Surface pressure distribution survey in normal triangular tube arrays

As a first step towards a validation database for models of fluidelastic instability, an experimental parametric study of the surface pressure on a cylinder in the third row of three normal triangular tube arrays (P/d=1.32P/d=1.32, 1.58 and 1.97) with air cross flow has been performed. A range of static tube displacements were examined. Forces were calculated from the pressure measurements providing an understanding of the force generation mechanism. The results show that the fluid forces do not scale proportionally with dynamic head. However, no simple parameterisation was found for the lift force. A bistable flow instability was observed in the pitch ratio of 1.58 even when the tube was displaced. This phenomena resulted in the large asymmetry observed in the pressure distribution around a static cylinder. It is concluded that the fluid forces which are related to fluidelastic instability are dependent on Reynolds number and pitch ratio.