Abstract: The wave-induced forces on a submarine pipeline near the ocean floor result from several components, such as inertial forces, drag forces, lift forces, and under certain conditions, eddy-induced forces. For a pipeline touching the bottom, or at small clearances above the bottom, the lift force is tille predominant force in the vertical direction. These loads on pipelines are due to the velocities and accelerations of orbital wave motion. For predicting the horizontal force components, the force coefficients in the well-known Morison equation were evaluated from prototype-scaled tests. In the case of vertical forces, the coefficients for another new model were introduced. For both of the equations, the force coefficients were evaluated on the basis of the least squares flt method. The coefficients were determined for a prototype-scaled pipeline under the influence of regular waves in transitional water.
Introduction The present investigations are based upon the assumption that the coefficients presented in this paper can be applied to determine the forces on horizontal pipelines due to regular and as well as irregular wave loads. The mathematical models are based upon the well-known MORISON equation for predicting the horizontal force and a formula for the transverse force deduced by PRESER [6]. By introducing force coefficients from the regular case into a new mathematical model and a new observation model for the stochastic case [9], the predicted time series provided satisfactory agreement for both the horizontally and the vertically-measured components over a wide range of test conditions. The on-bottom stability analysis of subsea pipelines is generally based on the well-known fundamental formula for hydrodynamic forces by MORISON. Both of the equations can also be applied to determine irregular loads on pipelines, because regular waves are treated as special stochastic waves in the following.