滑移效应下纤维绕流场及过滤阻力的数值计算与分析

考虑实际纳米/微米纤维表面的流体滑移效应,采用数值方法求解滑移流动机理下纳米/微米纤维绕流场及过滤阻力,分析讨论了Knudsen数Knf和填充率C对纤维近壁面速度分布及纤维过滤阻力的影响规律.结果表明,对纳米/亚微米纤维过滤情形,纤维表面流体的滑移效应导致纤维绕流场与非滑移条件下情形有显著差异,尤其在高填充率下,纤维表...     

水燥浆的滑移速度修正模型

在煤水混合物的流动过程中存在着滑移效应,但是在用传统的Mooney方法和Jastzebski方法对高浓度水煤浆的滑移特性进行分析时,没能得出一致的结果.笔者基于前人对滑移的假设,通过多管径管流试验,研究了高浓度水煤浆管内流动的滑移现象,分析了滑移引起的附加流量对总流量的影响,提出了选取最佳滑移指数确定水煤浆真实流变特性的本构模型和方程,指出高浓度浆态非牛顿流体存在屈服应力.     

设备地震载荷的一种新的计算方法

本文从一全新的“以柔克刚”的设计思想出发,提出了一个用于确定设备地震载荷的计算方法。与现有计算方法的最大区别是:该方法在设备底部设置了滑移隔震装置,设备底部不再看作是刚性固定,改以“抗震”为主要目的为以“减震”为主要目的,由此建立了基础滑移隔震设备的计算模型和运动方程,并对求解途径提出了建议。     

UHMWPE薄膜熔体挤出壁面滑移的研究

在壁面滑移条件下建立了超高相对分子质量聚乙烯(UHMWPE)鱼尾形流道挤出过程有限元模型,模拟了不同滑移系数对挤出成型过程的影响.由Navier线性滑移定律建立了挤出模具壁面熔体所受剪切应力与熔体滑移速度之间的关系,基于Polyflow软件,采用不同滑移系数对鱼尾形流道中UHMWPE熔体的三维等温流动开展了有限元模拟,...     

一种求解数据校正问题的基于经验增强的方法

基于机理模型的数据校正问题中,过程系统比较复杂时就要面临求解大规模非线性规划问题.如果直接求解,由于方程维数大且为非线性,问题自由度大,因此求解难度较高,容易导致求解收敛失败.数据校正问题的特点是当测量变量的测量值发生变化时对同一过程对象模型重复地进行求解计算.基于此特点,今提出了一种基于经验增强的求解方法.此方法通过...     

定热通量加热下微三角形槽道中滑移流动的换热特性

微三角形截面通道是现代工程实际应用中常涉及到的流动通道.针对微三角形槽道利用正交函数法求解了滑移流区内带温度跳跃边界条件的能量方程,对不可压缩气体在微三角形槽道内充分发展层流滑移流动的换热特性进行了理论分析,获得了轴向定热通量加热、周向均匀壁面温度条件下微三角形槽道内的温度分布和换热特性的分析解.计算结果表明：正交函数法适用于微三角形槽道内滑移流动换热特性的分析计算;在滑移流区,微三角形槽道内的平均Nusselt数随Knudsen数的增加而减小,其随高宽比变化的分布曲线随Knudsen数的增加而平行下移,Nusselt数比随Knudsen数的变化关系基本不受高宽比的影响.     

挤出过程中NR/CBR胶料壁滑移行为的研究——Ⅰ.压力振荡现象

聚合物流体流动过程中的壁滑移现象是其粘弹性的重要特征之一。应用Monsanto加工性能试验机考察了NR/CBR胶料在毛细管挤出流动中的壁滑移行为及其影响因素。在简化条件下,应用张量分析方法,导出描述产生壁滑移时的压力变化与挤出过程参变量及试样物性之间关系的数学模型,以及临界滑移距离的计算公式。研究结果表明,临界压力降测量数据与理论预测值软为吻合。     

