Fluid Excitation Forces on a Tightly Packed Tube Bundle Subjected in Cross-Flow

Abstract

Fluid excitation forces acting on stationary cylinders with cross-flow are the coupling of vortex shedding and turbulence buffeting. Those forces are significant in the analytical framework of fluid-induced vibration in heat exchangers. A bench-scale experimental setup with an instrumented test bundle is constructed to measure fluid excitation forces acting on cylinders in the normal triangular tube arrays (P/D = 1.28) with water cross-flow. The lift and drag forces on stationary cylinders are measured directly as a function of Reynolds number with a developed piezoelectric transducer. The results show that the properties of fluid excitation forces, to a great extent, largely depend upon the locations of cylinders within bundle by comparison to the inflow variation. A quasi-periodic mathematical model of fluid excitation forces acting on a circular cylinder is presented for a tightly packed tube bundle subjected to cross-flow, and the bounded noise theory is applied between fR = 0.01 and fR = 1. The developed model is illustrated with lots of identification results based on the dominant frequency, the intensity of random frequency, and the amplitude of fluid excitation forces. A second model has been developed for fluid excitation forces between fR = 1 and fR = 6 with the spectrum index introduced. Although still preliminary, each model can predict the corresponding forces relatively well.