Experimental comparison of measurement techniques for drop size distributions in liquid/liquid dispersions

An online measurement technique for drop size distribution in stirred tank reactors is needed but has not yet been developed. Different approaches and different techniques have been published as the new standard during the last decade. Three of them (focus beam reflectance measurement, two-dimensional optical reflectance measurement techniques and a fiber optical FBR sensor) are tested, and their results are compared with trustful image analysis results from an in situ microscope. The measurement of drop sizes in liquid/liquid distribution is a major challenge for all tested measurement probes, and none provides exact results for the tested system of pure toluene/water compared to an endoscope. Not only the size analysis but also the change of the size over time gives unreasonable results. The influence of the power input on the drop size distribution was the only reasonable observation in this study. The FBR sensor was not applicable at all to the used system. While all three probes are based on laser back scattering, the general question of the usability of this principle for measuring evolving drop size distributions in liquid/liquid system is asked. The exterior smooth surface of droplets in such systems is leading to strong errors in the measurement of the size of the drops. That leads to widely divergent results. A different measurement principle should be used for online measurements of drop size distributions than laser back scattering.     

A class of elastic-plastic stress distributions

Similarity methods are used to find solutions to the equations governing elastic-plastic torsion of a solid of revolution. The solutions are expressed in terms of integrals of two ordinary differential equations.     

Adomian修正分解法的后处理方法比较

Adomian修正分解法在求解非线性微分方程中得到广泛应用。Adomian修正分解法的主要特点在于计算简单快速,并且不需要进行线性化或离散化。但是Adomian修正分解法的计算精度取决于其收敛域。为了扩大Adomian修正分解法的收敛域,需要对所得解进行后处理,目前常见的后处理方法包括Padé近似、LaplacePadé近似和多步迭代方法。本文首先简要回顾了Adomian修正分解法,然后讨论了这三种后处理方法,最后通过Duffing振子为例对这些后处理方法的优缺点进行讨论和分析。数值计算结果表明,多步迭代方法能够加速Adomian修正分解法解的收敛,并扩大其收敛域。     

A comparison of different analytical techniques for identifying structures in turbulence

Vortical structures play an important role in the kinematics and dynamics of turbulence, but in order to understand this role we require techniques to identify and classify them. Proper Orthogonal Decomposition (POD), conditional sampling with ensemble statistics, and conditional sampling with conditional statistics are applied to a simple test function and the results are compared to determine the strengths and weaknesses of each approach. The second method gives the closest approximation to the test signal and is the easiest to use, although it is sensitive to the choice of conditions. None of these techniques can give much insight into the dynamics of turbulence, or into the organisation of eddies with complex, fine-scale structure.New methods for investigating complex (self-similar) structures based on fractal and wavelet analyses are presented. Methods of distinguishing between locally (accumulating) and globally (fractal) self-similar structures are suggested.     

An experiment for determining the Euler load by direct computation

A direct algorithm is presented for computing the Euler load of a column from experimental data. The method is based on exact inextensional theory for imperfect columns, which predicts two distinct deflected shapes at loads near the Euler load. The bending stiffness of the column appears in the expression for the Euler load along with the column length; therefore, the experimental data allow a direct computation of bending stiffness. Experiments on graphite-epoxy columns of rectangular cross section are reported in the paper. The bending stiffness of each composite column computed from experiment is compared with predictions from laminated plate theory.     

A comparison of high-speed photography and accelerometer data-reduction techniques

A simple experimental test is discussed by which the theoretical kinematic quantities of a moving target can be determined. Experimental data are collected by means of high-speed photography and accelerometers, and the results of the two techniques are compared. It will be shown for the case of interest that the high-speed photography will yield results that are better than those obtained from the accelerometer data.     

Strain gage method for determining stress intensities of sharp-notched strips

An efficient and simple strain gage method for determining the stress intensities of sharp-notched strips is proposed. The bisector of the notch angle is inclined to the edge so that the mixed-mode loading is created simultaneously at the notch tip. A theory of determining the stress intensities using strain gages is described on the basis of the two-dimensional theory of elasticity. Experiments on specimens with various notch shapes are carried out to verify the theoretical results. Experimental results are in good agreement with theoretical results.     

