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51.
The lattice Boltzmann method, an alternative approach to solving a fluid flow system, is used to analyze the dynamics of particles suspended in fluid. The interaction rule between the fluid and the suspended particles is developed for real suspensions where the particle boundaries are treated as no-slip impermeable surfaces. This method correctly and accurately determines the dynamics of single particles and multi-particles suspended in the fluid. With this method, computational time scales linearly with the number of suspensions,N, a significant advantage over other computational techniques which solve the continuum mechanics equations, where the computational time scales asN
3. Also, this method solves the full momentum equations, including the inertia terms, and therefore is not limited to low particle Reynolds number. 相似文献
52.
Aqueous suspensions of silicon dioxide porous nanoparticles (average size 10–30 nm, average pore size 5.8 nm) were obtained via ultrasonic dispersing. As was shown through recording SiO molecular lines in a moving single-bubble sonoluminescence spectrum, these nanoparticles penetrate into the bubble and then undergo decay. Similarly, suspensions of SiO2 nanoparticles, the pores of which were saturated with ruthenium dodecacarbonyl or elemental sulfur, were obtained by impregnation of the initial powder with solutions of these reagents in chloroform followed by evaporation of the solvent. Single-bubble sonoluminescence spectra of these suspensions contain more intense lines of Ru or S and Sn+ as compared with the SiO lines. This also proves the involvement of water insoluble ruthenium and sulfur compounds into bubble sonoluminescent reactions in the heterogenic aqueous medium. Using the method of comparing the experimentally obtained and computer simulated luminescent spectra, we determined the effective electronic temperature TeRu, which was 9000 ± 500 K, in non-equilibrium plasma of a bubble levitating in the ultrasonic field. 相似文献
53.
Gerald G. Fuller Kaye Smith Wesley R. Burghardt 《Journal of statistical physics》1991,62(5-6):1025-1039
This paper presents experimental results on the use of spectroscopic optical polarimetry to study structure in dense systems of rigid particles and rigid polymer liquid crystals. These measurements probe microstructural anisotropy induced by the application of electric fields in the case of dense suspensions of rigid spheres, or flow fields in the case of polymer liquid crystals. It is demonstrated that conservative linear dichroism can measure moments of the particle pair distribution function in dense suspensions. In liquid crystals, the dichroism is a result of field-induced anisotropy in the defect structure of the material. 相似文献
54.
Baptiste Mary Charles Dubois Pierre J. Carreau Patrick Brousseau 《Rheologica Acta》2006,45(5):561-573
Ultrafine aluminum powder was identified as very promising fuels for novel energetic materials formulations. However, the large specific surface area of this powder facilitates its oxidation and greatly reduces its shelf life. Therefore, different coating processes were proposed to solve this problem. The rheology of viscous suspensions of nanoparticles still remains poorly understood and the effect of the coating of such particles on the flow behavior is even more difficult to assess. We have studied the rheology of ultrafine aluminum suspensions in three low molecular weight polymers of different viscosities: a hydroxy-terminated polybutadiene, a polypropylene glycol, and a polysiloxane. The nanosize aluminum powder was previously coated by a thin layer of high-density polyethylene using an in situ polymerization process. The rheological characterization of the suspensions was conducted by the means of steady and oscillatory shear flow measurements for noncoated and coated particles. The effect of the coating process on the rheology of the suspensions is discussed in terms of the interactions between the particles and the suspending fluids. 相似文献
55.
Xiaoli Wang Lucun Guo 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,324(1-3):126-130
The role of tetramethyl ammonium hydroxide (TMAH) in determining the rheological properties of aqueous zirconia suspensions containing polyacrylate (PANH4) was investigated. At acidic pH, the addition of TMAH after PANH4 could result in a much higher stability in zirconia slurries than that with only polymer as dispersant. While in alkaline media, it was more easily realized to lower yield stress of suspensions by adding TMAH before PANH4. Moreover, the both TMAH and PANH4 contained systems were found to need the less polyacrylate for obtaining complete dispersion than those stabilized with PANH4 alone. 相似文献
56.
F.R. Molino J.-F. Berret G. Porte O. Diat P. Lindner 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(1):59-72
We study the behavior under flow of soft spherical micelles forming a fcc phase at high volume fraction. Due to the size (300 ?) of the elementary objects, the structure can be investigated through
X-rays and neutron scattering, at rest and under flow in a Couette cell. Using scattering in two perpendicular directions,
different mechanisms of flow are identified. At intermediate shear (around 100 s-1) the system exhibits the so called layer sliding mechanism where two dimensional hexagonal compact planes of spheres align
themselves with the Couette cell walls. At lower shear rate, the fcc structure is locally preserved, and the flow is mediated by defects between crystallites. At high shear rate, we observe
the melting of the structure and a liquid-like structure factor. Moreover, we were able to use the existence of the layer
sliding regime to generate a fcc monocrystal by annealing the satcking faults between the decorrelated planes created by the layer sliding.
