Experimental and numerical study on vibrations of a helical pipe with fluid flow

This paper presents the results of a study of the dynamics of a spiral tube with fluid flow. A copper helical pipe fixed at both ends is chosen for the study. The influence of the flow velocity on the natural frequencies of the system is investigated using a linear model. Experimental results confirmed the adequacy of the model assuming the pipe centreline to be extensible. The analysis of the natural vibration modes of the spiral tube and the effect of flow on the change in the shape of the modes is carried out. Underlying the analysis of the dynamic behaviour of a pipe conveying pulsating fluid flow is a nonlinear model. The effects of pulsation frequency, pulsation amplitude and the flow velocity on the system's vibrations are examined. Time histories, phase portraits, motion trajectories, vibration modes and spectra are analysed, also in the form of spectrograms as a function of the pulsation frequency. It was verified that resonance vibrations are excited particularly in the natural vibration ranges. The results of numerical simulations and experimental observation show the spatial character of vibrations with significant amplitudes, showing their increasing complexity at higher excitation frequencies.