Determining the Hydrodynamic Coefficients of a BOP Available to Purchase

Blow-out preventers (BOPs) can be subjected to vortex induced vibration and also oscillating wave-induced loads from attached risers. Typically, the response of the BOP is estimated using heuristic codes and assumed hydrodynamic coefficients (added mass and drag) of the BOP and attached structures. In current practice, complex structures such as a BOP are tested in a tow basin using physical models to find these coefficients. An alternative, which is explored here, is to use computational fluid dynamics (CFD). Two BOP designs have been tested in 1:12 scale. We use CFD to simulate these experiments and to calculate forces on the models the resulting force histories. Added mass and drag coefficients are calculated from the CFD results at various Keulegan-Carpenter numbers and the results are compared with data derived from tow tank experiments. It is shown that the CFD simulations can provide an alternative to tow tank experiments over a wide range of experimental parameters. CFD simulations are also used to predict the hydrodynamic coefficients of a full scale structure and the results compared with the model scale results.