Computational study of flow past a cylinder with combined in-line and transverse oscillation

A computational study of the two dimensional flow past an oscillating cylinder is carried out using vorticity and stream function as the dependent variables. With the use of a log-polar coordinate transformation, the nondimensional vorticity transport equations in a non-inertial frame attached to the cylinder are solved using the ADI and SLOR finite difference schemes. The effects of combined in-line and transverse oscillation of the cylinder in the lock-in range of frequency on the time history of the drag and lift are investigated at a Reynolds number of 100. In addition, the influence of position amplitude of the cylinder's transverse oscillation on the lock-in range of frequency, mean drag, amplitude of drag and maximum lift is studied. The time histories of drag and lift forces in the case of combined oscillation are compared with the cases of the cylinder oscillating in the in-line and transverse directions separately. The dominant frequency components in the drag and the lift variations are determined using a Fourier frequency analysis.This research work was financially supported through a University of Windsor Postgraduate Scholarship and grants from the Natural sciences and Engineering Research Council of Canada (Grant Numbers: A-2190 and A-1403).     

Effect of carbon blacks on relaxation phenomenon of chlorobutyl vulcanizates

The effect of the types of carbon black on the physicomechanical, dynamic mechanical, and dielectric relaxation spectra in chlorobutyl vulcanizates was studied. The primary relaxation (α transition, the glass transition) was studied by dynamic mechanical analysis as a function of temperature (?60 to +100°C) and by positron annihilation lifetime spectroscopy (?70 to +100°C). Irrespective of the type of carbon black that was used, all composites showed glass‐transition temperatures in the range of ?29 to ?33°C, which was explained on the basis of the relaxation dynamics of polyisobutylene chains in the vicinity of the fillers. The secondary relaxation (α* or β relaxation) was studied using dielectric relaxation spectra in the frequency range of 100–10⁶ Hz. The nonlinear strain dependent dynamical parameters (Payne effect) were also evaluated at dynamic strain amplitudes of 0.07–5%. The nonlinearity in the tan δ and storage modulus was explained by the concept of filler–polymer interactions and the interaggregate attraction (filler networking). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1809–1820, 2006     

Pervaporation separation of water‐isopropanol mixtures using polymeric membranes: Modeling and simulation aspects

Pervaporation technique was used to separate water + isopropanol azeotropic mixtures at 30°C using pure sodium alginate, pure poly(vinyl alcohol), and blend membranes of sodium alginate containing 10 and 20 mass % of poly(vinyl alcohol). The membrane performance was studied by calculating flux, selectivity, pervaporation separation index, and enrichment factor. Pure sodium alginate membrane gave the highest pervaporation separation index for all compositions of water. Pervaporation experiments were carried out for 10 mass % containing water + isopropanol mixture at 30, 40, and 50°C. The Arrhenius activation parameters were computed. The PV results have been analyzed by considering complete mixing and plug flow models. Design parameters, like membrane area, permeate concentrations, flux, stage cut, separation selectivity, etc., have been calculated for different feed compositions of water in the mixture. Results are explained in terms of sorption‐diffusion principles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1143–1153, 2005     

Relaxation behavior of conductive carbon black reinforced EPDM microcellular vulcanizates

Dynamic mechanical analysis and dielectric relaxation spectra of conductive carbon black reinforced microcellular EPDM vulcanizates were used to study the relaxation behavior as a function of temperature (−90 to +100°C) and frequency (0.01–10⁵ Hz). The effect of filler and blowing agent loadings on dynamic mechanical and dielectric relaxation characteristics has been investigated. The effect of filler and blowing agent loadings on glass transition temperature was marginal for all the composites (T_g value was in the range of −39 to −35°C), which has been explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. Strain-dependent dynamical parameters were evaluated at dynamic strain amplitudes of 0.07–5%. The nonlinearity in storage modulus has been explained based on the concept of filler–polymer interaction and interaggregate attraction (filler networking) of carbon black. The variation in real and complex part of impedance with frequency has been studied as a function of filler and blowing agent loading. Additionally, the effect of crosslinking on the dielectric relaxation has also been reported. POLYM. ENG. SCI., 47:984–995, 2007. © 2007 Society of Plastics Engineers     

Physico‐mechanical,dynamic mechanical,and swelling properties of sodium chloride filled chlorobutyl vulcanizates

The effect of addition of rigid, nonreinforcing, and noninteracting filler viz. finely ground NaCl in chlorobutyl vulcanizates on properties such as physicomechanical, dynamic mechanical, and swelling has been studied. The nonreinforcing effect of NaCl in the system was studied by Russel and Cunnenn analysis and Kraus plots. Mechanical measurements of stress and strain at the break of filled and unfilled samples showed no appreciable change in the mechanical behavior of the system. The dynamic mechanical analysis showed that there is no change at all in the glass transition temperature with addition of NaCl filler. The damping properties showed an increase with increase in filler loading because of the filler–filler friction. The swelling behavior of NaCl‐filled CIIR was studied for a period of 60 days in four different solvents of varying chemical energy potential viz. water, chloroform, acetone, and tetrahydrofuran (THF). The degree of swelling was found to increase continuously with time in water, which is a good solvent for the filler, and in THF, which is a good solvent for the polymer matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 707–714, 2006     

