Vertical concentration distribution of fine settling particles in a pulsatile laminar open channel flow

Abstract

Sedimentation in river and drainage systems frequently increases flood risks, making the study of particle dispersion crucial for effective flood damage control. In the present research, the transport of fine settling particles in a laminar, periodic flow through an open channel is analytically investigated using the multi-scale homogenization method. To investigate how settling velocity affects the dispersion process of fine particles in a tidal wetland, Dhar et al. (2022) studied the dispersion coefficient and mean concentration of the settling particles applying the method of moments. The mean and transverse real concentration distributions of settling particles are analytically derived from the governing equation, and the influence of settling velocity, oscillation Reynolds number, and Schmidt number on the dispersivity and concentration profile of the settling particles is investigated. The results show a vertical non-uniformity of longitudinal concentration distribution due to the introduction of settling velocity. It is also observed that the sedimentation effect for purely oscillatory flow is negligibly small compared to that of the steady and oscillatory flow with a nonzero mean. Pulsatile behavior is observed in the difference rate profile between Taylor’s mean and present mean concentration. The study sheds light on the behavior of settling particles and can be useful for understanding sedimentation and wastewater treatment processes.