摘要:

AbstractIn previously reported studies it has been shown that a rugged two‐dimensional fineparticle profile boundary may exhibit different ruggedness at different levels of scrutiny. The different types of ruggedness can sometimes be described by a boundary fractal dimension the magnitude of which can be related to the physical processes which formed the fineparticle. New data illustrating this fact is presented. Detailed examination of some rugged fineparticle boundaries and similar structures suggests that some boundaries exhibit more than one level of ruggedness around the perimeter of the profile. Data illustrating this fact are presented. The possible physical significance of the multifractal structure around the perimeter of a fineparticle profile is discussed. The need for objective criteria to be followed when splitting profiles into regions of different ruggedness is discussed. The possibility of basing the partition algorithm on the inspection of the sequential chord length generated in an equipaced exploration of the perimeter is suggeste

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060101

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractPulse holography can be used as a method for the experimental investigation of transport processes that occur in flows of dispersed phases. Since a complete evaluation of a hologram involves the measurement and recording of the position of every individual particle, it delivers all the information about the spatial distribution of particles at the instant of exposure.An exact knowledge of the spatial distribution of the dispersed phase is particularly important for those chemical engineering processes which require the spatial distribution of particles to be as homogeneous as possible. Maximum homogeneity is achieved when the particles are distributed purely randomly. For this case, the distributions of distances between neighbouring particles are calculated. They represent a standard which can be adopted as the basis for the assessment of real particle distributions, such as exist momentarily in flows of dispersed phases and are determined by the evaluation of pulse holograms.

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060102

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractA new basis for the prediction of the drop size and velocity distribution in a spray is developed, using the maximum entropy formalism. The prediction considers the imposition of integral conservation constraints for mass, momentum and mechanical energy on the breakup of an undulating liquid sheet. The resulting drop size distribution is similar to the widely used empirical distributions, while the velocity distribution is Gaussian, with a variance that decreases with increasing drop size. Measurements were made in a simple water spray using the Phase/Doppler technique to obtain the joint size/velocity PDF. Photographic measurements were used to obtain an estimate of the geometry of the breakup region, necessary as input to the model. Good agreement was found between the measurements and the predictions, except in the region where drag forces had strongly influenced the distribution. This discrepancy was expected, as drag effects were not included in the model.

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060103

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractA linear regularized technique, requiring noa prioriinformation, is described for the inversion of correlation data obtained from dynamic light scattering measurements of polymer/colloidal suspensions. The procedure allows the determination of the characteristic linewidth distribution function, which is normally the first step towards obtaining a particle size distribution.

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060104

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractA prism‐cell light‐scattering spectrometer has been modified to accept both a diode‐array detector for measurements of angular distribution of scattered intensity and a photomultiplier tube for measurements of time‐dependent intensity‐intensity correlation function. This spectrometer permits the practice of light scattering at small scattering angles down to a few degrees. Here we make a brief study of the reliability of characteristic linewidth distributions obtained by several methods of analysis on the correlation data, which correspond to a reasonably broad unimodal distribution. Then the prism‐cell light‐scattering spectrometer is used to characterize a polymer solution consisting of two different molecular weights. To obtain characteristic linewidth distribution, the correlation data are analyzed by both the constrained regularization method (CONTIN) and the maximum‐entro

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060105

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractIn addition to chemical composition, geometric properties such as particle size, particle shape, specific surface area and microporosity are important for the production of sintered materials. They influence, e.g., the packing density of green bodies, the sinter activity and the microstructure of the final products. Different measuring methods are surveyed, with a critical view of sensitivity and evaluation of measurement data, and new devices are discussed, including laser and centrifuge methods for particle size measurement and sorption methods with krypton as adsorbate for the measurement of specific surface area and microporosity. Finally, a correlation between the particle size and the specific surface area using fractals is discussed.

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060106

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060107

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractPresented here is new unified theory on particle motion in a turbulent dilute two‐phase suspension flow. Results of numerical calculations based on this theory have been found to agree closely with results of recent in‐situ local measurements of a two‐phase flow in a vertical pipe by the use of the non‐intrusive laser‐Doppler anemometry. In particular, a more plausible explanation is now provided for the measured peculiar migratory behaviors of particles in the region close to the

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060108

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractAn electrodynamic balance and a frequency shifted Laser Doppler Anemometer (LDA) were used to obtain rotational velocity data from nonspherical particles undergoing pure rotation. A charged oil shale particle (150μm × 150 μm × 60 to 80 μm thick) was suspended in an electric field and rotated at a constant velocity by subjecting it to a vertical air jet. The measuring volume of the LDA was located on the particle, and Doppler bursts were observed from both stationary and rotating particles. This observation suggests that micron‐sized surface irregularities can act as individual scattering sources for LDA measurements. Signal analysis was performed with a counter type processor and a PDP‐11 computer. The particle motion was recorded on video tapes from which the true rotational velocity and maximum radius of rotation were obtained. Within the experimental uncertainties, the maximum rotation‐induced surface velocity measured with the LDA agreed well with that obtained from v

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060109

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractA laser multi‐focus velocimeter (LMFV) for measuring particle diameter, velocity and refractive index simultaneously is described. A phase diffraction grating with pulse width modulation is used to obtain several focal points with almost equal intensity and to construct the optical system. The fringes of the LMFV using multi‐beam interference have a sharper intensity distribution and wider period than those of a laser Doppler velocimeter using two‐beam interference. Therefore, the LMFV makes it possible to measure high velocities and large particle diameters with high accuracy. The validity of the method was confirmed theoretically and experimen

ISSN:0934-0866    

DOI:10.1002/ppsc.19890060110

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY