Energy Technology Data Exchange (ETDEWEB)

This paper is an introduction course in modelling turbulent thermohydraulics, aimed at computational fluid dynamics users. No specific knowledge other than the Navier Stokes equations is required beforehand. Chapter I (which those who are not beginners can skip) provides basic ideas on turbulence physics and is taken up in a textbook prepared by the teaching team of the ENPC (Benque, Viollet). Chapter II describes turbulent viscosity type modelling and the 2k-{epsilon} two equations model. It provides details of the channel flow case and the boundary conditions. Chapter III describes the `standard` (R{sub ij}-{epsilon}) Reynolds tensions transport model and introduces more recent models called `feasible`. A second paper deals with heat transfer and the effects of gravity, and returns to the Reynolds ...

International Nuclear Information System (INIS)

Results of three-dimensional laminar and standard K-#epsilon# turbulent numerical simulations of natural convection cooling of ten cubic aluminum blocks mounted on an insulated plate, facing a shrouding wall, are presented. This geometry is chosen so that comparison with experimental results is possible. The considered problem is of great practical importance because it simulates the case of heated electronic chips, mounted on printed board assemblies, which are frequently encountered in electronic industry applications. The problem is mathematically modeled by the three-dimensional conservation differential equations of mass, momentum, energy and turbulent kinetic energy and dissipation (for the turbulent flow model). IN this paper, these equations are numerically solved by a finite volume method and the laminar and turbulent results are ...

Science.gov (United States)

Turbulent flow in a 2D channel with repeated rectangular rib roughness was numerically simulated using a low Reynolds number form of the k-epsilon turbulence model. Friction factors and average Stanton numbers were calculated for various pitch to rib height ratios and bulk Reynolds numbers. Comparisons with experiment were generally adequate, with the predictions of friction superior to those for heat transfer. The effect of variable properties for channel flow was investigated, and the results showed a greater effect for friction than for heat transfer. Comparison with experiment yielded no clear conclusions. The turbulence model was also validated for a related problem, that of flow downstream of an abrupt pipe expansion.

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Turbulent premixed methane-air combustion in a cylindrical chamber is numerically simulated considering radiation effect. Reaction rates are considered as minimum rates between Arrhenius rates and eddy break up rates. A five step reduced mechanism is used. Turbulent modeling is done via standard k-{epsilon} model imposed by empirical inlet boundary conditions. Source terms of energy equation consist of reaction rates and radiation effects. The discrete ordinate method (DOM) is employed to solve the radiative transfer equation (RTE) and the weighted sum of gray gas model (WSGGM) is imposed to consider radiation effect of non-gray gases. The results indicate that in the case of turbulent combusting flows, the effect of radiation of gases can affect the temperature and species concentrations. The numerical results obtained considering radiation ...

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Combustion in a ceramic tube produces a nearly discontinuous change in temperature of the premixed fuel and air at the flame front, from room temperature up to the adiabatic flame temperature ([approximately]2,100 K). The upstream Reynolds number for a stable flame in a 9.5-mm tube is in the range of 3,000-6,000, corresponding to turbulent flow. Owing to property changes that accompany the severe increase in temperature at the flame front, the downstream Reynolds number is reduced below the transitional value ([approximately]2,100); consequently the turbulence decays while the velocity profile approaches the parabolic one characteristic of laminar flow. A previous study of ours revealed that, far downstream from the flame front, the turbulent energy decayed exponentially with downstream distance. This paper examines the asymptotic behavior of the k-[epsilon] ...

Energy Technology Data Exchange (ETDEWEB)

Full text of publication follows: Hydrogen release and distribution in nuclear power plant containment is an important safety issue. Selection of a proper turbulence model is important for accurate estimation of the mixing process. The selection of turbulence model is dictated by the best compromise between accuracy and computational efforts. For this, three different turbulence models, viz. Standard k-{epsilon}, RNG k-{epsilon} and Reynolds Stress Model, based on Reynolds averaged Navier Stokes equations (RANS) approach, were used. The computations were done using the CFD code FLUENT, which is based on the control volume methodology. The computational results were compared with the experimental results of HYMIS test facility, where helium was used to simulate hydrogen. The processes of helium plume ...

Energy Technology Data Exchange (ETDEWEB)

The buoyancy driven convective flow fields are steady circulatory flows which were made between surfaces maintained at two fixed temperatures. They are ubiquitous in nature and play an important role in many engineering applications. Application of a natural convection can reduce the costs and efforts remarkably. This paper focuses on the sensitivity study of turbulence analysis using CFD (Computational Fluid Dynamics) for a natural convection in a closed rectangular cavity. Using commercial CFD code, FLUENT and various turbulent models were applied to the turbulent flow. Results from each CFD model will be compared each other in the viewpoints of grid resolution and flow characteristics. It has been showed that: -) obtaining general flow characteristics is possible with relatively coarse grid; -) there is no significant difference between results from finer grid resolutions than ...

Science.gov (United States)

No Abstract Available

Science.gov (United States)

... Lincoln Laboratory Distribution Models for Optical Scintillation Due to Atmospheric Turbulence RR Parenti RJ Susiela Group 107 ...

Energy Technology Data Exchange (ETDEWEB)

The buoyancy driven convective flow fields are steady circulatory flows which were made between surfaces maintained at two fixed temperatures. They are ubiquitous in nature and play an important role in many engineering applications. Especially, in last decades, natural convection in a close loop or cavity becomes the main issue in the molecular biology for the polymerase chain reaction (PCR). Application of a natural convection can reduce the costs and efforts remarkably. This paper focuses on the sensitivity study of turbulence analysis using CFD for a natural convection in a closed rectangular cavity. Using commercial CFD code, FLUENT, various turbulent models were applied to the turbulent flow. Results from each CFD model will be compared each other in the viewpoints of flow characteristics. This work will suggest the best turbulent ...

Energy Technology Data Exchange (ETDEWEB)

The aim of this study concerns the use of numerical methods for the resolution of the Reynolds Averaged Navier Stokes equations adapted to the simulation of the cooling of the trailing edge of a stator in a high pressure turbine. These methods, based on the elsA solver developed at ONERA, use a four steps Runge Kutta time discretization scheme and a Jameson centered space discretization scheme. The scheme is applied through a finite volume approach on control volume centered on the cells of a multi-block structured mesh. Turbulence is simulated either through the algebraic Michel model, or through the one-transport-equation Spalart-Allmaras model, or through the two-transport-equations k 1, k {omega} and k {epsilon} models, and through ASM model. A simulation of the flow in a bidimensional stator, without cooling, is ...

Energy Technology Data Exchange (ETDEWEB)

Momentum transfer through an air-water interface was studied in a horizontal rectangular channel through experimental and numerical analysis. The liquid flow Reynolds numbers, based on hydraulic diameters, were 11500 and 17000. The air flow Reynolds number varied from 0 to 3260. In experiments, velocity distribution was measured by hot-film and hot-wire probes. The effect of the liquid flow Reynolds number and the direction of interfacial shear stress was investigated by performing the cocurrent and countercurrent experiments. The modified k-{epsilon} model was able to reproduce these experimental results qualitatively. The range of applicability of the modified k-{epsilon} model was also discussed. (author).

Wastenet

... The relation between turbulence structure and a scalar detected using a new statistical test for the change in fractal dimension of a time-series, Department of Geography, University of Durham Workshop on Coherent Structures in Rivers Keylock C.J., Nishimura K., Nemoto M., Ito Y. 2006. The wake structure from fractal fences: implications for the control of turbulent suspensions, Warwick Turbulence ...

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Different calculated models are presented for turbulent break-off flows and their classification, reflecting the sequence of historical development. The study was done based on equations of viscous liquid of the Navier-Stokes type with development of special phenomenological models of turbulence which take into consideration real properties of the break-off flows based on simpler models of flow presented in the work. In order to calculate two-dimensional turbulent flows, a method of viscous-nonviscous interaction is used. It employs numerical solutions for nonviscous flow and integrated methods of calculating the dissipative region. This method can be extended for calculating the transonic break-off flows, and also break-off in an incompressible fluid when there is cavitation.

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This experiment investigated the effects of free-stream turbulence intensity, length scale, Reynolds number, and leading-edge velocity gradient on stagnation-region heat transfer. Heat transfer was measured in the stagnation region of four models with elliptical leading edges downstream of five turbulence-generating grids. Stagnation-region heat transfer augmentation increased with decreasing length scale but an optimum scale was not found. A correlation was developed that fit heat transfer data for isotropic turbulence to within {+-}4 percent but did not predict data for anisotropic turbulence. Stagnation heat transfer augmentation caused by turbulence was unaffected by the velocity gradient. The data of other researchers compared well with the correlation. A method of predicting heat transfer downstream of the stagnation point was developed. 28 refs., 12 ...

International Nuclear Information System (INIS)

This paper describes the study of particles' dispersion in an isotropic turbulent flow. The particle's motion and the turbulent flow characteristics are calculated independently. While the particles' displacement is computed by the author's code, the flow is simulated with a commercial code : PowerFLOW. The particles and the flow are coupled through the relative velocity component of the aerodynamic force. When the simulated flow is turbulent, a turbulence regeneration model is used in order to get the flow instantaneous velocity. Validation of the method is done by comparing the particles' dispersion obtained with experimental results from literature and with the results calculated by FLUENT. Good accordance is found between numerical studies and experimental results. However, comparison between results of PowerFLOW coupled to the author's code and results from FLUENT shows ...

Science.gov (United States)

The Baldwin-Lomax model is used in many CFD codes because it is quick and easy to implement. In this

International Nuclear Information System (INIS)

The present work summarizes efforts on the simulation of natural convection cooling within the IFMIF target and test cell. The simulations have been performed with the STAR-CD code using the k-#omega# high-Reynolds number turbulence model. A dedicated thermohydraulic model has been devised including Lithium loop components. Nuclear heat production has been calculated by the Monte-Carlo code McDeLicious for different parts of the target and test cell walls and was used as input for the STAR-CD simulations. Helium atmospheres at several pressures from 0.1 to 10"-"5 MPa have been investigated. In order to limit the maximum temperature of the concrete walls to 80 deg. C it was necessary to add thermal insulation layers to the hot Lithium loop surfaces and a conceptual system of two cooling layers in different depths of the concrete walls.

Energy Technology Data Exchange (ETDEWEB)

This paper presents research work concerning the mathematical modelling of air pollution in the Athens basin. A mathematical model based on aerodynamics and conservation equations together with turbulence modelling in body-fitted coordinates is used to provide the necessary input information to a similar but more detailed (i.e. small scale) model around Athens. Both models consist of solving the full Navier-Stokes equations and take into account the precise topography of the region. Different roughness heights are used for sea, coastal regions and land. The smaller scale model makes use of a two-equation turbulence model ({kappa}-{epsilon}) and the large scale model assumes a constant turbulence viscosity. The pollutant sources used in these ...

British Library Electronic Table of Contents (United Kingdom)

Abstract In this paper, the effect of several turbulence parameters during various flow conditions in Owens Valley, educed from coherent Doppler lidar data have been studied. Radial velocity structure functions are processed to estimate the turbulent kinetic energy (TKE) dissipation rate, integral length scale and velocity variance, assuming a theoretical model for isotropic wind fields. Corrections for turbulence measurements have been considered to address the complications due to inherent volumetric averaging of radial velocity over each range gate, noise of the lidar data, and the assumptions required to estimate effects of smaller scales of motion on turbulence quantities. Using data from the Terrain-induced Rotor Experiment (T-REX) in April-May 2006, vertical profiles of wind and tur...

International Nuclear Information System (INIS)

The time behaviors of intermittent turbulence in Gledzer-Ohkitani-Yamada model are investigated. Two kinds of orbits of each shell which is in the inertial range are discussed by portrait analysis in phase space. We find intermittent orbit parts wandering randomly and the directions of unstable quasi-periodic orbit parts of different shells form rotational, reversal and locked cascade of period three with shell number. We calculate the critical scaling of intermittent turbulence and the extended self-similarity of the two parts of orbit and point out that nonlinear scaling in inertial-range is decided by intermittent orbit parts.

CERN Document Server

Turbulence in the positive column of a glow discharge

International Nuclear Information System (INIS)

Etching of SiO_2 rods has been obtained with a dc torch with argon as the process gas in an air environment at atmospheric pressure; the high temperature of the plasma jet causes vaporization of the exposed area. The apparatus and torch operative parameters have been set up to obtain a depth etch rate of up to 0.6 mm min"-"1 corresponding to 0.826 g min"-"1. An enthalpy probe has been employed to monitor the plasma conditions before the thermal plasma etching process and from the experimental etch rate a surface rod temperature of T_s_u_r = 2057 K has been derived. Etching has been obtained with uniformity over the entire exposed area with peak to peak differences below 1%. The plasma to rod heat transfer has been simulated using a commercial CFD code Fluent (copyright). The model consists of a non-steady two-dimensional simulation for a compressible turbulent fluid, with an adapted grid calculation. Boundary conditions ...

Energy Technology Data Exchange (ETDEWEB)

The catalytically stabilised thermal combustion (CST) of lean hydrogen-air mixtures was investigated numerically in a turbulent channel flow configuration using a two-dimensional elliptic model with detailed heterogeneous and homogeneous chemical reactions. Comparison between turbulent and laminar cases having the same incoming mean properties shows that turbulence inhibits homogeneous ignition due to increased heat transport away from the near-wall layer. The peak root-mean-square temperature and species fluctuations are always located outside the extent of the homogeneous reaction zone indicating that thermochemical fluctuations have no significant influence on gaseous combustion. (author) 4 figs., 6 refs.

CERN Document Server

Sediment transport over wave-induced ripples is a very complex phenomenon where available models fail to provide accurate predictions. For coastal engineering applications, the 1-DV advection-diffusion equation could be used with an additional parameter {\\alpha} related to the process of vortex shedding above ripples (Absi, 2010). The aim of this study is to provide simple practical analytical tools. An analytical eddy viscosity profile was validated by DNS data of turbulent channel flows (Absi et al., 2011). In this study, we will show that: (1) the period-averaged eddy viscosity in oscillatory boundary layers could be described by this simple analytical formulation; (2) The shape of the vertical profile is validated by period-averaged eddy viscosity of baseline (BSL) k-{\\omega} model (Suntoyo and Tanaka, 2009) for sinusoidal and asymmetric waves; (3) The vertical eddy viscosity profile depends on ...

