On the number of tubes required to study oscillating vortices and frequency spectrums of tube arrays in cross flow

The oscillating vortices are of much practical importance in the analysis of the fluid-induced vibrations in cross-flow of a steam generator. However, the investigations on the vortex shedding, unsteady lifts, frequency spectrums, and the required number of tubes to study the phenomenon are very limited. In this work, a series of numerical experiments of a triangular array of tubes with a pitch ratio of 1.633 have been performed. The lift coefficients of the tubes were monitored to examine the effects of the numbers of tube rows and columns on the flow and fluid dynamics. The Fast Fourier Transform (FFT) method was used to figure out frequency spectrums of lifts of the cylinder bundle. Results show that the oscillating vortices generated by the tube arrays have greatly enriched the frequency spectrums. On the basis of the investigation of the unsteady lift performances, vortex shedding of tube arrays, eleven columns and eight rows were recommended. Furthermore, the fluid induced vibrations of a cylinder were investigated, and a fluid dynamics enhancement was observed.