OTRC Project Summary
|Model-the-Model: Validating Analysis Models for Deepwater Structures with Model Tests
|E. G. Ward and M. H. Kim
|DeepStar Industry Consortia
Final Report ID#
|DS5401B(Click to view final report abstract)
Note: This study was part of a broader DeepStar Project "Global Performance of Deepwater Structures - Post Model Test Study and Guideline Development."
Verifying the predicted design responses of FPS’s in deep and
ultra deep water depths presents significant challenges. Due
to the depth and scope of mooring and riser systems, a
completely scaled model of the FPS and its moorings and
risers is simply too large to test in present model basin. A
combination of physical model testing and numerical
modeling as shown in Figure 1 is recommended to verify the
responses of prototype FPS designs.
The general approach is to use a scale model of the
FPS hull and deck with equivalent (sometimes referred to as
“truncated”) mooring and riser systems for the model tests. A
numerical model that describes the dynamic responses of the
moored FPS with risers to winds, wave, and currents is used to
design the equivalent mooring and riser systems, and then
used to interpret and extend the model test results to predict
the prototype FPS responses at the full design water depth.
The numerical model should be carefully calibrated and
validated with data from the model tests. The validated
numerical model is then adjusted to incorporate the prototype
geometry, prototype scale properties and coefficients for drag
and damping, and actual (non-truncated and non-simplified)
moorings and risers, and then used to predict the design
responses of the prototype FPS. A favorable comparison
between these predicted and the design responses serves to
verify the design.
The robustness of the calibrated and validated
numerical model to capture the important physics and
complex interactions at both model scale and at prototype
scale is critical to this overall process of using model tests and
numerical models to validate the design responses of the
prototype FPS. Thus the careful calibration and verification of
the numerical model with model data is important to the
success of this process.
A study was completed to investigate this
recommended procedure involving the combination of
physical model testing and numerical modeling. The overall
results are presented in the final report, and provide a description of
the accuracy that can be expected from numerical models that
have been calibrated and verified with model tests.
Related Publications: Ward, E. G., Hansen, V. L., Kim, M. H., Wang, L., (2004), “Model the Model: Validating Analysis Models for Deepwater Structures with Model Tests”, Offshore Technology Conference (OTC 16586), Houston, May.
Standsberg, C. T., S. Karlsen, E. G. Ward, J. E. W. Wichers and M. B. Irani, (2004) “Model Testing for Ultra Deep Water”, OTC Paper 16587, Offshore Technology Conference, Houston, May.
Hansen, V. L., Wang, L., Ward, E. G., and Sodahl, N., (2004), “Guidelines on Coupled Analysis of Deepwater Floating Systems” OTC Paper 16588, Offshore Technology Conference, Houston, May.