Experimental exploration of the ship surfriding in bichromatic following seas with the view to expand the understanding of this phenomenon in irregular wave conditions
Abstract
Broaching-to is a sudden and uncontrollable turn in following or stern quartering waves. The phenomenon is typically preceded by surf-riding. The ship is captured by a wave approaching from her stern, accelerates to the wave celerity and loses directional stability regardless of the steering effort. The violent turn resulting from the directional instability may result in a collision or lead to a large angle of heel, possibly even capsizing. As fast, small to mid-size ships are especially vulnerable to broaching, the potential loss of directional stability in waves is of particular concern for the rapidly increasing fleet of autonomous vessels. The vital aspect allowing for the awareness and avoidance of this dangerous event is an identification of the conditions leading to the surf-riding phenomenon. The identification of surf-riding when it is already occurring is ineffective as it is too late for effective countermeasures.For the sake of reaching progress in understanding the phenomenon, the problem can be simplified by limiting the number of components in the irregular wave model. Spyrou et al. considered bi-chromatic wave, i.e. an irregular waves modeled just withtwo components. The interference of the two components of the bi-chromatic wave have been demonstrated analytically and numericallyto be sufficient to see that the condition for surf-riding may appear, disappear or move but this has not yet been observed in experiments. The considered ship models need to be built and equipped with the propulsion system, steering gear and control system. The setup-testing series and the pilot study will be carried out in the small towing tank belonging to Gdansk University of Technology. The full range of experimental research will be conducted in the external towing tank, which is long enough to test relatively largeship models in order to mitigate the scale effect.The expected results shall address two main research questions, i.e.: 1) whether the phenomena related to the surf-riding and broaching-to can be observed in a model experiment and 2) what are the model test facility and condition requirements for observing the phenomena in bichromatic and more generally irregular wave? This knowledge will potentially influence ship design and operations through a greater understanding of challenges to the fast and efficient sailing of small to mid-size autonomous vessels.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 13, 2023
- Source ID
- N629092312083
Entities
People
- Przemysaw Krata
Organizations
- Gdańsk University of Technology
- Office of Naval Research
- United States Navy