水煤浆的滑移速度修正模型

在煤水混合物的流动过程中存在着滑移效应,但是在用传统的Mooney方法和Jastr- zebski方法对高浓度水煤浆的滑移特性进行分析时,没能得出一致的结果。笔者基于前人对滑移的假设,通过多管径管流试验。研究了高浓度水煤浆管内流动的滑移现象,分析了滑移引起的附加流量对总流量的影响,提出了选取最佳滑移指数确定水煤浆真实流变特性的本构模型和方程。指出高浓度浆态非牛顿流体存在屈服应力。     

基于F-K滑移流模型的柱面微槽气浮密封浮升能力分析

由于气浮密封薄膜引发的滑移流现象频发,本文针对一种新型柱面螺旋槽气浮密封,基于线性化Boltzmann方程（F-K 模型）,引入流量因子,建立稀薄气体润滑的F-K滑移流模型。采用高精度八点差分法和Newton-Raphson迭代法求解气膜压力,解决了表面槽-台阶跃、径向偏心与极薄气膜三者耦合下对求解发散和计算精度的影响。将计算结果与现有研究对比,并考察了气体滑移流效应与运行参数的内在关联,研究结果验证了新型柱面螺旋槽气浮密封在高速、低压、小膜厚和大偏心下具有较为明显的滑移流效应;此外,虽然槽深、槽数和槽长的增加提高了气膜浮力,但是增强了槽内滑移流动的响应。研究结果为拓宽动压密封应用范围提供理论了基础。     

非均匀气固两相系统中多尺度传质模型

建立了适用于气固循环流化床的多尺度传质模型 .从过程与尺度的角度出发 ,将非均匀气固两相流中的传质过程分解为静态与动态的过程 ,并将前者分解为稀相内、密相内以及稀密相间 3个尺度下的传质 ;在用多尺度能量最小 (EMMS)模型求解已知物系性质和操作条件的非均匀气固两相流体动力学参数的基础上 ,借助于前人的研究结果 ,利用相对滑移速度、空隙率等参数求解传质系数 ,求得轴向的浓度场分布 ,并讨论非均匀两相流动结构对传质效率的影响     

硝酸镧对电沉积Ni—P合金镀层性能的影响

Ni-P合金以其优异的耐蚀,耐磨性能,以及对环境的友好性,代替铬广泛应用于机械、汽车、电子、半导体等领域。但是传统的Ni—P合金镀层要么耐蚀性能好、力学性能差,要么力学性好,耐蚀性能差。此课题用在镀液中加入硝酸镧的方法,寻求解决之道。通过做不加硝酸镧和加硝酸镧的对比实验,运用XL300W／TWP扫描电镜对镀层表面形貌进行扫描,结果表明,在镀液中添加硝酸镧可以提高镀层的沉积速率,改善镀层表面形貌和组织结构,提高镀层的耐蚀性能。     

普通水泥与超细水泥注浆性能分析及其黄土注浆效果对比研究

通过析水率、黏度、结石体强度、耐久性等试验,对普通水泥与超细水泥这两种注浆材料进行了材料性能对比研究.结果表明:超细水泥有更好的稳定性,在水灰比大于0.8时,有更低的黏度,其结石体的强度更高,有致密的结构,耐久性好.在黄土的模拟注浆试验中,对注浆的效果进行总结,两种注浆材料劈裂土体形态类似,验证符合力学规律.通过对土体进行土工试验,超细水泥挤密土体的效果更好,其土体抗剪强度提高、压缩性降低比普通水泥注浆土体明显,结果表明超细水泥有着更适合的黄土注浆前景.     

