PIV measurements on flow behavior behind a mooring line with imposed top-end motion

Experimental investigation on the flow behavior of a mooring line with imposed top-end motions were performed in a water flume. The surge and heave motions were driven by a programmable electrical motor at the fairlead position. The Particle Image Velocimetry technique (PIV) was employed to capture the instantaneous flow fields around the mooring line at both the horizontal and vertical planes. Compared with the stationary mooring line, the instantaneous vorticity contours behave much more complicated for the mooring line under the imposed surge and heave motions. The coherent vortices are formed along the curvature of the catenary mooring line, oblique vortex shedding is observed with multiple small scale vortices. The vortex strength behind the mooring line under the surge motion is larger than that under the heave motion.