A NUMERICAL SOLUTION OF THE FLOW AROUND A SPHERE IN A CIRCULAR CYLINDER

A numerical solution of the Navier-Stokes equations is presented for Poiseuille flow around an axially placed, fixed sphere in a circular cylinder. Streamlines and isovorticity lines are calculated from the governing equations for the strearnfunction and the vorticity. Isobars are calculated from a Poisson equation, derived from the Navier-Stokes equations. The pressure and vorticity distribution on the surface of the sphere, the additional pressure drop and the drag coefficients are presented. Solutions are obtained for Reynolds numbers up to 150 (based on cylinder diameter and mean velocity). The wall effects are examined by comparison with results of previous investigations for an unbounded flow around a sphere.     

DYNAMIC EFFECTS OF BUBBLE MOTION

The dynamic effects of the motion of single bubbles entrained in a liquid are investigated. Extensive original experimental results are presented on the pressures associated with the motion of large, isolated spherical cap air bubbles rising both freely and through constricting orifices in a vertical cylindrical pipe filled with quiescent water. The pressures, measured at the pipe wall, were found to be as high as the dynamic bubble pressure for translational bubble motion, and an order of magnitude larger for oscillatory bubble motion following bubble formation.     

Bacterial Proteinase Reduces Maturation Time of Dry Fermented Sausages

The effect of proteinases, from Lactobacillus paracasei subsp. paracasei NCDO151 and from Bacillus licheniformis (Alcalase, NOVO Nordisk), on the ripening of dry sausages was compared. Increased levels of starter bacteria, d-lactic acid, a sharper pH-drop and changes in chromato-graphic profiles (by gas chromatography/mass spectrometry) indicated that the enzyme from Lactobacillus paracasei accelerated the dry sausage ripening. This effect was not detected in sausages with the Alcalase enzyme. Higher sensory scores on maturity flavor, color, hardness and others, confirmed that sausages containing proteinase from L. paracasei showed the same maturity after 14 days as those without enzymes or with the Alcalase enzyme after 28 days.     

Accelerated ripening of dry fermented sausage by addition of a Lactobacillus proteinase

Accelerated ripening of dry sausage was investigated by adding two different concentrations of proteinase isolated from Lactobacillus paracasei ssp. paracasei NCD0151 to sausage mixtures. Sausages with proteinase showed a greater pH decrease and a greater increase in lactic acid formation, water loss, protein degradation and peptide formation than control, no enzyme, sausages. Changes were most pronounced in the sausages containing 12 Ug^-1 proteinase. Addition of proteinase caused a specific increase in glutamate, serine and lysine content. Sensory evaluation after 14 days of ripening showed a significant increase in flavour intensity, maturity flavour, acidity, bitter taste and hardness in the proteinase-containing sausages. Addition of proteinase induced changes earlier in the fermentation and ripening period than in the control, thereby indicating an acceleration of maturation.     

Grain-Boundary and Surface Segregation of Ba-Ti-O Phases in Rutile

The solubility of barium in rutile and the formation and morphology of second phase at external and internal surfaces of single-crystal and polycrystalline rutile (TiO,₂) have been studied for various heat treatments up to 1450°C and in several configurations of the barium source. It has been found that barium is not incorporated into the rutile lattice but instead forms an amorphous, quasi-liquid film of Ba-Ti-O at high temperature (=1400°C) which covers the grain boundaries and the external surfaces. On cooling or annealing at lower temperature (=1100°C) the continuous film breaks up to form isolated segregation patterns. Transport of the second phase by surface and grain-boundary diffusion is rapid and reversible by heat treatment.     

Mechanical Behavior of Samhire

The present state of the knowledge of the mechanical behavior of sapphire is reviewed. Sapphire deforms plastically at temperatures above 900°C, the most common mode of deformation being slip on the basal plane in the 〈11     0〉 direction. Under certain conditions, however, slip may occur on prism planes or twinning may occur. A yield point is often observed, which appears to be related to the multiplication of dislocations by a mechanism controlled by the motion of dislocations through the lattice, rather than by the tearing of dislocations from an impurity (or defect) atmosphere. The dynamics of yielding and flow is similar and can be expressed by either of two thermally activated equations. In one, the effect of stress is principally on the pre-exponential factor; in the other, its effect is principally on the activation energy. There are insufficient data to permit a positive decision between the two, or to positively identify the rate-controlling dislocation mechanism. For 60°-oriented crystals fracture generally occurs on a plane approximately normal to the tensile stress and the fracture surface is conchoidal. In the range 1100° to 1500°C, the tensile fracture stress decreases with increase in plastic strain, independent of temperature and strain rate. The mechanism of failure in this case seems to be the interaction of edge dislocations with pre-existing cracks.     

Phosphate-Bonded Talc: A Superior Block-Talc Substitute

Phosphate-bonded talc shows advantages over block talc, which indicates that it is a superior substitute for this strategically important raw material. A satisfactory product has been made using talc from domestic sources. It has been formed by various methods, such as dry pressing, hydrostatic pressing, or hot pressing. Some factors that control the properties of the end product have been investigated, and the mechanical and dielectric properties are compared with those of natural block talc.