Limits of fully turbulent flow in a stirred tank

In a stirred tank, the flow has been considered fully turbulent for all Reynolds numbers greater than 2x10(4). In fully turbulent flow, the power number is constant, and increases in the Reynolds number do not affect the shape of the dimensionless velocity profiles. Both of these conditions are met for Re(1)greater than or equal to 2x10(4) close to the impeller, where the velocity profiles scale with D/2 and V-TiP This paper shows a new method for scaling velocities in a stirred tank in which the velocity profiles in the bulk of the tank are scaled with the characteristic velocity and length scale in the wall jet that is formed along the baffle of the tank. By means of this scaling argument it was determined that fully turbulent flow in the top third of the tank does not exist for Re-I=2x10(4). This is important for design of vessels where H>T, since the lack of fully turbulent flow means that the velocity profiles will be affected both by the characteristic velocity scale and the fluid viscosity. It also provides some insights required for the characterization of turbulence and the application of computational fluid dynamics (CFD) to conditions in the bulk of the tank.