International Nuclear Information System (INIS)

This report summarizes the results and activities funded by this three-year award. The principal goal of this project was to determine the thermal conductivity in clusters of galaxies. Intracluster plasmas possess chaotic magnetic fields. Since charged particles are constrained to move primarily along magnetic field lines, the topology of intracluster magnetic fields slows particle diffusion relative to the non-magnetized case, thereby reducing the thermal conductivity. Our first approach to this problem was to employ the static-magnetic-field approximation. In reality, intracluster magnetic field lines are constantly moving, since they are advected by turbulent intracluster motions. The turbulent velocities, however, are much smaller than the rapid speeds of thermal electrons, which make the dominant contribution to the thermal conductivity. In the static-field approximation, one neglects turbulent motions of field lines, ...

Energy Technology Data Exchange (ETDEWEB)

Fuel spray and air motion characteristics and combustion in direct injection (DI) diesel engines was studied using computational models of the commercial CFD-code FIRE. Physical subprocesses modelled included Lagrangian spray droplet movement and behaviour (atomisation, evaporation and interaction of spray droplets) and combustion of evaporated liquid spray in the gas phase. Fuel vapour combustion rate was described by the model of Magnussen and Hjertager. The standard k,{epsilon}-model was used for turbulence. In order to be able to predict combustion accurately, the fuel spray penetration should be predicted with reasonable accuracy. In this study, the standard drag coefficient had to be reduced in order to match the computed penetration to the measured one. In addition, the constants in the submodel describing droplet breakup also needed to be adjusted for closer agreement with ...

Science.gov (United States)

The effect of velocity gradient on stagnation region heat transfer augmentation by free stream turbulence was investigated. Heat transfer was measured in the stagnation region of four models with elliptical leading edges with ratios of major to minor axes of 1:1, 1.5:1, 2.25:1, and 3:1. Four geometrically similar, square bar, square mesh, biplane grids were used to generate free stream turbulence with different intensities and length. Heat transfer measurements were made for the following ranges of parameters: Reynolds number, based on leading edge diameter, 37,000 to 228,000; dimensionless leading edge velocity gradient, 1.20 to 1.80; turbulence intensity, 1.1 to 15.9%; and length scale to leading edge diameter ratio, 0.05 to 0.30. Stagnation point heat transfer augmentation by free stream turbulence can be predicted using a modified version of a previously developed correlation ...

Science.gov (United States)

The current status of a computational aeroacoustics (CAA) approach to simulate broadband noise is reviewed. The method rests on the use of steady Reynolds averaged Navier-Stokes (RANS) simulation to describe the time-averaged motion of turbulent flow. By means of synthetic turbulence the steady one-point statistics (e.g. turbulence kinetic energy) and turbulent length- and time-scales of RANS are translated into fluctuations having statistics that very accurately reproduce the initial RANS target-setting. The synthetic fluctuations are used to prescribe sound sources which drive linear perturbation equations. The whole approach represents a methodology to solve statistical noise theory with state-of-the-art CAA tools in the time-domain. A brief overview of the synthetic turbulence model and its numerical discretization in terms of the random particle-mesh (RPM) ...

Energy Technology Data Exchange (ETDEWEB)

The influence of location of airborne particle source, ventilation rate, air inlet size, supply air velocity, air outlet location, and heat source on the distributions of airborne particle concentration and draught risk in an operating room is investigated. The investigation is carried out by using a flow program with the k-[epsilon] model of turbulence. Based on a standard case, five cases, each with one changed parameter, are computed, and the detailed field distributions of air velocity, temperature, airborne particle concentration, and draught risk are presented. The parametric study concludes that, for a better air quality and thermal comfort, it is desirable to use a higher inflow rate, a larger inlet area, and a uniform velocity profile of supply air. Outlet location and heat source have little influence on the distributions of the particle concentration in the room. It has also been found that the distributions of ...

Energy Technology Data Exchange (ETDEWEB)

Blade fatigue life is an important element in determining the economic viability of the Vertical-Axis Wind Turbine (VAWT). A principal source of blade fatigue is thought to be the stochastic (i.e., random) aerodynamic loads created by atmospheric turbulence. This report describes the theoretical background of the VAWT Stochastic Aerodynamic Loads (VAWT-SAL) computer code, whose purpose is to numerically simulate these random loads, given the rotor geometry, operating conditions, and assumed turbulence properties. A Double-Multiple-Stream Tube (DMST) analysis is employed to model the rotor's aerodynamic response. The analysis includes the effects of Reynolds number variations, different airfoil sections and chord lengths along the blade span, and an empirical model for dynamic stall effects. The mean ambient wind is assumed to have a shear profile which is described by either a power law or a ...

Energy Technology Data Exchange (ETDEWEB)

The suitability of the turbulent combustion flamelets model in order to predict the index of NO{sub x} production in turbulent flames of hydrogen diffusion is analyzed. In the flamelet approach, the turbulent flame is equivalent to a group of laminar flames submitted to a mechanical stretching which generates a chemical disequilibrium. This effect can be described by the stretching or by the scalar dissipation ratio. A numerical modeling is performed in order to evaluate the advantages of both approaches and to compare the behaviour of the NO{sub x} emission index with the experiments of Chen and Driscoll. This study shows that predictions of NO{sub x} emission indexes have a correct behaviour with respect to the Damkoehler number only when the scalar dissipation ratio is used as a parameter to describe the chemical state outside equilibrium. Predictions of the flamelet ...

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The Meteorological Information System (MIS) comprising the meteorological instruments, the computers, and the software for data processing and recording, is part of the KfK safety and control system. In 1982 is was equipped with an independent data processing system. The report explains the arrangement and the operation of the sensors and thw two process computers. For selected meteorological situations the ability of the system is demonstrated, i.e., the presentation of the vertical profiles of wind, temperature and turbulence in the lower atmospheric boundary layer as well as the calculation and graphical representation of the transport and dispersion into the KfK environment of radioactive pollutants being released by the nuclear installations of the KfK into the atmosphere.

Energy Technology Data Exchange (ETDEWEB)

This report documents the results of a project funded by DoD's Strategic Environmental Research and Development Program (SERDP) on the science behind development of predictive models for soot emission from gas turbine engines. Measurements of soot formation were performed in laminar flat premixed flames and turbulent non-premixed jet flames at 1 atm pressure and in turbulent liquid spray flames under representative conditions for takeoff in a gas turbine engine. The laminar flames and open jet flames used both ethylene and a prevaporized JP-8 surrogate fuel composed of n-dodecane and m-xylene. The pressurized turbulent jet flame measurements used the JP-8 surrogate fuel and compared its combustion and sooting characteristics to a world-average JP-8 fuel sample. The pressurized jet flame measurements demonstrated that the surrogate was representative of JP-8, with a somewhat higher tendency to ...

Science.gov (United States)

A mathematical model describing the behavior of a gas of any density released into a turbulent atmosphere was developed. A numerical treatment was established for two dimensional flow. An understanding of the effects of accidental or continuous release wa...

Energy Technology Data Exchange (ETDEWEB)

As lidar technology is able to provide fast data collection at a resolution of meters in an atmospheric volume, it is imperative to promote a modeling counterpart of the lidar capability. This paper describes an integrated capability based on data from a scanning water vapor lidar and a high-resolution hydrodynamic model (HIGRAD) equipped with a visualization routine (VIEWER) that simulates the lidar scanning. The purpose is to better understand the spatial and temporal representativeness of the lidar measurements and, in turn, to extend their utility in studying turbulence fields in the atmospheric boundary layer. Raman lidar water vapor data collected over the Pacific warm pool and the simulations with the HIGRAD code are used for identifying the underlying physics and potential aliasing effects of spatially resolved lidar measurements. This capability also helps improve the trade-off between spatial-temporal resolution ...

Energy Technology Data Exchange (ETDEWEB)

This paper describes the development of a computational multiphase fluid dynamics (CMFD) model of the Fischer Tropsch (FT) process in a Slurry Bubble Column Reactor (SBCR). The CMFD model is fundamentally based which allows it to be applied to different industrial processes and reactor geometries. The NPHASE CMFD solver [1] is used as the robust computational platform. Results from the CMFD model include gas distribution, species concentration profiles, and local temperatures within the SBCR. This type of model can provide valuable information for process design, operations and troubleshooting of FT plants. An ensemble-averaged, turbulent, multi-fluid solution algorithm for the multiphase, reacting flow with heat transfer was employed. Mechanistic models applicable to churn turbulent flow have been developed to provide a fundamentally based ...

International Nuclear Information System (INIS)

Nowadays, computational fluid dynamics is being applied in many fronts to improve the understanding of the flow and heat transfer behaviour in engineering applications. Unfortunately, there are not so many computational investigations regarding the ventilation and temperature distribution in discs-brakes. In this respect, this study presents a (CFD) analysis is carried out to investigate temperature distributions and flow patterns through disc brakes. The final goal is the development of shapes that optimize heat dissipation rates dictating the stopping capability of disc brakes. High performance discs brakes have a variety of cooling channels and the optimization of these passages is a challenging task for the manufacturing industry. High values of heat transfer coefficients of disc-brake configurations, are the most critical quantities during the design phase of new braking systems. In this context, a parametric study of the influence of the fin orientation concerning the cooling ...

Energy Technology Data Exchange (ETDEWEB)

The wavenumber-frequency spectral densities of turbulent wall pressure fluctuations are investigated over a rigid flat plate. Nonlinear Reynolds stress terms of the inhomogeneous Orr-Sommerfeld equation are regarded as a known forcing function. The forcing function is modeled after Bark{close_quote}s hydrodynamic bursting formulation. The inhomogeneous Orr-Sommerfeld equation is solved by the method of Eckhaus in terms of discrete homogeneous solutions. The method of Eckhaus is then extended and proved for the continuous Orr-Sommerfeld eigenfunctions. Turbulent wall pressure fluctuations in terms of wavenumber-frequency spectral densities are numerically computed and compared to the experimental results of Martin as well as to his transformation of Blake{close_quote}s data fitted to a modified Corcos model. The wavenumber-frequency spectral densities numerically computed from the discrete eigenfunctions ...

International Nuclear Information System (INIS)

This study presents a dynamic analysis of a rotor supported by two turbulent flow model journal bearings and lubricated with couple stress fluid under nonlinear suspension. The dynamics of the rotor center and bearing center is studied. The dynamic equations are solved using the Runge-Kutta method. The analysis methods employed in this study is inclusive of the dynamic trajectories of the rotor center and bearing center, power spectra, Poincare maps and bifurcation diagrams. The maximum Lyapunov exponent analysis is also used to identify the onset of chaotic motion. The results show that the values of dimensionless parameters l* strongly influence dynamic motions of bearing and rotor centre. It is found that couple stress fluid improve the stability of the system when l* > 0.4 even if the flow of this system is turbulent. We also demonstrated that the dimensionless rotational speed ratios s and the dimensionless ...

Energy Technology Data Exchange (ETDEWEB)

The objective of this manuscript is to fully derive a geophysical multiphase model able to ''accommodate'' different multiphase turbulence approaches; viz., the Reynolds Averaged Navier-Stokes (RANS), the Large Eddy Simulation (LES), or hybrid RANSLES. This manuscript is the first part of a larger geophysical multiphase project--lead by LANL--that aims to develop comprehensive modeling tools for large-scale, atmospheric, transient-buoyancy dusty jets and plume (e.g., plinian clouds, nuclear ''mushrooms'', ''supercell'' forest fire plumes) and for boundary-dominated geophysical multiphase gravity currents (e.g., dusty surges, diluted pyroclastic flows, dusty gravity currents in street canyons). LES is a partially deterministic approach constructed on either a spatial- or a temporal-separation between the large and ...

British Library Electronic Table of Contents (United Kingdom)

Although past research has reported the benefits of intuition in new product decision-making (i.e., higher quality product; enhanced customer satisfaction), intuition has largely been studied as an individual phenomenon and little work has examined the role of intuition on new product development (NPD) project teams. Furthermore, in a turbulent environment, NPD project teams may rely more on intuitive judgments, and other factors such as experience and stress may also influence the relationship between team intuition and team decision making. Drawing from the organizational design literature on creativity in decision making, this study builds a conceptual model of NPD team intuition and its effect on the team's ability to generate creative new products. We then derive hypotheses regarding ...

International Nuclear Information System (INIS)

Co-current stratified flow of liquid metal and water was investigated in a horizontal rectangular channel. Position of the interface pressure drop and direct contact heat transfer between these immisci ble liquids were measured in a fully developed flow. A turbulence model was proposed to explain the experimental results considering that the turbulence is damped near the liquid-liquid interface by surface tension. The analytical results showed good agreement with the experimental ones. Main results are that (1) position of the interface mainly depends on the flow rate ratio of both liquids, that (2) the pressure drop is approximately proportional to square of the average velocity of water, and that (3) heat transfer rate at direct contact interface is several times higher than that of co-current flow separated by a thin solid plate. (author).

Science.gov (United States)

... Originator-supplied keywords include: Turbulators, Heat transfer augmentation, Enhancement, Fire tube boilers. (Author). ...

CERN Document Server

Site measurements were collected at Mount John University Observatory in 2005 and 2007 using a purpose-built scintillation detection and ranging system. $C_n^2(h)$ profiling indicates a weak layer located at 12 - 14 km above sea level and strong low altitude turbulence extending up to 5 km. During calm weather conditions, an additional layer was detected at 6 - 8 km above sea level. $V(h)$ profiling suggests that tropopause layer velocities are nominally 12 - 30 m/s, and near-ground velocities range between 2 -- 20 m/s, dependent on weather. Little seasonal variation was detected in either $C_n^2(h)$ and $V(h)$ profiles. The average coherence length, $r_0$, was found to be $7 \\pm 1$ cm for the full profile at a wavelength of 589 nm. The average isoplanatic angle, $\\theta_0$, was $1.0 \\pm 0.1$ arcsec. The mean turbulence altitude, $\\bar{h_0}$, was found to be $2.0\\pm0.7$ km above sea level. No average in the Greenwood frequency, $f_G$, ...

