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11.
Li Hong-bo Wu Chao Zheng Yong-gang 《Journal of Petroleum Science and Engineering》2004,44(3-4):223-229
Economical and efficient long-distance oil and natural gas pipe transportation technologies are greatly demanded. Nowadays, oil and gas mixed transportation is gradually put into practice and researchers pay much attention on the theories of two-phase flow in pipe. Methods that can efficiently solve problems of this field are being put forward including hydraulic approach. A new approach, the Rotatable Coordinate Axis, is proposed in this paper. It is used to study the hydraulic characters of two-phase stratified flow in pipe. Based on the new method, the plane flow model for stratified turbulent flow in pipe is built. Then, we can obtain the analytic formulas of velocity, discharge etc. in wells and pipes by this model. To prove the theory of the plane flow model, experiments of aeration in stratified pipe is conducted with the aeration experiment device. The experiment data showed that aeration could effectively achieve the resistance reduction in pipeline, which can offer great theory support to the development of oil and natural gas mixed transportation technology. 相似文献
12.
Hui Gao 《International Journal of Heat and Mass Transfer》2003,46(4):749-754
Stratified oil-water two-phase turbulent flow in a horizontal tube is numerically simulated using a volume of fluid model. A single momentum equation is solved throughout the domain. The RNG k-ε model combined with a near-wall low-Re turbulence model is applied to each phase, and a continuum surface force approximation is adopted for the calculation of surface tension. The simulation is performed in a time-dependent way and the final solution which corresponds to steady-state flow is analyzed. Results of pressure loss, slip ratio, local phase fraction profile and the axial velocity profile are verified by experimental data in literature. Based on the numerical results of extensive calculations, the flow field characteristics are explored and correlations for pressure loss and hold-up are presented. 相似文献
13.
对高校信息技术基础课程的特点和实施分层教学的必要性进行了分析,提出基于网络平台的开放式分层教学模式的构建流程,并概述了此模式的优点。 相似文献
14.
Reduction in cooling loss due to the heat transfer from burning gas to the combustion chamber wall is very important for improving the thermal efficiency in hydrogen engines. The previous research has shown that the direct injection stratified charge can be a technique to reduce the cooling loss and improve thermal efficiency in hydrogen combustion. For effective reductions in cooling loss by the stratified charge, it is very important to know the relation between the fuel injection conditions and mixture distribution. The current research employs the laser induced breakdown spectroscopy as a method to measure the hydrogen concentration distribution in the direct injection stratified charge. Measurement of instantaneous local equivalence ratio by the method clears the characteristics of mixture formation in hydrogen direct injection stratified charge. This research also tries to actively control the mixture distribution using a split fuel injection. 相似文献
15.
考虑到中国证券交易的限制规定及现实投资者并非完全理性的决策行为,给出了组合投资收益-损失风险双目标概率准则的整数规划模型。通过证券收益经验分布,应用分层抽样的随机模拟,并结合动态变化算子的遗传算法,构造GASS II遗传模拟混合算法,进行概率准则模型的优化求解。股票相关性由其秩相关系数给出,算法将秩和区间划分相联系,指导分层抽样。GASS II算法能有效刻画收益分布的“高峰厚尾”,激发遗传算法的隐含并行搜索特性,避免早熟现象,提高寻优效率与精度。最后给出了一个投资组合实证分析算例的收益-损失风险有效前沿。 相似文献
16.
The stability of stratified three phase flow (water-oil-gas) was analyzed using two approaches: A straight forward Kelvin-Helmholtz stability analysis on the two interfaces termed here the “exact” approach and a simplified approach. 1 n the “exact” approach the two interfaces (water-oil and oil-gas) are perturbed, while in the simplified approach the perturbed interface is only the upper oil-gas interface. Both approaches include the viscous Kelvin-Helmholtz analysis in which the shear stresses are laken into account and the inviscid K H analysis where the shear stresses are neglected. Comparison with some experimental results suggests that the simplified method is a better predictor of the transition from stratified flow than the “exact” approach, suggesting, perhaps, that the stability analysis on the upper interface alone is preferred. 相似文献
17.
18.
M.C.L. Papple M. Shoukri B. Latto M.H.I. Baird 《Chemical Engineering Communications》1991,103(1):167-179
A numerical study of the formation and transport of vortex rings in a cylindrical tank initially occupied by a thermally stratified fluid is presented. A control-volume based finite-difference technique (Patankar's SIMPLER method) is used. The formation of a vortex ring was simulated by injecting a quantity of a fluid through a tube centrally located near the free surface. Initially, the fluid in the tank was stably thermally stratified, with a low density in the upper half and higher density in the lower half. Buoyancy effects were considered. Modelling aspects are discussed and the formation and transport of a vortex ring in the stratified fluid as well as the resulting mixing characteristics are presented. 相似文献
19.
Multi-approach back-analysis of a roof bed collapse in a mining room excavated in stratified rock 总被引:1,自引:0,他引:1
Leandro R. Alejano Javier Taboada Fernando García-Bastante Pedro Rodriguez 《International Journal of Rock Mechanics and Mining Sciences》2008,45(6):899-913
Roof bed deformation mechanics is a complex topic in mining practice. There are a number of empirical, analytical and numerical techniques that can be used to analyze and design underground excavations in stratified rock masses. Each has particular drawbacks, however, so the use of just one approach in order to obtain consistent and economic designs is not practical. To deepen understanding of this topic, it is useful to study real failure in mines. In this paper we describe how a roof bed failure in an underground mine, excavated in a stratified rock mass, was back-analyzed using different approaches, namely, the empirical stability graph method, the analytical voussoir techniques, and the numerical discrete element method. The study enabled us to better understand the conditions of failure and to define the most significant parameters affecting the failure. It has also been shown how relaxation or loss of confinement stress can play an important role in roof bed deformation. 相似文献
20.