下出料门支撑梁设计方法的比较

分析下出料门支撑梁的变形和强度对设备安全性能影响时,用有限元方法(ANSYS软件)和工程力学(材料力学)的方法分别进行计算、分析、比较。材料力学分析结果相对ANSYS软件分析结果较为保守,也欠精确,偏离实际的程度比较大。因此在分析类似工程问题中运用ANSYS分析更具有现实意义。     

A model for the flow of cement pastes

This paper presents a simple mathematical model of the flow behaviour of fresh cement pastes and mortars based on a soil mechanics approach. A soil mechanics model can mimic many of the features of the pastes rheological behaviour indicating that physical, as well as chemical, factors might control many of these.Specifically, we have developed a simple mathematical model of the evolution of the packing of the clinker or sand grains and its effect on the flow of the paste or mortar. This not only incorporates the role of the pore water but also copes with the large deformations typical of the mixing and placement of mortars. This model is used here to simulate small cyclic deformations with a large drift accumulating in one direction, and is able to capture both the liquefaction and locking phenomena seen in practice when mortars are vibrated.     

压滤机过滤压密过程的解析

本文将压滤机的过滤压密过程按三维数学模型进行解析,所解出之过滤压密理论方程与实验数据吻合较好;所提出之工业过滤压密方程对压滤机的设计、选型或校核计算等都具有一定的指导意义.     

固体断裂过程中裂纹尖端应力场奇异性分析与数值计算

常规的力学分析计算无法正确评价带裂纹和缺陷元件的力学特性,本文结合断裂力学分析手段,通过有限元对裂纹尖端应力场的奇异性进行了分析计算和数值模拟,并指出了该计算方法在实际工程中的应用价值。     

The application of soil mechanics to spouted bed design

The annular material around a spout may be considered to be a loosely packed assembly of particles with its behavior described by effective stresses using the Mohr-Coulomb failure criterion as employed in soil mechanics. The work shows the development of a height-independent stress model together with an interpretation of the mathematical results in physical terms. The form of a simple equation for spout diameter is shown which gives some information about the interactions between the spout and the annular material.     

Predicting the normalized,undrained shear strength of saturated fine-grained soils using plasticity-value correlations

In soil mechanics, the plasticity of fine-grained soils is expressed using the plasticity index. This represents the difference between the water content at the liquid and plastic limits, which are often collectively referred to as the Atterberg (or consistency) limits. They are of key importance in soil mechanics because they determine, in a simple way, the interaction between the solid and liquid phases in soils, and thus provide the possibility to classify soils into groups with similar mechanical properties. As the Atterberg limits are the most distinctive and the easiest property of fine-grained soils to measure, several researchers have tried to use them to predict various mechanical properties, such as the normalized, undrained shear strength of fine-grained soils. The most widely used expression for predicting this value from the plasticity index was suggested by Skempton. Since then, there have been several studies to examine the validity of his relation. A lot of the data agree with this relation; however, there is an equally large volume of data that contradicts it. The present study shows that the correlation between the normalized undrained shear strength of cohesive soils and the plasticity index really exists, but it is not as simple as was suggested by previous studies. By considering the mineralogical properties of clay minerals and their impact on the quantity and state of water in soils, it was found that there is no uniform criterion to determine the normalized undrained shear strength from the plasticity index for all fine-grained soils.     

Multi-dimensional model of a spouted bed

A multi-dimensional model is developed to describe the fluid and particle dynamic behaviour of spouted beds. The position of the spout-annulus interface is determined by a variational analysis. Two-fluid equations are used to represent gas and solids motions in the spout while the vector Ergun equation and soil mechanics equations are employed to describe, respectively, gas and solids behaviour in the annulus. Using numerical finite difference methods, the set of governing equations is solved subject to carefully chosen boundary conditions. The model predictions of key hydrodynamic characteristics are in reasonable agreement with available measured data selected from the literature to represent a wide range of experimental conditions.     

摩擦效应对某PBX炸药动态力学性能的影响

基于分离式霍普金森压杆(SHPB)围压加载下的试样受力模型,考虑试样与套筒间的摩擦效应,建立了动态力学性能参量(动态泊松比及动态杨氏模量)的修正方法,并以某浇注PBX炸药为例,分别以常规方法和修正方法计算了4种试样的动态力学性能,并进行了对比。结果表明,对于实验所用的浇注PBX炸药,在应变率300~2000s~(-1)内,修正方法与常规方法所获得的动态参量误差不超过5%,可以忽略摩擦效应对此PBX炸药动态参量的影响。