Hydrodynamic Forces on Multitube Production Risers Exposed to Currents and Waves

Abstract

This paper presents the experimental results of a joint industry riser test program. Over a five-year period, an extensive experimental investigation of hydrodynamic loads acting on various production risers was carried out. The program included the laboratory testing of many multitube riser configurations as well as a single cylinder. Several major oil companies sponsored the project. The tests were made with rather large-scale models which were: 1) held stationary in steady current, 2) moved at constant speed or constant acceleration through a quiescent fluid or through a moving fluid, and 3) held stationary in oscillating flow or in steady current superimposed on oscillating flow. The primary objective of this investigation was to establish an accurate measurement of the hydrodynamic forces on bundle-type risers. The findings from this study will be presented in two papers. In the first, we shall present the hydrodynamic force coefficients for some marine risers consisting of one or more cylinders interacting either only with currents or oscillatory flow separately. In a companion paper, the pertinent data for the joint presence of the oscillatory flow and currents will be discussed. Among the results outlined here are the drag, inertia, and lift coefficients for various composite risers as a function of the Reynolds and Keulegan-Carpenter numbers. An analysis and synthesis of the test data are also presented.