Yaw Dynamics and Instability of Autonomous Vessels in Following and Stern Quartering Waves
Abstract
The general objective of the proposed research is to contribute to the understanding and prevention of the so-called direct broaching-to behavior of ships in steep following/quartering seas. This is a phenomenon of course instability, experienced as a sudden dangerous oscillatory build-up of yaw deviation from the commanded course. However, direct broaching-to does not involve surf-riding, like in the more widely known mode of ship broaching-to. Direct broaching-to is identified as particularly important for ships operating with a high level of autonomy, since an onboard Master#s shiphandling experience cannot be invoked and the current autopilots cannot eliminate phenomena with little understood physics. Towards achieving the set goal, improvements in the state-of-art will be targeted, addressing: a) the derivation of an engineering-level mathematical model suitable for investigating qualitatively and quantitatively direct broaching-to; b) the development of a valid theory that couldexplain its generation from sound scientific principles;c) the proposal of algorithmic and practical ship design and operation criteria, that will be sufficient for eliminating occurrences of direct broaching-to. A two-level, maneuvering type, mathematical modeling approach will be adopted. In the first level will be used a semi-empirical MMG-type propeller and rudder. In the second level will be involved a fast implementation of the Boundary Element Method (#vortex lattice# numerical scheme). The investigation of ship dynamics will include the cases of: a) regular waves; and b) irregular waves; with corresponding derivation of deterministic and stochastic course stability criteria. For the regular waves, the so-called continuation method of nonlinear dynamics will be employed for deriving the organization of the dynamical system#s steady states, with parallel examination of stability through Floquet#s theory. For the stochastic dynamics investigation, leading to the estimation of this instability#s probability, will be applied two techniques that have good potential for dealing with rare phenomena. These are: a) The Path Integration method; b) The clustering of phase-space trajectories. Results obtained by these two methods will be compared against each other, while considering, in parallel, their computational requirements.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 14, 2024
- Source ID
- N629092512001
Entities
People
- Konstantinos Kostas Spyrou
Organizations
- Office of Naval Research
- United States Navy