Particle Dynamics in a Turbulent Channel Flow by Lagrangian Measurements.

Abstract

Motion of solid particles in a fully-developed channel flow of water was investigated by Lagrangian measurement techniques. Digital particle image velocimetry and a CCD camera mounted on a moving shuttle with mean streamwise velocity of particle were used to detect particle motion and fluid along the particle path simultaneously. Five classes of particles were dispersed in the flow upstream of the test section. It was observed that a force due to fluid pressure gradient and viscous stresses can be dominant in a particle dynamic equation when particle density ratio was close to unity. Lagrangian velocity spectrum of particle which has the density ratio less than unity was found to be higher than that of fluid along the particle path in the low-wave-number region, which is consistent with theory by Mei (1996). Lagrangian autocorrelation of velocity of both heavier particle and fluid decreased rapidly with increasing values of the particle time constant.