Transport model of active particles in a tidal wetland flow.

• A model is given for migration of active particles in a tidal wetland flow. • An analytical solution is derived for mass distribution of active particles. • An analytical solution is given for moving velocity of active particles. • A numerical analysis is performed for longitudinal dispersion coefficient. • Effects of parameters on dispersion of active particles are given. A concentration transport model has been formulated to characterize the transport of a mass of self-propelling active particles in an unsteady wetland flow at the phase-averaged scale. The vertical distribution and motion of mass center are rigorously derived for an active-particle cloud in the tidal wetland flow by use of the concentration moment method, while the longitudinal dispersivity is calculated by means of finite difference method. It is found that the distribution of total quantity of active particles in each streamline in the tidal wetland flow is identical to that in the fully developed wetland flow. The velocity and longitudinal dispersivity of mass center of the active-particle cloud eventually reach a stable oscillatory status for the case of tidal wetland flow rather than an asymptotic constant velocity which occurs in the steady wetland flow. The effects of dimensionless parameters on the amplitude, phase and period of the velocity of mass center and longitudinal dispersivity are discussed in detail for the active-particle cloud in the tidal wetland flow. [ABSTRACT FROM AUTHOR]