黏度计测量原理分析与改进

通过分析物理实验教学中常用的两种黏度计的原理,指出它们都存在由测量原理带来的系统误差,并介绍一种能克服上述系统误差的黏度测量装置．     

转筒黏度计测量液体黏度方法研究

用黏性流体力学理论求得测量装置中旋转液体径向速度梯度的理论公式,进而得到转筒法测量黏度的较精确公式.指出了国内的一些教材和文献在推导中使用近似公式的错误,用参数估计的方法求得测量装置的摩擦阻力力矩,使测量结果得到进一步校正.实验研究表明:按照近似公式与精确公式计算求得的径向速度梯度之差可达到13.1%,求得的液体黏度之差可达到28.6%;在蓖麻油的温度为25.5℃时测得测量装置的摩擦阻力力矩为9.482×10-5 N·m,相当于0.540克重物产生的力矩.     

黏度计保护盒的研制及应用

介绍了黏度计保护盒的研制、安装及其应用.     

转子转速和流体空间对旋转法测量黏度的影响

研究了测定流体的黏度实验中转子转速和流体空间对旋转法测量黏度的影响,推导出转子偏转角与黏度测量误差之间的关系式,并应用实验数据进行了验证;流体空间对黏度测量的影响随流体空间直径的增大而减小,当流体空间直径达到102.38 mm后,测量的黏度值趋于稳定.     

水包油乳液的流变特性和黏度实验研究

采用超声波乳化法制备了不同类型的水包油乳液,对其粒径、流变特性、黏度等物性进行了表征。结果表明:O/W乳液的粒径随超声处理时间的延长而逐渐变小,油的浓度对粒径的影响较小,导热油乳液比橄榄油乳液具有更大的粒径。实验制备的不同质量分数、不同粒径、不同乳化剂含量的O/W乳液均可视为牛顿流体,这些O/W乳液的黏度随温度升高而减小,随着粒径的减小、油和乳化剂浓度的增大而增加。基于实验数据,采用多元非线性回归分析法和人工神经网络法为O/W乳液建立了新的黏度模型,这些模型考虑了流体的热物理性质、油浓度、油滴尺寸和温度的影响。     

步进轮摆共振法测量流体黏度

在液体中做受迫振动的摆球可以在特定的情形下达到共振,所以只要改变摆球的摆动频率,并测量摆球达到最大摆幅时的共振频率,就能实现流体黏度的测量．通过计算机模拟,验证了在0.1～1.5Pa·s范围内黏度与共振频率呈线性关系,给出了计算流体黏度与共振频率的简化公式,设计了实验系统,并通过实验验证了上述理论．探究了摆长、温度和Q值对流体黏度测量的影响,并分析了实验系统的性能误差和进一步改进的措施．     

法拉第旋转镜对旋转光纤磁光性能测量的影响

为了解决随机线性双折射对光纤磁光特性测量的影响,采用旋转光纤（SF）结合法拉第旋转镜（FRM）的测量方法,研究了FRM对旋转光纤磁光特性测量的影响。首先,从理论方面研究旋转光纤与FRM的引入如何减小光纤中的随机线性双折射对磁光特性测量的影响,并搭建基于FRM的旋转光纤磁光特性测试系统。当光源波长为1310 nm时,FRM作用前的旋转光纤费尔德常数都比未旋转光纤的大,且旋转光纤的节距越短,费尔德常数越大。特别是旋转光纤的节距为1.0 mm时,其费尔德常数为0.8304 rad/（T·m）,比未旋转光纤的费尔德常数[0.8029 rad/（T·m）]增大了约3.43%。当测试系统加入FRM后,不同光纤的费尔德常数测量值相较于未使用FRM的光纤费尔德常数测量值都有一定幅度的增大,尤其相比于节距为1.0 mm时的旋转光纤更进一步提高了7.50%,并且在FRM作用前后不同光纤费尔德常数测量值的均方差分别为0.99%和0.61%,说明FRM的引入提高了掺杂光纤费尔德常数的测量精度与稳定性。     

基于光电转换原理测量流体压强的微小变化

设计并制备了一种通过光电转换的方法测量流体压强微小变化的新装置.将被测量的流体压强变化量转化为弹簧的位移量,再通过硅光二极管将弹簧的位移量转变为可测量的电信号.利用胡克定律,光强与距离的关系式,以及硅光二极管的光电响应关系式推导出流体压强微小变化的关系式,通过集成运算放大电路实现装置转换成可视化读数,能满足对流体总压及其微小变化的测量.压强测量的最小精度为6 Pa,满足对流体压强微小变化测量的要求.     

