Response characteristics of optical probes

An optical probe capable of measuring local void fraction and interface velocities in water-air or water-steam environments was developed, constructed, and calibrated in an air-water loop. The probe was found to be sensitive to both the interface velocity and the phase present at the probe tip. The dependence of the output on the bubble velocity was related to a thin water film left on the probe tip during the passage of the bubble, whose thickness was increasing with the bubble velocity. The various probe tip geometry response characteristics were evaluated using a computer program.