阻垢剂耦合吸附/沉淀的室内实验及数学模拟

通过室内实验研究了阻垢剂在多孔介质中滞留的机理。关于阻垢剂的滞留机理,普遍有两个观点,即"吸附"和"沉淀",并且前人用不同但相关的模拟方法证实了这些观点。这些模拟方法已成功地应用于油田挤注处理的模拟。为了详细分析特定滞留机理(如纯吸附),需要在油田"相关条件"下进行认真的室内实验研究。本文通过一系列实验来对比研究纯吸附与耦合的吸附/沉淀,且耦合吸附/沉淀数学模拟的结果与实验结果保持一致。

也谈蒙特卡罗模拟在经济预测中的应用

蒙特卡罗(monte carlo)模拟,又称模拟抽样法或统计试验法,是一种以数理统计理论为指导的模拟技术。用蒙特卡罗模拟求解某一问题,不象通常数理统计方法那样,通过真实的试验来完成,而是抓住事物运动过程的基本数量和物理特征,运用数学方法模拟求解。虽然数字模拟试验方法早已出现,但由于必须进行成百,甚至上千次的模拟运算,才能获得有意义的结果,因而使它的应用受到了限制。随着电子计算机技术的发展,才使得进行大量数学模拟实验成为可能。所以。

不同构造变形带中“静水压力”的差别

地壳应力状态主要是由重力和构造作用力引起的,作者明确提出其静水压力部分是由重力所附加的静水压力和由构造作用力所附加的静水压力叠合而成。本文用有限元模型数学模拟实验证实,处在挤压变形带、剪切变形带到引张变形带(及地域)中岩石所承受的构造附加静水压力有逐次变小的规律性,利用这种规律可解释构造作用力影响成岩成矿作用的物理化学环境及制约其化学过程的动力学问题,为开展构造物理化学研究奠定了基础。

NOx Absorption in Full Scale Plant Columns with Structured Packings

A mathematical model of nitrogen oxide （NOx） absorption is adopted and solved for adiabatic operation of a column with structured packings on the basis of the film theory. Removal rate, outlet concentration, oxidation degree of NOx and outlet acid concentration, liquid acid temperature are simulated and tested. The gas phase reactions and equilibria, gas phase mass transfer, interracial equilibria, and liquid phase reactions are considered in the model. Absorption of nitrogen oxides is studied in packed with Mellapak 250Y columns in series in an industrial process of 20000 t oxalic acid per year. Favorable agreement is shown between the model predictions and the on-site observations.

Accurate level set method for simulations of liquid atomization

Computational fluid dynamics is an efficient numerical approach for spray atomization study, but it is challenging to accurately capture the gas-liquid interface. In this work, an accurate conservative level set method is intro- duced to accurately track the gas-liquid interfaces in liquid atomization. To validate the capability of this method, binary drop collision and drop impacting on liquid film are investigated. The results are in good agreement with experiment observations. In addition, primary atomization （swirling sheet atomization） is studied using this method. To the swirling sheet atomization, it is found that Rayleigh-Taylor instability in the azimuthal direction causes the primary breakup of liquid sheet and complex vortex structures are clustered around the rim of the liq- uid sheet. The effects of central gas velocity and liquid-gas density ratio on atomization are also investigated. This work lays a solid foundation for further studvin~ the mechanism of s^rav atomization.

Numerical simulation and experimental study of the hydrodynamics of a modeled reef located within a current

The hydrodynamic forces and flow field of artificial reef models in steady flow were numerically investigated using the RNG κ-ε turbulent model. The numerical simulation results are consistent with results observed by experimental means. A comparative study indicates that the corresponding errors of forces between calculated values and values observed in the experiment vary in the range of2.3%-11.2% and that the corresponding errors of velocities vary in the range of 1.3%-15.8%. The flow field numerical results show that upstream and vortices exist when the current passes over and through the surface of the reef model. This study suggests that the numerical simulation method can be applied to predict the forces and flow field associated with artificial reefs.

A Comparative Study on Hydrodynamic Performance of Double Deflector Rectangular Cambered Otter Board

In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the otter board had a good hydrodynamic performance with the maximum lift-to-drag ratio(K_(MAX) = 3.70).The flow separation occurred when the angle of attack(AOA) was at 45?,which revealed that the double deflector structure of the otter board can delay the flow separation.Numerical simulation results showed a good agreement with experiment ones,and could predict the critical AOA,which showed that it can be used to study the hydrodynamic performance of the otter board with the advantage of flow visualization.However,the drag coefficient in flume tank was much higher than that in wind tunnel,which resulted in a lower lift-to-drag ratio.These may be due to different fluid media between flume tank and wind tunnel,which result in the big difference of the vortexes around the otter board.Given the otter boards are operated in water,it was suggested to apply both flume tank experiment and numerical simulation to study the hydrodynamic performance of otter board.

