This work presents results from detailed chemical kinetics calculations of electronically excited OH (A 2 Ȉ, denoted as OH*) and CH (A 2 ǻ, denoted as CH*) chemiluminescent species in laminar premixed and non-premixed counterflow methane-air flames, at atmospheric pressure. Eight different detailed chemistry mechanisms, with added elementary reactions that account for the formation and destruction of the chemiluminescent species OH* and CH*, are studied. The effects of flow strain rate and equivalence ratio on the chemiluminescent intensities of OH*, CH* and their ratio are studied and the results are compared to chemiluminescent intensity ratio measurements from premixed laminar counterflow natural gas-air flames. This is done in order to numerically evaluate the measurement of equivalence ratio using OH* and CH* chemiluminescence, an experimental practice that is used in the literature. The calculations reproduced the experimental observation that there is no effect of strain rate on the chemiluminescent intensity ratio of OH* to CH*, and that the ratio is a monotonic function of equivalence ratio. In contrast, the strain rate was found to have an effect on both the OH* and CH* intensities, in agreement with experiment. The calculated OH*/CH* values showed that only five out of the eight mechanisms studied were within the same order of magnitude with the experimental data. A new mechanism, proposed in this work, gave results that agreed with experiment within 30%. It was found that the location of maximum emitted intensity from the excited species OH* and CH* was displaced by less than 65 and 115 ȝm, respectively, away from the maximum of the heat release rate, in agreement with experiments, which is small relative to the spatial resolution of experimental methods applied to combustion applications, and, therefore, it is expected that intensity from the OH* and CH* excited radicals can be used to identify the location of the reaction zone.Calculations of the OH*/CH* intensity ratio for strained non-premixed counterflow methane-3 air flames showed that the intensity ratio takes different values from those for premixed flames, and therefore has the potential to be used as a criterion to distinguish between premixed and non-premixed reaction in turbulent flames.

Calculated values of the three velocity components and measured values of the longitudinal component are reported for the flow of water in a 90° bend of 40 x 40mm cross-section; the bend had a mean radius of 92mm and was located downstream of a 1[sdot ]8m and upstream of a 1[sdot ]2m straight section. The experiments were carried out at a Reynolds number, based on the hydraulic diameter and bulk velocity, of 790 (corresponding to a Dean number of 368). Flow visualization was used to identify qualitatively the characteristics of the flow and laser-Doppler anemometry to quantify the velocity field. The results confirm and quantify that the location of maximum velocity moves from the centre of the duct towards the outer wall and, in the 90° plane, is located around 85% of the duct width from the inner wall. Secondary velocities up to 65% of the bulk longitudinal velocity were calculated and small regions of recirculation, close to the outer corners of the duct and in the upstream region, were also observed.The calculated results were obtained by solving the Navier–Stokes equations in cylindrical co-ordinates. They are shown to exhibit the same trends as the experiments and to be in reasonable quantitative agreement even though the number of node points used to discretize the flow for the finite-difference solution of the differential equations was limited by available computer time and storage. The region of recirculation observed experimentally is confirmed by the calculations. The magnitude of the various terms in the equations is examined to determine the extent to which the details of the flow can be represented by reduced forms of the Navier–Stokes equations. The implications of the use of so-called ‘partially parabolic’ equations and of potential- and rotational-flow analysis of an ideal fluid are quantified.

The velocity and flux of spherical glass beads with nominal diameters of 200, 80 and 40 μm have been obtained by phase-Doppler anemometry in a round unconfined air jet over the first 28 diameters. The jet diameter was 15 mm and the exit velocity was 13 ms -1 giving a Reynolds number of 13 000 and a timescale of 1.15 ms, which increased quadratically with axial distance: the bead inertial time constants were 298, 48 and 12 ms. The purposes of the experiments were to quantify the velocity and flux characteristics of the beads and of the gas phase in the presence of the beads as a function of bead diameter and of the mass loading in the jet nozzle. Due to the large inertia of the 200 μm beads, the mean bead velocity downstream of the exit of the jet was constant and independent of mass loading up to 0.37 and the axial root mean square (r.m.s.) bead velocity decayed by about one-fifth : at the exit of the jet, the axial r.m.s. bead velocity was higher than that of the corresponding clean jet. The mean centreline velocity of the 80 μm beads decayed to about one-half of the bead exit velocity by 28 diameters downstream and was independent of mass loading up to 0.86. The decay rate of the mean gas centreline velocity in the presence of the beads reduced as the loading increased because of momentum transfer from the discrete to the gaseous phase. The axial r.m.s. velocity of the beads was comparable to that of the gas phase and both decreased with increasing loading and the rate of spread of the half width of the jet increased with increasing loading. For the 40 μm beads, the decay rate of the mean centreline velocity of the beads decreased with increasing loading and, in contrast to the 80 μm beads, the rate of spread decreased with increasing loading up to 0.80. The axial r.m.s. velocity of the beads became largest at a position downstream of the nozzle exit, which moved downstream with increasing loading and was larger than the axial r.m.s. velocity of the clean jet, although the beads were not expected to be responsive to the frequencies of the energy-containing eddies. The bead axial r.m.s. velocity was more than twice as large as the radial r.m.s. velocity and the correlation coefficient of the cross correlation was larger than that of the clean jet. The large bead turbulence, anisotropy and strong correlation coefficient are explained by the superposition of bead trajectories from regions of different bead mean velocity and are not because of acquisition of axial turbulent motion from the gaseous phase.

We demonstrate the potential of highly-doped semiconductor epilayers as building blocks for mid-infrared plasmonic structures. InAs epilayers are grown by molecular beam epitaxy and characterized by Hall measurements and optical techniques. We show that the plasma frequency of our material can be controlled across a broad range of mid-infrared frequencies. Subwavelength disks are fabricated out of our material, and localized plasmonic resonances are observed from these structures. Experimental results are compared to both numerical simulations and a simple quasistatic dipole model of our disks with good agreement.

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