Large-scale oscillations of a feedstream inside a stirred tank reactor

Recent studies have shown feedstreams inside stirred tank reactors to oscillate. When multiple feed points are used, these oscillations can cause feedstreams to overlap. The objective of this study is to determine a description of the oscillations that can be used to prevent the feedstreams to overlap. The oscillations are analyzed by determining the displacements of the centers of the mass of a feedstream in radial cross sections. The growth of the root-mean-square radius of these displacements with time is linear, corresponding to the initial growth stage. The growth rate of the root-mean-square radius with time proved to equal the velocity fluctuations related to turbulent motions with a size larger than the diameter of the feedstream, indicating that these large-scale turbulent motions are responsible for large-scale oscillations. With the description obtained for the root-mean-square radius, the minimal distance between two feed pipes necessary to prevent the overlap of the feedstreams can be calculated.