This paper documents a series of experiments conducted at the Glasgow University towing/wave tank to investigate the dynamic response characteristics of TLPs (Heidrun model ∼1 :100). These experiments can be grouped into four types: wave force measurement, forced oscillation, added resistance and tuft flow visualisation. The experimental setup and analysis techniques are reviewed and a selection of the results are presented and discussed.
Throughout the world there are a large number of unexploited oil reserves in deep water which are beyond the economic capabilities of fixed jacket type structures. The TLP concept is widely accepted as a viable alternative to jacket type structures for use in these deep water environments, Mercier et al (1991). Due to the dynamic nature of TLPs there exist low and high frequency resonant motions induced by 2nd order difference and sum-frequency forces respectively, Kim and Yue (1988). In the surge mode the difference-frequency induced motions are a principle hydrodynamic design criteria and need to be estimated accurately in order to minimise pretension requirement and tether load variations (due to set-down). To determine the dynamic response characteristics of a TLP the hydrodynamic excitation and reaction forces must be calculated accurately. Wave frequency (1st order) hydrodynamic forces and responses can be predicted accurately, however there is still a degree of uncertainty regarding the mechanisms governing the 2nd order transient (Ringing) and resonant responses (Springing and Slow Drift). The research aims are to investigate experimentally the hydrodynamic excitation and reaction forces acting on TLPs in extreme waves and currents. The approach followed was one of design/construction and testing of a ∼1: 100 scale model of Heidrun TLP enabling both global and local excitation and reaction forces to be measured for a range of extreme conditions. In addition quantitative and qualatative flow field measurements were obtained to supplement the hydrodynamic force measurements.
