Simulation and Experimental Estimation of the Free Wavenumbers for Helically Grooved Tubes

Abstract

The dynamic characterisation of elastic tubes is relevant to many fields in the industry. They are a key component for many processes involving fluid flow, heating, or cooling, etc., where grooves are frequently introduced to alter flow, and thus enhance heat transfer. Thin-walled tubes with helical features have been previously studied numerically and analytically, but experimental observation is still missing. In this paper, the wave propagation characteristics of a cylindrical tube with helicoidal grooves are investigated experimentally. The Wave Finite Element method is applied to a 3D model of this structure and a correlation method is used on a physical tube to experimentally observe the splitting of the degenerate dispersion branch into two. As opposed to a tube without grooves, both numerical and experimental methods show that the tubes with helicoidal grooves possess two distinctive but closely valued bending wave branches in the dispersion curves. The effect of the grooves is also visible in the mode shapes of the tubes of finite length, which will also be presented, where bending modes become unrestricted to lying in a single preferential direction.