摘要:

AbstractA comprehensive description of gas‐particle flows requires the knowledge of thedistribution statesof the particulate phase. To determine these distribution states in the first instance, optical methods are suitable, in particular double pulse holography. It yields a maximum amount of information, because as animagingmethod it allows the determination of position, size and velocity of each individual particle of a collectivesimultaneously. The consequence is that the spatial distribution of the particles can be determined, as well as the frequency distributions of all the relevant quantities, such as diameter, velocity, momentum and energy as well as their local dependence and correlation. In the present case double pulse holography was employed to study different gas‐particle flows at the outlet of a vertical tube (length 1 m, diameter 50 mm, mean gas velocity 3 m/s, Re = 10000). The dispersed phases consisted of water droplets with a broad size spectrum from 3 to 100 m̈m, and of glass spheres ranging from 20 to 35 μm.The most important results which are discussed in this paper are:1the local dependence of concentration, mean size and mean particle velocity,2the frequency distributions of particle size and velocity,3the distributions of energy and momentum as function of particle size,4the correlation of particle velocity with particle size.The results reflect the different behaviour of the two particulate phases

ISSN:0934-0866    

DOI:10.1002/ppsc.19870040102

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractA film flotation technique has been developed for assessing the hydrophobicity/hydrophilicity of an assembly of particles which have a distribution of surface energies. With this method, particles are partitioned by placing them on the surface of a series of aqueous solutions of different surface tensions and determining the fraction imbibed into the liquid. From the results, a cumulative distribution of particles versus their critical wetting surface tension (surface energy) can be made. The mean critical wetting surface tension can be used as an index for making correlations with surface‐based processe

ISSN:0934-0866    

DOI:10.1002/ppsc.19870040103

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractLaser diffraction spectrometry (LDS) is often claimed to operate on the principle of Fraunhofer diffraction. This is only true, however, if particles are large compared to the wavelength of light or if the ratio of the refractive indices of the disperse and continuous phases,m, is clearly different from unity. In this study it has been established that LDS, as applied to particle and droplet sizing in suspensions and emulsions, is based on Miescattering. Scattering patterns of single particles may be calculated if the refractive indices of both phases are known. Thus, a theoretical basis has been provided for the application of LDS to size‐measurement in suspensions and emulsions, and for extension of this method to the lower size ranges and those cases in which the refractive indices of the disperse and continuous phases are similar. Extension of the work presented in this paper will enable the calculation of scattering matrices so that calibration of the apparatus with standard materials may be avoide

ISSN:0934-0866    

DOI:10.1002/ppsc.19870040104

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractIt is shown that the number of particles which may be placed upon a slide is surprisingly limited if each particle is to be isolated. This is particularly relevant if automatic image analysis of size or shape is to be achieved without tedious editing. Using a simple mathematical treatment it is possible to calculate, for any particular size of particle, the number of particles on a slide which should not be exceeded.

ISSN:0934-0866    

DOI:10.1002/ppsc.19870040105

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractCharacterization of the roughness of surfaces of individual features present inSEMimages is obtained from the slope and intercept of a plot of the brightness difference between pixels as a function of their separation distance, in directions parallel and perpendicular to the scan lines within the outlines of the feature. The descriptive namescontrastandtextureare given to the intercept and slope of this plot, respectively. These parameters can be used to classify features, just as measures of size, shape, etc. are used for selection, distribution plots and statistical comparison. Evidence is also shown for a correlation between thetextureand the fractal dimension of the feature profile, and consequently with the surface fractal dimension of the feature.

ISSN:0934-0866    

DOI:10.1002/ppsc.19870040106

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractThe present paper gives an introduction to laser Doppler anemometry. The fundamental principles of this measuring technique, as well as the basic features of its instrumental realizations, are explained. The application of laser Doppler anemometry to fluid investigations often requires an adaptation of the LDA‐system to the measuring problem. Basic formulas for the lay‐out and adaptation are gi

ISSN:0934-0866    

DOI:10.1002/ppsc.19870040107

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractOne well documented method for finding the fractal dimension of a silhouette involves approximating the silhouette with polygons which have all but one side equal and the vertices of which fall upon the silhouette edge. These are constructed using a divider stepping method or a computer algorithm which mimics this process. If one does not complete the polygon with an unequal side, as is usually done, but continues the analysis by stepping around the silhouette several times, the dividers start to „walk in their own footsteps”︁ and describe an equilateral polygon in the silhouette. These phenomena, termed polygonal harmonics, are examined and discussed in detail. A rule is developed for harmonic stability and specific cases of the circle, triangle and smooth curves are examined to gain insight into the convergence pr

ISSN:0934-0866    

DOI:10.1002/ppsc.19870040108

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19870040109

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19870040110

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractThe Malvern Particle Sizer, developed in 1977, is used extensively for measuring the size distribution of solid particles and drops. It has several modes of operation based ona prioriassumption of a particle size distribution function and a so‐called “model independent” programme in which no prior assumptions are made about the nature of the size distribution. Unfortunately neither the developers nor the manufacturers of the instrument have revealed the algorithm which is used to obtain the particle size distribution from the light scattering data. A number of people who have attempted to verify the performance of the instrument using the model‐independent programme have encountered discrepancies which cannot be explained without knowing the details of the Malvern inversion algorithm.The results obtained in this paper show that the light scattering data recorded, using the hardware of the Malvern instrument, can be successfully processed using Shifrin's inversion technique in order to the obtain particle size distribution. The use of Shifrin's inversion algorithm, which is described fully in the open literature, has a number of advantages over Malvern's proprietary software in the context of particle sizing research. It provides the research worker with a simple and mathematically elegant alternative method of processing the light scattering data which is particularly suitable for investigating the limits of applicability of the Fraunhofer diffraction particle‐sizing

ISSN:0934-0866    

DOI:10.1002/ppsc.19870040111

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY