Wave and current forces at a bottom-mounted submarine pipeline

ABSTRACT Aristodemo, F., Tomasicchio, G.R. and Veltri, P., 2013. Wave and current forces at a bottom-mounted submarine pipeline. The present work deals with the analysis of in-line and transverse forces for a bottom-mounted slender pipeline subjected to periodic motions characterized by non-linear Stokes and cnoidal waves, and also with a superimposed positive current. Full-scale laboratory tests were conducted in the large wave flume of CSMI at Padua, Italy, and characterized by a longitudinal vertical wall which was built in the flume to create two separate channels where simultaneous measurements of pressures, velocities and surface elevations were performed. The experimental dataset was defined by 39 tests with periodic waves using a smoother cylinder, 14 tests with periodic waves using a rougher cylinder and 11 tests with periodic waves plus currents, leading to a Keulegan-Carpenter number ranging from 4 to 13. The hydrodynamic coefficients of Morison and transverse force models were deduced from the time records of kinematics and pressures at the cylinder through the evaluation of the performances of time and frequency domain techniques such as the ordinary and the weighted least squares. The comparisons between experimental and calculated non-linear forces in terms of peaks, associated phase shifts and spectral densities show acceptable accuracy as regards the Morison force components and a poor estimation of the vertical forces.