Detachment of Solid Particulate Soils in a Laminar Flow—Influence of Particle Diameter on the Detachment of Spherical Glass Particles

Experimental studies were made on detaching glass particles with a diameter of 4.0 ∼ 28.0 μm from a glass substrate using a double cylindrical washing device producing laminar flow. The force of particle removal was estimated from the viscosity resistance of the laminar flow imposed on the particles, and the relation between said force and the diameter of the particles was also examined. The greater the diameter of the par ticles, the more difficult their removal as given by the order of 4.0 < 28.0 < 22.2 < 17.6 < 12.8 < 7.6 μm, except in the case of 4.0 μm. The force F _{H ,1/2} of particle removal at 50% efficiency is shown in the ascending order of particle size, i.e., 7.6 < 4.0 < 12.8 < 17.6 < 22.2 < 28.0 μm, and its range falls in 1.17 ∼ 34.6 × 10 ^-4 dyn. For particles with a diameter of 12.8 μm or more, the force of removal per unit volume is almost constant, i.e., 3.01 ∼ 3.49 × 10 ^-7 dyn. The relation between the force of the particle removal and the hydrodynamic function could be graphically traced on the continuous line of locus, without exception, as the result of the calculation made in consideration of the intermolecular force acting between the particle and the sub strate.