Slip velocities of solid particles in turbulently agitated liquid

Separation of nonmetallic inclusion by flotation is the most important method for the clean steel production. In order to clarify the capability of inclusion separation in tundish or mould for continuous caster. In the present study, the terminal velocities of glass beads (density p=2410kg/m³) and silica balloons (p=580kg/m³) were measured in a mechanically agitated water vessel. Firstly the axial distribution of particle concentration in the agitated water was measured from a scattered light intensity obtained by a silicon photodiode. The ratio of particle terminal velocity to turbulent diffusivity, v_t/D_t, was derived from the axial distribution of particle concentration by comparing with the theoretical distribution obtained by the equation of balance between flotation/sedimentation flux and diffusion flux. And then, the value of D_t, was measured by the complete mixing time of the vessel and consequently the value of v _t was calculated from the ratio, v_t/D_t. Finally the values of v_t were correlated with several variables like particle diameter, densities of particle and water, energy-dissipation rate, etc., and a dimensionless correlation of drag coefficient was derived. From this correlation, relation between the velocity of ascending Al₂O ₃ particle in liquid steel and particle diameter were estimated at various values of energy-dissipation rate.