Calm water resistance and self propulsion simulations including cavitation for an LNG carrier in extreme trim conditions

Maasch, M. and Turan, O. and Khorasanchi, M. and Fang, Ivy (2017) Calm water resistance and self propulsion simulations including cavitation for an LNG carrier in extreme trim conditions. In: International Conference on Shipping in Changing Climates 2017, 2017-09-05 - 2017-09-06, UCL.

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Abstract

In recent years many studies and real-life applications dealing with trim optimisation have shown that operating a ship at small trim angles can improve the energy efficiency by up to 5% depending on ship speeds and loading conditions. This efficiency gain mainly results from the re-positioning of underwater hull features, such as the bulbous bow or the stern bulb. Different to the above described approach the present study deals with operating a LNG Carrier at an extreme bow-up trim angle of Ɵ = −1.9 deg. In order to predict the performance, URANS virtual towing tank simulations in calm water were performed for both, nominal resistance conditions and self-propulsion conditions including cavitation. The numerical results, including the ship resistance, the nominal propeller wake field and the simulation of propeller cavitation in self-propulsion conditions indicated a largely improved performance. Due to a significant reduction in nominal resistance by up to 27.5% the ship selfpropulsion point in extreme trim conditions was found at a lower propeller rotation rate compared to level trim conditions. This also reduced the cavitation volume and finally resulted in a delivered power reduction of up to 28.8%.

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