Liquid Turbulence Spectra in Two-Phase Bubbly Flow Under Turbulence Augmentation and Suppression Conditions

An experimental investigation was performed in air-water bubbly flow to study the liquid turbulence spectra in a 200mm diameter vertical pipe. A dual optical probe was used to measure the local void fraction and bubble diameter while the liquid velocities were measured using hot-film anemometry. Experiments were performed at two liquid superficial velocities of 0.2 and 0.68m/s for gas superficial velocities in the range of 0 to 0.18m/s. Generally, as the void fraction increases there is a turbulence augmentation. However, a turbulence suppression was observed near the pipe wall at the higher liquid flow rate for low void fraction. In the augmentation case, the turbulence spectra showed a significant increase in the energy at the wave number range comparable to the bubble diameter. In the suppression case, the spectra showed that suppression initially occurs at the low wave number range and then extends to higher wave numbers as suppression increased.