are shown to satisfy the principles of concentration and temperature superposition commonly employed in the empirical correlation of real polymer-fluid properties. The thermodynamic validity of the equation of state is found to be a crucial factor for the achievement of time-temperature superposition. With these models, RPF is demonstrated to be an accurate and convenient virtual rheometer for the acquisition of steady shear-rate rheological properties. It complements, confirms, and extends the results obtained with the standard LEC configuration, and it can be used with the output from other particle-based methods, including molecular dynamics, Brownian dynamics, smooth particle hydrodynamics, and the lattice Boltzmann method.
Diffusion in Poiseuille and Couette flows of binary mixtures of incompressible newtonian fluids
International Nuclear Information System (INIS)
Caetano Filho, E.; Qassim, R.Y.
1981-07-01
Using the continuum theory of binary mixtures of incompressible Newtonian fluids, Poiseuille and Couette flows are studied with a view to determining whether diffusion occurs in such flows. It is shown that diffusion is absent in the Couette case. However, in Poiseuille flow there are significant differences between the velocities of the species comprising the mixture. This result is in broad agreement with that of Mills for similar mixtures of nonuniform composition. (Author) [pt
Constraint and flow: Poiseuille shear response of a surfactant ...
Indian Academy of Sciences (India)
we have begun measurements of the Poiseuille surface shear response of sponge phases a situation in which one might expect effects from an interplay between these dynamic and geometric effects. Keywords. Neutron scattering; soft condensed matter. PACS Nos 61.12.Ex; 82.70.Dd. †Previously: HFIR Center for Neutron ...
Linear Stability of Plane Poiseuille Flow in an Infinite Elastic Medium and Volcanic Tremors
Sakuraba, A.; Yamauchi, H.
2013-12-01
The linear stability of a plane compressible laminar (Poiseuille) flow sandwiched between two semi-infinite elastically deformable media was investigated with the aim of presenting a general explanation for the excitation of volcanic tremors, which are characterized as long-period and long-lasting seismic events uniquely observed at active volcanoes. Results show that there are several regimes of instability and these primarily depend on the symmetry of the oscillatory fluid and solid motion, wavelength, and fluid viscosity. It is found that the antisymmetric (flexural) instability, involving two parallel Rayleigh waves traveling against the Poiseuille flow, occurs at a critical flow speed much slower than that of symmetric instability. Symmetric instability involves a slow Krauklis (crack) wave traveling with the Poiseuille flow, and it is unlikely that this is the cause of volcanic tremors. The critical flow speed for the antisymmetric instability decreases inversely proportional to the wavelength, and the asymptotic solution is derived when the wavelength is very long. The physical mechanism of this instability can be understood as a simple friction drag on the Rayleigh-wave particle motion caused by the main Poiseuille flow. Based on numerical calculations and analytical consideration, we conclude that the antisymmetric instability is possibly produced by a basaltic magma flow of 1 m/s through a dike of thickness 1 m and extending for several kilometers; this origin can explain some of the characteristics of volcanic tremors. A schematic explanation for the antisymmetric instability. A solid particle (open circle) at the boundary moves along an ellipse (dotted line). White arrows represent the perturbed fluid and solid velocities. The plane Poiseuille flow is represented by black arrows with its parabolic envelop.
Lateral Migration and Rotational Motion of Elliptic Particles in Planar Poiseuille Flow
Qi, Dewei; Luo, Li-Shi; Aravamuthan, Raja; Strieder, William; Bushnell, Dennis M. (Technical Monitor)
2002-01-01
Simulations of elliptic particulate suspensions in the planar Poiseuille flow are performed by using the lattice Boltzmann equation. Effects of the multi-particle on the lateral migration and rotational motion of both neutrally and non-neutrally buoyant elliptic particles are investigated. Low and intermediate total particle volume fraction f(sub a) = 13%, 15%, and 40% are considered in this work.
The Bernoulli-Poiseuille Equation.
Badeer, Henry S.; Synolakis, Costas E.
1989-01-01
Describes Bernoulli's equation and Poiseuille's equation for fluid dynamics. Discusses the application of the combined Bernoulli-Poiseuille equation in real flows, such as viscous flows under gravity and acceleration. (YP)
A continuum theory for two-phase flows of particulate solids: application to Poiseuille flows
Monsorno, Davide; Varsakelis, Christos; Papalexandris, Miltiadis V.
2015-11-01
In the first part of this talk, we present a novel two-phase continuum model for incompressible fluid-saturated granular flows. The model accounts for both compaction and shear-induced dilatancy and accommodates correlations for the granular rheology in a thermodynamically consistent way. In the second part of this talk, we exercise this two-phase model in the numerical simulation of a fully-developed Poiseuille flow of a dense suspension. The numerical predictions are shown to compare favorably against experimental measurements and confirm that the model can capture the important characteristics of the flow field, such as segregation and formation of plug zones. Finally, results from parametric studies with respect to the initial concentration, the magnitude of the external forcing and the width of the channel are presented and the role of these physical parameters is quantified. Financial Support has been provided by SEDITRANS, an Initial Training Network of the European Commission's 7th Framework Programme
Directory of Open Access Journals (Sweden)
Hifdi Ahmed
2012-07-01
Full Text Available The linear stability of plan Poiseuille flow of an electrically conducting viscoelastic fluid in the presence of a transverse magnetic field is investigated numerically. The fourth-order Sommerfeld equation governing the stability analysis is solved by spectral method with expansions in lagrange’s polynomials, based on collocation points of Gauss-Lobatto. The critical values of Reynolds number, wave number and wave speed are computed. The results are shown through the neutral curve. The main purpose of this work is to check the combined effect of magnetic field and fluid’s elasticity on the stability of the plane Poiseuille flow. Based on the results obtained in this work, the magnetic field is predicted to have a stabilizing effect on the Poiseuille flow of viscoelastic fluids. Hence, it will be shown that for second-order fluids (K 0 is that the critical Reynolds numbers Rec increase when the Hartman number M increases for certain value of elasticity number K and decrease for others. The latter result is in contrast to previous studies.
Experimental scaling law for the subcritical transition to turbulence in plane Poiseuille flow.
Lemoult, Grégoire; Aider, Jean-Luc; Wesfreid, José Eduardo
2012-02-01
We present an experimental study of the transition to turbulence in a plane Poiseuille flow. Using a well-controlled perturbation, we analyze the flow by using extensive particle image velocimetry and flow visualization (using laser-induced fluorescence) measurements, and use the deformation of the mean velocity profile as a criterion to characterize the state of the flow. From a large parametric study, four different states are defined, depending on the values of the Reynolds number and the amplitude of the perturbation. We discuss the role of coherent structures, such as hairpin vortices, in the transition. We find that the minimal amplitude of the perturbation triggering transition scales asymptotically as Re(-1).
Conoscopic observation of director reorientation during Poiseuille flow of a nematic liquid crystal
Holmes, C. J.; Cornford, S. L.; Sambles, J. R.
2009-10-01
Director reorientation under pressure driven (Poiseuille) flow is observed conoscopically for the liquid crystal 5CB aligned at an azimuthal angle of 45° to the direction of flow. A polyimide surface treatment (AL 1254) is used to promote planar homogeneous alignment and rubbed to produce an initial azimuthal alignment angle ϕ0. Conoscopic interference figure rotation is documented as a function of flow rate and compared to that produced from numerical models using Leslie-Ericksen-Parodi theory. Model and data show excellent agreement.
Beyond Poiseuille: Preservation Fluid Flow in an Experimental Model
Directory of Open Access Journals (Sweden)
Saurabh Singh
2013-01-01
Full Text Available Poiseuille’s equation describes the relationship between fluid viscosity, pressure, tubing diameter, and flow, yet it is not known if cold organ perfusion systems follow this equation. We investigated these relationships in an ex vivo model and aimed to offer some rationale for equipment selection. Increasing the cannula size from 14 to 20 Fr increased flow rate by a mean (SD of 13 (12%. Marshall’s hyperosmolar citrate was three times less viscous than UW solution, but flows were only 45% faster. Doubling the bag pressure led to a mean (SD flow rate increase of only 19 (13%, not twice the rate. When external pressure devices were used, 100 mmHg of continuous pressure increased flow by a mean (SD of 43 (17% when compared to the same pressure applied initially only. Poiseuille’s equation was not followed; this is most likely due to “slipping” of preservation fluid within the plastic tubing. Cannula size made little difference over the ranges examined; flows are primarily determined by bag pressure and fluid viscosity. External infusor devices require continuous pressurisation to deliver high flow. Future studies examining the impact of perfusion variables on graft outcomes should include detailed equipment descriptions.
Nonlinear travelling waves in rotating Hagen–Poiseuille flow
Pier, Benoît; Govindarajan, Rama
2018-03-01
The dynamics of viscous flow through a rotating pipe is considered. Small-amplitude stability characteristics are obtained by linearizing the Navier–Stokes equations around the base flow and solving the resulting eigenvalue problems. For linearly unstable configurations, the dynamics leads to fully developed finite-amplitude perturbations that are computed by direct numerical simulations of the complete Navier–Stokes equations. By systematically investigating all linearly unstable combinations of streamwise wave number k and azimuthal mode number m, for streamwise Reynolds numbers {{Re}}z ≤slant 500 and rotational Reynolds numbers {{Re}}{{Ω }} ≤slant 500, the complete range of nonlinear travelling waves is obtained and the associated flow fields are characterized.
Poiseuille flow to measure the viscosity of particle model fluids.
Backer, J.A.; Lowe, C.P.; Hoefsloot, H.C.J.; Iedema, P.D.
2005-01-01
The most important property of a fluid is its viscosity, it determines the flow properties. If one simulates a fluid using a particle model, calculating the viscosity accurately is difficult because it is a collective property. In this article we describe a new method that has a better signal to
Thermal ignition in a reactive variable viscosity Poiseuille flow ...
African Journals Online (AJOL)
In this paper, we investigate the thermal ignition in a strongly exothermic reaction of a variable viscosity combustible material flowing through a channel with isothermal walls under Arrhenius kinetics, neglecting the consumption of the material. Analytical solutions are constructed for the governing nonlinear boundary-value ...
A Poiseuille-based coronary angiographic index for prediction of fractional flow reserve.
Jaffe, Ronen; Halon, David A; Roguin, Ariel; Rubinshtein, Ronen; Lewis, Basil S
2013-08-10
Coronary revascularization is commonly based on the angiographic finding of percent diameter stenosis (%DS) >50 while lesion length (LL), which contributes to flow-limitation according to Poiseuille's equation, is disregarded. Fractional flow reserve (FFR) is superior to assessment of %DS for identifying flow-limiting lesions, but the technology is invasive and relatively expensive. We developed a Poiseuille-based angiographic index, incorporating both minimal lumen diameter (MLD) and LL, for improved assessment of the hemodynamic significance of intermediate coronary lesions. The present study was designed to test the hypothesis that the Poiseuille-based angiographic index correlated better with FFR measurements than angiographic assessment of %DS. We performed quantitative coronary angiography (QCA) and FFR measurements in 46 intermediate coronary lesions in 41 symptomatic patients referred for diagnostic coronary angiography. From QCA we determined LL, MLD and %DS and calculated an angiographic index, the LL/MLD(4) ratio. Mean LL was 14.2 ± 7.8 (range: 4.3-38.8) mm, MLD 1.4 ± 0.4 (range: 0.6-2.3) mm, %DS 46 ± 12 (range: 25-74) and FFR 0.85 ± 0.09 (range: 0.55-1.00). Fractional flow reserve correlated inversely with %DS (R=-0.39, p=0.008) and with the LL/MLD(4) ratio (R=-0.66, pvalue of 0.80 corresponded with a LL/MLD(4) ratio of 12 (p=0.003) but not with a %DS of 50 (p=NS). A LL/MLD(4) ratio ≤ 12 had a specificity of 94% and negative predictive value of 82% for excluding hemodynamically significant lesions with FFR (≥ 0.80). The LL/MLD(4) ratio was superior to standard angiographic measurement of %DS for exclusion of hemodynamically significant coronary lesions. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.
Non-modal stability in Hagen-Poiseuille flow of a Bingham fluid
Liu, Rong; Liu, Qiu Sheng
2014-01-01
Linear stability in Hagen-Poiseuille flow of a Bingham fluid is considered. Bingham fluid exhibits a yield stress in addition to a plastic viscosity. A Bingham number B, which describes the ratio of yield and viscous stresses, is used to characterize the behavior of Bingham-Hagen-Poiseuille flow. The effects of B on the stability are investigated using the energy method and the non-modal stability theory. The energy analysis shows that the non-axisymmetric disturbance has the lowest critical energy Reynolds number for all B. The global critical energy Reynolds number Reg increases with B. At sufficient large B, Reg has the order of B1/2. For the non-modal stability, we focus on response to external excitations and initial conditions. The former is studied by examining the ɛ-pseudospectrum, and the latter is by examining the energy growth function G(t). For the problem of response to external excitations, the maximum response is achieved by non-axisymmetric and streamwise uniform disturbances at the frequency of ω = 0, with a possible choice of the azimuthal wavenumbers of n = 1, 2, or 3. For the problem of response to initial conditions, it is found that there can be a rather large transient growth even though the linear operator of the Bingham-Hagen-Poiseuille flow has no unstable eigenvalue. For small B, the optimal disturbance is in the form of streamwise uniform vortices and streaks. For large B, the optimal disturbance is in the form of oblique waves. The optimal energy growth decreases and the optimal azimuthal wavenumber increases with the increase of B.
Vesicle dynamics in a confined Poiseuille flow: From steady state to chaos
Aouane, Othmane; Thiébaud, Marine; Benyoussef, Abdelilah; Wagner, Christian; Misbah, Chaouqi
2014-09-01
Red blood cells (RBCs) are the major component of blood, and the flow of blood is dictated by that of RBCs. We employ vesicles, which consist of closed bilayer membranes enclosing a fluid, as a model system to study the behavior of RBCs under a confined Poiseuille flow. We extensively explore two main parameters: (i) the degree of confinement of vesicles within the channel and (ii) the flow strength. Rich and complex dynamics for vesicles are revealed, ranging from steady-state shapes (in the form of parachute and slipper shapes) to chaotic dynamics of shape. Chaos occurs through a cascade of multiple periodic oscillations of the vesicle shape. We summarize our results in a phase diagram in the parameter plane (degree of confinement and flow strength). This finding highlights the level of complexity of a flowing vesicle in the small Reynolds number where the flow is laminar in the absence of vesicles and can be rendered turbulent due to elasticity of vesicles.
Density Distribution of Liquid Argon in Nano-channel Poiseuille Flows
She, Jiangwei; Wang, Yuyi; Zhou, Zhe-Wei
2017-11-01
The density layering parallel to the boundaries of liquid has been measured in many experiments and also observed in molecular dynamics (MD) simulations. In this study, a detail and systematic investigation of density distribution in nano-scale Poiseuille flows is carried out. Through analyzing the difference of density distribution curves obtained under different conditions, the influence of interaction parameters, configuration form of solid wall and temperature on the layering are investigated. The internal mechanism is also explored in this paper. The detail description of the density distribution results and simulation algorithm is given. National natural science foundation (A020405).
DEFF Research Database (Denmark)
Javier Alvarez, Nicolas; Uguz, A. Kerem
2013-01-01
-examines the Marangoni-Bénard instability for a three-layer system with deformable interfaces undergoing Poiseuille flow. Taking into account the deformability of the interface reveals new physics. Linear stability analysis shows that at small wave numbers a deformable interface is of the orders of magnitude less...... stable than a non-deformable interface. At large wave numbers, both a rigid and a deformable interface have the same stability. Furthermore, a base planar Poiseuille flow affects the linear stability of the system and the type of instability when the interface is allowed to deform. Flow stabilizes...
Doi, Toshiyuki
2018-04-01
Slow flows of a rarefied gas between two plane parallel walls with nonuniform surface properties are studied based on kinetic theory. It is assumed that one wall is a diffuse reflection boundary and the other wall is a Maxwell-type boundary whose accommodation coefficient varies periodically in the direction perpendicular to the flow. The time-independent Poiseuille, thermal transpiration and Couette flows are considered. The flow behavior is numerically studied based on the linearized Bhatnagar–Gross–Krook–Welander model of the Boltzmann equation. The flow field, the mass and heat flow rates in the gas, and the tangential force acting on the wall surface are studied over a wide range of the gas rarefaction degree and the parameters characterizing the distribution of the accommodation coefficient. The locally convex velocity distribution is observed in Couette flow of a highly rarefied gas, similarly to Poiseuille flow and thermal transpiration. The reciprocity relations are numerically confirmed over a wide range of the flow parameters.
Mehdizadeh, A.; Oberlack, M.
2010-10-01
Laminar and turbulent Poiseuille-Ekman flows at different rotation rates have been investigated by means of analytical and numerical approaches. A series of direct numerical simulations (DNSs) with various rotation rates (Ro2=0-1.82) for Reynolds number Reτ0=180 based on the friction velocity in the nonrotating case has been conducted. Both (laminar and turbulent) flow states are highly sensitive to the rotation. Even a small rotation rate can reduce the mean streamwise velocity and induce a very strong flow in the spanwise direction, which, after attaining a maximum, decreases by further increasing the rotation rate. It has been further observed that turbulence is damped by increasing the rotation rate and at about Ro2=0.145 a transition from the fully turbulent to a quasilaminar state occurs. In this region Reynolds number is only large enough to sustain some perturbations and the mean velocity profiles have inflection points. The instability of the turbulent shear stress is probably the main reason for the formation of the elongated coherent structures (roll-like vortices) in this region. In the fully turbulent parameter domain all six components of Reynolds stress tensor are nonzero due to the existence of the spanwise mean velocity. The Poiseuille-Ekman flow in this region can be regarded as a turbulent two-dimensional channel flow with a mean flow direction inclining toward the spanwise direction. Finally, due to the further increase in the rotation rate, at about Ro2=0.546 turbulence is completely damped and the flow reaches a fully laminar steady state, for which an analytical solution of the Navier-Stokes equations exists. The DNS results reproduce this analytical solution for the laminar state.
DEFF Research Database (Denmark)
Mortensen, Asger; Okkels, Fridolin; Bruus, Henrik
2005-01-01
We consider pressure-driven, steady-state Poiseuille flow in straight channels with various cross-sectional shapes: elliptic, rectangular, triangular, and harmonic-perturbed circles. A given shape is characterized by its perimeter P and area A which are combined into the dimensionless compactness...... number C= P-2/A, while the hydraulic resistance is characterized by the well-known dimensionless geometrical correction factor a. We find that a depends linearly on C, which points out C as a single dimensionless measure characterizing flow properties as well as the strength and effectiveness of surface......-related phenomena central to lab-on-a-chip applications. This measure also provides a simple way to evaluate the hydraulic resistance for the various shapes....
Markesteijn, A.P.; Hartkamp, Remco; Luding, Stefan; Westerweel, J.
2012-01-01
The viscosity-temperature relation is determined for the water models SPC/E, TIP4P, TIP4P/Ew, and TIP4P/2005 by considering Poiseuille flow inside a nano-channel using molecular dynamics. The viscosity is determined by fitting the resulting velocity profile (away from the walls) to the continuum
Absolute and convective instabilities in combined Couette-Poiseuille flow past a neo-Hookean solid
Patne, Ramkarn; Shankar, V.
2017-12-01
Temporal and spatio-temporal stability analyses are carried out to characterize the occurrence of convective and absolute instabilities in combined Couette-Poiseuille flow of a Newtonian fluid past a deformable, neo-Hookean solid layer in the creeping-flow limit. Plane Couette flow of a Newtonian fluid past a neo-Hookean solid becomes temporally unstable in the inertia-less limit when the parameter Γ = V η/(GR) exceeds a critical value. Here, V is the velocity of the top plate, η is the fluid viscosity, G is the shear modulus of the solid layer, and R is the fluid layer thickness. The Kupfer-Bers method is employed to demarcate regions of absolute and convective instabilities in the Γ-H parameter space, where H is the ratio of solid to fluid thickness in the system. For certain ranges of the thickness ratio H, we find that the flow could be absolutely unstable, and the critical Γ required for absolute instability is very close to that for temporal instability, thus making the flow absolutely unstable at the onset of temporal instability. In some cases, there is a gap in the parameter Γ between the temporal and absolute instability boundaries. The present study thus shows that absolute instabilities are possible, even at very low Reynolds numbers in flow past deformable solid surfaces. The presence of absolute instabilities could potentially be exploited in the enhancement of mixing at low Reynolds numbers in flow through channels with deformable solid walls.
International Nuclear Information System (INIS)
Silva, Goncalo; Leal, Nuno; Semiao, Viriato
2008-01-01
Microfluidics is a promising technology, although the governing physical mechanisms are still not quite understood due to the difficulties arising in measuring at such small scales. This work intends to bring some insight on the influence of surface phenomena in microscale flows by proposing a different method to quantify such influence. In this new method, detailed velocity measurements are performed to evaluate the influence on the flow of the surface phenomena instead of using measured bulk flow properties. For that micro-Particle Image Velocimetry (micro-PIV) is used to characterize the flow kinematics inside a DantecDynamics microchannel (with hydraulic diameter of 637 μm) that possesses rather rough walls (relative roughness of 1.6%) and a very irregular cross-section shape. Two-dimensional velocity profiles were measured in 61 horizontal planes to define the three-dimensional laminar flows (Re ≤ 50). Integration of the velocity profiles yielded volumetric flow rates with a maximum deviation of 3% from the measured volume of fluid discharged as function of time, which gives the magnitude of the bias error of the experimental technique. Effects of walls roughness were quantified by comparing Poiseuille numbers obtained from experimental velocity profiles against those obtained from CFD predictions for the same operating conditions but with hydrodynamically smooth walls, according to the new method proposed herein. Those Poiseuille numbers differed 11% demonstrating the need to account for wall roughness in microflows
Henríquez Rivera, Rafael G.; Zhang, Xiao; Graham, Michael D.
2016-10-01
A mechanistic model, derived from kinetic theory, is developed to describe segregation in confined multicomponent suspensions such as blood. It incorporates the two key phenomena arising in these systems at low Reynolds number: hydrodynamic pair collisions and hydrodynamic migration. Two flow profiles are considered: simple shear flow (plane Couette flow) and plane Poiseuille flow. The theory begins by writing the evolution of the number density of each component in the suspension as a master equation with contributions from migration and collisions. By making judicious approximations for the collisions, this system of integrodifferential equations is reduced to a set of drift-diffusion equations. We focus attention on the case of a binary suspension with a deformable primary component that completely dominates the collision dynamics in the system and a trace component that has no effect on the primary. The model captures the phenomena of depletion layer formation and margination observed in confined multicomponent suspensions of deformable particles. The depletion layer thickness of the primary component is predicted to follow a master curve relating it in a specific way to confinement ratio and volume fraction. Results from various sources (experiments, detailed simulations, master equation solutions) with different parameters (flexibility of different components in the suspension, viscosity ratio, confinement, among others) collapse onto the same curve. For sufficiently dilute suspensions the analytical form predicted by the drift-diffusion theory for this curve is in excellent agreement with results from these other sources with only one adjustable parameter. In a binary suspension, several regimes of segregation arise, depending on the value of a "margination parameter" M . Most importantly, in both Couette and Poiseuille flows there is a critical value of M below which a sharp "drainage transition" occurs: one component is completely depleted from the bulk
Directory of Open Access Journals (Sweden)
Sergey G. Chefranov
2012-11-01
Full Text Available Aims This paper deals with solving of a century-old paradox of linear stability for the Hagen-Poiseuille flow. A new mechanism of dissipative hydrodynamic instability has been established herein, and a basis for the forming of helical structural organization of bloodstream and respective energy effectiveness of the cardiovascular system functioning has been defined by the authors. Materials and methods Theory of hydrodynamic instability, Galerkin’s approximation. Results A new condition Re > Reth-min ≈ 124 of linear (exponential instability of the Hagen-Poisseuille (HP flow with respect to extremely small by magnitude axially-symmetric disturbances of the tangential component of the velocity field is obtained. The disturbances necessarily shall have quasi-periodic longitudinal variability along the pipe axis that corresponds to the observed data. Conclusion We show that the obtained estimate of value of Reth-min corresponds to the condition of independence of the main result (on the linear instability of the HP flow when Re > Reth-min from the procedure of averaging used in the Galerkin approximation. Thus, we obtain the possible natural mechanism for the blood swirling flows formations observed in the aorta and the large blood vessels.
Large eddy simulations of Taylor-Couette-Poiseuille flows in a narrow-gap system
Poncet, Sébastien; Viazzo, Stéphane; Oguic, Romain
2014-10-01
The present paper concerns Large-Eddy Simulations (LES) of turbulent Taylor-Couette-Poiseuille flows in a narrow-gap cavity for six different combinations of rotational and axial Reynolds numbers. The in-house numerical code has been first validated in a middle-gap cavity. Two sets of refined LES results, using the Wall-Adapting Local Eddy Viscosity (WALE) and the Dynamic Smagorinsky subgrid-scale models available within an in-house code based on high-order compact schemes, have been then compared with no noticeable difference on the mean flow field and the turbulent statistics. The WALE model enabling a saving of about 12% of computational effort has been finally used to investigate the influence on the hydrodynamics of the swirl parameter N within the range [1.49 - 6.71]. The swirl parameter N, which compares the effects of rotation of the inner cylinder and the axial flowrate, does not influence significantly the mean velocity profiles. Turbulence intensities are enhanced with increasing values of N with remarkably high peak values within the boundary layers. The inner rotating cylinder has a destabilizing effect inducing asymmetric profiles of the Reynolds stress tensor components. The rotor and stator boundary layers exhibit the main characteristics of two-dimensional boundary layers. Turbulence is also mainly at two-component there. Thin coherent structures appearing as negative (resp. positive) spiral rolls are observed along the rotor (resp. stator) side. Their inclination angle depends strongly on the value of the swirl parameter, which fixes the intensity of the crossflow. On the other hand, the intensity and the size of the coherent structures observed within the boundary layers are governed by the effective Reynolds number. For its highest value, they penetrate the whole gap. Finally, the results have been extended to the non-isothermal case in the forced convection regime. A correlation for the Nusselt number along the rotor has been provided showing a
Ramesh, K.
2017-07-01
In the current article, we have discussed the Poiseuille flow of an incompressible magnetohydrodynamic Jeffrey fluid between parallel plates through homogeneous porous medium using slip boundary conditions under the effect of heat transfer. The equations governing the fluid flow are modeled in Cartesian coordinate system. The energy equation is considered under the effects viscous dissipation and heat generation. Analytical solutions for the velocity and temperature profiles are obtained. The effects of the various involved parameters on the velocity and temperature profiles are studied and the results are presented through the graphs. It is observed from our analysis that, with increase of slip parameter and pressure gradient increase the velocity. The temperature is an increasing function of heat generation parameter, Brinkman number, thermal slip parameter and non-Newtonian fluid parameter.
Energy Technology Data Exchange (ETDEWEB)
Martinand, D.
2003-01-15
This analytical study deals with the spatio-temporal evolution of linear thermo-convective instabilities in a horizontal fluid layer heated from below (the Rayleigh--Benard system) and subject to a horizontal pressure gradient (Poiseuille flow). The novelty consists of a spatially inhomogeneous temperature, in the form of a two-dimensional bump imposed on the lower plate, while the upper plate is kept at a constant temperature. The inhomogeneous boundary temperature and the mean flow of the Rayleigh--Benard--Poiseuille system break the symmetries of the classical Rayleigh--Benard system. The instabilities of interest are therefore spatially localised packets of convection rolls. If a mode of this type is synchronized, it is called a global mode. Assuming that the characteristic scale of the spatial variation of the lower plate temperature is large compared to the wavelength of the rolls, global modes are sought in the form of Eigenmodes in the confined vertical direction, modulated by a two-dimensional WKBJ expansion in the slowly-varying horizontal directions. Such an expansion breaks down at points where the group velocity of the instability vanishes, i.e. at WKBJ turning points. In the neighbourhood of one such point, located at the top of the temperature bump, the boundedness of the solution imposes a selection criterion for the global modes which provides the growth rate (or equivalently the critical threshold), the frequency and the wave vector of the most amplified global mode. This study thus generalizes to two-dimensional cases the methods used and the results obtained for one-dimensional inhomogeneities. The analysis is first applied to a simplified governing equation obtained by an envelope formalism and the analytical results are compared with numerical solutions of the amplitude equation. The formalism is finally applied to the Rayleigh--Benard--Poiseuille system described by the Navier--Stokes equations with the Boussinesq approximation. (author)
Das, Sayan; Chakraborty, Suman
2018-02-01
The effect of surface viscosity on the motion of a surfactant-laden droplet in the presence of a non-isothermal Poiseuille flow is studied, both analytically and numerically. The presence of bulk-insoluble surfactants along the droplet surface results in interfacial shear and dilatational viscosities. This, in turn, is responsible for the generation of surface-excess viscous stresses that obey the Boussinesq-Scriven constitutive law for constant values of surface shear and dilatational viscosities. The present study is primarily focused on finding out how this confluence can be used to modulate droplet dynamics in the presence of Marangoni stress induced by nonuniform distribution of surfactants and temperature along the droplet surface, by exploiting an intricate interplay of the respective forcing parameters influencing the interfacial stresses. Under the assumption of negligible fluid inertia and thermal convection, the steady-state migration velocity of a non-deformable spherical droplet, placed at the centerline of an imposed unbounded Poiseuille flow, is obtained for the limiting case when the surfactant transport along the interface is dominated by surface diffusion. Our analysis proves that the droplet migration velocity is unaffected by the shear viscosity whereas the dilatational viscosity has a significant effect on the same. The surface viscous effects always retard the migration of a surfactant-laden droplet when the temperature in the far-field increases in the direction of the imposed flow although the droplet always migrates towards the hotter region. On the contrary, if a large temperature gradient is applied in a direction opposite to that of the imposed flow, the direction of droplet migration gets reversed. However, for a sufficiently high value of dilatational surface viscosity, the direction of droplet migration reverses. For the limiting case in which the surfactant transport along the droplet surface is dominated by surface convection, on
Usha, R.; Chattopadhyay, Geetanjali; Millet, Severine
2017-11-01
Understanding of stability characteristics of two-fluids system in confined complex geometries is crucial in industrial applications and natural phenomena. This study is motivated by the necessity to understand possible drag reduction using superhydrophobic surfaces or liquid-infused surfaces or surfaces with complex features which can be modeled as porous substrates with appropriate properties. A linear stability analysis of Poiseuille flow of viscosity-stratified two-layer immiscible fluids system in a porous channel with anisotropic and inhomogeneous permeability is analyzed. The flow in the porous medium is governed by the generalized Darcy model with Beavers-Joseph condition at the interface of the liquid-porous layers. The resulting generalized eigenvalue problem is solved numerically and the temporal linear stability analysis shows the existence of three distinct modes of instability; a porous mode, an interface mode and a shear mode. The influence of the variations in anisotropic and inhomogeneous properties of the porous medium on the interface and shear mode instabilities is assessed.The study reveals a possibility of controlling instabilities in two-layer flows in a rigid channel by designing a wall of the channel as a porous surface with appropriate properties.
Stotz, I. L.; Iaffaldano, G.; Davies, D. R.
2018-01-01
The Pacific Plate is thought to be driven mainly by slab pull, associated with subduction along the Aleutians-Japan, Marianas-Izu-Bonin, and Tonga-Kermadec trenches. This implies that viscous flow within the sub-Pacific asthenosphere is mainly generated by overlying plate motion (i.e., Couette flow) and that the associated shear stresses at the lithosphere's base are resisting such motion. Recent studies on glacial isostatic adjustment and lithosphere dynamics provide tighter constraints on the viscosity and thickness of Earth's asthenosphere and, therefore, on the amount of shear stress that asthenosphere and lithosphere mutually exchange, by virtue of Newton's third law of motion. In light of these constraints, the notion that subduction is the main driver of present-day Pacific Plate motion becomes somewhat unviable, as the pulling force that would be required by slabs exceeds the maximum available from their negative buoyancy. Here we use coupled global models of mantle and lithosphere dynamics to show that the sub-Pacific asthenosphere features a significant component of pressure-driven (i.e., Poiseuille) flow and that this has driven at least 50% of the Pacific Plate motion since, at least, 15 Ma. A corollary of our models is that a sublithospheric pressure difference as high as ±50 MPa is required across the Pacific domain.
Hu, J; Yin, X Y; Henry, D; Hadid, H Ben
2009-08-01
The spatiotemporal evolution of Poiseuille-Rayleigh-Bénard flows in binary fluids with Soret effect is investigated by carrying out fully nonlinear two-dimensional numerical simulations initiated by a pulselike disturbance. The traveling wave packets for positive as well as negative separation factors psi are obtained numerically for ethanol-water-like mixtures (Prandtl number Pr=10 , Lewis number Le=0.01) and selected combinations of Rayleigh and Reynolds numbers at psi=0.01, 0.1 and psi=-0.1. The characteristics of the wave fronts and the transitions observed between absolute and convective instabilities when changing the parameters are compared with the results previously obtained by linear spatiotemporal stability analysis. The simulations are in very good agreement with the stability results, which confirms the validity of both approaches. Finally, in order to characterize the possible interaction between the two wave packets of the so-called downstream and upstream modes for psi<0, the spatiotemporal stability analysis is used to detect a boundary curve in the (Re, Ra) parameter region beyond which the two wave packets will never completely separate. Numerical simulations illustrate the different evolutions of the wave packets on both sides of this boundary.
Directory of Open Access Journals (Sweden)
Sidra Aman
2017-01-01
Full Text Available Applications of carbon nanotubes, single walls carbon nanotubes (SWCNTs and multiple walls carbon nanotubes (MWCNTs in thermal engineering have recently attracted significant attention. However, most of the studies on CNTs are either experimental or numerical and the lack of analytical studies limits further developments in CNTs research particularly in channel flows. In this work, an analytical investigation is performed on heat transfer analysis of SWCNTs and MWCNTs for mixed convection Poiseuille flow of a Casson fluid along a vertical channel. These CNTs are suspended in three different types of base fluids (Water, Kerosene and engine Oil. Xue [Phys. B Condens. Matter 368, 302–307 (2005] model has been used for effective thermal conductivity of CNTs. A uniform magnetic field is applied in a transverse direction to the flow as magnetic field induces enhancement in the thermal conductivity of nanofluid. The problem is modelled by using the constitutive equations of Casson fluid in order to characterize the non-Newtonian fluid behavior. Using appropriate non-dimensional variables, the governing equations are transformed into the non-dimensional form, and the perturbation method is utilized to solve the governing equations with some physical conditions. Velocity and temperature solutions are obtained and discussed graphically. Expressions for skin friction and Nusselt number are also evaluated in tabular form. Effects of different parameters such as Casson parameter, radiation parameter and volume fraction are observed on the velocity and temperature profiles. It is found that velocity is reduced under influence of the exterior magnetic field. The temperature of single wall CNTs is found greater than MWCNTs for all the three base fluids. Increase in volume fraction leads to a decrease in velocity of the fluid as the nanofluid become more viscous by adding CNTs.
Directory of Open Access Journals (Sweden)
A. Zeeshan
2018-03-01
Full Text Available The motivation of the current article is to explore the energy activation in MHD radiative Couette-Poiseuille flow nanofluid in horizontal channel with convective boundary conditions. The mathematical model of Buongiorno [1] effectively describes the current flow analysis. Additionally, the impact of chemical reaction is also taken in account. The governing flow equations are simplified with the help of boundary layer approximations. Non-linear coupled equations for momentum, energy and mass transfer are tackled with analytical (HAM technique. The influence of dimensionless convergence parameter like Brownian motion parameter, radiation parameter, buoyancy ratio parameter, dimensionless activation energy, thermophoresis parameter, temperature difference parameter, dimensionless reaction rate, Schmidt number, Brinkman number, Biot number and convection diffusion parameter on velocity, temperature and concentration profiles are discussed graphically and in tabular form. From the results, it is elaborate that the nanoparticle concentration is directly proportional to the chemical reaction with activation energy and the performance of Brownian motion on nanoparticle concentration gives reverse pattern to that of thermophoresis parameter. Keywords: Convective boundary conditions, Activation energy, Chemical reaction, Couette-Poiseuille flow, Thermal radiation, Nanofluid
National Research Council Canada - National Science Library
Zhou, Hong; Forest, M. G
2006-01-01
.... The morphology has various physical realizations, all coupled through the model equations: the orientational distribution of the ensemble of rods, anisotropic viscoelastic stresses, and flow feedback...
Zeeshan, A.; Shehzad, N.; Ellahi, R.
2018-03-01
The motivation of the current article is to explore the energy activation in MHD radiative Couette-Poiseuille flow nanofluid in horizontal channel with convective boundary conditions. The mathematical model of Buongiorno [1] effectively describes the current flow analysis. Additionally, the impact of chemical reaction is also taken in account. The governing flow equations are simplified with the help of boundary layer approximations. Non-linear coupled equations for momentum, energy and mass transfer are tackled with analytical (HAM) technique. The influence of dimensionless convergence parameter like Brownian motion parameter, radiation parameter, buoyancy ratio parameter, dimensionless activation energy, thermophoresis parameter, temperature difference parameter, dimensionless reaction rate, Schmidt number, Brinkman number, Biot number and convection diffusion parameter on velocity, temperature and concentration profiles are discussed graphically and in tabular form. From the results, it is elaborate that the nanoparticle concentration is directly proportional to the chemical reaction with activation energy and the performance of Brownian motion on nanoparticle concentration gives reverse pattern to that of thermophoresis parameter.
Variations of Roughness Coefficients with Flow Depth of Grassed Swale
Mustaffa, N.; Ahmad, N. A.; Razi, M. A. M.
2016-07-01
Grassed swales are the best management practice (BMP), which has been widely used to reduce the peak flow, reduce water pollution through vegetated filtration, and improve the groundwater recharge. Universiti Tun Hussein Onn Malaysia (UTHM) is using the approach of grassed swales recommended by the Department of Irrigation and Drainage Malaysia (DID) for reducing the risk of flooding and controlling the water pollution. This paper investigates the variations of roughness coefficients with the flow depth of grassed swales in the campus of UTHM. Fieldwork was carried out on the grassed swale to collect the hydraulic data, which including the levelling work, measuring the flow depth and flow velocity of the swale. The flow depth of swale was taken at three points divided along the width of swale and the flow velocity is captured three times at each of the point. The variations of roughness coefficients of grassed swales are presented in Manning's equation, and the results reveal that the n value increases with the increasing of flow depth. Manning's coefficient value found in this study is in the range of 0.110 to 0.756, which are higher than the value proposed by the Urban Stormwater Management Manual for Malaysia (MSMA). The relationships of flow depth and velocity at each section of the swale are portrayed in graphs, which show that the velocity increases with the decreasing of flow depth. The outcomes of this study can be concluded that the variation of Manning's coefficient value is influenced by the swale profile, flow depth, flow velocity, and as well as the vegetation used in the grassed swale concerned.
Local heat transfer coefficient for turbulent flow in rod bundles
International Nuclear Information System (INIS)
Fernandez y Fernandez, E.; Carajilescov, P.
1983-03-01
The correlation of the local heat transfer coefficients in heated triangular array of rod bundles, in terms of the flow hydrodynamic parameters is presented. The analysis is made first for fluid with Prandtl numbers varying from moderated to high (Pr>0.2), and then extended to fluids with low Prandtl numbers (0.004 [pt
Resistance coefficient during ice slurry flow through pipe sudden constriction
Directory of Open Access Journals (Sweden)
Ł. Mika
2010-07-01
Full Text Available Due to the adverse environmental effects of some commonly-used refrigerants, efforts are still underway to find new cooling mediumsthat would be safer to the ozone layer and would not increase the greenhouse effect. Ice slurry as a new ecological coolant suits theprocesses requiring the preservation of constant and equal temperature in the cooling process of the full section of the cooled solid. Thanks to that, ice slurry can find a wide potential application in such branches of industry, as heat treatment, materials engineering, or foundry. In this paper, flow systems which are commonly used in fittings elements such as diameter’s reductions in ice slurry pipelines, are experimentally investigated. In the study reported in this paper, the consideration was given to the specific features of the slurry flow in which the flow qualities depend mainly on the volume fraction of solid particles. The results of the experimental studies on the flow resistance, presented herein, enabled to determine the resistance coefficient during the ice slurry flow through the pipe sudden constriction. The volume fraction of solid particles in the slurry ranged from 5 to 30%. The recommended and non-recommended range of the Reynolds number for the ice slurry flow through the pipe sudden constriction were presented in this paper. The experimental studies were conducted on a few variants of the most common reductions of copper pipes. Further studies on the determination of the resistance coefficient in the remaining fittings elements of the pipeline were recommended in the paper as well as the further theoretical studies intended to determine the theoretical relations to calculate the resistance coefficient in all the fittings elements in the pipeline (on the basis of the experimental studies and to elaborate the calculation pattern of the entire ice slurry system.
CHARACTERIZATION OF RENAL BLOOD FLOW REGULATION BASED ON WAVELET COEFFICIENTS
DEFF Research Database (Denmark)
Pavlov, A.N.; Pavlova, O.N.; Mosekilde, Erik
2010-01-01
. A reduction in the variability of the wavelet coefficients in hypertension is observed at both the microscopic level of the blood flow in efferent arterioles of individual nephrons and at the macroscopic level of the blood pressure in the main arteries. The reduction is manifest in both of the main frequency...... domains of nephron autoregulation and is likely to reflect a reduced flexibility of the cardiovascular system during hypertension.......The purpose of this study is to demonstrate the possibility of revealing new characteristic features of renal blood flow autoregulation in healthy and pathological states through the application of discrete wavelet transforms to experimental time series for normotensive and hypertensive rats...
Assessment of closure coefficients for compressible-flow turbulence models
Huang, P. G.; Bradshaw, P.; Coakley, T. J.
1992-01-01
A critical assessment is made of the closure coefficients used for turbulence length scale in existing models of the transport equation, with reference to the extension of these models to compressible flow. It is shown that to satisfy the compressible 'law of the wall', the model coefficients must actually be functions of density gradients. The magnitude of the errors that result from neglecting this dependence on density varies with the variable used to specify the length scale. Among the models investigated, the k-omega model yields the best performance, although it is not completely free from errors associated with density terms. Models designed to reduce the density-gradient effect to an insignificant level are proposed.
Pressure drop coefficient of laminar Newtonian flow in axisymmetric diffusers
International Nuclear Information System (INIS)
Rosa, S.; Pinho, F.T.
2006-01-01
The laminar flow of Newtonian fluids in axisymmetric diffusers has been numerically investigated to evaluate the pressure-loss coefficient as a function of Reynolds number, diffusion angle and expansion ratio. The numerical simulations were carried out with a finite-volume based code using non-orthogonal collocated grids and second order accurate differencing schemes to discretize all terms of the transport equations. The calculations were carried out for Reynolds numbers between 2 and 200, diffusion angles from 0 deg. to 90 deg. and expansion ratios of 1.5 and 2 and the data are presented in tabular form and as correlations. A simplified 1D theoretical analysis helped explain the various contributions to the loss coefficient and its difference relative to the reversible pressure variation due to differences between the actual and fully developed friction losses, distortions of the velocity profiles and pressure non-uniformity upstream and downstream of the expansion section
Air Flows in Gravity Sewers - Determination of Wastewater Drag Coefficient
DEFF Research Database (Denmark)
Bentzen, Thomas Ruby; Østertoft, Kristian; Vollertsen, Jes
2016-01-01
Several experiments have been conducted in order to improve the understanding of the wastewater drag and the wall frictional force acting on the headspace air in gravity sewers. The aim of the study is to improve the data basis for a numerical model of natural sewer ventilation. The results...... of the study shows that by integrating the top/side wall shear stresses the log-law models for the air velocity distribution along the unwetted perimeter resulted in a good agreement with the friction forces calculated by use of the Colebrook-White formula for hydraulic smooth pipes. Secondly, the water...... surface drags were found by log-law models of the velocity distribution in turbulent flows to fit velocity profiles measured from the water surface and by integrating the water surface drags along the wetted perimeter, mean water surface drags were found and a measure of the water surface drag coefficient...
International Nuclear Information System (INIS)
Valdés, José R.; Rodríguez, José M.; Saumell, Javier; Pütz, Thomas
2014-01-01
Highlights: • We develop a methodology for the parametric modelling of flow in hydraulic valves. • We characterize the flow coefficients with a generic function with two parameters. • The parameters are derived from CFD simulations of the generic geometry. • We apply the methodology to two cases from the automotive brake industry. • We validate by comparing with CFD results varying the original dimensions. - Abstract: The main objective of this work is to develop a methodology for the parametric modelling of the flow rate in hydraulic valve systems. This methodology is based on the derivation, from CFD simulations, of the flow coefficient of the critical restrictions as a function of the Reynolds number, using a generalized square root function with two parameters. The methodology is then demonstrated by applying it to two completely different hydraulic systems: a brake master cylinder and an ABS valve. This type of parametric valve models facilitates their implementation in dynamic simulation models of complex hydraulic systems
Discharge Coefficient Measurements for Flow Through Compound-Angle Conical Holes with Cross-Flow
Directory of Open Access Journals (Sweden)
M. E. Taslim
2004-01-01
Full Text Available Diffusion-shaped film holes with compound angles are currently being investigated for high temperature gas turbine airfoil film cooling. An accurate prediction of the coolant blowing rate through these film holes is essential in determining the film effectiveness. Therefore, the discharge coefficients associated with these film holes for a range of hole pressure ratios is essential in designing airfoil cooling circuits. Most of the available discharge coefficient data in open literature has been for cylindrical holes. The main objective of this experimental investigation was to measure the discharge coefficients for subsonic as well as supersonic pressure ratios through a single conical-diffusion hole. The conical hole has an exit-to-inlet area ratio of 4, a nominal flow length-to-inlet diameter ratio of 4, and an angle with respect to the exit plane (inclination angle of 0°, 30°, 45°, and 60°. Measurements were performed with and without a cross-flow. For the cases with a cross-flow, discharge coefficients were measured for each of the hole geometries and 5 angles between the projected conical hole axis and the cross-flow direction of 0°, 45°, 90°, 135°, and 180°. Results are compared with available data in open literature for cylindrical film holes as well as limited data for conical film holes.
Study for discharge coefficient of flow nozzles. Prediction by using numerical simulation
International Nuclear Information System (INIS)
Ikeda, Hiroshi; Sakai, Norio; Yamamoto, Yasushi; Arai, Kenji; Matsumoto, Masaaki
2008-01-01
In nuclear plant, as water feeding into reactor have much effect on thermal power of plant, it is important to measure accurately the flow rate of water. Flow nozzle is on of typical differential pressure type flow meters and the discharge coefficient is used to calculate the flow rate. This coefficient is given by actual experiment and theory. We studied the theoretical assumption of the discharge coefficient curve using numerical simulation and evaluated the effect of flow nozzle configuration on the coefficient numerically and experimentally. As the result, numerical simulation can predict the discharge coefficient of theoretical curve within 0.3%. And we found that the throat length and throat tapping location of flow nozzle have much effect on the coefficient. (author)
Yamaguchi, H.; Takamori, K.; Perrier, P.; Graur, I.; Matsuda, Y.; Niimi, T.
2016-01-01
The viscous slip coefficient for helium-argon binary gas mixture is extracted from the experimental values of the mass flow rate through a microtube. The mass flow rate is measured by the constant-volume method. The viscous slip coefficient was obtained by identifying the measured mass flow rate through a microtube with the corresponding analytical expression, which is a function of the Knudsen number. The measurements were carried out in the slip flow regime where the first-order slip bounda...
Breckler, Jennifer L.; Christensen, Tina; Sun, Wendy
2013-01-01
Biology students enrolled in a typical undergraduate physiology course encounter Poiseuille's law, a physics equation that describes the properties governing the flow of blood through the circulation. According to the equation, a small change in vessel radius has an exponential effect on resistance, resulting in a larger than expected change in…
Numerical study on over reading coefficient in wet steam flow measurement
International Nuclear Information System (INIS)
Bai Xuesong; Yuan Dewen; Yan Xiao; Peng Xingjian
2013-01-01
This paper investigated the flow process of wet steam in Venturi under interested conditions with CFD simulation software. The effect of pressure, mass flow rate, throat radius on over reading factor was analyzed. This paper aims to improve the wet steam over reading model and the prediction accuracy in wet steam. The results prove that the mass flow has a small effect on over reading coefficient, while the effect that throat radius has on over reading coefficient increases as the pressure rises. (authors)
Kurokawa, Junichi; Morikawa, Masahiro
1986-01-01
In order to determine the flow characteristics of a transient flow in a circular pipe, an accelerated and a decelerated flow are studied, and effects of acceleration upon the formation of a velocity profile, transition and a friction coefficient are determined for a wide range of accelerations. The results of the accelerated flow show that there are two patterns in the formation of a sectional velocity profile and transition, one of which is observed when the acceleration is relatively large ...
Semi-empirical model for heat transfer coefficient in liquid metal turbulent flow
International Nuclear Information System (INIS)
Fernandez y Fernandez, E.; Carajilescov, P.
1982-01-01
The heat transfer by forced convection in a metal liquid turbulent flow for circular ducts is analyzed. An analogy between the momentum and heat in the wall surface, is determined, aiming to determine an expression for heat transfer coefficient in function of the friction coefficient. (E.G.) [pt
Digital Repository Service at National Institute of Oceanography (India)
Vethamony, P.; Chandramohan, P.; Sastry, J.S.; Narasimhan, S.
flow theory. Variations of added-mass and damping coefficients with respect to water depth, wave period and float size have been obtained. Variations of added-mass and damping coefficients with wave period show that these hydrodynamic coefficients...
Exceptional high Seebeck coefficient and gas-flow-induced voltage in multilayer graphene
Li, Xuemei; Yin, Jun; Zhou, Jianxin; Wang, Qin; Guo, Wanlin
2012-04-01
Seebeck coefficient of graphene is an important parameter for defining its thermoelectric performance and thus practical applications, such as gas-flow-induced voltage. Here, we find a unique layer-dependence of the graphene Seebeck coefficient that exceptionally increases with increasing thickness to reach a peak value at six layers that is ˜77% higher than monolayer and ˜296% higher than graphite, unlike the monotonic decrease in electric resistance. However, the gas flow-induced voltage is significantly higher in 2, 4, 5, 6, and 7 layered graphene samples than in 1, 3, and 8 layered ones, against the prevailing wisdom that it should be proportional to Seebeck coefficient.
Directory of Open Access Journals (Sweden)
Hou-lin Liu
2014-03-01
Full Text Available The phenomenon of cavitation is an unsteady flow, which is nearly inevitable in pump. It would degrade the pump performance, produce vibration and noise and even damage the pump. Hence, to improve accuracy of the numerical prediction of the pump cavitation performance is much desirable. In the present work, a homogenous model, the Zwart-Gerber-Belamri cavitation model, is considered to investigate the influence of the empirical coefficients on predicting the pump cavitation performance, concerning a centrifugal pump. Three coefficients are analyzed, namely the nucleation site radius, evaporation and condensation coefficients. Also, the experiments are carried out to validate the numerical simulations. The results indicate that, to get a precise prediction, the approaches of declining the initial bubble radius, the condensation coefficient or increasing the evaporation coefficient are all feasible, especially for declining the condensation coefficient, which is the most effective way.
Directory of Open Access Journals (Sweden)
Liu Hou-lin
2014-03-01
Full Text Available The phenomenon of cavitation is an unsteady flow, which is nearly inevitable in pump. It would degrade the pump performance, produce vibration and noise and even damage the pump. Hence, to improve accuracy of the nu¬merical prediction of the pump cavitation performance is much desirable. In the present work, a homogenous model, the Zwart-Gerber-Belamri cavitation model, is considered to investigate the influence of the empirical coefficients on predicting the pump cavitation performance, concerning a centrifugal pump. Three coefficients are analyzed, namely the nucleation site radius, evaporation and condensation coefficients. Also, the experiments are carried out to validate the numerical simulations. The results indicate that, to get a precise prediction, the approaches of declining the initial bubble radius, the condensation coefficient or increasing the evaporation coefficient are all feasible, especially for de¬clining the condensation coefficient, which is the most effective way.
Forsyth, Peter; McGilvray, Matthew; Gillespie, David R. H.
2017-01-01
This paper reports an experimental and numerical study of the development and coupling of aerodynamic flows and heat transfer within a model ribbed internal cooling passage to provide insight into the development of secondary flows. Static instrumentation was installed at the end of a long smooth passage and used to measure local flow features in a series of experiments where ribs were incrementally added upstream. This improves test turnaround time and allows higher-resolution heat transfer coefficient distributions to be captured, using a hybrid transient liquid crystal technique. A composite heat transfer coefficient distribution for a 12-rib-pitch passage is reported: notably the behaviour is dominated by the development of the secondary flow in the passage throughout. Both the aerodynamic and heat transfer test data were compared to numerical simulations developed using a commercial computational fluid dynamics solver. By conducting a number of simulations it was possible to interrogate the validity of the underlying assumptions of the experimental strategy; their validity is discussed. The results capture the developing size and strength of the vortical structures in secondary flow. The local flow field was shown to be strongly coupled to the enhancement of heat transfer coefficient. Comparison of the experimental and numerical data generally shows excellent agreement in the level of heat transfer coefficient predicted, though the numerical simulations fail to capture some local enhancement on both the ribbed and smooth surfaces. Where this was the case, the coupled flow and heat transfer measurements were able to identify missing velocity field characteristics.
Adiabatic wall temperature and heat transfer coefficient influenced by separated supersonic flow
Directory of Open Access Journals (Sweden)
Leontiev Alexander
2017-01-01
Full Text Available Investigations of supersonic air flow around plane surface behind a rib perpendicular to the flow direction are performed. Research was carried out for free stream Mach number 2.25 and turbulent flow regime - Rex>2·107. Rib height was varied in range from 2 to 8 mm while boundary layer thickness at the nozzle exit section was about 6 mm. As a result adiabatic wall temperature and heat transfer coefficient are obtained for flow around plane surface behind a rib incontrast with the flow around plane surface without any disturbances.
Transport coefficients in high-temperature ionized air flows with electronic excitation
Istomin, V. A.; Oblapenko, G. P.
2018-01-01
Transport coefficients are studied in high-temperature ionized air mixtures using the modified Chapman-Enskog method. The 11-component mixture N2/N2+/N /N+/O2/O2+/O /O+/N O /N O+/e- , taking into account the rotational and vibrational degrees of freedom of molecules and electronic degrees of freedom of both atomic and molecular species, is considered. Using the PAINeT software package, developed by the authors of the paper, in wide temperature range calculations of the thermal conductivity, thermal diffusion, diffusion, and shear viscosity coefficients for an equilibrium ionized air mixture and non-equilibrium flow conditions for mixture compositions, characteristic of those in shock tube experiments and re-entry conditions, are performed. For the equilibrium air case, the computed transport coefficients are compared to those obtained using simplified kinetic theory algorithms. It is shown that neglecting electronic excitation leads to a significant underestimation of the thermal conductivity coefficient at temperatures higher than 25 000 K. For non-equilibrium test cases, it is shown that the thermal diffusion coefficients of neutral species and the self-diffusion coefficients of all species are strongly affected by the mixture composition, while the thermal conductivity coefficient is most strongly influenced by the degree of ionization of the flow. Neglecting electronic excitation causes noticeable underestimation of the thermal conductivity coefficient at temperatures higher than 20 000 K.
Experimental measurement of fluid force coefficients for helical tube arrays in air cross flow
International Nuclear Information System (INIS)
Shen Shifang; Liu Reilan
1993-01-01
A helical coil steam generator is extensively used in the High Temperature Gas Cooled Reactor (HTGCR) and Sodium Cooled Reactor (SCR) nuclear power stations because of its compact structure, good heat-exchange, and small volume. The experimental model is established by the structure parameter of 200MW HTGCR. The fluid elastic instability of helical tube arrays in air cross flow is studied in this experiment, and the fluid force coefficients of helical tube arrays having the same notational direction of two adjacent layers in air cross flow are obtained. As compared to the fluid force coefficients of cylinder tube arrays, the fluid force coefficients of helical tube arrays are smaller in the low velocity area, and greater in the high velocity area. The experimental results help the study of the dynamic characteristics of helical tube arrays in air cross flow
Integral linear momentum balance in combining flows for calculating the pressure drop coefficients
International Nuclear Information System (INIS)
Bollmann, A.
1983-01-01
Equations for calculating the loss coefficient in combining flows in tee functions are obtained by an integral linear momentum balance. It is a practice, when solving this type of problem, to neglect the pressure difference in the upstream location as well as the wall-fluid interaction in the lateral branch of the junction. In this work it is demonstrated the influence of the above parameters on the loss coefficient based on experimental values and by apropriate algebraic manipulation of the loss coefficient values published by previous investigators. (Author) [pt
Influence of Boussinesq coefficient on depth-averaged modelling of rapid flows
Yang, Fan; Liang, Dongfang; Xiao, Yang
2018-04-01
The traditional Alternating Direction Implicit (ADI) scheme has been proven to be incapable of modelling trans-critical flows. Its inherent lack of shock-capturing capability often results in spurious oscillations and computational instabilities. However, the ADI scheme is still widely adopted in flood modelling software, and various special treatments have been designed to stabilise the computation. Modification of the Boussinesq coefficient to adjust the amount of fluid inertia is a numerical treatment that allows the ADI scheme to be applicable to rapid flows. This study comprehensively examines the impact of this numerical treatment over a range of flow conditions. A shock-capturing TVD-MacCormack model is used to provide reference results. For unsteady flows over a frictionless bed, such as idealised dam-break floods, the results suggest that an increase in the value of the Boussinesq coefficient reduces the amplitude of the spurious oscillations. The opposite is observed for steady rapid flows over a frictional bed. Finally, a two-dimensional urban flooding phenomenon is presented, involving unsteady flow over a frictional bed. The results show that increasing the value of the Boussinesq coefficient can significantly reduce the numerical oscillations and reduce the predicted area of inundation. In order to stabilise the ADI computations, the Boussinesq coefficient could be judiciously raised or lowered depending on whether the rapid flow is steady or unsteady and whether the bed is frictional or frictionless. An increase in the Boussinesq coefficient generally leads to overprediction of the propagating speed of the flood wave over a frictionless bed, but the opposite is true when bed friction is significant.
Controlling the Internal Heat Transfer Coefficient by the Characteristics of External Flows
Zhuromskii, V. M.
2018-01-01
The engineering-physical fundamentals of substance synthesis in a boiling apparatus are presented. We have modeled a system of automatic stabilization of the maximum internal heat transfer coefficient in such an apparatus by the characteristics of external flows on the basis of adaptive seeking algorithms. The results of operation of the system in the shop are presented.
A Simple Student Laboratory on Osmotic Flow, Osmotic Pressure, and the Reflection Coefficient.
Feher, Joseph J.; Ford, George D.
