Author(s)

Y. Perets, B. Rivin, I. Bronstein, R. Harari & E. Sher

Abstract

Preliminary experiments were performed for studying flow induced vibration of a rod wrapped by transverse shapes corrugation (repeated ribs) and subjected to axial flow. Flexible rods with different repeated ribs pitches and widths were tested. The vibration amplitude was measured and the damping ratio of every rod was evaluated, in order to estimate the amplification effect of the repeated ribs on the rod, compared to the results on a smooth rod. The effect of different parameters on the vibration is being discussed. It was found that the repeated ribs have an effect on the pressure drop increases produced by the turbulence augmentations. Empirical correlations form of the vibration amplitude at middle rod span is being proposed. Keywords: flow induced vibration, corrugation, repeated ribs. 1 Introduction Corrugation structures or repeated ribs are well known as a heat transfer enhancement technique in various engineering applications such as: heat exchanger, insert technology, air conditioning and refrigeration systems, chemical reactors, fuel rod and control rod components. In the literature the repeated ribs are treated as a roughness geometry problem or as a boundary layer separation and reattachment problem. The repeated ribs create local wall turbulence due to the flow separation and reattachment between the ribs which enhance the heat transfer. At the same time, turbulence is accompanied by increases of pressure fluctuations and flow resistance. Various studies have been preformed in order to evaluate the friction coefficient of repeated ribs roughness (Lewis [1]; Wilkie et al. [2]; Webb et al. [3]). The ribs were characterized by geometric parameters: pitch (p), width (b) and height (e).

Keywords

flow induced vibration, corrugation, repeated ribs.