Mooring Optimization in Time Domain Using Harmony Search

The design of a mooring system is a time consuming task, owing to the large number of design cases, software interfaces and changing requirements. Although frequency domain is a faster method, the behavior of a turret moored FPSO and the loads applied on mooring system in a certain environment are most accurately predicted in the time domain. This does not help in reducing design time. Therefore an automated time domain harmony search based mooring optimization methodology, that uses industry standard software Orcaflex and Ariane7 through a MATLAB interface, has been developed. Harmony search is a phenomenon-mimicking algorithm inspired by the improvisation process of musicians. In the algorithm, each musician (= decision variable) plays (= generates) a note (= a value) for finding a best harmony (= global optimum) all together. The methodology is applied to design a mooring system for a large turret moored FPSO in deep water and harsh environment as a case study. The objective is to minimize the load on the turret chain table with feasible solutions that satisfy all the design constraints without manual intervention. An optimized solution is found within 5 days and the rate at which different mooring configurations are assessed is in excess of 160 per day. This paper outlines the developed process and how it may benefit the industry as an efficient mooring design methodology.