Wake II model for hydrodynamic forces on marine pipelines

The hydrodynamic force model for prediction of forces on marine pipelines as described in this research includes flow history effect (wake effects) and time dependence in the force coefficients. The wake velocity correction is derived by using a closed-form solution to the linearized Navier-Stokes equations for oscillatory flow. This is achieved by assuming that the eddy viscosity in the wake is only time dependent and of a harmonic sinusoidal form. The wake correction in this derivation generated four empirical parameters that have been estimated on the basis of Exxon Production Research Company (EPR) data that represent the measure field data and reflect a wide range of flow conditions.; The forces predicted by the Wake II Model have been compared to EPR Wake Model in terms of time histories (force shape) and magnitudes of peak forces. Overall, the model predictions by the Wake II Model are satisfactory and represent a substantial improvement over the predictions of the conventional models. The conventional force models representing adaptations of Morison's equation with ambient velocity and constant coefficients give predictions that are in poor agreement with the measurements especially for the lift force component. The Wake II Force Model can be used for marine pipeline on-bottom stability design calculations for regular waves with various pipe diameters.