“…Before a measurement, the velocity and directional characteristics of the probe must be calibrated in defined flow conditions. The calibration procedures and a more detailed description of the measuring technique are given elsewhere (Menzel et al, 1989; Menzel, 1990). In addition, the local gas holdup was measured by the well-known one-point electroconductivity microprobe technique (Serizawa et 1975; etc.).…”