Experimental investigation of turbulence structure in two-phase bubbly flow
The liquid-phase turbulent structure and the phase distribution of an air-water, bubbly, upward flow in a circular channel were investigated experimentally. The liquid-phase local flow parameters, such as mean liquid velocity, turbulent intensity and Reynolds stress, were measured, using both one- and two-dimensional hot-film anemometer probes. The void fraction, bubble frequency, bubble velocity and bubble size were measured by a dual-sensor resistivity probe. Statistical turbulence properties of the continuous phase, such as eddy scales, and dissipation and production rate of turbulent kinetic energy were obtained, using power spectral analysis. The experiments were conducted in a well-calibrated air-water testing loop. Data were taken by an on-line computerized data acquisition system. Two new phase-discrimination methods, which were based on threshold combinations of level and slope, were developed to identify the phases for both the hot-film anemometer and resistivity probes. Results indicate that the introduction of bubbles into the liquid stream promotes turbulence relative to the local velocity of each phase. However, increasing the liquid flow rate at constant gas flow rate lowers the relative turbulence, both in the liquid- and gas phase, over the whole cross-section. The mean bubble size ranged from 2 to 4 mm. The bubbles tended to migrate toward the wall. Thus, the void fraction, bubble frequency and bubble size, profiles showed distinct peaks near the wall and were relatively flat in the core in all test conditions investigated. Phase velocity and the turbulent intensity profiles for each phase separately depended in similar ways upon the superficial velocities of the phases. Liquid-phase turbulence suppression was found under high liquid flow and low void fraction conditions. The turbulent intensity and shear stress were suppressed by the bubbles, both in the axial and lateral directions.
- Research Organization:
- Northwestern Univ., Evanston, IL (USA)
- OSTI ID:
- 6901154
- Country of Publication:
- United States
- Language:
- English
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