Measurements of frequencies and spatial correlations of coherent structures in rod bundle flows

Cross-wire anemometry was used to identify and characterize coherent flow pulsations in isothermal air flow near the gap regions of a five-rod bundle with a design pitch-to-diameter ratio of 1.149 and contained in a quasi-trapezoidal duct. It was confirmed that such pulsations are quasi-periodic and contribute significantly to the velocity fluctuations across the gap. The frequency of pulsations was found to decrease with diminishing rod-wall gap size in the range between 0.015D and 0.250D, where D is the rod diameter. The pulsations in a rod-wall gap and an adjacent rod-rod gap were strongly coupled and occurred at the same frequency as one rod was displaced towards the duct wall. (c) 2006 Elsevier B.V. All rights reserved.