Conversion of Fly Ash to Swelling Mica: A New Approach for Recycling Fly Ash

Swelling mica exhibits unique characteristics for purification of drinking water contaminated by heavy metals and for selective removal of Sr²⁺ and Ba²⁺ ions from nuclear waste solution. As a new approach to recycle fly ash, conversion of fly ash to swelling mica has been attempted and ion-exchange properties of fly ash-derived swelling mica (referred to hereinafter as FA-swelling mica) were examined in this study. Thermal treatment of fly ash with MgO in the presence of excess NaF led to the formation of swelling mica along with trace quantities of impurities. A swelling mica of good quality was obtained from the reactant ratio of fly ash 1 g : MgO 0.75 g : NaF 1.75 g. Unlike gel or kaolinite-derived synthetic Na-4-micas, FA-swelling mica exhibited heterogeneity in its framework. Its uptake capacity for Sr²⁺ ions was estimated to be 17.4 meq/100 g from 0.1 mM SrCl₂ aqueous solution and 5.0 meq/100 g from 0.5 N NaCl solution containing the same Sr²⁺ concentration. These capacities are less than that of metakaolin-derived Na-4-mica. However, its ion exchange capacity for divalent transitional metal ions was estimated to be 284 meq/100 g from their inaqueous solutions and 206 meq/100 g from the 0.5 N NaCl solution containing the mixed metal ions of Cd²⁺, Co²⁺, Mn²⁺, Ni²⁺ and Zn²⁺ each at 1 mN concentration. These capacities are comparable to that of metakaolin-derived Na-4-mica. Its selectivity for transition metal ions is as follows: Zn²⁺ > Ni²⁺ Co²⁺ Cd²⁺ > Mn²⁺ and this is consistent with the G° values from Gibbs-Duhem equation. These results clearly showed that fly ash could be converted to swelling mica with high uptake capacity for divalent transitional metal ions. Therefore, conversion of fly ash to highly pure swelling mica will lead to a resource from waste.     

Temperature-programmed desorption vs. N2 desorption in determining pore-size distribution of mesoporous silica molecular sieves

Two mesoporous silica molecular sieves, one synthesized by cationic template method and another by neutral template route, were characterized for their pore-size distribution by a novel Temperature-Programmed Desorption (TPD) method and the widely used N₂ desorption method. The pore-size distributions determined by the two methods agree quite well and are within experimental errors. For example, TPD method gave a pore size distribution (radius) centered at 14 Å while N₂ desorption method showed a peak centered at 13.3 Å. for the mesoporous silica prepared by cationic template route. The new TPD method based on thermogravimetric analysis is a viable option for mesopore characterization of silica-based materials.     

Synthesis of zeolite rho: Aging temperature effect

This paper focuses on deciphering the gel aging temperature effect on the crystallization of zeolite rho(RHO). Increased gel aging temperature (from room temperature to 55°C and no aging) caused an increase in induction periods and decreased the crystallization rate during the synthesis of RHO. Other crystalline phases such as chabazite were formed along with increasing aging temperature. The largest crystal size of RHO increased proportionally to aging temperatures up to about 9 m. These results suggest that aging temperature greatly affected the crystallization, the crystal sizes, the purity and the formed crystalline phases during the synthesis of zeolite rho. This study suggests that most of RHO nuclei are formed during gel aging and their formation is depressed by the increased aging temperatures.     

Selective separation of copper and nickel by solvent extraction using LIX 984N

Selective separation of copper and nickel from ammoniacal/ammonium carbonate medium was carried out by using LIX 984N diluted with deodourised kerosene. The study of the influence of equilibration time, equilibrium pH, extractant concentration and selective stripping of copper and nickel has been optimized. It was found that both the metal extractions were unaffected by the changes in pH. Nickel extraction equilibrium was reached at a longer contact time than that for copper and nickel extraction depends greatly on the extractant concentration in the organic phase. Co-extraction, ammonia scrubbing and selective stripping of copper and nickel were performed for a solution containing 3 g dm^− 3 each of copper and nickel and 60 g dm^− 3 ammonium carbonate. The extraction and the percentage of stripping for nickel and copper were almost quantitative.     

Conditions for entrainment into a FeOx containing slag for a carbon-containing particle in an entrained coal gasifier

When incompletely gasified coal particles impact the slag layer in an entrained slagging gasifier, a situation will arise where the particles will either get engulfed by the slag or re-entrained into the circulating gas. This will be determined by a balance of forces acting on the particle which in turn is governed by the slag and particle properties, and pertinent gasifier conditions, namely temperature, and particle impact velocity. In this paper a model is introduced that takes into account, the drag-, capillary-, and added mass-forces and predicts the behavior of spherical particles of different sizes and slags of different FeO_x contents. The model predicts that particles either get completely submerged, settle at an incompletely separated position, or oscillate at the interface. A sensitivity analysis was performed showing that for a particle of certain size and impact velocity, submersion is most strongly promoted by a low slag viscosity (largely influenced by FeO_x content) and contact angle (determined by whether or not-reactive wetting and liquid Fe formation occurs).