1995-01-01
Describes a laboratory exercise containing a practical series of experiments that novice students can perform within two hours. The exercise provides a confirmation of van't Hoff's law while placing more emphasis on osmotic flow than pressure. Students can determine parameters such as the reflection coefficient which stress the interaction of both…
Dorao, C. A.; Drewes, S.; Fernandino, M.
2018-02-01
During the past few decades, heat transfer during convective flow boiling inside pipes has been widely studied with the goal of unveiling the physics of the process. Different heat transfer mechanisms have been suggested based on different assumptions. This fact has resulted in a large number of models including different dimensionless numbers and in some cases up to a dozen of adjusted parameters. Here, we show that the convective flow boiling heat transfer coefficient is equivalent to the one for single-phase flow when the influence of the vapour velocity is taken into account.
On the skin friction coefficient in viscoelastic wall-bounded flows
International Nuclear Information System (INIS)
Housiadas, Kostas D.; Beris, Antony N.
2013-01-01
Highlights: ► We decompose the skin friction coefficient to its individual contributions. ► The contributions are evaluated using simulation results in turbulent channel flow. ► We present a fitting curve for the drag reduction. ► A new formula for the skin friction coefficient is also developed. ► The results agree well with experimental data from the literature. -- Abstract: Analysis of the skin friction coefficient for wall bounded viscoelastic flows is performed by utilizing available direct numerical simulation (DNS) results for viscoelastic turbulent channel flow. The Oldroyd-B, FENE-P and Giesekus constitutive models are used. First, we analyze the friction coefficient in viscous, viscoelastic and inertial stress contributions, as these arise from suitable momentum balances, for the flow in channels and pipes. Following Fukagata et al. (Phys. Fluids, 14, p. L73, 2002) and Yu et al. (Int. J. Heat. Fluid Flow, 25, p. 961, 2004) these three contributions are evaluated averaging available numerical results, and presented for selected values of flow and rheological parameters. Second, based on DNS results, we develop a universal function for the relative drag reduction as a function of the friction Weissenberg number. This leads to a closed-form approximate expression for the inverse of the square root of the skin friction coefficient for viscoelastic turbulent pipe flow as a function of the friction Reynolds number involving two primary material parameters, and a secondary one which also depends on the flow. The primary parameters are the zero shear-rate elasticity number, El 0 , and the limiting value for the drag reduction at high Weissenberg number, LDR, while the secondary one is the relative wall viscosity, μ w . The predictions reproduce both types A and B of drag reduction, as first introduced by Virk (Nature, 253, p. 109, 1975), corresponding to partially and fully extended polymer molecules, respectively. Comparison of the results for the
Prediction of the heat transfer coefficient for ice slurry flows in a horizontal pipe
Energy Technology Data Exchange (ETDEWEB)
Kousksou, T.; Jamil, A.; Zeraouli, Y. [Laboratoire de Thermique Energetique et Procedes, Avenue de l' Universite, BP 1155, 64013 Pau Cedex (France); El Rhafiki, T. [Laboratoire de Thermique Energetique et Procedes, Avenue de l' Universite, BP 1155, 64013 Pau Cedex (France); Laboratoire d' Energetique, Mecanique des Fluides et Sciences des Materiaux, Universite AbdelMalek Essaidi, 90000 Tetouan (Morocco)
2010-06-15
In this study, heat transfer for ice slurry flows was investigated. For the experiments, ice slurry was made from 9% ethanol-water solution flow in a 20 mm internal diameter, 1000 mm long horizontal copper tube. The ice slurry was heated by a cylindrical electrical resistance. Experiments of the melting process were conducted with changing the ice slurry mass flux rate and the heat flux. The enthalpy-porosity formulation was used to predict the ice slurry temperature and the local values of heat transfer coefficient in the exchanger. Measurements and data acquisition of ice slurry temperature and mass flow rate at the inlet and outlet are performed. It was found that the heat transfer rates increase with the mass flow rate, the ice fraction and the heat flux density. However, the effect of ice fraction appears not to be significant at high mass flow rates. In addition, the correlation proposed by Christensen and Kauffeld gives good agreement with numerical results. (author)
Prediction of the heat transfer coefficient for ice slurry flows in a horizontal pipe
International Nuclear Information System (INIS)
Kousksou, T.; Jamil, A.; El Rhafiki, T.; Zeraouli, Y.
2010-01-01
In this study, heat transfer for ice slurry flows was investigated. For the experiments, ice slurry was made from 9% ethanol-water solution flow in a 20 mm internal diameter, 1000 mm long horizontal copper tube. The ice slurry was heated by a cylindrical electrical resistance. Experiments of the melting process were conducted with changing the ice slurry mass flux rate and the heat flux. The enthalpy-porosity formulation was used to predict the ice slurry temperature and the local values of heat transfer coefficient in the exchanger. Measurements and data acquisition of ice slurry temperature and mass flow rate at the inlet and outlet are performed. It was found that the heat transfer rates increase with the mass flow rate, the ice fraction and the heat flux density. However, the effect of ice fraction appears not to be significant at high mass flow rates. In addition, the correlation proposed by Christensen and Kauffeld gives good agreement with numerical results.
McGivern, W Sean; Manion, Jeffrey A
2011-11-18
A reversed-flow gas-chromatography (RF-GC) apparatus for the measurement of binary diffusion coefficients is described and utilized to measure the binary diffusion coefficients for several systems at temperatures from (300 to 723)K. Hydrocarbons are detected using flame ionization detection, and inert species can be detected by thermal conductivity. The present apparatus has been utilized to measure diffusion coefficients at substantially higher temperatures than previous RF-GC work. Characterization of the new apparatus was accomplished by comparing measured binary diffusion coefficients of dilute argon in helium to established reference values. Further diffusion coefficient measurements for dilute helium in argon and dilute nitrogen in helium (using thermal conductivity detection) and dilute methane in helium (using flame ionization detection) were performed and found to be in excellent agreement with literature values. The measurement of these well-established diffusion coefficients has shown that specific experimental conditions are required for accurate diffusion measurements using this technique, particularly at higher temperatures. Numerical simulations of the diffusion experiments are presented to demonstrate that artifacts of the analysis procedure must be specifically identified to ensure accuracy, particularly at higher temperatures. Published by Elsevier B.V.
Nofuentes, M.; Polo, M. J.
2012-04-01
One-dimensional modelling of solute transport in shallow water flows relies on an accurate approximation of the longitudinal dispersion coefficient, E, especially under transient conditions of the water flow during the solute residence time. Previous approaches have used expressions (e.g., the Rutherford equation) that allow the inclusion of spatiotemporal variability of E during the transport process, but their accuracy is reduced in marked transient regimes since the data were obtained from experimental work in rivers. This work proposes a different approach from experimental work with slow, shallow flows over porous media in fertigation essays, and provides us with a simple, parametric sigmoid function to estimate a priori effective values of E from simple measurements of flow characteristics and variables. The results have been successfully validated and compared to the Rutherford equation approach. Furthermore, the methodology to develop this characteristic function can be easily adapted for application in other practical cases.
Spreading Coefficient of Buoyant Jet flow in the Shallow and Deep Ambient Current
Directory of Open Access Journals (Sweden)
reza sajadifar
2017-01-01
Full Text Available Introduction: In this research the spreading coefficient of dense flow under the jet hydraulic in the surrounding fluids of clean water and at the accepting environment with the low depth and high depth has been analyzed. The analyzed parameters are included of discharge injection, density of contaminating fluid, diameter and angle of the contraction of jet nozzle and shallow and deep water ambient fluid. Materials and methods: These tests are being conducted in the flume laboratory. The results obtained from the tests show that the circulation coefficient is a function of contaminating density and the depth of the accepting environment, such that with increase in the density, the accepting environment depth coefficient will an increase and circulation and coefficient dispersal with the densities of 15, 30, 50, 200 g/lit, are 0/121, 0/135, 0/153, and 0/196 respectively. On the one hand, in the accepting environment depth it has been shown that increase in the Froude density number up to 30 causes decreases in the circulation and coefficient dispersal and then this coefficient will be used in the constant amount of 0/1. Results and Discussion: Results showed that the profiles taken by the GOSEN distribution function and also coordinate the direction taken compliance with about 8/9% errors. Therefore the amount of dispersion of drained stream with accepted error and the use of accepted axial- radial coordinate have been extracted. The most speed has been taken place in the central line and getting further from the center reduces the speed. On the one hand, along the moving path the limits of Jet reduce which is surrounding conditions. On the other hand, considering the continuity coordination in different places from the jet, and reduction of speed, the dispersion width increases. And also according to the analysis conducted it is clear that speed profiles measured is consistent with Gussein distribution. Generally the flow of the sank jets, which
Heat transfer coefficient for flow boiling in an annular mini gap
Directory of Open Access Journals (Sweden)
Hożejowska Sylwia
2016-01-01
Full Text Available The aim of this paper was to present the concept of mathematical models of heat transfer in flow boiling in an annular mini gap between the metal pipe with enhanced exterior surface and the external glass pipe. The one- and two-dimensional mathematical models were proposed to describe stationary heat transfer in the gap. A set of experimental data governed both the form of energy equations in cylindrical coordinates and the boundary conditions. The models were formulated to minimize the number of experimentally determined constants. Known temperature distributions in the enhanced surface and in the fluid helped to determine, from the Robin condition, the local heat transfer coefficients at the enhanced surface – fluid contact. The Trefftz method was used to find two-dimensional temperature distributions for the thermal conductive filler layer, enhanced surface and flowing fluid. The method of temperature calculation depended on whether the area of single-phase convection ended with boiling incipience in the gap or the two-phase flow region prevailed, with either fully developed bubbly flow or bubbly-slug flow. In the two–phase flow, the fluid temperature was calculated by Trefftz method. Trefftz functions for the Laplace equation and for the energy equation were used in the calculations.
Measurements of elliptic flow and higher-order Fourier coefficients with the ATLAS experiment
Jia, J; The ATLAS collaboration
2011-01-01
We report the measurements of collective harmonic flow coefficients $v_n$ for $n=2-6$ in Pb+Pb collisions at sqrt(s_NN)=2.76 TeV with the ATLAS detector. They are extracted via an event plane method based on the ATLAS Forward Calorimeter over a broad range in $p_T$, $eta$ and centrality. The $v_n$ coefficients are found to change weakly within $|eta|<2.5$ and all with the same qualitative trend as a function of $p_T$: all rise up to 3-4 GeV, and then fall towards higher $p_T$. The high statistical precision of the $v_2$ term, allow us to clearly determine its trend out to 20 GeV for a broad centrality classes. The same harmonic flow coefficients are also obtained via a Fourier analysis of the two-particle $Deltaphi-Deltaeta$ correlation with a large $Deltaeta$ gap. A detailed comparison with the event plane method allow us to determine the regions of the two-particle phase space (in $p_T$ and $Deltaeta$ and centrality), in which the collective phenomena play a dominating role. The physics implications ...
Experimental Determination of Heat Transfer Coefficient in Two-phase Annular Flow
Dressler, Kristofer; Fehring, Brian; Morse, Roman; Livingston-Jha, Simon; Doherty, James; Chan, Jason; Brueggeman, Colby; Berson, Arganthael
2017-11-01
The goal of the presented work is to validate published mechanistic heat transfer models in two-phase annular flow under transient conditions. Annular flow occurs in many steam generation and refrigeration systems. Knowledge of the heat transfer coefficient (HTC) between the wall and the thin liquid film is critical to the design and safe operation of these systems. In heat exchangers with multiple parallel channels, thermal hydraulic instabilities often lead to unsteady flow conditions. The current study is performed in a facility capable of producing pulsed two-phase, single-species annular flow in a heated test section while simultaneously measuring local film thickness and wall temperature using non-intrusive optical techniques. Available correlations between the HTC and wall shear at steady state are compared to our measurements. The HTC can be derived from the known heating power and measured wall temperature, while wall shear is deduced from film thickness measurements. The validity of steady-state correlations under oscillating flow conditions is assessed by performing tests at a variety of pulse frequencies and amplitudes.
Large scale steam flow test: Pressure drop data and calculated pressure loss coefficients
International Nuclear Information System (INIS)
Meadows, J.B.; Spears, J.R.; Feder, A.R.; Moore, B.P.; Young, C.E.
1993-12-01
This report presents the result of large scale steam flow testing, 3 million to 7 million lbs/hr., conducted at approximate steam qualities of 25, 45, 70 and 100 percent (dry, saturated). It is concluded from the test data that reasonable estimates of piping component pressure loss coefficients for single phase flow in complex piping geometries can be calculated using available engineering literature. This includes the effects of nearby upstream and downstream components, compressibility, and internal obstructions, such as splitters, and ladder rungs on individual piping components. Despite expected uncertainties in the data resulting from the complexity of the piping geometry and two-phase flow, the test data support the conclusion that the predicted dry steam K-factors are accurate and provide useful insight into the effect of entrained liquid on the flow resistance. The K-factors calculated from the wet steam test data were compared to two-phase K-factors based on the Martinelli-Nelson pressure drop correlations. This comparison supports the concept of a two-phase multiplier for estimating the resistance of piping with liquid entrained into the flow. The test data in general appears to be reasonably consistent with the shape of a curve based on the Martinelli-Nelson correlation over the tested range of steam quality
Constraint and flow: Poiseuille shear response of a surfactant ...
Indian Academy of Sciences (India)
assemble to form some basic morphologies – globular micelles, highly extended theadlike micelles and membrane bilayers – which themselves order to display a rich variety of mesophase symmetries and properties. In membrane systems one of ...
Constraint and flow: Poiseuille shear response of a surfactant ...
Indian Academy of Sciences (India)
Abstract. To minimize their free energy in aqueous solution, surfactant molecules self-assemble to form some basic morphologies – globular micelles, highly extended thead- like micelles and membrane bilayers – which themselves order to display a rich variety of mesophase symmetries and properties. In membrane ...
Directory of Open Access Journals (Sweden)
Orlov Vladimir Aleksandrovich
2012-10-01
The software is also capable of generating graphs (curves to describe the relations in question. The proposed methodology and the software designated for the calculation of Chezy and roughness coefficients makes it possible for users to identify the hydraulic properties of pipelines made of advanced materials or having advanced coatings. The availability of the above information is to optimize the selection of the pipeline repair material on the basis of the assessment of hydraulic compatibility between the sections of the pipeline in operation and those being repaired.
Leung, Lap Yin; Mao, Chen; Srivastava, Ishan; Du, Ping; Yang, Chia-Yi
2017-07-01
The purpose of this study was to demonstrate that the flow function (FFc) of pharmaceutical powders, as measured by rotational shear cell, is predominantly governed by cohesion but not friction coefficients. Driven by an earlier report showing an inverse correlation between FFc and the cohesion divided by the corresponding pre-consolidation stress (Wang et al. 2016. Powder Tech. 294:105-112), we performed analysis on a large data set containing 1130 measurements from a ring shear tester and identified a near-perfect inverse correlation between the FFc and cohesion. Conversely, no correlation was found between FFc and friction angles. We also conducted theoretical analysis and estimated such correlations based on Mohr-Coulomb failure model. We discovered that the correlation between FFc and cohesion can sustain as long as the angle of internal friction at incipient flow is not significantly larger than the angle of internal friction at steady-state flow, a condition covering almost all pharmaceutical powders. The outcome of this study bears significance in pharmaceutical development. Because the cohesion value is strongly influenced by the interparticle cohesive forces, this study effectively shows that it is more efficient to improve the pharmaceutical powder flow by lowering the interparticle cohesive forces than by lowering the interparticle frictions. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.
Directory of Open Access Journals (Sweden)
Mikielewicz Dariusz
2016-06-01
Full Text Available In the paper presented are the results of calculations using authors own model to predict heat transfer coefficient during flow boiling of carbon dioxide. The experimental data from various researches were collected. Calculations were conducted for a full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the in-house model. The results show the importance of taking into account the surface tension as the parameter exhibiting its importance in case of the flow in minichannels as well as the influence of reduced pressure. The calculations were accomplished to test the sensitivity of the heat transfer model with respect to selection of the appropriate two-phase flow multiplier, which is one of the elements of the heat transfer model. For that purpose correlations due to Müller-Steinhagen and Heck as well as the one due to Friedel were considered. Obtained results show a good consistency with experimental results, however the selection of two-phase flow multiplier does not significantly influence the consistency of calculations.
Mass transfer coefficient of slug flow for organic solvent-aqueous system in a microreactor
International Nuclear Information System (INIS)
Tuek, Ana Jurinjak; Anic, Iva; Kurtanjek, Zelimir; Zelic, Bruno
2015-01-01
Application of microreactor systems could be the next break-through in the intensification of chemical and biochemical processes. The common flow regime for organic solvent-aqueous phase two-phase systems is a segmented flow. Internal circulations in segments cause high mass transfer and conversion. We analyzed slug flow in seven systems of organic solvents and aqueous phase. To analyze how slug lengths in tested systems depend on linear velocity and physical and chemical properties of used organic solvents, regression models were proposed. It was shown that models based on linearization of approximation by potentials give low correlation for slug length prediction; however, application of an essential nonlinear model of multiple layer perception (MLP) neural network gives high correlation with R 2 =0.9. General sensitivity analysis was applied for the MLP neural network model, which showed that 80% of variance in slug length for the both phases is accounted for the viscosity and density of the organic phases; 10% is accounted by surface tension of the organic phase, while molecular masses and flow rates each account for 5%. For defined geometry of microreactor, mass transfer has been determined by carrying out the neutralization experiment with NaOH where acetic acid diffuses from organic phase (hexane) into aqueous phase. Estimated mass transfer coefficients were in the range k L a=4,652-1,9807 h -1
Mass transfer coefficient of slug flow for organic solvent-aqueous system in a microreactor
Energy Technology Data Exchange (ETDEWEB)
Tuek, Ana Jurinjak; Anic, Iva; Kurtanjek, Zelimir; Zelic, Bruno [University of Zagreb, Zagreb (Croatia)
2015-06-15
Application of microreactor systems could be the next break-through in the intensification of chemical and biochemical processes. The common flow regime for organic solvent-aqueous phase two-phase systems is a segmented flow. Internal circulations in segments cause high mass transfer and conversion. We analyzed slug flow in seven systems of organic solvents and aqueous phase. To analyze how slug lengths in tested systems depend on linear velocity and physical and chemical properties of used organic solvents, regression models were proposed. It was shown that models based on linearization of approximation by potentials give low correlation for slug length prediction; however, application of an essential nonlinear model of multiple layer perception (MLP) neural network gives high correlation with R{sup 2}=0.9. General sensitivity analysis was applied for the MLP neural network model, which showed that 80% of variance in slug length for the both phases is accounted for the viscosity and density of the organic phases; 10% is accounted by surface tension of the organic phase, while molecular masses and flow rates each account for 5%. For defined geometry of microreactor, mass transfer has been determined by carrying out the neutralization experiment with NaOH where acetic acid diffuses from organic phase (hexane) into aqueous phase. Estimated mass transfer coefficients were in the range k{sub L}a=4,652-1,9807 h{sup -1}.
Measurement of off-diagonal transport coefficients in two-phase flow in porous media.
Ramakrishnan, T S; Goode, P A
2015-07-01
The prevalent description of low capillary number two-phase flow in porous media relies on the independence of phase transport. An extended Darcy's law with a saturation dependent effective permeability is used for each phase. The driving force for each phase is given by its pressure gradient and the body force. This diagonally dominant form neglects momentum transfer from one phase to the other. Numerical and analytical modeling in regular geometries have however shown that while this approximation is simple and acceptable in some cases, many practical problems require inclusion of momentum transfer across the interface. Its inclusion leads to a generalized form of extended Darcy's law in which both the diagonal relative permeabilities and the off-diagonal terms depend not only on saturation but also on the viscosity ratio. Analogous to application of thermodynamics to dynamical systems, any of the extended forms of Darcy's law assumes quasi-static interfaces of fluids for describing displacement problems. Despite the importance of the permeability coefficients in oil recovery, soil moisture transport, contaminant removal, etc., direct measurements to infer the magnitude of the off-diagonal coefficients have been lacking. The published data based on cocurrent and countercurrent displacement experiments are necessarily indirect. In this paper, we propose a null experiment to measure the off-diagonal term directly. For a given non-wetting phase pressure-gradient, the null method is based on measuring a counter pressure drop in the wetting phase required to maintain a zero flux. The ratio of the off-diagonal coefficient to the wetting phase diagonal coefficient (relative permeability) may then be determined. The apparatus is described in detail, along with the results obtained. We demonstrate the validity of the experimental results and conclude the paper by comparing experimental data to numerical simulation. Copyright © 2015 Elsevier Inc. All rights reserved.
Ghamlouch, T.; Roux, S.; Bailleul, J.-L.; Lefèvre, N.; Sobotka, V.
2017-10-01
Today's aerospace industrial first priority is the quality improvement of the composite material parts with the reduction of the manufacturing time in order to increase their quality/cost ratio. A fabrication method that could meet these specifications especially for large parts is the autoclave curing process. In fact the autoclave molding ensures the thermal control of the composite parts during the whole curing cycle. However the geometry of the tools as well as their positioning in the autoclave induce non uniform and complex flows around composite parts. This heterogeneity implies non-uniform heat transfers which can directly impact on part quality. One of the main challenges is therefore to describe the flow field inside an autoclave as well as the convective heat transfer from the heated pressurized gas to the composite part and the mold. For this purpose, and given the technical issues associated with instrumentation and measurements in actual autoclaves, an autoclave model was designed and then manufactured based on similarity laws. This tool allows the measurement of the flow field around representative real industrial molds using the PIV technique and the characterization of the heat transfer thanks to thermal instrumentation. The experimental results are then compared with those derived from numerical simulations using a commercial RANS CFD code. This study aims at developing a semi-empirical approach for the prediction of the heat transfer coefficient around the parts and therefore predicts its thermal history during the process with a view of optimization.
DEFF Research Database (Denmark)
Ratkovich, Nicolas Rios; Berube, P.R.; Nopens, I.
2011-01-01
One of the operational challenges associated with membrane bioreactors (MBRs) is the fouling of the membranes. In tubular side-stream MBRs, fouling reduction can be achieved through controlling the hydrodynamics of the two-phase slug flow near the membrane surface. The two-phase slug flow induces......) cannot be applied directly. As an alternative, in this work, a multidisciplinary approach was selected, by exploiting dimensionless analysis using the Sherwood number. Mass transfer coefficients were measured at various superficial velocities of gas and liquid flow in a tubular system. Due...... to the variability of the mass transfer coefficient obtained for each experimental condition, the results were compiled into, mass transfer coefficient histograms (MTH) for analysis. A bimodal MTH was observed, with one peak corresponding to the mass transfer induced by the liquid flow, and the other peak induced...
DEFF Research Database (Denmark)
Jeong, Cheol-Ho; Choi, Sang-Hyeon; Lee, Ikjin
2017-01-01
chamber significantly, whereas the flow resistivity is a rather reproducible material property, from which the absorptive characteristics can be calculated through reliable models. Using Sabine absorption coefficients measured in 13 European reverberation chambers, the maximum a posteriori......A Bayesian analysis is applied to determine the flow resistivity of a porous sample and the influence of the test chamber based on measured Sabine absorption coefficient data. The Sabine absorption coefficient measured in a reverberation chamber according to ISO 354 is influenced by the test...... and the uncertainty of the flow resistivity and the test chamber’s influence are estimated. Inclusion of more than one chamber’s absorption data helps the flow resistivity converge towards a reliable value with a standard deviation below 17%...
Jeong, Cheol-Ho; Choi, Sang-Hyeon; Lee, Ikjin
2017-03-01
A Bayesian analysis is applied to determine the flow resistivity of a porous sample and the influence of the test chamber based on measured Sabine absorption coefficient data. The Sabine absorption coefficient measured in a reverberation chamber according to ISO 354 is influenced by the test chamber significantly, whereas the flow resistivity is a rather reproducible material property, from which the absorptive characteristics can be calculated through reliable models. Using Sabine absorption coefficients measured in 13 European reverberation chambers, the maximum a posteriori and the uncertainty of the flow resistivity and the test chamber's influence are estimated. Inclusion of more than one chamber's absorption data helps the flow resistivity converge towards a reliable value with a standard deviation below 17%.
Simple Flows of Pseudoplastic Fluids Based on Dehaven Model
Directory of Open Access Journals (Sweden)
Walicka A.
2017-12-01
Full Text Available In this paper three simple flows of visco-plastic fluids of DeHaven type or fluids similar to them are considered. These flows are: Poiseuille flow in a plane channel, Poiseuille flow through a circular pipe and rotating Couette flow between two coaxial cylinders. After presentation DeHaven model it was presented some models of fluids similar to this model. Next it was given the solutions of equations of motion for three flows mentioned above.
Simple Flows of Pseudoplastic Fluids Based on Dehaven Model
Walicka, A.
2017-12-01
In this paper three simple flows of visco-plastic fluids of DeHaven type or fluids similar to them are considered. These flows are: Poiseuille flow in a plane channel, Poiseuille flow through a circular pipe and rotating Couette flow between two coaxial cylinders. After presentation DeHaven model it was presented some models of fluids similar to this model. Next it was given the solutions of equations of motion for three flows mentioned above.
International Nuclear Information System (INIS)
Mehta, Balkrishna; Khandekar, Sameer
2014-01-01
Highlights: • Infra-red thermographic study of Taylor bubble train flow in square mini-channel. • Design of experiments for measurement of local streamwise Nusselt number. • Minimizing conjugate heat transfer effects and resulting errors in data reduction. • Benchmarking against single-phase flow and three-dimensional computations. • Local heat transfer enhancement up to two times due to Taylor bubble train flow. -- Abstract: In mini/micro confined internal flow systems, Taylor bubble train flow takes place within specific range of respective volume flow ratios, wherein the liquid slugs get separated by elongated Taylor bubbles, resulting in an intermittent flow situation. This unique flow characteristic requires understanding of transport phenomena on global, as well as on local spatio-temporal scales. In this context, an experimental design methodology and its validation are presented in this work, with an aim of measuring the local heat transfer coefficient by employing high-resolution InfraRed Thermography. The effect of conjugate heat transfer on the true estimate of local transport coefficients, and subsequent data reduction technique, is discerned. Local heat transfer coefficient for (i) hydrodynamically fully developed and thermally developing single-phase flow in three-side heated channel and, (ii) non-boiling, air–water Taylor bubble train flow is measured and compared in a mini-channel of square cross-section (5 mm × 5 mm; D h = 5 mm, Bo ≈ 3.4) machined on a stainless steel substrate (300 mm × 25 mm × 11 mm). The design of the setup ensures near uniform heat flux condition at the solid–fluid interface; the conjugate effects arising from the axial back conduction in the substrate are thus minimized. For benchmarking, the data from single-phase flow is also compared with three-dimensional computational simulations. Depending on the employed volume flow ratio, it is concluded that enhancement of nearly 1.2–2.0 times in time
Kotsalos, Efthimios; Brezovska, Boryana; Sevastos, Dimitrios; Vagena, Artemis; Koliadima, Athanasia; Kapolos, John; Karaiskakis, George
2017-11-17
This work focuses on the influences of surfactants on the activity coefficients, γ, of methanol in binary mixtures with water, as well as on the mass transfer coefficients, k c , for the evaporation of methanol, which is a ubiquitous component in the troposphere, from mixtures of methanol with water at various surfactant's and methanol's concentrations. The technique used is the Reversed-Flow Gas Chromatography (R.F.G.C.), a version of Inverse Gas Chromatography, which allows determining both parameters by performing only one experiment for the k c parameter and two experiments for the γ parameter. The k c and γ values decrease in the presence of the three surfactants used (CTAB, SDS, TRITON X-100) at all methanol's and surfactant's concentrations. The decrease in the methanol's molar fraction, at constant number of surfactant films leads to a decrease in the k c and γ values, while the decrease in the surfactant's concentration, at constant methanol's molar fraction leads to an increase in both the k c and γ parameters. Mass transfer coefficients for the evaporation of methanol at the surfactant films, are also calculated which are approximately between 4 and 5 orders of magnitude larger than the corresponding mass transfer coefficients at the liquid films. Finally, thicknesses of the boundary layer of methanol in the mixtures of methanol with water were determined. The quantities found are compared with those given in the literature or calculated theoretically using various empirical equations. The precision of the R.F.G.C. method for measuring γ and k c parameters is approximately high (94.3-98.0%), showing that R.F.G.C. can be used with success not only for the thermodynamic study of solutions, but also for the interphase transport. Copyright © 2017 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Vasyl IVANIV
Full Text Available For intake cylindrical nozzles with orthogonal lateral jet outlets, dependences of the flow coefficient on (1 Reynolds number , (2 jet-to-main stream turning angle , which is measured relative to the direction of the main stream in a collector-pipeline, as well as (3 the ratio of the diameter of the outlet hole of the nozzle to that of the collector-pipeline are obtained. The ratio influences the value of the coefficient of flow more considerably than the jet-to-main stream turning angle does. The magnitude of flow coefficient varies most abruptly in the range of the magnitude of the ratio from 0.35 to 0.40. For adjustment of non-uniformity of the fluid inflow into the pressure pipelines along their lengths, the nozzles of 0.35 0.40 are the most suitable ones.
International Nuclear Information System (INIS)
Kuban, V.
1991-01-01
Single-channel coaxial segments were used for the introduction of an aqueous or octan-1-ol solution of an organic substance directly into a continuous flow of the other solvent. The analytical signal was measured simultaneously on both aqueous and organic phase segments by an 'on-tube' fast-reading spectrophotometric detector (ca. 3 ms time resolution) and treated mathematically. The octan-1-ol-water phase signal ratio corresponds to the partition coefficient of the organic substances. The applicability of the method is demonstrated by the determination of partition coefficients of phenol, citric acid, acetylsalicylic acid and sodium salicylate. (author). 8 refs.; 3 figs.; 1 tab
Energy Technology Data Exchange (ETDEWEB)
Kuban, V. (Royal Institute of Technology, Stockholm (Sweden). Department of Analytical Chemistry)
1991-08-01
Single-channel coaxial segments were used for the introduction of an aqueous or octan-1-ol solution of an organic substance directly into a continuous flow of the other solvent. The analytical signal was measured simultaneously on both aqueous and organic phase segments by an 'on-tube' fast-reading spectrophotometric detector (ca. 3 ms time resolution) and treated mathematically. The octan-1-ol-water phase signal ratio corresponds to the partition coefficient of the organic substances. The applicability of the method is demonstrated by the determination of partition coefficients of phenol, citric acid, acetylsalicylic acid and sodium salicylate. (author). 8 refs.; 3 figs.; 1 tab.
Weinstein, H.; Lavan, Z.
1975-01-01
Analytical investigations of fluid dynamics problems of relevance to the gaseous core nuclear reactor program are presented. The vortex type flow which appears in the nuclear light bulb concept is analyzed along with the fluid flow in the fuel inlet region for the coaxial flow gaseous core nuclear reactor concept. The development of numerical methods for the solution of the Navier-Stokes equations for appropriate geometries is extended to the case of rotating flows and almost completes the gas core program requirements in this area. The investigations demonstrate that the conceptual design of the coaxial flow reactor needs further development.
Directory of Open Access Journals (Sweden)
Monzavi A
2002-07-01
Full Text Available Waxes have a lot of applications in dentistry. Such materials are of thermoplastic type that undergoes deformation in different temperatures. Two important properties of base plate waxes are flow and their coefficient of linear thermal expansion. Recently, different institutions, inside the country, produce dentistry waxes, while they have not been standardized. Consequently, consumers' dissatisfaction are observed. In this research, the two above- mentioned factors were compared between three kinds of Iranian waxes with Cavex that is foreign production, based on test number 24 of ADA. To measure the flow rate in the temperatures of 23, 37 and 45°c, Wilcoxon statistical analysis was used. The results showed that in 23°c, the flow rate of Cavex and Azardent waxes met ADA standards; however, it was not true for two others types. In 37°c, the flow of none of the waxes was standardized and in 45°c their flow was acceptable, moreover, thermal expansion coefficient, for Cavex and Azardent types, was based on ADA standard.
Duan, Yifei; Feng, Zhi-Gang
2017-12-01
Kinetic theory (KT) has been successfully used to model rapid granular flows in which particle interactions are frictionless and near elastic. However, it fails when particle interactions become frictional and inelastic. For example, the KT is not able to accurately predict the free cooling process of a vibrated granular medium that consists of inelastic frictional particles under microgravity. The main reason that the classical KT fails to model these flows is due to its inability to account for the particle surface friction and its inelastic behavior, which are the two most important factors that need be considered in modeling collisional granular flows. In this study, we have modified the KT model that is able to incorporate these two factors. The inelasticity of a particle is considered by establishing a velocity-dependent expression for the restitution coefficient based on many experimental studies found in the literature, and the particle friction effect is included by using a tangential restitution coefficient that is related to the particle friction coefficient. Theoretical predictions of the free cooling process by the classical KT and the improved KT are compared with the experimental results from a study conducted on an airplane undergoing parabolic flights without the influence of gravity [Y. Grasselli, G. Bossis, and G. Goutallier, Europhys. Lett. 86, 60007 (2009)10.1209/0295-5075/86/60007]. Our results show that both the velocity-dependent restitution coefficient and the particle surface friction are important in predicting the free cooling process of granular flows; the modified KT model that integrates these two factors is able to improve the simulation results and leads to better agreement with the experimental results.
Duan, Yifei; Feng, Zhi-Gang
2017-12-01
Kinetic theory (KT) has been successfully used to model rapid granular flows in which particle interactions are frictionless and near elastic. However, it fails when particle interactions become frictional and inelastic. For example, the KT is not able to accurately predict the free cooling process of a vibrated granular medium that consists of inelastic frictional particles under microgravity. The main reason that the classical KT fails to model these flows is due to its inability to account for the particle surface friction and its inelastic behavior, which are the two most important factors that need be considered in modeling collisional granular flows. In this study, we have modified the KT model that is able to incorporate these two factors. The inelasticity of a particle is considered by establishing a velocity-dependent expression for the restitution coefficient based on many experimental studies found in the literature, and the particle friction effect is included by using a tangential restitution coefficient that is related to the particle friction coefficient. Theoretical predictions of the free cooling process by the classical KT and the improved KT are compared with the experimental results from a study conducted on an airplane undergoing parabolic flights without the influence of gravity [Y. Grasselli, G. Bossis, and G. Goutallier, Europhys. Lett. 86, 60007 (2009), 10.1209/0295-5075/86/60007]. Our results show that both the velocity-dependent restitution coefficient and the particle surface friction are important in predicting the free cooling process of granular flows; the modified KT model that integrates these two factors is able to improve the simulation results and leads to better agreement with the experimental results.
Directory of Open Access Journals (Sweden)
sana mousavian
2015-05-01
Full Text Available Extraction of sugar from sugarcane produces a high volume of effluent carrying large amounts of organics and BOD5. Discharging the effluent into rivers and into the environment endangers the aquatic life and increases the risks of environmental pollution. This study was conducted in 2012 to determine the kinetic coefficients of the anaerobic treatment systems (UASB at the wastewater treatment plant of Imam Khomeini Sugarcane Agro-industrial Plant in Shushtar. The parameters of BOD5, COD, and TSS were measured at the inlet and outlet of the WWTP. Subsequently, the operation and design parameters of the system were determined. Using the modified Monod Equations, the kinetic coefficients Ks, Y, Kd, μ max, and K max for employing the UASB process at the WWPT in question were calculated as 506.4mg/l, 0.11 g VSS/g COD, 0.0045 d-1, 0.0069 d-1, and 0.055 d-1, respectively. The kinetic coefficients obtained in this study can be used in the steering and operation as well as fundamental design of similar plants, especially in hot areas.
International Nuclear Information System (INIS)
Khalisanni Khalid; Rashid Atta Khan; Sharifuddin Mohd Zain
2012-01-01
Evaporation of vaporize organic liquid has ecological consequences when the compounds are introduced into both freshwater and marine environments through industrial effluents, or introduced directly into the air from industrial unit processes such as bioreactors and cooling towers. In such cases, a rapid and simple method are needed to measure physicochemical properties of the organic liquids. The Reversed-Flow Gas Chromatography (RF-GC) sampling technique is an easy, fast and accurate procedure. It was used to measure the diffusion coefficients of vapors from liquid into a carrier gas and at the same time to determine the rate coefficients for the evaporation of the respective liquid. The mathematical expression describing the elution curves of the samples peaks was derived and used to calculate the respective parameters for the selected liquid pollutants selected such as methanol, ethanol, 1-propanol, 1-butanol, n-pentane, n-hexane, n-heptane and n-hexadecane, evaporating into the carrier gas of nitrogen. The values of diffusion coefficients found were compared with those calculated theoretically or reported in the literature. The values of evaporation rate were used to determine the activation energy of respective samples using Arrhenius equation. An interesting finding of this work is by using an alternative mathematical analysis based on equilibrium at the liquid-gas interphase, the comparison leads to profound agreement between theoretical values of diffusion coefficients and experimental evidence. (author)
New coefficients of performance in the A. A. ultrasonic flow measurement
International Nuclear Information System (INIS)
Baraza Peregrin, A.
2014-01-01
The basic principle of this system is to measure the velocity rate of flow of water in two flat with four points each for later through a process of numerical integration to calculate the total flow that passes through the section. During this process, is It also measures the speed of sound in water used to calculate their temperature. The system can operate with only a plane of measurement and its eight sets of sensors of correct measures, but by using the two flat and with 8 sets of sensors, measurement has less uncertainty. Normally the measure is being performed using the two planes. (Author)
Drexel, Rober E; Mcadams, William H
1945-01-01
Report reviews published data and presents some new data on heat transfer to air flowing in round tubes, in rectangular ducts, and around finned cylinders. The available data for heat transfer to air in straight ducts of rectangular and circular cross section have been correlated in plots of Stanton number versus Reynolds number to provide a background for the study of the data for finned cylinders. Equations are recommended for both the streamlined and turbulent regions, and data are presented for the transition region between turbulent and laminar flow. Use of hexagonal ends on round tubes causes the characteristics of laminar flow to extend to high Reynolds numbers. Average coefficients for the entire finned cylinder have been calculated from the average temperature at the base of the fins and an equation which was derived to allow for the effectiveness of the fins. The available results for each finned cylinder are correlated herein in terms of graphs of Stanton number versus Reynolds number. In general, for a given Reynolds number, the Stanton number increases with increases in both spacing and width of the fins, and is apparently independent of cylinder diameter and temperature difference. For a given coefficient of heat transfer improved baffles and rough or wavy surfaces give a substantial reduction in pumping power per unit of heat transfer surface and a somewhat smaller decrease in pressure drop. (author)
Model for definition of heat transfer coefficient in an annular two-phase flow
International Nuclear Information System (INIS)
Khun, J.
1976-01-01
Near-wall heat exchange in a vertical tube at high vapor velocity in a two-phase vapor and liquid flow is investigated. The flow divides inside the tube into a near-wall liquid film and a vapor nucleus containing liquid droplets, with the boundaries being uniform. The liquid film thickness determines the main resistance during heat transfer between the wall and vapor nucleus. The theoretical model presented is verified in water vaporization experiments, the R12 cooling agent and certain hydrocarbons. The loss of friction pressure is determined by the Lockart-Martinelli method. The approximately universal Carman velocity profile is used to evaluate the velocity in film, and basing on this, film thickness is determined. The parameter ranges were: Resub(vap)=10 4 -3x10 6 , Resub(liq.)=0.9-10. The theoretical model ensures good correlation with the experiment
Directory of Open Access Journals (Sweden)
Lotfollah Saghaie
2003-08-01
Full Text Available The partition coefficients (Kpart , in octanol/water system of a range of bidentate ligands containing the 3-hydroxypyridin-4-one moiety were determined using shake flask and automated continuous flow methods (filter probe method. The shake flask method was used for extremely hydrophilic or hydrophobic compounds with a Kpart values greater than 100 and less than 0.01. For other ligands which possess moderate lipophilicity (Kpart values between 0.01-100 the filter probe method was used. Also the partition coefficient of four ligands with moderate lipophilicity was determined by shake flask method in order to check comparability of these two methods. While the shake flask method was able to determine either extremely hydrophilic or hydrophobic compounds efficiently, the filter probe method was unable to measure such Kpart values. Although, determination of the Kpart values of all compounds is possible with the classical shake-flask method, the procedure is time consuming. In contrast, the filter probe method offers many advantages over the traditional shake-flask method in terms of speed, efficiency of separation and degree of automation. The shake-flask method is the method of choice for determination of partition coefficients of extremely hydrophilic and hydrophobic ligands.
Dynamical flow arrest in confined gravity driven flows of soft jammed particles.
Chaudhuri, Pinaki; Mansard, Vincent; Colin, Annie; Bocquet, Lyderic
2012-07-20
Using numerical simulations, we study the gravity driven flow of jammed soft disks in confined channels. We demonstrate that confinement results in increasing the yield threshold for the Poiseuille flow, in contrast to the planar Couette flow. By solving a nonlocal flow model for such systems, we show that this effect is due to the correlated dynamics responsible for flow, coupled with the stress heterogeneity imposed for the Poiseuille flow. We also observe that with increasing confinement, the cooperative nature of the flow results in increasing intermittent behavior. Our studies indicate that such features are generic properties of a wide variety of jammed materials.
Coward, Adrian V.; Papageorgiou, Demetrios T.; Smyrlis, Yiorgos S.
1994-01-01
In this paper the nonlinear stability of two-phase core-annular flow in a pipe is examined when the acting pressure gradient is modulated by time harmonic oscillations and viscosity stratification and interfacial tension is present. An exact solution of the Navier-Stokes equations is used as the background state to develop an asymptotic theory valid for thin annular layers, which leads to a novel nonlinear evolution describing the spatio-temporal evolution of the interface. The evolution equation is an extension of the equation found for constant pressure gradients and generalizes the Kuramoto-Sivashinsky equation with dispersive effects found by Papageorgiou, Maldarelli & Rumschitzki, Phys. Fluids A 2(3), 1990, pp. 340-352, to a similar system with time periodic coefficients. The distinct regimes of slow and moderate flow are considered and the corresponding evolution is derived. Certain solutions are described analytically in the neighborhood of the first bifurcation point by use of multiple scales asymptotics. Extensive numerical experiments, using dynamical systems ideas, are carried out in order to evaluate the effect of the oscillatory pressure gradient on the solutions in the presence of a constant pressure gradient.
Qu, Junbo; Yan, Tie; Sun, Xiaofeng; Chen, Ye; Pan, Yi
2017-10-01
With the development of drilling technology to deeper stratum, overflowing especially gas cut occurs frequently, and then flow regime in wellbore annulus is from the original drilling fluid single-phase flow into gas & liquid two-phase flow. By using averaged two-fluid model equations and the basic principle of fluid mechanics to establish the continuity equations and momentum conservation equations of gas phase & liquid phase respectively. Relationship between pressure and density of gas & liquid was introduced to obtain hyperbolic equation, and get the expression of the dimensionless eigenvalue of the equation by using the characteristic line method, and analyze wellbore flow regime to get the critical gas content under different virtual mass force coefficients. Results show that the range of equation eigenvalues is getting smaller and smaller with the increase of gas content. When gas content reaches the critical point, the dimensionless eigenvalue of equation has no real solution, and the wellbore flow regime changed from bubble flow to bomb flow. When virtual mass force coefficients are 0.50, 0.60, 0.70 and 0.80 respectively, the critical gas contents are 0.32, 0.34, 0.37 and 0.39 respectively. The higher the coefficient of virtual mass force, the higher gas content in wellbore corresponding to the critical point of transition flow regime, which is in good agreement with previous experimental results. Therefore, it is possible to determine whether there is a real solution of the dimensionless eigenvalue of equation by virtual mass force coefficient and wellbore gas content, from which we can obtain the critical condition of wellbore flow regime transformation. It can provide theoretical support for the accurate judgment of the annular flow regime.
Transport coefficients for electrolytes in arbitrarily shaped nano- and microfluidic channels
DEFF Research Database (Denmark)
Mortensen, Niels Asger; Olesen, Laurits Højgaard; Bruus, Henrik
2006-01-01
We consider laminar flow of incompressible electrolytes in long, straight channels driven by pressure and electro-osmosis. We use a Hilbert space eigenfunction expansion to address the general problem of an arbitrary cross-section and obtain general results in linear-response theory for the hydra......We consider laminar flow of incompressible electrolytes in long, straight channels driven by pressure and electro-osmosis. We use a Hilbert space eigenfunction expansion to address the general problem of an arbitrary cross-section and obtain general results in linear-response theory...... for the hydraulic and electrical transport coefficients which satisfy Onsager relations. In the limit of non-overlapping Debye layers, the transport coefficients are simply expressed in terms of parameters of the electrolyte as well as the geometrical correction factor for the Hagen-Poiseuille part of the problem....... In particular, we consider the limits of thin non-overlapping as well as strongly overlapping Debye layers, respectively, and calculate the corrections to the hydraulic resistance due to electro-hydrodynamic interactions....
International Nuclear Information System (INIS)
Nekimken, H.L.
1987-01-01
A search for simpler and more effective ways to perform various actinide and lanthanide separations is in progress. Emphasis has been on evaluating ligands for their ability to complex and extract metal ions under a variety of experimental conditions. To evaluate effectively these extractants and to ultimately correlate structural features with extraction capabilities, a large volume of distribution coefficient (Kd) data must be acquired. Kd data for each ligand should be obtained as a function of such variables as ligand and metal ion concentration, pH, and organic solvent employed. Unfortunately, batch Kd experiments are generally time consuming and tedious. A computer controlled flow injection analysis system has been developed to obtain rapid on-line Kd data. A diluter/dispenser is utilized to generate the various aqueous metal ion samples. Results indicate this FIA system can be used to effectively determine Kd values for certain chemical systems. The FIA apparatus should also be useful for other applications that require on-line extraction and/or detection (or kinetics studies). Reasonably good agreement has been obtained between batch and FIA Kd values for the extraction of Pb(II), Zn(II) and Cd(II) by dithizone. Fe(III) by 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (PMBP) and uranyl by the 5-thione derivative of BMBP (SPMBP). A study of the uranyl-SPBMP chemical system with FIA is now nearing completion
Suhas, B. G.; Sathyabhama, A.
2018-02-01
The experimental study is carried out to determine forced convective and subcooled flow boiling heat transfer coefficient in conventional rectangular channels. The fluid is passed through rectangular channels of 0.01 m depth, 0.01 m width, and 0.15 m length. The parameters varied are heat flux, mass flux, inlet temperature and volume fraction of ethanol. Forced convective heat transfer coefficient increases with increase in heat flux and mass flux, but effect of mass flux is less significant. Subcooled flow boiling heat transfer increases with increase in heat flux and mass flux, but the effect of heat flux is dominant. During the subcooled flow boiling region, the effect of mass flux will not influence the heat transfer. The strong Marangoni effect will increase the heat transfer coeffient for mixture with 25% ethanol volume fraction. The results obtained for subcooled flow boiling heat transfer coefficient of water are compared with available literature correlations. It is found that Liu-Winterton equation predicts the experimental results better when compared with that of other literature correlations. An empirical correlation for subcooled flow boiling heat transfer coefficient as a function of mixture wall super heat, mass flux, volume fractions and inlet temperature is developed from the experimental results.
Relaminarization of fluid flows
International Nuclear Information System (INIS)
Narasimha, R.; Sreenivasan, K.R.
1979-01-01
The mechanisms of the relaminarization of turbulent flows are investigated with a view to establishing any general principles that might govern them. Three basic archetypes of reverting flows are considered: the dissipative type, the absorptive type, and the Richardson type exemplified by a turbulent boundary layer subjected to severe acceleration. A number of other different reverting flows are then considered in the light of the analysis of these archetypes, including radial Poiseuille flow, convex boundary layers, flows reverting by rotation, injection, and suction, as well as heated horizontal and vertical gas flows. Magnetohydrodynamic duct flows are also examined. Applications of flow reversion for turbulence control are discussed
Taylor, Maynard F.; Kirchgessner, Thomas A.
1959-01-01
Measurements of average heat transfer and friction coefficients and local heat transfer coefficients were made with helium flowing through electrically heated smooth tubes with length-diameter ratios of 60 and 92 for the following range of conditions: Average surface temperature from 1457 to 4533 R, Reynolds numbe r from 3230 to 60,000, heat flux up to 583,200 Btu per hr per ft2 of heat transfer area, and exit Mach numbe r up to 1.0. The results indicate that, in the turbulent range of Reynolds number, good correlation of the local heat transfer coefficients is obtained when the physical properties and density of helium are evaluated at the surface temperature. The average heat transfer coefficients are best correlated on the basis that the coefficient varies with [1 + (L/D))(sup -0,7)] and that the physical properties and density are evaluated at the surface temperature. The average friction coefficients for the tests with no heat addition are in complete agreement with the Karman-Nikuradse line. The average friction coefficients for heat addition are in poor agreement with the accepted line.
Indian Academy of Sciences (India)
This is a simple exercise in elementary fluid dynamics for the undergraduate and .... ΔP is the pressure difference which is ρgH(t), and η is the coefficient of viscosity. It should be noted that the Hagen–Poiseuille equation can only. 72. RESONANCE ... decreasing in the top tank and increasing in the lower tank. Let h(t) be the ...
MacLeod, Morgan; Antoni, Andrea; Murguia-Berthier, Ariadna; Macias, Phillip; Ramirez-Ruiz, Enrico
2017-03-01
This paper examines the properties of flows around objects embedded within common envelopes in the simplified context of a “wind tunnel.” We establish characteristic relationships between key common envelope flow parameters like the Mach number and density scale height. Our wind tunnel is a three-dimensional, Cartesian geometry hydrodynamic simulation setup that includes the gravity of the primary and secondary stars and allows us to study the coefficients of drag and accretion experienced by the embedded object. Accretion and drag lead to a transformation of an embedded object and its orbit during a common envelope phase. We present two suites of simulations spanning a range of density gradients and Mach numbers—relevant for flow near the limb of a stellar envelope to the deep interior. In one suite, we adopt an ideal gas adiabatic exponent of γ =5/3, in the other, γ =4/3. We find that coefficients of drag rise in flows with steeper density gradients and that coefficients of drag and accretion are consistently higher in the more compressible, γ =4/3 flow. We illustrate the impact of these newly derived coefficients by integrating the inspiral of a secondary object through the envelopes of 3{M}⊙ (γ ≈ 5/3) and 80{M}⊙ (γ ≈ 4/3) giants. In these examples, we find a relatively rapid initial inspiral because, near the stellar limb, dynamical friction drag is generated mainly from dense gas focused from deeper within the primary-star’s envelope. This rapid initial inspiral timescale carries potential implications for the timescale of transients from early common envelope interaction.
Cangioli, Filippo; Pennacchi, Paolo; Vannini, Giuseppe; Ciuchicchi, Lorenzo
2018-01-01
The influence of sealing components on the rotordynamic stability of turbomachinery has become a key topic because the oil and gas market is increasingly demanding high rotational speeds and high efficiency. This leads the turbomachinery manufacturers to design higher flexibility ratios and to reduce the clearance of the seals. Accurate prediction of the effective damping of seals is critical to avoid instability problems; in recent years, "negative-swirl" swirl brakes have been used to reverse the circumferential direction of the inlet flow, which changes the sign of the cross-coupled stiffness coefficients and generates stabilizing forces. Experimental tests for a teeth-on-stator labyrinth seal were performed by manufacturers with positive and negative pre-swirl values to investigate the pre-swirl effect on the cross-coupled stiffness coefficient. Those results are used as a benchmark in this paper. To analyse the rotor-fluid interaction in the seals, the bulk-flow numeric approach is more time efficient than computational fluid dynamics (CFD). Although the accuracy of the coefficients prediction in bulk-flow models is satisfactory for liquid phase application, the accuracy of the results strongly depends on the operating conditions in the case of the gas phase. In this paper, the authors propose an improvement in the state-of-the-art bulk-flow model by introducing the effect of the energy equation in the zeroth-order solution to better characterize real gas properties due to the enthalpy variation along the seal cavities. The consideration of the energy equation allows for a better estimation of the coefficients in the case of a negative pre-swirl ratio, therefore, it extend the prediction fidelity over a wide range of operating conditions. The numeric results are also compared to the state-of-the-art bulk-flow model, which highlights the improvement in the model.
National Research Council Canada - National Science Library
Thomas, Scott
2000-01-01
.... A computer model was developed using a finite difference solution which finds the mean velocity, Poiseuille number, and volumetric flow rate in terms of the groove geometry, meniscus contact angle...
Slip velocity and Knudsen layer in the lattice Boltzmann method for microscale flows.
Kim, Seung Hyun; Pitsch, Heinz; Boyd, Iain D
2008-02-01
We present mesoscopic fluid-wall interaction models for lattice Boltzmann (LB) model simulations of microscale flows. The exact solution of the slip velocity for the LB equation with the Bhatnagar-Gross-Krook collision operator is obtained for Poiseuille flow at finite Knudsen numbers. With a consistent definition of the Knudsen number, the slip coefficients of the LB equation with the standard D2Q9 scheme are found to be slightly larger than those of the Boltzmann equation with the same boundary condition, which makes the standard LB method remain quantitatively accurate only for small Knudsen numbers. By modifying the nonequilibrium energy flux or introducing the effective relaxation time, the LB method is analytically shown to reproduce the slip phenomena up to second order in the Knudsen number. For the standard LB method, the Knudsen layer is captured only with modification of the relaxation dynamics such as in the effective relaxation time model.
Satoh, Akira; Hayasaka, Ryo; Majima, Tamotsu
We have treated a dilute dispersion composed of ferromagnetic rodlike particles with a magnetic moment normal to the particle axis, such as hematites, to investigate the influences of the magnetic field strength, shear rate, and random forces on the orientational distribution of rodlike particles and also on transport coefficients, such as viscosity and diffusion coefficient. In the present analysis, these rodlike particles are assumed to conduct the rotational Brownian motion in a simple shear flow as well as an external magnetic field. The results obtained here are summarized as follows. In the case of a strong magnetic field and a smaller shear rate, the rodlike particle can freely rotate in the xy-plane with the magnetic moment continuing to point the magnetic field direction. On the other hand, for a strong shear flow, the particle has a tendency to incline in the flow direction with the magnetic moment pointing to the magnetic field direction. In the case of the magnetic field applied normal to the direction of the sedimentation, the diffusion coefficient gives rise to smaller values than expected, since the rodlike particle sediments with the particle axis inclining toward directions normal to the movement direction and, of course, toward the direction along that direction.
Energy Technology Data Exchange (ETDEWEB)
Agbodemegbe, V.Y., E-mail: vincevalt@gmail.com [Karlsruhe Institute of Technology, Institute of Fusion and Reactor Technique, Kaiserstrasse 12, Karlsruhe (Germany); Cheng, Xu, E-mail: xu.cheng@kit.edu [Karlsruhe Institute of Technology, Institute of Fusion and Reactor Technique, Kaiserstrasse 12, Karlsruhe (Germany); Akaho, E.H.K, E-mail: akahoed@yahoo.com [School of Nuclear and Allied Sciences, University of Ghana, PO Box AE 1, Kwabenya, Accra (Ghana); Allotey, F.K.A, E-mail: fkallotey@gmail.com [Institute of Mathematical Sciences, PO Box LG 197, Legon, Accra (Ghana)
2015-04-15
Highlights: • Investigate spacer grid with split-type mixing vanes. • Extent of predictability of experimental data by STAR-CCM+. • Reliability of two equation turbulence models. • Resistance to cross-flow through gaps. - Abstract: Mass transfer by diversion cross-flow through gaps is an important inter-subchannel interaction in fuel bundle of power reactors. It is normally due to the lateral pressure difference between adjacent sub-channels. This phenomenon is augmented in the presence of flow deflectors and is referred to as, directed cross-flow. Diversion cross-flow carries the momentum and energy of flow and hence affects the velocity and temperature profile in the rod bundle. The resistance to cross-flow in the transverse momentum equations is specified by the cross-flow resistant coefficient which is the subject of concern in the present study. In order to obtain data to correlate cross-flow resistance coefficient, computational fluid dynamic simulation using STAR-CCM+ was performed for flow of water at the bundle Reynolds number of Re1 = 3.4×10{sup 4} through a 5 × 5 rod bundle geometry supported by spacer grid with split mixing vanes for which the rod to rod pitch to diameter ratio was 1.33 and the rod to wall pitch to diameter ratio was 0.74. The two layer k-epsilon turbulence model with an all y+ automatic wall treatment function in STAR-CCM+ were adopted for an isothermal single phase (water) flow through the geometry. The objectives were to primarily investigate the extent of predictability of the experimental data by the computational fluid dynamic (CFD) simulation as a measure of reliability on the CFD code employed and also apply the simulation data to develop correlations for determining resistance coefficient to cross-flow. Validation of simulation results with experimental data showed good correlation of mean flow parameters with experimental data whiles turbulent fluctuations deviated largely from experimental trends. Generally, the
Ardhapurkar, P. M.; Sridharan, Arunkumar; Atrey, M. D.
2014-01-01
The recuperative heat exchanger governs the overall performance of the mixed refrigerant Joule-Thomson cryocooler. In these heat exchangers, the non-azeotropic refrigerant mixture of nitrogen-hydrocarbons undergoes boiling and condensation simultaneously at cryogenic temperature. Hence, the design of such heat exchanger is crucial. However, due to lack of empirical correlations to predict two-phase heat transfer coefficients of multi-component mixtures at low temperature, the design of such heat exchanger is difficult.
Simulation of Plane Poiseuille Flow of a Rarefied Gas with an Extended Lattice Boltzmann Method
National Research Council Canada - National Science Library
Teixeira, Christopher M
2005-01-01
.... The accuracy of the new method is first demonstrated by validating the desired power-law viscosity-temperature relationship over the range of power-law exponents typically found in single component fluids...
Axial Couette-Poiseuille flow of power-law viscoplastic fluids in concentric annuli
Czech Academy of Sciences Publication Activity Database
Filip, Petr; David, Jiří
2003-01-01
Roč. 40, 3/4 (2003), s. 111-119 ISSN 0920-4105 R&D Projects: GA AV ČR IAA2060004 Institutional research plan: CEZ:AV0Z2060917 Keywords : boreholes * channel geometry * viscoplastic materials Subject RIV: BK - Fluid Dynamics Impact factor: 0.570, year: 2003
Barr, P. K.
1980-01-01
An analysis is presented of the reliability of various generally accepted empirical expressions for the prediction of the skin-friction coefficient C/sub f/ of turbulent boundary layers at low Reynolds numbers in zero-pressure-gradient flows on a smooth flat plate. The skin-friction coefficients predicted from these expressions were compared to the skin-friction coefficients of experimental profiles that were determined from a graphical method formulated from the law of the wall. These expressions are found to predict values that are consistently different than those obtained from the graphical method over the range 600 Re/sub theta 2000. A curve-fitted empirical relationship was developed from the present data and yields a better estimated value of C/sub f/ in this range. The data, covering the range 200 Re/sub theta 7000, provide insight into the nature of transitional flows. They show that fully developed turbulent boundary layers occur at Reynolds numbers Re/sub theta/ down to 425. Below this level there appears to be a well-ordered evolutionary process from the laminar to the turbulent profiles. These profiles clearly display the development of the turbulent core region and the shrinking of the laminar sublayer with increasing values of Re/sub theta/.
