Recirculating Flow Region Research Articles

The base-flow and near-wake problem at very low Reynolds numbers - Part 1. The Stokes approximation

The general solutions of the Stokes approximate equations of motion are derived for two-dimensional and axisymmetric flows in the half-space x > 0, for an arbitrarily given velocity field in the plane x = 0. There is assumed to be no solid surface in the half-space. According to whether the velocity at infinity is zero or not, the solutions can be said to describe either jet-type or wake-type flows. Only the latter category is considered; numerical examples are worked out and properties of the base flow at very low Reynolds numbers are investigated. A recirculating flow region may exist, but the flow properties are not sensitive to this feature.

Concentration fluctuations in a stirred baffled vessel

AbstractA stirred vessel is maintained in a quasisteady state by continuously introducing water and a conductive tracer solution and continuously removing the resulting mixture by overflow. Detailed properties of the system are elucidated by measuring tracer concentration changes with a conductivity probe in a volume element of the order of 0.3 cu. mm. By the use of suitable electronic equipment the following statistical concentration parameters are measured in experiments with three diameters of flat‐bladed turbines and with a tenfold range of rotational speed: temporal mean, total root‐mean‐square fluctuation, spectral distribution of fluctuations, and Eulerian micro time scale. Results are interpreted in terms of behavior of time‐average and fluctuation measures in three regions, the generation region within the impeller volume, the decay region which starts in the horizontal fluid sheet issuing from the impeller, and the recirculation flow region in the vessel.Generation of concentration fluctuations within the confines of the impeller is described in terms of a model involving gross mixing, without significant decay, in the wake of each flat blade. Distributions of mean and fluctuating concentrations are suggested to provide a measure of uniformity in the vessel as a whole. The former, in particular, was remarkably constant throughout the vessel.