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The experimental study on flow characteristics of the turbulent falling film flowing along a vertical Perspex plate was carried out using ultrasonic Doppler velocimetry (UDV, a non-intrusive technique) at 1.85 × 104 ≤ Reynolds number of the liquid film (Rel ) ≤ 3.69 × 104. The instantaneous velocity of the turbulent falling film at different Rel was measured to investigate the velocity distribution, fluctuation range, turbulence intensity, and the flow behavior in falling films. The results showed that the increase of Rel reduced the length of the development region and accelerated turbulent falling films to a steady flow state. There were mainly two reasons for the change of the velocity gradient in films: the amplitude of interfacial waves and the collision of the liquid that has different velocity directions. When the falling films were away from the inlet, the mass transfer within falling films may be dominated by the lateral movement rather than Rel .

Radial bubble velocities, chord lengths, and local gas holdups were measured by a dual-tip conductivity probe in a slender particle-containing scrubbing–cooling chamber. The annulus region of the bubbling bed was divided into three regions according to the radial distributions of bubble velocity, bubble size, and local gas holdup. Bubble velocity distributions were obtained by the kernel density estimation, and the relationships between mean bubble velocity and diameter were discussed. The interfacial area was calculated by the size distribution of total bubbles in the bed which was transformed from that of total bubbles touching the probe by an analytical transformation method. Effects of superficial gas velocity, fiber volume fraction, and aspect ratio on the distributions of bubble velocity and interfacial area were discussed. The experimental interfacial area values were in good agreement with the calculated ones obtained by the modified Besagni and Inzoli correlation.