深井旋转轴套流场的CFD模拟

旋转轴套在超深井工作时,其井下流动是三维湍流流动,旋转轴套的旋转和表面曲率效应以及随之而来的哥氏力和离心力,使流场在超深井的流动中极其复杂,同时,由于流体介质泥浆属于液固两相流,更致使内部流场测试困难,而且超深井中的工况在使用常规方法已很难得到较准确的数据。为此,将计算流体力学软件Fluent应用于超深井下流场的模拟,基于Navier-Stokes方程和Reynolds应力方程模型,建立多种仿真模型,在相同条件下,使用CFD仿真软件Fluent模拟仿真的不同结果,优化与旋转轴套叶片设计相关的几何参数,提高     

Some breakage characteristics of ultra-fine wet grinding with a centrifugal mill

A centrifugal mill is a high-power intensity media mill that can be used for ultra-fine grinding, employing centrifugal forces generated by gyration of the axis of the mill tube in a circle. The mill charge motion is quite different depending on the ratio of the gyration diameter to the mill diameter (G / D ratio), varying from a motion similar to that of a conventional tumbling media mill to that of a vibration mill. In this study, a centrifugal mill was constructed with an arrangement where the gyration diameter could be readily adjusted. The batch grinding characteristics of three different minerals (limestone, talc and illite) in water with dispersing agent were investigated at various G / D ratios. It was found that the optimum G / D ratio in terms of the specific energy consumption to give a desired fineness of product was different for the three minerals. This was due to their different reactions to the breakage mechanisms provided by the mill charge motion at varying G / D ratios. The size distributions became progressively narrower at increased grinding times, and particles finer than about 0.1 μm were not detected even for prolonged grinding times. Measurement of specific surface areas indicated that this was not due to an artifact of the size measurements by laser diffractometry. This implies that there is a limitation in which particles finer than 0.1 μm are not produced under the conditions tested in this type of mill, but further investigation is needed for experimental verification of this limit of comminution.     

Numerical Investigation of Submarine Hydrodynamics and Flow Field in Steady Turn

This paper presents numerical simulations of viscous flow past a submarine model in steady turn by solving the Reynolds-Averaged Navier?Stokes Equations (RANSE) for incompressible, steady flows. The rotating coordinate system was adopted to deal with the rotation problem. The Coriolis force and centrifugal force due to the computation in a body-fixed rotating frame of reference were treated explicitly and added to momentum equations as source terms. Furthermore, velocities of entrances were coded to give the correct magnitude and direction needed. Two turbulence closure models (TCMs), the RNG model with wall functions and curvature correction and the Shear Stress Transport (SST) model without the use of wall functions, but with curvature correction and low-Re correction were introduced, respectively. Take DARPA SUBOFF model as the test case, a series of drift angle varying between 0° and 16° at a Reynolds number of 6.53×106 undergoing rotating arm test simulations were conducted. The computed forces and moment as a function of drift angle during the steady turn are mostly in close agreement with available experimental data. Though the difference between the pressure coefficients around the hull form was observed, they always show the same trend. It was demonstrated that using sufficiently fine grids and advanced turbulence models will lead to accurate prediction of the flow field as well as the forces and moments on the hull.     

浅基础地基荷载-变形特性的分析研究

在土体主应力方向的旋转过程中,主应力方向与塑性主应变增量方向之间存在着非共轴现象,非共轴现象对应力-应变关系具有显著的影响。通过有限元二次开发,将角点结构非共轴理论应用到有限元程序ABAQUS中;对密砂单剪试验进行数值模拟,研究了非共轴现象及其对应力-应变关系的影响;采用离心模型试验方法,对圆形浅基础作用下饱和密砂地基荷载-变形特性进行试验研究;对离心模型试验进行数值模拟,将试验结果与数值计算结果进行对比,对非共轴模型的计算结果的合理性进行验证。研究结果表明:非共轴现象对浅基础地基荷载-变形特性具有显著的影响;当选取合理的非共轴塑性模量时,非共轴模型的计算结果与离心模型试验结果比较接近。     

层状边坡倾倒变形多级折断面分布深度计算模型

针对反倾层状岩质斜坡倾倒变形折断面空间展布缺乏定量判断的问题,以地质原型和变形机制分析为基础,考虑岩层自重、上覆岩层盖重、侧向压力、岩层间的摩擦力等作用,提出了岩板倾倒折断的独立悬臂梁模型和独立简支梁模型。采用板梁的最大拉应力破坏准则,推导出了倾倒变形各阶段岩层的临界折断深度公式。利用地质原型对推导的公式进行了验证,并通过离心试验获取了倾倒变形各阶段的坡形参数,对边坡各阶段折断深度进行了定量评价。研究表明：理论模型可计算倾倒变形层间剪切错动、弱倾倒破坏、强倾倒破坏等各阶段岩层的折断长度;岩层折断长度与岩层分布高程、拉应力、岩梁自身重度呈负相关,与岩层内摩擦角、岩层厚度、抗拉强度呈正相关;根据倾倒变形各阶段力学参数,计算倾倒体各级折断面分布位置,结果与地质原型和离心试验结果吻合。该研究成果对倾倒变形边坡稳定性评价具有一定的理论和实际意义。     

