Study of turbulent heat transfer of aviation kerosene flows in a curved pipe at supercritical pressure

The now and heat transfer characteristics of China No. 3 aviation kerosene in a heated curved tube under supercritical pressure are numerically investigated by a finite volume method. A two-layer turbulence model, consisting of the RNG k-epsilon two-equation model and the Wolfstein one-equation model, is used for the simulation of turbulence. A 10-species kerosene surrogate model and the NIST Supertrapp software are applied to obtain the thermophysical and transport properties of the kerosene at various temperature under a supercritical pressure of 4 MPa. The large variation of thermophysical properties of the kerosene at the supercritical pressure make the flow and heat transfer more complicated, especially under the effects of buoyancy and centrifugal force. The centrifugal force enhances the heat transfer, but also increases the friction factors. The rise of the velocity caused by the variation of the density does not enhance the effects of the centrifugal force when the curvature ratios are less than 0.05. On the contrary, the variation of the density increases the effects of the buoyancy. (C) 2010 Elsevier Ltd. All rights reserved.

Kinetic Studies of Gas Flows

Our recent studies on kinetic behaviors of gas flows are reviewed in this paper. These flows have a wide range of background, but share a common feature that the flow Knudsen number is larger than 0.01. Thus kinetic approaches such as the direct simulation Monte Carlo method are required for their description. In the past few years, we studied several micro/nano-scale flows by developing novel particle simulation approach, and investigated the flows in low-pressure chambers and at high altitude. In addition, the microscopic behaviors of a couple of classical flow problems were analyzed, which shows the potential for kinetic approaches to reveal the microscopic mechanism of gas flows.

Characteristic rainfall for warning of debris flows

A characteristic rainfall is introduced to overcome the difficulties encountered in determining a critical rainfall value for triggering debris flow. The characteristic value is defined as the rainfall at which debris-flow occurrence probability shows a rapid increase, and can be used as a warning rainfall threshold for debris flows. Investigation of recorded debris flows and 24-hour rainfall data at Jiangjia basin, Yunnan Province, in southwestern China, demonstrates the existence of such a characteristic rainfall. It was found that the characteristic rainfall corresponds to the daily rainfall of 90% cumulative probability by analyzing the basin's daily rainfall histogram. The result provides a simple and useful method for estimating a debris-flow warning rainfall threshold from the daily rainfall distribution. It was applied to estimate the debris-flow warning rainfall threshold for the Subaohe basin, a watershed in the 2008 Wenchuan earthquake zone with many physical characteristics similar to those of the Jiangjia basin.

Probability of Sediment Incipient Motion Under Complex Flows

Presented in this paper is a mathematical model to calculate the probability of the sediment incipient motion, in which the effects of the fluctuating pressure and the seepage are considered. The instantaneous bed shear velocity and the pressure gradient on the bed downstream of the backward-facing step flow are obtained according to the PIV measurements. It is found that the instantaneous pressure gradient on the bed obeys normal distribution. The probability of the sediment incipient motion on the bed downstream of the backward-facing step flow is given by the mathematical model. The predicted results agree well with the experiment in the region downstream of the reattachment point while a large discrepancy between the theory and experiment is seen in the region near the reattachment point. The possible reasons for this discrepancy are discussed.

A finite-element algorithm for modeling variably saturated flows

A general numerical algorithm in the context of finite element scheme is developed to solve Richards’ equation, in which a mass-conservative, modified head based scheme (MHB) is proposed to approximate the governing equation, and mass-lumping techniques are used to keep the numerical simulation stable. The MHB scheme is compared with the modified Picard iteration scheme (MPI) in a ponding infiltration example. Although the MHB scheme is a little inferior to the MPI scheme in respect of mass balance, it is superior in convergence character and simplicity. Fully implicit, explicit and geometric average conductivity methods are performed and compared, the first one is superior in simulation accuracy and can use large time-step size, but the others are superior in iteration efficiency. The algorithm works well over a wide variety of problems, such as infiltration fronts, steady-state and transient water tables, and transient seepage faces, as demonstrated by its performance against published experimental data. The algorithm is presented in sufficient detail to facilitate its implementation.