Received: 7 July 1997 / Received in final form: 16 January 1998 / Accepted: 5 March 1998 相似文献
57.
The release of H2O2 by plant cell suspensions elicited with crude hyphal wall preparations has been studied in a complex of plant genotypes (two
cvs ofCapsicum annuum and one of C.frutescens) and fungus species(Phytophthora capsici, Ph. parasitica andVerticillium dahliae), representing several combinations of compatibility and both host and nonhost resistance. Production of H2O2 was revealed as peroxidasedependent and catalase-inhibited fluorescence quenching of an extracellular probe (Pyranine).
All the plant genotypes responded to at least one elicitor, but the cell sensitivity showed a great age-dependent variability.
Riboflavine and Mn2+ added in the incubation medium acted to some extent as primers for activated cell response, as well as a high Na+ concentration. Cell rest condition, however, was not removed. Some quantitative features of responsive plant/elicitor combinations
(dose-response relation and lasting time) have been recorded.
The complex PO/H2O2 of elicited cells could perform detectable lignin-like polymerization of an exogenous natural substrate (coniferyl alcohol).
The time-course of pyranine oxidation and lignin-like polymer formation could be recorded by adopting a fluorimetric procedure
that allowed sequential observations on the same cell sample. In one instance, the cell reaction seemed associated with thein planta host/parasite incompatibility. 相似文献
58.
In this paper, fiber motion near a planar wall was investigated using a planar shear flow apparatus. Fibers were placed (one
at a time) perpendicular to the flow direction at various locations throughout the flow field. The location and orientation
of each fiber versus time was measured, using an image processing system, until the fiber aligned with the flow direction.
When the centroid of the fiber was located at distances greater than a fiber length from the wall, Jeffery's equations governing
particle motion were verified. For distances less than a fiber length and greater than a fiber diameter from the wall, the
fiber experienced an increased rate of rotation. In this regime, the motion of the fiber could be described by Jeffery's equations
if an increased effective shear rate was used. The effective shear rate was found to increase logarithmically with decreasing
separation distance. The wall effect was higher for longer aspect ratio fibers and was also a function of orientation; fibers
oriented perpendicular to the wall rotated faster than those oriented parallel to the wall at the same separation distance.
Once the fiber aligned with the flow direction, it ceased to rotate within the field of view. In this orientation, the wall
had a stabilizing effect on the fiber. In efforts to relate the increase in shear rate to the aspect ratio of the fiber and
the separation distance between the fiber and a solid wall, a translation model based on the work of De Mestre and Russel
was explored. This model allows one to quantify the increase in shear rate experienced by the fiber due to the presence of
a wall or obstruction in the flow field. However, the model has its limitations and care should be taken when applying this
model outside its realm of validity. When compared to experimental data, the translation model provides a very good estimate
of the increased shear rate experienced by the fiber when it is located less than 2/3 of a fiber length from a planar wall.
Received: 20 April 2000 Accepted: 28 September 2000 相似文献
59.
For three different types of polymer latex particles with widely different particle charges the structure of suspensions before and after crystallization is investigated. A liquid-like ordered state was achieved by shear melting crystal-like ordered samples. The structure factors S(Q) of the liquid-like suspensions are analyzed in terms of the resealed mean spherical approximation (RMSA) of Hansen and Hayter. The Bragg diffraction pattern of the crystallized samples shows that the structure is b.c.c. It is found that the particle number concentration n and the distance of nearest neighbours in corresponding liquid- and crystal-like states differ by less than 4 %. In the second part of the paper, Bragg diffraction was used to determine the crystallite size distribution in samples of different particle concentration. 相似文献
60.
G. Peng J.-U. Sommer A. Blumen 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(1):73-79
We investigate numerically, using the bond-fluctuation model, the adsorption of many random AB-copolymers with excluded volume
interactions at the interface between two solvents. We find two regimes, controlled by the total number of polymers. In the
first (dilute) regime, the copolymers near the interface extend parallel to it, while in the second regime they extend perpendicular
to it. The density at the interface and the density in the bulk depend differently on the total number of copolymers: In the
first regime the density at the interface increases more rapidly than in the bulk, whereas the opposite is true in the second
regime.
Received 4 March 1998 and Received in final form 22 September 1998 相似文献