Abstract
Generation and growth of isolated turbulent puff and slug in the initial stage of a transitional pipe flow of dilute surfactant (C_<14>TABr) water solution were investigated by LDV and wall pressure measurement. The experiment was carried out using straight grass tubes of inside diameter D=2.61mm and total length L=1527mm and D=5.02mm and L=2712mm. Large perturbation was introduced by a ring-shaped roughness element installed at a downstream location of 77D from the pipe entrance. The puff generated at larger concentration than 260ppm and the critical Reynolds number, at which the puff began to generate, increased with the concentration.
