摘要：
A local thermal non-equilibrium model has been considered for the case of thermally fully developed flow within a constant heat flux tube filled with a porous medium. Exact temperature profiles for the fluid and solid phases are found after combining the two individual energy equations and then transforming them into a single ordinary differential equation with respect to the temperature difference between the solid phase and the wall subject to constant heat flux. The exact solutions for the case of metal-foam and air combination reveal that the local thermal equilibrium assumption may fail for the case of constant heat flux wall. The Nusselt number is presented as a function of the Peclet number, which shows a significant increase due to both high stagnant thermal conductivity and thermal dispersion resulting from the presence of the metal-foam.
摘要：
Avinyl functional microemulsion was successfully prepared via polycondensation between polysiloxane prepolymer and a modifier (vinyl silane coupling agent with alkoxy groups). The polysiloxane prepolymer was prepared by ring-opening of D<inf>4</inf> (octamethylcyclotetrasiloxane). The structure and properties of vinyl functional microemulsion were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR), photon correlation spectroscopy (PCS). FTIR Spectroscopy result showed that vinyl groups were successfully introduced into the polysiloxane molecules. The variation in pH, amount of vinyl coupling agent and catalyst were studied in relation to the properties of the final microemulsion. The results indicated that under strong acidic more coagulum and higher percentage of conversion occurred in the microemulsion. TEM results also revealed that particles are densely packed in strong acidic condition but become sparsely distributed in weak acidic condition. An increase in the vinyl coupling agent content leads to an increase in formation of coagulum and in particle size, but it lowers the particle size distribution. The smaller ratio of the average surface coverage of surfactant leads to higher amount of coagulation which is in linear dependence to the increased amount of vinyl coupling agent modifier. Photon correlation spectroscopy results show that increasing the amount of vinyl coupling agent modifier increases the particles size, while reduces the particles size distribution. It can be concluded that the coagulum weight fraction increases linearly with higher amount of catalyst. An increase in the vinyl coupling agent modifier leads to an increase in the coagulum. The microemulsion shows stability when the amount of catalyst is about 3.0-4.0 wt%.
摘要：
Effects of tortuosity and dispersion on the effective thermal conductivity of fluid-saturated porous media are investigated analytically with help of a volume averaging theory. Firstly, a general expression for the effective stagnant thermal conductivity has been derived using a unit cell model, which consists of rectangular solids with connecting arms in an in-line arrangement. The validity of the expression for the stagnant thermal conductivity has been confirmed comparing the present results with available experimental and theoretical data for packed beds, porous foams and wire screens. Secondly, an general expression for the thermal dispersion conductivity has been sought with help of the two energy equations for solid and fluid phases, derived on the basis of a volume averaging theory. It has been shown that the interstitial heat transfer between the solid and fluid phases is closely associated with the thermal dispersion. The resulting expressions for the longitudinal and transverse thermal dispersion conductivities agree well with available experimental data and empirical correlations.
关键词：
aerodynamics;bifurcation;flow through porous media;haemodynamics;lung;mass transfer;pneumodynamics;lung;porous media;bifurcation;mass transfer;gas exchange
摘要：
A porous media approach was proposed to investigate the characteristics of the bifurcating airflow and mass transfer within a lung. The theory of porous media was introduced in order to deal with a large number of bifurcations and a vast scale difference resulting from bifurcations. Upon introducing a two-medium treatment for the air convection and the diffusion in its surrounding wall tissue, the oxygen mass transfer between the inhaling air and the tissue was considered along with the effects of the blood perfusion on the mass transfer within the tissue. The overall mass transfer resistance between the inlet of the trachea and the blood in the capillaries was obtained on the basis of the porous media approach. The analysis reveals that there exists the optimal number of the bifurcation levels, namely, 23, that yields the minimum overall mass transfer resistance for the mass transport from the external air to the red blood cells. The finding is consistent with Bejan's constructal law, namely, that for a flow system to persist in time, it must evolve in such a way that it provides easier access to its currents.
摘要：
In order to analyze mechanism of casing damage, the uniaxial compression experiment and creep experiment of interbedded mudstone samples from Sanan development area of Daqing Oilfield under different water contents were carried out. The changes of the mudstone’s mechanical parameters and creep characteristics with the increment of water saturation were studied. The results indicate that the rock strength and elastic modulus decrease rapidly with the increment of water content, at the same time, the creep strain and creep strain rate of steady state increase with the increment of water content, and also the steady state creep strain rate is enhanced with the increment of deviatoric stress. Through the creep characteristic curves, a non-linear creep constitutive equation of mudstone considering the change of water contents is established, which will be used in future numerical analysis.
摘要：
At the present time, the mechanics of seepage in fracture-cavity carbonate reservoir is not very clear. Fracture-cavity carbonate reservoir was simplified as regular fracture-cavity net model and rules of seepage in it were studied by numerical simulation based on Navier-Stokes equation (N-S equation). Results showed that flux exponentially Increased along with the Increase of fracture width but flux and diameter of cavity had linear relationship; the seepage in fracture-cavity also obeyed the Dairy's law, bnt the permeability was bigger than the fracture model's, which represented different performance of flow; fracture width had more impact to seepage than diameter of cavity.
摘要：
An understanding of the dynamic behavior of trace elements leaching from coal mine spoil is important in predicting the groundwater quality. The relationship between trace element concentrations and leaching times, pH values of the media is studied. Column leaching tests conducted in the laboratory showed that there was a close correlation between pH value and trace element concentrations. The longer the leaching time, the higher the trace element concentrations. Different trace elements are differently affected by pH values of leaching media. A numerical model for water flow and trace element transport has been developed based on analyzing the characteristics of migration and transformation of trace elements leached from coal mine spoil. Solutions to the coupled model are accomplished by Eulerian-Lagrangian localized adjoint method. Numerical simulation shows that rainfall intensity determined maximum leaching depth. As rainfall intensity is 3.6ml/s, the outflow concentrations indicate a breakthrough of trace elements beyond the column base, with peak concentration at 90cm depth. And the subsurface pollution range has a trend of increase with time. The model simulations are compared to experimental results of trace element concentrations, with reasonable agreement between them. The analysis and modeling of trace elements suggested that the infiltration of rainwater through the mine spoil might lead to potential groundwater pollution. It provides theoretical evidence for quantitative assessment soil-water quality of trace element transport on environment pollution.
摘要：
Geodetic deformation severely affects the development of the oilfield and probably causes casing damage or abandonment of injection wells and producers. Therefore, it is meaningful to survey and study three-dimensional geodetic deformation in the process of the oilfield development. In order to study this issue, 11-year long term surveying of three-dimensional geodetic deformation has been carried out while developing Naner area in Daqing oilfield. Basic rules of 3-D geodetic deformation have been obtained through surveying. Results show that production and injection under high pressure may cause the changes of surface elevation, and geodetic deformation correlates with simultaneous formation pressure. Precautions and relative technological measurements have been put forward in the waterflood development in Naner region and provide theoretical guidelines for the production and casing preservation of the oilfield. Finally, surveying results are interpreted by porous elastic theory. Mathematical model to calculate 3-D geodetic deformation is put forward in the course of the oilfield development.
摘要：
From the generalized constitutive law of geo-material elastic-plastic model, the problem of model identification among one model type is transformed to a problem of parameter identification. So, using the new bionics algoritlun-Immune Evolutionary Programming (IEP) proposed by author recently, the elastic-plastic model identification among one model type is studied, and a new model identification method is proposed. At last, this method is verified by a numerical example. The results show that, this method can get the suitable geo-material model when only displacements are known.
