Is Velocity Gradient a Valid Turbulent Flocculation Parameter?

Abstract

The familiar Camp‐Stein equation for the root‐mean‐square velocity gradient G is widely used in the design of rapid mixing and flocculation facilities. The literature related to turbulent phenomena, power required in turbulent mixing, turbulent flocculation modeling, paddle configuration, and the impact of temperature on flocculation was reviewed and re‐analyzed, leading to the conclusions that G is only a valid parameter for the flocculation of particles smaller than the Kolmogoroff microscale of turbulence, which is not typical of common water or wastewater flocculation practice. Mean power input per unit mass to the two thirds power is a more appropriate flocculation parameter than G for common water and wastewater flocculation practice because the important turbulent eddies are larger than the Kolmogoroff microscale. This region of turbulent eddy flocculation should be independent of temperature, but dependent on paddle configuration.