Effect of the flow approach angle on the dynamics of loosely-supported tube arrays

摘要

This paper presents an investigation of the dynamics of loosely supported tube arrays subjected to cross-flow. Of special interest is the effect of the flow approach angle, as well as the clearances between the tubes and their supports, on the fretting wear parameters such as the impact force and the tube response level. Experiments were conducted in an air tunnel on triangular and square tube arrays with a pitch-to-diameter ratio of 1.5 and 1.73, respectively. The interaction between the fluidelastic instability and the acoustic resonance was illustrated. It was found that (i) both the vibration response and the measured force level were highly dependent on the support clearance, and (ii) the presence of acoustic resonance decreased the vibration amplitude and the impact force level. This is due to the interaction between the acoustic particle velocity, the required flow redistribution and the time lag with the tube motion to sustain fluidelastic instability.