Triton-He-3 relative and differential flows as probes of the nuclear symmetry energy at supra-saturation densities

Using a transport model coupled with a phase-space coalescence afterburner, we study the triton-He-3 (t-He-3) ratio with both relative and differential transverse flows in semicentral Sn-132 + Sn-124 reactions at a beam energy of 400 MeV/nucleon. The neutron-proton ratios with relative and differential flows are also discussed as a reference. We find that similar to the neutron-proton pairs, the t-He-3 pairs also carry interesting information regarding the density dependence of the nuclear symmetry energy. Moreover, the nuclear symmetry energy affects more strongly the t-He-3 relative and differential flows than the pi(-)/pi(+) ratio in the same reaction. The t-He-3 relative flow can be used as a particularly powerful probe of the high-density behavior of the nuclear symmetry energy.

TRITON-(HE)-H-3 RELATIVE AND DIFFERENTIAL FLOWS AND THE HIGH DENSITY BEHAVIOR OF NUCLEAR SYMMETRY ENERGY

Using a transport model coupled with a phase-space coalescence after-burner we study the triton-He-3 relative and differential transverse flows in semi-central Sn-132 + Sn-124 reactions at a beam energy of 400 MeV/nucleon. We find that the triton-He-3 pairs carry interesting information about the density dependence of the nuclear symmetry energy. The t-He-3 relative flow can be used as a particularly powerful probe of the high-density behavior of the nuclear symmetry energy.

Pressure drops of single and two-phase flows through T-type microchannel mixers

In this paper, preliminary experimental results are presented on pressure drop characteristics of single and two-phase flows through two T-type rectangular microchannel mixers with hydraulic diameters of 528 and 333 mum, respectively. It is shown that both N-2 and water single-phase laminar flows in microchannels, with consideration of experimental uncertainties, are consistent with classic theory, if additional effects, such as entrance effects that will interfere with the interpretation of experimental results, are eliminated by carefully designing the experiments. The obtained pressure drop data of N-2-water two-phase flow in micromixers are analyzed and compared with existing flow pattern-independent models. It is found that the Lockhart-Martinelli method generally underpredicts the frictional pressure drop. Thereafter, a modified correlation of C value in the Chisholm's equation based on linear regression of experimental data is proposed to provide a better prediction of the two-phase frictional pressure drop. Also among the homogeneous flow models investigated, the viscosity correlation of McAdams indicates the best performance in correlating the frictional pressure drop data (mean deviations within +/-20% for two micromixers both). Finally it is suggested that systematic studies are still required to accurately predict two-phase frictional performance in microchannels. (C) 2004 Elsevier B.V. All rights reserved.

Spatial and temporal flows of China's forest resources: Development of a framework for evaluating resource efficiency

Science & Technology Basic Work Program of China: Scientific Survey of the Middle-lower Reaches of Lantsang River and the Great Shangri-La Region [2008FY110300]; National Basic Research Program of China (973 Program): Ecosystem Services and Ecological Safety of the Major Terrestrial Ecosystems of China [2009CB421106]; National Natural Science Foundation of China [30670374]; EU ; European Commission, DG Research [003874]

Strongly nonlinear long interfacial waves in uniform basic flows and their dispersion relationship

In this paper, long interfacial waves of finite amplitude in uniform basic flows are considered with the assumption that the aspect ratio between wavelength and water depth is small. A new model is derived using the velocities at arbitrary distances from the still water level as the velocity variables instead of the commonly used depth-averaged velocities. This significantly improves the dispersion properties and makes them applicable to a wider range of water depths. Since its derivation requires no assumption on wave amplitude, the model thus can be used to describe waves with arbitrary amplitude.

