Measurements have been made of the local heat transfer coefficients to an air flow downstream of an axisymmetric abrupt expansion in a circular pipe with a constant wall heat flux. The experimental technique uses an electrically heated thin gold film on a plastic substrate. The flow upstream of the expansion was unheated and fully developed. Runs were made with small diameter to large diameter ratios of 0.267 to 0.800 and over the Reynolds numbers range of 5,300 to 87,000 (based on downstream diameter). The results include measurements near the expansion corner region where no previous measurements have been reported. These provide clear evidence of a secondary recirculation. Comparisons are also made with previous experimental results in the region of reattachment.

It has been proposed to protect the structural walls of a future laser fusion reactor with a curtain or fluid-wall of liquid lithium jets. As part of the investigation of this concept, experiments have been performed on planar sheet water jets issuing vertically downward from slit nozzles. The nozzles were subjected to transverse forced harmonic excitation to simulate the vibrational environment of the laser fusion reactor, and experiments were run at both 1 atm and at lower ambient pressures. Linear stability theory is shown to predict the onset of the unstable regime and the initial spatial growth rates quite well for cases where the amplitudes of the nozzle vibration are not too large and the waveform is nearly sinusoidal. In addition, both the linear theory and a simplified trajectory theory are shown to predict the initial wave envelope amplitudes very well. For larger amplitude nozzle excitation, the waveform becomes highly nonlinear and nonsinusoidal and can resemble a sawtooth waveform in some cases; these latter experimental results can only be partially explained by existing theories at the present time.

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This paper describes an experimental technique for measuring the local heat transfer coefficient in complex flows. The technique employs a gold-coated plastic sheet to generate a nearly uniform wall heat flux. The sheet is mounted on an insulated substrate of the desired shape and heating is achieved by passing an electrical current through the gold coating. Three applications of this technique are described: heat transfer downstream of an abrupt expansion, heat transfer from a cylinder in crossflow, and nonuniform circumferential heating in a pipe. For each of these applications the effect of the wall conduction on the surface heat flux is evaluated and found to be small. The effect of nonuniformities in the gold coating, and of the resistance temperature coefficient, are also evaluated and likewise are found to be quite small. Methods of correcting for each of these small effects are presented for the above applications.

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