Nonlinear Inertia Forces on Bodies

Isaacson, Michael

doi:10.1061/jwpcdx.0000150

Cited by 14 publications

(1 citation statement)

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“…In fact, more detailed theoretical investigations show th a t neither is completely correct. Isaacson (1979), quoted also Sarpkaya & Isaacson (1981), using results of Taylor (1928), derived expressions for the in viscid forces on a general body in a general flow, but these are m arred by the fact th a t the body is assumed to be 'small ' in all dimensions, and so the results were not rigorously proven for cylinders which have one ' long' axis, except in special cases where th a t axis is irrelevent. There is also an error of \ in the off-diagonal terms, as already noted by Rainey (1989a).…”

Section: Previous Assessments Of Inviscid-flow Forces On Cylindersmentioning

confidence: 99%

Hydrodynamic forces on fixed submerged cylinders

Manners

Rainey

1992

Proc. R. Soc. Lond. A

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Wave loads on the cylindrical members of fixed offshore structures are generally calculated by using Morison’s Equation. The inertia force component of this equation is conventionally quoted in a form derived from theoretical calculations for a uniformly accelerating fluid. In this paper the correct form for the inertia force in a general fluid flow is derived from first principles by pressure integration and, independently, from earlier work, by energy arguments. It is shown that, for the thin cylinder limiting case, the transverse force on a circular cylinder is incorrectly given by the conventional approach, in that the product of transverse fluid velocity (in the direction of the required force) with the longitudinal velocity gradient should be added to the water particle acceleration, when computing the added-mass component of the force. Axial divergence, in other words, appears to play the role of a rate-of-change of added mass. It is shown that the mathematical origin of this extra term is the classical three-dimensional flow feature of a ‘zonal harmonic’, which produces a convective fluid acceleration but zero loading. A more elaborate formula is derived for non-circular cylinders, and the nature of point loads occurring at cylinder ends is also discussed.

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Section: Previous Assessments Of Inviscid-flow Forces On Cylindersmentioning

confidence: 99%