The reduction of the ship roll motions is a very important aim in the pleasure craft design because of its strong influence on the comfort onboard. Fin stabilizers have been used to reduce the roll motion of ships in underway condition for years, since they generate the stabilizing moment working as a couple of foils with opposite angle of attack i.e. a symmetrical foil in an incoming flow generates a lift that is proportional to the square of the velocity and to its angle of attack, their effects at low and null speed are almost nil. For this reason anti-roll tanks have been adopted on many ships to reduce the roll at anchor but with serious drawbacks. The tanks have to be made quite large and have to be installed in a proper position to produce a considerable roll damping so it has a really strong influence on the internal arrangement. In the last 15 years, pulled by the growing market of the pleasure craft and the request of higher comfort standards, different stabilizing systems have been studied. The gyro stabilizers and the Zero Speed Fin are the most used, both of them are able to produce a stabilizing effect at zero speed and even in underway condition, the main differences between them are that the first one takes more time to be turned on and off, on the other hand the fins increase the hull resistance and can be damaged in collision with some floating object. The working principle of the gyroscope is well known on the contrary the principle behind the zero speed stabilizers, explained as ‘‘paddle’’ Ooms 2002 [1], has not been deeply investigated yet. In literature it is possible to find analytical hydrodynamic models and 2D CFD simulations [2], and other works in which fins are compared with antiroll tanks and their use in anchored conditions is discussed [3,4] while CFD simulations of three dimensional model or model tests are not present. This research has the objective to find out the correct setting to realize an analysis of a zero speed fin with the commercial CFD code Star-CCM+, and later, using this model, to gain a deep understanding of the fluid dynamical behaviour.
CFD Analysis of a Zero Speed Active Fin
BRIZZOLARA, STEFANO;VIVIANI, MICHELE
2012-01-01
Abstract
The reduction of the ship roll motions is a very important aim in the pleasure craft design because of its strong influence on the comfort onboard. Fin stabilizers have been used to reduce the roll motion of ships in underway condition for years, since they generate the stabilizing moment working as a couple of foils with opposite angle of attack i.e. a symmetrical foil in an incoming flow generates a lift that is proportional to the square of the velocity and to its angle of attack, their effects at low and null speed are almost nil. For this reason anti-roll tanks have been adopted on many ships to reduce the roll at anchor but with serious drawbacks. The tanks have to be made quite large and have to be installed in a proper position to produce a considerable roll damping so it has a really strong influence on the internal arrangement. In the last 15 years, pulled by the growing market of the pleasure craft and the request of higher comfort standards, different stabilizing systems have been studied. The gyro stabilizers and the Zero Speed Fin are the most used, both of them are able to produce a stabilizing effect at zero speed and even in underway condition, the main differences between them are that the first one takes more time to be turned on and off, on the other hand the fins increase the hull resistance and can be damaged in collision with some floating object. The working principle of the gyroscope is well known on the contrary the principle behind the zero speed stabilizers, explained as ‘‘paddle’’ Ooms 2002 [1], has not been deeply investigated yet. In literature it is possible to find analytical hydrodynamic models and 2D CFD simulations [2], and other works in which fins are compared with antiroll tanks and their use in anchored conditions is discussed [3,4] while CFD simulations of three dimensional model or model tests are not present. This research has the objective to find out the correct setting to realize an analysis of a zero speed fin with the commercial CFD code Star-CCM+, and later, using this model, to gain a deep understanding of the fluid dynamical behaviour.
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