Viscosity measurements of GaInSn eutectic alloys were performed in a homebuilt device for low (9%) and high (95%) relative humidity for shorter (450 min) and longer (1800 min) time periods. At constant exposure time a characteristic increase of viscosity is observed with increasing humidity. For high humidity, high viscosity is obtained after a short time.Assuming that the measured viscosity change is strongly related to the absorption of oxygen, XPS was applied to the chemical and quantitative analysis of differently prepared samples. In all cases, Ga is predominantly oxidized at the surface whereas Ga atoms in the metallic state are located deeper inside. Besides Ga 2 O 3 (the most stable oxide phase), the less stable Ga 2 O is detected. Indium and tin are almost stable in their metallic state. With increasing humidity the thickness of the oxide film increases in our case from about 19Å to 25Å, assuming a layer-by-layer model. The presented results confirm our assumption of the increase in viscosity of the GaInSn system as a consequence of the preferential oxidation of gallium in the near-surface region.

Stereoscopic particle image velocimetry and planar laser induced fluorescence measurements of hydroxyl radical are simultaneously applied to measure, respectively, local turbulence intensities and flame front position in premixed ethylene-air flames stabilized on a bluff body. Three different equivalence ratios, 0.55, 0.63, and 0.7, and three different Reynolds numbers, 14 000, 17 000, and 21 000, are considered. Laser measurements were made for five different flame configurations within the ranges above and in the corresponding cold flows. By comparing the measurements of the cold and the corresponding hot flows, the effect of heat release on the turbulence and its interaction with the flame front is studied. All the flames are in the thin reaction zone regime. Typical flow features forming behind the bluff body are observed in the cold flows, whereas in the reacting flows the mean velocities and thus the shape, size, and characteristics of the recirculating eddy behind the bluff body are strongly influenced by the heat release. The strong acceleration across the mean flame and the radial outward shift of the stagnation plane of the recirculating eddy yield negative radial velocities which are absent in the corresponding cold flow cases. The spatial intermittency of the flame front leads to an increase in the turbulent kinetic energy. Although a decrease in the mean and rms values of the strain rate tensor e ij components is observed for the reacting case as one would expect, the local flow acceleration across the flame front leads to a substantial increase in the skewness and the kurtosis of the probability density functions ͑PDFs͒ of e ij components. The turbulence-scalar interaction is studied by analyzing the orientation of the flame front normal with the eigenvectors of e ij . The PDFs of this orientation clearly show that the normals have an increased tendency to align with the extensive strain rate, which implies that the scalar gradients are destroyed by the turbulence as the scalar isosurfaces are pulled apart. This result questions the validity of passive scalar turbulence physics commonly used for premixed flame modeling. However, the influence of Lewis number on this alignment behavior is not clear at this time.

The shadowgraph method is applied to thermal convection experiments and electro-hydrodynamic convection (EHC) in nematic liquid crystals. In both cases convection leads to a spatially periodic field of the refractive index causing a spatially periodic intensity modulation of parallel light passing the cell. Close to the onset of convection the temperature or director field is given by linear stability analysis. Knowing these functions the determination of their amplitudes becomes possible by means of the shadowgraph method, The method is demostrated using various examples of thermal and EHC convection experiments.

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The design and experimental characterization of a burner is described, which has favourable characteristics for the accurate calibration of a range of optical thermometry techniques. The burner supports stable laminar flames and combines many of the advantages of several widely used burner designs without their disadvantages. It permits the application of point measurement techniques, line-of-sight techniques and planar imaging techniques; trace species, such as metal atoms, can be easily introduced into the flame. The implementation of the burner is described, followed by the presentation of data obtained from coherent anti-Stokes Raman scattering (CARS) measurements and numerical simulations. Spatially resolved measurements were performed over the entire flame profile at three different stoichiometries and factors causing systematic and random errors are described in detail. Measurement errors on mean temperatures were determined to be less than 1%. The shot-to-shot measurement precision was determined to be 3.5-4.0% (FWHM of temperature probability density function). The burner design together with the data presented in this paper can be used for the validation and calibration, respectively, of a variety of combustion thermometry techniques. Complete details of the burner design together with the obtained temperature data will be provided on the World Wide Web. Other researchers intending to validate and calibrate their own laser-based thermometry techniques will be able to cost-effectively reconstruct this burner and adopt the characterization presented here, thus being able to apply it without the need of their own basic validation. The authors are confident that a reconstructed burner, which is applied under the same conditions, will yield the same high level of accuracy and precision as that presented in this paper.