BEHAVIORS OF FLUID MUD UNDER OSCILLATORY FLOW

Hiroyuki Yamanishi, Tetsuya Kusuda

Abstract


Characteristics of settling velocity of fine particles and movements and the mechanism of maintenance of the fluid mud layer under oscillatory flow are investigated to control the transport flux of suspended solids in estuaries and the coastal zone. Settling velocity of fine particles under oscillatory flow is reduced as a function of only the local concentration. Motion of fluid mud depends on shear stress acting on the interface between the overlying water layer and the fluid mud layer and the horizontal pressure gradient. Especially, the horizontal pressure gradient causes a phase lag between the overlying water layer and the fluid mud movements. Velocity profiles calculated by a linearized model agree well with the measured velocity profiles in spite of assuming the kinematic viscosity in the fluid mud layer to be homogeneous. The apparent viscosity in the fluid mud layer is approximately 200 times as large as that of pure water.

Keywords


oscillatory flow; fluid mud; mud

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