Experimental Calibration of Bifurcation Superstructure of Nonlinear System

Results of a medium-scale experimental study revealing the underlying superstructure in bifurcation sets of a submerged, moored ocean system are reported. The experimental model, assimilating nonlinear moored structural responses, consists of a spherical buoy and attached multipoint mooring lines. The model is excited under a periodic wave field in a closed channel. Sources of system nonlinearity include complex geometric restoring force and coupled fluid-structure interaction exciting forces. Experimental setup, configuration, and classification of the measured results are described. Characteristic motions observed include harmonic, subharmonic, and ultraharmonic responses. Nonlinear primary and secondary resonances in the response are identified in frequency response diagrams, which also indicate the existence of intricate patterns of the nonlinear global behavior.