Adam, Jaroslav; Aggarwal, Madan Mohan; Aglieri Rinella, Gianluca; Agnello, Michelangelo; Agrawal, Neelima; Ahammed, Zubayer; Ahmad, Shakeel; Ahn, Sang Un; Aiola, Salvatore; Akindinov, Alexander; Alam, Sk Noor; Silva De Albuquerque, Danilo; Aleksandrov, Dmitry; Alessandro, Bruno; Alexandre, Didier; Alfaro Molina, Jose Ruben; Alici, Andrea; Alkin, Anton; Alme, Johan; Alt, Torsten; Altinpinar, Sedat; Altsybeev, Igor; Alves Garcia Prado, Caio; An, Mangmang; Andrei, Cristian; Andrews, Harry Arthur; Andronic, Anton; Anguelov, Venelin; Anticic, Tome; Antinori, Federico; Antonioli, Pietro; Aphecetche, Laurent Bernard; Appelshaeuser, Harald; Arcelli, Silvia; Arnaldi, Roberta; Arnold, Oliver Werner; Arsene, Ionut Cristian; Arslandok, Mesut; Audurier, Benjamin; Augustinus, Andre; Averbeck, Ralf Peter; Azmi, Mohd Danish; Badala, Angela; Baek, Yong Wook; Bagnasco, Stefano; Bailhache, Raphaelle Marie; Bala, Renu; Balasubramanian, Supraja; Baldisseri, Alberto; Baral, Rama Chandra; Barbano, Anastasia Maria; Barbera, Roberto; Barile, Francesco; Barnafoldi, Gergely Gabor; Barnby, Lee Stuart; Ramillien Barret, Valerie; Bartalini, Paolo; Barth, Klaus; Bartke, Jerzy Gustaw; Bartsch, Esther; Basile, Maurizio; Bastid, Nicole; Basu, Sumit; Bathen, Bastian; Batigne, Guillaume; Batista Camejo, Arianna; Batyunya, Boris; Batzing, Paul Christoph; Bearden, Ian Gardner; Beck, Hans; Bedda, Cristina; Behera, Nirbhay Kumar; Belikov, Iouri; Bellini, Francesca; Bello Martinez, Hector; Bellwied, Rene; Belmont Iii, Ronald John; Belmont Moreno, Ernesto; Espinoza Beltran, Lucina Gabriela; Belyaev, Vladimir; Bencedi, Gyula; Beole, Stefania; Berceanu, Ionela; Bercuci, Alexandru; Berdnikov, Yaroslav; Berenyi, Daniel; Bertens, Redmer Alexander; Berzano, Dario; Betev, Latchezar; Bhasin, Anju; Bhat, Inayat Rasool; Bhati, Ashok Kumar; Bhattacharjee, Buddhadeb; Bhom, Jihyun; Bianchi, Livio; Bianchi, Nicola; Bianchin, Chiara; Bielcik, Jaroslav; Bielcikova, Jana; Bilandzic, Ante; Biro, Gabor; Biswas, Rathijit; Biswas, Saikat; Bjelogrlic, Sandro; Blair, Justin Thomas; Blau, Dmitry; Blume, Christoph; Bock, Friederike; Bogdanov, Alexey; Boggild, Hans; Boldizsar, Laszlo; Bombara, Marek; Bonora, Matthias; Book, Julian Heinz; Borel, Herve; Borissov, Alexander; Borri, Marcello; Bossu, Francesco; Botta, Elena; Bourjau, Christian; Braun-Munzinger, Peter; Bregant, Marco; Breitner, Timo Gunther; Broker, Theo Alexander; Browning, Tyler Allen; Broz, Michal; Brucken, Erik Jens; Bruna, Elena; Bruno, Giuseppe Eugenio; Budnikov, Dmitry; Buesching, Henner; Bufalino, Stefania; Buncic, Predrag; Busch, Oliver; Buthelezi, Edith Zinhle; Bashir Butt, Jamila; Buxton, Jesse Thomas; Cabala, Jan; Caffarri, Davide; Cai, Xu; Caines, Helen Louise; Calero Diaz, Liliet; Caliva, Alberto; Calvo Villar, Ernesto; Camerini, Paolo; Carena, Francesco; Carena, Wisla; Carnesecchi, Francesca; Castillo Castellanos, Javier Ernesto; Castro, Andrew John; Casula, Ester Anna Rita; Ceballos Sanchez, Cesar; Cepila, Jan; Cerello, Piergiorgio; Cerkala, Jakub; 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2016-09-28
The elliptic, triangular, quadrangular and pentagonal anisotropic flow coefficients for $\\pi^{\\pm}$, $\\mathrm{K}^{\\pm}$ and p+$\\overline{\\mathrm{p}}$ in Pb-Pb collisions at $\\sqrt{s_\\mathrm{{NN}}} = 2.76$ TeV were measured with the ALICE detector at the Large Hadron Collider. The results were obtained with the Scalar Product method, correlating the identified hadrons with reference particles from a different pseudorapidity region. Effects not related to the common event symmetry planes (non-flow) were estimated using correlations in pp collisions and were subtracted from the measurement. The obtained flow coefficients exhibit a clear mass ordering for transverse momentum ($p_{\\mathrm{T}}$) values below $\\approx$ 3 GeV/$c$. In the intermediate $p_{\\mathrm{T}}$ region ($3 < p_{\\mathrm{T}} < 6$ GeV/$c$), particles group at an approximate level according to the number of constituent quarks, suggesting that coalescence might be the relevant particle production mechanism in this region. The results for $p_{\\m...
Higher harmonic flow coefficients of identified hadrons in Pb-Pb collisions at √{s_{NN}}=2.76 TeV
Adam, J.; Adamová, D.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmad, S.; Ahn, S. U.; Aiola, S.; Akindinov, A.; Alam, S. N.; Albuquerque, D. S. D.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alfaro Molina, R.; Alici, A.; Alkin, A.; Alme, J.; Alt, T.; Altinpinar, S.; Altsybeev, I.; Alves Garcia Prado, C.; An, M.; Andrei, C.; Andrews, H. A.; Andronic, A.; Anguelov, V.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arcelli, S.; Arnaldi, R.; Arnold, O. W.; Arsene, I. C.; Arslandok, M.; Audurier, B.; Augustinus, A.; Averbeck, R.; Azmi, M. D.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Balasubramanian, S.; Baldisseri, A.; Baral, R. C.; Barbano, A. M.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartalini, P.; Barth, K.; Bartke, J.; Bartsch, E.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batista Camejo, A.; Batyunya, B.; Batzing, P. C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bello Martinez, H.; Bellwied, R.; Belmont, R.; Belmont-Moreno, E.; Beltran, L. G. E.; Belyaev, V.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhat, I. R.; Bhati, A. K.; Bhattacharjee, B.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Biro, G.; Biswas, R.; Biswas, S.; Bjelogrlic, S.; Blair, J. T.; Blau, D.; Blume, C.; Bock, F.; Bogdanov, A.; Bøggild, H.; Boldizsár, L.; Bombara, M.; Bonora, M.; Book, J.; Borel, H.; Borissov, A.; Borri, M.; Bossú, F.; Botta, E.; Bourjau, C.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Brucken, E. J.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Butt, J. B.; Buxton, J. T.; Cabala, J.; Caffarri, D.; Cai, X.; Caines, H.; Calero Diaz, L.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Carena, F.; Carena, W.; Carnesecchi, F.; Castillo Castellanos, J.; Castro, A. J.; Casula, E. A. R.; Ceballos Sanchez, C.; Cepila, J.; Cerello, P.; Cerkala, J.; Chang, B.; Chapeland, S.; Chartier, M.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Chauvin, A.; Chelnokov, V.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Cho, S.; Chochula, P.; Choi, K.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Colocci, M.; Conesa Balbastre, G.; Conesa del Valle, Z.; Connors, M. E.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortés Maldonado, I.; Cortese, P.; Cosentino, M. R.; Costa, F.; Crkovska, J.; Crochet, P.; Cruz Albino, R.; Cuautle, E.; Cunqueiro, L.; Dahms, T.; Dainese, A.; Danisch, M. C.; Danu, A.; Das, D.; Das, I.; Das, S.; Dash, A.; Dash, S.; De, S.; De Caro, A.; de Cataldo, G.; de Conti, C.; de Cuveland, J.; De Falco, A.; De Gruttola, D.; De Marco, N.; De Pasquale, S.; De Souza, R. D.; Deisting, A.; Deloff, A.; Dénes, E.; Deplano, C.; Dhankher, P.; Di Bari, D.; Di Mauro, A.; Di Nezza, P.; Di Ruzza, B.; Diaz Corchero, M. A.; Dietel, T.; Dillenseger, P.; Divià, R.; Djuvsland, Ø.; Dobrin, A.; Domenicis Gimenez, D.; Dönigus, B.; Dordic, O.; Drozhzhova, T.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Ehlers, R. J.; Elia, D.; Endress, E.; Engel, H.; Epple, E.; Erazmus, B.; Erdemir, I.; Erhardt, F.; Espagnon, B.; Estienne, M.; Esumi, S.; Eulisse, G.; Eum, J.; Evans, D.; Evdokimov, S.; Eyyubova, G.; Fabbietti, L.; Fabris, D.; Faivre, J.; Fantoni, A.; Fasel, M.; Feldkamp, L.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Fernández Téllez, A.; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Feuillard, V. J. G.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Francisco, A.; Frankenfeld, U.; Fronze, G. G.; Fuchs, U.; Furget, C.; Furs, A.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A. M.; Gajdosova, K.; Gallio, M.; Galvan, C. D.; Gangadharan, D. R.; Ganoti, P.; Gao, C.; Garabatos, C.; Garcia-Solis, E.; Garg, K.; Gargiulo, C.; Gasik, P.; Gauger, E. F.; Germain, M.; Gheata, M.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Giubilato, P.; Gladysz-Dziadus, E.; Glässel, P.; Goméz Coral, D. M.; Gomez Ramirez, A.; Gonzalez, A. S.; Gonzalez, V.; González-Zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Grabski, V.; Grachov, O. A.; Graczykowski, L. K.; Graham, K. L.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Gronefeld, J. M.; Grosse-Oetringhaus, J. F.; Grosso, R.; Gruber, L.; Guber, F.; Guernane, R.; Guerzoni, B.; Gulbrandsen, K.; Gunji, T.; Gupta, A.; Gupta, R.; Guzman, I. B.; Haake, R.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Hamon, J. C.; Harris, J. W.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Heckel, S. T.; Hellbär, E.; Helstrup, H.; Herghelegiu, A.; Herrera Corral, G.; Herrmann, F.; Hess, B. A.; Hetland, K. F.; Hillemanns, H.; Hippolyte, B.; Horak, D.; Hosokawa, R.; Hristov, P.; Hughes, C.; Humanic, T. J.; Hussain, N.; Hussain, T.; Hutter, D.; Hwang, D. S.; Ilkaev, R.; Inaba, M.; Incani, E.; Ippolitov, M.; Irfan, M.; Isakov, V.; Ivanov, M.; Ivanov, V.; Izucheev, V.; Jacak, B.; Jacazio, N.; Jacobs, P. M.; Jadhav, M. B.; Jadlovska, S.; Jadlovsky, J.; Jahnke, C.; Jakubowska, M. J.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, C.; Jena, S.; Jimenez Bustamante, R. T.; Jones, P. G.; Jusko, A.; Kalinak, P.; Kalweit, A.; Kang, J. H.; Kaplin, V.; Kar, S.; Karasu Uysal, A.; Karavichev, O.; Karavicheva, T.; Karayan, L.; Karpechev, E.; Kebschull, U.; Keidel, R.; Keijdener, D. L. D.; Keil, M.; Mohisin Khan, M.; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Khatun, A.; Kileng, B.; Kim, D. W.; Kim, D. J.; Kim, D.; Kim, H.; Kim, J. S.; Kim, J.; Kim, M.; Kim, S.; Kim, T.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Kiss, G.; Klay, J. L.; Klein, C.; Klein, J.; Klein-Bösing, C.; Klewin, S.; Kluge, A.; Knichel, M. L.; Knospe, A. G.; Kobdaj, C.; Kofarago, M.; Kollegger, T.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Kondratyuk, E.; Konevskikh, A.; Kopcik, M.; Kour, M.; Kouzinopoulos, C.; Kovalenko, O.; Kovalenko, V.; Kowalski, M.; Koyithatta Meethaleveedu, G.; Králik, I.; Kravčáková, A.; Krivda, M.; Krizek, F.; Kryshen, E.; Krzewicki, M.; Kubera, A. M.; Kučera, V.; Kuhn, C.; Kuijer, P. G.; Kumar, A.; Kumar, J.; Kumar, L.; Kumar, S.; Kurashvili, P.; Kurepin, A.; Kurepin, A. B.; Kuryakin, A.; Kweon, M. J.; Kwon, Y.; La Pointe, S. L.; La Rocca, P.; Ladron de Guevara, P.; Lagana Fernandes, C.; Lakomov, I.; Langoy, R.; Lapidus, K.; Lara, C.; Lardeux, A.; Lattuca, A.; Laudi, E.; Lea, R.; Leardini, L.; Lee, S.; Lehas, F.; Lehner, S.; Lemmon, R. C.; Lenti, V.; Leogrande, E.; León Monzón, I.; León Vargas, H.; Leoncino, M.; Lévai, P.; Li, S.; Li, X.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Ljunggren, H. M.; Lodato, D. F.; Loenne, P. I.; Loginov, V.; Loizides, C.; Lopez, X.; López Torres, E.; Lowe, A.; Luettig, P.; Lunardon, M.; Luparello, G.; Lupi, M.; Lutz, T. H.; Maevskaya, A.; Mager, M.; Mahajan, S.; Mahmood, S. M.; Maire, A.; Majka, R. D.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manko, V.; Manso, F.; Manzari, V.; Mao, Y.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Margutti, J.; Marín, A.; Markert, C.; Marquard, M.; Martin, N. A.; Martinengo, P.; Martínez, M. I.; Martínez García, G.; Martinez Pedreira, M.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Mastroserio, A.; Matyja, A.; Mayer, C.; Mazer, J.; Mazzilli, M.; Mazzoni, M. A.; Meddi, F.; Melikyan, Y.; Menchaca-Rocha, A.; Meninno, E.; Mercado Pérez, J.; Meres, M.; Mhlanga, S.; Miake, Y.; Mieskolainen, M. M.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Mischke, A.; Mishra, A. N.; Mishra, T.; Miskowiec, D.; Mitra, J.; Mitu, C. M.; Mohammadi, N.; Mohanty, B.; Molnar, L.; Montaño Zetina, L.; Montes, E.; Moreira De Godoy, D. A.; Moreno, L. A. P.; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Mühlheim, D.; Muhuri, S.; Mukherjee, M.; Mulligan, J. D.; Munhoz, M. G.; Münning, K.; Munzer, R. H.; Murakami, H.; Murray, S.; Musa, L.; Musinsky, J.; Naik, B.; Nair, R.; Nandi, B. K.; Nania, R.; Nappi, E.; Naru, M. U.; Natal da Luz, H.; Nattrass, C.; Navarro, S. R.; Nayak, K.; Nayak, R.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; Negrao De Oliveira, R. A.; Nellen, L.; Ng, F.; Nicassio, M.; Niculescu, M.; Niedziela, J.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Noferini, F.; Nomokonov, P.; Nooren, G.; Noris, J. C. C.; Norman, J.; Nyanin, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Oh, S. K.; Ohlson, A.; Okatan, A.; Okubo, T.; Oleniacz, J.; Oliveira Da Silva, A. C.; Oliver, M. H.; Onderwaater, J.; Oppedisano, C.; Orava, R.; Oravec, M.; Ortiz Velasquez, A.; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Ozdemir, M.; Pachmayer, Y.; Pagano, D.; Pagano, P.; Paić, G.; Pal, S. K.; Palni, P.; Pan, J.; Pandey, A. K.; Papikyan, V.; Pappalardo, G. S.; Pareek, P.; Park, W. J.; Parmar, S.; Passfeld, A.; Paticchio, V.; Patra, R. N.; Paul, B.; Pei, H.; Peitzmann, T.; Peng, X.; Pereira Da Costa, H.; Peresunko, D.; Perez Lezama, E.; Peskov, V.; Pestov, Y.; Petráček, V.; Petrov, V.; Petrovici, M.; Petta, C.; Piano, S.; Pikna, M.; Pillot, P.; Pimentel, L. O. D. L.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Ploskon, M.; Planinic, M.; Pluta, J.; Pochybova, S.; Podesta-Lerma, P. L. M.; Poghosyan, M. G.; Polichtchouk, B.; Poljak, N.; Poonsawat, W.; Pop, A.; Poppenborg, H.; Porteboeuf-Houssais, S.; Porter, J.; Pospisil, J.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puccio, M.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rajput, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Rami, F.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Ravasenga, I.; Read, K. F.; Redlich, K.; Reed, R. J.; Rehman, A.; Reichelt, P.; Reidt, F.; Ren, X.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Ristea, C.; Rodríguez Cahuantzi, M.; Rodriguez Manso, A.; Røed, K.; Rogochaya, E.; Rohr, D.; Röhrich, D.; Ronchetti, F.; Ronflette, L.; Rosnet, P.; Rossi, A.; Roukoutakis, F.; Roy, A.; Roy, C.; Roy, P.; Rubio Montero, A. J.; Rui, R.; Russo, R.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Saarinen, S.; Sadhu, S.; Sadovsky, S.; Šafařík, K.; Sahlmuller, B.; Sahoo, P.; Sahoo, R.; Sahoo, S.; Sahu, P. K.; Saini, J.; Sakai, S.; Saleh, M. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Šándor, L.; Sandoval, A.; Sano, M.; Sarkar, D.; Sarkar, N.; Sarma, P.; Scapparone, E.; Scarlassara, F.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schmidt, M.; Schuchmann, S.; Schukraft, J.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, R.; Šefčík, M.; Seger, J. E.; Sekiguchi, Y.; Sekihata, D.; Selyuzhenkov, I.; Senosi, K.; Senyukov, S.; Serradilla, E.; Sevcenco, A.; Shabanov, A.; Shabetai, A.; Shadura, O.; Shahoyan, R.; Shangaraev, A.; Sharma, A.; Sharma, M.; Sharma, M.; Sharma, N.; Sheikh, A. I.; Shigaki, K.; Shou, Q.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Sielewicz, K. M.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Simonetti, G.; Singaraju, R.; Singh, R.; Singhal, V.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Slupecki, M.; Smirnov, N.; Snellings, R. J. M.; Snellman, T. W.; Song, J.; Song, M.; Song, Z.; Soramel, F.; Sorensen, S.; Sozzi, F.; Spiriti, E.; Sputowska, I.; Spyropoulou-Stassinaki, M.; Stachel, J.; Stan, I.; Stankus, P.; Stenlund, E.; Steyn, G.; Stiller, J. H.; Stocco, D.; Strmen, P.; Suaide, A. A. P.; Sugitate, T.; Suire, C.; Suleymanov, M.; Suljic, M.; Sultanov, R.; Šumbera, M.; Sumowidagdo, S.; Swain, S.; Szabo, A.; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Tabassam, U.; Takahashi, J.; Tambave, G. J.; Tanaka, N.; Tarhini, M.; Tariq, M.; Tarzila, M. G.; Tauro, A.; Tejeda Muñoz, G.; Telesca, A.; Terasaki, K.; Terrevoli, C.; Teyssier, B.; Thäder, J.; Thakur, D.; Thomas, D.; Tieulent, R.; Tikhonov, A.; Timmins, A. R.; Toia, A.; Trogolo, S.; Trombetta, G.; Trubnikov, V.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ullaland, K.; Uras, A.; Usai, G. L.; Utrobicic, A.; Vala, M.; Valencia Palomo, L.; Van Der Maarel, J.; Van Hoorne, J. W.; van Leeuwen, M.; Vanat, T.; Vande Vyvre, P.; Varga, D.; Vargas, A.; Vargyas, M.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vauthier, A.; Vázquez Doce, O.; Vechernin, V.; Veen, A. M.; Velure, A.; Vercellin, E.; Vergara Limón, S.; Vernet, R.; Vickovic, L.; Viinikainen, J.; Vilakazi, Z.; Villalobos Baillie, O.; Villatoro Tello, A.; Vinogradov, A.; Vinogradov, L.; Virgili, T.; Vislavicius, V.; Viyogi, Y. P.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; von Haller, B.; Vorobyev, I.; Vranic, D.; Vrláková, J.; Vulpescu, B.; Wagner, B.; Wagner, J.; Wang, H.; Wang, M.; Watanabe, D.; Watanabe, Y.; Weber, M.; Weber, S. G.; Weiser, D. F.; Wessels, J. P.; Westerhoff, U.; Whitehead, A. M.; Wiechula, J.; Wikne, J.; Wilk, G.; Wilkinson, J.; Willems, G. A.; Williams, M. C. S.; Windelband, B.; Winn, M.; Yalcin, S.; Yang, P.; Yano, S.; Yin, Z.; Yokoyama, H.; Yoo, I.-K.; Yoon, J. H.; Yurchenko, V.; Zaborowska, A.; Zaccolo, V.; Zaman, A.; Zampolli, C.; Zanoli, H. J. C.; Zaporozhets, S.; Zardoshti, N.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zgura, I. S.; Zhalov, M.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhang, C.; Zhang, Z.; Zhao, C.; Zhigareva, N.; Zhou, D.; Zhou, Y.; Zhou, Z.; Zhu, H.; Zhu, J.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zinovjev, G.; Zyzak, M.
2016-09-01
The elliptic, triangular, quadrangular and pentagonal anisotropic flow coefficients for π±, K± and p+overline{p} in Pb-Pb collisions at √{s_{NN}}=2.76 TeV were measured with the ALICE detector at the Large Hadron Collider. The results were obtained with the Scalar Product method, correlating the identified hadrons with reference particles from a different pseudorapidity region. Effects not related to the common event symmetry planes (non-flow) were estimated using correlations in pp collisions and were subtracted from the measurement. The obtained flow coefficients exhibit a clear mass ordering for transverse momentum ( p T) values below ≈ 3 GeV/ c. In the intermediate p T region (3 fairly well by a hydrodynamical model (iEBE-VISHNU) that uses initial conditions generated by A Multi-Phase Transport model (AMPT) and describes the expansion of the fireball using a value of 0.08 for the ratio of shear viscosity to entropy density ( η/s), coupled to a hadronic cascade model (UrQMD). Finally, expectations from AMPT alone fail to quantitatively describe the measurements for all harmonics throughout the measured transverse momentum region. However, the comparison to the AMPT model highlights the importance of the late hadronic rescattering stage to the development of the observed mass ordering at low values of p T and of coalescence as a particle production mechanism for the particle type grouping at intermediate values of p T for all harmonics. [Figure not available: see fulltext.
Discrete Boltzmann Method with Maxwell-Type Boundary Condition for Slip Flow
Zhang, Yu-Dong; Xu, Ai-Guo; Zhang, Guang-Cai; Chen, Zhi-Hua
2018-01-01
The rarefied effect of gas flow in microchannel is significant and cannot be well described by traditional hydrodynamic models. It has been known that discrete Boltzmann model (DBM) has the potential to investigate flows in a relatively wider range of Knudsen number because of its intrinsic kinetic nature inherited from Boltzmann equation. It is crucial to have a proper kinetic boundary condition for DBM to capture the velocity slip and the flow characteristics in the Knudsen layer. In this paper, we present a DBM combined with Maxwell-type boundary condition model for slip flow. The tangential momentum accommodation coefficient is introduced to implement a gas-surface interaction model. Both the velocity slip and the Knudsen layer under various Knudsen numbers and accommodation coefficients can be well described. Two kinds of slip flows, including Couette flow and Poiseuille flow, are simulated to verify the model. To dynamically compare results from different models, the relation between the definition of Knudsen number in hard sphere model and that in BGK model is clarified. Support of National Natural Science Foundation of China under Grant Nos. 11475028, 11772064, and 11502117 Science Challenge Project under Grant Nos. JCKY2016212A501 and TZ2016002
International Nuclear Information System (INIS)
Sankar, D. S.; Lee, U Sik
2016-01-01
This theoretical study investigates three types of basic flows of viscous incompressible Herschel-Bulkley fluid such as (i) plane Couette flow, (ii) Poiseuille flow and (iii) generalized Couette flow with slip velocity at the boundary. The analytic solutions to the nonlinear boundary value problems have been obtained. The effects of various physical parameters on the velocity, flow rate, wall shear stress and frictional resistance to flow are analyzed through appropriate graphs. It is observed that in plane Poiseuille flow and generalized Couette flow, the velocity and flow rate of the fluid increase considerably with the increase of the slip parameter, power law index, pressure gradient. The fluid velocity is significantly higher in plane Poiseuille flow than in plane Couette flow. The wall shear stress and frictional resistance to flow decrease considerably with the increase of the power law index and increase significantly with the increase of the yield stress of the fluid. The wall shear stress and frictional resistance to flow are considerably higher in plane Poiseuille flow than in generalized Couette flow.
Pillai, Indu M Sasidharan; Gupta, Ashok K
2017-05-15
A continuous flow electrochemical reactor was developed, and its application was tested for the treatment of textile wastewater. A parallel plate configuration with serpentine flow was chosen for the continuous flow reactor. Uniparameter optimization was carried out for electrochemical oxidation of synthetic and real textile wastewater (collected from the inlet of the effluent treatment plant). Chemical Oxygen Demand (COD) removal efficiency of 90% was achieved for synthetic textile wastewater (initial COD - 780 mg L -1 ) at a flow rate of 500 mL h -1 (retention time of 6 h) and a current density of 1.15 mA cm -2 and the energy consumption for the degradation was 9.2 kWh (kg COD) -1 . The complete degradation of real textile wastewater (initial COD of 368 mg L -1 ) was obtained at a current density of 1.15 mA cm -2 , NaCl concentration of 1 g L -1 and retention time of 6 h. Energy consumption and mass transfer coefficient of the reactions were calculated. The continuous flow reactor performed better than batch reactor with reference to energy consumption and economy. The overall treatment cost for complete COD removal of real textile wastewater was 5.83 USD m -3 . Copyright © 2017 Elsevier Ltd. All rights reserved.
Powell, W. B.
1973-01-01
A methodology is described for the analysis of a transient temperature measurement made in a flat or curved plate subjected to convective heat transfer, such that the surface heat flux, the hot-gas temperture, and the gas heat transfer coefficient can be determined. It is shown that if the transient temperature measurement is made at a particular point located nearly midway in the thickness of the plate there is an important simplification in the data analysis process, in that the factor relating the surface heat flux to the measured rate of rise of temperature becomes invariant for a Fourier Number above 0.60 and for all values of the Biot Number. Parameters are derived, tabulated, and plotted which enable straightforward determination of the surface heat flux, the hot-gas temperature, of the plate, the rate of rise of temperature, the plate thickness and curvature, and the mean thermal properties of the plate material at the test temperature.
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X. Y. Ji
2010-12-01
Full Text Available The gas-liquid two-phase mass transfer process in microchannels is complicated due to the special dynamical characteristics. In this work, a novel method was explored to measure the liquid side volumetric mass transfer coefficient kLa. Pressure transducers were utilized to measure the pressure variation of upward gas-liquid two-phase flow in three vertical rectangular microchannels and the liquid side volumetric mass transfer coefficient kLa was calculated through the Pressure-Volume-Temperature correlation of the gas phase. Carbon dioxide-water, carbon dioxide-ethanol and carbon dioxide-n-propanol were used as working fluids, respectively. The dimensions of the microchannels were 40 µm×240 µm (depth×width, 100 µm×800 µm and 100 µm×2000 µm, respectively. Results showed that the channel diameter and the capillary number influence kLa remarkably and that the maximum value of kLa occurs in the annular flow regime. A new correlation of kLa was proposed based on the Sherwood number, Schmidt number and the capillary number. The predicted values of kLa agreed well with the experimental data.
Tuo, Shengquan
2017-01-01
The mixed higher-order flow harmonics and nonlinear response coefficients of charged particles are presented as a function of $p_{\\rm{T}}$ and centrality in PbPb collisions at $\\sqrt{s_{NN}}$ = 2.76 TeV and 5.02 TeV with the CMS detector. The results are obtained using the scalar product method, and cover a $p_{\\rm{T}}$ range from 0.3 GeV/c to 8.0 GeV/c, pseudorapidity $\\vert\\eta\\vert <$ 2.4, and a centrality range of 0-60$\\%$. The mixed harmonic results at 5.02 TeV are compared to the matching higher-order flow harmonics from two-particle correlations, which measure $v_n$ values with respect to the $n$-th order event plane. It is observed that the nonlinear response coefficients of the odd harmonics are larger than the even harmonics ones. The results are compared with hydrodynamic predictions using different shear viscosity to entropy density ratios and different initial conditions.
International Nuclear Information System (INIS)
Amanifard, N.; Nariman-Zadeh, N.; Borji, M.; Khalkhali, A.; Habibdoust, A.
2008-01-01
Three-dimensional heat transfer characteristics and pressure drop of water flow in a set of rectangular microchannels are numerically investigated using Fluent and compared with those of experimental results. Two metamodels based on the evolved group method of data handling (GMDH) type neural networks are then obtained for modelling of both pressure drop (ΔP) and Nusselt number (Nu) with respect to design variables such as geometrical parameters of microchannels, the amount of heat flux and the Reynolds number. Using such obtained polynomial neural networks, multi-objective genetic algorithms (GAs) (non-dominated sorting genetic algorithm, NSGA-II) with a new diversity preserving mechanism is then used for Pareto based optimization of microchannels considering two conflicting objectives such as (ΔP) and (Nu). It is shown that some interesting and important relationships as useful optimal design principles involved in the performance of microchannels can be discovered by Pareto based multi-objective optimization of the obtained polynomial metamodels representing their heat transfer and flow characteristics. Such important optimal principles would not have been obtained without the use of both GMDH type neural network modelling and the Pareto optimization approach
Fluid Flow in a Porous Tree-Shaped Network
Miguel, A. F.
2014-01-01
Tree-shaped flow networks connect one point to an inﬁnity of points and are everywhere in Nature. These networks often own minimal flow resistance and vessel sizes obey to scaling power-laws. In this paper presents a model for fluid flow through a tree-shaped network with porous tubes. Hagen–Poiseuille flow is assumed for tubes and Darcy flow for the porous wall.
International Nuclear Information System (INIS)
Nariai, Hideki; Kobayashi, Michiyuki; Matsuoka, Takeshi.
1982-01-01
Two-phase friction pressure drop and heat transfer coefficients in a once-through steam generator with helically coiled tubes were investigated with the model test rig of an integrated type marine water reactor. As the dimensions of the heat transfer tubes and the thermal-fluid conditions are almost the same as those of real reactors, the data applicable directly to the real reactor design were obtained. As to the friction pressure drop, modified Kozeki's prediction which is based on the experimental data by Kozeki for coiled tubes, agreed the best with the experimental data. Modified Martinelli-Nelson's prediction which is based on Martinelli-Nelson's multiplier using Ito's equation for single-phase flow in coiled tube, agreed within 30%. The effect of coiled tube on the average heat transfer coefficients at boiling region were small, and the predictions for straight tube could also be applied to coiled tube. Schrock-Grossman's correlation agreed well with the experimental data at the pressures of lower than 3.5 MPa. It was suggested that dryout should be occurred at the quality of greater than 90% within the conditions of this report. (author)
Sams, E. W.
1952-01-01
An investigation of forced-convection heat transfer and associated pressure drops was conducted with air flowing through electrically heated Inconel tubes having various degrees of square-thread-type roughness, an inside diameter of 1/2 inch, and a length of 24 inches. were obtained for tubes having conventional roughness ratios (height of thread/radius of tube) of 0 (smooth tube), 0.016, 0.025, and 0.037 over ranges of bulk Reynolds numbers up to 350,000, average inside-tube-wall temperatures up to 1950deg R, and heat-flux densities up to 115,000 Btu per hour per square foot. Data The experimental data showed that both heat transfer and friction increased with increase in surface roughness, becoming more pronounced with increase in Reynolds number; for a given roughness, both heat transfer and friction were also influenced by the tube wall-to-bulk temperature ratio. Good correlation of the heat-transfer data for all the tubes investigated was obtained by use of a modification of the conventional Nusselt correlation parameters wherein the mass velocity in the Reynolds number was replaced by the product of air density evaluated at the average film temperature and the so-called friction velocity; in addition, the physical properties of air were evaluated at the average film temperature. The isothermal friction data for the rough tubes, when plotted in the conventional manner, resulted in curves similar to those obtained by other investigators; that is, the curve for a given roughness breaks away from the Blasius line (representing turbulent flow in smooth tubes) at some value of Reynolds number, which decreases with increase in surface roughness, and then becomes a horizontal line (friction coefficient independent of Reynolds number). A comparison of the friction data for the rough tubes used herein indicated that the conventional roughness ratio is not an adequate measure of relative roughness for tubes having a square-thread-type element. The present data, as well
Nanoscale Fluid Flows in the Vicinity of Patterned Surfaces
Cieplak, Marek; Koplik, Joel; Banavar, Jayanth R.
2006-03-01
Molecular dynamics simulations of dense and rarefied fluids comprising small chain molecules in chemically patterned nanochannels predict a novel switching from Poiseuille to plug flow along the channel. We also demonstrate behavior akin to the lotus effect for a nanodrop on a chemically patterned substrate. Our results show that one can control and exploit the behavior of fluids at the nanoscale using chemical patterning.
Flow Coefficients of Monosleeve Valves
1941-01-01
no air could go through the encl ports. When the end port was being tested, the solder was remo ~ed from one encl of the manifolcl and the center port...H., ” and Stoner, H. M.: Precision Timing of Sporting Events. Elec. Eng., vol. 52, no. 6, June 1933, pp. 386-391. Anon.: Fluid Meters. Their Theory
Estimation of mass transfer parameters in a Taylor-Couette-Poiseuille heterogeneous reactor
Directory of Open Access Journals (Sweden)
Resende M. M.
2004-01-01
Full Text Available A bench-scale, continuous vortex flow reactor (VFR, with a radius ratio, h, equal to 0.48 and an aspect ratio, G, equal to 11.19 was studied. This reactor may be used in the enzymatic hydrolysis of polypeptides obtained from sweet cheese whey with enzymes immobilized on agarose gel. Operational conditions were 2410 < Re q < 11793 and 30-min residence time for glycerol-water, 14% w/w, 27ºC (Re ax = 1.1 and for water, 38ºC (Re ax = 1.5. Residence time distributions (RTDs were obtained after pulse injections of different tracers (including dyed solid particles. Mass transfer coefficients of a lumped-parameter model of the reactor were estimated from these data. Model fitting to experimental data was accurate. Working conditions were selected so that transport properties of the fluids would be similar to the ones in the actual process at the final stages of whey hydrolysis.
DNS Study of the Turbulent Taylor-Vortex Flow on a Ribbed Inner Cylinder
Directory of Open Access Journals (Sweden)
Takahiro Tsukahara
2013-01-01
Full Text Available Turbulent Taylor-vortex flows over regularly spaced square ribs mounted on a rotating inner cylinder surface were investigated using direct numerical simulations (DNSs for a Reynolds number of 3200 (based on the inner-wall velocity and the gap width between two cylinders in an apparatus with an inner-to-outer radius ratio of 0.617, while varying the streamwise interval of the ribs. We examined the flow and pressure fields around each rib, focusing on the recirculation zone, the frictional drag coefficient, and the pressure (form drag. Our results for the Taylor-Couette flows were compared to DNS for plane Poiseuille flows over ribbed surfaces performed by Leonardi et al. (2003. We determined the qualitative consistency between them with respect to the roughness effect, which depends significantly on the rib interval, but the rate of increase in the flow resistance was remarkably dampened by roughness in the present flows. Taylor vortices remaining over roughened cylinder surfaces were found to induce quick pressure recovery behind each rib, leading to less pressure drag and an enhanced backflow in the recirculation zone.
Sabine absorption coefficients to random incidence absorption coefficients
DEFF Research Database (Denmark)
Jeong, Cheol-Ho
2014-01-01
into random incidence absorption coefficients for porous absorbers are investigated. Two optimization-based conversion methods are suggested: the surface impedance estimation for locally reacting absorbers and the flow resistivity estimation for extendedly reacting absorbers. The suggested conversion methods...
Simulations of Bingham plastic flows with the multiple-relaxation-time lattice Boltzmann model
Chen, SongGui; Sun, QiCheng; Jin, Feng; Liu, JianGuo
2014-03-01
Fresh cement mortar is a type of workable paste, which can be well approximated as a Bingham plastic and whose flow behavior is of major concern in engineering. In this paper, Papanastasiou's model for Bingham fluids is solved by using the multiplerelaxation-time lattice Boltzmann model (MRT-LB). Analysis of the stress growth exponent m in Bingham fluid flow simulations shows that Papanastasiou's model provides a good approximation of realistic Bingham plastics for values of m > 108. For lower values of m, Papanastasiou's model is valid for fluids between Bingham and Newtonian fluids. The MRT-LB model is validated by two benchmark problems: 2D steady Poiseuille flows and lid-driven cavity flows. Comparing the numerical results of the velocity distributions with corresponding analytical solutions shows that the MRT-LB model is appropriate for studying Bingham fluids while also providing better numerical stability. We further apply the MRT-LB model to simulate flow through a sudden expansion channel and the flow surrounding a round particle. Besides the rich flow structures obtained in this work, the dynamics fluid force on the round particle is calculated. Results show that both the Reynolds number Re and the Bingham number Bn affect the drag coefficients C D , and a drag coefficient with Re and Bn being taken into account is proposed. The relationship of Bn and the ratio of unyielded zone thickness to particle diameter is also analyzed. Finally, the Bingham fluid flowing around a set of randomly dispersed particles is simulated to obtain the apparent viscosity and velocity fields. These results help simulation of fresh concrete flowing in porous media.
Steady laminar flow of fractal fluids
Energy Technology Data Exchange (ETDEWEB)
Balankin, Alexander S., E-mail: abalankin@ipn.mx [Grupo Mecánica Fractal, ESIME, Instituto Politécnico Nacional, México D.F., 07738 (Mexico); Mena, Baltasar [Laboratorio de Ingeniería y Procesos Costeros, Instituto de Ingeniería, Universidad Nacional Autónoma de México, Sisal, Yucatán, 97355 (Mexico); Susarrey, Orlando; Samayoa, Didier [Grupo Mecánica Fractal, ESIME, Instituto Politécnico Nacional, México D.F., 07738 (Mexico)
2017-02-12
We study laminar flow of a fractal fluid in a cylindrical tube. A flow of the fractal fluid is mapped into a homogeneous flow in a fractional dimensional space with metric induced by the fractal topology. The equations of motion for an incompressible Stokes flow of the Newtonian fractal fluid are derived. It is found that the radial distribution for the velocity in a steady Poiseuille flow of a fractal fluid is governed by the fractal metric of the flow, whereas the pressure distribution along the flow direction depends on the fractal topology of flow, as well as on the fractal metric. The radial distribution of the fractal fluid velocity in a steady Couette flow between two concentric cylinders is also derived. - Highlights: • Equations of Stokes flow of Newtonian fractal fluid are derived. • Pressure distribution in the Newtonian fractal fluid is derived. • Velocity distribution in Poiseuille flow of fractal fluid is found. • Velocity distribution in a steady Couette flow is established.
Adam, J.; Adamová, D.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmad, S.; Ahn, S. U.; Aiola, S.; Akindinov, A.; Alam, S. N.; Albuquerque, D. S. D.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alfaro Molina, R.; Alici, A.; Alkin, A.; Alme, J.; Alt, T.; Altinpinar, S.; Altsybeev, I.; Alves Garcia Prado, C.; An, M.; Andrei, C.; Andrews, H. A.; Andronic, A.; Anguelov, V.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arcelli, S.; Arnaldi, R.; Arnold, O. W.; Arsene, I. C.; Arslandok, M.; Audurier, B.; Augustinus, A.; Averbeck, R.; Azmi, M. D.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Balasubramanian, S.; Baldisseri, A.; Baral, R. C.; Barbano, A. M.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartalini, P.; Barth, K.; Bartke, J.; Bartsch, E.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batista Camejo, A.; Batyunya, B.; Batzing, P. C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bello Martinez, H.; Bellwied, R.; Belmont, R.; Belmont-moreno, E.; Beltran, L. G. E.; Belyaev, V.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhat, I. R.; Bhati, A. K.; Bhattacharjee, B.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Biro, G.; Biswas, R.; Biswas, S.; Bjelogrlic, S.; Blair, J. T.; Blau, D.; Blume, C.; Bock, F.; Bogdanov, A.; Bøggild, H.; Boldizsár, L.; Bombara, M.; Bonora, M.; Book, J.; Borel, H.; Borissov, A.; Borri, M.; Bossú, F.; Botta, E.; Bourjau, C.; Braun-munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Brucken, E. J.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Butt, J. B.; Buxton, J. T.; Cabala, J.; Caffarri, D.; Cai, X.; Caines, H.; Calero Diaz, L.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Carena, F.; Carena, W.; Carnesecchi, F.; Castillo Castellanos, J.; Castro, A. J.; Casula, E. A. R.; Ceballos Sanchez, C.; Cepila, J.; Cerello, P.; Cerkala, J.; Chang, B.; Chapeland, S.; Chartier, M.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Chauvin, A.; Chelnokov, V.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Cho, S.; Chochula, P.; Choi, K.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Colocci, M.; Conesa Balbastre, G.; Conesa Del Valle, Z.; Connors, M. E.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortés Maldonado, I.; Cortese, P.; Cosentino, M. R.; Costa, F.; Crkovska, J.; Crochet, P.; Cruz Albino, R.; Cuautle, E.; Cunqueiro, L.; Dahms, T.; Dainese, A.; Danisch, M. C.; Danu, A.; Das, D.; Das, I.; Das, S.; Dash, A.; Dash, S.; De, S.; De Caro, A.; De Cataldo, G.; De Conti, C.; De Cuveland, J.; De Falco, A.; De Gruttola, D.; De Marco, N.; De Pasquale, S.; De Souza, R. D.; Deisting, A.; Deloff, A.; Dénes, E.; Deplano, C.; Dhankher, P.; Di Bari, D.; Di Mauro, A.; Di Nezza, P.; Di Ruzza, B.; Diaz Corchero, M. A.; Dietel, T.; Dillenseger, P.; Divià, R.; Djuvsland, Ø.; Dobrin, A.; Domenicis Gimenez, D.; Dönigus, B.; Dordic, O.; Drozhzhova, T.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Ehlers, R. J.; Elia, D.; Endress, E.; Engel, H.; Epple, E.; Erazmus, B.; Erdemir, I.; Erhardt, F.; Espagnon, B.; Estienne, M.; Esumi, S.; Eulisse, G.; Eum, J.; Evans, D.; Evdokimov, S.; Eyyubova, G.; Fabbietti, L.; Fabris, D.; Faivre, J.; Fantoni, A.; Fasel, M.; Feldkamp, L.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Fernández Téllez, A.; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Feuillard, V. J. G.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Francisco, A.; Frankenfeld, U.; Fronze, G. G.; Fuchs, U.; Furget, C.; Furs, A.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A. M.; Gajdosova, K.; Gallio, M.; Galvan, C. D.; Gangadharan, D. R.; Ganoti, P.; Gao, C.; Garabatos, C.; Garcia-solis, E.; Garg, K.; Gargiulo, C.; Gasik, P.; Gauger, E. F.; Germain, M.; Gheata, M.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Giubilato, P.; Gladysz-dziadus, E.; Glässel, P.; Goméz Coral, D. M.; Gomez Ramirez, A.; Gonzalez, A. S.; Gonzalez, V.; González-zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Grabski, V.; Grachov, O. A.; Graczykowski, L. K.; Graham, K. L.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Gronefeld, J. M.; Grosse-oetringhaus, J. F.; Grosso, R.; Gruber, L.; Guber, F.; Guernane, R.; Guerzoni, B.; Gulbrandsen, K.; Gunji, T.; Gupta, A.; Gupta, R.; Guzman, I. B.; Haake, R.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Hamon, J. C.; Harris, J. W.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Heckel, S. T.; Hellbär, E.; Helstrup, H.; Herghelegiu, A.; Herrera Corral, G.; Herrmann, F.; Hess, B. A.; Hetland, K. F.; Hillemanns, H.; Hippolyte, B.; Horak, D.; Hosokawa, R.; Hristov, P.; Hughes, C.; Humanic, T. J.; Hussain, N.; Hussain, T.; Hutter, D.; Hwang, D. S.; Ilkaev, R.; Inaba, M.; Incani, E.; Ippolitov, M.; Irfan, M.; Isakov, V.; Ivanov, M.; Ivanov, V.; Izucheev, V.; Jacak, B.; Jacazio, N.; Jacobs, P. M.; Jadhav, M. B.; Jadlovska, S.; Jadlovsky, J.; Jahnke, C.; Jakubowska, M. J.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, C.; Jena, S.; Jimenez Bustamante, R. T.; Jones, P. G.; Jusko, A.; Kalinak, P.; Kalweit, A.; Kang, J. H.; Kaplin, V.; Kar, S.; Karasu Uysal, A.; Karavichev, O.; Karavicheva, T.; Karayan, L.; Karpechev, E.; Kebschull, U.; Keidel, R.; Keijdener, D. L. D.; Keil, M.; Mohisin Khan, M.; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Khatun, A.; Kileng, B.; Kim, D. W.; Kim, D. J.; Kim, D.; Kim, H.; Kim, J. S.; Kim, J.; Kim, M.; Kim, S.; Kim, T.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Kiss, G.; Klay, J. L.; Klein, C.; Klein, J.; Klein-bösing, C.; Klewin, S.; Kluge, A.; Knichel, M. L.; Knospe, A. G.; Kobdaj, C.; Kofarago, M.; Kollegger, T.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Kondratyuk, E.; Konevskikh, A.; Kopcik, M.; Kour, M.; Kouzinopoulos, C.; Kovalenko, O.; Kovalenko, V.; Kowalski, M.; Koyithatta Meethaleveedu, G.; Králik, I.; Kravčáková, A.; Krivda, M.; Krizek, F.; Kryshen, E.; Krzewicki, M.; Kubera, A. M.; Kučera, V.; Kuhn, C.; Kuijer, P. G.; Kumar, A.; Kumar, J.; Kumar, L.; Kumar, S.; Kurashvili, P.; Kurepin, A.; Kurepin, A. B.; Kuryakin, A.; Kweon, M. J.; Kwon, Y.; La Pointe, S. L.; La Rocca, P.; Ladron De Guevara, P.; Lagana Fernandes, C.; Lakomov, I.; Langoy, R.; Lapidus, K.; Lara, C.; Lardeux, A.; Lattuca, A.; Laudi, E.; Lea, R.; Leardini, L.; Lee, S.; Lehas, F.; Lehner, S.; Lemmon, R. C.; Lenti, V.; Leogrande, E.; León Monzón, I.; León Vargas, H.; Leoncino, M.; Lévai, P.; Li, S.; Li, X.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Ljunggren, H. M.; Lodato, D. F.; Loenne, P. I.; Loginov, V.; Loizides, C.; Lopez, X.; López Torres, E.; Lowe, A.; Luettig, P.; Lunardon, M.; Luparello, G.; Lupi, M.; Lutz, T. H.; Maevskaya, A.; Mager, M.; Mahajan, S.; Mahmood, S. M.; Maire, A.; Majka, R. D.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal’kevich, D.; Malzacher, P.; Mamonov, A.; Manko, V.; Manso, F.; Manzari, V.; Mao, Y.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Margutti, J.; Marín, A.; Markert, C.; Marquard, M.; Martin, N. A.; Martinengo, P.; Martínez, M. I.; Martínez García, G.; Martinez Pedreira, M.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Mastroserio, A.; Matyja, A.; Mayer, C.; Mazer, J.; Mazzilli, M.; Mazzoni, M. A.; Meddi, F.; Melikyan, Y.; Menchaca-rocha, A.; Meninno, E.; Mercado Pérez, J.; Meres, M.; Mhlanga, S.; Miake, Y.; Mieskolainen, M. M.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Mischke, A.; Mishra, A. N.; Mishra, T.; Miskowiec, D.; Mitra, J.; Mitu, C. M.; Mohammadi, N.; Mohanty, B.; Molnar, L.; Montaño Zetina, L.; Montes, E.; Moreira De Godoy, D. A.; Moreno, L. A. P.; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Mühlheim, D.; Muhuri, S.; Mukherjee, M.; Mulligan, J. D.; Munhoz, M. G.; Münning, K.; Munzer, R. H.; Murakami, H.; Murray, S.; Musa, L.; Musinsky, J.; Naik, B.; Nair, R.; Nandi, B. K.; Nania, R.; Nappi, E.; Naru, M. U.; Natal Da Luz, H.; Nattrass, C.; Navarro, S. R.; Nayak, K.; Nayak, R.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; Negrao De Oliveira, R. A.; Nellen, L.; Ng, F.; Nicassio, M.; Niculescu, M.; Niedziela, J.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Noferini, F.; Nomokonov, P.; Nooren, G.; Noris, J. C. C.; Norman, J.; Nyanin, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Oh, S. K.; Ohlson, A.; Okatan, A.; Okubo, T.; Oleniacz, J.; Oliveira Da Silva, A. C.; Oliver, M. H.; Onderwaater, J.; Oppedisano, C.; Orava, R.; Oravec, M.; Ortiz Velasquez, A.; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Ozdemir, M.; Pachmayer, Y.; Pagano, D.; Pagano, P.; Paić, G.; Pal, S. K.; Palni, P.; Pan, J.; Pandey, A. K.; Papikyan, V.; Pappalardo, G. S.; Pareek, P.; Park, W. J.; Parmar, S.; Passfeld, A.; Paticchio, V.; Patra, R. N.; Paul, B.; Pei, H.; Peitzmann, T.; Peng, X.; Pereira Da Costa, H.; Peresunko, D.; Perez Lezama, E.; Peskov, V.; Pestov, Y.; Petráček, V.; Petrov, V.; Petrovici, M.; Petta, C.; Piano, S.; Pikna, M.; Pillot, P.; Pimentel, L. O. D. L.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Ploskon, M.; Planinic, M.; Pluta, J.; Pochybova, S.; Podesta-lerma, P. L. M.; Poghosyan, M. G.; Polichtchouk, B.; Poljak, N.; Poonsawat, W.; Pop, A.; Poppenborg, H.; Porteboeuf-houssais, S.; Porter, J.; Pospisil, J.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puccio, M.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rajput, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Rami, F.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Ravasenga, I.; Read, K. F.; Redlich, K.; Reed, R. J.; Rehman, A.; Reichelt, P.; Reidt, F.; Ren, X.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Ristea, C.; Rodríguez Cahuantzi, M.; Rodriguez Manso, A.; Røed, K.; Rogochaya, E.; Rohr, D.; Röhrich, D.; Ronchetti, F.; Ronflette, L.; Rosnet, P.; Rossi, A.; Roukoutakis, F.; Roy, A.; Roy, C.; Roy, P.; Rubio Montero, A. J.; Rui, R.; Russo, R.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Saarinen, S.; Sadhu, S.; Sadovsky, S.; Šafařík, K.; Sahlmuller, B.; Sahoo, P.; Sahoo, R.; Sahoo, S.; Sahu, P. K.; Saini, J.; Sakai, S.; Saleh, M. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Šándor, L.; Sandoval, A.; Sano, M.; Sarkar, D.; Sarkar, N.; Sarma, P.; Scapparone, E.; Scarlassara, F.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schmidt, M.; Schuchmann, S.; Schukraft, J.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, R.; Šefčík, M.; Seger, J. E.; Sekiguchi, Y.; Sekihata, D.; Selyuzhenkov, I.; Senosi, K.; Senyukov, S.; Serradilla, E.; Sevcenco, A.; Shabanov, A.; Shabetai, A.; Shadura, O.; Shahoyan, R.; Shangaraev, A.; Sharma, A.; Sharma, M.; Sharma, M.; Sharma, N.; Sheikh, A. I.; Shigaki, K.; Shou, Q.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Sielewicz, K. M.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Simonetti, G.; Singaraju, R.; Singh, R.; Singhal, V.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Slupecki, M.; Smirnov, N.; Snellings, R. J. M.; Snellman, T. W.; Song, J.; Song, M.; Song, Z.; Soramel, F.; Sorensen, S.; Sozzi, F.; Spiriti, E.; Sputowska, I.; Spyropoulou-stassinaki, M.; Stachel, J.; Stan, I.; Stankus, P.; Stenlund, E.; Steyn, G.; Stiller, J. H.; Stocco, D.; Strmen, P.; Suaide, A. A. P.; Sugitate, T.; Suire, C.; Suleymanov, M.; Suljic, M.; Sultanov, R.; Šumbera, M.; Sumowidagdo, S.; Swain, S.; Szabo, A.; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Tabassam, U.; Takahashi, J.; Tambave, G. J.; Tanaka, N.; Tarhini, M.; Tariq, M.; Tarzila, M. G.; Tauro, A.; Tejeda Muñoz, G.; Telesca, A.; Terasaki, K.; Terrevoli, C.; Teyssier, B.; Thäder, J.; Thakur, D.; Thomas, D.; Tieulent, R.; Tikhonov, A.; Timmins, A. R.; Toia, A.; Trogolo, S.; Trombetta, G.; Trubnikov, V.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ullaland, K.; Uras, A.; Usai, G. L.; Utrobicic, A.; Vala, M.; Valencia Palomo, L.; Van Der Maarel, J.; Van Hoorne, J. W.; van Leeuwen, Marco; Vanat, T.; Vande Vyvre, P.; Varga, D.; Vargas, A.; Vargyas, M.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vauthier, A.; Vázquez Doce, O.; Vechernin, V.; Veen, A. M.; Velure, A.; Vercellin, E.; Vergara Limón, S.; Vernet, R.; Vickovic, L.; Viinikainen, J.; Vilakazi, Z.; Villalobos Baillie, O.; Villatoro Tello, A.; Vinogradov, A.; Vinogradov, L.; Virgili, T.; Vislavicius, V.; Viyogi, Y. P.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; Von Haller, B.; Vorobyev, I.; Vranic, D.; Vrláková, J.; Vulpescu, B.; Wagner, B.; Wagner, J.; Wang, H.; Wang, M.; Watanabe, D.; Watanabe, Y.; Weber, M.; Weber, S. G.; Weiser, D. F.; Wessels, J. P.; Westerhoff, U.; Whitehead, A. M.; Wiechula, J.; Wikne, J.; Wilk, G.; Wilkinson, J.; Willems, G. A.; Williams, M. C. S.; Windelband, B.; Winn, M.; Yalcin, S.; Yang, P.; Yano, S.; Yin, Z.; Yokoyama, H.; Yoo, I.-k.; Yoon, J. H.; Yurchenko, V.; Zaborowska, A.; Zaccolo, V.; Zaman, A.; Zampolli, C.; Zanoli, H. J. C.; Zaporozhets, S.; Zardoshti, N.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zgura, I. S.; Zhalov, M.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhang, C.; Zhang, Z.; Zhao, C.; Zhigareva, N.; Zhou, D.; Zhou, Y.; Zhou, Z.; Zhu, H.; Zhu, J.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zinovjev, G.; Zyzak, M.
2016-01-01
The elliptic, triangular, quadrangular and pentagonal anisotropic flow coefficients for π±, K± and p+p ¯ ¯ ¯ p+p¯ in Pb-Pb collisions at s NN − − − √ =2.76 sNN=2.76 TeV were measured with the ALICE detector at the Large Hadron Collider. The results were obtained with the Scalar Product method,
On Laminar Flow of Non-Newtonian Fluids in Porous Media
Fayed, Hassan E.
2015-10-20
Flow of generalized Newtonian fluids in porous media can be modeled as a bundle of capillary tubes or a pore-scale network. In general, both approaches rely on the solution of Hagen–Poiseuille equation using power law to estimate the variations in the fluid viscosity due to the applied shear rate. Despite the effectiveness and simplicity, power law tends to provide unrealistic values for the effective viscosity especially in the limits of zero and infinite shear rates. Here, instead of using power law, Carreau model (bubbles, drops, and particles in non-Newtonian fluids. Taylor & Francis Group, New York, 2007) is used to determine the effective viscosity as a function of the shear strain rate. Carreau model can predict accurately the variation in the viscosity at all shear rates and provide more accurate solution for the flow physics in a single pore. Using the results for a single pore, normalized Fanning friction coefficient has been calculated and plotted as a function of the newly defined Reynolds number based on pressure gradient. For laminar flow, the variation in the friction coefficient with Reynolds number has been plotted and scaled. It is observed that generalized Newtonian fluid flows show Newtonian nature up to a certain Reynolds number. At high Reynolds number, deviation from the Newtonian behavior is observed. The main contribution of this paper is to present a closed-form solution for the flow in a single pore using Carreau model, which allows for fast evaluation of the relationship between flux and pressure gradient in an arbitrary pore diameter. In this way, we believe that our development will open the perspectives for using Carreau models in pore-network simulations at low computational costs to obtain more accurate prediction for generalized Newtonian fluid flows in porous media.
International Nuclear Information System (INIS)
Marten, K.; Yonekawa, S.; Hoffmann, H.
1987-05-01
Advanced pressurized water reactors as well as sodium cooled fast reactors, in their breeding and absorber elements, use tightly packed rod bundles with hexagonally arranged rods. Helical wires or helical fins serve as spacers. The pressure loss coefficients of twelve bundles with helical wires were determined systematically in water experiments. High measuring accuracy was achieved by very precise fabrication of the bundles and the shroud as well as by investigations of the proper measuring techniques. The results show a dependency of the loss coefficients on the Reynolds number and on the P/D and H/D ratios of the bundles. These results together with available systematic experimental results of investigations at P/D > 1.1 were used to develop a correlation to determine the pressure loss coefficients of tightly and widely packed hexagonally arranged rod bundles with helical wire spacers. These correlations were used to recalculate and compare results of pressure loss investigations found in the literature; good agreement was demonstrated. Hence, calculation methods exist for a broad range of applications to determine the pressure loss coefficients of hexagonally arranged rod bundles with helical wires for spacers. (orig./HP) [de
Czech Academy of Sciences Publication Activity Database
Heynderickx, P. M.; Španěl, Patrik; Van Langenhove, H.
2014-01-01
Roč. 367, APR 2014 (2014), s. 22-28 ISSN 0378-3812 Institutional support: RVO:61388955 Keywords : SIFT-MS * Octanol-water partition coefficient * bubble column Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.200, year: 2014
Flow induced crystallisation of penetrable particles
Scacchi, Alberto; Brader, Joseph M.
