An experimental study on laminar-turbulent transition in a pulsating pipe flow

Experiments were made to study the process of laminar-turbulent transition in the developing region of a pulsating pipe flow. Particular interest was placed upon the initial growth of velocity fluctuations near the pipe wall. Shown by the hot-wire velocity signals measured and the output signals of the MEMS thermal film sensors flushed with the wall surface, the initial disturbances appeared intermittently like a packet of waves in every cycle of pulsation. The characteristics of the disturbances were further analyzed with the Hilbert-Huang Transformation (HHT), from which the characteristic frequency could be identified quantitatively. The results obtained provide valuable information relevant to understanding the initial laminar-turbulent transition in a pulsating pipe flow.