Measurements have been made of the heat-transfer rate to the stagnation point of catalytic spheres and cylinders placed in the slow flow of dissociated oxygen produced in a glow-discharge tube. The use of a rapid-response thin-film heat-transfer gauge permitted operation in a transient mode; that is, a step function of atoms was produced by suddenly turning on the rf discharge. Use of this technique leads to small error in the measurement of heat transfer. Operating conditions, range of pertinent parameters, as well as flow tube and probe diameters were selected to conform with the results of the theoretical analysis for this flow. Specifically, the Reynolds number based on diffusion Ua/D, where U is the flow velocity, a is the probe radius, and D the diffusion coefficient, was varied from about 0.2–0.8, and the catalytic parameter K = kwa/D, where kw is the effective speed of the surface reaction, took on values from about 0.3–1.7. The freestream atom concentration was determined by the familiar NO titration technique. Comparison of the measurements with the theoretical results has led to the determination of surface catalytic efficiency of silver oxide and oxygen atoms and the O–O2 diffusion coefficient. These values are γ = 0.15±15% and Dp = 200 cm2/sec·mm Hg±30%. Preliminary measurements of catalytic efficiency of other metals are also presented.

Turbulent spots have been identified as a transition mechanism in shock tube boundary layer flows for a range of weak shocks at initial pressures near one atmosphere in air, using thin-film wall temperature gauges. The shape and growth rate of the spots is consistent with that found by other investigators in sub- and supersonic steady flows. A study of naturally occurring and artificially generated turbulent spots, and of flow tripping by two- and three-dimensional roughness elements, has shown the existence of an unconditionally stable region behind the shock, in which finite disturbances will not cause flow breakdown or transition to turbulence. The limit of this stable region is given by Reδ = 1.7 ± 0.3 × 103, based on boundary layer thickness at 99% of free-stream velocity. In the absence of artifical perturbations, laminar flow is seen to persist for times as much as a factor 5 longer than those seen by previous investigators. These maximum transition times were limited by flow tripping at wall discontinuities, and hence represent only a lower bound on the ultimate duration of laminar flow attainable in shock tubes.

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The ordinary glow-discharge tube has been used extensively to study both surface and gas-phase recombination rates, as well as chemiluminescent reactions, typically at room temperature. The combination of a glow-discharge flow tube with a shock-tube driver to provide a considerable extension of atom fluxes, temperatures, and densities for the study of these kinetic processes is described. In operation, the ordinary glow-discharge-tube situation appropriate to the particular process under study is first established and, then, a shock is propagated into the predissociated gas by a driver upstream of the rf region. Typically, the shock strength is less than that which causes further dissociation. Under these conditions, the effect of the shock is to compress, heat, and accelerate to high speed those species already in the glow tube. The high temperature and compression provide a means for studying the temperature dependence of gas-phase recombination processes and chemiluminescent reactions, while the high-speed flow, in increasing the atom flux, provides a means for studying surface-catalysis phenomena occurring on a short time scale (<1 msec). Application of the present technique to determine the temperature dependences of the NO–O and CO–O chemiluminescent reactions is described in considerable detail.

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