抄録
Micro bubble has unique characteristics.One of them is drag reduction.The drag reduction of pipe flow has been studied with the addition of the surface-active agents and/or polymer.They may pollute the environment after disposition,therefore the limitation occurs in the using them for the practical fractional drag reduction of pipe flow.Micro bubbles generated from air have no possibility of such pollutions.In this study,the frictional pressure drop is measured in vertical pipes.When micro bubbles are generated by the pressurized dissolution method,the drag reduction is not remarkable.On the other hand,when micro bubbles are generated by the shearing flow method,the drag reduction clearly occurs.The effects of void fraction and Reynolds number on the drag reduction are not clear.
