Effect of Pitch Ratio and Tube Support Conditions on the Dynamic Behavior of a Low Mass-Damping Parameter Parallel Triangular Array

To better explain the basic aspects of fluidelastic instability (FEI) in tube arrays, a rigorous research program has been initiated. In this research, the authors executed a series of water-flow experiments utilizing a fully flexible, parallel triangular tube array (a cluster of 9 brass rods). To examine the effect of pitch ratio on the onset of FEI, four pitch-to-diameter ratios of 1.27, 1.37, 1.48, and 1.62 were tested. To investigate the effect of flat bar support on the stability threshold, a series of experiments were carried out for each pitch ratio with varied tube/support clearances. The findings of these experimental investigations and a full description of the flow loop, including the utilized instrumentation, are reported. The current results show good agreement with the available data from previous investigations and interesting findings in terms of the effect of the pitch ratio and support clearance on the stability threshold.