2018-03-01
For a system of Brownian particles interacting via a soft exponential potential we investigate the interaction between equilibrium crystallisation and spatially varying shear flow. For thermodynamic state points within the liquid part of the phase diagram, but close to the crystallisation phase boundary, we observe that imposing a Poiseuille flow can induce nonequilibrium crystalline ordering in regions of low shear gradient. The physical mechanism responsible for this phenomenon is shear-induced particle migration, which causes particles to drift preferentially towards the center of the flow channel, thus increasing the local density in the channel center. The method employed is classical dynamical density functional theory.
Directory of Open Access Journals (Sweden)
Song-Gui Chen
2016-01-01
Full Text Available This paper presents a three-dimensional (3D parallel multiple-relaxation-time lattice Boltzmann model (MRT-LBM for Bingham plastics which overcomes numerical instabilities in the simulation of non-Newtonian fluids for the Bhatnagar–Gross–Krook (BGK model. The MRT-LBM and several related mathematical models are briefly described. Papanastasiou’s modified model is incorporated for better numerical stability. The impact of the relaxation parameters of the model is studied in detail. The MRT-LBM is then validated through a benchmark problem: a 3D steady Poiseuille flow. The results from the numerical simulations are consistent with those derived analytically which indicates that the MRT-LBM effectively simulates Bingham fluids but with better stability. A parallel MRT-LBM framework is introduced, and the parallel efficiency is tested through a simple case. The MRT-LBM is shown to be appropriate for parallel implementation and to have high efficiency. Finally, a Bingham fluid flowing past a square-based prism with a fixed sphere is simulated. It is found the drag coefficient is a function of both Reynolds number (Re and Bingham number (Bn. These results reveal the flow behavior of Bingham plastics.
International Nuclear Information System (INIS)
Satake, Masaaki; Yoneda, Kimitoshi; Fujiwara, Kazutoshi; Domae, Masafumi
2011-01-01
Flow accelerated corrosion (FAC) is one of the serious wall thinning problems when power plants are operating. FAC has been studied in water single-phase flow. The methods of evaluation of wall thinning rate in FAC are constructed from the results of these studies. On the other hand, FAC in water-steam two-phase flow has been hardly studied, so that methods of evaluation of wall thinning rate in it flow have not been constructed. In this report, a few researches about FAC in two-phase flow are investigated. From these researches, firstly FAC in two-phase flow is assumed to occur in annular flow. Secondly, liquid film velocity and liquid film thickness are dealt as the important hydrodynamic factors on FAC in the two phase flow. Besides, partition of pH control agent into water-vapor two phase flow is one of the water-chemical factors in the two phase flow. A water-air two phase annular flow is simulated. From the results, liquid film thicknesses in the simulation are under that of experimental results, and shear stresses are over that of experimental results. (author)
Yadav, Rupesh J.; Kore, Sandeep S.; Joshi, Prathamesh S.
2017-12-01
The experimental and numerical Nusselt number and friction factor investigation for turbulent flow through a non-circular duct with twisted-tape inserts have been presented. The non-circular ducts include square, hexagonal duct. The results of non-circular ducts are compared with circular duct. All the ducts have same equivalent diameter. The twist ratios used for the experiment are Y = 3.5, 4.5, 5.5 and 6.5. Experiments were carried out on square duct, hexagonal duct and circular duct. The Reynolds number lied between 10,000 and 1, 05,000. The present study is restricted to the flow of air at Pr = 0.7 only and within a narrow temperature range of 40 to 75 ΟC, within which the compressible nature of air can be neglected. The results reveal that, both Nusselt number and friction factor increases as the side of non-circular duct increases. Maximum Nusselt number and friction factor is obtained in case of circular duct with twisted tape. Further the correlations of Nu and f are given for different non circular duct with twisted tape insert for engineering applications for the turbulent regime. Since the thermal performance factor (η) is observed to be within the range of 0.8 to 1.13 for both circular and noncircular ducts, the overall benefit of using twisted tape in the flow field shall nevertheless be marginal.
Yadav, Rupesh J.; Kore, Sandeep S.; Joshi, Prathamesh S.
2018-05-01
The experimental and numerical Nusselt number and friction factor investigation for turbulent flow through a non-circular duct with twisted-tape inserts have been presented. The non-circular ducts include square, hexagonal duct. The results of non-circular ducts are compared with circular duct. All the ducts have same equivalent diameter. The twist ratios used for the experiment are Y = 3.5, 4.5, 5.5 and 6.5. Experiments were carried out on square duct, hexagonal duct and circular duct. The Reynolds number lied between 10,000 and 1, 05,000. The present study is restricted to the flow of air at Pr = 0.7 only and within a narrow temperature range of 40 to 75 ΟC, within which the compressible nature of air can be neglected. The results reveal that, both Nusselt number and friction factor increases as the side of non-circular duct increases. Maximum Nusselt number and friction factor is obtained in case of circular duct with twisted tape. Further the correlations of Nu and f are given for different non circular duct with twisted tape insert for engineering applications for the turbulent regime. Since the thermal performance factor (η) is observed to be within the range of 0.8 to 1.13 for both circular and noncircular ducts, the overall benefit of using twisted tape in the flow field shall nevertheless be marginal.
Directory of Open Access Journals (Sweden)
M.Y. Malik
2014-06-01
Full Text Available The present work concerns the pressure dependent viscosity in Carreau fluid through porous medium. Four different combinations of pressure dependent viscosity and pressure dependent porous medium parameters are considered for two types of flow situations namely (i Poiseuille flow and (ii Couette flow. The solutions of non-linear equations have been evaluated numerically by Shooting method along with Runge-Kutta Fehlberg method. The physical features of pertinent parameters have been discussed through graphs.
Energy Technology Data Exchange (ETDEWEB)
Flyckt, V M M; Raaymakers, B W; Lagendijk, J J W [Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht (Netherlands)
2006-10-07
Prediction of the temperature distribution in the eye depends on how the impact of the blood flow is taken into account. Three methods will be compared: a simplified eye anatomy that applies a single heat transfer coefficient to describe all heat transport mechanisms between the sclera and the body core, a detailed eye anatomy in which the blood flow is accounted for either by the bioheat approach, or by including the discrete vasculature in the eye and the orbit. The comparison is done both for rabbit and human anatomies, normo-thermally and when exposed to homogeneous power densities. The first simplified model predicts much higher temperatures than the latter two. It was shown that the eye is very hard to heat when taking physiological perfusion correctly into account. It was concluded that the heat transfer coefficient describing the heat transport from the sclera to the body core reported in the literature for the first simplified model is too low. The bioheat approach is appropriate for a first-order approximation of the temperature distribution in the eye when exposed to a homogeneous power density, but the discrete vasculature down to 0.2 mm in diameter needs to be taken into account when the heterogeneity of the temperature distribution at a mm scale is of interest.
International Nuclear Information System (INIS)
Flyckt, V M M; Raaymakers, B W; Lagendijk, J J W
2006-01-01
Prediction of the temperature distribution in the eye depends on how the impact of the blood flow is taken into account. Three methods will be compared: a simplified eye anatomy that applies a single heat transfer coefficient to describe all heat transport mechanisms between the sclera and the body core, a detailed eye anatomy in which the blood flow is accounted for either by the bioheat approach, or by including the discrete vasculature in the eye and the orbit. The comparison is done both for rabbit and human anatomies, normo-thermally and when exposed to homogeneous power densities. The first simplified model predicts much higher temperatures than the latter two. It was shown that the eye is very hard to heat when taking physiological perfusion correctly into account. It was concluded that the heat transfer coefficient describing the heat transport from the sclera to the body core reported in the literature for the first simplified model is too low. The bioheat approach is appropriate for a first-order approximation of the temperature distribution in the eye when exposed to a homogeneous power density, but the discrete vasculature down to 0.2 mm in diameter needs to be taken into account when the heterogeneity of the temperature distribution at a mm scale is of interest
Flyckt, V. M. M.; Raaymakers, B. W.; Lagendijk, J. J. W.
2006-10-01
Prediction of the temperature distribution in the eye depends on how the impact of the blood flow is taken into account. Three methods will be compared: a simplified eye anatomy that applies a single heat transfer coefficient to describe all heat transport mechanisms between the sclera and the body core, a detailed eye anatomy in which the blood flow is accounted for either by the bioheat approach, or by including the discrete vasculature in the eye and the orbit. The comparison is done both for rabbit and human anatomies, normo-thermally and when exposed to homogeneous power densities. The first simplified model predicts much higher temperatures than the latter two. It was shown that the eye is very hard to heat when taking physiological perfusion correctly into account. It was concluded that the heat transfer coefficient describing the heat transport from the sclera to the body core reported in the literature for the first simplified model is too low. The bioheat approach is appropriate for a first-order approximation of the temperature distribution in the eye when exposed to a homogeneous power density, but the discrete vasculature down to 0.2 mm in diameter needs to be taken into account when the heterogeneity of the temperature distribution at a mm scale is of interest.
Early Regimes of Water Capillary Flow in Slit Silica Nanochannels
DEFF Research Database (Denmark)
Oyarzua, Elton; Walther, Jens Honore; Mejia, Andres
2015-01-01
on the dynamics of capillaryfilling. The results indicate that the nanoscale imbibition process is divided into three main flow regimes:an initial regime where the capillary force is balanced only by the inertial drag and characterized by aconstant velocity and a plug flow profile. In this regime, the meniscus...... velocity profiles identify the passage froman inviscid flow to a developing Poiseuille flow. Gas density profiles ahead of the capillary front indicatea transient accumulation of air on the advancing meniscus. Furthermore, slower capillary filling ratescomputed for higher air pressures reveal a significant...... retarding effect of the gas displaced by the advancing meniscus....
Humble, Leroy V; Lowdermilk, Warren H; Desmon, Leland G
1951-01-01
An investigation of forced-convection heat transfer and associated pressure drops was conducted with air flowing through smooth tubes for an over-all range of surface temperature from 535 degrees to 3050 degrees r, inlet-air temperature from 535 degrees to 1500 degrees r, Reynolds number up to 500,000, exit Mach number up to 1, heat flux up to 150,000 btu per hour per square foot, length-diameter ratio from 30 to 120, and three entrance configurations. Most of the data are for heat addition to the air; a few results are included for cooling of the air. The over-all range of surface-to-air temperature ratio was from 0.46 to 3.5.
Prediction of friction coefficients for gases
Taylor, M. F.
1969-01-01
Empirical relations are used for correlating laminar and turbulent friction coefficients for gases, with large variations in the physical properties, flowing through smooth tubes. These relations have been used to correlate friction coefficients for hydrogen, helium, nitrogen, carbon dioxide and air.
Heat transfer coefficient for boiling carbon dioxide
DEFF Research Database (Denmark)
Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik
1998-01-01
Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The calculated heat transfer coeeficient has been compared with the Chart correlation of Shah. The Chart Correlation predits too low heat transfer coefficient but the ratio...
Estimating Runoff Coefficients Using Weather Radars
DEFF Research Database (Denmark)
Ahm, Malte; Thorndahl, Søren Liedtke; Rasmussen, Michael R.
2012-01-01
This paper presents a method for estimating runoff coefficients of urban drainage catchments based on a combination of high resolution weather radar data and insewer flow measurements. By utilising the spatial variability of the precipitation it is possible to estimate the runoff coefficients...
DEFF Research Database (Denmark)
Knoop, Hans Henrik
2006-01-01
FLOW. Orden i hovedet på den fede måde Oplevelsesmæssigt er flow-tilstanden kendetegnet ved at man er fuldstændig involveret, fokuseret og koncentreret; at man oplever stor indre klarhed ved at vide hvad der skal gøres, og i hvilket omfang det lykkes; at man ved at det er muligt at løse opgaven...
Elliptic flow coefficients from transverse momentum conservation
Bzdak, Adam; Ma, Guo-Liang
2018-01-01
We calculate the k -particle (k =2 ,4 ,6 ,8 ) azimuthal cumulants resulting from the conservation of transverse momentum. We find that c2{k } >0 and, depending on the transverse momenta, c2{k } can reach substantial values even for a relatively large number of particles. The impact of our results on the understanding of the onset of collectivity in small systems is emphasized.
Meng, Xuhui; Guo, Zhaoli
2015-10-01
A lattice Boltzmann model with a multiple-relaxation-time (MRT) collision operator is proposed for incompressible miscible flow with a large viscosity ratio as well as a high Péclet number in this paper. The equilibria in the present model are motivated by the lattice kinetic scheme previously developed by Inamuro et al. [Philos. Trans. R. Soc. London, Ser. A 360, 477 (2002), 10.1098/rsta.2001.0942]. The fluid viscosity and diffusion coefficient depend on both the corresponding relaxation times and additional adjustable parameters in this model. As a result, the corresponding relaxation times can be adjusted in proper ranges to enhance the performance of the model. Numerical validations of the Poiseuille flow and a diffusion-reaction problem demonstrate that the proposed model has second-order accuracy in space. Thereafter, the model is used to simulate flow through a porous medium, and the results show that the proposed model has the advantage to obtain a viscosity-independent permeability, which makes it a robust method for simulating flow in porous media. Finally, a set of simulations are conducted on the viscous miscible displacement between two parallel plates. The results reveal that the present model can be used to simulate, to a high level of accuracy, flows with large viscosity ratios and/or high Péclet numbers. Moreover, the present model is shown to provide superior stability in the limit of high kinematic viscosity. In summary, the numerical results indicate that the present lattice Boltzmann model is an ideal numerical tool for simulating flow with a large viscosity ratio and/or a high Péclet number.
Electrochemical response and separation in cyclic electric field-flow fractionation.
Chen, Zhi; Chauhan, Anuj
2007-03-01
Electric field-flow fractionation (EFFF) is a separation technique that couples a lateral electric field with axial Poiseuille flow to separate particles on the basis of size and/or mobility. In unidirectional EFFF, the field rapidly decreases in time due to charging of the double layer. The field strength could be increased by performing EFFF with cyclic electric fields. In cyclic electric field-flow fractionation (CEFFF), a periodic voltage, which can be either sinusoidal or square-wave, is applied in the lateral direction. In this paper, we measure the electrochemical response of CEFFF, i.e., the current-time response for a given time-dependent voltage and then utilize this electrochemical response in a transport model to predict separation. The CEFFF device studied here comprises two gold-coated glass plates separated by a spacer. The transient current profiles are measured for a step change and cyclic square-shaped voltage. The current profile is compared with the equivalent circuit model, and is fitted to a sum of two decaying exponentials. The dependence of the electrochemical response on voltage, frequency, channel thickness, and salt concentration is studied. Next, the electrochemical data are utilized in the convection-diffusion equation to develop a model for separation by CEFFF. The equations are solved by using a combination of analytical and numerical techniques to determine the mean velocity and the dispersion coefficient of molecules, and to determine the effect of various parameters on the separation efficiency of the EFFF device. Also, the model predictions are compared with experimental data available in the literature.
Transport Coefficients of Fluids
Eu, Byung Chan
2006-01-01
Until recently the formal statistical mechanical approach offered no practicable method for computing the transport coefficients of liquids, and so most practitioners had to resort to empirical fitting formulas. This has now changed, as demonstrated in this innovative monograph. The author presents and applies new methods based on statistical mechanics for calculating the transport coefficients of simple and complex liquids over wide ranges of density and temperature. These molecular theories enable the transport coefficients to be calculated in terms of equilibrium thermodynamic properties, and the results are shown to account satisfactorily for experimental observations, including even the non-Newtonian behavior of fluids far from equilibrium.
Roughness coefficients for stream channels in Arizona
Aldridge, B.N.; Garrett, J.M.
1973-01-01
When water flows in an open channel, energy is lost through friction along the banks and bed of the channel and through turbulence within the channel. The amount of energy lost is governed by channel roughness, which is expressed in terms of a roughness coefficient. An evaluation of the roughness coefficient is necessary in many hydraulic computations that involve flow in an open channel. Owing to the lack of satisfactory quantitative procedure, the ability of evaluate roughness coefficients can be developed only through experience; however, a basic knowledge of the methods used to assign the coefficients and the factors affecting them will be a great help. One of the most commonly used equations in open-channel hydraulics is that of Manning. The Manning equation is 1.486
Directory of Open Access Journals (Sweden)
Zhenrong JING
2017-06-01
Full Text Available Swept wing is widely used in civil aircraft, whose airfoil is chosen, designed and optimized to increase the cruise speed and decrease the drag coefficient. The parameters of swept wing, such as sweep angle and angle of attack, are determined according to the cruise lift coefficient requirement, and the drag coefficient is expected to be predicted accurately, which involves the instability characteristics and transition position of the flow. The pressure coefficient of the RAE2822 wing with given constant lift coefficient is obtained by solving the three-dimensional Navier-Stokes equation numerically, and then the mean flow is calculated by solving the boundary layer (BL equation with spectral method. The cross-flow instability characteristic of boundary layer of swept wing in the windward and leeward is analyzed by linear stability theory (LST, and the transition position is predicted by eN method. The drag coefficient is numerically predicted by introducing a laminar/turbulent indicator. A simple approach to calculate the lift coefficient of swept wing is proposed. It is found that there is a quantitative relationship between the angle of attack and sweep angle when the lift coefficient keeps constant; when the angle of attack is small, the flow on the leeward of the wing is stable. when the angle of attack is larger than 3°, the flow becomes unstable quickly; with the increase of sweep angle or angle of attack the disturbance on the windward becomes more unstable, leading to the moving forward of the transition position to the leading edge of the wing; the drag coefficient has two significant jumping growth due to the successive occurrence of transition in the windward and the leeward; the optimal range of sweep angle for civil aircraft is suggested.
A driving mechanism of a turbulent puff in pipe flow
International Nuclear Information System (INIS)
Shimizu, Masaki; Kida, Shigeo
2009-01-01
A turbulent puff is numerically realized in a circular pipe flow driven by a constant uniform external force. The periodic boundary condition is imposed in the axial direction with a period of 16π pipe radius. The Reynolds number based on the pipe radius, the centerline velocity of the Hagen-Poiseuille flow corresponding to the external force, is 3000. Starting with the Hagen-Poiseuille flow superposed by a disturbance of finite amplitude, an equilibrium puff of about 11π pipe radius in length emerges and advects with nearly the mean flow velocity. Turbulence in the puff generates a number of low-speed streaks accompanied by streamwise vortices along the pipe wall. These low-speed streaks move upstream relative to the puff, across the trailing edge and create strong thin vortex layers, arched above the streaks, together with the laminar flow coming from upstream. The vortex layers, whose thickness is typically a few times smaller than the width, are unstable to roll up, through the Kelvin-Helmholtz instability, and induce velocity fluctuations that propagate downstream faster than the puff itself and enhance the turbulent activity in it. This self-sustenance cycle of an equilibrium puff is numerically verified.
Stopping times in cessation flows of Bingham plastics with slip at the wall
Philippou, Maria; Damianou, Yiolanda; Kaoullas, George; Georgiou, Georgios C.
2012-09-01
We solve numerically the cessation of axisymmetric Poiseuille flow of a Bingham plastic assuming that slip occurs along the wall. A power-law expression is used to relate the wall shear stress to the slip velocity. The numerical results show that the velocity becomes and remains uniform before complete cessation and that the stopping time is finite only when the exponent sBingham number and the volumetric flow rate decays exponentially. When s>1, the decay is much slower, i.e. polynomial. The asymptotic expressions for the volumetric flow rate in the case of full-slip are also derived.
Silva, Goncalo; Semiao, Viriato
2017-07-01
The first nonequilibrium effect experienced by gaseous flows in contact with solid surfaces is the slip-flow regime. While the classical hydrodynamic description holds valid in bulk, at boundaries the fluid-wall interactions must consider slip. In comparison to the standard no-slip Dirichlet condition, the case of slip formulates as a Robin-type condition for the fluid tangential velocity. This makes its numerical modeling a challenging task, particularly in complex geometries. In this work, this issue is handled with the lattice Boltzmann method (LBM), motivated by the similarities between the closure relations of the reflection-type boundary schemes equipping the LBM equation and the slip velocity condition established by slip-flow theory. Based on this analogy, we derive, as central result, the structure of the LBM boundary closure relation that is consistent with the second-order slip velocity condition, applicable to planar walls. Subsequently, three tasks are performed. First, we clarify the limitations of existing slip velocity LBM schemes, based on discrete analogs of kinetic theory fluid-wall interaction models. Second, we present improved slip velocity LBM boundary schemes, constructed directly at discrete level, by extending the multireflection framework to the slip-flow regime. Here, two classes of slip velocity LBM boundary schemes are considered: (i) linear slip schemes, which are local but retain some calibration requirements and/or operation limitations, (ii) parabolic slip schemes, which use a two-point implementation but guarantee the consistent prescription of the intended slip velocity condition, at arbitrary plane wall discretizations, further dispensing any numerical calibration procedure. Third and final, we verify the improvements of our proposed slip velocity LBM boundary schemes against existing ones. The numerical tests evaluate the ability of the slip schemes to exactly accommodate the steady Poiseuille channel flow solution, over
Silva, Goncalo; Semiao, Viriato
2017-07-01
The first nonequilibrium effect experienced by gaseous flows in contact with solid surfaces is the slip-flow regime. While the classical hydrodynamic description holds valid in bulk, at boundaries the fluid-wall interactions must consider slip. In comparison to the standard no-slip Dirichlet condition, the case of slip formulates as a Robin-type condition for the fluid tangential velocity. This makes its numerical modeling a challenging task, particularly in complex geometries. In this work, this issue is handled with the lattice Boltzmann method (LBM), motivated by the similarities between the closure relations of the reflection-type boundary schemes equipping the LBM equation and the slip velocity condition established by slip-flow theory. Based on this analogy, we derive, as central result, the structure of the LBM boundary closure relation that is consistent with the second-order slip velocity condition, applicable to planar walls. Subsequently, three tasks are performed. First, we clarify the limitations of existing slip velocity LBM schemes, based on discrete analogs of kinetic theory fluid-wall interaction models. Second, we present improved slip velocity LBM boundary schemes, constructed directly at discrete level, by extending the multireflection framework to the slip-flow regime. Here, two classes of slip velocity LBM boundary schemes are considered: (i) linear slip schemes, which are local but retain some calibration requirements and/or operation limitations, (ii) parabolic slip schemes, which use a two-point implementation but guarantee the consistent prescription of the intended slip velocity condition, at arbitrary plane wall discretizations, further dispensing any numerical calibration procedure. Third and final, we verify the improvements of our proposed slip velocity LBM boundary schemes against existing ones. The numerical tests evaluate the ability of the slip schemes to exactly accommodate the steady Poiseuille channel flow solution, over
Schnitzer, Ory; Yariv, Ehud
2017-07-01
The gross amplification of the fluid velocity in pressure-driven flows due to the introduction of superhydrophobic walls is commonly quantified by an effective slip length. The canonical duct-flow geometry involves a periodic structure of longitudinal shear-free stripes at either one or both of the bounding walls, corresponding to flat-meniscus gas bubbles trapped within a periodic array of grooves. This grating configuration is characterized by two geometric parameters, namely the ratio κ of channel width to microstructure period and the areal fraction Δ of the shear-free stripes. For wide channels, κ ≫1 , this geometry is known to possess an approximate solution where the dimensionless slip length λ , normalized by the duct semiwidth, is small, indicating a weak superhydrophobic effect. We here address the other extreme of narrow channels, κ ≪1 , identifying large O (κ-2) values of λ for the symmetric configuration, where both bounding walls are superhydrophobic. This velocity enhancement is associated with an unconventional Poiseuille-like flow profile where the parabolic velocity variation takes place in a direction parallel (rather than perpendicular) to the boundaries. Use of matched asymptotic expansions and conformal-mapping techniques provides λ up to O (κ-1) , establishing the approximationλ ˜κ-2Δ/33 +κ-1Δ/2π ln4 +⋯, which is in excellent agreement with a semianalytic solution of the dual equations governing the respective coefficients of a Fourier-series representation of the fluid velocity. No similar singularity occurs in the corresponding asymmetric configuration, involving a single superhydrophobic wall; in that geometry, a Hele-Shaw approximation shows that λ =O (1 ) .
Particle migration and sorting in microbubble streaming flows
Thameem, Raqeeb; Hilgenfeldt, Sascha
2016-01-01
Ultrasonic driving of semicylindrical microbubbles generates strong streaming flows that are robust over a wide range of driving frequencies. We show that in microchannels, these streaming flow patterns can be combined with Poiseuille flows to achieve two distinctive, highly tunable methods for size-sensitive sorting and trapping of particles much smaller than the bubble itself. This method allows higher throughput than typical passive sorting techniques, since it does not require the inclusion of device features on the order of the particle size. We propose a simple mechanism, based on channel and flow geometry, which reliably describes and predicts the sorting behavior observed in experiment. It is also shown that an asymptotic theory that incorporates the device geometry and superimposed channel flow accurately models key flow features such as peak speeds and particle trajectories, provided it is appropriately modified to account for 3D effects caused by the axial confinement of the bubble. PMID:26958103
Nozzle geometry variations on the discharge coefficient
Directory of Open Access Journals (Sweden)
M.M.A. Alam
2016-03-01
Full Text Available Numerical works have been conducted to investigate the effect of nozzle geometries on the discharge coefficient. Several contoured converging nozzles with finite radius of curvatures, conically converging nozzles and conical divergent orifices have been employed in this investigation. Each nozzle and orifice has a nominal exit diameter of 12.7×10−3 m. A 3rd order MUSCL finite volume method of ANSYS Fluent 13.0 was used to solve the Reynolds-averaged Navier–Stokes equations in simulating turbulent flows through various nozzle inlet geometries. The numerical model was validated through comparison between the numerical results and experimental data. The results obtained show that the nozzle geometry has pronounced effect on the sonic lines and discharge coefficients. The coefficient of discharge was found differ from unity due to the non-uniformity of flow parameters at the nozzle exit and the presence of boundary layer as well.
Navier–Stokes flow in converging–diverging distensible tubes
Directory of Open Access Journals (Sweden)
Taha Sochi
2015-09-01
Full Text Available We use a method based on the lubrication approximation in conjunction with a residual-based mass-continuity iterative solution scheme to compute the flow rate and pressure field in distensible converging–diverging tubes for Navier–Stokes fluids. We employ an analytical formula derived from a one-dimensional version of the Navier–Stokes equations to describe the underlying flow model that provides the residual function. This formula correlates the flow rate to the boundary pressures in straight cylindrical elastic tubes with constant-radius. We validate our findings by the convergence toward a final solution with fine discretization as well as by comparison to the Poiseuille-type flow in its convergence toward analytic solutions found earlier in rigid converging–diverging tubes. We also tested the method on limiting special cases of cylindrical elastic tubes with constant-radius where the numerical solutions converged to the expected analytical solutions. The distensible model has also been endorsed by its convergence toward the rigid Poiseuille-type model with increasing the tube wall stiffness. Lubrication-based one-dimensional finite element method was also used for verification. In this investigation five converging–diverging geometries are used for demonstration, validation and as prototypes for modeling converging–diverging geometries in general.
Second coefficient of viscosity in air
Ash, Robert L.; Zuckerwar, Allan J.; Zheng, Zhonquan
1991-01-01
Acoustic attenuation measurements in air were analyzed in order to estimate the second coefficient of viscosity. Data over a temperature range of 11 C to 50 C and at relative humidities between 6 percent and 91 percent were used. This analysis showed that the second coefficient of viscosity varied between 1900 and 20,000 times larger than the dynamic or first coefficient of viscosity over the temperature and humidity range of the data. In addition, the data showed that the molecular relaxation effects, which are responsible for the magnitude of the second coefficient of viscosity, place severe limits on the use of time-independent, thermodynamic equations of state. Compressible flows containing large streamwise velocity gradients, like shock waves, which cause significant changes in particle properties to occur during time intervals shorter than hundredths of seconds, must be modeled using dynamic equations of state. The dynamic model approach is described briefly.
Kerr scattering coefficients via isomonodromy
Energy Technology Data Exchange (ETDEWEB)
Cunha, Bruno Carneiro da [Departamento de Física, Universidade Federal de Pernambuco,50670-901, Recife, Pernambuco (Brazil); Novaes, Fábio [International Institute of Physics, Federal University of Rio Grande do Norte,Av. Odilon Gomes de Lima 1722, Capim Macio, Natal-RN 59078-400 (Brazil)
2015-11-23
We study the scattering of a massless scalar field in a generic Kerr background. Using a particular gauge choice based on the current conservation of the radial equation, we give a generic formula for the scattering coefficient in terms of the composite monodromy parameter σ between the inner and the outer horizons. Using the isomonodromy flow, we calculate σ exactly in terms of the Painlevé V τ-function. We also show that the eigenvalue problem for the angular equation (spheroidal harmonics) can be calculated using the same techniques. We use recent developments relating the Painlevé V τ-function to Liouville irregular conformal blocks to claim that this scattering problem is solved in the combinatorial sense, with known expressions for the τ-function near the critical points.
Prestarlike functions with negative coefficients
Directory of Open Access Journals (Sweden)
H. Silverman
1979-01-01
Full Text Available The extreme points for prestarlike functions having negative coefficients are determined. Coefficient, distortion and radii of univalence, starlikeness, and convexity theorems are also obtained.
Investigation on Thrust and Moment Coefficients of a Centrifugal Turbomachine
Directory of Open Access Journals (Sweden)
Bo Hu
2018-04-01
Full Text Available In radial pumps and turbines, the centrifugal through-flow in both the front and the back chambers is quite common. It strongly impacts the core swirl ratio, pressure distribution, axial thrust and frictional torque. In order to investigate these relationships experimentally, a test rig was designed at the University of Duisburg-Essen and described in this paper. Based on both the experimental and numerical results, correlations are determined to predict the impacts of the centrifugal through-flow on the core swirl ratio, the thrust coefficient and the moment coefficient. Two correlations respectively are determined to associate the core swirl ratio with the local through-flow coefficient for both Batchelor type flow and Stewartson type flow. The correlations describing the thrust coefficient and the moment coefficient in a rotor-stator cavity with centripetal through-flow (Hu et al., 2017 are modified for the case of centrifugal through-flow. The Daily and Nece diagram distinguishing between different flow regimes in rotor-stator cavities is extended with a through-flow coordinate into 3D. The achieved results provide a comprehensive data base which is intended to support the calculation of axial thrust and moment coefficients during the design process of radial pumps and turbines in a more accurate manner.
The Discharge Coefficient of a Centre-Pivot Roof Window
DEFF Research Database (Denmark)
Iqbal, Ahsan; Afshari, Alireza; Nielsen, Peter V.
2012-01-01
Accuracy in estimation of airflow through windows is the key parameter for modelling and designing of naturally ventilated buildings. The flow through windows is usually described by the orifice flow plate equation. This equation involves the discharge coefficient. In practice, often a constant...... value of discharge coefficient is used. The constant value of discharge coefficient leads to deceptive airflow estimation in the cases of centre-pivot roof windows. The object of this paper is to study and evaluate the discharge coefficient of the centre pivot roof window. Focus is given...... on unidirectional flows i.e. inflow and outflow. CFD techniques are used to predict the airflow through the modelled window. Analytical orifice flow equation is used to calculate the discharge coefficient. Results are compared with experimental results. It is concluded that the single value of the discharge...
Coefficient estimates of negative powers and inverse coefficients for ...
Indian Academy of Sciences (India)
λ. Using this we shall determine the ... Univalent; starlike; meromorphic functions; subordination; coefficient bounds; inverse ...... [6] FitzGerald C H, Quadratic inequalities and coefficient estimates for Schlicht functions, Arch. Ration. Mech. Anal.
Lattice fluid dynamics from perfect discretizations of continuum flows
International Nuclear Information System (INIS)
Katz, E.; Wiese, U.
1998-01-01
We use renormalization group methods to derive equations of motion for large scale variables in fluid dynamics. The large scale variables are averages of the underlying continuum variables over cubic volumes and naturally exist on a lattice. The resulting lattice dynamics represents a perfect discretization of continuum physics, i.e., grid artifacts are completely eliminated. Perfect equations of motion are derived for static, slow flows of incompressible, viscous fluids. For Hagen-Poiseuille flow in a channel with a square cross section the equations reduce to a perfect discretization of the Poisson equation for the velocity field with Dirichlet boundary conditions. The perfect large scale Poisson equation is used in a numerical simulation and is shown to represent the continuum flow exactly. For nonsquare cross sections one can use a numerical iterative procedure to derive flow equations that are approximately perfect. copyright 1998 The American Physical Society
Continuous surface force based lattice Boltzmann equation method for simulating thermocapillary flow
Energy Technology Data Exchange (ETDEWEB)
Zheng, Lin, E-mail: lz@njust.edu.cn [School of Energy and Power Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Zheng, Song [School of Mathematics and Statistics, Zhejiang University of Finance and Economics, Hangzhou 310018 (China); Zhai, Qinglan [School of Economics Management and Law, Chaohu University, Chaohu 238000 (China)
2016-02-05
In this paper, we extend a lattice Boltzmann equation (LBE) with continuous surface force (CSF) to simulate thermocapillary flows. The model is designed on our previous CSF LBE for athermal two phase flow, in which the interfacial tension forces and the Marangoni stresses as the results of the interface interactions between different phases are described by a conception of CSF. In this model, the sharp interfaces between different phases are separated by a narrow transition layers, and the kinetics and morphology evolution of phase separation would be characterized by an order parameter via Cahn–Hilliard equation which is solved in the frame work of LBE. The scalar convection–diffusion equation for temperature field is resolved by thermal LBE. The models are validated by thermal two layered Poiseuille flow, and two superimposed planar fluids at negligibly small Reynolds and Marangoni numbers for the thermocapillary driven convection, which have analytical solutions for the velocity and temperature. Then thermocapillary migration of two/three dimensional deformable droplet are simulated. Numerical results show that the predictions of present LBE agreed with the analytical solution/other numerical results. - Highlights: • A CSF LBE to thermocapillary flows. • Thermal layered Poiseuille flows. • Thermocapillary migration.
Continuous surface force based lattice Boltzmann equation method for simulating thermocapillary flow
International Nuclear Information System (INIS)
Zheng, Lin; Zheng, Song; Zhai, Qinglan
2016-01-01
In this paper, we extend a lattice Boltzmann equation (LBE) with continuous surface force (CSF) to simulate thermocapillary flows. The model is designed on our previous CSF LBE for athermal two phase flow, in which the interfacial tension forces and the Marangoni stresses as the results of the interface interactions between different phases are described by a conception of CSF. In this model, the sharp interfaces between different phases are separated by a narrow transition layers, and the kinetics and morphology evolution of phase separation would be characterized by an order parameter via Cahn–Hilliard equation which is solved in the frame work of LBE. The scalar convection–diffusion equation for temperature field is resolved by thermal LBE. The models are validated by thermal two layered Poiseuille flow, and two superimposed planar fluids at negligibly small Reynolds and Marangoni numbers for the thermocapillary driven convection, which have analytical solutions for the velocity and temperature. Then thermocapillary migration of two/three dimensional deformable droplet are simulated. Numerical results show that the predictions of present LBE agreed with the analytical solution/other numerical results. - Highlights: • A CSF LBE to thermocapillary flows. • Thermal layered Poiseuille flows. • Thermocapillary migration.
Pressure driven water flow through hydrophilic alumina nanomembranes
Beskok, Ali; Koklu, Anil; Sengor, Sevinc
2017-11-01
We present an experimental study that focuses on pressure-driven flow of distilled water through alumina membranes with 5, 10 and 20 nm pore radii. The nanopore geometry, pore size and porosity are characterized using scanning electron microscopy images taken pre and post-flow experiments. Comparisons of these images have shown reduction in the pore size, which is attributed to precipitation of hydroxyl groups on alumina surfaces. Measured flowrates compared with the Hagen-Poiseuille flow relations consistently predict 2.2 nm reductions in the pore size for three different membranes. This behavior can be explained by the formation of a thick stick layer of water molecules over hydroxylated alumina surfaces, evidenced by water droplet contact angle measurements that exhibit increased hydrophilicity of alumina surfaces. Other possible effects of the mismatch between theory and experiments such as unaccounted pressure losses in the system or the streaming potential effects were also considered, but shown to be negligible for current experimental conditions.
Unsaturated soil moisture drying and wetting diffusion coefficient measurements in the laboratory.
2009-09-01
ABSTRACTTransient moisture flow in an unsaturated soil in response to suction changes is controlled by the unsaturated moisture diffusion coefficient. The moisture diffusion coefficient can be determined by measuring suction profiles over time. The l...
Multiple Temperature Model for Near Continuum Flows
International Nuclear Information System (INIS)
XU, Kun; Liu, Hongwei; Jiang, Jianzheng
2007-01-01
In the near continuum flow regime, the flow may have different translational temperatures in different directions. It is well known that for increasingly rarefied flow fields, the predictions from continuum formulation, such as the Navier-Stokes equations, lose accuracy. These inaccuracies may be partially due to the single temperature assumption in the Navier-Stokes equations. Here, based on the gas-kinetic Bhatnagar-Gross-Krook (BGK) equation, a multitranslational temperature model is proposed and used in the flow calculations. In order to fix all three translational temperatures, two constraints are additionally proposed to model the energy exchange in different directions. Based on the multiple temperature assumption, the Navier-Stokes relation between the stress and strain is replaced by the temperature relaxation term, and the Navier-Stokes assumption is recovered only in the limiting case when the flow is close to the equilibrium with the same temperature in different directions. In order to validate the current model, both the Couette and Poiseuille flows are studied in the transition flow regime
Quadrature formulas for Fourier coefficients
Bojanov, Borislav
2009-09-01
We consider quadrature formulas of high degree of precision for the computation of the Fourier coefficients in expansions of functions with respect to a system of orthogonal polynomials. In particular, we show the uniqueness of a multiple node formula for the Fourier-Tchebycheff coefficients given by Micchelli and Sharma and construct new Gaussian formulas for the Fourier coefficients of a function, based on the values of the function and its derivatives. © 2009 Elsevier B.V. All rights reserved.
Measuring of heat transfer coefficient
DEFF Research Database (Denmark)
Henningsen, Poul; Lindegren, Maria
Subtask 3.4 Measuring of heat transfer coefficient Subtask 3.4.1 Design and setting up of tests to measure heat transfer coefficient Objective: Complementary testing methods together with the relevant experimental equipment are to be designed by the two partners involved in order to measure...... the heat transfer coefficient for a wide range of interface conditions in hot and warm forging processes. Subtask 3.4.2 Measurement of heat transfer coefficient The objective of subtask 3.4.2 is to determine heat transfer values for different interface conditions reflecting those typically operating in hot...
Peltier coefficient measurement in a thermoelectric module
International Nuclear Information System (INIS)
Garrido, Javier; Casanovas, Alejandro; Chimeno, José María
2013-01-01
A new method for measuring the Peltier coefficient in a thermocouple X/Y based on the energy balance at the junction has been proposed recently. This technique needs only the hot and cold temperatures of a thermoelectric module when an electric current flows through it as the operational variables. The temperature evolutions of the two module sides provide an evident and accurate idea of the Peltier effect. From these temperatures, the heat transfer between the module and the ambient is also evaluated. The thermoelectric phenomena are described in the framework of an observable theory. Based on this procedure, an experiment is presented for a university teaching laboratory at the undergraduate level. (paper)
Energy Technology Data Exchange (ETDEWEB)
Fabrega, S. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires
1970-07-01
This report begins with a presentation of various statistical methods which make it possible to take into account the uncertainties involved in thermal calculations for nuclear reactors. The use of the variance addition theorem ({sigma} method) for calculating the probability of a thermal accident in a reactor is now very common. This method has still certain fundamental problems however (correlation between the variables, non-linearity) which results in it being abandoned in favour of less elegant methods, which are also less rigorous, e.g. the Monte Carlo method. We have attempted to show in this work how it is possible to generalize the {sigma} method to take into account the difficulties which limits its use. The great advantage of the {sigma} method is that it is relatively fast to apply and is also analytical. It enables one to understand the intricacies of the phenomena and the influence of various conditions which can be imposed in the construction of a reactor. The last part of this work is dedicated to an application of the 3-{sigma} method to the calculation of the safety margin in the case of the phenomenon of flow redistribution. Numerical results are given for the case of a high flux reactor. They show that the improvement in the performance due to the use of the statistical method is quite substantial ; whereas the sum of the uncertainties means that the maximum available power (which would be obtained if there were no uncertainty) should be divided by 1.6 approximately, this power should be divided by 1.25 if the average accident frequency is assumed to be 1 in a thousand. The accident frequency decreases very rapidly if the power is still further diminished; a division by 1.33 lowers the frequency to about 1 in 10,000. It thus appears than in practice the statistical method leads to a decrease by a factor of at least 2 in the loss of performance due to the uncertainties.
Converting Sabine absorption coefficients to random incidence absorption coefficients
DEFF Research Database (Denmark)
Jeong, Cheol-Ho
2013-01-01
are suggested: An optimization method for the surface impedances for locally reacting absorbers, the flow resistivity for extendedly reacting absorbers, and the flow resistance for fabrics. With four porous type absorbers, the conversion methods are validated. For absorbers backed by a rigid wall, the surface...... impedance optimization produces the best results, while the flow resistivity optimization also yields reasonable results. The flow resistivity and flow resistance optimization for extendedly reacting absorbers are also found to be successful. However, the theoretical conversion factors based on Miki's model...
Kuznetsov equation with variable coefficients
Indian Academy of Sciences (India)
like solutions of the PDE in (2+1) dimension with variable coefficients. ... Shivamoggi [12] gives only four polynomial conservation laws of the ZK equation ..... [3] P J Olver, Application of Lie group to differential equation (Springer, New York,.
Fuel Temperature Coefficient of Reactivity
Energy Technology Data Exchange (ETDEWEB)
Loewe, W.E.
2001-07-31
A method for measuring the fuel temperature coefficient of reactivity in a heterogeneous nuclear reactor is presented. The method, which is used during normal operation, requires that calibrated control rods be oscillated in a special way at a high reactor power level. The value of the fuel temperature coefficient of reactivity is found from the measured flux responses to these oscillations. Application of the method in a Savannah River reactor charged with natural uranium is discussed.
International Nuclear Information System (INIS)
Fietier, Nicolas; Deville, Michel O.
2003-01-01
This paper presents the development of spectral element methods to simulate unsteady flows of viscoelastic fluids using a closed-form differential constitutive equation. The generation and decay Poiseuille planar flows are considered as benchmark problems to test the abilities of our computational method to deal with truly time-dependent flows. Satisfactory results converging toward steady-state regimes have been obtained for the flow through a four-to-one planar abrupt contraction with unsteady algorithms. Time-dependent simulations of viscoelastic flows are prone to numerical instabilities even for simple geometrical configurations. Possible methods to improve the numerical stability of the computational algorithms are discussed in view of the results carried out with numerical simulations for the flows through a straight channel and the four-to-one contraction
Clustering Coefficients for Correlation Networks
Directory of Open Access Journals (Sweden)
Naoki Masuda
2018-03-01
Full Text Available Graph theory is a useful tool for deciphering structural and functional networks of the brain on various spatial and temporal scales. The clustering coefficient quantifies the abundance of connected triangles in a network and is a major descriptive statistics of networks. For example, it finds an application in the assessment of small-worldness of brain networks, which is affected by attentional and cognitive conditions, age, psychiatric disorders and so forth. However, it remains unclear how the clustering coefficient should be measured in a correlation-based network, which is among major representations of brain networks. In the present article, we propose clustering coefficients tailored to correlation matrices. The key idea is to use three-way partial correlation or partial mutual information to measure the strength of the association between the two neighboring nodes of a focal node relative to the amount of pseudo-correlation expected from indirect paths between the nodes. Our method avoids the difficulties of previous applications of clustering coefficient (and other measures in defining correlational networks, i.e., thresholding on the correlation value, discarding of negative correlation values, the pseudo-correlation problem and full partial correlation matrices whose estimation is computationally difficult. For proof of concept, we apply the proposed clustering coefficient measures to functional magnetic resonance imaging data obtained from healthy participants of various ages and compare them with conventional clustering coefficients. We show that the clustering coefficients decline with the age. The proposed clustering coefficients are more strongly correlated with age than the conventional ones are. We also show that the local variants of the proposed clustering coefficients (i.e., abundance of triangles around a focal node are useful in characterizing individual nodes. In contrast, the conventional local clustering coefficients
Coefficient adaptive triangulation for strongly anisotropic problems
Energy Technology Data Exchange (ETDEWEB)
D`Azevedo, E.F.; Romine, C.H.; Donato, J.M.
1996-01-01
Second order elliptic partial differential equations arise in many important applications, including flow through porous media, heat conduction, the distribution of electrical or magnetic potential. The prototype is the Laplace problem, which in discrete form produces a coefficient matrix that is relatively easy to solve in a regular domain. However, the presence of anisotropy produces a matrix whose condition number is increased, making the resulting linear system more difficult to solve. In this work, we take the anisotropy into account in the discretization by mapping each anisotropic region into a ``stretched`` coordinate space in which the anisotropy is removed. The region is then uniformly triangulated, and the resulting triangulation mapped back to the original space. The effect is to generate long slender triangles that are oriented in the direction of ``preferred flow.`` Slender triangles are generally regarded as numerically undesirable since they tend to cause poor conditioning; however, our triangulation has the effect of producing effective isotropy, thus improving the condition number of the resulting coefficient matrix.
Drop Pinch-Off for Discrete Flows from a Capillary
Directory of Open Access Journals (Sweden)
Wilson M.C.T.
2013-07-01
Full Text Available The problem of drop formation and pinch-off from a capillary tube under the influence of gravity has been extensively studied when the internal capillary pressure gradient is constant. This ensures a continuous time independent flow field inside the capillary tube typically of the Poiseuille flow type. Characteristic drop ejection behaviour includes: periodic drop ejection, drop ejection with associated satellite production, complex dripping, chaotic behaviour and jetting. It is well known that this characteristic behaviour is governed by the Weber (We and Ohnesorge (Oh numbers (for a given Bond number and may be delineated in a We verses Oh operability diagram. An in-depth physical understanding of drop ejection is also of great importance to industry where the tight control of drop size and ejection velocity are of critical importance in industrial processes such as sealants used in electronics assembly and inkjet printing. However, the use of such a continuous flow approach for drop ejection in industry is often impractical since such flows cannot be operator controlled. For this reason it is important to investigate so-called discrete pipe flows where the flow can be turned on and off at will. This means the flow inside the pipe is now time-dependent being controlled in a step-wise fashion. As a first stage in the investigation of drop pinch-off behaviour in discrete pipe flows this paper will study the critical pinch-off time required for drop ejection starting from a pendant drop. This is the discrete amount of time the pipe flow is turned on for in order for a drop to be ejected from the capillary. A Newtonian incompressible free-surface CFD flow code developed at the University of Leeds is used to investigate the critical pinch-off time for a range of internal pipe velocities (the central flow maximum in Poiseuille flow. It is found that the time required for drop ejection to occur decreases exponentially with internal pipe velocity
Non-constant retardation coefficient
International Nuclear Information System (INIS)
Wang Zhiming; Gu Zhijie; Yang Yue'e; Li Shushen
2004-12-01
Retardation coefficient is one of the important parameters used in transport models describing radionuclide migration in geological media and usually regarded as a constant in the models. The objectives of the work are to understand: (1) Whether the retardation coefficient, R d , is a constant? (2) How much effect is R d on calculated consequence if R d is not constant? (3) Is the retardation coefficient derived from distribution coefficient, k d , according to conventional equation suitable for safety assessment? The objectives are achieved through test and analysis of the test results on radionuclide migration in unsaturated loess. It can be seen from the results that retardation coefficient, R d , of 85 Sr is not constant and increases with water content, θ, under unsaturated condition. R d , of 85 Sr derived from k d according to conventional equation can not be used for safety assessment. R d , used for safety assessment should be directly measured, rather than derived from k d . It is shown from calculation that the effect of R d on calculated consequence is very considerable. (authors)
Coefficient estimates of negative powers and inverse coefficients for ...
Indian Academy of Sciences (India)
1 an(−λ, f )zn for z ∈ D. (1.4). One of the well-known extremal problems in the theory of univalent functions is to esti- mate the modulus of the Taylor coefficients an(−λ, f ) given by (1.4). This problem has been extensively studied in the literature ...
Taylor, C. (Editor); Chin, J. H. (Editor); Homsy, G. M. (Editor)
1991-01-01
Consideration is given to the impulse response of a laminar boundary layer and receptivity; numerical transition to turbulence in plane Poiseuille flow; large eddy simulation of turbulent wake flow; a viscous model and loss calculation of a multisplitter cascade; vortex initiation during dynamic stall of an airfoil; a numerical analysis of isothermal flow in a combustion chamber; and compressible flow calculations with a two-equation turbulence model and unstructured grids. Attention is also given to a 2D calculation of a buoyant flow around a burning sphere, a fast multigrid method for 3D turbulent incompressible flows, a streaming flow induced by an oscillating cascade of circular cylinders, an algebraic multigrid scheme for solving the Navier-Stokes equations on unstructured meshes; and nonlinear coupled multigrid solutions to thermal problems employing different nodal grid arrangements and convective transport approximations.
Harmonic functions with varying coefficients
Directory of Open Access Journals (Sweden)
Jacek Dziok
2016-05-01
Full Text Available Abstract Complex-valued harmonic functions that are univalent and sense preserving in the open unit disk can be written in the form f = h + g ‾ $f=h+\\overline{g}$ , where h and g are analytic. In this paper we investigate some classes of univalent harmonic functions with varying coefficients related to Janowski functions. By using the extreme points theory we obtain necessary and sufficient convolution conditions, coefficients estimates, distortion theorems, and integral mean inequalities for these classes of functions. The radii of starlikeness and convexity for these classes are also determined.
Minimum wall pressure coefficient of orifice plate energy dissipater
Directory of Open Access Journals (Sweden)
Wan-zheng Ai
2015-01-01
Full Text Available Orifice plate energy dissipaters have been successfully used in large-scale hydropower projects due to their simple structure, convenient construction procedure, and high energy dissipation ratio. The minimum wall pressure coefficient of an orifice plate can indirectly reflect its cavitation characteristics: the lower the minimum wall pressure coefficient is, the better the ability of the orifice plate to resist cavitation damage is. Thus, it is important to study the minimum wall pressure coefficient of the orifice plate. In this study, this coefficient and related parameters, such as the contraction ratio, defined as the ratio of the orifice plate diameter to the flood-discharging tunnel diameter; the relative thickness, defined as the ratio of the orifice plate thickness to the tunnel diameter; and the Reynolds number of the flow through the orifice plate, were theoretically analyzed, and their relationships were obtained through physical model experiments. It can be concluded that the minimum wall pressure coefficient is mainly dominated by the contraction ratio and relative thickness. The lower the contraction ratio and relative thickness are, the larger the minimum wall pressure coefficient is. The effects of the Reynolds number on the minimum wall pressure coefficient can be neglected when it is larger than 105. An empirical expression was presented to calculate the minimum wall pressure coefficient in this study.
Integer Solutions of Binomial Coefficients
Gilbertson, Nicholas J.
2016-01-01
A good formula is like a good story, rich in description, powerful in communication, and eye-opening to readers. The formula presented in this article for determining the coefficients of the binomial expansion of (x + y)n is one such "good read." The beauty of this formula is in its simplicity--both describing a quantitative situation…
Effective Viscosity Coefficient of Nanosuspensions
Rudyak, V. Ya.; Belkin, A. A.; Egorov, V. V.
2008-12-01
Systematic calculations of the effective viscosity coefficient of nanosuspensions have been performed using the molecular dynamics method. It is established that the viscosity of a nanosuspension depends not only on the volume concentration of the nanoparticles but also on their mass and diameter. Differences from Einstein's relation are found even for nanosuspensions with a low particle concentration.
Irrational "Coefficients" in Renaissance Algebra.
Oaks, Jeffrey A
2017-06-01
Argument From the time of al-Khwārizmī in the ninth century to the beginning of the sixteenth century algebraists did not allow irrational numbers to serve as coefficients. To multiply by x, for instance, the result was expressed as the rhetorical equivalent of . The reason for this practice has to do with the premodern concept of a monomial. The coefficient, or "number," of a term was thought of as how many of that term are present, and not as the scalar multiple that we work with today. Then, in sixteenth-century Europe, a few algebraists began to allow for irrational coefficients in their notation. Christoff Rudolff (1525) was the first to admit them in special cases, and subsequently they appear more liberally in Cardano (1539), Scheubel (1550), Bombelli (1572), and others, though most algebraists continued to ban them. We survey this development by examining the texts that show irrational coefficients and those that argue against them. We show that the debate took place entirely in the conceptual context of premodern, "cossic" algebra, and persisted in the sixteenth century independent of the development of the new algebra of Viète, Decartes, and Fermat. This was a formal innovation violating prevailing concepts that we propose could only be introduced because of the growing autonomy of notation from rhetorical text.
Principles of physics in surgery: the laws of flow dynamics physics for surgeons - Part 1.
Srivastava, Anurag; Sood, Akshay; Joy, S Parijat; Woodcock, John
2009-08-01
In the field of medicine and surgery many principles of physics find numerous applications. In this article we have summarized some prominent applications of the laws of fluid mechanics and hydrodynamics in surgery. Poiseuille's law sets the limits of isovolaemic haemodilution, enumerates limiting factors during fluid resuscitation and is a guiding principle in surgery for vascular stenoses. The equation of continuity finds use in non-invasive measurement of blood flow. Bernoulli's theorem explains the formation of post-stenotic dilatation. Reynolds number explains the origin of murmurs, haemolysis and airflow disturbances. Various forms of oxygen therapy are a direct application of the gas laws. Doppler effect is used in ultrasonography to find the direction and velocity of blood flow. In this first part of a series of articles we describe some applications of the laws of hydrodynamics governing the flow of blood and other body fluids.
Heat unit-based crop coefficient for grapefruit trees
International Nuclear Information System (INIS)
Martin, E.C.; Hla, A.K.; Waller, P.M.; Slack, D.C.
1997-01-01
The onset and rate of sap moving up the branches of grapefruit (Citrus paradisi Macfadyen) trees were monitored hourly using portable sap flow sensors at Waddell, Arizona. Hourly reference evapotranspiration (ETo) estimates were calculated using data from a nearby weather station. Crop water use was estimated from soil moisture measurements using a neutron probe. These data were used to first delineate the upper and lower temperature threshold values for the determination of heat units. A heat unit-based crop coefficient was then derived from a correlation of the crop coefficient with heat units over a crop year. The heat unit-based crop coefficient was found to be similar to crop coefficients derived by other reseachers
Transport Coefficients for Holographic Hydrodynamics at Finite Energy Scale
Directory of Open Access Journals (Sweden)
Xian-Hui Ge
2014-01-01
Full Text Available We investigate the relations between black hole thermodynamics and holographic transport coefficients in this paper. The formulae for DC conductivity and diffusion coefficient are verified for electrically single-charged black holes. We examine the correctness of the proposed expressions by taking charged dilatonic and single-charged STU black holes as two concrete examples, and compute the flows of conductivity and diffusion coefficient by solving the linear order perturbation equations. We then check the consistence by evaluating the Brown-York tensor at a finite radial position. Finally, we find that the retarded Green functions for the shear modes can be expressed easily in terms of black hole thermodynamic quantities and transport coefficients.
Coefficient of performance of Stirling refrigerators
E Mungan, Carl
2017-09-01
Stirling coolers transfer heat in or out of the working fluid during all four stages of their operation, and their coefficient of performance depends on whether the non-isothermal heat exchanges are performed reversibly or irreversibly. Both of these possibilities can in principle be arranged. Notably, if the working fluid is an ideal gas, the input of energy in the form of heat during one isochoric step is equal in magnitude to the output during the other isochoric step in the cycle. The theoretical performance of the fridge can then attain the reversible Carnot limit if a regenerator is used, which is a high heat capacity material through which the gas flows. Various Stirling refrigerator configurations are analysed in this article at a level of presentation suitable for an introductory undergraduate thermodynamics course.
Extinction Coefficient of Gold Nanostars
de Puig, Helena; Tam, Justina O.; Yen, Chun-Wan; Gehrke, Lee; Hamad-Schifferli, Kimberly
2015-01-01
Gold nanostars (NStars) are highly attractive for biological applications due to their surface chemistry, facile synthesis and optical properties. Here, we synthesize NStars in HEPES buffer at different HEPES/Au ratios, producing NStars of different sizes and shapes, and therefore varying optical properties. We measure the extinction coefficient of the synthesized NStars at their maximum surface plasmon resonances (SPR), which range from 5.7 × 108 to 26.8 × 108 M−1cm−1. Measured values correl...
Sarkarinejad, Khalil; Sarshar, Maryam Asadi; Adineh, Sadegh
2018-02-01
One of the main characteristic of the Zagros foreland fold-and-thrust belt and the Zagros foreland folded belt are wide distributions of surface extrusion from the Hormuz salt diapirs. This study examines the structure and kinematic of channel flow in the Karmostaj salt diapir in the southwestern part of the Zagros foreland folded belt. This diapir has reached the surface as a result of the channel flow mechanism and has extruded in the southern limb of the Kuh-Gach anticline which is an asymmetric décollement fold with convergence to the south. Structural and microstructural studies and quantitative finite strain (Rs) and kinematic vorticity number (Wk) analyses were carried out within this salt diapir and its namakier. This was in order to investigate the structural evolution in the salt diapiric system, the characteristics and mechanism of the salt flow and the distribution of flow regimes within the salt diapir and interaction of regional tectonics and salt diaprism. The extruded salt has developed a flow foliation sub-parallel to the remnant bedding recorded by different colors, a variety of internal folds including symmetrical and asymmetrical folds and interference fold patterns, shear zones, and boudins. These structures were used to analyze mechanisms and history of diapiric flow and extrusion. The microstructures, reveal various deformation mechanisms in various parts of salt diapir. The measurements of finite strain show that Rs values in the margin of salt diapir are higher than within its namakier which is consistent with the results of structural studies. Mean kinematic vorticity number (Wm) measured in steady state deformation of diapir and namakier is Wm = 0.45-0.48 ± 0.13. The estimated mean finite deformation (Wm) values indicate that 67.8% pure shear and 32.2% simple shear deformation were involved; the implications of which are discussed. The vorticity of flow indicates that in the early stage of growth, Poiseuille flow was the dominate
Hydrodynamics beyond Navier-Stokes: the slip flow model.
