The Effect Of Radiation Velocity Potentials On The
Drift Force On A Submerged Sphere
Author(s)
S. H. Mousavizadegan & M. Rahman
Abstract
The effect of the motion of a submerged sphere on the horizontal drift force
is investigated analytically. The multipole expansion method is used to derive
analytical solutions for the diffraction and radiation velocity potentials in a series
of associated Legendre functions. The second-order steady force is obtained by
the far field method. The effect of all velocity potentials is taken into account
in derivation of the horizontal drift force. The total contribution of the radiation
velocity potential is minimal to the horizontal drift force if the center of mass is
at a distance less than twenty percent of the radius from the center of the sphere.
The effect of the radiation velocity potential in vicinity of the resonant frequency
is augmented and may create a relatively large horizontal drift force.
Keywords: drift forces, radiation, diffraction, multipole expansion.
1 Introduction
Marine structures are usually designed to operate in a wave environment.
Structural loading of the body surface under the water and unsteady motions of
the body are two of the principal resulting problems. When the characteristic
body dimension is comparable to the wave length, the potential effects dominate.
The presence of the body alters the pattern of wave propagation in the vicinity of
the structure and causes wave scattering. The body may also oscillate and cause the
radiation of waves if the constraints are not sufficiently rigid. As a consequence,
the body experiences reacting forces from the surrounding fluid and constraints.
Due to the complexity of the associated boundary value problems with the wavebody
interactions in the frame of the potential flow theory, analytical solutions
can be obtained for a few special geometries. In general, a numerical solution of
Laplace’s equation along with the associated boundary conditions is imperative.
Keywords
drift forces, radiation, diffraction, multipole expansion.
Related Book
Other papers in this volume
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