化学机械抛光中纳米颗粒的作用分析

化学机械抛光（chemical mechanical polishing, CMP）是用于获取原子级平面度的有效手 段.目前，CMP的抛光液通常使用纳米级颗粒来加速切除和优化抛光质量.这类流体的流变性 能必须考虑微极性效应的影响.对考虑微极性效应的运动方程的求解，有助于了解CMP的作用 机理.数值模拟表明，微极性将提高抛光液的等效黏度从而在一定程度上提高其承载能力， 加速材料去除.这在低节距或低转速下尤为明显，体现出其具有尺寸依赖性.通过改变抛光液 中粒子的微极性，用实验研究了微极性效应对CMP中材料去除速率的影响，证明了分析的合 理性. 关键词： 化学机械抛光 微极流体 抛光液 流变特性 材料去除速率     

旋转液体特性实验测量重力加速度不确定度研究

重力加速度测量实验是大学生物理实验必修课实验内容之一,在实验过程中由于仪器使用不当或操作不正确,在计算结果时存在不同的偏差。不确定度是衡量测量精度的重要指标,本文计算了三种不同情况测量重力加速度时的不确定度,主要考虑了激光照射透明挡板的角度r、激光垂直入射点的偏差Δx和激光垂直入射方向的偏差β对重力加速度的不确定度。通过计算,当透明挡板向上/下偏移的角度为5°时,不确定度为1.496 3 m/s~2;当激光向左/右偏移5 mm时,不确定度为1.0044 m/s~2;当激光向左和向右偏移的角度为5°时,不确定度分别为1.551 5 m/s~2和1.250 8 m/s~2。本文可为减小旋转液体测量重力加速度误差提供理论依据。     

转筒法测液体黏度关系式比较研究

对文献中转筒法测液体黏度的几个关系式进行了比较研究,指出了其中的问题.     

Negative magneto-rheological effect of a dispersion composed of spindle-like hematite particles

We have experimentally investigated the negative magneto-rheological effect that is theoretically predicted to appear in a dispersion composed of spindle-like hematite (α-Fe₂O₃) particles. The spindle-like hematite particles were synthesized by aging a solution of FeCl₃ and KH₂PO₄ for 72?h at 373?K. The particle size distribution was determined by digital image analysis from electronic microscope observation of the particles. In the present study we considered a glycerol–water-based dispersion in order to clarify the influence of the shear rate and the magnetic field strength on the negative magneto-rheological effect. Measurement of the viscosity was carried out using a rotational-type rheometer in an external magnetic field generated by Helmholtz coils. The main results obtained can be summarized as follows. The viscosity of a hematite/glycerol–water dispersion relative to that with no applied magnetic field decreases with increasing magnetic field strength: that is, we observed the negative viscosity effect that has previously been predicted from theoretical considerations. Moreover, the negative magneto-rheological effect is observed to decrease with increasing shear rate, which also agrees qualitatively with the theoretical prediction.     

Electron resonance spectra of NCS and vibronically-excited NCO in the gas phase

Near 25 °C, ab initio calculations of the zero-density viscosity of helium gas η _He have an uncertainty of approximately 0.001%, which is 1/40th of the uncertainty of the best measurements. The uncertainties of the published calculations for neon and argon are probably much larger. This paper presents new measurements of the viscosities of neon, argon, and krypton at 25 °C made with a capillary viscometer that was calibrated with helium. The resulting viscosity ratios are η _Ne/η _He?=?1.59836?±?0.00037, η _Ar/η _He?=?1.13763?±?0.00030, and η _Kr/η _He?=?1.27520?±?0.00040. The argon ratio agrees with a recent, unpublished calculation to within the combined uncertainty (measurement plus calculation) of 0.032%. The neon ratio is smaller than the calculated value by 0.13%.     

