Process of transition to turbulence in an oscillatory turbulent pipe flow

Turbulence occurred in the major arteries can be important in the development of a variety of pathophysiological conditions including atherosclerosis, hemolysis, thrombosis, etc. We tried to characterize the effects of unsteadiness in the transition process in order to understand the nature of turbulence in the aorta. Experiments were conducted in a purely oscillatory pipe flow using hot wire anemometer and analyzed by means of statistical methods based on an ensemble averaging technique, also calculated the local phase power spectrum with moving window. The transition to turbulence occurred in the middle of the deceleration phase. The turbulent intensity began to rise and reached the maximum within the transition process. In the neighborhood of the wall the intensity after the transition increased to three times as large as that in central region. It is noted that the Kurtosis increased significantly before the transition process at the edge of stokes-layer. The integral scale also rises during the acceleration phase and shows a sudden decay after the transition. There appears to be a remarkable increase of integral scale at the middler region in the cross section. The large eddies generated in the outer region of stokes-layer causes the energy transport to small eddies during the transition process.