Forced vibration of a fully immersed pipe aspirating water: Experimental investigation

This study experimentally investigates the dynamics of a fully immersed pipe aspirating water under horizontal excitation at the upper end. The experiment is conducted to examine the effect of the internal flow velocity and the different inlet shapes, straight, bellmouth, T-shape, and L-shape, on the frequency response characteristics of the pipe. Through a series of experiments, it is found that a non-dimensional internal flow velocity at U = 3.8 significantly changes the response characteristics, the natural frequencies and the response amplitude. The different inlet shapes, however, show negligible influence on the vibrational characteristics within the present experimental conditions. In addition, this experiment observes several unexpected dynamic behaviors, including stable vibration without the excitation, high-frequency vibration induced by the T-shape inlet, and a large-amplitude oval trajectory behavior with the excitation. Overall, this experimental investigation provides significant physical evidence for verifying the theoretical models of aspirating pipes.