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Maneuvering Hydrodynamics of Ellipsoidal Forms
Citation Link: https://doi.org/10.15480/882.677
Publikationstyp
Technical Report
Date Issued
1977
Sprache
English
Author(s)
TORE-DOI
The hydrodynamical forces and moments acting on a tri-axial ellipsoid moving
in an incompressible and inviscid fluid are analysed. The rigid ellipsoid is
allowed to move in the most general manner with time dependent velocity and six
degrees of freedom. The force and moment express ions are obtained by applying the Lagally theorem to the image singularities system representing the body in the presence of exterior disturbances. First expressions for the Lagally force and moment acting on a maneuvering ellipsoid in an unbounded medium are derived and then these express ions are generalized to include the effect of an exterior source moving in an arbitrary manner. It is also shown how the Lagally expressions for an exterior source can be used to obtain closed form express ions for the hydrodynamical forces and moments acting on a maneuvering ellipsoid in the presence of arbitrary exterior disturbance. The analysis which is based on the application of ellipsoidal harmonics is demonstrated in a simple case of propeller-hull interaction. Here the motion of the ellipsoid is restricted to the major axis and the propeller at the stern is represented by an isolated sink in accordance with Dickmann's model. Practical expressions for the thrust deduction coefficient, wake fraction and propeller induced vibration are then derived for ellipsoidal, spheroidal and spherical hulls.
in an incompressible and inviscid fluid are analysed. The rigid ellipsoid is
allowed to move in the most general manner with time dependent velocity and six
degrees of freedom. The force and moment express ions are obtained by applying the Lagally theorem to the image singularities system representing the body in the presence of exterior disturbances. First expressions for the Lagally force and moment acting on a maneuvering ellipsoid in an unbounded medium are derived and then these express ions are generalized to include the effect of an exterior source moving in an arbitrary manner. It is also shown how the Lagally expressions for an exterior source can be used to obtain closed form express ions for the hydrodynamical forces and moments acting on a maneuvering ellipsoid in the presence of arbitrary exterior disturbance. The analysis which is based on the application of ellipsoidal harmonics is demonstrated in a simple case of propeller-hull interaction. Here the motion of the ellipsoid is restricted to the major axis and the propeller at the stern is represented by an isolated sink in accordance with Dickmann's model. Practical expressions for the thrust deduction coefficient, wake fraction and propeller induced vibration are then derived for ellipsoidal, spheroidal and spherical hulls.
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