Dissipative particle dynamics simulation on the rheological properties of heavy crude oil

The rheological properties of heavy crude oil have a significant impact on the production, refining and transportation. In this paper, dissipative particle dynamics (DPD) simulations were performed to study the effects of the addition of light crude oil and emulsification on the rheological properties of heavy crude oil. The simulation results reflected that the addition of light crude oil reduced the viscosity effectively. The shear thinning behaviour of crude oil mixtures were becoming less distinct as the increase of the mass fraction of light crude oil. According to the statistics, the shear had an influence on the aggregation and spatial orientation of asphaltene molecules. In addition, the relationship between the viscosity and the oil mass fraction was investigated in the simulations of emulsion systems. The viscosity increased with the oil mass fraction slowly in oil-in-water emulsions. When the oil mass fraction was higher than 50%, the increase became much faster since systems had been converted into water-in-oil emulsions. The equilibrated morphologies of emulsion systems were shown to illustrate the phase inversion. The surfactant-like feature of asphaltenes was also studied in the simulations.     

Effect of Bamboo Flour (BF) Content on the Dynamic Rheological Characteristics of BF-filled High-density Polyethylene (HDPE)

The effects of bamboo flour (BF) content on the dynamic rheological properties of BF-filled HDPE composites were investigated. Our findings showed that the addition of BF caused an enhancement of the non-Newtonianism of wood-plastic composites (WPCs) melt as well as the appearance of some new relaxation processes. In addition, the viscosity and modulus of the BF-filled HDPE composites showed a remarkable increase at 170?°C and 190?°C when the BF content exceeded 30%, which could be associated with the solid-like property of the WPCs at high BF loading, we propose. The present study we suggest will be useful to the formula design as well as the optimization of processing parameters for WPCs in general.     

Lattice electrons on a cylinder surface in the presence of rational magnetic flux and disorder

We consider a disordered two-dimensional system of independent lattice electrons in a perpendicular magnetic field with rigid confinement in one direction and generalized periodic boundary conditions (GPBC) in the other direction. The objects investigated numerically are the orbits in the plane spanned by the energy eigenvalues and the corresponding center of mass coordinate in the confined direction, parameterized by the phase characterizing the GPBC. The Kubo Hall conductivity is expressed in terms of the winding numbers of these orbits. For vanishing disorder the spectrum of the system consists of Harper bands with energy levels corresponding to the edge states within the band gaps. Disorder leads to broadening of the bands. For sufficiently large systems localized states occur in the band tails. We find that within the mobility gaps of bulk states the Diophantine equation determines the value of the Hall conductivity as known for systems with torus geometry (PBCs in both directions). Within the spectral bands of extended states the Hall conductivity fluctuates strongly. For sufficiently large systems the generic behavior of localization-delocalization transitions characteristic for the quantum Hall effect are recovered.     

Experimental study and CFD simulation of rotational eccentric cylinder in a magnetorheological fluid

In this study, a magnetorheological (MR) fluid is prepared using carbonyl iron filings and low viscosity lubricating oil. The effects of magnetic field and weight percentage of particles on the viscosity of the MR fluid have been measured using a rotational viscometer. The yield stress under an applied magnetic field was also obtained experimentally. In the absence of an applied magnetic field, the MR fluid behaves as a Newtonian fluid. When the magnetic field is applied, the MR fluid behaves like Bingham plastics with a magnetic field dependent yield stress. Afterward, the results compared with those of CFD simulation of two eccentric cylinders in the MR fluid. Results show that the influences of MR effects, caused by the applied magnetic field, on the model characteristics are significant and not negligible. The viscosity is enhanced by increasing of the magnetic field, eccentricity ratio and weight percentage of suspensions. The MR effects and increasing of weight percentage and eccentricity ratio also provide an enhancement in the yield stresses and required total torque for rotation of inner cylinder. Also the simulation results indicate a good representation of the experiment by the model.     

Determination of the Pressure Dependence of the Shear Viscosity of Polymer Melts Using a Capillary Rheometer with an Attached Counter Pressure Chamber

A capillary rheometer with an attached counter pressure chamber was used to determine the effect of pressure on the shear viscosity of several polymer melts, i.e., poly(?-caprolactam) (PA6), poly(ethylene terephthalate) (PET), low-density polyethylene (LDPE), and polypropylene (PP). In order to study the rheological properties of the polymer melts at a constant pressure, the measured values of shear viscosity were recalculated with respect to a series of pressures by the least square fitting based on the Barus equation. Different calculation methods were used to calculate the pressure coefficients from the recalculated viscosity values. The resulting pressure coefficients of the shear viscosity demonstrated that the degree of the pressure dependence was highest for PP, followed by PET and then LDPE. PA6 exhibited the lowest pressure coefficient.