Uncertainty analysis of ship model Zig-zag tests

According to resolution MSC.137 (76), the repeated Zig-zag tests (±10°/10°, ±20°/20°) of a calibration ship model were carried out by free running method. Based on the recommended procedures and guidelines of International Towing Tank Conference (ITTC, 2017), uncertainty analysis for ship model Zig-zag tests in free running way was studied. The calculation steps of the uncertainty analysis were supplemented and refined contrasting to the ITTC standard. Considering the difference between precision limit and deviation limit, the uncertainty influenced by the main factors were analyzed respectively. The total uncertainty of the test results was calculated by combining the relative uncertainty of the factors above. The result shows that the uncertainty of each overshoot angle is around 1% to 3% at 95% confidence level. The repeat testing is the decisive factor affecting the uncertainty of the results, which is consistent with the relevant conclusion of the ITTC guideline. The uncertainty analysis method and calculation steps in this paper can be used as a reference for other ship motion. © 2021 Editorial Board of Journal of Huazhong University of Science and Technology. All right reserved.