Science.gov (United States)

The ionization, excitation, and radiative recombination rates for highly stripped ions are cal- culated with Maxwellian and non-Maxwellian electron distribution functions of the type Cmexp(-vm/wm) (2<=m<=5) as encountered in laser-heated plasmas and certain types of turbulent plasmas. The direct-radiative-recombination rates are found to decrease by at most 30% as m is increased from 2 to 5. On the other hand, the ionization and excitation rates are found to be strongly reduced if the transition energy ? exceeds twice the local temperature kBTe. The effect of this on the distribution of energy levels and degrees of ionization in laser-produced plasmas could be important.

International Nuclear Information System (INIS)

''Magnetic braking'' of the plasma toroidal rotation in the high confinement H mode by applied resonant, low m,n=1 static error fields is used in DIII-D [Nucl. Fusion 31, 875 (1991)] as an independent control to evaluate the E_rxB stabilization of microturbulence in the plasma core. In the core (#rho# approx-lt 0.9) of a tokamak, the radial electric field and its shear are dominated by toroidal rotation. The fundamental quantity for shear stabilization of microturbulence is shear in the velocity of the fluctuations v_p_e_r_p_e_n_d_i_c_u_l_a_r#approx#E_rxB/B#centre dot#B which in the core is v_p_e_r_p_e_n_d_i_c_u_l_a_r#approx#v_#phi#B_#theta#/ B_#phi#. With magnetic braking greatly decreasing the toroidal rotation and thus reducing the core radial electric field and shear, far infrared (FIR) measurements of density microturbulence show downshifting in frequency near #rho##approx#0.8 as a result of the reduced Doppler shift (#omega##approx#k_#theta#E_r/B_#phi#) and a ...

International Nuclear Information System (INIS)

At the RIKEN-RAL Muon Facility, ?- to ? sticking K? X-rays were observed for the first time taking advantage of the pulsed beam structure. The precision of the present measurements was insufficient to distinguish between theoretical models, however the observed K?/K? X-ray intensity ratio tends to be smaller than most of these theoretical predictions.

Energy Technology Data Exchange (ETDEWEB)

A brief review and assessment of field measurement programs that provide data for mixed layer diffusion research is presented. The majority of programs emphasize either the meteorological aspects of the mixed layer or plume characterization. Few programs are available that provide the complimentary blend of plume and appropriate meteorological measurements needed to adequately validate mixed layer diffusion theory. Three major U.S. EPA (Environmental Protection Agency) field programs that provide data bases for model development and validation of mixed layer diffusion processes are described and discussed in more detail. The Regional Air Pollution Study (RAPS) focused on measurements of surface and mixed layer turbulent transport processes in the urban environment. The Tennessee Plume Study (TPS) obtained a database with coincident measurement of boundary layer turbulent structure and plume dispersion for a large coal-fired ...

CERN Document Server

A possibility of geophysical measurements using the large scale laser interferometrical gravitational wave antenna is discussed. An interferometer with suspended mirrors can be used as a gradiometer measuring variations of an angle between gravity force vectors acting on the spatially separated suspensions. We analyze restrictions imposed by the atmospheric noises on feasibility of such measurements. Two models of the atmosphere are invoked: a quiet atmosphere with a hydrostatic coupling of pressure and density and a dynamic model of moving region of the density anomaly (cyclone). Both models lead to similar conclusions up to numerical factors. Besides the hydrostatic approximation, we use a model of turbulent atmosphere with the pressure fluctuation spectrum f^{-7/3} to explore the Newtonian noise in a higher frequency domain (up to 10 Hz) predicting the gravitational noise ...

International Nuclear Information System (INIS)

A theoretical model is presented to describe the electromagnetic, heat transfer and fluid flow phenomena within a magnetron plasma torch and in the resultant plume, by using a commercial computational fluid dynamics (CFD) code FLUENT. Specific calculations are presented for a pure argon system (i.e., an argon plasma discharging into an argon environment), operated in a turbulent mode. An important finding of this work is that the external axial magnetic field (AMF) may have a significant effect on the behavior of arc plasma and thus affects the resulting plume. The AMF impels the plasma to retract axially and expand radially. As a result, the plasma intensity distribution on the cross section of torch seems to be more uniform. Numerical results also show that with AMF, the highest plasma temperature decreases and the anode arc root moves upstream significantly, while the current density distribution at the anode is more concentrated with a ...

Energy Technology Data Exchange (ETDEWEB)

A steady-state mathematical model was developed for a bare collector. Results obtained by previous authors for heat transfer and friction in rectangular ducts with periodic disturbances were employed to evaluate the effect of such disturbances on bare collector efficiency and on its pressure drop. An effective efficiency, which takes into account extra heat obtained and additional mechanical (electric) energy consumption for moving air when heat-transfer augmentation devices are employed, was defined. Simulation results are given for a bare collector, with and without perturbations, showing efficiency and effective efficiency dependence on collector dimensions, solar radiation intensity, disturbance diameter and pitch for collector performance optimization. (author).

International Nuclear Information System (INIS)

The entrainment flow rate distribution, the gas velocity profile, and the concentration profile of droplets across the channel cross section in fully developed region of a horizontal rectangular channel of 150 mm width and 50 mm height were measured. The concentration profile of droplets was expressed by a simple equation based on a constant diffusion coefficient model. From this equation the effects of gravity and turbulent diffusion of droplets on the concentration profile were evaluated. The characteristic mean settling velocity of a group of droplets with various diameters was derived, and using this value the mean diffusion coefficient of the group of droplets was obtained. (author).

International Nuclear Information System (INIS)

Full text of publication follows: As the coolant experiences no phase change in the core, SCWRs, unlike LWRs, cannot use design criteria based on the critical heat flux concept. The commonly accepted practice in SCWRs is to specify cladding temperature limits that must be met during transient and accident events. Therefore for the design of the SCWR, it is very important to predict the heat transfer coefficient to the supercritical water coolant with great accuracy. Our recent study focuses on the critical issue of measuring heat transfer to supercritical water at prototypical SCWR conditions and to develop the tools to predict the SCWR thermal behavior. A heat transfer test loop using a surrogate fluids, CO_2, is under construction. The reason of using CO_2 instead of water is that (i) valuable insight of the physical phenomena can be obtained with this fluid, and (ii) some existing facilities already used surrogate fluids, which in general have lower critical pressure and ...

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A phenomenological model of turbulent combustion has been developed and validated against data from wide ranging tests on a Ricardo E6 engine. Most tests used iso-octane, with a range of air fuel ratios and ignition timings, for tests at full throttle (with and without knock) and at part throttle. Some full throttle tests were also conducted with methanol and toluene. The engine performance was characterized by mean and coefficient of variation (CoV) of: the peak pressure, the maximum rate of pressure rise, the IMEP, the burn rate and flame speed measurements. The results have been used to argue that the cycle-by-cycle variations in combustion should be characterized by the CoV of IMEP in preference to the CoV of the maximum cylinder pressure. Evidence is also presented to support the observation that the cycle-by-cycle variations in combustion are lower when the early combustion is more rapid. It has also been shown that the CoV of IMEP is a ...

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A flow pattern or flow regime is the characteristics spatial distribution of the phases of fluid in a duct. Since heat transfer and pressure drop are dependent on the characteristic distribution of the phases, it is necessary to describe flow patterns in an appropriate manner so that a hydrodynamic or heat transfer theory applicable to that pattern can be chosen. The objective of the present analysis is to create a flow regime map based on physical modeling of vapor/liquid interaction phenomena in a microgravity environment. In the present work, four basic flow patterns are defined: dispersed flow, stratified flow, slug flow, and annular flow. Fluid properties, liquid and vapor flow rates, and pipe size were chosen as the principal parameters. It is assumed that a transition from one flow pattern to another will occur when there is a change in the dominant force which controls that flow pattern. The forces considered in this modeling are ...

Science.gov (United States)

... AGARD AR-319, Volume 2. Knight, D., Zhou ... a Turbulent Boundary Layer in a Supersonic Flow. ... of Development of Separated Flows in Compression ...

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Frictional pressure drop and heat transfer performance in a very narrow rectangular channel having one-sided constant heat flux and repeated-ribs for turbulent flow have been investigated experimentally, and their experimental correlations were obtained using the least square method. The rib pitch-to-height ratios(p/k) were 10 and 20 while holding the rib height constant at 0.2mm, the Reynolds number(Re) from 2,414 to 98,458 under different channel heights of 1.2mm, 2.97mm, and 3.24mm, the rib height-to-channel equivalent diameter(k/De) of 0.03, 0.04, and 0.09 respectively. The results show that the rib-roughened surface augments heat transfer 2-3 times higher than that of the smooth surface with the expense of 2.8-4 times higher frictional pressure drop under Re=5000-10{sup 5}, p/k=10, and H=1.2mm. Experimental results obtained by channel height, H=1.2mm shows a little bit higher heat transfer and ...

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Full text of publication follows:In the current thermal-hydraulic system analysis codes using the two-fluid model, the empirical correlations that are based on the two-phase flow regimes and regime transition criteria are being employed as closure relations for the interfacial transfer terms. Due to its inherent shortcomings, however, such static correlations are inaccurate and present serious problems in the numerical analysis. In view of this, a new dynamic approach employing the interfacial area transport equation has been studied. The interfacial area transport equation dynamically models the two-phase flow regime transitions and predicts continuous change of the interfacial area concentration along the flow field. Hence, when employed in the thermal-hydraulic system analysis codes, it eliminates artificial bifurcations stemming from the use of the static flow regime transition criteria. Therefore, the interfacial area transport equation ...

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Large-eddy-simulations are performed for the heat transfer and the wake flow of a thin rotating disk subjected to an outer parallel passing stream of air. Above a critical value for the angular velocity of the disk, heat transfer augmentation sets on. This is strongly related to a flow instability that leads to a periodic vortex generation at the counter-moving disk side. The resulting phenomena are captured by the classical Landau model. For higher angular velocities the wake becomes fully turbulent, and here the transition to turbulence seems to be very abrupt. In this regime, a periodic vortex generation is observable at the co-moving disk side, too. (orig.) [German] Grobstruktur-Simulationen werden fuer die Waermeuebertragung und die Nachlaufstroemung fuer eine duenne rotierende Scheibe in einem aeusseren parallelen Luftstrom durchgefuehrt. Oberhalb eines kritischen Wertes fuer die Rotationsgeschwindigkeit setzt eine ...

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The control problem associated to a class of horizontal-axis fixed-pitch variable-speed low-power wind energy conversion systems, working in the partial load region, consisting in the energy conversion maximization, is approached here under the assumption that the wind turbine model and its parameters are poorly known. Using a new approach derived from the optimum seeking methods category, generically called Maximum Power Point Tracking (MPPT), the proposed control solution aims at driving the average position of the operating point near to optimality. Instead of inducing sinusoidal search signals, the wind turbulence is here used as search disturbance. The high-speed shaft's average rotational speed is slowly adjusted using the Fast Fourier Transform processing of some available measures from the system as an estimate of the operating point's position/distance to optimality. Numerical simulations are used for preliminary ...

British Library Electronic Table of Contents (United Kingdom)

Most gas dynamic computations in industrial ducts are done in one dimension with cross-section-averaged Euler equations. This poses a fundamental difficulty as soon as geometrical discontinuities are present. The momentum equation contains a non-conservative term involving a surface pressure integral, responsible for momentum loss. Definition of this integral is very difficult from a mathematical standpoint as the flow may contain other discontinuities (shocks, contact discontinuities). From a physical standpoint, geometrical discontinuities induce multidimensional vortices that modify the surface pressure integral. In the present paper, an improved 1D flow model is proposed. An extra energy (or entropy) equation is added to the Euler equations expressing the energy and turbulent pressure ...

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No abstract prepared.

International Nuclear Information System (INIS)

This specialist meeting on Advanced Instrumentation and Measurements Techniques was held in Santa Barbara (USA) in 1997 and attracted some 70 participants in ten technical sessions and a session of the round table discussions, with a total of 41 papers. It was intended to bring together the international experts in multi-phase flow instrumentation, experiment and modeling to review the state-of-the-art of the two-phase flow instrumentation methods and to discuss the relation between modeling needs and instrumentation capabilities. The following topics were included: Modeling needs and future direction for improved constitutive relations, interfacial area transport equation, and multi-dimensional two-fluid model formulation; local instrumentation developments for void fraction, interfacial area, phase velocities, turbulence, entrainment, particle size, thermal non-equilibrium, shear ...

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Quantitative digital imaging, using planar laser light scattering techniques is being developed for the analysis of turbulent and reacting flows. Quantitative image data, implying both a direct relation to flowfield variables as well as sufficient signal and spatial dynamic range, can be readily processed to yield two-dimensional distributions of flowfield scalars and in turn two-dimensional images of gradients and turbulence scales. Much of the development of imaging techniques to date has concentrated on understanding the requisite molecular spectroscopy and collision dynamics to be able to determine how flowfield variable information is encoded into the measured signal. From this standpoint the image is seen as a collection of single point measurements. The present effort aims at realizing necessary improvements in signal and spatial dynamic range, signal-to-noise ratio and spatial resolution in the imaging system as well as developing ...

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The objective of this work is to improve the process for CO{sub 2} capture by alkanolamine absorption/stripping by developing an alternative solvent, aqueous K{sub 2}CO{sub 3} promoted by piperazine. Thermodynamic modeling predicts that the heat of desorption of CO{sub 2} from 5m K+/2.5 PZ from 85 kJ/mole at 40 C to 30 kJ/mole at 120 C. Mass transfer modeling of this solvent suggests that carbonate and general salt concentration play a major role in catalyzing the rate of reaction of CO{sub 2} with piperazine. Stripper modeling suggests that with the multipressure stripper, the energy consumption with a generic solvent decreases by 15% as the heat of desorption is decreased from 23.8 to 18.5 kcal/gmol. A second pilot plant campaign with 5m K+/2.5 PZ was successfully completed.

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Fluctuations in the flux of runaway electrons to the limiter have been measured during many PLT discharges. Oscillations at 60, 120, and 720 Hz are driven by variations in the vertical magnetic field which moves the plasma major radius. Fluctuations are seen in the range of 2 ..-->.. 20 kHz due to MHD magnetic islands which extend to the plasma surface. A continuous spectrum of fluctuations is observed up to 200 kHz which correlates with drift-wave turbulence. The magnitude of the driven fluctuations can be used to measure transport properties of the runaway electrons. The amplitude of electron motion due to the MHD and drift-wave oscillations, and hence a measure of the radial size of the instability, can be determined as a function of frequency. The slope of the frequency power spectrum of the drift-wave-induced fluctuations steepens with increasing runaway electron drift orbit displacement during the current drop at ...

