The fluid mechanics and heat transfer characteristics of film cooling are three-dimensional and highly complex. To understand this problem better, an experimental study was conducted in a low-speed wind tunnel on a row of six rectangular jets injected at 90 deg to the crossflow (mainstream flow). The jet-to-crossflow velocity ratios (blowing ratios) examined were 0.5, 1.0, and 1.5, and the jet spacing-to-jet width ratio was 3.0. No significant temperature difference between jet and crossflow air was introduced. Mean velocities and six flow stresses were measured using a three-component laser-Doppler velocimeter operating in coincidence mode. Seeding of both jet and cross-stream air was achieved with a commercially available smoke generator. Flow statistics are reported in the form of vector plots, contours, and x-y graphs, showing velocity, turbulence intensity, and Reynolds stresses. To complement the detailed measurements, flow visualization was accomplished by transmitting the laser beam through a cylindrical lens, thereby generating a narrow, intense sheet of light. Jet air only was seeded with smoke, which was illuminated in the plane of the light sheet. Therefore, it was possible to record on video tape the trajectory and penetration of the jets in the crossflow. Selected still images from the recordings are presented. Numerical simulations of the observed flow field were made by using a multigrid, segmented, k–ε CFD code. Special near-wall treatment included a nonisotropic formulation for the effective viscosity, a low-Re model for k, and an algebraic model for the length scale. Comparisons between the measured and computed velocities show good agreement for the nonuniform mean flow at the jet exit plane. Velocities and stresses on the jet centerline downstream of the orifice are less well predicted, probably because of inadequate turbulence modeling, while values off the centerline match those of the experiments much more closely.
In a search for alkane candidates for 193 nm immersion fluids, several alkanes and cycloalkanes were
synthesized, purified, and screened to ascertain their absorption at 193 nm, refractive index, and temperature
dispersion coefficient in the context of the actual application. In general, cycloalkanes, and more specifically
polycycloalkanes, possess a higher refractive index than do linear alkanes. Decalin, cyclodecane,
perhydrophenanthrene (PHP), perhydrofluorene (PHF), and perhydropyrene (PHPY) are examined as
potential second- and third-generation immersion fluids. The use of perhydropyrene, which possesses a
high refractive index of 1.7014 at 193 nm, may be limited as an immersion fluid because of high absorption
at 193 nm. Mixtures of cycloalkanes can lead to a higher enhancement of the refractive index together
with a decrease of the viscosity. Exhaustive purification of the fluids is a critical step in determining the
real absorption of the different fluids at 193 nm. Even very small traces of impurities possessing a high
absorption coefficient at 193 nm can lead to an unacceptably high level absorption at 193 nm, previously
incorrectly attributed to the alkane instead of the absorbing impurities.
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