Dynamics of stretched flexible tubes conveying fluid

Silicone polymer tubes offer improved resistance to erosion, light in weight, non-toxic and corrosionresistant, and hence they are used in many pharmaceuticals as well as medical applications. Usually, the evaluation of the fundamental frequency and the mode shape of fluid conveying pipes are vital in the dynamic analysis of tubes, where the flow parameters like fluid velocity, damping ratio as well as the sagging of flexible structures affect the fundamental frequency and stability. Coriolis mass flow meter (CFM) is a precision flow measurement device which gives precise readings of mass flow rates. This device demands an accurate evaluation of the influence of flow parameters like damping ratio and fluid flow velocity on the fundamental frequency of the system. The flexible tubes possess higher damping ratios, which helps in fast dissipation of the undulations caused by fluid-structure interaction and flow-induced vibrations, compared to the metal tubes. However, the higher damping ratios can sometimes result in destabilisation of the system. The novelty of this paper lies in the development of a unique experimental technique to find the impact of the tube pre-stretch on natural frequency and damping ratio, the influence of mass and stiffness participation of flexible tubes conveying fluid. The damping ratio of the silicone tube is examined by experimenting with different flow velocities and pre-stretches. Study reveals that the pre-stretching of tubes initially decreases the damping ratio, and beyond a particular prestretch, the damping ratio increases. Also it is found that for highly pre-stretched tubes, the variation of natural frequency upon different fluid flow velocity is negligible. (c) 2019 Elsevier Ltd. Selection and Peer-review under responsibility of the scientific committee of the International Mechanical Engineering Congress 2019: Materials Science.