天津市人口郊区化特征及其动力因素

基于"五普""六普"街道、乡镇数据,运用GIS及人口密度模型分析天津市人口郊区化的时空演变特征,并根据2005—2015年各区县数据,剖析其动力因素。结果表明:天津市中心区繁荣与郊区化并存,属于市中心发展型郊区化;天津已形成多中心格局,副中心人口聚集效应日益显著;人口郊区化伴随就业岗位的郊区化,但人口和产业存在空间分异现象;土地、住房制度改革及郊区经济发展加快了人口郊区化进程,公共服务的集中延缓了人口向郊区迁移,滨海新区发展、交通与通信网络的现代化为人口向郊区的迁移创造了条件。提出进一步推进城市组团式发展、推动产业结构与布局调整及以公共服务引导人口流动等措施实现中心城区人口向郊区有序分流。     

Current Nature of the Kuroshio in the Vicinity of the Kii Peninsula

The Kuroshio flows very close to Cape Shionomisaki when it takes a straight path. The detailed observations of the Kuroshio were made both on board the R/V Seisui-maru of Mie University and on board the R/V Wakayama of the Wakayama Prefectural Fisheries Experimental Station on June 11–14, 1996. It was confirmed that the current zone of the Kuroshio touches the coast and bottom slope just off Cape Shionomiaki, and that the coastal water to the east of the cape was completely separated from that to the west. The relatively high sea level difference between Kushimoto and Uragami could be caused by this separation of the coastal waters when the Kuroshio takes a straight path. This flow is rather curious, as the geostrophic flow, which has a barotropic nature and touches the bottom, would be constrained to follow bottom contours due to the vorticity conservation law. The reason why the Kuroshio leaves the bottom slope to the east of Cape Shionomisaki is attributed to the high curvature of the bottom contours there: if the current were to follow the contours, the centrifugal term in the equation of motion would become large and comparablee to the Coriolis (or pressure gradient) term, and the geostrophic balance would be destroyed. This creates a current-shadow zone just to the east of the cape. As the reason why the current zone of the Kuroshio intrudes into the coastal region to the west of the cape, it is suggested that the Kii Bifurcation Current off the southwest coast of the Kii Peninsula, which is usually found when the Kuroshio takes the straight path, has the effect of drawing the Kuroshio water into the coastal region. The sea level difference between Kushimoto and Uragami is often used to monitor the flow pattern of the Kuroshio near the Kii Peninsula. It should be noted that Uragami is located in the current shadow zone, while Kushimoto lies in the region where the offshore Kuroshio water intrudes into the coastal region. The resulting large sea level difference indicates that the Kuroshio is flowing along the straight path.     

非连续变形分析中块体大转动问题研究

原有非连续变形分析（DDA）采用一阶近似后的位移增量表达式更新块体构形,推导相关子矩阵,且对不同时步计算出的应变增量直接叠加,当模拟的块体发生大转动时往往会产生较大误差。为考虑块体转动与变形的耦合作用,引入先变形、后转动的块体位移增量表达式。重新推导了惯性力子矩阵,将块体转动时的离心力与科氏力加到荷载矩阵中。计算时对应变分量及其相关变量进行坐标变换与修正,并采用新引入的位移增量表达式计算块体顶点位移,进行后接触修正与更新块体构形。数值算例表明,改进后的程序能够消除转动带来的误差,自动考虑了块体转动时离心力和科氏力引起的变形,应变计算精度更高。改进方法克服了块体体积自由膨胀、应变场畸变等问题,给出了合理的块体应变。     

固体颗粒表面吸附水层厚度实验研究

以玻璃微珠为对象,探索堆积固体颗粒表面吸附水层厚度随驱动压力梯度的变化规律。结果表明：完全浸润的堆积固体颗粒之间存在3种不同性质的水,因其受表面作用力的大小不同,可用离心法加以区分。随着离心力的增加,依次驱替出自由水、毛管水和吸附水层水。结合重量分析,用离心法可得到不同驱动压力梯度下的吸附水量及吸附水层厚度。吸附水层厚度是水动力学条件的函数,其随驱动压力梯度的变化规律为解释多孔介质中水相的渗流特性提供依据。     

Stability Study of a Tide Embankment Subjected to Sea Level Variations Using Centrifugal Model Tests

To investigate the behavior of dredged-sea-sand fill compacted inside tide embankments with a damaged geosynthetic mat, centrifugal model tests and numerical simulation were conducted, both considering variations in sea level. The results from the three centrifugal model tests demonstrate that the subsidence of the dredged-sea-sand fill inside tide embankments with a damaged geosynthetic mat was strongly affected by the loss of dredged-sea-sand into the filter layers with large particles and a decrease in the bearing capacity of the filter layers with small particles. In addition, a comparison of the test and simulation results confirms that the loss of sand into the filter layer and the subsidence of the dredged-sea-sand fill were well reproduced by the numerical simulation.