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Technology
Assessment & Research (TA&R) Program
| Project Number |
361 |
| Date of Summary |
March
16, 2004 |
| Subject |
VIV CFD
Loads and Responses of Tubular Members – Numerical Prediction of the
Nonlinear Hydrodynamic Forces and Responses of Flexible Offshore Structures |
| Performing Activity |
Texas A&M
University, Offshore Technology Research Center (OTRC) |
| Principal Investigator |
Dr. John Kallinderis |
| Contracting Agency |
Minerals Management
Service |
| Estimated Completion |
October 31, 2002 |
| Description |
The offshore industry estimates
VIV hydrodynamic forces based on empirical measurements or low-order fluid
dynamic models calibrated for shallow water applications. Comparisons of the
predicted forces and responses of flexible structures with experimental data
reveal the shortcomings of these models, especially in the design of
deepwater systems. Hence, the motivation of the proposed research to employ
flow-structure interaction methods based on solving the Navier-Stokes and
structural dynamics equations of motion to provide predictions of the forces
and responses of risers and spars. Two issues of the numerical methods have
been identified; 1) the computational expense required for full
three-dimensional simulations of straked risers and spars can be prohibitive
in some cases, and 2) certain degree of over prediction of the drag
coefficient for super critical Reynolds numbers for cases of perfectly
smooth cylinders. |
| Progress |
Method for solving the Navier-Stokes equations, which is
based on the artificial compressibility approach, has been tested in terms
of accuracy and computing resources requirement. The issue of the allowable
timestep size was investigated next. The timestep size for time-accurate
simulations is dictated by the size of the smallest element for several of
the popular CFD methods. It is quite typical that very small elements exist
in most of the meshes employed. As a consequence, the timesteps used are
very small which renders vortex-induced vibrations (VIV) simulations
prohibitively expensive in many cases studied. This issue becomes more
serious as the Reynolds number increases.
Copyrighted, professional journal articles where published as a result of
this study. They will not be published on this website. |
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