The physical, mechanical, and thermal properties of polycrystalline TiB2 are examined with an emphasis on the significant dependence of the properties on the density and grain size of the material specimens. Using trend analysis, property relations, and interpolation methods, a coherent set of trend values for the properties of polycrystalline TiB2 is determined for a mass fraction of TiB2 ⩾ 98 %, a density of (4.5±0.1) g/cm3, and a mean grain size of (9±1) µm.

A self-consistent, single-valued representation of the major physical, mechanical, and thermal properties of a sintered α-SiC is presented. This comprehensive set of properties is achieved by focusing on a narrowly defined material specification in which boron and carbon are used as sintering aids to produce a dense ceramic (⩾98% of the theoretical maximum density) with a grain size of (6±2) μm. Such a representation is highly desirable in applications of concurrent engineering practices and for the increasing use of electronic processing of product specifications.

An empirical model spectral line shape has been considered for the R1 and R2 fluorescence lines of ruby to investigate the possibility of improvements in the precision and the reproducibility of pressure measurements at high temperature using the ruby fluorescence technique. Other advantages, such as using the ruby method to obtain a simultaneous measurement of pressure and temperature or to obtain quantitative estimates of pressure distributions under nonhydrostatic conditions, have also been considered.

Abstract:The interaction between oscillating-grid turbulence and a solid, impermeable boundary (positioned below, and aligned parallel to the grid) is studied experimentally. Instantaneous velocity measurements, obtained using two-dimensional particle imaging velocimetry in the vertical plane through the centre of the (horizontal) grid, are used to study the effect of the boundary on the rms velocity components, the vertical flux of turbulent kinetic energy (TKE), and the terms in the Reynolds stress transport equation. Identified as a critical aspect of the interaction is the blocking of a vertical flux of TKE across the boundary-affected region. Terms of the Reynolds stress transport equations show that the blocking of this energy flux acts to increase the boundarytangential turbulent velocity component, relative to far-field trend, but not the boundarynormal velocity component. The results are compared with previous studies of the interaction between zero-mean-shear turbulence and a solid boundary. In particular, the data reported here is in support of viscous and 'return-to-isotropy' mechanisms governing the intercomponent energy transfer previously proposed, respectively, by Perot & Moin [J. Fluid Mech., vol. 295, 1995, pp. 199-227] and Walker et al. [J. Fluid Mech., vol. 320, 1996, pp. 19-51], although we note that these mechanisms are not independent of the blocking of energy flux and draw parallels to the related model proposed by Magnaudet [J.

Particle resuspension and erosion induced by a vortex ring interacting with a sediment layer was investigated experimentally using flow visualization (particle image velocimetry), high-speed video, and a recently developed light attenuation method for measuring displacements in bed level. Near-spherical sediment particles were used throughout with relative densities of 1.2–7 and diameters (d) ranging between 90 and 1600 μm. Attention was focused on initially smooth, horizontal bedforms with the vortex ring aligned to approach the bed vertically. Interaction characteristics were investigated in terms of the dimensionless Shields parameter, defined using the vortex-ring propagation speed. The critical conditions for resuspension (whereby particles are only just resuspended) were determined as a function of particle Reynolds number (based on the particle settling velocity and d). The effects of viscous damping were found to be significant for d/δ<15, where δ denotes the viscous sublayer thickness. Measurements of bed deformation were obtained during the interaction period, for a range of impact conditions. The (azimuthal) mean crater profile is shown to be generally self-similar during the interaction period, except for the most energetic impacts and larger sediment types. Loss of similarity occurs when the local bed slope approaches the repose limit, leading to collapse. Erosion, deposition, and resuspension volumes are analyzed as a function interaction time, impact condition, and sediment size.