Experimental investigation on the vortex-induced vibration of the vertical riser fitted with the water jetting active vibration suppression device

In this paper, a type of water jetting active vibration suppression device was designed. Experimental studies were carried out to investigate the dynamic responses and the vortex-induced vibration suppression effect for a vertical riser with the water jetting active vibration suppression device in a wave-current flume. By varying the multi-stage outflow velocities and the test spacings, the characteristic parameters such as dominant frequency, dimensionless displacement and mode of the riser after vibration suppression under different test spacings of the water jetting active vibration suppression device were analyzed. The results show that the vibration suppression device effectively suppresses the VIV of the riser under different test spacings. The coupling relationship between test spacing and reduced velocity is the key factor for the optimal vibration suppression effect of the active vibration suppression device. The amplitude of the displacement after suppression is significantly reduced compared with that before suppression, and the best suppression efficiency can reach 92%. At the same time, it is found that not the smaller the test spacing is, the better the vibration suppression effect is, but there is a sensitive region during test spacing. As the reduced velocity increases, the test spacing of the water jetting active vibration suppression device is changed from 7.5D to 10.0D, the efficiency of vibration suppression is polarized and obvious "transition region" appears.