Benchmark Model Tests on the DeepStar Theme Structures FPSO, SPAR and TLP
Authors: Wichers Johan , Devlin Paul V. 
Published: October 2008

In the framework of the studies on the DeepStar Theme Structures for deepwater in the Gulf of Mexico, contractors and research institutes have carried out series of pre-model test computations. The DeepStar Theme Structures are a turret moored FPSO, a classic SPAR and a standard TLP. The Theme Structures were exposed to hurricane and loop-current condition. The scatter was significant in the pre-model test computational results. In order to compare the computed results with results of model tests, a series of benchmark model tests were carried out. Based on the model tests results post-model test validation analysis and guidelines for ultra deepwater model tests and coupled analysis for deepwater structures were carried out.

In this paper, the sequence of the DeepStar Theme Structure developments will be given briefly and the philosophy behind and the performance of the benchmark model tests will be presented.

Introduction

In the framework of the DeepStar Theme Structures studies for deep water in the Gulf of Mexico, contractors and research institutes carried out series of pre-model test computations. The computations were carried out based on the technical specifications for the Theme Structures and weather conditions. The structures were exposed to hurricane and loopcurrent condition. The FPSO and Spar were installed in 3,000, 6,000 and 10,000 ft of water depth, while the TLP was installed in 3,000 and 6,000 ft. Comparing the pre-model test computation results of the same structures as carried out by different participants, the scatter was significant. In order to compare the computed results with results of model tests, a series of benchmark model tests were carried out.

The motivation for the selected model scale and the description of the model basin facility is given. The description is given of the model manufacturing including mooring lines and risers. Further, the calibration of hurricane and loop-current environmental conditions is presented. A hurricane and a loop-current current profile had to be adjusted to match the specifications. In addition, the associated turbulences were measured in the basin. The results are presented. Concerning the waves, attention was given to not only the wave spectra but also to the wave group spectra. The Theme Structures were exposed to an API wind spectra. The procedure to adjust the wind spectra is described.

The test set-up, instrumentation, data reduction and the program of the benchmark model tests will be presented.

Finally some conclusions are drawn.

Since the results of the benchmark model test program will be used for post-model test computations (model-the-model), the performance and the reporting of the model test set-up must be as accurate as possible.

In the same framework of the DeepStar Theme Structures project, guidelines for model testing in ultra deepwater and guidelines for coupled analysis of deepwater floating structures are established.

This paper documenting the benchmark model tests is the first in a series of papers covering the DeepStar Theme Structures project. The other papers deal with prediction of the responses of the Theme Structures (model test vs. analysis), and development of guidelines for model test in ultra deepwater and for coupled analysis of deepwater systems.