Abstract
The effect of drag reducing surfactant (C14TABr) additives on the transition in pipe flow has been investigated through pressure drop measurement, LDV measurement and flow visualization. The experiment was carried out using the glass tube of diameter D=5.02 mm and D=2.61 mm. Two types of flow were experimented upon : the flow that decreased background -turbulences as much as possible and the flow that was disturbed by a ring-shaped roughness element. In the flow of the former, the following was understood : within the range from Re=3 000 to 4 500, a temporary rapid increase in the friction factor appeared although the flow was quasi-laminar. In a concentration that exceeds 400 ppm, a turbulent transition happened gradually and vaguely, not drastically as Re increased. In the flow of the latter, the following was understood : although in the case of water a turbulent patch generated in the initial stage of the transition in Re>2450 was a turbulent slug, the present study suggests that in 260 ppm, the turbulent puff was generated in the initial stage of the transition in Re=3 500. Furthermore, turbulent patches were not generated in the concentration above 400 ppm.
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