マイクロバブルを含む円管内流の抵抗係数測定

抄録

It is known that the critical Reynolds number of turbulent transition in the straight-pipe flow is about 2300. However, it is reported that turbulent transition is delayed when there are micro-bubbles in water. And the drag was reduced in same Reynolds number range. To confirm the effect of the drag reduction, it is important to make a laminar flow at the entrance of the test section. To keep flow stable, we ensure the long entrance section of about 4 m. Then we measured the differential pressure and calculated friction factor in the straight pipe with circular cross section. The inner diameter of the pipe is 20 mm. In this experiment, turbulent transition took place at the same Reynolds number range when we use water with micro-bubbles and without micro-bubbles.