关键词: shear dispersion, oscillatory flow, memory function, contaminant contraction

Abstract: If the vertically-mixing time is comparable with that of period oscillatory current, the contaminant contraction may occur. The coefficient of shear dispersion is negative (singularity). According to the two-dimensional delay-diffusion equation derived by the author^[7]: where u(t),v(t) are vertically-averaged velocities, the equations for X(t), Y(t), central displacement, dispersion tensor, had been derived. is positive when t is small. If the is large, the memory functions may be negative. Also the expressions for and X, Y had been obtained.

Key words: shear dispersion, oscillatory flow, memory function, contaminant contraction