New promising generation of twin-gondola LNG carriers optimised with the aid of CFD calculations
Author Valkhof, H.H., Minguito, E., en Kooiker, K.
Title New promising generation of twin-gondola LNG carriers optimised with the aid of CFD calculations
Conference/Journal SNAME Annual Meeting
Month October
Year 2005

Abstract
This paper describes the design of a twin gondola LNG carrier for Navantia. The twin gondola aft body has proven to be an adequate design concept, but due to the complexity of the flow around the aft body the design should be carried out with great care. Computational Fluid Dynamics (CFD) tools are extremely valuable in the hydrodynamic optimization process of the hull. In this design both potential flow codes and viscous flow codes have been used to obtain the optimum hull form. Special interest has been paid to the shape and the orientation of the gondolas. The performance of the resulting design has been verified by model tests in MARIN’s Deep Water Towing Tank.

The design started by performing calculations with MARIN’s non-linear potential flow code RAPID, based on initial lines supplied by Navantia. In this phase the bulbous bow and the shape of the hull have been optimised, while furthermore for a few variants the pressure distributions around the gondolas have been studied in order to obtain a first impression of the optimum gondola orientation. Viscous effects, however play an important role in the flow around the aft body and therefore the shape of the aft body and the orientation of the gondola’s have been further improved by using MARIN’s viscous flow code PARNASSOS. .With the results of the PARNASSOS calculations it was possible to make decisions with regard to the horizontal angle and the inclination of the gondolas, the slope of the buttocks in the area between the gondolas. Special attention has been paid to avoid flow separation around the aft body. The wake field in the propeller plane has been improved by optimising the shape of the gondolas. The gondolas have been oriented in such a way that maximum efficiency is achieved. Scale effects have been studied by conducting calculations for both model scale and full scale.

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