Settling velocity and porosity of large suspended particle

The settling velocity of large suspended particles which were formed in turbid water due to re-coagulation was measured in the laboratory, and the relation to the particle diameter which was taken as that of a sphere with the same volume, was obtained. This is, however, different from Stokes' law in regard to the relation to the particle diameter, though the Reynolds numbers are almost in the region of Stokes' law. This may be caused by the change of apparent density with the particle diameter. Stokes' law for a porous particle was applied to the settling velocity and the diameter found was compared with the real diameter to obtain an expression for the porosity. From the result, it is considered that the large suspended particles of “marine snow” have a porosity of above 90 %.