Abstract
Wind propulsion for commercial ships has been identified as a key component in the energy transition for the maritime industry. The sailing hybrid ship will operate with leeway (drift) angles to produce a lateral force known as sideforce, for steady operation under sail. In this paper, experimental results for the sailing performance of ships fitted with bilge keel appendages are presented. Systematic variations in appendage height, length, and position were tested, including several special cases (multiple bilge keels). The appendage typology is shown to mitigate the strong ‘destabilizing’ yaw moment that is characteristic of wind-assisted commercial vessels and to promote the non-linear sideforce component. The working principal for bilge keels—promotion of flow separation—can be employed to specify the separation location for components of the vessel vortex wake to improve the sailing performance of the ship.
Highlights
Wind assist, an environmentally friendly auxiliary propulsion system for commercial ships, is identified by [31, 41,42,43, 46], among others, as a key intervention for the energy transition in the maritime shipping space
The center of lateral resistance (CLR) moves aft as the leeway angle increases, an effect that is driven by an increase in flow separation along the bilges
For the very low aspect ratios considered in this study, for both the ship hull and the bilge keels, the linear lift coefficient is expected to be independent of the chord, corresponding to the ship length or bilge keel length
Summary
An environmentally friendly auxiliary propulsion system for commercial ships, is identified by [31, 41,42,43, 46], among others, as a key intervention for the energy transition in the maritime shipping space. The technical and commercial viability of sailing for modern commercial vessels has been the subject of study since the OPEC oil crisis of 1973 (see, for example, [39]). The researchers Fujiwara and Ueno have published a series of studies associated with a new (planned) demonstration vessel, the Wind Challenger [36], including testing of a 1/3 scale prototype of a collapsible solid wing sail [14], and a presentation of towing tank results for systematic variation in appendage configurations [32].
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