An extensive model test program on the hydrodynamic forces on a submarine pipeline resting on the sea bottom and exposed to steady current, regular waves, combined steady current and regular waves, irregular waves, and combined steady current and irregular waves has been performed. The hydrodynamic forces in both the in-line and the cross-flow directions have been analyzed using three different methods, i.e., least-squares-fit analysis based on Morison-type equations, Fourier analysis, and maximum force analysis. The force coefficients associated with each method have been determined for a wide range of environmental conditions. The results of the tests are presented in terms of the calculated force coefficients and their dependence on various nondimensional parameters is discussed. Furthermore, comparisons with other test data are presented.

The weight coating requirements for assuring the on-bottom stability of several pipelines in the Arabian Gulf have been determined through an integrated design procedure including mathematical modelling for determining extreme wave conditions, field measurements of currents and physical model testing to establish the magnitude of the hydrodynamic forces.

The paper describes the results of a model test series with the purpose of determining the hydroelastic vibrations of a nearbed pipeline span exposed to flow conditions created by steady current, waves and waves superimposed on steady current. The study has been conducted using a model composed of a spring-mounted rigid pipe segment and a flat plate simulating the sea bed. The hydroelastic cross-flow vibrations of the pipe segment are presented as function of the flow velocity, flow condition (waves and/or steady current) and the relative distance of the pipe to the seabed. A simple approach to analyze the vibrations caused by an irregular wave train is presented.

No abstract

No abstract