Time-domain analysis of frequency dependent inertial wave forces on cylinders

  • Authors:
  • Steen Krenk

  • Affiliations:
  • -

  • Venue:
  • Computers and Structures
  • Year:
  • 2013

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Abstract

Mono-pile structures are attractive for small well-head platforms and foundation of offshore wind turbines at moderate water depth. Their diameter of several meters makes them prone to simultaneous occurrence of frequency-dependent inertial forces and non-linear drag. The present paper presents a simple time-domain procedure for the inertial force, in which the frequency dependence is represented via a simple explicit time filter on the wave particle acceleration or velocity. The frequency dependence of the inertia coefficient is known analytically as a function of the wave-number, and the relevant range of waves shorter than about six times the diameter typically corresponds to deep water waves. This permits a universal non-dimensional frequency representation, that is converted to rational form to provide the relevant filter equation. Simple time-domain simulations demonstrate the reduction of the resonant part of the response for natural structural frequencies above the dominating wave frequency.