Science.gov (United States)

A computational fluid dynamics (CFD) is coupled with a computational structural dynamics (CSD) to simulate the unsteady rotor flow with aeroelasticity effects. An unstructured upwind Navier-Stokes solver was developed for this simulation, with 2nd order time-accurate dual-time stepping method for temporal discretization and low Mach number preconditioning method. For turbulent flows, both the Spalart-Allmaras and Menter's SST model are available. Mesh deformation is achieved through a fast dynamic grid method called Delaunay graph map method for unsteady flow simulation. The rotor blades are modeled as Hodges & Dowell's nonlinear beams coupled flap-lag-torsion. The rotorcraft computational structural dynamics code employs the 15-dof beam finite element formulation for modeling. The structure code was validated by comparing the natural frequencies of a rotor model with UMARC. The ...

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This paper describes a 1993 field experiment entitled Marine Aerosol Properties and Thermal Imager Performance Trial (MAPTIP) conducted by NATO AC/243 Panel 04/RSG.8 and 04/RSG.5 in the Dutch coastal waters. Objectives were: to improve and validate vertical marine aerosol models by providing an extensive set of aerosol and meteorological measurements, within a coastal environment at different altitudes and for a range of meteorological conditions; make aerosol and meteorological observations in the first 10 m of the ocean surface with a view to extending existing aerosol models to incorporate near-surface effects; and to assess marine boundary layer effects on thermal Imaging systems. Aerosol and meteorological instruments, as well as thermal imagers and calibrated targets, were utilized. This network of instrumentation has provided a comprehensive database of aerosol size distribution profiles and relevant meteorological variables throughout ...

International Nuclear Information System (INIS)

For the determination of the thermal-hydraulic performances of rough surfaces, the method of evaluation is particularly important. In order to increase confidence in the results, a new evaluation procedure was introduced. This procedure is based on the transformation of simple channel experimental results to equal boundary conditions, and on the suitable application and confirmation of these transformed values in more complicated flow channel geometries. Existing methods, applied to the results obtained in an annular channel, do not fulfil all the transformation requirements. Thus a new, more complete transformation method, which uses the turbulent eddy diffusivity model, was developed. To check the quality of this transformation, within the scope of the new evaluation procedure, the results of experimental investigation in annular channels and in a bundle of hexagonal geometry were used together with the predictions of benchmark calculations. ...

International Nuclear Information System (INIS)

Supernova explosions within wind-driven bubbles are studied with 2D hydrodynamical calculations. Two different density distributions for the ejecta are considered: (i) a smooth, unfragmented power-law stratification, and (ii) a fragmented distribution. As in 1D models, the presence of the shell of interstellar swept-up matter causes the rapid evolution of the remnant to the radiative phase. The main 2D effects, for both fragmented and unfragmented ejecta, include: (i) substantial chaotic deviations from a purely radial flow in the remnant interior, (ii) efficient turbulent mixing between the ejecta and the shocked wind, resulting in homogenization of the former wind cavity, and (iii) severe distortion of the wind-driven shell by cooling and Rayleigh-Taylor instabilities. (author).

International Nuclear Information System (INIS)

An evolutionary model of dynamical processes in protostellar disks is described and illustrated with graphs of typical results. The effective transport mechanisms are discussed, including thermal convection, nonaxisymmetric gravitational instabilities in the outer regions of disks, and wave propagation. Consideration is then given to the stages of dynamical evolution, FU Ori outburst phenomena, unsteady accretion-disk flows, and nonlinear feedback as a mechanism to modulate mass transfer. The simulations show that mass redistribution is determined by angular-momentum transfer, which in turn is regulated by the effective viscosity generated by convectively driven turbulence. Significant mass transfer occurs as a result of mixing of infalling material with disk gas and is affected by the tidal torque associated with the growth of nonaxisymmetric disturbances in the outer disk. The time scale for disk evolution is found to be about 1 Myr. 72 refs.

International Nuclear Information System (INIS)

Radon concentration measurements in atmosphere were taken in years from 1997 to 1999 in Milan and at pre-alpine sites located north of Lombardy. In this paper the results of measuring campaigns and a comparison of radon levels observed in the hilly area north of the town and on the pre-Alps are reported. The general criteria of the measurements and the interpretative models of radon concentration are presented. The Lake Maggiore area shows evidence of a great nocturnal stability and frequent formation of Nocturnal Stable Layer. The peculiar findings in the high altitude stations confirm the use of radon as an indicator of atmospheric dispersion of pollutants in an area with complex orography. The afternoon minimum values are concordant for the different stations: this implies a remixing in afternoon hours over the whole area investigated.

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This thesis discusses an advanced dynamical two-dimensional cylinder symmetric model for the high temperature part of the carbothermic silicon metal process, and its computer encoding. The situation close to that which is believed to exist around one of three electrodes in full-scale industrial furnaces is modelled. This area comprises a gas filled cavity surrounding the lower tip of the electrode, the metal pool underneath and the lower parts of the materials above. The most important phenomena included are: Heterogeneous chemical reactions taking place in the high-temperature zone (above 1860 {sup o}C), Evaporation and condensation of silicon, Transport of materials by dripping, Turbulent or laminar fluid flow, DC electric arcs, Heat transport by convection, conduction and radiation. The results from the calculations, such as production rates, gas- and temperature distributions, furnace- and particle geometries, fluid ...

International Nuclear Information System (INIS)

The interfacial area transport equation dynamically models the two-phase flow regime transitions and predicts continuous change of the interfacial area concentration along the flow field. Hence, when employed in the numerical thermal-hydraulic system analysis codes, it eliminates artificial bifurcations stemming from the use of the static flow regime transition criteria. Accounting for the substantial differences in the transport phenomena of various sizes of bubbles, the two-group interfacial area transport equations have been developed. The group 1 equation describes the transport of small-dispersed bubbles that are either distorted or spherical in shapes, and the group 2 equation describes the transport of large cap, slug or churn-turbulent bubbles. The source and sink terms in the right-hand-side of the transport equations have been established by mechanistically modeling the creation and destruction of bubbles due to ...

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The understanding of fission product deposition in realistic steam generator conditions is needed for release estimates in PSA studies, and for the design of efficient accident management procedures. This is considered very important because primary-to-secondary leakages risk dominant sequences in many plants. Furthermore, the decay heat of the fission product deposits adds to the thermal load to the steam generator tubes also in other sequences, especially in case of cold leg leakages. This brings out the concern of induced steam generator tube ruptures in cases, where the steam generators are initially intact. The experimental data showed that the highest deposited fraction within the tubes were found in cases with lowest flow velocities. The minimum value of the deposited fraction was observed at intermediate flow velocities. With these relatively low Reynolds numbers, the results calculated with deposition models agree well with the experiments. At high ...

British Library Electronic Table of Contents (United Kingdom)

SummaryPermeable pavement functions as a porous infrastructure interface allowing the infiltration and evaporation of rainfall-runoff while functioning as a relatively smooth load-bearing surface for vehicular transport. Hydraulic conductivity (k) of permeable pavement is an important hydraulic property and is a function of the pore structure. This study examines k for a cementitious permeable pavement (CPP) through a series of pore-structure models. Measurements utilized include hydraulic head as well as total porosity, (t), effective porosity (e), tortuosity (Le/L) and pore size distribution (PSD) indices generated through X-ray tomography (XRT). XRT results indicate that the permeable pavement pore matrix is hetero-disperse, with high tortuosity and t!=e. Power law models of k-t and k-e...

British Library Electronic Table of Contents (United Kingdom)

Abstract We address the fundamental question of matching the rest-frame K-band luminosity function (LF) of galaxies over the Hubble time using semi-analytic models after modification of the stellar population modelling. We include the Maraston evolutionary synthesis models, which feature a higher contribution by the thermally pulsating asymptotic giant branch (TP-AGB) stellar phase, into three different semi-analytic models, namely the De Lucia and Blaizot version of the Munich model, morgana and the Menci model. We leave all other input physics and parameters unchanged. We find that the modification of the stellar population emission can solve the mismatch between models and the observed rest-frame K-band luminosity from the brightest galaxies derived from UKIRT Infrared Deep Sky Survey d...

CERN Document Server

We present a model of inflation in a supergravity framework in the Einstein frame where the Higgs field of the next to minimal supersymmetric standard model (NMSSM) plays the role of the inflaton. Previous attempts which assumed non-minimal coupling to gravity failed due to a tachyonic instability of the singlet field during inflation. A canonical K\\"{a}hler potential with \\textit{minimal coupling} to gravity can resolve the tachyonic instability but runs into the $\\eta$-problem. We suggest a model which is free of the $\\eta$-problem due to an additional coupling in the K\\"{a}hler potential which is allowed by the Standard Model gauge group. This induces directions in the potential which we call K-flat. For a certain value of the new coupling in the (N)MSSM, the K\\"{a}hler potential is special, because it can be ...

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The two-phase annular regime is characterized by a high velocity gas stream flowing through the core of the tube surrounded by a thin, highly agitated liquid film flowing concurrently along the tube wall. Part of the liquid may be entrained as droplets in the gas phase. The specific goals of this study were to measure fully developed rates of interchange and entrained fraction over a wide range of flow variables in the upward configuration of the annular regime, to obtain a more fundamental understanding of liquid interchange phenomena via studies of liquid film characteristics and to develop an improved design correlation for the entrained fraction. Towards this end, air-water experiments were conducted in two vertical pipe lines, 2.54 and 4.20 cm in diameter. Air velocities ranging from 20 to 120 m/s and total liquid flow rates ranging from 10 to 100 g/s were investigated. Two models for the rate of atomization, proposed by Tatterson (1975) and Leman (1985), were ...

Science.gov (United States)

A general relativistic model for the formation and acceleration of lowmass-loaded jets from systems containing accreting black holes is presented. The model is based on previous numerical results and theoretical studies in the Newtonian regime, but modified to include the effects of space-time curvature in the vicinity of the event horizon of a spinning black hole. It is argued that the boundary layer between the Keplerian accretion disk and the event horizon is best suited for the formation and acceleration of the accretion-powered jets in active galactic nuclei and micro-quasars. The model presented here is based on matching the solutions of three different regions: i- a weakly magnetized Keplerian accretion disk in the outer part, where the transport of angular momentum is mediated through the magentorotational instability, ii- a strongly magnetized, advection-dominated and turbulent-free boundary ...

International Nuclear Information System (INIS)

... Institute of Plasma Physics of the National Science Center 'Kharkov Institute

Science.gov (United States)

... Agard Report 272,1960 ... and reattached subsonic turbulent flows obtained downstream ... of flow separations due to deflected control surfaces. ...

International Nuclear Information System (INIS)

The computer programme COMMIX-2 describes steady state and transient multidimensional single- and two-phase fluid flows with heat transfer in nuclear reactor components and multicomponent systems. Originally from the Argonne National Laboratory, the code has been further developed at the Kernforschungszentrum Karlsruhe. The original Point-SOR iterative method for the solution of a Poisson-like equation describing the pressure distribution in the fluid as well as the transport of enthalpy and turbulent quantities has been complemented with iterative and direct line- and block-methods. None of the newly implemented methods is original in itself but their implementation into the computer code, which can describe the most general shapes of definition domains, gave a code speed-up by a factor of 2-5, depending on the problem treated. The code capabilities are assessd by the calculation of a benchmark problem involving the numerical simulation of thermal buoyancy ...

Science.gov (United States)

The kWh model finds the kWh outputs of each plant and reservoir capacities of hydro and pumped storage plants and minimizes the sum of fixed charges for constructing the reservoirs and generating facilities, also the fuel costs of thermal and nuclear plants. It is a linear programming problem whose constants are represented by nonlinear functions of kW running capacity of each plant. The optimal pattern of nuclear and thermal units is found by solving the linear programming problem derived for the pumped storage and hydroplants. Excluding the upper bound constraints, the number of constraint equations are few and do not increase with the number of units, although the number of variables increases. The computing time increases only in proportion to the number of groupings of generating units. Sensitivity analysis can be done easily. The detailed operational behavior of each generating unit can be taken ...

International Nuclear Information System (INIS)

Frictional pressure drop and heat transfer performance in a very narrow rectangular channel having one-sided constant heat flux and repeated-ribs were studied experimentally for turbulent water flows. Their empirical correlations were derived for designing target cooling channels to remove high heat flux generated at target plates in a high-intensity proton accelerator system. The rib pitch-to-height ratios (p/k) were 10 and 20 while holding the rib height constant at 0.2 mm, the Reynolds number (Re) from 2,400 to 98,500 under different channel heights (H) of 1.2 mm and 3.2 mm, the rib height-to-channel equivalent diameter ratio (k/D_e) of 0.088 and 0.036, respectively. The results show that the rib-roughened surface augments heat transfer by about 2-2.5 times compared with the smooth surface at the expense of around 2.5 times higher frictional pressure drop under a range of Re=8,000-to-30,000 at ...

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Two computational problems were worked on for this study. The first chapter examines the option of coal combustion using oxygen feed with carbon dioxide recycle to control the adiabatic flame temperature. Computer simulations using an existing state-of-the-art 3-dimensional computer code for turbulent reacting flows with reacting particles were employed to study the effects of increased carbon dioxide mole fraction on the char burnout, radiant heat transfer, metal partitioning, and NOx formation. The second chapter compares assumptions for the CO/CO{sub 2} ratio at the surface of mineral inclusions made in previous studies to predictions obtained from a pseudo-steady state kinetic model (SKIPPY) for a single porous particle. The detailed kinetic simulations from SKIPPY for varying particle sizes and bulk gas compositions were used to develop algebraic expressions for the CO/CO{sub 2} ratio that can be incorporated into metal vaporization ...