The Choice of Model of External Load in Problem of Synthesis of Adequate Mathematical Description

The problem of mathematical simulation of motion of dynamic systems characteristics and their coincidence with real experimental data which correspond to these characteristics is investigated in this paper. Mathematical description of process will be named as adequate mathematical description if the results of mathematical simulation by the help of this description coincide with experiment with inaccuracy of initial data. The synthesis of such description is very important at mathematical modeling and forecast of motion of real physical phenomena. The specified problem is still poorly investigated and hardly adapted to formalization. The requirements to the adequate mathematical description of dynamic system are considered for the case when mathematical description of dynamic systems is represented by linear system of the ordinary differential equations. In this paper the mathematical model of process is given a priori with inexact parameters and then the models of external loads are being determined for which the results of simulation coincide with experiment. The methods of obtaining of the steady models of external loads are suggested. The example of the adequate description construction of the main mechanical line dynamics of rolling mill is given.

Condition to Gain More Profits and Promote Cooperation by Tit-for-Tat Strategy in Finite and Repeated Prisoner＇s Dilemma

As a basic study to prevent accidents or concealment caused by violation of rules or regulations （which are regarded as uncooperative behavior）, an attempt was made to clarify the condition necessary for promoting cooperation when the tit-for-tat strategy is adopted in the finite and repeated prisoner＇s dilemma situations. A mathematical model, in which three different strategies （tit-for-tat, all defection （individualism）, and all cooperation （altruism）） exist, was constructed in order to demonstrate the condition that can promote cooperative behaviors. As a result of an agent-agent computer simulation, it was shown that the tit-for-tat strategy promoted more cooperation than other strategies when the number of agents adopting the tit-for-tat strategy was dominant in the population and the discount parameter was larger. Next, it was explored how the tit-for-tat strategy in the finite and repeated prisoner＇s dilemma promotes cooperation using a human-agent computer simulation. In other words, the condition under which cooperative behavior is encouraged was clarified. In the simulation experiment, the discount rate was controlled as an experimental variable. As well as the first experiment above, the dominant occupation of the tit-for-tat strategy was found to lead to the promoted cooperation. Concerning the effect of discount parameter on the cooperative behavior, the cooperation rate tended to increase with the increase of discount parameter only when the t-t-for-tat strategy is dominant. As a whole, the type of change of discount parameter did not affect the cooperation rate.

Biomechanics of the Intervertebral Disc in Compression： Experimental and Numerical Study

Loading history and age are factors for disc degeneration and disc biomechanics; however, their relationship is unclear. To evaluate disc biomechanics, we conducted an experimental, anatomical and numerical approach to distinguish discs with mild and severe degeneration. In the experimental procedure, 10 cadaveric lumbar discs are tested to static and dynamic compression, and the elastic and viscous moduli and the dynamic parameters are reported. The morphology of disc degeneration is gained with MRI （magnetic resonance imaging） and used to generate a nonlinear finite element model of a degenerated disc, and assisted with the experimental results in order to numerically investigate the distribution of stresses and strains within the disc. The results show a promising methodology for the study of intervertebral disc biomechanics and in general other tissues, organs and medical devices.

Construction of the Coherent-Mode Representation of an Optical Planar Source from the Results of Young＇s Experiment

A new definition of the alternative coherent-mode representation of a random planar source with the a priori unknown statistical properties is proposed. This definition is based on the measurements of the source cross-spectral density followed by the optimal approximation of the obtained results in the chosen basis of modal functions. The proposed definition is illustrated by the results of numerical simulation.

A Teaching Experiment in Modelling through Scale Reduction Methods： A Bridge to Later Trigonometric Methods

In a teaching experiment, Japanese Grade 9 students investigated how to measure the height of an aerial balloon using different models involving angles and distances, and also to evaluate the models they developed. As novices to mathematical modelling, they needed to decide which of several possible models were both valid and practicable, and the errors in measurement that are likely to arise. Opportunities to construct and use paper models, as scale reductions of the real situation, and discussing their results in small groups were effective in moving forward the thinking of many students on the dimensions mentioned above. While students were less able to identify different sources of errors, many came to appreciate the need to learn trigonometric techniques that are more suitable in dealing with problems of this kind.

Numerical Prediction of Flow Patterns after Various Pipe Fittings

An accurate prediction of flows using CFD depends on a large number of factors. In addition to discretizing the flow region, the correct definition of boundary or initial conditions and the choice of suitable numerical methods, the applied turbulence model influences the results of the flow simulation to a great extent. Therefore, a validation of the results with the experimental data is of great importance for a correct selection of a turbulence model. It is the scope of this paper to assess different turbulence models for the simulation of pipe flows. The calculation results of pipe flows through a combination of 90~ elbows and a 1/3 segmental orifice are compared with experimental measurement results. This has the advantage that the suitability of the turbulence models for simulating both shear and swirl flows can be investigated. Thus, the k-ω, k-ε model and the Launder Reece Rodi Reynolds stress model are compared with each other and experimental results. Furthermore, this investigation is extended through including a much more c detached-eddy simulation. This model provides better prediction of the flow by resolving the large eddies and modeling the small ones. The experimental results originate from LDV measurements over the entire pipe cross-section. This measuring method provides velocity vectors over the measured surface.

