Suppression of three-dimensional flow instabilities in tube bundles

Abstract

We study the generation of three-dimensional vorticity in tightly packed tube bundles. In particular, our goal is to investigate which conditions (if any) enable the flow to remain two-dimensional for Re4180. We calculated two- and three-dimensional flow through periodic rotated square tube bundles with tight packing, P=D 1⁄4 1:5, using a high resolution pseudo-spectral code with penalization. The tubes are cylinders whose response is modelled as a rigid harmonic oscillator forced by the flow-induced lift. We find that at Re 1⁄4 200 tube motion completely suppresses the three-dimensional instability. At Re 1⁄4 1000 tube motion does not suppress the three-dimensional instability, although the flow does have increased spanwise correlation and the Strouhal number for the two- and three-dimensional flows is approximately the same. The tight packing alone does not suppress the three-dimensional instability. Three- dimensional vorticity drastically reduces fluid forces acting on the tube compared with an equivalent two-dimensional flow.