Instability due to Viscosity Stratification Downstream of a Centerline Injector

A common injector geometry upstream of a static mixer is the centerline injector. A flow instability can arise due to viscosity differences between the injected core‐flow and the outer co‐flow. This instability can adversely affect the effectiveness of the mixing operation. An experimental investigation of miscible viscosity‐stratified flow in a circular geometry was performed using Laser Induced Fluorescence (LIF) and Particle Image Velocimetry (PIV). The experimental results for the stable region agree with the analytical results. The unstable region exhibits different modes depending on the viscosity ratio, volume flux ratio, and Reynolds number. The modes include wavy core‐flow with fissures and wavy core‐flow with core breakup. The time‐averaged experiment velocity profiles for the unstable core indicate a broadening of the jet at the centerline, which is consistent with the LIF visualization.     

Mathematical analysis of viscometric (polymer) flow fields in capillaries: Taylor dispersion revisited

A general formulation for capillary flow of two miscible fluids – one a dilute plug of polymer fluid inserted into a fully developed Poiseuille flow of the other, a Newtonian stream – is examined for its long time behavior. Phenomenologically, the system evolves from an initial state, that of a plug within the boundaries of sharp, well defined fronts inside a Newtonian stream, to a more homogenized state in the very long time scale. This problem was addressed by G.I. Taylor but with regard to a system of two Newtonian fluids, leading to the well-known results commonly described as `Taylor axial dispersion'. In this paper, a general and systematic perturbation analysis is presented from which Taylor's result is recovered as a special case of a more general solution which applies to fluids incorporating elastic properties. In particular, the influence of viscoelasticity and (polymer) diffusivity on the observed pressure profile in the capillary conduit is examined. This effect is clearly separated out for small Peclet number flows using asymptotic and numerical analysis. The results identify the influence of fluid viscosity, elasticity, and diffusivity on the observed pressure profile and form the basis for the improved characterization of polymeric elasticity using capillaries – a finding that is of significant scientific and commercial interest. These results were obtained by the authors as a class of observations resulting from the perturbation analysis of forced-flow capillary devices in viscoelastic fluid property investigation.     

中压甲铵冷凝器防结垢方法探讨

分析中压甲铵冷凝器的工艺流程和操作条件，指出设计中的不足，找出其结垢的非药剂因素——温度和流速，对一些相关改造的成败提出观点，并提出增设加压泵回流控温和增大上、回水压差的新思路。     

Energy Dissipation at the Slug Nose and the Modeling of Solids Transport in Intermittent Flow

It is shown, by means of Lagrangian momentum and power balances across the slug nose in slug flow, that the power dissipated due to sudden expansion of the fluid in the film immediately downstream of the slug nose is greater than the power lost due to viscous action at the pipe wall but that it may not be large enough to materially aid particle transport. This has the implication that sand transport in intermittent flow may be considered as transport in a hybrid flow of hydraulic conveying and stratified flow when the length of the mixing section at the slug nose is short compared to the length of the slug body.     

Piston-driven laminar flow and heat transfer in a plane channel with a sudden expansion

 This paper presents a numerical study of piston-driven heat transfer and fluid flow in a plane channel containing a sudden expansion. The numerical method employed is based on a control-volume-based finite element method for incompressible flow with a staggered and moving grid and SIMPLER algorithm for pressure-velocity coupling. The numerical results show a good agreement with the experimental data reported in the literature. Results concerning time and space evolution of the thermal and flow fields are presented for different values of the expansion ratio, the initial clearance volume, and the piston velocity. Received: 20 April 2002 / Accepted: 23 January 2003     

导流能力测试系统的研制

压裂后裂缝的导流能力直接关系着压裂缝的渗流能力，是客观评价压裂效果的重要指标之一。文章介绍了基于AT89C52单片机的导流能力测试系统的系统要求、测试原理以及其设计方案，阐述了各个测控通道，给出了测控系统电路方框图。     

Homogeneous Plastic Flow of Fully Amorphous and Partially Crystallized Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) Bulk Metallic Glass

The homogeneous plastic flow of fully amorphous and partially crystallized Zr(41.2)Ti(13.8)Cu(12.5)Ni(10)Be(22.5) bulk metallic glass (Vitl) has been investigated by compression tests at high temperatures in supercooled liquid region. Experimental results show that at sufficiently low strain rates, the supercooled liquid of the fully amorphous alloy reveals Newtonian flow with a linear relationship between the flow stress and strain rate. As the strain rate is increased, a transition from linear Newtonian to nonlinear flow is detected, which can be explained by the transition state theory. Over the entire strain rate interval investigated, however, only nonlinear flow is present in the partially crystallized alloy, and the flow stress for each strain rate is much higher. It is found that the strain rate-stress relationship for the partially crystaltized alloy at the given temperature of 646 K also obeys the sinh law derived from the transition state theory, similar to that of the initial homogeneous amo     

Synthesis of diamond crystals and films using an oxygen-acetylene flame under atmosheric pressure

Diamond growth with rates up to 100 to 140 μm/hr was achieved using an oxygen-acetylene combustion spraying technique in an atmospheric environment. Investigations on the processing indicated that the gas flow ratio, substrate position, substrate temperature, temperature distribution, and substrate pretreatment were the most important factors affecting the growth of diamond crystals. Evaluation by means of X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and electron probe microanalysis showed that the synthesized diamond was nearly perfect in morphology, structure, and purity.     

水平管气力输送数值模拟

本文采用粒子追踪理论对水平管中粒子流动状态进行了数值模拟.文中提出了一种新的粒子碰撞模型,并忽略粒子的旋转和扬力,仅考虑气流阻力和重力对粒子的影响,在输送量为9.13×10~3kg/s,混合比约0.3的条件下,通过数值计算得知:由于粒子间的碰撞,使得异径粒子的速度趋向平均化;粒子间的碰撞是粒子悬浮的原因之一;粒子的浓度沿管轴向是随时间而发生变化的.     

调整我国产业结构的若干思考

在国有企业产权制度改革中，改革不合理的产业结构是主要内容之一。不合理的产业结构带来了资产流量与存量产出效益的巨大损失，并放大了市场信号的失真度。因此强化产业结构的调整，是深化经济体制改革，使国民经济持续发展的保证。本文在分析产业结构不合理现状的基础上，提出了对调整我国产业结构的见解。