海洋における鉛直弾性管の制振

概要

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In the design of a flexible off-Shore riser, which is connected to a spring at the top and clamped at the sea bed, it is desirable to reduce both the riser deflection and the bending moment due to random wave excitation forces. Assuming that the motion of the riser is two dimensional in the vertical plane, these design requirements can be effectively satisfied if appropriate stiffness and damping are given to the riser. In this study, we employed the statistical equivalent linearization technique to linearize a nonlinear fluid drag force, and an approximate mode superposition method (Rayleigh Ritz's method) to transform the governing equation of motion into a set of discrete finite dimensional state equations. A sub-optimal control theory with control structural constraints is applied to determine appropriate stiffness and damping. The required optimal stiffness and damping are determined by a trade-off between the rms values of the lateral displacement and the bending moment of the riser.
社団法人日本機械学会の論文
1990-03-25