城市发展与地质环境相互作用机制及数量分析—北海市可持续发展战略研究

Based on a viewpoint of an intricate system demanding high, this thesis advances a new concept that urban sustainable development stratagem is a high harmony and amalgamation among urban economy, geo-environment and tech-capital, and the optimum field of which lies in their mutual matching part, which quantitatively demarcates the optimum value field of urban sustainable development and establishes the academic foundation to describe and analyze sustainable development stratagem. And establishes a series of cause-effect model, a analysissitus model, flux model as well as its recognizing mode for urban system are established by the approach of System Dynamics, which can distinguish urban states by its polarity of entropy flows. At the same time, the matter flow, energy flow and information flow which exist in the course of urban development are analyzed based on the input/output (I/O) relationships of urban economy. And a new type of I/O relationships, namely new resources-environment account, are established, in which both resource and environment factors are considered. All above that settles a theoretic foundation for resource economy and environment economy as well as quantitative relationships of inter-function between urban development and geoenvironment, and gives a new approach to analyze natinal economy and urban sustainable development. Based on an analysis of the connection between resource-environmental construct of geoenvironment and urban economy development, the Geoenvironmental Carrying Capability (GeCC) is analyzed. Further more, a series of definitions and formula about the Gross Carrying Capability (GCC), Structure Carrying Capability (SCC) and Impulse Carrying Capability (ICC) is achieved, which can be applied to evaluate both the quality and capacity of geoenvironment and thereunder to determine the scale and velocity for urban development. A demonstrative study of the above is applied to Beihai city (Guangxi province, PRC), and the numerical value laws between the urban development and its geoenvironment is studied by the I/O relationship in the urban economy as following: · the relationships between the urban economic development and land use as well as consumption of underground water, metal mineral, mineral energy source, metalloid mineral and other geologic resources. · the relationships between urban economy and waste output such as industrial "3 waste", dust, rubbish and living polluted water as well as the restricting impact of both resource-environmental factors and tech-capital on the urban grow. · Optimization and control analysis on the reciprocity between urban economy and its geoenvironment are discussed, and sensitive factors and its order of the urban geoenvironmental resources, wastes and economic sections are fixed, which can be applied to determine the urban industrial structure, scale, grow rate matching with its geoenvironment and tech-capital. · a sustainable development stratagem for the city is suggested.

Uma análise de cenários à luz das tendências atuais: sua importância para gestão do capital humano nas organizações.

Este trabalho analisa os cenários previstos por Peter Drucker (1985) e Alvin Toffler (1990) sob a perspectiva da obra de Thomas Friedman (2005). Friedman, em sua obra ?O mundo é plano?, descreve os fatores determinantes do cenário econômico e tecnológico do século XXI. A análise efetuada neste trabalho evidencia que os paradigmas da sociedade da informação na qual vivemos, que são descritos por Friedman (2005), comprovam grande parte das predições efetuadas há mais de uma década por Drucker e Toffler. Estes autores contribuiram para a construção do ?presente? de diversas organizações uma vez que seus pensamentos embasaram o planejamento estratégico de várias empresas e instituições. Este trabalho visa ressaltar que projeções de futuro criteriosas, sustentadas por fatos e tendências, são importantes ferramentas para o desenvolvimento de ações empresariais, dentre elas, o estabelecimento de estratégias de gestão de pessoas.

Can theories of social capital explain dissenting patterns of engagement in the new Europe?

Korosteleva-Polglase, Elena, 'Can theories of social capital explain dissenting patterns of engagement in the new Europe?', Contemporary Politics, (2006) 12(2) pp.175-191 RAE2008

Inter-regional transfer trade flows in the English football league

Perdikis, Nicholas, Thomas, Dennis, Inter-regional transfer trade flows in the English football league', Tijdschrift voor Economie en Management (2002) 47 (4) 477-509 RAE2008

Quantum Flows as Markovian Limit of Emission, Absorption and Scattering Interactions

Gough, John, (2004) 'Quantum Flows as Markovian Limit of Emission, Absorption and Scattering Interactions', Communications in Mathematical Physics 254 pp.498-512 RAE2008