A direct numerical simulation of transition phenomena in a mixed convection channel flow

This study intends to provide an increased understanding of the laminar-turbulent transition phenomena for the buoyancy-assisted heated vertical channel flow during the early transient stage. The spectral method with weak formulation is applied in the direct numerical simulation. Initial disturbances consist of the finite-amplitude two-dimensional TS wave and a pair of three-dimensional oblique waves for the K-type disturbances. The results from the harmonic energy competitions of different wave modes show that for the buoyancy-assisted heated flow, the (k_x=1, k_z=1) or (1,1) and (1,0) modes would gain energy immediately and start to rise at almost the same rate. This phenomenon is different from that of the buoyancy-opposed flow, where the (1,1) mode decays slowly in the beginning until other modes gain enough energy and then it begins to grow quickly and overtakes the (1,0) mode after a short time period. These different transition patterns match with the experimental results that the flow transition is supercritical and subcritical for the buoyancy-assisted and -opposed flows, respectively. Buoyancy-assisted heated flow transition follows the general trend of an isothermal flow in the beginning, but the thermal-buoyant force is crucial in accelerating the instability and also causing notable differences during the subsequent transition process. All of the results for the vortex structures development, kinetic energy budget of the disturbances, flow visualization by tagged fluid particles, and the local temperature fluctuations are consistent in pointing to a clear pattern for the buoyancy-assisted heated flow transition.     

Characterization of dynamic behavior of a spout-fluid bed with Shannon entropy analysis

Differential pressure fluctuation time series were obtained at different locations in a two-dimensional spout-fluid bed with a cross section of 300 × 30 mm and height 2000 mm. Shannon entropy analysis of differential pressure fluctuations was developed to characterize the dynamic behavior. Effects of two important operating parameters (spouting gas velocity and fluidizing gas flow rate) on the Shannon entropy were examined. It was demonstrated that a spout-fluid bed at a high spouting gas velocity or fluidizing gas flow rate was a deterministic chaos system since the Shannon entropies at all bed locations increased sharply and asymmetric unstable flows occurred. Shannon entropies were found to be significantly different at various bed locations. Shannon entropies of different flow regimes were distinct, so they were used to identify the flow regimes. The results show that the Shannon entropy helps to grasp the complex characteristics of dynamic behavior in spout-fluid beds.     

天铁炼钢厂四流中间包流场的水模实验及优化

介绍了天铁炼钢厂中间包水模实验原理和过程，分析了斜、直、圆三种型式挡渣墙模拟结果，提出了合理的挡渣控流方案，在生产实践中使用效果良好。     

德国联邦物理技术研究院(PTB)气体微流量计量评介

在真空技术应用中 ,高精度气体微流量计用于连续膨胀法校准系统压力的产生、漏孔漏率的测量以及真空泵抽速的测定。PTB先后研制了三代气体微流量计 ,第一代为手动型 ,第二代为半自动型 ,第三代为全自动型。本文详细介绍了PTB研制的气体微流量计的性能和特点 ,并介绍了气体微流量计在真空漏孔的漏率测量方面的应用。另外 ,还介绍了PTB最近研制的大气压力下漏孔漏率测量系统的性能和特点     

开流形的曲率与拓扑

应用比较几何的方法研究了完备非紧且具有特定曲率条件的黎曼流形，证明了在一定Pinching条件限制下，流形具有有限拓扑型或者微分同胚于R^n。     

Semianalytical Model for Drawdown due to Pumping a Partially Penetrating Large Diameter Well

A semianalytical model is developed for computing drawdowns in and around a partially penetrating large diameter well. The new model can take into account an unsteady pumping discharge and thus drawdowns during recovery can be computed. This model can also yield the unsteady contributions from well and aquifer storages to the pumped discharge. While developing the model, the flow from the bottom of the well is also accounted.     

Experimental Study of Ice Jam Thickening under Dynamic Flow Conditions

River ice jams are a common occurrence on northern rivers, and their formation can present a severe flood risk to nearby communities. As more and more river regulation projects are developed to provide an alternative to fossil fuels for electrical power-generating capacity, our need to understand the mechanisms associated with ice jam formation under variable flow conditions becomes more vital. This is because, at present, hydropeaking operations are often severely curtailed during the ice-affected seasons due to concerns that sudden flow fluctuations might instigate ice jams and associated flooding. Here, an experimental investigation explores the effects of rapid increases in discharge on ice jam formation and evolution. It is found that the thickness of ice jams formed under highly dynamic flow conditions tend to be slightly thinner than those formed during steady carrier flows for comparable discharges. Also, despite the highly dynamic nature of these consolidation events, the resulting ice thicknesses appear reasonably well approximated by steady flow theory.     

特低渗油藏渗流特征及增产技术研究

从特低渗储层渗流机理研究出发，分析了其渗流规律——非达西渗流特征；根据储层中上覆岩石围压变化，通过室内试验表述了其对渗透率伤害。研究提出了改善渗流特征的注水条件、井网优化和压裂对策，可以有效提高这类油藏的开发效果。     

大型储罐基础非平面倾斜问题的探讨

大型储罐因基础产生非平面倾斜而影响其正常使用的情况在工程中时有发生,文章通过对某油罐工程中基础沉降观测结果的分析,探讨了储罐基础产生非平面倾斜的原因。相邻储罐之间的相互影响、充水预压未达到规范要求以及地基处理措施不当是引起储罐基础非平面倾斜的主要因素。针对相邻储罐间的相互影响,根据现行《石油化工企业设计防火规范》和《石油化工企业钢储罐地基与基础设计规范》的规定,提出以下建议:储罐布置的净距除应满足防火规范规定外,有条件时也应适当考虑对基础沉降的影响,当采用复合地基时,相邻储罐间的净距不宜小于0.6 D;当占地面积成为主要矛盾,储罐间的净距只能限制在防火规范规定的最小范围时,在地基处理时就应采取有效措施,以尽可能减少相邻储罐的相互影响。