Spectral Analysis of Fluid Flow in Oscillating Grid Reactor

Abstract

A methodology for quantifying flow‐field characteristics from laser Doppler velocimeter (LDV) measurements was developed. This methodology was used to quantitatively investigate two mixing conditions (0.25 Hz and 0.75 Hz) in an oscillating grid reactor. The resulting time records of fluid velocity in the reactor verified that the fluid motion was significantly different for the two mixing conditions. A computer program was developed based on theoretical work of others to calculate the power spectral density function directly from the randomly sampled LDV data. These power spectra, calculated from velocity‐time records, were used to quantify the length scales occurring in the reactor and their associated frequencies, the differences in the fluid motion associated with the two mixing conditions, and the differences in fluid motion with respect to measurement plane and measurement position in the reactor. Significant differences were observed in the larger‐scale fluid motions and not in the smaller‐scale (higher frequency) fluid motions.