A comparison of flame detection techniques for premixed-charge combustion in spark ignition engines

Work performed at the Combustion Research Facility and supported by the U. S. Dept. of Energy, Division of Energy Conversion and Utilization Technologies     

一种确定结合材料界面端应力强度因子的数值方法

基于弹性力平面问题的基本方程,给出了结合材料界面端的应力奇异性特征方程以及位移场和奇异应力场。提出了一种确定结合材料界面端应力强度因子的数值外插方法。对界面端区域进行了有限元网格单元划分。经过具体实例检验进一步确定了求解应力强度因子的最佳方向,该数值外插法的计算结果精度符合工程应用的要求,为工程材料强度的评价提供了有效的计算途径。     

A numerical method for determining the shear stress of magnetorheological fluids using the parallel-plate measuring system

This work proposes a new numerical method for determining the shear stress, which does not need any preassumption about the exact behavior of the fluid to achieve absolute data using a parallel-plate measuring system. The ability for representing different behaviors along the entire shear-rate range makes this method particularly interesting for the study of magnetorheological (MR) fluids. In this work, the conversion factors used by the rheometer for concentric-cylinder, cone-plate, and parallel-plate measuring systems are first analyzed. This analysis shows that the software used by the rheometer is not appropriate for the quantitative characterization of non-Newtonian fluids using the parallel-plate measuring system. Therefore, a new method for conversion of the parameters measured by the rheometer to the rheological parameters of the fluid is proposed; simultaneously, this new method is compared with other correction methods proposed in the literature: the Rabinowitsch-type method and the single-point method. Finally, the proposed method is applied for the quantitative characterization of an MR fluid.     

极坐标中应力与应力函数关系式的直接推导

给出了极坐标中应力与应力函数关系式的一种直接推导.     

A direct complex stress function approach for modelling stiffened panels containing multiple site damage

The analysis of stiffened panel structures containing multiple site damage (MSD) is addressed through the complex variable method, in association with the requirement for displacement compatibility. The method is extended by replacing the usual single crack stress and displacement functions by those for a series of arbitrary straight collinear cracks which are used to model exactly the main and secondary crack damage in the sheet. It is shown that the problem can be reduced to a system of linear equations for the unknown forces at the attachment points between the sheet and the stiffener from which the stress intensity factor of the collinear cracks can be determined. The stress intensity factor and the attachment force distribution are determined for several configurations and compared with those from numerically based approaches.     

Diffractography vs. holography—A stress analyst's comparison

Holographic interferometry provides an elegant and very sensitive displacement measurement means for the experimental stress analyst. Recently however, a related optical techniques, “diffractography”, has been developed which offers an alternative to holography in many cases, particularly in those experiments where information along one or more discrete lines is sufficient. This paper compares both approaches and presents new experimental data on deflections of a cantilever steel plate obtained using both techniques.     

A method for determining ultrahigh temperatures

The problem of determining high and ultrahigh temperatures is urgent in connection with mastering the technology of new high-power energy sources. The known methods of measuring temperatures by using thermocouples, ultrasound, or optical devices can either be used only over limited temperature ranges or are very difficult to apply in practice. The present article describes a method of determining temperature based on the phenomenon of rethermalization of neutrons. The neutron is used as an agent interacting with the hot medium. When neutrons are scattered by atoms of a hot medium there is a change in their energy spectrum which is uniquely related to the kinetic temperature of the medium. In principle there is no apparent upper limit of the temperatures which can be measured by this method.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 8–11, May–June, 1979.The authors thank G. A. Ilyasova and M. Ya. Bankrashkova for their kind assistance in calculating the neutron energy spectra.     

Graphical methods for determining the resulting photoelastic effect of compound states of stress

The aim of this work is to give a simplified representation of an interesting subject, namely, the calculation of the photoelastic effect behind a system in which the principal stresses or secondary principal stresses rotate about the direction of the propagation of light. The methods are described in a popular form for understanding the essential features and the necessary graphical operations for solving these complicated problems. Further, the relations between the different methods are shown. Thej-circle technique is improved in order to simplify the operations and a new possibility in applying Wulff's grid is introduced in photoelasticity. The graphical tools can then be applied as so-called “rotation rules.” Some examples related to recent papers which present theoretical results or new methods are given in order to study the function of these “rotation rules” and to recognize the power of these methods.