Improving the Performance of an Electro-Hydraulic Load-Sensing Proportional Control Valve

The paper deals with the simulation and the experimental verification of the hydraulic behavior of an electro-hydraulic load-sensing proportional control valve. An innovative CAE （computer aided engineering） methodology, developed combining CFD （computational fluid dynamics） simulations with lumped and distributed numerical modeling, is firstly introduced and tailored by comparing the numerical results with measurements coming from an experimental campaign performed for a wide range of pressure loads and metered flow rates. Then, both the reliability and the limits of the numerical approach are highlighted through a detailed numerical vs. experimental comparison, involving the pressure of the main hydraulic lines, the flow rate through the first section and the local compensator displacement. Finally, the CAE methodology has been applied for assessing the internal ducts hydraulic permeability and the local compensator spring pre-load influence on the control valve metering curves. At the end of this analysis, an optimized design configuration, featuring a maximum controlled volumetric flow rate increased of more than 25%, has been proposed.

星系大撞击探秘

1994年7月的"彗木之吻"使天文学家们亲眼目睹了一场天体大撞击的宇宙奇观和悲剧般后果。然而,这不过是在太阳系范围上的一次普通天体撞击现象。倘若两个对面飞驰而来的星系相撞,或被此"擦肩而过",那便是天体力学上一个惊人庞大的宇宙过程。

Internal heat transfer coefficients in microporous media with rarefaction effects

The internal heat transfer of different gases in microporous media was investigated experimentally and numerically.The experimental test section had a sintered bronze porous media with average particle diameters from 11 μm to 225 μm.The Knudsen numbers at the average inlet and outlet pressures of each test section varied from 0.0006 to 0.13 with porosities from 0.16 to 0.38.The particle-to-fluid heat transfer coefficients of air,CO 2 and helium in the microporous media were determined experimentally.The results show that the Nusselt numbers for the internal heat transfer in the microporous media decrease with decreasing the particle diameter,d p,and increasing Knudsen number for the same Reynolds number.For Kn>0.01,the rarefaction affects the internal heat transfer in the microporous media.A Nusselt number correlation was developed that includes the influence of rarefaction.The computational fluid dynamics(CFD) numerical simulation was carried out to do the pore scale simulation of internal heat transfer in the microporous media considering the rarefaction effect.Pore scale three-dimensional numerical simulations were also used to predict the particle-to-fluid heat transfer coefficients.The numerical results without slip-flow and temperature jump effects for Kn<0.01 corresponded well with the experimental data.The numerical results with slip-flow and temperature jump effects for 0.01<Kn<0.13 are lower than the numerical results without rarefaction effects,but closer to the experimental data.The numerical results with rarefaction effects can accurately simulate the unsteady heat transfer in the microporous media.

Experimental and numerical investigations on dynamic and acoustic responses of a thermal post-buckled plate

Experiments were carried out for a clamped rectangular aluminum plate to study the dynamic and acoustic behaviors in both pre-and post-buckling ranges under thermal loads.Plate temperature was elevated from ambient value to the level above the theoretical critical buckling temperature of the plate.In the whole test temperature range,the measured frequencies decreased to the minimum values in sequence,and then turned to increase as temperature rose.The softening effect of thermal stresses played the leading role in the decreasing stage and the stiffening effect of thermal buckling deflection became the major influence factor in the increasing stage.The later one could drive the temperature equilibrium point of the heated plate to move towards lower temperature range.All the frequencies would not drop to zero due to the inherent initial deflection which provides additional stiffness to the plate.Dynamic responses state two variation trends in different temperature ranges,shifting toward the lower frequency range and closing up in the mid-frequency range.The characters of spectrum responses changed gradually as the temperature was elevated.Numerical simulations gave predictions with same variation trend as the test results.

Helium-3 global optical model potential with energies below 250 MeV

A new set of global phenomenological optical model potential parameters has been obtained for helium-3 projectile, by simultaneously fitting the experimental data of helium-3 total reaction cross sections and elastic scattering angular distributions in the mass range of target nuclei 20〈〈A〈209 at incident energies below 250 MeV. A comparison has been made between the extracted helium-3 global optical model potential parameters and the existing ones. The calculated results of total reaction cross sections and elastic scattering angular distributions are also agreement. compared with experimental data with their satisfactory

Reacting Flow of Hydrogen Chloride and Ammonia in Experimental and Numerical Modelling

The experimental and numerical investigations of the flow with reaction of two gases: hydrogen chloride HC1 and ammonia NH3 were performed. The article contains description of the visualisation method of the formation and flow of particles of ammonia chloride NH4Cl. Analyses of mean concentration and variance of concentration fluctuations of dispersed phase were performed for different outputs of gases. Numerical calculations were performed for analysed phenomenon. Both numerical and visualisation results were matched and compared.