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Using a facility named SPHINX, which can accommodate a heat transfer test with CO{sub 2} at supercritical pressure, a series of tests was performed. The test geometries include tubes with the inner diameter of 4.4, 6.32 and 9 mm. a concentric annular passages with 8 x 10 mm, and an eccentric annular passages with 9.5 x 12.5 mm. Based on the test results, heat transfer correlations were developed and compared with the existing correlations. The heat transfer deterioration which may occur at certain conditions of heat and mass flux, were carefully studied and the published criteria were reviewed against our test results. Numerical calculation by using commercial CFD code, Fluent, were performed in order to provide the pre-test information for the heat transfer tests. Various turbulence models were evaluated and reliable models were suggested for each case

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A multi-faceted research program has been performed to investigate in detail several aspects of free and forced convective cooling of underground electric cable systems. There were two main areas of investigation. The first one reported in this volume dealt with the fluid dynamic and thermal aspects of various components of the cable system. In particular, friction factors for laminar flow in the cable pipes with various configurations were determined using a finite element technique; the temperature distributions and heat transfer in splices were examined using a combined analytical numerical technique; the pressure drop and heat transfer characteristics of cable pipes in the transitional and turbulent flow regime were determined experimentally in a model study; and full-scale model experimental work was carried out to determine the fluid dynamic and thermal characteristics of entrance and exit chambers for the cooling ...

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Atmospheric transport represents one of the critically important pathways for the distribution of pollutants from any oil shale operation. Our experience in studying eastern and western shale resources and operation suggest many common features regarding the atmospheric domain, but also many significant differences. Any issue of atmospheric transport and dispersion can be broken down into major elements: source factors which include the spatial and temporal distribution of pollutant sources as well as their chemical and physical characteristics, boundary conditions which include the character of the underlying surface as a lower boundary and the large scale meteorological circulations as an ''upper'' boundary; and meteorological structure is the resulting wind, temperature, moisture, and turbulence environment in the volume of air occupied by emitted material in an atmosphere subjected to the boundary conditions described above. ...

International Nuclear Information System (INIS)

This thesis was carried out at Forsmark Nuclear Power Plant. The power plant in Forsmark consists of three boiling water reactors (BWR) which produce about 17% of Swedish electricity. In a BWR the nuclear reactions are used to boil water inside the reactor vessel. The water works both as a coolant and as a moderator and the resulting steam is used directly to run the turbines. A problem when running a BWR at low flow conditions is the density wave oscillations that might occur to the water flow inside the fuel assemblies. These oscillations arise due to the connection between power and flow rate in a heated channel with two-phase flow. In order to improve the stability performance of the channel an orifice plate is placed at the inlet of each fuel assembly. Today these orifice plates have sharp edges and a constant resistance coefficient. Experimental work has been done with progressive orifices, the edge of which is half-oval in shape. The advantage of progressive orifices is the ...

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The purpose of this thesis is to study the behaviour of the simultaneous flow of oil and water in horizontal pipes. In this connection, two test facilities are used. Both facilities have horizontal test sections with inner pipe diameters equal to 2 inches. The largest facility, called the model oil facility, has reservoirs of 1 m{sub 3} of each medium enabling flow rates as high as 30 m{sub 3}/h, which corresponds to mixture velocities as high as 3.35 m/s. The flow rates of oil and water can be varied individually producing different flow patterns according to variations in mixture velocity and input water cut. Two main classes of flows are seen, stratified and dispersed. In this facility, the main focus has been on stratified flows. Pressure drops and local phase fractions are measured for a large number of flow conditions. Among the instruments used are differential pressure transmitters and a traversing gamma densitometer, respectively. The flow patterns that ...

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This work was carried out to understand the behavior of the solid and gas phases in a CFB riser. Only the riser is modeled as a straight pipe. A model with linear algebraic approximation to solids viscosity of the form, {musubs} = 5.34{epsisubs}, ({espisubs} is the solids volume fraction) with an appropriate boundary condition at the wall obtained by approximate momentum balance solution at the wall to acount for the solids recirculation is tested against experimental results. The work done was to predict the flow patterns in the CFB risers from available experimental data, including data from a 7.5-cm-ID CFB riser at the Illinois Institute of Technology and data from a 20.0-cm-ID CFB riser at the Particulate Solid Research, Inc., facility. This research aims at modeling the removal of hydrogen sulfide from hot coal gas using zinc oxide as the sorbent in a circulating fluidized bed and in the process indentifying the ...

International Nuclear Information System (INIS)

The aim of the work in this thesis is to investigate the convective and diffusive transport in the TM chemistry transport model, and to investigate some aspects of the consequences for NOx. The large inaccuracy and uncertainty in the description of processes like convection and turbulent diffusion, the strong dependence of the radiative forcing of ozone on its vertical distribution, and the strong dependence of the ozone production on the distribution of NOx, are the main motivation. The availability of the ERA-40 data, where convective data and vertical diffusion coefficients are archived, allows a study of the effect of different convective mass flux sets, and different vertical diffusion coefficients on the model-simulated distribution of tracers. In this thesis the following questions are addressed : (1) How large is the sensitivity of the (model simulated) distribution of ozone and nitrogen oxides ...

International Nuclear Information System (INIS)

Quark models of production of cumulative particles and the EMC effect are analyzed. It is shown that all these models are characterized by a universal relation between the spectrum of cumulative nucleons and the cross section for cumulative particles containing valence quarks of the nucleus. This relation is tested for the deuteron, and the role of secondary nuclear processes for heavy nuclei is discussed. It is noted that the ''sea'' cumulative particles (K"-, p-bar) are particularly important for understanding the nature of the difference between the structure functions of a nucleus and of a free nucleon.

International Nuclear Information System (INIS)

Quark models of cumulative particle production and EMS effect are analyzed. All the models are characterized by a universal relationship between the spectrum of cumulative nucleons and the cross section of cumulative particles containing valence nuclear quarks. This relationship is tested for a deuteron. The role is discussed played by secondary nuclear processes for heavy nuclei. A special role of ''sea'' cumulative particles (K"-, p-bar) is pointed out in understanding the nature of the difference between the structure functions of a nucleus and of free nucleon.

CERN Document Server

In this paper, for a given sequentially Yoneda-complete T_1 quasi-metric space (X,d), the domain theoretic models of the hyperspace K_0(X) of nonempty compact subsets of (X,d) are studied. To this end, the $\\omega$-Plotkin domain of the space of formal balls BX, denoted by CBX is considered. This domain is given as the chain completion of the set of all finite subsets of BX with respect to the Egli-Milner relation. Further, a map $\\phi:K_0(X)\\rightarrow CBX$ is established and proved that it is an embedding whenever K_0(X) is equipped with the Vietoris topology and respectively CBX with the Scott topology. Moreover, if any compact subset of (X,d) is d^{-1}-precompact, \\phi is an embedding with respect to the topology of Hausdorff quasi-metric H_d on K_0(X). Therefore, it is concluded that (CBX,\\sqsubseteq,\\phi) is an $\\omega$-computational model for the ...

Energy Technology Data Exchange (ETDEWEB)

The present volume on modeling of batteries and fuel cells discusses the significance of the effectiveness factor for flooded porous electrodes, active pore distribution spectroscopy for characterizing porous battery electrodes, the agglomerate model for porous electrodes, and dynamic-performance measurements of battery cells for electric vehicles and other applications. Attention is given to mathematical modeling of a primary zinc/air battery, mathematical modeling of Grace Li-TiS2 cells, modeling of electrocrystallization processes in battery systems, and rotating disk electrode studies in molten Li/K carbonate eutectic. Topics addressed include the variability of nickel oxide cathode dissolution in molten carbonate fuel cells, water transport properties of fuel cell ionomers, modeling water content effects in polymer electrolyte fuel ...

International Nuclear Information System (INIS)

Natural convection of vaporizing Deuterium at 25 K transports the heat generated in the moderator cell of the cold neutron source to a He cooled condenser. The thermohydraulics of this thermosiphon were precalculated and the results verified by experiments in a 1:1 model using D_2 as fluid. The experimental results show that the thermosiphon operates stable. The demanded liquid content of the cell as well as wall temperatures below 50 K can be ensured by a proper design of the cell outlet flow geometry. A 7 min. loss of cryogenic power results in transient temperatures of the cell wall of not more than 300 K.

International Nuclear Information System (INIS)

Conduction properties of Rb"+ ion in Rb-Al-priderite and K"+ ion and Rb"+ ion in (K,Rb)-Al-priderite, were investigated by NMR using "2"7Al in the framework as a probe. Size effect was observed remarkably in the activation energies. Frequency dependence of T_1 in Rb-Al-priderite at a low temperature indicates that the relaxation behavior of "2"7Al in Rb-Al-priderite can be described by the continuum model. Barrier height distributions and 'attempt frequencies' in both samples obtained by a curve-fitting method are discussed in comparison with those of K-Al-priderite. (orig.).

UK PubMed Central (United Kingdom)

Model phosphate-metal solvation complexes have been studied by ab-initio self-consistent-field techniques. The complexes studied include (RO)2PO2-(R = H or CH3) with Li+, Na+, K+, Be++, Mg++, Ca++,...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

This report describes the work carried out to analyze and design a circuit for use in 1200 kV gas insulated substations. The first part of the project was devoted to a thorough analysis of the requirements for the circuit breaker from the standpoint of the electrical system in which it would operate. A conceptual design was selected and all of the components of the circuit breaker were designed, modeled and verified. Finally a plan was prepared for the construction of a complete circuit breaker.

Science.gov (United States)

Thermal Cavity Receivers,". JPL. Publication. 83-97,. 1983. 5Hall, III, C.A., Glakpe, E.K., Cannon,. J.N., and. Kerslake,. T.W., "Modeling ...

International Nuclear Information System (INIS)

The SMART (System-integrated Modular Advanced ReacTor) which is a 330 MWt advanced integral PWR was developed by the KAERI (Korea Atomic Energy Institute) for electricity generation and seawater desalination. A thermal hydraulic evaluation and analysis of the SMART is performed by the TASS /SMR-S (Transient And Setpoint Simulation/System integrated Modular Reactor-Safety). The TASS/SMR-S code has various models reflecting the design features of the SMART such as the drift flux model, the core models (core power and core heat transfer model), the component models, and the specific models. One of the core models is the core heat transfer model. The role of this model is to calculate the heat flux and radial temperature profiles at a fuel rod surface using the relevant heat transfer correlations for all ...

Energy Technology Data Exchange (ETDEWEB)

The proton momentum distributions of (39)K,(40)Ca and (48)Ca are calculated from the model-independent charge distributions obtained from analyses of electron elastic scattering and muonic atoms, and also from the charge distributions calculated from the single-particle potential method in the framework of the flucton model. The sensitivities of the momentum distribution to different regions of the charge distribution are determined. The analysis is extended to the neutron distributions using the single-particle potential method, and the differences between the proton and neutron momentum distributions are examined. The resulting momentum distribution in the case of (40)Ca is used for analyzing the quasielastic electron scattering.

Energy Technology Data Exchange (ETDEWEB)

A detailed experimental investigation of the application of fractal geometry concepts in determining the turbulent burning velocity in the wrinkled flame regime of turbulent premixed combustion was conducted. The fractal dimension and cutoff scales were determined for six different turbulent flames in the wrinkled flame regime, where the turbulence intensity, turbulent length scale, and equivalence ratio were varied. Unlike previous reports, it has proved possible to obtain the fractal dimension and inner and outer cutoffs from individual flame images. From this individual data, the pdf distributions of all three fractal parameters, along with the distribution of the predicted increase in surface area, may be determined. The analysis of over 300 flame images for each flame condition provided a sufficient sample size to accurately define the pdf distributions and their means. ...

CERN Document Server

It is widely accepted that the prompt transient signal in the 10 keV - 10 GeV band from gamma-ray bursts (GRBs) arises from multiple shocks internal to the ultra-relativistic expansion. The detailed understanding of the dissipation and accompanying acceleration at these shocks is a currently topical subject. This paper explores the relationship between GRB prompt emission spectra and the electron (or ion) acceleration properties at the relativistic shocks that pertain to GRB models. The focus is on the array of possible high-energy power-law indices in accelerated populations, highlighting how spectra above 1 MeV can probe the field obliquity in GRB internal shocks, and the character of hydromagnetic turbulence in their environs. It is emphasized that diffusive shock acceleration theory generates no canonical spectrum at relativistic MHD discontinuities. This diversity is commensurate with the significant range of spectral indices discerned in ...

Energy Technology Data Exchange (ETDEWEB)

Essential to today's modern refineries and the gasoline production process are fluidized catalytic cracking units. By using a computational fluid dynamics (CFD) code developed at Argonne National Laboratory to simulate the riser, parametric and sensitivity studies were performed to determine the effect of catalyst inlet conditions on the riser hydrodynamics and on the product yields. Simulations were created on the basis of a general riser configuration and operating conditions. The results of this work are indications of riser operating conditions that will maximize specific product yields. The CFD code is a three-dimensional, multiphase, turbulent, reacting flow code with phenomenological models for particle-solid interactions, droplet evaporation, and chemical kinetics. The code has been validated against pressure, particle loading, and product yield measurements. After validation of the code, parametric studies were performed on ...

Energy Technology Data Exchange (ETDEWEB)

The results of an experimental investigation of the performance of a small bore engine with a swirl chamber when operating as a dual fuel engine with commercial methane as the gaseous fuel were presented in this paper. The experiment involved using a 3-dimensional computational fluid dynamics model to predict the performance of the engine. A detailed chemical kinetics for the gaseous fuel component, consisting primarily of methane and a reduced detailed chemical kinetics for the diesel fuel while considering the turbulent combustion processes an associated performance of a dual fuel engine with a swirl chamber were incorporated in the simulation. The study experimentally and numerically investigated the effects of changes in the quantities of the liquid fuel pilot and gaseous fuels on the combustion processes, engine performance, cyclic variations, and emissions. The paper discussed the experimental approach and results. It also discussed the ...

Energy Technology Data Exchange (ETDEWEB)

The electrical resistivity, Hall effect, and magnetic susceptibility of single-crystal UPd[sub 2]Si[sub 2] have been studied between 4.2 and 300 K. A large anisotropy was observed in both the magnetic and transport properties. There is a quadratic temperature dependence of the resistivity for a range of temperatures between 4.2 and 80 K. At higher temperatures, the resistivity indicates a Kondo-type behavior. The behavior of these quantities is accounted for by the magnetic phase transitions at 108 and 136 K reported from neutron-scattering studies. At high temperatures, the magnetic susceptibility of UPd[sub 2]Si[sub 2] is Curie-Wiess-like along the [ital c] axis. The temperature dependence of the Hall coefficient above 108 K is accounted for by a theoretical model invoking skew scattering of conduction electrons by localized magnetic moments.

