Settling velocity of particles in a grid-generated turbulence

The purpose of this study is to examine the retardation of the settling velocity of a particle in the turbulent flow generated by an oscillating grid through a numerical simulation and a hydraulic experiment. First, we measured trajectories of glass beads in a grid-generated turbulence to verify the validity of the numerical simulation for particle behavior. Next, we examined the dynamic response of particles utilizing wavelet analysis and the relationship between the retardation of the mean settling velocity and the turbulent characteristic. As a result, we could identify low-frequency components that particles would easily follow, and high-frequency components that would affect the motion of particles in vertical fluid velocity fluctuations, respectively. Furthermore, it was found that the retardation of the mean settling velocity depends on the spectral distribution of high-frequency, and that the retardation rates increase with increases in turbulent intensity.