Turbulent Structure With Microbubbles Generated by Electrolysis in a Horizontal Channel Flow

The turbulent structure of flow field with microbubbles which is generated by electrolysis in a horizontal water channel is investigated at Reynolds number Re_m = 24000 (based on the channel height). Firstly, Shadow Image Technique (SIT) is applied to investigate the relation between the shape and the velocity of microbubbles. The experiments have been carried out at the current value 100mA, 200mA, 300mA. The amount of gas generated by electrolysis per unit time is estimated 1.89–5.67 mm³/s. The void fraction is 0.95 × 10⁻⁵ – 2.93 × 10⁻⁴ %. The mode of the equivalent diameter is 5–10 μm regardless of the condition of the current value. In contrast the mean of the equivalent diameter increases with the increasing of the current value. The mean streamwise velocity of microbubbles increases with the current value. Secondly, Particle Image Velocimetry (PIV) is applied to investigate the turbulent structure in a microbubble channel flow. The experiments have been carried out at the current value 250mA, 300mA. The streamwise mean velocity decreases with the increasing of the current value. The velocity normal from the wall increases by microbubbles. The turbulent intensity with microbubble is bigger than that without microbubble. The Reynolds shear stress with microbubble, however, is smaller than that without microbubble. The decreasing of contribution to the friction coefficient of the turbulent component is calculated about 6.4 % using FIK identify at a low void fraction 2.93 × 10⁻⁴ %. The increasing of the frequency of inner interaction and outer interaction causes the decreasing of Reynolds shear stress is clarified by quadrant analysis.