International Nuclear Information System (INIS)

The diagonal and symmetric Bianchi type IX models are coupled to a homogeneous spinor field. An action for the combined fields is constructed, where the orthonormal basis used is given explicitly in terms of the metric. This allows one to vary the action with respect to the metric and the spinor fields only. Next, a Hamiltonian formulation is given, and a qualitative solution for the problem is presented. We also show that the k = +1 FRW (Friedmann--Robertson--Walker) model is not compatible with a homogeneous spinor field, while the more complicated models are.

Energy Technology Data Exchange (ETDEWEB)

This report summarizes the work performed under the Sandia Laboratory Directed Research and Development (LDRD) project ``Optical Diagnostics for Turbulent and Multiphase Flows.`` Advanced optical diagnostics have been investigated and developed for flow field measurements, including capabilities for measurement in turbulent, multiphase, and heated flows. Particle Image Velocimetry (PIV) includes several techniques for measurement of instantaneous flow field velocities and associated turbulence quantities. Nonlinear photorefractive optical materials have been investigated for the possibility of measuring turbulence quantities (turbulent spectrum) more directly. The two-dimensional PIV techniques developed under this LDRD were shown to work well, and were compared with more traditional laser Doppler velocimetry (LDV). Three-dimensional PIV techniques were developed and tested, but due ...

CERN Document Server

Gemini North adaptive optics imaging spectroscopy is presented for the Galactic ultra-compact HII (UCHII) region K3-50A. Data were obtained in the K-band using the Near-infrared Integral Field Spectrograph (NIFS) behind the facility adaptive optics module ALTAIR in natural guide star mode. The NIFS data cube reveals a complex spatial morphology across the 0.1 pc scale of the 3'' UCHII region. Comparison of the nebular emission to Cloudy ionization models shows that the central source must have an effective temperature between about 37000 K and 45000 K with preferred values near 40000 K. Evidence is presented for sharp density variations in the nebula which are interpreted as a clearing of material nearest the central source. High excitation lines of FeIII and SeIV show that the ionization of the nebula clearly changes with distance from the central source. A ...

Energy Technology Data Exchange (ETDEWEB)

High-pressure, lean, premixed methane/air flames are investigated experimentally to determine turbulent flame speeds (s{sub T}). The results are based on the statistical analysis of single-shot OH-PLIF images. The influences of pressure (p = 5 - 14.4 bars) and equivalence ratio ( {phi} 0.43 - 0.56) on the turbulent flame speed are discussed. The analysis reveals that s{sub T} is independent of pressure and it depends strongly on equivalence ratio. The turbulent flame speed at {phi} = 0.56 is about 3 times higher than at {phi} = 0.43 because of the higher integral reaction rate caused by the higher fuel concentration and therefore higher adiabatic flame temperature. (author)

Science.gov (United States)

... lated Reynolds number for separation is too small. Now ... lol (1959). 6.) F.Schultz-Grunow On stability of Couette flow, AGARD- ...

Science.gov (United States)

... roughness. Since T u'v' and q v'"F the heat transfer augmentation is the square root of the skin friction augmentation: - 1/2 (( St - ,Cf 0 ...

International Nuclear Information System (INIS)

We investigate the asymptotic properties of the Bianchi type IX cosmological model in the brane-world scenario. The matter content is assumed to be a combination of a perfect fluid and a minimimally coupled scalar field that is restricted to the brane. A detailed qualitative analysis of the Bianchi type IX brane-world containing a scalar field having an exponential potential is undertaken. It is found that the brane-Robertson-Walker solution is a local source for the expanding Bianchi type IX models, and if k"2<2 the ever-expanding Bianchi IX models asymptote to the power-law inflationary solution. The only other local sink is the contracting brane-Robertson Walker solution. An analysis of the Bianchi type IX models with a scalar field with a general potential is discussed, and it is shown that in the case of expanding models, for physical scalar field ...

CERN Document Server

We study the WZNW models based on nonstandard bilinear forms. We approach the problem from algebraic, perturbative and functional exact methods. It is shown that even in the case of integer k we can find irrational CFT's. We prove that when the base group is noncompact with nonabelian maximal compact subgroup, the Kac-Moody representations are nonunitary.

International Nuclear Information System (INIS)

The possibility of having properly designed multinational fuel cycle agreements which would contribute to public acceptance of nuclear energy are explored. The advantages of existing international cooperation in the field of uranium enrichment and nuclear waste disposal and reprocessing are discussed. The possible forms of multinational co-operation under an international organisation, committed the non-proliferation and operating under international law and covering storage facilities, security of raw materials and the nuclear fuel cycle are summarised in model form. (U.K.).

Energy Technology Data Exchange (ETDEWEB)

To represent a heterogeneous unsaturated fractured rock by its homogeneous equivalent, Monte Carlo simulations are used to obtain upscaled (effective) flow properties. In this study, we present a numerical procedure for upscaling the van Genuchten parameters of unsaturated fractured rocks by conducting Monte Carlo simulations of the unsaturated flow in a domain under gravity-dominated regime. The simulation domain can be chosen as the scale of block size in the field-scale modeling. The effective conductivity is computed from the steady-state flux at the lower boundary and plotted as a function of the averaging pressure head or saturation over the domain. The scatter plot is then fitted using van Genuchten model and three parameters, i.e., the saturated conductivity K{sub s}, the air-entry parameter {alpha}, the pore-size distribution parameter n, corresponding to this model are considered as the ...

Energy Technology Data Exchange (ETDEWEB)

Quark models of production of cumulative particles and the EMC effect are analyzed. It is shown that all these models are characterized by a universal relation between the spectrum of cumulative nucleons and the cross section for cumulative particles containing valence quarks of the nucleus. This relation is tested for the deuteron, and the role of secondary nuclear processes for heavy nuclei is discussed. It is noted that the ''sea'' cumulative particles (K/sup -/, p-bar) are particularly important for understanding the nature of the difference between the structure functions of a nucleus and of a free nucleon.

International Nuclear Information System (INIS)

In order to practice design-by-analysis of thermohydraulics design of BWR fuel rod bundles, the subchannel analysis would play a major role. There, one of the immediate concerns is improvement in its predictive capability of boiling transition phenomena on the fuel rod surface. This capability strongly depends on the modeling of thermohydraulics phenomena of interests: 1) vapor-liquid redistribution by inter-subchannel exchanges due to the diversion cross flow, turbulent mixing and void drift, 2) liquid film behaviors, 3) transition of two-phase flow regimes, 4) droplet entrainment and deposition and 5) spacer-droplet interactions. These are considered to be five key factors in understanding the BT in BWR fuel rod bundles. This paper describes a progress and current status in the second year of the three year project on developing generalized boiling transition models with the above five key factors being focused on. A ...

Energy Technology Data Exchange (ETDEWEB)

The new frustrated square-lattice system, Pb{sub 2}VO(PO{sub 4}){sub 2}, has been investigated using polarised neutron scattering. From these studies, made on powdered samples, we have determined the nature of the exchange interactions and the magnetic ordering for this novel quantum magnet. Quantum order from disorder occurs at low temperature, and the ground state observed below the Neel temperature T {sub N}{approx}3.7 K is a collinear antiferromagnet. At room temperature there are no magnetic correlations and it is possible to model the scattering with the V{sup 4+} magnetic form factor. However, at T{approx}20 K, a temperature well into the paramagnetic phase, magnetic correlations are observed, and these spin correlations have been modelled using a high-temperature series expansion. Ferromagnetic nearest-neighbour exchange J {sub 1}{approx}-2 K and antiferromagnetic ...

CERN Document Server

In this paper, we consider the downlink of large-scale multi-cellular OFDMA-based networks and study performance bounds of the system as a function of the number of users $K$, the number of base-stations $B$, and the number of resource-blocks $N$. Here, a resource block is a collection of subcarriers such that all such collections, that are disjoint have associated independently fading channels. We derive novel upper and lower bounds on the sum-utility for a general spatial geometry of base stations, a truncated path loss model, and a variety of fading models (Rayleigh, Nakagami-$m$, Weibull, and LogNormal). We also establish the associated scaling laws and show that, in the special case of fixed number of resource blocks, a grid-based network of base stations, and Rayleigh-fading channels, the sum information capacity of the system scales as $\\Theta(B \\log\\log K/B)$ for extended networks, and as ...

Energy Technology Data Exchange (ETDEWEB)

The change of the transport coefficient due to the fusion energy source is studied. The scale invariance property of the reduced set of equations is investigated in the presence of the self-heating term due to the fusion reaction. The pressure gradient as well as the fusion power are the free energy sources that dictate the turbulent transport. It is shown that the burning transport coefficient can have a form with much wider variety, and that the transport property could be different owing to the self-heating by the fusion reactions. (author)

International Nuclear Information System (INIS)

This book contains nine selections. Some of the titles are: High Heat-Flux, Forced-Convection Heat Transfer for Tubes with Twisted-Tape Inserts; Heat Transfer Augmentation by Interrupted Surfaces - Experimental Consideration; Turbulent Flow Heat Transfer from Externally Roughened Tubes in Axial Flow in Concentric Pipe Heat Exchangers; and Heat Transfer Enhancement of Turbulent Flow in Pipes with an Internal Circular Rib.

Energy Technology Data Exchange (ETDEWEB)

This work proposes an innovative blend of potassium carbonate (K{sub 2}CO{sub 3}) and piperazine (PZ) as a solvent for CO{sub 2} removal from combustion flue gas in an absorber/stripper. The equilibrium partial pressure and the rate of absorption of CO{sub 2} were measured in a wetted-wall column in 0.0 to 6.2 m K{sup +} and 0.6 to 3.6 m PZ at 25 to 110 C. The equilibrium speciation of the solution was determined by {sup 1}H NMR under similar conditions. A rigorous thermodynamic model, based on electrolyte non-random two-liquid (ENRTL) theory, was developed to represent equilibrium behavior. A rate model was developed to describe the absorption rate by integration of eddy diffusivity theory with complex kinetics. Both models were used to explain behavior in terms of equilibrium constants, activity coefficients, and rate constants. The addition of potassium to the amine increases the ...

Energy Technology Data Exchange (ETDEWEB)

A comprehensive Scanning Tunneling Microscopy (STM) study of submonolayer nucleation and growth of 2D islands in Ag/Ag(100) homoepitaxy for temperature between 295K and 370K is presented. The initial stages of multilayer kinetic roughening is also studied. Analysis of an appropriate model for metal (100) homoepitaxy, produces estimates of 350 meV for the terrace diffusion barrier, 400 meV for the adatom bond energy, and 25 meV for the additional Ehrlich-Schwoebel step-edge barrier.

Energy Technology Data Exchange (ETDEWEB)

One year of research on validating the performance of the Cable Monitoring and Rating System (CMARS) is reported. The performance testing was conducted on underground 230-kV and 345-kV pipe type cable circuits owned by the New Jersey Public Service Electric and Gas Co. Laser temperature monitoring systems and a data acquisition system were installed. Software installation and development is discussed. The CMARS testing program is described. (LCL)

International Nuclear Information System (INIS)

Heat capacities and densities of aqueous MgCl/sub 2/, CaCl/sub 2/, and SrCl/sub 2/ from the accompanying paper are combined with literature data up to 473 K to yield temperature-dependent equations by using the ion-interaction model of Pitzer. These heat capacity equations have been integrated to yield the enthalpy and the Gibbs energy. The enthalpy parameters for 298 K are evaluated in separate calculations using published high-temperature osmotic data as well as heats of dilution, while the Gibbs energy parameters for 298 K are taken from the literature. The range of validity of the final equations is described.

International Nuclear Information System (INIS)

Neutron diffraction and magnetometric measurements on polycrystalline samples of DyPd_2Si_2 and ErPd_2Si_2 were carried out in the temperature range from 2 to 293 K. Both compounds show tetragonal ThCr_2Si_2 type crystal structure and order at 12 K in a sine modulated magnetic structure with propagation vectors k=[0.609,0,0.155] and [0.575, 0, 0.083] respectively. The oscillatory character of magnetic order found in RPd_2Si_2 (R=Tb-Er) compounds suggests exchange interaction described by the RKKY model to be dominant, but the non-monotonic dependence of respective Neel temperatures on the number of f-electrons indicates the influence of a crystalline electric field (CEF) on the magnetic behaviour in this series. (orig.).

International Nuclear Information System (INIS)

The virucidal effect of _6_0Co gamma radiation was studied in cell culture medium and in liquid swine manure involving the most important porcine viruses that can be spread by liquid manure. The radiation doses (20 kGy and 30 kGy) were determined in preliminary experiments employing a porcine enterovirus from the serogroup 1 (Teschen group). In the main experiment, the following viruses were employed: swine vesicular disease (SVD) virus, type C foot-and-mouth disease (FMD) virus, a field strain of Aujeszky's disease (AD) virus, transmissible gastroenteritis (TGE) virus, as well as bovine viral diarrhoea (BVD) virus. The latter strain served as a model for hog cholera virus. The results of the experiments indicate that safe disinfection of the virus infected liquid swine manure by ionizing radiation requires a radiation dose of 30 kGy. (author).

Energy Technology Data Exchange (ETDEWEB)

This paper presents thermodynamic and kinetic data collected for aqueous blends of piperazine (PZ), an ethylamine, and potassium carbonate (K{sub 2}CO{sub 3}). Mixtures of K{sup +} and PZ have been investigated in a wetted-wall column at 40 to 80{sup o}C, typical conditions for an industrial absorber. The addition of 0.6 m PZ to 20 wt% (3.6 m) K{sub 2}CO{sub 3} increases the rate of CO{sub 2} absorption by a factor of ten from the value in unpromoted solutions at 60{sup o}C. The addition of PZ increases the heat of absorption from 4 kcal/mol in 3.6 m K{sup +} to 10 kcal/mol when 0.6 m PZ is added. The capacity, ranging from 0.4 to 0.7 mol-CO{sub 2}/kg-H{sub 2}O, approaches that of monoethanolamine (MEA) solutions and seems to be a strong function of K{sup +} concentration. Speciation of the solution was obtained using proton nuclear magnetic reasonance (NMR), verifying and ...

