Experimental observations of a secondary load cycle in the force acting on a vertical cylinder exposed to long and steep waves are discussed. A complementary discussion of the occurrence of ringing of models of offshore structures is given. The height of the secondary load cycle is typically up to about 0.1-0.15 times the peak to peak force on the cylinder. The load cycle is observed for a nondimensional wavenumber kR in the range 0,1-0.33 and for a Froude number Fr =ωζ_m/{(gD)~(1/2)} exceeding about 0.4. Pronounced ringing occurs for the same parameter range, (k the wavenumber, R the cylinder radius, ω the wave frequency, ζ_m the maximal wave elevation, g the acceleration of gravity, D - 2R.)
展开▼