Yudistiawan, Wahyu P; Ansumali, Santosh; Karlin, Iliya V
2008-07-01
Recently, analytical solutions for the nonlinear Couette flow demonstrated the relevance of the lattice Boltzmann (LB) models to hydrodynamics beyond the continuum limit [S. Ansumali, Phys. Rev. Lett. 98, 124502 (2007)]. In this paper, we present a systematic study of the simplest LB kinetic equation-the nine-bit model in two dimensions--in order to quantify it as a slip flow approximation. Details of the aforementioned analytical solution are presented, and results are extended to include a general shear- and force-driven unidirectional flow in confined geometry. Exact solutions for the velocity, as well as for pertinent higher-order moments of the distribution functions, are obtained in both Couette and Poiseuille steady-state flows for all values of rarefaction parameter (Knudsen number). Results are compared with the slip flow solution by Cercignani, and a good quantitative agreement is found for both flow situations. Thus, the standard nine-bit LB model is characterized as a valid and self-consistent slip flow model for simulations beyond the Navier-Stokes approximation.
Axial and radial velocities in the creeping flow in a pipe
Directory of Open Access Journals (Sweden)
Zuykov Andrey L'vovich
2014-05-01
Full Text Available The article is devoted to analytical study of transformation fields of axial and radial velocities in uneven steady creeping flow of a Newtonian fluid in the initial portion of the cylindrical channel. It is shown that the velocity field of the flow is two-dimensional and determined by the stream function. The article is a continuation of a series of papers, where normalized analytic functions of radial axial distributions in uneven steady creeping flow in a cylindrical tube with azimuthal vorticity and stream function were obtained. There is Poiseuille profile for the axial velocity in the uniform motion of a fluid at an infinite distance from the entrance of the pipe (at x = ∞, here taken equal to zero radial velocity. There is uniform distribution of the axial velocity in the cross section at the tube inlet at x = 0, at which the axial velocity is constant along the current radius. Due to the axial symmetry of the flow on the axis of the pipe (at r = 0, the radial velocities and the partial derivative of the axial velocity along the radius, corresponding to the condition of the soft function extremum, are equal to zero. The authors stated vanishing of the velocity of the fluid on the walls of the pipe (at r = R , where R - radius of the tube due to its viscous sticking and tightness of the walls. The condition of conservation of volume flow along the tube was also accepted. All the solutions are obtained in the form of the Fourier - Bessel. It is shown that the hydraulic losses at uniform creeping flow of a Newtonian fluid correspond to Poiseuille - Hagen formula.
Flow with Negative Differential Viscosity
川口, 明彦; Akihiko, KAWAGUCHI; 京大人環; Graduate School of Human and Enviromental Studies, Kyoto University
2000-01-01
Only a monotonous flow appears to the movement of the incompressible flow body in a porous medium under a simple condition according to Darcy's law. However, the character of the flow changes greatly if we think about the model by which the temperature dependency in the coefficient of viscosity is considered. Becoming of the inclination of pressure deifference-flow velocity specific characteristics nagative if we think about the one-dimensnional flow under a suitable condition, that is, "Flow...
Rouvas, C.; Childs, D. W.
1993-01-01
In identifying the rotordynamic coefficients of a high-Reynolds-number hydrostatic bearing, fluid-flow induced forces present a unique problem, in that they provide an unmeasureable and uncontrollable excitation to the bearing. An analysis method is developed that effectively eliminates the effects of fluid-flow induced excitation on the estimation of the bearing rotordynamic coefficients, by using power spectral densities. In addition to the theoretical development, the method is verified experimentally by single-frequency testing, and repeatability tests. Results obtained for a bearing are the twelve rotordynamic coefficients (stiffness, damping, and inertia coefficients) as functions of eccentricity ratio, speed, and supply pressure.
Study of transport coefficients of nanodiamond nanofluids
Pryazhnikov, M. I.; Minakov, A. V.; Guzei, D. V.
2017-09-01
Experimental data on the thermal conductivity coefficient and viscosity coefficient of nanodiamond nanofluids are presented. Distilled water and ethylene glycol were used as the base fluid. Dependences of transport coefficients on concentration are obtained. It was shown that the thermal conductivity coefficient increases with increasing nanodiamonds concentration. It was shown that base fluids properties and nanodiamonds concentration affect on the rheology of nanofluids.
Measurements of thermal accommodation coefficients.
Energy Technology Data Exchange (ETDEWEB)
Rader, Daniel John; Castaneda, Jaime N.; Torczynski, John Robert; Grasser, Thomas W.; Trott, Wayne Merle
2005-10-01
A previously-developed experimental facility has been used to determine gas-surface thermal accommodation coefficients from the pressure dependence of the heat flux between parallel plates of similar material but different surface finish. Heat flux between the plates is inferred from measurements of temperature drop between the plate surface and an adjacent temperature-controlled water bath. Thermal accommodation measurements were determined from the pressure dependence of the heat flux for a fixed plate separation. Measurements of argon and nitrogen in contact with standard machined (lathed) or polished 304 stainless steel plates are indistinguishable within experimental uncertainty. Thus, the accommodation coefficient of 304 stainless steel with nitrogen and argon is estimated to be 0.80 {+-} 0.02 and 0.87 {+-} 0.02, respectively, independent of the surface roughness within the range likely to be encountered in engineering practice. Measurements of the accommodation of helium showed a slight variation with 304 stainless steel surface roughness: 0.36 {+-} 0.02 for a standard machine finish and 0.40 {+-} 0.02 for a polished finish. Planned tests with carbon-nanotube-coated plates will be performed when 304 stainless-steel blanks have been successfully coated.
The influence of numerical models on determining the drag coefficient
Directory of Open Access Journals (Sweden)
Dobeš Josef
2014-03-01
Full Text Available The paper deals with numerical modelling of body aerodynamic drag coefficient in the transition from laminar to turbulent flow regimes, where the selection of a suitable numerical model is problematic. On the basic problem of flow around a simple body – sphere selected computational models are tested. The values obtained by numerical simulations of drag coefficients of each model are compared with the graph of dependency of the drag coefficient vs. Reynolds number for a sphere. Next the dependency of Strouhal number vs. Reynolds number is evaluated, where the vortex shedding frequency values for given speed are obtained numerically and experimentally and then the values are compared for each numerical model and experiment. The aim is to specify trends for the selection of appropriate numerical model for flow around bodies problem in which the precise description of the flow field around the obstacle is used to define the acoustic noise source. Numerical modelling is performed by finite volume method using CFD code.
Extinction Coefficient of Gold Nanostars.
de Puig, Helena; Tam, Justina O; Yen, Chun-Wan; Gehrke, Lee; Hamad-Schifferli, Kimberly
2015-07-30
Gold nanostars (NStars) are highly attractive for biological applications due to their surface chemistry, facile synthesis and optical properties. Here, we synthesize NStars in HEPES buffer at different HEPES/Au ratios, producing NStars of different sizes and shapes, and therefore varying optical properties. We measure the extinction coefficient of the synthesized NStars at their maximum surface plasmon resonances (SPR), which range from 5.7 × 10 8 to 26.8 × 10 8 M -1 cm -1 . Measured values correlate with those obtained from theoretical models of the NStars using the discrete dipole approximation (DDA), which we use to simulate the extinction spectra of the nanostars. Finally, because NStars are typically used in biological applications, we conjugate DNA and antibodies to the NStars and calculate the footprint of the bound biomolecules.
Chung, S.
1973-01-01
Heat transfer phenomena of rarefied gas flows is discussed based on a literature survey of analytical and experimental rarefied gas dynamics. Subsonic flows are emphasized for the purposes of meteorological thermometry in the high atmosphere. The heat transfer coefficients for three basic geometries are given in the regimes of free molecular flow, transition flow, slip flow, and continuum flow. Different types of heat phenomena, and the analysis of theoretical and experimental data are presented. The uncertainties calculated from the interpolation rule compared with the available experimental data are discussed. The recovery factor for each geometry in subsonic rarefied flows is also given.
On the Decrease of the Oceanic Drag Coefficient in High Winds
Donelan, Mark A.
2018-02-01
The sheltering coefficient - prefixing Jeffreys' concept of the exponential wave growth rate at a gas-liquid interface - is shown to be Reynolds number dependent from laboratory measurements of waves and Reynolds stresses. There are two turbulent flow regimes: wind speed range of 2.5 to 30 m/s where the drag coefficients increase with wind speed, and wind speed range of 30 to 50 m/s where sheltering/drag coefficients decrease/saturate with wind speed. By comparing model calculations of drag coefficients - using a fixed sheltering coefficient - with ocean observations over a wind speed range of 1 to 50 m/s a similar Reynolds number dependence of the oceanic sheltering coefficient is revealed. In consequence the drag coefficient is a function of Reynolds number and wave age, and not just wind speed as frequently assumed. The resulting decreasing drag coefficient above 30 m/s is shown to be critical in explaining the rapid intensification so prominent in the climatology of Atlantic hurricanes. The Reynolds number dependence of the sheltering coefficient, when employed in coupled models, should lead to significant improvements in the prediction of intensification and decay of tropical cyclones. A calculation of curvature at the wave crest suggests that at wind speeds above 56.15 m/s all waves-breaking or not-induce steady flow separation leading to a minimum in the drag coefficient. This is further evidence of the veracity of the observations of the oceanic drag coefficient at high winds.
Relative Effects of Asymmetry and Wall Slip on the Stability of Plane Channel Flow
Directory of Open Access Journals (Sweden)
Sukhendu Ghosh
2017-12-01
Full Text Available The effect of wall velocity slip on the stability of a pressure-driven two-dimensional asymmetric channel flow is examined by considering Navier slip condition on the channel walls. The two-parameter families of mean velocity profiles are considered to approximate the underlying asymmetric basic flow. Competing effects of skewness and maximum velocity on the stability of the flow are explored for a range of model parameters. The Orr–Sommerfeld system of the asymmetric flow is solved using a Chebyshev spectral collocation method for both symmetric and non-symmetric type slip boundary conditions. Numerical results indicate that moderate asymmetry in the basic flow has a significant role on the stability of the Poiseuille-kind parallel/nearly parallel flows. Wall slip shows a passive control on the instability of the asymmetric flow by increasing or decreasing the critical Reynolds number and the set of unstable wave numbers. The stabilizing/destabilizing effect of slip velocity on the flow instability is weak or strong depending on the presence of velocity slip at the upper or lower wall. Velocity slip has a profound grip on the flow behaviour by changing the shear rate inside the perturbed flow.
Estimating the Sabine absorption coefficient of fibrous materials for various backing conditions
DEFF Research Database (Denmark)
Jeong, Cheol-Ho
2017-01-01
Since absorber manufacturers cannot provide the absorption coefficients for all possible mounting conditions, acousticians have difficulties knowing the absorption characteristics of their own configurations. This paper aims to predict the Sabine absorption coefficient for various mounting...... conditions by extracting the air flow resistivity of the test specimen and the frequency-dependent effect of the chamber on the measured absorption coefficients. Two homogeneous fibrous absorbers are measured for experimental validation, showing good agreements between the predictions and measurements...
Evidence for validity of ileal digestibility coefficients in monogastrics.
Columbus, Daniel; de Lange, Cornelis F M
2012-08-01
Measures of amino acid (AA) digestibility are used widely to estimate bioavailability of AA in feed and food ingredients for monogastric animals. In principle, the digestibility assay is simpler than in vivo assessments of AA bioavailability and allows for simultaneous estimation of the bioavailability of all AA in an experimental diet. It is generally assumed that absorption of intact AA in the hindgut of monogastrics is minimal, even though colonocytes do contain AA transporters and have been shown to absorb AA. This assumption is supported by the observation that infusion of AA into the hindgut does not improve nitrogen balance in monogastrics. In addition, growth performance of monogastrics is more highly correlated with ileal than faecal AA digestibility. Therefore, ileal digestibility coefficients provide better estimates of AA bioavailability than faecal digestibility coefficients. Measures of apparent ileal digestibility (AID) of AA are confounded with endogenous gut AA losses (EAAL). The curvilinear increase in AID of AA with increasing dietary AA level has been attributed to the relatively large contribution of EAAL to total ileal AA flows at low dietary AA levels. Subtracting basal EAAL from total ileal AA flows yields standardized ileal digestibility (SID) coefficients that appear to be more additive than AID coefficients in mixtures of feed ingredients. An implicit assumption when using SID AA coefficients in diet formulation is that the post-absorptive utilization of AA is not influenced by the dietary protein source. This assumption appears inappropriate when using feed or food ingredients that have been over-heated, induce large amounts of EAAL, or contain substantial amounts of fermentable fibre. Improved understanding of processes that contribute to the discrepancy between bioavailability and ileal digestibility will allow a more effective use of AA digestibility coefficients in diet formulation.
Factorization of Transport Coefficients in Macroporous Media
DEFF Research Database (Denmark)
Shapiro, Alexander; Stenby, Erling Halfdan
2000-01-01
We prove the fundamental theorem about factorization of the phenomenological coefficients for transport in macroporous media. By factorization we mean the representation of the transport coefficients as products of geometric parameters of the porous medium and the parameters characteristic...
Local Transfer Coefficient, Smooth Channel
Directory of Open Access Journals (Sweden)
R. T. Kukreja
1998-01-01
Full Text Available Naphthalene sublimation technique and the heat/mass transfer analogy are used to determine the detailed local heat/mass transfer distributions on the leading and trailing walls of a twopass square channel with smooth walls that rotates about a perpendicular axis. Since the variation of density is small in the flow through the channel, buoyancy effect is negligible. Results show that, in both the stationary and rotating channel cases, very large spanwise variations of the mass transfer exist in he turn and in the region immediately downstream of the turn in the second straight pass. In the first straight pass, the rotation-induced Coriolis forces reduce the mass transfer on the leading wall and increase the mass transfer on the trailing wall. In the turn, rotation significantly increases the mass transfer on the leading wall, especially in the upstream half of the turn. Rotation also increases the mass transfer on the trailing wall, more in the downstream half of the turn than in the upstream half of the turn. Immediately downstream of the turn, rotation causes the mass transfer to be much higher on the trailing wall near the downstream corner of the tip of the inner wall than on the opposite leading wall. The mass transfer in the second pass is higher on the leading wall than on the trailing wall. A slower flow causes higher mass transfer enhancement in the turn on both the leading and trailing walls.
Symmetry chains and adaptation coefficients
International Nuclear Information System (INIS)
Fritzer, H.P.; Gruber, B.
1985-01-01
Given a symmetry chain of physical significance it becomes necessary to obtain states which transform properly with respect to the symmetries of the chain. In this article we describe a method which permits us to calculate symmetry-adapted quantum states with relative ease. The coefficients for the symmetry-adapted linear combinations are obtained, in numerical form, in terms of the original states of the system and can thus be represented in the form of numerical tables. In addition, one also obtains automatically the matrix elements for the operators of the symmetry groups which are involved, and thus for any physical operator which can be expressed either as an element of the algebra or of the enveloping algebra. The method is well suited for computers once the physically relevant symmetry chain, or chains, have been defined. While the method to be described is generally applicable to any physical system for which semisimple Lie algebras play a role we choose here a familiar example in order to illustrate the method and to illuminate its simplicity. We choose the nuclear shell model for the case of two nucleons with orbital angular momentum l = 1. While the states of the entire shell transform like the smallest spin representation of SO(25) we restrict our attention to its subgroup SU(6) x SU(2)/sub T/. We determine the symmetry chains which lead to total angular momentum SU(2)/sub J/ and obtain the symmetry-adapted states for these chains
Standards for Standardized Logistic Regression Coefficients
Menard, Scott
2011-01-01
Standardized coefficients in logistic regression analysis have the same utility as standardized coefficients in linear regression analysis. Although there has been no consensus on the best way to construct standardized logistic regression coefficients, there is now sufficient evidence to suggest a single best approach to the construction of a…
Anomalous Seebeck coefficient in boron carbides
International Nuclear Information System (INIS)
Aselage, T.L.; Emin, D.; Wood, C.; Mackinnon, I.D.R.; Howard, I.A.
1987-01-01
Boron carbides exhibit an anomalously large Seebeck coefficient with a temperature coefficient that is characteristic of polaronic hopping between inequivalent sites. The inequivalence in the sites is associated with disorder in the solid. The temperature dependence of the Seebeck coefficient for materials prepared by different techniques provides insight into the nature of the disorder
Coefficient rings of formal group laws
International Nuclear Information System (INIS)
Buchstaber, V M; Ustinov, A V
2015-01-01
We describe the coefficient rings of universal formal group laws which arise in algebraic geometry, algebraic topology and their application to mathematical physics. We also describe the homomorphisms of these coefficient rings coming from reductions of one formal group law to another. The proofs are based on the number-theoretic properties of binomial coefficients. Bibliography: 37 titles
Soccer Ball Lift Coefficients via Trajectory Analysis
Goff, John Eric; Carre, Matt J.
2010-01-01
We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin…
Diffusion coefficient in photon diffusion theory
Graaff, R; Ten Bosch, JJ
2000-01-01
The choice of the diffusion coefficient to be used in photon diffusion theory has been a subject of discussion in recent publications on tissue optics. We compared several diffusion coefficients with the apparent diffusion coefficient from the more fundamental transport theory, D-app. Application to
Incremental Aerodynamic Coefficient Database for the USA2
Richardson, Annie Catherine
2016-01-01
In March through May of 2016, a wind tunnel test was conducted by the Aerosciences Branch (EV33) to visually study the unsteady aerodynamic behavior over multiple transition geometries for the Universal Stage Adapter 2 (USA2) in the MSFC Aerodynamic Research Facility's Trisonic Wind Tunnel (TWT). The purpose of the test was to make a qualitative comparison of the transonic flow field in order to provide a recommended minimum transition radius for manufacturing. Additionally, 6 Degree of Freedom force and moment data for each configuration tested was acquired in order to determine the geometric effects on the longitudinal aerodynamic coefficients (Normal Force, Axial Force, and Pitching Moment). In order to make a quantitative comparison of the aerodynamic effects of the USA2 transition geometry, the aerodynamic coefficient data collected during the test was parsed and incorporated into a database for each USA2 configuration tested. An incremental aerodynamic coefficient database was then developed using the generated databases for each USA2 geometry as a function of Mach number and angle of attack. The final USA2 coefficient increments will be applied to the aerodynamic coefficients of the baseline geometry to adjust the Space Launch System (SLS) integrated launch vehicle force and moment database based on the transition geometry of the USA2.
International Nuclear Information System (INIS)
Ferreira, W.R.
1983-09-01
Here, the mixture coefficients are determined in tests which simulate two symmetric and two assymetric coolant channels of a water cooled reactor. It was studies the effects of coolant flow and of the distance among the coolant channels on these coefficients. The technique used to determine the mixture coefficients was to introduce a tracer (methylene blue) into the flow. The determination of the tracer concentration at the end of the channels was made by means of spectrophotometric analysis. (author)
Energy coefficients for a propeller series
DEFF Research Database (Denmark)
Olsen, Anders Smærup
2004-01-01
The efficiency for a propeller is calculated by energy coefficients. These coefficients are related to four types of losses, i.e. the axial, the rotational, the frictional, and the finite blade number loss, and one gain, i.e. the axial gain. The energy coefficients are derived by use...... of the potential theory with the propeller modelled as an actuator disk. The efficiency based on the energy coefficients is calculated for a propeller series. The results show a good agreement between the efficiency based on the energy coefficients and the efficiency obtained by a vortex-lattice method....
Index-free heat kernel coefficients
van de Ven, Anton E. M.
1998-08-01
Using index-free notation, we present the diagonal values 0264-9381/15/8/014/img1 of the first five heat kernel coefficients 0264-9381/15/8/014/img2 associated with a general Laplace-type operator on a compact Riemannian space without boundary. The fifth coefficient 0264-9381/15/8/014/img3 appears here for the first time. For the special case of a flat space, but with a gauge connection, the sixth coefficient is given too. Also provided are the leading terms for any coefficient, both in ascending and descending powers of the Yang-Mills and Riemann curvatures, to the same order as required for the fourth coefficient. These results are obtained by directly solving the relevant recursion relations, working in the Fock-Schwinger gauge and Riemann normal coordinates. Our procedure is thus non-covariant, but we show that for any coefficient the `gauged', respectively `curved', version is found from the corresponding `non-gauged', respectively `flat', coefficient by making some simple covariant substitutions. These substitutions being understood, the coefficients retain their `flat' form and size. In this sense the fifth and sixth coefficient have only 26 and 75 terms, respectively, allowing us to write them down. Using index-free notation also clarifies the general structure of the heat kernel coefficients. In particular, in flat space we find that from the fifth coefficient onward, certain scalars are absent. This may be relevant for the anomalies of quantum field theories in ten or more dimensions.
The effects of permeability and radiation on the stability of plane ...
African Journals Online (AJOL)
A study on the effects of permeability and radiation on Couette-Poiseuille flow stability was carried out. Solutions to the governing hydrodynamic equations was developed using the method of undetermined coefficients. On the basis of linear theory using analysis of normal modes, it was observed that both parameters, ...
Symmetry properties of macroscopic transport coefficients in porous media
Lasseux, D.; Valdés-Parada, F. J.
2017-04-01
We report on symmetry properties of tensorial effective transport coefficients characteristic of many transport phenomena in porous systems at the macroscopic scale. The effective coefficients in the macroscopic models (derived by upscaling (volume averaging) the governing equations at the underlying scale) are obtained from the solution of closure problems that allow passing the information from the lower to the upper scale. The symmetry properties of the macroscopic coefficients are identified from a formal analysis of the closure problems and this is illustrated for several different physical mechanisms, namely, one-phase flow in homogeneous porous media involving inertial effects, slip flow in the creeping regime, momentum transport in a fracture relying on the Reynolds model including slip effects, single-phase flow in heterogeneous porous media embedding a porous matrix and a clear fluid region, two-phase momentum transport in homogeneous porous media, as well as dispersive heat and mass transport. The results from the analysis of these study cases are summarized as follows. For inertial single-phase flow, the apparent permeability tensor is irreducibly decomposed into its symmetric (viscous) and skew-symmetric (inertial) parts; for creeping slip-flow, the apparent permeability tensor is not symmetric; for one-phase slightly compressible gas flow in the slip regime within a fracture, the effective transmissivity tensor is symmetric, a result that remains valid in the absence of slip; for creeping one-phase flow in heterogeneous media, the permeability tensor is symmetric; for two-phase flow, we found the dominant permeability tensors to be symmetric, whereas the coupling tensors do not exhibit any special symmetry property; finally for dispersive heat transfer, the thermal conductivity tensors include a symmetric and a skew-symmetric part, the latter being a consequence of convective transport only. A similar result is achieved for mass dispersion. Beyond the
DEFF Research Database (Denmark)
Jeong, Cheol-Ho; Chang, Ji-ho
2015-01-01
Absorption coefficients measured in reverberation chambers, Sabine absorption coefficients, suffer from two major problems. Firstly, they sometimes exceed unity. Secondly, the reproducibility of the Sabine absorption coefficients is quite poor, meaning that the Sabine absorption coefficients vary...... resistivity optimization outperforms the surface impedance optimization in terms of the reproducibility....
Viscous heating in fluids with temperature-dependent viscosity: implications for magma flows
Directory of Open Access Journals (Sweden)
A. Costa
2003-01-01
Full Text Available Viscous heating plays an important role in the dynamics of fluids with strongly temperature-dependent viscosity because of the coupling between the energy and momentum equations. The heat generated by viscous friction produces a local temperature increase near the tube walls with a consequent decrease of the viscosity which may dramatically change the temperature and velocity profiles. These processes are mainly controlled by the Peclét number, the Nahme number, the flow rate and the thermal boundary conditions. The problem of viscous heating in fluids was investigated in the past for its practical interest in the polymer industry, and was invoked to explain some rheological behaviours of silicate melts, but was not completely applied to study magma flows. In this paper we focus on the thermal and mechanical effects caused by viscous heating in tubes of finite lengths. We find that in magma flows at high Nahme number and typical flow rates, viscous heating is responsible for the evolution from Poiseuille flow, with a uniform temperature distribution at the inlet, to a plug flow with a hotter layer near the walls. When the temperature gradients induced by viscous heating are very pronounced, local instabilities may occur and the triggering of secondary flows is possible. For completeness, this paper also describes magma flow in infinitely long tubes both at steady state and in transient phase.
Energy Technology Data Exchange (ETDEWEB)
He, Fan [Beijing University of Civil Engineering and Architecture, Beijing (China); Hua, Lu; Gao, Li jian [Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (China)
2016-03-15
Blood flow distributions were evaluated using various computational strategies. Three commonly used wall conditions in arterial modeling were employed, namely rigid, dynamic and compliant walls. The results show that the velocity distributions are similar under rigid and dynamic walls, developing into the Poiseuille flow, but they are blunt under compliant walls. The peak pressure under rigid walls is highest, but the model of dynamic walls has a good approximation of pressure against the model of compliant walls. The results indicate that a model of compliant walls appears to be a computationally and reasonably accurate approximation of blood velocity distributions compared with the analysis under rigid or dynamic walls. Introducing fluid-structure interaction into arterial modeling is necessary to ensure reliable results and information. However, a model of dynamic walls seems to be a computationally inexpensive yet reasonably accurate approximation for pressure.
International Nuclear Information System (INIS)
Petrasch, Joerg; Meier, Fabian; Friess, Hansmartin; Steinfeld, Aldo
2008-01-01
A computer tomography based methodology is applied to determine the transport properties of fluid flow across porous media. A 3D digital representation of a 10-ppi reticulate porous ceramic (RPC) sample was generated by X-ray tomographic scans. Structural properties such as the porosity, specific interfacial surface area, pore-size distribution, mean survival time, two-point correlation function s 2 , and local geometry distribution of the RPC sample are directly extracted from the tomographic data. Reference solutions of the fluid flow governing equations are obtained for Re = 0.2-200 by applying finite volume direct pore-level numerical simulation (DPLS) using unstructured, body-fitted, tetrahedral mesh discretization. The permeability and the Dupuit-Forchheimer coefficient are determined from the reference solutions by DPLS, and compared to the values predicted by selected porous media flow models, namely: conduit-flow, hydraulic radius theory, drag models, mean survival time bound, s 2 -bound, fibrous bed correlations, and local porosity theory-based models. DPLS is further employed to determine the interfacial heat transfer coefficient and to derive a corresponding Nu-correlation, which is compared to empirical correlations
development of a new drag coefficient model for oil and gas
African Journals Online (AJOL)
eobe
In order to transport solid entrained multiphase fluids, especially through a pipeline, ... and design of multiphase processes especially when ... flow in pipeline. One challenge is that the drag coefficient cannot be expressed in an analytical form for a wide range of particle Reynolds numbers, because the flow condition during ...
Apparatus for measurement of coefficient of friction
Slifka, A. J.; Siegwarth, J. D.; Sparks, L. L.; Chaudhuri, Dilip K.
1990-01-01
An apparatus designed to measure the coefficient of friction in certain controlled atmospheres is described. The coefficient of friction observed during high-load tests was nearly constant, with an average value of 0.56. This value is in general agreement with that found in the literature and also with the initial friction coefficient value of 0.67 measured during self-mated friction of 440C steel in an oxygen environment.
Extended obstruction tensors and renormalized volume coefficients
Graham, C. Robin
2009-01-01
The behavior under conformal change of the renormalized volume coefficients associated to a pseudo-Riemannian metric is investigated. It is shown that they define second order fully nonlinear operators in the conformal factor whose algebraic structure is elucidated via the introduction of "extended obstruction tensors". These together with the Schouten tensor constitute building blocks for the coefficients in the ambient metric expansion. The renormalized volume coefficients have recently bee...
Index-free Heat Kernel Coefficients
van de Ven, Anton E. M.
1997-01-01
Using index-free notation, we present the diagonal values of the first five heat kernel coefficients associated with a general Laplace-type operator on a compact Riemannian space without boundary. The fifth coefficient appears here for the first time. For a flat space with a gauge connection, the sixth coefficient is given too. Also provided are the leading terms for any coefficient, both in ascending and descending powers of the Yang-Mills and Riemann curvatures, to the same order as require...
Comparing linear probability model coefficients across groups
DEFF Research Database (Denmark)
Holm, Anders; Ejrnæs, Mette; Karlson, Kristian Bernt
2015-01-01
This article offers a formal identification analysis of the problem in comparing coefficients from linear probability models between groups. We show that differences in coefficients from these models can result not only from genuine differences in effects, but also from differences in one or more...... of the following three components: outcome truncation, scale parameters and distributional shape of the predictor variable. These results point to limitations in using linear probability model coefficients for group comparisons. We also provide Monte Carlo simulations and real examples to illustrate...... these limitations, and we suggest a restricted approach to using linear probability model coefficients in group comparisons....
Regression Models for Predicting Force Coefficients of Aerofoils
Directory of Open Access Journals (Sweden)
Mohammed ABDUL AKBAR
2015-09-01
Full Text Available Renewable sources of energy are attractive and advantageous in a lot of different ways. Among the renewable energy sources, wind energy is the fastest growing type. Among wind energy converters, Vertical axis wind turbines (VAWTs have received renewed interest in the past decade due to some of the advantages they possess over their horizontal axis counterparts. VAWTs have evolved into complex 3-D shapes. A key component in predicting the output of VAWTs through analytical studies is obtaining the values of lift and drag coefficients which is a function of shape of the aerofoil, ‘angle of attack’ of wind and Reynolds’s number of flow. Sandia National Laboratories have carried out extensive experiments on aerofoils for the Reynolds number in the range of those experienced by VAWTs. The volume of experimental data thus obtained is huge. The current paper discusses three Regression analysis models developed wherein lift and drag coefficients can be found out using simple formula without having to deal with the bulk of the data. Drag coefficients and Lift coefficients were being successfully estimated by regression models with R2 values as high as 0.98.
Directory of Open Access Journals (Sweden)
Yari Ehsan
2016-04-01
Full Text Available The paper mainly aims to study computation of added mass coefficients for marine propellers. A three-dimensional boundary element method (BEM is developed to predict the propeller added mass and moment of inertia coefficients. Actually, only few experimental data sets are available as the validation reference. Here the method is validated with experimental measurements of the B-series marine propeller. The behavior of the added mass coefficients predicted based on variation of geometric and flow parameters of the propeller is calculated and analyzed. BEM is more accurate in obtaining added mass coefficients than other fast numerical methods. All added mass coefficients are nondimensionalized by fluid density, propeller diameter, and rotational velocity. The obtained results reveal that the diameter, expanded area ratio, and thickness have dominant influence on the increase of the added mass coefficients.
Boiling flow through diverging microchannel
Indian Academy of Sciences (India)
Effect of mass flux (118–1182 kg/m2-s) and heat flux (1.6–19.2 W/cm2) on single and two-phase pressure drop and average heat transfer coefficient has been studied. Concurrently, flow visualization is carried out to document the various flow regimes and to correlate the pressure drop and average heat transfer coefficient ...
Derivation of stable Burnett equations for rarefied gas flows.
Singh, Narendra; Jadhav, Ravi Sudam; Agrawal, Amit
2017-07-01
A set of constitutive relations for the stress tensor and heat flux vector for the hydrodynamic description of rarefied gas flows is derived in this work. A phase density function consistent with Onsager's reciprocity principle and H theorem is utilized to capture nonequilibrium thermodynamics effects. The phase density function satisfies the linearized Boltzmann equation and the collision invariance property. Our formulation provides the correct value of the Prandtl number as it involves two different relaxation times for momentum and energy transport by diffusion. Generalized three-dimensional constitutive equations for different kinds of molecules are derived using the phase density function. The derived constitutive equations involve cross single derivatives of field variables such as temperature and velocity, with no higher-order derivative in higher-order terms. This is remarkable feature of the equations as the number of boundary conditions required is the same as needed for conventional Navier-Stokes equations. Linear stability analysis of the equations is performed, which shows that the derived equations are unconditionally stable. A comparison of the derived equations with existing Burnett-type equations is presented and salient features of our equations are outlined. The classic internal flow problem, force-driven compressible plane Poiseuille flow, is chosen to verify the stable Burnett equations and the results for equilibrium variables are presented.
Probability based calibration of pressure coefficients
DEFF Research Database (Denmark)
Hansen, Svend Ole; Pedersen, Marie Louise; Sørensen, John Dalsgaard
2015-01-01
.3, the Eurocode partial factor of 1.5 for variable actions agrees well with the inherent uncertainties of wind actions when the pressure coefficients are determined using wind tunnel test results. The increased bias and uncertainty when pressure coefficients mainly are based on structural codes lead to a larger...
Problems with Discontinuous Diffusion/Dispersion Coefficients
Directory of Open Access Journals (Sweden)
Stefano Ferraris
2012-01-01
accurate on smooth solutions and based on a special numerical treatment of the diffusion/dispersion coefficients that makes its application possible also when such coefficients are discontinuous. Numerical experiments confirm the convergence of the numerical approximation and show a good behavior on a set of benchmark problems in two space dimensions.
Parabolic by Shilov systems with variable coefficients
Directory of Open Access Journals (Sweden)
V. A. Litovchenko
2017-12-01
Full Text Available Because of the parabolic instability of the Shilov systems to change their coefficients, the definition parabolicity of Shilov for systems with time-dependent $t$ coefficients, unlike the definition parabolicity of Petrovsky, is formulated by imposing conditions on the matricant of corresponding dual by Fourier system. For parabolic systems by Petrovsky with time-dependent coefficients, these conditions are the property of a matricant, which follows directly from the definition of parabolicity. In connection with this, the question of the wealth of the class Shilov systems with time-dependent coefficients is important.A new class of linear parabolic systems with partial derivatives to the first order by the time $t$ with time-dependent coefficients is considered in this work. It covers the class by Petrovsky systems with time-dependent younger coefficients. A main part of differential expression of each such system is parabolic (by Shilov expression with constant coefficients. The fundamental solution of the Cauchy problem for systems of this class is constructed by the Fourier transform method. Also proved their parabolicity by Shilov. Only the structure of the system and the conditions on the eigenvalues of the matrix symbol were used. First of all, this class characterizes the wealth by Shilov class of systems with time-dependents coefficients.Also it is given a general method for investigating a fundamental solution of the Cauchy problem for Shilov parabolic systems with positive genus, which is the development of the well-known method of Y.I. Zhitomirskii.
A gain-coefficient switched Alexandrite laser
International Nuclear Information System (INIS)
Lee, Chris J; Van der Slot, Peter J M; Boller, Klaus-J
2013-01-01
We report on a gain-coefficient switched Alexandrite laser. An electro-optic modulator is used to switch between high and low gain states by making use of the polarization dependent gain of Alexandrite. In gain-coefficient switched mode, the laser produces 85 ns pulses with a pulse energy of 240 mJ at a repetition rate of 5 Hz.
Coefficient Alpha Bootstrap Confidence Interval under Nonnormality
Padilla, Miguel A.; Divers, Jasmin; Newton, Matthew
2012-01-01
Three different bootstrap methods for estimating confidence intervals (CIs) for coefficient alpha were investigated. In addition, the bootstrap methods were compared with the most promising coefficient alpha CI estimation methods reported in the literature. The CI methods were assessed through a Monte Carlo simulation utilizing conditions…
Regularity of the interband light absorption coefficient
Indian Academy of Sciences (India)
In experimental studies the absorption coefficient is a means to study the band gaps at ... to l2( ), where. ⊂ Zd is a finite set. (usually taken to be a lattice cube centred at the origin) and λ±,uλ± are eigenvalues and eigenfunctions of H. ±. ,ω . Then the interband light absorption coefficient A for such finite volume models can.
Helioseismic Solar Cycle Changes and Splitting Coefficients
Indian Academy of Sciences (India)
tribpo
Abstract. Using the GONG data for a period over four years, we have studied the variation of frequencies and splitting coefficients with solar cycle. Frequencies and even-order coefficients are found to change signi- ficantly with rising phase of the solar cycle. We also find temporal varia- tions in the rotation rate near the solar ...
Determination of the surface drag coefficient
DEFF Research Database (Denmark)
Mahrt, L.; Vickers, D.; Sun, J.L.
2001-01-01
This study examines the dependence of the surface drag coefficient on stability, wind speed, mesoscale modulation of the turbulent flux and method of calculation of the drag coefficient. Data sets over grassland, sparse grass, heather and two forest sites are analyzed. For significantly unstable ...
Implications of NGA for NEHRP site coefficients
Borcherdt, Roger D.
2012-01-01
Three proposals are provided to update tables 11.4-1 and 11.4-2 of Minimum Design Loads for Buildings and Other Structures (7-10), by the American Society of Civil Engineers (2010) (ASCE/SEI 7-10), with site coefficients implied directly by NGA (Next Generation Attenuation) ground motion prediction equations (GMPEs). Proposals include a recommendation to use straight-line interpolation to infer site coefficients at intermediate values of ̅vs (average shear velocity). Site coefficients are recommended to ensure consistency with ASCE/SEI 7-10 MCER (Maximum Considered Earthquake) seismic-design maps and simplified site-specific design spectra procedures requiring site classes with associated tabulated site coefficients and a reference site class with unity site coefficients. Recommended site coefficients are confirmed by independent observations of average site amplification coefficients inferred with respect to an average ground condition consistent with that used for the MCER maps. The NGA coefficients recommended for consideration are implied directly by the NGA GMPEs and do not require introduction of additional models.
Gini coefficient as a life table function
Directory of Open Access Journals (Sweden)
2003-06-01
Full Text Available This paper presents a toolkit for measuring and analyzing inter-individual inequality in length of life by Gini coefficient. Gini coefficient and four other inequality measures are defined on the length-of-life distribution. Properties of these measures and their empirical testing on mortality data suggest a possibility for different judgements about the direction of changes in the degree of inequality by using different measures. A new computational procedure for the estimation of Gini coefficient from life tables is developed and tested on about four hundred real life tables. The estimates of Gini coefficient are precise enough even for abridged life tables with the final age group of 85+. New formulae have been developed for the decomposition of differences between Gini coefficients by age and cause of death. A new method for decomposition of age-components into effects of mortality and composition of population by group is developed. Temporal changes in the effects of elimination of causes of death on Gini coefficient are analyzed. Numerous empirical examples show: Lorenz curves for Sweden, Russia and Bangladesh in 1995, proportional changes in Gini coefficient and four other measures of inequality for the USA in 1950-1995 and for Russia in 1959-2000. Further shown are errors of estimates of Gini coefficient when computed from various types of mortality data of France, Japan, Sweden and the USA in 1900-95, decompositions of the USA-UK difference in life expectancies and Gini coefficients by age and cause of death in 1997. As well, effects of elimination of major causes of death in the UK in 1951-96 on Gini coefficient, age-specific effects of mortality and educational composition of the Russian population on changes in life expectancy and Gini coefficient between 1979 and 1989. Illustrated as well are variations in life expectancy and Gini coefficient across 32 countries in 1996-1999 and associated changes in life expectancy and Gini
Experimental approach for measuring cylindrical flexoelectric coefficients
Zhang, Shuwen; Liu, Kaiyuan; Wu, Tonghui; Xu, Minglong; Shen, Shengping
2017-10-01
Flexoelectricity is a property of dielectric materials by which applied strain gradients induce electric polarizations within dielectric materials. Experimental research into the tensor components of the flexoelectric coefficient is essential. In this work, an experimental approach for measurement of the flexoelectric coefficient tensor components in cylindrical coordinates is developed. Two different experimental methods are designed to obtain the two related unknown flexoelectric coefficient tensor components. Theoretical and finite element analyses are developed and simplified for each experiment, and the related designs are then tested to obtain the coupled electric polarization charges. The two unknown flexoelectric coefficient tensor components of polyvinylidene fluoride are then decoupled. This work provides an experimental method that can be used to obtain multiple unknown flexoelectric coefficient tensor components in solid dielectric materials.
Laser alteration of accommodation coefficient for isotope separation
International Nuclear Information System (INIS)
Keck, J.C.
1976-01-01
This patent describes a method and an apparatus for separating isotope types by inducing an isotopically selective vibrational excitation of molecules containing at least one atom of the element type whose isotopes are to be separated. Vibrational excitation is induced in the molecules by finely tuned, narrow bandwidth laser radiation applied to a gaseous flow of the molecules. Isotopic separation of the molecules is achieved from the enhanced difference in diffusion rates for the molecules due to an alteration of the accommodation coefficients in the excited molecules. 40 claims, 4 figures
Measurements of the gaseous multiplication coefficient in pure isobutane
Energy Technology Data Exchange (ETDEWEB)
Lima, Iara B.; Vivaldini, Tulio C.; Goncalves, Josemary A.C.; Botelho, Suzana; Tobias, Carmen C.B., E-mail: ccbueno@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Ridenti, Marco A.; Pascholati, Paulo R. [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Fisica. Lab. do Acelerador Linear; Fonte, Paulo; Mangiarotti, Alessio [Universidade de Coimbra (Portugal). Dept de Fisica. Lab. de Instrumentacao e Fisica Experimental de Particulas
2009-07-01
In this work we present the preliminary studies of the first Townsend coefficient behavior in isobutane for reduced electric fields ranging from 173 Td up to 281 Td by means of signal amplitude analysis. The measurements were based on the Pulsed Townsend technique. The experimental setup consists of two parallel plates housed in a stainless steel chamber at gas flow regime. In our configuration, the primary electrons are produced by irradiating the cathode with a fast nitrogen laser (700 ps pulse duration). In order to validate the technique and to analyze effects of non-uniformity, results for nitrogen are also presented. (author)
Measurements of the gaseous multiplication coefficient in pure isobutane
International Nuclear Information System (INIS)
Lima, Iara B.; Vivaldini, Tulio C.; Goncalves, Josemary A.C.; Botelho, Suzana; Tobias, Carmen C.B.; Ridenti, Marco A.; Pascholati, Paulo R.; Fonte, Paulo; Mangiarotti, Alessio
2009-01-01
In this work we present the preliminary studies of the first Townsend coefficient behavior in isobutane for reduced electric fields ranging from 173 Td up to 281 Td by means of signal amplitude analysis. The measurements were based on the Pulsed Townsend technique. The experimental setup consists of two parallel plates housed in a stainless steel chamber at gas flow regime. In our configuration, the primary electrons are produced by irradiating the cathode with a fast nitrogen laser (700 ps pulse duration). In order to validate the technique and to analyze effects of non-uniformity, results for nitrogen are also presented. (author)
Energy Technology Data Exchange (ETDEWEB)
Takebe, Shinichi; Abe, Masayoshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
2001-03-01
The distribution coefficient is very important parameter for environmental impact assessment on the disposal of radioactive waste arising from research institutes. The literature survey in the country was mainly carried out for the purpose of selecting the reasonable distribution coefficient value on the utilization of this value in the safety evaluation. This report was arranged much informations on the distribution coefficient for inputting to the database for each literature, and was summarized as a literature information data on the distribution coefficient. (author)
Variation in aerodynamic coefficients with altitude
Directory of Open Access Journals (Sweden)
Faiza Shahid
Full Text Available Precise aerodynamics performance prediction plays key role for a flying vehicle to get its mission completed within desired accuracy. Aerodynamic coefficients for same Mach number can be different at different altitude due to difference in Reynolds number. Prediction of these aerodynamics coefficients can be made through experiments, analytical solution or Computational Fluid Dynamics (CFD. Advancements in computational power have generated the concept of using CFD as a virtual Wind Tunnel (WT, hence aerodynamic performance prediction in present study is based upon CFD (numerical test rig. Simulations at different altitudes for a range of Mach numbers with zero angle of attack are performed to predict axial force coefficient behavior with altitude (Reynolds number. Similar simulations for a fixed Mach number â3â and a range of angle of attacks are also carried out to envisage the variation in normal force and pitching moment coefficients with altitude (Reynolds number. Results clearly depict that the axial force coefficient is a function of altitude (Reynolds number and increase as altitude increases, especially for subsonic region. Variation in axial force coefficient with altitude (Reynolds number slightly increases for larger values of angle of attacks. Normal force and pitching moment coefficients do not depend on altitude (Reynolds number at smaller values of angle of attacks but show slight decrease as altitude increases. Present study suggests that variation of normal force and pitching moment coefficients with altitude can be neglected but the variation of axial force coefficient with altitude should be considered for vehicle fly in dense atmosphere. It is recommended to continue this study to more complex configurations for various Mach numbers with side slip and real gas effects. Keywords: Mach number, Reynolds number, Blunt body, Altitude effect, Angle of attacks
Variation in aerodynamic coefficients with altitude
Shahid, Faiza; Hussain, Mukkarum; Baig, Mirza Mehmood; Haq, Ihtram ul
Precise aerodynamics performance prediction plays key role for a flying vehicle to get its mission completed within desired accuracy. Aerodynamic coefficients for same Mach number can be different at different altitude due to difference in Reynolds number. Prediction of these aerodynamics coefficients can be made through experiments, analytical solution or Computational Fluid Dynamics (CFD). Advancements in computational power have generated the concept of using CFD as a virtual Wind Tunnel (WT), hence aerodynamic performance prediction in present study is based upon CFD (numerical test rig). Simulations at different altitudes for a range of Mach numbers with zero angle of attack are performed to predict axial force coefficient behavior with altitude (Reynolds number). Similar simulations for a fixed Mach number '3' and a range of angle of attacks are also carried out to envisage the variation in normal force and pitching moment coefficients with altitude (Reynolds number). Results clearly depict that the axial force coefficient is a function of altitude (Reynolds number) and increase as altitude increases, especially for subsonic region. Variation in axial force coefficient with altitude (Reynolds number) slightly increases for larger values of angle of attacks. Normal force and pitching moment coefficients do not depend on altitude (Reynolds number) at smaller values of angle of attacks but show slight decrease as altitude increases. Present study suggests that variation of normal force and pitching moment coefficients with altitude can be neglected but the variation of axial force coefficient with altitude should be considered for vehicle fly in dense atmosphere. It is recommended to continue this study to more complex configurations for various Mach numbers with side slip and real gas effects.
Reshadi, Milad; Saidi, Mohammad Hassan; Ebrahimi, Abbas
2017-04-01
This paper presents an analysis of the combined electro-osmotic and pressure-driven axial flows of viscoelastic fluids in a rectangular microchannel with arbitrary aspect ratios. The rheological behavior of the fluid is described by the complete form of Phan-Thien-Tanner (PTT) model with the Gordon-Schowalter convected derivative which covers the upper convected Maxwell, Johnson-Segalman and FENE-P models. Our numerical simulation is based on the computation of 2D Poisson-Boltzmann, Cauchy momentum and PTT constitutive equations. The solution of these governing nonlinear coupled set of equations is obtained by using the second-order central finite difference method in a non-uniform grid system and is verified against 1D analytical solution of the velocity profile with less than 0.06% relative error. Also, a parametric study is carried out to investigate the effect of channel aspect ratio (width to height), wall zeta potential and the Debye-Hückel parameter on 2D velocity profile, volumetric flow rate and the Poiseuille number in the mixed EO/PD flows of viscoelastic fluids with different Weissenberg numbers. Our results show that, for low channel aspect ratios, the previous 1D analytical models underestimate the velocity profile at the channel half-width centerline in the case of favorable pressure gradients and overestimate it in the case of adverse pressure gradients. The results reveal that the inapplicability of the Debye-Hückel approximation at high zeta potentials is more significant for higher Weissenberg number fluids. Also, it is found that, under the specified values of electrokinetic parameters, there is a threshold for velocity scale ratio in which the Poiseuille number is approximately independent of channel aspect ratio.
Reshadi, Milad; Saidi, Mohammad Hassan; Ebrahimi, Abbas
2018-02-01
This paper presents an analysis of the combined electro-osmotic and pressure-driven axial flows of viscoelastic fluids in a rectangular microchannel with arbitrary aspect ratios. The rheological behavior of the fluid is described by the complete form of Phan-Thien-Tanner (PTT) model with the Gordon-Schowalter convected derivative which covers the upper convected Maxwell, Johnson-Segalman and FENE-P models. Our numerical simulation is based on the computation of 2D Poisson-Boltzmann, Cauchy momentum and PTT constitutive equations. The solution of these governing nonlinear coupled set of equations is obtained by using the second-order central finite difference method in a non-uniform grid system and is verified against 1D analytical solution of the velocity profile with less than 0.06% relative error. Also, a parametric study is carried out to investigate the effect of channel aspect ratio (width to height), wall zeta potential and the Debye-Hückel parameter on 2D velocity profile, volumetric flow rate and the Poiseuille number in the mixed EO/PD flows of viscoelastic fluids with different Weissenberg numbers. Our results show that, for low channel aspect ratios, the previous 1D analytical models underestimate the velocity profile at the channel half-width centerline in the case of favorable pressure gradients and overestimate it in the case of adverse pressure gradients. The results reveal that the inapplicability of the Debye-Hückel approximation at high zeta potentials is more significant for higher Weissenberg number fluids. Also, it is found that, under the specified values of electrokinetic parameters, there is a threshold for velocity scale ratio in which the Poiseuille number is approximately independent of channel aspect ratio.
Soccer ball lift coefficients via trajectory analysis
Energy Technology Data Exchange (ETDEWEB)
Goff, John Eric [Department of Physics, Lynchburg College, Lynchburg, VA 24501 (United States); Carre, Matt J, E-mail: goff@lynchburg.ed [Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)
2010-07-15
We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin parameters that have not been obtained by today's wind tunnels. Our trajectory analysis technique is not only a valuable tool for professional sports scientists, it is also accessible to students with a background in undergraduate-level classical mechanics.
Divergence-free smoothing for MRV data on stenosed carotid artery phantom flows
Im, Chaehyuk; Ko, Seungbin; Song, Simon
2017-11-01
Magnetic Resonance Velocimetry (MRV) is a versatile technique for measuring flow velocity using an MRI machine. It is frequently used for visualization and analysis of blood flows. However, it is difficult to accurately estimate hemodynamics parameters like wall shear stress (WSS) and oscillatory shear index (OSI) due to its low spatial resolution and low signal-to-noise ratio. We suggest a divergence-free smoothing (DFS) method to correct the erroneous velocity vectors obtained with MRV and improve the estimation accuracy of those parameters. Unlike previous studies on DFS for a wall-free flow, we developed a house code to apply a DFS method to a wall-bounded flow. A Hagen-Poiseuille flow and stenosed carotid artery phantom flows were measured with MRV. Each of them was analyzed for validation of the DFS code and confirmation on the accuracy improvement of hemodynamic parameters. We will discuss the effects of DFS on the improvement of the estimation accuracy of velocity vectors, WSS, OSI and etc in detail This work was supported by the National Research Foundation of Korea(NRF) Grant funded by the Korea government(MSIP) (No. 2016R1A2B3009541).
Determination of heat transfer coefficient between a fluid and a wall
International Nuclear Information System (INIS)
Petit, D.; Dard, J.; Degiovanni, A.
1981-01-01
The authors show the extent to which one can assume the existence of a constant heat transfer coefficient between a fluid and a wall in transient thermal conditions, and the means of estimating it. After reviewing investigations reported in the literature (coefficient assumed constant or not), they present two models based on a pulse method: sudden increase in wall temperature, cooling by fluid flow, temperature recording of the wall face not in contact with the fluid-wether or not the fluid is heated. They present the experimental system, define the tranfer coefficient, and make the calculation from the thermogram obtained. For water and air, they analyze the variations in coefficient as a function of fluid flow rate, initial pulse, temperature detector position, and show that the method proposed yields reproducible results [fr
Transport Coefficients from Large Deviation Functions
Directory of Open Access Journals (Sweden)
Chloe Ya Gao
2017-10-01
Full Text Available We describe a method for computing transport coefficients from the direct evaluation of large deviation functions. This method is general, relying on only equilibrium fluctuations, and is statistically efficient, employing trajectory based importance sampling. Equilibrium fluctuations of molecular currents are characterized by their large deviation functions, which are scaled cumulant generating functions analogous to the free energies. A diffusion Monte Carlo algorithm is used to evaluate the large deviation functions, from which arbitrary transport coefficients are derivable. We find significant statistical improvement over traditional Green–Kubo based calculations. The systematic and statistical errors of this method are analyzed in the context of specific transport coefficient calculations, including the shear viscosity, interfacial friction coefficient, and thermal conductivity.
Friction coefficient dependence on electrostatic tribocharging.
Burgo, Thiago A L; Silva, Cristiane A; Balestrin, Lia B S; Galembeck, Fernando
2013-01-01
Friction between dielectric surfaces produces patterns of fixed, stable electric charges that in turn contribute electrostatic components to surface interactions between the contacting solids. The literature presents a wealth of information on the electronic contributions to friction in metals and semiconductors but the effect of triboelectricity on friction coefficients of dielectrics is as yet poorly defined and understood. In this work, friction coefficients were measured on tribocharged polytetrafluoroethylene (PTFE), using three different techniques. As a result, friction coefficients at the macro- and nanoscales increase many-fold when PTFE surfaces are tribocharged, but this effect is eliminated by silanization of glass spheres rolling on PTFE. In conclusion, tribocharging may supersede all other contributions to macro- and nanoscale friction coefficients in PTFE and probably in other insulating polymers.
Explicit formulas for Clebsch-Gordan coefficients
International Nuclear Information System (INIS)
Rudnicki-Bujnowski, G.
1975-01-01
The problem is to obtain explicit algebraic formulas of Clebsch-Gordan coefficients for high values of angular momentum. The method of solution is an algebraic method based on the Racah formula using the FORMAC programming language. (Auth.)
Heat transfer coefficient of cryotop during freezing.
Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J
2013-01-01
Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).
Form coefficient of helical toroidal solenoids
International Nuclear Information System (INIS)
Amelin, V.Z.; Kunchenko, V.B.
1982-01-01
For toroidal solenoids with continuous spiral coil, winded according to the laws of equiinclined and simple cylindrical spirals with homogeneous, linearly increasing to the coil periphery and ''Bitter'' distribution of current density, the analytical expressions for the dependence between capacity consumed and generated magnetic field, expressions for coefficients of form similar to Fabry coefficient for cylindrical solenoids are obtained and dependence of the form coefficient and relative volume of solenoid conductor on the number of revolutions of screw line per one circumvention over the large torus radius is also investigated. Analytical expressions of form coefficients and graphical material permit to select the optimum geometry as to capacity consumed both for spiral (including ''force-free'') and conventional toroidal solenoids of magnetic systems in thermonulear installations
Modeling Ballasted Tracks for Runoff Coefficient C
2012-08-01
In this study, the Regional Transportation District (RTD)s light rail tracks were modeled to determine the Rational Method : runoff coefficient, C, values corresponding to ballasted tracks. To accomplish this, a laboratory study utilizing a : rain...
Estimation of Okun Coefficient for Algeria
KORI YAHIA, Abdellah
2018-01-01
The objective of this paper is to investigate the presence of Okun’s (1962) relationship for Algeria for the 1970- 2015 period. Two methodologies are employed to estimate the Okun coefficient: An Autoregressive Distributed Lag (ARDL) linear model and a Bayesian Normal Linear Regression model. The results indicate an Okun coefficient of about -0.2 which suggests some rigidity of the labour market in Algeria.
Measuring Resource Inequality: The Gini Coefficient
Directory of Open Access Journals (Sweden)
Michael T. Catalano
2009-07-01
Full Text Available This paper stems from work done by the authors at the Mathematics for Social Justice Workshop held in June of 2007 at Middlebury College. We provide a description of the Gini coefficient and some discussion of how it can be used to promote quantitative literacy skills in mathematics courses. The Gini Coefficient was introduced in 1921 by Italian statistician Corrado Gini as a measure of inequality. It is defined as twice the area between two curves. One, the Lorenz curve for a given population with respect to a given resource, represents the cumulative percentage of the resource as a function of the cumulative percentage of the population that shares that percentage of the resource. The second curve is the line y = x which is the Lorenz curve for a population which shares the resource equally. The Gini coefficient can be interpreted as the percentage of inequality represented in the population with respect to the given resource. We propose that the Gini coefficient can be used to enhance students’ understanding of calculus concepts and provide practice for students in using both calculus and quantitative literacy skills. Our examples are based mainly on distribution of energy resources using publicly available data from the Energy Information Agency of the United States Government. For energy resources within the United States, we find that by household, the Gini coefficient is 0.346, while using the 51 data points represented by the states and Washington D.C., the Gini coefficient is 0.158. When we consider the countries of the world as a population of 210, the Gini coefficient is 0.670. We close with ideas for questions which can be posed to students and discussion of the experiences two other mathematics instructors have had incorporating the Gini coefficient into pre-calculus-level mathematics classes.
Experimental heat transfer coefficients between a surface and fixed and fluidized beds with PCM
Izquierdo-Barrientos, María Asunción; Sobrino, Celia; Almendros-Ibáñez, José Antonio
2015-01-01
This work presents an experimental study to determine the capacity of a phase change material (PCM) in granular form to be used in fixed and bubbling fluidized beds for thermal energy storage. The experimental measurements are focused on determination of the heat transfer coefficient between a heated surface immersed in the bed and the granular PCM. The flow rate is varied to quantify its influence on the heat transfer coefficient. The PCM used is Rubitherm GR50 with a phase change tem...
Sharp Spectral Asymptotics and Weyl Formula for Elliptic Operators with Non-smooth Coefficients
International Nuclear Information System (INIS)
Zielinski, Lech
1999-01-01
The aim of this paper is to give the Weyl formula for eigenvalues of self-adjoint elliptic operators, assuming that first-order derivatives of the coefficients are Lipschitz continuous. The approach is based on the asymptotic formula of Hoermander''s type for the spectral function of pseudo differential operators having Lipschitz continuous Hamiltonian flow and obtained via a regularization procedure of nonsmooth coefficients
Sharp Spectral Asymptotics and Weyl Formula for Elliptic Operators with Non-smooth Coefficients
Energy Technology Data Exchange (ETDEWEB)
Zielinski, Lech [Universite Paris 7 (D. Diderot), Institut de Mathematiques de Paris-Jussieu UMR9994 (France)
1999-09-15
The aim of this paper is to give the Weyl formula for eigenvalues of self-adjoint elliptic operators, assuming that first-order derivatives of the coefficients are Lipschitz continuous. The approach is based on the asymptotic formula of Hoermander''s type for the spectral function of pseudo differential operators having Lipschitz continuous Hamiltonian flow and obtained via a regularization procedure of nonsmooth coefficients.
Boiling flow through diverging microchannel
Indian Academy of Sciences (India)
118–. 1182 kg/m2-s) and heat flux (1.6–19.2 W/cm2) on single and two-phase pressure drop and average heat transfer coefficient has been studied. Concurrently, flow visu- alization is carried out to document the various flow regimes and to ...
Monitoring device for local power peaking coefficient
International Nuclear Information System (INIS)
Mitsuhashi, Ishi
1987-01-01
Purpose: To monitor the local power peaking coefficients obtained by the method not depending on the combination of fuel types. Method: A plurality of representative values for the local power distribution determined by the nuclear constant calculation for one fuel assembly are memorized regarding each of the burn-up degree and the void coefficient on every positions and fuel types in fuel rod assemblies. While on the other hand, the representative values for the local power distribution as described above are compensated by a compensation coefficient considering the effect of adjacent segments and a control rod compensation coefficient considering the effect due to the control rod insertion relative to the just-mentioned compensation coefficient. Then, the maximum value among them is selected to determine the local power peaking coefficient at each of the times and each of the segments, which is monitored. According to this system, the calculation and the working required for the fitting work depending on the combination of fuel types are no more required at all to facilitate the maintenance as well. (Horiuchi, T.)
