Investigation of a ship’s hydroelasticity and seakeeping performance by means of large-scale segmented self-propelling model sea trials

Abstract

The traditional laboratory models for the hydroelasticity and seakeeping performance of ships are tested in calm water and in uni-directional, artificially generated waves. A new alternative to the tank model measurement methodology is to conduct experiments using large-scale models in actual sea conditions. To implement the tests, a large-scale segmented self-propelling model and testing system were designed and assembled. A buoy wave meter was adopted to record the coastal waves that the model encountered during the tests. The analysis of the results of waves in sheltered waters by the spectral method shows good agreement with ISSC spectra. To investigate the difference between this new methodology and the traditional towing tank tests, a small-scale model, whose type and configuration are the same as those of the large-scale model ship, was used and tests were conducted in a towing tank. Comparison of the two experimental results shows that there is a remarkable difference in the response characteristics between the large-scale model at sea and the small-scale model in the tank. Numerical simulations of the responses of the ship under equivalent sea states were also carried out. The influence of directional spreading functions on the results was analyzed by a numerical approach. The classical model tests under long-crested waves in the towing tank over-estimate the motion and wave load responses; however, large-scale model tests carried out at sea are more reasonable for ship design and scientific research.