An Experimental Study of Flow-Induced Vibration and the Associated Flow Perturbations in a Parallel Triangular Tube Array

The results of an experimental investigation of the flow perturbations associated with tube vibrations along the interstitial flow path are presented. A parallel triangular tube array consisting of seven rows and six columns of aluminum tubes with a pitch ratio of 1.54 was studied. Measurements of the interstitial flow perturbations along the flow lane were recorded using a hot-wire anemometer while monitoring the tube vibration in the longitudinal and transverse directions. A single flexible tube located in the third row of a rigid array was instrumented with pressure transducers to monitor the surface pressure variations. The flow perturbation amplitude and phase with respect to the tube vibrations were obtained at a number of locations along the flow lane in the array. The effects of tube vibration amplitude and frequency, turbulence level, location of measurements, and mean gap velocity on the flow perturbation amplitude and relative phase were investigated. It is found that the flow perturbations are most pronounced at the point of flow separation from the tube and decay rapidly with distance from this point. It appears that the time delay between tube vibration and flow perturbation is associated with flow separation and vorticity generation from the vibrating tube.