Cross-Flow-Induced Vibrations of Finite Tube Banks in In-Line Arrangements

Abstract

A systematic experimental investigation was carried out to classify the flow-induced vibrational responses of cantilever tubes in the streamwise and transverse directions within one-, two- and three-row in-line arrangements. Experiments were conducted with transverse pitch ratios of 1.33, 1.72 and 2.0 and longitudinal pitch ratios of 1.33, 1.67, 2.0, 2.67, 3.33 and 4.0 at various natural frequencies in the range 5.7 to 26 Hz. The rigid tubes were mounted on flexible cantilever rods and the monitored tube could be any one in any of the three rows. The velocity range started from very small amplitudes of vibration and proceeded up to maximum possible amplitudes, i.e. up to severe banging of the free ends of neighbouring tubes. The vibrational response was found to depend on the position of the monitored tube in the bank, velocity and tube arrangement. The vibration of a monitored tube in the single row tended to be in a streamwise direction. Maximum amplitudes always occurred in the second row of tubes, with oval vibration in the transverse direction. When the third row of tubes was added, the tube in it vibrated in a similar oval manner, but with smaller maximum amplitudes and in a more random fashion.