It is difficult to make model tests by using the conventional reduced scale for floating structures in the deepwater field. The currently widely used method is the hybrid model test, which requires equivalent truncated designs to be matched first. Using static characteristics similar to the design criteria of equivalent truncated design, selecting appropriate objective function, and using genetic optimization algorithm, the mooring system equivalent truncated mathematical model is designed by in-house computer programs. Restoring force characteristic curves of the truncated mooring system, top tension and displacement characteristic curves of a single mooring line are drawn with the designed various parameters within the written static characteristic calculation programs and compared with that of the full depth mooring system. The results of developed programs are checked by the hydrodynamic calculation software, OrcaFlex, and the dynamic characteristics differences between truncated and full depth system are compared with the software AQWA. Relying on the ocean engineering test tank of Harbin Engineering University and a working depth of 1500m, taut moored Floating Production Storage and Offloading tanker and catenary moored Catenary Anchor Leg Mooring system are to be made equivalent truncated optimized designs of 700m and 500m, respectively. The results show that the developed equivalent truncated optimized design programs are feasible for model tests of deepwater floating system.
The model test becomes difficult with the increase of water depth due to the size limitation of the tanks. So new model test solutions are studied around the world. Studies have shown that despite the scale effects becoming increasingly significant, small-scale model testing is still feasible (Luo, 1994). However, the available depth remains limited in the marine engineering basin, even with small scale model tests, and it is very difficult to measure the varying forces and the motion response in practical applications.
