Physical Oceanography, Vol. 16, No. 4, 2006
KINETICS OF SUSPENSIONS IN THE COASTAL ZONE OF THE SEA
V. A. Ivanov, V. Z. Dykman, and O. I. Efremov
We present the results of development of the kinetic approach to the description of motion of
suspended solid particles in the coastal zone. By using the probability distribution function of
particles over the settling velocities, the corresponding distributions of terrigenous particles are
constructed for broad ranges of their diameters. We propose a model of the vertical profile of
mass concentration of suspensions based on the relationship between the parameters of the prob-
ability distribution and the characteristics of the velocity field of the surface waves in the shal-
low-water zone. The requirements to the composition of the “Donnaya Stantsiya” measurement
system (following from theoretical concepts) are analyzed.
In analyzing the grain-size composition of suspensions in the bulk of oceanic waters, the attention of the re-
searchers is mainly given to the difficulties connected with large variations of the densities of particles of differ-
ent diameters and possible mass flows through the spectrum caused by the complex mechanisms of interaction of
various biogenic fractions [1, 2]. In the coastal zone, where terrigenous suspensions are predominant, the solid
particles have, for the most part, the same density. Under these conditions, the kinetics of the processes of sus-
pension and sedimentation of particles is significantly simplified and it could be expected that the analyzed prob-
ability distribution functions fairly well describe the physical nature of the phenomenon and, hence, can be used
as a convenient tool for the analysis of motion of suspensions under various hydrological conditions.
The behavior of a system of discrete particles in a turbulent flow of fluid depends on the concentration of
these particles and their relative sizes (as compared with the scale of turbulence). For low concentrations, the in-
teraction between particles can be neglected and each particle can be regarded as a single object in the turbulent
flow. As a rule, it is also supposed that the particles are small as compared with the smallest wavelength of the
turbulent motion. Most likely, these approximations remain true for all depths in the coastal zone, except the
lowest bottom layer whose thickness is equal to several centimeters .
Even under these assumptions, the equations of motion of a solid particle in an inhomogeneous flow are
quite complicated . Therefore, the experimental estimates demonstrating the decrease in the mean settling
velocity of particles in a pulsating fluid W
as compared with their settling velocity in immobile water W are
of great importance .
The lowered mean settling velocity of particles in the presence of turbulence W
is expressed via the velo-
city W as follows:
where Q is a coefficient guaranteeing proper dimensionality (independent of W
), ε is a parameter characteriz-
ing the ratio of the mean-square value of inertial acceleration in the turbulent flow α to the acceleration g
particle with density ρ
falling in a fluid with density ρ,
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol.
Translated from Morskoi Gidrofizicheskii Zhurnal, No.
49–61, July–August, 2006. Original article submitted April 4, 2005; re-
vision submitted April 19, 2005.
234 0928-5105/06/1604–0234 © 2006 Springer Science+Business Media, Inc.