Analytical model of reactive transport processes with spatially variable coefficients.
Simpson, Matthew J; Morrow, Liam C
2015-05-01
Analytical solutions of partial differential equation (PDE) models describing reactive transport phenomena in saturated porous media are often used as screening tools to provide insight into contaminant fate and transport processes. While many practical modelling scenarios involve spatially variable coefficients, such as spatially variable flow velocity, v(x), or spatially variable decay rate, k(x), most analytical models deal with constant coefficients. Here we present a framework for constructing exact solutions of PDE models of reactive transport. Our approach is relevant for advection-dominant problems, and is based on a regular perturbation technique. We present a description of the solution technique for a range of one-dimensional scenarios involving constant and variable coefficients, and we show that the solutions compare well with numerical approximations. Our general approach applies to a range of initial conditions and various forms of v(x) and k(x). Instead of simply documenting specific solutions for particular cases, we present a symbolic worksheet, as supplementary material, which enables the solution to be evaluated for different choices of the initial condition, v(x) and k(x). We also discuss how the technique generalizes to apply to models of coupled multispecies reactive transport as well as higher dimensional problems.
In-situ measurement of electroosmotic drag coefficient in Nafion membrane for the PEMFC.
Peng, Zhe; Morin, Arnaud; Huguet, Patrice; Schott, Pascal; Pauchet, Joël
2011-11-10
A new method based on hydrogen pump has been developed to measure the electroosmotic drag coefficient in representative PEMFC operating conditions. It allows eliminating the back-flow of water which leads to some errors in the calculation of this coefficient with previously reported electrochemical methods. Measurements have been performed on 50 μm thick Nafion membranes both extruded and recast. Contrary to what has been described in most of previous published works, the electroosmotic drag coefficient decreases as the membrane water content increases. The same trend is observed for temperatures between 25 and 80 °C. For the same membrane water content, the electroosmotic drag coefficient increases with temperature. In the same condition, there is no difference in drag coefficient for extruded Nafion N112 and recast Nafion NRE212. These results are discussed on the basis of the two commonly accepted proton transport mechanisms, namely, Grotthus and vehicular.
Estimating subcatchment runoff coefficients using weather radar and a downstream runoff sensor.
Ahm, Malte; Thorndahl, Søren; Rasmussen, Michael R; Bassø, Lene
2013-01-01
This paper presents a method for estimating runoff coefficients of urban drainage subcatchments based on a combination of high resolution weather radar data and flow measurements from a downstream runoff sensor. By utilising the spatial variability of the precipitation it is possible to estimate the runoff coefficients of the separate subcatchments. The method is demonstrated through a case study of an urban drainage catchment (678 ha) located in the city of Aarhus, Denmark. The study has proven that it is possible to use corresponding measurements of the relative rainfall distribution over the catchment and downstream runoff measurements to identify the runoff coefficients at subcatchment level.
Qian, Tiezheng
2009-10-29
This paper starts with an introduction to the Onsager principle of minimum energy dissipation which governs the optimal paths of deviation and restoration to equilibrium. Then there is a review of the variational approach to moving contact line hydrodynamics. To demonstrate the validity of our continuum hydrodynamic model, numerical results from model calculations and molecular dynamics simulations are presented for immiscible Couette and Poiseuille flows past homogeneous solid surfaces, with remarkable overall agreement. Our continuum model is also used to study the contact line motion on surfaces patterned with stripes of different contact angles (i.e. surfaces of varying wettability). Continuum calculations predict the stick-slip motion for contact lines moving along these patterned surfaces, in quantitative agreement with molecular dynamics simulation results. This periodic motion is tunable through pattern period (geometry) and contrast in wetting property (chemistry). The consequence of stick-slip contact line motion on energy dissipation is discussed. © 2009 IOP Publishing Ltd.
Absorption coefficients for water vapor at 193 nm from 300 to 1073 K
Kessler, W. J.; Carleton, K. L.; Marinelli, W. J.
1993-01-01
Measurements of the water absorption coefficient at 193 nm from 300 to 1073 K are reported. The measurements were made using broadband VUV radiation and a monochromator-based detection system. The water vapor was generated by a saturator and metered into a flowing, 99 cm absorption cell via a water vapor mass flow meter. The 193 nm absorption coefficient measurements are compared to room temperature and high temperature shock tube measurements with good agreement. The absorption can be parameterized by a nu3 vibrational mode reaction coordinate and the thermal population of the nu3 mode.
Determination of re-aeration coefficients on high mountain rivers using nuclear techniques
International Nuclear Information System (INIS)
Fajardo, Marco
2001-01-01
The rivers Machangara and Guayllabamba in Quito, Ecuador, currently are highly polluted, mainly due to human and industrial residues from the city. The objective of this survey is to establish the dynamics of dissolved oxygen in these rivers using the Krypton 85 method to determine the re aeration coefficient in representative sectors of the rivers. In addition, conventional test tracers establish mean flow speed and flow longitudinal dispersion coefficients. The results of this study will be useful for future water quality modelling of these rivers, in order to define their behaviour and auto depurative capacity to treat sludge waters from Quito
International Nuclear Information System (INIS)
Picanco, Marco Antonio Silva; Bandarra Filho, Enio Pedone; Passos, Julio Cesar
2006-01-01
Two-phase flow heat transfer has been exhaustively studied over recent years. However, in this field several questions remain unanswered. Heat transfer coefficient prediction related to nucleate and convective boiling have been studied using different approaches, numerical, analytical and experimental. In this work, an experimental analysis, data representation and heat transfer coefficient prediction on two-phase heat transfer on nucleate and convective boiling are presented. An empirical correlation is obtained based on genetic algorithms search engine over a dimensional analysis of the two-phase flow heat transfer problem. (author)
Energy Technology Data Exchange (ETDEWEB)
Picanco, Marco Antonio Silva [Regional University of Jaragua do Sul (UNERJ), SC (Brazil)], e-mail: mpicanco@unerj.br; Bandarra Filho, Enio Pedone [Federal University of Uberlandia (UFU), MG (Brazil). Fac. de Engenharia Mecanica], e-mail: bandarra@mecanica.ufu.br; Passos, Julio Cesar [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Dept. de Engenharia Mecanica. Lab. de Engenharia de Processos e Tecnologia de Energia], e-mail: jpassos@emc.ufsc.br
2006-07-01
Two-phase flow heat transfer has been exhaustively studied over recent years. However, in this field several questions remain unanswered. Heat transfer coefficient prediction related to nucleate and convective boiling have been studied using different approaches, numerical, analytical and experimental. In this work, an experimental analysis, data representation and heat transfer coefficient prediction on two-phase heat transfer on nucleate and convective boiling are presented. An empirical correlation is obtained based on genetic algorithms search engine over a dimensional analysis of the two-phase flow heat transfer problem. (author)
Directory of Open Access Journals (Sweden)
Abolfazl Nasseri
2017-03-01
Full Text Available Introduction: Due to sensitiveness of flow to roughness coefficient (RC, selection of this coefficient is important in earth canals designing purposes. Precision selection of this coefficient is necessary for design and operation of earthen canals purposes. Overestimation of the actual amount of this coefficient will cause an underestimation for flow velocity. Accordingly, sedimentation in the earth canals will reduce canals’ capacitances. Adversely, underestimation of this coefficient will cause an overestimation for flow velocity and water flux in the earth canals. It will also increase the risk of soil erosion in the channels. This coefficient is expressed by Manning, Chezy and Darcy Weisbach equations. While, hydraulic engineers have selected Manning equation to estimate the flow rate in open channels due to ease of use and acceptable precision in the application of this equation. Water for crop production in Moghan, as one of the most important agricultural centers in Iran, is supplied from Moghan-Meel diversion dam via main canal of irrigation and drainage network with a capacity of 80 m3 s-1 with a length of 116 km. All of the branched 63-channel from the main channel are earthen. Continual sedimentation in the earth canals reduced the capacity of them and re-estimation the capacity of this canals needs to the precise quantities of variables such as roughness coefficient. Because the overestimation of the actual value of the coefficient would reduce the canals’ capacity and underestimation of the coefficient increase the risk of erosion in earth canals. The analysis of the correlation among variables, regression, analysis of statistical distribution of variables, analysis of variance of variables and the analysis of the events probabilities for stochastic variables can be made by statistical methods. Therefore, these methods were applied to analysis of roughness coefficient in the earth canals. Also, due to the importance of roughness
Connecting the Rheological Behavior of Clathrate Hydrate Slurries to Flow Performance
Geri, Michela; Venkatesan, Rama; McKinley, Gareth; MIT Team; Chevron ETC Team
2014-11-01
Clathrate hydrates represent a major flow assurance issue for deep water drilling operations. To develop a proper constitutive model, an extensive set of rheological measurements has been performed on a model hydrate forming emulsion. Upon hydrate formation a sharp increase in the fluid viscosity is observed (by a factor of 100 to 1000). Steady shear measurements show that the hydrate slurry has a shear thinning behavior as well as a yield stress on the order of 1-10 Pa which increases with aging of the fluid. Thixotropy becomes evident as a hysteretic behavior in the flow curve, even when no rheological aging has occurred. Creep tests also reveal that the fluid microstructure accumulates back stress. Oscillatory measurements show that in the linear viscoelastic region hydrate slurries develop viscoelastic gel-like behavior with the elastic modulus exceeding the viscous modulus. These characteristics guide the development of an elastoviscoplastic constitutive model that can capture the salient dynamic features in simple unidirectional flows (e.g. steady or transient Poiseuille) such as apparent wall slip, plug flow or excessive pressure drop in start-up flow.
Direct numerical simulation of cellular-scale blood flow in microvascular networks
Balogh, Peter; Bagchi, Prosenjit
2017-11-01
A direct numerical simulation method is developed to study cellular-scale blood flow in physiologically realistic microvascular networks that are constructed in silico following published in vivo images and data, and are comprised of bifurcating, merging, and winding vessels. The model resolves large deformation of individual red blood cells (RBC) flowing in such complex networks. The vascular walls and deformable interfaces of the RBCs are modeled using the immersed-boundary methods. Time-averaged hemodynamic quantities obtained from the simulations agree quite well with published in vivo data. Our simulations reveal that in several vessels the flow rates and pressure drops could be negatively correlated. The flow resistance and hematocrit are also found to be negatively correlated in some vessels. These observations suggest a deviation from the classical Poiseuille's law in such vessels. The cells are observed to frequently jam at vascular bifurcations resulting in reductions in hematocrit and flow rate in the daughter and mother vessels. We find that RBC jamming results in several orders of magnitude increase in hemodynamic resistance, and thus provides an additional mechanism of increased in vivo blood viscosity as compared to that determined in vitro. Funded by NSF CBET 1604308.
Identification of material flow systems.
Bauer, G; Deistler, M; Gleiss, A; Glenck, E; Matyus, T
1997-01-01
Material Flow Analysis (MFA) has become an important instrument in environmental science and pollution research. In this paper, we look at the MFA problem as a particularly structured system identification problem. Special emphasis is given to the linear, static case, where we describe a procedure for reconciliating the flow measurements and for estimating the unmeasured flows and the transfer coefficients by taking into account a priori restrictions such as balance equations.
Lattice cell diffusion coefficients. Definitions and comparisons
International Nuclear Information System (INIS)
Hughes, R.P.
1980-01-01
Definitions of equivalent diffusion coefficients for regular lattices of heterogeneous cells have been given by several authors. The paper begins by reviewing these different definitions and the unification of their derivation. This unification makes clear how accurately each definition (together with appropriate cross-section definitions to preserve the eigenvalue) represents the individual reaction rates within the cell. The approach can be extended to include asymmetric cells and whereas before, the buckling describing the macroscopic flux shape was real, here it is found to be complex. A neutron ''drift'' coefficient as well as a diffusion coefficient is necessary to produce the macroscopic flux shape. The numerical calculation of the various different diffusion coefficients requires the solutions of equations similar to the ordinary transport equation for an infinite lattice. Traditional reactor physics codes are not sufficiently flexible to solve these equations in general. However, calculations in certain simple cases are presented and the theoretical results quantified. In difficult geometries, Monte Carlo techniques can be used to calculate an effective diffusion coefficient. These methods relate to those already described provided that correlation effects between different generations of neutrons are included. Again, these effects are quantified in certain simple cases. (author)
Experimental methodology for obtaining sound absorption coefficients
Directory of Open Access Journals (Sweden)
Carlos A. Macía M
2011-07-01
Full Text Available Objective: the authors propose a new methodology for estimating sound absorption coefficients using genetic algorithms. Methodology: sound waves are generated and conducted along a rectangular silencer. The waves are then attenuated by the absorbing material covering the silencer’s walls. The attenuated sound pressure level is used in a genetic algorithm-based search to find the parameters of the proposed attenuation expressions that include geometric factors, the wavelength and the absorption coefficient. Results: a variety of adjusted mathematical models were found that make it possible to estimate the absorption coefficients based on the characteristics of a rectangular silencer used for measuring the attenuation of the noise that passes through it. Conclusions: this methodology makes it possible to obtain the absorption coefficients of new materials in a cheap and simple manner. Although these coefficients might be slightly different from those obtained through other methodologies, they provide solutions within the engineering accuracy ranges that are used for designing noise control systems.
Radon emanation coefficients in sandy soils
International Nuclear Information System (INIS)
Holy, K.; Polaskova, A.; Baranova, A.; Sykora, I.; Hola, O.
1998-01-01
In this contribution the results of the study of an influence of the water content on the emanation coefficient for two sandy soil samples are reported. These samples were chosen on the because of the long-term continual monitoring of the 222 Rn concentration just in such types of soils and this radon concentration showed the significant variations during a year. These variations are chiefly given in connection with the soil moisture. Therefore, the determination of the dependence of the emanation coefficient of radon on the water content can help to evaluate the influence of the soil moisture variations of radon concentrations in the soil air. The presented results show that the emanation coefficient reaches the constant value in the wide interval of the water content for both sandy soil samples. Therefore, in the common range of the soil moisture (5 - 20 %) it is impossible to expect the variations of the radon concentration in the soil air due to the change of the emanation coefficient. The expressive changes of the radon concentration in the soil air can be observed in case of the significant decrease of the emanation coefficient during the soil drying when the water content decreases under 5 % or during the complete filling of the soil pores by the water. (authors)
Kang, Donggu; Payor, James
2015-01-01
We consider flow rounding: finding an integral flow from a fractional flow. Costed flow rounding asks that we find an integral flow with no worse cost. Randomized flow rounding requires we randomly find an integral flow such that the expected flow along each edge matches the fractional flow. Both problems are reduced to cycle canceling, for which we develop an $O(m \\log(n^2/m))$ algorithm.
Computation of Clebsch-Gordan and Gaunt coefficients using binomial coefficients
International Nuclear Information System (INIS)
Guseinov, I.I.; Oezmen, A.; Atav, Ue
1995-01-01
Using binomial coefficients the Clebsch-Gordan and Gaunt coefficients were calculated for extremely large quantum numbers. The main advantage of this approach is directly calculating these coefficients, instead of using recursion relations. Accuracy of the results is quite high for quantum numbers l 1 , and l 2 up to 100. Despite direct calculation, the CPU times are found comparable with those given in the related literature. 11 refs., 1 fig., 2 tabs
Curvature of Indoor Sensor Network: Clustering Coefficient
Directory of Open Access Journals (Sweden)
2009-03-01
Full Text Available We investigate the geometric properties of the communication graph in realistic low-power wireless networks. In particular, we explore the concept of the curvature of a wireless network via the clustering coefficient. Clustering coefficient analysis is a computationally simplified, semilocal approach, which nevertheless captures such a large-scale feature as congestion in the underlying network. The clustering coefficient concept is applied to three cases of indoor sensor networks, under varying thresholds on the link packet reception rate (PRR. A transition from positive curvature (“meshed” network to negative curvature (“core concentric” network is observed by increasing the threshold. Even though this paper deals with network curvature per se, we nevertheless expand on the underlying congestion motivation, propose several new concepts (network inertia and centroid, and finally we argue that greedy routing on a virtual positively curved network achieves load balancing on the physical network.
Control in the coefficients with variational crimes
DEFF Research Database (Denmark)
Evgrafov, Anton; Marhadi, Kun Saptohartyadi
2012-01-01
We study convergence of discontinuous Galerkin-type discretizations of the problems of control in the coefficients of uniformly elliptic partial differential equations (PDEs). As a model problem we use that of the optimal design of thin (Kirchhoff) plates, where the governing equations are of the......We study convergence of discontinuous Galerkin-type discretizations of the problems of control in the coefficients of uniformly elliptic partial differential equations (PDEs). As a model problem we use that of the optimal design of thin (Kirchhoff) plates, where the governing equations...... to “volumetric” Lebesgue norm, changes of the coefficients is generally speaking not continuous. We utilize the lifting formulation of the discontinuous Galerkin method to deal with this issue.Our main result is that limit points of sequences of designs verifying discrete versions of stationarity can also...
Optical distortion coefficients of laser windows
International Nuclear Information System (INIS)
Klein, C.A.
1989-01-01
This paper addresses the problem of describing and evaluating thermal lensing phenomena that occur as a result of the absorption of laser light in solid windows. The aberration-function expansion method is applied for deriving the two optical distortion coefficients χ + and χ - that characterize the degradation in light intensity at the Gaussian focus of an initially diffraction-limited laser beam passing through a weakly absorbing stress-birefringent window. In a pulsed mode of operation, the concept of an effective optical distortion coefficient. χ eff, which properly combines the coefficients χ + and χ - in terms of potential impact on focal irradiances, then leads to the definition of a figure of merit for distortion. The theory and the calculations presented in this papers provide simple analytical tools for predicting the optical performance of a window-material candidate in a specific system's environment
Effects of incomplete mixing on chemical reactions under flow heterogeneities.
Perez, Lazaro; Hidalgo, Juan J.; Dentz, Marco
2016-04-01
Evaluation of the mixing process in aquifers is of primary importance when assessing attenuation of pollutants. In aquifers different hydraulic and chemical properties can increase mixing and spreading of the transported species. Mixing processes control biogeochemical transformations such as precipitation/dissolution reactions or degradation reactions that are fast compared to mass transfer processes. Reactions are local phenomena that fluctuate at the pore scale, but predictions are often made at much larger scales. However, aquifer heterogeities are found at all scales and generates flow heterogeneities which creates complex concentration distributions that enhances mixing. In order to assess the impact of spatial flow heterogeneities at pore scale we study concentration profiles, gradients and reaction rates using a random walk particle tracking (RWPT) method and kernel density estimators to reconstruct concentrations and gradients in two setups. First, we focus on a irreversible bimolecular reaction A+B → C under homogeneous flow to distinguish phenomena of incomplete mixing of reactants from finite-size sampling effects. Second, we analise a fast reversible bimolecular chemical reaction A+B rightleftharpoons C in a laminar Poiseuille flow reactor to determine the difference between local and global reaction rates caused by the incomplete mixing under flow heterogeneities. Simulation results for the first setup differ from the analytical solution of the continuum scale advection-dispersion-reaction equation studied by Gramling et al. (2002), which results in an overstimation quantity of reaction product (C). In the second setup, results show that actual reaction rates are bigger than the obtained from artificially mixing the system by averaging the concentration vertically. - LITERATURE Gramling, C. M.,Harvey, C. F., Meigs, and L. C., (2002). Reactive transport in porous media: A comparison of model prediction with laboratory visualization, Environ. Sci
Criterions for fixing regulatory seismic acceleration coefficients
International Nuclear Information System (INIS)
Costes, D.
1988-03-01
Acceleration coeffficients to be taken into account in seismic areas for calculation of structures are defined in national seismic regulations. Joined to the described qualitative requirements, these coefficients represent a balance between precaution costs and avoided damages, both in terms of material repairing costs and damage to human life. Persons in charge of fixing these coefficients must be informed of corresponding quantitative aspects. Data on seismic motions occurrencies and consequences are gathered here and convoluted to mean damage evaluations. Indications on precaution costs are joined, which shows that currently recommended levels of seismic motions are high relatively to financial profitability, and represent in fact an aethical choice about human life value [fr
Dependence of sputtering coefficient on ion dose
International Nuclear Information System (INIS)
Colligon, J.S.; Patel, M.H.
1977-01-01
The sputtering coefficient of polycrystalline gold bombarded by 10-40 keV Ar + ions had been measured as a function of total ion dose and shown to exhibit oscillations in magnitude between 30 and 100%. Possible experimental errors which would give rise to such an oscillation have been considered, but it is apparent that these factors are unable to explain the measurements. It is proposed that a change in the Sublimation Energy associated with either bulk damage or formation of surface topographical features arising during ion bombardment may be responsible for the observed variations in sputtering coefficient. (author)
Absorption coefficient instrument for turbid natural waters
Friedman, E.; Cherdak, A.; Poole, L.; Houghton, W.
1980-01-01
The paper presents an instrument that directly measures multispectral absorption coefficient of turbid natural water. Attention is given to the design, which is shown to incorporate methods for the compensation of variation in the internal light source intensity, correction of the spectrally dependent nature of the optical elements, and correction for variation in the background light level. In addition, when used in conjunction with a spectrally matched total attenuation instrument, the spectrally dependent scattering coefficient can also be derived. Finally, it is reported that systematic errors associated with multiple scattering have been estimated using Monte Carlo techniques.
A drying coefficient for building materials
DEFF Research Database (Denmark)
Scheffler, Gregor Albrecht; Plagge, Rudolf
2009-01-01
, in many cases such a coefficient would be highly appreciated, e.g. in interaction of industry and research or for the distinction and selection of suitable building materials throughout design and practise. This article first highlights the importance of drying experiments for hygrothermal...... and defined as a new and independent material parameter. It contains information about the moisture transport properties throughout the wide range of moisture contents from hygroscopic up to saturation. With this new and valuable coefficient, it is now possible to distinguish and select building materials...
Shear viscosity coefficient of liquid lanthanides
Energy Technology Data Exchange (ETDEWEB)
Patel, H. P., E-mail: patel.harshal2@gmail.com; Thakor, P. B., E-mail: pbthakore@rediffmail.com; Prajapati, A. V., E-mail: anand0prajapati@gmail.com [Department of Physics, Veer Narmad South Gujarat University, Surat 395 007, Gujarat (India); Sonvane, Y. A., E-mail: yas@ashd.svnit.ac.in [Department of Applied Physics, S. V. National Institute of Technology, Surat 395 007, Gujarat (India)
2015-05-15
Present paper deals with the computation of shear viscosity coefficient (η) of liquid lanthanides. The effective pair potential v(r) is calculated through our newly constructed model potential. The Pair distribution function g(r) is calculated from PYHS reference system. To see the influence of local field correction function, Hartree (H), Tailor (T) and Sarkar et al (S) local field correction function are used. Present results are compared with available experimental as well as theoretical data. Lastly, we found that our newly constructed model potential successfully explains the shear viscosity coefficient (η) of liquid lanthanides.
Reaction rate calculations via transmission coefficients
International Nuclear Information System (INIS)
Feit, M.D.; Alder, B.J.
1985-01-01
The transmission coefficient of a wavepacket traversing a potential barrier can be determined by steady state calculations carried out in imaginary time instead of by real time dynamical calculations. The general argument is verified for the Eckart barrier potential by a comparison of transmission coefficients calculated from real and imaginary time solutions of the Schroedinger equation. The correspondence demonstrated here allows a formulation for the reaction rate that avoids difficulties due to both rare events and explicitly time dependent calculations. 5 refs., 2 figs
Vertical diffuse attenuation coefficient (Kd) based optical ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
The optical classification of the different water types provides vital input for studies related to primary productivity, water clarity and determination of euphotic depth. Image data of the IRS-. P3 MOS-B, for Path 90 of 27th February, 1998 was used for deriving vertical diffuse attenuation coefficient (Kd) and an optical ...
Coefficient Omega Bootstrap Confidence Intervals: Nonnormal Distributions
Padilla, Miguel A.; Divers, Jasmin
2013-01-01
The performance of the normal theory bootstrap (NTB), the percentile bootstrap (PB), and the bias-corrected and accelerated (BCa) bootstrap confidence intervals (CIs) for coefficient omega was assessed through a Monte Carlo simulation under conditions not previously investigated. Of particular interests were nonnormal Likert-type and binary items.…
Tracking Time-Varying Coefficient-Functions
DEFF Research Database (Denmark)
Nielsen, Henrik Aalborg; Nielsen, Torben Skov; Joensen, Alfred K.
1999-01-01
A conditional parametric ARX-model is an ARX-model in which the parameters re replaced by smooth functions of an, possibly multivariate, externalinput signal. These functions are called coefficient functions is suggested. Essentially, in its most simple form, this method is a combination of recur...
Ideal related K-theory with coefficients
DEFF Research Database (Denmark)
Eilers, Soren; Restorff, Gunnar; Ruiz, Efren
2017-01-01
In this paper, we define an invariant, which we believe should be the substitute for total K-theory in the case when there is one distinguished ideal. Moreover, some diagrams relating the new groups to the ordinary K-groups with coefficients are constructed. These diagrams will in most cases help...
Regularity of the Interband Light Absorption Coefficient
Indian Academy of Sciences (India)
In this paper we consider the interband light absorption coefficient (ILAC), in a symmetric form, in the case of random operators on the -dimensional lattice. We show that the symmetrized version of ILAC is either continuous or has a component which has the same modulus of continuity as the density of states.
Prediction of longitudinal dispersion coefficient using multivariate ...
Indian Academy of Sciences (India)
Keywords. River water quality; artificial neural network; longitudinal dispersion coefficient; pollution transmission ... Error indices showed that MARS model has suitable performanceand is more accurate compared to multi-layer neural network model and empirical formulas. Results ofthe Gamma test and MARS model ...
Friction Coefficient Determination by Electrical Resistance Measurements
Tunyagi, A.; Kandrai, K.; Fülöp, Z.; Kapusi, Z.; Simon, A.
2018-01-01
A simple and low-cost, DIY-type, Arduino-driven experiment is presented for the study of friction and measurement of the friction coefficient, using a conductive rubber cord as a force sensor. It is proposed for high-school or college/university-level students. We strongly believe that it is worthwhile planning, designing and performing Arduino…
Molar extinction coefficients of some fatty acids
DEFF Research Database (Denmark)
Sandhu, G.K.; Singh, K.; Lark, B.S.
2002-01-01
) and stearic acid (C18H36O2), has been measured at the photon energies 81, 356, 511, 662, 1173 and 1332 keV. Experimental values for the molar extinction coefficient, the effective atomic number and the electron density have been derived and compared with theoretical calculations. There is good agreement...
Effective stress coefficient for uniaxial strain condition
DEFF Research Database (Denmark)
Alam, M.M.; Fabricius, I.L.
2012-01-01
one dimensional rock mechanical deformation. We further investigated the effect of boundary condition on the stress dependency of effective stress coefficient and discussed its application in reservoir study. As stress field in the reservoirs are most unlikely to be hydrostatic, effective stress...... determined under uniaxial strain condition will be more relevant in reservoir studies. Copyright 2012 ARMA, American Rock Mechanics Association....
Modelling of power-reactivity coefficient measurement
International Nuclear Information System (INIS)
Strmensky, C.; Petenyi, V.; Jagrik, J.; Minarcin, M.; Hascik, R.; Toth, L.
2005-01-01
Report describes results of modeling of power-reactivity coefficient analysis on power-level. In paper we calculate values of discrepancies arisen during transient process. These discrepancies can be arisen as result of experiment evaluation and can be caused by disregard of 3D effects on neutron distribution. The results are critically discussed (Authors)
Pressure-viscosity coefficient of biobased lubricants
Film thickness is an important tribological property that is dependent on the combined effect of lubricant properties, material property of friction surfaces, and the operating conditions of the tribological process. Pressure-viscosity coefficient (PVC) is one of the lubricant properties that influe...
Bayesian Meta-Analysis of Coefficient Alpha
Brannick, Michael T.; Zhang, Nanhua
2013-01-01
The current paper describes and illustrates a Bayesian approach to the meta-analysis of coefficient alpha. Alpha is the most commonly used estimate of the reliability or consistency (freedom from measurement error) for educational and psychological measures. The conventional approach to meta-analysis uses inverse variance weights to combine…
Infinite matrices, wavelet coefficients and frames
Directory of Open Access Journals (Sweden)
N. A. Sheikh
2004-01-01
Full Text Available We study the action of A on f∈L2(ℝ and on its wavelet coefficients, where A=(almjklmjk is a double infinite matrix. We find the frame condition for A-transform of f∈L2(ℝ whose wavelet series expansion is known.
Rate coefficient for the reaction N + NO
Fox, J. L.
1994-01-01
Evidence has been advanced that the rate coefficient for the reaction N + NO right arrow N2 + O has a small positive temperature dependence at the high temperatures (900 to 1500 K) that prevail in the terrestrial middle and upper thermosphere by Siskind and Rusch (1992), and at the low temperatures (100 to 200 K) of the Martian lower thermosphere by Fox (1993). Assuming that the rate coefficient recommended by the Jet Propulsion Laboratory evaluation (DeMore et al., 1992) is accurate at 300 K, we derive here the low temperature value of the activation energy for this reaction and thus the rate coefficient that best fits the Viking 1 measured NO densities. We find that the fit is acceptable for a rate coefficient of about 1.3 x 10(exp -10)(T/300)(exp 0.5)exp(-400/T) and better for a value of about 2.5 x 10(exp -10)(T/300)(exp 0.5)exp(-600/T)cu cm/s.
Cohomology with coefficients for operadic coalgebras
Indian Academy of Sciences (India)
Corepresentations of a coalgebra over a quadratic operad are defined, and various characterizations of them are given. Cohomology of such an operadic coalgebra with coefficients in a corepresentation is then studied. Author Affiliations. Anita Majumdar1 Donald Yau2. Department of Mathematics, Indian Institute of ...
Problems on Divisibility of Binomial Coefficients
Osler, Thomas J.; Smoak, James
2004-01-01
Twelve unusual problems involving divisibility of the binomial coefficients are represented in this article. The problems are listed in "The Problems" section. All twelve problems have short solutions which are listed in "The Solutions" section. These problems could be assigned to students in any course in which the binomial theorem and Pascal's…
Power coefficient anomaly in Joyo, (2)
International Nuclear Information System (INIS)
Ishikawa, Makoto; Yamashita, Yoshioki; Sasaki, Makoto; Nara, Yoshihiko.
1981-12-01
In this report, the presumption about the mechanism having caused the power coefficient anomaly in Joyo during the 75 MW power-raising test in 1979 is described. After the previous report, the new information about the results of the post-irradiation examination and the analysis of the power coefficient of Joyo were able to be obtained. From these information, the mechanism of causing the anomaly was presumed as follows. In 50 MW operation, the fuel burnup reached about 10,000 MWD/ton at the end of second cycle, and produced fission gas was almost retained in fuel pellets. When the power was raised from 50 MW to 75 MW for the first time, the fission gas began to be released when 50 MW was somewhat exceeded. The fission gas release caused the temperature rise and cracking of fuel pellets, and elongated fuel stack length abruptly. These phenomena induced to enlarge the fuel expansion reactivity effect and Doppler reactivity effect, and caused the anomalous behavior of power coefficient. After reaching 75 MW, the fuel stack length did not respond normally to reactor power change, and the magnitude of power coefficient became smaller. The reactivity was lost considerably from the core after the anomaly. (Kako, I.)
A Graphical Interpretation of Probit Coefficients.
Becker, William E.; Waldman, Donald M.
1989-01-01
Contends that, when discrete choice models are taught, particularly the probit model, it is the method rather than the interpretation of the results that is emphasized. This article provides a graphical technique for interpretation of an estimated probit coefficient that will be useful in statistics and econometrics courses. (GG)
Vertical diffuse attenuation coefficient (Kd) based optical ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
mary production and diffuse attenuation coeffi- cient (Austin 1981; Sathyendranath et al 2000). The Indian IRS-P3 ... oceanic and coastal production of phytoplank- ton (Tyler 1975; Pennock and Sharp 1986). As a result basic ... cient to the plant pigment content. The term dif- fuse attenuation coefficient, most commonly used.
Recursive harmonic analysis for computing Hansen coefficients
Adel Sharaf, Mohamed; Hassan Selim, Hadia
2010-12-01
We report on a simple pure numerical method developed for computing Hansen coefficients by using a recursive harmonic analysis technique. The precision criteria of the computations are very satisfactory and provide materials for computing Hansen's and Hansen's like expansions, and also to check the accuracy of some existing algorithms.
An alternative coefficient for sound absorption
Wijnant, Ysbrand H.; Kuipers, E.R.; de Boer, Andries; Sas, P; Jonckheere, S.; Moens, D.
2013-01-01
The acoustic absorption coefficient is a number that indicates which fraction of the incident acoustic power impinging on a surface is being absorbed. The incident acoustic power is obtained by spatial integration of the incident intensity, which is (classically) defined as the time-averaged
Skidding Coefficients on an Alluvial Soil
W. N. Darwin
1965-01-01
The Southern Hardwoods Laboratory is studying the influence of ground conditions and load characteristics on the performance of skidding vehicles in southern bottom lands. The exploratory test was aimed at evaluating the effects of bark on skidding coefficients, but it also yielded information on other log characteristics and on effects of soil moisture.
Effective stress coefficient for uniaxial strain condition
DEFF Research Database (Denmark)
Alam, Mohammad Monzurul; Fabricius, Ida Lykke
2012-01-01
The effective stress coefficient, introduced by Biot, is used for predicting effective stress or pore pressure in the subsurface. It is not a constant value. It is different for different types of sediment and it is stress dependent. We used a model, based on contact between the grains to describe...
Determination of the convective heat transfer coefficient
Spierings, D.; Bosman, F.; Peters, T.; Plasschaert, F.
The value of the convective heat transfer coefficient (htc) is determined under different loading conditions by using a computer aided method. The thermal load has been applied mathematically as well as experimentally to the coronal surface of an axisymmetric tooth model. To verify the assumptions
Hou, T. H.
1985-01-01
High quality long fiber reinforced composites, such as those used in aerospace and industrial applications, are commonly processed in autoclaves. An adequate resin flow model for the entire system (laminate/bleeder/breather), which provides a description of the time-dependent laminate consolidation process, is useful in predicting the loss of resin, heat transfer characteristics, fiber volume fraction and part dimension, etc., under a specified set of processing conditions. This could be accomplished by properly analyzing the flow patterns and pressure profiles inside the laminate during processing. A newly formulated resin flow model for composite prepreg lamination process is reported. This model considers viscous resin flows in both directions perpendicular and parallel to the composite plane. In the horizontal direction, a squeezing flow between two nonporous parallel plates is analyzed, while in the vertical direction, a poiseuille type pressure flow through porous media is assumed. Proper force and mass balances have been made and solved for the whole system. The effects of fiber-fiber interactions during lamination are included as well. The unique features of this analysis are: (1) the pressure gradient inside the laminate is assumed to be generated from squeezing action between two adjacent approaching fiber layers, and (2) the behavior of fiber bundles is simulated by a Finitely Extendable Nonlinear Elastic (FENE) spring.
DEFF Research Database (Denmark)
Matteoni, G.; Georgakis, C.T.
2012-01-01
of their inherent surface roughness and shape, which might present a significant disturbance for the surrounding wind flow. The present study focuses on the experimental determination, based on static wind tunnel tests, of the aerodynamic coefficients of full-scale bridge cable section models both perpendicular...
Estimating Subcatchment Runoff Coefficients using Weather Radar and a Downstream Runoff Sensor
DEFF Research Database (Denmark)
Ahm, Malte; Thorndahl, Søren Liedtke; Rasmussen, Michael R.
2013-01-01
This paper presents a method for estimating runoff coefficients of urban drainage subcatchments based on a combination of high resolution weather radar data and flow measurements from a downstream runoff sensor. By utilising the spatial variability of the precipitation it is possible to estimate...
Energy Technology Data Exchange (ETDEWEB)
Sugama, H.; Nishimura, S.
2002-05-01
A novel method to obtain the full neoclassical transport matrix for general toroidal plasmas by using the solution of the linearized drift kinetic equation with the pitch-angle-scattering collision operator is shown. In this method, the neoclassical coefficients for both poloidal and toroidal viscosities in toroidal helical systems can be obtained, and the neoclassical transport coefficients for the radial particle and heat fluxes and the bootstrap current with the non-diagonal coupling between unlike-species particles are derived from combining the viscosity-flow relations, the friction-flow relations, and the parallel momentum balance equations. Since the collisional momentum conservation is properly retained, the well-known intrinsic ambipolar condition of the neoclassical particle fluxes in symmetric systems is recovered. Thus, these resultant neoclassical diffusion and viscosity coefficients are applicable to evaluating accurately how the neoclassical transport in quasi-symmetric toroidal systems deviates from that in exactly-symmetric systems. (author)
Meta-analysis on Macropore Flow Velocity in Soils
Liu, D.; Gao, M.; Li, H. Y.; Chen, X.; Leung, L. R.
2017-12-01
Macropore flow is ubiquitous in the soils and an important hydrologic process that is not well explained using traditional hydrologic theories. Macropore Flow Velocity (MFV) is an important parameter used to describe macropore flow and quantify its effects on runoff generation and solute transport. However, the dominant factors controlling MFV are still poorly understood and the typical ranges of MFV measured at the field are not defined clearly. To address these issues, we conducted a meta-analysis based on a database created from 246 experiments on MFV collected from 76 journal articles. For a fair comparison, a conceptually unified definition of MFV is introduced to convert the MFV measured with different approaches and at various scales including soil core, field, trench or hillslope scales. The potential controlling factors of MFV considered include scale, travel distance, hydrologic conditions, site factors, macropore morphologies, soil texture, and land use. The results show that MFV is about 2 3 orders of magnitude larger than the corresponding values of saturated hydraulic conductivity. MFV is much larger at the trench and hillslope scale than at the field profile and soil core scales and shows a significant positive correlation with the travel distance. Generally, higher irrigation intensity tends to trigger faster MFV, especially at field profile scale, where MFV and irrigation intensity have significant positive correlation. At the trench and hillslope scale, the presence of large macropores (diameter>10 mm) is a key factor determining MFV. The geometric mean of MFV for sites with large macropores was found to be about 8 times larger than those without large macropores. For sites with large macropores, MFV increases with the macropore diameter. However, no noticeable difference in MFV has been observed among different soil texture and land use. Comparing the existing equations to describe MFV, the Poiseuille equation significantly overestimated the
Weyl q-coefficients for uq(3) and Racah q -coefficients for suq(2)
International Nuclear Information System (INIS)
Asherova, R.M.; Smirnov, Yu.F.; Tolstoy, V.N.
1996-01-01
With the aid of the projection-operator technique, the general analytic expression for the elements of the matrix that relates the U and T bases of an arbitrary finite-dimensional irreducible representation of the uq(3) quantum algebra (Weyl q-coefficients) is obtained for the case where the deformation parameter q is not equal to a square root of unity. The procedure for resummation of q-factorial expressions is used to prove that, modulo phase factors, these Weyl q-coefficients coincide with Racah q-coefficients for the suq(2) quantum algebra. It is also shown that, on the basis of one general formula, the q-analogs of all known general analytic expressions for the 6j symbols (and Racah coefficients) of the Lie algebras of the angular momentum can be obtained by using this resummation procedure. The symmetry properties of these q coefficients are discussed. The result is formulated in the following way: the general formulas for the q-6j symbols (Racah q-coefficients) of the suq(2) quantum algebra are obtained from the general formulas for the conventional 6j symbols (Racah coefficients) of the su(2) Lie algebra by replacing directly all factorials with q-factorials, the symmetry properties of the q-6j symbols being completely coincident with the symmetry properties of the conventional 6j symbols
Directory of Open Access Journals (Sweden)
Xiaodong Wang
2017-11-01
Full Text Available A multi-scale phase-field approach, which couples the mesoscopic crystallization with the microscopic orientation of chain segments and macroscopic viscoelastic melt flow, is proposed to study how the crystal growth of semi-crystalline polymers is affected by flows. To make the simulation feasible, we divide the problem into three parts. In the first part, a finitely extensible nonlinear elastic (FENE dumbbell model is used to simulate the flow induced molecular structure. In the second part, formulas for estimating the density, orientation and aspect ratio of nuclei upon the oriented molecular structure are derived. Finally, in the third part, a massive mathematical model that couples the phase-field, temperature field, flow field and orientation field is established to model the crystal growth with melt flow. Two-dimensional simulations are carried out for predicting the flow effect on the crystal growth of isotactic polystyrene under a plane Poiseuille flow. In solving the model, a semi-analytical method is adopted to avoid the numerical difficult of a “high Weissenberg number problem” in the first part, and an efficient fractional step method is used to reduce the computing complexity in the third part. The simulation results demonstrate that flow strongly affects the morphology of single crystal but does not bring a significant influence on the holistic morphology of bulk crystallization.
CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks
Yang, H. Q.; West, Jeff
2015-01-01
Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.
Meromorphic univalent function with negative coefficient
Directory of Open Access Journals (Sweden)
A. Dernek
1994-01-01
Full Text Available Let Mn be the classes of regular functions f(z=z−1+a0+a1z+… defined in the annulus 00, (n∈ℕ0, where I0f(z=f(z, If(z=(z−1−z(z−1−2∗f(z, Inf(z=I(In−1f(z, and ∗ is the Hadamard convolution. We denote by Γn=Mn⋃Γ, where Γ denotes the class of functions of the form f(z=z−1+∑k=1∞|ak|zk. We obtained that relates the modulus of the coefficients to starlikeness for the classes Mn and Γn, and coefficient inequalities for the classes Γn.
Head-wave coefficients in anisotropic media
Chapman, Chris
2018-03-01
Reflections and transmissions from interfaces can generate head waves. Although the kinematic properties of head waves are modelled simply using ray concepts, the dynamic properties require an extension of ray theory or the use of wave theory. Head waves are important in exploration and crustal seismology as they indicate the existence of an interface and the velocity of the generating wave. Head waves have been described in the literature for isotropic media but the extension to anisotropic media seems to be lacking. The expressions for the head-wave coefficients using ray concepts or wave theory differ, and their equality is not obvious. This paper extends the theory for head-wave coefficients to anisotropic media using both ray theory and wave theory, and generalizes the proof of equality of the two methods. Simple numerical examples confirm this equality and indicate how the head-wave results can be calculated in anisotropic media and included in a ray-tracing algorithm.
Gate Control Coefficient Effect on CNFET Characteristic
International Nuclear Information System (INIS)
Sanudin, Rahmat; Ma'Radzi, Ahmad Alabqari; Nayan, Nafarizal
2009-01-01
The development of carbon nanotube field-effect transistor (CNFET) as alternative to existing transistor technology has long been published and discussed. The emergence of this device offers new material and structure in building a transistor. This paper intends to do an analysis of gate control coefficient effect on CNFET performance. The analysis is based on simulation study of current-voltage (I-V) characteristic of ballistic CNFET. The simulation study used the MOSFET-like CNFET mathematical model to establish the device output characteristic. Based on the analysis of simulation result, it is found that the gate control coefficient contributes to a significant effect on the performance of CNFET. The result also shown the parameter could help to improve the device performance in terms of its output and response as well. Nevertheless, the characteristic of the carbon nanotube that acts as the channel is totally important in determining the performance of the transistor as a whole.
Doppler coefficient measurements in Zebra Core 5
International Nuclear Information System (INIS)
Baker, A.R.; Wheeler, R.C.
1965-11-01
Measurements using a central hot loop in Zebra Core 5 are described. Results are given for the Doppler coefficients found in a number of assemblies with PuO 2 and 16% PuO 2 /84% depleted UO 2 pins, loaded with different combinations of steel, sodium or void pins. The mixed oxide results are in general about 20% more negative than was calculated using the FD2 data set, but agreement is good if the plutonium contributions in the calculations are omitted. The small positive Doppler coefficient calculated for Pu239 was not observed, and two measurements indicated instead a small negative effect. The Doppler effect in the mixed oxide systems was found to vary approximately as 1/T. The results from the empty loop and non-fissile assemblies indicate either a small negative Doppler effect in steel or alternatively the presence of an unexplained expansion effect. (author)
The coefficient of friction, particularly of ice
International Nuclear Information System (INIS)
Mills, Allan
2008-01-01
The static and dynamic coefficients of friction are defined, and values from 0.3 to 0.6 are quoted for common materials. These drop to about 0.15 when oil is added as a lubricant. Water ice at temperatures not far below 0 °C is remarkable for low coefficients of around 0.05 for static friction and 0.04–0.02 for dynamic friction, but these figures increase as the temperature diminishes. Reasons for the slipperiness of ice are summarized, but they are still not entirely clear. One hypothesis suggests that it is related to the transient formation of a lubricating film of liquid water produced by frictional heating. If this is the case, some composition melting a little above ambient temperatures might provide a skating rink that did not require expensive refrigeration. Various compositions have been tested, but an entirely satisfactory material has yet to be found
Analytical expressions for the electron backscattering coefficient
International Nuclear Information System (INIS)
August, H.J.; Wernisch, J.
1989-01-01
Several analytical expressions for the electron backscattering coefficient for massive homogeneous samples are compared with experimental data, directing special attention to the dependence of this quantity on the electron acceleration energy. It is shown that this dependence generally cannot be neglected. The expression proposed by Hunger and Kuechler turns out to be better than that of Love and Scott, although even the better formula can be slightly improved by a small modification. (author)
Effective stress coefficient for uniaxial strain condition
DEFF Research Database (Denmark)
Alam, M.M.; Fabricius, I.L.
2012-01-01
The effective stress coefficient, introduced by Biot, is used for predicting effective stress or pore pressure in the subsurface. It is not a constant value. It is different for different types of sediment and it is stress dependent. We used a model, based on contact between the grains to describ...... determined under uniaxial strain condition will be more relevant in reservoir studies. Copyright 2012 ARMA, American Rock Mechanics Association....
Varying coefficients model with measurement error.
Li, Liang; Greene, Tom
2008-06-01
We propose a semiparametric partially varying coefficient model to study the relationship between serum creatinine concentration and the glomerular filtration rate (GFR) among kidney donors and patients with chronic kidney disease. A regression model is used to relate serum creatinine to GFR and demographic factors in which coefficient of GFR is expressed as a function of age to allow its effect to be age dependent. GFR measurements obtained from the clearance of a radioactively labeled isotope are assumed to be a surrogate for the true GFR, with the relationship between measured and true GFR expressed using an additive error model. We use locally corrected score equations to estimate parameters and coefficient functions, and propose an expected generalized cross-validation (EGCV) method to select the kernel bandwidth. The performance of the proposed methods, which avoid distributional assumptions on the true GFR and residuals, is investigated by simulation. Accounting for measurement error using the proposed model reduced apparent inconsistencies in the relationship between serum creatinine and GFR among different clinical data sets derived from kidney donor and chronic kidney disease source populations.
Ahmed, Syed Muzamil; Kazi, S. N.; Khan, Ghulamullah; Sadri, Rad; Dahari, Mahidzal; Zubir, M. N. M.; Sayuti, M.; Ahmad, Pervaiz; Ibrahim, Rushdan
2018-03-01
Heat transfer coefficients were obtained for a range of non-wood kenaf bast pulp fiber suspensions flowing through a circular pipe heat exchanger test loop. The data were produced over a selected temperature and range of flow rates from the flow loop. It was found that the magnitude of the heat transfer coefficient of a fiber suspension is dependent on characteristics, concentration and pulping method of fiber. It was observed that at low concentration and high flow rates, the heat transfer coefficient values of suspensions were observed higher than that of the heat transfer coefficient values of water, on the other hand the heat transfer coefficient values of suspensions decreases at low flow rates and with the increase of their concentration. The heat transfer were affected by varying fiber characteristics, such as fiber length, fiber flexibility, fiber chemical and mechanical treatment as well as different pulping methods used to liberate the fibers. Heat transfer coefficient was decreased with the increase of fiber flexibility which was also observed by previous researchers. In the present work, the characteristics of fibers are correlated with the heat transfer coefficient of suspensions of the fibers. Deviations in fiber properties can be monitored from the flowing fiber suspensions by measuring heat transfer coefficient to adjust the degree of fiber refining treatment so that papers made from those fibers will be more uniform, consistent, within the product specification and retard the paper production loss.
A finite-volume numerical method to calculate fluid forces and rotordynamic coefficients in seals
Athavale, M. M.; Przekwas, A. J.; Hendricks, R. C.
1992-01-01
A numerical method to calculate rotordynamic coefficients of seals is presented. The flow in a seal is solved by using a finite-volume formulation of the full Navier-Stokes equations with appropriate turbulence models. The seal rotor is perturbed along a diameter such that the position of the rotor is a sinusoidal function of time. The resulting flow domain changes with time, and the time-dependent flow in the seal is solved using a space conserving moving grid formulation. The time-varying fluid pressure reaction forces are then linked with the rotor center displacement, velocity and acceleration to yield the rotordynamic coefficients. Results for an annular seal are presented, and compared with experimental data and other more simplified numerical methods.
Stokes Approach to Preferential Flow at the Darcy-Scale
Germann, Peter; Bogner, Christina
2017-04-01
Preferential Flow in soils is fast, limited to infiltration and occupies but a small portion of porosity. However, how fast is it, how much water is involved, what is its flow rate, and how far is it carried? Supported with numerous measurements a Stokes approach to preferential flow provides the answers at the operational Darcy-scale. The approach to preferential flow in permeable media (pm) stresses momentum dissipation during viscous flow. Thus, a laminar water film percolates through a pm. The dynamic film is initially determined by the thickness F (m) and the specific contact area L (m2 m-3) per unit volume of the medium. Input to the medium's surface is a pulse with volume flux density q (ms-1) that starts and ends at times TB and TE. A specific pulse and the intrinsic properties of a pm determine F and L. A water content wave (WCW) envelops the spatio-temporal evolution of a water film. A WCW is completely described with a set of analytical relationships that are based on F, L, and the water's viscosity. The approach is an extension of Hagen-Poiseuille's law of flow in concentric conduits. It also evolves seamlessly from extending Darcy's law into non-saturated pm. Experimental determination of F and L follows either from drainage flow or from rapid soil moisture recordings during the passing of a WCW, for instance, with TDR-equipment. Parameters from numerous infiltration experiments in the field, in soil columns, in sand boxes, and lysimeters demonstrate the approach's broad applicability, thus framing the spatio-temporal extensions, velocities and volume flux densities of preferential flows. The specific contact area L is considered the locus of water, heat, particle and solute transfer between a WCW and the sessile parts of a pm. A recent analysis of delayed Br-breakthrough with respect to drainage flow supports the feasibility of the Stokes approach to preferential flow at the Darcy-scale. A perspective of modeling sequences of input pulses will
Energy Technology Data Exchange (ETDEWEB)
Wanninger, Andreas; Ceuca, Sabin Cristian; Macian-Juan, Rafael [Technische Univ. Muenchen, Garching (Germany). Dept. of Nuclear Engineering
2013-07-01
Different approaches for the calculation of Direct Contact Condensation (DCC) using Heat Transfer Coefficients (HTC) based on the Surface Renewal Theory (SRT) are tested using the CFD simulation tool ANSYS CFX. The present work constitutes a preliminary study of the flow patterns and conditions observed using different HTC models. A complex 3D flow pattern will be observed in the CFD simulations as well as a strong coupling between the condensation rate and the two-phase flow dynamics. (orig.)
Comparison of field-measured radon diffusion coefficients with laboratory-measured coefficients
International Nuclear Information System (INIS)
Lepel, E.A.; Silker, W.B.; Thomas, V.W.; Kalkwarf, D.R.
1983-04-01
Experiments were conducted to compare radon diffusion coefficients determined for 0.1-m depths of soils by a steady-state method in the laboratory and diffusion coefficients evaluated from radon fluxes through several-fold greater depths of the same soils covering uranium-mill tailings. The coefficients referred to diffusion in the total pore volume of the soils and are equivalent to values for the quantity, D/P, in the Generic Environmental Impact Statement on Uranium Milling prepared by the US Nuclear Regulatory Commission. Two soils were tested: a well-graded sand and an inorganic clay of low plasticity. For the flux evaluations, radon was collected by adsorption on charcoal following passive diffusion from the soil surface and also from air recirculating through an aluminum tent over the soil surface. An analysis of variance in the flux evaluations showed no significant difference between these two collection methods. Radon diffusion coefficients evaluated from field data were statistically indistinguishable, at the 95% confidence level, from those measured in the laboratory; however, the low precision of the field data prevented a sensitive validation of the laboratory measurements. From the field data, the coefficients were calculated to be 0.03 +- 0.03 cm 2 /s for the sand cover and 0.0036 +- 0.0004 cm 2 /s for the clay cover. The low precision in the coefficients evaluated from field data was attributed to high variation in radon flux with time and surface location at the field site
Effects of fluid flow on heat transfer in large rotating electrical machines
International Nuclear Information System (INIS)
Lancial, Nicolas
2014-01-01
EDF operates a large number of electrical rotating machines in its electricity generation capacity. Thermal stresses which affect them can cause local heating, sufficient to damage their integrity. The present work contributes to provide methodologies for detecting hot spots in these machines, better understanding the topology of rotating flows and identifying their effects on heat transfer. Several experimental scale model were used by increasing their complexity to understand and validate the numerical simulations. A first study on a turbulent wall jet over a non-confined backward-facing step (half-pole hydro-generator) notes significant differences compared to results from confined case: both of them are present in an hydro-generator. A second study was done on a small confined rotating scale model to determinate the effects of a Taylor-Couette-Poiseuille on temperature distribution and position of hot spots on the heated rotor, by studying the overall flow regimes flow. These studies have helped to obtain a reliable method based on conjugate heat transfer (CHT) simulations. Another method, based on FEM coupled with the use of an inverse method, has been studied on a large model of hydraulic generator so as to solve the computation time issue of the first methodology. It numerically calculates the convective heat transfer from temperature measurements, but depends on the availability of experimental data. This work has also developed new no-contact measurement techniques as the use of a high-frequency pyrometer which can be applied on rotating machines for monitoring temperature. (author)
Hariharan, Gokul; Jovanovic, Mihailo; Kumar, Satish
2017-11-01
The study of non-modal amplification of distributed body forces in channel flows of viscoelastic fluids has provided useful insight into the mechanisms that may govern the initial stages of transition to elastic turbulence. However, distributed body forces are not easy to implement in experiments and there is a need to examine amplification of localized body forces. In this work, we use the linearized governing equations to examine such amplification in plane Poiseuille flow of FENE-CR fluids. We first identify the location at which the impulsive excitations experience the largest amplification and then analyze the energy of the fluctuations and resulting flow structures. For both a Newtonian fluid at high Reynolds number and a viscoelastic fluid at low Reynolds number, the largest amplification occurs for disturbances that are located near the channel wall. Analysis of the energy evolution shows that the localized point force directed in the spanwise direction has the largest impact and that the streamwise velocity is most affected. For viscoelastic fluids we observe the development of vortical structures away from the source of impulsive excitation, a feature absent in Newtonian fluids that may provide a mechanism for the initial stages of transition to elastic turbulence.
Energy Technology Data Exchange (ETDEWEB)
Jason, L., E-mail: ludovic.jason@cea.fr [Atomic Energy Commission (CEA), DEN, DANS, DM2S, SEMT, Mechanics and System Simulation Laboratory (LM2S), F-91191 Gif sur Yvette (France); LaMSID, UMR CNRS-EDF-CEA 8193, F-92141 Clamart (France); Masson, B. [Electricité de France (EDF), SEPTEN, F-69628 Villeurbanne (France)
2014-10-01
Highlights: • The contribution focuses on the gas transfer through reinforced concrete structures. • A continuous approach with a damage–permeability law is investigated. • It is significant, for this case, only when the damage variable crosses the section. • In this case, two localized approaches are compared. • It helps at evaluating a “reference” crack opening for engineering laws. - Abstract: In this contribution, different techniques are compared to evaluate the gas flow rate through a representative section of a reinforced and prestressed concrete containment structure. A continuous approach is first applied which is based on the evaluation of the gas permeability as a function of the damage variable. The calculations show that the flow rate becomes significant only when the damage variable crosses the section. But in this situation, the continuous approach is no longer fully valid. That is why localized approaches, based on a fine description of the crack openings, are then investigated. A comparison between classical simplified laws (Poiseuille flow) and a more refined model which takes into account the evolution of the crack opening in the depth of the section enables to define the validity domain of the simplified laws and especially the definition of the associated “reference opening”.
The influence of aerodynamic coefficients on the elements of classic projectile paths
Directory of Open Access Journals (Sweden)
Damir D. Jerković
2011-04-01
Full Text Available The article deals with the results of the research on the influence of aerodynamic coefficient values on the trajectory elements and the stability parameters of classic axisymmetric projectiles. It presents the characteristic functions of aerodynamic coefficients with regard to aerodynamic parameters and the projectile body shape. The trajectory elements of the model of classic axisymmetric projectiles and the analyses of their changes were presented with respect to the aerodynamic coefficient values. Introduction Classic axisymmetric projectiles fly through atmosphere using muzzle velocity as initial energy resource, so the aerodynamic force and moment have the most significant influence on the motion of projectiles. The aerodynamic force and moment components represented as aerodynamic coefficients depend on motion velocity i. e. flow velocity, the flow features produced by projectile shape and position in the flow, and angular velocity (rate of the body. The functional dependence of aerodynamic coefficients on certain influential parameters, such as angle of attack and angular velocity components is expressed by the derivative of aerodynamic coefficients. The determination of aerodynamic coefficients and derivatives enables complete definition of the aerodynamic force and moment acting on the classic projectile. The projectile motion problem is considered in relation to defining the projectile stability parameters and the conditions under which the stability occurs. The comparative analyses of aerodynamic coefficient values obtained by numerical methods, semi empirical calculations and experimental research give preliminary evaluation of the quality of the determined values. The flight simulation of the motion of a classic axisymetric projectile, which has the shape defined by the aerodynamic coefficient values, enables the comparative analyses of the trajectory elements and stability characteristics. The model of the classic projectile
Numerical determination of lateral loss coefficients for subchannel analysis in nuclear fuel bundles
Energy Technology Data Exchange (ETDEWEB)
Sin Kim; Goon-Cherl Park [Seoul National Univ., Seoul (Korea, Republic of)
1995-09-01
An accurate prediction of cross-flow based on detailed knowledge of the velocity field in subchannels of a nuclear fuel assembly is of importance in nuclear fuel performance analysis. In this study, the low-Reynolds number {kappa}-{epsilon} turbulence model has been adopted in two adjacent subchannels with cross-flow. The secondary flow is estimated accurately by the anisotropic algebraic Reynolds stress model. This model was numerically calculated by the finite element method and has been verified successfully through comparison with existing experimental data. Finally, with the numerical analysis of the velocity field in such subchannel domain, an analytical correlation of the lateral loss coefficient is obtained to predict the cross-flow rate in subchannel analysis codes. The correlation is expressed as a function of the ratio of the lateral flow velocity to the donor subchannel axial velocity, recipient channel Reynolds number and pitch-to-diameter.
