1. For the large-diameter deeply submerged pipe tested,
the wave-induced horizontal loads were predominantly inertial,
and the values of C1 remained fairly constant in spite
of the different sea states tested. The mean values of C1 obtained
were somewhat smaller than the values predicted by
potential-flow theory for the same bottom clearance and under
the assumption of uniform unsteady flow.
2. In cases where current-induced velocities were considerably larger than wave-induced velocities, drag forces became important. In those cases, values of inertia coefficients were up to 20 percent smaller than those found for waves only.
3. In the inertia-dominated regime, the use of a frequency-domain analysis has proven to predict very well the distribution of peak horizontal forces. In the same way, the mean-square method has proven to predict well the distribution of combined peak horizontal wave and current forces.
4. Mean values of drag and inertia coefficients obtained from the wave-by-wave analysis are consistent with those predicted by the previous two methods. Among the prediction methods used, the least-square fitting technique over the whole wave cycle yielded the smallest standard deviation for the force coefficients.
5. The time-dependent lift force acting on the pipe consisted of two components: an inertial force component that dominated in the absence of strong currents, and a force component due to vortex shedding which dominated in the presence of larger waves and stronger currents. Also, for the bottom clearance tested (e/D = 0.73), the mean lift force acting on the pipe was practically zero.
2. In cases where current-induced velocities were considerably larger than wave-induced velocities, drag forces became important. In those cases, values of inertia coefficients were up to 20 percent smaller than those found for waves only.
3. In the inertia-dominated regime, the use of a frequency-domain analysis has proven to predict very well the distribution of peak horizontal forces. In the same way, the mean-square method has proven to predict well the distribution of combined peak horizontal wave and current forces.
4. Mean values of drag and inertia coefficients obtained from the wave-by-wave analysis are consistent with those predicted by the previous two methods. Among the prediction methods used, the least-square fitting technique over the whole wave cycle yielded the smallest standard deviation for the force coefficients.
5. The time-dependent lift force acting on the pipe consisted of two components: an inertial force component that dominated in the absence of strong currents, and a force component due to vortex shedding which dominated in the presence of larger waves and stronger currents. Also, for the bottom clearance tested (e/D = 0.73), the mean lift force acting on the pipe was practically zero.
Comments