Energy Technology Data Exchange (ETDEWEB)

The physics and technology of this new Cerenkov detector are discussed, including materials studies, construction techniques, and resolution measurements. Sources of resolution error are individually identified and measured where possible. The results of all studied indicate that the measurement resolution is understood. This work has led to the adoption of a large scale ring imaging detector as part of a new high energy physics spectrometer, the SLD, at the Stanford Linear Accelerator Center. Results from an amplitude analysis of strange meson final states in K/sup /minus//p ..-->.. /ovr K/sub 0//..pi../sup /minus//p interactions are presented. The data derive from a 4 event/nb exposure of the LASS (large Aperture Superconducting Solenoid) spectrometer to an 11 GeV/c K/sup /minus// beam. The data sample consists of /approximately/100,000 vents distributed over the Dalitz plot of the channel. The process is observed to ...

International Nuclear Information System (INIS)

Epidermal growth factor receptor (EGFR) gene alterations have been found in human lung cancers. However, there is no information on the factors inducing EGFR mutations. In rodents, K-ras mutations are frequently found in many lung carcinogenesis models, but hitherto, Egfr mutations have not been reported. Their presence was therefore investigated in representative lung carcinogenesis models with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosobis(2-hydroxypropyl)amine (BHP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MelQx) and ethyl carbamate (urethane), as well as X-ray irradiation. With the chemical carcinogenesis models, no mutations were detected in Egfr, which is in clear contrast to the high rates observed in either codon 12 or 61 of K-ras (21/23 of the lung tumors induced with NNK, 4/5 with MelQx, 1/4 with urethane and 7/18 with BHP). However, in the ...

International Nuclear Information System (INIS)

A model for the simulation of the time dependent behavior and the analysis of the equilibrium of the coupled system of storage ring and Free Electron Laser (FEL) is presented. The analysis comprises both amplifier and oscillator FEL. Bunch lengthening and energy widening due to wake forces are taken into account in a self-consistent way. The method is based on a mapping algorithm for means and correlations of the electron distribution function, pioneered by K. Hirata. The evolution of the laser field in the oscillator FEL is described by K. Hirata. The evolution of the laser field in the oscillator FEL is described by supermodes. The model is used to simulate an FEL in a small 500 MeV storage ring with 100 m circumference. Typical values for the output power, spatial, and spectral characteristics of the emitted radiation are presented.

International Nuclear Information System (INIS)

The magnetic hyperfine constants of the V sub(K) center in CaF_2, SrF_2 and BaF_2 have been calculated, assuming a phenomenological model, based on the F"-_2 'central molecule', to describe the wave function of the defect. The introduction of covalence with the ions neighboring the 'central molecule', has shown that this is a better description for the defect than a simple 'central molecule' model. It was also shown that the results for the hyperfine constants are strongly dependent on the relaxations of these neighboring ions, which have been determined by fitting the experimental data. The present results are compared with other previous calculations where similar and different methods have been used. A better description for the wave function of the defect is suggested. (author).

Energy Technology Data Exchange (ETDEWEB)

This project is aimed at development of optimum combustion technology with diversified fuels, e.g., naphtha and LCO, for gas turbines and others as power sources for topographical energy supply. The combustion under the microgravity is also investigated using the underground facilities at Japan Microgravity Center. Described herein are the FY 2000 results. For construction of combustion model and simulation, the combustion reactions for various liquid fuels are simplified to calculate ignition delay, adiabatic flame temperature and laminar burning velocity with an error less than about 3%. The microgravity combustion experiments are conducted for spray dispersed into a cylinder, to find flame propagation velocities changing with the vaporization characteristics of liquid fuels, and also to construct the combustion models. The premixed turbulent combustion simulation program is developed using a probability density function ...

Science.gov (United States)

Four-enzyme section of the shikimate pathway (Aro B, D, E, and K) of Streptococcus pneumoniae has been studied. Kinetic properties of the individual enzymes and three- and four-enzyme linked reactions have been characterized in vitro. On the basis of the data measured in spectrophotometric and LC-MS experiments, kinetic mechanisms of the enzymes have been suggested and all kinetic parameters have been identified. Kinetic models for these three- and four-enzyme sections of the shikimate pathway have been constructed and validated. The model of the four-enzyme section of shikimate pathway has been employed to design an inhibition-sensitive reconstituted pathway for a high-throughput screening effort on the shikimate pathway. It was demonstrated that using the model it was possible to optimize this reconstituted pathway in such a way to provide equal sensitivity of the enzymes to inhibition. PMID:16921527

Energy Technology Data Exchange (ETDEWEB)

The dry deposition of pollutants can be calculated from the concentration of pollutants in the atmosphere and deposition velocity. To calculate deposition velocity, turbulence parameters such as friction velocity and Monin-Obukhov length are used. However, due to the difficulties in observation of turbulence parameters, usually mean values of wind speed and temperature observed using conventional meteorological instruments are used to estimate the dry deposition. The dry deposition velocity is the function of aerodynamic resistance (R{sub a}), sublayer resistance (R{sub b}), surface resistance (R{sub c}). R{sub a} and R{sub b} are calculated from turbulence parameters and R{sub c} is related to surface characteristics. The purpose of the present study is to compare the dry deposition obtained using the data sets of mean values and turbulence parameters measured by sonic anemometer-thermometer. The field ...

International Nuclear Information System (INIS)

Apparent molar volumes of aqueous methyldiethanolamine and its salt were determined with platinum vibrating tube densitometers over a range of temperatures from 283K=K and at pressures from 0.1MPa to 20MPa. Apparent molar heat capacities were obtained using a Sodev Picker flow microcalorimeter at a pressure of 0.1MPa and within the temperature range of 283K=K. Apparent molar adiabatic and isothermal compressibilities at a pressure of 0.1MPa were obtained at temperatures from 283K=K with speed of sound measurements. The experimental results were extrapolated to infinite dilution to obtain values for the standard partial molar volumes V"o, heat capacities C_p"o, and isothermal compressibilities #kappa#_T"o. The standard partial molar volumes V"o for the neutral amine and its salt show increasingly positive and negative ...

International Nuclear Information System (INIS)

Effects of PbO on the repassivation kinetics of alloy 690TT were examined using the rapid scratching electrode technique under a potentiostatic condition to elucidate the influence of PbO on SCC resistance of the alloy. The repassivation kinetics of the alloy was analyzed in terms of the current density flowing from the scratch, i(t), as a function of the charge density that has flowed from the scratch, q(t). Repassivation on the scratched surface of the alloy occurred in two kinetically different processes; passive film initially nucleated and grew according to the place exchange model in which log i(t) is linearly proportional to q(t) with a slope of 1/K, and then grew according to the high field ion conduction model in which log i(t) is linearly proportional to 1/q(t) with a slope of cBV. 1/K and cBV are parameters representing the SCC susceptibility as well as repassivation rate of the alloy at an ...

CERN Document Server

Connectivity and capacity are two fundamental properties of wireless multi-hop networks. The scalability of these properties has been a primary concern for which asymptotic analysis is a useful tool. Three related but logically distinct network models are often considered in the asymptotic analysis, i.e. the dense network model, the extended network model and the infinite network model, which consider respectively a network deployed in a finite area with a sufficiently large node density, a network deployed in a sufficiently large area with a fixed node density, and a network deployed in $\\Re^{2}$ with a sufficiently large node density. The infinite network model originated from continuum percolation theory and asymptotic results obtained from the infinite network model have often been applied to the dense and extended networks. In this paper, through two case ...

British Library Electronic Table of Contents (United Kingdom)

Turbulent shear flows on shallow continental shelves (here shallow means that the interaction with the solid, no-slip bottom is important) are of great importance because tide- and wind-driven flows on the shelf are drivers of the transfer of momentum, heat, and mass (gas) across the air?sea interface. These turbulent flows play an important role because vertical mixing and current are vectors for the transport of sediment and bioactive material on continental shelves. Understanding the dynamics of this class of flows presents complications because of the presence of a free surface and also because the flow can be driven by a pressure gradient (a tidal current), a stress at the free surface (a wind-driven current), or a combination of both. In addition, the flow can be modified by the pres...

Energy Technology Data Exchange (ETDEWEB)

A model for energy transport in a solid particle cavity receiver is developed and applied to the design and analysis of a receiver for the Central Receiver Test Facility (CRTF), Albuquerque, New Mexico. The model gives thermal performance results - including particle temperatures, cavity efficiencies, and wall temperatures - which directly affect the economic and technical feasibility of a solid particle receiver. In addition, design criteria relevant to the configuration of a solid particle cavity receiver are developed. Results for CRTF indicate that at design conditions particle temperatures will exceed 1200/sup 0/K with cavity efficiencies on the order of 75%.

Energy Technology Data Exchange (ETDEWEB)

The objective of this work is to improve the process for CO{sub 2} capture by alkanolamine absorption/stripping by developing an alternative solvent, aqueous K{sub 2}CO{sub 3} promoted by piperazine. Progress has been made in this reporting period on three subtasks. A simple thermodynamic model has been developed to represent the CO{sub 2} vapor pressure and speciation of the new solvent. A rate model has been formulated to predict the CO{sub 2} flux with these solutions under absorber conditions. A process and instrumentation diagram and process flow diagram have been prepared for modifications of the existing pilot plant system.

Energy Technology Data Exchange (ETDEWEB)

Electric currents induced due to 60 Hz magnetic fields in a human body placed in a close proximity of various high voltage transmission lines are computed. A realistic model of the human body from the anatomical and electrical point of view with resolution of 1.3 cm for the body and 0.665 cm for the head is used. The computations are performed using the impedance method. Three representative configurations of high voltage transmission lines, namely 500 kV, 138 kV and 25 kV are analyzed. The results indicate that the maximum current densities of the order of 0.2 {micro}A/cm{sup 2} can be induced in a lineman working on a 500 kV line (0.5 m away from closest conductors). A good correlation can be seen between the computed magnetic field in the location of the human body and the induced current densities. The induced currents computed here and estimated from measured magnetic fields in ...

Energy Technology Data Exchange (ETDEWEB)

With the launch of the new L 16/24 engine, Holeby Diesel is introducing a completely new diesel engine as part of a new family of 1000 and 1200 r/min, heavy-fuel auxiliary diesel sets. These cover a range between 425 and 770 kW at 50 Hz, or between 475 and 855 kW at 60 Hz electrical output. Said to be the first of a new generation, the L 16/24 engine family consists of 5 to 9 in-line cylinder versions with an output of 100 kW per cylinder at 1200 r/min. (Power is 10% less when running at 1000 r/min.) The specific fuel consumption is announced to be 187 g/kWh {+-}3% at 85% load, running on heavy fuel up to 700 cSt/150{degree}C from start to stop of the engine. Compactness was a further design criteria: the result is an auxiliary unit with only one meter in width, two meters in height, and 4.0 to 5.4 m in length, depending on the engine model used.

CERN Document Server

Aims: I have analyzed a sample of seven nearby edge-on galaxies observed in the V and K'-band, in order to infer the properties of the dust distribution. Methods: A radiative transfer model, including scattering, have been used to decompose each image into a stellar disk, a bulge, and a dust disk. The parameters describing the distributions have been obtained through standard X^2 minimization techniques. Results: The dust disks fitted to the V-band images are consistent with previous work in literature: the radial scalelength of dust is larger than that for stars (h_d/h_s ~ 1.5); the dust disk has a smaller vertical scalelength than the stellar (z_d/z_s ~ 1/3); the dust disk is almost transparent when seen face-on (central, face-on, optical depth tau_0 =0.5-1.5). Faster radiative transfer models which neglect scattering can produce equivalent fits, with changes in the derived parameters within the accuracy of full fits ...

Energy Technology Data Exchange (ETDEWEB)

In 1976, the US Department of Energy and New York State - ERDA granted a contract for the development of a +-600 kV dc underground transmission cable system looking to inevitable future requirements in the US for economic, high-capacity, long-distance underground transmission linking remote generating stations to metropolitan load centers. This project was comprehensive and dealt with three separate system components, i.e., cable, splice, and terminals. In each instance, for each component, development required an intensive R and D effort, focused on the following categories: insulating materials, model testing, design of full-scale prototype, manufacturer of prototype, and laboratory development testing. Insulating papers and oils were selected, and model studies performed, for both self-contained type and pipe type oil-filled cables. However, only the pipe cable design was finally designated for full-size cable ...

CERN Document Server

Gas and stars in spiral galaxies are modelled with the DUAL code, using hydrodynamic and N-body techniques. The simulations reveal morphological differences mirroring the dual morphologies seen in B and K' band observations of many spiral galaxies. In particular, the gaseous images are more flocculent with lower pitch angles than the stellar images, and the stellar arm-interarm contrast correlates with the degree of morphological decoupling.

Energy Technology Data Exchange (ETDEWEB)

We propose a generalization of the character formulas of the SU(2) Kac-Moody algebra to higher genus Riemann surfaces. With this construction, we show that the modular invariant partition funciton of the SO(4) k = 1 Wess-Zumino model is equivalent, in arbitrary genus Riemann surfaces, to that of free fermion theory.

Wastenet

...] gueconwpa~05-05-05 How is Macro News Transmitted to Exchange Rates? (December 2003) by Martin D. D. Evans(Georgetown University and NBER) and Richard K. Lyons(U.C. Berkeley and NBER, Haas School of Business) [Downloadable!] gueconwpa~05-05-04 A New Micro Model of Exchange Rate Dynamics (March 2004) by Martin D. D. Evans(Georgetown University and ...

Energy Technology Data Exchange (ETDEWEB)

The purpose of this work is to determine the extent to which drill water might be expected to be imbibed by core samples taken from densely welded tuff. In a related experimental study conducted in G-Tunnel, drill water imbibition by the core samples was observed to be minimal. Calculations were carried out with the TOUGH code with the intent of corroborating the imbibition observations. Due to the absence of hydrologic data pertaining directly to G-Tunnel welded tuff, it was necessary to apply data from a similar formation. Because the moisture retention curve was not available for imbibition conditions, the drainage curve was applied to the model. The poor agreement between the observed and calculated imbibition data is attributed primarily to the inappropriateness of the drainage curve. Also significant is the value of absolute permeability (k) assumed in the model. Provided that the semi-log plot of the drainage and ...

Energy Technology Data Exchange (ETDEWEB)

Toroidicity Alfven Eigenmodes (TAE) in ITER can be driven unstable by two groups of energetic particles, the 3.5 MeV {alpha}-particle fusion products and the tangentially injected 1MeV beam ions. Stability conditions are established using the perturbative NOVA/NOVA-K codes. A quasi-linear diffusion model is then used to assess the induced redistribution of energetic particles.