Unsteady axisymmetric flow of a micropolar fluid between the ...
African Journals Online (AJOL)
The influence of several parameters on dimensionless velocities is presented through plots. The behavior of skin friction and couple stress coefficients is tabulated against various values of the pertinent parameters. Keywords: Unsteady flow, micropolar fluid, radial stretching, skin friction coefficient, couple stress coefficient
On separation of exchange term from the coefficient of the ...
Indian Academy of Sciences (India)
Abstract. The purpose of this analysis is to introduce the separated exchange coefficient and to graphically investigate it. This coefficient, depending on the electromagnetic constant plus two coefficients of the electromechanical and magnetomechanical couplings, form the coefficient of magnetoelectromechanical coupling ...
Determination of coefficient matrices for ARMA model
International Nuclear Information System (INIS)
Tran Dinh Tri.
1990-10-01
A new recursive algorithm for determining coefficient matrices of ARMA model from measured data is presented. The Yule-Walker equations for the case of ARMA model are derived from the ARMA innovation equation. The recursive algorithm is based on choosing appropriate form of the operator functions and suitable representation of the (n+1)-th order operator functions according to ones with the lower order. Two cases, when the order of the AR part is equal to one of the MA part, and the optimal case, were considered. (author) 5 refs
Kinetic coefficients in isotopically disordered crystals
International Nuclear Information System (INIS)
Zhernov, Arkadii P; Inyushkin, Alexander V
2002-01-01
Peculiarities of the behavior of kinetic coefficients, like thermal conductivity, electric conductivity, and thermoelectric power, in isotopically disordered materials are reviewed in detail. New experimental and theoretical results on the isotope effects in the thermal conductivity of diamond, Ge, and Si semiconductors are presented. The suppression effect of phonon-drag thermopower in the isotopically disordered Ge crystals is discussed. The influence of dynamic and static crystal lattice deformations on the electric conductivity of metals as well as on the ordinary phonon spectrum deformations is considered. (reviews of topical problems)
Transport coefficients in copper vapor arc plasmas
International Nuclear Information System (INIS)
Rahal, A.M.; Rahhaoui, B.; Vacquie, S.
1985-01-01
The presence of copper vapors modifies the properties of arc discharges. The paper deals with a region not investigated earlier, where in the core of the positive column of very short or high current arcs there is a high copper concentration. At these values the relative losses take a greater part in the energy balance. Using the charged-charged collision integrals, the transport coefficients (axial temperature, thermal and electric conductivity, viscosity) of the plasma with higher copper vapor concentration are calculated as the function of the arc current intensity. (D.Gy.)
Quenching of Einstein-coefficients by photons
International Nuclear Information System (INIS)
Aumayr, F.; Lee, W.; Skinner, C.H.; Suckewer, S.
1991-03-01
Experimental evidence is presented for the change of Einstein's A- coefficients for spontaneous transitions from the upper laser level of argon ion laser discharge due to the presence of the high- intensity laser flux. To demonstrate that this quenching effect cannot be attributed to a reduction in self-absorption of the strong spontaneous emission line, absorption and line profile measurements have been performed. Computer modelling of the reduction of self absorption due to Rabi splitting also indicated that this effect is too small to explain the observed quenching of spontaneous line emissions. 13 refs., 11 figs
Effective Diffusion Coefficients in Coal Chars
DEFF Research Database (Denmark)
Johnsson, Jan Erik; Jensen, Anker
2001-01-01
Knowledge of effective diffusion coefficients in char particles is important when interpreting experimental reactivity measurements and modeling char combustion or NO and N2O reduction. In this work, NO and N2O reaction with a bituminous coal char was studied in a fixed-bed quartz glass reactor....... In the case of strong pore diffusion limitations, the error in the interpretation of experimental results using the mean pore radius could be a factor of 5 on the intrinsic rate constant. For an average coal char reacting with oxygen at 1300 K, this would be the case for particle sizes larger than about 50...
Friction coefficient determination by electrical resistance measurements
Tunyagi, A.; Kandrai, K.; Fülöp, Z.; Kapusi, Z.; Simon, A.
2018-05-01
A simple and low-cost, DIY-type, Arduino-driven experiment is presented for the study of friction and measurement of the friction coefficient, using a conductive rubber cord as a force sensor. It is proposed for high-school or college/university-level students. We strongly believe that it is worthwhile planning, designing and performing Arduino and compatible sensor-based experiments in physics class in order to ensure a better understanding of phenomena, develop theoretical knowledge and multiple experimental skills.
A numerical model for boiling heat transfer coefficient of zeotropic mixtures
Barraza Vicencio, Rodrigo; Caviedes Aedo, Eduardo
2017-12-01
Zeotropic mixtures never have the same liquid and vapor composition in the liquid-vapor equilibrium. Also, the bubble and the dew point are separated; this gap is called glide temperature (Tglide). Those characteristics have made these mixtures suitable for cryogenics Joule-Thomson (JT) refrigeration cycles. Zeotropic mixtures as working fluid in JT cycles improve their performance in an order of magnitude. Optimization of JT cycles have earned substantial importance for cryogenics applications (e.g, gas liquefaction, cryosurgery probes, cooling of infrared sensors, cryopreservation, and biomedical samples). Heat exchangers design on those cycles is a critical point; consequently, heat transfer coefficient and pressure drop of two-phase zeotropic mixtures are relevant. In this work, it will be applied a methodology in order to calculate the local convective heat transfer coefficients based on the law of the wall approach for turbulent flows. The flow and heat transfer characteristics of zeotropic mixtures in a heated horizontal tube are investigated numerically. The temperature profile and heat transfer coefficient for zeotropic mixtures of different bulk compositions are analysed. The numerical model has been developed and locally applied in a fully developed, constant temperature wall, and two-phase annular flow in a duct. Numerical results have been obtained using this model taking into account continuity, momentum, and energy equations. Local heat transfer coefficient results are compared with available experimental data published by Barraza et al. (2016), and they have shown good agreement.
A low-dimensional tool for predicting force decomposition coefficients for varying inflow conditions
Ghommem, Mehdi
2013-01-01
We develop a low-dimensional tool to predict the effects of unsteadiness in the inflow on force coefficients acting on a circular cylinder using proper orthogonal decomposition (POD) modes from steady flow simulations. The approach is based on combining POD and linear stochastic estimator (LSE) techniques. We use POD to derive a reduced-order model (ROM) to reconstruct the velocity field. To overcome the difficulty of developing a ROM using Poisson\\'s equation, we relate the pressure field to the velocity field through a mapping function based on LSE. The use of this approach to derive force decomposition coefficients (FDCs) under unsteady mean flow from basis functions of the steady flow is illustrated. For both steady and unsteady cases, the final outcome is a representation of the lift and drag coefficients in terms of velocity and pressure temporal coefficients. Such a representation could serve as the basis for implementing control strategies or conducting uncertainty quantification. Copyright © 2013 Inderscience Enterprises Ltd.
Directory of Open Access Journals (Sweden)
Balla Hyder H.
2015-01-01
Full Text Available Cu and Zn-water nanofluid is a suspension of the Cu and Zn nanoparticles with the size 50 nm in the water base fluid for different volume fractions to enhance its Thermophysical properties. The determination and measuring the enhancement of Thermophysical properties depends on many limitations. Nanoparticles were suspended in a base fluid to prepare a nanofluid. A coated transient hot wire apparatus was calibrated after the building of the all systems. The vibro-viscometer was used to measure the dynamic viscosity. The measured dynamic viscosity and thermal conductivity with all parameters affected on the measurements such as base fluids thermal conductivity, volume factions, and the temperatures of the base fluid were used as input to the Artificial Neural Fuzzy inference system to modeling both dynamic viscosity and thermal conductivity of the nanofluids. Then, the ANFIS modeling equations were used to calculate the enhancement in heat transfer coefficient using CFD software. The heat transfer coefficient was determined for flowing flow in a circular pipe at constant heat flux. It was found that the thermal conductivity of the nanofluid was highly affected by the volume fraction of nanoparticles. A comparison of the thermal conductivity ratio for different volume fractions was undertaken. The heat transfer coefficient of nanofluid was found to be higher than its base fluid. Comparisons of convective heat transfer coefficients for Cu and Zn nanofluids with the other correlation for the nanofluids heat transfer enhancement are presented. Moreover, the flow demonstrates anomalous enhancement in heat transfer nanofluids.
Numerical analysis of choked converging nozzle flows with surface ...
Indian Academy of Sciences (India)
Variation of discharge coefficients for sonic nozzles with flow geometry and Reynolds num- ber was reported by Paik et al (2000), who determined higher discharge coefficients with the increase of mass flow rate. Lear et al (1997) modelled dissipative effects of heat trans- fer on the exit kinetic energy and on nozzle efficiency ...
measurements of distribution coefficients and lipophilicity values
African Journals Online (AJOL)
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KEY WORDS. KEY WORDS: Betulinic acid, Oleanolic acid, Hollow fibre supported liquid membrane, Distribution .... The temperature of the drying gas, N2, was 300 ºC and the flow rate of the nebulizing gas,. N2, was 40 .... Sample pH optimization for the selective HFSLM extraction and separation of the isomers (BA and OA).
The convergence coefficient across political systems.
Gallego, Maria; Schofield, Norman
2013-01-01
Formal work on the electoral model often suggests that parties or candidates should locate themselves at the electoral mean. Recent research has found no evidence of such convergence. In order to explain nonconvergence, the stochastic electoral model is extended by including estimates of electoral valence. We introduce the notion of a convergence coefficient, c. It has been shown that high values of c imply that there is a significant centrifugal tendency acting on parties. We used electoral surveys to construct a stochastic valence model of the the elections in various countries. We find that the convergence coefficient varies across elections in a country, across countries with similar regimes, and across political regimes. In some countries, the centripetal tendency leads parties to converge to the electoral mean. In others the centrifugal tendency dominates and some parties locate far from the electoral mean. In particular, for countries with proportional electoral systems, namely, Israel, Turkey, and Poland, the centrifugal tendency is very high. In the majoritarian polities of the United States and Great Britain, the centrifugal tendency is very low. In anocracies, the autocrat imposes limitations on how far from the origin the opposition parties can move.
Sets of Fourier coefficients using numerical quadrature
International Nuclear Information System (INIS)
Lyness, J. N.
2001-01-01
One approach to the calculation of Fourier trigonometric coefficients f(r) of a given function f(x) is to apply the trapezoidal quadrature rule to the integral representation f(r)=(line i ntegral)(sub 0)(sup 1) f(x)e(sup -2(pi)irx)dx. Some of the difficulties in this approach are discussed. A possible way of overcoming many of these is by means of a subtraction function. Thus, one sets f(x)= h(sub p-1)(x)+ g(sub p)(x), where h(sub -1)(x) is an algebraic polynomial of degree p-1, specified in such a way that the Fourier series of g(sub p)(x) converges more rapidly than that of f(x). To obtain the Fourier coefficients of f(x), one uses an analytic expression for those of h(sub p-1)(x) and numerical quadrature to approximately those of g(sub p)(x)
Full wave-field reflection coefficient inversion.
Dettmer, Jan; Dosso, Stan E; Holland, Charles W
2007-12-01
This paper develops a Bayesian inversion for recovering multilayer geoacoustic (velocity, density, attenuation) profiles from a full wave-field (spherical-wave) seabed reflection response. The reflection data originate from acoustic time series windowed for a single bottom interaction, which are processed to yield reflection coefficient data as a function of frequency and angle. Replica data for inversion are computed using a wave number-integration model to calculate the full complex acoustic pressure field, which is processed to produce a commensurate seabed response function. To address the high computational cost of calculating short range acoustic fields, the inversion algorithms are parallelized and frequency averaging is replaced by range averaging in the forward model. The posterior probability density is interpreted in terms of optimal parameter estimates, marginal distributions, and credibility intervals. Inversion results for the full wave-field seabed response are compared to those obtained using plane-wave reflection coefficients. A realistic synthetic study indicates that the plane-wave assumption can fail, producing erroneous results with misleading uncertainty bounds, whereas excellent results are obtained with the full-wave reflection inversion.
The Convergence Coefficient across Political Systems
Schofield, Norman
2013-01-01
Formal work on the electoral model often suggests that parties or candidates should locate themselves at the electoral mean. Recent research has found no evidence of such convergence. In order to explain nonconvergence, the stochastic electoral model is extended by including estimates of electoral valence. We introduce the notion of a convergence coefficient, c. It has been shown that high values of c imply that there is a significant centrifugal tendency acting on parties. We used electoral surveys to construct a stochastic valence model of the the elections in various countries. We find that the convergence coefficient varies across elections in a country, across countries with similar regimes, and across political regimes. In some countries, the centripetal tendency leads parties to converge to the electoral mean. In others the centrifugal tendency dominates and some parties locate far from the electoral mean. In particular, for countries with proportional electoral systems, namely, Israel, Turkey, and Poland, the centrifugal tendency is very high. In the majoritarian polities of the United States and Great Britain, the centrifugal tendency is very low. In anocracies, the autocrat imposes limitations on how far from the origin the opposition parties can move. PMID:24385886
Thermal neutron diffusion cooling coefficient for plexiglass
International Nuclear Information System (INIS)
Drozdowicz, K.
1992-08-01
The thermal neutron diffusion cooling coefficient is a macroscopic material parameter. It is needed for description of the decay of the thermal neutron pulse in a medium and gives information of the diffusion cooling of the thermal neutron spectrum in a bounded volume. Experimental results from various measurements for plexiglass are overviewed in the paper. A method for theoretical, exact calculation of the parameter is presented. The formula utilizes some other thermal neutron parameters and a cooling function, i.e. the function which describes the deviation of the neutron spectrum in a bounded system from the distribution in an infinite one. The energy dependence of the function is obtained numerically from relations which results from the eigenvalue problem of the scattering operator when both the decay constant and the spectrum of the thermal neutron flux are developed on powers of the geometrical buckling. The case of a 1/ν absorption cross section is considered. The calculation utilizes a synthetic scattering function elaborated for hydrogenous media by GRANADA (1985). The influence of some quantities used in the calculation on the final result is investigated. The obtained value of the diffusion cooling coefficient for plexiglass is C = 6514 cm 4 s -1 at the temperature of 20 degrees C. The uncertainty is estimated to be ± 100 cm 4 s -1 within the physical model of the scattering kernel used. (au)
Hall, Eric
2016-01-09
The Monte Carlo (and Multi-level Monte Carlo) finite element method can be used to approximate observables of solutions to diffusion equations with lognormal distributed diffusion coefficients, e.g. modeling ground water flow. Typical models use lognormal diffusion coefficients with H´ older regularity of order up to 1/2 a.s. This low regularity implies that the high frequency finite element approximation error (i.e. the error from frequencies larger than the mesh frequency) is not negligible and can be larger than the computable low frequency error. We address how the total error can be estimated by the computable error.
Sandberg, Mattias
2015-01-07
The Monte Carlo (and Multi-level Monte Carlo) finite element method can be used to approximate observables of solutions to diffusion equations with log normal distributed diffusion coefficients, e.g. modelling ground water flow. Typical models use log normal diffusion coefficients with H¨older regularity of order up to 1/2 a.s. This low regularity implies that the high frequency finite element approximation error (i.e. the error from frequencies larger than the mesh frequency) is not negligible and can be larger than the computable low frequency error. This talk will address how the total error can be estimated by the computable error.
Questionnaire discrimination: (re-introducing coefficient δ
Directory of Open Access Journals (Sweden)
Hankins Matthew
2007-05-01
Full Text Available Abstract Background Questionnaires are used routinely in clinical research to measure health status and quality of life. Questionnaire measurements are traditionally formally assessed by indices of reliability (the degree of measurement error and validity (the extent to which the questionnaire measures what it is supposed to measure. Neither of these indices assesses the degree to which the questionnaire is able to discriminate between individuals, an important aspect of measurement. This paper introduces and extends an existing index of a questionnaire's ability to distinguish between individuals, that is, the questionnaire's discrimination. Methods Ferguson (1949 1 derived an index of test discrimination, coefficient δ, for psychometric tests with dichotomous (correct/incorrect items. In this paper a general form of the formula, δG, is derived for the more general class of questionnaires allowing for several response choices. The calculation and characteristics of δG are then demonstrated using questionnaire data (GHQ-12 from 2003–2004 British Household Panel Survey (N = 14761. Coefficients for reliability (α and discrimination (δG are computed for two commonly-used GHQ-12 coding methods: dichotomous coding and four-point Likert-type coding. Results Both scoring methods were reliable (α > 0.88. However, δG was substantially lower (0.73 for the dichotomous coding of the GHQ-12 than for the Likert-type method (δG = 0.96, indicating that the dichotomous coding, although reliable, failed to discriminate between individuals. Conclusion Coefficient δG was shown to have decisive utility in distinguishing between the cross-sectional discrimination of two equally reliable scoring methods. Ferguson's δ has been neglected in discussions of questionnaire design and performance, perhaps because it has not been implemented in software and was restricted to questionnaires with dichotomous items, which are rare in health care research. It is
Smart conducting polymer composites having zero temperature coefficient of resistance
Chu, Kunmo; Lee, Sung-Chul; Lee, Sangeui; Kim, Dongearn; Moon, Changyoul; Park, Sung-Hoon
2014-12-01
Zero temperature coefficient of resistance (TCR) is essential for the precise control of temperature in heating element and sensor applications. Many studies have focused on developing zero-TCR systems with inorganic compounds; however, very few have dealt with developing zero-TCR systems with polymeric materials. Composite systems with a polymer matrix and a conducting filler show either a negative (NTC) or a positive temperature coefficient (PTC) of resistance, depending on several factors, e.g., the polymer nature and the filler shape. In this study, we developed a hybrid conducting zero-TCR composite having self-heating properties for thermal stability and reliable temperature control. The bi-layer composites consisted of a carbon nanotube (CNT)-based layer having an NTC of resistance and a carbon black (CB)-based layer having a PTC of resistance which was in direct contact with electrodes to stabilize the electrical resistance change during electric Joule heating. The composite showed nearly constant resistance values with less than 2% deviation of the normalized resistance until 200 °C. The CB layer worked both as a buffer and as a distributor layer against the current flow from an applied voltage. This behavior, which was confirmed both experimentally and theoretically, has been rarely reported for polymer-based composite systems.Zero temperature coefficient of resistance (TCR) is essential for the precise control of temperature in heating element and sensor applications. Many studies have focused on developing zero-TCR systems with inorganic compounds; however, very few have dealt with developing zero-TCR systems with polymeric materials. Composite systems with a polymer matrix and a conducting filler show either a negative (NTC) or a positive temperature coefficient (PTC) of resistance, depending on several factors, e.g., the polymer nature and the filler shape. In this study, we developed a hybrid conducting zero-TCR composite having self
Flow shapes and higher harmonics in anisotropic transverse collective flow
Energy Technology Data Exchange (ETDEWEB)
Argintaru, Danut; Baban, Valerica [Constanta Maritime University, Faculty of Navigation and Naval Transport, Constanta (Romania); Besliu, Calin; Jipa, Alexandru; Grossu, Valeriu [University of Bucharest, Faculty of Physics, Bucharest (Romania); Esanu, Tiberiu; Cherciu, Madalin [Institute of Space Sciences Bucharest-Magurele, Bucharest (Romania)
2017-01-15
In this paper we show that by using a jet-finder algorithm (the Anti-k{sub T} one) on UrQMD/C simulated (Au+Au at 4, 10 and 15A GeV) collisions, we can identify different flow shape structures (single flow stream events, two flow streams events, three flow streams events, etc.) and order the bulk of events in equivalence flow shape classes. Considering these flow streams as the main directions of anisotropic transverse flow, we show that the Fourier coefficients v{sub n} of anisotropic flow are better emphasized when we analyze the different event flow shape classes than when the events are mixed. Also, if we do not know the real orientation of the reaction plane, we can use as reference the Flow stream 1 - the main particle flow stream - orientation (Ψ{sub Flowstream} {sub 1}) to highlight the initial shape of the participant nuclear matter in a central to peripheral collision, and the orientation of the participant plane of order n. (orig.)
APRECOT - analysis program for reactivity coefficient tests
International Nuclear Information System (INIS)
Telford, A.R.R.
1979-05-01
A computer program has been written which provides a rapid and convenient analysis route for fuel temperature coefficient of reactivity measurements, as carried out at Hinkley Point 'B' Power Station. This replaces the earlier, more tedious, iterative analysis using KINAGRAX. The program has been tested by analysing computer simulations of reactor tests. This has shown that APRECOT introduces errors which are small (approximately 11/2%) in comparison with other sources of error (approximately 10%), that the effect of axial flux shape changes is acceptably small and that effects due to xenon, which is not modelled in the current version of the program, can be dealt with adequately. This note describes the APRECOT method, including details of input and output to the program and gives results of the numerical tests made of the method. (author)
Stochastic algorithm for simulating gas transport coefficients
Rudyak, V. Ya.; Lezhnev, E. V.
2018-02-01
The aim of this paper is to create a molecular algorithm for modeling the transport processes in gases that will be more efficient than molecular dynamics method. To this end, the dynamics of molecules are modeled stochastically. In a rarefied gas, it is sufficient to consider the evolution of molecules only in the velocity space, whereas for a dense gas it is necessary to model the dynamics of molecules also in the physical space. Adequate integral characteristics of the studied system are obtained by averaging over a sufficiently large number of independent phase trajectories. The efficiency of the proposed algorithm was demonstrated by modeling the coefficients of self-diffusion and the viscosity of several gases. It was shown that the accuracy comparable to the experimental one can be obtained on a relatively small number of molecules. The modeling accuracy increases with the growth of used number of molecules and phase trajectories.
Clustering stocks using partial correlation coefficients
Jung, Sean S.; Chang, Woojin
2016-11-01
A partial correlation analysis is performed on the Korean stock market (KOSPI). The difference between Pearson correlation and the partial correlation is analyzed and it is found that when conditioned on the market return, Pearson correlation coefficients are generally greater than those of the partial correlation, which implies that the market return tends to drive up the correlation between stock returns. A clustering analysis is then performed to study the market structure given by the partial correlation analysis and the members of the clusters are compared with the Global Industry Classification Standard (GICS). The initial hypothesis is that the firms in the same GICS sector are clustered together since they are in a similar business and environment. However, the result is inconsistent with the hypothesis and most clusters are a mix of multiple sectors suggesting that the traditional approach of using sectors to determine the proximity between stocks may not be sufficient enough to diversify a portfolio.
Tracking time-varying coefficient-functions
DEFF Research Database (Denmark)
Nielsen, Henrik Aalborg; Nielsen, Torben Skov; Joensen, Alfred K.
2000-01-01
A method for adaptive and recursive estimation in a class of non-linear autoregressive models with external input is proposed. The model class considered is conditionally parametric ARX-models (CPARX-models), which is conventional ARX-models in which the parameters are replaced by smooth, but oth......A method for adaptive and recursive estimation in a class of non-linear autoregressive models with external input is proposed. The model class considered is conditionally parametric ARX-models (CPARX-models), which is conventional ARX-models in which the parameters are replaced by smooth...... is a combination of recursive least squares with exponential forgetting and local polynomial regression. It is argued, that it is appropriate to let the forgetting factor vary with the value of the external signal which is the argument of the coefficient functions. Some of the key properties of the modified method...
Molar extinction coefficients of some fatty acids
DEFF Research Database (Denmark)
Sandhu, G.K.; Singh, K.; Lark, B.S.
2002-01-01
The attenuation of gamma rays in some fatty acids, viz. formic acid (CH2O2), acetic acid (C2H4O2), propionic acid (C3H6O2), butyric acid (C4H8O2), n-hexanoic acid (C6H12O2), n-caprylic acid (C8H16O2), lauric acid (C12H24O2), myristic acid (C14H28O2), palmitic acid (C16H32O2), oleic acid (C18H34O2......) and stearic acid (C18H36O2), has been measured at the photon energies 81, 356, 511, 662, 1173 and 1332 keV. Experimental values for the molar extinction coefficient, the effective atomic number and the electron density have been derived and compared with theoretical calculations. There is good agreement...
Thermal expansion coefficient determination by CBED
International Nuclear Information System (INIS)
Angelini, P.; Bentley, J.
1984-01-01
The present application of CBED involves measurements of thermal-expansion coefficients by measurement of changes in HOLZ line positions as a function of temperature. Previous work on this subject was performed on Si at a constant accelerating voltage of 100 kV between about 90 and 600 K. Diffraction patterns were recorded and line shifts correlated to lattice parameter changes. Differences were noted between values determined by CBED and accepted thermal expansion values. Significant HOLZ line interactions and splitting occurring in the (111) patterns were noted to contribute to the differences. Preliminary measurements have been made on Al, Al 2 O 3 , and single-crystal tau (Ni/sub 20.3/Ti/sub 2.7/B 6 ). An example of changes in HOLZ lines present in (114) patterns for Al are shown and the effect of temperature on the position of lines in the pattern illustrated
Upper bounds for flexoelectric coefficients in ferroelectrics
Yudin, P. V.; Ahluwalia, R.; Tagantsev, A. K.
2014-02-01
Flexoelectric effect is the response of electric polarization to the mechanical strain gradient. At the nano-scale, where large strain gradients are expected, the flexoelectric effect becomes appreciable and may substitute piezoelectric effect in centrosymmetric materials. These features make flexoelectricity of growing interest during the last decade. At the same time, the available theoretical and experimental results are rather contradictory. In particular, experimentally measured flexoelectric coefficients in some ferroelectric materials largely exceed theoretically predicted values. Here, we determine the upper limits for the magnitude of the static bulk contribution to the flexoelectric effect in ferroelectrics, the contribution which was customarily considered as the dominating one. The magnitude of the upper bounds obtained suggests that the anomalously high flexoelectric coupling documented for perovskite ceramics can hardly be attributed to a manifestation of the static bulk effect.
Thermal linear expansion coefficient of structural graphites
International Nuclear Information System (INIS)
Virgil'ev, Yu.S.
1995-01-01
The data now available on radiation induced changes of linear thermal expansion coefficients (CTE) for native structural carbon materials (SCM) irradiated with high fluences are summarized. For different types of native and foreign SCM dose dependences of CTE changes in the temperature range of 300...1600 K and at fluences up to (2...3)x10 22 n/cm 2 (E>0.18 meV) are compared. On the base of this comparison factors defined the CTE changes under neutron irradiation are revealed and the explanation of observed phenomena is offered. Large number of the factors revealed does not allowed to calculate CTE radiation induced changes. 39 refs.; 16 figs.; 5 tabs
Effective Electrocardiogram Steganography Based on Coefficient Alignment.
Yang, Ching-Yu; Wang, Wen-Fong
2016-03-01
This study presents two types of data hiding methods based on coefficient alignment for electrocardiogram (ECG) signals, namely, lossy and reversible ECG steganographys. The lossy method is divided into high-quality and high-capacity ECG steganography, both of which are capable of hiding confidential patient data in ECG signals. The reversible data hiding method can not only hide secret messages but also completely restore the original ECG signal after bit extraction. Simulations confirmed that the perceived quality generated by the lossy ECG steganography methods was good, while hiding capacity was acceptable. In addition, these methods have a certain degree of robustness, which is rare in conventional ECG stegangraphy schemes. Moreover, the proposed reversible ECG steganography method can not only successfully extract hidden messages but also completely recover the original ECG data.
Friction Experiments for Dynamical Coefficient Measurement
Directory of Open Access Journals (Sweden)
J. J. Arnoux
2011-01-01
Full Text Available An experimental study, including three experimental devices, is presented in order to investigate dry friction phenomena in a wide range of sliding speeds for the steel on steel contact. A ballistic setup, with an air gun launch, allows to estimate the friction coefficient between 20 m/s and 80 m/s. Tests are completed by an adaptation of the sensor on a hydraulic tensile machine (0.01 m/s to 3 m/s and a pin-on-disk tribometer mounted on a CNC lathe (1 to 30 m/s. The interactions at the asperity scale are characterized by a white light interferometer surface analysis.
Measurement of model coefficients of skin sympathetic vasoconstriction
International Nuclear Information System (INIS)
Severens, Natascha M W; Van Marken Lichtenbelt, Wouter D; Frijns, Arjan J H; Kingma, Boris R M; De Mol, Bas A J M; Van Steenhoven, Anton A
2010-01-01
Many researchers have already attempted to model vasoconstriction responses, commonly using the mathematical representation proposed by Stolwijk (1971 NASA Contractor Report CR-1855 (Washington, DC: NASA)). Model makers based the parameter values in this formulation either on estimations or by attributing the difference between their passive models and measurement data fully to thermoregulation. These methods are very sensitive to errors. This study aims to present a reliable method for determining physiological values in the vasoconstriction formulation. An experimental protocol was developed that enabled us to derive the local proportional amplification coefficients of the toe, leg and arm and the transient vasoconstrictor tone. Ten subjects participated in a cooling experiment. During the experiment, core temperature, skin temperature, skin perfusion, forearm blood flow and heart rate variability were measured. The contributions to the normalized amplification coefficient for vasoconstriction of the toe, leg and arm were 84%, 11% and 5%, respectively. Comparison with relative values in the literature showed that the estimated values of Stolwijk and the values mentioned by Tanabe et al (2002 Energy Build. 34 637–46) were comparable with our measured values, but the values of Gordon (1974 The response of a human temperature regulatory system model in the cold PhD Thesis University of California, Santa Barbara) and Fiala et al (2001 Int. J. Biometeorol. 45 143159) differed significantly. With the help of regression analysis a relation was formulated between the error signal of the standardized core temperature and the vasoconstrictor tone. This relation was formulated in a general applicable way, which means that it can be used for situations where vasoconstriction thresholds are shifted, like under anesthesia or during motion sickness
Stochastic and collisional diffusion in two-dimensional periodic flows
International Nuclear Information System (INIS)
Doxas, I.; Horton, W.; Berk, H.L.
1990-05-01
The global effective diffusion coefficient D* for a two-dimensional system of convective rolls with a time dependent perturbation added, is calculated. The perturbation produces a background diffusion coefficient D, which is calculated analytically using the Menlikov-Arnold integral. This intrinsic diffusion coefficient is then enhanced by the unperturbed flow, to produce the global effective diffusion coefficient D*, which we can calculate theoretically for a certain range of parameters. The theoretical value agrees well with numerical simulations. 23 refs., 4 figs
Oxygen transport in waterlogged soils, Part II. Diffusion coefficients
International Nuclear Information System (INIS)
Obando Moncayo, F.H.
2004-01-01
Several equations are available for Oxygen Transport in Waterlogged Soils and have been used for soils and plants. All of them are some form of first Fick's law as given by dQ = - DA(dc/dx)/dt. This equation illustrates some important aspects of aeration in waterlogged soils; first, D is a property of the medium and the gas, and is affected by temperature T. Likewise, the amount of diffusing substance dQ in dt is a direct function of the cross sectional area A and inversely proportional to the distance x. In fact, increasing the water content of air-dry soil, drastically decreases A and creates a further resistance for the flow of oxygen through water films around root plants, soil micro organisms and soil aggregates. The solid phase is also limiting the cross-section of surface of the free gaseous diffusion and the length and tortuosity of diffusion path in soil. In most of cases, soil gas porosity and tortuosity of soil voids are expressed in the equations of diffusion as a broad 'diffusion coefficient' (apparent coefficient diffusion). The process of soil respiration is complicated, involves many parameters, and is difficult to realistically quantify. With regard to the oxygen supply, it is convenient to distinguish macro and micro models, and hence, the flux of oxygen is assumed to have two steps. The first step is related to oxygen diffusion from the atmosphere and the air-filled porosity. The second step is related to the oxygen diffusion through water-films in and around plant roots, soil micro organisms and aggregates. Because of these models we obtain coefficients of macro or micro diffusion, rates of macro or micro diffusion, etc. In the macro diffusion process oxygen is transferred in the soil profile, mainly from the soil surface to a certain depth of the root zone, while micro diffusion deals with the flux over very short distances. Both processes, macro and micro diffusion are highly influenced by soil water content. Of course, if water is added to
Scheibler, Robin; Hurley, Paul
2012-03-01
We present a novel, accurate and fast algorithm to obtain Fourier series coefficients from an IC layer whose description consists of rectilinear polygons on a plane, and how to implement it using off-the-shelf hardware components. Based on properties of Fourier calculus, we derive a relationship between the Discrete Fourier Transforms of the sampled mask transmission function and its continuous Fourier series coefficients. The relationship leads to a straightforward algorithm for computing the continuous Fourier series coefficients where one samples the mask transmission function, compute its discrete Fourier transform and applies a frequency-dependent multiplicative factor. The algorithm is guaranteed to yield the exact continuous Fourier series coefficients for any sampling representing the mask function exactly. Computationally, this leads to significant saving by allowing to choose the maximal such pixel size and reducing the fast Fourier transform size by as much, without compromising accuracy. In addition, the continuous Fourier series is free from aliasing and follows closely the physical model of Fourier optics. We show that in some cases this can make a significant difference, especially in modern very low pitch technology nodes.
T.W. Appelboom; G.M. Chescheir; F. Birgand; R.W. Skaggs; J.W. Gilliam; D. Amatya
2010-01-01
Watershed modeling has become an important tool for researchers. Modeling nitrate transport within drainage networks requires quantifying the denitrification within the sediments in canals and streams. In a previous study, several of the authors developed an equation using a term called a mass transfer coefficient to mathematically describe sediment denitrification....
T. W. Appelboom; G. M. Chescheir; R. W. Skaggs; J. W. Gilliam; Devendra M. Amatya
2006-01-01
Watershed modeling has become an important tool for researchers with the high costs of water quality monitoring. When modeling nitrate transport within drainage networks, denitrification within the sediments needs to be accounted for. Birgand et. al. developed an equation using a term called a mass transfer coefficient to mathematically describe sediment...
Hassan, Ali; Ramzan, Naveed; Umer, Asim; Ahmad, Ayyaz; Muryam, Hina
2018-02-01
The enhancement in the convective heat transfer coefficient of the ethylene glycol (EG) base cuprous oxide (Cu2O) nanofluids were investigated. The nanofluids of different volume concentrations i-e 1%, 2.5% and 4.5% were prepared by the two step method. Cuprous oxide (Cu2O) nanoparticles were ultrasonically stirred for four hours in the ethylene glycol (EG). The experimental study has been performed through circular tube geometry in laminar flow regime at average Reynolds numbers 36, 71 and 116. The constant heat flux Q = 4000 (W/m2) was maintained during this work. Substantial enhancement was observed in the convective heat transfer coefficient of ethylene glycol (EG) base cuprous oxide (Cu2O) nanofluids than the base fluid. The maximum 74% enhancement was observed in convective heat transfer coefficient at 4.5 vol% concentration and Re = 116.
DEFF Research Database (Denmark)
Zafiryadis, Frederik; Meyer, Knud Erik; Gökhan Ergin, F.
Skin friction drag coefficients are determined for marine antifouling coatings in pristine condition by use of Constant Temperature Anemometry (CTA) with uni-directionalhot-wires. Mean flow behaviour for varying surface roughness is analysed in zero pressure gradient, flat plate, turbulentboundary...... drag coefficients as well as roughness Reynolds numbers for the various marine coatings across the range of Rex by fitting of the van Driest profile. The results demonstrate sound agreement with the present ITTC method for determining skin friction coefficients for practically smooth surfaces at low...... layers for Reynolds numbers from Rex =1:91x105 to Rex = 9:54x105. The measurements were conducted at the Technical University of Denmark in a closed-loop wind tunnel redesigned for investigations as this. Ensemble averages of the boundary layer velocity profiles allowed for determination of skin friction...
Seasonal variations of Manning's coefficient depending on vegetation conditions in Tärnsjö, Sweden
Plakane, Rūta; Di Baldassarre, Giuliano; Okoli, Kenechukwu
2017-04-01
Hydrological modelling and water resources management require observations of high and low river flows. To estimate them, rating curves based on the characteristics of the river channel and floodplain are often used. Yet, multiple factors can cause uncertainties in rating curves, one of them being the variability of the Manning's roughness coefficient due to seasonal changes of vegetation. Determining this uncertainty has been a challenge, and depending on vegetation conditions on a stream, values can temporarily show an important deviation from the calibrated rating curve, enhancing the importance to understand changes in Manning's roughness coefficient. Examining the aquatic vegetation on the site throughout different seasonal conditions allows one to observe changes within the channel. By depending on cyclical changes in Manning's roughness coefficient values, different discharges may correspond to the same stage conditions. In this context, we present a combination of field work and modelling exercise to the variation of the rating curve due to vegetation changes in a Swedish stream.
George, I J; Matthews, P S J; Whalley, L K; Brooks, B; Goddard, A; Baeza-Romero, M T; Heard, D E
2013-08-21
Laboratory studies were conducted to investigate the kinetics of HO2 radical uptake onto submicron inorganic salt aerosols. HO2 reactive uptake coefficients were measured at room temperature using an aerosol flow tube and the Fluorescence Assay by Gas Expansion (FAGE) technique that allowed for measurements to be conducted under atmospherically relevant HO2 concentrations ([HO2] = 10(8) to 10(9) molecule cm(-3)). The uptake coefficient for HO2 uptake onto dry inorganic salt aerosols was consistently below the detection limit (γ(HO2) atmospheric models (γ(HO2) = 0.1-1.0). Evidence is presented showing that the HO2 uptake coefficients onto aqueous salt aerosol particles are dependent both on the exposure time to the aerosol and on the HO2 concentration used.
Experimental Identification of Dynamic Coefficients of Tilting-Pad Bearings with Active Lubrication
DEFF Research Database (Denmark)
Salazar, Jorge Andrés González; Cerda Varela, Alejandro Javier; Santos, Ilmar
This article presents the experimental identification of the equivalent dynamic coefficients of an activelylubricated bearing under different lubrication regimes, namely: passive (no injection flow), hybrid (constant injection flow) and feedback-controlled (variable injection flow) lubrication....... The main goal is to provide an overview on the feasibility of modifying its dynamic properties via active lubrication. The pressurized oil injection flow, which enables the hybrid and the feedback-controlled lubrication regimes, is regulated by a hydraulic control system composed of a) a high pressure oil...... bearing featuring active lubrication under light load conditions, is used for such a goal. The experimental identification is performed in the frequency domain by means of the measured FRFs and a finite element model of the rotor. The comparison between results under the different lubrication regimes...
Determination of the convection coefficients of the new core of the RA6
International Nuclear Information System (INIS)
Silin, Nicolas; Masson, Viviana P.; Azcona, Maria A.; Delmastro, Dario F.; Mateos Bickel, Daniel E.; Eckardt, S.
2007-01-01
The experimental reactor RA-6 has a core with fuel elements formed by flat plates, refrigerated by a flow of water. The fluid movement in the core is downward, which is advantageous from the point of view that water is turned away from the pool mouth. For the study of the heat transfer in the fuel elements correlations developed for flat parallel plates are often used. Under the project for core replacement and power augmentation in the experimental reactor RA-6 there is a need to increase the cooling flow of the core. In the new conditions the hydrodynamic flow regime is transitional. This fact combined with the high heat flux and the downward flow of coolant make the design correlations must be verified. Therefore the objective of this work is to experimentally determine the coefficient of convection between the fuel plates in the reactor core in the range of 3000 2 and 150 C degrees wall temperature. (author) [es
Phase-field-based lattice Boltzmann modeling of large-density-ratio two-phase flows
Liang, Hong; Xu, Jiangrong; Chen, Jiangxing; Wang, Huili; Chai, Zhenhua; Shi, Baochang
2018-03-01
In this paper, we present a simple and accurate lattice Boltzmann (LB) model for immiscible two-phase flows, which is able to deal with large density contrasts. This model utilizes two LB equations, one of which is used to solve the conservative Allen-Cahn equation, and the other is adopted to solve the incompressible Navier-Stokes equations. A forcing distribution function is elaborately designed in the LB equation for the Navier-Stokes equations, which make it much simpler than the existing LB models. In addition, the proposed model can achieve superior numerical accuracy compared with previous Allen-Cahn type of LB models. Several benchmark two-phase problems, including static droplet, layered Poiseuille flow, and spinodal decomposition are simulated to validate the present LB model. It is found that the present model can achieve relatively small spurious velocity in the LB community, and the obtained numerical results also show good agreement with the analytical solutions or some available results. Lastly, we use the present model to investigate the droplet impact on a thin liquid film with a large density ratio of 1000 and the Reynolds number ranging from 20 to 500. The fascinating phenomena of droplet splashing is successfully reproduced by the present model and the numerically predicted spreading radius exhibits to obey the power law reported in the literature.
Barney, Rebecca; Nourgaliev, Robert; Delplanque, Jean-Pierre; McCallen, Rose
2017-11-01
Heat transfer is quantified and contrasted for the Poiseuille flow of a fluid at both subcritical and supercritical thermodynamic conditions in a circular pipe subject to a uniform wall heat flux. The conditions considered are relevant to Supercritical Water Reactor (SCWR) applications. In the supercritical thermodynamic regime, a fluid can exhibit large density variations of density, thermal conductivity, and viscosity, which will affect flow and heat transfer characteristics significantly. An advanced equation of state for supercritical water was implemented in a 2D and 3D Arbitrary Lagrangian-Eurlerian multi-physics simulation tool called ALE3D developed at Lawrence Livermore National Laboratory. A newly developed, robust, high-order in space and time, fully implicit reconstructed discontinuous Galerkin (rDG) method is used to enable the numerical simulation of convective heat transfer with supercritical water. Results demonstrate the capability of this approach to accurately capture the non-linear behavior and enhanced heat transfer with supercritical water. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Information management release number LLNL-ABS-736004. Work is supported by the Integrated University Program Graduate Fellowship. Opinions, findings, conclusions or recommendations expressed are of the authors and do not necessarily reflect the views of DOE office of NE.
Gas-liquid mass transfer coefficient of methane in bubble column reactor
International Nuclear Information System (INIS)
Lee, Jaewon; Ha, Kyoung-Su; Lee, Jinwon; Kim, Choongik; Yasin, Muhammad; Park, Shinyoung; Chang, In Seop; Lee, Eun Yeol
2015-01-01
Biological conversion of methane gas has been attracting considerable recent interest. However, methanotropic bioreactor is limited by low solubility of methane gas in aqueous solution. Although a large mass transfer coefficient of methane in water could possibly overcome this limitation, no dissolved methane probe in aqueous environment is commercially available. We have developed a reactor enabling the measurement of aqueous phase methane concentration and mass transfer coefficient (k L a). The feasibility of the new reactor was demonstrated by measuring k L a values as a function of spinning rate of impeller and flow rate of methane gas. Especially, at spinning rate of 300 rpm and flow rate of 3.0 L/min, a large k L a value of 102.9 h -1 was obtained
Luo, X.; Hong, Y.; Lei, X.; Leung, L. R.; Li, H. Y.; Getirana, A.
2017-12-01
As one essential component of the Earth system modeling, the continental-scale river routing computation plays an important role in applications of Earth system models, such as evaluating the impacts of the global change on water resources and flood hazards. The streamflow timing, which depends on the modeled flow velocities, can be an important aspect of the model results. River flow velocities have been estimated by using the Manning's equation where the Manning roughness coefficient is a key and sensitive parameter. In some early continental-scale studies, the Manning coefficient was determined with simplified methods, such as using a constant value for the entire basin. However, large spatial variability is expected in the Manning coefficients for the numerous channels composing the river network in distributed continental-scale hydrologic modeling. In the application of a continental-scale river routing model in the Amazon Basin, we use spatially varying Manning coefficients dependent on channel sizes and attempt to represent the dominant spatial variability of Manning coefficients. Based on the comparisons of simulation results with in situ streamflow records and remotely sensed river stages, we investigate the comparatively optimal Manning coefficients and explicitly demonstrate the advantages of using spatially varying Manning coefficients. The understanding obtained in this study could be helpful in the modeling of surface hydrology at regional to continental scales.
Saeidi, Sheida
hydrodynamic flows. In addition, the corrosion behavior was found to be different between the side wall of the duct (parallel to the magnetic field) and the Hartmann wall (perpendicular to the magnetic field) due to formation of high-velocity jets at the side walls. Further analysis was performed for corrosion in the Hartmann flow, which is the MHD analog of the hydrodynamic Poiseuille flow. The main goal of the analysis is to elucidate the effect of a magnetic field on the corrosion mass loss in the case when the applied magnetic field is perpendicular to the flow-confining wall. It was found that the corrosion rate is strongly dependent of the ratio between the thickness of the concentration boundary layer and that of the magnetohydrodynamic Hartmann boundary layer. Analysis of the effect of a magnetic field on corrosion of RAFM steel in a turbulent PbLi flow is performed using numerical simulations. As demonstrated, for all three magnetic field orientations, decrease of the corrosion rate occurs as the magnetic field increases. However, a wall-normal magnetic field has a stronger effect on the reduction of the corrosion rate compared to the other two magnetic field orientations due to more intensive turbulence suppression. For the case of a wall-normal magnetic field, a correlation for the turbulent dimensionless mass transfer coefficient (Sherwood number, Sh) has been constructed based on the numerical data, which shows the effect of the flow velocity via the Reynolds number (Re) and that of the applied magnetic field via the Hartmann number (Ha): Sh = Sh0 -- 0.792x( Ha1.289), where Sherwood number in a purely hydrodynamic flow Sh0 is a function of Re. The developed analytical and computational tools have been used in the calculations of the corrosion mass loss in the poloidal ducts of the DCLL blanket under conditions of the so-called US DEMO reactor. The analysis includes parametric studies, using the electrical conductivity of the insulating flow channel insert (FCI
Su, Wei; Lindsay, Scott; Liu, Haihu; Wu, Lei
2017-08-01
Rooted from the gas kinetics, the lattice Boltzmann method (LBM) is a powerful tool in modeling hydrodynamics. In the past decade, it has been extended to simulate rarefied gas flows beyond the Navier-Stokes level, either by using the high-order Gauss-Hermite quadrature, or by introducing the relaxation time that is a function of the gas-wall distance. While the former method, with a limited number of discrete velocities (e.g., D2Q36), is accurate up to the early transition flow regime, the latter method (especially the multiple relaxation time (MRT) LBM), with the same discrete velocities as those used in simulating hydrodynamics (i.e., D2Q9), is accurate up to the free-molecular flow regime in the planar Poiseuille flow. This is quite astonishing in the sense that less discrete velocities are more accurate. In this paper, by solving the Bhatnagar-Gross-Krook kinetic equation accurately via the discrete velocity method, we find that the high-order Gauss-Hermite quadrature cannot describe the large variation in the velocity distribution function when the rarefaction effect is strong, but the MRT-LBM can capture the flow velocity well because it is equivalent to solving the Navier-Stokes equations with an effective shear viscosity. Since the MRT-LBM has only been validated in simple channel flows, and for complex geometries it is difficult to find the effective viscosity, it is necessary to assess its performance for the simulation of rarefied gas flows. Our numerical simulations based on the accurate discrete velocity method suggest that the accuracy of the MRT-LBM is reduced significantly in the simulation of rarefied gas flows through the rough surface and porous media. Our simulation results could serve as benchmarking cases for future development of the LBM for modeling and simulation of rarefied gas flows in complex geometries.
Agopian, K. G.
1974-01-01
The problem of inviscid, steady transonic conical flow, formulated in terms of the small disturbance theory, is studied. The small disturbance equation and similarity rules are presented, and a boundary value problem is formulated for the case of a supersonic freestream Mach number. The equation for the perturbation potential is solved numerically using an elliptic finite difference system. The difference equations are solved with a point relaxation algorithm that is also capable of capturing the shock wave during the iteration procedure by using the boundary conditions at the shock. Numerical calculations, for shock location, pressure distribution and drag coefficient, are presented for a family of nonlifting conical wings. The theory of slender wings is also presented and analytical results for pressure and drag coefficients are obtained.
Calculations of the nozzle coefficient of discharge of wet steam turbine stages
International Nuclear Information System (INIS)
Jinling, Z.; Yinian, C.
1989-01-01
A method is presented for calculating the coefficient of discharge of wet steam turbine nozzles. The theoretical formulation of the problem is rigorously in accordance with the theory of two-phase wet steam expansion flow through steam turbine nozzles. The computational values are plotted as sets of curves in accordance with orthogonality test principles. They agree satisfactorily both with historical empirical data and the most recent experimental data obtained in the wet steam two-phase flow laboratory of Xian Jiaotong University. (author)
Merzkirch, Wolfgang
1974-01-01
Flow Visualization describes the most widely used methods for visualizing flows. Flow visualization evaluates certain properties of a flow field directly accessible to visual perception. Organized into five chapters, this book first presents the methods that create a visible flow pattern that could be investigated by visual inspection, such as simple dye and density-sensitive visualization methods. It then deals with the application of electron beams and streaming birefringence. Optical methods for compressible flows, hydraulic analogy, and high-speed photography are discussed in other cha
On separation of exchange term from the coefficient of the ...
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 86; Issue 6 ... plus two coefficients of the electromechanical and magnetomechanical couplings, form the coefficient of magnetoelectromechanical coupling (CMEMC), a very important characteristic used for analysingmagnetoelectroelastic smart (composite) materials.
Influence of roughness parameters on coefficient of friction under ...
Indian Academy of Sciences (India)
mm). Peak count. FD. Fractal dimension. Figure 3. Correlation coefficient between coefficient of friction and roughness parameters under lubricated conditions. White and black bars represent positive and negative correlations, respectively.
Solution of heat equation with variable coefficient using derive
CSIR Research Space (South Africa)
Lebelo, RS
2008-09-01
Full Text Available are considered. The first one involves quadratic approximation of the variable coefficient by direct integration. This case is studied using a conic domain. The second case approximates the variable coefficient quadratically and by step functions. The solution...
Prediction of octanol/water partition coefficient of selected ferrocene ...
African Journals Online (AJOL)
water partition coefficient of selected ferrocenes bearing different substituents, the calculation is based on the adaptation of the Rekker method. Our prediction of obtained theoretical partition coefficients values of logP for all studied substituted ...
On separation of exchange term from the coefficient of the ...
Indian Academy of Sciences (India)
coefficients of the electromechanical and magnetomechanical couplings, form the coefficient of magnetoelectromechanical coupling (CMEMC), a very important characteristic used for analysing magnetoelectroelastic smart (composite) materials. It was analytically and graphically demon- strated that the CMEMC can have a ...
Rajkumar, T.; Bardina, Jorge; Clancy, Daniel (Technical Monitor)
2002-01-01
Wind tunnels use scale models to characterize aerodynamic coefficients, Wind tunnel testing can be slow and costly due to high personnel overhead and intensive power utilization. Although manual curve fitting can be done, it is highly efficient to use a neural network to define the complex relationship between variables. Numerical simulation of complex vehicles on the wide range of conditions required for flight simulation requires static and dynamic data. Static data at low Mach numbers and angles of attack may be obtained with simpler Euler codes. Static data of stalled vehicles where zones of flow separation are usually present at higher angles of attack require Navier-Stokes simulations which are costly due to the large processing time required to attain convergence. Preliminary dynamic data may be obtained with simpler methods based on correlations and vortex methods; however, accurate prediction of the dynamic coefficients requires complex and costly numerical simulations. A reliable and fast method of predicting complex aerodynamic coefficients for flight simulation I'S presented using a neural network. The training data for the neural network are derived from numerical simulations and wind-tunnel experiments. The aerodynamic coefficients are modeled as functions of the flow characteristics and the control surfaces of the vehicle. The basic coefficients of lift, drag and pitching moment are expressed as functions of angles of attack and Mach number. The modeled and training aerodynamic coefficients show good agreement. This method shows excellent potential for rapid development of aerodynamic models for flight simulation. Genetic Algorithms (GA) are used to optimize a previously built Artificial Neural Network (ANN) that reliably predicts aerodynamic coefficients. Results indicate that the GA provided an efficient method of optimizing the ANN model to predict aerodynamic coefficients. The reliability of the ANN using the GA includes prediction of aerodynamic
Test-field method for mean-field coefficients with MHD background
Rheinhardt, M.; Brandenburg, A.
2010-01-01
Aims: The test-field method for computing turbulent transport coefficients from simulations of hydromagnetic flows is extended to the regime with a magnetohydrodynamic (MHD) background. Methods: A generalized set of test equations is derived using both the induction equation and a modified momentum equation. By employing an additional set of auxiliary equations, we obtain linear equations describing the response of the system to a set of prescribed test fields. Purely magnetic and MHD backgro...
Re-evaluation of SiC permeation coefficients at high temperatures
Energy Technology Data Exchange (ETDEWEB)
Yamamoto, Yasushi, E-mail: yama3707@kansai-u.ac.jp [Faculty of Engineering Science, Kansai Univ., Yamate-cho, Suita, Osaka 564-8680 (Japan); Murakami, Yuichiro; Yamaguchi, Hirosato; Yamamoto, Takehiro; Yonetsu, Daigo [Faculty of Engineering Science, Kansai Univ., Yamate-cho, Suita, Osaka 564-8680 (Japan); Noborio, Kazuyuki [Hydrogen Isotope Research Center, Univ. of Toyama, Toyama, Toyama 930-8555 (Japan); Konishi, Satoshi [Institute of Advanced Energy, Kyoto Univ., Gokasho, Uji, Kyoto 611-0011 (Japan)
2016-11-01
Highlights: • The deuterium permeation coefficients of CVD-SiC at 600–950 °C were evaluated. • The wraparound flow was reduced to less than 1/100th of the permeation flow. • CVD-SiC materials are very effective as hydrogen isotope permeation barriers. - Abstract: Since 2007, our group has studied the deuterium permeation and diffusion coefficients for SiC materials at temperatures above 600 °C as a means of evaluating the tritium inventory and permeation in fusion blankets. During such measurements, control and evaluation of the wraparound flow through the sample holder are important, and so the heated sample holder is enclosed by a glass tube and kept under vacuum during experimental trials. However, detailed studies regarding the required degree of vacuum based on model calculations have shown that the wraparound flow is much larger than expected, and so can affect measurements at high temperatures. We therefore modified the measurement apparatus based on calculations involving reduced pressure in the glass tube, and are now confident that the measurement error is only several percent, even at 950 °C. In this paper, recent experimental results obtained with a chemical vapor deposition (CVD)-SiC sample over the temperature range of 600–950 °C are presented, showing that the permeation coefficient for CVD-SiC is more than three orders of magnitude smaller than that for stainless steel (SS316) at 600 °C, and that at 950 °C, the coefficient for CVD-SiC is almost equal to that for SUS316 at 550 °C.
Measurements of soil-solution distribution coefficient
International Nuclear Information System (INIS)
Tsukada, Hirofumi; Hasegawa, Hidenao; Hisamatsu, Shunichi; Sakurai, Naoyuki; Koyama, Kenji
1999-01-01
The soil-solution distribution coefficient (Kd) is defined as the ratio of element concentrations in a soil-solid phase to that in a solution phase. It is commonly used as an important parameter for transfer models of radionuclides in different environments, such as describing the migration behavior in the geosphere and transfer behavior in the biosphere. We plan to measure the Kd of elements by means of an extraction method in soils throughout Aomori Prefecture and to probe related factors affecting their variance. However, Kd values vary widely, dependent upon conditions of measurements even if a similar soil sample is measured. Therefore, measurement conditions for the Kd of elements were examined in the present study and the following conditions were adopted. A collected soil sample was passed through a 2 mm sieve and dried at 50degC. The ratio of solution to solid was 10. The mixture sample was shaken for 24 h at 20degC in a clean centrifuge bottle which was made of polypropylene copolymer (PPCO). According to the literature, common soil types in Aomori Prefecture are as follows: andosols in the Sanpachi-Kamikita region, gray lowland and upland soils in the Tsugaru region, sand-dune regosols in Kizukuri-machi, peat soils around lakes and so on. The Kd values for those soil types will be measured hereafter. (author)
Townsend coefficients of gases in avalanche counters
International Nuclear Information System (INIS)
Brunner, G.
1978-01-01
Though much work has been done by many authors in the last few years in the development and application of avalanche counters for ion radiation, it is based upon values of the Townsend coefficients as the essential gas parameter, which were determined many years ago for much lower reduced field strengths F/p than prevail in such counters. Therefore absolute determinations of α in vapours of methyl alcohol, cyclohexane, acetone, and n-heptene were performed under original conditions of avalanche counters. The values obtained do not differ by more than 30%-50% from the former values indeed, extrapolated over F/p for the first three mentioned substances, but the amounts of A and B in the usual representation α/p=A exp(-B(F/p)) are much greater for the stronger reduced fields. This is of importance for such counter properties as the dependence of pulse heights on pressure, voltage, electrode distance etc., which are governed by other combinations of A and B than α/p itself. A comparison of results for different ionic radiations shows a marked influence of the primary ionization density along the particle tracks which is hard to explain. (Auth.)
Asymmetrical slip propensity: required coefficient of friction.
Seo, Jung-suk; Kim, Sukwon
2013-07-31
Most studies in performing slips and falls research reported their results after the ipsilateral leg of subjects (either right foot or left foot) was guided to contact the contaminated floor surface although many studies indicated concerns for asymmetries of legs in kinematic or kinetic variables. Thus, the present study evaluated if dominant leg's slip tendency would be different from non-dominant leg's slip tendency by comparing the Required Coefficient of Friction (RCOF) of the two lower limbs. Forty seven health adults participated in the present study. RCOF was measured when left or right foot of subjects contacted the force platforms respectively. Paired t-test was performed to test if RCOF and heel velocity (HCV) of dominant legs was different from that of non-dominant legs. It was suggested that the asymmetry in RCOFs and HCV between the two lower limbs existed. The RCOFs of non-dominant legs were higher than that of dominant legs. The results indicated that asymmetry in slip propensity, RCOF, was existed in lower extremity. The results from the study suggested that it would be benefit to include a variable, such as asymmetry, in slips and falls research.
Coefficient of Friction of Human Corneal Tissue.
Wilson, Tawnya; Aeschlimann, Rudolf; Tosatti, Samuele; Toubouti, Youssef; Kakkassery, Joseph; Osborn Lorenz, Katherine
2015-09-01
A novel property evaluation methodology was used to determine the elusive value for the human corneal coefficient of friction (CoF). Using a microtribometer on 28 fresh human donor corneas with intact epithelia, the CoF was determined in 4 test solutions (≥5 corneas/solution): tear-mimicking solution (TMS) in borate-buffered saline (TMS-PS), TMS in phosphate-buffered saline (TMS-PBS), TMS with HEPES-buffered saline (TMS-HEPES), and tear-like fluid in PBS (TLF-PBS). Mean (SD) CoF values ranged from 0.006 to 0.015 and were 0.013 (0.010) in TMS-PS, 0.006 (0.003) in TMS-PBS, 0.014 (0.005) in TMS-HEPES, and 0.015 (0.009) in TLF-PBS. Statistically significant differences were shown for TMS-PBS versus TLF (P = 0.0424) and TMS-PBS versus TMS-HEPES (P = 0.0179), but not for TMS-PBS versus TMS-PS (P = 0.2389). Successful measurement of the fresh human corneal tissue CoF was demonstrated, with values differing in the evaluated buffer solutions, within this limited sample size.
