1989 Volume 50 Issue 2 Pages 115-128
The behavior of suspended matter in the gravity wave field is investigated by using a finite amplitude wave theory, under the assumption that the mixture of suspended matter and fluid behaves like a sort of fluid (fluid mixture) with density varying linearly with suspended matter concentration.
Based on the governing equations for suspended matter and fluid mixture, which is inviscid and irrotational, a numerical analysis is carried out to obtain the flow velocity of the fluid mixture, suspended matter concentration and suspended matter transport rate for various non dimensional parameters. The main results are as follows : 1) The amplitude of flow velocity is nearly equal to that for the case in which the density of the fluid mixture is assumed to be constant (ρ=constant), the difference being within 5%. 2) Mean suspended matter concentration averaged over a wave period decreases exponentially with the height above the bottom. 3) Amplitude of the variation of suspended matter concentration is larger near the bottom when the non-dimensional diffusion coefficient Dz is smaller, and it is larger near the water surface when Dz is larger. 4) Mean suspended matter concentration is almost equal to that for ρ=constant, and the amplitude of the variation of suspended matter concentration is smaller than that for ρ=constant by 10% at most near the bottom. 5) Suspended matter transport rate in the horizontal direction averaged over a wave period increases rapidly as ws/Dz (ws : non- dimensional falling velocity) becomes smaller and is smaller than that for ρ=constant, by 20% at most for smaller values of ws/Dz. 6) Computed results with respect to mean suspended sediment concentration agree well with the experimental data of HOM-MA et al. (1964) and NODA and IWASA (1971) except for those in close proximity to the bottom.
