Captive Model Tests and 6-DoF Simulations of a BB2 Submarine near the Free Surface

Abstract

Depth and course keeping/changing abilities of the submarine at the snorkel depth are important for the accomplishment of its near-surface tactical missions. Recently X-form stern plane configurations of submarines are often used for higher control effectiveness, compared to cross-form configurations. In this study, a BB2 submarine which was introduced as the generic submarine model in previous studies are tested and its manoeuvres are simulated near the snorkel depth. A 1/15-scaled BB2 submarine model is constructed and captive model tests are carried out at the full-scale operating depth up to 30 meter. Planar motion mechanism (PMM) tests of the model are performed in a towing tank of Korea Research Institute of Ships and Ocean Engineering (KRISO) at three kinds of depths such as 30 meter, 15 meter (snorkel condition), and surfaced condition. 6-DoF appended hull forces and moments, drags and lifts on the control planes, and propeller thrusts are measured in the model tests. Vertical PMM tests including forced rolling motion tests are conducted at the deepest depth, 30 meter. And horizontal PMM tests are performed at each depth respectively so that depth-varying horizontal plane hydrodynamic coefficients can be identified. 6-DoF mathematical models of the submarine are established with the hydrodynamic coefficients obtained by the present captive model tests. For a practical purpose, assuming that the free surface effects are negligibly small at the depth of 30 meter, turn and zig-zag manoeuvres are simulated by using the coefficients from the tests at the depth of 30 meter. And the simulations are compared with the fully-submerged depth free-run test data opened in other previous study. Simulated manoeuvring characteristics are in good agreements with the previous free-run model tests.