The dynamics of imperfectly supported hanging pipes conveying fluid: An experimental study

Abstract

An experimental investigation was conducted to examine the effect of imperfection in the clamping of cantilevered pipes discharging or aspirating fluid. Interest in fluid-conveying cantilevered pipes stems not only from their capability to display rich dynamical behaviour but also from their presence in industrial applications; in the latter, geometric imperfections allowing for translational and rotational motions at their supported end may well be present. Six cases were studied, with three of them involving water-discharging pipes surrounded by air and three involving water-aspirating pipes submerged in water. The discharging pipe cases studied involved (i) a perfectly supported cantilevered pipe, while cases (ii) and (iii) utilized imperfectly supported pipes with the positive clamping replaced by a short flexible rubber tube, which allowed non-zero lateral and rotational motion at the clamped end. Cases (iv) – (vi) of the cantilevered aspirating pipes were analogous to those of the discharging pipes, but the pipes were submerged in water. Imperfectly supported discharging pipes developed larger static deformations, leading to a static instability, prior to the onset of oscillatory instability. Imperfect cantilevered aspirating pipes behaved similarly. However, the source of the increased static deformation for the imperfectly hanging discharging pipes appeared to be related to added translational motion, whilst for imperfectly supported aspirating pipes the increased static deformation was mainly due to rotation at the support.