Study of C sub(D), C sub(M), C sub(L) and wave forces on pipe lines near the ocean-bottom

The wave forces on pipes near the ocean bottom are studied with model test in this paper. Comparisons of four different methods show that the uncommonly used method - Least Square Mass (LSM) is the most stable one. The in-line and transverse forces on the pipe, which is placed at various distances from the bottom of the wave tank, are measured. The force transfer coefficients (C sub(D), C sub(M), C sub(L)) are much larger when the pipe is near the bottom than when it is free. But the coefficients do not increase unlimitedly: they reach their maxima at xi (gap ratio = e/D) = 0.1 (gap ratio xi = e/D). An interesting result is that the ratio of lift force frequency (f' sub(L)) to wave frequency (f sub(w)) is 2.0. In the paper, the curves of coefficients are given.