Host: The Japan Society of Mechanical Engineers
Name : Mechanical Engineering Congress,Japan
Date : September 11, 2016 - September 14, 2016
We examined pipe flow transitions to a turbulent puff, which is a local turbulence containing relaminarizing front and hardly fluctuating rear parts, against adding perturbation in a constant mass flux facility. Probability curve of the puff creation with respect to the intensity of perturbation displayed multiple thresholds for the transition at Reynolds number, Re = 1,900. Simple dye visualization confirmed that there is formation of hair-pin vortex array against the injecting small jet as the perturbations. Velocity field measurement by PIV elucidated that the transition does not depend on the intensity of hair-pin vortices represented by the circulation, but depends on place of the vortices. The vortices staying at the central region of the pipe keeps deformation of the base flow profiles and induces gradual transition in the downstream positions
