Diffusion

Abstract

If two liquids are to be mixed in macroscopic applications, it is usual to generate some turbulence which facilitates mixing very much. Turbulence is achieved when the Reynolds’ number Re becomes larger than approximately 1,500. The Reynolds’ number is the ratio of inertial and friction forces in a flow. The inertial forces are described by the product of the density ρ _F of the liquid, a characteristic length L of the vessel or a rigid structure in interaction with the flow, and the velocity v of the flow. The frictional forces are described by the viscosity η of the fluid:

$$\rm Re: = \frac{{{\rho_{\rm{F}}}\ L}}{\eta }v. $$

(335)