Volatilization: a soil degassing coefficient for iodine
International Nuclear Information System (INIS)
Sheppard, M.I.; Thibault, D.H.; Smith, P.A.; Hawkins, J.L.
1994-01-01
Iodine, an element essential to some animals, is ubiquitous in the biosphere. Unlike other metallic elements, molecular I is volatile, and other inorganic species present in aerated soils, such as I - and IO 3 - , may also volatilize as hydrides, hydrogen iodide (HI), or hydrogen iodates (HIO 3 , HIO 4 ). Methyl iodide has been measured in soils, and it is likely evolved from soils and plants. The long-lived radioisotope 129 I is abundant in nuclear wastes, and its high solubility in groundwater makes it an important element in the performance assessment of underground disposal facilities. Overestimates of soil I residence half-times by traditional foodchain models may be due to underestimation of volatilization. Field and lysimeter experiments over a 3-year period, and direct trapping experiments in the laboratory are reported. The results, combined with values from the literature, indicate the soil I degassing coefficient for a wide range of soil types, vegetated and bare, wet and dry, is lognormally distributed with a geometric mean of 2.1 x 10 -2 year -1 , a range of 1.8 x 10 -4 to 3.1 year -1 and a geometric standard deviation of 3.0. The results of a biosphere model simulation including degassing reduces soil I concentrations fivefold and increases air concentrations 25-fold at steady state, compared to simulations without degassing. (author)
First-principles calculations of flexoelectric coefficients
Hong, Jiawang; Vanderbilt, David
2013-03-01
Flexoelectricity, which is the linear response of polarization to a strain gradient, can have a significant effect on the functional properties of dielectric thin films, superlattices and nanostructures. Despite growing experimental interest, there have been relatively few theoretical studies of flexoelectricity, especially in the context of first-principles calculations. In this talk, we present a complete theory of both the electronic (or ``frozen-ion'')[1] and lattice contributions to flexoelectricity, and demonstrate a supercell method for calculating the flexoelectric coefficients using first-principles density-functional methods. Results are presented for cubic materials including CsCl and SrTiO3. In order to obtain all the elements of the flexoelectric tensor, transverse as well as longitudinal, we carry out calculations on supercells extended along different orientations (e.g., [110] as well as [100]), taking special care to carry out conversions between objects calculated under fixed E or fixed D electric boundary conditions in different parts of the procedure. In this way, all the elements of both the electronic and lattice contributions to the flexoelectric tensor are determined.
Automatic Subspace Learning via Principal Coefficients Embedding.
Peng, Xi; Lu, Jiwen; Yi, Zhang; Yan, Rui
2017-11-01
In this paper, we address two challenging problems in unsupervised subspace learning: 1) how to automatically identify the feature dimension of the learned subspace (i.e., automatic subspace learning) and 2) how to learn the underlying subspace in the presence of Gaussian noise (i.e., robust subspace learning). We show that these two problems can be simultaneously solved by proposing a new method [(called principal coefficients embedding (PCE)]. For a given data set , PCE recovers a clean data set from and simultaneously learns a global reconstruction relation of . By preserving into an -dimensional space, the proposed method obtains a projection matrix that can capture the latent manifold structure of , where is automatically determined by the rank of with theoretical guarantees. PCE has three advantages: 1) it can automatically determine the feature dimension even though data are sampled from a union of multiple linear subspaces in presence of the Gaussian noise; 2) although the objective function of PCE only considers the Gaussian noise, experimental results show that it is robust to the non-Gaussian noise (e.g., random pixel corruption) and real disguises; and 3) our method has a closed-form solution and can be calculated very fast. Extensive experimental results show the superiority of PCE on a range of databases with respect to the classification accuracy, robustness, and efficiency.
Correlation and path coefficient analysis of some quantitative traits ...
African Journals Online (AJOL)
Thirty-seven wheat genotypes and three check varieties were studied for correlation and path coefficient analysis of some quantitative traits in wheat at Kisan (P.G), College, Simbhaoli in India. Generally, the estimates of genotypic correlation coefficients were higher than the corresponding phenotypic correlation coefficients ...
Transfer coefficients in elliptical tubes and plate fin heat exchangers
International Nuclear Information System (INIS)
Saboya, S.M.
1979-09-01
Mean transfer coefficients in elliptical tubes and plate fin heat exchangers were determined by application of heat and mass transfer analogy in conjunction with the naphthalene sublimation technique. The transfer coefficients are presented in a dimensionless form as functions of the Reynolds number. By using the least squares method analytical expressions for the transfer coefficients were determined with low scattering. (E.G.) [pt
On Estimation and Hypothesis Testing Problems for Correlation Coefficients
Kraemer, Helena Chmura
1975-01-01
A selection of statistical problems commonly encountered in psychological or psychiatric research concerning correlation coefficients are re-evaluated in the light of recently developed simplifications in the forms of the distribution theory of the intraclass correlation coefficient, of the product-moment correlation coefficient, and the Spearman…
Temperature Control of Autothermal Reformer System with Coefficient Diagram Method
Srisiriwat, N.; Wutthithanyawat, C.
2017-10-01
The objective of this paper is to design the autothermal reformer (ATR) temperature control by using a coefficient diagram method (CDM). The adiabatic temperature is a main controlled variable of the ATR which is a combination of endothermic and exothermic reactions. The simulation results of control parameters were calculated to maintain the ATR reaction temperature by manipulating air feed flow rate. In this work, two strategies of ATR temperature controller system with and without the feed temperature control of a preheater unit are compared to investigate the appropriate controller system when the change of surrounding temperature is considered as a key disturbance. The results showed that by using the CDM, the stability and robustness for controlling the ATR temperature system were considered to offer the proper control parameters and the designed temperature control of ATR system gave a good performance to maintain the controlled variables and reject the disturbance. Moreover, the ATR control system design with the feed temperature controller can compensate the surrounding temperature better than that without the feed temperature control.
Spectral functions and transport coefficients from the functional renormalization group
Energy Technology Data Exchange (ETDEWEB)
Tripolt, Ralf-Arno
2015-06-03
In this thesis we present a new method to obtain real-time quantities like spectral functions and transport coefficients at finite temperature and density using the Functional Renormalization Group approach. Our non-perturbative method is thermodynamically consistent, symmetry preserving and based on an analytic continuation from imaginary to real time on the level of the flow equations. We demonstrate the applicability of this method by calculating mesonic spectral functions as well as the shear viscosity for the quark-meson model. In particular, results are presented for the pion and sigma spectral function at finite temperature and chemical potential, with a focus on the regime near the critical endpoint in the phase diagram of the quark-meson model. Moreover, the different time-like and space-like processes, which give rise to a complex structure of the spectral functions, are discussed. Finally, based on the momentum dependence of the spectral functions, we calculate the shear viscosity and the shear viscosity to entropy density ratio using the corresponding Green-Kubo formula.
Lubrication approximation for micro-particles moving along parallel walls
Ekiel-Jezewska, M. L.; Wajnryb, E.; Blawzdziewicz, J.; Feuillebois, F.
2008-01-01
Lubrication expressions for the friction coefficients of a spherical particle moving in a fluid between and along two parallel solid walls are explicitly evaluated in the low-Reynolds-number regime. They are used to determine lubrication expression for the particle free motion under an ambient Poiseuille flow. The range of validity and the accuracy of the lubrication approximation is determined by comparing with the corresponding results of the accurate multipole procedure. The results are ap...
Air flow around suspended cables
Directory of Open Access Journals (Sweden)
Gołębiowska Irena
2017-01-01
Full Text Available The impact of wind on construction structures is essential issue in design and operation. In particular, the wind can cause the dengerous vibrations of slender structures with low rigidity, eg. vibrations of cables of suspension and cable-stayed bridges or high voltage transmision lines, thus understanding of wind flow around such constructions is significant. In the paper the results of the analysis of wind flow around the cables for different Reynolds number is presented. The analysed flow meets the Navier-Stokes and continuity equations. The circle and elipse section of the cable is analysed. The discusion of vorticity, drag and lift coefficients and cases due to different angle of wind flow action is presented. The boundary layer and its infuence on total flow is analysed.
Directory of Open Access Journals (Sweden)
Gülfen TUNA
2013-03-01
Full Text Available The aim of this study is to test the validity of Downside Capital Asset Pricing Model (D-CAPM on the ISE. At the same time, the explanatory power of CAPM's traditional beta and D-CAPM's downside beta on the changes in the average return values are examined comparatively. In this context, the monthly data for seventy three stocks that are continuously traded on the ISE for the period 1991-2009 is used. Regression analysis is applied in this study. The research results have shown that D-CAPM is valid on the ISE. In addition, it is obtained that the power of downside beta coefficient is higher than traditional beta coefficient on explaining the return changes. Therefore, it can be said that the downside beta is superior to traditional beta in the ISE for chosen period.
Rate Coefficients for the OH + (CHO)2 (Glyoxal) Reaction Between 240 and 400 K
Feierabend, K. J.; Talukdar, R. K.; Zhu, L.; Ravishankara, A. R.; Burkholder, J. B.
2006-12-01
Glyoxal (CHO)2, the simplest dialdehyde, is an end product formed in the atmospheric oxidation of biogenic hydrocarbons, for example, isoprene. As such, glyoxal plays a role in regional air quality and ozone production in certain locations. Glyoxal is lost in the atmosphere via UV photolysis and reaction with OH. However, the currently available rate coefficient data for the OH + glyoxal reaction is limited to a single room- temperature measurement made using the relative rate method. A determination of the rate coefficient temperature dependence is therefore needed for a more complete interpretation of the atmospheric processing of glyoxal. This study reports the rate coefficient for the OH + (CHO)2 reaction measured under pseudo- first-order conditions in OH ([(CHO)2] > 1000 [OH]0). OH radicals were produced using 248 nm pulsed laser photolysis of H2O2 or HNO3 and detected by pulsed laser induced fluorescence. The concentration of glyoxal in the reactor was determined using three independent techniques; gas flow rates as well as in situ UV and IR absorption. The total pressure in the reactor was varied from 40 to 300 Torr (He), and the rate coefficient was found to be independent of pressure over the temperature range studied. The rate coefficient exhibits a negative temperature dependence between 240 and 400 K consistent with the dependence previously observed for many other aldehydes. Our room-temperature rate coefficient is smaller than the relative rate value that is currently recommended for use in atmospheric model calculations. Our measured rate coefficients are discussed with respect to those for other aldehydes. The atmospheric implications of our work will also be discussed.
International Nuclear Information System (INIS)
H.H. Liu; Y. Zhang
2006-01-01
The exchange of solute mass (through molecular diffusion) between fluid in fractures and fluid in the rock matrix is called matrix diffusion. Owing to the orders-of-magnitude slower flow velocity in the matrix compared to fractures, matrix diffusion can significantly retard solute transport in fractured rock, and therefore is an important process for a variety of problems, including remediation of subsurface contamination and geological disposal of nuclear waste. The effective matrix diffusion coefficient (molecular diffusion coefficient in free water multiplied by matrix tortuosity) is an important parameter for describing matrix diffusion, and in many cases largely determines overall solute transport behavior. While matrix diffusion coefficient values measured from small rock samples in the laboratory are generally used for modeling field-scale solute transport in fractured rock (Boving and Grathwohl, 2001), several research groups recently have independently found that effective matrix diffusion coefficients much larger than laboratory measurements are needed to match field-scale tracer-test data (Neretnieks, 2002; Becker and Shapiro, 2000; Shapiro, 2001; Liu et al., 2003,2004a). In addition to the observed enhancement, Liu et al. (2004b), based on a relatively small number of field-test results, reported that the effective matrix diffusion coefficient might be scale dependent, and, like permeability and dispersivity, it seems to increases with test scale. This scale-dependence has important implications for large-scale solute transport in fractured rock. Although a number of mechanisms have been proposed to explain the enhancement of the effective matrix diffusion coefficient, the potential scale dependence and its mechanisms are not fully investigated at this stage. The major objective of this study is to again demonstrate (based on more data published in the literature than those used in Liu et al. [2004b]) the potential scale dependence of the effective
Directory of Open Access Journals (Sweden)
Phillip Burgers
Full Text Available For a century, researchers have used the standard lift coefficient C(L to evaluate the lift, L, generated by fixed wings over an area S against dynamic pressure, ½ρv(2, where v is the effective velocity of the wing. Because the lift coefficient was developed initially for fixed wings in steady flow, its application to other lifting systems requires either simplifying assumptions or complex adjustments as is the case for flapping wings and rotating cylinders.This paper interprets the standard lift coefficient of a fixed wing slightly differently, as the work exerted by the wing on the surrounding flow field (L/ρ·S, compared against the total kinetic energy required for generating said lift, ½v(2. This reinterpreted coefficient, the normalized lift, is derived from the work-energy theorem and compares the lifting capabilities of dissimilar lift systems on a similar energy footing. The normalized lift is the same as the standard lift coefficient for fixed wings, but differs for wings with more complex motions; it also accounts for such complex motions explicitly and without complex modifications or adjustments. We compare the normalized lift with the previously-reported values of lift coefficient for a rotating cylinder in Magnus effect, a bat during hovering and forward flight, and a hovering dipteran.The maximum standard lift coefficient for a fixed wing without flaps in steady flow is around 1.5, yet for a rotating cylinder it may exceed 9.0, a value that implies that a rotating cylinder generates nearly 6 times the maximum lift of a wing. The maximum normalized lift for a rotating cylinder is 1.5. We suggest that the normalized lift can be used to evaluate propellers, rotors, flapping wings of animals and micro air vehicles, and underwater thrust-generating fins in the same way the lift coefficient is currently used to evaluate fixed wings.
Transfer coefficients for terrestrial foodchain: their derivation and limitations
International Nuclear Information System (INIS)
Ng, Y.C.; Colsher, C.S.; Thompson, S.E.
1979-01-01
Transfer coefficients to predict the passage of isotopes from the environment to terrestrial foods have been derived for various radionuclides of importance in the nuclear fuel cycle. These data update and extend previously recommended handbook values. We derive transfer coefficients to terrestrial foods and describe the systematics of the derived transfer coefficients. Suggestions are offered for changes in the values of transfer coefficients to terrestrial foods that now appear in federal regulatory guides. Deficiencies in our present knowledge concerning transfer coefficients and limitations in the use of these values to ensure compliance with radiation protection standards are discussed
The Constrained Vapor Bubble Experiment - Interfacial Flow Region
Kundan, Akshay; Wayner, Peter C., Jr.; Plawsky, Joel L.
2015-01-01
Internal heat transfer coefficient of the CVB correlated to the presence of the interfacial flow region. Competition between capillary and Marangoni flow caused Flooding and not a Dry-out region. Interfacial flow region growth is arrested at higher power inputs. 1D heat model confirms the presence of interfacial flow region. 1D heat model confirms the arresting phenomena of interfacial flow region Visual observations are essential to understanding.
Modeling fluid flow in open channel with circular cross‐section ...
African Journals Online (AJOL)
Flow in a closed conduit is regarded as open channel flow, if it has a free surface. This study considers unsteady non]uniform open channel flow in a closed conduit with circular cross]section. We investigate the effects of the flow depth, the cross section area of flow, channel radius, slope of the channel, roughness coefficient ...
Changes in Electrokinetic Coupling Coefficients of Granite under Triaxial Deformation
Directory of Open Access Journals (Sweden)
Osamu Kuwano
2012-01-01
Full Text Available Electrokinetic phenomena are believed to be the most likely origin of electromagnetic signals preceding or accompanying earthquakes. The intensity of the source current due to the electrokinetic phenomena is determined by the fluid flux and the electrokinetic coupling coefficient called streaming current coefficient; therefore, how the coefficient changes before rupture is essential. Here, we show how the electrokinetic coefficients change during the rock deformation experiment up to failure. The streaming current coefficient did not increase before failure, but continued to decrease up to failure, which is explained in terms of the elastic closure of capillary. On the other hand, the streaming potential coefficient, which is the product of the streaming current coefficient and bulk resistivity of the rock, increased at the onset of dilatancy. It may be due to change in bulk resistivity. Our result indicates that the zeta potential of the newly created surface does not change so much from that of the preexisting fluid rock interface.
2003-10-01
Maddalon, D. V.; Fisher, D. F.; Jennett , L. A.; Fischer, M. C .; “Simulated Airline Service Experience With Laminar-Flow Control Leading-Edge Systems...Width of disturbance or step, calibration constant in King’s Law CD Drag coefficient CL Lift coefficient Cp Pressure coefficient c Wing or HLF...nacelle fan cowl chord length Cd Section drag coefficient C ’ƒ Skin friction coefficient Cl Section lift coefficient dB Decibel E Anemometer output
The Effect of Shape Memory on Red Blood Cell Motions
Niu, Xiting; Shi, Lingling; Pan, Tsorng-Whay; Glowinski, Roland
2013-11-01
An elastic spring model is applied to study the effect of the shape memory on the motion of red blood cell in flows. In shear flow, shape memory also plays an important role to obtain all three motions: tumbling, swinging, and tank-treading. In Poiseuille flow, cell has an equilibrium shape as a slipper or parachute depending on capillary number. To ensure the tank-treading motion while in slippery shape, a modified model is proposed by introducing a shape memory coefficient which describes the degree of shape memory in cells. The effect of the coefficient on the cell motion of red blood cell will be presented.
Comparison of boiling heat transfer coefficient and pressure drop correlations for evaporators
International Nuclear Information System (INIS)
Eskin, N.; Arslan, G.
2009-01-01
Evaporator design is an important aspect for the HVAC industry. As the demand for more efficient and compact heat exchangers increase, researches on estimation of two-phase flow heat transfer and pressure drop gain importance. Due to complexity of the hydrodynamic and heat transfer of the two-phase flow, there are many experimental studies available for refrigerants int he literature. In this study, a model for boiling heat transfer in a horizontal tube has been developed and the simulation results are compared with experimental ones published in the literature. In these comparisons, heat transfer coefficient is calculated by using Kattan-Thome-Favrat (1998), Shah (1982), Kandilikar (1990), Chaddock and Brunemann (1967) correlations under different operational conditions such as saturation pressure, mass flux, the type of refrigerant and two phase flow pattern. Besides that flow pattern has also been considered in the simulation by using Thome and El Hajal (2002) model. For pressure drop Lockhart-Martinelli (1949), Mueller-Steinhagen-Hack (1986) and Groennerund (1979) correlations are used in simulations. Local vapor quality change at each experimental condition through the model is determined. Roughness is an important parameter for frictional pressure drop. Friction coefficient is determined by using Churchill (1977) model. (author)
Lenzen, Matthias; Merklein, Marion
2017-10-01
In the automotive sector, a major challenge is the deep-drawing of modern lightweight sheet metals with limited formability. Thus, conventional material models lack in accuracy due to the complex material behavior. A current field of research takes into account the evolution of the Lankford coefficient. Today, changes in anisotropy under increasing degree of deformation are not considered. Only a consolidated average value of the Lankford coefficient is included in conventional material models. This leads to an increasing error in prediction of the flow behavior and therefore to an inaccurate prognosis of the forming behavior. To increase the accuracy of the prediction quality, the strain dependent Lankford coefficient should be respected, because the R-value has a direct effect on the contour of the associated flow rule. Further, the investigated materials show a more or less extinct rate dependency of the yield stress. For this reason, the rate dependency of the Lankford coefficient during uniaxial tension is focused within this contribution. To quantify the influence of strain rate on the Lankford coefficient, tensile tests are performed for three commonly used materials, the aluminum alloy AA6016-T4, the advanced high strength steel DP800 and the deep drawing steel DC06 at three different strain rates. The strain measurement is carried out by an optical strain measurement system. An evolution of the Lankford coefficient was observed for all investigated materials. Also, an influence of the deformation velocity on the anisotropy could be detected.
Roughness coefficient and its uncertainty in gravel-bed river
Directory of Open Access Journals (Sweden)
Ji-Sung Kim
2010-06-01
Full Text Available Manning's roughness coefficient was estimated for a gravel-bed river reach using field measurements of water level and discharge, and the applicability of various methods used for estimation of the roughness coefficient was evaluated. Results show that the roughness coefficient tends to decrease with increasing discharge and water depth, and over a certain range it appears to remain constant. Comparison of roughness coefficients calculated by field measurement data with those estimated by other methods shows that, although the field-measured values provide approximate roughness coefficients for relatively large discharge, there seems to be rather high uncertainty due to the difference in resultant values. For this reason, uncertainty related to the roughness coefficient was analyzed in terms of change in computed variables. On average, a 20% increase of the roughness coefficient causes a 7% increase in the water depth and an 8% decrease in velocity, but there may be about a 15% increase in the water depth and an equivalent decrease in velocity for certain cross-sections in the study reach. Finally, the validity of estimated roughness coefficient based on field measurements was examined. A 10% error in discharge measurement may lead to more than 10% uncertainty in roughness coefficient estimation, but corresponding uncertainty in computed water depth and velocity is reduced to approximately 5%. Conversely, the necessity for roughness coefficient estimation by field measurement is confirmed.
Dour, G.; Dargusch, M.; Davidson, C.; Nef, A.; St John, D.
2013-01-01
This paper presents a design for a robust sensor suitable for determining heat flow and heat transfer coefficient in high pressure die casting.A design methodology for the sensor is presented, together with the conclusions of this analysis.A sensor has been manufactured to these principles and some typical results from its operation are introduced.
Boyles, Tom H; Gatley, Elizabeth; Wasserman, Sean; Meintjes, Graeme
2017-03-01
Patients with HIV-associated cryptococcal meningitis (CM) commonly present with raised intracranial pressure (ICP). Aggressive management of raised ICP reduces mortality but requires manometers, which are unavailable in most resource-limited settings. The law of Poiseuille states that the rate of flow of liquid through a tube is directly proportional to the difference in pressure between each end, and it may be possible to indirectly determine ICP by measuring flow of CSF through a spinal needle rather than using a manometer. A convenience sample of CM patients requiring lumbar puncture (LP) (with 22-G spinal needle) for ICP measurement and control were enrolled. ICP was first measured using a narrow bore manometer. After removing the manometer, the number of drops of CSF flowing from the spinal needle in 15 seconds was counted. Thirty-two patients had 89 LPs performed (range, 1-23). Fifty-four had high opening pressure with a CSF flow rate of 16-200 drops/min, and 35 had normal pressure with a CSF flow rate of 8-140 drops/min. Area under the fitted receiver operator character curve was 0.89. A flow rate cutoff to define high pressure of ≥40 drops/min correctly classified 75 of 89 LPs (accuracy 84%). It is technically feasible to indirectly estimate CSF pressure to an accuracy that is clinically useful by counting drops of CSF flowing from a spinal needle. The optimal cutoff value for defining high pressure using a standard 22-G spinal needle is ≥40 drops/min. These findings have the potential to improve CM management in resource-limited settings.
Maqbool, Khadija; Anwar Bég, O.; Sohail, Ayesha; Idreesa, Shafaq
2016-05-01
The theoretical analysis of magnetohydrodynamic (MHD) incompressible flows of a Burgers fluid through a porous medium in a rotating frame of reference is presented. The constitutive model of a Burgers fluid is used based on a fractional calculus formulation. Hydrodynamic slip at the wall (plate) is incorporated and the fractional generalized Darcy model deployed to simulate porous medium drag force effects. Three different cases are considered: namely, the flow induced by a general periodic oscillation at a rigid plate, the periodic flow in a parallel plate channel and, finally, the Poiseuille flow. In all cases the plate(s) boundary(ies) are electrically non-conducting and a small magnetic Reynolds number is assumed, negating magnetic induction effects. The well-posed boundary value problems associated with each case are solved via Fourier transforms. Comparisons are made between the results derived with and without slip conditions. Four special cases are retrieved from the general fractional Burgers model, viz. Newtonian fluid, general Maxwell viscoelastic fluid, generalized Oldroyd-B fluid and the conventional Burgers viscoelastic model. Extensive interpretation of graphical plots is included. We study explicitly the influence of the wall slip on primary and secondary velocity evolution. The model is relevant to MHD rotating energy generators employing rheological working fluids.
International Nuclear Information System (INIS)
Liles, D.R.
1982-01-01
Internal boundaries in multiphase flow greatly complicate fluid-dynamic and heat-transfer descriptions. Different flow regimes or topological configurations can have radically dissimilar interfacial and wall mass, momentum, and energy exchanges. To model the flow dynamics properly requires estimates of these rates. In this paper the common flow regimes for gas-liquid systems are defined and the techniques used to estimate the extent of a particular regime are described. Also, the current computer-code procedures are delineated and introduce a potentially better method is introduced
Modified Regression Correlation Coefficient for Poisson Regression Model
Kaengthong, Nattacha; Domthong, Uthumporn
2017-09-01
This study gives attention to indicators in predictive power of the Generalized Linear Model (GLM) which are widely used; however, often having some restrictions. We are interested in regression correlation coefficient for a Poisson regression model. This is a measure of predictive power, and defined by the relationship between the dependent variable (Y) and the expected value of the dependent variable given the independent variables [E(Y|X)] for the Poisson regression model. The dependent variable is distributed as Poisson. The purpose of this research was modifying regression correlation coefficient for Poisson regression model. We also compare the proposed modified regression correlation coefficient with the traditional regression correlation coefficient in the case of two or more independent variables, and having multicollinearity in independent variables. The result shows that the proposed regression correlation coefficient is better than the traditional regression correlation coefficient based on Bias and the Root Mean Square Error (RMSE).
Object detection by correlation coefficients using azimuthally averaged reference projections.
Nicholson, William V
2004-11-01
A method of computing correlation coefficients for object detection that takes advantage of using azimuthally averaged reference projections is described and compared with two alternative methods-computing a cross-correlation function or a local correlation coefficient versus the azimuthally averaged reference projections. Two examples of an application from structural biology involving the detection of projection views of biological macromolecules in electron micrographs are discussed. It is found that a novel approach to computing a local correlation coefficient versus azimuthally averaged reference projections, using a rotational correlation coefficient, outperforms using a cross-correlation function and a local correlation coefficient in object detection from simulated images with a range of levels of simulated additive noise. The three approaches perform similarly in detecting macromolecular views in electron microscope images of a globular macrolecular complex (the ribosome). The rotational correlation coefficient outperforms the other methods in detection of keyhole limpet hemocyanin macromolecular views in electron micrographs.
Calibration of integral diffraction coefficients of TIAP crystal
International Nuclear Information System (INIS)
Gan Xinshi; China Academy of Engineering Physics, Mianyang; Yang Jiamin; Yi Rongqing; Zhang Jiyan; Zhao Yang; Zhao Yidong; Cui Mingqi; Deng Aihong
2007-01-01
The first, second and third order integral diffraction coefficients of TIAP crystal were calibrated at 4B7 X-ray source on Beijing synchrotron radiation facility with photon energy ranging from 2.1 keV to 6.0 keV. It is shown that the peak diffraction coefficients of the TIAP crystal are rather high. The first order integral diffraction coefficient tends to increase with the decreasing photon energy. But in the range of 2.6 keV to 5.4 keV, the integral diffraction coefficient is about 1.53 x 10 -4 rad. The diffraction coefficients decrease gradually as the diffraction order increases. The second order integral diffraction coefficient is only 1/4 of the first order, and the third order is about one magnitude lower than the first order. The calibrated TIAP crystal can be used to quantitatively analyze X-ray spectrum of laser-produced plasma. (authors)
Osmotic second virial cross coefficients for star and linear polystyrenes
International Nuclear Information System (INIS)
Striolo, Alberto; Prausnitz, John M.
2000-01-01
Experimental osmotic second virial cross coefficients are reported for linear and 8-arm star polystyrenes in three solvents: toluene, cyclohexane, and methylcyclohexane. The osmotic second virial cross coefficient for 8-arm star and linear polystyrene is always positive and within the osmotic second virial coefficients measured for the single polymers. The positive cross coefficient indicates net repulsion between the two different polymers in dilute solution. The extent of repulsion is greatest in toluene and least in cyclohexane. To relate the macroscopic second virial coefficient to microscopic interactions, the potential of mean force between linear and 6-arm star polymers was computed by molecular simulation. The interaction between nonbonded polymer segments is given by a square-well potential. Well width was set equal to one half of the segment diameter. Different solvent conditions were investigated by using different well depths. Potentials of mean force were then used to compute the osmotic second virial cross coefficients. (c) 2000 American Institute of Physics
Verifying reciprocal relations for experimental diffusion coefficients in multicomponent mixtures
DEFF Research Database (Denmark)
Medvedev, Oleg; Shapiro, Alexander
2003-01-01
into Onsager coefficients and a subsequent symmetry check make it possible to evaluate different thermodynamic models with regard to their possibility of being used for prediction of the transport properties. We performed several checks of this kind for ternary mixtures of hydrocarbons and alcohols, where......The goal of the present study is to verify the agreement of the available data on diffusion in ternary mixtures with the theoretical requirement of linear non-equilibrium thermodynamics consisting in symmetry of the matrix of the phenomenological coefficients. A common set of measured diffusion...... diffusion coefficients into Onsager coefficients for a non-ideal mixture involves derivatives of the chemical potentials and, thus, should be based on a certain thermodynamic model (cubic equation of state (EoS), an activity coefficient model, etc.). Transformation of the Fickian diffusion coefficients...
International Nuclear Information System (INIS)
Linjun, Xie; Guohong, Xue; Ming, Zhang
2016-01-01
Graphical abstract: HDS stress coefficient test apparatus. - Highlights: • This paper performs mathematic deduction to the physical model of Hold Down Spring (HDS), establishes a mathematic model of axial load P and stress, stress coefficient and friction coefficient and designs a set of test apparatuses for simulating the pretightening process of the HDS for the first time according to a model similarity criterion. • The mathematical relation between the load and the strain is obtained about the HDS, and the mathematical model of the stress coefficient and the friction coefficient is established. So, a set of test apparatuses for obtaining the stress coefficient is designed according to the model scaling criterion and the friction coefficient of the K1000 HDS is calculated to be 0.336 through the obtained stress coefficient. • The relation curve between the theoretical load and the friction coefficient is obtained through analysis and indicates that the change of the friction coefficient f would influence the pretightening load under the condition of designed stress. The necessary pretightening load in the design process is calculated to be 5469 kN according to the obtained friction coefficient. Therefore, the friction coefficient and the pretightening load under the design conditions can provide accurate pretightening data for the analysis and design of the reactor HDS according to the operations. - Abstract: This paper performs mathematic deduction to the physical model of Hold Down Spring (HDS), establishes a mathematic model of axial load P and stress, stress coefficient and friction coefficient and designs a set of test apparatuses for simulating the pretightening process of the HDS for the first time according to a model similarity criterion. By carrying out tests and researches through a stress testing technique, P–σ curves in loading and unloading processes of the HDS are obtained and the stress coefficient k f of the HDS is obtained. So, the
Energy Technology Data Exchange (ETDEWEB)
Linjun, Xie, E-mail: linjunx@zjut.edu.cn [College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014 (China); Guohong, Xue; Ming, Zhang [Shanghai Nuclear Engineering Research & Design Institute, Shanghai 200233 (China)
2016-08-01
Graphical abstract: HDS stress coefficient test apparatus. - Highlights: • This paper performs mathematic deduction to the physical model of Hold Down Spring (HDS), establishes a mathematic model of axial load P and stress, stress coefficient and friction coefficient and designs a set of test apparatuses for simulating the pretightening process of the HDS for the first time according to a model similarity criterion. • The mathematical relation between the load and the strain is obtained about the HDS, and the mathematical model of the stress coefficient and the friction coefficient is established. So, a set of test apparatuses for obtaining the stress coefficient is designed according to the model scaling criterion and the friction coefficient of the K1000 HDS is calculated to be 0.336 through the obtained stress coefficient. • The relation curve between the theoretical load and the friction coefficient is obtained through analysis and indicates that the change of the friction coefficient f would influence the pretightening load under the condition of designed stress. The necessary pretightening load in the design process is calculated to be 5469 kN according to the obtained friction coefficient. Therefore, the friction coefficient and the pretightening load under the design conditions can provide accurate pretightening data for the analysis and design of the reactor HDS according to the operations. - Abstract: This paper performs mathematic deduction to the physical model of Hold Down Spring (HDS), establishes a mathematic model of axial load P and stress, stress coefficient and friction coefficient and designs a set of test apparatuses for simulating the pretightening process of the HDS for the first time according to a model similarity criterion. By carrying out tests and researches through a stress testing technique, P–σ curves in loading and unloading processes of the HDS are obtained and the stress coefficient k{sub f} of the HDS is obtained. So, the
Taylor coefficients and coefficient multipliers of Hardy and Bergman-type spaces
Jevtić, Miroljub; Arsenović, Miloš
2016-01-01
This book provides a systematic overview of the theory of Taylor coefficients of functions in some classical spaces of analytic functions and especially of the coefficient multipliers between spaces of Hardy type. Offering a comprehensive reference guide to the subject, it is the first of its kind in this area. After several introductory chapters covering the basic material, a large variety of results obtained over the past 80 years, including the most recent ones, are treated in detail. Several chapters end with discussions of practical applications and related topics that graduate students and experts in other subjects may find useful for their own purposes. Thus, a further aim of the book is to communicate to non-specialists some concrete facts that may be of value in their own work. The book can also be used as a textbook or a supplementary reference for an advanced graduate course. It is primarily intended for specialists in complex and functional analysis, graduate students, and experts in other related...
On some properties of SU(3 fusion coefficients
Directory of Open Access Journals (Sweden)
Robert Coquereaux
2016-11-01
Full Text Available Three aspects of the SU(3 fusion coefficients are revisited: the generating polynomials of fusion coefficients are written explicitly; some curious identities generalizing the classical Freudenthal–de Vries formula are derived; and the properties of the fusion coefficients under conjugation of one of the factors, previously analyzed in the classical case, are extended to the affine algebra suˆ(3 at finite level.
Coefficient of restitution of model repaired car body parts
D. Hadryś; M. Miros
2008-01-01
Purpose: The qualification of influence of model repaired car body parts on the value of coefficient of restitution and evaluation of impact energy absorption of model repaired car body parts.Design/methodology/approach: Investigation of plastic strain and coefficient of restitution of new and repaired model car body parts with using impact test machine for different impact energy.Findings: The results of investigations show that the value of coefficient of restitution changes with speed (ene...
Clebsch-Gordan and Racah coefficients of SUpq(2)
International Nuclear Information System (INIS)
Kachurik, I.I.
1993-01-01
Explicit expressions for the Clebsch-Gordan coefficients and for the Racah coefficients of the two-parametric quantum algebra SU pq (2) are derived. They are given as finite sums and as terminating basic hypergeometric functions 3 φ 2 and 4 φ 3 . It is indicated how other expressions for these coefficients can be derived with the help of basic hypergeometric functions. (author). 11 refs
Table for constructing the spin coefficients in general relativity
International Nuclear Information System (INIS)
Cocke, W.J.
1989-01-01
The spin coefficients in spinor calculus in Riemannian space-time are linear functions of the curls of the connecting quantities (the Infeld--Van der Waerden symbols). We show that in the Newman-Penrose formalism the expressions for the spin coefficients are quite manageable, if they are written in terms of the Newman-Penrose tetrad vectors. We present a table of the components of the spin coefficients explicitly in terms of the curls of the individual tetrad vectors
On the Connection Coefficients of the Chebyshev-Boubaker Polynomials
Directory of Open Access Journals (Sweden)
Paul Barry
2013-01-01
Full Text Available The Chebyshev-Boubaker polynomials are the orthogonal polynomials whose coefficient arrays are defined by ordinary Riordan arrays. Examples include the Chebyshev polynomials of the second kind and the Boubaker polynomials. We study the connection coefficients of this class of orthogonal polynomials, indicating how Riordan array techniques can lead to closed-form expressions for these connection coefficients as well as recurrence relations that define them.
DCFPAK: Dose coefficient data file package for Sandia National Laboratory
Energy Technology Data Exchange (ETDEWEB)
Eckerman, K.F.; Leggett, R.W.
1996-07-31
The FORTRAN-based computer package DCFPAK (Dose Coefficient File Package) has been developed to provide electronic access to the dose coefficient data files summarized in Federal Guidance Reports 11 and 12. DCFPAK also provides access to standard information regarding decay chains and assembles dose coefficients for all dosimetrically significant radioactive progeny of a specified radionuclide. DCFPAK was designed for application on a PC but, with minor modifications, may be implemented on a UNIX workstation.
On the connection coefficients of the Chebyshev-Boubaker polynomials.
Barry, Paul
2013-01-01
The Chebyshev-Boubaker polynomials are the orthogonal polynomials whose coefficient arrays are defined by ordinary Riordan arrays. Examples include the Chebyshev polynomials of the second kind and the Boubaker polynomials. We study the connection coefficients of this class of orthogonal polynomials, indicating how Riordan array techniques can lead to closed-form expressions for these connection coefficients as well as recurrence relations that define them.
Rossinskyi, Volodymyr
2018-02-01
The biological wastewater treatment technologies in anoxic and aerobic bioreactors with recycle of sludge mixture are used for the effective removal of organic compounds from wastewater. The change rate of sludge mixture recirculation between bioreactors leads to a change and redistribution of concentrations of organic compounds in sludge mixture in bioreactors and change hydrodynamic regimes in bioreactors. Determination of the coefficient of internal recirculation of sludge mixture between bioreactors is important for the choice of technological parameters of biological treatment (wastewater treatment duration in anoxic and aerobic bioreactors, flow capacity of recirculation pumps). Determination of the coefficient of internal recirculation of sludge mixture requires integrated consideration of hydrodynamic parameter (flow rate), kinetic parameter (rate of oxidation of organic compounds) and physical-chemical parameter of wastewater (concentration of organic compounds). The conducted numerical experiment from the proposed mathematical equations allowed to obtain analytical dependences of the coefficient of internal recirculation sludge mixture between bioreactors on the concentration of organic compounds in wastewater, the duration of wastewater treatment in bioreactors.
Theory and Experiment of Binary Diffusion Coefficient of n-Alkanes in Dilute Gases.
Liu, Changran; McGivern, W Sean; Manion, Jeffrey A; Wang, Hai
2016-10-10
Binary diffusion coefficients were measured for n-pentane, n-hexane, and n-octane in helium and of n-pentane in nitrogen over the temperature range of 300 to 600 K, using reversed-flow gas chromatography. A generalized, analytical theory is proposed for the binary diffusion coefficients of long-chain molecules in simple diluent gases, taking advantage of a recently developed gas-kinetic theory of the transport properties of nanoslender bodies in dilute free-molecular flows. The theory addresses the long-standing question about the applicability of the Chapman-Enskog theory in describing the transport properties of nonspherical molecular structures, or equivalently, the use of isotropic potentials of interaction for a roughly cylindrical molecular structure such as large normal alkanes. An approximate potential energy function is proposed for the intermolecular interaction of long-chain n-alkane with typical bath gases. Using this potential and the analytical theory for nanoslender bodies, we show that the diffusion coefficients of n-alkanes in typical bath gases can be treated by the resulting analytical model accurately, especially for compounds larger than n-butane.
Directory of Open Access Journals (Sweden)
Tekelioğlu Murat
2017-01-01
Full Text Available An experimental method was proposed to assess the natural and forced convective heat transfer coefficients on highly conductive bodies. Experiments were performed at air velocities of 0m/s, 4.0m/s, and 5.4m/s, and comparisons were made between the current results and available literature. These experiments were extended to arbitrary-shape bodies. External flow conditions were maintained throughout. In the proposed method, in determination of the surface convective heat transfer coefficients, flow condition is immaterial, i.e., either laminar or turbulent. With the present method, it was aimed to acquire the local heat transfer coefficients on any arbitrary conductive shape. This method was intended to be implemented by the heat transfer engineer to identify the local heat transfer rates with local hot spots. Finally, after analyzing the proposed experimental results, appropriate decisions can be made to control the amount of the convective heat transfer off the surface. Limited mass transport was quantified on the cooled plate.
Classification of coefficients of variation in experiments with commercial layers
Directory of Open Access Journals (Sweden)
DE Faria Filho
2010-12-01
Full Text Available This study aimed at determining a specific classification of coefficients of variation in experiments with commercial layers. Coefficients of variation were collected from papers published in Brazilian journals between 2000 and 2009 for performance, internal egg quality, and eggshell quality parameters. The coefficients of variation of each parameter were classified as low, intermediate, high, and very high according to the ratio between the median and the pseudo-sigma. It was concluded that the parameters used in experiments with commercial layers have a specific classification of coefficients of variation, and that this must be considered to evaluate experimental accuracy.
Diffusion coefficient of three-dimensional Yukawa liquids
Energy Technology Data Exchange (ETDEWEB)
Dzhumagulova, K. N.; Ramazanov, T. S.; Masheeva, R. U. [IETP, Al Farabi Kazakh National University, 71, al Farabi ave., Almaty 050040 (Kazakhstan)
2013-11-15
The purpose of this work is an investigation of the diffusion coefficient of the dust component in complex plasma. The computer simulation of the Yukawa liquids was made on the basis of the Langevin equation, which takes into account the influence of buffer plasma on the dust particles dynamics. The Green–Kubo relation was used to calculate the diffusion coefficient. Calculations of the diffusion coefficient for a wide range of the system parameters were performed. Using obtained numerical data, we constructed the interpolation formula for the diffusion coefficient. We also show that the interpolation formula correctly describes experimental data obtained under microgravity conditions.
Passive and active flow augmentation : From diffusers to multi-rotor machines
De Oliveira Andrade, G.L.; Balbino Dos Santos Pereira, R.; van Bussel, G.J.W.; Avallone, F.; Ragni, D.
2017-01-01
Flow augmentation consists in modifying mass flow across the actuation plane of a rotor to enhance energy extraction or propulsive efficiency. The talk sketches the distinction between passive and active rotor augmentation strategies. Power coefficient trends are compared analytically while
Moisture Transfer in Concrete: Numerical Determination of the Capillary Conductivity Coefficient
Directory of Open Access Journals (Sweden)
Simo Elie
2017-03-01
Full Text Available We numerically investigated moisture transfer in buildings made of concrete. We considered three types of concrete: normal concrete, pumice concrete and cellular concrete. We present the results of a 1-D liquid water flow in such materials. We evaluated the moisture distribution in building materials using the Runge-Kutta fourth-and-fifth-order method. The DOPRI5 code was used as an integrator. The model calculated the resulting moisture content and other moisture-dependent physical parameters. The moisture curves were plotted. The dampness data obtained was utilized for the numerical computation of the coefficient of the capillary conductivity of moisture. Different profiles of this coefficient are represented. Calculations were performed for four different values of the outdoor temperature: -5°C, 0°C, 5°C and 10°C. We determined that the curves corresponding to small time intervals of wetting are associated with great amplitudes of the capillary conductivity . The amplitudes of the coefficient of the capillary conductivity decrease as the time interval increases. High outdoor temperatures induce high amplitudes of the coefficient of the capillary conductivity.
Moisture Transfer in Concrete: Numerical Determination of the Capillary Conductivity Coefficient
Simo, Elie; Dzali Mbeumo, Pascal Durant; Mbami Njeuten, Jeanne Claude
2017-03-01
We numerically investigated moisture transfer in buildings made of concrete. We considered three types of concrete: normal concrete, pumice concrete and cellular concrete. We present the results of a 1-D liquid water flow in such materials. We evaluated the moisture distribution in building materials using the Runge-Kutta fourth-and-fifth-order method. The DOPRI5 code was used as an integrator. The model calculated the resulting moisture content and other moisture-dependent physical parameters. The moisture curves were plotted. The dampness data obtained was utilized for the numerical computation of the coefficient of the capillary conductivity of moisture. Different profiles of this coefficient are represented. Calculations were performed for four different values of the outdoor temperature: -5°C, 0°C, 5°C and 10°C. We determined that the curves corresponding to small time intervals of wetting are associated with great amplitudes of the capillary conductivity . The amplitudes of the coefficient of the capillary conductivity decrease as the time interval increases. High outdoor temperatures induce high amplitudes of the coefficient of the capillary conductivity.
Laminar flow in a recess of a hydrostatic bearing
San Andres, Luis A.; Velthuis, Johannes F. M.
1992-01-01
The flow in a recess of a hydrostatic journal bearing is studied in detail. The Navier-Stokes equations for the laminar flow of an incompressible liquid are solved numerically in a two-dimensional plane of a typical bearing recess. Pressure- and shear-induced flows, as well as a combination of these two flow conditions, are analyzed. Recess friction, pressure-ram effects at discontinuities in the flow region, and film entrance pressure loss effects are calculated. Entrance pressure loss coefficients over a forward-facing step are presented as functions of the mean flow Reynolds number for pure-pressure and shear-induced laminar flows.
TRACG-CFD analysis of ESBWR reactor water cleanup shutdown cooling system mixing coefficient
Energy Technology Data Exchange (ETDEWEB)
Gallardo, J. [UNAM, Facultad de Ingenieria, Ciudad Universitaria, 04510 Ciudad de Mexico (Mexico); Marquino, W.; Mistreanu, A.; Yang, J., E-mail: euqrop@hotmail.com [General Electric Hitachi Nuclear Energy, Wilmington, 28401 North Carolina (United States)
2015-09-15
The ESBWR is a 1520 nominal [M We] Generation III+ natural circulation boiling water reactor designed to high levels of safety utilizing features that have been successfully used before in operating BWRs, as well as standard features common to A BWR. In September of 2014, the US NRC has certified the ESBWR design for use in the USA. The RWCU/Sdc is an auxiliary system for the ESBWR nuclear island. Basic functions it performs include purifying the reactor coolant during normal operation and shutdown and providing shutdown cooling and cooldown to cold shutdown conditions. The performance of the RWCU system during shutdown cooling is directly related to the temperature of the water removed through the outlets, which is coupled with the vessel and F W temperatures through a thermal mixing coefficient. The complex three-dimensional (3-D) geometry of the BWR downcomer and lower plenum has a great impact on the flow mixing. Only a fine mesh technique like CFD can predict the 3-D temperature distribution in the RPV during shutdown and provide the RWCU/Sdc system inlet temperature. Plant shutdown is an unsteady event by nature and was modeled as a succession of CFD steady-state simulations. It is required to establish the mixing coefficient (which is a function of the heat balance and the core flow) during the operation of the RWCU system in the multiple shutdown cooling modes, and therefore a range of core flows needs to be estimated using quasi steady states obtained with TRACG. The lower end of that range is obtained from a system with minimal power decay heat and core flow; while the higher end corresponds to the power at the beginning of RWCU/Sdc operation when the cooldown is transferred to the RWCU/Sdc after the initial depressurization via the turbine bypass valves. Because the ESBWR RWCU/Sdc return and suction designs provide good mixing, the uniform mixing energy balance was found to be an adequate alternative for deriving the mixing coefficient. The CFD mass flow
TRACG-CFD analysis of ESBWR reactor water cleanup shutdown cooling system mixing coefficient
International Nuclear Information System (INIS)
Gallardo, J.; Marquino, W.; Mistreanu, A.; Yang, J.
2015-09-01
The ESBWR is a 1520 nominal [M We] Generation III+ natural circulation boiling water reactor designed to high levels of safety utilizing features that have been successfully used before in operating BWRs, as well as standard features common to A BWR. In September of 2014, the US NRC has certified the ESBWR design for use in the USA. The RWCU/Sdc is an auxiliary system for the ESBWR nuclear island. Basic functions it performs include purifying the reactor coolant during normal operation and shutdown and providing shutdown cooling and cooldown to cold shutdown conditions. The performance of the RWCU system during shutdown cooling is directly related to the temperature of the water removed through the outlets, which is coupled with the vessel and F W temperatures through a thermal mixing coefficient. The complex three-dimensional (3-D) geometry of the BWR downcomer and lower plenum has a great impact on the flow mixing. Only a fine mesh technique like CFD can predict the 3-D temperature distribution in the RPV during shutdown and provide the RWCU/Sdc system inlet temperature. Plant shutdown is an unsteady event by nature and was modeled as a succession of CFD steady-state simulations. It is required to establish the mixing coefficient (which is a function of the heat balance and the core flow) during the operation of the RWCU system in the multiple shutdown cooling modes, and therefore a range of core flows needs to be estimated using quasi steady states obtained with TRACG. The lower end of that range is obtained from a system with minimal power decay heat and core flow; while the higher end corresponds to the power at the beginning of RWCU/Sdc operation when the cooldown is transferred to the RWCU/Sdc after the initial depressurization via the turbine bypass valves. Because the ESBWR RWCU/Sdc return and suction designs provide good mixing, the uniform mixing energy balance was found to be an adequate alternative for deriving the mixing coefficient. The CFD mass flow
Maillet; Coveney
2000-08-01
The behavior of two-dimensional binary and ternary amphiphilic fluids under flow conditions is investigated using a hydrodynamic lattice-gas model. After the validation of the model in simple cases (Poiseuille flow, Darcy's law for single component fluids), attention is focused on the properties of binary immiscible fluids in porous media. An extension of Darcy's law which explicitly admits a viscous coupling between the fluids is verified, and evidence of capillary effects is described. The influence of a third component, namely, surfactant, is studied in the same context. Invasion simulations have also been performed. The effect of the applied force on the invasion process is reported. As the forcing level increases, the invasion process becomes faster and the residual oil saturation decreases. The introduction of surfactant in the invading phase during imbibition produces new phenomena, including emulsification and micellization. At very low fluid forcing levels, this leads to the production of a low-resistance gel, which then slows down the progress of the invading fluid. At long times (beyond the water percolation threshold), the concentration of remaining oil within the porous medium is lowered by the action of surfactant, thus enhancing oil recovery. On the other hand, the introduction of surfactant in the invading phase during drainage simulations slows down the invasion process-the invading fluid takes a more tortuous path to invade the porous medium-and reduces the oil recovery (the residual oil saturation increases).
Terrón-Mejía, Ketzasmin A; López-Rendón, Roberto; Goicochea, Armando Gama
2017-08-29
The need to extract oil from wells where it is embedded on the surfaces of rocks has led to the development of new and improved enhanced oil recovery techniques. One of those is the injection of surfactants with water vapor, which promotes desorption of oil that can then be extracted using pumps, as the surfactants encapsulate the oil in foams. However, the mechanisms that lead to the optimal desorption of oil and the best type of surfactants to carry out desorption are not well known yet, which warrants the need to carry out basic research on this topic. In this work, we report non equilibrium dissipative particle dynamics simulations of model surfactants and oil molecules adsorbed on surfaces, with the purpose of studying the efficiency of the surfactants to desorb hydrocarbon chains, that are found adsorbed over flat surfaces. The model surfactants studied correspond to nonionic and cationic surfactants, and the hydrocarbon desorption is studied as a function of surfactant concentration under increasing Poiseuille flow. We obtain various hydrocarbon desorption isotherms for every model of surfactant proposed, under flow. Nonionic surfactants are found to be the most effective to desorb oil and the mechanisms that lead to this phenomenon are presented and discussed.
Yang, Peng; Chen, Hui; Liu, Yingwen
2017-06-01
In this paper, a two-dimensional axisymmetric model of a thermoacoustic Stirling engine with a short tube where the cross section narrows has been developed. The transient streamlines and vortex formation through short tubes with different diameters in oscillatory flow have been investigated visually by computational fluid dynamics. Three dimensionless parameters, Reynolds number (Re), Keulegan-Carpenter number (KC), and Womersley number (Wo), are used to describe the flow regime and vortex characteristic throughout the short tube. High Re and Wo numbers indicate that the oscillatory flow develops into the turbulent flow through the short tube. The KC number has a direct effect on the transition of streamlines and the development of the vortex. For a small cross section where KC ≈ 1, streamlines rotate and the vortex forms at both sides of the short tube. The vortex stays in the main flow region, and intensity varies as streamlines are convected downstream. The velocity along the radius presents a Poiseuille profile within the influence of the vortex. For a large cross section where KC < 1, streamlines pass the short tube with little rotation and the vortex disappears in the main flow region and confines near the short tube. The velocity profile tends to be flat. The nonlinear effects including instantaneous pressure drop and power dissipation throughout the short tube are also discussed. It shows that the time averaged pressure drop is generated at the cost of power dissipation. Finally, the "effectiveness" is applied to evaluate the performance of the short tube. The results suggest that increasing the diameter of the short tube is in favor of reducing power dissipation, which is beneficial to improve "effectiveness."
Determining the Coefficient of Discharge for a Draining Container
Hicks, Ashley; Slaton, William
2014-01-01
The flow of fluids through open containers is a topic studied frequently in introductory physics classes. A fluid mechanics class delves deeper into the topic of fluid flow through open containers with holes or barriers. The flow of a fluid jet out of a sharp-edged orifice rarely has the same area as the orifice due to a fluid flow phenomenon…
Investigation on the Flow in a Rotor-Stator Cavity with Centripetal Through-Flow
Directory of Open Access Journals (Sweden)
Bo Hu
2017-10-01
Full Text Available Daily and Nece distinguished four flow regimes in an enclosed rotor-stator cavity, which are dependent on the circumferential Reynolds number and dimensionless axial gap width. A diagram of the different flow regimes including the respective mean profiles for both tangential and radial velocity was developed. The coefficients for the different flow regimes have also been correlated. In centrifugal pumps and turbines, the centripetal through-flow is quite common from the outer radius of the impeller to the impeller eye, which has a strong influence on the radial pressure distribution, axial thrust and frictional torque. The influence of the centripetal through-flow on the cavity flow with different circumferential Reynolds numbers and dimensionless axial gap width is not sufficiently investigated. It is also quite important to convert the 2D Daily and Nece diagram into 3D by introducing the through-flow coefficient. In order to investigate the impact of the centripetal through-flow, a test rig is designed and built up at the University of Duisburg-Essen. The design of the test rig is described. The impact of the above mentioned parameters on the velocity profile, pressure distribution, axial thrust and frictional torque are presented and analyzed in this paper. The 3D Daily and Nece diagram introducing the through-flow coefficient is also organized in this paper.
Aerodynamic coefficients of stationary dry inclined bridge cables in laminar flow
DEFF Research Database (Denmark)
Matteoni, Giulia; Georgakis, Christos; Ricciardelli, Francesco
2011-01-01
Stay cables are the most flexible elements of cable-stayed bridges. When exposed to wind loading, they often undergo large amplitude vibrations, thus motivating serious design concerns. In most cases, vibrations are observed in the presence of water rivulets or ice accretions, which lead...... to an effective change in the cable cross section, and its aerodynamic properties. On the other hand, divergent, self-excited vibrations have been observed in the field also for dry, inclined stay cables, in warm temperatures. The need for reliable design guidelines for inclined stay cables has motivated...
Enzyme mass-transfer coefficient in aqueous two-phase systems using static mixer extraction column.
Rostami, K; Alamshahi, M
2002-09-01
Recent technical advances in aqueous two-phase systems (ATPS) have made this a sound technique for the extraction of biomacromolecules. The extraction of alpha-amylase was investigated using aqueous two-phase systems formed by sodium sulphate-polyethylene glycol (PEG) in water in a 47-mm inner diameter spray column packed with three types of static mixers. The effects of dispersed-phase flow rate, phase composition, column height and diameter were studied. The extraction column was operated in a semi-batch manner. It was found that the hold-up and volumetric mass transfer coefficients increased with an increase in dispersed (PEG-rich) phase velocity and decreased with increasing phase composition. Empirical correlations were developed for fractional dispersed-phase hold-up and volumetric mass transfer coefficients.
Energy Technology Data Exchange (ETDEWEB)
Gierczak, T.; Talukdar, R.; Lovejoy, E.R.; Ravishankara, A.R. (National Oceanic and Atmospheric Administration, Boulder, CO (USA) Univ. of Colorado, Boulder (USA)); Vaghjiani, G.L. (Univ. of Dayton Research Inst., Edwards AFB, CA (USA))
1991-03-20
The rate coefficients for the reactions of OH with five halocarbons (CF{sub 3}CH{sub 2} (HFC 134a), CF{sub 3}CHClF (HCFC 124), CF{sub 3}CHCl{sub 2} (HCFC 123), CH{sub 3}CHF{sub 2} (HFC 152a), and CH{sub 3}CF{sub 2}Cl (HCFC 142b)), which are proposed as alternatives to chlorofluoromethanes, have been measured. A pulsed pholtolysis system and a discharge flow apparatus were used to measure the rate coefficients between approximately 210 and 425 K. Use of the complementary techniques enabled identification of systematic errors and minimization of these errors. The obtained values are compared with values previously measured by other groups. This data base is used in the subsequent paper to calculate the atmospheric lifetimes of the five compounds.
Vibration Analysis of a Framework Structure by Generalized Transfer Stiffness Coefficient Method
Bonkobara, Yasuhiro; Kondou, Takahiro; Ayabe, Takashi; Choi, Myung-Soo
A generalized transfer stiffness coefficient method using graph theory is developed in order to improve the applicability of the transfer stiffness coefficient method. In the new method, an analytical model is expressed by a weighted signal-flow graph, and the graph is contracted according to the series and parallel contraction rules. The computational complexity and the memory requirement for the contraction process are both minimized by choosing the optimal contraction route. In addition, it is possible to develop a data-driving program that is applicable to various structures without updating the source program. An algorithm based on the present method is formulated for the in-plane longitudinal and flexural coupled free and forced vibration analyses of a two-dimensional framework structure. Furthermore, an overview for applying the method to a three-dimensional framework structure is briefly presented. The validity of the present algorithm is confirmed by the results of numerical computations.
Experimental determination of the attachment coefficients of atoms and ions on monodisperse aerosols
International Nuclear Information System (INIS)
Porstendoerfer, J.; Roebig, G.; Ahmed, A.
1979-01-01
The attachment coefficients of 212 Pb atoms and ions were measured for aerosols in the diameter range 0.1 to 5 μm. The attachment of the Tn-decay products to the aerosol was carried out in laminar flow through a cylindrical tube. Under the same experimental conditions (but without aerosols) the diffusion coefficient of the atoms was determined. The generation of the monodisperse di-2-ethylhexyl sebacate (DEHS) aerosol was carried out by controlled condensation of vapour upon nuclei. The aerosols had standard deviations of 3 to 5%. The aerosol size distributions and concentrations were determined by means of an aerosol size spectrometer, which measured the intensity of the scattered light from single-particles or droplets. The experimental results agree well with the values of the diffusion attachment theory based on the kinetic theory of gases with the assumption of a sticking probability of the Pb atoms, S = 1. (author)
Determination of gamma ray attenuation coefficients of Al–4% Cu ...
Indian Academy of Sciences (India)
Gamma ray attenuation coefficients of metal matrix composites have been investigated. For this purpose, the linear attenuation coefficients of composites containing boron carbide (B4C) at different rates have been measured using a gamma spectrometer that contains a NaI(Tl) detector and MCA at 662, 1173 and 1332 keV, ...