The Friction Factors of Oscillating Pipe Flows

In this study, the friction factors of oscillating pipe flows are experimentally investigated. As the oscillating pipe flow, the pendulation of water column in the special vertical U-tube, which has about the 2 m long horizontal straight foot pipe, is utilized. The results of experiments show that the momentary friction factors in the accelerating state are smaller and in the decelerating state are larger than that in steady state for each Reynolds numbers.