CERN Document Server

Two dimensional gyrokinetics is a simple paradigm for the study of kinetic turbulence. We study the inertial range dual cascade, assuming a homogeneous and isotropic random forcing. This cascade occurs in phase-space (two dimensions in position-space plus one dimension in velocity-space) via the nonlinear phase-mixing process, at scales smaller than the Larmor radius. At these scales, we show that the turbulence is self-similar and exhibits power law spectra in position and velocity-space. The velocity-space spectrum is treated via a Hankel transform which fits naturally with the mathematical framework of gyrokinetics. We derive the exact relations for third order structure functions, in analogy to Kolmogorov's four-fifths law. For scales larger than the Larmor radius, the two dimensional gyrokinetic system may be reduced to the well-studied Charney--Hasegawa--Mima equation or the vorticity equation describing incompressible two dimensional ...

Science.gov (United States)

Related to other research on the effectiveness of flow boiling heat transfer augmentation using various types of turbulators this investigation comprises a definitive study of the effect of large discrete roughness elements on heat transfer over the entir...

Science.gov (United States)

Radiation Measurement in Crew Compartment. DTO 805: .... spacecraft and aircraft propulsion, and hazardous waste disposal. ...... combustion reactions in a turbulent chemical kinetic flow reactor using laser induced fluorescence and ...

Science.gov (United States)

Jul 8, 2008 ... This case involves the flow over the ONERA M6 wing. ... The wind tunnel tests are documented by Schmitt and Charpin in the AGARD Report AR-138 ... supersonic flow, shocks, and turbulent boundary layers separation). ...

Energy Technology Data Exchange (ETDEWEB)

The design considerations and computational fluid dynamics (CFD) modeling of a high efficiency, low emissions, hydrogen-fueled engine for use as the prime mover of a series hybrid automobile is described. The series hybrid automobile uses the engine to generate electrical energy via a lightweight generator, the electrical energy is stored in a power peaking device (like a flywheel or ultracapacitor) and used as required to meet the tractive drive requirements (plus accessory loads) through an electrical motor. The engine/generator is stopped whenever the energy storage device is fully charged. Engine power output required was determined with a vehicle simulation code to be 15 to 20 kW steady state with peak output of 40 to 45 kW for hill climb. Combustion chamber and engine geometry were determined from a critical review of the hydrogen engine experiments in the literature combined with a simplified global engine ...

Energy Technology Data Exchange (ETDEWEB)

The productivity characteristics of perforated gas well are investigated for the first time under real conditions considering drilling damage, perforation compacted zone and anisotropy in this paper. A non-linear finite element model for non-Darcy flow in perforated gas reservoir is built to consider the effects of twelve factors on productivity ratio (PR) of perforated gas well. The nomographs for two cases are presented in this paper. Compared with previous works, the following results are found: (1) the effects of drilling damage and perforation diameter on PR of gas well are more remarkable than that in oil well; (2) any perforation phase may be the best or the worst as to perforating gas well, which depends on anisotropy, drawdown and that whether or not perforations are beyond drilling damage zone; (3) the increase in perforation length hardly improve PR of gas well when perforations have been beyond drilling damage zone. The new method is suggested to ...

International Nuclear Information System (INIS)

The aim of this paper is to investigate the fluid dynamic behaviour of a commercial hydraulic proportional valve in order to evaluate and justify its global performances and, in particular, to analyze the effects of some additional design features on the reduction of the force required to maintain the valve open. The proposed analysis has been performed by applying the commercial computational fluid dynamics (CFD) code, Fluent, to the solution of the three dimensional turbulent flow field through a circumferential sector of the entire valve for different spool strokes. The reliability of the employed modelization is demonstrated by the comparison between the computed flow rate curve and the corresponding experimental data provided by the manufacturer. With regard to the metering edge design, it is shown that the cylindrical hole provided on the top of the hemi-spherical notch to improve metering at small valve openings has no influence on the ...

Energy Technology Data Exchange (ETDEWEB)

The core bypass flow in a prismatic very high temperature gas-cooled reactor (VHTR) is one of the important design considerations which impacts considerably on the integrity of reactor core internals including operating fuels. The interstitial gaps are an inherent presence in the reactor core because of tolerances in manufacturing the blocks and the inexact nature of their installation. Furthermore, the geometry of the graphite blocks changes over the lifetime of the reactor because of thermal expansion and irradiation damage. The occurrence of hot spots in the core and lower plenum and hot streaking in the lower plenum (regions of very hot gas flow) will be affected by the bypass flow. In the present study, three-dimensional computational fluid dynamic (CFD) calculations of a typical prismatic VHTR are conducted to understand better the bypass flow phenomenon and establish the evaluation method in the reactor core using commercial CFD code FLUENT. Parametric calculations changing ...

Energy Technology Data Exchange (ETDEWEB)

Geological, geophysical, thermal, petrophysical and hydrological data available for the East Mesa hydrothermal system that are pertinent to the construction of a computer model of the natural flow of heat and fluid mass within the system are assembled and correlated. A conceptual model of the full system is developed and a subregion selected for quantitative modeling. By invoking the Boussinesq approximation, valid for describing the natural flow of heat and mass in a liquid hydrothermal system, it is found practical to carry computer simulations far enough in time to ensure that steady-state conditions are obtained. Initial calculations for an axisymmetric model approximating the system demonstrate that the vertical formation permeability of the deep East Mesa system must be very low (k/sub v/ approx. 0.25 to 0.5 md). Since subsurface temperature and surface heat flow data exhibit ...

International Nuclear Information System (INIS)

Multi-machine experimental observations indicate resilience in the temperature profiles at low pedestal temperatures,whereas at high pedestal temperatures the profile stiffness seems to disappear.The change of the profile behavior impacts the energy confinement,basically due to a strong non-linear dependence of the energy transport on the pedestal temperature together with different critical conditions for the onset of turbulence in the ions and electrons.This possible explanation for the different observations is based on the assumption that both ion and electron energy transport is governed by turbulence which sets in at a critical temperature gradient as well as on a significant energy equipartition between electrons and ions.

Energy Technology Data Exchange (ETDEWEB)

The results of this study show that Monte Carlo simulations of diffusion in homogeneous turbulence can be formulated in terms of the Eulerian space-time velocity autocorrelation function. Numerical results obtained using this approach agree with results obtained by Taylor (1921) using the Lagrangian autocorrelation function. Use was made of the equivalence of the Lagrangian and Eulerian Monte Carlo approaches to derive analytic relations between the Lagrangian integral time scale and the Eulerian integral space and time scales. These analytic results were verified by comparison to Monte Carlo simulations and to other theoretical results. They are in general agreement with many existing theories and semi-empirical relations.

Energy Technology Data Exchange (ETDEWEB)

Results are presented from a numerical model of the steady-state energy transfer in molten-salt-in-tube solar cavity receivers that includes convective energy transfer at a local (spatially resolved) level. Molten salt energy absorption and gray radiative transfer between all cavity surfaces are also included. This model is applied to the Molten Salt Subsystem Component Test Experiment (MSS/CTE) cavity receiver. Results for this receiver indicate the global (entire cavity) receiver thermal efficiency is invariant within a few percent to most parameters investigated, although front surface temperatures of the nonabsorbing walls vary considerably, and are particularly sensitive to the type of convective submodel used. Absorption efficiencies indicate the effects of the cavity enclosure environment. For all conditions investigated, tube inner wall temperatures remain under 855 K, ensuring that the salt remains chemically ...

British Library Electronic Table of Contents (United Kingdom)

The effects of pore curvature and surface heterogeneity on the adsorption of water on a graphitic surface at 298 K were investigated using a Grand Canonical Monte Carlo (GCMC) simulation. Slit and cylindrical pores are used to study the curvature effects. To investigate the surface heterogeneity the functional group and the structural defect on the surface were specifically considered. The hydroxyl group (OH) is used as a model for the functional group and the water potential model proposed by Muller et al. is used to calculate the water interaction. For the homogeneous cylinder, the pore filling occurs at a pressure lower than the saturation pressure of the water model, while it is greater in the case of homogeneous slit pore. The size of hysteresis loop is more sensitive to the length of...

Science.gov (United States)

This is a continuation of our paper [Liu, M., Wang, K., 2010. Persistence and extinction of a stochastic single-species model under regime switching in a polluted environment, J. Theor. Biol. 264, 934-944]. Taking both white noise and colored noise into account, a stochastic single-species model under regime switching in a polluted environment is studied. Sufficient conditions for extinction, stochastic nonpersistence in the mean, stochastic weak persistence and stochastic permanence are established. The threshold between stochastic weak persistence and extinction is obtained. The results show that a different type of noise has a different effect on the survival results. PMID:20816991

Energy Technology Data Exchange (ETDEWEB)

The liquid/vapor coexistence density, the partial vapor pressure, and the heat of vaporization were calculated using Gibbs ensemble Monte Carlo simulation techniques. Long-range interactions such as charge-charge, charge-dipole, and dipole-dipole were evaluated using Ewald summation techniques. A polarizable potential model was used to describe the water-water interactions (Dang and Chang, J. Chem. Phys. 106, 8149, 1997). The model yields good agreement with the corresponding experimental data in the lower temperature region and moderate agreement in the higher temperature region. The critical temperature and density were estimated to be 565 K and 0.28 g/cm3.

Energy Technology Data Exchange (ETDEWEB)

The main objective of the present study is twofold: (i) to analyze thermal loads of the geothermally and passively heated solar greenhouses; and (ii) to investigate wind energy utilization in greenhouse heating which is modeled as a hybrid solar assisted geothermal heat pump and a small wind turbine system which is separately installed in the Solar Energy Institute of Ege University, Izmir, Turkey. The study shows 3.13% of the total yearly electricity energy consumption of the modeled system (3568 kWh) or 12.53% of the total yearly electricity energy consumptions of secondary water pumping, brine pumping, and fan coil (892 kWh) can be met by using small wind turbine system (SWTS) theoretically. According to this result, modeled passive solar pre heating technique and combined with geothermal heat pump system (GHPS) and SWTS can be economically preferable to the conventional space ...

CERN Document Server

The General Spectral Modeling (GSM) code employs the quasi-static approximation, a standard, low-density methodology that assumes the ionization balance is separable from a determination of the excited-state populations that give rise to the spectra. GSM also allows for some states to be treated only as contributions to effective rates. While these two approximations are known to be valid at low densities, this work investigates using such methods to model high-density, non-LTE emission spectra and determines at what point the approximations break down by comparing to spectra produced by the LANL code ATOMIC which makes no such approximations. As both approximations are used by other astrophysical and low-density modeling codes, the results should be of broad interest. He-like K$\\alpha$ emission spectra are presented for Ni, Fe, and Ca, in order to gauge the effect of both approximations employed in ...

International Nuclear Information System (INIS)

K and L-shell x-ray production cross sections were measured using #alpha#-particle beams of 14.00 to 34.16 MeV. The K-shell measurements ranged from Z = 20 to Z = 50 and included Ca, Sc, Ti, V, Fe, Ni, Cu, Zn, Ga, Br, Rb, Sr, Y, Mo, Ag, In, and Sn while the L-shell measurements ranged from Z = 55 to Z = 92 and included Cs, Ba, Ce, Gd, Tm, Lu, Au, Pb, Th, and U. Thin metallic foils were used for the measurements and corrections for self-attenuation were negligible. A liquid nitrogen cooled Si(Li) detector and associated pulsed optical electronics were used in detecting x-rays. Absolute cross sections with an uncertainty of +-10 percent are presented for the elements measured. Also smoothed cross sections are presented which were generated by a three term polynomial fit of the experimental data points. By use of available fluorescence yields the K-shell data were converted to ionization cross sections and compared to various ...

International Nuclear Information System (INIS)

A new algorithm for constructing extensions of the Virasoro algebra by primary fields - so called W-algebras - is presented. With the help of REDUCE all W-algebras with one further primary field up to conformal dimension 9 were calculated. Furthermore I give an interpretation of the obtained results using fusion algebras. The algorithm could also be used for constructing extensions of the super Virasoro algebra which play an important role in superstring theory. I present two examples here. With using representation theory of Kac-Moody algebras I determine the minimal field content of the super W_3 algebra. Finally, the general coset models SU(2)_kxSU(2)_m/SU(2)_k_+_m and SU(3)_kxSU(3)_m/SU(3)_k_+m are investigated. I calculate which W-algebras are likely contained in these cosets. (orig.).

British Library Electronic Table of Contents (United Kingdom)

Political leaders in numerous nations argue for an upper limit of the global average surface temperature of 2 K above the pre-industrial level, in order to attempt to avoid the most serious impacts of climate change. This paper analyzes what this limit implies in terms of radiative forcing, emissions pathways and abatement costs, for a range of assumptions on rate of ocean heat uptake and climate sensitivity. The primary aim is to analyze the importance of ocean heat uptake for radiative forcing pathways that temporarily overshoot the long-run stabilization forcing, yet keep the temperature increase at or below the 2 K limit. In order to generate such pathways, an integrated climate-economy model, MiMiC, is used, in which the emissions pathways generated represent the least-cost solution o...

British Library Electronic Table of Contents (United Kingdom)

Soil erodibility (the K factor in the Universal Soil Loss Equation, USLE) is an important index to measure soil susceptibility to water erosion, and an essential parameter needed for soil erosion prediction. To evaluate the appropriateness of the nomograph and other methods for estimating the K factor for the USLE and to develop a relationship for soil erodibility estimation for Chinese soils, a set of soil erodibility values was calculated using soil loss data from natural runoff plots at 13 sites in eastern China. The definition of soil erodibility in relation to the USLE was strictly followed. Comparing these measured values to those estimated using the nomograph method, the method adopted for the EPIC model and the formula of Shirazi and Boersma, we found that all these estimated soil ...

International Nuclear Information System (INIS)

Magnetization, neutron diffraction and "1"6"6Er Moessbauer measurements on ErPd_2Si_2 are reported. Below 4.8 K ErPd_2Si_2 orders AF with complex modulated magnetic structures, where the Er moments are aligned along the c-axis. At 1.5 K a squared structure with #mu#_E_r #approx# 7.8(1)#mu#_B is found while a saturation Er moment of 8.2(2)#mu#_B is inferred from the hyperfine field data. The temperature dependence of the Moessbauer spectra in the paramagnetic region is explained in the framework of a relaxation model implying excited crystal field levels. Its analysis is used to estimate the B"m_n CEF parameters. (orig.).