Abstract
The presence of particles modifies the stability of the flow transition process to turbulence in two-phase flow. The objective of the study is experimentally to elucidate the transition process of a plane vertical Poiseuille flow containing solid particles, focusing in particular on the effects of particle volume fractions. Reynolds number based on the channel half-width and centerline velocity was set at Re=2500, 3000, and the volume fractions of particles, φv, ranged from 4.0×10-6 to 1.2×10-5. The time series of velocity of both phases were measured by a modified LDV, so that the spectral evolution of small disturbances under two conditions (that is, the inherent and forced fluctuations with respect to the growth of the flow disturbance) could be invesigated to clarify the transition mechanism of two-phase flow. The results revealed that the presence of particles suppressed and enhanced the disturbances. Moreover, the evolutionary mechanism of disturbances can be explained by calculating the scale of the wavelength of the fundamental distufbance and the distance between particles.
